“Smart” Ag Nanostructures for Plasmon-Enhanced Spectroscopies

Abstract

Silver is an ideal candidate for surface plasmon resonance (SPR)-based applications because of its great optical cross-section in the visible region. However, the uses of Ag in plasmon-enhanced spectroscopies have been limited due to their interference via direct contact with analytes, the poor chemical stability, and the Ag(+) release phenomenon. Herein, we report a facile chemical method to prepare shell-isolated Ag nanoparticle/tip. The as-prepared nanostructures exhibit an excellent chemical stability and plasmonic property in plasmon-enhanced spectroscopies for more than one year. It also features an alternative plasmon-mediated photocatalysis pathway by smartly blocking "hot" electrons. Astonishingly, the shell-isolated Ag nanoparticles (Ag SHINs), as "smart plasmonic dusts", reveal a ∼1000-fold ensemble enhancement of rhodamine isothiocyanate (RITC) on a quartz substrate in surface-enhanced fluorescence. The presented "smart" Ag nanostructures offer a unique way for the promotion of ultrahigh sensitivity and reliability in plasmon-enhanced spectroscopies.

Shell‐Isolated Tip‐Enhanced Raman and Fluorescence Spectroscopy

“…Theeasiest way to protect aAgtip from oxidation is to store it in an itrogen glovebox with low oxygen and water content, which can prolong the lifetime of the tip to several months. [9] Thes hell-isolated tips exhibit longer lifetime;however, this chemical method is not general and tedious to scale up,g reatly limiting the application of the shell-isolated tips.T herefore,t he development of more general methods would be of great significance. [6] Thetip can also be protected by encapsulation with self-assembled monolayers (SAMs) of molecules whose Raman signals do not overlap with the signals of the analyte.…”

“…[8] Recently,the Zenobi group and the Li group have developed aw et chemical method to prepare shell-isolated tips by coating silica shells onto the surface of Au or Ag tips. [9] Thes hell-isolated tips exhibit longer lifetime;however, this chemical method is not general and tedious to scale up,g reatly limiting the application of the shell-isolated tips.T herefore,t he development of more general methods would be of great significance.…”

Quantitative detection using two‐dimension shell‐isolated nanoparticle film

“…This technique is a universal approach; it has been applied in various areas, including electrochemistry, food safety, material science, and biology . We also found that the stability of Ag‐based substrates can be significantly improved using shell‐isolated nanoparticle‐enhanced Raman spectroscopy; this enhancement was preserved even after 1 month …”

Shell‐Isolated Nanoparticle‐Enhanced Raman Spectroscopy at Single‐Crystal Electrode Surfaces

“…[ 120 ] In order to meet different system requirements, different types of SHINs have been prepared. [ 126,127 ] Second, the inert shell should be very thin as the SHINERS signal intensity will be signifi cantly decreased with the increasing shell thickness. In our case, the suitable diameter of gold cores is 55 nm [ 121 ] for SHINERS measurements, and bigger diameter gold NPs, such as 120 nm, can be synthesized for enormous enhancements ( Figure 6 A,B).…”