Monodispersed Ag Nanoparticles Research Articles

Study on fabrication and optical properties of monodisperse Ag-Au alloy nanostructure

This study addresses challenges in various fields by creating a new method for uniform, size- and composition-controlled Ag-Au alloy nanoparticles in organic solvents. Building on prior research, we demonstrate control over nanoparticle properties by varying complexing agents, surfactants, and reducing agents. Optimal conditions using surfactant SOA and reducing agent TBAB yielded small, monodisperse Ag nanoparticles ideal for alloying with Au. The reaction time significantly impacts final morphology and surface plasmon resonance (SPR) properties of the resultant Ag-Au alloy nanoparticles. Interestingly, Au nanoparticles formed under identical conditions shared a similar size with 60-minute Ag-Au alloys, evidenced by a single SPR peak at 520 nm. This control over Ag-Au nanoalloy composition and size opens doors for promising applications.

Monodispersed Ag nanoparticles deposited on Ni-based coordination polymer composite with enhanced photocatalytic degradation for bisphenol A

Exploring effective methods to improve photoresponse and charge separation efficiency is the key to preparing high-performance photocatalysts. A novel Ni-based coordination polymer, namely {[Ni(TIPA)2]·2Ac·6 H2O}n (Ni-TIPA), was designed and synthesized hydrothermally using the ligand tri-(4-imidazole phenyl) amine (TIPA). The metal-to-ligand charge transfer (MLCT) of Ni-TIPA is visually demonstrated by theoretical calculations as the key to enhanced charge separation efficiency. A series of novel silver-deposited Ni-TIPA composites (Ag@Ni-TIPA-X, X = 1, 2, 3) and excellent light-driven photocatalytic activity were prepared using a simple photoreduction method at room temperature. The prepared Ag@Ni-TIPA-2 composite had excellent photocatalytic performance for degrading bisphenol A (BPA) under ultraviolet light irradiation. The excellent photocatalytic performance might be attributed to MLCT and the surface plasmon resonance (SPR) of Ag nanoparticles, which improved hole-electron separation capability, and the formation of Schottky junctions. The intermediates in the BPA degradation process were further predicted and analyzed by electrostatic potential (ESP), orbital-weighted dual descriptor (ODD), and liquid chromatography-mass spectrometry (LC-MS) technologies, and the possible degradation mechanisms were deduced deeply. The work as a new reference might be provided for the efficient optimization of photocatalysts for BPA degradation.

Highly effective antibacterial properties of self-formed Ag nanoparticles/Zr-Ag granular films

Zr-Ag granular films are prepared by magnetron sputtering, on which monodisperse Ag nanoparticles are controllably fabricated through thermal annealing the thin films. The self-formation behaviors of Ag nanoparticles are temperature and Ag content dependent. At the annealing temperature of 360 ℃, the Zr-41.0 wt% Ag granular films have the highest number density of Ag nanoparticles. In vitro antibacterial experiments show that the Ag nanoparticles/Zr-Ag granular films exhibit an excellent antibacterial property, even more than 99.99% for both Escherichia coli and Staphylococcus aureus. The remarkable antibacterial activity can be ascribed to the release of Ag+ from Ag nanoparticles/Zr-Ag granular films and mechanical antibacterial effect of Ag nanoparticles. The results are helpful to the flexible fabrication and development of granular films with high antibacterial performances on different substrates.

Polydopamine microcapsules loaded Ag nanoparticles for catalytic reduction of organic pollutants

We demonstrate a simple approach for fabricating polydopamine microcapsules decorated with silver nanoparticles (Ag@PDA MCs) as highly efficient catalysts for water purification. Polydopamine microcapsules (PDA MCs) were formed on the MnCO3 template from self-polymerization and the removal of template under mild EDTA solution, followed by in situ reduction of Ag+ by PDA and growth of monodispersed Ag nanoparticles. Under optimized conditions, the Ag@PDA MCs exhibits 41.56 wt% of Ag loading contents and superior catalytic performance for the degradation of organic pollutants with rate constant of 2.93 min-1 for methylene blue and 1.03 min-1 for 4-nitrophenol. The excellent catalytic activity can mainly be ascribed to high surface roughness of microcapsules, high Ag loading ratio, and uniform distribution of Ag nanoparticles. In addition, this catalyst can be recycled for five times with degradation efficiency higher than 98%. The Ag@PDA MCs possessed fast reduction rate, high catalytic activity, and good recyclability as well as facile preparation and easy separation, showing great potential for the application in wastewater treatment.

