Here we study ultrathin gold films near the percolation threshold fabricated by electron-beam deposition on monolayer CVD graphene. The advantages of such hybrid graphene/gold substrates for surface-enhanced Raman spectroscopy are discussed in comparison with conventional substrates without the graphene layer. The percolation threshold is determined by independent measurements of the sheet resistance and effective dielectric constant by spectroscopic ellipsometry. The surface morphology of the ultrathin gold films is analyzed by the use of scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the thicknesses of the films in addition to the quartz-crystal mass-thickness sensor are also measured by AFM. We experimentally demonstrate that the maximum SERS signal is observed near and slightly below the percolation threshold. In this case, the region of maximum enhancement of the SERS signal can be determined using the figure of merit (FOM), which is the ratio of the real and imaginary parts of the effective dielectric permittivity of the films. SERS measurements on hybrid graphene/gold substrates with the dye Crystal Violet show an enhancement factor of ~10 Surface-enhanced Raman spectroscopy (SERS) ,2,3,4 isVarious strategies have been suggested to realize a strong and robust FE effect. One of the ways to get strong FE is to create structures with so-called “hot spots” ,18,19 thAs previously shown by near-field and two-photon luminescence microscopy ,25, the 2/Si wafers with and without a single-layer CVD graphene for SERS applications.In this research, we focus on a comprehensive analysis of ultrathin gold films with thicknesses close to the percolation threshold, deposited on SiO2 on the surface (SiO2/Si). The second one was the same silicon wafer, but with a single-layer of CVD graphene, which covered more than 95% of the substrate area (graphene/SiO2/Si). Before metal deposition, the graphene substrates were annealed at 250 °C in a vacuum chamber 10−6 Torr for 1 h to remove residual PMMA and water. The thin gold films for all types of substrate were deposited in one mode by electron beam evaporation in a Nano Master NEE-4000  installation at a high vacuum, with the pressure of residual gases in the chamber being no more than 5 × 10−6 Torr and a deposition rate of 0.5 Å/s, at room temperature (23 °C). Each thickness of the gold film was deposited simultaneously for both types of substrate in one cycle. As a material for deposition, granules of gold produced by Kurt J. Lesker with a purity of 99.999% were used. The quoted “thickness” of the gold films are the average nominal coverage values measured by the quartz oscillator.The ultrathin gold films with thicknesses ranging from 3 to 10 nm with a step size of 1 nm were deposited onto two types of substrates. The first type was a silicon wafer with a thin 90 nm thick layer of SiOThe fabricated films were subsequently imaged by scanning electron microscope (SEM) JEOL JSM-7001F . The thickness of the films and their roughness were measured by an atomic force (AFM) neaSNOM Microscope . Electrical measurements were carried out using a 4-probe station  from Jandel with a collinear geometry of the location of the probes and started with 10 nA, gradually increasing the current to 100 μA.®, J. A. Woollam Co., Lincoln, NE, USA) operating in the wavelength range of 280–3300 nm. The data were collected at multiple angles of incidence from 65° to 75° with a step of 5° and the optical constants of the gold films were obtained by point-by-point fitting of the ellipsometry spectra with 10 nm steps [The dielectric function spectra of the Au thin film were evaluated from data measured using a variable-angle spectroscopic ellipsometer (WVASEnm steps . To be inm steps .2/Si and graphene/SiO2/Si) were covered by an aqueous 10−6 mol/L solution of CV for approximately 1 h and subsequently gently blown dry with compressed air.The experimental setup used for Raman measurements was a confocal scanning Raman microscope Horiba LabRAM HR Evolution . All measurements were carried out using linearly polarized excitation at a wavelength of 632.8 nm, 300 lines/mm diffraction grating, and ×100 objective (N.A. = 0.90), whereas we used unpolarized detection to have a significant signal-to-noise ratio. The spot size was ~0.43 μm. The Raman spectra were recorded with 0.26 mW incident powers and an integration time of 1 s at each point. The statistics were collected from 15 × 15 points maps with a step of 0.8 μm from at least 10 different places of the sample. These scan parameters were selected as a compromise between minimum damage/bleaching of the dye molecules and significant signal-to-noise ratios. Raman dye Crystal Violet (CV) was used for the Raman characterization. Directly before the Raman measurement, the gold films deposited on two substrates  indicates the single layer of graphene ,47, and bstrates a–d. The graphene .2/Si substrate is greater than on SiO2/Si. The data in Routinely, the thickness of the deposited films is estimated by the quartz sensor in an electron beam evaporation installation, but the real thickness can be different. For the gold films, the quoted “thickness” is the average nominal coverage measured by the quartz oscillator. We accurately measured the thickness of the gold films and their roughness by AFM and compared how the obtained values correlate with the detector readings. The results of the AFM measurements are presented in 2/Si substrate can be determined by sheet resistance measurements [2/Si substrate begin to conduct at thicknesses of 8 nm. Therefore, we can assume that the percolation threshold for such films is between 7 and 8 nm. Because graphene has very high electrical conductivity, the definition of the percolation threshold for the graphene/SiO2/Si substrate is more complicated than for previous samples, since this type of sample has conductivity at all thicknesses due to graphene. The sheet resistance of graphene was measured and the value ranged from 700 to 1600 Ω/sq. For films on graphene/SiO2/Si substrate, conductivity is observed over the entire range, but films can be considered percolated when their sheet resistance is much lower than the sheet resistance of graphene. According to this criterion, we can estimate that the percolation threshold is between 5 and 6 nm. Mostly, electrical measurements are enough to uniquely determine the film thickness at which there is a percolation threshold.Although we have shown the difference in thicknesses between those measured by AFM and by the quartz sensor, in the further representation of the experimental data we used the thicknesses given by the quartz sensor. Before the Raman measurements, we found a percolation threshold for deposited films by electrical and optical methods. The percolation threshold for films on the SiOurements ,41. The 2/Si substrate, we used ellipsometry as an additional method to determine the percolation threshold. Ellipsometry measurements give effective optical constants of gold films and can be used to determine the percolation threshold.However, as we cannot uniquely determine these thicknesses for the gold films on the graphene/SiO2/Si substrate starting from 8 nm , which is equal to −ε’/ε” and is presented in 2/Si e and graSi  and ~6.0 × 104 (for the 6 nm gold film deposited on the graphene/SiO2/Si substrate). Thus, the comparison of the hybrid graphene/gold substrates and substrates without graphene shows that, although the level of the SERS signal for the substrate with graphene is almost the same or even slightly lower, the ability to quench of luminescence provides a great advantage over other substrates. There is another interesting feature. If we compare the EF for the film with thickness 7 nm (this thickness is the percolation thresholds for the case of gold on SiO2/Si substrate) on SiO2/Si (EF ~ 1.1 × 105), and graphene/SiO2/Si substrates (EF ~ 2.1 × 104), a significant difference can be observed. Indeed, the presence of only one graphene layer on a SiO2/Si substrate can affect the thickness of the percolation threshold for the gold films and leads to the difference in SERS signal in near one order of magnitude.For the calculation of enhancement, we use the analytical enhancement factor (EF) expression, which quantifies how much more signal can be expected from SERS in comparison with normal Raman for the same experimental parameters . The ave2/Si and graphene/SiO2/Si. We demonstrated that the thickness of the deposited gold films measured by AFM and sensor values can vary significantly. The percolation threshold has been determined by two independent experimental methods as a four-probe measurement of the sheet resistance and spectroscopic ellipsometry. These methods show good agreement with each other for both types of substrate with and without graphene. According to them, the thicknesses of the percolation threshold is between 7 and 8 nm for the films on the SiO2/Si substrate and between 6 and 7 nm on the graphene/SiO2/Si substrate. The maximum SERS signal was obtained for the gold films with thicknesses near the percolation threshold in the case of both types of substrate and amounted to be ~6.0 × 104 (graphene/SiO2/Si) and ~1.1 × 105 (SiO2/Si), respectively. SERS measurements of the dye Crystal Violet demonstrated the ability of graphene to effectively quench luminescence by an average of ~60%. Thus, the substrates with and without graphene show comparable SERS signals. However, the presence of graphene shows the ability to quench luminescence, which provides a great advantage over other types of SERS substrates. Our results demonstrate that the high intensity of the SERS signal is also observed for the films thicknesses adjacent with the percolation threshold, but only for thicknesses slightly below. Additionally, we show a strong correlation between FOM and intensity of SERS spectra. The maximum EF for both types of substrate corresponds to zero slopes of the FOM curves in the infrared region. We propose to use FOM curves as an additional criterion for finding the percolation threshold and the thicknesses of the films that exhibit the maximum EF. We believe that the reported results will be interesting for SERS applications, especially for bio- and molecular sensing.In summary, this article presents a detailed study of semi-continuous gold films near the percolation threshold deposited on two types of substrate—SiO


