Characteristic Absorption Peak Research Articles

Mixed-frequency medium-voltage aging analysis of epoxy in the absence of partial discharges and dielectric heating

Premature failures of polymeric insulation under inverter-type electrical stress are predominantly associated with partial discharge (PD) erosion or dielectric heating. In the present contribution, an approach for aging analysis in the absence of the aforementioned mechanisms is proposed and applied to anhydride-cured epoxy samples, which are designed with a recessed shape to achieve PD-free aging. Dielectric heating was found to be negligible under all applied experimental conditions. Aging of samples was performed with a specialized setup for the generation of mixed-frequency medium-voltage (MF-MV) waveforms under controlled temperature and humidity conditions. The health state of samples was evaluated before and after different aging sequences by analysis of potential aging markers, namely the short-term AC breakdown strength, the complex dielectric permittivity (real and imaginary part), the volume resistivity, the glass transition temperature and the characteristic absorbance peaks obtained by Fourier-transform infrared spectroscopy (FTIR). Of these, only the breakdown strength exhibited significant aging effects under hygroelectric stress, which is hypothesized to be attributed to localized microcracking caused by electromechanical stress. Pure electrical MF-MV stress (i.e. at room temperature and dry conditions) was not found to be critical under the applied experimental conditions. By means of FTIR, hydrolysis was excluded as a possible aging mechanisms. In summary, the proposed aging analysis approach was found to be suitable to reveal aging effects empirically as well as to give indications about the underlying aging mechanisms without the need for excessively long or accelerated lifetime testing.

Purification and Identification of EPS Produced by Five Lactic Acid Bacteria and Evaluation of Their Effects on the Texture of Fermented Goat Milk

Extracellular polysaccharide (EPS) produced by five lactic acid bacteria (Limosilactobacillus fermentum B55, Limosilactobacillus fermentum B62, Lactiplantibacillus plantarum 7830, Pediococcus acidilactici B30, and Lactobacillus helveticus K2) were purified and identified, and their effects on the texture of fermented goat milk were evaluated. The purified EPS fractions EPS 1a, EPS 2b, EPS 3c, EPS 4d, and EPS 5e of strains B62, 7830, K2, B55, and B30 were obtained with ion exchange chromatography, and their molecular weights were 2.41 × 104, 1.62 × 104, 6.42 × 103, 6.45 × 103, and 1.26 × 104 Da, found using gel permeation chromatography. The infrared spectrum results showed that these substances all contained polysaccharide characteristic absorption peaks, most of which contained O-H bonds, C-H bonds, hydroxyl and carboxyl bonds, and groups. The analysis of monosaccharide composition presented that EPS1a was composed of guluronic acid, rhamnose, and galactose, with a molar ratio of 2.7:1:2.4; EPS2b and EPS3c were composed of guluronic acid; EPS4d was composed of guluronic acid, glucose, and galactose, with a molar ratio of 1:1.1:1.2; and EPS5e was composed of glucose and galactose, with a molar ratio of 1.6:1, indicating the differences in the composition and structure of EPS produced by various strains. Compared with the control group that only had the starter added, adding EPS-producing strains could promote acid production and improve the texture of fermented goat milk, and its acidity, hardness, consistency, viscosity, and viscosity index were higher.

Synthesis of polyglycerol fatty acid esters catalyzed by lipase and evaluation of its emulsification properties

