Atomic Method Research Articles

Existence state of Ti in diamond-like carbon coatings and its effects on hybrid structure and residual stress: Molecular dynamics simulations

In this study, the modified embedded atom method potential function is selected via the LAMMPS platform and OVITO interface software to describe the interatomic interaction potential, which is used to simulate the existence states of doped Ti in Ti-doped diamond-like coatings as well as their effect on the hybrid structure, hardness, and residual stress of the coatings. The results indicate that Ti atoms preferentially combine with C atoms to form Ti–C bonds, thus rendering it difficult to form metallic Ti clusters. The formation of Ti-C bond clusters with high extent of ordering (nanoc-TiC) in the coating is related to the density (or sp3C fraction) of the coating; the higher the density, the higher is the critical content of Ti (CV-Ti) required to form nanoc-TiC. When the density of the coating ranges from 2.4 to 3.6 g/cm3, the CV-Ti is 2–6 at.%. When the Ti content in the coating is less than CV-Ti, Ti atoms existed only in amorphous Ti–C clusters, which is not conducive to the stability of the sp3C phase and significantly reduces the residual stress and hardness of the coating. When the CV-Ti is exceeded, nanoc-TiC formed and grew until the hybrid C–C bonds in the coating disappeared completely, thus increasing the residual stress of the coating.

Correlation between essential and toxic elements in maternal blood during early pregnancy and atrial septal defects/ventricular septal defects/patent ductus arteriosus in offspring.

Congenital heart defects (CHDs) are the most common congenital malformation in the world. Recent studies have found that essential and toxic trace element levels may play a crucial role in the risk of neonatal malformation. However, the relationships between element levels in early pregnancy and CHD risk among humans remain unclear. This study investigates the association between maternal essential element (copper [Cu], zinc [Zn], calcium [Ca], manganese [Mg] and iron [Fe]) and toxic element (lead [Pb] and cadmium [Cd]) levels during early pregnancy and CHDs. A hospital-based case-control study was conducted, including 181 cases and 218 controls. Eligible participants underwent antenatal examination during gestational weeks 11-14 and trace element levels were detected by the atomic absorption method. Multi-variable logistic regression was used to examine the associations between the level of maternal trace elements and CHD risks. Higher levels of Ca in early pregnancy were associated with lower risk of ASD/VSD risks. Moreover, higher Fe, Pb, and Cd levels in the first trimester were associated with higher risks of all CHD and the subtypes risks, and the tests for trend were significant (all p < .05). The restricted cubic spline analysis showed that there was a nonlinear inverted u-shaped dose-response relationship between levels of Zn, Pb, and Cd in the first trimester and risk of CHDs (non-linearity test p < .05). A moderate increase in Zn and Ca levels and a decrease in Pb and Cd levels during early pregnancy are needed to reduce the incidence of CHDs in the Chinese population.

Exploring mass transfer mechanisms in sintering processes through molecular dynamics simulation

Molecular dynamics simulation was employed to delve into the mechanism of neck formation in a two-particle sintering model. Specifically, this study simulated the behavior of two nickel (Ni) nanoparticles, each with a diameter of 12 nanometers, utilizing the Embedded Atom Method (EAM) interatomic potential at a high temperature of 1200 K. Indeed, in this study, a meticulous examination of atom displacements enabled the evaluation of the neck formation mechanism through both qualitative and quantitative analyses. The qualitative assessments, encompassing forward and backward imaging techniques, indicated that diffusion and semi-convection were likely the most prominent mass transfer mechanisms during the sintering process of two nickel nanoparticles. For a quantitative analysis of the mass transfer mechanisms, Mean Square Displacement and Relative Mean Square Displacement were employed. The results of this analysis pertaining to neck formation revealed that the diffusion mechanism contributed to 17.6 % of the atomic displacement, with an associated magnitude of 2.7 Å. Furthermore, the analysis revealed that the contribution and average value of the semi-convection movement accounted for 82.4 % and 12.6 Å, respectively. Consequently, given the concurrent operation of both mass transfer mechanisms in this study, it becomes evident that semi-convection mass transfer can be established as the primary mechanism regulating the rate of neck formation.

