Tc) between ≈4 and ≈6 K, with Tc’s strongly dependent on the confinement of the Ca layer and the induced charge carrier concentration in graphene. We find that Ca is the only dopant that induces superconductivity in graphene laminates above 1.8 K among several dopants used in our experiments, such as potassium, caesium and lithium. By revealing the tunability of the superconducting response through doping and confinement of the metal layer, our work shows that achieving superconductivity in free-standing, metal decorated monolayer graphene is conditional on an optimum confinement of the metal layer and sufficient doping, thereby bringing its experimental realization within grasp.Despite graphene’s long list of exceptional electronic properties and many theoretical predictions regarding the possibility of superconductivity in graphene, its direct and unambiguous experimental observation has not been achieved. We searched for superconductivity in weakly interacting, metal decorated graphene crystals assembled into so-called graphene laminates, consisting of well separated and electronically decoupled graphene crystallites. We report robust superconductivity in all Ca-doped graphene laminates. They become superconducting at temperatures ( Although some aspects of its superconductivity remain under debate141516171415in situ ARPES measurements on metal decorated graphene20Tc ~ 6 K. Due to the nature of these experiments, however, they could not provide direct evidence of the emergence of intrinsic superconductivity.Graphene, a zero-gap semimetal, can be transformed into a metallic, semiconducting or insulating state by either physical or chemical modification12457891112In this report, we have investigated the possibility of inducing superconductivity in graphene by decorating it with K, Cs, Li and Ca. To this end, we used so-called graphene laminates (GLs) that consist of graphene crystals arranged in a layered manner, similar to bulk graphite. However, unlike in graphite, crystallites within a GL are rotationally disordered and exhibit larger interlayer separations. This is known to result in effective decoupling of individual layers so that their electronic band structure corresponds to that of isolated graphene2324M(T), for Ca-GL and Li-GL. Zero field cooling (ZFC) data for Ca-GL clearly shows a diamagnetic transition at ≈6.0 K . The onset transition temperature found from H = 0 M(T) curves is H the samples clearly exhibit the Meissner effect (inset in M(T) with increasing H: both the diamagnetic response and Tc decrease as expected. The T-dependent upper critical field, Hc2(T)  see  exhibitsR(T) (see Tc ≈ 12 K. The much higher Tc compared to that found in M(T) measurements indicates sample inhomogeneity, possibly due to the presence of some intercalated few-layer graphene  measurements. The relatively small (factor of 2) drop in resistance is due to partial degradation of the sample: unlike all other techniques used in our study, transport measurements required relatively long air exposure of the samples before data could be taken. The resulting partial degradation of the samples was apparent from the colour change (see below) after the measurements; it was also apparent from magnetization measurements that showed an order of magnitude smaller diamagnetic moment compared to Further evidence for superconductivity in Ca-GLs was obtained from the temperature dependence of their electrical resistivity, R(T) see . The zerTo find out whether the observed superconducting response corresponds to a bulk layered system similar to intercalated graphite or, alternatively, is representative of superconductivity within individual graphene crystals, we have prepared mixed laminates where graphene crystallites are interspersed with BN flakes (GBNLs), and RGOLs where graphene flakes have larger separations compared to GLs, ≈3.6 Å versus ≈3.4 Å . The mixTc : d ≈ 5.1 and 5.4 Å vs 4.5 Å  were fabricated as reported earlier232425Metal intercalation was done in either high vacuum or an argon-filled glove box to avoid exposure of the highly reactive alkali-/alkali-earth metals and the intercalated samples to ambient moisture and oxygen. We have used both pure-metal vapour transport10H applied and the magnetisation M measured as a function of increasing temperature, T . The field-cooling (FC) part of an M(T) curve was obtained on cooling the sample to 1.8 K in the same H.Magnetisation measurements were performed on 4 × 4 mm square samples using Quantum Design MPMS XL7 SQUID magnetometer . In the For electrical transport measurements, we have fabricated GL devices in van-der-Pauw geometry, i.e. four contacts were made with silver paint in the corners of a 3 × 3 mm square sample of a graphene laminate. The devices were then intercalated with Ca using vapour transport technique, transferred to a container inside the glove box and quickly cooled down to liquid nitrogen temperature to avoid degradation. Later, the samples were transferred to a liquid helium cryostat, cooled down to 0.3 K and the resistance of the device continuously monitored while cooling. All transport measurements were performed using standard four probe DC measurement techniques using Keithley’s 2400 source-meter and 2182 A nanovoltmeter. Raman spectra were acquired using a Renishaw micro Raman spectrometer with a 514 nm excitation using a laser power <1 mW. Due to the extreme sensitivity of the samples to air, they were sealed inside quartz tubes in the inert atmosphere of a glove box to avoid degradation.Optical reflectivity measurements were carried out using an Energetiq laser-driven light source (available wavelength range 190 nm–2.4 μm), where the light passed through a broadband fibre into a reflective collimator, a neutral density filter wheel and a 70/30 beam splitter before being focused with a 25× objective (NA – 0.65) onto the sample. To prevent degradation of the samples, they were covered with a thin film of paraffin oil and sealed inside a glass cell in the inert atmosphere of a glove box. To eliminate reflection from the glass plate encapsulating the sample, we used a refractive index matching gel. The sample was brought into focus with a three-dimensional stage manipulation system. The reflected light passed back through the lens and beam splitter, before being split again (92/8) to allow a digital image to be simultaneously captured by the camera (8%), with the remaining light (92%) then focused along another broadband fibre to the Ocean Optics spectrometer for analysis. The obtained digital images allowed us to confirm that the samples remained stable (did not degrade) during the measurements by monitoring their colour. The spectra were taken at 345–1040 nm wavelengths, using a silver mirror as a reference.How to cite this article: Chapman, J. et al. Superconductivity in Ca-doped graphene laminates. Sci. Rep.6, 23254; doi: 10.1038/srep23254 (2016).


Graphene by virtue of its structural properties has the potential to address this issue. Studies have indicated that use of monolayer graphene can be used to filter micro volumes of saline solution. Unfortunately it is extremely difficult, resource intensive and almost impractical with current technology to fabricate operational devices using mono-layered graphene. Nevertheless, graphene based devices still hold the key to solve this problem due to its nano-sieving ability. Here we report synthesis of oxidized graphene frameworks and demonstrate a functional device to desalinate and purify seawater from contaminants including Na+ and Cl− ions, dyes and other microbial pollutants. Micro-channels in these frameworks help in immobilizing larger suspended solids including bacteria, while nano-sieving through graphene enables the removal of dissolved ions (e.g. Cl−). Nano-sieving incorporated with larger frameworks has been used in filtering Na+ and Cl− ions in functional devices.The small size of Na Optical, chemical and electrical measurements reveal that these frameworks filter the solution efficiently by utilizing sieving at micro and nano scale. Filtration capability is significantly better than that of mono-layer graphene membranes. Membranes are easy to fabricate, reusable and economically viable. This is expected to have wide implications in meeting the demand for fresh water, a matter of global concern, at lower costExtraordinary properties of graphene make it a potential candidate for nano-sieving in desalination. Molecular dynamics simulations suggests better salt rejection in graphene oxide based frameworks than existing technologies+ and Cl− ions has created a bottleneck in the development of filtration devices to filter these ions from saline solution. De-ionization of saline water is achieved by thermal898111213+ ions. As an alternative to expensive graphene based filters, green methods are being used to synthesize graphene based materials+ and Cl− ions for the production of fresh water from saline source at industrial or individual level; hence there is an urgent need to address this global issue12The small size of NaD/IG ratio of ~0.6471 in their Raman signature shown in top right inset in D/IG ratio can be used to study point like defects in graphene, thereby suggesting the presence of point like defects in the oxidized graphene membrane which act as nanopores for sieving of small ions. This is also supported by UV-Vis signature at ~270 nmThe 3D oxidized graphene framework used in this study was synthesized by charring fresh sugarcane bagasse for about 10 minutes. Thermal processing in air leads to slight oxidation of the 3D graphene frameworks in Analysis of the micrograph suggest that the thermal processing of sugarcane bagasse produces interconnected hierarchical porous structures forming a 3D network of micro-channels made of oxidized graphene. Formation of diffused hexagonal pattern in FFT micrograph is seen in bottom right inset in Microscopic analysis of the membranes after filtration of 0.5 M NaCl solution in + and Cl− ions at room temperature under atmospheric pressure. Results suggest that the filtrate obtained using 3D oxidized graphene membranes qualify to be labeled as fresh water. The filtrate obtained using sea water as feed was also tested for different elemental solvents such as chlorides, residual chlorine, phosphorous and fluorides  at the end of filtering 10 ml and approaches to ~13 g (91.02%) after filtering 490 ml of 0.5 M NaCl solution (−2h−1 was observed for 0.5 M NaCl solution corresponding to an osmotic pressure of ~22.5 bar at room temperature. A device was fabricated (It is observed that ~29.20 mg/ml (99.95%) of NaCl is filtered in the 1solution . The NaC9 mg/ml 9.34% at tbricated  using sybricated .260/I230  as feed solution to the levels much better than the acceptable limits of fresh water (TDS < 990). These are not only simple to synthesize and easy to fabricate and recyclable but also highly economical to use in point of use applications.To conclude, we have synthesized 3D oxidized graphene framework using green method. The membrane fabricated using these frameworks are highly efficient in removing Na2 holes to provide structural stability from flow of tap water. This assembly was finally mounted inside a plastic case. Microstructural characterizations were performed using TEM and FEGSEM. Raman spectroscopy was performed using Witec alpha 300RAS confocal-raman imaging system using 532 nm laser for excitation. The UV-Vis spectrum was obtained using shimadzu UV2600 UV-Vis spectrophotometer. Water quality tests were performed using commercial test kits “Aquacheck”. The details vital parameters test for evaluating the health of water has been provided in Porous 3D oxidized graphene membranes (~1.2 cm diameter) were prepared by thermally processing for device fabrication. The pellet was sandwiched between two plastic filters with ~1 mmHow to cite this article: Pawar, P. B. et al. 3D Oxidized Graphene Frameworks for Efficient Nano Sieving. Sci. Rep.6, 21150; doi: 10.1038/srep21150 (2016).


