The ability to change the secondary electron emission properties of nitrogen-doped graphene (N-graphene) has been demonstrated. To this end, a novel microwave plasma-enabled scalable route for continuous and controllable fabrication of free-standing N-graphene sheets was developed. High-quality N-graphene with prescribed structural qualities was produced at a rate of 0.5 mg/min by tailoring the high energy density plasma environment. Up to 8% of nitrogen doping levels were achieved while keeping the oxygen content at residual amounts (~ 1%). The synthesis is accomplished via a single step, at atmospheric conditions, using ethanol/methane and ammonia/methylamine as carbon and nitrogen precursors. The type and level of doping is affected by the position where the N-precursor is injected in the plasma environment and by the type of precursors used. Importantly, N atoms incorporated predominantly in pyridinic/pyrrolic functional groups alter the performance of the collective electronic oscillations, i.e. plasmons, of graphene. For the first time it has been demonstrated that the synergistic effect between the electronic structure changes and the reduction of graphene π-plasmons caused by N doping, along with the peculiar “crumpled” morphology, leads to sub-unitary (< 1) secondary electron yields. N-graphene can be considered as a prospective low secondary electron emission and plasmonic material. This phenomenon is responsible for the formation of electron clouds (e-clouds) in particle accelerators, which affect particle beam trajectories and introduce beam instabilities. In addition, electron bombardment of the tube walls introduces pressure rise and additional heat loads of these cryogenic systems. All this makes e-cloud effect the major limitation of beam luminosity of modern particle accelerators. Similarly, e-cloud formed in microwave generators of satellite communication devices affects electron trajectories and introduces noise in the communication systems.The development of low Secondary Electron Emission (SEE) materials is of great importance for modern technologies, overarching from space applications (e.g. telecommunication satellites) to particle accelerators. For instance, a significant potential difference between the dielectric and conductive part of satellites can arise due to a difference in their secondary electron yields (SEYs) induced by cosmic rays, igniting discharges that can disrupt normal operation or even destroy the equipment. Additionally, in the presence of an alternating electric field and under resonant conditions, secondary electrons can accelerate to high enough velocities to strike the material and free additional electrons, which can then be accelerated and so forth, leading to an exponential increase of the number of free electrons, a process known as multipacting15. SEE is a surface process that often is not well determined because it depends on the type of the material but also on surface finish, i.e., surface contaminants and morphology. Equally important to have surfaces with low SEY is assuring that these are chemically stable, i.e., inert, as well as conductive. In principle, the potential for electron avalanches formation is avoided by using materials with SEY < 1, but in some applications the threshold can be higher.Since SEE occurs in the topmost 5 nm layer of the material being struck by the primary electrons, the techniques usually employed to mitigate multipacting rely on surface modification by deposition a thin film of a material with lower SEY16. Recent investigations have demonstrated that SEY can be further reduced using a graphene coating of the surface18. Potential advantage of this material in respect to amorphous carbon is its superior chemical inertness. Sian et al. have reported a maximum SEY of 1.4 in Stainless Steel samples coated with graphene using electrophoretic deposition (EPD), down from the 2.4 for the uncoated substrate19. Jie Wang et al. have shown that depositing 6–8 layers of graphene in a copper substrate by CVD lowers the maximum SEY to 1.2520. However, considering practical applications, depositing previously synthesized graphene powder is highly relevant and advantageous as compared of direct growing graphene on the substrates. Sub-unitary values of SEY were reported by Montero et al., in aluminium surfaces coated with graphene nanoplatelets, with significant improvements being obtained by simple change of substrate roughness21. Although, the lack of data regarding essential characteristics of the used graphene  as well as surface finish makes difficult to assess contribution of graphene to the low SEY values reported in their work.Altering the surface composition in order to reduce the SEY has been extensively studied. Carbon-based thin films, in particular of the amorphous kind, are routinely used for this purpose in particle accelerators due to their relatively low SEY (0.95–1.05). By applying an amorphous carbon thin film to a Stainless-Steel surface using DC Magnetron Sputtering, the SEY can be reduced from 2.4 to about 1 while leaving the bulk of the material and its properties virtually unchanged22 and different means of its coating on metallic surfaces. However, in spite of significant development of the graphene market (there are about 250 companies worldwide producing graphene and its derivatives in different forms) massive application of this material is not yet achieved in any area. It has been recently argued by Kauling and co-authors that the reason why graphene did not yet experience a takeoff in any technology is in a low quality of the commercially available graphene and in the lack of its derivatives with tailored properties23. The results of the systematic analysis of commercial graphene purchased from 60 different companies ended up with disappointing conclusions: material produced by the majority of companies contain no more than 10% of graphene; not a single company offers a material with more than 50% of pure graphene; not a single product contains more than 60% of sp2 carbon. To this end, a highly competitive plasma-based alternative that circumvents the drawbacks of conventional chemical technologies has been developed24.The search for low SEY materials to mitigate e-cloud effect has become an important technological demand. New materials with better performance should, ideally, be produced via large-scale, cost-effective, and environmentally clean technologies. In this respect, graphene could become a prime low SEY material candidate due to its electronic structure, chemical inertness31. The advantages of this approach are in its reproducibility and ability to control morphological, structural and functional properties of the synthesized material. The end-result is production of graphene sheets, highly doped by nitrogen (up to 8%at.), collected with ~ 40% in the form of single atomic layers, with very low-content of oxygen (< 1%) and high-ratio of sp2/sp3 carbons (~ 15)31. Coating of stainless steel and copper by this material has recently been performed using electrophoretic deposition, which reduced SEY of samples from about 2.4 to 1.0. Moreover, air exposure of such sample and/or high vacuum baking at about 150 °C for 64 h changes the SEY for just few percent32.It has been reported, for the first time, application of microwave-driven plasmas in atmospheric pressure for the single-step production of N-doped high quality free-standing graphene sheets33. Both processes contribute to the generation of internal secondary electrons by their direct excitation from the valence band or via Landau damping, respectively34. During the transport of internal secondary electrons through the material, which is the second step of SEE, energy loss processes again take place, so that only minority of electrons reaches the surface with sufficient energy to be emitted. The energy loss efficiency of primary and internal secondary electrons depends on the electronic structure, e.g. density of states in the valence band and above the vacuum level, or the ability for plasmon excitation. Doping of graphene by foreign atoms, such as nitrogen, modifies its electronic properties, and significantly affects graphene plasmon performance22. In addition to the usual for pristine graphene, π and π + σ plasmons, low-energy 2D-plasmons appear in doped graphene22. In this regard, the properties of N-graphene are conferred by N atoms within the carbon lattice, where they typically form pyridinic, pyrrolic, graphitic and oxidized nitrogen functional groups. For instance, it was reported that incorporation of nitrogen in the graphene scaffold affects the material work function, depending on the type of functional groups formed: graphitic nitrogen decreases work function, whilst presence of pyridinic and pyrrolic groups affects its increase35. N-doping shifts the Fermi level and opens a band gap near the Dirac point. Each graphitic N can contribute ~ 0.5 electron to π network of the graphene lattice, resulting in an n-doping effect. However, pyridinic and pyrrolic N are formed at the edges or defect sites. These defects impose the p-doping effect accompanied with a downshift of the Fermi level towards the Dirac point and withdrawing electrons from the graphene sheet, i.e., inducing electron-deficient nature of the valence band38.Secondary electron yield of graphene can be further improved by tailoring its electronic structure. Following the three-step model commonly considered describing the SEE, in the first step primary electrons impinging surface lose their energy inside the material mainly by excitation of valence electrons and the creation of plasmons42. Other direct synthesis methods, such as ball milling, solvothermal synthesis, segregation growth, arc plasma, etc. have the potential to provide homogeneous doping, contrasting with post-treatment methods that provide surface doping only. Solvothermal approach typically involves mixing of lithium nitride with tetrachloromethane under moderate to high pressure and temperature that facilitate the interaction of precursors during the synthesis43. The method provides high yield and high doping levels but with very high oxygen content (larger than nitrogen one). Graphene oxide (GO) and nitrogen precursors  are the initial materials for wet chemical methods and thermal treatment. The high temperature required for GO thermal treatment makes the process costly and inefficient. Although the wet chemical approaches can provide cost-efficient large-scale production, they rely on the use of harsh chemistry (e.g. strong acids)48. Moreover, these methods are based on lengthy/complex batch procedures that do not provide control over the assembly process. Plasma post-treatment methods offer short reaction times, low power consumption, but also low yield, inhomogeneous doping, and high level of oxygen content47. To foster N-graphene as a cost-effective material with low SEY several challenges need to be addressed. In the first place is development of a method for large-scale production of N-graphene relying on cost-effective and environmentally friendly synthesis processes, capable of providing controllable and reproducible nitrogen doping.Despite of the numerous approaches available for N-graphene synthesis, either by direct or post-synthesis treatment, many issues remain unsolved, such as the ability to control the type and level of doping. The direct CVD method, for instance, requires high temperature, vacuum systems and suffers from metal interference, low yields and high costs2 radicals, and C atoms, in the high energy–density plasma environment, which translates in an effective control over the energy and material fluxes towards growing nanostructures in the assembly “mild” zone of the reactor, constitutes these methods’ most crucial advantage. Raman spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Near Edge X-ray-absorption fine-structure spectroscopy (NEXAFS) were used to probe the morphological, chemical and microstructural features of the produced material. The secondary electron emission properties of synthesized free-standing N-graphene sheets with different level of doping and dominant pyridinic/pyrrolic N bonding configuration have been examined. The morphology of N-graphene sheets, characterized by wrinkles and lateral corrugations, contributes to suppression of secondary electron emission due to the efficient recapturing of emitted electrons. Furthermore, the changes in the electronic structure of graphene induced by well-controlled level and type of nitrogen doping, with the correspondent changes in the performance of graphene plasmons, have demonstrated the potential to translate in sub unitary (< 1) SEY values. Since the procedure for electrophoretic deposition of free-standing graphene that preserves its overall properties was already developed32, properly customized free-standing N-graphene with low SEY is a promising low secondary electron yield material of interest in accelerators and space technologies.To this end, the synthesis of N-doped graphene through plasma treatment presents significant advantages relatively to other technologies because plasma systems simultaneously comprise thermal and chemical reactor functions along with catalytic properties. Moreover, it provides the ability to control the amount and localization of energy and matter delivered from plasma bulk to developing nanostructures at atomic scale level, the key to achieve the desired morphological, electronic and functional properties of targeted materials. In this work we intent to provide substantial evidence that microwave plasma technologies can be used as a competitive and disruptive alternative route to the chemical methods for the production of self-standing N-graphene sheets with