[Using PAA template to fabricate SERS substrate and the SERS detection of melamine]

The authors have got silver film with orderly arranged nanoparticles as the surface-enhanced Raman spectra (SERS) substrates using porous anodic alumina templates (PAA). A silver film (99.99%) with the thickness of several millimeters was thermally evaporated onto the PAA templates and the SERS substrate was got after removing the PAA templates in hydrochloric acid. SERS spectra of pyridine (0.01 mol x L(-1)) were measured on Renishaw 2000 Ramanscope with a He-Ne (632.8 nm) laser as an excitation source in backscattering geometry, and the average enhancement factors were more than 10(5). The authors compared SERS spectra of pyridine from the SERS substrates and from Ag film evaporated directly on glass slide, and the former was 30 times stronger than the latter. The authors got different SERS spectra of pyridine while changing the excitation laser power. It was found that the relationship between the peak intensity of SERS spectra and the excitation laser power was linear as the normal Raman spectrum. We used the substrates to detect melamine, 2.5 mg x L(-1) melamine solution could be recognized al though excitation laser power was below 1 mW.