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One-step synthesis of nitrogen-doped graphene from a sole aromatic precursor
摘要： A cheap aromatic precursor (1,10-phenanthroline) with heteroatom and planar-structure was designed to synthesize large-scale, continuous and mostly single-layer nitrogen-doped graphene (NG) films by one-step chemical vapor deposition method. The NG sheets can be obtained even at 600 ℃. The results indicated that the content and type of doped N are intensely relied on the growth temperature. Our fabrication approach provides an economic synthetic route and potentially promotes the practical application of graphene-based materials.
关键词： chemical vapor deposition,thin films,graphene,nitrogen-doped
更新于2025-09-23 15:21:01
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Optically controlled millimetre-wave switch with stepped-impedance lines
摘要： Nitrogen (N) placement can impact nitrogen use efficiency, but its effect on greenhouse gas (GHG) emissions remain unclear. The objective of this study is to compare the effects of four different N horizontal placement methods (i.e., annular canal (An), radial canal (Ra), band (Ba), and nest fertilization (Ne)) with urea broadcast (Br) on nitrous oxide (N2O), methane (CH4), and soil heterotrophic respiration carbon dioxide (CO2) emissions from an apple orchard to assess the seasonal and spatial variations in these gas emissions. The total cumulative GHG emissions are determined through spots that are differentiated as fertilized or unfertilized. A field simulation study is conducted in an apple orchard, and all N sources have an application rate of 300 kg N ha?1. from the Br treatment are significantly lower than those of other treatments, and the emissions from the Ne treatment are 1.7-fold higher than those of the Br treatment. Surprisingly, the cumulative N2O emissions from the Br treatment are significantly higher than those of the other four treatments. N horizontal placement does not significantly influence the soil CH4 sink. The CO2 emissions in the Br treatment are higher than in other treatments. High N2O emissions in the Br treatment result in a significantly higher GHG exchange than in other treatments, while the Ne treatment significantly reduces the GHG exchange throughout the measurement period. Therefore, optimizing N placement may serve as an effective way to reduce GHG emissions from arable soils.
关键词： nitrogen placement,nitrous oxide,nest fertilization,greenhouse gas emissions,nitrogen use efficiency
更新于2025-09-23 15:19:57
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Strong polarization of individual nuclear spins weakly coupled to nitrogen-vacancy color centers in diamond
摘要： We experimentally demonstrate high degree of polarization of 13C nuclear spins weakly interacting with nitrogen-vacancy (NV) centers in diamond. We combine coherent microwave excitation pulses with optical illumination to provide controlled relaxation and achieve a polarity-tunable, fast nuclear polarization of degree higher than 85% at room temperature for remote 13C nuclear spins exhibiting hyperfine interaction strength with NV centers of the order of 600 kHz. We show with the aid of numerical simulation that the anisotropic hyperfine tensor components naturally provide a route to control spin mixing parameter so that highly efficient nuclear polarization is enabled through careful tuning of nuclear quantization axis by external magnetic field. We further discuss spin dynamics and wide applicability of this method to various target 13C nuclear spins around the NV center electron spin. The proposed control method demonstrates an efficient and versatile route to realize, for example, high-fidelity spin register initialization and quantum metrology using nuclear spin resources in solids.
关键词： nitrogen-vacancy (NV),nitrogen-vacancy center,spin initialization,hyperfine interaction,spin polarization
更新于2025-09-23 15:19:57
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Nitrogen-Sulfur-Doped Graphene Quantum Dots with Metal Ion-Resistance for Bioimaging
摘要： The development of ultra-stable and highly fluorescent heteroatoms-doped graphene quantum dots (GQDs) for bioimaging remains a challenge due to the fluorescence quenching caused by binding between the heteroatoms-based functional groups of the GQDs and common metal ions in biological systems. Here, we developed a facile hydrothermal method to prepare nitrogen-sulfur doped GQDs (NS-GQDs). The fluorescence signals of the NS-GQDs are highly stable in the existence of different metal ions. Two natural products, aspartic acid and cysteine, were utilized as the carbon precursors and heteroatomic (nitrogen and sulfur) sources. The produced NS-GQDs showed a quantum yield up to 19.3 ± 1.7 % with a maximum emission of 480 nm under the excitation of 400 nm. The elemental analysis, including X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR), were performed to characterize the composition and surface groups of NS-GQDs. Additionally, the NS-GQDs not only showed notable photostability, but also thermostability and chemical stability. Moreover, the NS-GQDs demonstrated very low cellular cytotoxicity in vitro. Finally, the NS-GQDs were applied for fluorescence imaging of cells, which also exhibited excellent fluorescent stability even with treatment of copper ions. The results indicated that the developed novel NS-GQDs have a promising potential to be used as ultra-stable fluorescent agent in the field of bioimaging and biosensing.
