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Controlling the fluorescence properties of nitrogen vacancy centers in nanodiamonds
摘要： Controlling the fluorescence properties of nitrogen vacancy centers in nanodiamonds is an important factor for their use in medical and sensor applications. However, reports providing a deep understanding of the potential factors influencing these properties are rare and focus only on a few influencing factors. The current contribution targets this issue and we report a comprehensive study of the fluorescence properties of NVs in nanodiamonds as a function of electron irradiation fluence and surface termination. Here we show that process parameters such as defect center interactions, in particular, different nitrogen defects and radiation induced lattice defects, as well as surface functionalities have a strong influence on the fluorescence intensity, fluorescence lifetime and the charge state ratio of the NV centers. By employing a time-correlated single photon counting approach we also established a method for fast macroscopic monitoring of the fluorescence properties of ND samples. We found that the fluorescence properties of NV centers may be controlled or even tuned depending upon the radiation treatment, annealing, and surface termination.
关键词： fluorescence lifetime,charge state ratio,nanodiamonds,surface termination,nitrogen vacancy centers,fluorescence properties,electron irradiation
更新于2025-09-19 17:15:36
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Studying the influence of deposition temperature and nitrogen contents on the structural, optical, and electrical properties of N-doped SnO2 films prepared by direct current magnetron sputtering
摘要： This report focuses on studying and investigating in detail the structural, electrical, and optical properties of p-type N-doped SnO2 (NTO) versus the deposition temperature and nitrogen content. P-type transparent conductive NTO films were deposited on quartz glass substrates using a direct current (DC) magnetron sputtering method. The substitution of oxygen by nitrogen in the SnO2 host lattice was verified using measurements such as X-ray photoelectron spectroscopy. The position of the N3? defect state in the band gap was determined using photoluminescence and ultra-violet-visible spectroscopy measurements. The data for the (110) to (101) rutile lattice planes changed, and the rutile (plane (101)) to cubic (plane (111)) SnO2 phase transition indicated the substitution of oxygen by nitrogen in the SnO2 host lattice. The best p-type conductive properties achieved were 8 × 10?2 Ω cm, 1.36 × 1019 cm?3, and 6.75 cm2 V?1 s?1 for the resistivity, hole concentration, and hole mobility, respectively, for film deposited at the optimum substrate temperature of 300 °C in a gas mixture of Ar and 50% N2.
关键词： deposition temperature,nitrogen content,p-type N-doped SnO2 thin film,X-ray photoelectron spectroscopy,DC magnetron sputtering,X-ray diffraction
更新于2025-09-19 17:15:36
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Acoustic wave transparency in nitrogen-vacancy centers in a photonic crystal
摘要： We show that the interaction of nitrogen-vacancy centers in diamond with a strain field in a photonic crystal can lead to acoustic wave transparency. This occurs due to the strong interaction of photons with the modified photonic reservoir near the photonic band edge created by the photonic crystal. For achieving this, we explore the properties of the spin states of the ground state of the nitrogen-vacancy centers, where one transition interacts with a strain field while the other transition has spontaneous emission that occurs near the edge of the photonic band gap, which should be in the microwave regime. We show that depending on the form of the photonic density of states acoustic wave transparency is obtained at one or two frequencies.
关键词： Induced transparency,Photonic crystal,Non-Markovian dynamics,Acoustic field,Nitrogen-vacancy center in diamond
更新于2025-09-19 17:15:36
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Cross-task perceptual learning of object recognition in simulated retinal implant perception
摘要： Anthropogenic nitrogen (N) enrichment can significantly alter soil chemical properties in various ecosystems. Previous manipulative N experiments mainly focused on the intensity of N addition on soil properties by changing N input rates. It remains unclear, however, whether frequency of N addition can affect soil chemical properties. We examined the effects of frequency (2 versus 12 applications yr?1) and rate (ranging from 0 to 50 g N m?2 yr?1) of N addition on soil chemical properties of pH, base cations, soil pH buffering capacity (pHBC), and soil available micronutrients in a temperate steppe with and without mowing. Mowing significantly increased the effective cation exchange capacity (ECEC), soil exchangeable Ca and Na, available Fe, and soil pHBC when N was applied at low frequency. Low frequency of N addition significantly decreased soil pH and exchangeable Na but increased soil exchangeable Mg without mowing; however, it increased soil exchangeable Na and available Zn with mowing, while available Fe and Mn increased both with and without mowing. Higher rates of N addition (≥20 g N m?2 yr?1) decreased soil pH, ECEC and exchangeable Ca but increased soil available Fe, Mn and Cu regardless of the mowing treatment and frequency of N addition. Changes in soil organic matter, pHBC and ECEC were the main reasons affecting soil pH across mowing and N application treatments. Our results indicate that frequency of N addition played an essential role in altering soil chemical properties. Simulating N deposition via large and infrequent N additions can underestimate (exchangeable Mg and available Fe and Mn) or overestimate (soil pH and exchangeable Na) changes in soil properties. Our results further suggest that the effects of frequency of N addition on soil chemical attributes in semi-arid grassland ecosystems can be regulated by appropriate mowing management.
