Graphene oxide wrapped individual silver nanocomposites with improved stability for surface-enhanced Raman scattering

Abstract

As one of the best materials for surface-enhanced Raman scattering (SERS), Ag suffers from its tendency to oxidation, posing serious limitations for its use as a reliable long-term SERS substrate. Graphene oxide (GO) is considered to be a promising SERS-active platform due to the observed chemical enhancement originating from the interaction between probe molecules and oxygen containing functional groups on its surface. Herein, we present the synthesis of core-shell GO wrapped individual Ag nanocomposites (NCs) by electrostatic assembly of GO on SiO 2 @Ag nanostructures. The SERS enhancement factor (EF) of probe molecules on SiO 2 @Ag@GO is 1.8 times that on SiO 2 @Ag, due to the chemical enhancement brought upon by GO. Moreover, the GO surrounding the SiO 2 @Ag nanoparticles (NPs) shields Ag from oxidation, making them remain stable and display highly retained SERS activities even after long-term storage, while the bare SiO 2 @Ag NPs would have lost $80% of the original activity after the same treatment. As the NCs have displayed enhanced and stable SERS activities, colloidal encapsulation by GO has been proven to be an efficient way to prepare a SERS substrate with long-term stability for practical applications. † Electronic supplementary information (ESI) available: Additional gures including TEM image of SiO 2 @Ag without addition of PVP, zeta potential measurements, bulk Raman spectra of 4-ATP, SiO 2 @Ag, and SiO 2 @Ag@GO, 4-ATP UV-vis absorption spectra, CV and RhB SERS, GO thickness effect, and reproducibility test of the SERS substrates. See

Polyethyleneimine-mediated seed growth approach for synthesis of silver-shell silica-core nanocomposites and their application as a versatile SERS platform

“…The broad absorption peak of Ag shell was observed from the SiO 2 @PEI@Ag, likely due to the coupling between neighboring Ag nanoparticles inside the shell region, and large scattering from the SiO 2 and Ag shell. 32 Similar observation was also reported by Liu and co-workers. 12 Moreover, as the Ag shells on the SiO 2 cores became continuous and thick, the plasmon resonance peaks slightly red-shied, and the peak width became narrower.…”

Biosensors based on graphene oxide and its biomedical application

“…Biomolecule detection [96][97][98][99][100][101][102][103][104][105], cell/tissue imaging [150,151] (standard deviation of the response (σ)/slope of the calibration curve (S))) of 100 pM. They also demonstrated that the GO-based sensing platform is feasible to detect metal ion as well as small molecules when complemented with the use of each known aptamer.…”

“…In addition, the various GO-noble metal nanocomposites have been widely applied to detect extremely small amount of pigments in food, H 2 O 2 , glucose, and polar antibiotics [98][99][100][101][102][103]. In addition to its role in the enhancement of SERS signal, the combination of graphene with metal nanoparticles has been used as a favorable hybrid structure for preventing the surface oxidation of metal nanoparticles [104,105].…”

Silver Nanoparticle-Embedded Thin Silica-Coated Graphene Oxide as an SERS Substrate

“…However, the chemical enhancement of GO itself exhibits low sensitivity. To overcome this, composites that integrate the advantages of GO and high electromagnetic enhancement of gold or silver nanoparticles (Au or Ag NPs) have been developed for SERS detection [39,40,41,42,43,44,45,46]. Metal NPs were deposited on the surface of GO via oxygen-containing functional groups, such as carbonyl and hydroxyl groups [47,48].…”