Abstract
Nanoplasmonics is currently experiencing an ongoing renaissance as a result of the booming research interest in LSPR-mediated but semiconductor-free photocatalysis and photoelectrochemistry directly over nanometals with excellent catalytic activity and conductive properties. To shed light on the underlying mechanism, the present study puts forward H2O2 as the probe molecule, with which the electroreduction at the phase boundary with photoexcited Ag nanowires (NWs) was systemically investigated. In particular, the reaction rate depends not only linearly on the illumination intensity but also on the resonant wavelength of the characteristic LSPR of the Ag NWs, evidently illustrating that the photoelectrochemical H2O2 reduction is mediated by the LSPR-induced energetic electrons of the Ag NWs. In addition to the mechanistic insights, the present study further highlights the great promise of such semiconductor-free LSPR-mediated photoelectrochemistry of H2O2 over Ag NWs in the analytical biochemistry field via proof-of-concept solar photoelectrochemical detection of ultradiluted H2O2 in PBS. The Ag NWs deposited on a carbon cloth substrate as the working electrode exhibit excellent sensitivity amounting to 118 μA cm−2 mM−1 under solar illumination, well outperforming that of the electrochemical counterpart measured in the dark by 50%.
Highlights
Nanoplasmonics, the localized surface plasmon resonance (LSPR) of primarily coinage metals (e.g., Au, Ag, and Cu) designed in a variety of nanoarchitectures, has been an important subject in the areas of broadband sunlight-driven chemical conversion for fuel generation and environmental remediation via semiconductor photocatalysis and photoelectrochemistry[1,2,3,4]
Structural and compositional characterization SEM was first carried out to investigate the morphology of Ag NWs/carbon cloth (CC), which consisted of numerous Ag NWs distributed over each carbon fiber of the CC substrate, for which the average diameter was ~120 nm and the length was ~10 μm (Fig. 1b, c)
UV–visible (UV–vis) spectroscopy was conducted to explore the optical property of the Ag NWs suspended in methanol, for which the photoabsorption peaked at ~400 nm, in excellent agreement with the characteristic resonant wavelength of the transverse-mode LSPR (T-LSPR) of Ag NWs reported in the literature (Fig. 2c)[1,5,13,22]
Summary
Nanoplasmonics, the localized surface plasmon resonance (LSPR) of primarily coinage metals (e.g., Au, Ag, and Cu) designed in a variety of nanoarchitectures, has been an important subject in the areas of broadband sunlight-driven chemical conversion for fuel generation and environmental remediation via semiconductor photocatalysis and photoelectrochemistry[1,2,3,4]. This, along with the seminal works done by pioneers including Linic[5,7], Christopher[6], Nordlander[8,9,10], Halas[8,9,10], and so forth[11] successfully demonstrating the photo(electro)chemistry directly on the surface of plasmonic metals, has stimulated tremendous research interest in gaining further insights into such plasmonic-carrier-driven reaction kinetics[4,5,6] Motivated by such a pressing need, in the present study, a systematic investigation into the interfacial charge transfer mechanism between photoexcited plasmonic silver (Ag) in a wire-like nanostructure and a hydrogen peroxide (H2O2) probe molecule was carried out. The Ag nanowire (NW) especially stands out, attributed to its
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