In this work, we report an available technique for the effective reduction of graphene oxide (GO) and the fabrication of nanostructured zirconia reduced graphene oxide powder via a hydrothermal method. Characterization of the obtained nano-hybrid structure materials was carried out using a scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). The confirmation that GO was reduced and the uniform distribution of zirconia nanoparticles on graphene oxide sheets during synthesis was obtained due to these techniques. This has presented new opportunities and prospects to use this uncomplicated and inexpensive technique for the development of zirconia/graphene nanocomposite powders. Over the past years carbon-based nanostructured materials such as carbon, CNTs (carbon nanotubes), graphene, CNFs (carbon nanofibers), fullerenes, etc. have accomplished swift evolution and extensive use because of their Van der Waals force and covalent bonding, chemical stability, and high stiffness and strength together with their low weight.The formation of graphene  raised n2 hybridisation that occurs during the formation of carbon atoms is in charge of its stand-out in-plane elastic and mechanical properties, namely Young modulus (0.5–1 TPa [The sp.5–1 TPa ) and ten.5–1 TPa ). Meanwh.5–1 TPa ,11. As a2) have received significant attention from the scientific circles as a potential material for various structural applications, because of their high mechanical characteristics, physical and chemical wear, and thermal stability coupled with corrosion resistance and zero toxicity [2.Recently, zirconia ceramics / 8 mol% yttria stabilized zirconia by colloidal processing subsequent spark plasma sintering and reported that the addition of GO-enriched layer into zirconia laminates is slowing down the probabilities of crack generation and propagation .In the work of Rao et al., the surface modified graphene zirconium oxide was synthesized and characterized as a nanocomposite material. It was utilized as an adsorbent for the removal of chlorophenols from aqueous solution. The removal efficiency was maximum towards 4-chlorophenol at pH 1.0 and decreased with increasing pH .Teymourian et al. reported the synthesis of the high performance zirconium dioxide-reduced graphene oxide composite and its application as a novel architecture for electrochemical sensing and biosensing purposes . Furthermore, Li et al. prepared zirconia/graphene nanosheets composite coatings using a plasma spraying technique. The obtained composite coating demonstrated low friction coefficient and improved wear resistance .Additionally, in recent years the production of nanostructured crystalline particles has gained attention, as they possess enhanced performance abilities over conventional coarser grain materials. In order to prepare nanocrystalline zirconia-based nanocomposites, different methods such as the sol/gel method , vapor pTherefore, in order to produce effectively isolated nanoparticles with a narrower size distribution, the hydrothermal methods are mentioned as having great potential ,45. ThisAll that is required for synthesis is to take a Teflon-lined stainless-steel autoclave and put the materials and precurcors in inside of it.Uniform nucleation processes and very low grain size highlighted are highlighted as the main benefits of this method. Therefore, the purpose of this work was to produce graphene oxide (GO) with the subsequent production of reduced graphene oxide (rGO), which is used as a support to anchor zirconia nanoparticles and leading to their uniform distribution on the surface of rGO. This special nano-hybrid structure provides the opportunity to obtain a uniform composite ceramic/graphene nanopowder that can be used as a raw material to fabricate dense multi-purpose zirconia-based composites reinforced with nanostructure graphene, which combine the desired properties of each component. Thus, the aim of the present work is to obtain a nanocomposite material when there is phase uniformity and good interfacial bonding between the graphene and matrix after sintering.3 and KMnO4 in concentrated H2SO4. Pure graphite powder was steadily added  into a hot concentration of H2SO4 solution that would be cooled in an ice bath. Afterward, KMnO4 was slowly added, in small doses, to keep the reaction temperature below 20 °C. Then the suspension was treated with a hydrogen peroxide (H2O2) solution and washed with HCl and H2O in order to complete the reaction with KMnO4. After filtration and drying, GO sheets were obtained. In the previous works, this process is decribed in further detail [Hummers’ method was used as synthesis technique of graphene oxide (GO) from graphite powder which was oxidized. Briefly, this approach involves Hummer’s reagents with low levels of NaNOr detail ,46,47.−1. The synthesis of reduced graphene oxide-nanozirconia (ZrO2/rGO) composites was carried out by means of a simple hydrothermal process, in which the GO suspension was used as the rGO precursor, N2H4·H2O and ZrOCl2·8H2O acted as the reducing agent and the nZrO2 precursor, respectively. Firstly, 40 mL of GO colloidal suspension was mixed with 20 mL of a ZrOCl2 solution (0.01 M) to obtain a mixed solution of GO and ZrOCl2 with a volume ratio of 2:1. After being sonicated for 30 min, 1 mL hydrazine hydrate was added to the mixture and was poured into a 200 mL stainless steel teflon-lined autoclave, which was sealed and maintained at 180 °C for 18 h, and then naturally cooled at room temperature. For the purpose of removing Cl-ions, the obtained material was washed, centrifuged, and re-dispersed five times in deionized water. Finally, the ZrO2/rGO nanocomposite powders were dried in a FreeZone2.5 freeze-drying system . The collector temperature is continuously set at −50 ± 2 °C.The as-prepared GO was exfoliated ultrasonically for 2 h in order to obtain a stable GO colloidal suspension with a concentration of 2.33 mg∙mL2/GO) composite powder was prepared following the same cycle without the addition of N2H4·H2O.Furthermore, the shell temperature and the chamber pressure were kept at 23 ± 2 °C and 0.02 ± 0.01 mbar, respectively, during the entire process . For comThe microstructure, crystalline structure, and surface morphology characterizations of the as-synthesized samples were evaluated by transmission electron microscopy JEM 3010 . To this end, nanopowders were placed on a TEM grid  .0 and on surface area basis q2 were compiled. A Gaussian normal distribution was fitted to the measured distribution in order to obtain the corresponding geometric mean particle diameters μg(q0) and μg(q2). The cumulative distribution of the particle diameters q0 was fitted with a sigmoid function to obtain the characteristic particle diameter d50. The specific surface area STEM of the zirconia nanoparticles was calculated from μg(q2) using the density of 5.68 g/cm2 and assuming spherical particles [As was described previously, the particle diameter distribution of the nanocrystalline zirconia was determined from TEM micrographs by measuring the diameters of about 800 zirconia nanoparticles in both synthesized nanopowders. From these data, the density distribution of the particle diameters on number basis qarticles . FurtherX-ray diffraction measurements were conducted using an Empyrean diffractometer  ranging from 5° to 70°. The step size was 0.05 with a scan speed of 0.06 /min. The diffractometer used Cu Kα radiation (λ = 1.5405981) working at 40 kV and with an intensity of 30 mA .TM2 Raman Microscope, Thermo FisherScientific, Waltham, MA, USA) with a wavelength of 532 nm and a laser power of 2.0 mW. The laser beam was focused through an optical microscope’s 50× objective lens to a spot size of 2 µm on the studied area . The accumulation time for each Raman spectrum was about 10 s [Raman spectra of studied materials were collected to identify the phase composition. The Raman setup is composed of a laser (DXRout 10 s .2/rGO and ZrO2/GO nanopowders were conducted separately using a Gaussian–Lorentzian function after performing a Shirley background correction.All X-ray photoelectron spectroscopy (XPS) measurements were carried out on a K-Alpha  photoelectron spectrometer equipped with a micro-focused monochromator Al Kα X-ray source. Peak fitting of the C1s and Zr3d spectra for ZrO−1 to 4000 cm−1 . For this purpose, potassium bromide (KBr) pellets (diameter 1.0–1.3 cm) of each powder sample were prepared using a uniaxial press [Fourier transform infrared (FTIR) spectra of the synthesized nanocomposite powders were measured  in the wavenumber range 500 cmal press .g(q0) and μg(q2) of the particle size distribution are 5.1 nm ± 0.8nm and 4.8 nm ± 1.2 nm, respectively, and the d50 diameter is 5.0 nm with an uncertainty of ± 0.8 nm for both ZrO2/GO and for ZrO2/rGO nanopowders. The specific surface area STEM of the nanopowders was calculated from the geometric mean diameter μg(q2) and reached a value of 110.0 m2/g.The nanozirconia crystals have a particularly spherical shape and they are uniformly dispersed. Almost no difference was found in particle size distribution and specific surface area. The geometric mean diameters μ2/rGO nanocomposite powder diffraction peaks in the region up to 20° are not presented as indicated in the case of GO and enables to say that the GO was well reduced during the reaction. In addition, analys of intensities and peaks location appearing in XRD data were compared with the infromation from the International Centre for Diffraction Data (ICDD) for tetragonal (PDF file no.01-083-0113) and monoclinic (PDF file no. 00-024-1165) structures.The most intense apparent peak located at 2θ = 10.8° in the curve of GO, and corresponds to the (001) reflection of GO . The resThe Raman spectra of all the studied materials are shown in −1 is the G band and it is the more intence than the 2D (2720 cm−1) and D (~1350 cm−1) bands  [−1 means that sp2 bonds were broken and, consequently, it indicates that a intended transformation of sp2 hybridization to sp3 was occurred, which shows a rise of the disorder in the sp2-hybridized carbon system [2/rGO  bands a. In the1) bands b–d, a imand sp3) . The morn system . This dim [2/rGO d powders2 nanoparticles onto the surface of the rGO causes additional changes in the characteristics of the vibrations in the material’s lattice. Therefore, the intensity of D bands after the reduction process is higher in comparison to the unreduced ZrO2/GO nanocomposite powders. It was suggested that, besides some defects in reduced graphene oxide, the presence of ZrO2 carbon lattice and consequently its structural changes. However, the elimination of oxygen containing groups leads to the restoration of ordered graphitic stacking in rGO and causes the appearance of 2D peak [It should be noted that after the graphite’s chemical oxidation process, the presence of peaks attributed to 2D band were not observed in GO b. It can 2D peak ,54,55.−1 is a second-order peak and denoted by S3.Another band, known as conjunction between D and G intensities and appears near 2900 cm−1, 269 cm−1, 407 cm−1 and 616 cm−1 were interpreted as tetragonal zirconia phases [S3/2D intesity ratio is related to the diminution in defects and involves a lower quantity of oxygen in graphene . Raman sa phases ,58.To investigate the chemical changes between reduced and not reduced graphene oxide powder XPS measurements have been carried out .2/GO  peak, C-C (sp3 C) peak and C=O (the carbonyl groups), respectively [For further interpretation and to better understand the mechanism of formation and the chemical states of elements, comprehensive analysis of C and Zr XPS spectra were carried out. The detailed C1s spectra of not-reduced and chemically reduced powders are shown in ectively ,60. Moreectively ,62,63, wectively .2/rGO powder had an additional peak at 285.9 eV ) and bending (δ (−OH)) vibrations of coordinated or absorbed water molecules retained on the ZrO2 suface [−1 indicates the existence of OH deformations in the C–OH groups [−1 [2 stretching mode demonstrates the broad absorption peaks around 2930 cm−1 [Obviously, the clear expresed absorption that appeared at peaks at 3420, 1635 and 1558 cm2 suface . The peaH groups . The Zr-oups [−1 ,74,75. M930 cm−1 .−1, while the O–H bending vibration of water molecules and the C=C skeleton stretching mode was assigned at 1626 cm-1 [−1. The peak located at 1227 cm−1 belongs to the C–O–C stretching vibration. The absorption bands at 1121 and 1072 cm−1 corespond to the epoxy C-O and the alkoxy C-O stretching vibration, respectively [−1 was recognized to stretching of the aromatic C=C mode, while the band at 1234 cm−1 corresponds to the epoxy C−O and C=O, indicates that GO was reduced incompletely [−1 was assigend to C=O stretching frequency belonging to the ZrO2/rGO nanocomposite was shifted to 1746 cm-1 because the relationship between the C=O group and Zr and its relative intensity was also decreased [2 solution provides the interaction between the oxygen-containing groups of GO and Zr(IV) and the appearance of two vibrational bands located at 1460 and 1395 cm−1, which were assigned to the creation of either a monodentate or bidentate complex [−1 can be assigned to the C=C stretching mode and Zr–O vibration, respectively [2 nanoparticles and rGO nanosheets occured, i.e., ceramic nanoparticles were directly attached to the surface of the rGO nanosheets.The C=O stretching vibration of –COOH and C=O was observed at 1735 cm626 cm-1 . The O–Hectively ,81,82,83mpletely ,85,86. Oecreased . The hyd complex ,79,80,812 nanoparticles were seen  plane surface. We believe that this synthesis route will allow for the effective production of uniform ceramic/graphene nanopowders that can be used as a building block to fabricate zirconia matrix composites reinforced with a homogenous nanostructure graphene after sintering.In the present work, a nanostructured ZrO


