Silver Nanostructures Research Articles

A comparative cytological study of silver and molybdenum oxide nanostructures against breast cancer cells

Cancer is a denying disease, and among a number of cancers types, breast cancer is a recurrent in females, which affect word widely. For these reasons, the work presented here to show the comparative cytological responses of breast (MCF-7) cancer cells with silver and molybdenum oxide nanostructures. The nanostructures were produced via chemical process and characterized. The crystallinities, their size and phases were determined with X-ray diffraction pattern (XRD), while the structural details were scrutinized via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) correspondingly. The nanorods (NRs) and nanoparticles (NPs) were exhibit and confirmed individual diameter of ∼50–60 nm and ∼15 nm separately. A cytotoxicity’s studies of MCF-7 cells were sway and reliant to their doses (1 to 100 μL/mL) with α-MoO3NRs and AgNPs established via 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) and Neutral Red Uptake (NRU) assays. The reactive oxygen species (ROS) were also upsurges slowly from 105, 124, 132, 148 and 108, 130,135, 165 with dissimilar concentrations of α-MoO3NRs and AgNPs (25, 50 and 100 μL/mL) with control reciprocally. Also gene expression (mRNA extraction) study with apoptotic markers in presence of α-MoO3NRs and AgNPs were up-regulated and shows apoptosis in cells. The study provides a possible comparative results related to the cytotoxicity’s in breast (MCF-7) cancer cell with AgNPs are high as compared to α-MoO3NRs also authenticated via gene expression study.

Synergistic redox of dual-shaped silver nanostructures for highly selective sensing of hydrogen peroxide

A novel growth-based plasmonic sensor for hydrogen peroxide (H2O2) determination was developed from dual-shaped silver nanostructures consisting of starch-stabilized yellow silver nanospheres (AgNSs) and citrate-capped red silver nanoprisms (AgNPrs). AgNPrs were enlarged through a unique mechanism of AgNSs dissolution to silver ions which are subsequently reduced to silver metal by H2O2. Citrate-capping maintains the lateral anisotropic growth by protecting the AgNPrs from oxidation while exposing the sensitive edges to Ostwald ripening. This highly unique process addresses the selectivity issues encountered with decomposition-based AgNSs/NPrs sensors. Absorbance values from the AgNSs decomposition and AgNPrs growth facilitated a more sensitive spectrophotometric assay through ratiometric analysis. Increasing the concentration of the AgNSs/NPrs sensor to 80:40 ppm also improved sensitivity of naked eye detection of H2O2 by generating a wide range of color transitions. Furthermore, selectivity, accuracy and precision evaluation suggest that the dual-shaped silver nanostructure sensor is a potential alternative to H2O2 determination by allowing a simple, rapid, highly selective, and sensitive measurement.

Catalytic degradation of methylene blue and bactericidal action by silver and CS-doped iron oxide nanostructures: Experimental and DFT approaches

In this research, Ag (3 and 6 wt %) and carbon sphere (CS) (3 wt. %) were successfully incorporated into Fe2O3 using a co-precipitation approach. This study aimed to degrade the methylene blue (MB) dye and investigate the bactericidal effect of doping-dependent Fe2O3. The pristine sample has good stability and is less toxic however showed poor degradation potency. To enhance the catalytic activity (CA), CS was introduced as it increases Fe2O3 adsorption capacity and improves metal oxide properties. Ag was incorporated into CS-Fe2O3, which created additional active sites and might generate reactive oxygen species (ROS). XRD patterns revealed the tetragonal and monoclinic structure of Fe2O3, and crystallinity was enhanced with dopants (Ag and CS). FTIR was performed to identify vibrational and rotational modes and functional groups of samples. SAED pattern represented the polycrystalline structure of Fe2O3 and (3 & 6 wt%) Ag/CS-Fe2O3. UV–vis spectroscopy depicted that absorption decreased with the increasing amount of Ag/CS and increased band gap energy (Eg). PL spectra of doped Fe2O3 represent the reduction in recombination rate resulting in enhanced CA. EDS spectra exhibited the presence of Fe, O, Na, Au, and C, which confirmed the elemental composition of pristine and doped samples. TEM images indicate nanorods (NRs) of Fe2O3, and HRTEM provides interlayer d-spacing increased upon doping. The nanostructures exhibited excellent CA for the degradation of MB dye in an acidic medium, around 99.44%. Ag/CS-Fe2O3 (6 wt %) nanostructures have shown a significant increase in the inhibition zone (3.65 mm) against Escherichia coli (E. coli) at high-level doses. This study suggests that (3 & 6 wt%) Ag/CS-Fe2O3 nanostructures revealed superior catalytic and antibacterial activity for wastewater treatment. First-principles calculations indicate that the adsorption energies show a relatively strong interaction between MB and (3 & 6 wt%) Ag/CS-Fe2O3.

