Enhanced Dye Degradation through Multi‐Particle Confinement in a Porous Silicon Substrate: A Highly Efficient, Low Band Gap Photocatalyst

Abstract

A platform is introduced for fabrication of a reusable and highly efficient low band gap photocatalyst by confining gold nanoparticles (AuNPs) in the pores of a nanopatterned Si monolith (AuNSM). Due to their size, a maximum of two AuNPs can assemble in a single pore, thus preventing agglomerations. Their access to the analyte provides more active sites for redox reaction, leading to enhanced efficiency. While proximity of nanoparticles enhances coupling efficiency, confinement prevents rapid recombination of photogenerated charge carriers, a major factor contributing to low efficiency of photocatalytic materials. Degradation of methyl orange (MO) is used to determine the photocatalytic efficacy of AuNSM compared to 1) bare silicon and 2) AuNPs randomly dispersed on silicon. After 90 min of exposure to UV light (λ = 353 nm) in the AuNSM, the MO absorption is <1%, indicating near complete degradation, while it is still 85% and 70% for systems (1) and (2), respectively. Finite element method simulations of the confined structure suggest that the AuNPs act as a mediator/receptacle for photogenerated charges rather than a source of them at this wavelength and thus enhance the performance of the photocatalyst by creating more effective Schottky junctions—preventing recombination of electrons and holes—rather than by a localized surface plasmonic resonance effect.

Weak Polyelectrolytes as Nanoarchitectonic Design Tools for Functional Materials: A Review of Recent Achievements

“…Upon the infiltration of weak polyion block domains with metal ions (Ni + , Al 3+ and Cr 2+ ), well-defined metal-oxide nanodots and/or nanowires were obtained and used to define etch masks for pattern transfer [ 217 ]. For instance, we recently reported the use of a high-contrast etch mask for pattern transfer into silicon substrates through ICP/RIE etching for the development of vertically coupled plasmonic arrays for use in surface enhanced Raman scattering [ 213 ], anti-reflective surfaces, and photocatalysts [ 218 ].…”

Removal of Organic Dyes from Water and Wastewater Using Magnetic Ferrite-Based Titanium Oxide and Zinc Oxide Nanocomposites: A Review

“…It is important to note that, besides the focus of the development of magnetic nanocomposites for water and wastewater treatment, new recent trend of development of new materials is emerging. For example, Mir et al [138] studied how confining AuNPs in a porous Si template can significantly enhance the photocatalytic activity of MO. The pores prevent agglomeration of nanoparticles and eliminate the need for any functionalization.…”

“…The results showed that the recyclable, low-band gap photocatalytic system has economic and environmental advantages that promote implementation of catalytic and separation processes in continuous flow mode, with the advantages associated with easier phase separation and product recovery, enhanced safety, and easier operation [138].…”

“…new materials is emerging. For example, Mir et al [138] studied how confining AuNPs a porous Si template can significantly enhance the photocatalytic activity of MO. T pores prevent agglomeration of nanoparticles and eliminate the need for a functionalization.…”

“…Heterogeneous photocatalysis technology is always looking for an ideal photocatalyst, one that is reusable and that possesses high photocatalytic efficiency, a large specific surface area, and ability to absorb visible light [138]. Thus, the recyclability of catalysts is one of the key steps towards the sustainable application of photocatalysts and development of heterogeneous photocatalysis technology for water and wastewater treatment.…”