Hollow Urchin-like Gold Nanoparticles:Preparation And Applications In SERS

Surface-enhanced Raman scattering（SERS）enables fast and highly sensitive detection of the analytes.Compared with traditional Raman detection,the SERS signals could be amplified by several orders of magnitude.Hollow urchin-like gold nanoparticles（HU-GNPs）are a novel nanostructure with rough surfaces and sharp branches,which can generate large amounts of"Hot spots"and lead to the enhancement of the surrounding electromagnetic field.Owing to their good SERS enhancement effects,HU-GNPs have potential application in biomedical and bioscience fields.In this paper,hollow urchin-like gold nanoparticles with good uniformity,morphology and SERS enhancement were prepared by seed-mediated growth method.And controllable synthesis of HU-GNPs was achieved by optimal experiments.In addition,due to the replacement reaction of Au-S bonds,glutathione（GSH）,cysteine（Cys）,and homocysteine（Hcy）could react with PNTP on the surface of SERS substrates,leading to the changes of SERS signals.This method provided a fast and ultrasensitive detection of these three biothiols,and possessed potential application value in many reserch fields,such as drug delivery.The details are as follows:1.Based on seed-mediated growth method,HU-GNPs with good morphology,uniform size,and excellent SERS enhancement were synthesized successfully by employing dopamine hydrochloride as reducing agent and polyvinyl pyrrolidone （PVP）as the surfactant and stabilizer.The morphology and SERS activity of as-prepared HU-GNPs were adjusted by controlling the various experimental conditions,such as the amount of silver seeds and HAuCl₄,the type of reducing agents and surfactants,reaction temperatures and reaction time,etc.2.The SERS substrates with good stability and uniformity were prepared via electrostatic self-assembly method under the assist of amine-terminated ITO glasses. This method is simple,convenient and reproducible.Besides,the stability and uniformity of as-obtained SERS substrates under different pH environment,salt solution and time were tested systematically.3.The ultrasensitive SERS detection of GSH,Cys and Hcy was achieved based on the replacement reaction of Au-S bond.In the first step,p-nitrothiophenol（PNTP）was absorbed on the surface of SERS substrate as Raman reporter,and the adsorption concentration and time were also optimized to achieve the best adsorption condition. Then,GSH,Cys and Hcy could react with PNTP on the surface of HU-GNPs on account of the replacement reaction.After that,these three biological thiols could be detected under 10^-9 M level via the change of SERS intensity.