Conformational equilibria of curcumin, a potential therapeutic agent, can be modulated by changing pH, temperature and solvent composition.

Dye-sensitized quantum dots (QDs) are promising candidates for dye-sensitized solar cells (DSSCs). Here, we report steady state (absorption and photoluminescence) optical measurements on several sizes of CdS QDs ligated with Coumarin 343 dye (C-343) and two different solvents, viz., chloroform and toluene. We further report detailed first principles density functional theory and time-dependent density functional theory studies of the geometric, electronic and optical (absorption and emission) properties of three different sized capped QDs, ligated with C-343 dye. The absorption spectrum shows a QD-size-independent peak, and another peak which shifts to blue with decrease in QD size. The first peak is found to arise from the dye molecule and the second one from the QD. Charge transfer using natural transition orbitals (NTOs) is found to occur from dye-to-QDs and is solvent-dependent. In the emission spectra, the luminescence intensity of the dye is quenched by the addition of the QD indicating a strong interaction between the QD and the dye.

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Photovoltaic (PV) materials with high efficiencies are currently the lead-based perovskites. However, nontoxic, stable, lead-free perovskites are of immense interest as environment-friendly green materials. Hence, using first-principles density functional theory (DFT), we investigate ligated CsSnX3 (X = Cl, Br, I)-derived quantum dots (QDs), to assess their suitability for PV cells. The well-known band gap increase due to quantum confinement effects is observed, with the excitonic energies quite close and exhibiting the same size dependence in all three types of QDs. The choice of ligands has no appreciable effect in altering the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap. Time-dependent DFT simulations show that all the QDs have good absorption in the useful UV–vis region of the spectrum, and the peaks are both size and halide dependent. Natural transition orbital analysis shows that interestingly, in most cases the charge transfer on optical excitation occurs from the halide p orbital to the Sn p orbital. The charge distribution assumes several interesting patterns, which may aid in charge collection. Larger QDs allow for greater charge separation and lower recombination rates, increasing the PV efficiency. Our work shows that good electronic and optical absorption properties, with appropriate band gaps and wide tunability, make H+ ligated CsSnX3-derived QDs (and in particular, CsSnI3-derived QDs) promising candidates for PV applications.

BackgroundAtorvastatin calcium (ATC), an anti-lipid biopharmaceutical class II drug, is widely prescribed as a cholesterol-lowering agent and is presently the world’s best-selling medicine. A large number of crystalline forms of ATC have been published in patents. A variety of solid forms may give rise to different physical properties. Therefore, the discovery of new forms of this unusual molecule, ATC, may still provide an opportunity for further improvement of advantageous properties.ResultsIn the present work, eight new solvates (Solvate I-VIII) have been discovered by recrystallization method. Thermal behaviour of ATC and its solvates studied by DSC and TGA indicate similar pattern suggesting similar mode of entrapment of solvent molecules. The type of solvent present in the crystal lattice of the solvates is identified by GC-MS analysis and the stoichiometric ratio of the solvents is confirmed by 1HNMR. The high positive value of binding energy determined from thermochemical parameters indicates deep inclusion of the solvent molecules into the host cavity. The XRPD patterns point towards the differences in their crystallanity, however, after desolvation solvate II, III, IV, V and VIII transform to isostructral amorphous desolvated solvates. The order of crystallinity was confirmed by solution calorimetric technique as the enthalpy of solution is an indirect measure of lattice energy. All the solvates behaved endothermically following the order solvate-VIII (1-butanol solvate) < solvate-I (isoproplyate) < solvate-V (methanol solvate) < solvate-III (ethonalate) < solvate-VI (acetone ethanol solvate) < solvate-IV (t-butanol solvate) < solvate-II (THF solvate) < solvate-VII (mixed hemi-ethanol hydrate). The positive value of the heat capacity of the solvate formation provides information about the state of solvent molecules in the host lattice. The solvents molecules incorporated in the crystal lattice induced local chemical environment changes in the drug molecules which are observed in 13CP/MAS NMR spectral changes.ConclusionsAqueous solubility of solvate-VIII was found to be maximum, however, solvate-I and VIII showed better reduction in total cholesterol and triglyceride levels as compared to atorvastatin against triton-induced dyslipidemia.

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In this paper we study some types of  η-Ricci solitons on Lorentzianpara-Sasakian manifolds and we give an example of  η-Ricci solitons on 3-dimensional Lorentzian para-Sasakian manifold. We obtain the conditions of  η-Ricci soliton on ϕ-conformally flat, ϕ-conharmonically flat and ϕ-projectivelyflat Lorentzian para-Sasakian manifolds, the existence of η-Ricci solitons implies that (M,g) is  η-Einstein manifold. In these cases there is no Ricci solitonon M with the potential vector field