Research Projects

Chlorofluorocarbons (CFCs) and and hydrochlorofluorocarbons (HCFCs) are potent greenhouse gases and major contributors to stratospheric ozone depletion. Owing to their exceptional chemical stability, largely due to the high strength of the carbon–fluorine (C–F) bond, CFCs and HFCs can persist in the atmosphere for decades after their release. This prolonged atmospheric lifetime underscores the urgent need to understand their degradation pathways, which is crucial for refining global climate models and designing effective environmental mitigation strategies. Recent advances in microdroplet chemistry have revealed that when bulk water is transformed into airborne microdroplets, it functions as a powerful microreactor, capable of facilitating chemical reactions that are otherwise slow or non-existent under bulk conditions. Our preliminary studies have demonstrated that C–F bond (strongest organic bond) cleavage is feasible in water microdroplets without the need for catalysts or extreme conditions (Nandy et al., JACS, 2025, 147, 26, 22542–22549). This unexpected reactivity is attributed to the distinctive interfacial environment of microdroplets, where organic molecules are subjected to asymmetric solvation, intense local electric fields, steep pH gradients, etc. These findings are likely to open up a previously underexplored avenue for environmental degradation pathways of CFCs and HCFCs. Therefore, this project aims to investigate the degradation of these halogenated hydrocarbons by aqueous microdroplets (laboratory analogues of airborne microdroplets) driven by the fundamental question of whether natural atmospheric aerosols, particularly water-rich forms such as clouds, fog, rain, and ocean spray, can actively participate in initiating such breakdown of CFCs. Thus, this proposal seeks to unveil a previously overlooked pathway for the spontaneous breakdown of halocarbon pollutants at the air–water interface of tiny microdroplets found in nature, offering a novel perspective on atmospheric self-cleaning mechanisms and pollutant remediation strategies. In the initial phase of the project, various microdroplet generation techniques, such as sonic spray, ultrasonic foggers, and jet sprays, will be optimized to atomize both pure and environmental water samples. These microdroplets will be exposed to trace levels of hydrochlorofluorocarbons (HCFCs) and a commercially available CFC standard (available for within a sealed reaction chamber. A portion of the resulting aerosol will be analyzed in real time using mass spectrometry, with the setup housed inside a glove box and interfaced via an ion transfer capillary. Mass spectra will be examined to identify degradation products, with mechanistic insights validated using isotopically labeled water (e.g., D₂O, H₂¹⁸O). Reactive intermediates will be monitored using gas mass analyzer, while factors such as droplet size, pH, salinity, and ambient gases (N₂, O₂, Ar) will be evaluated for their influence on reaction efficacy. In the final stage, time-resolved GC-MS and TCD analyses will be performed to map degradation kinetics, supported by thermodynamic studies and theoretical inestigations. The successful completion of this study is expected to provide strong evidence that natural aqueous aerosols may serve as a sink for CFCs. These insights will significantly enhance our understanding of environmental halocarbon degradation and may pave the way for novel, sustainable remediation strategies based on interfacial microdroplet chemistry. In short: such a finding would be paradigm-shifting, with implications across physical chemistry, climate science, and environmental policy, challenging the long-held belief that CFCs are chemically inert in the lower atmosphere. This advancement could also pave the way for the development of future water-based technologies aimed at mitigating CFC/HCFC pollution, such as the deployment of water spray systems near emission sources for sustainable remediation.