We attribute the high performance to the elimination of possible deep charge traps, most probably at the graphene/GaSe nanosheets interface. This result demonstrates high photoconductive gain and fast photoresponse can be achieved simultaneously and a clean interface is the key to the high performance of these hybrid devices.While high photoconductive gain has been recently achieved in graphene-based hybrid phototransistors using semiconductor two-dimensional transition/post-transition metal dichalcogenides or quantum dots sensitizers, obtaining fast photoresponse simutaneously remains a challenge that must be addressed for practical applications. In this paper we report a graphene/GaSe nanosheets hybrid photodetector, in which GaSe nanosheets provide a favorable geometric link to graphene conductive layer through van Der Waals force. After a vacuum annealing process, a high gain in exceeding 10 The oppositely charged carriers are trapped in the QD layer within their lifetime, providing a photo-gating effect on the PbS-QD/graphene FET (GFET) channel conductance1620q is electron charge, η is quantum efficiency, A is detector area, Φs is incident light photon flux densityl and inversely proportional to the carrier mobility in photoconductive channel μc and the bias voltage Vbias8 reported in graphene/PbS-QD and graphene/TMDC nanosheets hybrid photodetectors161718where oCμm elemental dimension were reported with a peak responsivity of 1.4 A/W under 240 nm illumination31327–108 and the fast photoresponse to visible light with both light-on and light-off time constants as short as 10 ms in the graphene/GaSe-nanosheet FET phototransistors.While these results are exciting, restrictions exist in slow transient response decay time in these hybrid photodetectors with photoresponse time typically in exceeding 100 ms due to the surface/interface charge trap states1624GaSe nanosheets were synthesized from bulk GaSe and details are summarized in Methods2 (90 nm)/Si substrates was patterned into micro-channels and Au/Ti electrodes were fabricated on top. The GaSe-nanosheet/methanol solution was deposited onto the graphene channels to form the graphene/GaSe nanosheet hybrid photodetector. The source-drain current (ID) versus back gate voltage (VBG) curves with/without GaSe nanosheets in dark are compared in ID versus VBG in dark and under 155 mW/cm2 Xenon light illumination taken on a representative graphene/GaSe-nanosheet hybrid GFET is shown in VSD (or Vbias in this paper) was kept at a larger bias of 1 V, which is needed to obtain higher photocurrent as described in the later part of this paper. Under an incident light, the Diract point shifts further to the right side as anticipated from photogenerated hole doping, inducing a positive photocurrent response at zero gate voltage bias as a result of the photo-gating effect, which is qualitatively consistent with previously reported graphene/PbS-QD phototransistorsIBG vs. VBG curves are also shown in The graphene/GaSe-nanosheet interface band diagram is illustrated schematically in 2] and after [2] the vacuum annealing to a 532 nm laser at comparable incident power intensities, and the back gate voltage Vbg = 0 V and source-drain voltage Vd = 1 V were maintained for both measurements. While the two curves follow a similar trend qualitatively, they differ considerably in both the magnitide of the photoresponse, defined as the difference of the source-drain current ID under illunimation with respect to in dark (or photocurrent ΔID), and the photoresponse time constants, defined as the consumed time corresponding to 50% magnitude rise/decay change upon incident light on/off. After the vacuum annealing, the ΔID increased by a factor of eight, which illustrates the importance in achieving a clean GFET channel interface since polar molecules adsorbed the channel respond to the electric field applied to the GFET and reduce the effective gating field sensed by GFETetectors , while t7. For example, at VBG = 0 V and incident power intensity of 198 mW/cm2, the carrier transient time l = 5 μm, μc ~ 320 cm2V−1s−1 [extracted from Vbias = 1 V, and 8 is obtained at lower incident power intensity of 5.7 × 10−3 mW/cm2 in our measurements. This result therefore demonstrates the feasibility of simultaneous achivement of both the high gain and fast response in the graphene/GaSe-nanosheet hybrid GFET photodetectors.It should be noted that this fast photoresponse is obtained together with a high gain in exceeding 10ID as function of source-drain bias voltage VSD  is summarized in VBG of 0 V and laser intensity of 198 mW/cm2. Apparently, the photocurrent ΔID is linearly dependent on the bias VSD in the entire measurement range, as described in equation ID vs. VBG at a constant VSD = 1 V. Interestingly, the maximum photocurrent was observed at ~VBG = 0 V while it decrases monotonically with increasing VBG abosulte value, which is qualitatively consistent with the photoresponse observed under Xenon light, as shown in The photocurrent ΔRI at different laser intensities is summarized in RI with increasing laser power intensity is in good agreement with ideal photoconductive response16RI ~ 3.5 × 105 A/W is obtained at 5.7 × 10−3 mW/cm2, the minimum controllable laser power intensity in our setup, and higher responsivity value is expected at lower incident laser intensity by following the trend in VSD = 1 V, VBG = 0 V and frequencies about 1.6 Hz, giving a detectivity D* up to 1.1 × 1010 cm.Hz1/2/W at 5.7 × 10−3 mW/cm2 intensity for 532 nm incident laser, where detectivity is calculated as Ad is the detection area and RI is lower than the best reported value of 106–107 A/W taken on the graphene/PbS-QD and graphene/TMDC hybrid photodetectors, several factors should be considered before a direct comparison is made. First, it is widely reported that the observed photoresponsivity decreases monotonically with increasing incident light power, and all the previously reported higher photoresponsivity results were obtained at light power intensity much lower than that of this work1618RI decreases linearly in the log-log scale from about 106 A/W at around 10−5 mW/cm2 to about 20 A/W at around 10 mW/cm2RI results were obtained in hybrid photodetectors167 A/W and maximum detectivity of 7 × 1013 cmHz1/2/W were obtained at 8 fW, corresponding to an incident power intensity of 1 × 10−9 mW/cm2 for the laser spot diameter of 1 mm.), considerably higher RI values are expected on graphene/GaSe-nanosheet hybrid GFET photodetectors at lower light intensity. Furthermore, it should be pointed out that the high gain  and fast response time are achieved simultaneously at zero VBG in this work on graphene/GaSe-nanosheets. This is in contrast to the mandatory high VBG in the range of −60 V to −40 V required to observe photoresponse in graphene/MoS2 hybridsRI was observed at VBG ~ −20 V, which is considerably better than the RI at zero VBG by a factor of 3–4. Finally, all the devices studied in this work were made using CVD graphene. In contrast, the high RI records obtained in previous graphene hybrid photodetectors were all obtained on exfoliated graphene flakes16The laser power intensity affects responsivity as summarized in 7 and fast photoresponse with response time constants around 10 ms have been demostrated simultaneously for the first time to our knowledge. In particular, the demonstrated fast and symmetric dynamic photoresponse is so far the best achieved in the graphene-based hybrid devices integrated with quantum dots or other two dimensional materials. The key to this achievement is the elimination of interfacial deep charge traps. The method developed for fabrication of GaSe nanosheets on CVD graphene is robust and low-cost, which is promising for large-scale device fabrication with compatibility to existing microfabrication procedures and on-chip integration with Si-based readout circuits.In summary, we have developed a graphene/GaSe-nanosheet hybrid GFET for photodetection. High gain in exceeding 102 (500 sccm:500 sccm) at 400 oC for 15 min to clean up residues of transfer process37−6 Torr for about three days in the probe station, which was found critical to removing the polar molecules adsorbed to the GFET channel during the device fabrication  was transferred onto heavily doped Si(100) substrate with 90 nm thermal oxide and annealed in Ar:HTransmission electron microscopy (TEM) imaging of the GaSe nanosheets was done at room temperature using a FEI Tecnai F20 XT field emission transmission electron microscope. Samples were prepared by directly depositing the sonicated GaSe-nanosheet/methanol solution onto a lacey carbon copper grid. The resolution of the instrument was 0.25 nm in TEM mode and 0.18 nm in scanning transmission electron microscopy mode with high angular annular diffraction (STEM-HAAD) mode for elemental analysis. Energy-dispersive X-ray (EDX) spectroscopy was conducted to analyze the sample’s chemical composition.−6 Torr at room temperature. A Xenon lamp was used as broad-band light source for preliminary tests and a 532 nm laser was used for detailed dynamic photoresponse measurements. The laser spot of 1.5 mm in diameter provided a uniform illumination over the GFET channel region. The power intensity was tuned using a continuously variable neutral density filter and calibrated using a Coherent FieldMaxII power meter with OP-2 probe. Electrical current noise spectra across the GFET channel were characterized by measuring the noise fluctuation on a resistor in serial with the GFET using a Stanford Research SR760 spectrum analyzer while keeping the required source-drain voltage across GFET channel.The back-gated field effect transport properties were characterized using an Agilent B1505A semiconductor device analyzer in a high-vacuum probe station of <2 × 10How to cite this article: Lu, R. et al. Graphene/GaSe-Nanosheet Hybrid: Towards High Gain and Fast Photoresponse. Sci. Rep.6, 19161; doi: 10.1038/srep19161 (2016).


