This study carried out a novel duplex surface treatment on aluminum alloy base to explore the potential improvement of wear and corrosion resistance. Regular arrayed dimple surface texture (DST) and groove surface texture (GST) were fabricated by using laser processing on 6065 aluminum alloy matrix (6065Al). Electrochemical deposition of Ni and Graphene/Ni coatings on textured surface was then performed in electrolytes with concentrations of 0, 0.5, 1 and 1.5 mg graphene. Surface morphology such as diameter of dimple and width of groove measured by C-PSCN stereo microscope presents addition of graphene helps to refine and homogenize the coating. Corrosion resistant properties of the duplex surface treatment were examined by electrochemical corrosion tests and wear resistant properties were tested by UMT-Tribo Lab friction and wear tester in a dry sliding condition at room temperature. Electrochemical corrosion tests results show that the corrosion resistance of samples is related to the specific surface texture and the dimple texture can improve the electrical corrosion parameters, such as the electrode potential, greatly. Friction and wear tests show that the textured Gr/Ni electroplating coating with the 1.5 mg graphene content has best wear properties under vertical friction and each index, such as the coefficient of friction and wear trace width, are superior to other conditions of samples. However, difficulty still arises with the electroplating process is the formation of natural oxide film on the surface of the aluminum alloy, hindering the direct reduction of metal ions on the surface of the aluminum alloy to obtain a plating layer with ideal adhesion situation [Aluminum alloy has been considered a good choice as a material in the aviation, aerospace, automotive, marine and chemical industries, due to its excellent specific strength and plasticity, high electrical conductivity, thermal conductivity and remarkable corrosion resistance . Yet, liituation . TherefoGraphene, with excellent electrical, thermal, chemical and mechanical properties, has gained extensive attention since its advent. Single-layer graphene is a planar thin film material which composed of carbon atoms in sp2 hybrid orbitals ,5. This Previous studies have demonstrated that graphene can be used as an additive for electroplated composite. Szeptycka  finishedWith the development of textured surface science, people now begin to re-recognize the wide application of non-smooth surfaces in various fields. Among of them, surface texture (ST) has been confirmed as an effective and economical surface treatment technique that can be applied to a great range of materials and it has been attached greater importance in various engineering fields. Ta  utilized2O3 composite cladding on AISI 1040 substrates by the cost-effective process of gas tungsten arc welding. The microscopic images showed coaxial fine grains in the weld composite surface, there are no cracks in the surface layer created and Al2O3 particles are distributed uniformly in the surface layer. The purpose of the research could achieve optimal parameters of claddings in an inexpensive method. Liu [However, neither the surface texture nor the surface coating can solve the corrosion resistance and wear resistance of aluminum alloy well . A combihod. Liu  preparedThus far, however, there has been little discussion about duplex treatments of surface modification-surface texturing for 6065 aluminum alloy matrix (6065Al). Inspired by bionic studies and taking the advantages of surface texturing and surface modification, in the present work, the surface texturing/composite electroplating (ST/CE) duplex treatments were applied on 6065Al. Regular arrayed dimple surface texture (DST) and groove surface texture (GST) were adopted and fabricated by using laser processing on 6065Al matrix respectively and electrochemical deposition of Ni and Gr/Ni coatings on textured surface was then performed in electrolytes with concentrations of 0, 0.5, 1 and 1.5 mg graphene. The influences of different texture and content of graphene on friction behavior and corrosion resistance were investigated by micrographs, electrochemical experiments and friction and wear experiments.This section presented procedures of the duplex treatments of surface modification-surface texturing on 6065Al matrix. The scheme of this processing is shown in The material selected for the present research work is Aluminum 6065 alloy, which is commercially available with dimension of 70 mm × 20 mm × 2 mm under cold-rolled condition and its composition is given in A P50Q pulsed fiber laser  with 1060 nm wavelength was employed here to fabricate the needed surface texture. Referring to other researchers, dimple and groove surface texture were adopted, which are based on the two typical wear resistant and corrosion resistant surfaces of lotus leaf and shark skin ,22. Deta2 saturated solution and 37% HCl mixed solution for 50–60 min at room temperature to remove surface rust. Electrolyte [In this experiment, an Ni plate  with a surface of 20 mm × 20 mm was used as the anode for electrodeposition. The cathode, with distance of 60 mm towards the anode, was a textured 6065Al plate with size of 20 mm × 20 mm. To improve the adhesion of coating, both electrodes were firstly immersed in 75% anhydrous ethanol and deoiled by ultrasonic heating with a PS-20A Digital Ultrasonic Cleaner  for 10 min. Then, the nickel plate was pickled in 3% hydrochloric acid for 15 min, and the textured sample plate was soaked in NiClctrolyte , as can 2 was applied. The electroplating time is 5 min at 40 °C and the stirring speed is 300 rpm. The samples were then washed with deionized water after electroplating process and finally put into the SX2-4-10 electric furnace  at 200 °C for 0.5 min for drying. Detailed electroplating parameters are shown in Here, multi-layer graphene aqueous solution was used supplied by Nanjing Ji nano company produced by using physical method . The composite plating solution was obtained through adding 1 ml with different concentration graphene aqueous solution  for comparing into nickel electrolyte and stirred sufficiently by ultrasonic vibration. Composite graphene electroplating were then started. During electro-deposition process, both the anode and the cathode were connected to the MS-155D electroplating power supply  and a constant current power with 13.75 A/dmSurface morphology such as diameter of dimple and width of groove were measured by C-PSCN stereo microscope (Nikon Corporation. Japan). Scanning electron microscopy (SEM) images of the samples were analyzed using an Su 8000 FE-SEM  and the amount of electrodeposited graphene was estimated by using an energy dispersive spectroscopy (EDS-550I) which was attached to the FE-SEM. The sectional images of the textured electroplating coatings were captured by MA100N-optical microscope .Electrochemical corrosion tests were carried out on CS2350 double channel electrochemical workstation  equipped with three-electrode system. Reference electrode and auxiliary electrode are saturated calomel electrode and platinum electrode, respectively. Sample obtained above was used as the working electrode. Results of the electrochemical corrosion test were obtained through the corresponding software CS Studio 5. Tafel lines were recorded at a scanning rate of 1 mV/s, which is low enough to have a good response for the system, from 0.8–0.2 V versus open circuit potential. Electrochemical impedances were obtained in the frequency range of 0.01 Hz–10 kHz and the amplitude of sinusoidal signal was 10 mV . These t3N4 ball with the diameter of 6 mm was selected as a counterpart. Test parameters are as follows: a normal load of 10N, sliding velocity of 5 mm/min, reciprocatory displacement of 10 mm and test time of 10 min. The worn surface was observed and examined for analyzing.UMT-TriboLab friction and wear tester  was employed to investigate the tribology behavior of coatings in a dry sliding condition at room temperature. A SiHere, to explore different texture surface influence on the friction result, two friction directions  for dimple texture surface were tested, referred to as D0 and D45 in the following 2+s would be preferably electrodeposited onto the graphene and lead to the formation of microbulges on the electroplating coatings. In the process of composite electrodeposition, Ni2+s would be preferentially electrodeposited onto graphene and encapsulated graphene which finally lead to form micro-convex bulges on the electroplating surface. This phenomenon can be found in 2+ to reduce, resulting in a fine grained and intact arrangement of Ni crystals [The average diameter of the original dimple shown in crystals . The chlFurthermore, by comparing 2, respectively. For DST/CE(Ni) samples, the corrosion potential increases to −618.63 mV, which means the corrosion resistance of 6065Al sheet is improved to a certain extent. Furthermore, there was a significant positive correlation between the corrosion resistance and graphene content from test result. The DST/CE(Ni+1.5Gr) get the most notable improvement of corrosion resistance. The corrosion potential of the composite coating moves forward to −601.69mV, and the corrosion current also decreases by 13.90% to 404.58 μA/cm2. Meanwhile, the corrosion test parameters of stripe textured composite electroplating coatings also appeared a similar trend. This result is consistent with another study [As can be seen from er study , in whicQuite possibly, these results are due to the excellent electrical conductivity of graphene that make the nickel have more nucleation points on the surface of the coating. The metal particles crystallized at these nucleation points will deposit at a faster rate, thus, the nucleation rate of the composite electroplating coating is higher than that of the pure nickel electroplating coating. During the process, graphene can effectively prevent the growth of metal grains, thereby refining the grain. Therefore, the addition of graphene composite electroplating coating can obtain a much more compact coating reflecting a better anti-corrosion effect.