controllable level and type of N doping, i.e. pirydinic, pyrrolic, graphitic, etc. A novel plasma approach is used to achieve in situ doping of the graphene sheets during their assembling and growth in the “mild” plasma zone of the reactor. The control on the type and level of doping has been achieved by changing of N-precursor injection position in the plasma environment, flux of the precursors, i.e. number density of N atoms as well as type of the N bonds configuration in the precursor utilized. Moreover, the possibility to tune the density and energy of the carbon building units, i.e. C24  induced microwave plasma at atmospheric pressure conditions24. The Carbon precursor (e.g. ethanol) mixed with background argon gas is injected in the "hot" high energy density zone where decomposition processes of the injected carbonaceous molecules take place as a result of particles collisions and intensified chemistry. The created radicals become precursors of chain reactions leading to creation of the main building blocks, i.e. carbon atoms and C2 radicals. The next "mild" zone in axial (z) direction includes the "near" plasma afterglow where the gas temperature drops from about 3,000 to 500 K. It is important to note that the gas temperature changes also radially due to the radial thermal losses. The radial profile of the temperature is approximately parabolic. The transport of gas-phase carbon atoms/molecules into colder zones through the so-called vaporization surface27 results in transformation into solid carbon nuclei. An isothermal plasma surface of about 2,500 K is considered as a “boundary of vaporization”. The transport of plasma generated carbon atoms/molecules into colder zones (outside of the vaporization boundary) of the reactor results in formation of solid carbon nuclei that are gradually withdrawn in the outlet plasma stream where kinetic processes of assembly and growth of “flowing” carbon nanostructures take place. Given the fact that the nucleation and growth processes are determined by the interplay of kinetic and thermodynamic factors, the engineering of structural qualities of targeted nanostructures was achieved via synergistic tailoring of the "hot" plasma environment and thermodynamic conditions in the “mild" zone of the plasma reactor. Therefore, by tailoring the temperature gradients, the density of carbon molecules and atoms as well as their residence time, selective synthesis of graphene sheets in a narrow range of operational parameters can be achieved. The processes of assembly and growth of graphene sheets take place in the “mild” plasma zone, during their flight with background gas flow.The reactor can be virtually separated in three different zones as can be seen from the scheme presented in Fig. 3NH2 → 2·CN + 5H2) in the “hot” discharge zone. Furthermore, the formation of HCN as “building blocks” for N-graphene, is due to reactions such as, ·CN + H2 → HCN + H· and ·CN + H· → HCN, occurring in the “mild” plasma zone. Considering down-to-top injection, a gas jet containing the N precursor is sprayed in the “mild” zone  with sufficiently high energy towards "mild" plasma zone. Here, in the larger volume, the departure from the supersaturation conditions of the environment prone to foster nanosheets assembly is deliberately preserved28. Therefore, in the larger volume, the density of carbon nuclei decreases, and, as a result, the conditions favor the creation of planar nanostructures. Moreover, the assembling process requires very fast delivering and stacking of building units and equally fast supply of enough energy to overcome all the actual potential barriers. Thus, the fluxes were adjusted to satisfy conditions for well-tuned residence time of the flowing nanostructures in the “assembly” zone of plasma reactor.Using the reactor with an expanding radius allows large power densities inside the sections with smaller radius and to achieve larger fluxes of building units .Free-standing N-graphene sheets have successfully been fabricated at a relatively high yield (~ 0.5 mg/min) using ethanol and methane as carbon precursors and ammonia and methylamine as nitrogen precursors. It should be noted that the selective synthesis of N-graphene sheets can be obtained in a very narrow range of discharge operational conditions as previously reportedIn the down-to-top scheme the nitrogen precursor injection point is in the “mild” plasma zone at a distance z = 12 cm from the launcher  across different locations, thus indicating nearly homogeneous nitrogen doping of graphene structure. The 2D to G peak intensities ratio (~ 1.2) and the full width at half maximum of the 2D-band (~ 52 cm−1) illustrate that the sample contains graphene sheets composed by few monolayers52. Synthesized free-standing graphene sheets contain few atomic layers, as estimated from the Raman and TEM results. Having in mind that the interlayer distance in the sheets is about 3.46 Å (as shown by XRD) the thickness of these structures is about 1–2 nm.Furthermore, considering a top-to-down injection scheme, carbon/nitrogen precursors have been injected into “hot” plasma region. Typical graphene morphology and corresponding Raman spectra measured at three randomly chosen sample regions are shown in Fig. 2 carbons, while the peak fitted at ~ 286 eV is mainly attributed to carbon bound to nitrogen53 , is quantified. Therefore, N-graphene prepared with methane/methylamine, holds a high nitrogen doping level (Atomic Concentration = 8%). The obtained results reinforce the advantages of the novel plasma-based method as compared with the chemical ones. The graphene lattice structure containing more than 60% sp2 carbons is well preserved after doping and the oxygen level is kept at residual amount, by contrast with the materials synthesized via chemical methods.The use of methane/methylamine as carbon/nitrogen precursors significantly increases the graphene doping level. The survey XPS spectrum Fig. a shows t58 and the σ* resonance at ~ 292 eV59 are detected. Additionally, a peak at ~ 287 eV is observed, which is attributed to C=N bond60. A pronounced peak is detected in N K-edge spectrum  and 402–410 eV (C) are attributed to pyridine-like bonding that arises from transitions from the K-shell to the unoccupied π* orbital64 and to N–C/N–H bonding65, respectively.Furthermore, the Near Edge X-ray-absorption fine-structure (NEXAFS) spectra, presented in Fig. X-ray diffraction analysis made shows that interlayer spacing is about 3.46 Å and exhibits small variations with level of doping . The measured levels of interlayer spacing are larger than those of graphite (3.35 Å) is to be noted.66. The measurement geometry utilizes a four-contact scheme, where pinching point contacts are located on the periphery of the pellet. This design provides measurement of the longitudinal conductivity as far as the current lines are parallel to the pellet surface. Due to the compressing, the individual sheets have parallel orientation, as seen in Fig. In order to assess the electrical conductivity of the graphene sheets and its temperature dependence, 0.1 g of the N-graphene powder was pressed into disc pellets of 8 mm diameter and about 3 mm of thickness. The electrical conductivity was measured applying the Van der Pauw method3 S m−1 are observed at temperature of 300 K. However, the real electrical conductivity should be even higher, considering that the measurements were performed on compressed disks made from individual N-graphene sheets, where a conductive network is formed through the matrix of highly conductive sheets having multiple interfaces between them.Figure 67. A non-monotonic temperature dependence in the measured electrical conductivity and “insulating” behavior at low temperatures is reported for CVD grown monolayer graphene68 and bilayer graphene69. The anomalous transport dependence on temperature in graphene is theoretically studied as arising entirely from disorder effects70. It should be noted that the graphene samples studied consist of compacted graphene sheets and therefore, the temperature dependencies σ(T) could be analyzed in the frame of disordered systems not being the aim of this investigation. We should note that the room temperature values σ (300 T) reveal explicit influence of the N doping content, with the higher atomic percentage showing higher conductivity.The temperature characteristics show thermally activated transport and non-metallic behavior. As resistance increases, conductivity decreases accordingly at decreasing temperature (i.e. dσ/dT > 0), as opposed to typical metal behavior. The measured σ(T) values increase by 65% as temperature T increases from 10 to 300 K. Typical insulators (high work function) or localized systems have dσ/dT > 0. Graphene is a rather unusual electronic material that often exhibits dσ/dT > 0 at certain carrier densities and temperature range while showing the expected "metallic" behavior dσ/dT < 0 in other density and temperature rangesConsidering the morphology and the high electrical conductivity, the properties of synthesized N-graphene flakes as a low secondary electron emission material have been investigated. Moreover, the typical graphene crumpled nature, yielding in highly corrugated surface morphology, can also contribute to reduce SEY. The SEY values of Highly Oriented Pyrolytic Graphite (HOPG) were used as a reference, since secondary electron emission properties of HOPG are well known.71. The setup consists of an electron gun and a large Faraday cup, connected to an electrometer. The sample is mounted on a sample holder placed inside the Faraday cup, in front of the entrance aperture. All measurements have been performed at normal incidence. The sample holder is galvanically decoupled from the Faraday cup. On the entrance of the Faraday cup there is a suppression electrode in the form of an aperture, kept on the potential of − 20 V, in order to reflect the electrons that would otherwise escape. When the sample is in shortcut with the Faraday cup, primary electron beam current Ip is measured. When the sample is biased negatively to − 15 V, the current of all electrons leaving the sample surface Itot is measured. Therefore, the ratio between the two currents is the total electron yield although its major part is secondary electron yield, and it is calculated by the following ratio:SEY measurements in the 40–1,000 eV have been performed on a home-made experimental setup similar to the one described inIt should be noted that SEY measured in this way encompasses not only so-called true secondary electrons (with kinetic energies bellow 50 eV), but also those that are elastically and inelastically backscattered.To restrict the study only to the graphene/N-graphene properties as low SEE materials, the graphene samples for SEY measurements were prepared by powering small quantity of graphene/N-graphene powder on an indium plate, which is then placed in-between two pieces of aluminium foil. Applying pressure of ~ 105 Pa on the plate provides enough adhesion between graphene and indium, while the surface morphology of the graphene sample is not affected. The estimated thickness of such graphene patch is few hundred micrometres, so that primary electrons cannot reach the substrate.32. The pristine graphene morphology is similar to that of N-graphene with low level of doping as evidenced by SEM images  excitation of inner shell electrons in electron-atom collisions , (b) excitation of valence electrons and (c) via excitation of bulk and surface plasmons, i.e., collective oscillations of valence electrons excited by primary electrons during their penetration into the material. The plasmon decay results in the excitation of single valence electrons, i.e. creation of electron–hole pairs in the process of Landau damping53. As seen, this peak is strongly decreased for N-graphene, which in turn results in lower production of internal secondary electrons via plasmons decay. In fact, the π–π* intensity decreases for higher doping levels as seen in Fig. 29, remain nearly the same regardless of the relative amount of N. Furthermore, a very small shift of π electron delocalization towards lower energies is observed for N doped graphene  and (14.5–27 eV), respectively. Both plasmon types have sufficient energy to generate internal secondary electrons in the process of Landau damping. A detailed comparison of the energy loss features in C 1s XPS spectra of pristine and N-graphene is shown in Fig.  eV and  and required doping configurations is about 160 €, much less than the prices of high-quality N-graphene available on the market , while exhibiting much lower SEY values than those of commercial carbons from reference suppliers. The synthesis method shows potential for controllable, large-scale fabrication of other graphene derivatives, while promoting microwave plasmas as a competitive, green, and cost-effective alternative to presently used chemical methods.Furthermore, the possibility to tune or suppress SEE is of fundamental importance in fostering N-graphene’s potential as a key player in improving the performance of low SEE coatings while preserving the properties of the substrates. The synergistic effect of the electronic structure modification and changes in the graphene plasmons behavior that result from the introduction of N atoms in the graphene scaffold, along with the peculiar “crumpled” morphology of the material lead to a decrease in the SEE.These results indicate that plasma-synthesized N-graphene can be considered as a prospective low secondary electron emission material. The demonstrated possibility to tune graphene plasmons behavior is particularly important in improving the performance of plasmonic materials and in inspiring innovative solutions.Supplementary information.


