Green Synthesis of Silver Nanoparticles Using Acacia ehrenbergiana Plant Cortex Extract for Efficient Removal of Rhodamine B Cationic Dye from Wastewater and the Evaluation of Antimicrobial Activity

Novel approach for green synthesis of stable gold nanoparticles with dried turmeric root extract: investigations on sensor and catalytic applications

In this study, we present the synthesis of gold nanoparticles (AuNPs) using a completely green synthesis method without the use of any additional functionalizing agent, except dried turmeric root extract. The significant synthesis parameters were optimized, and the applicability of AuNPs was investigated in areas such as plasmonic and fluorescent sensing of aluminum (Al3⁺) and chromium (Cr3⁺) ions, reduction of 4-nitrophenol (4-NP), and degradation of methylene blue (MB) and methyl orange (MO) dyes. Characterization studies were performed using UV-Vis spectroscopy, TEM, FTIR, and XRD, revealing that the AuNPs predominantly had a spherical morphology and a very small particle size of 8.5 nm, with stability maintained up to 120 days. The developed AuNP-based plasmonic sensors relied on aggregation-induced decreases in absorption, along with a red shift in the spectra. Fluorescence sensing demonstrated a linear increase in intensity with increasing concentrations of Al3⁺ and Cr3⁺, with detection limits of 0.83 and 1.19 nM, respectively. The catalytic activities of AuNPs were tested in reducing 4-NP and degradations of MB and MO dyes (binary system) in tap water and wastewater, with the reactions following pseudo-first-order kinetics. This study highlights the potential of AuNPs synthesized from turmeric roots for various environmental and sensing applications.

Crystallographic structure, antibacterial effect, and catalytic activities of fig extract mediated silver nanoparticles

Silver nanoparticles (Ag NPs) play a pivotal role in the current research landscape due to their extensive applications in engineering, biotechnology, and industry. The aim is to use fig (Ficus hispida Linn. f.) extract (FE) for eco-friendly Ag NPs synthesis, followed by detailed characterization, antibacterial testing, and investigation of bioelectricity generation. This study focuses on the crystallographic features and nanostructures of Ag NPs synthesized from FE. Locally sourced fig was boiled in deionized water, cooled, and doubly filtered. A color change in 45 mL 0.005 M AgNO3 and 5 mL FE after 40 min confirmed the bio-reduction of silver ions to Ag NPs. Acting as a reducing and capping agent, the fig extract ensures a green and sustainable process. Various analyses, including UV-vis absorption spectrophotometry (UV), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDX) and Transmission electron microscopy (TEM) were employed to characterize the synthesized nanoparticles, and Gas chromatography-mass spectrometry (GC-MS) analysis of the fig extract revealed the presence of eleven chemicals. Notably, the Ag NPs exhibited a surface plasmon resonance (SPR) band at 418 nm, confirmed by UV analysis, while FTIR and XRD results highlighted the presence of active functional groups in FE and the crystalline nature of Ag NPs respectively. With an average particle size of 44.57 nm determined by FESEM and a crystalline size of 35.87 nm determined by XRD, the nanoparticles showed strong antibacterial activities against Staphylococcus epidermidis and Escherichia coli. Most importantly, fig fruit extract has been used as the bio-electrolyte solution to generate electricity for the first time in this report. The findings of this report can be the headway of nano-biotechnology in medicinal and device applications.

Fabrication of a sustainable superhydrophobic surface of Ag-NPs@SA on copper alloy for corrosion resistance, photocatalysis, and simulated distribution of Ag atoms

Artificial superhydrophobic surfaces that do not absorb water, like the lotus leaf, show tremendous promise in numerous applications. However, superhydrophobic surfaces are rarely used because of their low stability and endurance. A stable organic superhydrophobic surface (SHS) composed of novel morphology Ag-nanoparticles (NPs) has been fabricated on a copper alloy via etching, immersion, spraying, and annealing treatment, along with a static water contact angle (WCA) of 158 ± 1° and sliding angle (SA) less than 2°. The surface texture, composition, and morphology of the substrate surfaces were explored by using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and DFT-based Ag atom distribution. The anti-corrosion study of non-coated and Ag-NP-coated copper alloy was undertaken using electrochemical impedance spectroscopy. Ag-NPs +SA@SHS enhanced the corrosion resistance as compared with bare Cu alloy. The water droplet rolled down the coated Cu alloy, removed the chalk powder from the surface, and indicated an excellent self-cleaning function. Photodegradation of Congo red (CR) and methylene blue (MB) dye samples was assessed by measuring the absorbance through UV-Visible spectrophotometry, where the Ag-NPs coated on the copper alloy were used as a catalyst. The performance of the SHS@Ag-NPs in the aqueous solution was 99.31% and 98.12% for industrial pollutants (CR and MB), with degradation rates of 5.81 × 10-2 s-1 and 5.89 × 10-2 s-1, respectively. These findings demonstrated a simple, rapid, and low-energy fabrication technique for SHS@Ag-NPs. This research reveals a valuable approach for the fabrication of SHS@Ag-NPs on various substrates to extend the superhydrophobic surfaces with ultra-fast self-healing properties, for outdoor applications such as anti-corrosion, for an innovative approach for the remediation of polluted water treatment, and for industrial applications.