The present study investigated the physicochemical properties of the newly synthesized polyglycerol fatty acid esters (PGFEs) and their potential application as food emulsifiers. It turned out that the complete removal of glycerol from crude polyglycerol was achieved by optimizing the molecular distillation temperature (120 °C). Moreover, novozym 435 was used to catalyze the synthesis of PGFEs with different aliphatic chain lengths, and the esterification rate of the obtained products was 93%∼98%. The characteristic absorption peak of the ester carbonyl group was displayed at 1738 cm−1, and that of C–O–C on the ether bond was at 1100 cm−1 and 1048 cm−1. Therefore, the synthesis can be determined to be PGFEs. Their hydrophilic lipophilic balance (HLB) values are >7, which can be used as oil-in-water emulsifiers. When curcumin nanoemulsions were constructed by PGFEs with various aliphatic chains as emulsifiers, it was found that all PGFEs in C10∼C18 can form stable curcumin nanoemulsions (encapsulation rate was >95%). PGFEs with longer aliphatic chains can stabilize nanoemulsions more efficiently (larger droplet sizes and lower ζ-electric potential), and showed better storage and UV stability. Whereas, medium-chain PGFEs emulsions, especially PGC, showed the best curcumin release efficiency, which theoretically supported the application of PGFEs to functional emulsion products.

The manganese(II) and cobalt(II) complexes of enrofloxacin showed comparable antibacterial activity: Synthesis, crystal structure and antibacterial activity

Enrofloxacin (EFX) is a third-generation fluoroquinolone drug especially used for animals world wide, which shows broad-spectrum and significant antibacterial activities. In this study, EFX was selected as the ligand to synthesize two transition metal complexes, EFX-Mn and EFX-Co, in which the bio-active metal ions, manganese(II) and cobalt(II), was set to be the active metal center. Their crystal structures were reported and characterized by X-ray single crystal diffraction analysis. Both the crystal structures of EFX-Mn and EFX-Co belong to the same monoclinic crystal system with P21/c space group. Viewed from the crystal structure of EFX-Mn or EFX-Co, the central Mn(II)/Co(II) adapted a six-coordinated octahedral configuration, respectively by two EFX ligands and two H2O co-ligands. The characteristic UV-Vis absorption peaks of both complexes were examined in tris-saline buffer solution in a time-dependent mode in 24 h, which suggested that the coordination status of EFX-Mn and EFX-Co in the solid state still maintained under near-physiological condition. In vitro antibacterial activity tests demonstrated that EFX-Mn and EFX-Co showed similar and significant growth inhibitory effects towards five typical pathogenic bacteria, compared with EFX itself. While for two gram-negative bacterial strains, E. coli and S. typhi, EFX-Mn and EFX-Co showed higher bactericidal effects than EFX, the bactericidal concentration of which was only a half as low as that of EFX.

Modification of the Structural and Functional Characteristics of Mung Bean Globin Polyphenol Complexes: Exploration under Heat Treatment Conditions.

During the storage and processing of mung beans, proteins and polyphenols are highly susceptible to interactions with each other. Using globulin extracted from mung beans as the raw material, the study combined it with ferulic acid (FA; phenolic acid) and vitexin (flavonoid). Physical and chemical indicators were combined with spectroscopy and kinetic methods, relying on SPSS and peak fit data to statistically analyze the conformational and antioxidant activity changes of mung bean globulin and two polyphenol complexes before and after heat treatment and clarify the differences and the interaction mechanism between globulin and the two polyphenols. The results showed that, with the increase in polyphenol concentration, the antioxidant activity of the two compounds increased significantly. In addition, the antioxidant activity of the mung bean globulin-FA complex was stronger. However, after heat treatment, the antioxidant activity of the two compounds decreased significantly. The interaction mechanism of the mung bean globulin-FA/vitexin complex was static quenching, and heat treatment accelerated the occurrence of the quenching phenomenon. Mung bean globulin and two polyphenols were combined through a hydrophobic interaction. However, after heat treatment, the binding mode with vitexin changed to an electrostatic interaction. The infrared characteristic absorption peaks of the two compounds shifted to different degrees, and new peaks appeared in the areas of 827 cm-1, 1332 cm-1, and 812 cm-1. Following the interaction between mung bean globulin and FA/vitexin, the particle size decreased, the absolute value of zeta potential increased, and the surface hydrophobicity decreased. After heat treatment, the particle size and zeta potential of the two composites decreased significantly, and the surface hydrophobicity and stability increased significantly. The antioxidation and thermal stability of the mung bean globulin-FA were better than those of the mung bean globulin-vitexin complex. This study aimed to provide a theoretical reference for the protein-polyphenol interaction mechanism and a theoretical basis for the research and development of mung bean functional foods.

