Harnessing Chemical Raman Enhancement for Understanding Organic Adsorbate Binding on Metal Surfaces.
Surface-enhanced Raman spectroscopy (SERS) is a known approach for detecting trace amounts of molecular species. Whereas SERS measurements have focused on enhancing the signal for sensing trace amounts of a chemical moiety, understanding how the substrate alters molecular Raman spectra can enable optical probing of analyte binding chemistry. Here we examine binding of trans-1,2-two(4-pyridyl) ethylene (BPE) to Au surfaces and understand variations in experimental data that arise from differences in how the molecule binds to the substrate. Monitoring differences in the SERS as a function of incubation time, a period of several hours in our case, reveals that the number of BPE molecules that chemically binds with the Au substrate increases with time. In addition, we introduce a direct method of accessing relative chemical enhancement from experiments that is in quantitative agreement with theory. The ability to probe optically specific details of metal/molecule interfaces opens up possibilities for using SERS in chemical analysis.
†Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.|∥Department of Electrical Engineering and Computer Sciences, UC Berkeley, Berkeley, California, United States.
Alexey T
AT
Zayak
‡The Moore Laboratory, Electrical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
Hyuck
H
Choo
§Waitt Advanced Biophotonics Center, Salk Institute, La Jolla, California 92037, United States.
Ying S
YS
Hu
†Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Daniel J
DJ
Gargas
†Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Stefano
S
Cabrini
∥Department of Electrical Engineering and Computer Sciences, UC Berkeley, Berkeley, California, United States.
Jeffrey
J
Bokor
†Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
P James
PJ
Schuck
†Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Jeffrey B
JB
Neaton
Raman spectroscopy; SERS; chemical enhancement; density functional theory; metal−organic interface