Replica symmetry breaking in a colloidal plasmonic random laser with gold-coated triangular silver nanostructures.

Plasmonic random lasers have drawn significant attention recently due to their versatility, low threshold, and the possibility of achieving tunable and coherent/incoherent outputs. However, in this Letter, the phenomenon of replica symmetry breaking is reported in intensity fluctuations of a rarely used colloidal plasmonic random laser (RL) illumination. Triangular nanosilver scatter particles produced incoherent RL action when used in a dimethylformamide (DMF) environment in a Rhodamine-6G gain medium. The use of gold-coated triangular nanosilver as the scatterer in place of triangular nanosilver offered a dual contribution of scattering and lower photo-reabsorption, which caused a reduction in the lasing threshold energy of 39% compared to that obtained with the latter. Further, due to its long-term photostability and chemical properties, a phase transition from the photonic paramagnetic to the glassy phase is observed experimentally in the RL system used. Interestingly, the transition occurs at approximately the lasing threshold value, which is a consequence of stronger correlation of modal behaviors at high input pump energies.

Plasmon-Driven Photochemical Reduction Reaction on Silver Nanostructures for Green Fabrication of Superhydrophobic Surface.

Green fabrication of superhydrophobic surface by water-based processing is still challenging, because introduction of the substances with hydrophilic moieties compromises its superhydrophobicity. Herein, a plasmon-driven photochemical reduction reaction under ultraviolet light (UVA) irradiation is first discovered and is applied to deoxygenation of hydrophilic organic adsorbates on rough nano-Ag coating for the formation of stable superhydrophobic surface. A nano-Ag coating with strong localized surface plasmon resonance in the UVA region is prepared by a water-based silver mirror reaction and results in a unique chemical reduction reaction on its surface. Consequently, the low residual hydrophilic functionalities and the formed cross-linked structure of the adsorbate on Ag nanoparticles (NPs) enables the coating to exhibit stable superhydrophobicity against to both air and water. The superhydrophobic Ag NP-coated sandpaper can also be used as a surface-enhanced Raman scattering (SERS) substrate to concentrate aqueous analytes for trace detection.

A Surface-Enhanced Raman Spectroscopy-Based Biosensor for the Detection of Biological Macromolecules: The Case of the Lipopolysaccharide Endotoxin Molecules.

The development of sensitive methods for the detection of endotoxin molecules, such as lipopolysaccharides (LPS), is essential for food safety and health control. Conventional analytical methods used for LPS detection are based on the pyrogen test, plating and culture-based methods, and the limulus amoebocyte lysate method (LAL). Alternatively, the development of reliable biosensors for LPS detection would be highly desirable to solve some critical issues, such as high cost and a long turnaround time. In this work, we present a label-free Surface-Enhanced Raman Spectroscopy (SERS)-based method for LPS detection in its free form. The proposed method combines the benefits of plasmonic enhancement with the selectivity provided by a specific anti-lipid A antibody (Ab). A high-enhancing nanostructured silver substrate was coated with Ab. The presence of LPS was quantitatively monitored by analyzing the changes in the Ab spectra obtained in the absence and presence of LPS. A limit of detection (LOD) and quantification (LOQ) of 12 ng/mL and 41 ng/mL were estimated, respectively. Importantly, the proposed technology could be easily expanded for the determination of other biological macromolecules.