Ag nanoparticle decorated graphene for improving tribological properties of fabric/phenolic composites

In the present study, graphene nanosheets (GNS) supporting monodispersed Ag nanoparticles (GNS/Ag) hybrid was constructed via an in-situ synthesis. The enhancement mechanism of friction and wear performance of Kevlar/PTFE (Poly-p-phenylene terephthamide)/(Polytetrafluoroethylene) phenolic composites reinforced by GNS/Ag hybrid was investigated by virtue of macroscopic experiments and microscopic molecular (MD) simulation. The results found that Ag nanoparticles were homogeneously anchored on the GNS surfaces. When 9 wt% GNS/Ag hybrid was incorporated into fabric composites, the friction coefficient and wear rate of Fabric-9GNS/Ag decreased by 40 % and 72 % because of synergistic enhancement of GNS and Ag nanoparticles. The MD simulation demonstrated that GNS/Ag hybrid had a strong interaction with molecular chains of PTFE, Kevlar and phenolic resin.

Green and Facile Synthesis of Pullulan-Stabilized Silver and Gold Nanoparticles for the Inhibition of Quorum Sensing.

Pullulan (Pull) decorated with monodisperse Ag and Au nanoparticles (NPs) was synthesized by a simple and green method. Samples were characterized by FTIR, UV–vis, NMR, XRD, TGA, SEM, XPS, DLS, and TEM. SEM images showed highly oriented microforms reported for the first time for Pull, because of the supramolecular self-assembling behavior of Pull chains. Antimicrobial and quorum sensing (QS) inhibition activities were tested against six pathogen bacteria and reporter and biomonitor strain. Pull decorated with NPs, in particular, Ag-modified ones, outperformed pristine Pull. The cell proliferation was tested with an MTT assay. NPs-decorated Pull was studied for the first time as an inhibitory agent against bacterial signal molecules and found to be a good candidate. The promising performance of AgNPs@Pull compared to the commercial antibiotic gentamicin showed that it has great potential as a therapeutic approach to overcome the bacterial resistance that has developed against conventional antibiotics.

Ag nanoparticles homogeneously anchored on kaolin synergistically improve the tribological performance of PBO/phenolic resin liner composites

In recent years, two dimensional hybrid materials have attracted immense attention in tribology field. However, kaolin shows potential value in catalysts and oil lubrication, and rarely in tribology of LC (liner composites). Herein, kaolin/Ag hybrids, in which mono-dispersed Ag nanoparticles (AgNPs) were dotted on kaolin, were prepared via in-situ reduction. The tribological behaviors of kaolin/Ag hybrids-reinforced PBO(poly(p-phenylene benzobisoxazole)/phenolic resin LC were evaluated. The results indicated that wear rate decreased but the friction coefficient slightly increased for sole kaolin filled PBO/phenolic resin LC. However, when kaolin/Ag hybrids were incorporated into PBO/phenolic resin LC, the wear rate and friction coefficient synchronously decreased. To understand the synergistic mechanism, worn surface morphology and a cross section of the tribofilm via FIB-TEM analyses are provided.