The as-synthesized graphene with incorporation of nitrogen groups possesses unique structure including thin layer thickness, high surface area, mesopores and vacancies. These structural features and their synergistic effects could not only improve ions and electrons transportation with nanometer-scale diffusion distances but also promote the penetration of electrolyte. The N-doped graphene exhibits high reversible capacity, superior rate capability as well as long-term cycling stability, which demonstrate that the N-doped graphene with great potential to be an efficient electrode material. The experimental results provide a new hydrothermal route to synthesize N-doped graphene with potential application for advanced energy storage, as well as useful information to design new graphene materials.Nitrogen-doped (N-doped) graphene has been prepared by a simple one-step hydrothermal approach using hexamethylenetetramine (HMTA) as single carbon and nitrogen source. In this hydrothermal process, HMTA pyrolyzes at high temperature and the N-doped graphene subsequently self-assembles on the surface of MgO particles (formed by the Mg powder reacting with H In the past decade, graphene has attracted wide attentions due to its fascinating characters and broad applications13622s22p3)3 is the next element to carbon (1s22s22p2) in the periodic table with only one less valence electron, which possesses higher electronegativity of N (χ = 3.04) than that of C (χ = 2.55). The doping of N would create polarization in the sp2 carbon network, thereby further influence the chemical and physical properties of graphene. Previous reports demonstrated that N doping is efficient in tuning the characters of graphene materials: the bandgap opening and charge-carrier concentration could be induced by only 0.4 at% doping of graphitic N1015Nitrogen (1s3 and nitric acid)2328To date, N-doped graphene materials can be obtained by various methods including plasma method212O). During this in-situ approach, graphene synthesis and nitrogen doping are simultaneously achieved. The as-synthesized graphene with nitrogen-containing functional groups possesses an average thickness of 4–10 nm with interconnected mesoporous system. The high surface area, mesopores and vacancies of the N-doped graphene are particularly beneficial for the reversibly storage of lithium ions. These structural features and their synergistic effects would promote ions and electrons transportation with nanometer-scale diffusion distances as well as be favorable to the penetration of electrolyte. Extensive research carried out on lithium ion batteries demonstrate that the N-doped graphene electrode exhibits high reversible capacity, superior rate capability as well as long-term cycling stability , which suggest its great potential to be an efficient electrode material candidate.In this paper, we developed a novel one-step hydrothermal method using HMTA as single carbon and nitrogen source. Briefly, HMTA pyrolyzes in high temperature and the N-doped graphene subsequently self-assembles on the surface of MgO particles 2 and release small molecules sp2 carbon clusterssp2 clusters may assemble into polyaromatic systems and finally into graphene. A variety of nitrogen atoms would residue from the precursors after the whole hydrolyzation and graphitization process; the attachment of the sp2 carbons to the remaining nitrogen atoms preserves the sp2 hybridization state in HMTA. 002) of the sample are about 0.34 nm, which is slightly larger than the d002 spacing of graphite (d002 = 0.335 nm)Structural characterization of the as-prepared sample was carried out by the powder X-ray diffraction (XRD). The morphology and microstructure of as-prepared samples were imaged by SEM tests. 2O and HMTA to obtain MgO and the MgO would agglomerate into clusters. Then, the MgO clusters would act as structural constructor, and the curled and overlapped nanosheets are synthesized on the surface of the MgO clusters. When the samples are washed by HCl, the two-dimensional structure of graphene is well maintained and the nanosheets reveal a curled morphology consisting of a thin crumpled paper-like structure.The formation process of the graphene nanosheets based on a solution-growth pathway could be deduced from the SEM images . Firstly002 spacing) is measured to be about 0.34 nm, which is larger than that of graphite (0.335 nm) and agreed with the interlayer spacing calculated by XRD pattern. It is worth noting that the basal planes are discontinuous and distorted, and some parts are wavy and turbostratic, indicating that the layer stacking is disordered−1 and 1586 cm−1, which could be ascribed to the well-documented D and G band2g mode corresponds to ordered sp2 bonded carbon and provides the formation of graphitic carbon. The D band arises from the breathing modes of six-atom rings of κ-point phonons of A1g symmetry with defects for activation−1) is the D-band overtone41Raman spectra have sensitive response to the crystallinity, defects and disorder of microstructure of carbon materials37sp2 domains. The ratio of D to G band integrated intensities (ID/IG) is usually used to estimate the average crystallite size along the a-axis (La) of sp2 regions in the graphene layer. The La could be calculated by the empirical Tuinstra-Koenig equation: La = (2.4 × 10−10) λ4(ID/IG)−1 37D/IG is 1.13, so the crystallite size of ordered sp2 regions surrounded by areas of nitrogened carbon atoms or defects is about 14.9 nm. As a consequence, the Raman spectrum reveals that the N-doped graphene are composed of few-layered structure with sufficient defects which is crucial to improve its lithium diffusion and storage properties.The D, G and 2D bands of graphene2g−1, as well as the high volume of mesopores  method). The N-doped graphene exhibits a characteristic type IV isotherm with a pronounced hysteresis at P/P0 = 0.4–0.8 between the adsorption and desorption branches, suggesting the existence of a large number of mesopores with uniform pore size distribution0 = 0.45) is significantly delayed comparing with the capillary condensation. This delay process2 condensed in the pore interiors to the exterior when the N2 is condensed in the narrower connecting pores0 = 0.4. In this case, the ink bottle-like pore networks account for the occurrence of broad hysteresis loops. Moreover, the adsorption and desorption branches do not close below P/P0 = 0.3, which indicates that chemical adsorption might occur in the mesopores; this chemical adsorption is irreversible so the adsorpted N2 could not be desorpted at lower pressure. The pore size distribution  . As show1 (0.7 V) and R2 (below 0.2 V) and two anodic peaks O1 (1.2 V) and O2 (0.2 V) during the first cycle. The R1 peak in the 1st cycle and disappeared in the following cycles could be assigned to the decomposition of the electrolyte and formation of solid electrolyte interphase (SEI) film on the surfaces of graphene in the first cycle2 peak and the counterpart anodic O2 peak could be attributed to Li ions insertion into the graphene layers1 peak indicated that the breaking of the bonds of the Li atom with the defects or other active sites during the charge processes takes place at high voltage+ produces good reversibility.+ of the first cycle begins at around 2.0 V vs. Li/Li+; the curve exhibits a slope plateau at 0.8 V which arises from the combination of Li ions adsorption on the structural defects in basal planes of the graphene layers and the formation of solid electrolyte interphase (SEI) film5856Galvanostatic charge/discharge of the sample was measured at a current rate of 100 mA/g in the potential range from 0.01 V to 3 V with Li foil as a counter electrode at room temperature (25 °C). s), resistance (R1) of the surface film formed on the electrodes and the contact problemsdl), charge-transfer resistance (Rct)D) related to the diffusion capacitance of lithium ions into the graphene electrodes1 = Ω and Rct = 2.738 Ω). In this case, the electrical conductive capability are improved, resulting in the high capacity and stable cycling performance.The above analysis well demonstrated that N-doped graphene is an excellent electrode material of Li-ion battery. To get further insight into the electrochemical process, electrochemical impedance spectroscopy (EIS) were carried out by three electrode system and the obtained Nyquist plots are presented in According to the above results, the significantly improved electrochemical performance of N-doped graphene get benefit from the unique structure by nitrogen doping61In summary, we have successfully prepared a new kind of N-doped graphene through a facile one-step hydrothermal approach. The as-synthesized graphene with incorporation of nitrogen groups possesses unique structure including high surface area, mesopores and vacancies, which is particularly important for the reversibly storage of lithium ions. The structural features and their synergistic effects could not only promote ions and electrons transportation with nanometer-scale diffusion distances but also benefit to the penetration of electrolyte. The N-doped graphene exhibits outstanding electrochemical properties such as high reversible capacity, superior rate capability as well as long-term cycling stability, which endow it great potential to be an efficient electrode material candidate, and the EIS test further indicates that the N-doped graphene is a good lithium ion battery. The experimental results provide a novel hydrothermal route to fabricate N-doped graphene material with potential application for advanced energy storage, as well as useful information to design new graphene materials for future applications.All reagents  were analytical purity and used without further purification.Details of a typical synthesis process are as follows: Hexamethylenetetramine , magnesium powder  and ultrapure water (3 mL) were added into a 20 ml stainless steel autoclave. The autoclave was sealed, put in an electric furnace, warmed up at a rate of 10 °C/min and maintained at 500 °C for 20 h, and was then cooled to room temperature naturally. The precipitate was filtered off, washed with distilled water, absolute ethanol, and hydrochloric acid solution (5 mol/L) for several times, and then dried in vacuum at 50 °C for 3 h.−1. The morphology of the graphene were observed using a JEOL JSM-6700F field emission scanning electron microscope (SEM) operated at 15 kV and Hitachi H7650 transmission electron microscope (TEM) operated at 100 kv. The high resolution images were recorded using a high resolution transmission electron microscope  operated at 200 kV. The surface areas of the sample were measured by TriStar II 3020  and calculated by N2 adsorption-desorption isotherms. The XPS tests were performed on a Thermo Scientific ESCALAB 250 X-ray photoelectronic spectrometer with a non-monochromated Mg Kα X-ray radiation as the excitation source. The Raman spectroscopy data were taken on a LABRAM-HR laser MicroRaman spectrometer with excitation wavelength of 514.5 nm (2.41 eV).The X-ray powder diffraction (XRD) measurements were carried out on a Bruker AXS D8 Advance X-ray diffractometer equipped with Cu Ka radiation (λ = 1.54182 Å) at a scanning rate of 10° min6 in ethylene carbonate/dimethyl carbonate (EC/DMC) with a volume ratio of 1:1. The galvanostatic charge/discharge tests were tested in the voltage range of 0.01–3.0 V using a computer-controlled multichannel battery test unit (LAND-CT2001A battery cycler) at room temperature. The typical cyclic voltammetry (CV) measurements were performed in the potential window of 0.01–3.0 V at a scanning rate of 0.1 mV/s on LK-2005A electrochemical workstation.The electrochemical performances were measured with CR2032 coin-type cells. The N-doped graphene acted as an anode electrode, and Li foil was used as a counter electrode. To prepare the working electrodes, the active materials (70 wt %) were mixed with Super P carbon black (20 wt %) and polyvinylidene fluoride (PVDF) (10 wt %). These materials were dissolved in N-methyl pyrrolidone (NMP) and ball milled for 5 hours at speed of 400 rpm to obtain uniform slurry. Then the slurry was coated on a Cu foil current collector and subsequently dried under vacuum at 80 °C for 12 h. The Celgard 2300 microporous membrane was used as polypropylene separator, and the electrolyte was a 1 mol/L solution of LiPFHow to cite this article: Xing, Z. et al. One-pot hydrothermal synthesis of Nitrogen-doped graphene as high-performance anode materials for lithium ion batteries. Sci. Rep.6, 26146; doi: 10.1038/srep26146 (2016).


