This constitutes a demonstration of an optoelectronically active device integrated directly atop graphene and paves the way towards a generation of flexible highly performing hybrid two-dimensional (2D)/0D optoelectronics.The realization of low-cost photodetectors with high sensitivity, high quantum efficiency, high gain and fast photoresponse in the visible and short-wave infrared remains one of the challenges in optoelectronics. Two classes of photodetectors that have been developed are photodiodes and phototransistors, each of them with specific drawbacks. Here we merge both types into a hybrid photodetector device by integrating a colloidal quantum dot photodiode atop a graphene phototransistor. Our hybrid detector overcomes the limitations of a phototransistor in terms of speed, quantum efficiency and linear dynamic range. We report quantum efficiencies in excess of 70%, gain of 10 The combination of fast photo-response and high gain plays a pivotal role in photodetector devices. Here the authors combine a colloidal quantum dot photodiode with a graphene phototransistor to overcome the speed, quantum efficiency and linear dynamic range limitations of available phototransistors. These parameters eventually determine the sensitivity of a photodetector quantified via the specific detectivity D*. D* is defined as NEP is the noise equivalent power, R is the responsivity, A is the optically active area of the detector, fB is the noise bandwidth and Sn is the noise spectral density of the detector.A vast number of applications calls for highly sensitive detectors that can sense light from the ultraviolet to the short-wave infrared (SWIR) range, covering a broad spectrum of 300–3,000 nm24678EQE) of these systems is a trade-off between light absorption, which increases for thicker sensitizing layers, and charge transfer, which decreases for thicker layers as it is limited by carrier diffusion towards the graphene channel. This has limited the quantum efficiency to about 25% for an optimized layer of CQDs of thickness 80 nmGraphene's unique properties such as high charge carrier mobility, atomically thin profile and broadband absorption has made this material a very attractive platform for photodetectors11121418EQE as high as 70–80% (limited by reflection), a sub-millisecond temporal response, a gain-bandwidth product on the order of 108 and a linear dynamic range in excess of 110 dB. This highly performing detector also exhibits very high sensitivity with experimentally measured D* of 1 × 1013 Jones.In this letter, we address these three main challenges by presenting a photodetector architecture that is essentially a graphene–CQD photodiode and a high-gain phototransistor. This is realized by transforming the electrically passive sensitizing layer to an active one, where the electric field in the photodiode significantly enhances charge collection due to carrier drift instead of solely relying on diffusion. Our devices operate in the visible, near-infrared and SWIR range and show an Our photodetector platform integrates a CQD photodiode atop a graphene transistor. The CQD photodiode consists of an indium tin oxide (ITO) top-contact acting as the cathode of the CQD photodiode, whereas graphene acts as the hole acceptor contact and the charge transport channel for the phototransistor. VTD). Considering first operation without VTD: on carrier photogeneration in the CQD layer, holes are transferred to the graphene via drift from the narrow depletion region formed in the PbS QD solid near the graphene–QD interface and via diffusion further away from the quasi-neutral region. Prior studies have shown that efficient charge collection in this configuration occurs at an optimum thickness of 80–90 nm of PbS QDs, limited by the short carrier diffusion length22The essence of the device operation is captured in the band structure, shown in τlifetime is the carrier lifetime of the trapped electrons in the sensitizing centres of PbS QDs and τtransit is the transit time of holes in the graphene channel.where VTD bias extends the depletion region in the 300-nm-thick CQD layer, amplifying thus the zone of efficient charge collection and concomitantly quantum efficiency. This enhancement is evident in VBD) and the top-contact bias (VTD), and VTD=1.2 V, as compared with photoresponse at VTD=0 V. Further increase of VTD results in opposite effects and fully suppresses the photo-induced voltage change at VTD=4 V. This phenomenon is observed for any VBD value for both n-doped and p-doped graphene channel, and this is due to increased leakage current from the CQD photodiode (as discussed below). It is important to note that changing the potential of the top electrode induces a corresponding change in graphene doping; however, this change is weak and cannot account for the observed change in photocurrent. This is clear in VTD as a result of suppressed gating via the CQD layer. g/∂n) extracted from the corresponding resistance curves that is not affected by the electric bias of the top-contact, from which we conclude that the photoresponse enhancement is not due to increasing transconductance . To corroborate our findings we also extracted the EQE of the phototransistor using the formula−1) of photoconductive detectors:To quantify the impact of the e on VTD . For a pλ the wavelength, e the elementary charge, h is the Planck constant, c the speed of light, RΩ is the detector's resistance in dark and G is the photoconductive gain given by the ratio of carrier lifetime over the transit time. Here the carrier lifetime is governed by the time constant of the graphene–CQD–ITO photodiode response, in contrast with the case of the passive QD layer, in which carrier lifetime is determined by the sensitizing traps of the PbS QDs. To estimate the carrier lifetime τlifetime in our devices, we measured the photoresponse bandwidth of the phototransistor by sweeping the light modulation frequency fc as demonstrated in VTD, reaching an electrical 3 dB bandwidth of 1.5 kHz for the optimum VTD, which corresponds to an effective τlifetime of 106 μs. The time response of the graphene–CQD–ITO photodiode when measured independently yields a temporal response composed of two time constant components . This yields a photoconductive gain G on the order of 105 and gain-bandwidth product of >1.5 × 108 Hz. The extracted EQE of the phototransistor  and RΩ and compensate for the slight gating effect, induced by VTD bias. Considering first the passively sensitized photodetector  wafer using a direct laser writer lithography. Ti/Pd electrodes (2 nm/40 nm thickness) were e-beam evaporated at a base pressure 10−3 mbar and lifted-off in warm acetone bath.Metal contacts were designed on a precleaned Si/SiOCVD graphene grown on copper foil was transferred by a poly(methyl methacrylate) (PMMA)-assisted wet process onto the substrate with metal contacts. Ammonium persulfate was used to etch the copper substrate. After the transfer, the substrate with metal contacts and PMMA/graphene film was dried overnight at room temperature. PMMA was then removed by warm acetone, followed by annealing in forming gas at 300 °C to remove residues.2 plasma etching were used to pattern the graphene layer. Graphene stripes had dimensions of 70 × 10 nm with 10 × 10 μm area between V+ and V− electrodes.Laser writer lithography and Ar/OThe synthesis of PbS nanocrystals was carried out under inert conditions using a Schlenk line as previously described in literature31Electron beam lithography (EBL) was used to pattern 30 × 30 μm windows in PMMA resist at the centre of the graphene Hall bars. Desired PbS CQDs were then spin-coated right on the PMMA. Lift-off in warm acetone performed directly after spin-coating removed PMMA together with the excess of CQDs. As a result, the CQDs remained only in the areas defined by the lithography. The areas were designed to ensure isolation of the graphene channel from the ITO electrode introduced next and to fully cover the central region of the graphene Hall-bar.−1 in octane) was spin-cast onto the substrate at 2,500 r.p.m. for 15 s. Deposition of each layer was followed by spin-casting of EDT solution (2 vol.% in isopropanol) and two rinse-spin steps with octane and isopropanol. All the spin-coating steps were performed under ambient condition and at room temperature. The resulting thicknesses of nine PbS–EDT layers were 300±20 nm, as determined by a profilometer (Alpha-Step IQ).PbS QD layers were fabricated by layer-by-layer spin-coating. For each layer, PbS solution  to form a transparent electrode on top of the PbS layer. EBL lithography allowed to form the overlapping area of ITO, CQD and graphene precisely between the V+ and V− electrodes and avoid shortening of ITO and graphene channels. Each fabricated chip contained up to seven devices with top-electrodes.−3 mbar) to improve the device stability. Device illumination was done through a viewport by a 635 nm wavelength diode laser, modulated with a mechanical chopper or turned on and off. The laser was coupled to a digital variable optical attenuator to provide output power tunability. In addition, a supercontinuum Vis/NIR laser (SuperK Select) was used to measure photoresponse spectra. Ithaco 1211 amplifier was used to measure ITD. Ithaco 1201 and Stanford SR810 amplifier were used for voltage read-out of photoresponse in combination with a mechanical light chopper with 250–3,000 Hz range.All transport measurements were carried out at room temperature, in a shielded enclosure and vacuum , where n is the charge carrier concentration in graphene, by taking a derivative of the RΩ (VBD) curve. Capacitive coupling of the 285-nm-thick SiO2 gate is 7 × 1010 cm−2 V−1.We calculate the transconductance of our phototransistor  and negative (hole) transconductance maximums using: ∂σ/∂n=e × μ, where e is elementary charge. Maximum transconductance of 2.4 S cm2 corresponds to 1,500 cm2 V−1 s−1 of electron mobility in graphene.Charge carrier mobility τtransit of charge carriers in the graphene channel is calculated as:Transit time The data that support the findings of this study are available from the corresponding authors upon request.How to cite this article: Nikitskiy, I. et al. Integrating an electrically active colloidal quantum dot photodiode with a graphene phototransistor. Nat. Commun. 7:11954 doi: 10.1038/ncomms11954 (2016).Supplementary Figures 1-5 and Supplementary Note 1


The resistance of WO3−x crystal sensors in response to relative humidity could be tuned from a negative to positive one by increasing the compositional x. And it was revealed that the positive humidity impedance was driven by the defects of oxygen vacancy. This result will extend the application field of humidity sensors, because the positive humidity impedance sensors would be more energy-efficient, easier to be miniaturized and electrically safer than their negative counterparts for their lower operation voltages. And we believe that constructing vacancies in semiconducting materials is a universal way to fabricate positive impedance humidity sensors.Resistivity-type humidity sensors have been investigated with great interest due to the increasing demands in industry, agriculture and daily life. To date, most of the available humidity sensors have been fabricated based on negative humidity impedance, in which the electrical resistance decreases as the humidity increases, and only several carbon composites have been reported to present positive humidity impedance. However, here we fabricate positive impedance humidity sensors only via single-component WO Resistivity-type humidity sensors, which can perceive and record the change in electrical resistance in response to that in environmental humidity, have been investigated with great interest due to the increasing demands in industry, agriculture and daily life1234672S, O2, NOx, COx, NH3 and so on12132O (humidity) based on WO3 (the only reported tungsten oxide based sensors in literature) are WO3 nanowire humidity sensor on chip manufactured using CMOS-MEMS technique3 thin-film sensor fabricated using deposition technology3 composites2O3 and WO33 composites3 to relative humidity (RH) is generally attributed to the water dissociative chemisorptions process that would result in the formation of hydroxyl groups on the surface of WO3 crystals; and then, electrons are accumulated on the WO3 surface. As a result, the resistance of WO3 crystals decreases with increasing RH17In sensing materials, semiconductor metal oxides are one of the most promising candidates for solid-state chemical sensors due to their high sensitivity, and quick response and recovery93−x crystals with a variety of oxygen-deficient stoichiometries, such as WO2.72, WO2.8, WO2.83 and WO2.9, can be easily prepared, since they are stable, ordered phases with precise stoichiometries. And the early studies revealed that oxygen vacancy can consistently account for the defect level and trap assisted conduction in semiconducting oxides2122233 would be affected by water vapor when the experiments were performed in air. These facts inspire us to design and fabricate