| Surface-enhanced Raman spectroscopy(SERS)is a analysis technology with fast,highly sensitive finger and print recognition characteristics,which highly depends on the materials properties and surface morphology of the SERS substrate.It is an important application of the nanotechnology,and has broad prospect and utilization in the many fields,such as chemistry,biomedical engineering and food safety.Recently,with the rapid development of electronic materials and micro-nano processing technologies,more and more micro-nano structures can be designed and fabricated for the SERS.In this work,we combined the new electronic materials with micro-nano fabrication technology to build composite micro-nano structure for SERS substrate through designing and optimizing the materials structure and process.The SERS mechanism of the substrates was discussed through the theoretical simulation.The certain application of the SERS substrate was demonstrated.The main content includes:(1)Au nanodots/graphene(Gr)composite structure SERS substrate was designed and fabricated by using monolayer Gr and Au nanodots materials.The SERS substrate was obtained by depositing uniform Au nanodots on monolayer Gr using anodic aluminum oxide(AAO)as template,and electron beam evaporation process.By optimazing the thickness of the Au layer,and the finite difference time domain method simulating the local electric field of Au nanodots structure,the best SERS substrate was achieved.The SERS signal of Au nanodots/Gr substrate was about 4.67 times stronger than that of uniform gold nanoarrays with the detection limit was 4.69× 10-9 M and the enhancement factor of 8.5× 104.The Au nanodots/Gr substrate also has good uniformity and stability,which shows that the relative standard deviation was about 12.2%,and the SERS intensity decreased 24.72%after one year of storage.(2)Large area SERS substrates were designed and fabricated by hybrid large area porous GaN nanostructures with Au/Ag.By controlling porous GaN morphology,the Au/Ag layer thickness and morphology,the detection limit of 1.13×10-13 M and enhancement factor of 2.5×108 of the large area SERS substrate were obtained with good uniformity and stability by using R6G as SERS probe.The high performance of the SERS substrate is attribute to the electromagnetic enhancement after hybrid GaN nanostructure with Au/Ag,which conformed by finite difference time domain method(FDTD)simulation.The potential application for the detection of miRNA(miR-K125-5p as breast cancer related biomarker)was evaluated with fluorescent molecular(FAM)as Raman target molecular and a sensitive miR-K12-5-5p detection with a limit down to 8.84×10-10 M was achieved,which confirming the potentialities of the Au/Ag/porous GaN hybrid SERS substrate for early-cancer diagnosis,and giving great potential to develop ultrasensitive SERS biosensors for various biological and chemical analyses.(3)SERS technology by modified superhydrophobic laser-induced graphene(LIG)was obtained through laser engraving technology and surface modification.At present,the maximum area that can be realized in our laboratory is 40 cm × 60 cm.It was found for the first time that LIG treated by organic solvents could obtain a pinning-free superhydrophobic surface,and the mechanism of organic solvents on the surface modification of LIG was analyzed by analyzing the structure and properties of the materials.The SERS detection performance of the constructed LIG superhydrophobic surface was tested by using R6G as the probe molecule.The detection limit of 10-17 M,and the enhancement factor of 9.7×1011 was achieved for the SERS with the relative standard deviation of about 6.4%.The FDTD method was used to study the distribution of electromagnetic filed intensity of 3D "Hot spots" on aggregated Au nanoparticles.Different concentrations of cytosine were detected by this SERS substrate as a demonstration.The detection limit of 10-7 M was obtained.The results indicated that the substrate has a good enhancement effect on cytosine. |
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