Uniform Ag Nanoparticles Research Articles

Selective Flocculation and H2O2-Free Oxidative Etching-Based Synthesis of Highly Monodisperse Ag Nanospheres for Uniform Quantum Dot Photoluminescence-Enhancing Plasmonic Cavity Applications.

Ag nanoparticles have garnered significant attention for their excellent plasmonic properties and potential use as plasmonic cavities, primarily because of their intrinsically low ohmic losses and optical properties in the visible range. These are particularly crucial in systems involving quantum dots that absorb light at low wavelengths, where the need for a high threshold energy of interband transitions necessitates the incorporation of Ag nanostructures. However, the synthesis of Ag nanoparticles still encounters challenges in achieving structural uniformity and monodispersity, along with chemical stability, consequentially inducing inconsistent and poorly reliable optical responses. Here, we present a two-step approach for synthesizing highly uniform spherical Ag nanoparticles involving depletion-induced flocculation and Cu(II)-mediated oxidative etching. We found that the selective flocculation of multitwinned Ag nanocrystals significantly enhances the uniformity of the resulting Ag nanostructures, leaving behind only single-crystalline and single-twinned nanostructures. Subsequent oxidative etching, in which cupric ions are directly involved in the reaction, was designed based on Pourbaix diagrams to proceed following thermodynamically favorable states and circumvent the generation of reactive chemical species such as H2O2. This leads to perfectly spherical shapes of final Ag nanoparticles with a synthetic yield of 99.5% and additionally reduces the overall reaction time. Furthermore, we explore the potential applications of these monodisperse Ag nanospheres as uniform plasmonic cavities. The fabricated Ag nanosphere films uniformly enhanced the photoluminescence of InP/ZnSe/ZnS quantum dots, showcasing their capabilities in exhibiting consistent plasmonic responses across a large area.

Preparation of uniform Ag nanoparticles with enhanced plasmon resonance intensity and antibacterial efficiency via two-step dewetting process

Preparation of uniform Ag nanoparticles with enhanced plasmon resonance intensity and antibacterial efficiency via two-step dewetting process

Enhanced Interfacial Charge Transfer/Separation By LSPR-Induced Defective Semiconductor Toward High Co2 RR Performance.

Solar-driven reduction of CO2 emissions into high-value-added carbonaceous compounds has been recognized as a sustainable energy conversion way. The high-efficiency charge separation and effective activation are the critical issues in the process. The local plasma effect of metal and the vacancy of semiconductors in the metal-semiconductor heterostructure can solve this issue extensively. Herein, an oxygen vacancy photocatalyst containing uniform Ag nanoparticles (Ag-20@Nb2 O5- x ) is designed, which exhibits an excellent reduction performance and the CO yield can reach 59.13 µmol g-1 with high selectivity. The carrier migration is accelerated and the activation of CO2 is facilitated by the local surface plasmon effect and oxygen vacancy. Moreover, the photocatalytic CO2 reduction mechanism is revealed based on the density functional theory and in situ technology in detail. This work provides an in-depth understanding of the design of more ingenious metal-semiconductor photocatalysts to achieve more efficient charge transfer.

Small-sized Ag nanoparticle stacked films promoted by sustainedly released surfactants for plasmonic broadband super absorption

Large-area, highly absorptive films stacked of uniform Ag nanoparticles (AgNPs) with sub-20 nm size were fabricated by magnetron sputtering at the presence of adhesive tape, during which O-containing compounds were sustainedly released from the adhesive glue that acted as gaseous surfactants to promote the nucleation and simultaneously suppress the coalescence of the AgNPs. Plasmonic absorbers of metal-insulator-metal (MIM) configuration with a gradient-thickness insulator layer were constructed by conformally depositing such small-sized AgNP stacked films (S-AgSFs) on alumina templates with V-shaped nanopores. The broadband optical impedance matching of this novel MIM structure enables broadband light absorption from ultraviolet to near-infrared region, by working together with the large absorption cross-section, strong interparticle plasmon coupling of closely stacking small-sized AgNPs, and the light-trapping effect of the porous template. The average absorbance reaches 96.8 % in the visible region and 86.7 % in the 200–1600 nm range, respectively, showing the great potential of this absorber for applications in antireflection, solar energy harvesting and utilizing, etc. This adhesive-tape-assisted physical vapor deposition approach is simple, cost-effective, and can be applied to various types of substrates, which will enrich the fabrication strategy of metal nanostructures with effectively controlled geometries and optical properties.