various WO3−x humidity resistors in which the different densities of oxygen vacancy might induce and modulate the humidity sensitivity.Furthermore, unlike most of the oxygen-deficient metal oxides, which are not stable , WO3−x) nano-/micron-structures (NMS) only by heating WO3 powder in S atomsphere in a vacuum tube furnace, and with the structured WO3−x crystals, humidity sensors were fabricated simply by screen-printing them onto ceramic substrates with Ag-Pd interdigital electrodes. Surprisingly, a positive humidity-sensitive property was found in the sensors prepared by single-component WO3−x crystals with high density of oxygen vacancies. And the resistance of WO3−x crystal sensors in response to relative humidity could be tuned from a negative to positive one by increasing the compositional x. We believe that our method not only provides a new avenue for fabricating highly effective positive humidity sensors by various metal oxides, but also creates a powerful platform to understand and design desirable semiconducting oxides humidity sensors. In addition, the findings on the positive resistance characteristics of single-component material humidity sensors can not only extend the application of humidity-sensitive resistor in different types of miniaturized devices, but also enrich and compensate for the humidity-sensing principles.Therefore, here we developed an approach to prepare oxygen-deficient tungsten oxides . The XRD pattern of the sample prepared at 1050 °C matches well with that of the monoclinic W19O55 . And the sample synthesized at 1150 °C consists of monoclinic W18O49 . However, the diffraction peaks of their corresponding annealed samples are all well assigned to those of the identical phase, monoclinic WO3 (JCPDS card no. 43-1035).After a systematical investigation7/2 and W4f5/2 lines, respectively, which can be assigned to those of the W6+ oxidation state7/2 and W4f5/2 lines, respectively, which can be attributed to those of the W5+ oxidation state7/2 line at 32.7 eV and W4f5/2 at 35.2 eV, indicating the existence of W4+ oxidation state on the sample surface6+ over W5+ and W4+ in the spectra, it was calculated that the formula of the three samples are WO2.9 (synthesized at 950 °C), WO2.89 (at 1050 °C) and WO2.72 (at 1150 °C), respectively, in which the mean valence of their W ions decreased from 5.58 to 5.27  analysis was carried out. The results are shown in 5.27 see . In addi3−x crystals exhibit a sharp signal at g =  2.28, while that of WO3 presents no obvious signals. The signal of the present oxygen-deficient WO3−x compounds could be attributed to oxygen vacancies. In literature, it was reported that the peak assigned to oxygen vacancies in metal oxides always has a g factor of 2.012829303−x compounds is more complex. Di Valentin and Pacchioni3−x, indicating that sometimes the oxidation state of the under-coordinated W ions is still formally of a chemical valence of + 6, while two extra electrons are trapped in the vacancy voids, which can be explained by the following synthetic expression: W6+/VO(2e−)/W6+ (VO is the oxygen vacancy). Thus, the shift of the g value for the present oxygen-deficient WO3−x compounds to a higher one might be owing to the presence of two charge centers (two unpaired electrons) trapped in the oxygen vacancy. Moreover, the sharp g signal of metal oxides becomes stronger with increasing concentration of oxygen vacancies2829303−x compounds, as the value of x increased, the sharp g signal gets stronger and stronger, indicating that the density of oxygen vacancies in them increases. But there is no signal in the ESR spectrum of WO3, implying that the annealed samples were almost completely oxidized, containing very little or even no oxygen vacancies. This result is also in good agreement with the XPS spectra.The electron spinning resonance (ESR) spectra of the as-prepared tungsten oxides NMS recorded at room temperature are displayed in 3−x crystals , the sensors fabricated with WO2.72 present the lowest impedance, and the impedance of the sensors fabricated with WO2.89 is lower than that with WO2.9, while the resistance of the sensors with WO3 is the highest. That is to say, under low RH environment, the higher the density of oxygen vacancies in tungsten oxide crystals, the lower the impedance of the senores fabricated with them, which is similar with the conduction behavior of many semiconducting oxidesThe dependence of impedance on RH was measured for the sensors fabricated with the obtained WOtals see , in whic2.72 NMS increases remarkably at low humidity (11~75% RH), and still increases somewhat at higher humidity (75~95% RH), presenting a completely positive resistance sensitivity to RH. With decreasing density of oxygen vacancies in tungsten oxide crystals, however, the fabricated sensors will present different sensing behaviors. The sensors fabricated with the as-prepared WO2.89 nanorods exhibits a positive resistance response to humidity in the range of 11–85% RH with slightly increased resistance. But at the humidity higher than approximately 85% RH, a negative response could be observed in such sensors, presenting an extreme point there (see the inset of 2.9 nanorods), the response curve recorded from the sensors still exhibits a similar sensing profile with that of WO2.89 sensors, but the extreme point was found at a lower humidity of about 54% RH. When it comes to WO3 NMS, with increasing RH, the impedance of the sensors fabricated with the annealed NMS rapidly decreased monotonously, presenting a completely negative resistance characteristic to RH, which is in accordance with the already reported humidity sensitivity of the sensors fabricated with other forms of WO3 materials153−x samples with x >  0.11 in this study), they will present a completely positive humidity-sensitivity in the entire RH range (here from 11–99%). With a medium x (0.1 ≤  x ≤  0.11 in this work), they will exhibit a positive humidity-sensitive property at low RH, but still a negative one at high RH. In such case, the extreme point may gradually move to a lower RH with decreasing x. When the density of oxygen vacancies is low (in samples with x <  0.1), for example with x =  0 as in the present WO3 NMS, the fabricated sensors may show an almost completely negative humidity sensitive characteristics in the entire RH range.Moreover, from 2.72 and WO2.89 increased, showing a positive resistance characteristic, but the humidity-sensitive resistors fabricated with WO2.9 and WO3 presented a negative humidity impedance characteristics, i.e., the impedance of the sensors decreased as the humidity increased. For the sensors with WO2.72, the impedance increased from 6.9–26 kΩ, presenting a gain of 276.8% as the humidity increased from 11–95% RH. As the density of oxygen vacancies decreased, the impedance gain of the fabricated sensors would decrease. For example, the sensors with WO2.89 still had a gain of about 33% with the impedance from 837–1114 kΩ. But when it comes to WO2.9, the impedance of the as-fabricated sensors decreased from 936–627 kΩ under similar RH environment. And the resistance of the sensors with WO3 even presented a sharp decrease from 20716–424 kΩ  and their recovery time  can be calculated. 3−x crystals, both of the response and recovery times changed dramatically as the environment humidity varied. The response time of the sensors with WO2.72 NMS was about 6 s, indicating that such sensors have a very good response to humidity, which is comparable with those of the well-known WO3 based sensors17183 NMS also displayed a smiliar, quick response time of 4 s in the humidification process. But for the sensors with WO2.89 and WO2.9 NMS, they should take a longer response time  in the humidification process. The sensors with WO2.72 or WO3 NMS would display a quick response time, because both of them simply present a completely positive or negative humidity sensitive characteristics in the entire RH range (11–99% RH). However, because the sensors with WO2.89 and WO2.9 NMS exhibit a positive humidity-sensitive property at low RH but still a negative one at high RH, their response times become longer. This phenomenon might be correlated with the strong competition between the oxygen vacancies induced positive humidity sensibility and water-related negative humidity sensitive property. As for the recovery time of the sensors fabricated with the obtained WO3−x crystals, as shown from the 3 is generally smaller than the one of hydroxyl groups from the oxygen vacancies33From the response and recovery characteristic curves as shown in 2.9 , the oxygen vacancies induced electrical conduction of the sensors is the primary mechanism at low humidity (lower than 85% RH), but the water-related electrolytic conduction would become dominating at high humidity (85–95% RH in this case), thus resulting in the turning point of impedance at 85% RH. As the density of oxygen vacancies is further reduced, the turning point of the sensor impedance will move toward a lower humidity (here at 54% RH for the WO2.9 sensors), and even disappear, presenting a totally negative humidity impedance characteristic (as shown in the present WO3 sensors).On the other hand, for the sensors with the present structured oxygen-deficient WO3−x crystalline NMS of different densities of oxygen vacancies. The resistance of WO3−x crystal sensors in response to relative humidity could be tuned by changing the compositional x. When the density of oxygen vacancies is high (in WO3−x samples with x >  0.11 in this study), they will present a completely positive impedance humidity-sensitivity in the entire RH range (here from 11–99%). With 0.1 ≤  x ≤  0.11, they will exhibit a positive impedance humidity-sensitive property at low RH, but still a negative one at high RH. In such case, the extreme point may gradually move to a lower RH with decreasing x. When the density of oxygen vacancies is low (in samples with x <  0.1), for example with x =  0 as in the present structured WO3 crystals, the fabricated sensors may show an almost completely negative impedance humidity sensitive characteristics in the entire RH range. Moreover, the sensors fabricated with WO2.72 crystals possess high sensitivity with a short response time of about 6 s, a recovery time of approximately 100 s and the largest humidity hysteresis of about 45.8% at 33% RH. The humidity sensitivity of the present tungsten oxides sensors may be controlled by the combination of oxygen vacancy induced electrical conduction and water-related electrolytic conduction.In summary, humidity sensors were successfully fabricated with WO3 powder  was loaded in a quartz boat located at the center of the furnace, while another boat with 1 g Aladdin-reagent S powder was located at the upstream from the WO3 powder. Before heating, the quartz tube was evacuated and flushed with Ar gas repeatedly for several times to deplete the residual gases. Then the furnace was heated up to the selected temperatures of 950, 1050 and 1150 °C with a dwelling time of 1 h. After that, the furnace was cooled down naturally to room temperature. Finally, powder-like products could be collected. For the purpose of comparison, a portion of the collected powders was annealed in air at 500 °C for 2 h in a muffle furnace.To fabricate the proposed tungsten oxides NMS, a high-temperature thermal evaporation process via a horizontal quartz tube furnace was usedg value calibration.The morphology of the obtained samples was examined by a field emission scanning electron microscope . The chemical composition was measured by an energy-dispersive X-ray (EDX) spectroscope attached to the SEM. The phase structure and composition were identified by XRD  in continuous scanning mode with a rate of 6°/min. The chemical state of the elements in the samples was investigated by XPS , and the results were calibrated by C1s line . The unpaired electron and defect in the samples were investigated by ESR  at room temperature with a microwave frequency of 9.44 GHz. Diphenylpicrylhydrazyl was used for the 3−x materials.Extended Data 2, Mg(NO3)2, NaCl, KCl and KNO3, which could present a relative humidity at 25 °C of approximately 11%, 33%, 54%, 75%, 85% and 95%, respectively. In typical measurement, each sensor was soaked at 25 °C in an atmosphere of different RH levels in the six chambers with different salt solutions till it reached the adsorption-desorption equilibrium for water, and then the impedances of the sensors with the RH and time were measured, respectively.The characteristic humidity sensitivity of the as-fabricated sensors, including impedance vs. relative humidity, response property and humidity hysteresis, was examined by a Keithley 2410 analyzer (USA). During the measurement, the applied operation voltage was AC 1 V and operation frequency was 1000 Hz. And the controlled humidity environment was achieved by a series of super-saturation aqueous solutions with different salts of LiCl, MgClHow to cite this article: Qian, J. et al. Positive impedance humidity sensors via single-component materials. Sci. Rep.6, 25574; doi: 10.1038/srep25574 (2016).


