Femtosecond stimulated Raman spectro-microscopy for probing chemical reaction dynamics in solid-state materials

Abstract

Femtosecond stimulated Raman spectroscopy (FSRS) is a chemically specific vibrational technique that has the ability to follow structural dynamics during photoinduced processes such as charge transfer on the ultrafast timescale. FSRS has a strong background in following structural dynamics and elucidating chemical mechanisms; however, its use with solid-state materials has been limited. As photovoltaic and electronic devices rely on solid-state materials, having the ability to track the evolving dynamics during their charge transfer and transport processes is crucial. Following the structural dynamics in these solid-state materials will lead to the identification of specific chemical structures responsible for various photoinduced charge transfer reactions, leading to a greater understanding of the structure–function relationships needed to improve upon current technologies. Isolating the specific nuclear motions and molecular structures that drive a desired physical process will provide a chemical blueprint, leading to the rational design and fabrication of efficient electronic and photovoltaic devices. In this perspective, we discuss technical challenges and experimental developments that have facilitated the use of FSRS with solid-state samples, explore previous studies that have identified structure–function relationships in charge transfer reactions, and analyze the future developments that will broaden and advance the field.

Decoding Chemical and Physical Processes Driving Plasmonic Photocatalysis Using Surface-Enhanced Raman Spectroscopies

“…Furthermore, molecular transformations occur on time scales of femtoseconds to picoseconds, requiring methods with high sensitivity and temporal resolution to elucidate the role of plasmons in the formation of reaction intermediates. 18 While during experiments it may take minutes for photoproduct to accumulate to the level detectable by downstream mass spectrometers, the bond-breaking and -making processes essential to any chemical reaction take place on the femtosecond to picosecond time scale of nuclear motion. 19 Our group and others have turned to transient and steady-state vibrational spectroscopy techniques in order to understand the impact of plasmon excitations on nearby molecules, with the ultimate goal of using the mechanistic insights obtained by these studies to improve the efficiency, yield, and selectivity of plasmon-driven chemistries.…”

“…It is difficult to determine which, or what combination, of these many plasmonic energy partitioning pathways is the dominant contributor in plasmon-mediated reactions given the short time scale of plasmon decay and small nanoconfined regions in which the reactions occur. Furthermore, molecular transformations occur on time scales of femtoseconds to picoseconds, requiring methods with high sensitivity and temporal resolution to elucidate the role of plasmons in the formation of reaction intermediates . While during experiments it may take minutes for photoproduct to accumulate to the level detectable by downstream mass spectrometers, the bond-breaking and -making processes essential to any chemical reaction take place on the femtosecond to picosecond time scale of nuclear motion .…”

Time-Resolved Vibrational and Electronic Spectroscopy for Understanding How Charges Drive Metal Oxide Catalysts for Water Oxidation

“…For example, by positioning an electrocatalyst/GaP working electrode in micrometer distance from the infrared ATR element with electrolyte solution sandwiched between and holding the applied potential just short of catalysis onset, a nanosecond light pulse would result in an incremental voltage jump above the catalysis onset, allowing time-resolved monitoring of catalytic intermediates with minimal disruption of interfacial electrical fields. Looking farther out, advanced ultrafast vibrational spectroscopic techniques with exceptional sensitivity, such as femtosecond stimulated Raman spectroscopy or field-resolved broadband infrared spectroscopy based on dual-comb quantum cascade laser technology, may lead to another jump in the knowledge of intermediate dynamics for guiding catalyst design improvements.…”

Mastering Femtosecond Stimulated Raman Spectroscopy: A Practical Guide

“…It is compatible with most solvents, including water, and is easily combined with a standard optical microscope for spectromicroscopy measurements. 35 Given that it is self-heterodyned with the broadband probe pulse, it is possible to acquire a complete vibrational spectrum in a single shot provided the user has high-quality filters to access the low-frequency spectral region. Additionally, the FSRS can be tuned to make use of resonance enhancement in ground or excited electronic states, thereby providing large signal enhancements and species selectivity.…”

“…Apart from its excellent temporal and spectral resolution, the FSRS technique has several other benefits. It is compatible with most solvents, including water, and is easily combined with a standard optical microscope for spectromicroscopy measurements . Given that it is self-heterodyned with the broadband probe pulse, it is possible to acquire a complete vibrational spectrum in a single shot provided the user has high-quality filters to access the low-frequency spectral region.…”