Volume 237, Issue 8

This comprehensive review article discusses the potential applications of graphene oxide-silver nanoparticles (GO-Ag NPs) in various fields, including biomedical, catalytic, electrochemical detection, and wastewater treatment technologies. GO-Ag NPs have gained significant attention due to their unique properties, such as excellent electrical, mechanical, and thermal conductivity, as well as their protective capabilities. The review summarizes the different starting materials and reducing agents that have been used to produce GO-Ag NPs with particle sizes ranging from 2 to 90 nm. Furthermore, the article highlights the various applications of GO-Ag NPs, such as their use in drug delivery, bioimaging, and cancer therapy. Additionally, the review discusses the potential of GO-Ag NPs in catalysis, electrochemical detection, and wastewater treatment. Overall, this review provides a comprehensive overview of the potential uses of GO-Ag NPs and emphasizes the need for further research to develop more straightforward methods for their production and application.

The intrinsic defect of ZnO depicts a crucial role in the charge transfer owing to the suppression of the exciton recombination, exhibiting superior semiconducting performance. In this study, the intrinsic defect of ZnO nanostructures prepared by direct thermal activation of 300–900 °C was investigated. X-ray diffraction (XRD) was employed to analyze phase, crystallite size, Zn–O bond length, and dislocation density. The relation of Williamson–Hall (W–H) was used to calculate crystallite size and micro-strain. The atomic coordination was approximated through the Rietveld method. Morphology and crystal growth investigation was carried on by scanning electron microscope (SEM) and tunneling electron microscope (TEM), exhibiting rod-like nanostructures transform to oval shape particle with high residual strain when increasing calcination temperature, exhibiting the crystal growth direction of (101). Specific surface and pore analysis reveals a significant value corresponding to SEM analysis. Fourier transform infrared spectroscopy (FT-IR) detected Zn–O stretching vibration bands, presenting a notable increase in the intensity when heat at 600 °C. Relating to the thermal regime, energy bandgap (Eg) was found to be 3.41–3.50 eV as increasing heat treatment temperatures. Photoluminescence (PL) was applied to determine intrinsic defects through emissive spectra. The surface charge was determined through the zeta potential measurement. The photo-induced dye degradation was measured to understand the effect of the defect in semiconductors. The X-ray photoelectron spectroscopy (XPS) confirms the wurtzite structure appearance, including the intrinsic defects. The observed intrinsic defects are discussed, associating with the structural constants, emissive spectra, cationic dye degradation, and binding energy.

Herein, a nanostructured ZnO/Fe 2 O 3 heterostructure and its graphene (Gr)-reinforced composite (ZnO/Fe 2 O 3 @Gr) have been synthesized via co-precipitation and post-ultrasonication approaches. The formation of heterojunction at the ZnO–Fe 2 O 3 interface reduces the bandgap and keeps the electron-hole pairs apart. The graphene plays multiple roles to boost the dye removal effectively of the ZnO/Fe 2 O 3 @Gr composite. The charge transfer aptitude, isolation of charge carriers, and resistance at the ZnO/Fe 2 O 3 -Graphene interface were also examined by Mott–Schottky, chronoamperometric, and impedance experiments. The performance of an as-synthesized ZnO/Fe 2 O 3 @Gr catalyst was explored for the mineralization of a cationic dye (crystal violet, CV) and phenol in visible-light ( λ above 400 nm) for 2 h. The ZnO/Fe 2 O 3 @Gr catalyst has mineralized 92.8 % CV dye and 50.86 % phenol after 2 h of visible-light irradiation. Moreover, the mineralization constant ( k ) comes to be 0.019 min −1 , which is 4.2, 2.3, and 1.7 times higher than ZnO, Fe 2 O 3 , and ZnO/Fe 2 O 3 catalysts, respectively. Increasing the dosage of the ZnO/Fe 2 O 3 @Gr catalyst from 10 mg to 30 mg increased the rate constant from 0.006 min −1 to 0.019 min −1 , thereby increasing the efficiency of CV dye mineralization from 58.5 % to 92.8 %. The tuned photocatalytic activity of the ZnO/Fe 2 O 3 @Gr is due to the formation of the ZnO–Fe 2 O 3 heterostructure and, preferentially, its conductive graphene. In fact, graphene serves the roles of an efficient electron collector, a transporter, and an effective UV/Vis light absorber, enabling the creation of active species that further boost the photocatalytic performance. According to the results of this study, the easiest and cheapest way to deal with toxic dyes in industrial waste is to make photocatalysts from semiconductive and carbonaceous materials that have integrated properties.