There is a huge interest in doped graphene and how doping can tune the material properties for the specific application. It was recently demonstrated that the effect of doping can have different influence on the electrochemical detection of electroactive probes, depending on the analysed probe, on the structural characteristics of the graphene materials and on the type and amount of heteroatom used for the doping. In this work we wanted to investigate the effect of doping on graphene materials used as platform for the detection of catechin, a standard probe which is commonly used for the measurement of polyphenols in food and beverages. To this aim we compared undoped graphene with boron-doped graphene and nitrogen doped graphene platforms for the electrochemical detection of standard catechin oxidation. Finally, the material providing the best electrochemical performance was employed for the analysis of real samples. We found that the undoped graphene, possessing lower amount of oxygen functionalities, higher density of defects and larger electroactive surface area provided the best electroanalytical performance for the determination of catechin in commercial beer samples. Our findings are important for the development of novel graphene platforms for the electrochemical assessment of food quality. Heteroatom doped graphene has been lately considered as an ultimate candidate for numerous applications due to the possibility to tailor the material characteristics and to improve the physicochemical, optical, structural and electronic properties123456791012131412In this work we investigate the effect of heteroatom doping on the detection of catechin, a polyphenol generally used as an index of food and beverage quality. A part from traditional techniques based on tedious and expensive chromatographic analysis161719We found that, for the examined case, the best electroanalytical response was provided by the undoped graphene which was the material possessing the highest C/O ratio and the largest D/G ratio and electroactive surface area as compared to both heteroatom doped graphene materials. This opens new possibilities in the choice of the best suited graphene platform for electrochemical applications.Glassy carbon (GC) electrodes, (diameter = 3 mm), Ag/AgCl reference electrode and platinum counter electrode were obtained from CH Instruments . Boron – doped diamond electrode with a doping level of 1000 ppm of B and an H terminated surface was purchased from Windsor Scientific.N,N-dimethylformamide (DMF), hydrochloric acid (37%), ethanol, sodium hydroxide, sodium chloride, sodium phosphate monobasic, sodium nitrate, potassium phosphate dibasic, potassium permanganate, potassium chloride, and (+)-catechin hydrate were purchased from Sigma Aldrich (Singapore). Milli-Q water (resistivity: 18.2 MΩcm) was used throughout the experiments. Beer samples were obtained from a local supermarket. Sample n.1 and sample n.2 are lager beers from different brands whilst sample n.3 is a stout beer.Graphite was provided by Asbury Carbons. Fuming nitric acid (>90%) was purchased from by J.T. Baker. Sulfuric acid (95–98%), potassium chlorate (98%), hydrogen peroxide (3%), A μAutolab type III electrochemical analyzer  connected to a personal computer and controlled by General Purpose Electrochemical Systems, GPES Version 4.9 software (Eco Chemie) was used to perform differential pulse voltammetry measurements.A Thermoscientific Finnpipette  was employed for the electrode modification with graphene materials.Thermally reduced graphene was prepared first by synthesising graphite oxide through the Staudenmaier method−1. The sample was flushed with nitrogen repeatedly before it was inserted by the magnetic manipulator into the preheated furnace and held for 3 minutes. The nitrogen flow rate was maintained at 1000 °C min−1 to remove any exfoliation by-products from the procedure.Thermally reduced graphene was prepared by introducing 0.2 g of graphite oxide into a quartz capsule connected to a magnetic manipulator, which was inside a vacuum tight tube furnace with controlled atmosphere. The magnetic manipulator created a temperature gradient of over 1000 °C min3Et2O). Exfoliation was performed in a bubbler filled with the liquid boron precursor at 20 °C and 1000 mbar. Nitrogen carrier gas with a flow rate of 100 mL/min was used and dilution was performed with 1 L/min nitrogen and hydrogen/nitrogen mixture (0.5 L/min N2 and 0.5 L/min H2). The reactor was continuously flushed with nitrogen and the flow of boron precursor was stabilised for 5 minutes before it was introduced into the hot region of the reactor. Exfoliation was then performed for 12 minutes at 1000 °C.Boron-doped graphene (BDG) was prepared from graphite oxide synthesized through Staudenmaier method. Graphite oxide was thermally exfoliated in the presence of a boron precursor, namely boron trifluoride diethyl etherate  into a flask under continuous stirring. The mixture was cooled in an ice bath before the addition of 15 g of potassium permanganate. Vigorous stirring was maintained for 2 hours to obtain a homogenous solution. After that, the mixture was cooled down and then reheated to 35 °C for 30 minutes. Subsequently, the mixture was diluted with 250 mL of deionised water and it was further heated to 70 °C. The temperature of the mixture was maintained for 15 minutes before it was further diluted with 1000 mL of deionised water. The removal of unreacted manganese dioxide and potassium permanganate was carried out by adding hydrogen peroxide (3%) into the mixture and decanting. Repeated centrifugation and redispersion into distilled water was performed with barium nitrate until a negative reaction to sulphate ions was observed. Graphite oxide slurry was then dried at 60 °C for 48 hours in a vacuum oven.Nitrogen-doped graphene was prepared by exfoliation of produced graphite oxide in ammonia atmosphere. A quartz glass capsule was filled with 100 mg of graphite oxide before it was connected to a magnetic manipulator and placed in a horizontal quartz glass reactor. The reactor was flushed continuously with nitrogen before it was introduced into the hot region. Then the nitrogen flow was changed to ammonia. The temperature of the mixture was maintained for 12 minutes at 600 °C and the ammonia flow rate of 300 mL/min was used to remove any exfoliation by-products. The synthesised thermally reduced graphene (TRG), boron-doped graphene (BDG) and nitrogen-doped graphene (NDG) were ultrasonicated for few minutes before each use. After ultrasonication, 1 μL of the material was deposited onto the surface of a glassy carbon (GC) working electrode. The solvent was left to evaporate at room temperature in order to obtain a randomly distributed film of the desired material on the electrode surface. After each measurement the surface of GC was cleaned by polishing with 0.05 μm alumina powder on a polishing cloth.Electrochemical experiments were performed in a 4 mL voltammetric cell at room temperature (25 °C) using a three electrode configuration.Differential pulsed voltammetry parameters used for the experiment were applied as follows: 3 s equilibration time, 50 ms modulation time, 0.5 s interval time, 25 mV modulation amplitude, and 4 mV step. The raw data obtained were treated by a baseline correction with a peak width of 0.01, using GPES software. Measurements were performed in a 4 mL solution containing various concentrations of standard analyte in 100 mM phosphate buffer solution (PBS) at pH 7.3. Catechin hydrate in increasing concentrations from 1.2 μM to 12.0 μM was used for the measurements, similarly to previous findingsThe analysis of commercial lager beer sample was performed by using a dilution factor of 1:10. Standard addition method was used for the analysis of real samples.In this study we wanted to compare the electrochemical performance of undoped and doped graphene platforms namely thermally reduced graphene (TRG), boron doped graphene (BDG), and nitrogen doped graphene (NDG) for the detection of catechin, an important polyphenol which is correlated to food quality. Unmodified glassy carbon (GC) electrode and boron doped diamond (BDD) electrode were also used as reference materials. We wanted to investigate if the presence of heteroatoms with different electronegativity could have an influence on the electrochemical response provided by the graphene platform, as it could be expected from previous works1213141524−1 is correlated to the presence of defects due to sp3 hybridized carbon whilst the G band at around cm−1 1560 indicates the sp2 hybridized carbon. The ratio between the intensities of D and G band provide information on the degree of disorders in the carbon structure of the material. As depicted in In order to gain more insight into the material properties, characterization was performed by XPS, Raman spectroscopy and prompt gamma-activation analysis−2 cm2 for GC, 2.58 × 10−2 cm2 for BDD, 4.72 × 10−2 cm2 for BDG, 8.62 × 10−2 cm2 for NDG and 1.78 × 10−1 cm2 for TRGk0 = 2.30 × 10−4 cm s−1, k0 = 2.03 × 10−4 cm s−1, k0 = 1.73 × 10−2 cm s−1, k0 = 6.49 × 10−2 cm s−1, k0 = 4.63 × 10−2 cm s−1 for GC, BDD, BDG, NDG, and TRG respectively. To summarize the characterization results, TRG is the material with lowest content of oxygen functionalities, highest amount of structural disorders and largest electroactive surface area.Moreover, from a previous electrochemical study to evaluate the electroactive surface area of all materials, the following results were obtained: 2.28 × 10The oxidation of catechin occurs sequentially at the catechol and resorcinol group respectivelyThe oxidation process is pH dependant, with a shift towards lower oxidation potentials when the pH of the solution is increased from 3.5 to 8.03 hybridized carbon and therefore lacks of the sp2 network that would be necessary to form π-π stacking interactions with the aromatic polyphenol used as probe. Such interactions, which are very likely to occur on both doped and undoped graphene materials, are able to promote an accelerated heterogeneous electron transferThe observed trend could be attributed to the structure of BDD which contains sp2) and the peak width at half height (W1/2) are consolidated in −1 on TRG, followed by BDG at 88.283 nA μM−1, NDG at 81.282 nA μM−1, GC at 68.267 nA μM−1 and finally BDD at 1.6946 nA μM−1.The response from the oxidation of catechin on bare GC, BDD, TRG, BDG and NDG was studied between 1.2–12.0 μM and the voltammograms were displayed in 2 ≥ 0.9797 for all graphene platforms. The influence of different materials on peak width at half height (W1/2) for 12.0 μM catechin was also investigated to correlate the parameter to the selectivity of the materials in the presence of interferences. With the data collated, BDD has the highest W1/2 while the other materials have similar W1/2 with slight improvement for TRG and NDG as compared to GC.Overall, both undoped and doped graphene materials showed enhanced sensitivity on the detection of