Colorimetric Detection of an Airborne Remote Photocatalytic Reaction Using a Stratified Ag Nanoparticle Sheet

Abstract

Photocatalysts are practically used for decomposition of harmful and fouling organic compounds. Among the photocatalytic reactions, remote oxidation via airborne species is a relatively slow process, so that a sensitive technique for its detection has been awaiting. Here, we investigated an airborne remote photocatalytic reaction of a TiO2 photocatalyst modified with Pt nanoparticles as co-catalysts via the color change caused by a decomposition of a multilayered silver nanoparticle sheet. The silver nanoparticle sheet fabricated by the Langmuir-Schaefer method on a gold substrate exhibits a unique multicolor depending upon the number of layers. The color originates from multiple light trapping in the stratified sheets that has a metamaterial characteristic along with an intra- and interlayer coupling of localized surface plasmon resonance (LSPR). The stepwise decomposition of the sheets was confirmed by the colorimetric data, which exhibited not only a monotonic decrease but also a maximized absorption of light when the film thickness reached the optimal thickness for light trapping or when the oxidation of the Ag core started. Scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and surface plasmon resonance (SPR) spectroscopy data provided a complete view of the decomposition process of this inorganic-organic nanocomposite film, and simulation by the transfer-matrix method explained a simultaneous plasmonic response rationally. The influence of the humidity and gas flow rate on the airborne remote photocatalytic reaction kinetics was examined by this colorimetric detection method, and it suggests that H2O in air plays an essential role in the reaction.

Two-Dimensional Empty Liquid Composed of a Patchy Metal Nanoparticle Network Structure for Transparent Plasmonic Devices

“…9 These films give rise to unique optical phenomena such as electromagnetically induced transparency (EIT), 10 where an extremely large color change is obtained depending on the number of layers deposited on a metal surface. As evidence that this phenomenon is derived from the metamaterial properties of condensed particle films, the experimental results are reproduced well by transfer-matrix method calculations, employing an effective medium approximation with high n and k. These films could act as plasmonic metamaterial light absorbers, have been used for colorimetric sensor applications, 11,12 and act as nanothickness plane light emitters, which confine LSPR-mediated enhanced fluorescence to the nanointerface and improve the spatial resolution of live-cell imaging. 13,14 Thus, LSPR coloration has great advantages for colorimetric applications 15,16 ; however, there are certain case in which LSPR coloration becomes an obstacle to use.…”

“…As evidence that this phenomenon is derived from the metamaterial properties of condensed particle films, the experimental results are reproduced well by transfer-matrix method calculations, employing an effective medium approximation with high n and k . These films could act as plasmonic metamaterial light absorbers, have been used for colorimetric sensor applications, , and act as nanothickness plane light emitters, which confine LSPR-mediated enhanced fluorescence to the nanointerface and improve the spatial resolution of live-cell imaging. , …”

Flexibly tunable surface plasmon resonance by strong mode coupling using a random metal nanohemisphere on mirror

“…Accordingly, the Ag sheet structures can act as plasmonic metamaterials. By using this structure, we reported several applications, such as colorimetric biosensing [35], photocatalytic reaction sensing [36], enhanced fluorescence imaging [37], and ultrahigh resolution imaging [38]. Herein, we introduce a new plasmonic metal nanostructure named nanohemisphere on mirror (NHoM) that provides similar splitting, enhancement, and increased Q-values of the SP resonance by similar mode coupling through the mirror image even with the use of random structures that are much simpler and easier to fabricate.…”

Photocatalytic Lithography

“…They described the • OH-mediated oxidation to be somewhat limited to certain molecular structures and much slower than the direct one. R. Degawa et al [17] analyzed the effect of different parameters (i.e., humidity and gas flow rate) on the remote oxidation of plasmonic silver nanoparticles by platinum-modified TiO 2 , while A. O. Kondrakov et al [18] analyzed the formation of • OH and H 2 O 2 in an aqueous environment. W. Kubo and T. Tatsuma analyzed the remote photooxidation of different photoactive inorganic materials (i.e., TiO 2 , ZnO, and WO 3 ) and their metal (Au, Pt, and Ag)-loaded counterparts, demonstrating the superiority of the latter, which apparently was due to processes involving plasmon resonance and hot electrons [19].…”