This approach eliminates the generation of toxic gases, simplifies the washing steps, and reduces the time required to prepare rGO. To validate the proposed method, we present spectroscopical and morphological studies, using energy-dispersive X-ray spectroscopy (EDS), UV-visible spectroscopy, infrared spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Thermal gravimetric analysis (TGA) is used to analyze the thermal properties of GO and rGO. This eco-friendly method proposes a complete guideline protocol toward large-scale production of oxidized graphene, with potential applications in supercapacitors, fuel cells, composites, batteries, and biosensors.The oxidative exfoliation of graphite is a promising approach to the large-scale production of graphene. Conventional oxidation of graphite essentially facilitates the exfoliation process; however, the oxidation procedure releases toxic gases and requires extensive, time-consuming steps of washing and reduction to convert exfoliated graphene oxide (GO) into reduced graphene oxide (rGO). Although toxic gases can be controlled by modifying chemical reactions, filtration, dialysis, and extensive sonication are unfavorable for large-scale production. Here, we report a complete, scalable, and green synthesis of GO, without NaNO Althougon atoms . Keepingon atoms ,10 or oxon atoms ,12. The on atoms , whereason atoms ,15,16. Son atoms ,18,19 toon atoms ,21.2−sp3 hybridization as a direct consequence of the degree of oxidation acquired during the oxidation process [4 and NaNO3 in concentrated H2SO4. This procedure involves the generation of toxic gases, such as NO2 and N2O4, and the residual Na+ and NO3− ions are difficult to remove during the processes of synthesizing and purifying GO [Typically, the oxidation–reduction of graphite uses strong oxidizing agents to yield graphene oxide (GO), an insulating carbon material . To date process  . Hummerfying GO ,30,31. W3. The authors successfully demonstrated that this modification does not decrease the yield of the product, but reduces toxic gas evolution and makes the disposal of wastewater more straightforward due to the absence of Na+ and NO3− ions [To circumvent these environmental and technical issues, Chen et al.  have impO3− ions . NeverthO3− ions . Hence, To support this direction, Abdolhosseinzadeh et al.  reported3 [To the best of our knowledge, a reliable method with the capability to supply the large demand for pristine GO and (undoped) rGO by using a green approach, a short-sonication time, and viable washing steps is still lacking. In this communication, such a method is presented, considering the environmental problem and technical limitations. We successfully demonstrate, through several spectroscopy and morphological studies, an eco-friendly and complete guideline protocol for large-scale production of GO by excluding NaNO3  and addi3 .2SO4, ACS reagent, 95.0–98.0%), potassium permanganate , hydrochloric acid , and citric acid  were obtained from Sigma Aldrich. All chemicals were used as received, without further purification. Graphite powder , sulfuric acid  was added, and the solution was stirred for 20 min at 2O2, 30%, Merk) and stirred up to turn the color of the solution from dark brown to yellowish. The resulting graphite oxide suspension was washed with 1:10 HCl solution and distilled water several times, each for 10 min by means of centrifugation at 3000 rpm until the pH was at ~6. The precipitated material was dried at 80 °C for 24 h.It is important to stress once more that the synthesis of GO is based on the approach of Ref. . HoweverInitially, 50 mg of resulting solid was dispersed in 500 mL of distilled water by sonication for 0.5 h, employing an ultrasonic bath  in continuous operation. Bath sonication is preferred to tip sonication because the direct positioning of the tip in the medium results in strong material fragmentation . The obtThe characteristic absorption spectra of GO and rGO were recorded using UV-vis spectroscopy . Infrared spectra were collected using a Fourier transform infrared spectrometer Jasco FT/IR-4000 . The thermal stability of GO and rGO was investigated using thermogravimetric analysis . The structure and surface morphology of the obtained materials were taken out on a transmission electron microscope  operating at 80 kV, and a scanning electron microscope  equipped with a JEOL-made dispersive X-ray spectrometer (EDS) with the accelerating voltage of 15 kV. Raman spectra were obtained using a Jasco NRS-500  spectrometer with a 532 nm laser wavelength . SEM samples were prepared by drop casting on aluminum substrates and dried at 80 °C for 2 h. Similarly, TEM and Raman samples were prepared by drop casting onto formvar-coated copper grids and glass substrates, respectively.The main intent of this work is to propose a general eco-friendly approach to large-scale production of oxidized graphene. In this sense, we have selected CA because it is a green and low-cost alternative for conventional reducing agents of GO  , C−1), C−1), and C−1). The broad peak observed at 3426 cm−1 is due to the hydroxyl groups  and more stable oxygenated functional groups, respectively [ectively . On the ectively . TGA cur−1 and the G peak at −1. Other less intense peaks also have been detected: the 2D peak at −1 and the D+G peak at −1. The D and D+G (the combination of D and G bands) peaks are ascribed to structural imperfections of GO and rGO  wD/IGI) is a common index for the density of defects on GO and rGO. As shown in earlier studies [The peak ratio between the intensity of D and G peaks  of rGO is shifted with respect to the 2D peak (−1) of GO. The latter was impossible to be fitted, and the maximum intensity value was removed from the data (−1. Furthermore, the 2D peak became more symmetrical in rGO, indicating the presence of few-layer-reduced graphene oxide.Unlike the 2D peak of monolayer graphene, which has high intensity, the 2D peak of GO and rGO is complex in shape and evolves with the number of layers . The prethe data c. The reSEM and TEM micrographs of GO and rGO are shown in 3 [.This asseveration is supported by TEM analysis. 3 ,30.Figu3 in the oxidation and adding CA in the reduction, which demonstrated to be an effective and inexpensive reducing agent for GO. EDS measurements showed a reduction effectivity from 0.5 to 1.5 h, while GO is in contact with CA under vigorous agitation. UV-visible spectra confirmed the reduction of GO into rGO. FTIR analysis demonstrated the presence of oxygen functional groups, which decreased in intensity after reduction. The thermal stability of rGO was found to be higher compared to GO. Raman spectra showed a high intensity of the D peak in GO, indicating the presence of basal/edge defects; however, the characteristic 2D peak of graphene arose in rGO. SEM measurements showed that the semitransparent layers were relatively free of impurities. TEM analysis presented similar features. However, rGO exhibited a more regular, transparent, and thin nanosheet. The proposed method prevents toxic gas evolution, prolonged sonication, and complicated washing steps, making it effective at preparing oxidized graphene on a large scale.In summary, we have established a complete and green protocol for the preparation of GO and rGO by excluding NaNO


The top priority of fire management agencies in Canada is to protect human life and property. Here we investigate if decades of aggressive fire suppression in the boreal biome of Canada has reduced the proportion of recently burned forests  near human communities, and thereby inadvertently increased the risk of wildfire. We measured the percentage of RBF, which are usually less flammable than older forests, up to a 25-km radius around communities compared to that in the surrounding regional fire regime zone. Our analysis of 160 communities across boreal Canada shows that 54.4% exhibited a deficit or lack of RBF, whereas only 15.0% showed a surplus. Overall, a majority (74.4%) of communities are surrounded by a low (≤10%) proportion of RBF, indicating a higher vulnerability of those communities to wildfire. These findings suggest that suppression policies are increasing flammability in the wildland–urban interface of boreal Canada. A primary element of modern wildfire management is to aggressively suppress small fires before they become large, but benefits can be offset by the fact that these practices promote older forests that are more ‘flammable’. Here the authors show that this downside puts numerous human communities at elevated risk of fires in boreal Canada. Identifying the drivers of this change is, however, challenging given that wildfire is a complex phenomenon influenced by several natural and human variables4. This includes changes in weather and climate resulting from increased atmospheric CO2, fuel  composition and continuity, human land use, and fire management policies and practices. Increasing population growth in wildfire-prone areas5 combined with projections of greater burn rates due to climate change could further exacerbate the risk of wildfire to people and property7. In Canada, this growing threat of wildfire requires a comprehensive approach to fire management8, of which one aspect is efficient fire suppression around communities. However, the effect that management policies and practices have had on boreal burn rates is still not fully understood9. For example, although people are responsible for more than half of ignitions in boreal Canada10, people also limit wildfire through fire-suppression activities, such as early detection and rapid initial attack, resulting in a net decrease in area burned by wildfires12. Fire suppression may thus result in a wildfire deficit that has directly contributed to an increase in the amount and continuity of flammable biomass, especially around communities14.Over the past half century, Canada’s forests have experienced an upward trend in annual area burned, particularly in western Canada1. Those large fires greatly reduce the amount of flammable material and are mostly lethal to trees15. Post-fire boreal forest stands that are <30 years in age are less likely to burn than older forests due to the combined effects of depletion of biomass after fire and the slow regrowth of vegetation  of high-latitude forests16. This leads to a reduced potential for fire ignition and subsequent propagation17, and this negative feedback between fire and fuels has been observed throughout the biome  would be substantially higher22.The wildfire regimes of the North American boreal forest are characterized by a combination of numerous small fires and relatively infrequent large high-intensity crown fires that have a disproportionate impact 24. The ‘intensive’ zone is managed with aggressive and systematic