The electromagnetically-induced transparency (EIT) resonance in a potassium microcell with a vapor column thickness of L = 30 μm on the D₁ line of the ³⁹K isotope was studied. The experimentally obtained width of EIT-resonance is 60 times narrower than the Doppler width of the potassium atom. In an external longitudinal magnetic field, the EIT-resonance splits into three spectrally narrow components. The theoretical curves calculated using the Rabi–Breit formula are in good agreement with the experimental results.

The method of surface-enhanced Raman spectroscopy (SERS) was used to study the electrode processes at the interface between Al and ionic liquid. This method has great promise in the field of studying electrochemical processes, since it allows one to determine the composition of the electrolyte in a thin near-electrode layer during electrode polarization. It was demonstrated that aluminum has SERS-activity in a chloroaluminate ionic liquid based on Et₃NHCl. Using the in situ SERS method, it was shown that with an increase in the cathodic polarization of the aluminum electrode, the intensity of the peaks associated with AlCl₄^– ion increases and the intensity of the peaks associated with Al₂Cl₇^– ion decreases. During anodic polarization of the electrode, the reverse process was observed: a decrease in the content of AlCl₄^– ions and an increase in the concentration of Al₂Cl₇^–. The concentrations of chloroaluminate anions in the near-electrode layer do not change at cathodic overpotentials (above the overpotential of reaching the limiting current) and at anodic overpotentials (above the passivation overpotential). The obtained dependences of the relative intensity of AlCl₄^– and Al₂Cl₇^– peaks on the electrode overpotential correlate with the stationary polarization curves. It has been experimentally proved that passivation of an aluminum electrode during anodic dissolution is caused by the formation of aluminum chloride on the electrode surface.

The up-conversion luminescence (UCL) spectra of fluorophosphate glasses doped with a pair of rareearth ions (REI) of ytterbium (4%) and thulium (0.1%) excited by radiation of a diode laser operating in a steady-state mode at wavelength of 975 nm are studied. Each of the observed UCL bands is a result of manifestation of several up-conversion processes (UCP) corresponding to luminescence of thulium ions from different excited states. These UCPs are characterized by different degrees of effective nonlinearity (EN). The effect of pump power on the UCL spectra formed by UCPs with different EN is studied. The possibility of separation of spectra corresponding to individual UCPs from the total experimentally measured UCL spectrum of fluorophosphate glass doped with a pair of REIs of ytterbium (4%) and thulium (0.1%) is demonstrated. The separation is based on the calculation of the EN based on the dependences of the UCL on the excitation power.

For the first time to our knowledge, a non-monotonic dependence of the stimulated Raman scattering threshold of 240-fs second-harmonic pulses of an ytterbium fiber laser (515 nm, 3 Hz, up to 11 μJ/pulse) in organic glass (polymethylmethacrylate, PMMA) on the stretching C-H vibrations has been discovered when moving the waist of the focused beam (lens F = 16 mm) from air into the sample volume. The first minimum of the threshold (~2 μJ) is found when the waist combines with the surface. Here, the maximum intensity and the maximum value of the nonlinear refractive index (nonlinear lens) supports channeling of the pump in the medium at the maximum length of the Raman exponential gain, taking into account that half of the beam caustic is in air. The second minimum is achieved by moving the entire beam caustic, stretched along the beam axis due to spherical aberration in a layer of ~1.8 mm near the sample surface. The subsequent movement of the waist is accompanied by a 5-fold increase in the Raman threshold due to conversion of a part of the pump pulse energy (515 nm) into the Stokes component (605 nm), the pulse of which is shifted forward due to the dispersion of the refractive index and group velocities. This delay of the pump pulse destroys the synergetic factor of action, which reduces the probability of a breakdown with a 5-fold increase in pump energy. At the PMMA sample thickness (10 mm), the delay reaches a value of ~480 fs. Note that the breakdown is observed with pump fluctuations in the vicinity of the minimum threshold (2 μJ) at the input surface of the PMMA sample.