Achieving effective antibacterial property on Ag/CoO-N photocatalytic composites

Acinetobacter baumannii (A. baumannii) was widely existed in medical wastewater and easily induced infections to threaten the human healthy. We herein reported Ag/CoO-N photocatalyst composites for effective inactivation of A. baumannii. Ag/CoO-N composites were prepared by N-doping to CoO crystal in supercritical fluid followed with photo-reduction of Ag under visible-light irradiation. N-species was incorporated in the crystal structure of CoO, on which uniform Ag nanoparticles were stably deposited. Thus, the satisfactory photocatalytic sterilization of A. baumannii irradiated by visible-light irradiation was attributed to the high capability of light trapping and the efficient separation of photo-charges. Due to photo-induced electrons as the main active species, Ag nanoparticles and CoO-N synergistically realized mineralization of cell membrane, which lead K+ ions leak from cell to crack structure of bacteria, the decrease of genetic materials, and the cripple of the self-repair function in bacteria, resulting in the final cell death.

Synthesis and characterization of silver nanoparticle-decorated coal gasification fine slag porous microbeads and their application in antistatic polypropylene composites

A conductive powder of coal gasification fine slag porous microbeads (CMs) coated with silver (Ag) nanoparticles was synthesized by a simplified electroless plating method. CMs were coated with uniform and dense Ag nanoparticles ([email protected]) to form a conductive structure consisting of internal conductive channels and a surface coating layer. The powder volume resistivity of [email protected] reached 1.47 Ω·cm. Subsequently, [email protected] were mixed with polypropylene (PP) to prepare an [email protected]@PP composite with a volume resistivity of 3.35 × 105 Ω·cm, a tensile strength of 26.06 MPa, and an elongation at break of 43.09%. Due to the high specific surface area (65.41 m2/g), small particle size (8.13 μm), and low density (1.51 g/cm3) of [email protected], the [email protected]@PP composite had better volume resistivity and mechanical properties than the PP composite filling with commercial silver-plated glass beads. The findings of this research could provide a theoretical foundation for future applications of [email protected]

Modified Ag nanoparticles on the regular array structure to improve the optical properties

The surface-enhanced Raman scattering (SERS) technique strongly depended on the excellent optical properties of the substrate. However, simply roughing of the metal surfaces to support SERS techniques suffer from the lack of uniform, and reproducibility to apply the SERS substrate. In this paper, we report that Ag nanoparticles are modified after sputtering Ag film on the cicada wing (CW) to preparate the SERS substrate for AgNPs/Ag-20/CW. Compared with Ag-20/CW, the AgNPs/Ag-20/CW has better polarization independence, and the RSD value is 6.1% which represents the excellent uniform of the substrate. The optical properties of SERS substrate are improved by modifying a large number of dense and uniform Ag nanoparticles on the Ag@CW.

Constructing supported Ag antibacterial nano-agent with high activity and stability for broad-spectrum antibiosis

The developing a green and facile synthetic approach of Ag-based antibacterial nanomaterials with controlled composition, size, and shape, to acquire high antibacterial activity and long-term durability, is of vital importance and remains a challenging goal. Herein, a novel LDHs-supported Ag antibacterial nanomaterial (Ag/CoAl-LDHs) are fabricated via an in situ deposition of the Ag nanoparticles onto the CoAl-LDHs surface. X-ray diffraction pattern (XRD) and High-resolution TEM (HRTEM) measurements confirm that the uniform Ag nanoparticles (the average particle size of 16.5 nm) are highly dispersed and firmly anchored onto CoAl-LDHs surface. As revealed by x-ray photoelectron spectroscopy (XPS), the CoAl-LDHs nanoplates play the roles of both a support and a reductant without any external, and there was a redox reaction between Co2+ in LDHs layers and Ag+ in AgNO3 solution, giving rise to in situ loading of Ag nanoparticles onto LDHs. Moreover, antibacterial experiments verify that Ag/CoAl-LDHs not only have efficient antibacterial activity against both Escherichia coli and Staphylococcus aureus, but also exhibit very stable antibacterial properties for both bacteria. Therefore, this research demonstrates a successful paradigm for the rational design and preparation of new antibacterial nanomaterials with high antibacterial activity and long-term durability.