fire-suppression policies due to its greater wildland–urban interface (WUI) and natural resource-related values . In this zone, fire management is focused on aggressive fire suppression that involves rapid detection and response to extinguish low-to-moderate intensity fires, while they are relatively small . In the more remote ‘extensive zone’, fires are often monitored but generally allowed to burn with minimal intervention, unless there are human values at risk, in which case active fire suppression is employed25. Fire management agencies throughout the country prioritize public safety and community protection over other values, regardless of the fire management zone26. In other words, while fire-suppression policies may affect fire regimes over broad areas27, their impacts are most pronounced close to communities.In Canada, fire management efforts are spatially variable and can be broadly split into ‘intensive’ and ‘extensive’ fire protection zones28. Have the long-term effects of fire management policies limited the prevalence of young stands and increased forest flammability around boreal communities? If such an increase is borne out, fires burning in the vicinity of some communities will likely be more intense  and be more difficult to control than those in the overall forest matrix29. Anecdotally, recent catastrophic wildfire events in the WUI have burned through forests that had been spared by wildfires for several decades. This was the case of the 2016 Fort McMurray wildfire , which became the costliest natural disaster in modern Canadian history ($3.64 billion CND in insured losses), as this 590,000-fire spread almost entirely through forests that had not burned since the 1940s or earlier.Decades of aggressive fire suppression around communities in boreal Canada likely has altered the forest mosaic by promoting the retention of older forest stands compared to what would have occurred under a naturally functioning fire regime30. This allowed us to: (1) compare the proportion of RBF around communities to that of the corresponding FRZ, (2) identify where high fire hazard (RBF ≤  10%) communities were located, and (3) qualitatively evaluate whether communities recently impacted by wildfire were predominantly surrounded by old forest, suggesting a fire deficit and increased risk of wildfire.Here, we investigate the potential flammability of forest cover surrounding communities relative to the overall forested landscape in the boreal biome of Canada. Specifically, we calculated the proportion of forest stands that burned <30 years ago (termed ‘recently burned forests’ (RBF)) in 5-km radius concentric bands (up to 25-km) around selected communities and compared this to the RBF percentage within the forest matrix further away from communities that are considered to have similar fire regimes (hereafter ‘fire regime zones’ (FRZ); Fig. Our results show a low percentage of RBF (forests <30 years old) around most communities Fig.  and a fiA majority (74.4%) of communities in the boreal biome of Canada are surrounded by older forests  within a 10-km radius Fig. . When rep < 0.05; Mann–Whitney test) greater percentage of open water in their vicinity (10-km radius) compared to randomly selected points in that zone  varied among FRZ. Communities in most FRZ  had a significantly  spent annually on firefighting crews, equipment, and aircrafts35. While suppression has proven effective in many parts of the boreal forest12, its effectiveness is likely to degrade as limited fire-suppression resources become increasingly overwhelmed under projected climate changes36.Wildland fires are dependent on three factors that are increasingly coinciding in time and space: flammable fuels, ignitions, and fire-conducive weather26 and that most fire ignitions (per unit area) occur closest to human development, firefighting resources are often stationed in or near communities. This allows them to attack many fires when they are small and low in intensity, thus increasing the probability of successful containment37. Extinguishing wildfires before they become large increases the age of the forest and the amount and continuity of flammable vegetation near communities, thereby unintentionally amplifying the fire hazard in the long run around these same values that we seek to protect. In fact, successful fire suppression without subsequent modification of the forest  will inevitably lead to vegetation conditions characteristic of a fire deficit. This effect, termed “fire paradox”38, has already been observed in many fire-prone ecosystems of the USA (refs. 40). Our results show that this is also occurring in parts of Canada.Given that protecting people and property is the highest priority for fire management agencies41. We show that, relative to the forest matrix, there is a significant lack of RBF within 5 km and up to 25 km for many communities in the Canadian boreal biome, a majority of which are located in the western half of Canada and in FRZ where settlements are generally more remote and the burn rates are higher. However, little or no fire deficit around a community does not necessarily imply low exposure to wildfire. In eastern Canada, for example, wildfires are inherently less frequent, generally resulting in lower fire deficits surrounding communities compared to western Canada. Consequently, forests in general and those around communities in eastern Canada are considerably older than those in western Canada  that burned several kilometers into an 8-year-old forest during 2 days of extreme weather22. Identifying the specific weather conditions at which the flammable biomass limitation is overcome represents an active area of research46; however, high-resolution historical reconstructions16 and meteorological analysis of particularly extreme fire seasons, such as the 2014 season in the Northwest Territories  management50, and, where feasible, prescribed burning52. There are, however, many physical, policy, and operational challenges to overcome. Mechanical fuel treatments require continued maintenance over time, are too expensive to apply across large boreal landscapes53, and are usually not designed to halt extreme wildfires54. Unlike the forests of other North American biomes, vegetation management in the boreal forest can be less focused on modifying forest structure  and instead emphasize changes to forest composition. For example, where possible and ecologically desirable, encouraging the establishment of deciduous stands through forestry practices represents an attractive option for drastically reducing the likelihood of wildfire over larger expanses of forest55.Our results reaffirm the urgent need for a more holistic approach to wildland fire management that emphasizes proactive mitigation to complement an efficient fire-suppression system as a means to reducing the risk of wildfires to communities57, the propensity of coniferous boreal forests to burn as high-intensity crown fires can make prescribed burning a risky proposition for some residents and decision-makers. The risk tolerance to prescribed burning may, however, increase as the need for hazard reduction becomes critical. For example, in Banff, Alberta , which welcomes millions of tourists annually, Parks Canada has garnered public approval to maintain an active prescribed burning program for forests adjacent to the town since the early 1990s. The risk to the community is minimized by burning almost exclusively during the spring and fall, and by burning small parcels frequently  rather than conducting single large burns, practices that are consistent with traditional indigenous burning practices in that area51.Although prescribed burning programs in boreal forests would reset the stand age and effectively reduce wildfire potential for decades to come58. Recognizing, however, that there is no single solution or silver bullet to reducing the risk of wildfires to communities, breaking the continuity of older, highly flammable forests must be an element of a comprehensive approach to managing wildland fire risk26.Large, high-intensity wildfires are inevitable in the boreal forest and the absence of other plausible factors explaining reductions of RBF around many communities lends credence to the presumption that fire management policies, particularly fire suppression, are contributing to a fire deficit. Identifying the critical proportion of RBF necessary to substantially reduce the risk remains an open question, but even a modest increase in the proportion of RBF could be highly beneficial in some instances, especially when fire management strategies maximize the use of non- or less-flammable features across the landscape. The disproportionately high density of ignitions around communities combined with a greater continuity of older forests in some locales in boreal Canada may increase the call for more fire suppression, especially if projections of more extreme fire weather are borne out59. This region is generally bounded to the north by the transition to tundra and to the south by prairie and temperate forest ecosystems. This study area was subdivided for analysis into 12 FRZ, ecographic units considered to have similar fire regimes30. Although the zonation exists for all of Canada, only those FRZ in the boreal biome were considered, and of these, zones with fewer than six communities  were excluded from the analyses summarized by FRZ (see below). All analyses were performed using the R software v3.6.1 and ArcGIS Enterprise v10.7 for Windows.The study area included all of boreal Canada Fig. , as defi60 based on the following criteria. Communities with a population <200 (ref. 61) were excluded from the analysis because many of them were temporary (or even abandoned) settlements. We removed communities with >30% natural or anthropogenic nonfuel within a 25-km buffer  to eliminate boreal communities with largely non-forested surroundings. Communities on islands in large lakes were also excluded. Next, we retained only one community from pairs or groups within 25 km of one another to eliminate spatial overlap in the analysis. A community was retained if its population was at least twice that of these nearby communities. If this condition was not met, the community with the greatest forest cover within 10 km was retained, based on land cover analysis of 2014 forest vegetation62. Finally, the remaining 160 community centroids were spatially corrected using aerial imagery .From an initial dataset of 381 boreal communities, 160 communities were selected from a geographic dataset of populated places63. Fire polygons were rasterized at a resolution of 250 m and overlaid to calculate time since fire. All permanent nonfuel  was masked out using the kNN Canadian land cover dataset62. We produced a map