Window Fabrication of Zinc Selenide Nanostructures: Synthesis and Properties

Zinc selenide (ZnSe) nanostructure’s optical and structural characteristics were investigated in this study. Pulse laser deposition of thin films on glass substrates was achieved using an Nd:YAG laser (wavelength 1064 nm) at different laser powers (100, 200, 300, 400 and 500 mJ) with fixed pulses 100 pulses, repetition rate 6 Hz and distance 10 cm between laser and the substrate with a thickness of films 200 nm. An atomic force microscope (AFM) and X-ray diffraction method were used to research the impact of altering the laser intensity on the structural characteristics. A branched (100) polycrystalline type and a plane (111) and branched (100) polycrystalline type are prevalent (002). In addition, AFM measurements further revealed that the smallest granular size achieved at high laser power was 48.40 nm at 100 mJ. The findings showed that it is possible to construct nanostructures with medium grain sizes of alumina (72.99 nm). The study of the relationship between laser energy and nanostructure optical characteristics was explored and it was discovered that the transitions had a specific range of 2.83–3.10 eV.

Tuning interfaces between Cu and oxide via atomic layer deposition method for CO2 hydrogenation to methanol

The specific Cu/10c-ZnO/CeO2 catalyst was designed using the atomic layer deposition method and the Cu+–Zn0–Ce4+ structure is the active site for methanol synthesis from CO2 hydrogenation.

RESPONSE SURFACE METHODOLOGY-BASED NOVEL LATTICE HEAT SINK OPTIMIZATION FOR ELECTROHYDRODYNAMIC (EHD) SPRAY COOLING

In recent years, the size of electronic equipment has become smaller, while the increased processing capacity has led to progressive elevation in the heat flux. As a result of this, the performance of this equipment decreases, and their service lives decrease. Although traditional cooling methods are insufficient to remove the surface heat, new cooling techniques, for example, electrohydrodynamic spray (EHD-spray) cooling, show promise in guaranteeing the operation of these systems under the intended conditions. EHD-spray, also known as electrospray, is an atomization method that provides equal and homogeneous droplets. Although EHD has been used in many studies in the literature, its use in heat transfer has only recently become an important research area. Studies on EHD-spray, which has important advantages such as requiring a very small amount of fluid and low energy, are limited, and there are almost no studies using finned heat sinks. In the study carried out, unique design heat sinks produced by the selective laser melting (SLM) method were optimized with the respond surface method (RSM) Box-Behnken design (BBD) management, that is one of the most effective design methods. In the study where heat sink surface area (HSSA), fluid composition ratio (FCR), and flow rate (FR) were used as variable parameters, the highest heat transfer coefficient (HTC) was found for 100&amp;#37; distilled water at a 17 mL/h flow rate, and the heat sink had the lowest surface area. The results show that EHD-spray is promising for cooling high-heat-flux systems.

EFFECT OF VACANCIES AND VOID DEFECTS ON THE STRUCTURAL AND MECHANICAL BEHAVIOR OF TUNGSTEN UNDER HARSH TEMPERATURE AND PRESSURE CONDITIONS

The body-centered cubic transition metal tungsten is frequently used as a pressure calibration material at high temperatures and pressures due to its outstanding mechanical and thermal properties. In this study, molecular dynamics simulations were performed to investigate the behavior of tungsten under harsh temperature and pressure conditions and the impact of fundamental defects, particularly vacancies, and voids, on its physical, structural, and mechanical properties through their correlation with elastic constants. The study also covers mechanical stability, elastic properties, brittleness and ductility, and hardness. The simulations utilized two different embedded atom methods and one modified embedded atom method interatomic potentials. The results show that the fundamental structural characteristics and properties of pure tungsten crystal, including lattice constant, density, cohesive and vacancy formation energies, elastic constants, and moduli in the ground state for all three potentials, are in good agreement with previous experimental and theoretical calculations and results. The calculated results demonstrate that the elastic constants-related properties for defective structures also have the same trend as the perfect crystal. The presence of defects in the crystal causes a decrease in properties at all temperatures and pressures, directly correlated to the fraction of crystal defects. As the percentage of vacancies increases, a further reduction in the elastic constants is observed. Likewise, these findings reveal that the presence of scattered vacancies in the crystal structure causes a more significant decrease in the substance&amp;apos;s properties than a void in the center of the crystal (with the same percentage). The presence of any vacancy weakens the interatomic bonds of the atoms around the vacancy, while the existence of a void in the center has less effect on the interatomic bonds of atoms further away from the center of the crystal.

