Peer-rewieved journal "Zhurnal Prikladnoii Spektroskopii"
B. I. Stepanov Institute of Physics of the National Academy of Sciences
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Application of Aluminum Foil as a SERS-Active Substrate in the Study of Artistic Pigments
The use of aluminum foil as a low-cost and promising SERS-active substrate is proposed. In model experiments with various artistic pigments, aluminum foil demonstrated plasmonic properties comparable to, and in some cases even superior to, traditional SERS-active substrates based on gold nanoparticles. When studying the samples taken from “Southern Landscape” supposedly by A. Kuprin and “The Virgin and Child” from the Church of St. John the Baptist in Borovtsy, the used inorganic pigments were identified, and time of the creation were defined.
Role of Multicenter Interactions in the Formation of Spectral-Luminescent Characteristics of 5,15-Diphenylporphyrin Derivatives
The peculiarities of formation of spectral-luminescent characteristics of 5,15-diphenylporphyrin derivatives with various architecture of peripheral substitution have been studied. Molecular conformation of the derivatives with various peripheral substituents in Сb and Сm-positions of the tetrapyrrole macrocycle was optimized with a density functional method. It has been shown that substitution of two diametrally opposite Сm-atoms leads to the macrocycle elongation in the direction of substitution which does not depend on Сb-substitution character; and dodecasubstituted derivatives are of a saddle-shaped character of macrocycle distortion. The quantum yield of 5,15-diphenylporphyrin fluorescence and its Сb-alkylated derivatives reduces in comparison with that of 5,10,15,20-tetraphenylporphyrin, and the attachment of nitrogroups and bromine atoms in para-position of the phenyl fragments leads to rising and quenching of the fluorescence respectively. It has been established that the attachment of two nitrogroups in Сm-positions of 5,15-diphenylporphyrin macrocycle leads to substantial bathochromic shifts of the absorption and fluorescence spectra with 100-fold fluorescence quenching due to significant gain of nonradiative deactivation of S1-state upon the saddle-shaped conformer formation.
Studying the Effect of Surfactants and Static Pressure on Sonoluminescence Brightness for Elemental Analysis
/ The use of sonoluminescence to determine elements in natural waters and artificial solutions faces challenges, the main of which is the low intensity of spectral lines. In most cases, only Na line at 590 nm is clearly visible. It has been found that adding surfactants to solutions of CaCl2, MnCl2, MgCl2, CuSO4, CrCl3, and seawater can sometimes enhance spectral lines, furthering the practical application of sonoluminescence elemental analysis. A brief overview of other physicochemical methods for enhancing the brightness of spectral lines in sonoluminescence is provided.
Polarization Switching Mechanism in Semiconductor Surface-Emitting Lasers
Based on the previously developed method for describing the polarized radiation formation in laser systems, numerical modeling of the polarization switching process in long-wavelength surface-emitting lasers (VCSEL) has been made. The analysis of the obtained results for output power, power of polarization modes, and degree of polarization showed, that in this case, there are no fundamental differences from the case of short-wavelength VCSELs that were studied earlier. This allowed for the formulation of a number of general conclusions regarding the mechanisms and dynamics of polarization characteristic formation in VCSELs, the main one being the assertion that the polarization switching process in VCSELs is a totally deterministic process transitioning from one limiting polarization to orthogonal one through a sequence of partially polarized states with a small change in current in the polarization switching region.
Statistics of Stokes Radiation Pulse Energy under SRS Excitation in Compressed Hydrogen by Two-Pulse Two-Frequency Nd:YAG-Laser Radiation
The statistical characteristics of the pulse energy generated at two-pulse two-frequency stimulated Raman scattering (SRS) in compressed hydrogen were experimentally studied. It was found that, for comparable SRS gain increments, the normalized standard deviation of the Stokes pulse energy generated under conditions of simultaneous four-photon parametric interaction and two-photon SRS is always smaller than the normalized standard deviation of the Stokes pulse energy generated under conditions of “classical” two-photon SRS. The physical mechanisms responsible for this behavior are discussed in the article.