Green route to fabrication of Semal-ZnO nanoparticles for efficient solar-driven catalysis of noxious dyes in diverse aquatic environments

This work successfully demonstrates a sustainable and environmentally friendly approach for synthesizing Semal-ZnO nanoparticles (NPs) using the aqueous leaf extract of Bombax ceiba L. These NPs exhibit an absorption peak at approximately 390 nm in the UV-visible spectrum and an energy gap (Eg) of 3.11 eV. Detailed analyses of the morphology and particle size using various spectroscopic and microscopic techniques, XRD, FE-SEM with EDS, and HR-TEM reveal crystallographic peaks attributable to the hexagonal phase, with an average crystal size of 17 nm. The Semal-ZnO NPs also exhibit a notable photocatalytic efficiency for degrading methylene blue (MB) and methyl orange (MO) under sunlight in different water samples collected from diverse natural sources, indicating that they are promising photocatalysts for environmental remediation. The photocatalytic efficiency of the biofabricated Semal-ZnO NPs is impressive, exhibiting a photodegradation rate of up to 99% for MB and 79% for MO in different water samples under exposure to sunlight. The novel phytofabricated Semal-ZnO NPs are thus a beacon of hope for the environment, with their desirable photocatalytic efficiency, pseudo-first-order kinetics, and ability to break down noxious dye pollutants in various aquatic environments.

Elucidating the structural, catalytic, and antibacterial traits of Ficus carica and Azadirachta indica leaf extract-mediated synthesis of the Ag/CuO/rGO nanocomposite

The present exploration demonstrates the efficient, sustainable, cost-effective, and environment-friendly green approach for the synthesis of silver (Ag)-doped copper oxide (CuO) embedded with reduced graphene oxide (rGO) nanocomposite using the green one-pot method and the green deposition method. Leaf extracts of Ficus carica and Azadirachta indica were used for both methods as reducing and capping agents. The effect of methodology and plant extract was analyzed through different characterization techniques such as UV-visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM). The lowest band gap of 3.0 eV was observed for the Ag/CuO/rGO prepared by the green one-pot method using F. carica. The reduction of graphene oxide (GO) and the formation of metal oxide was confirmed through functional group detection using FT-IR. Calculation of thermodynamic parameters showed that all reactions involved were nonspontaneous and endothermic which shows the stability of nanocomposites. XRD studies revealed the crystallinity, phase purity and small average crystallite size of 32.67 nm. SEM images disclosed that the morphology of the nanocomposites was spherical with agglomeration and rough texture. The particle size of the nanocomposites calculated through HRTEM was found in agreement with the XRD results. The numerous properties of the synthesized nanocomposites enhanced their potential against the degradation of methylene blue, rhodamine B, and ciprofloxacin. The highest percentage degradation of Ag/CuO/rGO was found to be 97%, synthesized using the green one-pot method with F. carica against ciprofloxacin, which might be due to the lowest band gap, delayed electron-hole pair recombination, and large surface area available. The nanocomposites were also tested against the Gram-positive and Gram-negative bacteria. RESEARCH HIGHLIGHTS: Facile synthesis of Ag/CuO/rGO nanocomposite using a green one-pot method and the green deposition method. The lowest band gap of 3.0 eV was observed for nanocomposite prepared by a green one-pot method using Ficus carica. Least average crystallite size of 32.67 nm was found for nanocomposite prepared by a green one-pot method using F. carica. Highest antibacterial and catalytic activity (97%) was obtained against ciprofloxacin with nanocomposite prepared through green one-pot method using F. carica. A mechanism of green synthesis is proposed.

Preparation of CS-LS/AgNPs Composites and Photocatalytic Degradation of Dyes

Synthetic dyes are prone to water pollution during use, jeopardizing biodiversity and human health. This study aimed to investigate the adsorption and photocatalytic assist potential of sodium lignosulfonate (LS) in in situ reduced silver nanoparticles (AgNPs) and chitosan (CS)-loaded silver nanoparticles (CS-LS/AgNPs) as adsorbents for Rhodamine B (RhB). The AgNPs were synthesized by doping LS on the surface of chitosan for modification. Fourier transform infrared (FT-IR) spectrometry, energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to confirm the synthesis of nanomaterials. The adsorption and photocatalytic removal experiments of RhB were carried out under optimal conditions (initial dye concentration of 20 mg/L, adsorbent dosage of 0.02 g, time of 60 min, and UV power of 250 W), and the kinetics of dye degradation was also investigated, which showed that the removal rate of RhB by AgNPs photocatalysis can reach 55%. The results indicated that LS was highly effective as a reducing agent for the large-scale production of metal nanoparticles and can be used for dye decolorization. This work provides a new catalyst for the effective removal of dye from wastewater, and can achieve high-value applications of chitosan and lignin.