Preparation of high-performance large-area perovskite solar cells by atomic layer deposition of metal oxide buffer layer

Perovskite solar cells have been widely recognized as the most promising new-type photovoltaic device due to its power conversion efficiency rapidly increasing from 3.8% to over 26% in merely fifteen years. However, the high performances are achieved mainly on small area cells with an active area lower than 0.1 cm&lt;sup&gt;2&lt;/sup&gt;. When enlarging the active area of perovskite solar cells, the efficiency falls dramatically. So, how to reduce the gap between performances of small area cells and large area cells gradually becomes a critical point in the path towards the commercialization of perovskite photovoltaic technology. Herein, a strategy of pre-growing thin layer of TiO&lt;sub&gt;2&lt;/sub&gt; on a rough FTO substrate by atomic layer deposition method before spin-coating SnO&lt;sub&gt;2&lt;/sub&gt; nanoparticles is proposed. Due to the inherent conformal film growth mode of atomic layer deposition, the FTO substrate can be completely covered by TiO&lt;sub&gt;2&lt;/sub&gt;, thus preventing the direct contact between local protrusions of FTO and perovskite layer and impeding the current leakage phenomenon, which can be verified by the measurements from X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy, and further proved by the dark current measurement. By using this method, the repeatability and consistency of the small area cell fabrication technology on the same substrate are improved obviously. The improved electron transport process revealed by photoluminescence results and incident light management process revealed by external quantum efficiency results also brings about better solar cell performances. More importantly, highly efficient 0.5 cm&lt;sup&gt;2&lt;/sup&gt; large area perovskite solar cells are fabricated through optimization of TiO&lt;sub&gt;2&lt;/sub&gt; thickness. When growing 200 cycles TiO&lt;sub&gt;2&lt;/sub&gt; (~9 nm in thickness) by using atomic layer deposition technology, the champion large area perovskite solar cell possesses a power conversion efficiency as high as 24.8% (certified 24.65%). The device performances also show excellent repeatability between different fabrication batches. The perovskite solar cell with TiO&lt;sub&gt;2&lt;/sub&gt; buffer layer grown by the atomic layer deposition method can still retain over 95% of its initial efficiency after having been stored in a nitrogen atmosphere for 1500 h. The technique proposed in this paper can be helpful in manufacturing perovskite solar cell modules in the realistic photovoltaic market and can be extended to the large area fabrication of other perovskite optoelectronic devices such as light emitting diode, laser and detector.

Green direct ultrasonic slurry sampling and electrothermal atomic absorption spectrometry method for metal analysis of solid plastics samples.

This work presents a "green" analytical method developed for the determination of potentially toxic metals such as aluminium, barium and chromium in solid plastics samples using the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry. The development of the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry entailed optimisation of the measuring conditions, which included optimisation of the temperature programme, selection of an appropriate liquid medium for slurry preparation, optimisation of the concentration and volume of the liquid medium and optimisation of the mass of the solid plastics sample. The following conditions were determined: the optimal pyrolysis temperature for aluminium, barium and chromium was in the range of 1300 °C to 1700 °C and the optimal atomisation temperature was in the range of 2100 °C to 2400 °C. The optimal liquid media for solid plastics samples were H2O, 0.2% (v/v) HNO3 and 0.2% (v/v) HCl. The optimal volume of liquid medium was in the range from 5 to 15 mL and the mass of the solid plastics samples was in the range from 30 to 100 mg. The limit of detection and limit of quantification were estimated as 0.06-0.52 ng g-1 and 0.22-1.69 ng g-1 for aluminium, 0.11-0.94 ng g-1 and 0.37-3.14 ng g-1 for barium and 0.07-0.31 ng g-1 and 0.25-1.04 ng g-1 for chromium. Relative standard deviation was below 5% for all plastic samples analysed. Based on the established validation parameters, the slurry sampling technique in conjunction with electrothermal atomic absorption spectrometry represents a viable technique for metal analysis of a variety of plastic materials. The concentrations of analytes in individual solid plastic samples were in the range of 1.36 ± 0.06 μg g-1 to 22.65 ± 0.66 μg g-1 for aluminium, 1.13 ± 0.03 μg g-1 to 6.01 ± 0.22 μg g-1 for barium and 0.60 ± 0.03 μg g-1 to 10.48 ± 0.46 μg g-1 for chromium.

Atomic Absorption Spectrophotometric Method for the Estimation of Micronutrients in Soil and their Effect on Plant Growth

Atomic Absorption Spectrophotometric Method for the Estimation of Micronutrients in Soil and their Effect on Plant Growth

Atmospheric air pollution of a mining town in the Kuzbass region by toxic metals

The paper analyses the results of active biomonitoring of atmospheric air pollution in the mining town of the Kuzbass region by the most toxic metals. The epiphytic moss Pylaisia polyantha (Hedw.) B. S. G. was used as a bioindicators; determination of metal content in moss samples was carried out using neutron activation analysis and atomic emission spectrometry methods. Based on the results of the study, spatial distributions for pollution levels of the most toxic metals were plotted and their sources were identified.