catechin as compared to bare GC, whilst among the doped graphenes, BDG showed a better sensitivity than NDG. All materials presented good linearity of response with RAs observed form the material characterization, TRG showed the lowest content of oxygen functionalities, the highest amount of structural disorders and the largest electroactive surface area. All these factors contributed to improve the material electroanalytical performance, thus resulting in enhanced sensitivity of the electrochemical signal. As for a comparison between the doped graphenes, BDG showed better calibration sensitivity as compared to NDG despite the lowest amount of defects and electroactive surface area presented by the former. Clearly, among the doped graphenes, the electrochemical response is mostly influenced by the kind of heteroatom rather than the properties of the materials. In fact, as recently demonstrated, the favourable thermodynamic interactions between the electron withdrawing boron and the electron donating oxygen groups of the analysed probe strongly influences the oxidation processGiven the best electrochemical performance of TRG in terms of sensitivity, selectivity and linearity of response, the material was chosen for the application to real sample analysis.2 ≥ 0.9589) and repeatability of results (RSD ≤ 10.44%) were achieved.The results obtained for three commercial beer samples and represented as catechin equivalents are depicted in Finally, in order to confirm the selectivity of the response towards catechin in real samples, a study on TRG was performed by measuring the concomitant current response of luteolin, another polyphenol present in beer. As it can be seen in 2 network which favours the interactions with the analyte by π-π stacking. As a result of that, an increased intensity of the peak current and a lower oxidation potential was observed on both undoped and doped graphene platforms.We investigated the influence of structural properties of doped and undoped graphene materials on their electrochemical performance for the assessment of catechin, a standard polyphenol commonly used as index of food quality. We observed that in general, graphene materials show an enhanced electroanalytical response when compared to bare glassy carbon and boron doped diamond electrodes. This is because of the larger electroactive surface area they possess, together with the spOverall, the undoped graphene namely thermally reduced graphene (TRG) provided the best analytical performance in terms of sensitivity, selectivity and linearity of response due to the intrinsic properties of the material such as lower content of oxygen functionalities, higher amount of structural disorders and larger electroactive surface area as compared to doped graphenes. We demonstrated that in the reported case, the outstanding material properties play a major role towards the oxidation of catechin rather than the nature of heteroatom used for the doping. In addition we found out that within the heteroatom doped materials, the best performance was provided by the boron doped graphene because of the favourable effect of boron in promoting the thermodynamic interactions between the analytical probe and the graphene platform. Finally, we demonstrated the suitability of TRG platform for the real sample analysis by determining the amount of polyphenols, expressed as catechin equivalents, in three commercial beer samples. These findings provide an insight into doped and undoped graphene suitability for food science application.How to cite this article: Chng, C.E. et al. Doped and undoped graphene platforms: the influence of structural properties on the detection of polyphenols. Sci. Rep.6, 20673; doi: 10.1038/srep20673 (2016).


Advanced electron microscopy and spectrum-imaging techniques were used to investigate the Co/Al2O3/graphene/SiO2 interfaces. Direct observation of pinhole contacts was achieved using FIB cross-sectional lamellas. Spatially resolved EDX spectrum profiles confirmed the presence of direct point contacts between the Co layer and the graphene. The high surface diffusion properties of graphene led to cluster-like Al2O3 film growth, limiting the minimal possible thickness for complete barrier coverage onto graphene surfaces using standard Al evaporation methods. The results indicate a minimum thickness of nominally 3 nm Al2O3, resulting in a 0.6 nm rms rough film with a maximum thickness reaching 5 nm.We report a detailed investigation of the structural and chemical characteristics of thin evaporated Al Concomitantly, the spin relaxation time was also enhanced by more than ninefold, reaching 771 ps at room temperatureet al.141314151617ca. microsecond)13413Graphene is a potential material for spintronic applications because of the combination of its expected long spin lifetime and high electron mobility. The spin diffusion distances observed in graphene are very long; i.e., few micrometers at room temperature1234513489et al.1et al. also evaluated the influence of barrier roughness on the spin relaxation mechanisms by using molecular beam epitaxy MgO and TiO2 seed layers as an alternative for the fabrication of smoother barrier layers on grapheneet al. demonstrated the use of sputtering to deposit continuous 1-nm-thick Al2O3 onto graphene, but this technique damaged the graphene structure and hence reduces the applicability of such an approach1522Tombros 2O3 barriers with variable thickness grown onto single-layer graphene sheets. Advanced electron microscopy and spectrum-imaging techniques were used to investigate the Co/Al2O3/graphene/SiO2 and Co/graphene/SiO2 interfaces. A direct cross-sectional observation of barrier pinholes is reported as well as results concerning the minimal barrier thickness necessary for complete graphene coverage using standard Al evaporation. The results are compared with standard thin Al2O3 deposition onto SiO2/Si substrates.In this work, we report a detailed investigation of the structural and chemical characteristics of traditional thin evaporated Al2O3 barrier samples were analyzed systematically by advanced (S)-TEM techniques. 2O3 barrier thicknesses. The analyses included two substrate regions: with and without graphene. It is important to notice that each Al2O3 barrier sample presents regions with and without graphene at the same substrate, leading to the same nominal barrier deposition for both graphene/SiO2 and SiO2 regions. Parts (a) and (c) of both 2 surface in a region without graphene. For both barrier thicknesses, it is possible to observe a homogenous layer covering the whole substrate surface. The Co layer is also observed as well as the top granular platinum-capping region, purposely deposited during the FIB lamella preparation to protect the integrity of the sample interface layers. It is important to note that both TEM and STEM images present similar features but in reverse contrast. The HAADF STEM images  growth2O3 layer having a minimum thickness of nominally 3 nm, which means thickness reaching a maximum thickness of ca. 5 nm. Although the nominal (3 nm) thickness may lead to complete barrier coverage, AFM measurements indicated a relative high rms roughness of ~0.6 nm  barrier samples, confirming that this thickness is the approximate limit for complete coverage of the graphene by the Al2O3. The Raman analyses are in concordance with the electron microscopy results, indicating that Raman spectroscopy in such experiment is a useful technique for probing the existence of pinholes in tunnel barriers on graphene over large areas.The use of Co sputtering deposition during the fabrication of ferromagnetic contacts may lead to moderate graphene damage. The Raman spectrum of graphene after direct (without barrier) Co deposition contained a prominent defects-related D bandoles see  online. 2O3 barriers. Only the 3-nm-thick  barrier provided complete coverage of the graphene surface, thereby preserving the graphene integrity during the Co deposition. No pinholes were directly or indirectly observed. However, this thicker barrier had a relative high rms roughness of ca. 0.6 nm. The high surface diffusion properties of graphene led to cluster-like Al2O3 film growth. This phenomenon limits the minimal possible thickness for complete barrier coverage on graphene surfaces using standard Al evaporation methods. The minimum required Al2O3 layer thickness for complete coverage of nominally 3 nm becomes ca. 5 nm in practice because of this clustering.In conclusion, direct observation of pinhole contacts was achieved using FIB cross-sectional and advanced high-resolution TEM and STEM analyses. Spatially resolved EDX spectrum profiling showed the nature of direct point-contacts between the Co ferromagnetic layer and the graphene. Raman spectroscopy indicated that moderate damage occurred over large areas of the graphene during the Co sputtering deposition. The presence of pinholes in the barrier structure provided a direct path for Co-carbon collisions. Such pinholes were widely distributed on the samples having 1- and 2-nm-thick  Al2 films that had been thermally grown on silicon substrates. Monolayer graphenes were initially localized using optical microscopy. The crystalline quality and the number of layers of each flake were probed using Raman spectroscopy . Al2O3 barriers were then deposited by thermal evaporation of aluminum in vacuo (base pressure of 10−7 Torr) with posterior ambient oxidation. Different nominal Al2O3 barrier thicknesses (expansion factor of 1.28 from Al thickness) were evaluated; i.e., 1, 2 and 3 nm. The samples were then coated with a Co layer, which represented the ferromagnetic electrodes of a spintronic device. A 4-nm-thick Co layer was deposited by DC-magnetron sputtering at 3 mTorr of Ar, 130 mA (ca. 160 V) and a base pressure of 10−7 Torr. The samples were monitored by Raman spectroscopy between each fabrication step. A Cs-corrected FEI Titan 80/300 S/TEM microscope was used to obtain scanning and conventional transmission electron micrographs of the Co/Al2O3/graphene/SiO2 interfaces. High-angle annular dark field (HAADF) images were acquired using the STEM mode. Space-resolved elemental analyses were performed via energy dispersive X-ray (EDX) spectroscopy to map the layer interfaces. The chemical nature of the Al2O3 barriers was also analyzed using electron energy loss spectroscopy (EELS). The cross-sectional (S)-TEM samples were previously prepared using focused ion beam (FIB) protocols for lamella preparation . Topographical aspects of the Al2O3 barriers were also acquired through atomic force microscopy measurements using a Bruker Multimode 8 AFM operated in the intermittent mode at a drive amplitude of 120 mV with a Si tip having k = 5 N/m.Graphene flakes were obtained by micromechanical cleavage of single-crystal graphite30How to cite this article: Canto, B. et al. On the Structural and Chemical Characteristics of Co/Al2O3/graphene Interfaces for Graphene Spintronic Devices. Sci. Rep.5, 14332; doi: 10.1038/srep14332 (2015).