Deposition of Ag nanoparticles on polydopamine-functionalized CNTs for improving the tribological properties of PPESK composites

In this study, CNTs were first modified by polydopamine (PDA) to facilitate their surface activation and then Ag nanoparticles were in-situ grown on CNT-PDA to obtain CNT-PDA/Ag. The effects of functionalized CNTs on the tribological behaviors of poly (phthalazinone ether sulfone ketone) (PPESK) were investigated. Results revealed that PDA layer could not only increase the active functional groups on the CNT surface, but also act as an activated platform for the deposition of mono-dispersed Ag nanoparticles. The decoration of Ag nanoparticles decreased the interaction among CNTs, which was conducive to their good dispersion. Besides, by filling 0.3 wt% CNT-PDA/Ag, the thermal properties of PPESK were significantly improved, and its friction-reduction and anti-wear performances were the best among all PPESK composites, due to the good interfacial interaction between CNTs and PPESK, the synergistic reinforcing and lubricating effect of CNTs and Ag nanoparticles, as well as the lubricating effect of transfer film.

In Situ Functionalization of Silver Nanoparticles by Gallic Acid as a Colorimetric Sensor for Simple Sensitive Determination of Melamine in Milk.

A simple and green colorimetric sensing assay strategy for highly efficient determination of melamine has been fabricated, which is based on the redox reaction of gallic acid with Ag+. Monodispersed Ag nanoparticles (AgNPs) were obtained using gallic acid as a reducing and stabilizing agent. However, the aggregate behavior of AgNPs was observed, while the melamine was present in the reaction medium. As a result, the color of the solution changed from vivid yellow to brown, and the density of the color was quantitatively correlated with the melamine concentration. The aggregation of AgNPs could be attributable to the formation of hydrogen bonds between melamine and gallic acid. The designed sensor exhibited a good detection limit of 0.099 μM (0.012 ppm), which was much lower than the safety limit in China (1.0 ppm) and EU (2.0 ppm). Additionally, the sensing assay displayed good selectivity toward melamine over other coexisting substances. Consequently, the proposed colorimetric sensor was successfully used for the determination of melamine detection in raw milk samples.

Mono-dispersed Ag nanoparticles decorated graphitic carbon nitride: An excellent lubricating additive as PPESK composite film

Studies show that two dimensional (2D) nanomaterial and its hybrid have a great promise in tribology for the special laminar microstructure. However, the majority of performed investigations about 2D graphitic carbon nitride (g-C3N4) nanosheets are most focused on energy storage, catalysis, adsorption, rarely tribology. In the present study, g-C3N4 supporting mono-dispersed Ag nanoparticle hybrid (g-C3N4/Ag) is prepared, and its microstructure and chemical composition are determined. More specifically, the tribological performance as the lubricating additive of poly phthalazinone ether sulfone ketone (PPESK) composite is investigated using the ball-on-disc friction tester. Moreover, the corresponding enhancement mechanism is well proposed based on the experimental analysis and theoretical simulation. Obtained results show that Ag nanoparticles with a size of about 10–20 nm are homogeneously anchored on g-C3N4 nanosheets, favoring for good compatibility between g-C3N4/Ag and PPESK. It is found that when 0.3 wt% of g-C3N4/Ag is added to PPESK, the friction coefficient and wear rate of PPESK decrease by 68.9% and 97.1%, respectively. These reductions are mainly attributed to the synergistic self-lubricating effect of Ag nanoparticles and g-C3N4 nanosheet, the formation of transfer film, as well as the limited effect of g-C3N4/Ag on the shear deformation of PPESK composite film. Furthermore, it is found that the proposed g-C3N4/Ag-PPESK composite still keeps reasonable friction-reducing and wear-resistant properties under heavy loads and high rotating speeds. The present study demonstrates that the proposed g-C3N4/Ag hybrid is an excellent lubricating additive for polymer composites.

A comparative study on the effect of monodisperse Au and Ag nanoparticles on the performance of organic photovoltaic devices

