Spectroelectrochemistry of Halide Anion Adsorption and Dissolution of Single Gold Nanorods

Abstract

A spectroelectrochemical flow cell is used to probe the localized surface plasmon resonance (LSPR) of the same single gold nanorods (AuNRs) in sodium fluoride, sodium chloride, and sodium bromide electrolytes using dark-field scattering microscopy. The changes in resonance energy, line width (full-width at half-maximum, fwhm), and peak intensity of a Lorentzian fit to single AuNR scattering spectra as the rods are charged are compared to determine the role of anion adsorption. We demonstrate that at positive potentials up to +0.25 V relative to a Pt quasi-reference electrode, the induced changes in the LSPR are independent of halide anion. At more positive potentials (+0.3 to +0.35 V) bromide and chloride ions damp the AuNR LSPR, observed as an increase in the line width. At the most positive potential investigated in all three electrolyte solutions (+0.35 V), the AuNR scattering intensity decreases irreversibly in bromide electrolyte, indicating dissolution. The kinetics of the bromide-mediated dissolution can be controlled by the electrolyte concentration and show that the change in resonance energy due to dissolution increases with each cycle from negative to positive potential.

Manipulation of the Geometry and Modulation of the Optical Response of Surfactant-Free Gold Nanostars: A Systematic Bottom-Up Synthesis

“… 1 , 27 , 44 − 46 There are few fundamental studies that have demonstrated the Au–halide chemical affinities and halide-concentration-dependent morphological and spectral tuning of Au NPs in different contexts. 47 Our method for the surfactant-free, seed-mediated growth of GNS uses HCl to adjust the pH of the growth solution, which introduces 2 mM final concentration of chloride (Cl – ) into the growth solution. To the best of our knowledge, no studies have been reported to understand the influence of halides on the surfactant-free/capping agent-free synthesis of anisotropic nanoparticles.…”

Toward a mechanistic understanding of plasmon-mediated photocatalysis

“…Most of these techniques measure the charging of plasmonic nanostructures by adsorbing them to a conductive substrate, which is typically indium tin oxide (ITO) [159,160]. Upon manipulation of the charge density of a plasmonic nanostructure, various changes to the plasmonic nanoparticle and the local environment can occur, including ionic rearrangement of the electrolyte solution, modifications to the particle morphology, and the ability to mediate specific chemical reactions at the particle surface [162][163][164]. As an example of the sensitivity of this approach, Collins et al correlated a 0.02 nm blue shift in the LSPR to the addition of 110 electrons to a single Au NR in an ion gel device [163].…”

Electrochemical synthesis of Au@semiconductor core–shell nanocrystals guided by single particle plasmonic imaging

“…On the other hand, it provides an opportunity to monitor the changes occurring on the NPs, for example, the in situ growth, etching, and chemical reactions. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Therefore, from the perspective of photocatalysts' synthesis, the growth of the semiconductor or metal could be monitored in real-time via dark-eld microscopy (DFM) by tracking the LSPR scattering variation. It will provide comprehensive understanding of the growth mechanism, as well as tailor the properties of photocatalysts precisely.…”