The Role of the Amino Acid Molecular Characteristics on the Formation of Fluorescent Gold- and Silver-Based Nanoclusters.

Role of amino acids like L-phenylalanine (Phe), L-glutamine (Gln) and L-arginine (Arg) is described and interpreted in terms of their potential for preparation of fluorescent molecular-like gold and silver nanostructures. We are among the first to demonstrate the effect of syntheses conditions as well as the molecular characteristics of Phe, Gln and Arg amino acids on the structure of the formed products. Comprehensive optical characterizations (lifetime, quantum yield (QY%)) of the blue-emitting products were also carried out. It was confirmed that for all Au-containing samples and for Gln-Ag system the characteristic fluorescence originates from few-atomic metallic nanoclusters (NCs) where the reduction of metal ions was promoted by citrate in some cases. Relatively high QY% (∼18 %) was obtained for Arg-stabilized Au NCs due to the existence of an electrostatic interaction between the electron rich, positively charged guanidium side chain of Arg and the negatively charged carboxylate group of citrate on the metallic surface. Size and structural analysis of the products were evaluated by infrared measurements and dynamic light scattering techniques.

Optical coupling of bio-inspired mustard protein-based bimetallic nanohybrids with propagating surface plasmon polaritons for femtomolar nitrite ion sensing: Cellphone-based portable detection device

Different classes of biologically and environmentally relevant molecules and ions are quantitatively and qualitatively analyzed using the synergistic approach wherein the properties of both the plasmonic nanomaterials and the fluorescent moieties are explored. In this study, such hybrid systems, called plasmophores (or plasmon coupled fluorophores), are investigated using the surface plasmon-coupled emission (SPCE) platform with silver, gold and silver-gold hybrid nano-structures synthesized via sustainable bio-inspired routes. A simple, rapid, user-friendly and green chemistry approach has been adopted using biocompatible mustard protein as both the reducing and capping agent during nanosynthesis. The morphologically and functionally tunable plasmonic nanomaterials were synthesized by simply exposing a mixture of the respective metal ions and protein to UV-light irradiation. Comprehensive analysis of the out-coupled spontaneous emission in the SPCE framework using spacer, cavity and extended cavity nanointerfaces yielded intriguing results, presenting optimum prerequisites for realizing high SPCE enhancements. More than a 950-fold improvement in the fluorescence signal intensity of rhodamine B was demonstrated utilizing the plasmonic cavity hotspots rendered by the hybrid coupling of the propagating surface plasmon polaritons of Ag with localized plasmon resonances of the bimetallic AgAu nanohybrids. The sharply directional and highly polarized SPCE enhancements, realized without increasing the illumination intensity, were utilized for quantitative detection of biologically relevant nitrite ions in drinking water samples at trace concentrations (limit of detection: 0.1 femtomolar). The applicability and relevance of the demonstrated method for sustainable use of plasmonic nanomaterials in photo-plasmonic research is presented by accomplishing the sensing using a cost-effective smartphone camera with a good correlation with the data obtained from a conventional detector system. Hence, the bio-nano-inspired strategy described here reveals several potential opportunities for the development of environmentally benign portable chemosensing devices for utility in academia and industry, especially for low-and-middle income countries.

Formulation of a modern anti-human breast cancer drug from silver nanoparticles green-synthesized using Allium saralicum

