SERS Detection Of Adenine And Cytosine By Patterned Silver Structure Immersion Plated On Silicon Nanoporous Pillar Array

The Raman spectrum belongs to the molecular vibration spectrum, provides the unique "fingerprint" information of molecular, and may apply in the fields of biological interaction analysis, disease diagnosis, analytical chemistry and so on. (?)wever, the normal Raman signal is extremely weak which limits its applications (?)eriously. The Raman signals can be efficiently enhanced by Surface-enhanced Caman scattering (SERS), which has been widely used in many fields. In the application of SERS, the selection and preparation of the active substrate is very important. In this article, the SERS substrate Ag/Si-NPA is fabricated by immersion plating based on silicon nanoporous pillar array (Si-NPA) which has regular (?)cture. Based on this prepared substrate, the Raman spectroscopy of adenine and (?)osine were obtained and analysed.The structure character of the SERS substrate Ag/Si-NPA was observed and (?)eral substrates of Ag/Si-NPA with different immersion time were prepared. Based on these substrates, the SERS spectrum of adenine with the concentration of (?)4 M were obtained and analyzed, and we found the best deposition time of the (?)tive substrate was 3 min.The SERS spectrum was analyzed and it could be inferred that the adenine molecules were vertically adsorbed on the surface of the substrate Ag/Si-NPA though N7. The SERS spectrum of adenine were obtained in low concentration from 10-5 to 10-9 M and it was found that the adenine was detected with the limiting concentration of 10-9 M. Through analyzing the transformation of vibrating peaks, we found the intensity of the peak 733cm-1 which characteristic the ring breathe vibration, become weaker gradually with the decrease of the adenine concentration. When the concentration of adenine was 10-8 M, the peak 733 cm-1 disappeared. According to the SERS surface selection rule, the state of adenine molecule absorbed un the substrate Ag/Si-NPA was changed. With the decrease of the concentration, the adenine molecules become parallel to the surface of the substrate from the state of the verticality. Then we studied where the adenine molecule adsorbed on the substrate when the SERS signal is best, and the result indicated when the adenine absorbed on the top of the silicon column, the SERS signal is perfect.The cytosine SERS spectrum has been obtained on the SERS active substrate of Ag/Si-NPA and simply analyzed its vibration peaks. The result, which is in accord with the literature report, is the cytosine molecule absorbed vertically with N3 on the surface of the active substrate. The SERS spectrums of cytosine with different concentration also been obtained and analyzed, and the result is the state of cytosine molecule absorbed on the substrate Ag/Si-NPA did not changed with the decrease of cytosine concentration.