Coal is one of the important sources of energies and its combustion produce sulfur dioxide in the atmosphere, which needs desulphurization to avoids the pollution issue. Coal desulfurization was performed using SnO 2 /TiO 2 nanocomposite under solar light irradiation. The SnO 2 /TiO 2 was synthesized by co-precipitation method and deposited on glass beads. The prepared SnO 2 /TiO 2 was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transfer infrared spectroscopy (FT-IR) techniques. The SnO 2 /TiO 2 nanocomposite desulfurization efficiency was performed under solar light irradiation and process variables, i.e., irradiation time, H 2 O 2 and pH were optimized for maximum desulfurization of coal. The SnO 2 /TiO 2 nanocomposite showed promising efficiency and 60 % sulfur removal was achieved under optimum conditions. Based on efficiency, the SnO 2 /TiO 2 nanocomposite has potential for the desulphurization of coal under solar light exposure, which will make the process highly economical feasible.

The present work outlines the successful synthesis of selenium nanoparticles (Se NPs) stabilized with gum shellac (GS) and their use as photocatalyst for the enhanced degradation of dyes. Se NPs were synthesized by a simple and cost effective chemical reduction method using selenious acid, GS and sodium borohydride. Gum shellac was used as stabilizing agent. The orange red gum shellac-selenium nanoparticles (GS–Se NPs) were characterized by UV–Vis spectroscopy, Fourier transform infra-red (FTIR), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The morphology of these particles appeared to be uniform and spherical as observed in SEM images. Energy dispersive X-ray spectroscopic profile showed the presence of elemental selenium, carbon and oxygen. The synthesized GS–Se NPs were investigated for their photo-catalytic efficiency towards degradation of methylene blue (MB) and methyl orange (MO) dye in aqueous media. Absorbance was measured at λ max 665 nm and 455 nm for MB and MO, respectively. Maximum degradation of MB in-comparison with MO obtained at 50 mg/L were 81.72 % and 71.42 % respectively. A very slow degradation rate was observed for the MO and MB in the absence of synthesized photocatalyst whereas greater percentage degradation was observed for the GS–Se NPs.

Nanocellulose is a promising bionanomaterial which has gained significant attention due to its diverse applications in many important areas. Thus, scientists and technologists are constantly searching for the most economical, sustainable, and eco-friendly production to fulfill its growing need. In this study, cellulose and nanocellulose were isolated from the plant of Ailanthus altissima utilizing a multi-step, environmentally friendly approach involving alkaline treatment and chlorine-free bleaching. The analysis of purified cellulose was conducted by utilizing modern techniques, such as X-ray Diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). XRD analysis determined the degree of crystallinity of extracted cellulose i.e. 67.41 % and crystallite size 43.4 Å by using Segal method and Scherrer equation respectively. The TGA curve showed the thermal degradation pattern of the cellulosic and nanocellulosic material. Furthermore, SEM technique was used to study the morphological changes in the surface of lignocellulosic fibers with chemical treatment. This novel biomass source has to be a potential usage for a wide range of applications in industrial processes.

The influence of dipeptide glycyl- l -valine (gly- l -val) on the micellization and surface active properties of two different gemini surfactants varying in their spacer group i.e. ethylene-1,2-bis ( N,N -dimethyl- N -dodecylammonium bromide) (12–2–12) and hexamethylene-1,6-bis-( N,N -dimethyl- N -dodecylammonium bromide) (12–6–12) was explored using tensiometry as well as conductivity technique. Conductivity measurements at several temperatures (293.15, 298.15, 303.15 and 308.15) K and tensiometric measurements at 298.15 K at several concentrations of dipeptide (0.02, 0.04 and 0.06) mol/kg were conducted so as to deduce the interactions amid dipeptide and two surfactants. Several parameters viz. critical micelle concentration (CMC) as well as the degree of ionization ( α ) along with various parameters associated with thermodynamics; standard entropy of micellization (ΔSm0${\Delta}{S}_{m}^{0}$), Gibbs free energy of micellization (ΔGm0${\Delta}{G}_{m}^{0}$) and standard enthalpy of micellization (ΔHm0${\Delta}{H}_{m}^{0}$) have been evaluated through conductivity data. Various additional thermodynamic parameters such as free energy of adsorption (ΔGad0${\Delta}{G}_{ad}^{0}$) and surface free energy (Gmins${\left(G\right.}_{\mathrm{min}}^{s}$) have been also estimated through surface tension measurements.