In order to synthesize a layer of narrow-gap indium antimonide (InSb) in the near-surface region of a Si single crystal, sequential high-dose implantation of Si with In⁺ and Sb⁺ ions with an energy of 30 keV and  a dose of 2×10¹⁶ cm^–2 was carried out. Annealing of implanted Si:(In+Sb) layers in the liquid phase regime was carried out with a powerful pulsed (~100 ns) ion beam (C⁺/H⁺) with energy of 300 keV and pulse energy density of 1.0 J/cm². Calculation of the total depth profile of the concentration of implanted In and Sb atoms taking into account ion sputtering showed their maximum concentration of 40 at.% at a depth of about 20 nm. Using the Rutherford backscattering of He⁺ ions, the segregation of impurity atoms to the Si surface as a result of pulsed annealing was detected. The spectra of X-ray diffraction in grazing beams and Raman light scattering indicate the formation of InSb phase with a tensile strain level of 0.6–0.7%. Using optical IR spectra, the electron concentration in the layer (2×10²⁰ cm^-3) due to the Sb donor impurity was estimated and the formation of an intense absorption band at 3.85 μm was shown. Photoresponse measurements on a diode mesa-structure at 300 K showed a shift in the photosensitivity edge to 1240 nm compared to a standard Si photodiode FD-24.

The results of studies of the crystalline structure and optical characteristics of disordered tin oxide films are presented. Tin oxide films were synthesized by means of magnetron sputtering of a tin target on glass substrate followed by 2-stage annealing in air. The microstructure of tin oxide films was analyzed by X-ray diffraction method and Raman spectroscopy. Transmission spectra of the samples were measured in the wave length range λ = 200–3000 nm. The optical constants of thin tin oxide films depending on the wavelength (refractive index n, absorption coefficient α) were determined using the envelope method. The possibility of synthesis of the tin oxide films with controllably varied optical parameters (absorption coefficient α up to 82 % in the visible range of electromagnetic spectra, refractive index n in the range of 2–2.6, Tauc optical gap in the range of 2.62–3.46 eV) by changing the temperature at the 2nd stage of oxidative annealing in the range of 325–475°C was demonstrated. 

A study of IR-spectra of multiple frustrated total internal reflection (MFTIR) of silica mineral aggregates containing various amounts of opal, chalcedony and quartz from barren volcanics and deposits of shallow gold-silver and medium-depth gold-quartz and gold-sulfide-quartz formations was carried out. Clear differences in the IR-spectra of MFTIR of opal-chalcedony-quartz aggregates from barren volcanics and the superore zone of the deposit of shallow gold-silver formation were revealed, consisting in the splitting of K₃ absorption band (475–490 cm^–1 into two peaks at 470–484 and 492–500 cm^–1), determined by the ratio of the contents of opal, chalcedony and quartz. A connection has been revealed between the variability of the ratios of the reflection bands intensities in the spectra with the values of the degree of the crystalline structure perfection and the crystallinity index of silica minerals and the depth of their formation. The indicated features of silica mineral aggregates can be used as typomorphic features for determination of their belonging to ore deposits of the shallow gold-silver formation and assessment of the erosional cut of such ore deposits. 

The features of the spectra of electron paramagnetic resonance (EPR) of MnIn₂S₄ single crystals at different temperatures are studied. It is established that EPR lines have a Lorentz shape. It is found that in the paramagnetic phase with a temperature decrease in the region of 6.8–60 K there is a strong increase in the range of resonance line ∆H and a shift in g-factor is observed, the values of which determine the proportional width of line ∆g(T) ∼ ∆H(T). The relaxation time is ~10^–10 s and increases with increasing temperature.

Using the thermal evaporation method, Sb₂(S_xSe_1-x)₃ films have been produced from powders of the binary compounds of Sb₂S₃ and Sb₂Se₃ at temperature of the substrate of 300℃. The effect exerted by the elemental composition ratio S/(S+Se) on optical and electric properties of Sb₂(S_xSe_1-x)₃ films has been studied. It has been demonstrated that the band gap width of Sb₂(S_xSe_1-x)₃ films is growing with an increase in the concentration of sulfur in the films produced. It has been found that the synthesized films feature low Urbach energies, offering their low-defect structure. Based on the temperature dependences of resistance, the presence of deep-lying levels within the band gap of synthesized films has been revealed. The activation energy of these deep-lying levels was varying in the range of 0.5–0.8 eV depending on the ratio of the atomic concentration S/(S+Se). These results indicate the possibility of producing effective solar cells based  on Sb₂(S_x,Se_1–x)₃ with the use of thermal evaporation from powders of the binary compounds of Sb₂S₃  and Sb₂Se₃. 