Effect of Annealing in an Atomic Oxygen Atmosphere on Photoluminescent and Electrical Properties of Hydrothermal Single Crystals ZnO
The effect of annealing in atomic oxygen atmosphere on the photoluminescence and electrical properties of high-quality ZnO single crystals grown by the hydrothermal method was studied. The spectrum of as-prepared ZnO samples exhibited a series of narrow lines in the ultraviolet region and long-wavelength emission peaking at 510 nm. The nature of the observed bands was discussed. Hall effect measurements indicated that the dominant donor in as-prepared ZnO samples had ED = 67 meV and ND = 3.6 × 1018 cm–3. After heat treatment in atomic oxygen atmosphere at 600–700°C for 1 h, ND value decreased to 3.7 × 1017 cm–3, while ED value did not change. Although, ZnO annealed at 800°C showed p-type conductivity with an acceptor concentration NA = 2.7 × 1016 cm–3.
Influence of Composition on the Electronic Structure of Manganites R1-xCaxMnO3 (R = Nd, Gd; x = 0.0, 0.2) According to X-Ray Photoelectron Spectroscopy Data
CaMnO3 and R1–xCaxMnO3 (R = Nd, Gd; x = 0.0, 0.2) manganites were studied using X-ray photoelectron spectroscopy (XPS). The core-level spectra of all the elements in the compounds were analyzed. Chemical shifts reflecting the evolution of the ion valence states depending on composition were identified. Based on an analysis of the multiplet splitting of Mn 3s spectra, the effective spin and charge states of Mn ions were determined. The obtained results expand the existing XPS database on the electronic structure of manganites and confirm the effectiveness of this method for analyzing the valence of manganese in complex oxides.
Use of Spectral Methods for the Analysis of Melanin Pigments in Antarctic Yeast Dothiora cannabinae BIM Y-383
Melaninogenesis during cultivation of the Antarctic yeast species Dothiora cannabinae BIM Y-383 was studied using electron spectroscopy and EPR methods. It was shown that this species synthesizes melanin optionally at the stages of stationary growth and culture death. Melanin was extracted from the yeast mycelium cultivated for 3, 6, 9, 12, and 16 days and its spectral properties were studied. To characterize it, the pigment was isolated and purified. Based on the optical density at 460 nm, the melanin content in the extracts on days 3, 6, 9, 12, and 16 of cultivation was calculated and was 22.2, 38.3, 42.4, 46.8, 54.9 mg per 1 g of sublimated mycelial biomass, respectively. The increase in melanin content at the stages of exponential growth, stationary phase and dying of D. cannabinae BIM Y-383 culture is manifested in an increase in the number of paramagnetic centers in the freeze-dried mycelium. The conducted studies revealed a high correlation between the melanin content in the obtained extracts, calculated by its optical density at 460 nm and the paramagnetic centers content in freeze-dried yeast mycelium samples.
Development and Validation of a Spectrophotometric Method for the Quantitative Determination of Total Triterpenoid and Steroid Compounds in Polypore Fungi
Polypore fungi represent a promising source of biologically active triterpenoid and steroid compounds; however, their quantitative determination is complicated by the lack of reference standards as well as the variety and structural similarity of the compounds. In this study, a spectrophotometric method based on the Liebermann–Burchard reaction was developed and validated for the determination of total triterpenes and steroids in polypore extracts. The optimal analytical conditions were established as follows: chloroform as the extraction solvent, extract-to-reagent ratio of 1:1, analytical wavelength of 665 nm, and reaction time of 90 minutes. The method demonstrated satisfactory specificity, accuracy (recoveries of 100.6–108.6%), precision (RSD ≤ 3.4%), and linearity in the range of 31.25–1000 μg/mL (R2 > 0.99). The obtained results confirm the applicability of the proposed approach for the standardization of fungal raw materials and the quality control of polypore-based products.