A prototype of ultrasensitive time-resolved fluoroimmunoassay for the quantitation of lead in plasma using a fluorescence-enhanced europium chelate label for the detection system.

This study describes the prototype of a novel ultra-sensitive time-resolved fluoroimmunoassay (TRFIA) for the quantification of lead (Pb) in plasma. The assay procedures were conducted in 96-microwell plates and involved the competitive binding format. The assay used a mouse monoclonal antibody, designated as 2C33, that specifically recognized the diethylenetriamine pentaacetic acid chelate of Pb (Pb-DTPA) but did not recognize Pb-free DTPA chelator. The antigen used for coating onto the inner surfaces of assay plate microwells was Pb-DTPA conjugated with bovine serum albumin protein (Pb-DTPA-BSA). The competitive binding reaction occurred between Pb-DTPA chelates, formed in the sample solutions by treating the samples with an excess DTPA, and the coated Pb-DTPA-BSA for a limited quantity of 2C33 antibody binding sites. The antigen-antibody complex formed in the plate wells was quantified by a europium-DTPA-labeled secondary antibody and a fluorescence enhancement solution. The conditions of the assay were refined, and its optimum procedures were established. The TRFIA was validated following the immunoassay validation guidelines, and all of the validation criteria were acceptable. The working range of the assay was 20-300 pg mL-1 and its limit of quantitation was 20 pg mL-1. Metals that are commonly encountered in blood plasma did not interfere with Pb in the analysis by the proposed TRFIA. The assay was applied to the quantitation of Pb in plasma samples with satisfactory accuracy and precision. The results were compared favorably with those obtained by atomic emission spectroscopy. In conclusion, the present study represents the first TRFIA for the quantitation of Pb in plasma. The assay is superior to the existing atomic spectrometric methods and other immunoassays for Pb in terms of sensitivity, convenience, and analysis throughputs. The proposed TRFIA is anticipated to effectively contribute to assessing Pb concentrations and controlling the exposure of humans to its potential toxicity.

Influence of the rat diet enrichment with oat β-gucans on the assimilation of B group vitamins, mineral elements and lipid metabolism

Despite the widespread use of oat β-glucans as ingredient of foods and dietary supplements, there is insufficient data on their effect on the metabolism of vitamins and minerals. The purpose of the study was to evaluate the effect of including oat bran with a high content of β-glucans (β-glucan) in the diet on the absorption of micronutrients and lipid metabolism in growing rats deficient in vitamins D, group B and trace elements (iron, copper, zinc). Material and methods. After the development of micronutrient deficiency (for 23 days), in order to assess the effect of oat bran (5%) with a high content of β-glucans on the correction of the micronutrient status of growing male Wistar rats (with initial body weight of 70.7±0.7 g), the missing micronutrients were introduced in the semi-synthetic diet deficient in vitamins D, group B, iron, copper and zinc within 7 days either along with β-glucan (1.47%) or without its addition. Indicators of micronutrient sufficiency (riboflavin serum concentration, daily urinary excretion of thiamine, riboflavin and 4-pyridoxic acid, measured by fluorometric methods; serum concentration and urinary excretion of calcium, magnesium, iron, zinc, copper, phosphorus, measured by the atomic absorption method or using standard methods on a biochemical analyzer) and the biochemical parameters of blood serum were compared with the parameters of rats adequately provided with all micronutrients throughout the experiment. Results. Replenishment of missing micronutrients in the diet of rats with deficiency in vitamins D and group B, iron, copper and zinc for 7 days led to the elimination of deficiency of vitamins B1, B2 and B6, regardless of the presence of β-glucans in the diet. At the same time, against the background of the presence of β-glucans in the feed, an increase in the absorption of iron was observed, as evidenced by an increase by 1.73 times in iron blood plasma level (р<0.05) and a tendency towards its urinary excretion decrease by 1.60 fold (р<0.10) compared to animals from the control group. Adding oat bran with β-glucans to the feed did not lead to a decrease in blood plasma level of total cholesterol and low-density lipoproteins cholesterol. The levels of high-density lipoprotein cholesterol and triglycerides in rats of all three groups did not have statistically significant differences. Conclusion. The presence of β-glucans in the diet had virtually no effect on the absorption of B vitamins and improved the absorption of iron.