Graphdiyne‐Stabilized Silver Nanoparticles as an Efficient Electrocatalyst for CO2 Reduction

Electrochemical CO2 reduction reaction (e‐CO2RR) into high‐value chemicals is a promising approach for sustainable energy research, but there remains a great challenge to develop efficient and stable catalysts. Herein, in situ synthesized uniform Ag nanoparticles (AgNPs) directly growing on the surface of 2D graphdiyne (GDY) for selectively reducing CO2 to CO with high efficiency and stability are reported. Due to the special electronic distribution of GDY, it not only serves as a template for the growth of AgNPs to prevent its aggregation, but also increases active sites and transformation of electrons through the intimate interaction between phase interface to enhance their cooperative catalytic effect, which highly improves the electrocatalytic performance of the nanocomposite. Through investigations, it is found that the Ag/GDY/CC nanocomposite electrochemically reduces CO2 to CO with Faraday efficiency up to 92.1% and current density of 25.74 mA/cm2 at the potential of −1.3 V versus reversible hydrogen electrode (RHE). Meanwhile, during catalysis, the Ag/GDY/CC composite maintains excellent stability with a high current density of ≈26 mA/cm2 (threefold higher than that of Ag/CC), unchanged for over 24 h. To the best knowledge, herein, the first experimental study of an efficient CO2 reduction electrocatalyst based on GDY is represented.

Chemisorbed Superoxide Species Enhanced the High Catalytic Performance of Ag/Co3O4 Nanocubes for Soot Oxidation.

The respective action mode between surface-adsorbed oxygen and bulk lattice oxygen during catalytic soot oxidation is still not fully recognized. Herein, a series of Ag-loaded Co3O4 catalysts with different Ag loading amounts were prepared by the impregnation method, and 5% Ag/Co3O4 presented competitive catalytic activity toward soot combustion with a T50 below 290 °C in 10% O2/N2. This remarkable improvement in catalytic performance could be primarily attributed to the enhanced Ag-Co3O4 metal-support interaction induced by the formation of uniform, dispersive, and suitable size metallic Ag nanoparticles. The activation, activity, consumption-regeneration, identification, and reaction of surface-adsorbed oxygen along with the activity of bulk lattice oxygen were characterized by various designed and in situ techniques. The results demonstrated that the chemisorbed superoxide species (O2-) play the potentially responsible role for boosting soot combustion, while the bulk lattice oxygen is much less active within the tested temperatures, inducing a negligible activity contribution. Moreover, soot-temperature programmed reduction, isothermal kinetic study, and density functional theory calculation provided supplementary support for the enhancement effect of Ag-Co3O4 combination in the activation and utilization of surface-adsorbed oxygen. The overall objective of this work is to identify the role of surface-adsorbed oxygen and bulk lattice oxygen for soot oxidation over Ag/Co3O4 catalysts.

Synergy of NTP-La1-xAgxMn1-yCoyO3-δ Hybrid for Soot Catalytic Combustion at Low Temperature

Ag and Co co-doped La1-xAgxMn1-yCoyO3-δ perovskites were prepared by the citric acid sol–gel method. The maximum solubility of Ag+ in LaMnO3 decreased with the increase of Co doped in B-site, which lead to the exsolution of excess Ag+ from A-site of perovskite. The exsolution progress is more favorable to the formation of uniform and stable Ag nanoparticles on the perovskite substrate. The non-thermal plasma (NTP) assisted La1-xAgxMn1-yCoyO3-δ for soot catalytic combustion had been investigated under diesel exhaust gas conditions. When La1-xAgxMn1-yCoyO3-δ was utilized as the catalyst without NTP, the soot could hardly be oxidized at 200 °C. However, when La1-xAgxMn1-yCoyO3-δ was combined with NTP, the efficiency of soot removal was dramatically improved. The NTP-La0.5Ag0.5Mn0.8Co0.2O3-δ hybrid had the highest soot removal efficiency and CO2 selectivity. The combination of NTP and La1-xAgxMn1-yCoyO3-δ could form a synergistic catalytic effect, which significantly promoted the combustion of soot at low temperature. The results of characterization and experiments indicated that the synergistic catalytic performance depended on the coordination of short-living species in plasma, adsorbed oxygen and Ag nanoparticles on surface of La1-xAgxMn1-yCoyO3-δ. Based on these results, the reaction mechanism of plasma-catalyst hybrid for soot catalytic combustion was proposed.

Detection of Soluble Mercury in Cinnabar Using a CV-Ag NPs SERS Probe.