Colorimetric and visual determination of uric acid based on decolorization of manganese dioxide nanosheet dispersions.

Serum levels of uric acid (UA) play an important role in the prevention of diseases. Developing a rapid and accurate way to detect UA is still a meaningful task. Hence, positively charged manganese dioxide nanosheets (MnO2NSs) with an average latter size of 100 nm and anultra-thin thickness of below 1 nm have been prepared. They can be well dispersed in water and form stable yellow-brown solutions. The MnO2NSs can be decomposed by UA via redox reaction, leading to a decline of a characteristic absorption peak (374 nm) and a color fading of MnO2NSs solution. On this basis, an enzyme-free colorimetric sensing system for the detection of UA has been developed. The sensing system shows many advantages, including a wide linear range of 0.10-50.0 μmol/L, a limit of quantitation (LOQ) of 0.10 μmol/L, a low limit of detection (LOD) of 0.047 μmol/L (3σ/m), and rapid response without need of strict time control. Moreover, a simple and convenient visual sensor for UA detection has also been developed by adding an appropriate amount of phthalocyanine to provide a blue background color, which helps to increase visual discrimination. Finally, the strategy has been successfully applied to detect UA in human serum and urine samples.

Green synthesis of silver nanoparticles with an antibacterial activity using Salvia officinalis aqueous extract

This report searched the rapid and simple green biosynthesis of silver nanoparticles (AgNPs) using Salvia officinalis aqueous extract. The visual color change from colorless/yellow to reddish brown was noticed indicating the phytosynthesis AgNPs during the process. The presence of functional groups in plant extract acted as reducing and capping agents for the formation of AgNPs was confirmed by FTIR. The fabricated AgNPs were characterized by ultraviolet–visible spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDX). The UV–Visible spectrum showed a characteristic absorption peak for Ag at around 457 nm with optical bandgaps of about 2.22 eV of AgNPs. XRD patterns at (111), (020), (022), (131), and (222) lattice planes depicted the production of face-centered cubic silver nano-structure with approximate crystal size ranges from≈20 nm by Scherrer’s formula. The predominantly spherical nanoparticles having an average size of 20 nm showed enhanced antibacterial activity against Salmonella typhimurium, Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli with more activity toward P. aeruginosa. Our green synthesis protocol required only 15 min for the conversion of silver ions into silver nanoparticles by heating is an efficient, rapid, simple, sustainable, cheap, and energy-efficient, alternative to conventional chemical/physical methods, a one-step application.

Structural, Optical and Antimicrobial Properties of Carbohydrate-Capped Cadmium Sulfide Nanoparticles

Cadmium sulfidenanoparticles (CdSNPs) were prepared through the chemical precipitation process where sweet potato starch and glucose-functioned as capping agents. Ultraviolet-Visible (UV-Vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques were applied for the analysis of prepared CdSNPs. The absorption peaks in the UV-Vis spectroscopy towards the lower wavelength region compared to the bulk CdS (512 nm) indicated the formation of CdS particles in the nanometer scale range. FTIR spectroscopy showed the characteristic absorption peaks of the CdSNPs along with the functional groups present in starch and glucose, suggesting the possible interaction between CdSNPs and capping agents. The XRD revealed crystallographic information such as the average crystallite size and shape of CdSNPs. Using the Scherrer equation, the average crystallite size of CdSNPs was determined to be 11.48 nm and 16.03 nm for starch-capped and glucose-capped CdSNPs (CdS-St andCdS-Gl)respectively. Antibacterial and antifungal activities of the prepared CdSNPs were found to be highly efficient for various pathogenic bacteria and fungi. Hence in the present study, the new synthetic route of CdSNPs was applied, and antimicrobial activities were performed

