Synthesis and antibacterial activity of nanoenhanced conjugate of Ag-doped ZnO nanorods with graphene oxide

Designing potent plasmonic Ag/TiO2 nanohetero-phase junction for visible light driven photo-catalysis and anti-bacterial effect

In this study, we have reported the impact of well-grown Ag nanoparticles on TiO2 nanofiber mat, focusing the efficiency in anti-bacterial properties with ROS generation. Herein, the nanoheterostructure sample was achieved using electrospinning technique, followed by a solvothermal approach. The core focus was based on the effect of growth of Ag nanoparticles by varying the solvothermal time as well as the molar weight of Ag precursor against both the anti-bacterial property with gram-negative (e.g. E. coli) and another gram-positive (e.g. E. faecalis) bacterium. Prior to the detailed anti-bacterial test, the morphological analysis and the heterojunction formation was thoroughly investigated which showed the clear growth of Ag nanoparticles upon altering the experimental parameters via HRTEM analysis. The investigation showed that superior antibacterial activity was exhibited for the higher Ag loaded heterojunction samples whereas there showed no effect in the absence of Ag nanoparticles for TiO2 nanofibers. This is basically due to the presence of higher superoxide radicals in the nanoheterojunction materials, which is proved by a systematic study using the NBT degradation test under dark and visible light environment. Moreover, this phenomenon can be elucidated by the surface plasmon resonance effect in Ag nanoparticles, which when illuminated under visible light generates electrons and is transferred to the conduction band of TiO2. This transfer promotes the generation of reactive oxygen species (ROS), resulting in the exceptional antibacterial properties observed in AgT-10 ˃ AgT-5 ˃ AgT-2.5 ˃ TiO2NF.

Fabrication of highly efficient ZnO-Pt catalysts assisted by biomass-derived carboxymethyl cellulose for the photodegradation of diverse antibiotics

Antibiotic contamination poses a substantial challenge to environmental, thereby necessitating the development of effective strategies for antibiotic elimination. This study utilized a hydrothermal reaction to incorporate the nano platinum (Pt) onto zinc oxide (ZnO), resulting in the formation of an efficient ZnO-Pt powder photocatalyst. Subsequently, biomass-derived carboxymethyl cellulose (CMC), modified via an acid-assisted freeze-thaw process, was employed as a matrix for fabricating the ZnO-Pt@CMC composite. Characterization of the synthesized materials was conducted using X-ray diffraction (XRD), Raman spectra (Raman), Fourier transform infrared spectrometer (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Afterwards, the photocatalytic performance of both ZnO-Pt and ZnO-Pt@CMC was assessed against a range of simulated antibiotic wastewater including sulfamethoxazole (SMX), ciprofloxacin (CIP), and oxytetracycline (OTC), under various conditions such as solution pH, catalyst dosage, antibiotic concentration, initial solution temperature, and light source. The ZnO-Pt catalyst demonstrated a degradation efficiency of 92.7 % for SMX within 180 min under xenon lamp irradiation, adhering to a pseudo-first-order kinetic model. Otherwise the ZnO-Pt@CMC exhibited degradation efficiencies of 80.6 % and 85.4 % for SMX and OTC over the same duration, while it demonstrated an exceptionally high photodegradation efficiency of 94.9 % for CIP and maintained its activity even after three consecutive cycles of use. Electrochemical impedance spectroscopy (EIS), linear scanning voltammetry (LSV), and radical quenching experiments showed that the introduction of Pt or CMC could increased the transfer and separation rate of ·OH and ·O2- during the photocatalytic degradation, along with a reasonable proposed degradation pathway for SMX.

Multispectral analysis and molecular docking of a zinc (II) complex interaction with bovine serum albumin and studies on antibacterial properties, and catecholase mimicry of the complex