Nanotechnology has immense potential for the development of novel and necessary products that benefit human health, the environment, and industries. Silver nanoparticles and their nanocomposites have gained tremendous importance in the field of nanotechnology owing to their widespread usage in various realms of science and technology, including electronics, biomedical, environmental protection, textile industry, cosmetics, therapeutics, photonics, agriculture, and so on. As the characteristic properties of silver nanostructures, like excellent SERS/SPR, surface properties, diversity in shape, surface charge, dissolution rate, controlled silver ion release for mediating the antimicrobial toxicity and cytotoxicity towards cancer cells, and efficient biocompatibility, which render them to be potential antimicrobial, anticancer and diagnostic agents. Recently, Allium saralicum extract has been used for green-synthesizing the silver nanoparticles and investigation of its biomedical effects. In the present research, we formulated a modern chemotherapeutic drug by silver nanoparticles (AgNPs) containing Allium saralicum‎ aqueous extract for the treatment of breast cancer. Characterization of AgNPs was done by UV-Vis, FT‐IR, TEM, and FE‐SEM. The bands at 488 and 539 cm−1 (belonging to the Ag-O bond) approves the production of silver nanoparticles. The spherical morphology with a range size of 13.9–55.2 nm is obtained for synthesized nanoparticles. The band at 434 nm approves the AgNPs formation. To survey the cytotoxicity and anti-human breast cancer effects of AgNO3, Allium saralicum‎, and AgNPs, MTT assay was used on the SK-BR-3, MDA-MB-231, AU565 [AU-565], and Hs 281. T cell lines. Silver nanoparticles had very low cell viability and anticancer properties dose-dependently against cancer cell lines without any cytotoxicity on the normal cell line. The best result of anticancer properties of AgNPs against the above cell lines was seen in the case of the MDA-MB-231 cell line. The IC50 of nanoparticles were 208, 250, 200, and 188 µg/ml against SK-BR-3, MDA-MB-231, AU565 [AU-565], and Hs 281. T cell lines, ‎respectively. ‎

Transformation of bimetallic Ag–Cu thin films into plasmonically active composite nanostructures

Formation of plasmonically active silver, copper and composite silver-copper nanostructures were studied in this paper. Metallic nanostructures were fabricated by thermal disintegration, so called dewetting, of the thin films in an argon atmosphere. The formation process of the nanostructures was in-situ observed by a novel method, based on resistance measurements. The influence of the material and thickness of the initial thin film on temperature of their disintegration was investigated. Electrical measurements were validated by scanning electron microscopy observations, while metallic the behavior of nanostructures was studied by XPS method. The formation of silver-copper nanocomposite structures was confirmed by UV–vis spectroscopy. Plasmon resonance with two characteristic peaks for nanocomposite structures was observed.

Green Synthesis of Controlled Shape Silver Nanostructures and Their Peroxidase, Catalytic Degradation, and Antibacterial Activity.

Nanoparticles with unique shapes have garnered significant interest due to their enhanced surface area-to-volume ratio, leading to improved potential compared to their spherical counterparts. The present study focuses on a biological approach to producing different silver nanostructures employing Moringa oleifera leaf extract. Phytoextract provides metabolites, serving as reducing and stabilizing agents in the reaction. Two different silver nanostructures, dendritic (AgNDs) and spherical (AgNPs), were successfully formed by adjusting the phytoextract concentration with and without copper ions in the reaction system, resulting in particle sizes of ~300 ± 30 nm (AgNDs) and ~100 ± 30 nm (AgNPs). These nanostructures were characterized by several techniques to ascertain their physicochemical properties; the surface was distinguished by functional groups related to polyphenols due to plant extract that led to critical controlling of the shape of nanoparticles. Nanostructures performance was assessed in terms of peroxidase-like activity, catalytic behavior for dye degradation, and antibacterial activity. Spectroscopic analysis revealed that AgNDs demonstrated significantly higher peroxidase activity compared to AgNPs when evaluated using chromogenic reagent 3,3',5,5'-tetramethylbenzidine. Furthermore, AgNDs exhibited enhanced catalytic degradation activities, achieving degradation percentages of 92.2% and 91.0% for methyl orange and methylene blue dyes, respectively, compared to 66.6% and 58.0% for AgNPs. Additionally, AgNDs exhibited superior antibacterial properties against Gram-negative E. coli compared to Gram-positive S. aureus, as evidenced by the calculated zone of inhibition. These findings highlight the potential of the green synthesis method in generating novel nanoparticle morphologies, such as dendritic shape, compared with the traditionally synthesized spherical shape of silver nanostructures. The synthesis of such unique nanostructures holds promise for various applications and further investigations in diverse sectors, including chemical and biomedical fields.

