Preparation And SERS Properties Of Alkanethiol Modified Polyaniline-silver Nanocomposite Material

Surface-enhanced Raman spectroscopy (SERS) has become a mature vibrationalspectroscopic technique and the number of applications in different areas such aschemical, material, and life sciences is rapidly increasing. However, further applicationsin industry level are still restricted due to lack of facile, low cost fabrication method ofreproducible, robust, high sensitivity SERS substrate.In this study by comparing method of the preprocessing of the polyaniline(PANI)film, the type of doping acid and soaking time of N-dodecyl mercaptan influcence onthe silver nanostructures, hydrophobicity and SERS performance, we found the optimalfabrication method of superhydrophobic substrate which combining superhydrophobiccondensation effect and high enhancement ability of lactic-acid doped homogeneous Agnanostructures on hydrazine preprocessing polyaniline. The size, morphology, elementalcomposition, contact angle, shape of deposition area and SERS perfomance of thesubstrate were characterized by SEM, EDS, Angle Contact Metering System,Fluorescence Microscope and SERS. Our caculated result indicates thatsuperhydrophobic substrate could exhibit21-fold molecule condensation and couldfurther amplify the SERS signal to achieve more sensitive detection. Thissuperhydrophoibc substrate is susccessfully applied to dectect small molecules such asmethylene blue, with limits of detection (LOD) of1order of magnitude lower thanthose on the hydrophilic substrate.With high signal reproducibility, the feasibility of using SERS-activesuperhydrophobic substrate for quantative dection is explored. Here we present acomprehensive study of the influence of spectra data pre-preocessing procedures onstatistical models and introudce the optimal chemometrics pre-processing approaches.Stable and reliable partial least squares (PLS) model was established for thequantification of methylene blue by SERS: R2=95.1%, RMSEP=0.225962. Formelamine, the LOD is10-6mol/L, and RMSEP=0.505226, R2=86.9%.To further expand the application of our substrate, we explore the potential ofalkanethiol partition layer-modified PANI-Ag substrate for SERS detection ofpolycyclic aromatic hydrocarbons. In this work, the alkanethiol chain length andconcentration was varied to find the optimal partition layer, and of those used,10-3mol/L hexanethiol yielded best SERS performance, for pyrene, LOD is10-7mol/L,for triphenylene, LOD is10-8mol/L.Alkanethiol modified polyaniline-silver nanocomposite SERS substrate could beexpected to widely used in the trace analysis in industry level in the future due to itsfacile fabrication, high signal reproducibility and good SERS performance.