of RBF by classifying any pixel with an age <30 years (1988–2017) as RBF, and any pixel with an age ≥30 years as non-RBF. Forest harvest areas, which were based on a Canada-wide Landsat-based 30-m resolution change-detection dataset from 1985–2015 , were not considered in the calculation of RBF.The National Burned Area Composite was used to analyze wildfire patterns across the study area34, for comparison; although the results were broadly similar, HFZ were too large and encompassed an unacceptable degree of variation in fire regimes, and were thus subsequently dropped.Statistics on RBF were computed for each community and FRZ. Concentric buffers, 5 km in width and centered on community boundaries, were used as analysis units, up to a maximum of 25 km. We calculated the percent RBF of the total area of forested lands within buffers after masking permanent nonfuels . To limit any interaction among neighboring communities, parts of buffers were removed where they overlapped another community’s buffer with a narrower radius . We removed all pixels within 2 km of community boundaries to limit the effects of outlying residences, infrastructure, and other compounding factors. The percentage of RBF within these concentric buffers, averaged for all communities of a FRZ, was compared against the percentage of RBF of the entire FRZ in which they were located. The analysis was also performed using an alternative fire zonation scheme, the homogeneous fire zones (HFZ)45. To investigate the sensitivity of this threshold, we repeated the analysis with a threshold of 20 (1998–2017) and 40 (1978–2017) years. The 20- and 40-year definitions of RBF yielded results coherent to those of the 30-year definition, suggesting that our results are not overly sensitive to the choice of age threshold  was disproportionately higher around our selected communities relative to the areas of the fire zones. Using the 5-km buffers, we compared the percentage area harvested near communities against percentage area harvested across FRZ for a 30-year period.We conducted several supplementary analyses to investigate whether other factors were related to the prevalence of RBF near communities, including ignition density, forest harvest percentage, and land cover. Ignition density was calculated within 5-km concentric buffers centered on our selected communities and compared to the ignition density outside of this buffered area, considering all fires larger than 0.1 ha from 1988–2017. We also verified if forest harvest from 1985–2015 , and deciduous forest, which is considered substantially less flammable than coniferous forests. The analysis of water was carried out using the Canada MODIS Land Cover Time SeriesFurther information on research design is available in the Supplementary InformationReporting Summary


PNNs restrict cortical network plasticity but the molecular mechanisms involved are unclear. We found that reactivation of ocular dominance plasticity in the adult visual cortex induced by chondroitinase ABC (chABC)-mediated PNN removal requires intact signaling by the neurotrophin receptor TRKB in PV+ neurons. Additionally, we demonstrate that chABC increases TRKB phosphorylation (pTRKB), while PNN component aggrecan attenuates brain-derived neurotrophic factor (BDNF)-induced pTRKB in cortical neurons in culture. We further found that protein tyrosine phosphatase σ , receptor for CSPGs, interacts with TRKB and restricts TRKB phosphorylation. PTPσ deletion increases phosphorylation of TRKB in vitro and in vivo in male and female mice, and juvenile-like plasticity is retained in the visual cortex of adult PTPσ-deficient mice (PTPσ+/−). The antidepressant drug fluoxetine, which is known to promote TRKB phosphorylation and reopen critical period-like plasticity in the adult brain, disrupts the interaction between TRKB and PTPσ by binding to the transmembrane domain of TRKB. We propose that both chABC and fluoxetine reopen critical period-like plasticity in the adult visual cortex by promoting TRKB signaling in PV+ neurons through inhibition of TRKB dephosphorylation by the PTPσ-CSPG complex.Perineuronal nets (PNNs) are an extracellular matrix structure rich in chondroitin sulfate proteoglycans (CSPGs), which preferentially encase parvalbumin-containing  by chondroitinase treatment, or by chronic antidepressant treatment. We now show that the effects of both chondroitinase and fluoxetine are mediated by the neurotrophin receptor TRKB in parvalbumin-containing (PV+) interneurons. We found that chondroitinase-induced visual cortical plasticity is dependent on TRKB in PV+ neurons. Protein tyrosine phosphatase σ , a receptor for PNNs, interacts with TRKB and inhibits its phosphorylation, and chondroitinase treatment or deletion of PTPσ increases TRKB phosphorylation. Antidepressant fluoxetine disrupts the interaction between TRKB and PTPσ, thereby increasing TRKB phosphorylation. Thus, juvenile-like plasticity induced by both chondroitinase and antidepressant treatment is mediated by TRKB activation in PV+ interneurons. Plasticity is the ability of the brain to change itself through establishing new neuronal connections and rewiring existing ones. Plasticity is prominent in early life and it peaks during so-called “critical periods” when the ability of the brain to adapt is at its highest . After t+) orchestrate synchronous neuronal oscillations and play a particularly important role in this process  around them  balance that take place because of maturation of cortical inhibitory interneurons. Fast-spiking interneurons expressing parvalbumin  might be a nexus that mediates plasticity processes induced by both methods. PTPσ is a receptor for CSPGs , and it + interneurons is essential for plasticity induced by chABC. While CSPGs removal by chABC injection into the visual cortex promotes ocular dominance shift, this effect is abolished in heterozygous mice with reduced TRKB in PV+ neurons (PV-TRKB+/−). We have confirmed that PTPσ interacts with TRKB, and genetic deficiency of PTPσ promotes TRKB phosphorylation (pTRKB) in vitro and in vivo. We further show that PTPσ deficiency promotes plasticity at network levels, as PTPσ+/− mice display critical period-like plasticity in the visual cortex in adulthood. Finally, we have observed that the antidepressant fluoxetine disrupts TRKB:PTPσ interaction in vitro and in vivo.We now demonstrate that TRKB activity in PVPTPRS gene (PTPσ+/− mice) and their wild-type (WT) littermates, C57BL/6J mice heterozygous for TRKB gene in PV+ interneurons (PV-TRKB+/−) and their PV-Cre littermates (PV-TRKB+/+), WT C57BL/6J mice were used in the experiments. BALB/c PTPσ+/− mice were originally developed by Michel Tremblay's lab  mice were generated by mating heterozygous floxed TRKB mice  littermates with intact TRKB in PV+ neurons were used as a control group for PV-TRKB+/− mice. The mice were four months old at the beginning of the experiments. WT C57BL/6J mice five months old were used to assess fluoxetine effect on TRKB:PTPσ interaction in the visual cortex in vivo. The mice were kept under standard laboratory conditions with 12/12 h light/dark cycle (lights on at 6 A.M.) and access to food and water ad libitum. All the procedures involving animals were done in compliance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals guidelines and were approved by the Experimental Animal Ethical Committee of Southern Finland (ESAVI/10 300/04.10.07/2016).BALB/c and C57BL/6J mice heterozygous for 2. The death was confirmed by ascertaining cardiac and respiratory arrest. The animals were decapitated, the visual cortices were dissected and stored at −80°C. Samples from the primary visual cortex were sonicated in NP lysis buffer  containing a protease and phosphatase inhibitor mix  and 2 mm Na2VO3. The homogenate was centrifuged for 15 min at 15,000 × g, 4°C. The supernatant was collected and used for further analysis. Protein levels were measured using DC Protein Assay kit  by colorimetric Lowry method in Varioskan Flash (Thermo Fisher Scientific).Mice were killed with COin vitro (DIV). For the experiments assessing the effect of PTPσ genetic deficiency on pTRKB in vitro, cortical cell cultures were prepared from BALB/c mouse embryos  extracted on E18 using the same protocol as described above for the rat cells. Mouse fibroblast cells stably expressing full-length TRKB (MG87.TRKB) or TRKA (MG87.TRKA) were cultured in DMEM supplemented with 10% fetal calf serum (FCS), 1% penicillin/streptomycin (PS), 1% L-glutamine, and 400 mg/ml G418. Human-derived HEK293T cells were cultured in DMEM supplemented with 10% FCS, 1% PS, and 1% L-glutamine.Cerebral cortical cell cultures were prepared from Wistar rat (Harlan Labs) embryos extracted on embryonic day (E)18 . The celWe transfected 70% confluent MG87.TRKA, MG87.TRKB, and HEK293T cell lines using Lipofectamine 2000 (Thermo Fischer Scientific). MG87.TRKA and MG87.TRKB cells were transfected with PTPσ (RefSeq number NM_019140) Myc-DDK-tagged open-reading frame (ORF) plasmid purchased from OriGene (#RR209636), pCMV6-Entry vector with C-terminal Myc-DDK Tag (#PS100001) was used to transfect control cells. HEK293T were transfected with GFP-tagged full-length TRKB plasmid , PBS with Tween 20 (PBST) was used for ELISA .Aggrecan was purchased from Sigma-Aldrich (A1960). Anti-phospho-TRKA (Tyr490)/TRKB  rabbit monoclonal antibody (mAb) was purchased from Cell Signaling Technology . Anti-TRKB goat polyclonal antibody (pAb) was bought from R&D Systems, #AF1494. Anti-phosphotyrosine mouse monoclonal antibody (clone PY20) was purchased from Bio-Rad (#MCA2472). Anti-PTPσ (SS-8) mAb was purchased from Santa Cruz Biotechnology (SC-100419). Secondary horseradish peroxidase (HRP)-conjugated antibodies were purchased from Bio-Rad (goat anti-rabbit #1705046 and goat anti-mouse #1705047) and from Invitrogen (rabbit anti-goat #611620). Enhanced chemiluminescent (ECL) substrate WesternBright Quantum HRP substrate (Advansta) was used for Western blotting (#K-12042). Pierce HRP ECL substrate was used to detect luminescence in ELISA . Tris-buffered saline with Tween 20 (TBST) was used for Western blotting ; 20 ng/ml BDNF was added to cortical cells for 10 min; 0.1 and 1 μm sodium orthovanadate and protease inhibitor mix. The homogenized suspension was centrifuged , and the resulting supernatant was used for analysis. For immunoprecipitation, TRKB was captured using anti-TRKB antibodies (R&D Systems). The samples were incubated with Sepharose, washed with NP lysis buffer twice and the proteins were separated by heating in 2× Laemmli buffer  for 5 min at 95°C. The samples were loaded to NuPAGE 4–12% Bis-Tris Protein polyacrylamide gels , and the proteins were separated according to their molecular weight using electrophoresis. The samples were