A method of recording of Raman scattering signals amplifying based on the use of photon traps and light guides has been proposed. The Raman scattering spectra of titanium dioxide micropowders placed in a photon trap were investigated at pulse-periodic laser excitation by a copper vapor laser. It has been found that using the developed photon traps and fiber-optic techniques in titanium dioxide microstructures at room temperature, a combination opalescence mode can be implemented, which consists in an abnormal increase of Raman scattering intensity into the spectra of secondary radiation.

The possibility of controlling the position of the luminescence maximum in the region of 440–510 nm of halide perovskite nanocrystals of mixed composition CsPbCl_xBr_3-x by changing the molar ratio of the initial reagents PbBr₂:PbCl₂ during synthesis, as well as by choosing a solvent for postsynthetic treatment of nanocrystals, has been demonstrated. Using X-ray fluorescence spectroscopy, it was found that the ratio of Br^–:Cl^– ions in the synthesized nanocrystals is lower than their ratio in the initial reagents. Using the Fourier transform infrared spectroscopy method, it was shown that postsynthetic treatment in acetone, in contrast to the treatment in acetonitrile, promotes the removal of oleylamine, predominantly along with bromide ion, from the surface of nanocrystals, which leads to a shift of the photoluminescence maximum to the short-wave region and a decrease in the quantum yield of photoluminescence. The results are important for the development of new combined luminophores based on perovskite nanocrystals when it is necessary to precisely select their color characteristics.

Nanosized crystalline silicon material with particle size in the range of 2–5 nm was synthesized by plasma treatment of commercial silicon micropowder consisting of submicron amorphous spherical particles with an average size of 250 nm under the action of electric discharge in ethanol. The properties of the obtained nanomaterials were studied using optical absorption and Raman spectroscopy, as well as electron microscopy methods. The possibility of additional laser-induced modification of the obtained nanostructures was considered. The silicon-containing nanomaterial synthesized in the work passed testing of electrochemical characteristics as an anode material for a lithium-ion battery and showed a specific capacity of ~800 mA ∙ h/g with a stable Coulomb efficiency of about 100% for 55 cycles.

The processes of magnetization reversal of a sample with cobalt nanowires oriented in the external magnetic field in an epoxy matrix have been studied. For this purpose, two complementary methods were used: the microscopic NMR spin-echo method using an additional magnetic videopulse and the macroscopic method of radiofrequency resonance magnetometry. These methods make it possible to obtain information about the coercive force of cobalt nanowires and the pinning force of domain walls in them from the sharp minima of the magnetometer resonance frequency and the thresholds for the decay of the double-pulse echo signal under the influence of a magnetic videopulse, respectively. The hysteresis dependence of the change in NMR resonance frequency at a cyclic change in the longitudinal external magnetic field has been obtained. The estimations of coercive forces and domain boundaries pinning forces in cobalt nanowires in an epoxy matrix are in satisfactory agreement with similar results obtained by other authors with the methods of magnetoresistance measuring.

Comparative study on the interaction of Hoechst 33258 (H33258) with single-stranded (ss-) polyribonucleotides poly(rA) and poly(rU) and double-stranded (ds-) poly(rA)-poly(rU) has been carried out with the method of fluorescence spectroscopy. Groove-binding compound H33258, being specific ligand for NA ds-structure, was revealed to bind to ss-RNA. It was revealed that H33258 shows higher preference to poly(rA)-poly(rU), formed due to the hybridization, than to ss-poly(rA) and poly(rU). Based on the fluorescence spectra the binding curves of H33258 to ss- and ds- polyribonucleotides were constructed and the values of binding constant K and number of bases per binding site n were determined. The obtained data elucidate that the binding constant of H33258 to ss-poly(rA) is 4-5 times higher, as compared to ss-poly(rU) one. It was also shown that H33258 affinity to poly(rA)-poly(rU) and ss-poly(rA) depends on the ionic strength of the solution, while for ss-poly(rU) such a dependence is not found.

