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Doping-induced giant rectification and negative differential conductance (NDC) behaviors in zigzag graphene nano-ribbon junction
摘要： By p-type and n-type doping on the electrode edges of V-notched zigzag graphene nano-ribbons (ZGNRs), four V-notched ZGNR-based PN-junctions are designed theoretically. The electronic transport properties of the doped and un-doped V-notched ZGNRs are studied applying non-equilibrium Green’s function method combined with the density functional theory. The numerical results show that, the doped systems are less conductive than the un-doped system, because after doping the transition states become localized. To our surprise, the ZGNR-based PN-junctions do not show obvious rectification by purely doping the boron atoms and nitrogen atoms on the edges of two ZGNR electrodes respectively. However, after hydrogenated the doped boron atoms and nitrogen atoms, the ZGNR systems present giant rectifications with the maximum rectification ratios up to 106 ～ 107, which attributed to the vanishing of overlap between left-electrode sub-band and right-electrode sub-band in the negative bias regime after the doped boron and nitrogen atoms being hydrogenated. Due to the same reason, the hydrogenated doping systems also show large negative differential conductance behaviors.
关键词： Giant rectification,Negative differential conductance,Graphene nano-ribbon junction,Boron and nitrogen doping
更新于2025-09-23 15:22:29
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Measuring the Lower Critical Field of Superconductors Using Nitrogen-Vacancy Centers in Diamond Optical Magnetometry
摘要： The lower critical magnetic field, Hc1, of superconductors is measured by optical magnetometry using ensembles of nitrogen-vacancy centers in diamond. The technique is minimally invasive and allows accurate detection of the vector magnetic field with subgauss sensitivity and submicrometer spatial resolution. These capabilities are used for detailed characterization of the first vortex penetration into superconducting samples from the corners. Aided by the revised calculations of the effective demagnetization factors of actual cuboid-shaped samples, these measurements provide precise determination of Hc1 and the related absolute value of the London penetration depth, λ. We apply this method to three well-studied superconductors: optimally doped Ba(Fe1?xCox)2As2, stoichiometric CaKFe4As4, and the high-Tc cuprate YBa2Cu3O7?δ. Our results compared well with the values of λ obtained with other techniques, thus adding another noninvasive and sensitive method to measure these important parameters of superconductors.
关键词： optical magnetometry,nitrogen-vacancy centers,London penetration depth,superconductors,lower critical field
更新于2025-09-23 15:22:29
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Photoelectrochemical Synthesis of Ammonia on the Aerophilic-Hydrophilic Heterostructure with 37.8% Efficiency
摘要： A unique aerophilic-hydrophilic heterostructure composed of Au nanoparticles highly dispersed in a poly(tetrafluoroethylene) porous framework is fabricated on a Si-based photocathode for N2-to-NH3 fixation. The amphipathic nature of the heterostructure is considered to be the origin of the enhanced nitrogen reduction reaction with efficient conversion efficiency and high production rate.
关键词： photoelectrochemical synthesis,ammonia,nitrogen reduction reaction,efficiency,aerophilic-hydrophilic heterostructure
更新于2025-09-23 15:22:29
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Effects of nitrogen-dopant bonding states on liquid-flow-induced electricity generation of graphene: A comparative study
摘要： We fabricate, measure and compare the effects of the bonding states of dopant nitrogen atoms in graphene devices, specifically on the liquid-flow-induced electricity by these devices. We find that nitrogen doping enhances the voltage induced by liquid flow regardless of the nitrogen bonding state. However, different nitrogen bonding states affect graphene’s conductivity differently: while graphitic nitrogen is suitable for electricity-generation applications, pyridinic nitrogen is hopeless for this purpose, due to the formation of symmetry-breaking defects of the latter.