Analysis of Stress-Induced Generation of Reactive Oxygen Species in Phalaenopsis ×hybridum Blume Protocorms Using the Redox-Dependent Fluorescent Dihydroethidium Probe
Methods for analyzing and studying the most important stress responses of epidermal cells of the protocorms of Phalaenopsis ×hybridum Blume – the synthesis of reactive oxygen species (ROS), in particular, the superoxide anion radical (О2●–) – were developed. Epifluorescence microscopy was adapted for this purpose in combination with the fluorescent probe dihydroethidium and a narrow-band fluorescent filter cube Nikon FITC B-2E/C. This approach made it possible to avoid artifacts arising from intense fluorescence in the red region of the spectrum upon binding of ethidium (a product of nonspecific oxidation of dihydroethidium) to DNA, and to successfully record the signal of 2-hydroxyethidium (2-OH-E+) in the green region of the spectrum, specific for the reaction with О2●–. Using the developed methods, ROS generation in Orchid protocorms subjected to mechanical damage, as well as osmotic and salt stress, was analyzed for the first time. It was shown that the above factors induced О2●–generation in the protocorm epidermis (registered as an increase in 2-OH-E+ fluorescence). The addition of enzymatic and low-molecular antioxidants, such as superoxide dismutase (SOD), catalase, dimethyl sulfoxide (DMSO), and thiourea, reduced stress-induced ROS synthesis in protocorms. The greatest decrease in fluorescence was observed in the presence of SOD and thiourea, indicating the specificity of the reaction of dihydroethidium with О2●–. The developed approaches can be applied to the analysis of the early stages of oxidative imbalance developing in the cells of Orchidaceae and other higher plants under the influence of abiotic stress factors.
Using spectrophotometric titration approach several fluorescent and profluorescent compounds were tested against human CYP17A1. It was found that 20αand 20β-NBD (7-nitrobenzoxadiazole) derivatives of pregnenolone bind in the active site of human CYP17A1 in a substrate-like manner with dissociation constants Kd = 21.5 ± 3.1 mcМ (20a-NBD-Preg) and Kd = 19.8 ± 1.8 mcМ (20b-NBD-Preg), respectively. It was found that the compounds are not metabolized by the enzyme due to the non-optimal positioning of the ligands in the active site caused by the presence of the bulky NBD group. The formation of ligand complexes with CYP17A1 leads to fluorescence quenching, which is stronger for 20a isomer, possibly due to the formation of a hydrogen bond with Asn202, as it was found using molecular docking simulation approach. The identified ligands are promising lead compounds for the development of novel molecular tools that can be used to study the functioning mechanism of human CYP17A1 and to search for high-affinity modulators of enzyme activity — novel effective drugs.
SpikeYOLO-RS: Improved Spike-Convolution Neural Network for Remote Sensing Image Object Detection
This paper studies how to increase accuracy of SpikeYOLO for remote sensing (RS) images analysis, and proposes an improvement method. First, a dynamic membrane potential attenuation mechanism is constructed and the fixed attenuation factor is reconstructed into a learnable parameter. Then, the membrane potential is updated through vectorized parallel computing. Learnable residual weights are introduced to improve the feature fusion capability and; finally, the calculation flow is adjusted. On the RSOD remote sensing dataset, we obtained 96.8% mAP 50 and 64.8% mAP 50:95, which are 6.7 and 2.3% higher than the previous stateof-the-art SpikeYOLO, respectively. On the NWPU-VHR-10 dataset, we obtained 92.8% mAP 50, which is 1.5% higher than SpikeYOLO with the same architecture.
Transformation of Phenol in Solid Mixtures with Humic Acids under Electron Beam Irradiation
The pulsed cathodoluminescence spectra of solid phenol, humic acids isolated from oxidized brown coal (Mongolia, China), including those subjected to mechanical activation, and mixtures of phenol with humic acids with a phenol content of 10, 30, 50, 70, and 90 wt.% were recorded. The spectra were recorded in the range from 350 to 850 nm upon irradiation with an electron beam of 2 ns duration with an average energy of 170 keV. The number of irradiation pulses, following at the frequency of 1 Hz, varied from 20 to 4000, while the absorbed dose from one pulse was about 1.4 kGy. It was shown that humic acids do not luminesce, but phenol emission appears in mixtures. The degree of phenol transformation in the mixtures under the action of an electron beam was determined by analyzing the pulsed cathodoluminescence spectra. The intense band at 375 nm is due to the transition from the triplet state T1 of phenol to the ground state S0. Two bands at 395 and 475 nm are formed by the transition from T1 state to the first and fourth vibrational levels of the ground state S0, and the long-wavelength band at 740 nm corresponds to Ti®T1 transition. With an increase in the number of irradiation pulses, the behavior of the intensities of all four phenol luminescence bands becomes extreme, indicating its transformation. The interaction of humic acids with phenol occurs through physical adsorption. The presence of humic acids in most samples inhibits the transformation of phenol molecules. The relative positions of the functional carboxyl group and the phenol molecule in the mixtures have an effect.