The monodisperse Au (~5 nm) and Ag (~3 nm) nanoparticles used in this study were obtained using surfactant-assistant solvothermal methods and characterized by XRD TEM and SEM. Then, these nanoparticles were embedded into the P3HT:PCBM photoactive layer at different ratios and the effects of the nanoparticles on the performance of the organic solar cells have been studied by varying the loading percent of the NPs in the range of 0.5–2 wt%. The best solar cell composition was determined to be 1 wt% for Au NPs and 0.5 wt% for Ag NPs. Optical absorption spectrum of P3HT:PCBM, P3HT:PCBM:AuNPs and P3HT:PCBM:AgNPs active layers were obtained using UV–visible spectroscopy. The J–V plots of ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al solar cells having 1.10−6 m2 OSC area and with different Au NPs and Ag NPs loading ratios in the P3HT:PCBM were obtained under air mass (AM) 1.5G illumination. Open circuit voltage, short-circuit current density, fill factor, and power conversion efficiency of the OSC were calculated. The highest PCE values were obtained as 3.35% for Au NPs and as 3.50% for Ag NPs doped devices. This increase in PCEs was explained by a plasmonic effect that stems from the metallic NPs.

Functionalization of kaolin clay with silver nanoparticles by Murraya koenigii fruit extract-mediated bioreduction process for antimicrobial applications

The emergence of multidrug-resistant microbes and newly outbreaking diseases are one of the major threats before mankind. This paves the way for researchers to explore new antimicrobial agents that possess common day-to-day applications. In this concern, we have fabricated the antimicrobial Ag-kaolin functional nanostructures by simple and sustainable protocol employing Murraya koenigii fruit extract. UV-visible spectra (UV-Vis) of the Ag-kaolin exhibit absorption peak at 430 nm which corresponds to the characteristic surface plasmon resonance of Ag nanoparticles. X-ray diffraction pattern (XRD) shows the diffraction peak at 37.6° confirms their face-centred cubic nature with (111) plane. Furthermore, the formation of Ag-kaolin functional nanostructures was confirmed through a scanning electron microscope (SEM) and energy-dispersive X-ray spectrum (EDX) analysis. The transmission electron microscopic (TEM) studies reveal the effective formation of quasi-spherical monodispersed Ag nanoparticles having 20–30-nm diameters on the kaolin clay. The bio-synthesized Ag-kaolin nanostructures showed excellent antimicrobial activity against pathogenic gram-positive (Staphylococcus aureus, Bacillus subtilis) and gram-negative (Escherichia coli) bacteria respectively with the inhibition zones of 26 mm, 25 mm and 30 mm.

Silver nanoparticles formation over Ti-Zr-Nb alloy via polyol synthesis

Ag nanoparticles (AgNPs) were formed over the surface of novel superelastic Ti-Zr-Nb alloy via polyol synthesis at room temperature. Two synthesis media were used for AgNPs formation: ethylene glycol (EG) and polyethylene glycol (PEG-400). AgNPs formation rate in different polyols was evaluated by UV-VIS spectroscopy. Based on the obtained results higher formation rate was ascribed to PEG-400. Morphology of the material’s surface, as well as chemical composition, were analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It was demonstrated that the usage of PEG-400 as synthesis media facilitates the formation of more monodisperse AgNPs evenly distributed over the alloy’s surface.

Modeling, design, and synthesis of gram-scale monodispersed silver nanoparticles using microwave-assisted polyol process for metamaterial applications

High-yield monodispersed silver (Ag) nanospheres were modeled, designed, and synthesized by microwave-assisted (MW-assisted) polyol method from AgNO 3 , polyvinyl pyrrolidone (PVP), and ethylene glycol (EG), as precursors, at 145 °C within a short reaction time of 2 min, and the results were compared to those of conventional polyol method. Maintaining the PVP:AgNO 3 molar ratio, the effect of increasing the amounts of AgNO 3 and PVP at a constant amount of EG (40 mL) on the final product was evaluated. The synthesized nanoparticles (NPs) were characterized by SEM, UV–Vis spectroscopy, FTIR and DLS analysis. The results showed that with increasing the amount of AgNO 3 to 0.5 and 1 g, monodispersed Ag nanoparticles (Ag NPs) with particle sizes of 54 and 61 nm were formed, as per the plasmon absorption peaks at 436 and 442 nm, respectively. Moreover, using 40 mL of the EG solution, we could obtain a high yield of the NPs (~90%). The sub-gram yield was excellently high, offering great opportunities for commercializing the procedure. Also, the proposed study paves a new way for Ag NPs realization for different practical applications ranging from MW to optics. • Mathematical description of the electromagnetic and thermal interaction obtained between the impinging waves and AgNPs. • New MW-assisted polyol process used to synthesized very high yield AgNPs. • The obtained yield corresponded to a significant fraction of a gram as well as higher degrees of monodispersity.

