Acetyl - Alanine, Sulfonamides And Other Functional Molecules And Metal Effects On Raman Spectroscopy Study

Surface-enhanced Raman scattering(SERS) Spectroscopy was used to observed the adsorption behavior of 2-amino-5-mercapto-1,3,4-thiadiazole(AMT) at the silver colloid.It is found that both the concentration and the time impact on adsorption fashion of AMT.As concentration at 10^-3 M,AMT molecules adsorb at the silver colloid surface in a titled orientation through two sulfur atoms of mercapto and thiadiazole ring.While the concentration decreased to 10^-4 M,AMT molecules perpendicularly attach onto the surface.At much lower concentration of 10^-5 M,AMT molecules tend to lie on the silver surface in a flat mode of ring.Surface-enhanced Raman scattering(SERS) spectroscopy was applied to observe the process and structure of N-acetylalanine molecules self-assembled at the silver surface.SERS data show that the N-acetylalanine molecules adsorb at the silver surface through the amino group and the entire carboxyl group in a perpendicular way after a self-reorganization.Results of SERS and X-ray photoelectron spectroscopic experiments indicate that the Ce³⁺ affects the structure of monolayers because of the binding reaction between the Ce³⁺ and the carbonyl along with the amino groups in N-acetylalanine.The Ce³⁺ capped by N-acetylalanine monolayers can be removed by adding EDTA solution and the original structure of monolayers is recovered. However,the impact of K⁺ on the structure of N-acetylalanine monolayers is slight and can be ignored.Sulfanilamides are the first effective chemotherapeutic agents to be employed systemically for the prevention and cure of bacterial infections in humans. Furthermore,sulfa drugs and their complexes have many applications,such as diuretic, antiglaucoma or antiepileptic drugs,among others.After the electrochemically roughened silver surface,SERS spectra of sulfanilamide SAMs on the silver surface were obtained at different pH media.Assignments of the obtained spectra were performed by the density functional theory(DFT) calculations at BLYP/6-311G method.Based on SERS producing mechanism,the adsorption fashions of sulfanilamide at the silver surfaces were deduced that the fully protonated sulfanilamide molecule adsorbed on the silver surface through N¹³H₂ group and benzene ring anchored in a relative perpendicularity way leading to N⁷H₂ and S¹⁰O₂ groups near the surface,while the completely deprotonated sulfanilamide molecule attached on the silver surface via N⁷H₂ group and the benzene ring was in a perpendicularity manner,as well as N¹³H₂ and S¹⁰O₂ groups far away from the silver surface.The electrode roughened by electrochemical method performs some disadvantages when compared to metal nanoparticles,such as bad stability and reproducibility.Silver and gold nanoparitcles as SERS active substrates possess high SERS enhancement.Water-soluble sol,which is employed in studies of water-soluble molecules adsorption,is applied in many areas,such as biochemisty and trace analysis. We report a facile method to prepared gold particles in nano-pearl-necklace pattern with considerable stablity(＞2months) by using of an environmentally benign reagent of inositol hexphosphate(IP₆).IP₆ acted as a tunable cross-linker to obtain a suitable separation(～2nm) between neighboring particles for surface plasmons by varying the dosage of IP₆,which demonstrate the high enhancement factor(＞10⁷) for 2-mercaptopyridine(2-Mpy) Raman scattering.