The spectral reflectance curve (SRC) of ethanol extracts of leaf pigments concentrated on filter paper was analyzed. The areas of the spectrum that are the most subject to change in the process of pathogenesis were identified. A change in the slope of the SRC was noted in the area connecting the point of maximum absorption of the studied pigment and the nearest point that is not related to its content. For the analysis of carotenoids in apple rootstock forms the range of 510−590 nm was informative; for chlorophyll were 640−670 nm and 670−700 nm. At different genotypes, the angular coefficient in the equation of the trend line to the study sector of SRC (k_510-590, k_640-670 and k_670-700) changed depending on the resistance of the host plant’s pigment apparatus to the parasite. The forms that showed the greatest resistance to the complex of pathogenic micromycetes and to the bacterium P. syringae were identified.

Using the method of differential absorption spectroscopy and technology of the electrochromic shift of pigment absorption, the electrochemical potential on the thylakoid membrane and its components in the primary leaves of 4-, 7- and 11-day-old seedlings of Hordeum vulgare L. was studied. It was found that during the ontogenesis of the first leaf, the proton motive force decreased and the proportion of its electrical component increased. Exposure to elevated temperature (40°C for 3 h) decreased the magnitudes of the electrochemical potential, proton gradient, and thylakoid membrane conductivity for protons, and also increased the electrical potential on the thylakoid membrane in young 4-day-old seedlings. In 7-day-old leaves, which have a fully formed photosynthetic apparatus, no significant changes in the formation of the electrochemical potential on the thylakoid membrane were detected as a result of 3-hours heat treatment at 40°C. In the senescent primary leaf of 11-day-old seedlings, a thermoinduced decrease in the electrical component of the proton motive force and an increase in the transthylakoid proton gradient were detected. It was concluded that the electrochemical potential of thylakoid membranes reacts differently to heat effects in Hordeum vulgare L. seedlings of different ages.

The patterns of diffraction and mixing of light waves on a phase reflection holographic grating formed in a cubic photorefractive crystal of (001)-cut have been studied. The mechanism of restoration and amplification of an object light wave during counter-propagating two-wave mixing in crystals of 23 and 43m symmetry classes has been analyzed. The conditions of a holographic experiment are considered under which the highest values of the diffraction efficiency of the reflection hologram and the relative intensity of the object wave are achieved. It is shown that the conditions for achieving the highest intensity of the object wave in crystals of symmetry classes 23 and 43m differ significantly, which is due to the influence of natural optical activity inherent in non-centrosymmetric crystals.

In the generalized Rayleigh–Gans–Debye approximation, the problem of sum-frequency generation by two plane elliptically-polarized waves in a thin optically-nonlinear surface layer of a spheroid-shaped dielectric particle is solved. Formulas for calculating the components of the electric intensity vector of the generated radiation in the far zone were obtained for two cases: the spheroid elongated and compressed along the symmetry axis. The most general form of the nonlinear dielectric susceptibility tensor, containing four non-chiral and three chiral independent components, is considered. A detailed description of methods for integrals calculation over the surface of the spheroid of tensor quantities encountered in problems of nonlinear generation in the surface layers of dielectric particles is given.

Antireflection coatings (ARC_S) increase the absorption of light and, therefore, a conversion efficiency of solar cells. Mullite was chosen as the ARC material for a silicon (Si) solar cell, the synthesis of which was carried out by melting a charge consisting of a mixture of Al₂O₃ and SiO₂ at a component concentration of 75 and 25 wt.%, respectively. It has been established that the integral reflection (R_S) of ARC_S based on mullite is about 6.0 times less than for silicon and about 2.5 times less than R_S of the coating based on silicon nitride. The electric characteristics measured by the solar simulator before and after vacuum deposition of the mullite film with thickness of 80—85 nm on the solar cell samples showed the increase of short-circuit current up to 49.5% and the rise of efficiency up to 6.8%.

