A review of physical, chemical and biological synthesis methods of bimetallic nanoparticles and applications in sensing, water treatment, biomedicine, catalysis and hydrogen storage

This article provides an in-depth analysis of various fabrication methods of bimetallic nanoparticles (BNP), including chemical, biological, and physical techniques. The review explores BNP's diverse uses, from well-known applications such as sensing water treatment and biomedical uses to less-studied areas like breath sensing for diabetes monitoring and hydrogen storage. It cites results from over 1000 researchers worldwide and >300 peer-reviewed articles. Additionally, the article discusses current trends, actionable recommendations, and the importance of synthetic analysis for industry players looking to optimize manufacturing techniques for specific applications. The article also evaluates the pros and cons of various fabrication methods, highlighting the potential of plant extract synthesis for mass production of capped BNPs. However, it warns that this method may not be suitable for certain applications requiring ligand-free surfaces. In contrast, physical methods like laser ablation offer better control and reactivity, especially for applications where ligand-free surfaces are critical. The report underscores the environmental benefits of plant extract synthesis compared to chemical methods that use hazardous chemicals and pose risks to extraction, production, and disposal. The article emphasizes the need for life cycle assessment (LCA) articles in the literature, given the growing volume of research on nanotechnology materials. This article caters to researchers at all stages and applies to various fields applying nanomaterials.

Size controlled silver nanoparticles on β-cyclodextrin/graphitic carbon nitride: an excellent nanohybrid material for SERS and catalytic applications

A nanohybrid (NH), having high dispersion of silver nanoparticles (AgNPs) on β-cyclodextrin (β-CD)/graphitic carbon nitride (g-CN), designated as AgNPs/β-CD/g-CN-NH, was synthesized and characterized. It was exploited for a couple of environmental remediation applications like SERS sensing and catalytic reduction of specific organic pollutants in water. It showed excellent SERS activity as a Raman probe for the detection of malachite green (MG). Its enhancement factor (EF) and detection limit for MG were equal to 7.26 × 10⁶ and 1 × 10^-9 M, respectively. The relative standard deviation (RSD) was equal to 3.8% which indicates high homogeneity of AgNP dispersion and signal reproducibility of the SERS substrate. The NH displayed high catalytic activity for the reduction of eosin yellow (EY) in the presence of NaBH₄ with the rate constant (k) of 0.1142 min^-1. A comparison of the present NH with other reported materials reveals better SERS and catalytic activities of the former than those of the latter. The SERS activity of the NH was also examined for sensing of other triphenylamine dyes like methyl violet (MV), and it was successful. The same NH also exhibited high catalytic activity towards the reduction of Congo red (CR). The results of both studies clarify that the NH is an excellent SERS substrate and efficient catalyst for the detection of organic environmental pollutants having structures similar to MG and their degradation. This is due to the distribution of the controlled size of AgNPs on g-CN promoted by β-CD. Therefore, we focus our attention on future environmental applications of the nanohybrid as a very cheap SERS substrate and a very active catalyst.

Microwave assisted green synthesis of silver nanoparticles for optical, catalytic, biological and electrochemical applications

Plant-derived nanoparticles have multi-functionalities owing to their ecological origin and biocompatible nature. A novel and stable silver nanoparticle (AgNP) was reported here using Cyanthillium cinereum (C. cinereum) as a reducing as well as capping agent by rapid microwave-assisted green method. The synthesized nanoparticles revealed their crystalline and spherical nature with an average size of 19.25 ± 0.44 nm in HR-TEM analysis. The excitation of electrons from occupied d-bands to states above the Fermi level while employing photoluminescence studies of AgNP indicated their awesome optical properties. Rapid decomposition of dangerous organic dyes like methylene blue and fuchsine in the catalytic presence of AgNP was evidenced from simple UV-visible spectral analysis. In vitro antioxidant potential assessed by DPPH assay indicated an IC50 value of 40.80 ± 0.14 μg/mL for the new AgNP. A substantial control on the growth of pathogenic bacteria such as Staphylococcus aureus and Klebsiella pneumonia can be achieved by synthesized nanoparticles as demonstrated by the well diffusion method. AgNP was also functioned as a non-enzymatic electrochemical sensor with a sharp oxidation peak with peak potentials at 0.366 V and it has a wide application as a bio sensor in neurobiology especially in the detection of neurotransmitters like dopamine with high sensitivity.

