A novel fabrication of Au-coated glass capillaries for chemical analysis by surface-enhanced Raman scattering

A novel method to deposit a highly surface-enhanced Raman scattering (SERS) active gold film onto the inside surface of a glass capillary is developed. Firstly, Au sol was synthesized by the reaction of HAuCl4 with poly(ethylenimine) (PEI), and then toluene and benzenethiol (BT) were added into the sol. The mixture was flowed through the glass capillary to obtain the SERS active Au film. The SERS activity of the Au-coated glass capillary was dependent on the amount of PEI and BT used. BT could be desorbed from the Au surface by treating with a mild borohydride solution, but maintaining the initial SERS activity. The best SERS enhancement factor at 632.8 nm excitation was on the order of 106. The detection limit of adenine is then as low as 1.0 × 10−6 M based on an S/N ratio of 3. All this suggests that the Au-coated capillary is an invaluable device for the microanalysis of effluent chemicals by SERS.