The study focuses on the synthesis and energy transfer mechanism between the cerium and praseodymium co-doped yttrium aluminum garnet (YAG) phosphors. Pure phase YAG:Ce,Pr powders were synthesized using a mixed fuel combustion method at a ~500°C furnace temperature. The luminescence spectra and the effect of the energy transfer mechanism from the Ce³⁺ to Pr³⁺ ions in YAG:Ce,Pr were examined. The influence of Si⁴⁺ doping in YAG:Ce,Pr phosphors was also studied. The emission intensity of Ce and Pr in YAG is enhanced by 33% with 1mol% Si codoping, without changing the peak wavelength, and it lowered the correlated color temperature.

The present paper reports the synthesis and photoluminescence (PL) properties of Eu³⁺-activated calcium aluminate (Ca₃Al₂O₆) phosphors. The samples were prepared by a conventional solid-state reaction method with different concentrations of Eu³⁺ ions, which was most suitable for large-scale production. The prepared phosphor sample was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), PL, and CIE chromaticity coordinate techniques. The XRD pattern indicated that the sample was mono-phased and crystallizes in a cubic structure. The crystallite size was found to be nearly 82 nm and the SEM images showed the formation of micro-rods at low resolution and at high resolution exhibited a cube-like morphology. The FTIR studies confirmed the formation of Ca₃Al₂O₆:Eu³⁺ phosphor. The PL excitation spectra found at 271 and 396 nm and the PL emission was observed in the range 500–750 nm for the Ca₃Al₂O₆ phosphor doped with Eu³⁺ ions and sharp peaks were found at 595, 616, 621, and 651 nm with high intensity. The present phosphor can act as a single host for red-orange light emission in display devices.

A simple solution technique was used for the synthesis of Co²⁺-doped ZnCdO nanopowder. A number  of investigational methods have been done on the synthesised powder to study the structural, morphological, and photoluminescence properties. X-ray diffraction (XRD) studies revealed that ZnO is in a hexagonal phase and CdO is in a cubic phase when the samples were calcined at 650°C for 2 h by raising the temperature at the speed of 15^o/min. Irregular shaped grains were observed from the scanning electron microscopy (SEM) images. Energy dispersive X-ray analysis (EDAX) indicated the existence of doped Co species and constituent metal ions. The bands at 417 and 460 cm^–1 confirmed the presence of ZnO and CdO molecules by Fourier transform infrared spectroscopy studies. From optical absorption studies, Dq, B and C (crystal field parameter and inter electronic repulsion parameters) were evaluated and found to be 980, 940, and 3800 cm^–1, thus confirming the doped Co²⁺ ions are in octahedral symmetry. Photoluminescence studies showed the emission peaks in the blue region at an excitation wavelength of 360 nm. CIE chromaticity coordinates were estimated at x = 0.1577, y = 0.0771.

Food additives, crucial for enhancing food quality, have raised concerns regarding their potential carcinogenicity, particularly in substances like malachite green (MG), previously removed from the United States Food and Drug Administration approved list due to identified cancer risks. This investigation delves into the nuanced domain of trace detection employing surface-enhanced Raman spectroscopy (SERS), leveraging the localized plasmon of silver nanoparticle substrates. The research involves a comprehensive comparison between solid and liquid-based SERS substrates. It utilizes diverse morphologies of silver nanostars (AgNSs) for sensitively detecting MG, substances of considerable interest in the food industry despite their acknowledged carcinogenic properties. A comprehensive characterization of diverse AgNS shapes, including TEM analysis and UV-Vis spectra, reveals distinct plasmon resonance peaks influenced by morphology and the surrounding medium. Finite-difference time-domain (FDTD) simulations underscore the influence of core size and arm number on local electric fields, generating robust hot spots along the edges. The surrounding medium also significantly influenced electric field intensity. SERS examinations reveal liquidbased substrates outperforming their solid counterparts, achieving a remarkable limit of detection (LOD) of 37 aM for MG. These findings were extensively examined in light of their consistency with FDTD simulations and the noticeable variations in enhancement factors observed among different configurations of solid substrates. Simultaneously, the study explores the high reproducibility of liquid-based substrates and endeavors to improve the poor reproducibility of the Raman signal by modifying the surface of solid-based substrates.