Using the sorption properties of diatomite from the Aktobe deposit in improving the quality of drinking water in Western Kazakhstan

The paper describes the results of monitoring studies of the quality of tap water in the city of Uralsk. A solution was found to use natural reserves of the mineral diatomite in the purification of drinking water. The natural sorbent diatomite was modified with hydrochloric acid before testing. Natural and modified diatomite samples were studied using X-ray fluorescence analysis and electron microscopy. In acid-activated diatomite, the specific surface area and porosity increase by 2.5 times. Xray fluorescence analysis of the elemental composition showed an increase in the silicon content in the sorbent. Organoleptic and physicochemical properties were studied in the original and diatomite-treated water: turbidity, taste, smell, color, hardness, permanganate oxidation, pH, iron and copper ions. The efficiency of sorption with respect to heavy metals was tested using the model toxicant copper sulfate. Determinations of copper and iron ions were carried out using the atomic spectrometry method. Hardness, permanganate oxidation, pH and organoleptic parameters were determined by standard methods. Treatment of water with natural and modified diatomite made it possible to significantly reduce water pollution according to the studied parameters. Filtering water with a modified diatomite sorbent allows you not only to purify water from unwanted impurities, but also to adjust its salt composition due to the intake of silicon. Based on the results of the work, we can conclude that, compared to natural, modified diatomite has higher adsorption properties in relation to copper and iron cations, increases pH, and also contributes to more effective water purification from unwanted impurities.

The synergistic effect mechanism of H2 generation during coal/ammonia co-pyrolysis

Coal/ammonia (NH3) co-combustion faces the problem of unstable ignition and combustion due to the high ignition temperature and low flame propagation speed of NH3. The pre-pyrolysis of coal and NH3 generates combustible gases such as hydrogen (H2) that aid in enhancing the stability of the subsequent ignition and combustion process. In this paper, the synergistic effect mechanism of H2 generation during coal/NH3 co-pyrolysis are investigated by constant temperature thermogravimetric experiments and reactive molecular dynamics (ReaxFF MD) simulations. The experimental results show that NH3 promotes coal pyrolysis, leading to an increase in the release of coal pyrolysis volatiles during coal/NH3 co-pyrolysis. Furthermore, both experimental and ReaxFF MD simulations results affirm a synergistic effect on H2 generation during coal/NH3 co-pyrolysis. The atomic labeling method is employed to reveal the mechanism of the synergistic effect on H2 generation during coal/NH3 co-pyrolysis. It is found that H2 generated solely from either coal or NH3 during co-pyrolysis is lower than that from the individual pyrolysis of coal or NH3, respectively. The synergistic effect on H2 generation during coal/NH3 co-pyrolysis is mainly attributed by the interactions between coal and NH3, resulting in the generation of coupling H2. The main reaction pathways for H2 generation during coal/NH3 co-pyrolysis are determined by analyzing the frequencies of H2 generation reactions. The mechanisms of the coupling H2 generation are revealed by tracing to the source of the important reactants in the main reactions for H2 generation. The coupling H2 are mainly formed through the directly pyrolysis of the coupling NHi, and the dehydrogenation reactions of the coupling hydrocarbons.

ДИНАМИКА КОНЦЕНТРАЦИЙ РАСТВОРЕННЫХ ФОРМ ТЯЖЕЛЫХ МЕТАЛЛОВ В ВОДЕ РЕКИ МОСКВЫ ПО ДАННЫМ МОНИТОРИНГОВЫХ ИССЛЕДОВАНИЙ В 2021-2023 ГОДА

Background. The Moskva River is a prime example of a natural urban watercourse subjected to strong and varied anthropogenic pressure. For many years, this river has been characterized by increased content of heavy metals. The exceedance of the maximum allowable concentrations of harmful substances in the waters of water bodies used for fishery can result in disruption of the normal functioning of aquatic ecosystems. Relevance. The summarized data collected over the course of monitoring surveys of the Moskva River for three years will be indicative of the relative contribution of natural and anthropogenic sources into its pollution. The aim of this work is to identify the dynamics of spatial and temporal distribution of heavy metals in the Moskva River water and its relation to hydrological seasons, as well as to assess the anthropogenic pressure exerted by the city of Moscow on the river. Methods. Water samples were collected in 2021-2023 during four hydrological seasons. Identification of heavy metals in the collected samples has been carried out using the atomic absorption method. Results. The analysis of the content of dissolved heavy metals (iron, cadmium, cobalt, manganese, copper, nickel, lead, and chrome) in the Moskva River water in various seasons of 2021-2023 has been conducted, and the same was done for zinc in 2023. The dynamics of the spatial and temporal distribution of these heavy metals has been identified, as well as its dependence on the hydrological phases. The influence of the urban infrastructure on the composition of the Moskva River water has been elucidated. Within the investigated area, the exceedance of the values prescribed by the water quality standards for the water bodies used for fishery (MACfish) has been recorded. Conclusion. The waters of the Moskva River have been characterized as polluted, mainly with iron, manganese, copper, and zinc. For lead, chrome, cobalt, nickel, and cadmium, no exceedance of the MACfish has been recorded. It has been found that the majority of the investigated elements were exceeding the values prescribed by the established standards in the spring season, but their concentrations decreased in summer.

