Formation Of Ag Nanoparticles Research Articles

High photocatalytic activity of Ag/Ag3PO4:W heterostructure formed by femtosecond laser irradiation

In this work, the W-doped Ag3PO4 was prepared by the chemical coprecipitation method and irradiated with a femtosecond laser (FL). The successful formation of the Ag/Ag3PO4:W heterostructure was confirmed by XRD analysis. A higher structural disorder in the [PO4] clusters was observed for the FL irradiated sample (Ag3PO4:W-FL), indicating the formation of Ag metallic from the Ag3PO4 structure. The photocatalytic activity of the samples was studied by photodegradation of rhodamine B under visible light irradiation. The formation of Ag nanoparticles on the surface of Ag3PO4:W led to a degradation rate constant 3.54 times higher than the nonirradiated sample. This higher photocatalytic activity was related to the surface plasmon resonance effect of the Ag metallic, which acts by capturing photoexcited electrons from the Ag3PO4:W, avoiding the recombination of electron-hole pairs, and thus improving the photocatalytic activity.

Optical and Structural Study of Biocompatible Silver-Chitosan Colloids

Nontoxic and biocompatible silver-chitosan colloids were prepared by direct chemical reduction. The Ag-chitosan colloids are drop cast on a glass slide and left to dry to obtain uniform, homogeneous films. The presence of chitosan prevented the growth of silver nanoparticles from agglomeration. The occurrence of localized surface plasmon resonance (LSPR) at ~ 400 nm in the optical absorption spectra indicated the formation of Ag nanoparticles which is the characteristic property of metal nanoparticles. The -prepared colloidal Ag nanoparticles are chemically stable and remain colloidal even after aging. The estimated average particle size is about 14nm and the face-centered cubic phase was observed in the XRD pattern. SEM images clearly showed the homogeneous distribution of silver nanoparticles.

Physicochemical investigation of the enhanced removal of methylene blue from aqueous solution using polydopamine/silver nanoparticles

Polydopamine/Ag (PDA/Ag) nanoparticles were synthesized for methylene blue (MB) removal from aqueous solution as a model dye. These particles were prepared in a modified literature procedure in which polydopamine (PDA) nanoparticles were first prepared via the oxidative polymerization of dopamine (DA) under alkaline conditions in the presence of oxygen. Subsequently, nanoparticulate PDA/Ag was accessed from direct reduction of silver precursor [Ag(NH3)2]+ ions by catechol amino groups in the PDA structure to form Ag nanoparticles (AgNPs) fixed on the PDA surface. Confirmation of the formation of the PDA and PDA/Ag nanoparticles, plus characterization of their surface morphologies was achieved. In the MB adsorption studies, the various factors affecting the dye adsorption and thermodynamic parameters were investigated in detail. This adsorption process can be described well by the Langmuir model. In order to gain a deeper molecular insight into this process, we investigated some possible local model structures of PDA/Ag nanoparticles and MB interaction with these structures using density functional theory (DFT) calculations. The results indicated that the adsorption energies (E ads) of MB on the PDA/Ag nanoparticles were higher than the E ads of MB on PDA nanoparticles, which was consistent with the experimental results. Our results provide a significant new finding for the role of Ag nanoparticles in the MB adsorption process on PDA/Ag nanoparticles. Readily accessible nanoparticulate PDA/Ag was shown to be a highly effective adsorbent for MB from aqueous solution and thus has significant potential for applications in wastewater dye removal.

Microfibrillated Cellulose-Silver Nanocomposite Based PVA Hydrogels and Their Enhanced Physical, Mechanical and Antibacterial Properties

