Absorption Of Ag Nanoparticles Research Articles

Effect of Silver Nanoparticles on the Optoelectronic Properties of Graphene Oxide Films

The effect of Ag nanoparticles (NPs) on the optical and optoelectronic properties of films based on graphene oxide has been studied. In the presence of Ag NPs, the morphology, as well as the thickness of graphene oxide films, were not changed. When Ag NPs were added, a change in the shape and position of the absorption bands and Raman spectra of graphene oxide was observed. It is shown that with the addition of Ag NPs, the G band of graphene oxide shifts to low frequencies, which may be the result of the absence of separate double bonds, while the ID/IG ratio was not changed, as did the number of Gr layers. In the absorption spectrum of the films, along with the absorption band of graphene oxide, a shoulder was registered, which can be associated with the absorption of Ag NPs. The optical density of Gr films with plasmonic NPs is higher than without them. Measurements of the optoelectronic characteristics showed that, in the presence of Ag NPs, an increase in the values of the photocurrent of graphene oxide is observed. The sensitivity of graphene oxide films was increased by almost 20 times when plasmonic NPs were added to them, and the detection ability increased by 25 times.The results obtained can be used in the development of new photosensitive devices for optoelectronic and applications.

Photocatalytic degradation of organic pollutants over visible light active plasmonic Ag nanoparticle loaded Ag2SO3 photocatalysts

In this work, the efficiency of organic pollutants degradation over Ag nanoparticles (NPs) loaded Ag2SO3 (AgSS) photocatalyst and the impact of reaction parameters on the degradation process are studied. Visible light active, AgSS plasmonic photocatalyst, was prepared by precipitation and chemical reduction method. The formation and well dispersion of cubic Ag NPs on the Ag2SO3 surface with enhanced visible light absorption was investigated by X-ray diffraction (XRD), Field-emission scanning electron microscopy (FESEM), Energy Dispersive X-ray analysis (EDX) and UV–vis-NIR spectrophotometer. The photocatalytic activity of the prepared photocatalysts was evaluated by organic dye and phenol degradation reaction. The effects of different factors such as catalyst composition, light source, initial pollutant concentration and pH of the solutions were studied using organic dye Rhodamine B (RhB). It was found that the localized surface plasmon resonance (LSPR) absorption of Ag NPs is strongly dependent on the size, shape and amount of the NPs loaded. 1-AgSS showed the best photodegradation performance with 99% RhB removal in 2 h. The photoactivity of the 1-AgSS was better at both high and low pH environment. The 1-AgSS composition showed reusability for five successive experimental cycles and good structural stability. Moreover, the formation of intermediates in phenol degradation reaction was confirmed over the 1-AgSS sample by UV-spectra and HPLC analysis. We believe that the synthesized AgSS photocatalysts have promising potential for the photocatalytic elimination of organic pollutants from industrial effluents.

Enhanced optical linearity and nonlinearity of Nd:YAG crystal embedded with Ag nanoparticles by prior Zn ion implantation

Nonlinear optical properties of nanocomposites exhibit wide nonlinear optical applications, but the nonlinear coefficient is not sufficiently high that it limits the potential application. Thus, we improve the nonlinear optical response of Nd:YAG by dual implantation with Zn and Ag ions to induce the formation of Ag nanoparticles (NPs) in the surface of a crystal. And the structural and optical properties of the NPs embedded in the Nd:YAG have been investigated. The surface plasmon resonance (SPR) absorption of Ag NPs in Nd:YAG crystal shows ~3 times enhancement with a narrower spatial distribution of NPs. Meanwhile, third-order nonlinear coefficients of the crystal embedded with NPs increase to 8 orders of magnitude larger than that of pure Nd:YAG due to the SPR effect. Furthermore, annealing can further modify SPR and nonlinear optical properties owing to improved crystalline structure. The present work provides an alternative route for enhancing the nonlinear optical properties and potential application in optical devices.

Structural, Optical and Plasmonic Properties of Ag-TiO2 Hybrid Plasmonic Nanostructures with Enhanced Photocatalytic Activity

Hybrid plasmonic nanostructures consisting of Ag nanoparticles decorated TiO2 nanorods with highly enhanced photocatalytic activity were synthesized by a facile wet chemical method. The structural, optical, plasmonic and photocatalytic properties of the synthesized Ag-TiO2 hybrid nanostructures were well characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), Raman spectroscopy, photoluminescence spectroscopy (PL) and UV-visible absorption spectroscopy. The photocatalytic activities of the as-synthesized Ag-TiO2 hybrid nanostructures were evaluated by studying sun light-driven photocatalytic degradation of methylene blue (MB) and methyl orange (MO) dyes in water. The results showed that Ag-TiO2 hybrid nanostructures exhibit highly enhanced photocatalytic activity towards degradation of MB and MO dyes and the photocatalytic efficiency increased with increase in Ag nanoparticle loading. The mechanism underlying the highly enhanced photocatalytic activity of Ag-TiO2 nanohybrids is proposed. We attribute the observed enhanced photocatalytic activity of Ag-TiO2 hybrid nanostructures to the efficient separation of photogenerated charge carriers in TiO2 due to the electron scavenging action of Ag nanoparticles and the improved sun light utilization by the plasmonic nanohybrids originating from the surface plasmon resonance (SPR) absorption of Ag nanoparticles.

