title: Monolayer detection on flat metal surface via surface enhanced Raman spectroscopy and sum frequency generation spectroscopy.
abstract: Monolayer detection on metal surface requires ultra high sensitivity. Sum Frequency Generation Spectroscopy (SFG) and Surface Enhanced Raman Spectroscopy (SERS) are regarded as two powerful techniques with submolecular sensitivity to detect adsorbents on metal surface. However, in some cases it's still challenge to characterize molecules or groups with relatively high intramolecular symmetry, such as 4-Nitrothiophenol (4NTP), on flat metal surface even combining these two techniques. Basically, this is due to that 4NTP with para-substituted phenol groups is SFG insensitive while flat metal surface is unfavorable to yield strong SERS enhancement. In this concern, a simple and efficient method, silver mirror method, was employed to facilitate the detection of 4NTP SAM on flat gold surface. Silver nanopheres with diameters around 300 nm was fabricated through silver mirror reaction and in situ formed milky overlayer on top of 4NTP SAM adsorbed on gold surface. Significant enhancement on SERS signal can be achieved with such special assembly structure of the "metal-molecule-metal" system. Generally, the silver mirror method provided a complementary approach to facilitate the spectroscopic applications of molecule level detection on various metal surfaces in situ.
authors.affiliation: State Key Laboratory of Coordination Chemistry, Nanjing National Laboratory of Microstructures, Department of Polymer Science and Engineering, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
authors.forename: Dawei
authors.initials: D
authors.lastname: Li
authors.forename: Jiao
authors.initials: J
authors.lastname: Chen
authors.forename: Haibing
authors.initials: H
authors.lastname: He
authors.forename: Rongping
authors.initials: R
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Lu
authors.forename: Xinping
authors.initials: X
authors.lastname: Wang
authors.forename: Gi
authors.initials: G
authors.lastname: Xue
mesh_terms: D000327:Adsorption; D000465:Algorithms; D008422:Materials Testing / Q000379:methods*; D008670:Metals / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013499:Surface Properties
chemical_list: D008670:Metals