Modification of cellulose with silver nanoparticles produces various nanocomposites with significantly developed properties. This work aims to prepare a PVA hydrogel modified with cellulose/silver nanocomposites having potential applications in various fields including biomedical, antimicrobial inhibition, textile wears, etc. Microfibrillated cellulose/silver nanocomposites hydrogels were prepared in the aqueous medium with aid of microwave-assisted heating. Different percentages of nanocomposites were incorporated in PVA hydrogel to enhance the properties of PVA hydrogel. Prepared products were characterized by UV–Visible spectroscopy, FTIR, TGA, XRD, and SEM. The swelling (in water saline, acidic and alkaline solution), tensile, thermal, and antibacterial properties were also examined. The formation of Ag nanoparticles (AgNPs) in the (MFC-Ag)NC was confirmed by XRD and UV–Vis spectra. UV–Vis spectra showed the characteristic peaks of Ag in the UV–Vis spectra at 425 nm. Final products exhibited significant porosity and maximum swelling of 519.44%. The thermal stability of hydrogel increased with an increased percentage of (MFC-Ag)NC. Hydrogels exhibited significant antimicrobial inhibition against multidrug-resistant microorganisms, including Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa.

Preparation and optical properties of silver sensitized 6Y–ZrO2: Er3+ translucent ceramics

We report a facile method to enhance the photoluminescence of 6Y–ZrO2: Er3+ translucent ceramics prepared via the vacuum sintering technique by introducing Ag. Ag atoms could be incorporated into the host at high temperatures; these atoms partially precipitated to form Ag nanoparticles during cooling. The intensities of green up-conversion, 1.5 and 2.7 μm emissions under 980 nm excitation, and the green down-conversion luminescence upon 377 nm excitation were improved via co-doping with Ag due to the modification of the local crystal field and the surface plasmon resonance effect. Based on the fluorescence intensity ratio of 2H11/2 → 4I15/2 versus 4S3/2 → 4I15/2, 6Y–ZrO2: 1 mol%Er3+, 0.67 μmol%Ag exhibited the maximal relative sensing sensitivity of 1.12 %K−1, which could be applied as a potential thermometer with good sensitivity. The present work sheds light on how to simultaneously enhance the emission intensity and thermal sensitivity of Er3+ in ceramics.

Development and Characterization of a Hydrogel Containing Silver Sulfadiazine for Antimicrobial Topical Applications. Part II: Stability, Cytotoxicity and Silver Release Patterns

Hydrogels are interesting for use in the treatment of topical wounds due to their virtually zero toxicity, and capacity for extended release of pharmaceuticals. Silver sulfadiazine (SSDZ) is the drug of choice in the treatment of skin burns. The aim of the study was to determine cytotoxicity, antimicrobial activity and stability of a PVA hydrogel with integrated silver sulfadiazine. SSDZ-hydrogels were prepared using 10% (w/w) PVA (either 89% or 99% hydrolyzed) and 1% (w/w) silver sulfadiazine. Cellular viability was assessed via MTS assays, antimicrobial activity via disk-diffusion and accelerated stability tests were carried out with analysis at 0, 30, 60, 90 and 180 days of storage at 40 ± 2 °C and a relative humidity of 75 ± 5%. The parameters evaluated included organoleptic characteristics, moisture, swelling ability, mechanical strength, FTIR, XRD, TGA and DSC, and silver release patterns via XRD and potentiometry. Cell viability tests indicated some cytotoxicity, although within acceptable levels. After 90 days of storage, SSDZ hydrogel samples exhibited a brown coloration, probably due to the formation of Ag or Ag2O nanoparticles. The SSDZ-loaded hydrogels suffered visual and physical changes; however, these changes did not compromise its use as occlusive wound dressings or its antimicrobial properties.

Uptake and depuration of Ag nanoparticles versus Ag ions by zebrafish through dietary exposure: characterization of Ag nanoparticle formation and dissolution in vivo and toxicokinetic modeling

The dynamic biological fate of silver nanoparticles as dissolution and neo-formation in zebrafish influences the number concentration-based versus mass concentration-based toxicokinetics.

A New Pathway for Superlubricity in a Multilayered MoS2-Ag Film under Cryogenic Environment.