Prospective Application of Nanoparticles Green Synthesized Using Medicinal Plant Extracts as Novel Nanomedicines

The use of medicinal plants in green synthesis of metal nanoparticles is increasing day by day. A simple search for the keywords "green synthesis" and "nanoparticles" yields more than 33,000 articles in Scopus. As of August 10, 2021, more than 4000 articles have been published in 2021 alone. Besides demonstrating the ease and environmental-friendly route of synthesizing nanomaterials, many studies report the superior pharmacological properties of green synthesized nanoparticles compared to those synthesized by other methods. This is probably due to the fact that bioactive molecules are entrapped on the surface of these nanoparticles. On the other hand, recent studies have confirmed the nano-dimension and biocompatibility of metal ash (Bhasma) preparations, which are commonly macerated with biological products and administered for the treatment of various diseases in Indian medicine since ancient times. This perspective article argues for the prospective medical application of green nanoparticles in the light of Bhasma.

Comparation of the phytotoxicity between chemically and green synthesized silver nanoparticles

Green synthesis of silver nanoparticles (Ag NPs) by using plants extracts has provided an eco-friendly alternation for industry and agriculture application. Here, we prepared Ag NPs by using the cucumber leaves and rice husk extracts, and further assessed the antimicrobial activity and phytotoxicity of green synthesized Ag NPs (g-Ag NPs) comparing with chemically synthesized Ag NPs (chem-Ag NPs). The chem-Ag NPs had strong antibacterial activity on the growth of Escherichia coli, while g-Ag NPs by rice husks (gr-Ag NPs) exhibited long-term antibacterial effects. In terms of phytotoxicity, the chem-Ag NPs induced over-generation of ROS and activated plant antioxidant defense systems, thus resulting in the upregulation of MDA and Zn contents and downregulation of antioxidant capacity, carotenoid, globulin and Mo contents. However, g-Ag NPs significantly promoted cucumber photosynthesis by increasing chlorophyll contents. Besides, the green synthesized Ag NPs by cucumber extracts (gc-Ag NPs) increased protein contents and gr-Ag NPs stimulated the upregulation of Mn and the downregulation of Al, which were all positive effects. Overall, compared with chem-Ag NPs, g-Ag NPs exhibited long-tern antimicrobial properties and attenuated toxicity to plants, which could be used as potential nanopesticide or nanoscale growth regulator in agriculture.

Utilizing waste corn-cob in biosynthesis of noble metallic nanoparticles for antibacterial effect and catalytic degradation of contaminants

In the present study, cost-effective, and environmentally friendly fabrication of silver and gold nanoparticles was performed by using aqueous extract of waste corn-cob. The formation of the metallic nanoparticles (MNPs) was optimized by UV-Vis method. The phytoconstituents were responsible for reduction of silver and gold ions to silver nanoparticles (CC-AgNPs) and gold nanoparticles (CC-AuNPs) which were demonstrated by Fourier-transform infrared (FTIR) spectroscopy while formation of AgCl was attributed to the presence of chloride ions in the aqueous extract. The crystalline nature of the AgNPs, AgCl, and AuNPs was confirmed using the X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns. Morphological studies showed that the synthesized CC-AgNPs existed in spherical shape with the size ranging from 2 to 28 nm possessing an average value of 11 nm while CC-AuNPs were present in the multiple shapes with size ranging from 5 to 50 nm possessing an average value of 35 nm. For studies on bioactive application, the CC-AgNPs exhibited a high antibacterial activity against three bacterial strains including Salmonella typhimurium, Bacillus cereus, and Staphylococcus aureus. In addition, the catalytic efficiency of MNPs was investigated for reduction of o-, m-, p-nitrophenols, and degradation of organic dyes including Eosin Y and Rhodamine 6G. The rate constants calculated from the kinetical data revealed that the biosynthesized nanoparticles are excellent catalysts in potential applications for treatment of wastewater. Graphical abstract .