Nanomaterial-decorated micromotors for enhanced photoacoustic imaging

Micro-and nanorobots have the potential to perform non-invasive drug delivery, sensing, and surgery in living organisms, with the aid of diverse medical imaging techniques. To perform such actions, microrobots require high spatiotemporal resolution tracking with real-time closed-loop feedback. To that end, photoacoustic imaging has appeared as a promising technique for imaging microrobots in deep tissue with higher molecular specificity and contrast. Here, we present different strategies to track magnetically-driven micromotors with improved contrast and specificity using dedicated contrast agents (Au nanorods and nanostars). Furthermore, we discuss the possibility of improving the light absorption properties of the employed nanomaterials considering possible light scattering and coupling to the underlying metal-oxide layers on the micromotor’s surface. For that, 2D COMSOL simulation and experimental results were correlated, confirming that an increased spacing between the Au-nanostructures and the increase of thickness of the underlying oxide layer lead to enhanced light absorption and preservation of the characteristic absorption peak. These characteristics are important when visualizing the micromotors in a complex in vivo environment, to distinguish them from the light absorption properties of the surrounding natural chromophores.

Effects of Ultrasound-Assisted Extraction on Structure and Rheological Properties of Flaxseed Gum

In this study, flaxseed gum (FG) was extracted using hot water extraction and ultrasonic-assisted extraction. The yield, molecular weight distribution, monosaccharide composition, structure, and rheological properties of FG were analyzed. The FG yield (9.18) achieved using ultrasound-assisted extraction (this sample was labeled as UAE) was higher than the yield (7.16) achieved with hot water extraction (this sample was labeled as HWE). The polydispersity, monosaccharide composition, and characteristic absorption peaks of the UAE were similar to that of the HWE. However, the UAE had a lower molecular weight and looser structure than the HWE. Moreover, zeta potential measurements indicated that the UAE exhibited better stability. An analysis of the rheological properties showed that the viscosity of the UAE was lower. Thus, the UAE had an effectively better yield of FG, preliminarily modified structure, and rheological properties, and provided a theoretical basis for its application in food processing.

Green Synthesis and Characterization of Copper Oxide Nanoparticles Using Tecoma Stans

Aims: An eco-friendly approach utilizing biologically-mediated processes has been developed for the fabrication of CuO nanoparticles using Tecoma stans leaves.
 Methodology: The synthesis of CuO nanoparticles was carried out using an environmentally friendly method, which involved the use of an aqueous solution of copper (II) sulfate and a leaf extract derived from Tecoma stans. The synthesized CuO nanoparticles were characterized using various instruments, including a UV-visible spectrophotometer, scanning electron microscopy, X-ray Diffraction Spectrometer, and Fourier-transform infrared spectroscopy.
 Results: The UV-Vis spectrum showed a characteristic absorption peak of CuO nanoparticles at 296 nm. The green-synthesized CuO nanoparticles were characterized using SEM, which revealed their morphological and structural characteristics and showed a mean particle size ranging from 20 nm to 200 nm. The FTIR spectrum, ranging from 584.63 cm-1 to 3430.41 cm-1, indicated the presence of various functional groups. X-ray powder diffraction (XRD) analysis confirmed the formation of monoclinic CuO with a crystalline nature, and an average particle size of 27.67 Å.
 Conclusion: The present study reports the development of a simple, low-cost, and biologically-mediated method for synthesizing CuO nanoparticles using an extract obtained from Tecoma stans leaves. The effectiveness of these nanoparticles can be evaluated through various biological activities, including antibacterial, antifungal, and cytotoxic assays.

Mycosynthesis of Silver Nanoparticles and Evaluation as Insecticidal Against the Sunn Pest Eurygaster testudinaria in Vitro