- ions to reach the matrix of dimple surface texture [Further analysis with data in  texture . On the The corrosion resistant properties of textured graphene/nickel composite electroplating coatings were evaluated by the electrochemical impedance tests. The Nyquist plots of all the surfaces with different treatments were shown by Friction coefficients of textured surfaces coated with different electroplate composites under stable friction and the variation trend of COF on the surface for all the samples are shown in From By comparing the friction coefficients of dimple and groove surface texture coatings, it can be seen from Besides this, by comparing the frictional coefficients of the groove texture surfaces under different frictional directions, it can be found that the lower the coincidence degree between frictional direction and stripped direction is, the more obvious the decrease of frictional coefficients is. When the frictional direction is perpendicular to the groove direction, the frictional coefficient is the lowest, which is 0.735. This is due to the spacing of the groove isolates the propagation of cracks and limits the increase of friction coefficient on the textured surface of the fringes .All the micrographs of those worn samples surface after the test are shown in Comparing with the friction scratches of all the specimens in It is also possible to verify that graphene reduces friction by comparing the trend of worn trace width on composite coatings with different graphene additions in (1)Graphene/Ni composite electroplating coating on groove and dimple textured 6065Al surface were prepared in this paper. Sectional images of the samples show the electroplating coatings and alloy matrix are connected uniformly and tightly. Electrochemical corrosion test results show that the corrosion resistance of the dimple textured graphene/Ni composite electroplating coating is better than that of the groove textured one due to the effect of those small air pockets created by dimple textured surface.(2)Friction and wear experiments revealed that the surface friction properties are related to the texture, the amount of graphene added and the direction of friction. Anti-friction performance of the groove textured graphene/Ni composite electroplating coating is higher than that of the dimple textured one.The following conclusions can be drawn from the present study:


The plasmon-induced transparency (PIT), which is destructive interference between the superradiation mode and the subradiation mode, is studied in patterned graphene-based terahertz metasurface composed of graphene ribbons and graphene strips. As the results of finite-difference time-domain (FDTD) simulation and coupled-mode theory (CMT) fitting, the PIT can be dynamically modulated by the dual-mode. The left (right) transmission dip is mainly tailored by the gate voltage applied to graphene ribbons (stripes), respectively, meaning a dual-mode on-to-off modulator is realized. Surprisingly, an absorbance of 50% and slow-light property of 0.7 ps are also achieved, demonstrating the proposed PIT metasurface has important applications in absorption and slow-light. In addition, coupling effects between the graphene ribbons and the graphene strips in PIT metasurface with different structural parameters also are studied in detail. Thus, the proposed structure provides a new basis for the dual-mode on-to-off multi-function modulators. At present, surface plasmon polaritons (SPPs), as a carrier for transmitting information and energy, have become a research hotspot in the sub-wavelength optics. Generally, they are produced by the interaction between the photons in the incident light field and the electrons on the metal or insulator surface , 2. The 2/(Vs), the group delay can be as high as 0.7 ps, representing the proposed metasurface also has distinguished slow-light functions. Moreover, coupling effects between the graphene ribbons and the graphene strips in PIT metasurface with different structural parameters also are studied in detail. Therefore, this research lays a solid foundation for the dual-mode on-to-off multi-function modulator.In this study, the proposed PIT metasurface, which consists of the periodic graphene ribbons and graphene strips, is easier to implement and fabricate. Through chemical vapor deposition (CVD) , the graVg1. Moreover, the graphene strips are connected with the right electrode using thin metal wires, and a gate voltage Vg2 is applied to modulate their Fermi levels , where ξ = ε/kBT. Moreover, ω, kB, σg, σinter, and σintra are the angular frequency of incident light, the Boltzmann constant, the conductivity of single-layer graphene, the inter-band, and intra-band contributions, respectively. In this work, the room temperature is T = 300 K; the thickness of the graphene is Δ = 0.34 nm. σinter can be ignored owing to kBT ≪ 2Ef in the terahertz band. Thus, σg can be expressed asHere, G(τ = μ0Ef/(evF2) [μ0 = 1 m2/(Vs) being the graphene mobility. Besides, the propagation constant β of the incident light on the graphene surface can be expressed as [Here, the electron relaxation time can be expressed as f/(evF2) , with μ0essed as 7\documeε1, ε2, and k0 are relative permittivity of silica and air, and the wave vector of the plane wave, respectively.Here, 1 and A2 serve as two antennas to describe the coupling effect between the graphene ribbon and the graphene strip. When the incident light is illuminated from A and exited from B, the relation can be obtained byIn Fig. γ1(2)= (iω – iω1(2) – γi1(2)– γo1(2)), in which the inter-loss coefficient is γi1(2)= ω1(2)/(2Qi1(2)) and the extra-loss coefficient is γo1(2)= ω1(2) /(2Qo1(2)). Additionally, Qi1(2) = Re(neff)/Im(neff) [neff= β/k0. The intra-loss quality factor can be obtained by 1/Qt1(2) = 1/Qi1(2) + 1/Qo1(2), with Qt1(2) = f/Δf being the quality factor of the whole system (Δf is 3 dB bandwidth). Following the conservation of energy, coupling relationship between two antennas is as follows:Here, Im(neff)  is the iμnm  and φ are the coupling coefficients and the phase difference between two antennas, respectively. Thus, we can obtain the transmission coefficient and the reflection coefficient of the proposed PIT metasurface.Here, the subscripts “+” and “–” represent that the antennas are illuminated in the same and opposite directions; the superscripts “in” and “out” represent the sign of the incident light entering and exiting the antennas. In addition, χ1(2) = iμ12(21) +(γo1(2)γo2(1))1/2eiφ. Then, the transmission and absorption of the proposed PIT metasurface can be obtained byWhere Very recently, the graphene ribbons, as one of the most promising candidates in the graphene series owing to the fact that they are greatly easy to achieve experimentally and can support localized plasmons (mainly based on Fabry-Perot-like standing wave resonance) –50 and pSo as to discuss the physical origin of the PIT effect, simulated transmission spectra of three graphene metasurfaces and electric field distributions of the entire structure and graphene strip at the resonance frequency are illustrated in Fig. Ef2 of the graphene strip is fixed at 1.0 eV, the Fermi level Ef1 of the graphene ribbon is changed to explore the PIT effect. In Fig. Ef1 increases from 0.6 eV to 1.2 eV, there is a significant change in dip1. For one thing, the transmittance of the dip1 is remarkably reduced indicating that an on-to-off modulation can be obtained. For another, the dip1 has an obvious blue-shift demonstrating that it is sensitive to the change of Fermi level Ef1 and can realize frequency modulation. Besides, when the Fermi level Ef1 of the graphene ribbon is fixed at 1.0 eV, a similar phenomenon occurs in Dip2 with the increase of the Fermi level Ef2. However, the blue-shift is more significantly observed in the left dip in both cases. When Fermi levels of the graphene strip and the graphene ribbon are both 1.0 eV, the resonance frequency of the superradiation mode and the monopole resonance frequency of the subradiation mode are basically 6.2 THz. Thus, the coupling between them forms a symmetrical PIT. When the