Sustainable synthesis of silver nanoparticles using exposed X-ray sheets and forest-industrial waste biomass: Assessment of kinetic and catalytic properties for degradation of toxic dyes mixture

Silver being the precious metal, its recovery from the waste and utilization is a worthy attempt. The present study represents a very promising sustainable approach for the synthesis of silver nanoparticles (AgNPs), where prime raw materials are waste products (silver metal extracted from waste X-ray sheets and Sal deoiled seed cake (DOC), a plant-based waste as reducing-capping agent). Upon reaction of silver nitrate extracted from waste X-ray sheets and Sal DOC extract at room temperature, the characteristic yellowish-brown color appeared within 30 min. Peak at 485-495 in UV-visible spectrophotometer confirmed the synthesis of AgNPs. X-ray waste synthesized (XRWS) AgNPs were polycrystalline in nature and have face centered cubic (fcc) lattice. Majority of them were polygonal in shape (size range 30-150 nm) with some flower like aggregates as revealed by Transmission Electron Microscope. The XRWS-AgNPs were stabilized by organic groups adhered to their surface and had good stability with a zeta potential of -27.60 mV. These XRWS-AgNPs could work as an efficient catalyst for the reduction of five selected azo dyes individually as well as mixture of these dyes. The degraded products of the individual dyes were identified using Gas Chromatography Mass Spectroscopy. Experimental values obtained for dye degradation study were fitted with first and second order linear kinetic model to know about rate of the reaction.

Multifunctionality of gold nanoparticles: Plausible and convincing properties

In a couple of decades, nanotechnology has become a trending area in science due to it covers all subject that combines diverse range of fields including but not limited to chemistry, physics and medicine. Various metal and metal oxide nanomaterials have been developed for wide range applications. However, the application of gold nanostructures and nanoparticles has been received more attention in various biomedical applications. The unique property of gold nanoparticles (AuNPs) is surface plasmon resonance (SPR) that determine the size, shape and stability. The wide surface area of AuNPs eases the proteins, peptides, oligonucleotides, and many other compounds to tether and enhance the biological activity of AuNPs. AuNPs have multifunctionality including antimicrobial, anticancer, drug and gene delivery, sensing applications and imaging. This state-of-the-art review is focused on the role of unique properties of AuNPs in multifunctionality and its various applications.

Microwave-assisted Synthesis of Hexagonal Gold Nanoparticles Reduced by Organosilane (3-Mercaptopropyl)trimethoxysilane

A novel synthesis of hexagonal gold nanoparticles (Au NPs) via hydrolyzed organosilane (3-mercaptopropyl)trimethoxysilane (MPTMS) using an ultrafast and environmentally friendly method is presented in this study. For the first time, organosilane MPTMS is used for chemical reduction of auric acid under ultrafast microwave irradiation. To the best of our knowledge, the use of organosilane for the synthesis of Au NPs has not been reported. The entire one-step process is convenient, rapid and cost-effective, as well as eco-friendly under alcohol-free aqueous media. Different characterization methods were carried out to investigate the properties of synthesized gold nanoparticles. transmission electron microscopy and scanning electron microscopy were used to investigate the morphology of as-synthesized Au NPs, while X-ray powder diffraction was applied to obtain the crystalline nature. Nuclear magnetic resonance was used to track the hydrolysis of organosilane MPTMS, which is employed for the first time as a reducing agent for the synthesis of Au NPs. The impact from microwave irradiation time and power, as well as the catalytic property of as-synthesized Au NPs, was investigated via ultraviolet-visible spectroscopy. The as-synthesized products include gold nanohexagon and two-dimensional hexagonal gold nanoplatelets, both of which are single-crystal with (1 1 1) planes as basal surfaces. From UV-vis spectra, it is found that the facile water-based fabrication of hexagonal Au NPs began within seconds of microwave irradiation and the size growth increased with the microwave power and time. Moreover, the efficient reduction of 4-nitrophenol to 4-aminophenol in the presence of as-synthesized Au NPs was observed, exhibiting a remarkable catalytic activity. The present simple, rapid and convenient one-step microwave process possess high scalability and useful for future applications such as catalysis, medical, biological, plasmonic sensors and electronics.