Multipass Excitation System for Raman Spectroscopy of Gases
The paper presents an optical system designed to improve the sensitivity of compact Raman gas analyzers based on multimode diode lasers. The factors that influence its effectiveness are considered. It is shown that the application of such a multipass system provides an increase in the intensity of Raman signals by more than 4 times. The conditions for increasing this gain are given.
Creation of an Optical Profile Diffraction Grating Based on Nanoporous Germanium by Sputtering with Bismuth Ions
A method is proposed for creating an optical profile diffraction grating based on nanoporous Ge layers by sputtering a single-crystal c-Ge substrate by Bi+ ions at an energy of E = 18 keV, an ion beam current density of J = 5 μA/cm2, and a dose range of D = 2.5 × 1016—1.0 × 1017 ion/cm2 through a copper mesh mask with a square cell size of 20 μm. During ion irradiation, c-Ge is sputtered in unmasked areas of the irradiated c-Ge, and a nanoporous Bi:PGe layer is formed. The formation of periodic Bi:PGe microstructures on the c-Ge surface was monitored using optical, electron, and probe microscopy. The operation of the diffraction grating was demonstrated by probing it with helium-neon laser radiation at a wavelength of 632.8 nm in the optical spectral range.
New Approach to Tuning the Scintillation Properties of PbWO4 Crystals to Expand the Energy Range of the Detecting -Rays
It is demonstrated that the introduction of strontium ions into the lead tungstate compound PbWO4 (PWO), which isomorphically substitute lead ions in the crystal lattice, allows one to vary the scintillation yield, its temperature dependence, and the parameters of the luminescence kinetics over a wide range. With 10% substitution of lead ions in the crystal lattice, the (Pb,Sr)WO4 compound is characterized by a scintillation yield of 1000 ph/MeV and a kinetics decay constant of 40 ns, while the temperature dependence of the scintillation yield is close to that of the PWO material. On the contrary, in the compound with 80% Sr instead of Pb, the yield reaches 10,000 ph/MeV with a decay constant of 600 ns. For the compound, the scintillation yield in the temperature range of 300—400 K is characterized by a temperature coefficient of –0.6 %/°C. The first compound is of interest for experiments in high-energy physics, including spectroscopy, starting from 10 MeV without detector cooling. The second is prospective for spectrometry in geological exploration and well logging, where operation at relatively high temperatures is required.
Breathing Dynamics of Cosh-Gaussian Laser Beams in Cubic Quintic Media with Axially Modulated Quintic Nonlinearity
The breathing behavior of Cosh–Gaussian laser beams is examined in the context of cubic-quintic nonlinear media, where the quintic nonlinearity is modulated along the propagation axis. Using the method of moments, evolution equations are derived to describe the beam’s spatial dynamics. The impact of this axial modulation on beam stability and oscillatory behavior is analyzed, revealing that controlled variation of the quintic term enables tunable breathing patterns. These modulated dynamics offer a flexible mechanism for managing beam propagation in nonlinear environments, with potential applications in laser beam shaping, optical filament control, and the design of nonlinear photonic devices.