transferred to polyvinylidene difluoride (PVDF) membrane, incubated in 1:1000 primary antibody dilution in 3% bovine serum albumin (BSA) in tris-phosphate buffer containing 0.1% Tween 20 (TBST) overnight at 4°C and subsequently incubated in HRP-conjugated secondary antibodies  for 1 h at room temperature (RT). The bands were visualized using chemiluminescent western blotting substrate in Fuji LAS3000 camera (Tamro Medlabs).The cells were lysed using NP lysis buffer containing 2 mm sodium bicarbonate and 42.6 mm sodium carbonate, pH 9.8). On day 2, the plate was incubated for 2 h at RT in the blocking buffer (3% BSA in PBST) to block non-specific binding. Homogenized and centrifuged brain samples or lysed cell samples were added to the plate and incubated overnight at 4°C. On day 3, the plate was washed four times with PBST using an automated plate washer (Thermo Fisher Scientific Wellwash Versa), and the samples were incubated in anti-phosphotyrosine or anti-pTRKB antibodies diluted 1:1000 in the blocking buffer overnight at 4°C. On day 4, the samples were washed four times in PBST and incubated with tertiary HRP-conjugated antibodies in the blocking buffer (1:5000) at RT for 1 h. Finally, ECL was added to the plate and luminescence was measured with 1-s integration time using Varioskan Flash plate reader (Thermo Fisher Scientific). Levels of TRKB:PTPσ interaction were evaluated by ELISA using a similar protocol. TRKB was captured using anti-TRKB antibodies, and anti-PTPσ were applied afterward to assess levels of PTPσ bound to TRKB.Levels of pTRKB were evaluated using ELISA for pTRKB developed in our lab . On day Cell-surface ELISA was conducted to assess PTPσ levels found on the cell surface as previously described . BrieflyTransparent skull surgery was conducted as described previously . Animals+/− versus WT experiment and 7 d for the PV-TRKB+/− versus WT experiment. The integrity of the suture was checked on a daily basis before the lights were on.MD was conducted by suturing the eye contralateral to the imaged hemisphere (left eye) with perma-hand silk thread (Ethicon). The length of the MD was 3.5 d for the PTPσ2:air.Optical imaging of intrinsic signals was conducted as previously described . Visual Four-month-old mice were used for the experiments. During week 1, the animals underwent transparent skull surgery. After 7 d, during week 2, the animals underwent the first session of the optical imaging under isoflurane anesthesia (IOS1). During week 3, the animals were injected with 50 mU of chABC in PBS or PBS into the binocular area of the visual cortex and were subjected to MD for 7 d. During week 4, the eyes were opened, and IOS2 immediately took place.Two-month-old mice were used for the experiments. During week 1, the animals underwent transparent skull surgery. After 7 d, the animals underwent the first session of the optical imaging (IOS1) followed by MD for 3.5 d. We have switched to the shorter MD length as compared with the previously described experiment since it has been recently demonstrated to be sufficient for the induction of the critical period-like plasticity . On day The mice were anesthetized with isoflurane combined with 0.05 mg/kg buprenorphine analgesia. Images acquired during the first session of the optical imaging were used to identify the binocular area of the visual cortex. A hole in the skull was made with a drill, and 50 mU of chABC in 1 µl of PBS or 1 µl of PBS was injected in the center of the binocular area using a microsyringe pump; 10-µl Nanofil syringe (WPI Nanofil) with drilled 1.1-mm outlet bore to accommodate 1.0-mm glass needle and custom-made bevelled borosilicate glass needles with a 50-µm tip diameter were used for the infusions. Infusions were done at the speed of 2 nl/s. After the surgery, the animals were left to recover in the home cage, and the second imaging session took place 7 d later.in vivo fluoxetine experiment . Parametric tests were preferentially used to gain statistical power. Exceptions were made whenever the data presented lacked homoscedasticity or when variables were discrete, in which cases non-parametric tests were chosen. The statistical tests used in each particular experiment and statistical values are described in the legend of figures, and statistical values are provided in p < 0.05. Statistical analysis and plots were made in GraphPad Prism 6 software. Data are presented as mean ± SEM. Detailed information on the statistical analysis of each experiment, and number of samples/animals used is given in The experiments were designed taking into account good laboratory practices and the 3Rs principle of animal research. Both sexes of mice were used in all the experiments involving animal testing, except for the Digestion of PNNs by chABC is a well-known activator of plasticity , and it + interneurons is involved in chABC-induced plastic changes. For that purpose, we generated mice heterozygous for full-length TRKB allele in PV+ interneurons , as previously shown . These data demonstrate that chABC-mediated reactivation of visual cortical plasticity is dependent on intact TRKB signaling in the PV+ interneurons.We tested the hypothesis that TRKB functioning in PVly shown . Howeverin vitro (DIV) for 7 d with 2 U/ml chABC for 30 min and checked the activation of TRKB by assessing its phosphorylation levels .Next, we assessed whether PNN digestion with chABC induces TRKB activation in primary cerebral cortical neurons. We treated rat cortical neurons grown s pTRKB; . We obsein vitro B.in vitro); however, it significantly decreased BDNF-induced pTRKB (C). Taken together, these data demonstrate that PNNs regulate plasticity in a TRKB-dependent manner in vivo and that PNNs exert negative effects on TRKB activation in vitro.After observing that PNN digestion with chABC treatment positively affects pTRKB, we investigated whether treatment with aggrecan, a major PNN component in the adult CNS, might have an opposing effect on pTRKB and render BDNF-induced TRKB activation less effective. We added 10 µg/ml aggrecan to the primary cortical neurons cultured for 6 DIV. After 24 h, we challenged the cells with 20 ng/ml BDNF for 10 min. Aggrecan treatment did not alter basal pTRKB levels , were transfected with myc-PTPσ, immunoprecipitated with anti-TRKB antibody and blotted for PTPσ. In the transfected samples, we observed a band below 250 kDa (A), which is consistent with the predicted molecular weight of the plasmid's product. Additionally, a 165-kDa band was observed in non-transfected cells, which corresponds to the endogenous mature full-length PTPσ . Since transgenic mice quite often develop compensatory mechanisms to counteract genetic deficiency, we wanted to confirm that neurons lacking PTPRS allele would present comparable reduction in PTPσ:TRKB protein interaction. We prepared E18 neuronal cultures from cortex of WT or PTPσ+/− littermates, and compared them after 7 DIV using co-immunoprecipitation. We observed a reduction of ∼50% in the interaction between TRKB and PTPσ in samples from PTPσ+/− mice as compared with WT (B). Then, we further investigated whether PTPσ influences pTRKB. We compared cortical pTRKB levels in embryonic cultures from PTPσ−/− and PTPσ+/− mice with those in cultures prepared from their WT littermates. Notably, PTPσ had a clear gene dosage-dependent suppressive effect on the basal pTRKB. PTPσ+/− cortical cultures demonstrate increased pTRKB as compared with cultures from their WT littermates, and PTPσ−/− samples demonstrate yet further increased pTRKB significantly differing from both PTPσ+/− and WT samples (C). We also checked the levels of pTRKB in samples from the adult visual cortex of mice heterozygous for PTPRS gene (PTPσ+/−). In line with our in vitro data, adult PTPσ+/− mice exhibit increased basal TRKB autophosphorylation in the visual cortex (D), despite having slightly reduced levels of total TRKB (E), which may represent a compensatory downregulation because of a long-term increase in pTRKB.Next, we set out to investigate the role of PTPσ in pTRKB by using mice heterozygous for PTPσ , indicating that closure of the critical period was delayed or prevented in the PTPσ+/− mice.Finally, we investigated whether increased TRKB signaling produced by genetic deficiency of PTPσ might render the cortical structures of PTPσ+/− mice F, indica+ interneurons in the amygdala and hippocampus, shifting PV+ interneurons toward an immature state and reopening brain plasticity (m) for 30 min. Fluoxetine dose-dependently reduced the interaction between TRKB and PTPσ in vitro as measured by ELISA (A). Since fluoxetine has been shown to increase pTRKB as fast as 30 min after systemic injection  and killed the animals 30 min after the injection. Acute fluoxetine treatment significantly reduced TRKB:PTPσ interaction in vivo (B).Antidepressants have been demonstrated to induce activation of TRKB receptors in the brain . Moreoveasticity . Therefoby ELISA A. Since njection , we chec in vivo B.C). These data indicate that fluoxetine does not affect PTPσ shedding and positioning on cell surface, and supports the idea that the decrease in PTPσ levels in co-IP experiments is a result of decreased interaction with TRKB.PTPσ is proteolytically processed by cleavage in the juxtamembrane region, leading to shedding of the extracellular domain . To ruleFig. 3m) failed to influence TRKB:PTPσ interaction in the cells carrying R427A/Y433F mutated TRKB (D), providing evidence that the site of interaction of PTPσ and fluoxetine with TRKB lies within the transmembrane region of TRKB.Antidepressants have recently been shown to directly interact with TRKB through the transmembrane region . Moreoveted TRKB D, provid+ interneurons. PNNs, extracellular structures rich in CSPGs, are associated with a reduction of plasticity in the adult brain. Maturation of PNNs coincides with the closure of the critical period  and in samples from the visual cortex of PTPσ+/− mice. Moreover, we observed that genetic deficiency of PTPσ delays the closure of critical period-like plasticity in the adult visual cortex, an effect that we demonstrated to be dependent on TRKB in PV+ neurons.CSPGs, major components of PNNs, have been shown to exert inhibitory action on plasticity through protein tyrosine phosphatase receptor type S . PTPσ ha with WT . Interes with WT . Faux et with WT . We have+ interneurons is sufficient for the induction of juvenile-like plasticity in the adult brain and necessary for the plasticity-inducing effects of fluoxetine (TRKB signaling is known to be critical for activation of plasticity by antidepressant drug treatment and for the behavioral consequences of it . Moreoveuoxetine . We now uoxetine . These dAntidepressants have recently been shown to directly interact with TRKB through its transmembrane domain . Our dat+ neurons, which releases TRKB from the PTPσ-mediated dephosphorylation and promotes its autophosphorylation. Chondroitinase treatment downregulates CSPG-mediated activation of PTPσ, which allows for enhanced signaling of TRKB (Our findings suggest a general mechanism responsible for the opening of critical period-like plasticity in the adult brain by chABC and antidepressant treatment . We prop of TRKB . Antidep of TRKB .+ interneurons is a critical regulator of chABC-induced and antidepressant-induced plasticity in the adult cortex. The similarity in the plasticity-promoting effects of chABC and antidepressants prompted us to focus on these two treatments, but there are a number of other methods known to reactivate juvenile-like plasticity in the adult cortex (+ interneurons.Taken together, our data reveal that interaction between TRKB and PTPσ in PVt cortex , such ast cortex , 2014 ant cortex . It will