Biogeochemical accumulation of trace elements in soils and plants of the Russian Far East

The accumulation of total mercury and other elements in soils and plants growing on them (legume and valerian families) selected in the Khabarovsk and Primorsky Territories, Buryatia, and the Amur Region was studied. The possibility of determining mercury in natural objects along with the natural atomic absorption method is also shown by X-ray fluorescence spectroscopy simultaneously with other trace elements. Analysis of the data obtained indicates that the main sources of trace elements at the test sites are, apparently, sources of natural origin – soils, underlying rocks, underground and surface waters, etc.

Evaluation of serum selenium level in patients with plaque-type psoriasis

Back ground Psoriasis may be accompanied by homeostatic imbalance of some trace elements such as selenium (Se) that may influence disease management. Se has antiproliferative and immune-modulating properties. There are limited data about the imbalance of Se level in psoriasis patients with equivocal findings. Objective Aim of the study was to evaluate serum Se level in plaque-type psoriasis patients with different severity and chronicity of disease. Patients and methods In this case–control study during 18 months, Se level was analyzed in serum samples of 54 psoriasis patients and 54 healthy volunteers. Se level was measured with atomic absorption method. The extent of psoriasis was investigated using the psoriasis area severity index and nail psoriasis severity index scores. Age, sex, duration of psoriasis, severity scores, and levels of Se were collected and analyzed by SPSS software. Results There was no significant difference in Se levels between two groups (P=0.323). Also median level of Se in patients with different duration time of psoriasis was not significantly different (P=0.157). But there was significant differences in the median level of Se in mild group compared with severe (P=0.035) and moderate group (P=0.018). There was a nonsignificant correlation between severity and duration of psoriasis with Se level. Conclusion Considering these nonsignificant difference, we think that Se imbalance is not probably an important factor in our psoriasis patients.

Highly selective fluorescence detection of L-selenium-methylselenocysteine in selenium-enriched Cardamine violifolia.

A feasible and practicable "off-on" type of fluorescence strategy for highly selective screening of L-selenium-methylselenocysteine (L-SeMC) in selenium-enriched Cardamine violifolia was developed using g-C3N4-MnO2 nanocomposites as fluorescent probes. The g-C3N4 nanosheets can emit blue fluorescence at 320 nm excitation wavelength with a fluorescence quantum yield of 28%. When MnO2 was deposited onto g-C3N4 nanosheets, the fluorescence of the g-C3N4 nanosheets was quenched due to fluorescence resonance energy transfer (FRET). After the addition of L-SeMC, MnO2 was reduced to Mn2+, which eliminated FRET and fluorescence was restored. Based on this, a quantitative method for the determination of L-SeMC was established. The fluorescence intensity of g-C3N4-MnO2 nanocomposites showed a good linear relationship with the concentration of L-SeMC in the range of 0-45 μg mL-1, the limit of detection (LOD, 3σ/K) was 8.25 ng mL-1 and the correlation coefficient was 0.9904. Common selenium compounds such as SeO2, Na2SeO3, SeMet and SeCys caused weak fluorescence intensity, which means that the developed method is highly selective to detect L-SeMC in a series of selenium compounds. Meanwhile, the technique was evaluated by spiking L-SeMC standards in C. violifolia extraction solutions and with 9 C. violifolia extraction specimens, receiving excellent accordance with results from the commercially available atomic fluorescence spectroscopy method.

High-Performance of InGaZnO TFTs With an Ultrathin 5-nm Al₂O₃ Gate Dielectric Enabled by a Novel Atomic Layer Deposition Method

High-Performance of InGaZnO TFTs With an Ultrathin 5-nm Al₂O₃ Gate Dielectric Enabled by a Novel Atomic Layer Deposition Method