Idiopathic pulmonary fibrosis acute exacerbation (IPF-AE) constitutes IPF’s most devastating event, representing the unexpected superimposition of diffuse alveolar damage of unknown etiology. Guidelines recommend high-dose steroids treatment despite unproven benefit. We hypothesized that previous immunosuppression and the administration of high-dose steroids adversely affect IPF-AE outcome.We studied all consecutive patients hospitalized in our department for IPF deterioration from 2007 to June 2013. Our protocol consisted of immediate cessation of immunosuppression (if any), best supportive care, broad-spectrum antimicrobials and thorough evaluation to detect reversible causes of deterioration. Patients were followed-up for survival; post-discharge none received immunosuppression.p = 0.041). As unique patients 35.3 % survived; 3 out of 6 (50 %) in the never treated group whereas three out of 11 (27.3 %) in the group receiving immunosuppression (p = 0.685). The history of immunosuppression significantly and adversely influenced survival (p = 0.035). Survival was greater in the never treated group compared to the immunosuppressed patients (p = 0.022). Post-discharge, our IPF-AE survivors had an 83 % 1-year survival.Twenty-four out of 85 admissions (28 %) fulfilled IPF-AE criteria. IPF-AE were analyzed both as unique events and as unique patients. As unique events 50 % survived; 3 out of 12 (25 %) in the group previously treated with immunosuppression whereas nine out of 12 (75 %) in the group not receiving immunosuppression (By applying the above mentioned protocol half of our patients survived. The history of immunosuppression before IPF-AE adversely influences survival. Avoiding steroids in IPF patients may favor the natural history of the disease even at the moment of its most devastating event. Idiopathic pulmonary fibrosis (IPF) is a dreadful, chronic and irreversibly progressive disease leading to death in all patients affected and IPF acute exacerbations (IPF-AE) constitute the most devastating event during its clinical course , 2. IPF-IPF-AE histological picture corresponds to the development of diffuse alveolar damage (DAD) upon usual interstitial pneumonia (UIP) . This coConvinced of its harmfulness, years before the PANTHER trial , the triFirstly, we reviewed the files of all consecutive patients admitted to the pulmonary department of a tertiary teaching hospital, “Attikon” University Hospital, from January 2007 to May 2011 with the diagnosis of pulmonary fibrosis. Secondly, we isolated the cases that represented IPF according to the 2011 IPF criteria . Among tChlamydophila Pneumoniae, Mycoplasma Pneumoniae), chest roentgenography, bronchoscopy, urinary antigen tests for Streptococcus pneumoniae and Legionella pneumophila, bronchoalveolar lavage (BAL), sputum sampling, nasopharyngeal aspirates, endotracheal aspiration, blood/sputum/BAL fluid cultures for microbes, mycobacteria, atypical pathogens, opportunistic infections, fungi, viruses, PFTs and cardiac echocardiography, whenever feasible taking into consideration the clinical condition of each patient. We separated admissions diagnosed as IPF-AE in 2 groups. The first group consisted of patients not receiving steroids or any other form of immunosuppressants prior to admission (treatment naïve or never treated) and the second group consisted of patients receiving prior to admission steroids or any other form of immunosuppressants (ever treated). Our treatment consisted of extended spectrum antimicrobials empirically initiated based mostly on the immunosuppression history of our patients. More precisely, patients never treated with steroids or/and immunosuppressants before the acute exacerbation event were set on antimicrobials for common gram positive, gram negative and atypical pathogens plus therapy against influenza virus pneumonia during the influenza season; patients previously treated with steroids or/and immunosuppressants received in addition to the above mentioned therapy, treatment for Pneumocystis jirovecii and occasionally for cytomegalovirus pneumonia in a documented case. All patients were followed-up after discharge for survival. None of them was treated with steroids or immunosuppression post discharge.The protocol that we applied in every patient admitted with the diagnosis of IPF deterioration has been described in previous publications , 6 and cThis work has been approved by “Attikon” hospital’s bioethics committee decision No 575/11-4-11. No patients’ consent was needed. Some of the data have been published in the form of an abstract [p values < 0.05 were considered statistically significant. Data were analyzed and graphs were created with StatsDirect 2.8.0, StatsDirect Ltd, Altrincham, Chesire, UK.Categorical variables are presented as n (%). Numerical variables are presented as median (range). Comparisons between groups were performed using Cox regression analysis in order to evaluate the influence of the previous use of immunosuppressive therapy on survival. Results are presented as hazard ratios (HR) with 95 % confidence intervals (CI) in parentheses. Time to death according to previous history of immunosuppressive therapy were evaluated with Kaplan-Meier survival curves and log-rank tests. Out of 164 admissions with the diagnosis of pulmonary fibrosis from January 2007 to May 2011, 53 were attributed to IPF representing 37 unique IPF patients. From June 2011 to June 2013 another 32 cases with IPF were admitted to our department (21 unique IPF patients). In total from 2007 to 2013 we recorded 85 IPF admissions that represent 58 unique IPF patients. Diagnosis was obtained by multidisciplinary approach according to 2011 IPF guidelines [Among the 85 IPF admissions an identifiable cause of the patient’s deterioration was found in 49 (58 %), that is 28 (33 %) cases of purulent tracheobronchitis, 7 (8 %) cases of pneumonia, 6 (7 %) cases of heart failure, 4 (5 %) cases of sepsis, 2 (2 %) cases of pulmonary embolism, 1 (1 %) case of pericarditis and 1 (1 %) case of pneumothorax (Table p = 0.007) whilst the need for mechanical ventilation was significantly increased in the ever treated group (p = 0.014). Regarding other parameters  no significant difference was found (Table The descriptives of never and ever treated with steroid groups are presented in Table nd Table . The majp = 0.041). When examining the IPF-AE not as unique events but as unique patients , then out of 17 IPF-AE patients, 6 (35.3 %) survived the exacerbation event. In the never treated group which comprised 6 patients, 3 (50 %) survived whereas in the ever treated group which comprised 11 patients only 3 (27.3 %) patients did (p = 0.685). A univariate Cox regression analysis identified the previous use of steroids as significantly and adversely influencing survival after AE in the ever and never treated groups, with a HR of 3.544 (95 % CI 1.090–11.514), p = 0.035  survived the exacerbation event. In the never treated group 9 (75 %) patients survived whereas in the ever treated group only 3 (25 %) patients did (p = 0.022)  with a 52 % 1-month, 45 % 3-month, 40 % 6-month and 40 % 1-year survival respectively. In the never treated group there was a 70 % 1-month, 65 % 3-month, 65 % 6-month and 65 % 1-year survival respectively , whereas in the ever treated group the median survival was 0.43 months (range 0.2–89) with a 30 % 1-month, 22 % 3-month, 17 % 6-month and 17 % 1-year survival respectively. These differences in survival following a log-rank test were found to be statistically significant  further validate our hypothesis that on the one hand provided a survival benefit in patients with lower lung capacity and on the other hand patients with higher lung capacity and comparable parameters of the exacerbation severity could not be helped by the applied protocol, thus were intubated and subsequently expired. In addition, median overall survival of those ever treated was just 0.43 months with a 17 % 1-year survival while never treated patients showed a 1-year survival of 65 %. Finally, withholding steroids in all survivors of our protocol 83 % of them were still alive 1 year after the exacerbation event.N-acetylcysteine not only had no evidence of physiological or clinical benefit but presented significantly increased rate of hospitalizations, exacerbations and deaths compared to the placebo arm [In 2012 a randomized, double-blind, placebo-controlled trial based on an independent protocol reviewed by a committee appointed by the National Heart, Lung, and Blood Institute, and conducted in 25 clinical centers under the auspices of the Idiopathic Pulmonary Fibrosis Clinical Research Network (IPFnet) was terminated prematurely when the interim analysis demonstrated that IPF patients treated with combination therapy with prednisone, azathioprine and Based on the above evidence it appears to us inconceivable to continue managing IPF patients who precipitate in acute exacerbation being under immunosuppressive treatment with a thirty to hundred fold higher doses of steroids (from 10–35 mg prednisone for the stable IPF patient to 1000 mg methylprednisolone iv pulses for one or more days) and await improvement. The results of our study present our management approach of the rapid deteriorating patient with IPF entering exacerbation by withdrawing corticosteroids and immunosuppressants.Our treatment, as already described, consisted of extended spectrum antimicrobials empirically initiated based mostly on the immunosuppression history of our patients. The protocol adopted by us reflects the common practice in every critical care unit where the critically ill patient developing an ARDS of unknown etiology, or during the evaluation for the detection of the etiologic factor, is managed not by high doses of pulse steroids but by extended spectrum antimicrobials since in this setting it is known that undetectable infection is the most common and the most treatable etiologic condition. Certainly by adopting the above protocol we are conscious that the results of our study are not easily comparable with previous retrospective studies