Photocurrent and photoacoustic detection of plasmonic behavior of CdSe quantum dots grown in Au nanogaps

TL;DR

This study demonstrates how Au plasmonics enhances photocurrent and photoacoustic signals in CdSe quantum dot nanogaps, revealing potential for improved photodetectors and sensors through plasmonic effects.

Contribution

It introduces integrated CdSe quantum dot/Au nanogap structures that utilize plasmonic absorption for enhanced photocurrent and photoacoustic detection, a novel approach in this context.

Findings

Photoacoustic signals are enhanced by about 20% due to plasmonic absorption.

Surface plasmon resonance occurs at approximately 500 nm in the structure.

Photocurrents can be tuned by bias voltage through energy transfer mechanisms.

Abstract

In this work, the influence of Au plasmonics on photocurrent generation in the visible wavelength range in integrated thiol-linked CdSe quantum dot/Au nanogap structures is demonstrated. The plasmonic absorption is sensed utilizing photoacoustic (PA) detection technique. The laser diode is modulated to generate the PA excitation that oscillates the air-filled cell. When light absorption increases, an enhanced acoustic signal is captured by a microphone. The observed enhancement in the PA response is related to plasmonic absorption by the Au layers and the response is further enhanced by about 20% due to CdSe QDs. In our structure, the surface plasmon resonance (SPR) wavelength is approximately 500 nm. The SPR is utilized for generating photocurrents in CdSe quantum dots. Due to energy transfer from the dot to closely spaced Au surface through thiol links, a smooth transmission channel of electrons is established that forms a detectable photocurrent, which can be tuned by a bias voltage. These plasmonic nanogap structures can enable higher sensitivity in photovoltaics, photodetection and sensing.