Synthesis and the enhanced visible-light-driven photocatalytic activity of BiVO4 nanocrystals coupled with Ag nanoparticles

BiVO4 nanocrystals coupled with Ag nanoparticles (Ag–BiVO4 heterogeneous nanostructures) have been prepared by a new strategy via combining a hydrothermal route with a polyol process, in which BiVO4 nanocrystals were first synthesized by a hydrothermal route, and then, Ag nanoparticles were grown on the surfaces of the presynthesized BiVO4 nanocrystals through a polyol process. The photocatalytic evaluations demonstrate that BiVO4 nanocrystals coupled with Ag nanoparticles exhibit the enhanced visible-light-driven photocatalytic activity for the degradation of methylene blue (MB) and rhodamine B (RhB). The energy alignment and diffuse reflectance property of Ag–BiVO4 heterogeneous nanostructures demonstrate that Ag nanoparticles attached on the surfaces of BiVO4 nanocrystals play double roles for the enhanced visible-light-driven photocatalytic activity. First, the Ag nanoparticles grown on the surfaces of BiVO4 nanocrystals may act as electron sinks to retard the recombination of the photogenerated electrons and holes in BiVO4 so as to improve the charge separation on its surfaces. Second, the Ag nanoparticles increase the visible light absorption of the Ag–BiVO4 photocatalyst due to surface plasmon resonance (SPR) of Ag nanoparticles. These double roles of Ag nanoparticles make Ag–BiVO4 heterogeneous nanostructures to exhibit the enhanced photocatalytic activity to decompose MB and RhB under visible light irradiation, compared to the pure BiVO4 nanocrystals. The enhanced photocatalytic activity is attributed to the charge transfer from BiVO4 to the attached Ag nanoparticles as well as SPR absorption of Ag nanoparticles. The present work not only provides an efficient route to enhance visible-light-driven photocatalytic activity of BiVO4, but also offers a new strategy for fabricating metal–semiconductor heterogeneous nanostructure photocatalysts, which are expected to show considerable potential applications in solar-driven wastewater treatment and water splitting.

Ag(x)@WO₃ core-shell nanostructure for LSP enhanced chemical sensors.

Exceptional properties of graphene have triggered intensive research on other 2D materials. Surface plasmon is another subject being actively explored for many applications. Herein we report a new class of core-shell nanostructure in which the shell is made of a 2D material for effective plasmonic propagation. We have designed a much enhanced chemical sensor made of plasmonic Agx@(2D-WO3) that combines above advantages. Specifically, the sensor response increases from 38 for Agx-WO3 mixture to 217 for the Agx@(2D-WO3) core-shell structure; response and recovery time are shortened considerably to 2 and 5 seconds; and optimum sensor working temperature is lowered from 370°C to 340°C. Light irradiation is found to increase the Agx@(2D-WO3) sensor response, particularly at blue wavelength where it resonates with the absorption of Ag nanoparticles. Raman scattering shows significantly enhanced intensity for both the 2D-WO3 shell and surface adsorbates. Both the resonance sensor enhancement and the Raman suggest that the improved sensor performance is due to nanoplasmonic mechanism. It is demonstrated that (1) 2D material can be used as the shell component of a core-shell nanostructure, and (2) surface plasmon can effectively boost sensor performance.

Photocatalytic Water Splitting over Ag/TiO<sub>2</sub> Nano-Wire Films

Plasmonic Ag decorated TiO2 nano-wire film was firstly prepared by the combination of a hydrothermal method and a microwave-assisted chemical reduction process. The results show that Ag deposited TiO2 film exhibits obvious visible light absorption due to surface plasmon resonance absorption of Ag nanoparticles. Besides, fluorescence quenching is observed in the composite film under the excitation of 250 nm. Photocatalytic tests show that Ag deposited TiO2 exhibits enhanced photocatalytic activity for H2 production by water splitting due to the synergistic effect between charge transfer and surface plasmon resonance absorption properties of Ag nanoparticles.

Surface/Interface Synergetic Effect-Induced Great Optical Spectral Change with Ag Content for Ag Nanoparticles Dispersed in Mesoporous SiO<sub>2</sub>

The evolution of optical absorption and photoluminescence (PL) spectra with different Ag content (from 0.14 wt % to 2.80 wt %) has been investigated for Ag/mesoporous SiO2 when heating in H2 and air. It has been found that, in accordance with alternating heat treatment of the sample with fairly low Ag content in H2 and air, the surface plasmon resonance (SPR) absorption of Ag nanoparticles alternately and reversibly appears and disappears, whereas its PL emission alternately disappears and appears. However, such reversible change can not happen in the sample with high Ag content. With gradual increase of Ag content, the two kinds of spectra take great and regular change. The results have firstly been discussed based on two contrary mechanisms coexisting in air at high temperature (i.e., oxidation reaction and thermal reduction reaction). In particular, the abnormal oxidation and the great optical change with Ag content is closely relative to surface/interface synergetic effect between Ag, O2 and SiO2 matrix despite SiO2 usually being regarded as a chemical inert medium to noble metals. The study would provide valuable reference for optical switch, gas sensor, nano optical modulation of SiO2-based optical devices, and give valuable information for surface/interface chemistry and catalysis in Ag nanoparticles and SiO2 assemble system.