describing the efficacy of specific pharmacological treatment with steroids and immunosuppressants in IPF-AE because such an alternative approach has not been examined before.Current practice for steroids use in IPF acute exacerbations originates from the first description of IPF-AE by Kondoh and coworkers in 1993  who alsop = 0.022). In contrast, the reported mortality of IPF-AE in most studies is very high, usually exceeding 50–60 % and the 3-month mortality rate following an exacerbation event reaches 60–90 % [In our study the never treated IPF-AE population presented a 65 % 1-year survival compared to a 1-year survival of 17 % and a median survival of only 0.43 months in the ever treated group. The overall differences in survival as discussed in the results are significant p = 0.02. In con 60–90 % . Song an 60–90 % . In 2003 60–90 % . The sam 60–90 % . Because 60–90 % . Kondoh  60–90 % . Yokoyam 60–90 % . Finally 60–90 % . In many 60–90 % .Pneumocystis jirovecii than patients not receiving steroids and 36 % of IPF patients grow bacteria in BAL fluid in the absence of clear signs of infection, even before immunosuppression [The survival benefit in IPF-AE patients treated with broad spectrum antimicrobials instead of high dose steroids shown in the present study could be attributed to the fact that they militate the role that microbial populations play in the pathogenesis of such a condition. It is common knowledge that IPF is a disease that severely damages the lung and that IPF lung is vulnerable to any hit, even minor, that could cause DAD in the same manner that direct and indirect lung injuries cause ARDS . Combinipression , 27. Morpression . Moreovepression . Woottonpression . All theIt is to be noted that a limitation of the present study is the small number of patients. Furthermore, it does not include a control arm of IPF-AE patients treated with high dose steroids. The main reason for such a “limitation” was firstly our long standing clinical experience according to which IPF-AE patients treated with high dose steroids didn’t survive and secondarily to it our firm position that such a therapeutic approach would not be appropriate to treat our IPF-AE patients. Of course we are very conscious of the fact that the responsibility of such a scientific opinion that contradicts the official guidelines, although the latter are based on poor evidence, cannot be easily shouldered and that it should be incontestably proved by a prospective properly designed trial examining the role of steroids in the AE-IPF. It is common sense that a single academic center like ours could never support by itself such a trial but needs the scientific, technical and financial support of the international scientific community and of official medical institutions that could conduct a multi-center trial designed and empowered to provide definitive answers to this already long lasting and crucial for IPF patients debate. We are convinced that our proposal reflects not only our view but also the evolving view of other experts that treat IPF-AE patients worldwide , 31, 32.In conclusion by applying the critically ill patient protocol on the management of IPF patients developing acute exacerbation we have shown that half of our patients survived. Furthermore, we found that the history of immunosuppression before IPF-AE adversely influences survival. Avoiding steroids in IPF patients may favor the natural history of the disease even at the moment of its most devastating event.


As of today the dominant technology is based on Si and obtaining graphene with Si is treated as the most advantageous solution. However, the formation of carbide during the growth process makes manufacturing graphene on Si wafers extremely challenging. To overcome these difficulties and reach the set goals, we proposed growth of high quality graphene layers by the CVD method on Ge(100)/Si(100) wafers. In addition, a stochastic model was applied in order to describe the graphene growth process on the Ge(100)/Si(100) substrate and to determine the direction of further processes. As a result, high quality graphene was grown, which was proved by Raman spectroscopy results, showing uniform monolayer films with FWHM of the 2D band of 32 cm It is an irrefutable fact that the best quality graphene in terms of structural integrity and electrical properties is obtained by mechanical cleavage of highly oriented pyrolytic graphite2Recently, single crystal hexagonal boron nitride (h-BN) has been proposed as an ideal substrate for epitaxial growth of grapheneLately, among many interesting methods developed worldwide781011141718Since graphene and its extraordinary properties were described and analyzed in depth, it has been considered as a material to be implemented in various fields. One of the leading ideas which appears to be a progressive concept is to apply graphene to complementary metal oxide semiconductor technology (CMOS). In order to widen the range of possible graphene applications, for example in high frequency electronics, it is desirable to grow graphene films directly on arbitrary insulators or semiconductor surfaces instead of on a most commonly used copper substrate. Ideally such insulating or semiconducting layers are deposited on Si wafers used commonly in integrated circuit (IC) manufacturing. Growing graphene directly on Si wafer surface is extremely challenging due to the tendency to form carbides. This forces researchers into looking for alternatives, for instance offered by germanium substratesex-situ removal of native oxides or preceding graphene growth with the deposition of fresh Ge layers, which, without a doubt adds value to the fabrication process. As an alternative to direct growth, graphene transferring from a copper substrate is considered. Ruoff et al.In this paper, we intend to present, for the first time, CVD growth of graphene on epitaxial Ge(100) layers deposited on Si(100) wafers, which is the preferred wafer orientation in CMOS technology. The cost advantage offered by this approach is linked with the bulk buying of wafers and what is even more important manufacturing compatibility of Si(100). Additionally, when compared with techniques described in other reportsAdditionally, in the literature there are examples of graphene growth modeling; however, the vast majority of these papers are related to graphene synthesis on substrates other than Ge(100)/Si(100), including mostly copper foils2728In order to determine and understand the kinetics of the graphene growth process on the Ge(100)/Si(100) substrate, the nucleation stage was investigated as a function of methane flow. During the processes different methane flow were introduced into the growth chamber. The processes were performed in such a way that the results of the initial steps of graphene growth were observed. In other words, the processes were stopped before graphene formed continuous films and, hence, graphene flakes rather than continuous films were visible on the surface of Ge(100)/Si(100). Next, after having obtained a set of samples partially covered by graphene, a round of longer processes was completed with the aim of observing the formation of a continuous graphene film and the accompanying side effects like discontinuities, grain boundaries or secondary  graphene ad-layers.4 flow varied from 5, through 10, up to 15 sccm (standard cubic centimeters per minute). The collected Raman spectroscopy results confirm the presence of graphene layers in the case each of the examined samples  relative to free-standing graphene indicate that on the surfaces of the samples more than one layer of graphene was obtained31D/IG ratio equal to 0.4, 0.57 and 0.76 for 5, 10 and 15 sccm, respectively can be accounted for by two factors, namely the distance between isolated defects or the existence of very small graphene monocrystalline domains of the order of 40 nm33At the first attempt the Raman quality was investigated as a function of methane partial pressure. As for the preset growth parameters, CH samples . WidenedThere is a direct correlation between carbon transport (as methane) and the growth rate of graphene flakes. The methane flow can also imply the nucleation rate (i.e. the number of new flake nucleations per time unit). In the simplest view, if growth is mass transport-limited, both values (growth rate and nucleation rate) should be close to proportional to the precursor partial pressure. In such a case, the precursor flow value does not affect the overall growth pattern of flakes, except the timescale. Several factors can disrupt this image. Nucleation can be quickly saturated by a finite number of nucleation defects on the substrate surface, as a result of which the growth rate increases faster than the nucleation rate. On the other hand, nucleation can get more efficient when the precursor flow is increased because of the limited migration of surface ad-atoms. The higher the precursor partial pressure, the shorter the time for single ad-atom to migrate and attach to a flake edge before getting companions and nucleating a new flake (even without any nucleation defects).4 flow equal to 5, 10 and 15 sccm are different and the relationship between the growth rate and the nucleation rate was not the same for various CH4 flows. In each pair of images (SEM and simulation) different areas are marked with arrows. The varied areas in bluescale in simulation pictures correspond to the number of graphene layers  seen in SEM images and the lighter blue areas in simulation images represent uncovered Ge surface, without graphene on top. Pictures suggest that the nucleation rate increases faster than the growth rate with raising the CH4 flow. Besides, the images show some secondary (2ML) or even 3ML or 4ML nucleations overgrowing the first layer (1ML). These ad-layers seem to nucleate and to increase their size with a highly varying rates, when comparing all three pictures.SEM images  show thaPN and PC, as follows:PN is the probability of growing the graphene unit cell in coordinates of a single unit cell  per time unit, if it does not have any already