Fermi level Ef1 of the graphene ribbon is increased from 0.6 eV to 1.0 eV, the monopole resonance frequency of the subradiation mode shifted from the left side to the 6.2 THz due to the change of the graphene ribbon conductivity. In the case, the coupling between the subradiation mode and the superradiation mode is weak owing to different resonance frequencies, generating a highly asymmetric PIT. The obvious blue-shift of the dip1 in Fig. Vg1 mainly regulates the left transmission dip, yet the right transmission dip is chiefly tailored by the gate voltage Vg2. Therefore, a dual-mode on-to-off modulator is realized. Meanwhile, the dual-mode modulation of plasmon-induced absorption (PIA) is also obtained in Fig. The dual-mode on-to-off modulation of PIT can be achieved by two gate voltages applied to the graphene ribbons and the graphene strips, as illustrated in Figs. Ef1 = Ef2 = 1.0 eV. On this basis, the graphene mobility is increased from 1.0 m2/(Vs) to 3.0 m2/(Vs) in a 1.0 m2/(Vs) step. As the graphene mobility increases, not only the transmission spectra show apparent red-shift, but also the 3 dB bandwidth of the transmission dips becomes narrower, meaning graphene mobility can also be used to dynamically modulate the PIT and quality factors of transmission dips. Here, transmission spectra of FDTD simulation and CMT fitting are still perfectly matched. It is known that the performances of the slow-light effect are better with the higher quality factor of the transmission dip. Therefore, the transmission phase shift and the group delay with different graphene mobilities are plotted in Fig. In addition, transmission spectra with different graphene mobilities are also studied, as illustrated in Fig. ϕ(ω) is the phase shift calculated by ϕ(ω) =  arg (t). The results show that both the group delay and the phase shift are 0 when the transmittance of the system is close to 1. Moreover, the large group delay occurs at the transmission peak and its surroundings owing to the fact that the graphene ribbon and the graphene strip have a strong coupling effect at the resonance frequency. When the graphene mobility reaches 3μ0, the group delay of the system can be as high as 0.7 ps. However, the group delay at the transmission dips reaches a large negative value, meaning fast light propagation in the system. Meanwhile, the phase shift has also changed dramatically at the transmission dips. Zhang et al. recently has proposed an absorption efficiency of 50% and slow-light performance with a patterned graphene structure [where tructure . Howeverl4 results in stepped red-shift in the left transmission dip and its quality factor is getting smaller, indicating the dependence of the graphene strip length on left transmission spectra. Fig. Finally, coupling effects between the graphene ribbons and the graphene strips in PIT metasurface with different structural parameters are studied in detail, as illustrated in Fig. In short, we have numerically simulated and theoretically calculated the PIT in the patterned metasurface composed of the graphene ribbons and the graphene strips, which is caused by destructive interference between the superradiant mode and the subradiant mode. Interestingly, the dual-mode on-to-off modulation of PIT can be achieved by two gate voltages applied to the graphene ribbons and the graphene strips. Moreover, an absorption rate of 50% and slow-light property of 0.7 ps are achieved, demonstrating the proposed PIT metasurface has important applications in absorption and slow-light. Furthermore, coupling effects between the graphene ribbons and the graphene strips in PIT metasurface with different structural parameters are studied in detail. Thus, this work provides potential applications for the implementation of dual-mode on-to-off multi-function modulators.


Our work manifests that the manipulation of metal size-dependent charge transfer between metal and support opens new avenues for developing high-active catalysts.Metal–support interaction is of great significance for catalysis as it can induce charge transfer between metal and support, tame electronic structure of supported metals, impact adsorption energy of reaction intermediates, and eventually change the catalytic performance. Here, we report the metal size-dependent charge transfer reversal, that is, electrons transfer from platinum single atoms to sulfur-doped carbons and the carbon supports conversely donate electrons to Pt when their size is expanded to ~1.5 nm cluster. The electron-enriched Pt nanoclusters are far more active than electron-deficient Pt single atoms for catalyzing hydrogen evolution reaction, exhibiting only 11 mV overpotential at 10 mA cm The charge transfer between metal and support is significant for catalysis, but little attention has been focused on charge transfer tuned by metal size. Here, authors report a metal size-dependent reversal of charge transfer between metal and carbon support in hydrogen evolution electrocatalysts. Classic strong metal–support interaction (SMSI) was proposed and termed first by Tauster et al. in 1978, involving the migration of oxide supports and encapsulation of metal particles during high-temperature reductive treatment, which effectively suppress CO adsorption1. After decades of research, SMSI has been intensively investigated and covered many kinds of interaction mechanisms including oxide encapsulation3, charge transfer7, synergistic reaction in catalytic process10 as well as anti-sintering of nanoparticles11.Supported nanoparticle catalysts play a crucial role in modern chemistry industry. It has been demonstrated in literature that the support, more than a carrier to finely disperse and stabilize metal, would interplay with supported metal and influence catalytic reactivity and selectivity15. The importance of charge transfer and electronic perturbations on reactivity was manifested recently by Rodriguez and coworkers, in which Pt nanoparticles contacting with ceria support showed enhanced ability to dissociate O–H bonds in water and finally achieved the best catalytic activity at the greatest electronic perturbation4. Such an electronic perturbation, arising from charge transfer between metal and support, was termed as electronic metal–support interaction (EMSI) by Campbell5. Many works have demonstrated that the charge transfer was relevant to the properties of supports, such as the reducibility16. Meanwhile, it was also reported that the preparation method17 could influence the d-band centers of supported metals. Although these studies concerning the effects of supports and treatment methods on charge transfer boost our understanding of EMSI, much less attentions have been focused on charge transfer tuned by metal itself, especially the particle size19.Charge transfer, as a typical SMSI that occurs at the interface between metal nanoparticle and support, can introduce electronic modification on metal particles and directly influence their adsorption behavior during catalytic process, which will eventually change their catalytic reactivity and selectivity20. Hydrogen is generally produced by water electrolysis, photocatalytic water splitting, and steam reforming of methane23. Among these technologies, water electrolysis transforms electrical energy to chemical energy directly with the merits of high efficiency, green and pure production, emerging a nice prospect for commercialization. Hydrogen evolution reaction (HER) is a vital reaction in water electrolysis and thus, looking for active, stable, and low cost catalyst to drive the HER and cut the cost for commercialization is significantly important and highly desired. Platinum-group metal (PGM) are the best catalysts for HER, however, the high price and the low abundance restrict their wide usage. The grand challenge is therefore to develop low cost PGM-free electrocatalysts25, or to greatly decrease the Pt loading by enhancing the specific activity of Pt or improving the utilization efficiency of Pt atoms29.As the diminishment of fossil fuel and deterioration of environment, hydrogen has become the focus of research and aroused interests of scientists around the world for its cleaning and reproductionHerein, we report the metal size-dependent charge transfer based on the mesoporous sulfur-doped carbon (S–C) supported Pt single atom and nanocluster catalysts Fig. . By spec2 g−1 were prepared by carbonization of molecular precursors with silica nanoparticles as templates  analyses revealed that the doped sulfur in S–C existed primarily in the form of C–S–C, together with a small amount of S–Ox species  was first performed to reveal the atomic-resolution structure of the Pt/S–C catalysts. For the PtSA/S–C catalyst prepared at 300 °C, we observed numerous atomically dispersed Pt species as well as a few loose ensembles of Pt atoms on the S–C support Fig. . When th Pt Fig. . X-ray dS–C Fig. . Energy-2, indicating the partially oxidized Pt species in these catalysts. The k space of k2-weighted Pt L3-edge in the Supplementary Fig. k2-weighted Fourier transform of extended X-ray adsorption fine structure (EXAFS) of Pt L3-edge of the Pt/S–C