Electrical Manipulation of Plasmonic Relaxation and the Application of Voltage-Modulated Plasmon Resonance to Biosensing

This paper reveals two studies on electrical controlled plasmonic responses, one for understanding the plasmon-phonon interactions and the other for demonstrating high-sensitivity EC (electrochemical)-SPR biosensors. In the first part, we experimentally study the effect of voltage controlled surface acoustic waves on localized surface Plasmon (LSP), which unveils exceptional properties of plasmon-phonon interaction. The experiment was conducted by depositing gold nanoparticles on an X-cut LiNbO
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to generate plasmonic oscillation, and fabricating an interdigital transducer monolithically to create surface acoustic wave pulses. The interaction between amplitude acoustic wave and plasmonic oscillation affects different plasmon dynamics and relaxation gradients, leading to a systematic change in LSP absorption.Second, we designed and investigated a novel voltage modulated optical biosensor based on a hybrid plasmonic and electrochemical phenomenon. The SPR (surface plasmon resonance) was generated from a thin layer of gold nanohole array on a glass substrate. The optical response under various voltage bias conditions were tested using the target analyte, C-Reactive Protein (CRP). We observed that SPR response is concentration-dependent and can be modulated by varying DC voltages or AC bias frequencies. The phenomenon is due to spatial re-distribution of electron concentration at the metal-solution interface. Our proposed voltage actuated sensor is permissible for various future optoelectronic integration for plasmonic and electrochemical sensing.