We provide a comprehensive picture of magnetotransport in graphene monolayers in the limit of nonquantizing magnetic fields. We discuss the effects of two-carrier transport, weak localization, weak antilocalization, and strong localization for graphene devices of various mobilities, through theory, experiments, and numerical simulations. In particular, we observe a minimum in the weak localization and strong localization length reminiscent of the minimum in the conductivity, which allows us to make the connection between weak and strong localization. This provides a unified framework for both localizations, which explains the observed experimental features. We compare these results to numerical simulation and find a remarkable agreement between theory, experiment, and numerics. Various graphene devices were used in this study, including graphene on different substrates, such as glass and silicon, as well as low and high mobility devices. This square root dependence leads to a very large lowest Landau level splitting, where the field quantization has been observed up to room temperature [Graphene has attracted a considerable amount of attention due to the ease in isolating a single sheet of graphite via mechanical exfoliation , 2. Despperature . While tμqB ≪ 1, where μq is the quantum mobility. In this regime, the Landau quantization does not play any role, but the valley degeneracy, the linear dispersion, and the underlying disorder potential lead to interesting magnetotransport phenomena such as two-carrier transport (2CT), weak localization (WL), weak antilocalization (WAL), and strong localization (SL).The goal of this work is to present a comprehensive understanding of the magnetoresistance of monolayer graphene in a regime where the Landau quantization is not important; that is, τe−1, and intravalley scattering, where electrons scatter within a valley as described by a rate τa−1. In general, intervalley stems from short range scattering, such as atomic defects, including grain boundaries, whereas intravalley scattering is long range and is typically stronger and also includes large scale inhomogeneities and charged impurities in the substrate. Long range potential variations are responsible for the existence of both carriers' types (electrons and holes) simultaneously at the charge neutrality point (CNP). The carrier distribution can be understood by assuming that the total carrier density is given by n − p = C|VG − VD|/e, C is the gate capacitance, VG the gate voltage, and VD the gate voltage at the charge neutrality point (CNP) with a total residual density n0 . n0 is composed of the thermal carriers plus remaining electrons and holes due to sample inhomogeneities as a consequence of the underlying disorder potential. This disorder induced residual density dominates at low temperatures. n and p are the carrier densities of electrons and holes, respectively. This allows us to define electron and hole mobilities, μn = σn/en and μp = σp/ep, where σn and σp are the corresponding electron and hole conductivities. Experimentally, μn and μp are often slightly different, which is likely due to the asymmetry of the scattering potential for electrons and holes.Most of the magnetotransport properties of graphene can be understood in terms of two types of scattering mechanisms: intervalley scattering, where electrons are scattered from one valley to the other (K to K′) with a rate hereby noted as 2+(n-p)2 , where nDorgan's  work, nμqB ≪ 1, this contribution can be evaluated using Drude's expression for two carriers, where ρxxη = ση−1 and ρxyη = sign(qη)B/eη for the two types of carrier densities (η = n or p). The total resistivity is then given by We start our magnetotransport analysis by discussing the simplest nontrivial contribution, which is due to the simultaneous existence of the two types of carriers near the CNP. As long as ρxx = (σn+σp)−1, and identifying ρmax as the zero field resistivity at the CNP, we obtainExpressing the conductivities in  in termsB the 2CT gives rise to a parabolic positive relative magnetoresistance before saturating to n0/|n − p| when B≃B1, which is valid as long as μqB ≪ 1. Close to the CNP, that is, |n − p | ≪n0, B0 is simply equal to the inverse median mobility and B1 ≫ B0, which is the regime where the 2CT effect is the largest. Away from the CNP (|n − p| ≫ n0), we have a maximum Δρ/ρ≃n0/nH, which decreases away from the CNP, since nH≃|n − p|, which is the Hall density, increases. The 2CT will play an important role, as long as μqB ≪ 1, to give rise to positive magnetoresistance due to large scale inhomogeneities. This effect is very important in graphene as compared to other two-dimensional systems because of the absence of a gap between the electron and hole carriers. The 2CT will serve as basis for the understanding of the classical contribution due to long range scattering, which will be present at all temperatures and even increases with temperature, since n0 increases with temperature due to the thermal activation of the electron and hole carriers.Hence, as a function of Pret can be expressed as [πDt)−1 in the integrant is the return probability (P0(t)) for diffusion constant D, the second term represents the short time cut-off (τe), below which no elastic scattering occurs, and the third term is the phase coherence time (τϕ) cut-off, beyond which phase coherence is lost. At low temperatures, where τϕ ≫ τe, this leads to the typical logarithmic WL correction of the conductivity δσ = −(4e2D/h)Pret≃−(e2/πh)ln(τϕ/τe).Moving beyond the Drude and classical description of transport, we need to include quantum effects, of which coherent backscattering is the most important contribution. Coherent backscattering leads to WL , 10. To essed as (5)Pret=PB(t), we have to solve for the return probability according to the field dependent diffusion equation [A is the vector potential. The solution to this diffusion equation can be evaluated for r = r′ and is given byτB = ħ/4eBD. At zero field we recover P0(t). In the long time limit, where we have PB(t)→(eB/h)et/2τB−, this leads to the field induced destruction of the phase coherence when approximately one flux penetrates the area LB2 = DτB. The full magnetic field dependence is obtained by inserting PB(t) into the expression of the coherent return probability and evaluating the integral; that is,Bϕ = ħ/4eDτϕ and Be = ħ/4eDτe are the characteristic magnetic fields for τϕ and τe, whereas ψ is the digamma function. The magnetic field correction to the coherent return probability is then given byF(z) = ψ(1/2 + 1/z) + ln(z), F(z)≃z2/24 for z ≪ 1, F(z)≃ln(1 + z/4eγ) for z ≫ 1, and γ is the Euler constant. The second term in  = ln(Bϕ/(Bϕ + Be)). This expression leads to the usual WL correction to the conductivity when expressing the conductivity correction in terms of the coherent return probability correction; that is, Δσ = −4e2DΔPret/h [To evaluate the magnetic field dependence of the return probability equation :(6)[∂∂tgiven byΔPret=Pre systems . The firΔPret/h , 14.τϕ (phase breaking) and τe (elastic). However, in graphene, we have two very different types of elastic scattering mechanisms: those that scatter electrons within a valley  and those that scatter between valleys . Here only intervalley scattering contributes to coherent backscattering; hence, the short time cut-off scattering time is provided by τe in graphene. Intervalley scattering is typically induced by short ranged impurities and can be due to grain boundaries or lattice defects. However, intravalley scattering is usually much stronger in graphene but does not contribute to coherent backscattering.In deriving  we assumB involving the scattering parameters τa and τe explicitly. They obtained the following expression:B⋆ = Ba + Be/2 and τ⋆ = ħ/4eDB⋆. This expression can also be obtained directly using (et/τe− in the magnetic field correction by (et/τe− + 2et/τ⋆−). While the first two terms in , where σ0 is related to the quantum conductance. For small corrections in the conductivity, this expression yields δLc/Lc≃δσ/σ0. However, for strong disorder this expression is not valid and we will evaluate Lc numerically below.Equation  tells usimension , which wimension , as Lc Lϕ > W and W is the width of the graphene ribbon. In this limit, the governing diffusion equation is no longer 2D but has to be replaced by the 1D analogue; that is, τb is given as usual by Lb2/D, where WLb [In many situations, both experimentally and numerically, one deals with a situation where the sample width is finite. This leads to a different field dependence, since the sample effectively becomes quasi-one-dimensional (Q1D) instead of 2D, when t)e-t/τb , where trea WLb . This leτe−1 ≫ τϕ−1 + τb−1 we obtain the following expression for the magnetic field correction of the coherent return probability:When σ = −4e2DΔPret/h, we recover the expression for the WL correction to the conductivity obtained by McCann and coworkers [Recalling that Δoworkers .τc, which has the effect of simply replacing 1/Lϕ2 by 1/Lcϕ2 = 1/Lϕ2 + 1/Lc2. We then obtain for the relative change in the coherent return probabilityBW = ħ/4eW2. This is the result for the Q1D limit, when Lϕ or Lc≫W. Here again we have ΔLc/Lc≃−ΔPret/Pret|Bϕ=0 for the relative change of the localization length.For the strong disorder case, we have to again introduce the localization time Lc numerically for graphene assuming that Lϕ ≫ Lc, W. There are two different limits: 2D and Q1D; that is, Lc ≪ W (the high disorder limit) and Lc ≫ W (the low disorder limit), respectively. These two limits are mainly determined by the amount of disorder in the system. For the numerical simulations, we will only consider short ranged disorder, since this is the relevant source for WL. The effect of long range disorder is to induce the coexistence of electrons and holes close to the charge neutrality point as well as WAL.We now move to evaluate t≃3 eV. The two ends of the graphene device are assumed to be connected to wide ohmic contacts with a quadratic dispersion. The short range disorder is implemented by adding a random onsite potential vi on every atom site uniformly distributed with −V/2 < vi < V/2. The magnetic field is simply a phase factor ϕ in the hopping term, where 2πϕ = 1 corresponds to one flux quantum in a hexagon. The two-terminal transmission probability T is then evaluated iteratively as a function of the length, L, of the system, using an efficient iterative Green's function method [T(L)〉e2/h, resistance 〈1/T(L)〉h/e2, or logarithm conductance 〈ln(T(L))〉 is obtained by averaging over many disorder configurations (〈·〉). For a given W and at large enough L, the system is always localized due to Anderson localization and Lc can be extracted whenever L ≫ Lc.To model the system accurately, we consider a tight binding model with a honeycomb structure with two types of edges: armchair and zigzag. The hopping term is given by n method . Similarn method , 24. TheLc with the analytical expressions derived above for the relative change in Lc, that is, testing  → L/Lc. Therefore, small variations in Lc lead to ΔRxx/Rxx≃−LΔLc/Lc2. This is assuming that Lϕ ≫ L. However, in experiments, where this