catalysts, as well as reference samples were shown in Fig. 32. The peak of PtSA/S–C at 1.8 Å in EXAFS could be ascribed to the Pt–S coordination by comparing with the EXAFS of PtS2 and PtO2. In contrast, PtNC/S–C showed an additional peak at 2.6 Å, close to the Pt–Pt contribution of Pt foil, suggesting the coexistence of Pt–Pt bonds along with the Pt–S bonds in the PtNC/S–C catalyst.We then measured X-ray absorption fine structure (XAFS) and XPS to characterize the coordination environments and the electronic structures of Pt species in the catalysts. The normalized X-ray absorption near edge structure (XANES) present in Supplementary Fig. k2-weighted EXAFS spectra was obtained in Fig. R space and k space. The WT intensity maximum of PtSA/S–C and PtS2 both occurred near R space of 1.7–1.8 Å and k space of 6 Å−1, confirming the similar coordination structure of Pt–S bonds in the first coordination shell. As for PtNC/S–C, besides the Pt–S bond, a new WT intensity maximum near 2.8 Å and 9 Å−1 appeared, which was associated with Pt–Pt bonding. Further quantitative analysis of the coordination structure was conducted by the fitting of R space of Pt/S–C  of the f spectra, rather close to the binding energy of PtS2 (73.1 eV), revealing the same nature of high oxidation state. Such high oxidation state of Pt in PtSA/S–C suggested the electron transfer from Pt atoms to S–C via the interfacial Pt–S bonds as revealed by above XAFS analyses. Compared to PtSA/S–C, the PtNC/S–C catalyst exhibited a negatively shifted binding energy of 71.8 eV. It is rather interesting that the binding energy of PtNC/S–C is similar to that of Pt/C, although the particle size of latter is larger, which may suggest that electron transfer reversely from the S–C support to Pt clusters. To rule out the possible influence of particle size-induced change of the binding energy shift34, we prepared the Pt nanoclusters supported on high-surface-area carbon black BP2000 support (PtNC/BP2000-300) with the similar Pt size as the ones supported on S–C (PtNC/S–C-500) and then compared their Pt 4f binding energy . In particular, about 0.069 electrons are transferred from Pt atom to S-Graphene in Pt1/S-Graphene, and conversely, 0.657 electrons are transferred to Pt38 from S-Graphene in Pt38/S-Graphene  and commercial Pt/C (0.684 A mg−1), respectively. Also, the activity comparison of PtNC/S–C with recently reported noble metal electrocatalysts in terms of the overpotential at 10 mA cm−2 and loading amount clearly indicated that PtNC/S–C exhibited almost the smallest loading and the best HER activity simultaneously , suggesting that both of them share the same rate-determining step, where two hydrogen intermediates desorb and form H2 molecular (Tafel step)28. Differently, PtSA/S–C showed a high Tafel slope of 46.92 mV dec−1, indicating the slow reaction kinetics of the Pt–S single sites. Moreover, PtNC/S–C exhibited remarkable exchange current density as high as 1.732 mA cm−2 . The Nyquist plots show a much smaller charge transfer resistance of PtNC/S–C than that of PtSA/S–C, demonstrating the rapid HER kinetics  with similar particle size but a lower electron density , PtNC/S–C showed a negligible loss of activity with a negative shift only about 4 mV at 60 mA cm−2, indicating the outstanding stability of the PtNC/S–C catalyst  was performed to explore the stability of the catalysts in Nyst Fig. . HAADF Syst Fig. . EDS eleyst Fig. .43. The corresponding hydrogen absorption free energy ΔG was −0.32, −0.28, −0.29, and −0.33 eV, respectively. The comparison of free energies of hydrogen atom on Pt slab, Pt38, and Pt38/S-Graphene are illustrated in Fig. 1/S-Graphene, the calculated free energy of hydrogen was 1.08 eV, implying that the single Pt atom loaded on S-Graphene exhibits low catalytic activity toward HER. Differently, the calculated free energy of hydrogen on Pt38/S-Graphene was as low as −0.07 eV on S5 site of Pt38 cluster, implying the superior catalytic activity of Pt38/S-Graphene over the Pt(111) surface and Pt1/S-Graphene. All the hydrogen absorption configuration of Pt38, Pt1/S-Graphene, and Pt38/S-Graphene were summarized in Supplementary Figs. 38 and was closed to that of Pt(111). However, the free energy dramatically reduced to −0.07 eV if Pt38 was supported on S-doped graphene, suggesting the pivotal role of the S-Graphene substrate in regulating the electronic structures of Pt and the HER performance  of hydrogen atom on surface of Pt slab and cluster were considered, as illustrated in Fig. nce Fig. .Fig. 6Hy1/S-Graphene and Pt38/S-Graphene, the charge analysis results (Δe) were correlated to the change of calculated absorption energies (δG) of hydrogen atom  slab, respectively. The HER catalytic activity of all four absorption sites (S1–S4) were enhanced when Pt(111) were negatively charged and the activity change trend was converse when Pt(111) were positively charged  and a decrease in bonding interaction at some other adsorption sites (δG > 0)  and 1.0 g Co(NO3)2·6H2O  were dissolved in 120 mL tetrahydrofuran  before 2.0 g SiO2 nanoparticles  were added under vigorous stirring to form a homogeneous solution. Then the solution was dried by a rotary evaporator and grinded to yield a mixed powder, which was subjected to pyrolysis at 800 °C (5 °C min−1) under N2 atmosphere for 2 h. Finally, the pyrolyzed product was etched successively in 2.0 M NaOH solution for 3 days at room temperature and in 0.5 M H2SO4 for 8 h at 90 °C to remove SiO2 templates and cobalt, respectively. Inductively coupled plasma-atomic emission spectrometer (ICP-AES) measurement indicated that the left cobalt content in S–C was negligible (<0.1 wt%).Mesoporous S–C supports were fabricated by the cobalt-assisted pyrolysis of molecular precursors with silica nanoparticles as templates2PtCl6 by ultrasonic treatment. Then the H2PtCl6/S–C solution was dried by using a rotary evaporator. Afterwards, the dried powder was subjected to tube furnace and reduced at 300 and 700 °C (5 °C min−1), respectively, under flowing Ar/H2 for 2 h to produce the PtSA/S–C and PtNC/S–C catalysts.The PtSA/S–C and PtNC/S–C catalysts were synthesized by conventional wet-impregnation method. Briefly, 50 mg S–C was well dispersed in 30 mL deionized water containing 7.0 mg H−1 with 2θ range of 10–90°. TEM analyses was conducted by a JEOL-2010F transmission electron microscope with an acceleration voltage of 200 kV. The aberration-corrected HAADF-STEM images were obtained using JEM ARM200F TEM operated at 200 kV. EDS mapping images were carried out on FEI Talos F200X, equipped with Super X-EDS system  at 200 kV. ICP-AES measurement was carried out using Optima 7300 DV. XPS measurements were carried out on a VG ESCALAB MK II X-ray photoelectron spectrometer with an exciting source of Mg Kα = 1253.6 eV.X-ray powder diffraction was performed with Japan Rigaku DMax-γA rotation anode x-ray diffractometer using Cu K-α radiation. The operation voltage and current were 40 kV and 150 mA. The scan speed was set at 1.2° min3-edge were acquired at the 1W1B beamline of the Beijing Synchrotron Radiation Facility operated at 2.5 GeV and 200 mA and at the BL14W1 beam line of Shanghai Synchrotron Radiation Facility (SSRF) operated at 3.5 GeV and 220 mA. The raw data analyses were conducted by using Athena program in IFEFFIT software package. The energy was first calibrated, then the pre-edge background of spectrum was subtracted and post-edge was normalized. k2-weighted EXAFS oscillations ranging from 2.5 to 12.2 Å were Fourier transformed to obtain a radial distribution function. The data fitting was carried out using Artemis program in IFEFFIT44. The passive electron factors, S02, were first determined by fixing Pt–Pt coordination number (CN) of experimental Pt foil data to be 12 and then were fixed to analyze other samples.XAFS data of Pt L2-saturated 0.5 M H2SO4 and potentials in this work are with respect to RHE.Electrochemical measurement was conducted by using Pine Instruments in a three-electrode electrochemical cell. Ag/AgCl was used as the reference electrode and graphite rod instead of Pt wire was chosen as the counter electrode to avoid the dissolution and re-deposition of Pt on the working electrode. A rotating disk glassy-carbon with diameter of 5 mm (Pine Instruments) was used as working electrode. The Ag/AgCl reference electrode was calibrated in HPt cm−2) and dried under ambient temperature. For comparison, the ink of commercial 20 wt% Pt/C (Johnson Matthey) was also prepared and deposited on the working electrode (10.2 μgPt cm−2). Before measurement, the catalysts were cycled, about 50 cycles between −0.25 and +1.0 V (vs. Ag/AgCl) to maximize the activity. Linear sweep voltammetry was taken from −0.15 to +0.05 V (vs. RHE) in N2-saturated 0.5 M H2SO4 at the scan rate of 2 mV s−1. The rotating speed of working electrode was set at 1600 r.p.m. to remove H2 gas bubble during the test. For the ADT, cyclic voltammetry was cycled between −0.15 and +0.15 V (vs. RHE) with the scan rate of 100 mV s−1 for 10,000 cycles. After that, the catalysts were cycled again between −0.25 and +1.0 V (vs. Ag/AgCl) for about 100 cycles