title: Surface enhanced Raman scattering of melamine on silver substrate: An experimental and DFT study.
abstract: Surface enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique that allows amplifying weak Raman signals by the excitation of localized surface plasmons. In this paper, we used nanoscale roughened silver surface to enhance Raman signals of melamine analyte. Silver nanoparticles were synthesized by wet-chemical method and employed for SERS measurement. Theoretically, optimized geometries and vibrational frequencies of melamine and melamine absorbed on silver-cluster surface were calculated by using the B3LYP/6-31G(d) method. Then, the predicted spectrograms are compared with the experimental Raman spectra. As a result, Raman signals of melamine were dramatically enhanced by using obtained silver nanoparticles as the substrate. Typical peaks of melamine at 676 and 983cm(-1) were enhanced and could be obviously observed in experiments. The calculated vibrational frequencies seem to relatively coincide with the experimental values. SERS effect of melamine on nanoscale silver was also explained by analyzing molecular frontier orbitals (HOMO and LUMO) melamine-silver complexes.
authors.affiliation: Institute of Research and Development, Duy Tan University, K7/25 Quang Trung, Danang, Viet Nam.
authors.forename: Nguyen Thi Thai
authors.initials: NT
authors.lastname: An
authors.affiliation: Institute of Research and Development, Duy Tan University, K7/25 Quang Trung, Danang, Viet Nam. Electronic address: daoduyquang@gmail.com.
authors.forename: Duy Quang
authors.initials: DQ
authors.lastname: Dao
authors.affiliation: Department of Chemistry, University of Science and Technology - The University of Danang, 54 Nguyen Luong Bang, Lien Chieu, Danang, Viet Nam. Electronic address: pcnam@dut.udn.vn.
authors.forename: Pham Cam
authors.initials: PC
authors.lastname: Nam
authors.affiliation: Department of Chemistry, Changwon National University, Changwon 641-773, Republic of Korea.
authors.forename: Bui The
authors.initials: BT
authors.lastname: Huy
authors.affiliation: Institute of Research and Development, Duy Tan University, K7/25 Quang Trung, Danang, Viet Nam.
authors.forename: Hong
authors.initials: H
authors.lastname: Nhung Tran
keywords: Density functional theory (DFT); HOMO; LUMO; Melamine; Silver nanoparticles; Surface enhanced Raman scattering (SERS)