Abstract Surface-enhanced Raman spectroscopy (SERS) has attracted considerable research interest over the last four decades because of its rapid vibrational spectroscopic detection, high sensitivity, and nondestructive technique for enhancing the generally weak signal from Raman scattering. Here, SERS substrates were fabricated by drop-casting Au nanoparticles (NPs) onto two substrates (Cu and Si wafers). The AuNPs (diameter = 7.3 nm) were synthesized from an Au metal ion solution with a concentration of 4.22 × 10−4 M via photochemical reduction using a femtosecond laser. The SERS substrates were tested for their ability to enhance the Raman signal of paraquat pesticides at 10 ppm. Six vibration peaks of the paraquat pesticides at 671, 838, 1187, 1294, 1530, and 1643 cm−1 were successfully detected and enhanced. The results showed that the SERS substrate on the Si wafer increased the Raman signal more than the Cu wafer.

Mango is considered to be one of the most cultivated tropical fruits around the world. India is one of the largest producers of mango, accounting for an estimated 45% of the total world mango fruit production. India exported 27,872 metric tons of mango, worth 327.45 crores in 2020-21. Mango is a perishable fruit with a very short shelf life, which leads to wastage. To minimize or utilize the wastage, alternative mango-based products are being produced. Mango wine is one of the alternatives for surplus mango production. It is cost-effective and helps minimize post-harvest losses. The Philippines is the largest manufacturer of mango-based alcoholic beverages, such as mango wine and rum. Locally, mango wine is a popular home-based alcoholic beverage in the Philippines. India and Kenya are also experiencing significant growth in fruit wine production. The available literature on the production and characterization of mango wine briefly describes the fermentation and characterization procedures followed. The physiochemical properties and volatile composition of mango wine, including ethanol, esters, total soluble solids, and sensory analysis, are also highlighted in the review. The study provides evidence that the antioxi

Assessment of groundwater potential cum regolith aquifer protective strength was carried out using the electrical resistivity method at Ikole Ekiti, Southwestern Nigeria, to assess its viability and susceptibility. The Vertical Electrical Sounding (VES) technique using the Schlumberger array was adopted. The acquired data was partially curve-matched, forward-modelled, and iterated using WinResist version 1.0 software. Charts, para sections, tables, and maps were generated from the results obtained to aid interpretations. The KH curve type, which indicates good protective capacity, is more predominant in the study area than other curve types. Parasections showed four (4) geoelectric layers, i.e., topsoil, upper saprolite, lower saprolite, and sap rock. A weathered layer is the principal aquifer unit identified in the area; it is appreciably thick, and the basement is fresh. The thickness of regolith ranges from 2 to 56 m, with an appreciable thickness that can sustain moderate groundwater yield in the southern region of Ikole. The layer above the regolith aquifer has an average thickness slightly below 20 m; therefore, areas without lateritic cover will be prone to pollution. The strength of the regolith aquifer was assessed by employing longitudinal conductance (LC) and Geoelectric Layer Susceptibility Index (GLSI) ratings. The inherent weakness of the LC rating (not accounting for the lateritic nature of soil) was complemented by the GLSI rating. The southern region of the study area where groundwater is feasible is evaluated to have moderate protective capacity. Therefore, sources of pollution, such as septic tanks and dump sites, should be located far away from the area.