The SYNTHESIS AND STUDY OF METAL-POLYMER NANOCOMPOSITES BASED ON A COPOLYMER OF POLYETHYLENE GLYCOL MALEATE WITH ACRYLIC ACID, AND ITS CATALYTIC PROPERTIES

Introduction. With the development of the chemical industry, the search for and synthesis of new, and modification of the existing nanocatalytic systems are of great importance. In view of this, the preparation of new catalysts by immobilization of transition metal metals in a polymer matrix becomes an important direction in chemical synthesis. Purpose of this work is to submit experimental data on the synthesis and study of the catalytic properties of silver and nickel nanostructures, immobilized in polymer matrices, based on a binary system of unsaturated polyester – polyethylene glycol maleate – with acrylic acid. Nanocomposites have been obtained by reducing a solution of nickel and silver metal salts with sodium hypophosphite in the presence of an ammonia solution of silver chloride. Methodology. By the methods of spectroscopy, microscopy the sizes, structure and morphology of polymer-stabilized nanoparticles are determined. Results. The obtained nanocomposites contain isolated Ag0 nanoparticles with a diameter of 60±10 nm, predominantly spherical in shape and metallic Ni0 with a cubic shape of 70±10 nm, uniformly distributed in the polymer matrix, as well as agglomerates on the surface of the polymer matrix, the dimensions of which vary within 150–200 nm. The catalytic activity of the synthesized nanocomposites, which show high efficiency in comparison with the standard metal catalysts, has been also studied.

Flow-based approach for scalable fabrication of Ag nanostructured substrate as a platform for surface-enhanced Raman scattering

The droplet-based biphasic reaction is an efficient strategy for the fabrication of surface-bound nanostructures. Here, we developed a process of fabricating ordered micro-ring arrays of silver (Ag) nanostructures from surface nanodroplet reaction on a micro-patterned hydrophobic substrate for reproducible detection by surface-enhanced Raman spectroscopy (SERS). Our process consisted of the generation of surface nanodroplet arrays, followed by a biphasic chemical reaction between droplets and the continuous flow of silver nitrate (AgNO3) precursor solution. The parameters in the formation and reaction of the droplet array were well controlled to maintain the uniformity of Ag nanostructures throughout the substrate. By scaling up the process parameters and the size of the microchamber, we were able to produce a SERS substrate with a surface area of ¿60 cm2 in a single run. Such a large area could be sufficient for analyzing more than a thousand samples. We demonstrated the repeatability of SERS measurements using Ag nanostructures by analyzing three environmental (rhodamine 6G, chlorpyrifos, triclosan), a biological (indoxyl sulfate), and a psychoactive drug (tetrahydrocannabinol) compounds. 2D mapping of SERS intensities was also performed for both small and large-scale substrates by collecting data from more than 100 locations on the substrate. Our work demonstrated droplet-based biphasic reaction as a simple approach for the fabrication of SERS substrate with a large area. The technique may help to eliminate the requirement for sophisticated equipment for the fabrication of SERS active substrate.

Synthesis of multicolor silver nanostructures for colorimetric sensing of metal ions (Cr3+, Hg2+ and K+) in industrial water and urine samples with different spectral characteristics

In this work, we have synthesized four different color (yellow, orange, green, and blue (multicolor)) silver nanostructures (AgNSs) by chemical reduction method where silver nitrate, sodium borohydride and hydrogen peroxide were used as reagents. The as-synthesized multicolor AgNSs were successfully functionalized with bovine serum albumin (BSA) and applied as a colorimetric sensor for the assaying of metal cations (Cr3+, Hg2+, and K+). The addition of metal ions (Cr3+, Hg2+, and K+) into BSA functionalized AgNSs (BSA-AgNSs) causes the aggregation of BSA-AgNSs, and are accompanied by visual color changes with red or blue shift in the surface plasmon resonance (SPR) band of BSA-AgNSs. The BSA-AgNSs show different SPR characteristic for each metal ions (Cr3+, Hg2+, and K+) with exhibiting different spectral shift and color change. The yellow color BSA-AgNSs (Y-BSA-AgNSs) act as a probe for sensing Cr3+, orange color BSA-AgNSs (O-BSA-AgNSs) act as probe for Hg2+ ion assay, green color BSA-AgNSs (G-BSA-AgNSs) act as a probe for the assaying of both K+ and Hg2+, and blue color BSA-AgNSs (B-BSA-AgNSs) act as a sensor for colorimetric detection of K+ ion. The detection limits were found to be 0.26 μM for Cr3+ (Y-BSA-AgNSs), 0.14 μM for Hg2+ (O-BSA-AgNSs), 0.05 μM for K+ (G-BSA-AgNSs), 0.17 μM for Hg2+ (G-BSA-AgNSs), and 0.08 μM for K+ (B-BSA-AgNSs), respectively. Furthermore, multicolor BSA-AgNSs were also applied for assaying of Cr3+, and Hg2+ in industrial water samples and K+ in urine sample.