before LSV measurement. The Nyquist plot of Pt/S–C and commercial Pt/C were obtained using Zahner work station at a potential of −0.24 V (vs. Ag/AgCl) over a frequency range of 0.1 Hz–100,000 Hz.2.0 mg catalysts was dispersed in 2.0 mL isopropanol containing 40 μL 5 wt% Nafion solution (Sigma-Aldrich) and then stirred for 1 day and sonicated for 2 h to get a homogeneous ink. Afterwards, a certain amount of ink was dropped on the working electrode  measurement was performed by utilizing CHI760 electrochemical workstation (Chenhua) to obtain solution resistance. The frequency range is between 0.01 and 100,000 Hz and initial voltage and amplitude voltage are set at 0 and 0.005 V (vs. Ag/AgCl), respectively.b is the Tafel slope, η is the overpotential, j is the current density, c is the intercept.Tafel slopes were obtained by linear fitting the plot derived from logarithm of current density vs. overpotential. The Tafel slopes were determined from Tafel equation:27:The exchange current density was obtained by formula46. The generalized gradient approximation (GGA) of the Perdew–Burke–Ernzerhof (PBE) functional and the projector augmented-wave (PAW) potential were employed48. An energy cutoff of 500 eV was used for the plane-wave expansion of the electronic wave function. All structures were fully relaxed until the maximum force on atom was <0.05 eV Å−1 and the convergence criterion of self-consistent calculation was 10–5 eV. Van der Waals correction was included by using the DFT-D3 method49. The thickness of vacuum layer was >12 Å.Spin-polarized DFT simulations were performed with the Vienna ab initio simulation package (VASP)n/S-Graphene, where n is the number of Pt atoms). A seven layers 2 × 2 × 1 supercells of Pt(111) slab with the atoms in the bottom three layers fixed at their bulk positions was used. A set of 7 × 7 × 1 k-points was sampled by using Monkhorst–Pack scheme50. Supercells of 6 × 6 and 8 × 8 graphene unitcells were used to model the Pt1/S-Graphene and Pt38/S-Graphene, respectively. A set of 2 × 2 × 1 k-points were sampled by using gamma-centered Monkhorst–Pack scheme to describe the Brillouin zone.To investigate the HER activity, we built models of Pt(111) slab and S-doped graphene supported Pt cluster (PtG) of the adsorption of hydrogen atom was calculated according to Eq.  and free H2 molecule, respectively. T is the temperature, which was chosen as 298.15 K. ΔEH was calculated according to Eq.  – ΔG(Pt38), where ΔG(Pt38/S-Graphene) and ΔG(Pt38) denote the free energy of the absorption of sites Pt38/S-Graphene and Pt38, respectively.The Gibbs free energy  – ρ(substrate) – ρ(Ptn), where ρ(system) denotes the charge density of the whole system, ρ(substrate) denotes the charge density of S-doped carbon substrate removing Ptn without relaxation, and ρ(Ptn) denotes the charge density of Ptn removing substrate and keeping the Pt atoms frozen. The difference in bader charge of each Pt atom is calculated according to Δe = e(Pt38/S-Graphene) − e(Pt38), where e(Pt38/S-Graphene) and e(Pt38) are the charge of each Pt atom in Pt38/S-Graphene and fully relaxed Pt38, respectively.To uncover the effect of S–C on the HER activity of PtSupplementary InformationPeer Review File


C) can not be effecively deceased guided by the Moore’s Law as before. The GFET has the problem of the device can not be effectively turned off, since the band-gap of the graphene is zero. To solve these problems, noticing the amount of the carriers in the 2 dementional semiconductor material is limited, we propose a Matel-Semi-Insulator-Semiconductor Field-Effect-Transistor (MSIS-FET) to replace the traditional MOS-FET. We verify our idea by fabricating the graphene MSIS-FETs using the natural Aluminium-oxide (Al-oxide) as the semi-insulator gate dielectric. From MSIS-FETs fabricated, we obtain following experimental results. The graphene MSIS-FET is turned off very well, a recorded high Ids on/off ratio of 5 × 107 is achieved. A saddle and close-loop shape transfer feature of Ids-Vgs is obtained first time for transistors. A non-volatile memory characteristics is observed. A carrier re-injection principle and a super-Low PC mechanism for semiconductor devices and integrated circuits (ICs) are found from the transfer feature of the graphene MSIS-FET. It is shown that the PC of the semiconductor devices and (ICs) can be reduced by over three orders of magnitude by using this new mechanism.The state-of-art Si Matel-Oxide-Semiconductor Field-Effect-Transistor (MOS-FET) meets the problem of the Power Consumption (P The operating principle of the Graphene-Field-Effect-Transistor (GFET) was similar to that of the Si MOS-FET, the gate dielcetric was still a insulator3. The present information technology based on the MOS-FET faces two problems which looks uncorrelated. The one is the Power Consumption (PC) of the Integrated Circuit (IC) is becoming a big problem, along with the information technology enters the cloud calculation and big date era, resulted from that, with the channel length or feature size of the MOS-FET scaling down, the PC can only be reduced linearly changed from previous squarely9. The second is that since the band-gap of the graphene is zero, the GFET can not be effectively turned off17. We think that the research discoveries from the GFET which is made from a single atomic layer can provide the solution to the first problem, because the substrate thickness of the Si Complementary-Metal-Oxide-Semicondector (CMOS) IC is becoming thin and thin. In decades, the feature size of the CMOS ICs using Si as the semiconducor material keeps being scaled down guided by the Moore’s Law. Nowaday, the 7 nm technology has developped to the industral production6, the 5 nm7 and even 3 nm8 technology are in the research period. In the advanced FINFET, the channels are at the two sizes of the FIN, so the effective thickness of the Si substrate is the half width of the FIN9. When the FIN width goes down to 3 nm8, the effective thickness of the Si substrate is 1.5 nm which is less than the thickness of 3 atomic layers of Si (0.543 × 3 nm)18.Since the silicon (Si) MOS-FET was born, the fuction of the device gate was to induce the carriers (electrons or holes) in the semiconductor channel by applying an electric field to the channel through the gate dielcetric which was an insulator22 and bilayer graphene26. But only limited sucsseses were achieved resulting GFET can not be used in digital logic Very Large Scale Integtation (VLSI) circuits up to now. Nobel prize winner, Dr. Novoselov predicted that the utility of graphene in logic circuits could be realized after 202511. The highist ratio of the Ids on/off was achieved by the GNR20 with the ratio value of 1 × 107. However, the GNR is too small to be applied to the VLSI circuits which need large chip area fabricated by the semiconductor planar process. Perhaps for this reason, people turned to investigate the devices made of 2D MOS2 materials with the band-gap recently31.Many efforts were done to solve the turn-off problem of the GFET, for example, by the way of the Graphene-Nano-Ribben (GNR)gs on which the electrons with negative charges in the channel would move toward the gate through the semi-insulaor gate dielectric.Recongnizing the traditional methods to turn off the GFET had a lot of problems and noticing a fact which may be ignored by people, the number of carriers in the 2D semiconductor is much smaller than that in the 3D semiconductor, we propose a novel device structure named as the MSIS-FET correspoding to tradtional MOS-FET. Namely, the semi-insulaor is used to replace the oxided layer or the insulator in the MOS-FET. We predicted that the graphene MSIS-FET could be turned off by the postive gate voltage Vds on/off ratio of 5 × 107 is achieved which is about 5 times lager than the previous record of 1 × 107 created by the GNR20. A saddle and close-loop shape transfer feature of Ids~Vgs is obtained which is obviously different from that of the semiconductor devices reported. A kind of the non-volatile memory characteristics is observed in the measurement of the graphene MSIS-FET, which gives out an important evidence to our turned-off thorey of the MSIS-FET device.Based on the analysis above, we fabricate the graphene MSIS-FET by using the natural Al-oxide as the gate dielectric. By testing the graphene MSIS-FETs fabricated, we obtain following experimental results. The graphene MSIS-FET with monolayer atom is turned off and on very well, the IC reduction may be, the transfer features of the reported FINFET8 and the Si MSIS-FET inferred from the graphene MSIS-FET are shown.We find a carrier re-injection principle and a super-Low power mechanism from the tested features of the graphene MSIS-FET. In order to show how the super-low power mechanism works and the degree of the P2 or HaO2, a layer of the natural Al-oxide is used as the gate dielectric. Figure gs) increasing during the turning-off procedure of the graphene MSIS-FET.The schematic diagram of the graphene MSIS-FET is shown in Fig. The fabrication process of the graphene MSIS-FET with the top gate is described in details in the Supplementary