This paper presents the synthesis process of a ligand known as 2-(naphthalene-1-yl)-1H-phenanthro[9,10-d]imidazole (NIP) and its metal complex with zinc (II), denoted as FA-128. The structural validation of FA-128 is accomplished through single-crystal X-ray diffraction (XRD). To explore the biological implications, FA-128's interaction with BSA is investigated. This exploration involves fluorescence and UV-vis absorption spectrometry techniques. The outcomes reveal the formation of robust complexes, as FA-128 significantly quenches the inherent fluorescence of BSA. Various aspects are examined, including binding constants, the count of binding sites, thermodynamic parameters, and energy transfer mechanisms. Evident alterations in BSA conformation are detected using synchronous fluorescence and circular dichroism (CD) spectrum techniques. The study proceeds to molecular docking, elucidating binding sites in the FA-128-BSA interaction. Biochemical reactions between metal complexes and proteins often trigger diverse conformational changes in protein structures. This understanding provides crucial insights into the impacts, mechanisms, and systemic transportation of numerous drugs within the body. FA-128 demonstrated superior antibacterial activity against Staphylococcus aureus (ZOI: 10.50 ± 0.50 mm, MIC: 100 μg/mL) and Klebsiella pneumoniae (ZOI: 13.0 ± 0.25 mm, MIC: 50 μg/mL). In addition, FA-128 has been evaluated as a catalytic system in the oxidation of 3,5-di-tert-butylcatechol (3,5DTBC) in a methanol solvent. FA-128 displays good catecholase-like activity with a significant turnover number (kcat) of 7.56 × 102 h-1, a Michaelis-Menten constant (KM) of 8.14 × 10-4 M, and a maximum reaction rate (Vmax) of 2.45 × 10-5 M s-1 under aerobic conditions.

Comparative analysis of the antimicrobial activity and dye degradation of metal oxides (TiO2, CdO, Mn2O3, and ZnO) nanoparticles using a green approach

A tremendous amount of recent work has been done on different metal oxide nanomaterials for biological activities and photocatalytic dye degradation. This work used the Cissus quadrangularis leaf extract to prepare TiO2, CdO, Mn2O3, and ZnO nanoparticles using a green synthesis approach. To ascertain the physicochemical characteristics of the generated metal oxide nanoparticles, various characterisation techniques were used. The X-ray diffraction technique was used to determine the composition of the crystal and phase. Metal oxide nanoparticles have been proven to be present through surface morphological investigations using a scanning electron microscope and energy dispersive spectroscopy analysis. UV-Vis and Fourier transform infrared spectra were used for spectroscopic analysis. X-ray photoelectron spectroscopy can determine a material's elemental composition in addition to the electronic and chemical states of its atoms. The nanomaterial's distinct morphology, which resembles rods, rose petals, platelets, and spheres, was discovered by scanning electron microscope. Synthesized metal oxide nanoparticles have demonstrated a remarkable efficiency of 87.5-90.6% when utilized as a catalyst towards the removal of the malachite green dye under UV light irradiation. Additionally, we use the disc diffusion method to assess antibiotic efficacy against Bacillus subtilis, Candida tropicalis, and Escherichia coli. ZnO nanoparticles had the greatest zones of inhibition for 80 μL doses, measuring 26.99 mm for Bacillus subtilis, 27.57 mm for Escherichia coli, and 25.28 mm for Candida tropicalis. The antimicrobial activity was strongly impacted by the size of the nanoparticles and increased with decreasing particle size. Overall, our research demonstrates that metal oxide nanoparticles are a promising photocatalytic agent for wastewater treatment and biological applications.

Green Synthesis of ZnO Nanoparticles and Ag-Doped ZnO Nanocomposite Utilizing Sansevieria trifasciata for High-Performance Asymmetric Supercapacitors

This study provides a comprehensive analysis of a biofabricated nanomaterial derived from Sansevieria trifasciata root extract, evaluating its structural, morphological, and optical properties for use in asymmetric supercapacitors. The nanomaterial comprises pristine ZnO nanoparticles (ZnO NPs) and a 1% Ag-doped ZnO nanocomposite (Ag@ZnO NC), synthesized through a green-assisted sol-gel autocombustion method. Employing techniques such as X-ray diffraction, ultraviolet-visible near-infrared, scanning electron microscopy-energy-dispersive X-rayspectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy, the study confirms a hexagonal wurtzite structure and nanocrystallites with spherical and hexagonal shapes (30 nm). Optical analysis reveals a red shift in the band gap with Ag doping, indicating improved conductivity. The material shows potential applications in solar cells, optoelectronics, spintronics, wastewater treatment, and high-performance asymmetric supercapacitors. Raman spectra validate the wurtzite phase and identify intrinsic defects. Electrochemical tests demonstrate remarkable supercapacitive behavior with a 94% capacitance retention after 10,000 cycles, highlighting its promise as advanced asymmetric supercapacitors.