Citrate silver nanoparticles impregnated cellulose as a photocatalytic filter in the degradation of organic dye in the aqueous media

Photocatalysis is a clean and efficient process pursued under light irradiation with a suitable photocatalyst to degrade a contaminant. We report citrate functionalization of silver nanoparticles (SNPs) for effective immobilization on cellulosic fabric. The porous cellulosic matrix could be explored as microfiltration membranes for the photocatalytic degradation of organic dyes in the aqueous media. Where valid, the citrate functionalized SNPs and the treated cellulose fabrics were considered for optical, structural, surface chemical, thermal, textile, flowability, photocatalytic, and antibacterial attributes. The SNPs expressed the bandgap energy of 2.56 and 2.43 eV and Urbach energy of 3.38 and 5.21 eV before and after functionalization with the citrate moieties, respectively. The liquid chromatographic and FTIR analyses indicated that the crystal violet (CV) organic dye has been successfully photodegraded to environmentally safer and nontoxic species on passing the contaminated water through the SNPs-treated cellulosic filter. The spectroscopic data also supported the said outcomes. The results demonstrated that the citrate-SNPs-treated cellulose could be efficiently employed as antibacterial photocatalytic membranes for degrading organic dyes in the aqueous media for multiple cycles.

Development of environmentally friendly catalyst Ag-ZnO@cellulose acetate derived from discarded cigarette butts for reduction of organic dyes and its antibacterial applications

The release of harmful organic dyes from different industries besides its degradation products is a major contributor to environmental contamination. The catalytic reduction of these organic pollutants using nanocomposites based on polymeric material presents potential advantages for the environment. In this study, novel nanocomposite based on cellulose acetate (CA)-derived from discharged cigarette butts and zinc oxide nanoparticles (ZnO NPs) was prepared utilizing a very simple and low-cost solution blending method and used as support for silver nanoparticles (Ag NPs). A simple reduction method was used to anchor different percentages of Ag NPs on the ZnO@CA nanocomposite surface via utilizing sodium borohydride as a reducing agent. The Ag-ZnO@CA nanocomposite was characterized using X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy. The TEM analysis showed spherical Ag NPs, with an average diameter of ∼17.6 nm, were uniformly anchored on the ZnO@CA nanocomposite surface. The prepared nanocomposites were evaluated as catalysts for the reduction of organic dyes in water. It was found that 10 % Ag-ZnO@CA nanocomposite showed a remarkable reduction of Rhodamine B (RhB), Rhodamine 6G (Rh6G), Methylene Blue (MB), and Sunset Yellow (SY) dyes in short time. In the presence of this nanocomposite, the rate constant, kapp values for RhB, Rh6G, MB, and SY were 0.3498 min-1, 1.51 min-1, 0.2292 min-1, and 0.733 min-1, respectively. This nanocomposite was recovered and reused in five successive cycles, with a negligible loss of its activity. Furthermore, the nanocomposites demonstrated moderate antibacterial activity toward Staphylococcus aureus and Escherichia coli. Thus, this study directed attention on recycling of waste material to a valuable nanocomposite and its applications in environmental protection.

Green Synthesis of TiO2 Using Impatiens rothii Hook.f. Leaf Extract for Efficient Removal of Methylene Blue Dye

In this work, TiO2 nanoparticles (NPs) were effectively synthesized by a green method using the Impatiens rothii Hook.f. leaf (IL) extract as a capping and reducing agent. The as-synthesized TiO2 NPs were characterized by different characterization methods such as the Brunauer-Emmett-Teller (BET) analysis, high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), diffused reflectance spectroscopy (DRS), and X-ray diffraction (XRD) and Raman spectroscopy. The specific surface area from BET analysis was found to be 65 m2/g. The average crystallite size from XRD analysis and average particle size from SEM analysis were found to be ∼11 and ∼25 nm, respectively. The Raman spectroscopy and XRD results showed that the biosynthesized (IL-TiO2) nanoparticles were purely anatase phase. XPS analysis illustrated the formation of Titania with an oxidation state of +4. The DRS study showcased that a blue-shifted intense absorption peak of IL-TiO2 (3.39 eV) compared to the bulk material reported in the literature (3.2 eV). HRTEM micrograph showed the presence of grain boundary with d spacings of 0.352, 0.245, and 0.190, which correspond to the lattice planes of (101), (004), and (200), respectively. From the EDX analysis, the weight percents of titanium and oxygen were found to be 54.33 and 45.67%, respectively. The photoinduced degradation of methylene blue (MB) dye was investigated in the presence of biosynthesized IL-TiO2 NPs photocatalyst. The effect of parameters like catalyst dosage (30 mg/L), initial concentration of MB (15 ppm), pH (10.5), and contact time (100 min) on the removal efficiency was optimized. The maximum photodegradation efficiency under the optimized conditions was found to be 98%.