Information  substrate to the SiOgs = 9 V, the device is turned off very well, Ids(off) = 8 pA, Ids(on) = 0.4 mA, the Ids on/off ratio is 5 × 107 which is about 5 times larger than the best reported ratio created by the GNR20. This experimental result has verifies that the graphene MSIS-FET can be turned off by a postive Vgs.After the fabrication, the graphene MSIS-FETs with the top gate are tested by the semiconductor parameter analysor of Agilent 4155B. Shown in Fig. 2 respectively. Both devices have the back-gate as shown in the schematic diagrams Fig. 2 can not. Both devices have the same graphene material and sizes. The Igs~Vgs features of two devices are shown in Fig. gs~Vgs features of the top-gate graphene MSIS-FET is shown in Fig. 3 MΩ, the resisitance of the 15 nm natural Al-oxide is about 1.8 × 104 MΩ, while the resisitance of the 5 nm natural Al-oxide plus 20 nm HaO2 is infinite. For the reason of the resisitance of the natural Al-oxide is quite large but it is not infinite, the natural Al-oxide is called as a semi-insulator.In order to verify the turn-off characteristics of the graphene MSIS-FET was caused by using the gate dielectric of the natural Al-oxide, the compaision experiments were done by fabricating both graphene transistors with the natural Al-oxide and natural Al-oxide plus HaOgs in about 24 hours. This phenomenon is similar to the performance of the floating gate non-volatile semiconductor memory, when the power supply is off, the state of device is keeping18. This experimental phenomenon provides a strong support to our turn-off principle because it indicates that, at this time, there are almost no electrons remaining in the graphene channel. The related tested results are shown and discussed in Supplementary Information . The Vgs corresponding to the LP point is named VLP. The appearance of the LP point for our graphene MSIS-FET is the result of the balance between the functions of the gate extracting electrons and inducing electrons. When Vgs is higher than the VLP, the function of the gate extracting electrons is stronger than that of inducing electrons, as a result, the Ids gets deceasing, until Vgs reaches the value corresponding to the point C, the graphene MSIS-FET is turned off.For importance and convenience of discussions, LP point is named for the point B in Fig. ds on-state will be.When we obtained the close-loop shape transfer feature of the graphene MSIS-FET shown in Fig. 8. The performance of the Si MSIS-FET shown in Fig. In order to explain more clearly how the super-low power mechanism works, Fig. 16, it can be seen that if the Vds is defined as 0.7 V, the Ids is fixed at 2 × 10−4 A. The black line in Fig. gs rising, the Ids rises like the AB line in Fig. gs reaches the VLP, the Ids reaches its maximum. When the Vgs exceeds VLP, the Ids deceases rapidly, until Vgs reaches 0.7 V, the Ids reaches its minimum, the device is turned off. The blue, purple and green lines indicate that by choosing different negative gate voltages during the turning on procedure, people can get the Ids of the Si MSIS-FET, IdsMSIS-FET, equaling to 1/10 (the blue line), 1/100 (the purple line) or 1/1000 (the green line) of 2 × 10−4 A. As a result, the PC can be reduced by orders of magnitude, since PC = Vds × IdsMSIS-FET. Therefore, the reduction of PC of the Si MSIS-FET is in a leaping or revolutionary way.Shown in Fig. C reduction discussed above can be understood by reviewing the way of the PC reduction for a traditional Si MOS-FET guided by the Moore’s Law. When the feature size is scaled down by a fact of 2, the PC can only be reduced by 2~4 times4.The importance of the amount of P2 and black phosphorus will have the same shape as in Fig. From Fig. Dirac, the operating carriers are holes, after the Vgs equals to the VDirac, the operating carriers are electrons3, however, for the MSIS-FETs with the band-gap, for example, for the Si NMOS, the operating carriers are electrons at all the time. In short, since no Ids mimium point caused by the Dirac point existing in the Si MSIS-FET, the saddle shape will not appear in its transfer feature. It needs to point out that the top edge of the parallelogram may not be horizontal. It may has a positive or negative slope depended on which fuction of the gate extracting and inducing the carriers is stronger. If the extracting one is stronger, the top edge will be down to the left before the LP point. Reversely, if the inducing one is stronger, then the top edge will be up to the left before the LP point. The other 2D material MSIS-FETs beside the graphene MSIS-FET may also be important applications of the MSIS-FET, because they can also realize the super-low power based on the machanism found in this paper.Since the existance of the Dirac point in the graphene MSIS-FET, before the Vgs equals to the Dirac Voltage Vgs. The saddle and close-loop transfer feature of the graphene MSIS-FET is measured first time. The non-volatile memory feature of the graphene MSIS-FET is observed which provides an evidence to our turn-off principle and may be used to form a new type semiconductor memory products.In this paper, we propose and experimentally demonstrate the graphene MSIS-FET. The graphene MSIS-FET is turned off and on very effectively by changing the polar of the VThe contribution of this paper to graphene electronics is that the planar fabrication process of the graphene MSIS-FET may let the graphene material be used much easier in the future. The most important contribution of this paper is the discoveries of the carrier re-injection principle and the super-low power mechanism of the graphene MSIS-FET by which the amount of electrons or holes in the semiconductor channel can be controlled first time by the people. The scientific significace of the MSIS-FET verified by our graphene MSIS-FET is that it makes people changing from passtively accepting the carrier amount in the MOS-FET channel fixed by the operating voltage to actively adjusting the carrier amount in the MSIS-FET channel, as a result, it creates a new way to realize the extremely low power semiconductor devices and ICs.Supplementary Information for A Novel Graphene Metal Semi-Insulator Semiconductor Transistor and Its New Super-Low Power Mechanism


In this paper, we carry out researches on randomized local binary features. Randomized local binary features have been used in many methods like RandomForests, RandomFerns, BRIEF, ORB and AKAZE to matching keypoints. However, in those existing methods, the randomness of feature operators only reflects in sampling position. In this paper, we find the quality of the binary feature space can be greatly improved by increasing the randomness of the basic sampling operator. The key idea of our method is to use a Randomized Intensity Difference operator  as a basic sampling operator to observe image patches. The randomness of RID operators are reflected in five aspects: grids, position, aperture, weights and channels. Comparing with the traditional incompletely randomized binary features , a completely randomized sampling manner can generate higher quality binary feature space. The RID operator can be used on both gray and color images. We embed different kinds of RID operators into RandomFerns and RandomForests classifiers to test their recognition rate on both image and video datasets. The experiment results show the excellent quality of our feature method. We also propose the evaluation criteria for robustness and distinctiveness to observe the effects of randomization on binary feature space. Many computer vision tasks such as vision-based sensors , action In this paper, we propose using more general randomized intensity difference sampling operator  to construct binary feature space for keypoints recognition. Comparing with the traditional randomized intensity tests sampling operators  used in BRIEF , ORB 1313, RandoRandomized local binary features have been widely used in keypoints matching and patches recognition. Their main characteristics are two points: one is randomly sampling within size-fixed image patch, the other is binary encoding of the sampling values. Many methods, including BRIEF , ORB 1313 and AKAfter reviewing the existing randomized local binary feature methods, we find that the common ground of these methods is that they all use nonrandom-weighted aperture-fixed point-pairs single-channel basic sampling operators to construct binary feature space. However, our researches in this paper indicate that those incompletely randomized sampling operators are not conducive to the separability and diversity of binary feature space and can can not give full play to the performance of the local binary feature method.In this subsection, we discuss the design of basic sampling operators. The traditional basic sampling operators used in ,18,19 arThe RIT operator is also used in the sampling patterns such as RSLBP , ORB 1313, FREAKn is the number of sampling cells within one RID operator. Each sampling cell Differently, we use completely randomized RID (Randomized Intensity Difference) sampling operators to construct binary feature space. RID operator