Biogenic synthesis and characterization of silver nanoparticles using aqueous leaf extract of Scoparia dulcis L. and assessment of their antimicrobial property

Naturally occurring phytochemicals serve as an excellent substitute in synthesizing nanomaterials. A process for the synthesis of silver nanoparticles (AgNPs) from the aqueous leaf extract of naturally occurring Scoparia dulcis is described here. The extracellular formation of AgNPs occurred within few minutes upon incubation of S. dulcis aqueous leaf extract (0.1 mL) (100% extract) with silver nitrate (2 mM AgNO₃) at 90 °C for 30 min, is first of its kind work. The appearance of bright yellow color with λ_max 420 nm confirm the formation of AgNPs. Zeta potential and X-ray diffraction (XRD) studies reveal stable AgNPs (-22.7 mV) and characteristic spectra for silver. Fourier transform infrared (FTIR) spectroscopy indicate the involvement of carboxyl, amine and hydroxyl groups in the synthetic process. Transmission electron microscopy (TEM) show the spherical nature of AgNPs measuring 3-18 nm in size. Additional characterization using Dynamic light scattering (DLS) revealed the average particle size distribution of AgNPs as around 8.2 nm. Further antimicrobial testing through agar disc diffusion plate method indicated that silver nanoparticles are potentially active against pathogenic bacteria such as Pseudomonas aeruginosa, Escherichia coli, Bacillus subtilis and Staphylococcus aureus and are only optimally active against fungi such as Aspergillus niger and Candida albicans and measurement of minimal inhibition concentration by standard microdilution method. In conclusion, the study suggests that successful synthesis of green nanoparticles (AgNPs) using aqueous S. dulcis leaf extract is simple, rapid, environmentally benign and economical. Moreover, these synthesized silver nanoparticles showed antimicrobial activity.

Silver and gold nanoparticles biosynthesized by aqueous extract of burdock root, Arctium lappa as antimicrobial agent and catalyst for degradation of pollutants

This study presents an efficient and facile method for biosynthesis of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) using aqueous extract of burdock root (BR), A. lappa, and their applications. The nanoparticles were characterized by ultraviolet-visible spectrophotometry, X-ray diffraction, transmission electron microscopy, energy dispersive X-ray, thermogravimetry, and differential thermal analysis. AgNPs capped the BR extract (BR-AgNPs) possessed roughly spherical geometry with an average diameter of 21.3 nm while uneven geometry of AuNPs capped the BR extract (BR-AuNPs) showed multi shapes in average size of 24.7 nm. The BR-AgNPs strongly inhibited five tested microorganism strains. In particular, the nanoparticles showed excellent catalytic activity for the conversion of pollutants within wastewater. Pseudo-first-order rate constants for the degradation of 4-nitrophenol, methyl orange, and rhodamine B were respectively found 6.77 × 10^-3, 3.70 × 10^-3, and 6.07 × 10^-3 s^-1 for BR-AgNPs and 6.87 × 10^-3, 6.07 × 10^-3, and 7.07 × 10^-3 s^-1 for BR-AuNPs. Graphical abstract ᅟ.

Green synthesis of silver nanoparticles supported on cellulose and their catalytic application in the scavenging of organic dyes

Green synthesis of cellulose supported silver nanoparticles using a seed extract of Hibiscus sabdariffa.