The measurement of vitamin B₁ in pure and pharmaceutical formulations was proposed by using a straightforward and sensitive spectrophotometric approach. Sulfacetamide (SFA) is diazotized, then coupled with vitamin B₁ in alkaline media to produce a coloured azo dye complex with a stability constant of 5.597×10⁵ L/mol. The product is stable, with a maximum absorption wavelength of 489.5 nm, molar absorptivity of 10108 L/mol ∙ cm, Sandell’s sensitivity of 0.0334 μg/cm², detection limit of 0.0135 μg/mL, and Beer's law being observed over the concentration range of 0.2–20.0 μg/mL. The stability constant and stoichiometry of the produced azo dye were calculated using the continuous variation (Job’s) and mole ratio methods. The suggested approach was used successfully in the determination of vitamin B₁ in its pharmaceutical formulations.

Line width studies of high field nuclear magnetic resonance (NMR) peaks have been seen more frequently in the recent literature. This study aims to compare the NMR line widths of HOD peaks of healthy and diseased blood, and densely bloody cysts taken from the jaw. Comparisons of HOD peak line widths  in healthy and diseased urine were also made. For this purpose, the blood, serum, and urine of 29 cancer patients, 17 diabetic patients, 28 healthy volunteers, and 20 intensely bloody samples from jaw cysts were collected. Mixtures were prepared by adding the 0.02-mL sample to 0.98 mL D₂O. Single pulse proton NMR measurements were performed at 400 MHz, and line widths were obtained from the half-height of the blood HOD peak. Statistical evaluations show that the line width of cancerous blood is different from normal blood (P = 0.032), while the line width of diabetic blood is not different (p = 0.072), whereas other groups and bloody jaw cysts are completely different (p<0.05). Similar results were found for urine groups. Line widths show a moderate correlation with each of the albumin and total protein groups (R around 0,56). Present data suggest that a comparison of healthy and diseased body fluids can be made by line width measurements of the HOD peak in the high NMR field. Data also suggest that the relaxivities of albumin (SerAlb), total protein (Ser-TP) are potential diagnostic indicators for cancerous blood.

The aim of this study is to address the problems of oil mixing during the sequential transportation of refined oil and the influence of temperature on the quality detection of refined oil. To better detect the quality of refined oil, UV-Visible transmission spectroscopic experiments of 92# gasoline, diesel oil, and their mixtures at different temperatures are performed. Then, the influence of temperature on the transmission spectrum is analyzed, and the transmittance-temperature compensation equations are obtained. Based on the double-thickness inversion model, the optical constants of the mixed refined oil at UV-Visible wavelengths are obtained, and the effect of temperature on the optical constants is analyzed. For a specified optical range, the transmittance of the mixed refined oil gradually increases with increasing temperature. The temperature has a certain effect on the optical constant of the refined oil; moreover, the relationships between the transmittance of the refined oil and the change in temperature are obtained at 364, 378, and 394 nm; these wavelengths are selected based on a combination of characteristic spectra calculated by a genetic algorithm. The obtained relationship can effectively remove the influence of temperature changes on the transmittance spectra of refined oil to improve the accuracy of detection.