Arabidopsis thaliana is negatively regulated by ABI4 and plays a key role in water uptake by seeds, ensuring that imbibed seeds proceed to germination.PTR2 in Arabidopsis thaliana, the physiological role of the tonoplast-localized, seed embryo abundant PTR2 is unknown. In the present study, a molecular physiological analysis of PTR2 was conducted using ptr2 mutants and PTR2CO complementation lines. Compared with the wild type, the ptr2 mutant showed ca. 6 h delay in testa rupture and consequently endosperm rupture because of 17% lower water content and 10% higher free abscisic acid (ABA) content. Constitutive overexpression of the PTR2 gene under the control of the Cauliflower mosaic virus (CaMV) 35S promoter in ptr2 mutants rescued the mutant phenotypes. After cold stratification, a transient increase in ABA INSENSITIVE4 (ABI4) transcript levels during induction of testa rupture was followed by a similar increase in PTR2 transcript levels, which peaked prior to endosperm rupture. The PTR2 promoter region containing multiple CCAC motifs was recognized by ABI4 in electrophoretic mobility shift assays, and PTR2 expression was repressed by 67% in ABI4 overexpression lines compared with the wild type, suggesting that PTR2 is an immediate downstream target of ABI4. Taken together, the results suggest that ABI4-dependent temporal regulation of PTR2 expression may influence water status during seed germination to promote the post-germinative growth of imbibed seeds.Peptide transporters (PTRs) transport nitrogen-containing substrates in a proton-dependent manner. Among the six PTRs in The online version of this article (10.1007/s11103-020-00967-3) contains supplementary material, which is available to authorized users. Seeds comprise the seed coat, endosperm, and embryo. Germination of dormant seeds commences with the uptake of water and terminates with the emergence of the radicle through the seed coat Bewley . During CYP707A , gibberellic acid (GA), ethylene, and auxin, and the antagonism between GAs (which stimulate seed germination) and ABA (which establishes and maintains seed dormancy) is the primary factor that regulates seed germination , ABA2 (encoding xanthoxin dehydrogenase), and ABA3 (encoding molybdenum cofactor sulfurase) genes, which in turn suppresses germination   and a wide range of nitrogen (N)-containing substrates, including nitrate, amino acids, and di-and tri-peptides , which is formed from vacuoles during seed maturation as a result of protein deposition and water displacement , seven ptr mutants (ptr1–6) including ptr2-1 and ptr2-2 alleles, two PTR2 complementation lines (PTR2CO2 and PTR2CO5), abi4 mutant, and ABI4 overexpressor (ABI4OE) were used in this study. Seeds from seed batches grown and harvested at the same time and stored for less than 2 weeks were treated with 70% ethanol for 1 min and then sterilized with 0.8% sodium hypochlorite. After washing five times with sterilized distilled water (SDW), seeds were imbibed in water in the dark at 4 °C for 2 days to break seed dormancy and then transferred to continuous light (30 µmol m−2 s−1) at 22 °C. Seeds were sown in SDW supplemented with 2% Glc, 1 µM ABA, 50 µM GA, ABA inhibitors (20 µM nordihydroguaiaretic and 10 µM diniconazole), 20 mM glycine di-peptide (Gly-Gly), 20 mM leucine di-peptide (Leu-Leu), or 10 ∝g ml−1 of a transcription inhibitor, Cordycepin. The osmotic potential of SDW was adjusted to − 0.23, − 0.39, − 0.68, or − 0.91 Mpa with polyethylene glycol 4000 .PTR genes were identified at The Arabidopsis Information Resource (TAIR) database (https://www.arabidopsis.org/index.jsp). Seeds of ptr1-1 (SLAK_131530), ptr2-1 (SALK_400_D08), ptr2-2 (SAL_65_B10), ptr3-2 (SALK_097591), ptr4-1 (SALK_062626), ptr5-2 (SALK_116120), and ptr6-1 (SALK_149283) were obtained from the Arabidopsis Biological Resource Center (ABRC) at Ohio State University, OH, USA. To map the T-DNA insertion sites, genomic DNA was isolated from the leaves of mutant plants using lysis buffer . Reverse transcription PCR (RT-PCR) was carried out using the SALK LBa1, LBba1, and LB1 primers and PTR2 gene-specific primers (Supplementary Table S1). The resulting PCR products were sequenced and compared with the genomic sequence of each gene to map the T-DNA insertion site .T-DNA insertion mutant lines of all six Arabidopsis PTR2 was amplified by PCR using sequence-specific primers (Supplementary Table S1). The PCR product was digested with XbaI and BamHI restriction endonucleases and cloned into the pJJ461 vector. The construct was confirmed by sequencing and transformed into Agrobacterium tumefaciens strain GV3101 by the freeze-thaw method. Transformation of ptr2 mutants was conducted using the floral dip method. PTR2CO lines with a single-copy of the hygromycin resistance (HygR) gene and PTR2 were identified by RT-PCR .The coding sequence of g for 10 min. Then, 600 µl of the supernatant (embryo extract) was transferred to an Eppendorf tube, followed by the additional of an equal volume (600 µl) of chloroform. The mixture was mixed thoroughly by shaking for 10 min at room temperature. After the addition of 600 µl of buffered phenol (pH 8.0), the organic phase was transferred to two new 2.0 ml Eppendorf tubes (300 µl each). Then, five volumes of methanol containing 0.1 M ammonium acetate were added to each tube, and the mixture was incubated at − 20 °C for 1 h to precipitate the proteins. Proteins were separated by centrifugation at 15,000×g for 10 min and washed first with 100% cold acetone and then with 80% cold acetone. The protein pellet was air dried and resuspended in SDS sample buffer . Proteins were separated by SDS-polyacrylamide gel electrophoresis (PAGE) using 15% resolving and 5% stacking polyacrylamide gels.Seed proteins was extracted using the chloroform-assisted phenol extraction (CAPE) method. Briefly, seeds (0.1 g fresh weight) were homogenized using a cold pestle and mortar in 1.0 ml buffer . The homogenate was centrifuged at 12,000×AP2M (at5g46630) gene  and treated with DNaseI (Takara). After NucleoSpin RNA Cleanup (Macherey-Nagel), cDNA was synthesized from 500 ng of total RNA using the iScript cDNA Synthesis Kit (Bio-Rad) and amplified by qRT-PCR on the CFX96 Real Time System (Bio-Rad) using the iQ™ SYBR Green Supermix (Bio-Rad), according to the manufacturer’s instructions. Reactions were performed in triplicate in a 10 µl volume, containing 5 µl SYBR Green Master Mix, 0.5 µl of each primer (10 pmol), 4 µl of 20-fold diluted cDNA, and 0.5 µl nuclease-free water, using the following conditions: 95 °C for 15 min, followed by 40 cycles of amplification at 94 °C for 10 s and 62 °C for 30 s, and lastly a final extension at 72 °C for 30 s. Fluorescence was measured at the end of each extension step. Amplification was followed by melting curve analysis, with continual fluorescence data acquisition during the 65 °C to 95 °C transition. A negative control containing water instead of cDNA template was included in each run. Raw data were analyzed with the CFX Manager software, and gene expression was normalized to the expression of −1) (Money Imbibed or germinating seeds (20 mg) were frozen in liquid N and ground using a pestle and mortar. The ground powder was immersed in 1 ml of 80% methanol and stored at 4 °C for 1 h. The extracts were filtered with C18 (Sep-Pak Vac) cartridges  to remove pigments and other polar materials. The filtered solution was dried and concentrated using a rotary vacuum concentrator and suspended in Tris-buffered saline (TBS). The level of ABA was determined using the enzyme-linked immunosorbent assay (ELISA) Kit (Agdia). To measure the seed water content, ca. 330 seeds immersed in SDW were collected at a given time, and external liquid was removed using a silica-based membrane column by spinning at 12,000 rpm for 5 min. Then, dry seed weight was subtracted from the fresh seed weight to determine the amount of water absorbed by the seeds. External osmotic potential of varying concentrations of PEG4000 was calculated from the estimated osmolality (mol kg1) Money .Escherichia coli and purified using a metal-affinity resin (Qiagen)  and competitor DNA fragments, including specific unlabeled fragment and ABI5 promoter fragment , were used with the purified GST-ABI4 protein in EMSAs .Glutathione S-transferase (GST)-tagged DNA-binding domain of ABI4 (GST-ABI4) was expressed in PTR2 and CaMV 35S promoters were cloned and fused to the β-glucuronidase (GUS) reporter gene in pCAMBIA3301 using primers listed in Supplementary Table S1. The resulting constructs were transiently transformed into the WT, abi4, and ABI4OE lines. Four-day-old seedlings grown in darkness were vacuum-infiltrated with Agrobacterium twice for 1 min each ; 4-methylubelliferone (Sigma-Aldrich) was used for calibration. Protein content was determined using bovine serum albumin as the standard 6, and 0.5 mM K4Fe(CN)6, and subsequently incubated in a staining solution containing 1 mM 5-bromo-4-chloro-3-indolyl-β-d-glucuronide (Duchefa)  were analyzed using the two-tailed Student’s t test, after normality assessment. Means with p values less than 0.05 were considered statistically significant.Data . Thus, PTR2 activity appears to be regulated at the post-transcriptional level during early seed germination and then at the transcriptional level during late seed germination.Publicly available microarray data show that transcript levels of α- and β-subunits of the legumin-type 12S globulins , suggesting a transcriptional regulation of both these genes during seed germination. However, transcripts of CYP707A3, CYP707A4, GTs, and BGs showed minimal or no changes (data not shown).We also quantified the water and ABA contents of germinating seeds, as aquaporin-independent uptake of water  and was almost complete at 36 HAS  or amplified by that of ABA and Glc , and was fully rescued by the overexpression of PTR2 under the control of the CaMV 35S promoter (35SCaMVp::PTR2) in the complementation lines PTR2CO2 and PTR2CO5 .To identify the physiological role of PTR2 in the seed germination process, ptr2-1 seeds exhibiting the delayed TR phenotype. Rapid water uptake during phase I was not affected by the PTR2 mutation. However, water uptake during phase II and phase III was lowered by 17% and 8%, respectively  and the GST-ABI4 fusion protein. The recombinant ABI4 protein containing only the DNA-binding domain bound directly to all PTR2 promoter fragments, like ABI5 (a positive control), but this binding was inhibited by unlabeled, cold fragments  and transformed into hypocotyls of WT, abi4, and ABI4OE. The expression of PTR2-GUS was lowered by 10% in the ABI4OE background, consistent with the results of the EMSA, thus confirming that ABI4 represses PTR2 transcription by directly binding to the CCAC motifs in PTR2 promoter , which is shaped by ABI4, suggests that PTR2 is involved in water uptake rather than in N mobilization from the endosperm to the growing axis. Our results are consistent with those of Song et al. , thus ruling out the role of PTR2 in the mobilization of seed storage proteins during seed maturation.Di- and tri-peptide sources available for the tonoplast-localized PTR2 seem different between the first half and second half of the water uptake phase II. Time-course analysis of water and storage protein contents of seeds clearly revealed that the inhibition of water uptake observed in the PTR2 belongs to NRT1/PTR family (NPF) proteins. In addition to nitrate and di- and tri-peptides, some NPFs are involved in the uptake of other substrates, such as nitrite, chloride, glucosinolates, auxin, ABA, GA, and jasmonates Electronic supplementary material 2 (DOCX 22 kb)Below is the link to the electronic supplementary material.


