Buffer Layer Assisted Growth of Ag Nanoparticles in Titania Thin Films

Abstract

Developing materials with improved photocatalytic activity is important for light energy conversion and storage within chemical bonds. Here we present a new type of hybrid film of silver nanoparticles (AgNPs) embedded within TiO x (x ≤ 2) to approach this goal, introducing visible light absorption via surface-plasmon excitation of the AgNPs. Silver nanoparticles were prepared by an ultrahigh vacuum (UHV) based buffer layer assisted growth method. The titania films as a substrate and protective layers were grown by the reactive layer assisted deposition (RLAD) technique; in both cases amorphous solid water (ASW) was the buffer material. The thin titania films and the AgNPs were ex situ characterized by UV−vis, micro-Raman, XRD, XPS, SEM, and TEM techniques. The titania protective layers on top of the silver particles were found to introduce a dielectric environment for the AgNPs, leading to a significant red-shift of their plasmon resonance from 460 to 530 nm, in addition to avoiding oxidation of the small nanoparticles. Photoinduced activity of these hybrid films has been tested following the degradation of methylene blue (MB) in aqueous solution under both UV and visible pulsed laser irradiation. Preliminary results have shown photocatalytic activity of the RLAD titania film with only marginal influence due to the presence of the AgNPs. Possible reasons for this observation are discussed.

Fabrication of Ag-modified hollow titania spheres via controlled silver diffusion in Ag–TiO2 core–shell nanostructures

“…To the best of our knowledge, the silver diffusion in TiO 2 nanostructures has been only investigated in the case of TiO 2 thin films [8,[21][22][23][24] and our studies are probably the first to discuss this process occurring in Ag@TiO 2 CSNs. Based on our results and the diffusion mechanism proposed for AgNPs on titania films [8,21], the silver diffusion in Ag@TiO 2 CSNs can occur in the following manner. Titania is oxidized in an air atmosphere and as a result, holes, which may further oxidize AgNPs surrounded by the titania shell, are generated.…”

“…In case of Ag@TiO 2 CSNs and depending on the annealing time, these ejected Ag clusters may either be accommodated within or on the titania shell. In the titania shell, these silver clusters could react with the TiO 2 host through the formation of a complex [Ag-(TiO 2 )] [21]. Upon reaching the surface of the titania shell positively charged silver species could also form AgNPs much smaller than the core of the initial Ag@TiO 2 CSNs.…”

Incorporation of ZnO and their composite nanostructured material into a cotton fabric platform for wearable device applications

“…The Ag-composite with ZnO is shown as positive, which means that the material is p-type, and it seen with a thermopower value of 471.9 V/K (see graph: AZ1), 132.2 V/K (see graph: AZ2) respectively. As a consequence, the growth process of ZnO is disrupted, when the Ag composites are introduced, and the growth process is again favored when enough Ag have recombined with the Zn material which may cause the positive effect on the charge separation efficiency (Hongi & Bredas, 2016;Zilberberg, Mitlin, Shankar, & Asscher, 2015). It is of great importance to note here that both the compounds (AZ1 and AZ2) possess the p type thermopower but AZ1 exhibit the higher value due to the intergranular crystal structure which plays an important role in charge transport.…”

Noble metal-titania hybrid nanoparticle clusters and the interaction to proteins for photo-catalysis in aqueous environments

“…[28,43] The turnover frequency, k * , is defined as the mass of MB converted on the basis of unit mass of TiO 2 (i.e., the active phase). Figure 3d, the peak mobility diameters of AgTiO 2 -NPCs versus C Ag were relative constant (≈ 80 nm), showing that the primary diameter was not dependent of C Ag over the concentration range we studied (i.e., the decorated AgNPs in TiO 2 -NPCs did not affect the physical size of the hybrid NPs).…”

“…[23][24][25][26][27] Therefore, the ligandnanoparticle interfacial interaction is important to the activity of photocatalysis, which affects the key material properties corresponding to the interfacial charge transfer described previously. [4,12,16,28] For example, the ligand-nanoparticle interaction affects the stability of TiO 2 -based hybrid NP and the corresponding abilities in the absorption of light irradiation. [29-32] Besides, the molecular adsorption also affects the oxidation-reduction cycle and the charge transport between the TiO 2 -based hybrid NP and the molecules presenting in the environment.…”