Fungi are used to synthesize metal nanoparticles such as silver nanoparticles (AgNPs) because of their specifications as lower toxicity and eco-friendly behavior. Extracellular mycosynthesis of Lecanicillium lecanii silver nanoparticles (AgNPs) was performed, which was done by a redox reaction, where the filtrate crude of L. lecanii acts as a reducing and stabilizing agent for the formation of nanoparticles. The green synthesized AgNPs were evaluated as insecticidal against the adults of sunn pest Eurygaster testudinaria. The AgNPs were characterized by ultraviolet-visible (UV–vis) spectroscopy, Fourier transform infrared (FITR) spectroscopy, X-ray diffraction (XRD), and Field Emission Scanning Electron Microscopy (FESEM). The UV–Vis spectroscopy showed a characteristic absorption peak at 418.5 nm due to surface plasma resonance. FESEM analysis showed that synthesized AgNPs were semi-spherical with an average size of 39.45 nm. The AgNPs showed strong activity in mortality of adults of E. testudinaria under conditions during different periods of time to recorded 100% at concentration 100 ppm compared with 0.00% in control treatment after 10 days from treatment.

Green synthesis of Zinc oxide nanoparticles using lemon extract for waste water treatment

The present work represents the study of effects on the photocatalytic activity of green synthesized Zinc oxide nanoparticles by using Zinc nitrate as a precursor with lemon juice extract for various temperatures (50˚C, 60˚C, 70˚C, 80˚C). XRD studies confirms the crystalline structure of green synthesized nanoparticles. The characteristic absorption peak of zinc oxide nanoparticles had been verified using UV–Visible and FTIR spectrum. The morphological study of the nanoparticles had been investigated by Scanning electron microscope (SEM). The Photodegradation of ZnO nanoparticles on Rhodamine-B(RhB) dye had been studied.

Structural characterization and antioxidant activity of a glycoprotein isolated from shiitake mushrooms

In this paper, the shiitake mushroom glycoprotein (SGP) was extracted from shiitake mushrooms and its structure was characterized and its antioxidant activity was investigated. SGP contained 33.42 ± 1.75% protein and 42.59 ± 1.95% sugar, with 17 amino acids and eight monosaccharides at concentrations of 81.52 mg/g and 42.62 μg/mg, respectively. SGP contained abundant hydrophobic amino acids and monosaccharides in terms of variety and concentration, which can improve the chelation of SGP to metal ions and effectively improve its antioxidant capacity. Moreover, SGP belongs to the type of O-glycopeptide bond, wherein the secondary structure was mainly β-strands, the sugar chain had a pyran ring configuration, and the characteristic absorption peaks of polysaccharides and proteins appeared at 3383 cm−1 and 2929 cm−1. The O-glycopeptide bond and β-strand structure played a positive role in slowing the half-life of antioxidant active substances. In addition, the antioxidant capacity of SGP increased with increases in SGP concentration within a certain range, and the total antioxidant capacity reached a maximum of 4.4 ± 0.18 μmol/mL when the SGP concentration was 8 mg/mL. This study improved the understanding of the structure and antioxidant activity of SGP, and contributed to the study of structure-activity relationships in the food industry.

Physicochemical Characterization and Antitumor Activity of Fucoidan and Its Degraded Products from Sargassum hemiphyllum (Turner) C. Agardh.

Fucoidan has many biological functions, including anti-tumor activity. Additionally, it has been suggested that low-molecular-weight fucoidans have greater bioactivities. This study aimed to examine the degradation, purification, physicochemical characterization and in vitro antitumor activity of fucoidan from Sargassum hemiphyllum (Turner) C. Agardh. Fucoidan was isolated using DEAE-cellulose-52 (F1, F2), Vc-H2O2 degration, and Sepharose CL-6B gel (DF1, DF2) from crude Sargassum fucoidans. Physicochemical characteristics of four isolated fucoidans were examined using chemical and monosaccharide composition, average molecular weight (Mw), and FTIR. Furthermore, the anti-proliferative effects of purified fucoidans on human hepatocellular carcinoma cells (HepG2), human Burkitt Lymphoma cells (MCF-7), human uterine carcinoma cells (Hela) and human lung cancer cells (A549) were analyzed by MTT method. The apoptosis of HepG2 cells was detected by flow cytometry. Our data suggest that the contents of polysaccharide, L-fucose and sulfate of DF2 were the highest, which were 73.93%, 23.02% and 29.88%, respectively. DF1 has the smallest molecular weight (14,893 Da) followed by DF2 (21,292 Da). The four fractions are mainly composed of fucose, mannose and rhamnose, and the infrared spectra are similar, all of which contain polysaccharide and sulfate characteristic absorption peaks. The results of MTT assay showed that the four fractions had inhibitory effects on HepG2 and A549 in the range of 0.5-8 mg/mL, and the four fractions had strong cytotoxic effects on HepG2 cells. DF2 had the best inhibitory effect on HepG2 (IC50 = 2.2 mg/mL). In general, the antitumor activity of Sargassum fucoidans is related to the content of L-fucose, sulfate and molecular weight, and Sargassum fucoidan has the best inhibitory effect on HepG2 hepatocellular carcinoma cells. Furthermore, when compared to MCF-7, Hela, and A549 cells, Sargassum fucoidans had the best capacity to reduce the viability of human hepatocellular carcinoma cells (HepG2) and to induce cell apoptosis, proving itself to have a good potential in anti-liver cancer therapy.

