Study On The Controlled Fabrication And The Bio-chemical Sensing Of AuFON-Au@AgNPs Hybrid SERS Substrate

In recent years,the issues on the serious infection disease,enviroment pollution,food and medicine safty have occurred more frequently and attracted more attentions,which have threaten the safty and health of the human beings.All of these have induced a terrible social panic and caused enormous economy damages.Effective and rapid bio-chemical sensing is the basis for the following treatments.In addition,there is also an urgent aquirement for on-site bio-chemical sensing strategies in the military applications,such as the bio-chemical antiterror,battle field environment monitoring,pathogenic microorganism detection in the huge closed space of capsule or submarine,and etc.The existing bio-chemical sensing methods exhibited some disadvantages when applied for on-site bio-chemical sensing,such as the low sensitivity,longer sensing time and huge equipment.Surface-enhanced Raman scattering technique is a powerful and promissing specturm identification strategy for on-site bio-chemical sensing with a high sensitivity and good specificity.By now,the bottleneck for SERS application is the controlled manufacture of high-performed SERS substrates.Thus,a hybrid SERS subatrate was fabricated by combining the metallic nanostructre array and the nanoparticles colliod.The nanostructure design,surface plasmon properity,fabrication procedure,SERS properity characterization,morphology optimation and bio-chemical applictions of the hybrid SERS substrate were studied in this work.The main research contents are as follows:1.The optimized design method for the hybrid SERS substrate was established.The electromagnetic field enhancement properity of the SERS substrate was calculated by the finite difference time domain method.And the enhancement mechanism of the hybrid substrate was investigated.Based on the requirements and the performance of the existing SERS substrates in bio-chemical sensing,we have brought out a byhrid fabrication strategy by combining the metallic nanostructure arrays and the nanoparticle colliods.We have calculated the electromagnetic field enhancement properity of the Au film over nanoparticle(AuFON),Au@Ag core-shell nanoparticles(Au@AgNPs)and hybrid SERS substrates by the finite difference time domain method.The rules between the SERS performance and the SERS substrates' geometry parameters were studied.The results show that new hotspots were introduced at the junctions between the AuFON and the Au@AgNPs,which increased the density of the hotspots.And the intensity of the hotspots was also enhanced by coupling of the electromagnetic field.2 The contolled fabrication procedure for the hybrid substrate was established.The AuFON substrate was fabricated by the nanosphere lithography technique.The Au@AgNPs colliods were prepared by the chemical reduction method.And they were connected covalently using the a functional polymer.According to the principle for hybrid SERS substrate design,the nanosphere lithography and the colliod preparation technique were studied.A series of new fabrication procedures were introduced in this work including the finite-area self-assembly,the rotation metal deposition and the standardized SERS-chip cut.The way to control the morphology and the geometric size of the AuFON and Au@AgNPs was studied.The extinction spectra of the Au@AgNPs were obtained.And the connection stractegies for the hybrid SERS substrate were discussed.The matterial component,structure morphology and spectra properities of the hybrid substrate were characterized.3 The SERS spectra test method for the hybrid SERS substrate was established.The geometric sizes of the hybrid substrate were optimized,and the SERS performance of the hybrid SERS substrate were characterized.With Rhodamine 6G and 4-Aminothiophenol as the Raman probes,the geometric sizes of the AuFON and the Au@AgNPs were optimized.The AuFON substrate etched for 2 minutes and the Au@AgNPs with the diameter of 50 nm were adopted in the hybrid substrate.The sensivity was studied and the enhancment factor was calculated.The enhancement factor of hybrid substrate was about 2.25×107,which was about 100-and 50-folds of the AuFON and the Au@AgNPs substrates',respectively.In addition,the homogeniety,the reproducibility and the stability of the hybrid substrate were characterized.4 The bio-chemical sensing strategy based on the hybrid substrate was established.The chemicals and the pathogenic microorganism were detected with SERS technique demonstrating the practicability of the hybrid SERS substrate.Some chemicals and pathogenic microorganism are of the special SERS spectra of their own.High sensitive sensing of the bio-chemical pollutions were realized with the hybrid SERS substrate.the chemicals adsorbed model on the SERS substrate was established.The hybrid substrate was competent for rapid,sensitive and selective sensing in the area of food safty.The detection limits were 10 nM,50nM and 10 nM for the paraquat,thiram and melamine,respectively.Besides,the SERS signal intensities and the concentrations fitted well with a linear function.With the colibacillus bacillus and bacillus subtilis as the examples,the capability of the hybrid SERS substrate in pathogenic microorganism sensing was validated.To further investigate the SERS sepctra,the principal component analysis method was utilized to indentify these two bacillus.