关键词： bioimaging,nitrogen doping,sulfur doping,fluorescence,Graphene quantum dots
更新于2025-09-23 15:19:57
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A feasibility quantitative analysis of NIR spectroscopy coupled Si-PLS to predict coco-peat available nitrogen from rapid measurements
摘要： Available nitrogen was an important index to evaluate the supply capacity of nitrogen fertilizer in planting environment. The study of coco-peat available nitrogen content rapid detection technology was of great significance for instructing scientific fertilization. In this study, near infrared (NIR) spectroscopy was used to realize rapid quantitative detection of available nitrogen in coco-peat. Seven different spectral pretreatment methods were adopted to pre-process spectral data with detection band range of 1000–2500 nm (full-band), and synergy interval partial least squares (Si-PLS) was used to screen the optimum combination sub-intervals reflecting coco-peat available nitrogen content from the original full-band spectral data and various pre-treated spectral data. The spectral prediction models of coco-peat available nitrogen based on full-band spectral data and optimal combined sub-intervals spectral data were respectively established, the improvement effects of different pretreatment methods on the accuracy of coco-peat available nitrogen spectral prediction models were analyzed, and the performances of the optimal full-band spectral prediction model and combined sub-intervals prediction model were compared. By analysis and comparison, the first derivative combined with Savitzky-Golay (S-G) smoothing was used to pre-process spectral data, Si-PLS was used to screen the spectral data of 1724–1784 nm, 1852–1922 nm, 1923–1999 nm and 2175–2272 nm, and then the optimal spectral prediction model of available nitrogen content in coco-peat could be established by using the four bands spectral data. For the optimal model, the correlation coefficient and root mean square error of calibration set were 0.994 and 6.998 mg/100 g respectively, the correlation coefficient and root mean square error of prediction set were 0.993 and 7.390 mg/100 g respectively, and the RPD was 8.062. It showed that the combination of NIR spectroscopy and Si-PLS could realize coco-peat available nitrogen quickly and accurately quantitative detection, Si-PLS could effectively reduce the input variables of the established model and simplify the complexity of the model. It also provided a reference for development of a coco-peat available nitrogen content rapid detection device based on characteristic band sub-intervals spectral data.
关键词： Full-band,Si-PLS,Coco-peat,Sub-interval,Available nitrogen
更新于2025-09-23 15:19:57
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Efficient generation of nitrogen vacancy centers by laser writing close to the diamond surface with a layer of silicon nanoballs
摘要： We proposed a method to effectively fabricate negatively charged nitrogen vacancy (NV?) centers close to the diamond surface by applying femtosecond laser writing technique. With a thick layer of silicon (Si) nanoballs coated, diamond surface was irradiated by high-fluence femtosecond laser pulses. A large number of NV? centers were created around the laser ablation crater area without thermal annealing. The distribution of the NV? centers was expanded to about 50 μm away from the crater center. To demonstrate the function of Si nanoballs, we performed the exactly same laser illumination process on the bare region of the sample surface. In this case, only a few NV? centers were generated around ablation crater. At distance of 32 μm away from crater centers, the NV? density for the case with nanoballs was up to 15.5 times higher compared to the case without nanoballs. Furthermore, we also investigated the influence of laser fluence and pulse number on the NV? density for the case with Si-nanoball layer. Finally, the formation mechanism of NV? centers and the role of Si nanoballs were explained via Coulomb explosion model. The method is demonstrated to be a promising approach to efficiently and rapidly fabricate NV? centers close to the surface of the diamond, which are significant in quantum sensing. Furthermore, the results provide deep insights into complex light-matter interactions.
关键词： single emitters,nitrogen vacancy centers in diamond,silicon nanoballs,femtosecond laser technique
更新于2025-09-23 15:19:57
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Mo-doped Zn, Co Zeolitic-Imidazolate Framework-derived Co9S8 Quantum Dots and MoS2 Embedded in Three-Dimensional Nitrogen Doped Carbon Nano???ake Arrays as an Efficient Trifunctional Electrocatalysts for ORR, OER and HER
摘要： Herein, we first propose a facile strategy to synthesize Co9S8 and MoS2 nanocrystals embedded in porous carbon nanoflake arrays supported on carbon nanofibers (Co9S8-MoS2/N-CNAs@CNFs) by the pyrolysis of Mo-doped Zn, Co zeolitic-imidazolate framework grown on carbon nanofibers and subsequent sulfuration. The electrocatalyst shows high and stable electrocatalytic performance, with half-wave potential of 0.82 V for ORR and overpotential at 10 mA cm-2 for OER (0.34 V) and HER (0.163 V), which outperform the metal-organic frameworks-derived transition metal sulfide catalysts reported so far. Furthermore, the Co9S8-MoS2@N-CNAs@CNFs are employed as an air cathode in a liquid-state and all-solid-state zinc-air battery, presenting high power density of 222 mW cm-2 and 96 mW cm-2, respectively. Such excellent catalytic activities are mainly owing to the unique three-dimensional structure and chemical compositions, optimal electronic conductivity, adequate surface area and the abundance of active sites. Thus, this work provides an important method for designing other metal-organic frameworks derived three-dimensional structural sulfide quantum dot multifunctional electrocatalyst for wider application in highly efficient catalysis and energy storage.
