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Single-Molecule Surface-Enhanced Raman Scattering as a Probe of Single-Molecule Surface Reactions: Promises and Current Challenges.

Abstract

The initial observations of surface-enhanced Raman scattering (SERS) from individual molecules (single-molecule SERS, SMSERS) have triggered ever more detailed mechanistic studies on the SERS process. The studies not only reveal the existence of extremely enhanced and confined fields at the gaps of Ag or Au nanoparticles but also reveal that the spatial, spectral, and temporal behaviors of the SMSERS signal critically depend on many factors, including plasmon resonances of nanostructures, diffusion (lateral and orientational) of molecules, molecular electronic resonances, and metal-molecule charge transfers. SMSERS spectra, with their molecular vibrational fingerprints, should in principle provide molecule-specific information on individual molecules in a way that any other existing single-molecule detection method (such as the ones based on fluorescence, mechanical forces, or electrical currents) cannot. Therefore, by following the spectro-temporal evolution of SMSERS signals of reacting molecules, one should be able to follow chemical reaction events of individual molecules without any additional labels. Despite such potential, however, real applications of SMSERS for single-molecule chemistry and analytical chemistry are scarce. In this Account, we discuss whether and how we can use SMSERS to monitor single-molecule chemical kinetics. The central problem lies in the experimental challenges of separately characterizing and controlling various sources of fluctuations and spatial variations in such a way that we can extract only the chemically relevant information from time-varying SMSERS signals. This Account is organized as follows. First, we outline the standard theory of SMSERS, providing an essential guide for identifying sources of spatial heterogeneity and temporal fluctuations in SMSERS signals. Second, we show how single-molecule reaction events of surface-immobilized reactants manifest themselves in experimental SMSERS trajectories. Comparison of the reactive SMSERS data (magnitudes and frequencies of discrete transitions) and the predictions of SMSERS models also allow us to assess how faithfully the SMSERS models represent reality. Third, we show how SMSERS spectral features can be used to discover new reaction intermediates and to interrogate metal-molecule electronic interactions. Finally, we propose possible improvements in experimental design (including nanogap structures and molecular systems) to make SMSERS applicable to a broader range of chemical reactions occurring under ambient conditions. The specific examples discussed in this Account are centered around the single-molecule photochemistry of 4-nitrobenzenethiol on metals, but the conclusions drawn from each example are generally applicable to any reaction system involving small organic molecules.

Authors+Show Affiliations

Department of Chemistry , Kunsan National University , Gunsan , Jeonbuk 54150 , Korea.Department of Chemistry , Seoul National University , Seoul 08826 , Korea.Department of Chemistry , Seoul National University , Seoul 08826 , Korea.Department of Chemistry , Seoul National University , Seoul 08826 , Korea.Department of Chemistry , Seoul National University , Seoul 08826 , Korea.Department of Chemistry , Seoul National University , Seoul 08826 , Korea.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

31609583

Citation

Choi, Han-Kyu, et al. "Single-Molecule Surface-Enhanced Raman Scattering as a Probe of Single-Molecule Surface Reactions: Promises and Current Challenges." Accounts of Chemical Research, 2019.
Choi HK, Lee KS, Shin HH, et al. Single-Molecule Surface-Enhanced Raman Scattering as a Probe of Single-Molecule Surface Reactions: Promises and Current Challenges. Acc Chem Res. 2019.
Choi, H. K., Lee, K. S., Shin, H. H., Koo, J. J., Yeon, G. J., & Kim, Z. H. (2019). Single-Molecule Surface-Enhanced Raman Scattering as a Probe of Single-Molecule Surface Reactions: Promises and Current Challenges. Accounts of Chemical Research, doi:10.1021/acs.accounts.9b00358.
Choi HK, et al. Single-Molecule Surface-Enhanced Raman Scattering as a Probe of Single-Molecule Surface Reactions: Promises and Current Challenges. Acc Chem Res. 2019 Oct 14; PubMed PMID: 31609583.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Single-Molecule Surface-Enhanced Raman Scattering as a Probe of Single-Molecule Surface Reactions: Promises and Current Challenges. AU - Choi,Han-Kyu, AU - Lee,Kang Sup, AU - Shin,Hyun-Hang, AU - Koo,Ja-Jung, AU - Yeon,Gyu Jin, AU - Kim,Zee Hwan, Y1 - 2019/10/14/ PY - 2019/10/15/entrez PY - 2019/10/15/pubmed PY - 2019/10/15/medline JF - Accounts of chemical research JO - Acc. Chem. Res. N2 - The initial observations of surface-enhanced Raman scattering (SERS) from individual molecules (single-molecule SERS, SMSERS) have triggered ever more detailed mechanistic studies on the SERS process. The studies not only reveal the existence of extremely enhanced and confined fields at the gaps of Ag or Au nanoparticles but also reveal that the spatial, spectral, and temporal behaviors of the SMSERS signal critically depend on many factors, including plasmon resonances of nanostructures, diffusion (lateral and orientational) of molecules, molecular electronic resonances, and metal-molecule charge transfers. SMSERS spectra, with their molecular vibrational fingerprints, should in principle provide molecule-specific information on individual molecules in a way that any other existing single-molecule detection method (such as the ones based on fluorescence, mechanical forces, or electrical currents) cannot. Therefore, by following the spectro-temporal evolution of SMSERS signals of reacting molecules, one should be able to follow chemical reaction events of individual molecules without any additional labels. Despite such potential, however, real applications of SMSERS for single-molecule chemistry and analytical chemistry are scarce. In this Account, we discuss whether and how we can use SMSERS to monitor single-molecule chemical kinetics. The central problem lies in the experimental challenges of separately characterizing and controlling various sources of fluctuations and spatial variations in such a way that we can extract only the chemically relevant information from time-varying SMSERS signals. This Account is organized as follows. First, we outline the standard theory of SMSERS, providing an essential guide for identifying sources of spatial heterogeneity and temporal fluctuations in SMSERS signals. Second, we show how single-molecule reaction events of surface-immobilized reactants manifest themselves in experimental SMSERS trajectories. Comparison of the reactive SMSERS data (magnitudes and frequencies of discrete transitions) and the predictions of SMSERS models also allow us to assess how faithfully the SMSERS models represent reality. Third, we show how SMSERS spectral features can be used to discover new reaction intermediates and to interrogate metal-molecule electronic interactions. Finally, we propose possible improvements in experimental design (including nanogap structures and molecular systems) to make SMSERS applicable to a broader range of chemical reactions occurring under ambient conditions. The specific examples discussed in this Account are centered around the single-molecule photochemistry of 4-nitrobenzenethiol on metals, but the conclusions drawn from each example are generally applicable to any reaction system involving small organic molecules. SN - 1520-4898 UR - https://www.unboundmedicine.com/medline/citation/31609583/Single-Molecule_Surface-Enhanced_Raman_Scattering_as_a_Probe_of_Single-Molecule_Surface_Reactions:_Promises_and_Current_Challenges L2 - https://dx.doi.org/10.1021/acs.accounts.9b00358 DB - PRIME DP - Unbound Medicine ER -