Numerical methods are widely used to study the solution of singularly perturbed equations. At the same time, their application to the solution of such equations encounters serious difficulties; they are associated with the presence of a small parameter at the highest derivative and the appearance in the solution area of ​​areas with high frequency-amplitude sawtooth jumps. In this case, the requirements for the efficiency and accuracy of numerical methods increase sharply. Although numerous methods have been developed to date, the question of the effectiveness and accuracy of numerical methods remains open. Until now, different methods with uniform and non-uniform steps have been mainly used to solve singularly perturbed equations. As the value of the small parameter decreases, to increase the accuracy, it is necessary to refine the step of the difference grid. This, in turn, leads to a strong increase in the order of the matrix in the linear algebraic system being solved. Along with difference methods, spectral methods can be used to solve problems. In spectral methods, the solution to the equation is sought in the form of finite series in Chebyshev polynomials. The derivatives present in the equation are determined by differentiating the selected final series. When differentiating series, the order of the approximating polynomials is reduced, and this, in turn, affects the accuracy of the method used. In this paper, it is proposed to use the preliminary integration method to solve singularly perturbed equations. The essence of this method is as follows. The highest derivative and the right-hand side of the differential equation are expanded into finite series in Chebyshev polynomials of the first kind. Unlike spectral methods, in the preliminary integration method the highest derivative is expanded into a finite series. Before solving the problem, the series for the highest derivative is preliminarily integrated until an expression for solving the problem is found in the form of a finite series. When integrating series, unknown integration constants appear; they are determined from additional conditions of the problem. Only after this, the series for solving the derivatives of the right side are put into a singularly perturbed equation and a system of linear algebraic equations is obtained for determining the unknown expansion coefficients. It should be noted that when integrating series, the smoothness of the approximating polynomials improves, and this, in turn, increases the accuracy of the proposed method. At the same time, the order of the matrix of the algebraic system being solved does not increase. This ensures, at the same costs required in the spectral method, that the proposed method can solve a singularly perturbed equation even for small values ​​of the small parameter of the problem. The high accuracy and efficiency of the preliminary integration method are demonstrated when solving a specific inhomogeneous singularly perturbed equation. The results of calculations are presented by comparing the approximate solution with the exact solution of the problem and with approximate solutions obtained by the spectral method.

In this paper, lignin and cellulose nanofibers were extracted and prepared from Bambusa vulgaris schrad (B. vulgaris: bamboo) before being subjected to characterization investigations. These extractions and preparations of the lignin and cellulose nanofibers were carried out chemically using alkali combined with bleaching treatments together with acid hydrolysis and sonication. The cellulose nanofibers were then subjected to morphological and dimensional characterization of the Zetasizer, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) instruments. The functional groups investigation, using Fourier Transform infrared spectroscopy (FTIR), and thermal degradation via the Thermogravimetric analysis (TGA), of the bamboo lignin and of the cellulose nanofibers were also carried out. Results revealed that the percentage yields of the bamboo lignin and bamboo nanofiber were 21.91 wt% and 33.6 wt% respectively. The SEM and TEM investigations indicated the prepared nanofibers were rod-like in morphology, having sizes ranging from 20 to 100 nm. FTIR showed that the lignin extracted from bamboo typified G-S type lignin while the nanofibers are completely devoid of lignin. TGA revealed that the lignin was more thermally stable than the nanofiber under the test conditions. The obtained lignin and cellulose nanofibers showed promise for possible application as reinforcement agents in biodegradable nanocomposite film preparation.

Developing nano-liquid materials with ultra-low concentrations leads to new or improved methods, as well as resolving issues in previous studies. Nano-liquid materials require special treatment because they are very sensitive materials. Many techniques have been developed, including the optical cavity technique, which depends on increasing the path length of the light beam between two dielectric mirrors to obtain more accurate and sensitive measurements. This method also provides beneficial information about the chemical composition. In this study, broadband cavity-enhanced absorption spectroscopy was used at a range of visible wavelengths to obtain spectra of rhodamine B (C28H31ClN2O3) at room temperature. The liquid phase of rhodamine B was chosen because it is the most complicated and volatile phase. The spectral analyses showed the fine structure of the aqueous solution of rhodamine B and the different molecular dynamics. The processes of the electron dynamics inside the molecules also changed at the ultra-low sample concentrations achieved working at the nanomolar scale. Combining experimental and data analysis via simulation programs has many benefits, such as reducing the time needed to study the materials, as it presents a typical design with fewer issues. In addition, costly, scarce, or difficult-to-store materials should be studied at low concentrations, and these combined studies can yield results without using these materials. The novelty of our research is the successful study of low concentrations of liquid samples. The high quality of the data, demonstrated by the goodness-of-fit parameters, allows for further analyses. Spectral analysis of nano-concentrations of rhodamine B shows new multiphoton absorption processes that drive the shifts in peak intensity. The solvent interaction effects caused changes in the binding energy states of the molecular structure of the sample. Here, we present a new spectral analysis of rhodamine B in aqueous solution using the broadband cavity-enhanced absorption spectroscopy (BBCEAS) technique.