关键词： Soil micronutrient,Soil acid buffering capacity,Nitrogen deposition,Base cation,Soil acidification,Semi-arid grassland
更新于2025-09-19 17:15:36
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Apparent delocalization of the current density in metallic wires observed with diamond nitrogen-vacancy magnetometry
摘要： We report on a quantitative analysis of the magnetic field generated by a continuous current running in metallic microwires fabricated on an electrically insulating diamond substrate. A layer of nitrogen-vacancy (NV) centers engineered near the diamond surface is employed to obtain spatial maps of the vector magnetic field, by measuring Zeeman shifts through optically detected magnetic resonance spectroscopy. The in-plane magnetic field (i.e., parallel to the diamond surface) is found to be significantly weaker than predicted, while the out-of-plane field also exhibits an unexpected modulation. We show that the measured magnetic field is incompatible with Ampère’s circuital law or Gauss’s law for magnetism when we assume that the current is confined to the metal, independent of the details of the current density. This result was reproduced in several diamond samples, with a measured deviation from Ampère’s law by as much as 94(6)% (i.e., a 15σ violation). To resolve this apparent magnetic anomaly, we introduce a generalized description whereby the current is allowed to flow both above the NV sensing layer (including in the metallic wire) and below the NV layer (i.e., in the diamond). Inversion of the Biot-Savart law within this two-channel description leads to a unique solution for the two current densities that completely explains the data, is consistent with the laws of classical electrodynamics, and indicates a total NV-measured current that closely matches the electrically measured current. However, this description also leads to the surprising conclusion that in certain circumstances the majority of the current appears to flow in the diamond substrate rather than in the metallic wire, and to spread laterally in the diamond by several micrometers away from the wire. No electrical conduction was observed between nearby test wires, ruling out a conventional conductivity effect. Moreover, the apparent delocalization of the current into the diamond persists when an insulating layer is inserted between the metallic wire and the diamond or when the metallic wire is replaced by a graphene ribbon. The possibilities of a measurement error, a problem in the data analysis, or a current-induced magnetization effect are discussed, but do not seem to offer a more plausible explanation for the effect. Understanding and mitigating this apparent anomaly will be crucial for future applications of NV magnetometry to charge transport studies.
关键词： diamond magnetometry,nitrogen-vacancy centers,Biot-Savart law,Ampère's law,magnetic field imaging,current density
更新于2025-09-19 17:15:36
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Quantum reference beacon–guided superresolution optical focusing in complex media
摘要： Optical scattering is generally considered to be a nuisance of microscopy that limits imaging depth and spatial resolution. Wavefront shaping techniques enable optical imaging at unprecedented depth, but attaining superresolution within complex media remains a challenge. We used a quantum reference beacon (QRB), consisting of solid-state quantum emitters with spin-dependent fluorescence, to provide subwavelength guidestar feedback for wavefront shaping to achieve a superresolution optical focus. We implemented the QRB-guided imaging with nitrogen-vacancy centers in diamond nanocrystals, which enable optical focusing with a subdiffraction resolution below 186 nanometers (less than half the wavelength). QRB-assisted wavefront-shaping should find use in a range of applications, including deep-tissue quantum enhanced sensing and individual optical excitation of magnetically coupled spin ensembles for applications in quantum information processing.
