Evolution of Hydrogen-Bond Interactions within Single Levitated Metastable Aerosols Studied by In Situ Raman Spectroscopy

Photoinduced Reactions of Nitrate in Aqueous Microdroplets by Triplet Energy Transfer

In-situ Raman spectroscopy of single levitated charged aqueous microdroplets irradiated by dual-beam (266 and 532 nm) lasers demonstrates that the nitrate anion (NO3-) can be depleted in the droplet through an energy transfer mechanism following excitation of sulfanilic acid (SA), a UV-absorbing aromatic organic compound. Upon 266 nm irradiation, a fast decrease of the NO3- concentration was observed when SA is present in the droplet. This photoinduced reaction occurs without the direct photolysis of NO3-. Instead, the rate of NO3- depletion was found to depend on the initial concentration of SA and the pH of the droplet. Based on absorption-emission spectral analysis and excited-state energy calculations, triplet-triplet energy transfer between SA and NO3- is proposed as the underlying mechanism for the depletion of NO3- in aqueous microdroplets. These results suggest that energy transfer mechanisms initiated by light-absorbing organic molecules may play a significant role in NO3- photochemistry.

Continuing progress in the field of two-dimensional correlation spectroscopy (2D-COS): Part III. Versatile applications

In this review, the comprehensive summary of two-dimensional correlation spectroscopy (2D-COS) for the last two years is covered. The remarkable applications of 2D-COS in diverse fields using many types of probes and perturbations for the last two years are highlighted. IR spectroscopy is still the most popular probe in 2D-COS during the last two years. Applications in fluorescence and Raman spectroscopy are also very popularly used. In the external perturbations applied in 2D-COS, variations in concentration, pH, and relative compositions are dramatically increased during the last two years. Temperature is still the most used effect, but it is slightly decreased compared to two years ago. 2D-COS has been applied to diverse systems, such as environments, natural products, polymers, food, proteins and peptides, solutions, mixtures, nano materials, pharmaceuticals, and others. Especially, biological and environmental applications have significantly emerged. This survey review paper shows that 2D-COS is an actively evolving and expanding field.