AgAu Hollow Nanoshells on Layered Graphene Oxide and Silica Submicrospheres as Plasmonic Nanozymes for Light-Enhanced Electrochemical H₂O₂ Sensing

Abstract

Localized surface plasmon resonance (LSPR) is a phenomenon derived from the interaction between light and nanostructures, and its outcomes have been explored mainly for applications in surface-enhanced Raman spectroscopy (SERS), phototherapy, and catalysis. Bimetallic nanostructures are able to synergically combine the properties of two different metals to create a tuned response to LSPR according to their composition, shape, and morphology. In this study, an in situ synthesis of AgAu bimetallic hollow nanoshells (NS) over layered graphene oxide (GO) and silica submicrospheres (SiO 2 ) is presented. The synthesized structures acted as peroxidase-like nanozymes in the plasmon-enhanced electrochemical sensing of H 2 O 2 . The nanozymes were submitted to 405, 533, and 650 nm laser irradiation while performing the hydrogen peroxide reduction reaction (HPRR) with a fast response speed (4 s), exhibiting enhancements in sensitivity of 122% (for Ag 79 Au 21 /GO at 533 nm, 787 μA mM −1 cm −2 ), 105% (for Ag 79 Au 21 /GO at 405 nm, 725 μA mM −1 cm −2 ), and 119% (for Ag 50 Au 50 /SiO 2 at 650 nm, 885 μA mM −1 cm −2 ) compared to the dark conditions when matching the LSPR band maximum for each synthesized structure. When laser stimuli did not match LSPR band maximum, lower enhancements were achieved in both cases. According to Michaelis−Menten enzyme kinetics, the nanozymes I max followed the same LSPR bias and K m app was lowered after LSPR stimuli, showing the smallest values upon 405 nm irradiation (0.599 mM for Ag 79 Au 21 /GO and 0.228 mM for Ag 50 Au 50 /SiO 2 ) demonstrating increased substrate affinity in comparison to values previously reported in enzymatic and nonenzymatic biosensors of H 2 O 2 . Thus, we propose that LSPR is the main mechanism involved in the faster electron transfer rates and the consequent enhancement of electrochemical H 2 O 2 sensitivities, I max , and K m app by the bimetallic nanozymes synthesized by this approach.

Mechanochemical Strategies for the Preparation of SiO2-Supported AgAu Nanoalloy Catalysts

“…Conversion, induction period and reaction rate constant strongly suggest that the bimetallic nanoalloys benefit from the synergy between silver and gold, just as previously reported (Wang et al, 2014;Kisukuri et al, 2016;da Silva et al, 2021). Although many examples of enhanced catalytic properties of bimetallic systems have been reported, the synergistic effect between metals in these systems is yet to be fully comprehended.…”

“…The specific combination of Ag and Au as noble metals in bimetallic systems offers the opportunity to minimize the cost of Au catalysts and, at the same time, enhance the material catalytic performance through use synergistic effects (Slater et al, 2014). Typically, Ag and Au are combined either in core-shell or in alloys to applications in biosensors (Jia et al, 2014), SERS (Chen et al, 2013;Girão et al, 2017), catalysis (Wang et al, 2014;Kisukuri et al, 2016;Rodrigues et al, 2016) or electrocatalysis (Nazir et al, 2017;Balasubramanian et al, 2020;da Silva et al, 2021). They may be either blended in nanocrystals comprised of the individual elements or in an alloyed or intermetallic atomic ordering (Gilroy et al, 2016).…”

“…This indicates that although there is the formation of alloy through both GRR and one-pot strategies indicated by the redshift in both samples, some remaining monometallic particles could have been formed, as well as regions of higher density of single element within the bimetallic nanostructure. Accordingly, in solution-based synthesis alloyed AgAu nanoparticles present a LSPR broadening and a redshift, varying their maxima starting from the AgNP used as templates to the near infrared (Vongsavat et al, 2011;Gilroy et al, 2016;da Silva et al, 2021).…”

Prospects of nano-carbons as emerging catalysts for enzyme-mimetic applications

“…Core-shell modifications are beneficial towards the enhancement of plasmatic effects, optical properties, charge separation, and biocompatibility. 105 The peroxidase-like activity of the core-shell nanostructure of Ag/Au over the GO core was also used for the electrochemical detection of H 2 O 2 . The incorporation of Ag and Au significantly enhances the sensitivity of GO.…”

Wavelength-Dependent Selective Acceleration of CO2 Reduction and H2 Evolution Using a Plasmonic Gold Nanorod Electrode

“…Photoelectrochemical solar-to-fuel conversion has been considered as a promising strategy for achieving a sustainable society. − In addition to established semiconductor-based electrodes, plasmonic electrodes have also attracted considerable attention owing to their unique light-harvesting properties associated with localized surface plasmon resonance (LSPR). − LSPR arises from the excitation of the collective oscillation of free electrons on a noble metal nanoparticle surface upon light irradiation, and hot carriers generated upon LSPR excitation have recently been reported to accelerate electrochemical reactions. − Namely, electron transfer between a plasmonic electrode and a reaction substrate can be promoted upon LSPR excitation, leading to the enhancement of electrocatalytic current under light irradiation. Furthermore, the use of a plasmonic electrode in combination with electrocatalysts enables us to accelerate an intended reaction including energy-storing reactions such as hydrogen (H 2 ) evolution, − carbon dioxide (CO 2 ) reduction, − nitrate reduction, and oxygen evolution. ,− …”