One-step and surfactant-less synthesis of highly dispersed Ag nanoparticles on graphene oxide as highly effective catalyst for removal of organic dyes

An aqueous based, room temperature, and surfactant-free synthetic route is reported to yield high density of mono-dispersed Ag nanoparticles (AgNPs) supported on graphene oxide (GO) nanosheets. The retaining of oxygen functionalities on GO structure during the redox reaction offers GO the dual role of effective capping and supporting agents to realize the excellent dispersity and stability of the Ag/GO nanocomposites in aqueous solutions. Besides, the size and density of AgNPs anchored on GO are also modulated by controlling the GO, hydrazine, and Ag+ ions at the proper amounts in the growth solution. The combination of high density, pristine surface and the synergistic effect endow the Ag/GO nanocomposites highly catalytic activity towards the reduction of methylene blue (MB) and methyl orange (MO). This rapid, clean, and straightforward procedure offers an attractive avenue for the facile synthesis of noble metallic nanocomposites based on graphene oxides as both stabilizing and supporting materials.

Hierarchical assembly of highly efficient visible-light-driven Ag/g-C3N4/kaolinite composite photocatalyst for the degradation of ibuprofen

A novel Ag/g-C3N4/kaolinite composite photocatalyst was fabricated for the first time through a two-step assembly strategy by employing in situ calcination and a photodeposition process. The synthesized Ag/g-C3N4/kaolinite composite reached a higher degradation rate of ibuprofen (IBP) with a reaction rate constant of 0.0113 min−1 at an Ag content of 7% under visible-light irradiation, which was approximately 1.87 times that of the Ag/g-C3N4 composite. Based on the physicochemical properties, the enhanced photocatalytic activity was attributed to the stronger adsorption property, wider photoresponse range and more efficient separation and transfer of electron-hole pairs. Furthermore, the incorporation of monodispersed Ag nanoparticles onto the g-C3N4/kaolinite sheets provided more reactive sites for the IBP degradation. In addition, according to the EPR study and trapping experiments, it was demonstrated that holes (h+) should be the key reactive species. A possible pathway of IBP degradation was also proposed based on the detected intermediates. Overall, the results of this work may facilitate the design of a novel visible-light-driven photocatalyst with a high efficiency that is derived from a natural mineral for environmental remediation.

Size-Controlled Growth of Silver Nanoparticles onto Functionalized Ordered Mesoporous Polymers for Efficient CO2 Upgrading.

Highly dispersed metallic silver nanoparticles (AgNPs) are promising heterogeneous catalysts for carboxylative coupling of terminal alkynes with CO2 under mild conditions. Yet, their size-controlled synthesis is very challenging because of the high surface energy. Here, we prepared a series of amino-functionalized ordered mesoporous polymers as hosts for anchoring AgNPs. Control experiments and computations showed that electron-rich amines were confined in mesochannels with varying electron density and steric hindrance, creating "localized active zones (LAZ)" to control the growth of AgNPs. The particle size of AgNPs grows along with the increased volume of LAZ around nitrogen species. We also revealed that the catalytic activity of Ag-based catalysts is size-dependent and increases with decreasing particle size. Building on these findings, we report a facile one-pot synthesis strategy for preparing an amine-incorporated ordered mesoporous polymer (NOMP) with a high specific surface area, small LAZ volume, and uniform amine sites with controllable loading. These features result in the formation of ultrasmall and monodispersed Ag nanoparticles. Remarkably, Ag@NOMP gave a quantitative target yield under the conditions of 1 atm CO2 pressure and 50 °C, showing superior catalytic activity in CO2 carboxylation compared to other mesoporous analogues.