In the current work a uniform morphological Ag nanoparticles (Ag NPs) were prepared with ascorbic acid as a reducing agent and citrate as a stabilizer. The surface of Ag NPs modified by crystal violet (CV) and potassium iodide (KI) was used as an aggregation agent to obtain CV modified Ag NPs (CV-Ag NPs) probes for detecting mercury ions. The mercury ions could be reduced to mercury molecules by citrate, and then deposited on the surface of Ag NPs, leading to the separation of CV molecules from the surface of Ag NPs. Therefore, the SERS signal intensity of CV decreased with the increase of the Hg2+ concentration and the concentration of Hg2+ was in the range of 1 × 10-11 to 1 × 10-5 M. Taking the change of the characteristic peak intensity of CV at 913 cm-1 as a reference, the SERS spectrum intensity of CV has a linear relationship with the Hg2+ concentration. The equation is y = -333.55x + 1343.05, where the linear correlation coefficient is R2 = 0.980, and the recovery rate is between 84.20 to 105.60%. Finally, the CV-Ag NPs probe was used to quickly detect soluble mercury in cinnabar. Compared with the conventional large-scale instrument detection method, this simple and fast method, can be applied for rapid detection of soluble mercury, and has a certain significance for concerning the research of mineral medicine processing mechanism.

Plasmonic composites WO3/Bi12O17Cl2 decorated with uniform Ag nanoparticles in tiny size: Synthesis, analyses, and visible-light photocatalytic performance

Various novel ternary composites Ag/WO3/Bi12O17Cl2 were successfully constructed through a rapid and facile microwave-assisted approach to decorate Ag nanoparticles onto WO3/Bi12O17Cl2 surface. Through analyses, three expected components were coexisted and formed n–p heterojunctions with Ag nanoparticles of uniform morphology and size below 20 nm. These plasmonic composites with favorable physiochemical properties showed greatly reinforced photocatalytic performance over degradation of Rhodamine B (RhB), methyl orange (MO), and tetracycline hydrochloride (TC) upon visible light irradiation. Moreover, these samples exhibited satisfactory structural stability and reusability in both aqueous and saline solution. Eventually, a plausible photocatalysis mechanism was speculated upon analytical and experimental results. Such investigation might provide a series of ternary composites with small size of Ag nanoparticles for sake of contaminants control and environmental preservation.

A ratiometric electrochemical microsensor for monitoring chloride ions in vivo.

Chloride ion (Cl-), the most common anion in animal brain, has been verified to play a vital role in maintaining normal physiological processes. Thus, development of a reliable platform to determine Cl- is of great significance for brain research involving Cl-. In this work, a ratiometric electrochemical microsensor (REM) for the in vivo measurement of cerebral Cl- was designed. To prepare REM, uniform Ag nanoparticles (Ag NPs) with nano-level sizes were synthesized via an adsorption-reduction process, which served as selective recognition elements for Cl- determination, while methylene blue (MB) was absorbed and acted as an inner reference unit to avoid the environmental interference of complicated brain systems. As a result, this developed REM exhibited high sensitivity and selectivity, as well as good stability, reproducibility and anti-biofouling. This reliable approach was established to monitor Cl- in mouse brain.

A N-doped porous carbon framework with Ag-nanoparticles toward stable lithium metal anodes

A 3D porous carbon framework embedded with uniform Ag nanoparticles (ADPCF) is fabricated by a one-step chemical blowing process. The ADPCF electrode exhibits great cycling stability for over 2500 h (1250 cycles) with small hysteresis.

In situ green growth of uniform and naked Ag nanoparticles on graphene oxide at room temperature and its enhanced catalytic performance

In situ growth of naked Ag nanoparticles on graphene oxide was achieved following a simple, green, and environment-friendly one-step stirring method. In the absence of extra reductant and stabilizer, the naked Ag nanoparticles formed on the surface of GO via a spontaneous redox reaction between Ag+ and GO at room temperature. The morphology and microstructure of the resultant heterogeneous nanostructures were characterized by various spectroscopic and microscopic techniques systematically. The characterization results showed that the naked metallic Ag nanoparticles with an average diameter of 4.31 ± 0.13 nm distribute homogeneously and tend to “stand” in line on GO. The well-known catalytic hydrogenation of 4-nitrophenol by NaBH4 was carried out to investigate the potential catalytic activity of the obtained heterogeneous Ag/GO nanocomposite. The obtained Ag/GO nanocomposite exhibited high catalytic ability with the apparent kinetics constant of 1.856 min−1 and high turnover frequency of 2131.6 h−1 and high structural and performance stability. It is believed that the small size and naked surface of the Ag nanoparticles, which provide abundant exposed catalytically active sites, facilitate greatly in improving the catalytic performance of Ag/GO. It is anticipated that the proposed green method is extendible to prepare other efficient noble-metal/GO nanocatalyst.

