Ultrathin Layer Solid Transformation Enabled Surface Enhanced Raman Spectroscopy

The rapid and sensitive detection of harmful small molecules and heavy metal ions is extremely important for public safety and human health,and is also the goal that people have been pursuing.The surface-enhanced Raman spectroscopy(SERS)based on metallic nanostructured materials is expected to achieve this goal.However,since the Raman cross sections(RCSs)of such small molecules and heavy metal ions are too small,efficient detection cannot be achieved by the conventional SERS.Aiming at this key problem,this thesis proposes a new SERS-based detection method relied on ultrathin layer solid transformation,and studies on the design and preparation of composite SERS substrates.The Raman response of the composite SERS substrate to the harmful gaseous small molecules and heavy metal ions in the solution was studied.Related devices were designed,and the practical applications were exp lored.The main inno vative points are pre se nted as fo llows.(1)Proposed the colloidal electrostatic self-assembly strategy for ultrathin metal oxides wrapped plasmonic metal nanoparticles(NPs).Developing a method of laser ablation in liquid for such strategy,and the uniform and thickness-controllable wrapping layer of the ultrathin oxide on the metal surface is realized.This provid es an easy way to achieve uniform wrapping layer of ultrathin oxide on the surface of the plasmo nic metal NPs.(2)Proposed the thiourea-induced shell isotropic growth strategy.By adding thiourea and metal ions into the plasmonic metal colloid solution,the uniform and thickness-controllable wrapping layer of the ultrathin sulfide on the metal surface can be achieved.The strategy is universal and can realize uniform wrapping layer of various sulfide layer.This work provides a simple and controllable method for wrapping uniform and ultrathin sulfide on the surface of plasmonic metal NPs.(3)Proposed a SERS detection strategy based on heterogeneous solid transition of composite SERS substrates.In this strategy,gold NPs wrapped with ultrathin sensitive layers such as oxides or sulfides are composite SERS substrates.Such strate gy successfully achieves the efficient dete ction of gaseous small mo lecules(suc h as H2S,CS2 and HCl,etc.)and typical heavy metal ions in solution(such as Hg2+,Cu2+ and Cd2+).These greatly expand the application range of SERS-based detection.(4)Established ultrathin layer solid transformation enabled SERS(ULST-SERS).The technology is universal and suitable for trace detection of various harmful small molecules and heavy metal ions.Through combined with heating chip,the method is suitable for efficient detection above room temperature with fast response and ultrahigh sensitivity.The ULST-SERS achieves the ppt level detection limit in minute level response time.(5)Proposed a conductometric response triggered SERS identification strategy for accurate real-time gas monitoring.The monitoring sensor is based on ultrathin oxides wrapped plasmonic metal NPs.This monitoring can achieve acccurate identificat'ion and sensitive monitoring of some harmful gas molecules.This work provides a new and flexible method for accurate real-time monitoring of gas molecules.It is believed that this work is a highly efficient method for the SERS detection of the small molecules and ions,namely ULST-SERS.This method has strong practical application value and prospects.Moreover,the ULST-SERS is believed as another important development after conventional SERS,TERS(Tip Enhanced Raman Spectroscopy),and SHINERS(Shell Isolated Nanoparticle Enhanced Raman Spectroscopy).