Gamma Radiation-Induced Synthesis and Characterization of Decahedron-Like Silver Nanostructure and Their Antimicrobial Application

AbstractIn the current study, a decahedron-like silver nanostructure (D-AgNs) was successfully created in an aqueous solution in the presence of Polyvinylpyrrolidone (PVP) as a capping agent using the gamma-radiolysis approach without the use of a reducing agent. The synthesized D-AgNs were characterized using various analytical tools such as UV–Vis. spectroscopy, SEM, XRD, HRTEM, EDX and FTIR. UV–Vis. absorption spectra showed considerable surface Plasmon resonance (SPR) bands at 350–600 nm, indicating that colloidal D-AgNs had been successfully synthesized. HRTEM image demonstrates well-dispersed uniformly decahedral shapes that are well separated from each other. The produced nanoparticles were effectively stabilized by PVP through interactions, confirmed by the FTIR anlaysis. The synthesis of D-AgNs using gamma radiation was accomplished, in addition its antimicrobial potential, antibiofilm activity, and the effect of UV rays were assessed. In addition, protein leakage assays and SEM imaging were employed to analyze the antimicrobial reaction’s mechanism. A wide variety of bacteria, including S. aureus, P. aeruginosa, and C. albicans, were deactivated by D-AgNs. In the antibiofilm assay, D-AgNs inhibited the biofilm formation of S. aureus (89.58%), E. coli (80.35%), and P. aureginosa (78.45%). After investigating the effect of D-AgNs on the growth curve of S. aureus, we concluded that D-AgNs affect the growth curve of S. aureus, and the curve was reduced to be 0.125. The formation of holes in the S. aureus cell membrane is explained by the fact that the amount of cellular protein released from the bacteria is directly proportional to the concentration of D-AgNs, which was determined to be 259.25 µg/ml at concentration equal to 1.0 mg/mL.

Thermal Transport and Physical Characteristics of Silver-Reinforced Biodegradable Nanolubricant

In this investigation, the thermal transport behavior of biodegradable lubricant reinforced with silver nanostructures (AgNs) at various filler fractions of 0.01, 0.05, 0.10, and 0.20 weight percent was evaluated over a temperature scan analysis, ranging from room temperature up to 60 °C. The experimental results revealed significant gradual enhancements in thermal conductivity as AgNs concentration and evaluating temperatures were increased. These improvements showed the important role of nanostructures’ interaction within the biodegradable lubricant. The thermal conductivity performance improved for nanolubricants ranging from 6.5% at 30 °C and 0.20 wt.% AgNs content up to a maximum 32.2%, which was obtained at 60 °C with 0.20 wt.% AgNs concentration. On the other hand, the thermal stability of reinforced lubricants was assessed through thermogravimetric kinetics analyses. The predictive curves resulting from the analyses indicated that there is an enhancement in both the onset temperature for decomposition and the percentage conversion under isothermal conditions for lubricants reinforced with AgNs. Specifically, the results show that the required temperature to achieve a 5% conversion is 100 °C higher than that calculated for bare lubricant. Moreover, the predictive analyses indicate that there is a delay in the decomposition time at isothermal conditions.

Facile Scale-Up of the Flow Synthesis of Silver Nanostructures Based on Norrish Type I Photoinitiators.