Since the discovery of TAR DNA-binding protein 43 (TDP-43) in 1995, our understanding of its role continues to expand as research progresses. In particular, its role in the pathogenesis of Alzheimer’s disease (AD) has drawn increasing interest in recent years. TDP-43 may participate in various pathogenic mechanisms underlying AD, such as amyloid β deposition, tau hyperphosphorylation, mitochondrial dysfunction, and neuroinflammation. Because AD is complex and heterogeneous, and because of the distinct characteristics of TDP-43, mostly seen in the oldest-old and those with more severe clinical phenotype, subcategorization based on specific features or biomarkers may significantly improve diagnosis and treatment. AD-like cognitive dysfunction associated with TDP-43 pathology may therefore be a distinct encephalopathy, referred to as limbic-predominant age-related TDP-43 encephalopathy (LATE). TAR DNA-binding protein 43 (TDP-43) is a 414-amino-acid protein encoded by the TAR DNA binding protein gene on chromosome 1p36  and amyotrophic lateral sclerosis (ALS). Similar findings were found in AD: pathological TDP-43 aggregation is more common in the limbic system of patients with AD, including the hippocampus, amygdala, and adjacent cortex , is a major component of senile plaques and is considered to be a major pathological change in AD , a significant contributor to disease (Gao et al., Mitochondria are organelles that can replicate independently in a variety of eukaryotic cells. They provide energy and also participate in nearly all types of cell death, including apoptosis and necrosis, and contribute to a number of important physiological functions (Kroemer et al., Neuroinflammation, characterized by microglial activation, astrocyte proliferation, and increased cytokine expression, is a key factor in the pathogenesis of AD. While acute inflammation protects the nervous system, chronic inflammation can contribute to AD development (Youmans and Wolozin, Many studies have demonstrated the importance of TDP-43 in the pathogenesis of AD (Amador-Ortiz et al., The AD-like cognitive dysfunction associated with TDP-43 pathology may represent a distinct encephalopathy because of its specific characteristics. Many researchers believe that the disease caused by TDP-43, characterized by changes in cognitive function, may be a novel disease: LATE (Nelson et al., Since the shorthand for the disease is LATE, the interesting question that could be asked is: is it too late to discover LATE? Most clinical trials for treatment of AD have failed (Doody et al., TDP-43 plays an important role in the CNS. Abnormal aggregation and localization of TDP-43 can cause mitochondrial dysfunction, aggravate neuroinflammation, and contribute to many diseases involving various regions of the brain. Abnormalities in TDP-43 in the upper and lower motor neurons can contribute to ALS, while abnormalities in TDP-43 in the frontal and temporal lobes can contribute to FTLD, and those in the limbic system to AD. TDP-43 contributes to various pathogenic processes underlying AD, such as Aβ deposition, tau hyperphosphorylation, mitochondrial dysfunction, and neuroinflammation. However, AD-like cognitive dysfunction associated with TDP-43 pathology appears to be distinct from that associated with AD. Therefore, AD-like cognitive dysfunction with TDP-43 as the main marker may be defined as a new encephalopathy, LATE, or may alternatively represent a subcategory of AD . Future WH and YZ contributed equally to this work and wrote the manuscript. WH, YZ, LT, ZB, JH, NH and YL contributed to the critical revision of the manuscript and read and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


To design efficient and powerful field emission cathodes, the screening effect is of great importance and should be traded off between screening and emitter number. It has long been found that to achieve maximum emission efficiency in an array, neighboring emitters are at two or three times their height from each other. However, this is only true for one-dimensional emitters, such as carbon nanotubes, but for graphene, a two-dimensional material, it is different. In this work, we found that to achieve maximum emission efficiency in an array of graphene, the separation of the emitter is four times the height, and it is insensitive to the anode voltage and the distance between the cathode and the anode. Field emitter arrays (FEAs) have been an active area of research for many years due to the high current densities, low voltage operation, and high pulse repetition that can be obtained ,3,4,5,6.Although much research has been done on the EFS, most of it has been based on the EFS from carbon nanotubes (CNT) arrays in simulations. For example, in 2000, Nilsson et al. found that an optimum intertube distance of two times the height of the CNT is strongest in accordance with the experiment . HoweverGraphene is a monolayer of carbon atoms packed into a dense honeycomb crystal structure that can be viewed as an individual atomic plane extracted from graphite . The atoIn this paper, we simulated the field screening effect in graphene arrays, and the effects of various parameters in the model on the field screening effect were investigated in detail. We also compared the simulated current density of the graphene sheet array that we optimized with some previous experimental results about field emission of graphene arrays prepared by different methods.l and thickness 2r are placed on a grounded cathode that is separated from the positive anode by distance d; the graphene is separated by a distance s, the anode voltage is U. Assuming that the thickness and height of the graphene in the array are the same and the top of the graphene sheet is assumed to be circular. The emitted current depends on the electric field in the vicinity of the graphene top. The emission array performance was studied by simulating a unit cell consisting of the integrated flake nanostructure and the anode.Because the radius of the curvature of the tip of the emitter is very small on the nanometer scale, and the device structure is relatively large, the skills of variable mesh are used. The accurate field strength at the tip of the emitter is obtained from denser grids, and sparse grids are used far from the emitter to speed up the program. Calculations were performed using the MAGIC software code. MAGIC is a particle-in-cell simulation code, which is a two-dimensional, finite-difference, time-domain code for the self-consistent simulation of the interaction between charged particles and electromagnetic fields. The full set of Maxwell equations and the complete Lorentz force equation were used. Space charge effects were automatically included. Boundary conditions included conductors, the surface of graphite nanoplatelets, and the cell-to-cell relationships using SYMMETRY MIRROR boundary conditions, which allowed us to simulate an entire array, not just a cell as in many previous works. J is calculated froms/l.A Fowler-Nordheim emission module was developed and inserted in MAGIC code to model the electron field emission from the surface. The current density Although the skill of variable grid is used to achieve simulation of the field emission characteristics of emitters with nanometer-scale thickness, because the thickness of graphene is an atomic scale and the total number of grids that MAGIC can draw is limited, even the skill of variable grid cannot simulate the electric field at the top of the emitter of the graphene sheet. Therefore, we firstly studied the effect of the thickness of graphite nanoplatelets to the screening effects; graphite nanoplatelet is a kind of graphite sheet with nanometer thickness, graphene is actually a graphite sheet with only one or more atomic layers. In the simulation, we changed the spacings between the graphite nanoplatelets in arrays with different thicknesses. s/l. The result shows that the law of change of electric field strength at the tip of the graphite nanoplatelet in the middle of the array caused by the field screening effect is insensitive to the thickness of the graphite nanoplatelets; the three curves are approximately coincident. All show that the electric field strength at the top of the emitter increases with the increase of the spacing of the array. For s/l > 5, the value of the normalization of the electric field strength reaches saturation. So, we focused on studying the effect of different spacings between the graphite nanoplatelets and the screening effects of graphite nanoplatelets arrays. Simulation with different thicknesses of graphite nanosheet arrays had almost no effect on the results; thus we used graphite nanosheets  instead of graphene to simulate.s/l = 0.5, there is almost no potential distribution around the top of the emitter. When s/l = 4, the interaction between emitters is very small, and the electric potential distribution is similar to that of a single emitter.We simulated the potential distribution of single platelets and graphene arrays with different spacings; the anode voltage was 400 V. s/l = 4 and U = 200 V.Because the field emission current is exponentially related to the electric field intensity at the top of the emitter, the emission current of the emitter at the center of the array is also simulated by a particle simulation method. U = 400 V and r = 20 nm. The current of graphite nanoplatelets in the middle of the array increases with the increase of spacing between graphite nanoplatelets; for s/l > 5, the value of current of graphite nanoplatelets in the middle of the array reaches saturation. The result demonstrates that with the increase of the spacing between graphite nanoplatelets, the screening effects decrease, the electric field strength increases, the current of graphite nanoplatelets in the array tends to be