grown closest neighbours – the “nucleation” case.PC is the probability of growing the graphene unit cell in coordinates of a single unit cell per unit time, if its closest neighbour has been already grown – the “continuation” case.In order to provide a more precise quantitative interpretation of both the growth statistics and the observed growth patterns of graphene on Ge(100)/Si(100) substrates we have developed a Monte-Carlo type model of the layered growth. The model employs two primary parameters, PC /PN). The employed term “unit cell” assigns an arbitrary unit lattice area, which in the limiting case can be the crystal lattice unit cell. When more than one nearest neighbour is already grown, the growth probability can be simply set as the additive function of these neighbours.The later used convenient parameter is a ratio of these two probabilities , 2) the probability ratio of continuation on the graphene layer to continuation on the substrate - . These factors describe the formation of the ad-layers. If analogous parameters were required for the description of higher order (ad-) ad-layers, they would be denoted as , ,  or similar.The model applies a pair of secondary parameters: 1) the probability ratio of secondary nucleation on the already grown graphene layer to nucleation on the substrate - (The simulation process consisted of repeating the following sequence: 1) Randomly selecting coordinates of a unit cell, 2) Checking the growth state of the nearest neighbour unit cells and assigning the growth probability value, 3) Drawing the occurrence of a given growth step event. The calculations were usually completed for the square lattice frame of 1000 × 1000 or 500 × 500 unit cells. The computed image of the primary (1ML) pattern  does not depend on the calculation frame dimension, when scaling the parameters as below.D is the calculation image frame dimension (in unit cells), whereas A and B assign two calculation setups. If the PC /PN ratio and image dimension are fixed, the image primary pattern does not depend on the PN absolute value, when scaling the time as below:where PC /PN ratio and the image dimension D describing growth. It is easy to show that this function is a quotient: In conclusion, the primary (1ML) image is defined by only two values. The first is the function of time describing progress in the growth process: PN,.. and PC,.. values correspond to the probabilities of the occurrence of growth of a graphene unit cell after single drawing of the coordinates of this unit cell (in a single sampling of this cell). The “time” value corresponds to the average number of samplings of a single unit cell .Several attempts to fit the microscope images of graphene on Ge(100)/Si(100) substrates with simulation have quickly given quite satisfactory patterns. Below  there arPC /PN) ratio decreases significantly with increasing the CH4 partial pressure – the continuation of the existing flakes becomes less preferred to nucleation of the new ones. Faster raising of the nucleation rate than the lateral growth rate with CH4 flow suggests that the nucleation is suppressed by some process, especially at a low precursor partial pressure. The most obvious explanation is as has been mentioned earlier: nucleation can be prevented by the migration of ad-atoms to the nearby flakes; when increasing the precursor flow, the time, in which ad-atom is lone, shortens. Before reaching a flake, the ad-atom transits into the ad-atom cluster. The clustering slows or stops migration and results in the nucleation.The fitting results show that the , which is related to the secondary (2ML) layers, does not exhibit a monotonic behaviour. The 2ML nucleation ratio  and even directly the nucleation rate alone  shows a strong minimum around the medium CH4 flow, while outside this minimum they depend on the CH4 flow in the same manner as in the case of the primary nucleation – the PN,2ML/PN ratio is almost constant there. We cannot offer a clear explanation for this effect yet. Such explanation would have to distinguish between the Ge(100)/Si(100) surface area and the 1ML graphene layer area as a substrate. It can, however, be supposed that the clustering process of ad-atoms includes an intermediate step during which they become exceptionally mobile on the graphene 1ML surface (while this does not take place on other surfaces) and this intermediate step is preferred by the medium precursor flow through a surface or by a gas phase reaction. Despite these differences in nucleation, the growth continuation parameter PC,2ML/PC regarding the secondary (2ML) graphene layer does not significantly depend on the CH4 partial pressure and is close to PC,2ML/PC = 1. It means that the continuation of flakes has a similar growth rate for both 1ML and 2ML flakes.The next parameter  flakes are very often overgrown by next-order layers, more often if the CH4 flow is higher. While the nucleation rate of higher-order (>2ML) ad-layers grow faster than the 1ML nucleation rate, the continuation rate seems to be more similar to the 1ML continuation rate.The nucleation rate of the higher secondary layers  seems to grow monotonically with the CHgr) and simulation time parameter within growth pairs is not directly proportional. This affected correlation and confirms the existence of a time offset before the nucleation becomes visible. The delay was clearly observed in other growth experiments, not shown in this paper. This offset partially results from the specific operation of the hardware; however, in its larger part it has to be induced by another factor. Most probably, it is related to the nucleation stage of 1ML graphene on Ge(100)/Si(100). The nucleation cluster with just a few atoms collects subsequent atoms much slower than a flake, until getting a regular lattice and becoming visible in SEM images.The relation between the experimental growth time /Si(100) is affected by the migration of ad-atoms on the surface and this nucleation can be increased by accelerated clustering of ad-atoms in a high precursor partial pressure. Secondly, there is a striking difference between the first ad-layer nucleation on graphene (2ML) and primary nucleation on germanium since the ad-layer (2ML) nucleation rate has a strong minimum for a particular precursor flow. Thirdly, the nucleation, as such is a relatively slowly progressing step, introducing a time delay before substantial covering by graphene begins.−1) and the 2D/G intensity ratio higher than 2 are observable, which confirms the presence of a high quality and homogeneous monolayer graphene film.On the basis of the above mentioned results further optimization steps in the growth process of graphene on Ge(100)/Si(100) substrates were made. The methane flow was reduced and the time of growth was extended. As a result, a uniform graphene film was achieved. Additionally, in order to confirm the presence of the high quality monolayer of graphene on Ge(100)/Si(100) substrates STM measurements were performed. In summary, the influence of the methane flow on the graphene nucleation mechanism, growth rate, uniformity and structural quality has been investigated. High quality graphene has been grown on Ge(100)/Si(100) substrates, which has been mainly confirmed by the results of Raman spectroscopy measurements. Also, the presented simulation and quantity analysis show that graphene growth on Ge(100)/Si(100) substrate can be described by a simple stochastic model with a very low number of parameters. The influence of the substrate lattice structure, extended defects and growth anisotropy are restrained enough to make such a description possible. The excellent alignment between the experiment and the simulation means that in the course of further investigation a convincing physical model can be proposed to describe the whole process of graphene growth. The presented attempt, including particularly direct growth on the Ge(100)/Si(100) substrate combined with modelling of the growth process, was shown here as a viable alternative enabling the introduction of graphene with its unique features to CMOS technology.2 in the ratio of 20:1. It was found that the optimal roughness of the substrate is achieved when the step growth is preceded by the substrate’s annealing at pure hydrogen atmosphere in order to in-situ reduce native oxidesIn the present work graphene films were synthesized in a 6-inch Aixtron Black Magic system by the CVD method. As a substrate we used (100)-oriented Ge layers deposited by the CVD method on Si (100) wafers. To ensure optimal temperature conditions, thus preventing Si diffusion through a Ge layer and Ge melting, the temperature was monitored and set separately and simultaneously in bottom and top heaters. The temperature was chosen in the range between 900 °C and 930 °C with a temperature ramp up rate of 20 °C/min. During the process of graphene deposition the pressure range of 700 to 780 mbar was sustained. Methane gas was used as a carbon precursor in the mixture of Ar and H−10 mbar with a Multiprobe P system made by Omicron GmbH.The characterization of the properties of graphene grown directly on Ge(100)/Si(100) substrates was performed by Raman spectroscopy using a Renishaw system with a 532 nm Nd:YAG laser as an excitation source with the laser spot diameter on the sample surface of approximately 0.3 μm. The surface of graphene was investigated using the In-Lens secondary electrons detector (true SE1) and the Energy selective Backscattered electron  detector, both positioned on the optical axis of the Gemini™ column of the Auriga CrossBeam Workstation (Carl Zeiss). The energy of primary electrons in the scanning beam was set at 500 eV so as to reveal the morphology of the ultra-thin layer of graphene (single layer) and simultaneously distinguish different phases present on the substrate based on the compositional contrast (low-loss BSE). STM measurements were conducted under base pressure of 2 × 10How to cite this article: Pasternak, I. et al. Graphene growth on Ge(100)/Si(100) substrates by CVD method. Sci. Rep.6, 21773; doi: 10.1038/srep21773 (2016).