Linearization is a classical approach to study matrix polynomial of the form P(lambda)=Sum lambdaj Aj, where A j Cnxn . It converts into a matrix pencil of the form L(lambda)=A+lambda B of high dimension, where A and B are matrices over C , and lambda is the spectral parameter. In this paper we consider Cubic two-parameter eigenvalue problems ( CTEP) and study three different linearization process of the problem. Usinglinearization techniques, CTEP is first converted into a linear two-parameter eigenvalue problem(L2EP) of coefficient matrices of different sizes. The main advantage of these linearizations lies in the fact that, after transforming them into suitable linearized forms, existing numerical techniques for linear multiparameter eigenvalue problems (LMEP) can be applied to CTEP without solving the original problem. While solving CTEP by formulating suitable linearizations, several transformations are generally used. In the current paper, it is also intended to report on these transformations, which have not been studied completely due to the complexity of their Kronecker structures.

Eryngium foetidum L. (Apiaceae) is known to possess many healthcare properties and has been used in the traditional system of medicine for various health issues. Despite that less scientific data on its photochemistry and antioxidant properties is limited. Therefore, this study aimed to document the photochemistry and antioxidant properties of leaves by following different extraction techniques to extract the plant constituents. Sonication (EN1), Soxhlet (EN2), maceration (EN3), and maceration with heat (EN4) were used as the extraction techniques while water was used as the extracting solvent. The HPLC method with a PDA detector was developed to compare the phytochemicals profile under each technique. The antioxidant capacities and content of saponins (SC), terpenoids (TC), flavonoids (TFC), tannins (TTC), alkaloids (AC), and polyphenolics (TPC) were determined spectrophotometrically. The EN2 and EN4 methods were identified using the HPLC-PDA application as yielding the highest overall results and giving a wide range of phytochemicals. The quantitative analyses resulted in high SC, TTC, TC, and TPC in the EN4 extraction process (185.84±0.54 mg SE/g, 36.99±0.64 mg TAE/g, 0.89±0.01 mM LE/g, and 37.37±0.65 mg GAE/g, respectively) and low in the EN1. TFC levels in EN2 were high (11.84±0.14 mg QE/g), whereas it was low in EN3. Furthermore, AC was higher in the extraction method EN3 (1.67±0.01 mg AE/g) and lower in the extraction technique EN2. The total antioxidant capacity was higher in the EN4 extract (47.17±0.20 mg Trolox Eq/g) and lower in the EN1 extract. The lowest IC50 in the 2,2′-Diphenyl-1-Picrylhydrazyl (DPPH) assay was noted for EN3 extract (12.91±0.02 mg/mL) revealing the highest scavenging activity than the other extracts. Based on HPLC and spectrophotometric analyses, maceration with heat (EN4) is recommended for efficiently extracting polyphenols and antioxidants from E. foetidum leaves. The application of heat would also improve the extraction efficiency of phytochemicals.

Peperomia pellucida (L.) Kunth, commonly known as ‘Sirih Cina,’ is a botanical plant recognised for its traditional application in various therapeutic contexts due to its bioactive compounds. Despite its potential benefits, its properties are sometimes underappreciated. The choice of solvent extraction significantly influences its biological properties. This research investigates the impact of diverse solvents on the extraction yield, antioxidant activity, and toxicity of P. pellucida leaf extracts. The selected solvents include natural deep eutectic solvents (NADES), distilled water, methanol, ethanol, and ethyl acetate. The extraction of P. pellucida leaves was conducted using an ultrasonic water bath apparatus. The aluminium chloride colorimetric assay was employed to determine the total flavonoid content (TFC), while the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to assess antioxidant activity. Moreover, the toxicological assessment of P. pellucida leaf extracts was performed using the brine shrimp lethality assay (BSLA) to determine LC50 (lethal concentration 50) values. NADES emerged as the most efficient solvent for extraction, yielding the highest extraction yield (17.39 ± 0.03%) and DPPH scavenging activity (83.31 ± 0.03%), while demonstrating non-toxicity in the BSLA (LC50 = 1597.62 µg/mL). Although NADES ranked third in terms of TFC, a moderate correlation between TFC and DPPH suggests that factors beyond TFC influence antioxidant activity. Overall, NADES exhibited antioxidant activity and showed non-toxicity towards brine shrimp. Therefore, NADES is a suitable solvent for exploring the medicinal potential of P. pellucida leaves as a source for therapeutic applications.