Study on the Experimental Accuracy of Raman Spectral Parameters
Raman spectroscopy is considered an essential spectroscopic technique due to its simplicity, non-destructive nature, and ability to provide molecular fingerprinting. These qualities make it applicable across numerous research fields. Accurate Raman data analysis can uncover remarkable sub-microscopic phenomena such as local structural changes, electron-phonon and spin-phonon coupling, and ionic displacements. Therefore, understanding the precision involved in collecting and analyzing Raman data has become critically important. Omitting proper calibration and validation methods can lead to significant errors. In this article, we present a study on how improper validation methods of a spectrometer and inaccurate data fitting can cause substantial inaccuracies in spectral parameters. We demonstrate that the accuracy of Raman spectral parameters heavily relies on the spectrometer’s validation process, the choice of fitting function, and the consideration of errors caused by instrument randomness and resolution. Additionally, our study offers a method for assessing the uncertainty of Raman spectral parameters for a given spectrometer system. This is crucial for optimization, especially when dealing with subtle changes in spectral parameters to reduce inaccuracies.
Eco-Friendly UV Spectroscopic Method for Precise Quantification of Daprodustat in Pharmaceuticals
Daprodustat is a new hypoxia-inducible factor prolyl hydroxylase inhibitor (HIF-PHI) and a novel med- ication for treating chronic kidney disease anaemia. Daprodustat boosts endogenous erythropoietin produc- tion, regulates iron metabolism, and is an alternative erythropoiesis-stimulating agent. The aim of this study is to develop and validate a simple, accurate, and environmentally friendly ultraviolet (UV) spectroscopic method for the quantitative analysis of daprodustat in pharmaceutical formulations. The UV spectrophotometric method was prepared using methanol as the solvent and validated according to the International Council for Harmonisation (ICH) Q2 (R2) guidelines. The process was tested for linearity, precision, accuracy, robustness, limit of detection (LOD), and quantification (LOQ). Daprodustat showed maximum absorbance λmax = 261.45 nm in methanol. The linearity range was 4–16 µg/mL, with a regression equation of y = 0.0577x + 0.0477 and a correlation coefficient R2 = 0.9983. The procedure demonstrated excellent precision (relative standard deviation (% RSD) < 2%) and recovery at 98–99%. The LOD and LOQ were 0.672 µg/mL and 2.0 µg/mL, respectively. The new UV spectrophotometric method for quantifying daprodustat in solid dispersions proved simple, accurate, and precise. Environmental sustainability was assessed using Analytical GREEness (AGREE) and the Green Analytical Procedure Index (GAPI). Accordingly, this validated UV spectroscopic method can be effectively used for routine quality control analysis of daprodustat in solid dispersions, providing a cost-effective and sustainable approach to analytical evaluation.
Analytical Quality by Design Assisted Spectroscopic Method Development for Estimation of Clevidipine Butyrate in Synthetic Mixture in Application to Greenness Study
Two simple, rapid, cost-effective, precise and accurate UV spectrophotometric methods have been developed for the estimation of Clevidipine butyrate, a dihydropyridine calcium channel blocker and antihypertensive agent, using an analytical quality by design approach. The characterization of Clevidipine butyrate was performed by melting point, differential scanning calorimetry, and FT-IR techniques. Using the analytical quality-by-design approach, the critical method variables selected were scanning speed and sampling interval via Central Composite Design, which demonstrated the work's resilience and optimised methodology. A method for UV spectroscopy was developed using two methods – method I, based on the maxima absorption method of zero-order spectrophotometrics with λmax of 238 and 362 nm, and Method II, based on the zeroorder area under curve method, wavelength range 233–243 and 353–371 nm, respectively. Both the developed methods were subjected to validation as per the guidelines set by the ICH. The methods showed good linearity in the concentration, ranging from 2 to 12 µg/mL, while the % Recovery of the developed methods was in a range of 98.41–100%. The methods showed good sensitivity and appropriate precision with an RSD less than 2%, and the methods were applied for determination of the Clevidipine synthetic mixture. The developed method’s greenness profile was evaluated and compared using the AGREE and MoGAPI tools and were found to be in compliance with twelve principles of green analytical chemistry.