Amelioration of phytotoxic impact of biosynthesized zinc oxide nanoparticles: Plant growth promoting rhizobacteria facilitates the growth and biochemical responses of Eggplant (Solanum melongena) under nanoparticles stress

The consistently increasing use of zinc oxide nanoparticles (ZnONPs) in crop optimization practices and their persistence in agro-environment necessitate expounding their influence on sustainable agro-environment. Attempts have been made to understand nanoparticle-plant beneficial bacteria (PBB)- plant interactions; the knowledge of toxic impact of nanomaterials on soil-PBB-vegetable systems and alleviating nanotoxicity using PBB is scarce and inconsistent. This study aims at bio-fabrication of ZnONPs from Rosa indica petal extracts and investigates the impact of PBB on growth and biochemical responses of biofertilized eggplants exposed to phyto-synthesized nano-ZnO. Microscopic and spectroscopic techniques revealed nanostructure, triangular shape, size 32.5 nm, and different functional groups of ZnONPs and petal extracts. Inoculation of Pseudomonas fluorescens and Azotobacter chroococcum improved germination efficiency by 22% and 18% and vegetative growth of eggplants by 14% and 15% under NPs stress. Bio-inoculation enhanced total chlorophyll content by 36% and 14 %, increasing further with higher ZnONP concentrations. Superoxide dismutase and catalase activity in nano-ZnO and P. fluorescens inoculated eggplant shoots reduced by 15-23% and 9-11%. Moreover, in situ experiment unveiled distortion and accumulation of NPs in roots revealed by scanning electron microscope and confocal laser microscope. The present study highlights the phytotoxicity of biosynthesized ZnONPs to eggplants and demonstrates that PBB improved agronomic traits of eggplants while declining phytochemicals and antioxidant levels. These findings suggest that P. fluorescens and A. chroococcum, with NPs ameliorative activity, can be cost-effective and environment-friendly strategy for alleviating NPs toxicity and promoting eggplant production under abiotic stress, fulfilling vegetable demands.

Photocatalytic degradation of antibiotics and antimicrobial and anticancer activities of two-dimensional ZnO nanosheets

Active pharmaceutical ingredients have emerged as an environmentally undesirable element because of their widespread exploitation and consequent pollution, which has deleterious effects on living things. In the pursuit of sustainable environmental remediation, biomedical applications, and energy production, there has been a significant focus on two-dimensional materials (2D materials) owing to their unique electrical, optical, and structural properties. Herein, we have synthesized 2D zinc oxide nanosheets (ZnO NSs) using a facile and practicable hydrothermal method and characterized them thoroughly using spectroscopic and microscopic techniques. The 2D nanosheets are used as an efficient photocatalyst for antibiotic (herein, end-user ciprofloxacin (CIP) was used as a model antibiotic) degradation under sunlight. It is observed that ZnO NSs photodegrade ~ 90% of CIP within two hours of sunlight illumination. The molecular mechanism of CIP degradation is proposed based on ex-situ IR analysis. Moreover, the 2D ZNO NSs are used as an antimicrobial agent and exhibit antibacterial qualities against a range of bacterial species, including Escherichia coli, Staphylococcus aureus, and MIC of the bacteria are found to be 5 μg/l and 10 μg/l, respectively. Despite having the biocompatible nature of ZnO, as-synthesized nanosheets have also shown cytotoxicity against two types of cancer cells, i.e. A549 and A375. Thus, ZnO nanosheets showed a nontoxic nature, which can be exploited as promising alternatives in different biomedical applications.

Antibacterial, antioxidant and fruit packaging ability of biochar-based silver nanoparticles-polyvinyl alcohol-chitosan composite film

Silver nanoparticles were prepared by loading Ag+ into biochar of waste barley distillers' grains shell by reduction with trisodium citrate, and this silver-loaded biochar was introduced into polyvinyl alcohol-chitosan. Various analysis with Fourier Transform Infrared spectroscopy, X-ray diffraction, Thermogravimetric analysis, and water contact angle revealed that biochar-based silver nanoparticle was incorporated into the polyvinyl alcohol-chitosan film, the biochar-based silver nanoparticles-polyvinyl alcohol-chitosan (C-Ag-loaded PVA/CS) composite film had good thermostability and hydrophobicity. Through the analysis via disk diffusion method, the composite containing 3 % of biochar-based silver nanoparticles-polyvinyl alcohol-chitosan had high antibacterial activity (inhibition zone: 18 mm against E. coli and 15 mm against S. aureus), and the bacterial membrane permeability was measured, indicating that C-Ag-loaded PVA/CS composite film could destroy the cell membrane, release intracellular substances, and have high antioxidant activity. During the storage, the weight loss rate of the biochar-based silver nanoparticles-polyvinyl alcohol-chitosan plastic wrap group was 0.14 %, and the titratable acid content only decreased by 0.061 %, which had a good effect on extending the shelf life of blueberries. The C-Ag-loaded PVA/CS composite film could also delay deterioration of blueberries and prolong storage time. Overall, this composite film had potential in food packaging and extending food shelf-life aspects.