Novel Enzyme-Free Multifunctional Bentonite/Polypyrrole/Silver Nanocomposite Sensor for Hydrogen Peroxide Detection over a Wide pH Range.

Precise designs of low-cost and efficient catalysts for the detection of hydrogen peroxide (H2O2) over wide ranges of pH are important in various environmental applications. Herein, a versatile and ecofriendly approach is presented for the rational design of ternary bentonite-silylpropyl-polypyrrole/silver nanoarchitectures (denoted as BP-PS-PPy/Ag) via the in-situ photo polymerization of pyrrole with salinized bentonite (BP-PS) in the presence of silver nitrate. The Pyrrolyl-functionalized silane (PS) is used as a coupling agent for tailoring the formation of highly exfoliated BP-PS-PPy sheet-like nanostructures ornamented with monodispersed Ag nanoparticles (NPs). Taking advantage of the combination between the unique physicochemical properties of BP-PS-PPy and the outstanding catalytic merits of Ag nanoparticles (NPs), the as-synthesized BP-PS-PPy/Ag shows a superior electrocatalytic reduction and high-detection activity towards H2O2 under different pH conditions (from 3 to 10). Intriguingly, the UV-light irradiation significantly enhances the electroreduction activity of H2O2 substantially, compared with the dark conditions, due to the high photoelectric response properties of Ag NPs. Moreover, BP-PS-PPy/Ag achived a quick current response with a detection limit at 1 μM within only 1 s. Our present approach is green, facile, scalable and renewable.

Monodispersed Ag Nanoparticle in Layered Double Hydroxides as Matrix for Laser Desorption/Ionization Mass Spectrometry

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) in the low-molecular-weight (LMW) range is a long-standing challenge because of the fragments from the matrix and the heterogeneity of the matrix-analyte crystals. In this work, a homogeneous film with the monodispersed Ag nanoparticles (Ag NPs) in the confined interlayer of layered double hydroxides (LDHs) has been achieved. The Ag NPs with advantageous optical absorption could realize the energy capture and transfer process, and LDHs with abundant hydroxyl groups are beneficial for the deprotonated reaction. Therefore, the as-prepared film exhibited interference-free deprotonated signals in negative-ion mode with high ionization efficiency. The uniform matrix-analyte spots were constructed through the homogeneous assembly process, contributing to the high reproducibility for both the liquid and gaseous samples. Good linearities were successfully realized in the range from 0.1 μM to 1.0 mM for glucose with the relative standard deviation (RSD) of 3.8%, and 0.2-2.0 mM with the average RSD of 4.5% for psoralen samples, respectively. It is believed that the proposed matrix could exhibit competitive advantages for MALDI detection in the LMW region, which may provide new insight into development for MALDI mass detection.

Naringin-Chalcone Bioflavonoid-Protected Nanocolloids: Mode of Flavonoid Adsorption, a Determinant for Protein Extraction.

In order to highlight the applications of bioflavonoids in materials chemistry, naringin and its chalcone form were used in the nanomaterial synthesis to produce flavonoid-conjugated nanomaterials in aqueous phase. Chalcone form proved to be excellent reducing as well as stabilizing agent in the synthesis of monodisperse Au, Ag, and Pd nanoparticles (NPs) of ∼5–15 nm, following in situ reaction conditions where no external reducing or stabilizing agents were used. The mechanism of NP surface adsorption of flavonoid was determined with the help of dynamic light scattering and zeta potential measurements. Surface-adsorbed flavonoids also allowed NPs to easily transfer into the organic phase by using aqueous insoluble ionic liquid. Pd NPs attracted the excessive amount of surface adsorption of both naringin as well as its chalcone form that in turn drove Pd NPs in self-assembled state in comparison to Au or Ag NPs. An amount of surface-adsorbed flavonoids selectively determined the extraction of protein fractions from complex zein corn starch protein solution. Self-assembled Pd NPs with a large amount of surface-adsorbed naringin preferentially extracted zein fraction of higher molar mass, whereas Au and Ag NPs almost equally extracted the zein fractions of lower molar masses.