saturated, and the behavior of the individual graphite nanoplatelet is similar to that of a single one. Therefore, we can weaken the screening effects and increase the current of each emitter of the array by changing the spacing between emitters in the array.Although the emission of a single emitter is not affected by the screening effects, the current of a single emitter is limited, which cannot meet the requirements of the device. According to the above simulated calculation, for graphene arrays, the screening effects can be neglected when the spacing between emitters is five times higher; on the other hand, due to the enlargement of the spacing between emitters, the number of emitters on a fixed area decreases and the total current on the surface decreases. Because the spacing between emitters is very close, the screening effects will affect the value of the current of each emitter in the array, which makes the total emitter current smaller. Therefore, it is necessary to find the appropriate array density by simulated calculation.Z-axis depth is 1 m in the MAGIC simulation software, the actual fixed area obtained is 10 square centimeters. We assumed that the current of each graphite nanoplatelet in the array is equal. When the spacing of graphite nanoplatelets in the array is twice the height of the emitter, the number of emitters on the area is 500, when the spacing of graphite nanoplatelets in the array is three times the height of the emitter, the number of emitters on the area is 333, and so on. The number of emitters on the launching surface decreases with the increase of the spacing of emitters, and then the total emission current of all emitters on the launching surface is calculated.So, we performed further simulation for a total array width of 1 mm. Because the default 2 as a function of the normalization spacing, for the aspect r  chosen to be 20 nm, 40 nm, and 80 nm, when the spacing of the graphite nanoplatelet between the array is four times the height of the graphite nanoplatelet, the total emission current of the emitter surface is the largest, and the law is the same for different thicknesses of graphite nanoplatelet. This also corroborates the results of previous simulations that if we focus on studying the effect of different spacings between graphite nanoplatelets and the screening effects of graphite nanoplatelets arrays, the results are insensitive to different thicknesses of graphite nanoplatelets. Therefore, in the later simulation, we still used graphite nanoplatelets with a thickness of 40 nm (r = 20 nm), instead of graphene sheets. On a fixed area of the emitter, the number of emitters on the emitter surface is determined by the distance between the emitters. The more the number of emitters on the emitter surface, the greater the emission current on the fixed area. However, the greater the number of emitters, the smaller the distance between emitters, and the more obvious the field screening effect becomes. In order to obtain the maximum field emission current on a fixed area, it is necessary to find a balance between the distance and the number of emitters. s/l = 4 is the equilibrium in our simulations.Firstly, the anode voltage was 200 V, we used a graphite nanoplatelet array with different thicknesses and changed the spacing between the graphite nanoplatelets in the array, then calculated the total current in this area. r = 20 nm); we changed the spacings between the graphite nanoplatelets in the array with different anode voltages and calculated the total emission current of the area. 2 as a function of the normalization spacing, for the anode voltage is chosen to be 150 V, 175 V, and 200 V. When the spacing of the graphite nanoplatelets in the array is four times the height of graphite nanoplatelets, the total emission current of the emitter surface is the largest, and the law is insensitive to anode voltages.The thickness of the graphite sheet was 40 nm  graphite nanosheets instead of graphene to simulate. We found that when the spacing between the graphene in the graphene array is five times the height of the graphene, the screening effect is greatly weakened. The current of graphene emitters in the array tends to be saturated, and the behavior of each individual graphite nanoplatelet is similar to that of a single one. We also found that when the spacing between the graphene in the graphene array is 4 times the height of the graphene, the total emission current of the emitter surface is the largest, and the law is insensitive to the anode voltage and the distance between cathode and anode. The emission current density of graphene arrays optimized by our simulation is better than in most previous experimental results about field emission of graphene array cathodes, the results of this simulation can provide guidance for the design of graphene array cathode emitters.In this paper, calculations were performed using the MAGIC software code, and the technique of variable mesh was used. We focused on the effect of different spacings between graphite nanoplatelets to study the screening effects of graphite nanoplatelets arrays. Simulations show that different thicknesses of graphite nanosheets in arrays have almost no effect on the results. Therefore, we used thicker (40 nm thickness,


The results show that the resistance of the sensors exhibited significant changes with increasing humidity, the response times of the two sensors within the relative humidity range of 23–97% were 49 s and 67 s, and the recovery times were 24 s and 43 s, respectively. Meanwhile, continuous breathing monitoring results indicate that the sensitivity of the sensors remained basically unchanged during 10 min of normal breathing and simulated apnea. The response of the sensor is still good after 30 days of use. We believe that the Schottky structure composite sensor is a very promising technology for human breathing monitoring.Two types of Schottky structure sensors (silicon nanowire (SiNW)/ZnO/reduced graphene oxide (rGO) and SiNW/TiO Sleep apnea hypopnea syndrome (SAHS) is a prevalent and potentially serious disorder with the occurrence of at least 30 apneas during normal 7-hour sleep, where each apnea time is at least 10 s . Therefo2) nanomaterials can also be used as moisture-sensitive components [2 was proposed as the sensitive layer of a humidity sensor, and Milad Ghalamboran reported TiO2–SnO2 composites for moisture detection [2/rGO Schottky composite metal nanomaterials were developed and used for sensitive detection of trace explosive vapors [With the rapid development of science and technology, more and more new materials have been developed for humidity-sensitive sensors in recent years, and composite nanomaterials have become a focus for research, including one-dimensional carbon, silicon, and semiconductor nanoparticles ,4. As a mponents  screen-petection . In addietection ,11,12,13etection ,15. The etection . Inspiree vapors ,18, and 2/rGO, which combine the advantages of graphene and metal oxide. We found that the resistance of the three-dimensional compound materials is sensitive to humidity, and the high sensitivity, fast response time, and excellent repeatability of the sensors provide high potential and very good prospects for the design of a portable human breathing monitoring system.In this paper, we report two kinds of Schottky structure humidity sensors, SiNW/ZnO/rGO and SiNW/TiO4 which had been stored in the refrigerator, quickly injected it into a sealed bottle filled with ice, sealed the bottom with deionized water, and quickly shook it until the ice melted. We immersed the SiNW array into the TiCl4 solution to obtain a TiO2-modified SiNW array [The design process of the Schottky structure sensor is shown in NW array ,22. FinaNW array ,24. 2 nanoparticles. It can be seen from the figure that the surface of the SiNWs was successfully decorated with TiO2 nanoparticles. 2/rGO Schottky heterojunction, and the inset is a side screenshot. The successful formation of the Schottky heterostructure involves a large number of defects on the surface, resulting in a significant increase in activity and improving the amount of water absorption. Because the doped TiO2 is relatively small, the existence of TiO2 cannot be directly seen in 2 nanoparticles. In 2. −1 and 1592 cm−1, corresponding to the D and G peaks, respectively. After reduction of graphene, both the D and G peaks shifted downward. I(D)/I(G) is the intensity ratio of the D-peak and G-peak, the D-peak represents defects in the C atom lattice, and the G-peak represents the in-plane expansion and contraction of C atom sp2 hybrid vibration. The I(D)/I(G) value of rGO (1.12) is clearly greater than that of GO (0.91), revealing the formation of new sp2.Scanning electron microscopy  was used to check the surface morphology of the prepared sensor. The surface properties were studied by X-ray photoelectron spectroscopy . The structural characteristics of the sensor were characterized by Raman scanning spectroscopy . 3COOK, K2CO3, NaCl, and K2SO4  at room temperature to simulate environmental relative humidity levels of 23%, 43%, 75%, and 97%, as shown in We used a classic saturated salt solution method to test the sensitivity of the developed sensors at different humidity levels ,26. Firs0 is the initial value of the sensor under dry conditions. The response time and recovery time of the sensor were defined as the time it takes for the resistance of the sensor to change from the initial value to 90% of the stable offset.The sensor was secured to the Printed Circuit Board (PCB) with conductive silver slurry, and copper wire electrodes were placed at both ends of the circuit board. The experimental data acquisition was performed using a miniature hardware terminal based on an STM32F030 microcontroller , which was controlled by an Android phone connected via Bluetooth. The resistance values were obtained by the voltage-divider circuit, and were collected and plotted on the phone after filtering and smoothing . As shown in 2/rGO were 49 s and 67 s, and the recovery times were 24 s and 43 s, respectively; the response and recovery times of SiNW/ZnO/rGO were better than those of SiNW/TiO2/rGO. For respiratory monitoring, SiNW/ZnO/rGO sensors are more suitable for human respiratory monitoring because of their faster response and better sensitivity. In short, these sensors based on Schottky structures have great potential for the development of future portable respiratory monitoring systems, and they also have certain implications for the development of new moisture-sensitive materials.In summary, we presented two Schottky structure sensors and demonstrated their good sensitivity and good repeatability in human breathing monitoring. The response times of SiNW/ZnO/rGO and SiNW/TiO