Electrostatic assembly of gold nanorods on a glass substrate for sustainable photocatalytic reduction via sodium borohydride

Abstract

Herein we adhere gold nanorods (Au NRs) to glass coverslips through electrostatic interactions by treating the glass coverslips with (3-aminopropyl)trimethoxysilane (APTMS) and polystyrene sulfonate (PSS). These Au NR-functionalized coverslips were used to demonstrate the sustainable, catalytic reduction of 4-nitroaniline by sodium borohydride. Au NRs in solution were compared to the Au NR coverslips and were found to have pseudo-first-order observed rate constants of 1.35 × 10⁻² min⁻¹ (2.79 × 10⁶ min⁻¹ per Au) and 4.12 × 10⁻² min⁻¹ (4.26 × 10⁵ min⁻¹ per Au), respectively. The same catalytic reaction was executed under photolysis (1000 W Xe lamp); free NRs and Au NR-functionalized coverslips demonstrate pseudo-first-order observed rate constants of 2.15 × 10⁻² min⁻¹ (4.44 × 10⁶ min⁻¹ per Au) and 6.28 × 10⁻² min⁻¹ (6.48 × 10⁵ min⁻¹ per Au), respectively, which are two orders of magnitude faster than the only other affixed catalyst, Au NP in polymer. In addition to being scalable in Au-NR layers, a representative Au NR-functionalized coverslip was re-used for three consecutive catalysis reactions before decrease in rate, and had a rate ∼65% of the original reaction after the fifth cycle. Thus, we have demonstrated an efficient and reusable, thermal and photochemical gold nanorod catalyst assembly that does not require a complex synthetic protocol or the use of specialized equipment.