Structural, optical, morphological, sun-light driven photocatalytic and antimicrobial investigations of Ag2S and Cu/Ag2S nanoparticles

This study focusses on the preparation of silver sulphide (Ag2S) and Cu-doped Ag2S (Cu/Ag2S) nanoparticles (NPs) by sol-gel method and demonstrated their photocatalytic and antibacterial applications. The X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) analysis demonstrated that the prepared NPs are effectively crystallized in the polycrystalline single-phase monoclinic geometry of Ag2S. The optical bandgap is significantly reduced, and for both the sample the average grain size is observed to have narrowed from 42 nm to 23 nm. Both NPs were confirmed to be spherical nature as observed by scanning electron microscopy (SEM), and the energy dispersive X-ray (EDX) spectroscopy analysis validated the presence of all necessary components at the expected concentrations in the obtained samples. Under the irradiation of sunshine, the photocatalytic properties of each sample were investigated for their ability to facilitate the photodegradation of a hazardous methylene blue (MB) dye in an aqueous solution. Cu/Ag2S sample possesses a profound photocatalytic reaction for the destruction of MB dye. Furthermore, the Cu-doped Ag2S NPs suppress the proliferation of Staphylococcus aureus and Escherichia coli. In comparison to pure Ag2S NPs, Cu/Ag2S showed enhanced antibacterial activity against both the bacteria. Current study suggests that the Cu doped Ag2S NPs could be a promising material for wastewater treatment and antimicrobial agents.

Ramegouda N, Puthiyillam P, Hasan MA, Islam S, Koradoor VB, Praveen AD, Khan MA. GO/CuO Nanohybrid-Based Carbon Dioxide Gas Sensors with an Arduino Detection Unit

A gas sensor is a device that detects the presence of gases in a specific area. This research work demonstrates the effectiveness of gas sensors based on graphene oxide (GO) and copper oxide (CuO) semiconductor nanomaterials for the detection of carbon dioxide. GO and CuO were prepared by the modified Hummer's method and precipitation method using CuCl2 as a precursor, respectively. These materials are made into a hybrid using poly(vinyl alcohol) (PVA)/poly(vinylpyrrolidone) (PVP) polymer solutions of low concentrations and are spin coated onto the pattern-etched copper-clad substrate. The sensor is tested using a source measurement unit (SMU) to obtain the change in the resistance of the sensor in open air and in a carbon dioxide environment. The fabricated sensor with an Arduino microcontroller detection unit showed a good sensing response of 60%.

Tunable optical and semiconducting properties of eco-friendly-prepared reduced graphene oxide

Wide bandgap oxidized graphenes have garnered particular interest among the materials explored for these applications because of their exceptional semiconducting and optical properties. This study aims to investigate the tunability of the related properties in reduced graphene oxide (rGO) for potential use in energy conversion, storage, and optoelectronic devices. To accomplish this, we scrutinized crucial parameters of the synthesis process such as reduction time and temperature. Our findings demonstrate that controlling these parameters makes it possible to customize the optical bandgap of reduced graphene oxide within a range of roughly 2.2 eV-1.6 eV. Additionally, we observed that reduced graphene oxide has strong and superior absorption in the visible region, which is attributable to the existence of OFGs and defects. Notably, our results indicate that the absorption coefficients of reduced graphene oxide are up to almost three times higher (7426 ml mg-1 m-1) than those observed in dispersions of exfoliated graphene and graphene oxide (GO). To complement our findings, we employed several spectroscopic and morphological characterizations, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and electrical measurements. The implications of our results are significant for the development and design of future semiconductors for energy conversion and optoelectronic applications.