is often not the case, Lϕ plays the role of effective sample size (Lϕ = L) so that when Lϕ ≪ L we can write ΔRxx/Rxx≃−LϕΔLc/Lc2 instead. This is often used in experiments to extract Lc from the temperature dependence of the resistance, since Lϕ also depends on temperature [Lϕ is constant, but Lc is magnetic field dependent. Hence, when Lϕ ≪ L we have, using ΔRxR/R ≪ 1), different contributions to the resistance are additive; hence the total effect on the resistance, including the two-carrier effect, yieldsLc−2 + Lϕ−2 = 4eBcϕ/ħ, Le−2 = 4eBe/ħ, B0≃ρmax/μρxx, and B1≃B0n0/nH.For small variations (Δμm) single crystal graphene. Monolayers of graphene were grown by chemical vapor deposition (CVD) of hydrocarbons on 25 μm thick commercial Cu foils. The CVD process used was similar to those described in previous works [While WL was observed in graphene in a number of previous experiments –29 and fus works –33.Lϕ≃50 nm and Lc≃120 nm, which shows that the localization length is of the same order of magnitude as the phase coherence length. The agreement between the fit and the data is quite remarkable over the entire available magnetic field range and only relies on three fitting parameters, in this case Bcϕ, Be, and Lϕ/Lc. The other parameters B0 and B1 are too large to significantly affect the fit. For even higher disorder, we expect Lc to be smaller than Lϕ and we would need to modify our assumption of the linear approximation used in (Lc(B) and its associated field dependence. This is amplified further for long but narrow samples (nanoribbons).We start with low mobility samples, which cannot be fitted with the standard WL theory  alone be used in . InsteadLϕ≃220 nm, Lc≃2.3 μm, and Le≃4.3 nm. Here again, the agreement between the fit and the data is quite remarkable, considering that the fit extends over the entire magnetic field range.The next step is to look at a large scale (~cm) graphene sample grown by CVD deposited on a glass slide with evaporated gold as contacts. The magnetic field dependence is shown in 2/Si substrate, where the doped silicon can be used as a back gate. The main difference is that this sample was grown using isotopically pure C13 methane gas instead of C12, so that the Raman peaks are shifted by Lϕ≃330 nm, Lc≃6 μm, Le≃120 nm, and a mean field effect mobility of μ≃0.18 m2/Vs, which is common for large scale CVD graphene, and a residual density of n0≃7.0 × 1011 cm−2.The next sample we are considering is a large scale (~cm) sized graphene sample grown by CVD and deposited on a standard SiOby 12/13 . Howevern and p type carriers. Strikingly, the quality of the fit is very remarkable over the entire available experimental magnetic field range.Interestingly, this is a prime example of a large parabolic-like positive magnetoresistance background, which cannot be fitted using WAL as per , since Wμm diameter) single graphene crystal grown by CVD [μn≃0.43 m2/Vs for electrons and μp≃0.63 m2/Vs for holes. The CNP was at VG = 5.4 V. Using ≃9 and found a remarkable agreement with the field effect mobility extracted from the gate voltage dependence. For the residual density we obtain n0≃5.8 × 1011 cm−2 using μ−1 = en0ρmax.We now turn to the higher mobility case, where we consider a graphene field effect device made out of a large , which all samples show, there is often a parabolic positive magnetoresistance which is mainly due to the 2CT effect because of large scale inhomogeneities in addition to WAL in very clean samples.The overall experimental behavior can be summarized as follows: at low temperatures, very low mobility samples show a very wide peak in the resistance at zero field  and from the presence of two types of carriers close to the CNP (the 2CT). While WL is generic to all disordered systems, both WAL and 2CT are specific to graphene, where both play an important role in the understanding of magnetotransport.


A broadband photodetector  based on such hybrid films is fabricated with a high photoresponsivity of >100 A W−1 and a fast response time of ∼100 μs. The combination of ultra-broad bandwidth, high responsivities and fast operating speeds affords new opportunities for facile and scalable fabrication of all-carbon optoelectronic devices.Graphene has emerged as a promising material for photonic applications fuelled by its superior electronic and optical properties. However, the photoresponsivity is limited by the low absorption cross-section and ultrafast recombination rates of photoexcited carriers. Here we demonstrate a photoconductive gain of ∼10 Graphene has excellent electronic properties but its photoresponsivity is limited by low absorption and the ultrafast recombination of photoexcited carriers. Here, the authors demonstrate fast, high responsivity and broadband photodetectors by combining graphene with single-wall carbon nanotubes. Combining low-dimensional nanomaterials into hybrid nanostructures is a promising avenue to obtain enhanced material properties and to achieve nanodevices operating with novel principles1−2 A W−1)1012−1 (ref. 17−12 W) due to the use of exfoliated graphene flakes 9 has been demonstratedBoth graphene and CNTs exhibit intriguing optical properties, such as broadband and tuneable light absorption, which make them promising materials for photodetectors82−1 ref. . However2−1 ref. −12 W due5 cm2 V−1 s−1 at room temperature11) in semiconducting SWNTs−3 AW−1) of single-tube photovoltaic devices greatly limits their practical use2-hybridized carbon allotropes, combined with the various strategies available for structural and chemical engineering of the interfacial electronic properties27SWNTs, on the other hand, are π-conjugated, 1D structures with nanometre diameters5, together with a high electrical bandwidth of∼104 Hz (response time∼100 μs) across visible to near-infrared range . The reported device constitutes a first implementation of large-area, quasi-2D SWNT–graphene hybrid film for optoelectronic devices and is envisaged to be important for optical communication, spectroscopy, remote sensing and high-resolution imaging applications. Equally important, we demonstrate for the first time the possibility of harvesting robust excitons widely supported in 1D systems by a 2D layered material. Our results not only open up new avenues for studying fundamental carrier transport and relaxation pathways in nanometre-scale, 1D van der Waals junctions, but also pave the way for constructing high-performance optoelectronic heterostructures by planar 1D–2D hybrid building blocks, other than the use of purely 2D layered materials.Here we demonstrate a proof-of-concept photodetector based on a planar atomically thin SWNT–graphene hybrid film. In our design, enhanced broadband light absorption is achieved in the hybrid film. Compared with pristine graphene photodetectors which exhibit only weak Schottky junction and high Auger recombination rate, the large built-in potential at the 1D-2D interface promotes effective separation of electron-hole pairs and reduces recombination of spatially isolated photocarriers. Furthermore, the trap-free interface enables a relatively fast operation rate. The devices exhibit a significant photoconductive gain of ∼102/Si substrate (see Methods). 2/Si substrate is measured to be ∼0.8 nm, indicative of single atom layer11 and S22 bands are found to be located at ∼1,800 and ∼1,000 nm with higher SWNTs loadings  as a function of the back-gate voltage (VG) under different illumination levels, where continuous negative shift of the voltage for Dirac point  is observed, confirming a photocurrent generation mechanism as depicted by 22 bandgap of the semiconducting SWNTs (∼1.2 eV), free electrons can be directly excited from the valence band to the conduction band. Photogenerated electrons in SWNTs are transferred to the graphene channel due to the built-in electric field, while the holes are trapped in the SWNTs due to the potential barrier at the interface. The conductance of the graphene channel decreases for VBG<VD where the carrier transport is hole-dominated, but increases for VBG>VD, where carrier transport is electron dominated. V) as a function of the illumination power, clearly revealing the high sensitivity of the SWNT–graphene device. ISD as a function of VG under different illumination power of 650 nm demonstrates effective tuning of the photocurrent and the photoresponsivity with the back-gate voltage, where a maximum photocurrent of >90 μA is obtained at a negative VBG around −20 V (VSD) for different optical powers at VBG=0 is clearly observed. −1, as compared with a bare graphene device∼10-2 A W−1. Since the responsivity does not show sign of saturation, higher photoresponse on the order of ∼1,000 A W−1 is expected at lower excitation power levels . The temporal photoresponse was measured at 173 K to suppress the outside interference including scattering centres from the substrate and charge-trapping surface statesResponse time is another key figure of merit for photodetectors and is also relevant in revealing the physical mechanism of the device operation. V × Cox/φphoton, where ΔV is the Dirac voltage shift, Cox is the capacitive coupling of the back-gate for 285 nm thick thermal oxide (7 × 1010 cm−2 V−1), φphoton is the photon flux. As shown in 2 V−1 s−1, respectively. This is superior to graphene sensitized with PbS QDs−9 s , thus the photoconductive gain G=τlifetime/τtransit (the ratio of the lifetime of the trapped holes over the electron transit time from source to drain) is on the order of ∼105 using a trapped carrier lifetime of ∼100 μs. Therefore the gain-bandwidth product of our SWNT–graphene device is on the order of 1 × 109 Hz (given by the product of ∼105 gain and ∼104 Hz of bandwidth), which is quantitatively similar to the PbS QD–graphene hybrid photodetectorThe EQE  was estimated using the parallel plate capacitor model−1, a typical specification for commercial photodetectors. The responsivity value is higher for shorter wavelengths than for longer ones . The responsivities for various wavelengths are summarized in ger ones , consistThe essential ingredients of our devices are the sensitivity to external electrostatic in graphene conductivity, the broadband and tuneable photon absorption in both graphene and SWNTs, and the high-speed transportation of photocarriers in the planar SWNT–graphene hybrid. To resolve the impact tube diameters and chiralities may have on the photodetection processes, we fabricated control devices using highly purified metallic tubes and 6, 5) chirality-enriched semiconducting SWNTs. Quite different photodetection mechanisms were revealed . Figure , 5 chira5, but also a fast response time of ∼100 μs and an ultra-broadband sensitivity across visible to near-infrared, covering the telecommunication band at ∼1.5 μm. Benefiting from the solution processability of SWNTs, large-scale growth and transfer of graphene, as well as compatibility with standard photolithography, our devices exhibit great potential for use in photodetection applications requiring large sensing area, high photoresponsivities, video-frame-rate processing and substrate flexibility. The results demonstrated here represent a significant step towards