A fundamental cryogenic study in tribology from 20 to 300 K revealed that a kind of disulfide film could exhibit a superlubricity state. Inspired by this, we designed a more delicate experiment and reported an extremely low friction coefficient for a multilayered MoS2-Ag film in a cryogenic environment against a bare steel ball under a high load. The results showed that the multilayered MoS2-Ag film could undergo a pressure exceeding 2 GPa to maintain a superlow friction coefficient of below 0.001 at 170 K. The film material was transferred to the sliding contacts to form an antifriction tribofilm. The superlubricity mechanism was attributed to the formation of MoS2-wrapped Ag nanoparticles accumulated at the sliding interface through nanoparticle movement and layered-structure sliding. This new kind of multilayered MoS2-Ag film provides a novel design for a solid lubricant and broadens the application of solid lubrication films under harsh working conditions for mechanical engineering.

A silver-based ink for assessing low activity photocatalytic films

A new type of photocatalytic activity indicator ink, paii, is described based on the photocatalysed reduction of Ag ions to the metal, rather than that of a dye, such as resazurin, Rz. UVA irradiation of an Ag ink film coating on a photocatalytic surface produces a brown colouration due to Ag nanoparticle formation. The Ag ink is easy to make and provides a simple method for the rapid assessment of photocatalytic films, with the added advantage of being particularly sensitive to low activity photocatalytic materials, such as commercial self-cleaning tiles for which no International Standards Organisation, ISO, test exists, including a Rz paii ISO. A felt-tipped pen applied Ag ink film is used to identify the presence of activity in a wide range of different materials, including examples of commercial self-cleaning glass, tile, paint and plastic awning materials. Unlike its well-established Rz paii counterpart, the Ag ink is effective on very hydrophobic and delicate, i.e. easily removed, photocatalytic films. A protocol is employed for the Ag ink to provide a quantitative measure of photocatalytic activity on both a low activity photocatalytic material, i.e. a Hytect™ tile, and a moderately active, reference photocatalytic material, Activ™ glass. The potential of the Ag ink to aid research and development into, and quality assurance of, low activity photocatalytic films, and also help in identifying activity in films previously considered inert, is discussed briefly.

Combined Small-Angle Neutron Scattering/Small-Angle X-ray Scattering Analysis for the Characterization of Silver Nanoparticles Prepared via Photoreduction in Water-in-Oil Microemulsions.

In this study, we used small-angle neutron scattering (SANS) and small-angle X-ray scattering (SAXS) to investigate the formation process of silver (Ag) nanoparticles (NPs) in water-in-oil (w/o) reverse microemulsions comprising sodium bis(2-ethylhexyl) sulfosuccinate (AOT), water, and organic solvents (such as benzene, octane, and decane) by the photoreduction of silver perchlorate (AgClO4). Combining SANS and SAXS, the structural changes in the w/o microemulsions before and after the formation of Ag NPs via photoreduction were quantitatively evaluated. From the SANS experiments performed using the contrast-variation method, the size of water cores containing Ag NPs and the thickness of the AOT shells were calculated using the core-shell hard-sphere model. The size of the Ag NPs and their aggregates was calculated via SAXS analysis based on the polydisperse sphere model with a Schulz-Zimm distribution. We found that aggregates of three or four primary Ag NPs are formed by, first, the aggregation of water droplets through the entanglement of the tails of the AOT shell, followed by the self-assembly of Ag NPs into their aggregates because of particle-particle attractive interactions.

Role of Ag+ Ions in Determining Ce3+ Optical Properties in Fluorophosphate and Sulfophosphate Glasses.

Understanding the interactions among dopant species and the role of the host lattice is of fundamental importance for the chemical formulation of optically active glasses. Here, we consider the archetypal dopant pair of Ag–Ce in complex fluorophosphate (PF) and sulfophosphate (PS) matrices, in which variable bonding environments and ligand selectivity exert distinct effects on dopant properties. The addition of Ag+ to PF glasses blue-shifts the ultraviolet (UV) cutoff wavelength of Ce3+ and enhances its photoluminescence (PL) intensity. In PS matrices, the exact opposite effect is observed: red-shifting the UV cutoff and lowering the PL intensity. No Ag–Ag pairs or cluster species were found in either matrix material; however, in PS, such clustering could be triggered by secondary broad-band UV–visible irradiation. The optical properties of Ag–Ce-codoped glasses are a result of the ionocovalent character of the Ag+–O–Ce3+ bond, the cross-relaxation process between Ag+ and Ce3+, and the redox ratio of Ce3+/Ce4+. In the PF glasses, the enhancement of the Ce3+ PL intensity is due to energy transfer from Ag+ to Ce3+ and a redox shift from Ce4+ to Ce3+. The more covalent Ag+–O–Ce3+ interactions in the PS series decrease the Ce3+/Ce4+ ratio. Moreover, photoinduced Ag clustering is facilitated in the more covalent environment, which indicates that glasses commonly used for Ag nanoparticle formation, such as silicate glasses, also possess more covalent Ag+–O bonding.