is random-weighted random-distributed multi-granular multi-channel sampling operator, which can be defined as follows:n) to represent the number of cells within a RID operator. For example, RID(4) means n = 4. As discussed in M-dimensional feature space, we need pre-generate numbers of RID operators and arrange them into M groups. Within each group, the number of sampling cells among different RID operators can be different from each other. RID means there are two kinds of RID operator in each group: RID(2) and RID(4). RID means there are three kinds of RID operator in each group: RID(2), RID(4) and RID(6). The aperture size of RID operators within each group is also randomly pre-selected in a specified range. Because keypoint neighborhood is usually a 31 × 31 image patch, the aperture range of RID operator cannot be larger than 31 × 31. In our paper, RID(2) means the aperture size of RID(2) operator is randomly selected in the range . RID(4) means the aperture size of RID(4) operator is randomly selected in the range . The weights of sampling cells within each RID operator are also randomly generated according to the condition in Equation (Equations  and 3)  3) definEquation  and haveEquation , which aIn this subsection, we discuss how to construct binary feature space using numbers of basic sampling operators.M-dimensional feature vector extracted from an image patch as: We denote T is a threshold that always equals the theoretical average value of sampling operators in The mapping F is controlled by the number of basic sampling operators in each group: V is S bits according to Equation  in those experiments.Therefore, the value size of feature space Equation  and we hT can be set to zero. If we put the RIT operator of Equation , , , ⋯. Under each aperture constraint, we test the recognition rate of RandomFerns classifier embedded with different RID operators. Finally, we plot the curves of recognition rate with respect to operator aperture range. The experiment results on both gray images and color images are illustrated in In this subsection, we keep M and S are fixed, the larger the operator aperture is, the more sampling redundancy exits in feature space. When the operator aperture become too small or too large, the recognition rate curves of random ferns classifier become falling down in both gray images and color images. The reason behind this phenomenon is that large aperture sampling operators can resist noises but omit the details. On the contrary, small aperture sampling operators can capture details, but cannot resist noises. Therefore, sampling operator aperture should be selected randomly in a specified proper range. The best aperture range of the six kinds of RID sampling operators are different from each other, which can be due to the number of sampling cells is different in their sampling templates. According to the experiment results in We can find from the experiment results in In this subsection, we make experiments to show the benefits of weights randomization to binary feature space. For comparison, we generate RID operators in two cases: in the first case the weights of sampling cells within every RID operator are non-randomized and kept fixed; in the second case the weights of sampling cells are randomly selected. In both cases the weights are set to meet the condition defined by Equation . Both raIn this subsection, we use different kinds of RID sampling operators to build binary feature space and combine the feature space with RandomFerns and RandomTrees classifiers  to test M = 40 and S = 8 within each method to keep the dimensions of feature space always same in the experiments. The experiments are made on both gray images and color images selected from VOC2011 dataset. The recognition rate of each tested method is computed in two cases: one test case is keeping the number of keypoints detected from each reference image fixed to be 300 while continuously increasing the number of training samples per keypoint, and the corresponding experiment results are illustrated in For the sake of fair, we set The experimental results illustrated in Now we discuss the computational burden of our method. To generate the sampling pattern, we only need to know the patch size of keypoint neighborhood, the aperture size range of sampling operator and the channels count of the image. This can be seen in algorithmic description in In this subsection, we compare the computational efficiency between our CBE-RID features and traditional MBE-RIT features. In the comparison experiment, we first randomly generate 100,000 image patches from some given images, just as The results in In this subsection, we compare the matching precision performance between our CBE-RID feature method and the existing state-of-art feature methods under different test situations including rotation, zooming, viewpoint changing, blurring, noises and light changing. The existing methods selected to be compared are as follows: ORB, BRIEF, SIFT, SURF, KAZE, AKAZE, CSLBP, RILBP, RandomFerns and RandomTrees. Some of these methods have its own keypoint detector while some are only provide descriptor extractor. If a method has detector, we will use it; if not, we use the detector same as the author used in his original paper. The implementation of the methods we selected to compare are from OpenCV library. Our CBE-RID feature method is also a descriptor extractor method and the ORB detector is used in our programs. Therefore, our method is denoted as ORB-CBERID(6), which use one kind of RID variants: RID(6) operator.The experimental results are illustrated in M = 40 and S = 8. In this subsection, we evaluate CBE-RID features in the real-world application of frame-to-frame matching on video dataset illustrated in The experiment results are illustrated in In this section, we first give the evaluation criteria for robustness and distinctiveness of local features, then make experiments using our evaluation criteria to obtain an insightful observation and explanation for our completely randomized local binary feature method. In this section, we try to answer three questions: the first question is how to measure robustness and distinctiveness; the second question is that how the aperture size of basic sampling operators influences robustness and distinctiveness; The third question is that how the weights randomization of basic sampling operators influences robustness and distinctiveness.f is a local feature method, P is an image patch, and v is descriptor vector of image patch P. Considering deformations occurring on image patch P as some kinds of disturbance, we have a mapping like this: Local feature method can be considered as a mapping from image space to a special feature space, expressed as: f has the ability of keeping invariant to some kinds of disturbance, which can be expressed as follows:P and the descriptor from distorted patch d is normalized descriptor distance from 0 to 1. We use 100 bins in the density histogram and ith bin. The robustness of a feature method requires that feature mapping f can make descriptor vectors from different keypoints separable as much as possible in their feature space. Let P and Q be image patches of two different keypoints, distinctiveness can be expressed as follows:P and Q, respectively. The greater the lower bound The distinctiveness of a feature method requires that the feature mapping Similar to Equation , distincIn this subsection, we discuss the effects of operator aperture on robustness and distinctiveness. To remove the influence of weights randomization and only consider the effect of the operator aperture, we use the nonrandom-weighted sampling operator to carry out the experiment. The quations  and 14)robustnesWe can see from the experimental results illustrated in In this subsection, we discuss the effects of weights randomization on robustness and distinctiveness. We use the random-weighted sampling operator to carry out the experiment to compare with the results in quations  and 14)robustnesWe can see from the experimental results illustrated in In this paper, we carry out researches on randomized local binary features under the background of keypoints recognition and image patches classification. We make experiments to analyze several key parameters that have significant impacts on the quality of the binary feature space. The parameters related to basic sampling operator mainly include position, aperture, weights, channel, pattern and count, which can control the sampling redundancy and multi-resolution observation of local image areas. Through our experiments, we find that the binary feature space constructed by completely randomized basic sampling operator has very good quality compared with the traditional incomplete randomized basic sampling operator. Further, the improvement of the quality of the binary feature space by the complete randomization of the sampling operator is consistent regardless of what classifier you use. It is worth mentioning that this complete randomization does not bring more computational burden and can be easily implemented without need of elaborate manual design.


