Ag@Au core-shell dendrites: a stable, reusable and sensitive surface enhanced Raman scattering substrate

Abstract

Surface enhanced Raman scattering (SERS) substrate based on fabricated Ag@Au core-shell dendrite was achieved. Ag dendrites were grown on Si wafer by the hydrothermal corrosion method and Au nanofilm on the surface of Ag dendritic nanostructure was then fabricated by chemical reduction. With the help of sodium borohydride in water, Au surface absorbates such as thiophene, adenine, rhodamine, small anions (Br– and I–), and a polymer (PVP, poly(N-vinylpyrrolidone)) can be completely and rapidly removed. After four repeatable experiments, the substrate SERS function did not decrease at all, indicating that the Ag@Au dendrite should be of great significance to SERS application because it can save much resource. Six-month-duration stability tests showed that the Ag@Au core-shell dendrite substrate is much more stable than the Ag dendrite substrates. We have also experimented on fast detection of Cd2+ at 10−8 M concentration by decorating single-stranded DNA containing adenine and guanine bases on the surface of this Ag@Au dendrite. Finite-difference time-domain simulations were carried out to investigate the influence of Au nanolayer on Ag dendrites, which showed that the local electric fields and enhancement factor are hardly affected when a 4 nm Au nanolayer is coated on Ag dendrite surface.

Site-Selective Controlled Dealloying Process of Gold-Silver Nanowire Array: a Simple Approach towards Long-Term Stability and Sensitivity Improvement of SERS Substrate

“…However, the previously reported techniques such as the use of metal oxide or inert metal coating layers only offer stability improvement at the sacrifice of SERS sensitivity1122232427282930313233. In order to truly examine the value of the proposed technique towards SERS substrate fabrication, the stability of both p-AuAg-NWs array (Fig.…”

“…Unlike our controlled dealloying process, Raman intensities for the 1078 and 1586 cm −1 Raman peaks were significantly improved by 72 and 124% and also maintained 100% of initial signal for at least 35 days. Several other materials such as graphene2429, silica31, Au23, polyvinyl alcohol (PVA)33 were employed as coating layer for an excellent stability improvement. Unfortunately, all of them also exhibited the initial reduction of SERS signal.…”

“…Several designs of SERS structures were demonstrated using a thin oxide layer (i.e. TiO 2 , Al 2 O 3 )1122, Au shell23, and graphene coatings24. Unfortunately, a long-term stability cannot be achieved without compromising SERS sensitivity.…”

Scalable Synthesis of Ag Networks with Optimized Sub-monolayer Au-Pd Nanoparticle Covering for Highly Enhanced SERS Detection and Catalysis

“…Many investigations focused on Ag-Au bimetallic structures due to their relatively low-cost and high performance, for example Ag-Au core-shell NPs24, dendrites25, alloy NPs26 and alloy/graphene hybrids27 with excellent catalytic activities. Bi-metallic compounds already allow tuning the catalytic activity via composition ratios.…”

“…Due to the simultaneous consumption of substrate material while adding newly growing crystals, GRR can result in hierarchically porous surfaces with many active corners and edges33. However, previous reports mainly focused on the synthesis of hollow3435, core-shell242536, or alloyed3738 nanostructures via GRR, accessible active inter-metal interfaces are limited, and the necessary amount of very expensive metals like Ru34, Pd3538, Pt37 and Au36 are high. It is expected that products through a GRR starting with highly porous interconnecting networks should have hierarchical structures with pore sizes from micron to only a few nanometers39.…”