Search

Environmental contamination due to increase in drug levels is reaching an alarming stage. An array of drugs, such as antibiotics, antidepressants, analgesics, and chemotherapy drugs, have been found to be polluting agriculture soils and rivers. Here we developed optical sensors based on terbium(III)-coated carbon quantum dots (Tb-CQDs) synthesized by carrying out a single-step one-pot hydrothermal process in an aqueous medium and characterized by using UV-visible, fluorescence, DLS, HRTEM and XRD measurements. Photophysical studies showed the ability of CQD-Tb to act as a chemosensor of the antidepressant drug clomipramine in aqueous medium. A competitive binding assay using CQD-Tb and clomipramine was carried out in the presence of other drugs. No interference resulted from the presence of the other drugs; and hence, the developed chemosensor can be used for selective detection of clomipramine. A functional group analysis was done using FTIR spectroscopy and a mechanism for drug binding with the chemosensor was derived. To target the interfacial behavior with different drugs, vibrational sum-frequency generation (VSFG) spectroscopy was carried out and further confirmed the ability of the synthesized CQD-Tb to act as a chemosensor for the selective detection of clomipramine in the presence of other drugs. [ABSTRACT FROM AUTHOR]

Carbon Quantum Dots (CQDs) have been extensively employed in various fields of science such as sensing, catalysis, and drug delivery. In this work, ionic liquid coated CQDs (IL@CQDs) have been used as catalysts for the rearrangement of a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) amide coupling intermediate. The rearranged product was confirmed by single crystal structure analysis and it was processed into organic nanoparticles (ONPs). An optical detection method was used to scrutinize the anion sensing properties. The ONPs were found to be sensitive and selective for the recognition of highly toxic cyanide ions through enhancement in the fluorescence intensity. The cyanide ion co-ordinates with the –NH groups of the product and restricts the rotation of molecules around the single bond. The ONPs coated over silica-beads were also showing CN− recognition in the solid state. The detection limit for CN− sensing was found to be 3.8 nM, and real sample analysis depicts more than 90% accuracy in detection. [ABSTRACT FROM AUTHOR]

The ordered arrangement of water molecules at solid surfaces is a consequence of hydrogen-bonding opportunities, electrostatic and dipolar interactions, and specific interactions with the surface. This perspective highlights recent understanding of this water structure at the solid–liquid interface. We discuss findings from three experimental techniques (attenuated total internal reflection infrared spectroscopy, second harmonic generation spectroscopy, and vibrationally-resonant sum-frequency generation spectroscopy) and two simulation approaches (molecular dynamics and Monte Carlo simulations). In each case, we also provide examples of how these techniques reveal the importance of interfacial water organization in rationalizing the structure of adsorbed biomolecules. [ABSTRACT FROM AUTHOR]

We present a comparison between sum frequency scattering (SFS) and reflection mode sum frequency generation (R-SFG). We have used scattering theory to describe both scattering experiments as well as reflection mode experiments. The interfacial vibrational spectrum of nanoscopic oil droplets dispersed in water was probed with SFS as well as with R-SFG. Spectra recorded in phase-matched R-SFG mode and spectra recorded with SFS from the same sample are different, which shows that different interfaces are measured. Scattering spectra at different scattering angles agree with nonlinear light scattering theory. We further present experiments with polymer films aimed at quantifying the comparative strength of R-SFG and SFS experiments.