关键词： Water-graphene interface,Nitrogen doped graphene,Flow-induced electricity generation
更新于2025-09-23 15:22:29
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Single Nickel Atoms Anchored on Nitrogen-Doped Graphene as a Highly Active Co-Catalyst for Photocatalytic H2 Evolution
摘要： Earth abundant nickel is a typical non-noble-metal cocatalyst used for photocatalytic hydrogen evolution (PHE). Ni nanoparticles, however, tend to aggregate during the hydrogen production process, significantly lowering their PHE activity. In this research, we report single nickel atoms anchored on nitrogen-doped graphene (Ni-NG) as a cocatalyst for PHE. We have demonstrated that Ni-NG is a robust and highly active cocatalyst for PHE from water. With only 0.0013 wt.% of Ni loading, the PHE activity of composite Ni-NG/CdS photocatalyst is 3.4 times greater than that of NG/CdS. The quantum efficiency of Ni-NG/CdS for PHE reaches 48.2% at 420 nm, one of the highest efficiencies for non-noble-metal based cocatalysts reported in literature. Photoluminescence spectral analyses and electrochemical examinations have indicated that Ni-NG coupled to CdS can serve not only as an electron storage medium to suppress electron-hole recombination, but also as an active catalyst for proton reduction reaction. Density functional theory calculation shows that the high activity of Ni-NG/CdS composite results from the single Ni atoms trapped in NG vacancies, which significantly reduces the activation energy barrier of the hydrogen evolution reaction. This approach may be valuable for developing robust and highly active noble-metal free cocatalysts for solar hydrogen production.
关键词： Non-noble Metal Cocatalyst,CdS,Photocatalytic Hydrogen Evolution,Nitrogen-Doped Graphene,Single Ni Atom Catalysts
更新于2025-09-23 15:21:21
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Fabrication of Two-Dimensional Arrays of Fluorescent Centers in Single-Crystalline Diamond Using Particle Beam Writing
摘要： Micrometer-scale patterning was performed using the particle beam writing technique with a focused heavy-ion microbeam, allowing the creation of a unique two-dimensional distribution of fluorescent centers in single-crystalline diamond. The focused nitrogen microbeam was scanned over the target of single-crystalline diamond prepared by chemical vapor deposition to create nitrogen-vacancy (NV) centers at defined positions. Imaging using a custom-built confocal fluorescence microscopy system revealed that the desired NV distribution was generated in the target crystal with a spatial resolution similar to the beam resolution. A two-dimensional matrix barcode test pattern was successfully generated in a diamond substrate to demonstrate the encryption of information inside a solid-state target.
关键词： diamond,particle beam writing,two-dimensional,chemical vapor deposition,nitrogen vacancy centers,confocal fluorescence microscopy
更新于2025-09-23 15:21:21
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Laser induced self-N-doped porous graphene as an electrochemical biosensor for femtomolar miRNA detection
摘要： We report a sensitive, yet low-cost biosensor based on laser induced graphene for femtomolar microRNA (miRNA) detection. Combined with the miRNA extraction and magnetic isolation process, the target miRNAs were purified for further detection using laser induced graphene sensor. The laser induced graphene was prepared by direct laser writing on commercial polyimide (PI) and patterned via a computer-aided design system as an electrode for electrochemical biosensing. We found that the laser reduction of PI resulted in nitrogen-doped porous graphene, not only improving its conductivity but also its sensitivity to nucleic acids. Preeclampsia specific miRNA hsa-miR-486-5p was magnetically purified and directly adsorbed on the surface of graphene electrode via graphene-miRNA affinity interaction. Surface attached miRNAs were then electrochemically quantified using [Fe(CN)6]3-/4- redox system. Our assay demonstrates detection of miRNA has-miR-486-5p up to concentrations as low as 10 fM with excellent reproducibility. Owing to its facile fabrication, low cost and high performance, the laser induced N-doped graphene biosensor presented here shows great potential for applications in detecting miRNA in biomedical applications.
关键词： electrochemical biosensor,porous graphene,laser induced graphene,nitrogen-doped,miRNA detection
更新于2025-09-23 15:21:01
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Ina??season potato yield prediction with active optical sensors
摘要： Crop yield prediction is a critical measurement, especially in the time when parts of the world are suffering from farming issues. Yield forecasting gives an alert regarding economic trading, food production monitoring, and global food security. This research was conducted to investigate whether active optical sensors could be utilized for potato (Solanum tuberosum L.) yield prediction at the mid.le of the growing season. Three potato cultivars (Russet Burbank, Superior, and Shepody) were planted and six rates of N (0, 56, 112, 168, 224, and 280 kg ha?1), ammonium sulfate, which was replaced by ammonium nitrate in the 2nd year, were applied on 11 sites in a randomized complete block design, with four replications. Normalized difference vegetation index (NDVI) and chlorophyll index (CI) measurements were obtained weekly from the active optical sensors, GreenSeeker (GS) and Crop Circle (CC). The 168 kg N ha?1 produced the maximum potato yield. Indices measurements obtained at the 16th and 20th leaf growth stages were significantly correlated with tuber yield. Multiple regression analysis (potato yield as a dependent variable and vegetation indices, NDVI and CI, as independent variables) could make a remarkable improvement to the accuracy of the prediction model and increase the determination coefficient. The exponential and linear models showed a better fit of the data. Soil organic matter content increased the yield significantly but did not affect the prediction models. The 18th and 20th leaf growth stages are the best time to use the sensors for yield prediction.