Derivative Spectrophotometric Methods for Estimation of Seratrodast in Bulk and in Formulation
Seratrodast is a 1,4-benzoquinone derivative belonging to the class of thromboxane A2 (TXA2) receptor antagonists and is employed for prophylactic management of asthma. The present report describes the validation of quick, simple, sensitive, and cost-effective zero-order, first-order, and second-order derivative spectrophotometric methods for the estimation of seratrodast in bulk and in its marketed tablet formulation. Exhaustive spectrophotometric analysis of the drug was carried out using a total of 23 parametric variations, which were evaluated in acetonitrile. Three selected method variants were assessed for their stability, indicating potential regarding stress-degraded solutions of the drug. The developed methods were validated with respect to linearity, accuracy, precision, and robustness. Excellent linearity was observed in the concentration range of 5.0–50.0 μg/mL with correlation coefficients above 0.999. The limits of detection were found to range from 0.54 to 0.70 µg/mL, and quantitation limits ranged from 1.66 to 2.14 μg/mL for the proposed method variants. The proposed methods were also employed for the assay of seratrodast in its marketed tablet formulation, and good recoveries ranging from 96.23 to 98.68% were obtained.
Preparation of Nitrogen-Doped Carbon Quantum Dots and Analysis and Detection of Vitamin B2
This paper focuses on the preparation of nitrogen-doped carbon quantum dots (N-CQDs) from citric acid and urea, and their application in the detection of Vitamin B2. Citric acid was used as the carbon source and urea as the nitrogen source. N-CQDs were prepared by heating, after which they displayed excellent fluorescence performance and stability. The structure of the sample was then characterized using UV-visible spectrophotometry, fluorospectrophotometry, and Fourier Transform Infrared spectroscopy. Optimal pH, ultrasonic reaction time, and Vitamin B2 concentration for the N-CQDs were studied and optimized. Under optimal conditions (50 µL of N-CQDs, 2 mL of buffer solution with pH 4.0, and a reaction time of 30 min), the analysis and detection using fluorospectrophotometry demonstrated that Vitamin B2 caused significant fluorescence quenching of the prepared N-CQDs. With the standard recovery rate above 80%, these N-CQDs can serve as fluorescence probes for the analysis and detection of Vitamin B2 in actual food.
Kinetic Spectrophotometric Quantification of Vitamin H in Pristine and Drug Formulations in Micellar Medium
A simple, effective, and accurate visible-spectroscopic technique has been established to evaluate vitamin H (VIT-H) in medicinal samples as well as in its pure form. The method depends on the inhibitory influence of VIT-H on the Hg2+-facilitated ligand substitution (LS) reaction between phenylhydrazine (PHZ) and [Fe(CN)6]4–. The strategy involves substituting CN– with PHZ in [Fe(CN)6]4–, resulting in the formation of a [Fe(CN)5 PHZ]3 complex. The VIT-H can be quantified between 0.017 and 1.710 μg/mL by monitoring the absorbance of the complex at 488 nm during the process. The established method enables the detection of VIT-H at concentrations as low as 0.163 μg/mL. Recuperation experiments confirmed the precision and accuracy of the method for VIT-H quantification. The proposed methodology has been successfully employed for the assessment of VIT-H in pure samples and diverse pharmaceuticals, showcasing remarkable accuracy and precision. The results corresponded with the prescribed analytical protocol. The suggested methodology remains unaffected by the excipients typically employed in medications.
Stability Indicating UV-Visible Spectrophotometric Method for the Estimation of Flunarizine Dihydrochloride Through Second-Order Derivative Spectroscopy
The presented study is a simple, precise and accurate stability-indicating second-order UV derivative spectroscopic method that is being studied under the different stated International Council for Harmonization (ICH) Guidelines because of its forced-degradation properties, and to establish a validating method for Flunarizine dihydrochloride in active pharmaceutical ingredients (API). Adhering to ICH guidelines, the analytical parameters, viz. linearity, range, precision, and accuracy, were validated. The method was based on thorough stress testing utilizing acid, base, thermal, photolytic and oxidative degradations, and it was found that a linear response is present in the concentration range of 10–60 μg/mL at 253 nm. The % relative standard deviation (RSD) for precision studies of interday and intraday were <1.29 and <1.17%, respectively. The developed analytical method for validating flunarizine dihydrochloride using second-order derivative spectroscopy is found to be simple and precise, and the percentage recovery was found to be within acceptable limits. It can be conveniently used for routine analysis. In the forced degradation studies of flunarizine dihydrochloride utilizing various parameters, such as acid, alkali, light and heat, the absorbance of the drug was noted to have decreased approximately 10% in both the formulation and the standard. Based on the results obtained, it was found that the proposed method is accurate, precise, and reproducible, and can be employed for quality control analysis.