Pluronic® F127 Hydrogel Containing Silver Nanoparticles in Skin Burn Regeneration: An Experimental Approach from Fundamental to Translational Research.

Presently, skin burns are considered one of the main public health problems and lack therapeutic options. In recent years, silver nanoparticles (AgNPs) have been widely studied, playing an increasingly important role in wound healing due to their antibacterial activity. This work is focused on the production and characterization of AgNPs loaded in a Pluronic® F127 hydrogel, as well as assessing its antimicrobial and wound-healing potential. Pluronic® F127 has been extensively explored for therapeutic applications mainly due to its appealing properties. The developed AgNPs had an average size of 48.04 ± 14.87 nm (when prepared by method C) and a negative surface charge. Macroscopically, the AgNPs solution presented a translucent yellow coloration with a characteristic absorption peak at 407 nm. Microscopically, the AgNPs presented a multiform morphology with small sizes (~50 nm). Skin permeation studies revealed that no AgNPs permeated the skin after 24 h. AgNPs further demonstrated antimicrobial activity against different bacterial species predominant in burns. A chemical burn model was developed to perform preliminary in vivo assays and the results showed that the performance of the developed AgNPs loaded in hydrogel, with smaller silver dose, was comparable with a commercial silver cream using higher doses. In conclusion, hydrogel-loaded AgNPs is potentially an important resource in the treatment of skin burns due to their proven efficacy by topical administration.

Dual-Signal Triple-Mode Optical Sensing Platform for Assisting in the Diagnosis of Kidney Disorders.

As known biomarkers of kidney diseases, N-acetyl-β-d-glucosaminidase (NAG) and β-galactosidase (β-GAL) are of great importance for the diagnosis and treatment of diseases. The feasibility of using multiplex sensing methods to simultaneously report the outcome of the two enzymes in the same sample is even more alluring. Herein, we establish a simple sensing platform for the concurrent detection of NAG and β-GAL using silicon nanoparticles (SiNPs) as a fluorescent indicator synthesized by a one-pot hydrothermal route. p-Nitrophenol (PNP), as a common enzymatic hydrolysis product of the two enzymes, led to the attenuation of fluorometric signal caused by the inner filter effect on SiNPs, the enhancement of colorimetric signal due to the increase of intensity of the characteristic absorption peak at around 400 nm with increasing reaction time, and the changes of RGB values of images obtained through a color recognition application on a smartphone. The fluorometric/colorimetric approach combined with the smartphone-assisted RGB mode was able to detect NAG and β-GAL with good linear response. Applying this optical sensing platform to clinical urine samples, we found that the two indicators in healthy individuals and patients (glomerulonephritis) with kidney diseases were significantly different. By expanding to other renal lesion-related specimens, this tool may show great potentials in clinical diagnosis and visual inspection.