facile and scalable fabrication of high-performance optoelectronic devices using all-carbon hybrid nanostructures and have substantial implications for fundamental investigation of the van der Waals interactions between layered materials and in-plane quantum wires, in the 1D limit.In summary, by combining large-area CVD grown graphene with atomically thin SWNT layer, we have formed a quasi-2D all-carbon hybrid film, which exhibits strikingly enhanced photodetection capabilities superior to either graphene or SWNTs. In contrast to previous charge trap based phototransistors, such hybrid film based photodetectors exhibit not only a significant photoconductive gain of ∼10N-methyl-2-pyrrolidone). The resultant suspensions are centrifuged with 10,000 g for 1 h before the supernatant is collected for the fabrication of SWNTs thin film on SiO2/Si wafer. CVD graphene is transferred on top of the SWNTs layer using the poly(methyl methacrylate) supported procedures. Electrodes are patterned by standard photolithography. Different metal composition (Ti/Au and Pd/Au) are subsequently deposited. The graphene channel is patterned by another photolithography and oxygen plasma etching.The graphene samples were grown on copper foil by CVD method, and Raman spectroscopy combined with optical microscope characterizations point to a defect-free single-layer sample. We use single-wall CNTs (SWNTs) from a commercial supplier (Carbon solutions Inc.). The phototransistors are fabricated as follows: SWNTs suspensions are produced by tip-sonicating 1 mg nanotube soot in 10 ml NMP (−6 torr) at room temperature and the data were collected by a Keithley-4200 semiconductor parameter analyzer. The temporal photoresponse was measured at 173 K for suppressing the outside interference.For photoresponse characterization, we used 405, 532, 650, 980 and 1,550 nm laser diodes, respectively. The beam is guided through an optical fiber with a FC/PC ferrule and is subsequently incident onto the channel of the devices without focusing. The beam at the device was measured to be Gaussian-shaped with a diameter of about 300 μm at 650 nm illumination. The area of the channel is <100 × 40 μm. Therefore, when calculating the photoresponsivity, we used only the portion of the incident light intensity that overlaps with the channel area. The electrical measurements were carried out in a closed cycle cryogenic probe station under vacuum .Supplementary Figures 1-8, Supplementary Notes 1-3 and Supplementary References


Numerous agents targeting PD-L1/PD-1 check-point are in clinical development. However, the correlation between PD-L1expression and prognosis of solid tumor is still in controversial. Here, we elicit a systematic review and meta-analysis to investigate the potential value of PD-L1 in the prognostic prediction in human solid tumors.Electronic databases were searched for studies evaluating the expression of PD-L1 and overall survival (OS) of patients with solid tumors. Odds ratios (ORs) from individual studies were calculated and pooled by using a random-effect model, and heterogeneity and publication bias analyses were also performed.A total of 3107 patients with solid tumor from 28 published studies were included in the meta-analysis. The median percentage of solid tumors with PD-L1 overexpression was 52.5%. PD-L1 overexpression was associated with worse OS at both 3 years  = 1.60 to 3.70, P < 0.0001) and 5 years  of solid tumors. Among the tumor types, PD-L1 was associated with worse 3 year-OS of esophageal cancer, gastric cancer, hepatocellular carcinoma, and urothelial cancer, and 5 year-OS of esophageal cancer, gastric cancer and colorectal cancer.These results suggest that expression of PD-L1 is associated with worse survival in solid tumors. However, the correlations between PD-L1 and prognosis are variant among different tumor types. More studies are needed to investigate the clinical value of PD-L1 expression in prognostic prediction and treatment option. Co‑stimulatory and co‑inhibitory receptors play a pivotal role in T cell biology, as they determine the functional outcome of T cell receptor (TCR) signaling and immune surveillance . HoweverHuman programmed death-ligand 1 (PD-L1 or B7-H1), as a dominant ligand, plays a central role in antigen-specific T cell response mediating PD-1-dependent immune suppression. The abnormal expression of these ligands has been linked with prognosis and treatment response of multiple malignancies. For instance, overexpression of PD-L1 has been observed in different solid tumors including melanoma , 6, coloDespite the clinical development of anti-PD-L1 therapies, the prognostic value of PD-L1 overexpression across different solid tumors is still unclear. Recently, it is reported that melanoma patients with PD-L1-expressing cells at the invasive tumor margin and inside tumors are more sensitive to anti-PD-1 therapy . AnotherHere, we present a meta-analysis evaluating the prognostic value of PD-L1 overexpression in solid tumor. The purpose of this study was to estimate the correlation of PD-L1 overexpression with survival in solid tumors, thereby shed more light on the development of PD-L1/PD-1 immune check-point targeted therapy and prognostic prediction.This meta-analysis was carried out in accordance with preferred reporting items for systematic reviews and meta-analyses statement .Pubmed, Web of Science and EBSCO were searched for studies evaluating the expression of PD-L1 and survival in solid tumors from 2002 to November 2014. The search terms included “programmed death-ligand 1” or “PD-L1” or “B7-H1” or “CD274” and “neoplasms” and the results were limited to human studies of solid tumors. In addition we used the entry “programmed death-ligand 1” or “PD-L1” or “B7-H1” or “CD274” and the name of each specific solid tumor to recognize additional studies. We identified a total of 350, 346 and 249 entries, respectively. Eligibility criteria were the measurement of PD-L1 by immunohistochemistry (IHC), availability of survival data for at least 3 years, and publication in English. Studies evaluating gene expression of PD-L1 measured by polymerase chain reaction were excluded from the analyses. Citation lists of retrieved articles were manually screened to ensure sensitivity of the search strategy. Study selection was based on the association of PD-L1 and survival. Inter-reviewer agreement was assessed using Cohen’s kappa coefficient. Disagreement was resolved by consensus.The primary endpoints were overall survival (OS) at 3 and 5 years. Tumors were classified by PD-L1 expression status using cut-offs as defined by individual studies.Two authors (Pin Wu and Dang Wu) independently extracted information using predefined data abstraction forms. The following details were extracted by 2 reviewers (Pin Wu and Dang Wu): tumor type, number of patients, antibody used for the evaluation, technique used to quantify PD-L1, and cut-off to determine PD-L1 positivity. Survival data were extracted from tables or Kaplan—Meier curves for both PD-L1 negative or low (control group) and PD-L1 positive or high expression .The relative frequency of survival at 3 and 5 years between the control and experimental groups was expressed as an odds ratio (OR) and its 95% confidence interval (CI). A number of sensitivity analyses were prespecified.2 statistics. Differences between subgroups were assessed using methods as previous described by Deeks et al [Data were extracted from the primary publications and analysed using RevMan 5.3 analysis software . Estimates of ORs were weighted and pooled using the Mantel—Haenszel random effect model. Statistical heterogeneity was assessed using the Cochran’s Q and Iks et al . SensitiThe search results have been shown in We identified 28 studies using IHC techniques for the assessment of PD-L1 expression. Characteristics of included studies are shown in A description of the antibodies used in the included studies is shown in 2 = 76%), so we conducted subgroup meta-analysis to explore whether the heterogeneity is due to different cancer types.A total of 25 studies reported data for OS at 3-years. Results showed that PD-L1 overexpression was associated with worse 3-year OS of solid tumors  . There wThree studies provided 3-year OS for lung cancer, 2 studies for hepatocellular carcinoma, 2 studies for melanoma, 2 studies for oropharyngeal squamous cell carcinoma, 4 studies for urothelial cancer, 3 studies for esophageal cancer, and 3 studies for gastric cancer. In the stratified analysis by cancer types, PD-L1 overexpression was associated with worse 3-year OS of esophageal cancer  , gastric2 = 79%), so we conducted subgroup meta-analysis according to different cancer types.A total of 25 studies reported data for OS at 5-years. Similar to the 3-year OS data, PD-L1 overexpression was significantly associated with worse 5-year OS of solid tumors  . There wFour studies provided 5-year OS for lung cancer, 3 studies for hepatocellular carcinoma, 2 studies for melanoma, 2 studies for oropharyngeal squamous cell carcinoma, 3 studies for urothelial cancer, and 3 studies for esophageal cancer. PD-L1 overexpression was associated with worse 5-year OS of esophageal cancer  , gastricRemoval of studies which did not report the PD-L1 antibody clone did not influence results for 3-year or 5-year OS . However, removal of the studies that did not report the cut-off value of PD-L1 overexpression increased the association between PD-L1 and worse 3-year and 5-year OS compared with PD-L1 low expression . Exclusion of these studies did not reduce heterogeneity for 5-year OS .PD-L1 overexpression has been observed in a substantial number of solid tumors. Moreover, numerous studies have demonstrated that PD-L1 plays a key role in cancer immune escape , 41. A dResults showed that overexpression of PD-L1 was associated with worse 3-year OS for all studies analyzed except for one study of melanoma and lung cancer, respectively , 11. StuA recent study reported that epithelial-originated cancer patients with positive expression of PD-L1 on tumor tissues were associated with significantly poorer OS when compared to those with negative expression of PD-L1 . Consist+ T cells distinctly located at the invasive tumor margin are associated with expression of the PD-1/PD-L1 immune inhibitory axis and may predict response to therapy [Besides, the PD-1 expression state of tumor infiltrating lymphocytes is another key point of the PD-1/PD-L1-mediated tumor immune escape. A recent study suggests that pre-existing CD8 therapy . Moreove therapy . The eviOur analyses show that overexpression of PD-L1 in solid tumor tissues, as measured by IHC, is associated with worse prognosis in different tumor types, which suggests that the development of strategies against the PD-L1/PD-1 axis would be a promising therapeutic approach for solid tumors. Moreover, further studies are required to investigate the potential role of PD-L1 expression in solid tumors for prognostic prediction as well as PD-L1 targeted treatment decision.S1 Fig(TIF)Click here for additional data file.S2 Fig(TIF)Click here for additional data file.S1 PRISMA Checklist(DOC)Click here for additional data file.