关键词： sensor technology,petiole sampling,potato,prediction models,multiple regression analysis,Yield prediction,nitrogen loss
更新于2025-09-23 15:21:01
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Defect engineered mesoporous 2D graphitic carbon nitride nanosheet photocatalyst for Rhodamine B degradation under LED light illumination
摘要： In this work, a nitrogen vacancy induced 2D mesoporous graphitic carbon nitrogen (g-C3N4) nanosheet photocatalyst was successfully synthesized through a simple two step thermal treatment method. The morphology of the nanosheet photocatalyst and the presence of nitrogen vacancy was explored through a wide range of characterization techniques. The as prepared photocatalyst possess an improved visible light absorption efficiency as confirmed from the UV-Visible diffuse reflectance spectroscopy (DRS). Moreover, the improved charge carrier separation efficiency of the nitrogen vacant material was demonstrated from the photoluminescence spectrum. Most importantly, the photocatalyst exhibited an excellent photodegradation efficiency towards rhodamine B (RhB) dye under the illumination of an 18 W LED light. The vacancy induced nanosheets demonstrated a degradation co-efficient of 0.074 min-1 in RhB degradation, which is 9.25 fold higher than that of the bulk g-C3N4. The nanosheets further exhibited an enhanced degradation efficiency toward tetracycline antibiotic. Furthermore, the photocatalyst displayed an outstanding stability even after 5 cycles. A plausible photocatalytic mechanism has also been explained based on the results obtained from the radical scavenging experiments. This study would provide insight into the defect induction mechanism into the 2D g-C3N4 nanosheet and expected to help in rationally designing vacancy induced materials with cost effective application in various environmental fields.
关键词： nitrogen vacancy,LED light irradiation,rhodamine B,mesoporous,2D g-C3N4 nanosheet
更新于2025-09-23 15:21:01
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Nanoscale magnetic imaging enabled by nitrogen vacancy centres in nanodiamonds labelled by iron-oxide nanoparticles
摘要： Nanodiamonds containing the nitrogen vacancy centre (NV) have a significant role in biosensing, bioimaging, drug delivery, and as biomarkers in fluorescence imaging, due to their photo-stability and biocompatibility. The optical read out of the NV unpaired electrons spin has been used in diamond magnetometry to image living cells and magnetically labelled cells. Diamond magnetometry is mostly based on the use of bulk diamond with a large concentration of NV centres in a wide field fluorescence microscope equipped with microwave excitation. It is possible to correlate the fluorescence maps with the magnetic field maps of magnetically labelled cells with diffraction limit resolution. Nanodiamonds have not as yet been implemented to image magnetic fields within complex biological systems at the nanometre scale. Here we demonstrate the suitability of nanodiamonds to correlate the fluorescence map with the magnetic imaging map of magnetically labelled cells. Nanoscale optical images with 17 nm resolution of nanodiamonds labelling fixed cells bound to iron oxide magnetic nanoparticles are demonstrated by using a single molecule localisation microscope. Nanoscale magnetic field images of the magnetised magnetic nanoparticles spatially assigned to individual cells are superresolved by the NV centres within nanodiamonds conjugated with the magnetic nanoparticles with 20 nm resolutions. Our method offers a new platform for super-resolution of optical magnetic imaging in biological samples conjugated with nanodiamonds and iron-oxide magnetic nanoparticles.
关键词： spin detection,superresolution,Nitrogen-vacancy centre,optical magnetic imaging,nanodiamonds
更新于2025-09-23 15:21:01