Graphene is widely used as the basic materials of nano optical devices and sensors on account of its special structures and excellent photoelectric properties. Graphene is considered as an ideal material for photodetectors because of its ultra-wide absorption spectrum from the ultraviolet to the terahertz band, ultrahigh carrier mobility and ultrafast photoreaction speed. In this study, a photothermal nano-device was made using graphene that was transferred to an electrode using an all-dry viscoelastic stamping method. The nano-device has the advantages of simplicity, high efficiency and instant measurement. This nano-device was used to measure the light absorption of graphene, and the calculated light absorption rate of graphene is basically consistent with previous research results. Experiments on irradiation at different wavelengths and thermal heating at different temperatures show that the nano-device has an excellent response to near-infrared and mid-infrared light. The conclusions provide an experimental basis for the research, design and fabrication of nano-devices, and this device can provide an effective method for detecting light and temperature in areas such as electronic components and solar cells. In recent years, the electronic components industry and the solar cell industry have developed rapidly, which have promoted higher requirements for the detection of light and heat. Graphene has the advantages of a large wavelength range of light detection, fast response speed, excellent thermal conductivity, etc.; therefore, nano-devices made of graphene can be used as sensors to meet the requirements of the future electronic-component industry and solar cell industry ,2. GraphThere have been many reports on the optical and thermal properties of graphene. Nair  used graPrevious researchers focused on the light absorption of graphene, but the experimental methods are relatively complicated, and there is a lack of a simple, effective and real-time nano-device that can monitor light and heat sensing. In this paper, a kind of nanometer device made of graphene, created using an all-dry viscoelastic stamping transfer method, has been applied, which is simple and efficient for doing research on light absorption, light response and thermal heating. This nano-device can provide effective guidance for the application of graphene and other two-dimensional materials in the electronic components industry and solar cell industry.The electrodes were obtained by ultraviolet photolithography and evaporation on a silicon oxide substrate. The manufacturing process of the electrode structure was as follows: (1) Silicon wafer cleaning: the 5-inch silicon wafer was soaked successively in acetone and isopropanol, and then put in deionized water and then blown with a nitrogen gun to remove grease and other impurities from the surface; (2) spin-coating the photoresist: AZ5214E photoresist was uniformly spin-coated on the silicon wafer using a homogenizer; (3) pre-baking: the sample was pre-baked in order to reduce the moisture in the photoresist and avoid the thermal cross-linking effect of the photoresist; (4) pre-exposure: the 5-inch silicon wafer was pre-exposed under a mask by an ultraviolet photoengraving machine; (5) baking: the pre-exposed samples were roasted again to modify the photoresist in the exposed area; (6) exposure: the mask plate was removed before the sample was exposed, and the exposure time was 12 s to ensure that ultraviolet light expose the photoresist thoroughly; (7) development: the sample was transferred to an MIF300 developer for development; (8) metal electrode evaporation and plating: metal electrode evaporation and plating were carried out using high temperature vacuum thermal evaporation equipment. The thickness of the Au deposited layer was 45 nm; and (9) lift off process: the sample was put in acetone solution for 30 min, and the metal was stripped in a heating stage at 75 °C, rinsed with deionized water, and blow-dried to complete the production.Graphene was obtained from graphite by heat-assisted mechanical stripping. The process used was as follows: (1) preparation of adhesive strips: the 3M Scotch tape was cut into rectangular strips, then placed the adhesive surface facing up on a clean and flat dust-free paper; (2) crystalline flake graphite transfer: tweezers were used to grab crystalline flake graphite in the middle of the strip along the width direction, so that the graphite crystals were sequentially transferred in the middle of the strip; (3) flattening of crystalline flake graphite: the tips of tweezers were used to touch the sticky graphite crystals to make sure that they are flat on the surface of the strip; (4) peeling: both ends of the strip were held and folded the strip in half for 10–15 times to ensure that two-thirds of the strip were covered with graphene; (5) preparation of flexible transfer substrate: polydimethylsiloxane (PDMS) was used as the material transfer substrate in the experiment to ensure that the van der Waals force between the material and the flexible transfer substrate was less than the van der Waals force between the material and the silicon substrate; (6) heat-assisted baking: the strip with graphene was adhered to the PDMS substrate and the whole sample was baked on a heating table for 1 min at 100 °C before peeling the strip in order to increase the probability of transferring the graphene to the PDMS; (7) rapid peeling: the strip needed be quickly peeled off after baking; and (8) screening of graphene: the PDMS substrate with graphene was placed on an optical microscope for screening. Samples with a thin thickness, uniform surface and regular shape were preferentially selected and then the position marks are made.Generally, the transfer method of two-dimensional materials depends on the use of polymer layers and wet chemistry, which sacrifices the performance of two-dimensional materials to some extent. The all-dry transfer method relies on a viscoelastic stamp and does not use any wet chemical steps . BecauseThere are two main types of interactions between light and graphene from the perspective of energy band transitions: inter-band transitions and intra-band transitions. The dominant transition mode depends on the energy of the photon. In the near-infrared and visible light bands, the light response is mainly inter-band transitions, and the absorption coefficient is determined by the fine structure constant. In this case, the light absorption of graphene can be regulated by adjusting the position of the Fermi plane due to the vesicle blocking principle. The energy at the K point of the two-dimensional graphene’s Bridgeport region is linearly related to momentum and the effective mass of the carrier is 0, which is a remarkable feature that distinguishes graphene from the electronic structure of conventional materials. This energy band relationship gives graphene unique physical properties, such as the quantum Hall effect and near-ballistic transport of carriers at room temperature. In terms of its optical properties, single-layer graphene has a high light absorption rate due to the linear distribution of Dirac electrons. Graphene absorbs 2.3% of each layer from the visible to the terahertz wide band .A constant pressure of 1 V was applied to both ends of the electrode, the incident light wavelength was 950 nm, the measurement time was 20 s, and the measured photocurrent curve is shown in In this experiment, light-emitting diodes with different wavelengths  were used to irradiate the fabricated device at the distance of 10 mm, as shown in The voltage-current diagram when the device is irradiated with 940 nm wavelength at different distances  is shown in In order to study the effect of light switching on the light absorption of the graphene device, the graphene device is irradiated intermittently with light at a wavelength of 850 nm and 940 nm. The nano-device was placed on a three-dimensional micrometer operating platform, and the relative position between the sample and the incident laser was adjusted through the change of the current over time. The position with the largest current change of the photoelectric device was taken as the laser irradiation position, that is, the area with the most significant photoelectric response. The left terminal was connected to the SMU1 of the semiconductor tester as a drain, and the right terminal was connected to the SMU3 of the semiconductor tester as a source. In the test, the bias voltage of drain terminal was set to 1 V, and the source terminal was grounded. The laser position is adjusted so that the laser focal plane was on the surface of the test device and the laser was approximately 10 cm away from the surface of the device. The light source was turned off during the first 30 seconds of the experiment, then the light source was turned on for 30–150 s, and so on. The resulting curve is shown in A constant voltage of 1 V was applied across the gold electrode, and the graphene device was irradiated with light of different wavelengths  at a distance of 10 mm. The resulting photocurrent relationship is shown in Transistor devices made of single-layer or few-layer of graphene with zero bandgap can be used as ultrafast photoelectric detectors. The graphene surface absorbs photons to produce electron–hole pairs that can be rapidly compounded, and the speed of the composite is dependent on the temperature and the concentration of electrons and holes. When an external electric field is applied, the electrons and voids can be pulled apart to produce a photocurrent, and the same effect can be achieved when there is a built-in electric field at the interface between the electrode and the graphene. Under the working condition of constant voltage, a change of carrier concentration is reflected as a change of current between source and drain, so the detection of light is realized. Graphene as a carrier transmission channel can improve the response speed of a light detection sensor device. By comparing the response time of the graphene nano-device with that of nanowires made by Hyungwoo , it can Since the maximum detection temperature in the field of electronics and solar cells generally does not exceed 100 °C, the graphene device is heated intermittently with a heating source at different temperatures  at a distance of 10 mm as shown in The photocurrent measured at a constant voltage of 1 V is shown in In this study, a photothermal nano-device is made by graphene, which is transferred to the electrode using an all-dry viscoelastic stamping method. This nano-device is simple and efficient for doing research on light absorption, light response and thermal heating. The light absorption rate of graphene measured by this nano-device is 2.216%, which is basically consistent with previous research. The experiment demonstrated that this graphene nano-device is effective and stable as sensors for detecting near-infrared light. It is proved that the graphene device has a faster and more sensitive response when detecting high temperature objects, through the irradiation with different temperatures. The conclusions of this paper provide an experimental basis for the research, design and fabrication of nano-devices, and provide effective guidance for the application of graphene and other two-dimensional materials in the electronic components industry and solar cell industry.