We predict the induction or suppression of magnetism in the valence shell of physisorbed and chemisorbed organic molecules on graphene occurring on the femtosecond time scale as a result of core level excitations. For physisorbed molecules, where the interaction with graphene is dominated by van der Waals forces and the system is non-magnetic in the ground state, numerical simulations based on density functional theory show that the valence electrons relax towards a spin polarized configuration upon excitation of a core-level electron. The magnetism depends on efficient electron transfer from graphene on the femtosecond time scale. On the other hand, when graphene is covalently functionalized, the system is magnetic in the ground state showing two spin dependent mid gap states localized around the adsorption site. At variance with the physisorbed case upon core-level excitation, the LUMO of the molecule and the mid gap states of graphene hybridize and the relaxed valence shell is not magnetic anymore. K points of the first Brillouin zone forming the Dirac cones9101215Graphene is a two dimensional crystalline allotrope of carbon with honeycomb lattice structure and has been extensively studied since its discovery in 2004123Pristine graphene does not display intrinsic magnetism and this limits its applications in magneto-electronics and active spintronics. This is due to the bipartite lattice structure of graphene explained by Lieb’s theorem181920212324272930et al., who showed that a rapid demagnetization is induced in Ni by using femtosecond optical pulses4041424346Time dependent effects in magnetism are an important topic of current interest. Ultrafast magnetization  has been investigated first by Beaurepaire 5H5N), 4-picoline radical (C6H6N) and pyridine radical (C5H4N), which are prototypes of different couplings with graphene. Interaction of pyridine with graphene is dominated by van der Waals forces, that of pyridine radical is mainly via chemisorption, while 4-Picoline radical is affected by both van der Waals forces and covalent bonding and represents an intermediate case between pyridine and pyridine radical. We evaluate the electronic properties for the molecules where the N atom is ionized and compare them to the ground state ones. We investigate how the electrons of the system relax around the core hole, inducing or suppressing magnetism in the valence shell depending on the type of adsorption.The motivation for this work is to understand the effect of core level excitations of adsorbed molecules on graphene, aiming at the limit where only one molecule in a diluted array of adsorbed species is core-excited. We take into account three molecules namely pyridine 484951For the excited state calculations, we use a pseudo-potential with a full core hole (FCH) created at the N 1s orbital of the molecule. We always consider a globally neutral system, where an additional electron is given to the valence shell56Eg and Em are the total energies of the isolated graphene substrate and of the gas phase molecule/radical, respectively. The adsorption energies are summarized in 5859pz orbitals of graphene as shown in π cloud remains almost parallel to graphene, at an angle of ~14° and at an average distance of 3.16 Å with respect to the substrate plane. Finally the pyridine radical, when adsorbed on graphene, forms a mostly covalent bond and orients itself perpendicular to the graphene plane as seen in aZ, defined as the height difference of the bonding carbon atom of graphene with respect to its nearest neighbours. This is visualized clearly in the acc). The results for the adsorption energies are better understood by taking pyridine radical as a reference. Picoline radical, in comparison, shows a lower value of acc and aZ, consistently with its lower reactivity. The more negative computed value of Eads is due to a stronger vdW interaction of its almost planar π cloud. In comparing pyridine molecule vs radical, we remark that in the case of covalently bonded systems on graphene, the deformation of the substrate requires a large energy cost that is lowering significantly the adsorption energy: almost 1 eV in similar systemsEads. Our effort will be to understand the effect of chemisorption and physisorption on the system magnetism in the ground and core excited states.We start by investigating the most stable configurations of pyridine, 4-picoline radical and pyridine radical adsorbed on graphene taking into account the translational as well as rotational degrees of freedom of the molecule. To check the stability of the system and quantitatively understand the energies involved during the adsorption process, we define the adsorption energy as To understand the electronic and magnetic properties of the system, we plot the total density of states (DOS) and that projected onto the molecular orbitals (MOPDOS). The latter is evaluated asδ function by a Gaussian function. The molecular states where In pyridine on graphene configuration as seen in z orbital is taken out of the π electron network2861μB magnetic moment. The molecule does not contribute directly to the formation of such states and magnetism is localized around the bonding site on graphene but on the other sublatticeBefore discussing the adsorption of 4-picoline and pyridine radicals on graphene, we recall that covalent adsorption of species bound to a C atom of graphene induces magnetism in the ground state of the system, as the respective pμB magnetic moment localized on the molecule. We remark that this magnetic configuration would occur upon 1s→LUMO excitation or, in case of photoionization, after the time needed to transfer an electron from graphene to the molecule to screen the core hole. As demonstrated by recent experiments for bipyridine molecules on grapheneWe are now in the position to study the electronic and magnetic properties for the three systems when a hole in the N 1s orbital of the molecule is created and one electron is added to the valence shell, as discussed in simulation details. The total DOS and the MOPDOS of the three molecules are shown in In the case of covalently bonded 4-picoline radical and pyridine radical, the system is magnetic in the ground state. Upon photo-ionization and relaxation of the valence shell around the core hole, the additional valence electron joins the one formerly in the midgap state and the system valence becomes spin degenerate. It remains so until the excited hole decays with a lifetime of a few femtoseconds. It is seen for the picoline and pyridine radical cases in Emin to Emax) is chosen to include either the MIDGAP-l or MIDGAP-h states. The ILDOS of the occupied MIDGAP-l and the unoccupied MIDGAP-h are plotted in π symmetry couples strongly with the facing pz orbitals of graphene which constitute the midgap states. This results in a larger energy splitting between the hybrid MIDGAP-l and MIDGAP-h states (0.55 eV) seen in the MOPDOS of μB magnetic moment, eventually occupying singly both MIDGAP-l and MIDGAP-h with the same spin. Such a configuration is less stable than the non-magnetic case by 0.36 eV. Relaxation towards the spin-compensated solution could occur by resonant transfer of two electrons with majority and minority spin to and from the surrounding graphene, respectively, provided this is faster than the core-hole lifetime.where the energy range , whose integral amounts to the additional valence electron. Let us consider first the results for physisorbed pyridine shown in ρ in terms of projection onto atomic orbitals according to Löwdin population analysis65ρ and noticing that larger charge lobes on graphene are depicted in ρ on the atoms of the molecule amounts to 63% for the 4-picoline radical and 59% for the pyridine radical cases.A further distinction between the different adsorption systems can be inferred by calculating the screening charge which is defined as Finally we remark that we deal with a local phenomenon independent of possible long range magnetic order. Given the limited extent of the core-level excitation, experiments to detect the local spin balance are conceivable when in the presence of the core hole, electrons are transferred from the substrate to the molecular LUMO levelWe have studied the magnetic properties of ground state and core-excited organic molecules on graphene from first principles. It is found that the adsorption mechanism plays an important role in inducing or suppressing magnetism in the valence shell of the system within the core hole lifetime. The physisorbed system where the interaction is dominated by van der Waals forces and initially non-magnetic in the ground state becomes magnetic when a core electron is excited. The system is magnetic until the core electron de-excites via one of the several electronic decay channels. An opposite behaviour can be appreciated when molecules are covalently bonded to graphene and the substrate is hence magnetic. Here magnetism is suppressed upon core electron excitation. The LUMO of the molecule hybridizes with the mid gap states of graphene forming spin-compensated bonding and anti bonding combinations. The valence shell remains non magnetic until the core electron de-excites. Since the time scale of the magnetism we are dealing with is in the order of a few femtoseconds and considering the recent advances in femtomagnetism and ultrafast measurements for adsorbed molecules, experiments complementing our work could soon be available.How to cite this article: Ravikumar, A. et al. Femtomagnetism in graphene induced by core level excitation of organic adsorbates. Sci. Rep.6, 24603; doi: 10.1038/srep24603 (2016).


