Single Gold Nanorod Charge Modulation in an Ion Gel Device

Abstract

A reliable and reproducible method to rapidly charge single gold nanocrystals in a solid-state device is reported. Gold nanorods (Au NRs) were integrated into an ion gel capacitor, enabling them to be charged in a transparent and highly capacitive device, ideal for optical transmission. Changes in the electron concentration of a single Au NR were observed with dark-field imaging spectroscopy via localized surface plasmon resonance (LSPR) shifts in the scattering spectrum. A time-resolved, laser-illuminated, dark-field system was developed to enable direct measurement of single particle charging rates with time resolution below one millisecond. The added sensitivity of this new approach has enabled the optical detection of fewer than 110 electrons on a single Au NR. Single wavelength resonance shifts provide a much faster, more sensitive method for all surface plasmon-based sensing applications.

Structural Change of a Single Ag Nanoparticle Observed by Dark‐field Microspectroscopy

“…Based on the understanding of electron injection on the PRRS spectrum of a single AgNP, the effect of electrochemical reduction on the PRRS spectrum of an oxidized single AgNP was studied . In this case, freshly immobilized AgNPs were repeatedly oxidized at +0.4 V and reduced at −0.4 V. As shown in Figure B, when a potential of +0.4 V was applied, the PRRS peak showed an obvious redshift and a decrease in intensity, as reported above.…”

Tracking Nanoelectrochemistry Using Individual Plasmonic Nanocavities

“…Electrochemical studies tracking Raman spectroscopy within gold gaps that sandwich a single molecular layer have proposed that the potential-dependent Raman emission depends on molecular torsion angles 9 . Shifts in the scattering resonance of single Au nanoparticles following application of a negative bias have been attributed to an increase in the NP electron concentration ( ) via electron transfer from the ITO substrate 11,12 . However this work suggests that the scattering cross-section scat ( ) is surprisingly nonlinear.…”

Charge‐Induced Shifts in Chiral Surface Plasmon Modes in Gold Nanorod Assemblies

“…Chemical charging or discharging is therefore an effective tool to tune surface plasmon resonance frequencies in plasmonic nanoparticles, through alteration of the electron density. As a general observation, an increase in free electron density results in a blue‐shift of the LSPR band, while removal of charges leads to a shift toward longer wavelengths . LSPR shifts due to changes in the electron density of silver and gold nanoparticles have been previously described .…”

“…LSPR shifts due to changes in the electron density of silver and gold nanoparticles have been previously described . In these reports, nanoparticles either in colloidal solution or immobilized on solid surfaces were charged through the addition of a strong reducing agent or by applying an electrochemical potential . Mulvaney and co‐workers have experimentally demonstrated that Au nanorods exhibit a drastic extinction blue‐shift when their free electron density is increased, through oxidation of added borohydride ions .…”