Preparation of a new surface-enhanced Raman scattering substrate and its application to the detection of E.coli

Objective: To develop a new type of Raman-enhanced substrate for rapid detection of E.coli based on lahel-free surface-enhanced Raman scattering (SERS) technology. Methods: Stober's improved method was used to prepare 360 nm silica (SiO₂) nanospheres. Prepared gold core-silver shell nanoparticles(Au@Ag) of different size were attached to 360 nm SiO₂ to fabricate the nanocomposites (SiO₂-Au@Ag) that were characterized by transmission electron microscopy (TEM) and UV-visucl light adsorption spectra (UV-Vis). PATP was detected to select SiO₂-Au@ Ag with optimal SERS effect. This optimal SiO₂-Au@ Ag was used to obtain the sensitivity of PATP and E.coli detection after a simple mixed cultivation. Results: TEM images showed that Au@Ag aggregated with the size of Au@Ag attached to 360 nm SiO₂. UV-Vis spectra indicated that the maximum absorption of Au@Ag and SiO₂-Au@Ag had a red shift with the invrease of Au@Ag size. The experiment results suggested that detection sensitivity of PATP by SiO₂-100 nm Au@Ag 10^-10 mol/L. while the lowest detectable E.coli concentration was 10⁵ CFU/ml. Conclusion: The 360 nm SiO₂ binding with 100 nm Au@Ag exhibits great potential for SERS applications. (authors)