Aluminum composites reinforced by graphene nanoplates(GNP) with a mass fraction of 0.5% (0.5 wt.% GNP/Al) were fabricated using cold pressing and hot pressing. An orthogonal test was used to optimize the fabrication parameters. Ball milling time, ball milling speed, and ultrasonic time have the largest influence on the uniformity of the graphene in the composites. Afterwards, the microstructure, interfacial properties, and fracture morphology of the composites obtained with different parameters were further analyzed. The results show that ball milling time and ball milling speed have obvious influences on the mechanical properties of the composite. In this paper, when the ball milling speed is 300 r/min and the ball milling time is 6 h, the dispersion uniformity of graphene in the 0.5 wt.% GNP/Al composite is the best, the agglomeration is the lowest, and the mechanical properties of the composites are the best, among which the tensile strength is 156.8 MPa, 56.6% higher than that of pure aluminum fabricated by the same process (100.1 MPa), and the elongation is 19.9%, 39.8% lower than that of pure aluminum (33.1%). Aluminum is a structural material used commonly in aerospace, automobile, machinery, electronics, and other fields because of its light weight, high strength, good ductility, easy processing, and so on ,2,3. TheIn recent years, research on graphene-reinforced Al composites has gradually increased. Yan et al.  used balAt present, there are still some problems in the fabrication of graphene-reinforced Al composites, such as how to disperse the graphene uniformly in the Al matrix ,25, how In this study, graphene nanoplates with a mass fraction of 0.5 were mixed with Al powder using ultrasonic dispersal in ethanol solution and ball milling, and the graphene-reinforced aluminum composites (0.5 wt.% GNP/Al) were prepared via cold pressing and vacuum hot pressing. To maximize the uniform dispersal of graphene in the Al matrix while retaining the integrity of the GNP to the greatest extent, the optimal fabrication parameter combination needs to be determined. Therefore, in this paper, the fabrication parameters were grouped by orthogonal testing, the effects of the five fabrication parameters on the dispersion uniformity of graphene were studied, and the main influential parameters were obtained. The effects of ultrasonication time, ball milling time, and ball milling speed on the mechanical properties or microstructures of the composites were studied, and the optimal parameters that ensure the largest strength of the 0.5 wt.% GNP/Al composites fabricated by the cold pressing and vacuum hot pressing were obtained.2/g and approximately 3–5 layers with a particle size of 0.1–5.0 μm. The pure Al powder produced by Shandong Sitaili Metal Materials Co., Ltd.  was used as the matrix whose particle size is approximately 30 μm; graphene was purchased from Qingdao Huagao Diluted Energy Co., Ltd.  with a specific surface area of approximately 400 mFirst, the pre-weighed graphene is mixed with an appropriate amount of industrial ethanol and placed in an ultrasonic cleaner  to reduce the agglomeration of graphene and increase its dispersibility. The ultrasonication time was set to 60 min or 90 min. Then, the alcoholic solution of graphene and Al powder prepared in the ethanol solution dispersion is packaged into a tank of a planetary ball mill  for ball milling. Stearic acid is used as the process control agent, which can increase the dispersibility and prevent cold welding. Nitrogen is used as a shielding gas to prevent Al powder from being oxidized.1, X2, X3, X4, and X5. As shown in 1 has 4 levels, while X2, X3, X4, and X5 have 2 levels.In this paper, ball milling speed, ball milling time, B-P ratio, ultrasonication time, and stearic acid content were selected as the factors to study. To simplify the experimental process, this paper uses the orthogonal test method to distribute the five fabrication parameters reasonably, and the orthogonal distribution table of parameters (L8 (4 × 24)) is shown in A particle size analyzer (Hydro-2000 Mu (A), Malvern instruments Ltd., Malvern, UK) was used to test the particle size distribution of the composite powders after ball milling. The purpose of ball milling is to achieve uniform dispersion of the graphene and uniform particle size of the composite powder. In the initial stage of this paper, the standard deviation value (SDV) of the particle size of the composite powder samples after ball milling, as shown in 1), the average value of SDV first changed from 0.39 (2 h) to a maximum of 2.0 (4 h), decreased to 0.055 (6 h), with a decrease ratio of 97.25%, and then increased to 1.775 (8 h). This shows that the ball milling time has a very obvious effect on the particle size homogenization of the composite powder, and the particle size of the powder is the most uniform when the ball milling time is 6 h. In addition, with the increase in ball milling speed (X2), the average value of SDV decreased from 3.52 (200 r/min) to 2.065 (300 r/min), with a decrease of 36.5%, indicating that the ball milling speed had a significant effect on the particle size homogenization of the composite powder, and the speed of 300 r/min could make the particle size more uniform. When the B-P ratio (X3) changed, the average value of SDV decreased from 2.90 to 2.675, a decrease of 7.8%, indicating that the ball-to-powder weight ratio has little impact on the particle size homogenization of the composite powder. When the ultrasonication time (X4) changed, the average value of SDV increased from 2.19 to 3.4, an increase of 35.6%, which indicates that the ultrasonication time has an obvious effect on the particle size homogenization of the composite powder. When the stearic acid content (X5) changed, the average value of SDV increased from 2.5825 to 2.755, an increase of 6.3%, indicating that the stearic acid content has little effect on the particle size homogenization of the composite powder. In summary, ball milling time (X1), ball milling speed (X2), and ultrasonication time (X4) are the three main factors affecting the particle size of the composites. In the following section, the effects of ultrasonication time (X4), ball milling time (X1), and ball milling speed (X2) on the properties of the composites and the mechanisms are further analyzed.The average SDV value of each factor at different levels is calculated to study the influence of the parameters on the dispersal of the composite, as shown in The composite powders with different parameters set by the orthogonal test were cold-pressed in a mold with a size of φ50 mm × 3 mm by a hydraulic press machine  at atmospheric temperature. The pressure was 500 MPa, the compression rate was 2 KN/min, and the holding time was 5 min. And then, the cold-pressed billets were hot-pressed in a vacuum thermocompressor  at 600 °C for 1 h with a pressure of 30 MPa supplied by another mould with the diameter of φ50 mm and then cooled in the furnace. Pure aluminium billet was also fabricated by the same processes.Samples were wire electrode cut from the hot-pressed billets of the composite and the pure Al billets for tensile testing, optical microscopy (OM), and SEM scanning. The size of the tensile samples ,29 is shA field emission SEM  was used to observe the morphology of the composite powder after milling and the tensile fracture morphology of the hot-pressed billets and to analyze the element of the composite (EDS). A Raman spectrometer  was used to test the components of the graphene, composite powders, cold-pressed, and the hot-pressed composite billets. X-ray diffraction  was used to analyze the components of the composite after vacuum hot pressing.The effects of the three major fabrication parameters on the properties of the 0.5 wt.% GNP/Al composites were studied via comparison of the macroscopic mechanical properties or microscopic characterization.−1, the G peak around 1580 cm−1, and the 2D peak around 2670 cm−1. It is known that the smaller the intensity ratio of the D peak to the G peak (ID/IG), the more complete the graphene, and the lower the intensity ratio of the 2D band to the G band(I2D/IG), the larger the number of layers. In this study, as shown in D/IG value of the original graphene in 2D/IG value is 0.269; the graphene ID/IG value is 1.19, and the I2D/IG value is 0.283 after ultrasound for 60 min, while the ID/IG value is 1.06 and the I2D/IG value is 0.622 after ultrasound for 90 min. The ID/IG value of graphene decreases while the I2D/IG value increases after ultrasound for 60 and 90 min, indicating that the graphene unfolded and the layer number decreased because of the ultrasonic action, and the longer the ultrasonic time is, the better the dispersion of graphene.Graphene has many surface atoms and dangling bonds and tends to agglomerate together to reduce the surface activity, which has a negative impact on the mechanical properties of the composites. In addition, due to the large density difference and poor wettability of the Al matrix and graphene, it is more difficult for graphene to uniformly disperse in the Al matrix. The polarity of ethanol is similar to that of graphene, and the van der Waals force between ethanol and graphene is greater than that between the graphene’s own layers. So, under the ultrasonic shaking, graphene in ethanol solution can unfold more easily, dispersing and extending without structural destruction. During high-energy ball milling, the deformation of powder is generally divided into three stages: from spherical to flattened, cold-welded to form larger plate-like particles, and broken to form smaller particles. Meanwhile, graphene was first dispersed on the surface of the flake Al powder and then cold welded into the Al particles. 1) when the ball milling speeds (X2) are 200 r/min and 300 r/min, respectively. D/IG value for 0.5 wt.% GNP composite powders with ball milling times. It can be seen from D/IG gradually increases, indicating that the graphene structure is gradually destroyed. At the same ball milling time, the Raman ratio ID/IG with 300 r/min is slightly higher than that at 200 r/min. This is because the high speed will cause a strong impact and a certain degree of damage to the graphene structure. However, the damage degree is limited, and when the ball milling speed is 200 r/min, the coating and bonding between the graphene and the matrix are worse than at 300 r/min, as shown in 3. The compactness can reach 99.6%. The density of the billet obtained using vacuum hot pressing is approximately 2.69 g/mm4C3 are detected, which may be due to the low content of graphene and the limited resolution of elements of the X-ray diffraction instrument [strument .p in v in To analyze the role of the graphene in the reinforcement of the composite, its distributions on the tensile fracture surface are compared in (1)4C3 were found in the composite. Graphene distributed on the grain boundaries can effectively hinder the growth of the grain during the vacuum hot-pressing sintering and play a role in grain refinements.The density of 0.5 wt.% GNP/Al prepared by cold pressing + vacuum hot pressing is high, and the interface bonding is perfect. No obvious oxidation phenomenon and Al(2)Ball milling time, ball milling speed, and ultrasonic time have great influences on the performance of 0.5 wt.% GNP/Al composites.(3)Adding 0.5% percentage of graphene in weight can obviously increase the strength of the Al matrix. When the ball milling speed was 300 r/min, the ball milling time was 6 h, the B-P ratio was 5:1, the graphene ultrasonic time was 90 min, and the stearic acid content was 1.5%, the graphene nanoplates were uniformly distributed in the Al matrix without being destroyed. The composite had the best comprehensive mechanical properties, with a tensile strength of 156.8 MPa, which is 56.6% higher than that of pure aluminum fabricated by the same process (100.1MPa), while the elongation is 19.9%, which is 39.8% lower than that of pure aluminum (33.1%).In this paper, 0.5 wt.% GNP/Al composites were prepared using ultrasonication + ball milling + cold pressing + vacuum hot pressing. The microstructure of 0.5 wt.% GNP/Al created by different fabrication parameters was systematically studied. The main conclusions are as follows:


N-acetylglucosamine kinase (NAGK), an enzyme of amino sugar metabolism, interacts with dynein light chain roadblock type 1 (DYNLRB1) and promotes the functions of dynein motor. Here, we report that NAGK interacts with nuclear distribution protein C (NudC) and lissencephaly 1 (Lis1) in the dynein complex. Yeast two-hybrid assays, pull-down assays, immunocytochemistry, and proximity ligation assays revealed NAGK–NudC–Lis1–dynein complexes around nuclei, at the leading poles of migrating HEK293T cells, and at the tips of migratory processes of cultured rat neuroblast cells. The exogenous expression of red fluorescent protein (RFP)-tagged NAGK accelerated HEK293T cell migration during in vitro wound-healing assays and of neurons during in vitro neurosphere migration and in utero electroporation assays, whereas NAGK knockdown by short hairpin RNA (shRNA) delayed migration. Finally, a small NAGK peptide derived from the NudC interacting domain in in silico molecular docking analysis retarded the migrations of HEK293T and SH-SY5Y cells. These data indicate a functional interaction between NAGK and dynein–NudC–Lis1 complex at the nuclear envelope is required for the regulation of cell migration.Recently, we showed that  Cell migration takes place during diverse developmental and pathogenic processes in multicellular organisms. Neuron migration during embryonic brain development essentially guides the complex layering of many structural and functional compartments. Neuronal progenitor cells (NPCs) are generated in spatially restricted ventricular zones (VZs) and undergo long-distance migration to reach their final destinations, e.g., the cortical plate (CP), to establish functional integrated neural circuitry ,2. NPCs Dynein complexed with lissencephaly 1 (Lis1) and doublecortin (DCX) mediates N–C coupling during neuronal migration, and dynein heavy chain generates nuclear movement , while LRecently, we identified a novel dynein interacting protein N-acetylglucosamine (GlcNAc) kinase . This enzyme phosphorylates GlcNAc to produce GlcNAc-6-phosphate, which is a component that is utilized in uridine diphosphate N-acetylglucosamine (UDP–GlcNAc) biosynthesis or energy metabolism in the GlcNAc recycling/salvage pathway. Human NAGK monomer is 37 kDa sized, composed of N-terminal  and C-terminal (large) domains , belongsDuring cell division, NAGK interacts with the perinuclear Dynein–Lis1–NudE1 complex during prophase nuclear invagination and with kinetochores during metaphase chromosome separation . These fThe yeast two-hybrid selection assay showed that NAGK strongly interacted with the C-terminal of NudC  interacted potently with the NudC CS domain. To improve understanding, free energy landscape analysis was conducted on the resultant trajectories to identify the most stable complex structure with the lowest energy minimum  maintained strong interactions with NudC during simulation, especially the Leu211 to Ile218 region, which indicated the presence of a major protein-binding interface in NudC. To achieve insight of the interaction between NAGK and NudC, we considered protein–protein docking simulation, which predicts complex structures from individual proteins. Accordingly, a full blind docking simulation was carried out to detect a putative binding site for NAGK in NudC. The docked complex obtained revealed a binding energy of −8.79 kcal/mol with a docking score of −29.35 kcal/mol . The com minimum Cc. Then,ith NudC Cd. As reinset, right panel, arrowheads). These findings indicate NAGK–NudC interacted at the leading edges of cell cortices during migration. NudC has a well-established role in migration, and thus, we examined the in situ colocalization of NAGK and NudC in migrating cells. First, semi-confluent (more than 95%) HEK293T cells were scratched as mentioned in Material and Methods, and then, cells were allowed to migrate toward “wounds” on coverslips. Then, immunocytochemistry (ICC) was performed using anti-NAGK and anti-β-tubulin primary antibodies to determine the migratory morphology of cells and the distribution of NAGK. Intracellularly, centrosomes were located in front of the nuclei with respect to the migration direction B. At theOur laboratory previously reported NAGK interacted with DYNLRB1 at neuronal dendrites , whereasinset 1, red arrowheads) and at cell cortices , and these were found to colocalize with DYNLRB1 ICC signals (green arrowheads). These results show NAGK interacted with NudC and dynein around nuclei and at cell cortices during cell migration. Next, NAGK–DYNLRB1 PLA was performed, followed by NudC ICC and DAPI counter-staining  using NAGK and NudC primary antibodies. To visualize NAGK–NudC–DYNLRB1 interactions, PLA was followed by ICC using anti-DYNLRB1 antibody, and nuclei were counter-stained with DAPI. NAGK–NudC interactions  due to PLA reactions were observed around nuclei  and near nuclear membranes , which suggested that NAGK participated in the neuronal migration in association with the NudC–Dynein complex. NAGK–DYNLRB1 PLA signals (red) also colocalized with NudC ICC signals (green) in leading neurites  were colocalized with DYNLRB1 ICC signals (green) in leading dendritic projections  and around nuclei . NAGK–Lis1 interactions were also observed in dendritic projections  and at nuclear peripheries  colocalized with NudC signals in migrating neurons . Together, these results show the colocalization of NAGK–Lis1–NudC at nuclear peripheries, in cell cortices, and in leading projections of migrating neurons.As NudC has been reported to interact with Lis1 during cell migration , we inveNeuronal migration has been reported to be compromised by dynein ,35 or NuNext, we used in utero electroporation to study the role of NAGK in neuronal migration in vivo during embryonic brain development. We introduced pDsRed2-NAGK Ba, pDsReIt was reported that NudC depletion significantly inhibited collective cell migration in a wound-healing experiment . To inve157WIAHQAVKIVFDSI171, and L198GILTHLYRDF208, we initially considered both regions for peptide design in order to confirm possible interactions with NudC binding domain   on cell migration, we performed two different types of wound-healing assays. First, we performed wound-healing assays after transfecting HEK293T cells with pDsRed2 or pDsRed2-NAGK and then further transfecting cells with the peptide. Percentages of migrating cells were calculated (defined as the percentages of transfected cells that migrated at migration fronts) after 48 h of incubation (p < 0.0001) greater than that of DsRed2 transfected cells. Transfection with peptide Y157WIAHQAVKIVFDSI171 significantly reduced the portion of percentage of pDsRed2–NAGK transfected cells (pDsRed2-NAGK + pep), but this was still higher than that of pDsRed2-transfected cells, which implied incomplete inhibition. Next, we performed similar assays by adding Y157WIAHQAVKIVFDSI171 peptide (25 µM) directly to the culture medium. As shown in 157WIAHQAVKIVFDSI171 specifically inhibited the NAGK–NudC interaction, thus affecting migration. Based on considerations of all observations, we propose that NAGK interacts with NudC and Lis1 on the dynein complex and promotes neuronal and non-neuronal cell migration.To examine the effects of the selected peptide . The “nuclear distribution” gene s fungus . NudC ge sapiens , and con sapiens ,39. The  sapiens , and its sapiens . This ev mutants ,43. HoweWe also present biological evidence regarding the colocalization of and the interaction between NAGK and the NudC–Lis1–dynein complex. First, we found that NAGK colocalized with NudC at the leading projections of cultured migratory neurons HEK293T cells) and in NPCs of the developing mouse cortex. A migratory phase of a neuron is characterized by a rostral position of the centrosome with respect to the nucleus in the migratory direction. In such migratory cells, we found MTs formed perinuclear cage-like structure at the rear and projecting into leading processes during migration, presumably to translocate nuclear MT structures to leading processes. The migratory phase was confirmed by DCX expression (a marker for migratory neurons) , and not3T cells Drosophila oocytes [Morris et al.  also rep oocytes . In acco oocytes ,34,49. A oocytes  proposed oocytes , which s oocytes ,29 and i oocytes . TherefoThe present study shows the functional significance of the interaction between NAGK with NudC and Lis1 in the dynein complex during cell migration. To verify these effects, we employed four different experimental migration models. First, we performed wound-healing assays , which sRing) and the other to dynein’s stalk, more specifically coiled-coil 1 (CC1) , the latter of which is required for the Lis1-induced weak MT-binding state. DeSantis et al. (2017) proposed that a single β-propeller binds at SiteRing and maintains dynein in a high-MT-affinity state by keeping the motor tightly bound to MT in preparation for cargo loading [Then, how does NAGK regulate dynein motor during cell migration? Dynein plays a central role in cell migration by pulling centrosomes and nuclei toward the (-) end of MT. Pulling a large cargo such as a nucleus at the molecular level probably requires the coordination of multiple dynein complexes. To date, Lis1 is the only dynein regulator known to interact directly with its motor domain. Lis1 may regulate dynein in two ways. First, at the motor and MT-binding side of the dynein complex, Lis1 may play a role in the loading of large cargoes, as multiple dyneins must be bound tightly to MT (+) ends. Lis1 has two quite different methods of regulating dynein because it can induce low or high affinity for MT . These d loading . This coSecond, on the tail side of the dynein heavy chain, NAGK would help transform the dynein complex to prepare it for cargo loading. The activation of dynein is accompanied by a structural change from the phi to the open form and light chain (LC)—heavy chain (HC) tail separation . The phiThe plasmids, including pDsRed2 vector, NAGK short hairpin (sh) RNAs and pDsRed2–NAGK, were used for transfection, as described previously ,27. AntiThe Institutional Animal Care and Use Committee of the College of Medicine, Dongguk University, approved all animal experiments  beforehand . On the The protein data bank (PDB) server was used for retrieving NudC (PDB id: 3QOR) and NAGK (PDB id: 2CH6) three-dimensional structures. The structures were fixed by adding hydrogen and correcting pH. The force field, Optimized Potential for Liquid Simulations (OPLS), was applied to minimize the energy of the structures ,60, usinYASARA Biosciences GmBH, Vienna, Austria) [+ and Cl− ions [Molecular dynamics simulation was conducted via YASARA dynamic software (Austria) , and theAustria) ,66,67, aAustria) ,68,69. WCl− ions . Energy Cl− ions ,72 and pCl− ions  and YASA157WIAHQAVKIVFDSI171 and L198GILTHLYRDF208) and NudC complexes were constructed from the lowest energy structures by free energy landscape analysis using Maestro Version 11.1.012. Peptide–protein complexes were also subjected to an additional 55 ns simulation using YASARA dynamic software following similar protocols. To select the peptide with better binding affinity, binding energy calculation was performed using the built-in MM-PBSA calculation. The mathematical details described previously [The NAGK peptides  was used for cells transfection with indicated plasmids by following the manufacturer’s guidelines.HEK293T and SH-SY5Y cells were grown on coverslips (coated by polylysine) in Dulbecco’s Modified Eagle Medium (DMEM) (Invitrogen) supplemented with Penicillin Streptokinase (1%) and fetal bovine serum (10%). LipofectamineFor pull-down assay, His-tagged NudC plasmid  was transiently transfected in HEK293T cells. The cells were lysed and collected after 48 h of incubation by using lysis buffer , 1% NP-40, 5% glycerol; pH 7.4) containing protease inhibitor cocktail , followed by washing with cold PBS. MagListo™ Ni-NTA magnetic silica resin  was allowed to bind with supernatant, which was then pulled down by following manufacturer’s instructions, as described earlier .The interested proteins were detected from the elution by using immunoblotting with respective antibodies, anti-NAGK , anti-DYNC1LI1 , or anti-DYNLRB1 , anti-Lis1  followed by 15% Tricine-SDS-PAGE separation and polyvinylidene difluoride (PVDF) membrane blotting. The blots were detected using an enhanced chemiluminescence (ECL) detection kit . To strip membranes, stripping buffer was used , and hybridization was performed with different primary and secondary antibodies.A wound-healing assay was conducted on 80% confluent cells, grown