With the rising popularity of whey protein as a dietary supplement, ensuring its quality has become imperative for consumer protection. Unscrupulous merchants sometimes adulterate whey protein with inexpensive vegetable protein to boost profits. Despite the criticality of this concern, reliable studies and relevant practical detection methods are currently limited. To fill this gap, this study adopted an integrated technique combining mid-infrared spectroscopy with machine learning to rapidly and accurately identify both single and multiple vegetable protein adulterants in whey protein. First, various recognition models were trained using AdaBoost-support vector classification (AdaBoost-SVC), AdaBoost-decision tree, K-nearest neighbor, SVC, and Gaussian Naive Bayes. Ten-fold cross-validation was subsequently used to determine the optimal spectra pre-processing combination, which included standard normal variate, first derivative, and Savitzky– Golay smoothing. Feature selection was then performed using the successive projection algorithm, principal component analysis, genetic algorithm (GA), and interval partial least squares with GA (iPLS-GA). The classification results revealed that the iPLS-GA-AdaBoost-SVC achieved the best performance on both the training and prediction sets, demonstrating the ability of the iPLS-GA to improve model stability and robustness. Overall, our findings underscore the potential applicability of the proposed method as an accurate and practical tool for improving the quality control of whey protein.

The pH optical sensors work on the principle of pH-related changes in the absorption or emission  of a probe. They have generated much interest during the past decades due to their wide applications  in fields such as analytical chemistry, biochemistry, clinical medical diagnosis, and environmental monitoring. Two Ruthenium(II) polypyridine complexes, [Ru(bpy)₂(hipp)]²⁺ (Ru1) and [Ru(bpy)₂(dcipp)]²⁺ (Ru2), were chosen as pH probes. Here, bpy denotes 2,2-bipyridine, hipp denotes 2-(1H-imidazo [4,5-f][1,10]phenanthrolin-2-yl)phenol, and dcipp denotes 2,4-dichloro-6-(1H-imidazo[4,5-f] [1,10]phenthrolin-2-yl)phenol, respectively. The pH effects on the absorption and emission spectra of Ru1 and Ru2 were investigated by pH titrations. Ru1 and Ru2 were found to be pH-sensitive and revealed different ionization constants, suggesting their potential use as optical pH sensors and applications in environmental monitoring.

Double beam UV-visible spectrophotometry and high-performance liquid chromatography (HPLC) techniques have been used to determine the antibacterial fluorescent phloxine B dye in dental preparations. In the visible wavelength range of 400 to 800 nm, the spectrophotometric signal was obtained at λ_max = 539 nm. The HPLC process used C-18 (5 μm) with a UV detector at 254 nm, 1.5 mL/min flow rate, 0.635 min retention time, and water, acetonitrile, and 2-propanol as the mobile phase. Several parameters have been used to analyze the performance of the HPLC and double-beam UV-visible spectrophotometry apparatuses, including stability, detection and quantification limits, calibration curves, and repeatability. The study focused on the repeatability of spectrophotometric and HPLC procedures for 8×10^–6 and 5×10^–6 mol/L of phloxine B. The results showed that the standard deviation (STD) for ten spectrophotometric measurements and eight HPLC measurements, respectively, was ±0.0004 and ±2.487 with relative standard deviation (RSD%) of 0.048 and 1.05%. Throughout the 90 minutes of the analysis period, the spectrophotometric and HPLC signals for 8×10^–6 and 5×10^–6 mol/L of phloxine B were shown to be exceptionally stable. The ranges of the calibration curves were 1×10^-6–2×10^–5 mol/L for the spectrophotometry and 1×10^–5–1×10^–4 mol/L for HPLC. Within the concentration ranges under consideration, they were assigned linear relations with correlation coefficients (r²) of 0.9995 for spectrophotometric and 0.99 for HPLC measurements. The detection limits for phloxine B were found to be 1.24×10^–8 mol/L (0.0103 ppm) and 8.25×10^–7 mol/L (0.068 ppm), respectively, using double beam UV-visible spectrophotometry and HPLC methods. These techniques use recovery rates ranging from 95 to 111% to determine the phloxine B dye that has been spiked in disclosing tablets and toothpaste samples. 