IONIC TO ELECTRONIC TRANSITION CONDUCTIVITY STUDIES OF LITHIUMBORATE RUBY GLASS-CERAMICS CONTAINING GOLD-NANO-PARTICLES

Glass-ceramics containing Au nanoparticles have been synthesized by selecting the base glass with specic composition 30Li2O–70B2O3 - x HAuCl4.3H2O [LBA] (x=0.01-0.06) all in wt % have been prepared by conventional melt quenching technique. The characteristic ruby color has been observed which is attributed due to the surface plasmon resonance of the Au nanoparticles uniformly embedded in the glass matrix. The imparted red color due to the presence of gold nanoparticles has been conrmed by studying the optical absorption spectra using UV-VIS spectrometer in the visible range (400-1000nm) which show a characteristic absorption peak at ~560nm. In order to check the crystallization/amorphous nature, the samples were powdered and characterized using XRD. The microstructural modications in the samples due to the addition of Au have been recorded using SEM. Further, the ESR studies reveal that the electronic state of gold is either Au0 or Au+. AC conductivity studies have been performed at RT over a frequency range 100 to 10MHz. AC conductivity data is tted by Almond-West law with power exponent 's'. The dc conductivity is found to be increasing with the increase of temperature for a typical ruby glass, but almost constant with dopant concentration

Carissa carandas L. fruit mediated in vitro synthesis of silver nanoparticles and their antioxidant and antibacterial activities

Currently, we synthesized silver nanoparticles (AgNPs) from the aqueous fruit extract of Carissa carandas L. and evaluated their antioxidant and antibacterial properties. The UV-visible spectra showed a characteristic absorption peak at 412 nm. The Fourier transform infrared (FTIR) spectroscopy exhibits intense peaks at 3430.23cm-1 and 1625.67cm-1 which indicates the involvement of flavonoids and other functional groups in the biosynthesis, capping, and stabilization of AgNPs. From XRD analysis, the average size of AgNPs was estimated to be 45nm. The biogenic AgNPs were spherical in shape and average size range between 10 to 95nm confirmed by HR-TEM analysis. The fabricated AgNPs by fruit extract were monitored for antioxidant activity using DPPH method. The fruit extract of AgNPs (IC50= 946.22μg/ml) had the highest antioxidant activity against standard ascorbic acid. The antibacterial activity was done using Staphylococcus aureus and Escherichia coli bacterial strains. It was found from the results that the bacterial strain S. aureus had the highest antibacterial activity when compared to E. coli and aqueous fruit extract. Thus, the present study exhibits synergistic antioxidant and antibacterial activity which may explore in future clinical treatment.

Colorimetric detection of uric acid based on enhanced catalytic activity of cobalt-copper bimetallic-modified molybdenum disulfide

A method for the quantification of uric acid (UA) by colorimetry using a four-in-one nanocomposite MoS2/PDA/CoCu as a novel nanozyme was proposed. The nanocomposite was prepared based on the deposition of metal cobalt and copper nanoparticles onto the surface of MoS2 nanosheets using polydopamine (PDA) as a stabilizer. The Michaelis-Menten model was used to monitor the catalytic efficiency of peroxidase-like reactions, and the results showed that the Michaelis constant Km (0.0076 mM and 0.0032 mM) values calculated by the Lineweaver-Burk equation were much lower than those of horseradish peroxidase and other reported nanozymes, demonstrating that MoS2/PDA/CoCu has excellent peroxidase-like activity. Theoretically, uric acid can produce allantoin and H2O2 in the presence of uricase and oxygen, respectively. The nanocomposite efficiently catalyzes H2O2 to produce hydroxyl radicals (•OH) that then oxidize colorless 3, 3′, 5, 5′-tetramethylbenzidine (TMB) to the blue oxidation product (ox-TMB) which corresponds to the characteristic absorption peak at 652 nm. Using optimal conditions, we constructed a sensitive visible visual colorimetric method combined with a designed smartphone for UA detection (0.5–200 μM, R2 = 0.995) with a limit of detection (S/N = 3) of 0.13 μM. When UA was detected in serum and urine samples, good recovery rates were obtained, indicating the great potential of this method for the detection of uric acid in clinical and daily life applications.