Cannabidiol-Mediated Green Synthesis, Characterization, and Cytotoxicity of Metal Nanoparticles in Human Keratinocyte Cells.

This study investigated a unique one-pot microwave-assisted green synthesis method of gold (Au) and silver (Ag) nanoparticles (NPs) using cannabidiol (CBD) as a capping and reducing agent. Furthermore, Au and Ag NPs were also chemically synthesized using poly(vinyl pyrrolidone), which functioned as reference materials when comparing the size, shape, and cytotoxicity of NPs. Synthesis parameters such as reaction time, temperature, and precursor molar ratio were optimized to control the size and shape of the biosynthesized NPs. Various characterization techniques such as transmission electron microscopy, ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were used to confirm the formation and properties of Au and Ag NPs. Both biosynthesized metal NPs were spherical and monodispersed, with average particle sizes of 8.4 nm (Au-CBD) and 4.8 nm (Ag-CBD). This study also explored the potential cytotoxicity of CBD-capped NPs in human keratinocyte cells, which was observed to be of minimal concern. The novel synthesis approach presented in this study is free from harsh chemical reagents; therefore, these NPs can be used in a wide array of applications, including the pharmaceutical and biomedical fields.

Quantification of Silicon in Rice Based on an Electrochemical Sensor via an Amplified Electrocatalytic Strategy.

Silicon plays a very important role in the growth of rice. The study of the relationship between rice and silicon has become a hot area in the last decade. Currently, the silica-molybdenum blue spectrophotometric method is mostly used for the determination of silicon content in rice. However, the results of this method vary greatly due to the different choices of reducing agents, measurement wavelengths and color development times. In this work, we present for the first time an electrochemical sensor for the detection of silicon content in rice. This electrochemical analysis technique not only provides an alternative detection strategy, but also, due to the rapid detection by electrochemical methods and the miniaturization of the instrument, it is suitable for field testing. Methodological construction using electrochemical techniques is a key objective. The silicon in rice was extracted by HF and becomes silica after pH adjustment. The silica was then immobilized onto the glassy carbon surface. These silica nanoparticles provided additional specific surface area for adsorption of sodium borohydride and Ag ions, which in turn formed Ag nanoparticles to fabricate an electrochemical sensor. The proposed electrochemical sensor can be used for indirect measurements of 10–400 mg/L of SiO2, and thus, the method can measure 4.67–186.8 mg/g of silicon. The electrochemical sensor can be used to be comparable with the conventional silicon-molybdenum blue spectrophotometric method. The RSD of the current value was only 3.4% for five sensors. In practical use, 200 samples of glume, leaf, leaf sheath and culm were tested. The results showed that glume had the highest silicon content and culm had the lowest silicon content. The linear correlation coefficients for glume, leaf, leaf sheath and culm were 0.9841, 0.9907, 0.9894 and 0.993, respectively.

Formation of nanoporous Ge layers by ion implantation at different temperatures of c-Ge substrate

The flat monocrystalline c-Ge wafers implanted by 108Ag + ions with the energy E = 30 keV, dose D = 1.3·1016 ion/cm2 and at current density J = 5 μA/cm2 for various substrate temperatures from 25 to 400 °C were studied. By scanning electron microscopy and optical reflection spectroscopy it was found that as a result of ion implantation in the temperature range from 25 to 300 °C an amorphous porous Ag:PGe layers of a spongy structure consisting of Ge nanowires on the c-Ge substrate surface are formed. The diameter of Ge nanowires increases from 16 to 24 nm with a rising of substrate temperature. It is shown that at the highest temperature of 400 °C, the porous structure does not form and the Ge surface remains flat on which the formation of Ag nanoparticles can be observed. A change in the level of the sample surface in dependence on substrate temperature due to swelling up to 280 °C was replaced by effective ion sputtering at higher temperatures.