L1 retrotransposons have co-evolved with their mammalian hosts for the entire history of mammals and currently compose ~ 20% of a mammalian genome. B1 retrotransposons are dependent on L1 for retrotransposition and span the evolutionary history of rodents since their radiation. L1s were found to have lost their activity in a group of South American rodents, the Sigmodontinae, and B1 inactivation preceded the extinction of L1 in the same group. Consequently, a basal group of sigmodontines have active L1s but inactive B1s and a derived clade have both inactive L1s and B1s. It has been suggested that B1s became extinct during a long period of L1 quiescence and that L1s subsequently reemerged in the basal group.Here we investigate the evolutionary histories of L1 and B1 in the sigmodontine rodents and show that L1 activity continued until after the L1-extinct clade and the basal group diverged. After the split, L1 had a small burst of activity in the former group, followed by extinction. In the basal group, activity was initially low but was followed by a dramatic increase in L1 activity. We found the last wave of B1 retrotransposition was large and probably preceded the split between the two rodent clades.Given that L1s had been steadily retrotransposing during the time corresponding to B1 extinction and that the burst of B1 activity preceding B1 extinction was large, we conclude that B1 extinction was not a result of L1 quiescence. Rather, the burst of B1 activity may have contributed to L1 extinction both by competition with L1 and by putting strong selective pressure on the host to control retrotransposition.The online version of this article (10.1186/s13100-019-0164-5) contains supplementary material, which is available to authorized users. They move through an RNA intermediate, but have non-homologous ends and use target-primed reverse transcription . L1  are relatively short, non-autonomous, non-LTR retrotransposons. SINEs do not encode proteins for their own retrotransposition and depend on the reverse transcriptase encoded by other transposable elements such as LINEs , 16. Alterential , 10, SINerential –17, and erential , 4. Amonerential , B1 is terential . B1s areerential , 21 and erential , 23. B1 erential , and theerential , 26.Both L1 and B1 have long histories of co-evolution with their host genomes. Unlike some LTR retrotransposons , 28, theLINEs and SINEs have considerable impact on the mammalian genome, although they were traditionally viewed as “junk DNA”. As LINEs and SINEs, including L1s and B1s, retrotranspose and recombine, they introduce genome instability  and causSince L1 retrotransposition is under strict control by multiple host defenses , it mighSigmodon carries inactive B1 and active L1, and the descendant genera carry both inactive L1 and B1 , four families shared by O. palustris and S. hispidus (L1-OS1 to L1-OS4) and two shared by P. maniculatus, O. palustris and S. hispidus . The other four B1 families (B1-OSP1–4) are shared by O. palustris, S. hispidus and P. maniculatus. The representation of these families in both O. palustris and S. hispidus genomes is fairly synchronized in time and comparable in copy number , and S. hispidus DNA was obtained from Texas Cooperative Wildlife Collection of the Texas A&M University (tissue ID: MUR15). Whole genome sequencing of each species was done in separate batches using MiSeq  at the IBEST Genomic Resources Core . Paired-end libraries were generated with an insert size of 450–550 bp; ~ 13 and 14 million total reads were generated for O. palustris and S. hispidus, respectively. Sequences were processed with SeqyClean (https://bitbucket.org/izhbannikov/seqyclean) and the paired-ends were joined with FLASH [O. palustris and 6.06 Gbp for S. hispidus, but we note that genome size within the sigmodontine rodents varies. Although the genome size of O. palustris is not documented to our knowledge, the genome size of sister species in Oryzomys suggest that Sigmodon genomes are 11–16% larger than those of Oryzomys [th FLASH . Genome Oryzomys .O. palustris and 214 Mbp for S. hispidus. P. maniculatus genome trace files were obtained from NCBI FTP site (ftp://ftp.ncbi.nlm.nih.gov/pub/TraceDB/peromyscus_maniculatus/). Reconstruction of the 3′ ends of O. palustris and S. hispidus L1s started with a 575 bp consensus seed in the 3′ half of L1 ORF2 generated following Cantrell et al. [O. palustris to capture the most recently active sequences; a higher percent identity (97–99%) and overhang length of at least 100 bp were used for S. hispidus. This assured a satisfactory consensus and exclusion of older L1 elements for each species. The 3′ 300 bp of the reconstructed L1s were then used as the reference sequences for COSEG analysis described below.L1 reconstructions for both species were generated based on partial genomic sequences generated by 454 Pyrosequencing  at the IBEST Genomic Resources Core, 203 Mbp of sequence for l et al. . A bioinl et al. . Brieflyl et al. , 73. TheO. palustris and S. hispidus were aligned with Lasergene MegAlign  and the consensus sequence (146 bp) was used as the reference sequence for COSEG analysis.B1 sequences from Rinehart et al.  were useO. palustris and S. hispidus were identified and characterized in similar fashion as described below and are summarized in Additional file L1 and B1 subfamilies in O. palustris and S. hispidus L1 ORF2 were each used as the initial L1 query sequences, and the full length B1 consensuses from each species, based on Rinehart et al. [O. palustris and S. hispidus MiSeq genomic DNA libraries (processed reads without assembly) were queried using RepeatMasker [http://www.repeatmasker.org/COSEGDownload.html) run to identify subfamilies based on shared, co-segregating sequence variants. All COSEG runs were conducted under default parameters except as noted. Parameters were set such that at least 250 sequences were required to form a L1 subfamily and 1000 were required to form a B1 subfamily. In order to identify older subfamilies, the consensus sequences of the subfamilies identified by the first COSEG run were used as queries to again search the O. palustris and S. hispidus MiSeq libraries using RepeatMasker. The identified sequences from the second RepeatMasker run were filtered for > 90% coverage and extracted. O. palustris and S. hispidus sequences are combined and a second COSEG run was carried out on the combined sequences. To avoid the possible formation of random subfamilies due to the short length of B1 and the high copy number of the detected sequences, the sequences required to form a subfamily was increased from 1000 (for the former separate run) to 2000, whereas this number for L1 remained unchanged at 250. The consensus sequences of the resulting COSEG subfamilies were trimmed to exclude ends that were not common to all subfamilies and the CpG sites were removed and, thus, treated as gaps by RepeatMasker and not counted for the divergence calculation. These modified subfamily consensus sequences were used for a final query of the individual O. palustris and S. hispidus MiSeq libraries using RepeatMasker. Sequences from this third run were assigned to subfamilies based on percent divergence and this information was stored for further analysis.The reconstructed 300 bp sequences from the 3′ end of t et al. , were usatMasker  with defatMasker   using the consensus sequences of subfamilies belonging to each family. Alignment and phylogeny of families were generated as described above for subfamilies. Histograms of L1 and B1 divergence distributions were generated by R [Subfamily consensus sequences generated by the second COSEG run of the ng PhyML  with theted by R  histograS. hispidus using RepeatScout [S. hispidus to find repetitive sequences. Identified repeats were then annotated using RepeatMasker. All L1-like sequences that overlaps with the 3′ 300 bp of S. hispidus L1 ORF2 were used as seeds to perform a COSEG analysis of L1s in S. hispidus following the approach described above. All RepeatScout-based L1 subfamilies Additional file 3:Table S1. Statistics and designation of L1 subfamilies and families. “Ory” stands for O. palustris and “Sig” stands for S. hispidus. “Peak” indicates the peak of the L1 divergence distribution of the subfamily or family identified by kernel smoothing. Copy numbers are normalized as copies per three Gbp of MiSeq sequence used for the search, which approximates the copy number per haploid genome. Designation of families is only shown after the first subfamily that belongs to it; all subsequent subfamilies belong to this family until the demarcation of the next family. Characters in family names: “S” represents S. hispidus-specific, “OS” for shared by O. palustris and S. hispidus and “OSP” for shared by O. palustris, S. hispidus and P. maniculatus. Numbers in the family names reflect their divergence among the family group with “1” being the youngest. Copy numbers of families are rounded sums of subfamily copy numbers per three Gbp of sequences and, thus, are occasionally off by one. (XLSX 14 kb)Additional file 4:Table S2. Statistics and designation of B1 subfamilies and families. “Ory” stands for O. palustris and “Sig” stands for S. hispidus. “Peak” indicates the peak of the B1 divergence distribution of the subfamily or family identified by kernel smoothing. Copy numbers are normalized as copies per three Gbp of MiSeq sequence used for the search. Designation of families is only shown after the first subfamily that belongs to it; all subsequent subfamilies belong to this family until the demarcation of the next family. Characters in family names: “OS” represents families shared by O. palustris and S. hispidus and “OSP” for families shared by O. palustris, S. hispidus and P. maniculatus. Numbers in the family names reflect their divergence within the family group with “1” being the youngest. Copy numbers of families are rounded sums of subfamily copy numbers per three Gbp of sequences.and S. hispidus genome. CpG sites with evidence of methylation-induced mutations were removed from the alignment. (XLSX 13 kb)Additional file 5:Alignment of L1 subfamily sequences used in the tables and figures. CpG sites with evidence of methylation-induced mutations were removed from the alignment. (FA 15 kb)Additional file 6:Alignment of B1 subfamily sequences used in the tables and figures. CpG sites with evidence of methylation-induced mutations were removed from the alignment. (FA 7 kb)Additional file 7:S. hispidus genome. CpG sites with evidence of methylation-induced mutations were removed from the alignment. (FA 21 kb)Alignment of L1 subfamily sequences based on RepeatScout-generated seeds and