in 12-mm diameter coverslip (coated with polylysine), as mentioned earlier . A steri® 2000 with pDsRed2 or pDsRed2–NAGK plasmids at 50% of cell confluency. Then, transfected cells are incubated for 48 h until confluent. Then, a linear scratch was made by using a pipette tip, and cells were washed and transfected with 1 μg Y157WIAHQAVKIVFDSI171 peptide  via Pierce protein transfection reagent , as mentioned previously [For peptide inhibition assays, cells were transfected by lipofectamineeviously . Migration activity was quantified as the percentage of migrating cells moving with the migratory front. When peptide was added directly to the medium, cells were incubated in a serum-free medium for 4 h. A linear scratch was made by using a pipette tip and washed. Cells were incubated with either peptide (25 μM) or DMSO containing low serum (1% FBS) medium. Cell migration rates were quantified by expressing recovered areas as percentages to total damaged areas.2 flasks [® 2000 reagent (Invitrogen). Geltrex® matrix (Gibco) was used for transfection and live-cell imaging. The plated neurospheres were further grown for 48 h to attain differentiated cortical neurons in the medium containing 2% B27 supplement, 500 mM L-glutamine, and 1% penicillin–streptomycin with no growth factors. After culturing for 48–60 h, differentiated cortical neurons cultures were used for live-cell imaging and ICC.NPCs were cultured, as mentioned earlier . In brie2 flasks . For ICCIn utero electroporation (IUE) was conducted following the previously described method . After aCells were fixed by sequential fixed in paraformaldehyde/methanol, and ICC was carried out as previously described . AccordiAn Olympus microscope BX53 was used to take the fluorescence images containing DAPI staining. A Leica research microscope (DM IRE2)  was used for taking fluorescence images in n = 20) in three different experiments were measured. For the in utero electroporation study, numbers of transfected neurons in cortical plates and intermediate and ventricular zones were calculated and described as total neurons percentages. Counting was done in a blinded way, which was carried out by independent experienced investigators. Within each cohort, the animal selection was made from random cages at a random time and season. By using natural intelligence, the sample size was chosen depending on the data variability; however, not less than n = 5. In order to compare two groups, the Student’s t-test was used, while multi-group comparisons were made by one-way ANOVA with Duncan’s multiple comparison post hoc test. The use of parametric tests was verified by the normality test. The predictions were considered statistically significant when the p values were <0.05. p values of <0.0001 indicated a highly significant prediction. Statiscal Software, GraphPad Prism v 8.0  and SPSS 19.0  were used for statistical calculations, where the data are presented as means ± SDs.Three different experiments were considered for wound-healing assays. For counting, cells not more than 500 were considered from the various positions of each coverslip after transfecting for 48 h and 72 h, respectively. For in vitro migration assays, distances migrated by neurons (In summary, the present study shows NAGK interacts with NudC and Lis1 in the dynein complex and thus promotes cell migration. Our data suggest the possibility that NAGK recruits NudC and Lis1 to make a NudC–NAGK–Lis1 tripartite interaction in the dynein complex. Based on these findings, we propose a dynein activation model involving “bivalent” NAGK, where the small domain of NAGK interacts with DYNRB1 to transform the NDD of dynein HC from the phi to the open state, “pushing up” the LCs tailing. Alternatively, the large domain of NAGK recruits NudC and binds Lis1 to coordinate motor power at high loads, such as pulling a nucleus in N-C coupling during migration.


N theoretical model of carrier transport, capture, and escape processes. The combined experimental and theoretical results clearly indicate that those LEDs with graphene transparent conductive electrodes at p-junctions will have a shorter hole transport time along the lateral direction and thus a more efficient current spreading and a larger luminescence area. In addition, a shorter hole transport time will also expedite hole capture processes and result in a shorter capture time and better light emitting efficiency. Furthermore, as more carrier injected into the active regions of LEDs, thanks to graphene transparent conductive electrodes, excessive carriers need more time to proceed carrier recombination processes in QWs and result in a longer carrier recombination time. In short, the LED samples, with the help of graphene electrodes, are shown to have a better carrier transport efficiency, better carrier capture efficiency, and more electron-hole recombination. These research results provide important information for the carrier transport, carrier capture, and recombination processes in InGaN/GaN MQW LEDs with graphene transparent conductive electrodes.In this work, InGaN/GaN multiple-quantum-wells light-emitting diodes with and without graphene transparent conductive electrodes are studied with current-voltage, electroluminescence, and time-resolved electroluminescence (TREL) measurements. The results demonstrate that the applications of graphene electrodes on LED devices will spread injection carriers more uniformly into the active region and therefore result in a larger current density, broader luminescence area, and stronger EL intensity. In addition, the TREL data will be further analyzed by employing a 2- Low resistance and transparent Ohmic contact to p-type GaN are crucial to improve current injection and light extraction efficiency of GaN-based LEDs10. Although device performance can be improved by using Indium Tin Oxide (ITO) used as a transparent conducting layer (TCL), the exclusive use of these oxides becomes problems such as cost, rarity supply of indium, and low optical transmittance in the ultraviolet wavelength regions10. One the other hand, graphene has been considered a promising material to replace ITO in GaN-based LEDs as a transparent conductive electrode17, because of its high transmittance in the UV region, carrier mobility, and conductivity. It has been demonstrated that the transparent 3D graphene foam was very effective in current spreading to enhance the performance of blue LEDs11. However, due to high sheet resistance and the large work function difference between graphene and p-GaN, the use of graphene as a TCL adversely increases the operating voltage of LEDs14. In addition, the poor adhesion of graphene on the devices also problematically results in a low current injection into LEDs7.III-nitrides have become the key material for light emitting diodes (LEDs), laser diodes, and solar cellsI-V) relationship, and quantum efficiency are the common measurements to characterize the device performance of GaN-based LEDs. Although device performance of GaN-based LEDs with graphene transparent conductive electrodes has been shown to be improved, these measurements cannot quantitatively describe carrier dynamic behaviors. Time-resolved electroluminescence (TREL) measurement under electrical fast pulse excitation is a power tool to explore the dynamic EL behaviors of carrier injection, carrier transport, carrier relaxation into active region, and carrier recombination at the excited states in active region of LEDs19. From the results of TREL measurements, nitrogen-polar InGaN/GaN LEDs with the opposite polarity and nonpolar m-plane InGaN/GaN LEDs with a low polarization effect were shown to provide the advantages of more carrier injection, transport, relaxation, and recombination19. However, the effects of graphene transparent conductive electrodes on the carrier dynamic behaviors of carrier injection, carrier transport, carrier capture into active region, and carrier recombination of InGaN/GaN LEDs with graphene transparent conductive electrodes are not well understood, and many important issues are yet to be studied.Electroluminescence (EL), output power, current-voltage , spectrometer , calibrated integrating sphere, and power meter. Without an ohmic Ni/Au contact, an indium dot melting on the sample surface was used as a n-type contact for the probe station. For TREL measurement, a pulse generator (Tektronix AFG3152C) was used to generate 2.0–5.0 V, 0.5 μs pulse width, and 1 kHz repetition rate voltage pulses to the LEDs. The light output was focused and detected by a photosensor module containing a metal package PMT and a high-voltage power supply circuit (Hamamatsu H10721-210) operating directly on the surface of each LED. The same PMT voltages of the TREL measurement were applied for the LEDs. The parasitic capacitance in the test circuit would introduce the same RC delay for the two LEDs. The transit EL signals were recorded by a digital oscilloscope (Agilent DSO 6052 A) with a 500 MHz bandwidth. The overall resolution of TREL system is less than 2 ns. The detailed measurement was described in our previous study19.1, LED2, and LED3 in this work) were prepared for the studies of device characteristics and carrier transport properties by using EL images, EL spectra, I-V, output power, and TREL measurements. Subsequently, graphene was transferred onto the p-GaN layer of these three InGaN/GaN MQW LEDs . The same measurements were conducted on the LED1G, LED2G, and LED3G samples. Device characteristics and carrier transport properties of InGaN/GaN MQW LEDs without and with multilayer graphene were compared and analyzed.Three InGaN/GaN MQW LEDs without graphene electrodes (denoted as LEDp-GaN layer: (a) Graphene was grown on a copper sheet by a chemical vapor deposition (CVD). (b) Poly (methyl methacrylate) (PMMA) was spin-coated on the graphene/copper sheet. (c) The copper sheet was etched in a 1 wt. % (NH4)2S2O8 solution11. (d) The graphene with PMMA was transferred onto the p-GaN layer of the InGaN/GaN LEDs. (e) The PMMA layer was removed by acetone solution.Fig. 1, LED2, and LED3) and their counterparts with grapheme electrodes . Each inset in Fig. 1, LED2, and LED3 samples are brighter near the upper positive electrode. For nitride semiconductors, the electron mobility is fast than hole mobility2. With a higher electron mobility, the electrons transport more quickly into the MQWs near the positive electrode and wait for holes to recombine. Once the slow-moving holes transport and are captured into MQWs, electron-hole pairs will recombine and generate luminescence. In addition, stronger EL intensities and larger luminescence area of the LED1G, LED2G, and LED3G samples show that graphene exhibits a good current spreading characteristic to distribute the injection current more uniformly.Figure 1G, LED2G, and LED3G samples are all red-shifted. Because of indium aggregation or phase separation in InGaN alloys, the EL emissions come from the recombination of localized excitons in In-rich InGaN clusters which formed spatial potential fluctuations and localized states for trapping carriers6. As shown later, the current density of the LED1G, LED2G, and LED3G samples are all larger than those of the LED1, LED2, and LED3 samples, respectively. With a good spreading characteristic of graphene, more carriers can more efficiently transport into spatially distributed potential minimums  for recombination22. Hence, the red-shifted EL peak positions of the LED1G, LED2G, and LED3G samples are observed.Figure I) and output power as functions of applied voltage V for the LED1 versus(vs.) LED1G, LED2 vs. LED2G, and LED3 vs. LED3G samples, respectively. The currents of the LED1G, LED2G, and LED3G samples are all larger than those of the LED1, LED2, and LED3 samples, respectively. Although the graphene/GaN contact resistance and work function difference are both large, the current spreading characteristic of graphene distributes more current to inject into active region and would not degrade the electrical characteristics. The largest current density of the LED3G sample implies that the LED3G has the best graphene transparent conductive electrode as well as the best sample quality. Also, when the injected current is increased and the carriers are over populated. Hence, a blue-shift EL peak was observed in Fig. 1G, LED2G, and LED3G samples contribute to more output power. This characteristics shows that graphene acting as transparent conductive