Switching On and Off of Interfacial Water Ordering at Air/Water Interface
Carbon quantum dots (CQDs) are recently famed and well developed class of fluorescent probe and have shown tremendous potential in numerous fields such as biosensing, bioimaging, drug delivery, and optoelectronics. After its accidental discovery, it has created huge excitement due to their unique features like chemical inertness, high water solubility, excellent biocompatibility, resistance to photo bleaching. Mostly it has been extensively studied to exploit its fluorescence properties through displacement assay for various applications by using conventional fluorescence spectroscopy. Fluorescence spectroscopy does not provide any information directly related to the structural changes of the system or its impact on the surrounding aqueous medium during displacement assay process. In my talk, I will provide a thorough discussion about our recent work on interfacial activities of carbon quantum dots and its impact on perturbing the pristine hydrogen bonding network of interfacial water structure at air/water interface. We have used surface specific and chemically sensitive sum frequency generation (SFG) vibrational spectroscopy to probe the air/water interface with the presence of QCDs and various metal ions. SFG is a nonlinear optical spectroscopic tool based on second order nonlinear optical process. It is quite fascinating to observe the role of various intermolecular interactions in terms of hydrogen bonding, electrostatic interaction during the process of interaction of the QCDs with various metal ions at the air/aqueous interface. I will also extend my discussion about the physics of surface protein unfolding and its kinetics through diffusion and intermolecular interactions at a neutral air/water interface.