Solid-state thermal dewetted silver nanoparticles onto electrochemically grown self-standing vertically aligned ZnO nanorods for three-dimensional plasmonic nanostructures

Three dimensional (3D) plasmonic nanostructures composed of silver nanoparticles decorated ZnO NRs arrays, have been fabricated by a process combining the electrochemical growth of ZnO NRs and further formation of Ag nanoparticles by the solid-state thermal dewetting (SSD) process. The effect of SSD parameters on the morphological, structural and optical properties of the Ag NPs decorated ZnO NRs arrays has been investigated. It is possible to tune the bandgap of the Ag NPs@ZnO nanorods array 3D plasmonic nanostructure by tailoring the Ag nanoparticle sizes, allowing light manipulation at the nanoscale. The silver nanoparticles attached to the ZnO NRs arrays experienced surface plasmonic coupling effect, causing enhancement in the room temperature photoluminescence (PL) UV emission and quenching the corresponding visible light one. An enhancement in the near band edge emission PL intensity of ZnO to the deep level emission PL intensity ratio after Ag NPs decoration of the ZnO nanostructures corresponding to ca. 11 folds has been observed, indicating that the defect emission is obviously suppressed.

Effect of Exchangeable Ions in Natural and Modified Zeolites on Ag Content, Ag Nanoparticle Formation and Their Antibacterial Activity.

To broaden the application of silver nanoparticles (AgNPs), which are well-known antibacterial agents, they are supported on different substrates to prevent aggregation, increase their surface area and antibacterial efficiency, and to be separated from the system more effectively at the end of treatment. To produce nanocomposites that consist of silver nanoparticles on natural and modified zeolites, silver ions (Ag+) were loaded onto zeolite (natural, Na-modified, H-modified) and then thermally reduced to AgNPs. The effect of the exchangeable cations in zeolite on Ag+ uptake, AgNPs formation, size and morphology was investigated by the TEM, SEM, EDX, XPS, UV-vis, XRD and BET methods. The silver amount in the nanocomposites decreased in the following order Na-modified zeolite > natural zeolite > H-modified zeolite. Microscopic techniques showed formation of AgNPs of 1–14 nm on natural and Na-modified zeolite, while the diameter of metal particles on H-modified zeolite was 12–42 nm. Diffuse reflectance UV-vis and XPS methods revealed the presence of both silver ions and AgNPs in the materials indicating that partial reduction of Ag+ ions took place upon heating at 400 °C in air. Additionally, antibacterial properties of the nanocomposites were tested against Escherichia coli, and it was found that Ag–containing composites originating from the Na-modified zeolite demonstrated the highest activity.

Innovative biosynthesis of silver nanoparticles using yeast glucan nanopolymer and their potentiality as antibacterial composite.

Nanometals (NM) frequently possess potent antimicrobial potentials to combat various pathogens, but their elevated biotoxicity limits their direct applications. The biosynthesis of NM and their capping/conjugation with natural biopolymers can effectually enhance NM stability and diminish such toxicity. Yeast β-glucan (βG), from Saccharomyces cerevisiae, was extracted and transformed to nanoparticles (NPs) using alkali/acid facile protocol. The βG NPs were innovatively employed for direct biosynthesis of silver nanoparticles (Ag NPs) without extra chemical processes. The physicochemical assessments (Fourier-transform infrared, X-ray diffraction, and transmission electron microscopy) validated NPs formation, interaction, and interior capping of Ag NPs in βG NPs. The synthesized βG NPs, Ag NPs, and βG-Ag NPs composite were negatively charged and had minute particlesizes with mean diameters of 58.65, 6.72, and 63.88 nm, respectively. The NPs (plain Ag NPs and composited βG-Ag NPs) exhibited potent comparable bactericidal actions, opposing Gram+ (Staphylococcus aureus) and Gram- (Escherichia coli, Salmonella Typhimurium, and Pseudomonas aeruginosa). Scanning micrographs, of treated S. aureus and S. Typhimurium with βG-Ag NPs, elucidated the powerful bactericidal actions of nanocomposite for destructing pathogens' cells. The inventive Ag NPs biosynthesis with βG NPs and the combined βG-Ag NPs nanocomposites could be impressively recommended as powerful antibacterial candidates with minor potential toxicity.