electrodes in InGaN/GaN MQW LEDs can improve device performance. From the better performance of LED1G, LED2G, and LED3G samples, the bonding between LED and graphene should be good.Figure 1, LED2, LED3, LED1G, LED2G, and LED3G samples, respectively. A stronger intensity, shorter response time, and steeply rising of the LED1G, LED2G, and LED3G samples imply a better carrier transport and carrier capture efficiency23. In the TREL results, the response time  states to the confined (quantum) states in the quantum-well region. A more detailed discussion on the physical meanings of 23.It should be noted that the rec as a function of applied pulse voltage for the LED1 vs. LED1G, LED2 vs. LED2G, and LED3 vs. LED3G samples, respectively. The effects of graphene transparent conductive electrodes on the carrier transport, capture, and recombination dynamics of InGaN/GaN MQW LEDs can be well revealed from these results. With the graphene transparent conductive electrodes, the transport times 1G and LED2G samples are slightly shorter in comparison with those of the samples without graphene. Meanwhile, the transport times 3G sample, due to its superior graphene quality, is much shorter than that of its without-graphene counterpart. In addition, a short transport time 1G, LED2G, and LED3G samples. In other word, due to the graphene electrode, more carriers transport in a larger luminescence area and consequently are captured more efficiently into the QWs. It should be noted that the response time obtained from the TREL and the transport time defined in the 2 N model roughly characterize the time span for carriers moving from the contact to the quantum-well region. Therefore, the injection efficiency is inversely proportional to the transport time23. As more carriers transport and are captured into QWs, more carriers will recombine in the QWs and have a longer recombination time 3G sample.Figure 2. When the holes and electrons were injected into the MQWs, due to their higher electron mobility, electrons will transport and be captured more efficiently into to the MQWs than holes. As a result, the p-junction becomes the dominant factor in determining the overall carrier injection and recombination efficiency.Based on the above observations, carrier injection, carrier transport, carrier capture, and recombination dynamic schemes were proposed in Fig. p-junction will expedite the transport processes of holes along the lateral direction and thus resulting a broader current spreading and a larger luminescence area. As schematically illustrated in Fig. 1G, LED2G, and LED3G samples have shorter transport and capture times, but longer recombination time than the LED1, LED2, and LED3 samples. The graphene transparent conductive electrodes can expedite carrier transport processes, shorten the transport time N theoretical model.As shown in Fig. N theoretical model of carrier transport, capture, and escape processes. The combined experimental and theoretical results clearly indicate that those LEDs with graphene transparent conductive electrodes at p-junctions will have a shorter hole transport time along the lateral direction and thus a more efficient current spreading and thus a larger luminescence area. A shorter hole transport time will also expedite hole capture processes and thus result in a short capture time. Furthermore, as more carrier injected into the active regions of LEDs, thanks to graphene transparent conductive electrodes, excessive carriers need more time to proceed carrier recombination processes in QWs and thus result in a longer carrier recombination time. The research results provide important information for the carrier transport, carrier capture, and recombination processes in InGaN/GaN MQW LEDs with graphene transparent conductive electrodes.In this work, InGaN/GaN MQW LEDs with and without graphene transparent conductive electrodes are studied with I-V, EL, and TREL measurements. The results demonstrate that the applications of graphene electrodes on LED devices will spread injection carriers more uniformly into the active region and therefore result in a larger current density, broader luminescence area, and stronger EL intensity. In addition, the TREL data will be further analyzed by employing a 2-Supplementary information.


The way an athlete focuses their attention when lifting a weight has the potential to influence strength development during training and performance outcomes during competition. The effects of attentional focus strategies during weightlifting tasks was investigated through a systematic review. Major databases  were searched using key terms relevant to attentional focus and weightlifting and reference lists of identified articles were also searched. Following screening, 16 articles were retained for analysis. The review showed that researchers have recruited experienced and novice weightlifters of both genders in their studies, although male experienced weightlifters are the most commonly studied demographic. Weightlifting tasks have varied from bench press, biceps curls, squats, and leg extensions with some studies using measures of force production against a force plate. The predominant manipulations have been between internal-associative and external-associative foci. An external attentional focus has shown to be beneficial in terms of movement economy as reflected in a variety of outcome measures. The results are interpreted within the framework provided by the Constrained Action Hypothesis and more generally the advantages of an external attentional focus for motor skill learning. An external focus of attention promotes automatic control of actions, thus preventing the motor system being constrained by conscious cognitive control. Implications for informing training programs for athletes and for advising athletes to maximize performance during competition are discussed. The action of lifting a weighted apparatus is ubiquitus in sport and exercise. It is used during training to develop muscle strength, muscle mass, and joint strength. It is is also a competitive sport in its own right, as reflected in its Olympic Games status and the formation of national and international governing bodies. The sport of weightlifting requires lifts of the snatch and the clean and jerk with athletes aiming to lift the heavest weight for their division during competition. Other competitive events, often referred to as powerlifting, require the deadlift, squat, and bench press. Weightlifting is also a key component of training for other sports and as part of a physical exercise program. In these situations, there are a multitude of different types of lifts according to the muscles required, equipment used, and the speed, duration, and complexity of the movements.The physical nature of weightlifting has naturally led to research on physical factors, such as physiology, biomechanics, diet, and injury. Comparatively less work has been conducted on the psychological processes associated with weightlifting. The psychology of weightlifting has been examined from various perspectives, including self-efficacy, intention, and self-regulation behaviors  and direction dimensions of Stevinson and Biddle . WiningeAttentional focus in weightlifting has been largely investigated from the attentional focus strategies of internal association and external association . This approach stems from the influential work by Wulf et al. demonstrating the performance benefits of an external attentional focus over an internal attentional focus in ski-simulator and balancing tasks  guidelines were followed for the literature search , the mean journal h-index was 86.33 , and seven journals were Q1 ranked. These citation metrics suggest that the journals that published this research were of moderate to high quality. The articles were coded by study characteristics , participant characteristics , and task characteristics (exercise/movement completed and equipment used).Following this selection process, a total of 12 articles from the database search, with a further four articles identified following the examiniation of the selected articles reference lists were obtained. As such, a total of 16 articles were included in the systematic review. The types of weightlifting tasks and equipment used in research on attentional focus strategies are shown in Lohse et al. , Lohse , and LohThe characteristics of the participants who have been studied in research are shown in Participants have tended to be experienced in weightlifting, although a sizeable portion of studies did not specify the participant experience level. Experienced participants are more likely to be well-practiced and to have develop automaticity in movements. Given the notion that an external focus of attention facilitates automatic motor processes  condition and that this is evidence for a beneficial effect of an external focus rather than a relative detrimental effect of an internal focus Wulf, . SimilarFurthermore, research has not always shown performance benefits with an external focus of attention. No differences between internal and external foci have been observed for time to failure or ratings of perceived exertion for a long duration force production task  can be achieved in practical terms. The first step in developing effective strategies is to identify what are the key elements that athletes should direct their attention to . For an internal focus, EMG recordings of muscles or movement sensors attached to the body can be used provide visual or auditory feedback to athletes. In addition, athletes should be aware that their own use of “psyching up” or self-talk might need to be modified to ensure that the appropriate attentional focus is used. For example, cue words like “strong” and “powerful” might inadvertently direct the athlete to focus their attention internally and should be modified accordingly during competition.The third consideration is how to tailor the approach to the specific context. In simple lifts, like the biceps curl, attentional focus instructions are relatively simple because the movement is constrained. However, compound lifts will involve multiple muscles and limbs. In addition, multiple component lifts like the clean and jerk involve discrete movements performed in sequence. Internal focus instructions might need to be varied according to the stage of the lift. Whether external focus instructions need to be varied across the lift remains to be determined. Based on the notion that external attentional focus benefits might result from both intramuscular efficiency and intermuscular efficiency . Research in our laboratory has shown that an external attentional focus has benefits to physical and psychological states during cardiovascular exercise tasks  attentional focus. Importantly, the studies conducted to date have typically been conducted in single-session designs. Thus, the long-term benefits of an external attentional focus remain to be determined. Similarly, transfer effects need to be established to determine whether beneficial attentional focus instructions practiced with one type of lifting exercise in the laboratory will transfer to real world training or competition or to other types of lifting exercises. In addition, it would be worthwhile to examine whether transfer occurs to similar sporting tasks. For example, some sports like shot put and discus, require a short-term maximal muscular effort. It would be informative to examine whether training in an external focus of attention transfers to these tasks  has emerged as a technology applied to sport (for reviews see Neumann, Weightlifting for physical conditioning or sport depends on many physical and psychological factors. Research examining cognitive strategies has shown that performance at the neuromuscular and behavioral level are influenced by the attentional foci that an athlete adopts. To maximize muscular efficiency, an external focus of attention is more optimal than an internal focus of attention or no specific focus in most cases. The challenge remains for researchers to further explore this effect and determine under which conditions it may be magnified. This information will assist in translational research that can allow athletes to reach a higher level of performance than might otherwise be possible.The author confirms being the sole contributor of this work and has approved it for publication.The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.