Optimized Low-Cost Liquid‒Liquid Extraction Mode for the Removal and Spectrophotometric Determination of Cr(VI) from Polluted Water
/ Chromium(VI), considered one of the most hazardous elements, directly affects human health and the environment. Therefore, in this study, a new approach is devised for liquid‒liquid extraction and spectrophotometric measurement of hexavalent chromium by employing a novel spectrophotometric reagent, where by 2-chlorobenzaldehyde Thiocarbohydrazone in dichloroethane is employed as a complexing reagent for chromium(VI) in the presence of potassium iodide, resulting in a yellow complex at room temperature. This approach offers a considerable benefit, being a straightforward procedure that does not require any extra solvent purification or preconcentration. The ternary [Cr(VI)-CBTCH-iodide] complex was quantitatively recovered in dichloroethane from 3.5 mol L hydrochloric acid medium. The maximum absorbance at λmax 415 nm was reached, and the sample was stable for 72 h. The method showed excellent analytical response, with a limit of detection of 0.32 µg/mL, a wide working range of up to 10.25 µg/mL, and reasonable accuracy (RSD < 2%, n = 5). The molar absorptivity and Sandell sensitivity of the ternary complex are 0.3535×104 L/mol × cm and 0.0147 µg/cm, respectively, whereas 2.496 is the enrichment factor. Using the log‒log plot method, the [Cr(VI)-CBTCH-iodide] complex composition was verified to be 1:2:2. There are no noticeable consequences of possibly interacting ions. Chromium(VI) was successfully extracted and determined simultaneously from alloy samples, contaminated water, and synthetic mixtures via this technology. The applied method has numerous advantages, including simplicity, low cost, ease of operation, rapid detection, low ligand consumption, and high sensitivity. The sensitivity of the analytical method was proven by selecting appropriate experimental conditions.
Online Detection of the Indoor Air Environment
Nowadays, people spend a significant amount of time living and working indoors. For that, online detection and classification of different indoor air environments is of great importance, which is very challenging because of the lack of unified standards. In this study, a novel classification model based on laser-induced breakdown spectroscopy (LIBS) and machine learning was established to detect indoor air environments. To study different indoor air environments, four different coatings or paints (rubber coating, wood coating, furniture paint, and interior paint) were taken as samples to ascertain the gas composition. The analysis of their spectra shows there are various metal elements in these gas compositions, including Ti, Ca, and Na. For volatile organic compounds (VOCs) present in coatings or paints, the intensities of C, H, and O, which are VOCs’ main ingredients, are compared to determine if there is a certain difference. The results verify that LIBS could be used to detect different indoor air environments. Principal component analysis was used to distinguish the four indoor air environments, and the training data set was stored for further identification. Furthermore, a classification model was established based on the improved error back propagation artificial neural network (BP-ANN), achieving a recognition accuracy of 93.4%. After model training, the model’s performance was tested using the spectra of different coatings or paints, and the recognition accuracy reached 98.2%. These results indicate that this method, combining LIBS and machine learning, has great potential for detecting the quality of the indoor air environments.
