Chapter 17 - Application of ultrafast infrared spectroscopy in elucidating electronic processes in materials

Abstract

With the rapid expansion of new technologies, new synthetic methodologies, comes an ever-increasing requirement for new materials. Synthesizing new materials for various applications, such as solar cells, photovoltaics, photocatalysis is of prime importance for advancing our life. The ability to design, synthesize, study, and control molecular properties has opened a vast frontier of research. With the help of modern spectroscopic tools, the newly synthesized molecules can be studied, enabling an understanding of how structure relates to function. One overlooked spectroscopic tool for measurements of molecular properties is time-resolved spectroscopy. Time-resolved absorption and emission spectra of molecular systems contain information about the excited-state population. Furthermore, it contains information regarding the interaction of the photoexcited molecule with the surrounding medium that controls intramolecular and intermolecular vibrational energy flow. One of the drawbacks of time-resolved electronic methods is that vibrational information is smeared out due to the coupling between fluctuating solvents and the electronic states. To decipher the physical mechanisms underlying broad and congested absorption/emission spectra, time-resolved vibrational spectroscopic techniques, such as infrared and Raman are developed. The sensitivity of molecular vibrations to their local environment can provide a handle to investigate and thereby controlling electronic processes in materials. In this regard, time-resolved infrared (TRIR) spectroscopy has proven to be an incomparable spectroscopic method to obtain structural information on a range of molecular systems with ultrafast time and high spectral resolution. Time-resolved experiments, crucial in characterization of the excited-state chemical processes, are essential for the development of new materials for solar cell applications, photocatalysis, etc. In this chapter, we discuss the recent state-of-the-art applications of TRIR spectroscopy in a range of materials. This chapter covers essential examples and recent developments in the application of TRIR spectroscopy in the field of organometallic chemistry, photoinduced CO2 reduction, development of solar cell materials and highlights the enormous contribution of the TRIR technique in advancing our understanding of excited-state structures.