Graphene exhibits unique 2-D structural, chemical, and electronic properties that lead to its many potential applications. In order to expand the scope of its usage, graphene hybrids which combine the synergetic properties of graphene along with metals/metal oxides and other nanostructured materials have been synthesized and are a widely emerging field of research. This review presents an overview of the recent progress made in the field of graphene hybrid architectures with a focus on the synthesis of graphene-carbon nanotube (G-CNT), graphene-semiconductor nanomaterial (G-SNM), and graphene-metal nanomaterial (G-MNM) hybrids. It attempts to identify the bottlenecks involved and outlines future directions for development and comprehensively summarizes their applications in the field of sensing and sensitized solar cells. Graphene exhibits extraordinary mechanical, thermal, and electronic properties such as high specific surface area per unit volume, high chemical stability, excellent thermal conductivity (up to 5000 W m−1 K−1)  , whose properties emerge in the axial direction, can be functionalized onto the surface of graphene, combining the properties of the two carbon allotropes in all directions while allowing for an increased active surface area and faster electron transfer kinetics. Similarly, combining metal/metal oxide nanoparticles (NPs) with graphene overcomes NP shortcomings of low stability and tendency to aggregate resulting in highly stable electrochemical sensing platforms for anchoring with good dispersion, excellent conductivity and catalytic properties of NPs. This transformation of 2D graphene into three-dimensional (3D) architectures expands the functionality of nanomaterials and serves as novel hybrid electrode material for applications in electronics , graphene-semiconductor nanomaterial (G-SNM), and graphene-metal nanomaterials (G-MNM) hybrid nanostructures based on graphene as a multifunctional platform. Nanoscale architecture is key for the performance of these novel materials, aspects such as size, geometry, chemistry of the building blocks, relative orientation of crystals, as well as the limitations and fabrication methods must be considered during development of devices that make use of graphene hybrids. Given their wide scope, we have briefly reviewed the applications of these graphene hybrids primarily in two of the most advanced fields, namely sensing and energy harvesting. This review shall enable the reader to realize the versatility graphene hybrid materials offer by virtue of their synergistic properties. Wherever applicable, the limitations of the present approaches and future research directions have been highlighted.assembly method synthesizes graphene and CNTs, SNMs, or MNMs separately and then assembles them together. The in situ method grows CNTs, SNMs, or MNPs directly on the graphene structures.Hybridization of graphene variants such as epitaxial graphene, graphene oxide (GO) or chemical vapor deposition (CVD) graphene, with CNTs, semiconducting nanomaterials (SNMs), and metal nanomaterials (MNM) can be done by two fundamentally different approaches. The This is a widely used method in graphene hybrid synthesis involving either self- or chemical assembly. Self-assembly is a technique based on the spontaneous organization that the components  undergo when encountered in a liquid media through simple physical dispersion. Chemical assembly uses a chemical linker or electrostatic interactions to assemble the components in a layer-by-layer-method to form lamellar architecture.2 structure to form a high surface area hybrid structure. Electrostatic or covalent assembly is carried out using highly oxygenated functional groups on GO or by introducing complementary functional groups in the sp2 lattice of CNTs and graphene through different chemistries.Graphene and CNTs interact via van der Waals forces or π –π interaction through their aromatic spGO prepared by Hummer's method has many oxygen containing functional groups and is therefore readily soluble in water. CNTs, however, tend to agglomerate in while suspended in water and surfactants are needed for uniform dispersion. The high dispersibility of GO in water and its π –π interaction with CNTs facilitates the dispersion of CNTs without use of surfactant. Additionally, the CNTs help prevent the restacking of GO sheet  with doctor-blade. The dried electrode was then treated with hydrazine vapor and annealed to completely reduce the GO.SNMs and graphene can be mixed in a liquid through mechanical stirring, bubbling, or sonication and induced into assembly by different interactions between the surfaces. GO is preferably used in aqueous reaction due to its hydrophilic nature compared to other forms of graphene. Yang et al.  preparedIntermolecular non-covalent forces, such as hydrophobic–hydrophobic/π –π interactions, between graphene and molecules with similar structure, like pyrene, can be used to graft semiconductor nanoparticles on graphene in suspension. Katsukis et al.  employed2 has been used to mediate the photochemical reduction of GO with simultaneous assembly of TiO2 NPs onto the surface of rGO, in a single step method that is environmentally friendly  were grown between the sheets using thermal pyrolysis of iron containing precursor to from a 3D pillared structure. 3D pillared structures made of CNTs in between parallel graphene sheets possess desirable out-of plane electronic transport and superior mechanical properties. They retain the intrinsic properties of the individual components and have improved surface area for applications such as immobilization of materials and electrolyte exchange through diffusion  and metal substrate (graphene growth) interaction, it may be necessary to use a two-step growth method. Specifically in the case of iron catalyst on copper foil it has been reported that CNT growth was difficult due to hindrance of the active catalyst surface by possible formation of Fe/Cu alloy , CVD, metal-organic vapor phase epitaxy (MOVPE), and atomic layer deposition (ALD) for the growth of SNM/graphene hybrids.CVD is one of the most common methods for ZnO growth on graphene, given the relatively low melting and boiling point temperature of Zn  by flowing oxygen and an organic Zn precursor in a gas phase reactor. The gas molecules break up when in contact with graphene surface and ZnO is immediately adsorbed onto the surface. This method results in highly crystalline material without defects such as stacking faults or dislocations .Yan et al.  synthesiin situ Cu2S/rGO hybrid 2, H2O, Na2S, and H2O, providing the ions for the CdS. The described stacking was repeated several times. Finally, the GO was reduced with hydrazine evaporation and annealed at 400°C  is a technique largely used for QD synthesis in variety of substrates. It has been combined with layer-by-layer to fabricate a stacked triple-composite with titania nanosheets (TNS), rGO, and QD (CdS). After one cycle of layer-by-layer stacking of TNS and GO, the material was subjected to the SILAR cycle, a successive immersion in solutions of Cd and produces AuNP on graphene  from redox center to the electrode.Enzymatic glucose biosensors primarily use glucose oxidase (GOx) which is stable and highly specific for glucose. Glucose oxidase catalyzes the oxidation of the glucose in the presence of oxygen to produce gluconolactone and hydrogen peroxide. Flavin adenine nucleotide (FAD) is the active center of the enzyme responsible for the redox reaction. First generation glucose biosensors electrochemically detect HDET is difficult to achieve with GOx enzyme on bare electrodes such as a glassy carbon electrode, as FAD is deeply embedded in the structure. Graphene based hybrids provide an efficient and highly conductive matrix for enzyme immobilization and faster electron transfer in achieving the DET for GOx without use of any mediator thus finding application in glucose sensing. Though exact mechanism by which theses hybrids achieve DET is unknown, proximity of highly conductive graphene and its 3D hybrids with superior electrochemical properties bring DET into reality. DET of GOx is characterized by the presence of FAD redox peaks in cyclic voltammetry with formal potential close to GOx standard electrode potential, i.e., between −0.4 and −0.5  (PLL) polymer as a linker. Cadmium sulfide (CdS) in the form of nanocrystals, hollow nanospheres, and nanoparticles have been successfully shown to achieve DET for the redox enzyme /graphene together yields a hybrid possessing electrochemical properties of metal and graphene and easy processibility of polymer. PANI provides compatible supporting matrices for both enzyme and AuNP   into electrical/optical signals for sensing. The large surface area and adsorptivity of SNM increases the electric response of sensors while graphene enhances adsorption of biomolecules and increases signal-to-noise ratio.2, wherein the resistance changes with varying H2 concentrations  , Surface-enhanced Raman Scattering (SERS), and Surface Plasmon resonance (SPR) phenomenon.Table Meng et al.  recently3 and NO2 has been reported with Ag/RGO composite with the lowest detection limit of 15 and 0.5 ppm by Phan and Chung , biomolecules (BSSC), and quantum dots (QSSC), deposited on a conductive transparent surface that conducts photogenerated electrons from the semiconductor into the external circuit.Sensitized solar cells (SSCs) have attracted considerable interest since Grätzel's group introduced nanostructured TiOGraphene in SSC has been applied in both photoanode and counter electrode, playing distinct roles. First, given its extremely high mobility, it can be used as transparent conductive film in the photoanode. As conductive film it would substitute currently used metal oxides, such as FTO and ITO, as it overcomes the disadvantages of the metal oxides, such as cost, sustainability, chemical and mechanical resistance, and higher transmittance in the near-infrared range , rGO and CdS QD has also confirmed the role of graphene in providing additional paths for electrons to be collected in the photoanode and a faster hole transport to the electrolyte, greatly suppressing electron-hole recombination (Yang et al., Son et al.  demonstr2/FTO counter electrode was 6.18%, only slightly lower than the 6.52% of a Pt counter electrode. Graphene's large surface area readily captures the electrons from redox couples in the electrolyte thereby easily reducing them. So, similar to its role as bridge as in the photoanode, the graphene facilitates electron transmission across the counter electrode/FTO interface. However, graphene absorbs light, therefore less light is reflected from the counter electrode and light harvesting efficiency is reduced in comparison to Pt. rGO/Cu2S on FTO has also been used as counter electrode for CdS/CdSe/ZnS QSSC by Radich et al. (2S exhibits higher photocatalytic activity toward polysulfide electrolyte reduction than Pt, and rGO platform stabilizes the nanoparticles, its large surface area promotes good dispersion and provides high number of reactive sites, while the good mobility serves to rapidly shuttle electrons to the Cu2S catalyst sites. The fill factor of the hybrid was increased in 75% in comparison to Pt, confirming the more efficient shuttling of electrons, resulting in one of the highest power conversion efficiency reported for liquid junction QDSSC.Graphene/SNMs also have been proven advantageous when used as counter electrode. Pt is a well-known counter electrode material due to its high electrocatalytic activity toward the most common electrolyte in SSC, iodide/triiodide. However, due to its scarcity and cost, finding inexpensive substitutes is crucial. A combination of highly electrocatalytic chalcogenide semiconductors and graphene on FTO have proven to be feasible substitutes for Pt (Liu et al., h et al.  and Santh et al.  with imp3−.Graphene-CNT hybrid materials have recently been studied for their use mainly as a counter electrode in SSC, but also as part of the photoanode and the electrolyte. Guang et al.  incorpor−3. The performance of Pt as counter electrode is hard to overlook, however, its high cost is a motivation to search for substitutes. Different architectures of the hybrid have been reported for this application that don't affect the performance of the cell significantly. Tripathi et al. (The main hybrid under this category is graphene-Pt, since Pt is the standard electrocatalyst for the reduction of Ii et al.  studied i et al.  reportedi et al.  has repoWhether as a transducer in mediatorless glucose biosensors, a photoactive material, electronic transfer aid, or charge collector platform, graphene's use has been steadily increasing and impacting modern day electronics. Hybridization of graphene with carbon nanomaterials and semiconductors can be performed by innumerable methods that continue to be discovered. Despite its excellent properties, graphene still has a long way to go before it can replace silicon or tin oxide films, largely because it's reproducibility and large scale production with process control of layer number still remain a challenge. When designing graphene hybrid materials great attention must be paid toward optimizing the intrinsic properties of the components simultaneously with the interface structure and mechanisms of electronic coupling, some of which are still unknown. As we have selectively reviewed the recent advances of graphene-CNT, graphene-SNM, and graphene-MNM hybrids with focus on sensing and energy conversion, it can be easily realized that this trend of using graphene hybrids with their multifunctionalities and multimodalities will continue to proliferate in fields of flexible electronics, medical diagnostics, chemical sensing, solar cells, and many other transduction devices.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.