Effect of ZnO Nanoparticles Dispersed in p-n-Undecyloxy Benzoic Acid Liquid Crystalline Compounds: Optical and Order Parameter Studies
This paper presents the optical and order parameter studies of a mixture of liquid crystalline (LC) materials, such as p-n-undecyloxy benzoic acid (11OBA), including the incorporation of zinc oxide (ZnO) nanoparticles (NPs) at different weight concentrations (0.5–2 wt.%). Studies, including optical absorption, photoluminescence (PL), birefringence, refractive indices, and order parameters, were undertaken on the prepared samples. A prominent absorption peak was observed approximately at 235 nm for both the pure and nano-dispersed liquid crystal samples. The PL spectra exhibit two distinct peaks, located at 367 and 618 nm, whereas ZnO NPs dispersed 11OBA showed a single peak at 392 nm. The peak observed at 367 nm is attributed to near-band-edge emission of free excitons, whereas the peak at 618 nm is indicative of deep-level emission, resulting from point defects such as vacancies and interstitials within the bandgap. The order of parameter values are also calculated for the mixture of the 11OBA LC compound dispersed with ZnO NPs using different models like Kuczynksi, Haller extrapolation, effective geometry, and Vuks at a stabilized nematic region in the visible range at 460, 500, 570, and 635 nm wavelengths.
“Protect-Deprotect” Based Fluorescent Probe for the Recognition of Norepinephrine
Research has shown a significant correlation between severe depression and reduced levels norepinephrine (NE) in brain tissue. Therefore, designing NE-specific fluorescent probes is highly challenging. We adopted a “protect-deprotect” strategy in which the 7-hydroxy-4-methylcoumarin fluorescence group was protected by a carbonic ester that linked to the departing thiophenol group. The probe then underwent two nucleophilic additions and eliminations by NE, which released the fluorophore and enabled specific fluorescence detection of NE with sensitivity and selectivity. This recognition mechanism was verified using the highresolution mass-spectrometry method.
Evaluation of the Antibacterial and Anticancer Properties of Green Zinc Oxide Nanoparticles Synthesized from Spent Camellia Sinensis (Tea) Leaves
Plant-based food waste contains high concentrations of phytochemicals, rendering it an appealing candidate for the eco-friendly production of metal nanoparticles. In this study, zinc oxide nanoparticles (ZnO NPs) were prepared from spent C. sinensis (tea) leaves, serving as both a reducing and a stabilizing agent. Zinc acetate dihydrate [(CH3COO)2Zn × 2H2O] was used as a precursor in the spent C. sinensis leaf extracts for the NPs synthesis. The physicochemical characterization of ZnO NPs was characterized using ultraviolet–visible spectroscopy (UV-VIS), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectrophotometer (EDX), X-ray diffraction (XRD), photoluminescence spectroscopy (PL), and dynamic light scattering (DLS). The synthesized ZnO NPs displayed a strong UV–Vis absorption peak at 370 nm, and a wurtzite hexagonal structure with an average crystalline size of 56 nm, as confirmed by XRD. The FESEM confirmed a spherical morphology, while EDX analysis indicated zinc as the predominant element, followed by oxygen. The antibacterial efficacy of ZnO NPs was assessed against both Gram-negative and Gram-positive pathogens, exhibiting optimal effectiveness against Streptococcus pyogenes and Staphylococcus aureus. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay revealed that ZnO NPs exhibited concentration-dependent anticancer activity against HeLa cells, with an IC50 of approximately 33.5 mM. Live–dead imaging confirmed a 4.6-fold and 3.5-fold increase in dead cells at IC50 concentrations after 24 and 48 h, respectively. Furthermore, treatment with ZnO NPs significantly elevated reactive oxygen species (ROS) production, indicating that their cytotoxicity is mediated through ROS generation and its lethal effects. Our findings suggest that ZnO NPs made from spent C. sinensis leaf extracts could have antibacterial and anticancer properties.
Synthesis, Characterization, and Photoluminescence Properties of Pr3+ Doped SrAl2B2O7
Sr1-xPrxAl2B2O7 (0.005 ≤ x ≤ 0.04) red-emitting phosphors were prepared by firing in air at 950ºC for 6 h. Using the XRD technique, the structural characterization of the prepared materials was examined. Additionally, FTIR was used to examine the Al-O and B-O bond characteristics in the crystal structure. Finally, using a spectrofluorometer, the luminescence property of Sr1-xPrxAl2B2O7 (0.005 ≤ x ≤ 0.04) was thoroughly examined at ambient temperature. The prepared SrAl2B2O7 materials with varying Pr3+ doping emitted radiation at three wavelengths in the red region (609, 622, and 645 nm) when exposed to 469-nm light.