Understanding blue shift of the longitudinal surface plasmon resonance during growth of gold nanorods

Aditya K Sahu,Anwesh Das,Satyabrata Raj,Anirudha Ghosh

doi:10.1088/2632-959x/abd966

Abstract

We have investigated in detail the growth dynamics of gold nanorods with various aspect ratios in different surrounding environments. Surprisingly, a blue shift in the temporal evolution of colloidal gold nanorods in aqueous medium has been observed during the growth of nanorods by UV–visible absorption spectroscopy. The longitudinal surface plasmon resonance peak evolves as soon as the nanorods start to grow from spheres, and the system undergoes a blue shift in the absorption spectra. Although a red-shift is expected as a natural phenomenon during the growth process of all nano-systems, our blue shift observation is regarded as a consequence of competition between the parameters of growth solution and actual growth of nanorods. The growth of nanorods contributes to the red-shift which is hidden under the dominating contribution of the growth solution responsible for the observed massive blue shift.

Highlights

Metal nanoparticles have generated huge attraction due to their different distinct properties as compared to their bulk counterparts
As a step forward, here we demonstrate the temporal evolution of longitudinal surface plasmon resonance (LSPR) positions and intensity and its correlation with the growth of gold nanorods in the medium
A significant blue shift is observed in LSPR peak against a nearly fixed transverse surface plasmon resonance (TSPR) peak position

Summary

Introduction

Metal nanoparticles have generated huge attraction due to their different distinct properties as compared to their bulk counterparts. The metal nanoparticles show outstanding optical properties associated with the tunability of their localized surface plasmon resonance (SPR) in the visible part of the spectrum [1]. SPR of noble metal nanoparticles is the collective oscillation of electrons induced by the electromagnetic radiation of light. Optical, catalytic properties have cropped up because of surface plasmon oscillations and have led to exciting applications in several branches of science and technology including information storage, optoelectronics, biological imaging, cancer therapy, etc [7,8,9,10,11,12]. The most challenging task in the synthesis of metal nanoparticles is to keep control over the shape and size of the particles. Spherical gold nanoparticles show a strong single absorption band in the visible region at about 520 nm whereas gold nanorods (NRs) show two absorption bands belonging to transverse and longitudinal LSPR [13]

Methods

Results

Conclusion