Laser Fabrication Of Hybrid Graphene/Silver Sers Chips And Their Applications

Graphene/silver is a promising composite structure for SERS chips with both the excellent performance of graphene and silver nanostructures.Graphene has been envisioned as one of the best shell materials for SERS chips to improve the stability owing to its atomic thickness,excellent optical transmittance and stable chemical property.Moreover,graphene can also function as additional signal enhancer,fluorescence quencher,and molecule enricher for SERS applications,making graphene/silver hybrids become an excellent platform for SERS detection.In this thesis,two approaches with low cost and fast speed based on laser processing for fabricating graphene/silver hybrids were proposed,in order to solve the issues in preparation of graphene/silver hybrid SERS chips.Furthermore,a portable and low-cost prototype for detecting SERS signals on the graphene/silver hybrid SERS chips was developed.The main work and results of this thesis are summarized as follows:(1)An automatic setup based on the laser-assisted chemical vapor deposition method was developed for the rapid synthesis of graphene.All the fabrication parameters that affect the quality and number of graphene layers,such as laser power,laser spot size,laser scanning speed,pressure of vacuum chamber,and flow rates of gases,can be precisely controlled and monitored by this setup during the preparation of graphene.The experimental results showed that multilayer graphene with few defects can be synthesized rapidly by this setup.(2)An approach based on the pulsed laser insitu deposition was put forward to prepare large-area silver nanostructures.The graphene/silver SERS chip with the hybrid structures of graphene/silver film/laser-textured Si surface(G/Ag/LTSi)was obtained after graphene was transferred to the surface of silver nanostructures.The G/Ag/LTSi SERS chip achieved an enhancement factor of 2.6×107 and exhibited a stable performance.Its excellent SERS activity can be maintained for 50 days in air at least.(3)A method based on femtosecond laser induced periodic surface structures was proposed for the rapid preparation of large-area silver nano-grating arrays with fluffy nanostructures.After the graphene was transferred to the surface of silver nano-grating arrays,the graphene/silver SERS chip(G/Ag_LIPSS/Si)with periodic silver nano-structure was obtained.The enhancement factor of G/Ag_LIPSS/Si was 3.4×106.Moreover,the G/Ag_LIPSS/Si exhibit good stability and homogeneity to boost the Raman intensity.The relative standard deviation of SERS intensity from different areas of G/Ag_LIPSS/Si was less than 2.5%,which suggested that G/Ag_LIPSS/Si can be used for quantitative or semi-quantitative Raman detection.(4)According to the features of fabricated graphene/silver hybrid SERS chips,a portable and low-cost prototype with simple optical configuration for the detection of SERS signals was developed.The detection limits achieved by this Raman prototype with the Raman enhancement of G/Ag/LTS and G/Ag_LIPSS/Si SERS chips were 10-9mol/L and 10-8ol/L,respectively.Furthermore,the Raman prototype with the signals enhancement of hybrid graphene/silver SERS chips were utilized to detect whether to add melamine in milk and whether the uric acid concentration was exceeded,respectively.In this thesis,new technologies based on laser processing were exploited for the rapid fabrication of hybrid graphene/silver SERS chips.In addition,a portable Raman prototype was developed according to the features of fabricated SERS chips.With the Raman signal enhancement of graphene/silver SERS chips,the Raman prototype can realize the detection of trace substances with low cost and fast speed,which is a powerful tool for food testing,disease diagnosis and environmental monitoring.