关键词： zeolitic-imidazolate framework,Co9S8 quantum dots,MoS2,nitrogen-doped carbon nanoflakes arrays,Zn-air battery,trifunctional electrocatalysts
更新于2025-09-23 15:19:57
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Comparison of 1-Propyl-5H-tetrazole and 1-Azidopropyl-5H-tetrazole as Ligands for Laser Ignitable Energetic Materials
摘要： Laser ignitable explosives are potential candidates in future applications for replacing toxic and very sensitive primary explosives, which are used in current devices. In this study, the literature unknown ligand 1-azidopropyl-5H-tetrazole (APT, 1) was synthesized for the first time and applied in energetic coordination compounds (ECC). The complexes are based on different 3d transition metals (Mn2+, Fe2+, Cu2+, and Zn2+) as well as various oxidizing anions (NO3?, ClO4?, ClO3?) and were tested towards their capability as laser ignitable explosives. Furthermore, analogous complexes based on the literature known ligand 1-propyl-5H-tetrazole (PT, 2) were investigated, for comparing the influence of the additional azide group towards the performance of the ECC. Toxicity measurements using Vibrio fischeri and the decreased sensitivities prove their usability as safer laser ignitable explosive with lower toxicities compared to currently used explosives.
关键词： tetrazole ligands,laser ignition,nitrogen heterocycles,structure elucidation,energetic coordination compounds
更新于2025-09-23 15:19:57
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Tapered ultra-high numerical aperture optical fiber tip for nitrogen vacancy ensembles based endoscope in a fluidic environment
摘要： Fixing a diamond containing a high density of Nitrogen-Vacancy (NV) center ensembles on the apex of a multimode optical fiber (MMF) extends the applications of NV-based endoscope sensors. Replacing the normal MMF with a tapered MMF (MMF-taper) has enhanced the fluorescence (FL) collection efficiency from the diamond and achieved a high spatial resolution NV-based endoscope. The MMF-taper’s high FL collection efficiency is the direct result of multiple internal reflections in the tapered region caused by silica, which has a higher refractive index (RI) than the surrounding air. However, for applications involving fluidic environments whose RI is close to or higher than that of the silica, the MMF-taper loses its FL collection significantly. Here, to overcome this challenge and achieve a high spatial resolution NV-based endoscope in a fluidic environment, we conceptually proposed a tapered ultra-high numerical aperture microstructured optical fiber (MOF) whose air capillaries at the tapered end are sealed. Since the end-sealed air capillaries along the tapered MOF (MOF-taper) have isolated the MOF core from the surrounding medium, the core retains its high FL collection and NV excitation efficiency in liquids regardless of their RI values. Replacing the MMF-taper with the MOF-taper will achieve a versatile NV-based endoscope that could potentially find widespread applications in fluidic environments where many biological processes and chemical reactions occur.
关键词： fluidic environment,Nitrogen-Vacancy (NV) center,fluorescence collection,endoscope,optical fiber
更新于2025-09-23 15:19:57
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Fluorescent-Nitrogen-Doped Carbon Quantum Dots Derived from Citrus Lemon Juice: Green Synthesis, Mercury(II) Ion Sensing, and Live Cell Imaging
摘要： In this study, we report a green and economical hydrothermal synthesis of fluorescent-nitrogen-doped carbon quantum dots (NCQDs) using citrus lemon as a carbon source. The prepared NCQDs possess high water solubility, high ionic stability, resistance to photobleaching, and bright blue color under ultraviolet radiation with a high quantum yield (～31%). High-resolution transmission electron microscopy (HRTEM) results show that the prepared NCQDs have a narrow size distribution (1?6 nm) with an average particle size of 3 nm. The mercury ion (Hg2+) sensing efficiency of the NCQDs was studied, and the result indicated that the material has high sensitivity, high precision, and good selectivity for Hg2+. The limit of detection (LOD) is 5.3 nM and the limit of quantification (LOQ) is 18.3 nM at a 99% confidence level. The cytotoxicity was evaluated using MCF7 cells, and the cell viabilities were determined to be greater than 88% upon the addition of NCQDs over a wide concentration range from 0 to 2 mg/mL. Based on the low cytotoxicity, good biocompatibility, and other revealed interesting merits, we also applied the prepared NCQDs as an effective fluorescent probe for multicolor live cell imaging.
关键词： mercury(II) ion sensing,citrus lemon juice,green synthesis,live cell imaging,fluorescent-nitrogen-doped carbon quantum dots
更新于2025-09-23 15:19:57