Targeted Antibacterial Therapy: Ag Nanoparticles Cluster with pH‐Triggered Reassembly in Targeting Antimicrobial Applications (Adv. Funct. Mater. 17/2020)

In article number 2000511, Zhengbao Zha, Tao He, and co-workers design uniform pH-responsive Ag nanoparticle clusters, triggered by the acidic micro-environment of bacterial infections, that could collapse and re-assemble into nonuniform Ag NPs assemblies, which result in improved antibacterial activities against methicillin-resistant Staphylococcus aureus and Escherichia coli.

Catalytic oxidation of toluene using a facile synthesized Ag nanoparticle supported on UiO-66 derivative

In this paper, dispersed Ag nanoparticles supported on UiO-66 derivative were prepared and the effect of Ag loading on the structure and performance of the catalysts for toluene oxidation were studied. The characteristics of the catalysts were studied by XRD, SEM, TEM, HRTEM, BET, ICP-OES, XPS, UV–vis and in situ DRIFTS. It was observed that UiO-66 structure of 2 wt% Ag catalyst (2Ag-U) was not damaged. When Ag loading was further increased to 10 wt% (10Ag-U), framework of UiO-66 collapsed and uniform Ag nanoparticles were dispersed on the surface of support. Further increasing Ag to 14 wt% (14Ag-U), large Ag nanoparticles were observed, and Ag species migrated to the bulk phase of the support, resulting in the decrease of surface Ag content. The 10Ag-U catalyst showed excellent catalytic performance due to higher lattice oxygen and surface Ag0 content. In addition, in situ DRIFTS analysis was used to explore toluene-catalyzed intermediates. It was found that toluene was converted to benzaldehyde and benzoic acid, eventually forming CO2 and H2O.

Preparation of Ag@SiO2@NH2 core-shell nanocomposites for the fluorescence enhancement of carbon quantum dots

In this paper, the fluorescence enhancement phenomenon of carbon quantum dots (C-QDs) via metal fluorescence effect has been investigated. Firstly, uniform Ag nanoparticles was prepared, which theoretically can supply a strong enhancement effect with a diameter as small as 20 nm. Then SiO2 shell was utilized to control the distance between Ag core and C-QDs while surface charge of as-synthesized Ag@SiO2 was further modified to bond C-QDs via electrostatic effect. Four different kinds of SiO2 shell, with thickness 12 nm, 15 nm, 20 nm, and 27 nm, were synthesized to study the enhancement effect of distance. With the increase of SiO2 shell, the fluorescence of Ag@SiO2@NH2-C-QDs nanocomposites rise first but then fall while the sample with the 20-nm shell obtained the best enhancement effect as high as 3.92-fold. Surface charge vibration of metal particles was used to explain this phenomenon.

Biotemplated synthesis of cellulose nanocrystal@PVP-assisted polydopamine@Ag nanoparticle as conductive composites

The controllable deposition of silver (Ag) nanoparticle onto functional materials is beneficial for a wide range of applications including conductive composites and electrically conductive adhesives. While the deposition of Ag nanoparticles on various substrates has been extensively studied, the fine control of the size, dispersion, growth, and colloidal stability of silver nanoparticles on complex high aspect-ratio nanomaterials is still a challenge. In this work, we report the synthesis of conductive composites of cellulose nanocrystal coated with a uniform layer of Ag nanoparticle. For this, we have used polyvinylpyrrolidone (PVP) as a coupling agent for the formation of polydopamine (PDA) on cellulose nanocrystal and the subsequent formation of uniform Ag nanoparticle. With continuously and closely packed Ag nanoparticles, the as-prepared conductive composites demonstrated promising applications as conductive composite paste for direct writing and as a co-filler for hybrid electrically conductive adhesives. As a conductive composite paste, no high-temperature sintering is required when it is written on paper, glass slide and fabrics to form conductive patterns. When served as a co-filler in electrically conductive adhesives, a small amount of conductive composites (1.5 wt%) largely enhanced conductivity and lap shear strength, while maintaining the excellent viscosity for easy operation in stencil printing and 3D printing.