This study emphasis the removal of methyl orange (MO) from aqueous medium by Raphanus caudatus powdered leaves biomass. Functional groups involved in the removal of MO dye from aqueous medium by leave biomass were identified by Fourier transform infrared (FTIR) spectroscopy analysis. It was seen that removal of dye molecules from aqueous medium was affected by the change in adsorption condition such as adsorbent dose, agitation time and pH of the medium. Maximum adsorption capacity of Raphanus caudatus leave biomass powder for MO dye was found as 30.86 mg/g. Regression factor ( R 2 ) value indicates the best fitting of Langmuir isotherm model for the adsorption process. Amount of adsorption energy calculated by Dubinin-Radushkevich (DR) isotherm model illustrates the chemical bond formation between dye and biomass particles. Recyclability results depict that biomass showed good adsorption capacity value for MO up to 4th reusability cycle.

One of the main ways that metallic materials lose their useful qualities is through dissolution; hence corrosion management is crucial for protecting the metal. In this paper, new thienylpicolinamidine derivatives, namely; 5-[5-(3,4,5-trimethoxyphenyl)thiophen-2-yl]picolinamidine hydrochloride salt (MA-1517), 5-[5-(4-methoxyphenyl)thiophen-2-yl]picolinamidine hydrochloride salt (MA-1543), and 5-[5-(3-chloro-4-methoxyphenyl)thiophen-2-yl]picolinamidine hydrochloride salt (MA-1516), were utilized as corrosion inhibitors for C-steel in 1.0 mol L −1 HCl. Their corrosion inhibiting impact can be demonstrated by experimental methods as chemical approaches (mass reduction) and electrochemical techniques (electrochemical impedance examination, EIS, and Tafel polarization). These methods gave inhibition efficiencies (IE%) of 97.41 %, 93.84 % and 91 % for MA-1517, MA-1543 and MA-1516, respectively at 323 K and concentration 17 × 10 −6  mol. L −1 . The rise in IE% with rising inhibitor concentration and temperature illustrate that the adsorption of these studied compounds is chemisorption, declared via the Langmuir isotherm. Thermodynamic and kinetic parameters are computed and discussed. Polarization research exhibits that these thienylpicolinamidines act as mixed type inhibitors. The outer part morphology of C-steel surfaces and the adsorption of these compounds on C-steel outer part can be checked by atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX). The mechanism of inhibition can be backed by quantum chemical examination and Monte Carlo model. A theoretical estimate proves that the use of cationic derivatives of pyridine is good impediments versus corroding of C-steel in HCl medium.

This research study reports on the extraction of nanocellulose followed by structural and thermal analysis and application of nanocellulose in hydroxypropyl methyl cellulose (HPMC) nanocomposite films. The cellulose nanocrystals were isolated from Artemisia scoparia straw through an alkaline treatment and bleaching process, followed by sulphuric acid hydrolysis. The HPMC nanocomposite films were prepared by a solution casting method and dried at room temperature. Fourier transform infrared-ray (FTIR) spectroscopy and thermogravimetric analysis (TGA) techniques were used to analyze the structural and thermal properties of the materials, including the cellulosic material, the nanomaterial, and the nanocomposites. The FTIR spectra indicated that the extraction procedure was adequate, demonstrating the removal of lignin and hemicellulose and the preparation of nanocellulose. The TGA results revealed the thermal degradation pattern of the cellulose and showed that the HPMC films had enhanced thermal stability. This research demonstrates that A. scoparia straw has potential for the extraction of cellulosic nanomaterial and a wide range of applications in nanocomposites.

This paper explores different techniques to combine and improve the electrochemical sensing activities of the transition metal chalcogenide. The transition metal chalcogenide was doped with a suitable dopant to tune the band structure. Surface-assisted nanotechnology was used to enrich the superficial properties of the doped material. Lastly, the nanostructured doped materials were physically mixed with the graphene nanoplates (GNPs) to improve the flow of charges and the stability of the electrochemistry. The most electrically conductive and common metal sulfides in nature were chosen and prepared using a cheap and easy wet-route method. Crystal structure, chemical functionality, texture, composition, and thermal stability of undoped, doped, and composite materials were determined using physicochemical techniques such as X-ray diffraction, FTIR, SEM, EDX, and TGA. N 2 -adsorption-desorption, current-voltage, and impedance studies show that the composite sample’s surface area, electrical conductivity, and charge transport properties are superior to those of the undoped and doped samples. Regarding electrochemical applications, the composite material supported a glassy carbon electrode (Co–Cu 2 S/Gr@GCE) with excellent Pb(II) ion sensing activity. Moreover, the sensitivity, detection, and quantification limits of the modified electrode for Pb(II) detection were computed to be 88.68 μAμMcm −2 , 0.091 μM, and 0.30 μM, respectively. The key features developed in the metal sulfide for its enhancement of electrochemical sensing activity are a high surface area, good conductivity, and fast electron transport by adopting nanotechnology, metal doping, and composite formation methodologies. Based on the results of the experiments, we can say that using multiple inputs to integrate the feature we want is an excellent way to make electrochemical systems for the next generation.