A PSII–rGO nanocomposite photocatalyst utilizing graphene oxide and PSII precursor was prepared in this study. In this proposed facile approach, PSII dimers were uniformly distributed on the reduced graphene oxide (rGO) sheets. The retained oxygen functional groups (OFGs) on rGO planes played a significant role in anchoring the PSII dimers. The samples were thoroughly characterized by X-ray diffraction (XRD), Raman spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, and Photoluminescence spectra (PL) analysis. The photocatalytic activity of PSII–rGO composites was further investigated by photodegrading methyl orange (MO). As a result, the prepared PSII–rGO photocatalyst exhibited a high absorptivity towards MO and efficient charge separation properties. The efficiency of the PSII–rGO composites (61%) towards the degradation of MO was significantly higher compared to pure PSII (25%), showing a 36% increase within 5 h under visible light. Finally, the corresponding mechanism of this enhancement was proposed and discussed in detail. After receiving photoelectrons from PSII, the rGO plane effectively transferred them to pollutants, thereby achieving a high photocatalytic degradation efficiency. The introduction of rGO improved the photocatalysis and sensing properties of PSII by facilitating rapid electron/charge division. Overall, the prepared PSII–rGO nanocomposite shows great potential for practical applications.

The present work aimed to develop a simple analytical method and validate the same for the estimation of Voriconazole using ultraviolet spectrophotometry. Methanol and artificial vaginal fluid (AVF) pH 4.1 were chosen as solvents for the development of the analytical method and the validation of the method was done for the different parameters. Voriconazole showed higher absorbance at 256 nm both in methanol and AVF pH 4.1. Linearity, precision, and accuracy as the analytical parameters were studied as per the International Conference of Harmonization (ICH) guidelines. The concentration range of 10–50 μg/mL in methanol and AVF pH 4.1 showed a linear response and followed Beer’s law with coefficient correlation values of 0.998 for methanol and 0.999 for AVF pH 4.1. The results for the accuracy and the repeatability parameter presented values that lie within the range of 98–102%, indicating a higher confidence interval. Regarding the method's sensitivity, the LOD for the drug in methanol and AVF pH 4.1 was found to be 2.55 and 2.00 μg/mL, respectively. The LOQ for the drug in methanol was 7.75 μg/mL and in AVF pH 4.1 was  6.08 μg/mL. The proposed, developed and validated method was simple, sturdy, cost-effective, and timesaving. The method could be further applied to calculate the entrapment efficiency of the drug-loaded nanostructured lipid carrier and tablet drug content.   

Two spectrophotometric approaches based on charge transfer complexation processes were developed, validated, and deployed for the detection of aprepitants in pharmaceutical dosages. In method A, the aprepitant reacts para chloranilic acid (p-CA) in acetonitrile, resulting in the formation of a purple-colored product. This product exhibited a maximum absorbance at a wavelength of 524 nm. In technique B, the combination of aprepitant and picric acid (PA) in chloroform results in the generation of chromophores having yellow coloration with a peak absorbance at 415 nm. Every experimental parameter was thoroughly examined and fine-tuned to optimize color development. The validation properties of the recommended spectrophotometric approaches, including linearity, range, precision, accuracy, specificity, robustness, detection, and quantification restrictions, were effectively evaluated. Within the concentration range of 10–60 μg/mL, both approaches exhibited a linear relationship with high correlation coefficient values. The suggested that the processes for quantifying aprepitants in dosage form are straightforward, rapid, precise, accurate, and costeffective. 

The p53 gene is an important tumour suppressor gene, which has an important impact on the early diagnosis of cancer. Here, inspired by the fact that single-stranded DNA (ss-DNA) can be nonspecifically adsorbed on the surface of nanogold, we report on a sensitive and cost-effective new method to detect the p53 gene by combining hybridization chain reaction (HCR) with gold nanoparticles. The long double helix structure generated by HCR could not be adsorbed on the nanogold surface after the addition of the p53 gene. When an appropriate amount of Na⁺ is introduced into the solution, the nanogold aggregates and the colour of the solution changes from red to blue-violet. The sensor has a high sensitivity with a detection limit of  2 nM visible to the naked eye and a quantitative detection limit of 0.2 nM using a UV-visible spectrophotometer. Notably, by combining fluorescence spectroscopy and gel electrophoresis, the science and specificity of p53 gene-induced HCR is systematically validated. The use of an enzyme-free, label-free colorimetric method to detect the p53 gene greatly reduces the complexity and cost of the experiment. This study has a broad market application prospect and provides a new method for early mass screening of cancer genes.