Influence of oxygen plasma treatment on structural and spectral changes in gold nanorods immobilized on indium tin oxide surfaces

Abstract

Oxygen plasma treatment is commonly used to sterilize gold nanoparticles by removing chemical contaminants from their surface while simultaneously inducing surface activation and functionalization of nanoparticles for biological, electrocatalytic, or electrochemical studies. In this study, we investigate the influence of oxygen plasma treatment on structural and localized surface plasmon resonance (LSPR) spectral changes of anisotropic gold nanorods (AuNRs) immobilized on an indium tin oxide (ITO) glass substrate. Unlike AuNRs deposited on a glass slide, no noticeable structural change or deformation of AuNRs on ITO was observed while increasing the oxygen plasma treatment time. This result indicates that ITO provides structural stability to AuNRs immobilized on its surface. Additionally, single-particle scattering spectra of AuNRs showed the broadening of LSPR linewidth within 60 s of oxygen plasma treatment as a result of the plasmon energy loss contributed from plasmon damping to ITO due to the removal of capping material from the AuNR surface. Nevertheless, an increase in the surface charge on the AuNR surface was observed by narrowing the LSPR linewidth after 180 s of plasma treatment. The electrochemical study of AuNRs immobilized on ITO electrodes revealed the surface activation and functionalization of AuNRs by increasing plasma treatment. Hence, in this study, a significant understanding of oxygen plasma treatment on AuNRs immobilized on ITO surfaces is provided.

Effect of Light Irradiation on Hot Electron-Mediated Photoreduction of Silver Ions on Single Gold Nanorods without a Reducing Agent

“…To investigate the structural and spectral variations of the AuNRs after exposure to a AgNO 3 solution under white light irradiation, AuNRs were prepared by drop-casting a AuNR solution on a precleaned glass substrate followed by treatment with oxygen plasma for 30 s to remove the CTAB layer from the AuNR surface. − As shown in Figure , a solution containing 150 mM AgNO 3 was then dropped on the AuNRs deposited on a glass substrate. The solution was left for 1 h to ensure that Ag was sufficiently adsorbed on the AuNR surface.…”

“…The concentration of AuNRs on the slide glass surface was controlled to be 1 μm –2 to characterize the single AuNRs and to minimize the interparticle LSPR coupling. Oxygen plasma treatment was performed using a plasma cleaner (PDC-32G-2, Harrick Plasma) at a maximum RF power of 18 W for 30 s to remove the CTAB adsorbed on the surface of AuNRs. − All Ag-coated samples for TEM, scanning electron microscopy (SEM), and XPS measurements were prepared by irradiation with a halogen lamp (OSL2, Thorlabs) while being immersed in AgNO 3 solution. In the sample preparation, the laboratory temperature was ∼25 °C.…”

Single-Particle Spectroelectrochemistry: Electrochemical Approaches for Tuning Chemical Interfaces and Plasmon Damping in Single Gold Nanorods

“…4−7 Single-particle dark-field (DF) microscopy and spectroscopy studies have successfully revealed that the withdrawal of hot-electron energy by surface thiol molecules at the Au−thiol interface results in the loss of LSPR spectral intensity, redshift, and line width broadening (full width at half-maximum [fwhm]) of the LSPR peak. 6,7,12,14,15,[18][19][20]22 Furthermore, in our recent studies, we demonstrated the tunability of the CID process by regulating the electron-withdrawing and electron-donating properties of thiophenol (TP) adsorbate molecules. 7 We also achieved in situ reversible tuning of CID by manipulating the host−guest supramolecular interactions.…”

“…11,23,24 In single-particle spectroelectrochemical studies, gold nanorods (AuNRs) have often been immobilized on highly transparent conducting oxide surfaces, such as indium tin oxide (ITO) substrates, which allow for the electrochemical manipulation of AuNRs and the monitoring of consecutive spectral changes at the Au/adsorbate interface. 11,22 Thus far, spectroelectrochemical techniques have been employed to analyze spectral responses caused by changes in the charge density and RI of the dielectric medium of plasmonic nanoparticles triggered by an electrochemical potential. 24−28 interface in an aqueous supporting electrolyte environment at the single-particle level.…”

“…Additionally, CTAB removal establishes sufficient contact between the AuNRs and the ITO layer to facilitate an enhanced reception of electrochemical signals. 22 Figure 1B shows the ensemble measurement of the UV−VIS−NIR extinction spectrum of the CTAB-stabilized AuNRs dispersed in distilled water. Two distinct longitudinal and transverse LSPR peaks appeared at about 521 and 677 nm, respectively.…”