Temperature-Dependent Optical Properties of Oxidized Graphenes

In this study, we investigate how changing important synthesis-related parameters can affect and control the optical characteristics of graphene oxide (GO) and reduced graphene oxide (rGO). These parameters include drying time and reduction time at two different temperatures. We obtain an understanding of their impact on optical transitions, optical bandgap, absorption coefficient, and absorbance spectrum width by analyzing these factors. Accordingly, GO has an optical bandgap of about 4 eV, which is decreased by the reduction process to 1.9 eV. Both GO and rGO display greater absorption in the visible spectrum, which improves photon capture and boosts efficiency in energy conversion applications. Additionally, our results show that GO and rGO have higher absorption coefficients than those previously reported for dispersions of exfoliated graphene. Defects in GO and rGO, as well as the presence of functional oxygen groups, are the main contributors to this increased absorption. Several measurements are carried out, including spectroscopic and morphological studies, to further support our findings.

Enhanced photocatalytic performance of auto-combusted nanoparticles for photocatalytic degradation of azo dye under sunlight illumination and hydrogen fuel production

In this study, an innovative nanomaterial was synthesized for hydrogen production from methanolysis on sodium borohydride (NaBH₄) in order to be a solution for future energy problems. The nanocomposite containing FeCo, which does not contain noble metals, and whose support material is Polyvinylpyrrolidone (PVP), was synthesized by means of a thermal method. TEM, XRD and FTIR characterization methods were used for the analysis of the morphological and chemical structure of the nanocomposite. Nanocomposite particle size was 2.59 nm according to XRD and 5.45 nm according to TEM analysis for scale of 50 nm. For catalytic properties of nanomaterial in the methanolysis reaction of NaBH₄, temperature, catalyst, substrate, and reusability experiments were carried out and kinetic calculations were obtained. Among the activation parameters of FeCo@PVP nanoparticles, turnover frequency, enthalpy, entropy and activation energy were calculated as 3858.9 min^-1, 29.39 kJ/mol, -139.7 J/mol.K, and 31.93 kJ/mol, respectively. As a result of the reusability test of the obtained FeCo@PVP nanoparticles catalysts, which was carried out for 4 cycles, the catalytic activity was 77%. Catalytic activity results are given in comparison with the literature. In addition, the photocatalytic activity of FeCo@PVP NPs was evaluated against MB azo dye under solar light irradiation for 75 min and was found to be as 94%.

Bimetallic Biogenic Pt-Ag Nanoparticle and Their Application for Electrochemical Dopamine Sensor

In this study, Silver-Platinum (Pt-Ag) bimetallic nanoparticles were synthesized by the biogenic reduction method using plant extracts. This reduction method offers a highly innovative model for obtaining nanostructures using fewer chemicals. According to this method, a structure with an ideal size of 2.31 nm was obtained according to the Transmission Electron Microscopy (TEM) result. The Pt-Ag bimetallic nanoparticles were characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffractometry (XRD), and Ultraviolet-Visible (UV-VIS) spectroscopy. For the electrochemical activity of the obtained nanoparticles in the dopamine sensor, electrochemical measurements were made with the Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) methods. According to the results of the CV measurements taken, the limit of detection (LOD) was 0.03 µM and the limit of quantification (LOQ) was 0.11 µM. To investigate the antibacterial properties of the obtained Pt-Ag NPs, their antibacterial effects on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria were investigated. In this study, it was observed that Pt-Ag NPs, which were successfully synthesized by biogenic synthesis using plant extract, exhibited high electrocatalytic performance and good antibacterial properties in the determination of dopamine (DA).

Recent advances and mechanism of antimicrobial efficacy of graphene-based materials: a review

Graphene-based materials have undergone substantial investigation in recent years owing to their wide array of physicochemical characteristics. Employment of these materials in the current state, where infectious illnesses caused by microbes have severely damaged human life, has found widespread application in combating fatal infectious diseases. These materials interact with the physicochemical characteristics of the microbial cell and alter or damage them. The current review is dedicated to molecular mechanisms underlying the antimicrobial property of graphene-based materials. Various physical and chemical mechanisms leading to cell membrane stress, mechanical wrapping, photo-thermal ablation as well as oxidative stress exerting antimicrobial effect have also been thoroughly discussed. Furthermore, an overview of the interactions of these materials with membrane lipids, proteins, and nucleic acids has been provided. A thorough understanding of discussed mechanisms and interactions is essential to develop extremely effective antimicrobial nanomaterial for application as an antimicrobial agent.

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