This data article shows the expression levels of specific podocyte injury markers and podocyte slit diaphragm protein nephrin in obese and lean Zucker rat glomeruli. It also contains information on the effect of the overexpression of transcription factor FOXC2 on the ratio of F- and G-actin and the expression level of ZO-1 in differentiated human podocytes. The article also shows data on the effect of treatments of differentiated podocytes with various factors associated with obesity and diabetes on the expression level of FOXC2. The detailed interpretation of these data and other aspects of podocyte injury mediated by upregulation of FOXC2 can be found in “Overexpression of transcription factor FOXC2 in cultured human podocytes upregulates injury markers and increases motility  Specifications table•The obese Zucker rats show a trend towards upregulation of podocyte injury markers in glomeruli.•The obese Zucker rats with the highest level of proteinuria express least nephrin in glomeruli.•in vitro does not change the F-actin/G-actin ratio, or the expression level of the tight junction protein ZO-1.Overexpression of FOXC2 in differentiated human podocytes •Several obesity and diabetes-associated factors were found not to upregulate FOXC2 in differentiated human podocytes.1Quantitative Western blotting reveals that podocyte injury markers active beta-catenin, desmin and fibronectin show a trend of upregulation in the glomeruli of 40 weeks old obese Zucker rats compared to lean controls A and B. 22.13VO4 and 1× Complete Proteinase Inhibitor Cocktail  at 4 °C for 30 min. Detergent-insoluble material was removed by centrifugation .Obese (fa/fa) and lean (fa/+) Zucker rats (Crl:ZUC-Leprfa) were obtained from Charles River Laboratories . Blood glucose values were measured from tail vein samples using OneTouch Ultra glucometer . The urinary albumin to creatinine ratio was determined from spot urine samples. Albumin was measured with rat albumin ELISA kit  and creatinine using CREA plus enzymatic assay  and Roche clinical chemistry analyzer . The exp2.275 μg of glomerular lysates were separated on a 10% SDS-PAGE gel, transferred to PVDF-FL membranes  and blocked with Odyssey blocking buffer  diluted 1:1 with phosphate buffered saline (PBS). The membranes were incubated with mouse anti-active β -catenin , mouse anti-desmin 37EH11 Treatment of cultured human podocytes with obesity- and diabetes-associated factorsConditionally immortalized human podocytes (AB8/13) were cultured as described in Datta et al. 2.3® . The expression levels of FOXC2 mRNA were normalized to GAPDH using the comparative Ct method (DDCt).Total RNA was isolated, treated with DNase I and reverse transcribed into complementary DNA (cDNA). The quantitative PCR was performed using TaqMan gene expression assays  for hFOXC2 (Assay ID: Hs00270951_s1) and hGAPDH  as in 2.4g centrifugation at 37 °C for 1 h that pellets the F-actin and leaves the G-actin in the supernatant. Samples of supernatant and pellet were separated by SDS-PAGE and actin was quantified by Western blotting using the rabbit polyclonal anti-actin antibody provided in the kit.FOXC2 was lentivirally overexpressed in differentiated human podocytes as described in Datta et al. 2.5t test .Results are presented as mean±SD. Statistical analysis was performed using Student׳s


The electrochemical capacitance of the material exhibits a dependence on bias voltage, a phenomenon observed by other groups when studying graphene quantum capacitance. The plasma-assisted graphitization, which dominates the graphitization process, is analyzed and discussed in detail.High surface area electrode materials are of interest for a wide range of potential applications such as super-capacitors and electrochemical cells. This paper describes a fabrication method of three-dimensional (3D) graphene conformally coated on nanoporous insulating substrate with uniform nanopore size. 3D graphene films were formed by controlled graphitization of diamond-like amorphous carbon precursor films, deposited by plasma-enhanced chemical vapour deposition (PECVD). Plasma-assisted graphitization was found to produce better quality graphene than a simple thermal graphitization process. The resulting 3D graphene/amorphous carbon/alumina structure has a very high surface area, good electrical conductivity and exhibits excellent chemically stability, providing a good material platform for electrochemical applications. Consequently very large electrochemical capacitance values, as high as 2.1 mF for a sample of 10 mm Ever since the first experimental proof of graphene’s existence3678910678910812Previous fabrication processes related to producing 3D graphene films on porous substrate have usually involved multiple fabrication steps and required the use of graphene oxide1112131415131413171820212) is achieved. The material properties of 3D graphene are analyzed by Raman spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS). The electrical and electrochemical properties are investigated by conductance measurements, Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS). The chemical stability of the material is studied by chemical etching using hydrofluoric acid (HF). Based on the results of the material characterization and analysis of the plasma-material interaction, it is concluded that the growth mechanism is a combination of deposition and graphitization of an ultrathin amorphous carbon layer on AAO in PECVD.This paper presents a technique for one-step graphene fabrication on nanoporous anodic aluminium oxide (AAO) using plasma-enhanced chemical vapor deposition (PECVD). We demonstrate direct catalyst-free graphene growth on AAO and investigate the formation of graphene in the nanopores. High effective surface area graphene grown over well-defined nanopores with large capacitance (as high as 2.1 mF for a sample of 10 mm9 cm−2 pore density). Unless specified otherwise, the following characterizations are made based on the sample fabricated by method 1.−1), G (1595 cm−1) and 2D (2691 cm−1) peaks. The rise of D and D’ (1629 cm−1) peaks suggest the existence of defects in the sample3 type defects242525−1, which is slightly larger than that of a commercially purchased CVD monolayer graphene on SiO2 (32.3 cm−1) consisting of a single 2D component but lower than of bilayer graphene (50 cm−1), which contains four 2D peak components1627) and 2D 91 cm−1 p) and 2D 91 cm−1 pand D’ 16 cm−1 pea2 carbon hybridization in the a-C-AAO samples−1 and the I(D)/I(G) is 1.8. The Raman spectrum indicates a defected few-layered graphene was obtained, confirming the temperature driven graphitization process16312 content in our study than in previous reports2331212223To analyze the atomic structure and a number of graphene layers in the samples, TEM studies of the G-AAO membranes have been performed. 332 fractions are 77.2% and 50.9% in G-AAO and in a-C-AAO, respectively, where glassy carbon (100% sp2) was used as the reference383 peak in G-AAO supports the presence of a remaining amorphous a-C carbon layer underneath graphene layersTo confirm the full coverage of the graphene layer over AAO, G-AAO was inserted in HF acid  for 22 hours to study the chemical stability of the materialTo test the continuity and electrical conductivity of the formed graphene layers on AAO we performed a two point probe electrical measurements. The sheet resistance measured horizontally along the surface, as schematically seen in s is the solution resistance and R the resistance to charge transfer to Electrochemical capacitance  of a G-A452O3 and α-Al2O3 formed at high temperature502O3 and α-Al2O3 were involved in the plasma-enhanced graphitization process to form graphene due to the ion bombardment on the surface by energetic particles, while in thermal annealing γ-Al2O3 was well separated by the a-C layer from the surface graphene layer. The detailed a-C/γ-Al2O3/AAO structure can be found in ref. The two presented fabrication methods of 3D graphene described in 2122233433It has also been observed in the experiments that the growth of graphene or a-C in PECVD can be effectively controlled by a proper choice of a spacer under the sample, while using the same plasma growth conditions. The use of dielectric spacer allowed direct production of graphene on AAO and reaching 600 °C higher sample temperature of AAO on a dielectric spacer compared to a metal stage. The ability to control the sample temperature by the spacer in the PECVD process was found also extremely important for graphene production reproducibility. In some occasions, it was possible to obtain G-AAO without separating the AAO from the stage but the repeatability was low. Only one experiment out of ten could successfully produce G-AAO without the spacer.Intuitively, the dielectric spacer plays two roles that both lead to an increase of the temperature of the sample in the plasma. Firstly, the spacer introduces thermal isolation between the sample and the stage and therefore reduces the thermal dissipation of the sample. Secondly, the spacer induces perturbation to the plasma near the sample surface, which can lead to complicated plasma-material interactions and a sample temperature change, because plasma is the only source ‘heating up’ the sample (plasma-enhanced graphitization). The increase in sample temperature has also a significant impact on the surface chemistry, which can strongly affect the carbon layer formation.For the quartz spacer of 0.35 mm thick, our calculation using Fourier’s lawEk) on substrate surface is mainly determined by the electric potential in plasma sheath and provides the energy for ions to bombard the substrate surface. Ions move directionally within the plasma sheath driven by the potential drop53Ek can be roughly estimated as Ek  ≈ 5.2Te ≈ 26 eVTe ≈ 5 eV is the electron temperatureEk a value greater than the energy released in chemical processes, for example, the hydrogen binding energy (around 4.5 eV)Analysing all the chemical processes in plasma including plasma-material interaction, and hence simultaneously tracking every charged particles collision event, requires massive Monte-Carlo simulations of plasma53The ion bombardment is believed important in PECVDλD, where λD is Debye length) is placed on the top of the metal stage, the stable ambipolar field is created on the dielectric surface for both low and high bias voltages, as demonstrated by the red and purple solid curves in φ0 is the potential determined by the ambipolar field. Therefore placing the dielectric on top of the metal provides a more stable plasma sheath than on the metal. The stable sheath offers continuous ion bombardment on AAO hence increases the temperature.By solving Poisson-Boltzmann equations53λD ≈ 53 μm if Te = 5 eV and the electron density is 1011 cm−3 in microwave plasma source53Although AAO itself is a dielectric, a rough estimation gives Another possible effect on temperature increase is surface charging, namely the accumulation of charges on the dielectric surface in plasma. Although the potentials on dielectric and on metal at far distance are found to be similar due to the same amount of net charges , the den3 with effective surface area of 883 cm2 was achieved. This implies the potential for using G-AAO as super-capacitors for energy or/and biological applications. The capacitance dependence on the bias voltage of G-AAO was also observed.The possibility of catalyst-free graphene growth on a porous dielectric AAO material was explored. Two different fabrication methods of graphene on AAO were developed based on plasma-enhanced and thermal graphitization of ultrathin a-C precursor layers in PECVD. Microscopic studies confirmed that defected FLG is conformally obtained on the whole internal and external surface of nanoporous AAO. The samples retained the well-defined nanoporous structure of the AAO and become well conductive after the graphene deposition process. Overgrowth of G-AAO and occlusion of pores was an intermittent problem, which can be avoided by using lower plasma power. Due to the large surface area of the porous structure, the electrochemical capacitance as large as 2.1 mF for the sample of 10 mmEELS and Raman strongly suggest that plasma-enhanced graphitization of a-C is the growth mechanism of G-AAO in PECVD. To improve the reliability of the G-AAO film production and achieve higher substrate temperature in PECVD for production of graphene, the sample plasma annealing process was investigated by studying the surface charging effect and the potential distribution on the plasma-material interface. It was found that introducing a dielectric spacer in between the sample and the metal stage leads to 600 °C higher sample temperature and improved repeatability than on the metal stage due to several reasons, such as stabilization of the plasma sheath, surface charge accumulation for direct annealing, and reduction of the power dissipation.2/CH4: 750/10 sccm; microwave power: 1.7 kW; pressure: 85 Torr. The temperature of the samples was monitored by an external pyrometer outside the chamber and a thermocouple in the molybdenum stage. Assistive stage heating prior to the PECVD process was used to prevent the quartz spacer from breaking due to the sudden temperature rise coming from plasma. Raman spectroscopic studies were conducted on a Renishaw inVia Raman Microscope with a laser wavelength of 532 nm and a laser spot size of 10 μm. SEM analyses were performed on FEI Nova Nanolab 200. TEM and EELS characterizations were conducted on a JEOL 2100F. The electron energy applied in EELS studies was 80 keV, and the collection angle was 16 mRad. 5 samples were tested in electrical and electrochemical measurements. Electrochemical impedance spectroscopy (EIS) data was acquired using an eDAQ z100 Electrochemical Impedance Analyzer connected to an eDAQ EA163 potentiostat. The frequency range in the EIS measurement was set from 1 kHz to 100 kHz, and the amplitude of the AC signal was kept as small as possible (30 mV) to minimise quantum capacitance effects. Capacitances values were estimated by fitting EIS data to a model circuit using ZMan v2.2 software .AAO samples with 55 nm pore diameter and 100 μm thickness  were placed within the growth chamber of a microwave PECVD system (iplas GmbH). Graphene (the one-step method) and a-C (the first step in the two-step method) were grown on AAO using the following reactor conditions: HHow to cite this article: Zhan, H. et al. Direct fabrication of 3D graphene on nanoporous anodic alumina by plasma-enhanced chemical vapor deposition. Sci. Rep.6, 19822; doi: 10.1038/srep19822 (2016).