关键词： complex media,nitrogen-vacancy centers,quantum imaging,superresolution,quantum reference beacon,optical focusing,wavefront shaping
更新于2025-09-19 17:15:36
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High-Resolution UAV-Based Hyperspectral Imagery for LAI and Chlorophyll Estimations from Wheat for Yield Prediction
摘要： The efficient use of nitrogen fertilizer is a crucial problem in modern agriculture. Fertilization has to be minimized to reduce environmental impacts but done so optimally without negatively affecting yield. In June 2017, a controlled experiment with eight different nitrogen treatments was applied to winter wheat plants and investigated with the UAV-based hyperspectral pushbroom camera Resonon Pika-L (400–1000 nm). The system, in combination with an accurate inertial measurement unit (IMU) and precise gimbal, was very stable and capable of acquiring hyperspectral imagery of high spectral and spatial quality. Additionally, in situ measurements of 48 samples (leaf area index (LAI), chlorophyll (CHL), and reflectance spectra) were taken in the field, which were equally distributed across the different nitrogen treatments. These measurements were used to predict grain yield, since the parameter itself had no direct effect on the spectral reflection of plants. Therefore, we present an indirect approach based on LAI and chlorophyll estimations from the acquired hyperspectral image data using partial least-squares regression (PLSR). The resulting models showed a reliable predictability for these parameters (R2 LAI = 0.79, RMSELAI [m2m?2] = 0.18, R2 CHL = 0.77, RMSECHL [μg cm?2] = 7.02). The LAI and CHL predictions were used afterwards to calibrate a multiple linear regression model to estimate grain yield (R2 yield = 0.88, RMSEyield [dt ha?1] = 4.18). With this model, a pixel-wise prediction of the hyperspectral image was performed. The resulting yield estimates were validated and opposed to the different nitrogen treatments, which revealed that, above a certain amount of applied nitrogen, further fertilization does not necessarily lead to larger yield.
关键词： hyperspectral,chlorophyll,UAV,pushbroom,regression,grain yield,LAI,nitrogen
更新于2025-09-19 17:15:36
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[Methods in Molecular Biology] || Total Nitrogen Determination by a Spectrophotometric Method
摘要： Being able to measure total nitrogen (TN) is important for following the nitrogen budget. In this chapter, we present the spectrophotometric method we use for determining TN. The method relies on oxidation and reduction steps, involving persulfate digestion of nitrogen compounds into nitrate followed by spectrophotometric determination.
关键词： Total nitrogen,Nutrient uptake
更新于2025-09-19 17:15:36
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Hydrothermal synthesis of manganese oxide and nitrogen doped graphene (NG-MnO <sub/>2</sub> ) nanohybrid for visible light degradation of methyl orange dye
摘要： MnO2 nanoparticles and its nanocomposite with nitrogen-doped graphene (NG) have been fabricated via simple hydrothermal synthesis procedure using water as a solvent. X-ray diffraction (XRD) analysis of the as-prepared samples was used to ascertain the phase purity and crystallite size. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were employed to study the surface features and particle size of the synthesised samples. The photocatalytic ability of the methyl orange (MO) dye with bare MnO2 and its hybrid with nitrogen-doped graphene (NG-MnO2) wer compared with visible light prompted degradation of the dye in absence of these catalysts. The prepared nanohybrid (NG-MnO2) showed improved photocatalytic efficacy as compared to the pure MnO2 nanoparticles. The strong ferromagnetic character of nanohybrid helps in easy separation of catalyst even with a bar magnet.
关键词： photodegradation,MnO2 nanoparticles,nitrogen-doped graphene,Methyl orange,visible light
更新于2025-09-19 17:15:36
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Online Milk Quality Assessment during Milking Using Near-infrared Spectroscopic Sensing System
摘要： In recent times, there has been an urgent requirement for a technique that can be used by dairy farmers to assess the quality of milk of an individual cow during milking. A near-infrared (NIR) spectroscopic sensing system was designed on an experimental basis for the online assessment of the three major milk constituents (fat, protein, and lactose), solids not fat (SNF), milk urea nitrogen (MUN), and somatic cell count (SCC). This system was used to obtain the NIR spectra of non-homogenized milk during milking over a wavelength range of 700 to 1,050 nm. Calibration models for predicting three major milk constituents, SNF, MUN and SCC of non-homogenized milk were developed, and the precision and accuracy of the models were validated. The coefficients of determination, standard errors of prediction, and bias values showed high levels of precision and accuracy for the prediction of the considered parameters. The results indicated that the developed NIR spectroscopic sensing system can be used to assess milk quality in real-time during milking. This system can provide dairy farmers with information concerning milk quality and physiological condition of each cow, and can therefore optimize dairy farm management.
关键词： calibration models,milk constituents,somatic cell count,solids not fat,milk urea nitrogen
更新于2025-09-19 17:13:59