Nanocellulose-Assisted Thermally Induced Growth of Silver Nanoparticles for Optical Applications.

Optically responsive materials are present in everyday life, from screens to sensors. However, fabricating large-area, fossil-free materials for functional biocompatible applications is still a challenge today. Nanocelluloses from various sources, such as wood, can provide biocompatibility and are emerging candidates for templating organic optoelectronics. Silver (Ag) in its nanoscale form shows excellent optical properties. Herein, we combine both materials using thin-film large-area spray-coating to study the fabrication of optical response applications. We characterize the Ag nanoparticle formation by X-ray scattering and UV–vis spectroscopy in situ during growth on the nanocellulose template. The morphology and optical properties of the nanocellulose film are compared to the rigid reference surface SiO2. Our results clearly show the potential to tailor the energy band gap of the resulting hybrid material.

Influence of Co contents on the microstructure and SERS performance of self-formed Ag nanoparticles/Ag-Co alloy films on flexible substrates

Self-formed Ag nanoparticles/Ag-Co alloy films with various Co contents were fabricated by sputtering Ag-Co composite target. Effects of Co contents in Ag-Co films on the microstructure and SERS performance of nanoparticles/alloy films were thoroughly investigated through SEM, TEM and Raman spectrometer. Amorphous Co in Ag-Co films restricted the growth of Ag grains in the films and promoted the formation and growth of Ag nanoparticles on the film’s surface. The size and number of Ag nanoparticles grown on the surface were closely related to Co contents in Ag-Co films, Ag-Co film thicknesses and annealing temperatures. Ag nanoparticles/Ag-Co films covered with Ag layers performed ultra-sensitive Raman signals due to forming abundant active hot spots. This flexible SERS substrate could detect 10−12 mol/L Rhodamine 6G (R6G), which indicated that this novel type of Ag nanoparticles/Ag-Co alloy films could be used and applied as high-efficient SERS substrates.

Application of Green Synthesized Metal Nanoparticles in the Photocatalytic Degradation of Dyes and Its Mathematical Modelling Using the Caputo–Fabrizio Fractional Derivative without the Singular Kernel

Textile dyes are untreated discharge into the environment which results in a significant increase in water pollution levels worldwide. Due to the continuous addition of toxic organic dyes, a necessary strategic model is required for the complete degradation of dyes in textile effluent. This paper considers the possibility of biological synthesis of silver and iron nanoparticles and their use in photocatalytic degradation. The immediate change of silver nitrate solution occurring from colorless to brown is observed after the addition of the aqueous leaf extract, indicating the successive reduction of Ag+ ions to the Ag nanoparticles. These formed Ag nanoparticles were subjected to examine the photocatalytic activity under the solar radiation for the degradation of methyl orange. Green synthesized Ag nanoparticles were found to successfully degrade methyl orange up to 95% between 70 hours than the initial exposure time. The absorbance of methyl orange was measured at 465 nm. The present paper is focused on fractional mathematical modelling of dye degradation in textile effluents using the Caputo–Fabrizio fractional derivative without the singular kernel. The iterative Laplace transform method is employed to obtain an analytic solution for the absorption transport equation. The obtained experimental results showing significant removal of dyes from textile wastewater are compared using modelling results. The innovative approach is in outstanding agreement with the findings of the experiment. The mathematical modelling for the dye removal process helps to design suitable environmental management studies to reduce the adverse effect caused by toxic wastewater. Model validation has been shown by comparing analytical simulated solutions with experimental results for photocatalytic degradation using silver and iron nanoparticles as eco-friendly and low-cost agents.