# Liquid Bridge-Induced SERS Hotspots: Nitrobenzene Grafting on Silver–Gold Nanoparticles

## TL;DR

This paper explores how nitrobenzene grafts onto silver@gold nanoparticles and how this affects SERS hotspot formation.

## Contribution

A novel method for generating and functionalizing SERS hotspots via acetonitrile liquid bridges on silver@gold nanoparticles.

## Key findings

- Silver reacts spontaneously with diazonium salt, preventing plasmon-induced grafting.
- SERS hotspots are formed via acetonitrile liquid bridges connecting nanoparticles.
- Photoexcitation accelerates gold's reaction with diazonium salt.

## Abstract

The crafting process of nitrobenzene on silver@gold nanoparticles
from a solution of 4-nitrobenzenediazonium-tetrafluoroborate in acetonitrile
strongly depends on the silver to gold ratio. The investigation of
SERS substrates consisting of gold, silver, and silver@gold nanoparticles,
prepared by employing a helium droplet-based synthesis approach, provides
insight into the underlying plasmon-enhancement mechanism. Gold reacts
slowly with the diazonium salt; however, the reaction can be accelerated
by photoexcitation at the surface plasmon resonance. In contrast,
silver reacts spontaneously, which prevents plasmon-induced local
grafting. UV/vis absorption spectroscopy and Raman spectroscopy indicate
that, in the case of silver, SERS hotspot formation is mediated by
acetonitrile liquid bridges that initially connect the nanoparticles.
This provides a novel approach to simultaneously generating and selectively
functionalizing SERS hotspots.