Silver nanoparticles have become one of the most commercially and industrially relevant nanomaterials of the 21st century, owing to their potent antibacterial properties, as well as their useful catalytic and optical properties. Although many methods have been explored to produce AgNPs, we favor the photochemical approach using photoinitiators to produce AgNPs, owing to the high degree of control over reaction conditions, and the generation of so-called AgNP 'seeds' that can be used as-is, or as precursors for other silver nanostructures. In this work, we explore the scale-up of AgNP synthesis using flow chemistry and assess the usefulness of a range of industrial Norrish Type 1 photoinitiators in terms of flow compatibility and reaction time, as well as the resulting plasmonic absorption and morphologies. We establish that while all the photoinitiators used were able to generate AgNPs in a mixed aqueous/alcohol system, photoinitiators that generate ketyl radicals showed the greatest promise in terms of reaction times, while also showing greater flow compatibility compared to photoinitiators that generate 𝛼-aminoalkyl and α-hydroxybenzyl radicals. These findings help to establish a guideline for adapting photochemical AgNP syntheses to flow systems, helping to improve the scalability of the method in one of the largest industries in nanomaterial chemistry.

Highly porous ZnO modified with photochemical deposition of silver nanostructure for ultra-sensitive triethylamine detection

Doping noble metals into semiconductor based gas sensors was proved to be an effective strategy in improving gas response properties. Here, we report a silver/silver (II) oxide nanoparticles (Ag/AgO NPs) modified highly porous ZnO nanocomposite. Firstly, the Ag NPs were evenly deposited on the surface of flower-like ZnCO3 precursors through a simple photochemical reduction method, which was then heated at 400 °C to give highly porous Ag/AgO/ZnO nanocomposite, accompaning with the dissociation of ZnCO3 after release of CO2. The interleaving ultrathin and porous sheet-like features of Ag/AgO/ZnO nanocomposite afford it excellent triethylamine (TEA) sensing performance with Ra/Rg = 90.3 at an operating temperature of 240 °C, and the response sensitivity is 5.5-fold higher than that of pure ZnO. Specifically, the porous Ag/AgO/ZnO nanocomposite exhibited a fast response/recovery time of 53 s/8 s and oustanding long-term cyclic stability. The enhanced gas sensing performance can be attributed to the sensitization of Ag/AgO NPs, significantly increasing the number of oxygen vacancies and thus providing more reactive sites. The synergistic interaction between Ag/AgO NPs and porous ZnO nanosheets also facilitates a fast electron transport and a high permeability for gas molecules. This work displays a feasible way of coupling photochemical reduction and pyrolysis strategy to develop highly porous ZnO nanosheets functionalized by noble metal NPs with remarkably enhanced gas response property.

Comparison of Blueberry and Dandelion Aqueous Extracts in the Synthesis of Gold and Silver Nanostructures, and Their Applications as Anti‐Pseudomonas aeruginosa Agent

AbstractWe performed a comparative study using aqueous extracts of dandelion flowers and blueberry fruits to synthesize gold‐ (Au) and silver‐ (Ag) nanostructures (NSs). The blueberry extracts gave nanowire and spherical AuNSs upon changing the ratio of the extracts to Au3+precursor while altering the ratio for the dandelion extracts resulted in formation of only anisotropic AuNSs. Similar results were obtained during the AgNSs, where the dandelion extracts resulted in formation of quasi‐spherical AgNSs at the tested ratio (extract/AgNO3 ratio) while altering the ratio for the blueberry extracts resulted in nanorod and nanoplates formation. We argued that this could be from dominancy of a lone compound or a group of compounds and tested this claim by introducing chrysin and amino acid mixtures to the blueberry extracts. Altering the added chrysin amount triggered nanoplate and spherical AuNSs formation while alteration in amino acid mixture content did not change the morphology, and spherical AuNSs were obtained. The antibacterial studies revealed the AgNSs are toxic to Pseudomonas aeruginosa with 8 μg/mL MBC (minimum bactericidal concentration) and 3 μg/mL values for the blueberry and dandelion extracts synthesized AgNSs while penicillin/streptomycin sulfate mixture carrying Dandelion‐AuNSs gave 12‐times lower MBC value in comparison to free penicillin/streptomycin sulfate mixture.

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.