Investigation of the thermal stability of the antihypertensive drug nebivolol under different conditions: Experimental and computational analysis

Journal of Thermal Analysis and Calorimetry - The thermal decomposition of the third-generation beta-blocker nebivolol (NEB) was investigated using thermogravimetric analysis (TG) under isothermal...     

Photochemical studies: Chromones,bischromones and anthraquinone derivatives

Photochemical reaction is a chemical reaction initiated by the absorption of energy in the form of light resulting in different types of reaction. Chromones, bischromones and anthraquinones are the bichromophoric molecules which contain the carbonyl group and double bond in conjugation. Photochemical reactions of these compounds result in the formation of such molecules which are not obtained via conventional methods. This review article describes the photochemical transformations of chromones, bischromones and anthraquinone derivatives and here main emphasis has been laid upon the intramolecular photochemical H-abstraction reactions that provide many exotic heterocyclics as the final photoproducts.     

New metal free organic dyes incorporating heterocyclic Benzofuran core as conjugated spacer: Synthesis,Opto-electrochemical,DFT and DSSC studies

Synthesis of a series of new organic photosensitizers, designated as BZ1 - BZ4 , was achieved by incorporating benzofuran core as π-spacer, triphenylamine (TPA) and 4-methoxy triphenylamine (4-MeO-TPA) as donors and cyanoacrylic acid (CAA) and rhodanine-3-acetic acid (RAA) as acceptor/anchoring groups. Structurally, dyes BZ1 and BZ2 carry TPA and 4-MeO-TPA as donors, respectively, whereas CAA constitutes as a common acceptor. On the other hand, BZ3 and BZ4 incorporate TPA and 4-MeO-TPA as donors, respectively, and RAA serves as a common acceptor. Key steps to access BZ1 - BZ4 involved Wittig olefination, reduction of cyano groups to aldehyde, and finally Knoevenagel condensation. In UV–visible spectra, dyes BZ1 - BZ4 exhibited intramolecular charge transfer (ICT) maxima in the range of 503 nm to 534 nm and their extinction coefficients varied from 22,600 to 40,400 M⁻¹ cm⁻¹. Using cyclic voltammetry and UV–visible data, we calculated the optical band gaps, (E₀₋₀) of BZ1-BZ4 to be 2.09, 2.00, 2.01, and 1.93 eV, respectively. DFT studies revealed that HOMOs of dyes were localized essentially on the donors triphenylamine groups, whereas the LUMOs are largely confined over electron acceptors CAA and RAA as well as partly diffused into the benzofuran spacer. DSSCs, configured using BZ1 - BZ4 as photosensitizers, showed fill factors (ff) in the range of 0.57 to 0.76, comparable to standard N3 dye (0.67). In addition, BZ1 and BZ2 dyes with CAA as an acceptor also exhibited decent open circuit voltage (V_oc) in the range of 0.61 to 0.63 relative to the 0.66 observed for N3 dye. Dyes BZ1-BZ2 carrying CAA as an acceptor exhibited an efficiency (η) of 2.03% and 1.49%, respectively, against the benchmark N3 dye, showing η of 5.02%. Due to poor V_oc and short circuit current density (I_sc), dyes BZ3-BZ4 carrying RAA as acceptor/anchoring group performed significantly poor, showing η of 0.08%, and 0.32%, respectively.     

Design of a portable luminescence bio-tool for on-site analysis of heavy metals in water samples

ABSTRACT

In this work, we report an innovative tool for heavy metal screening in water samples. This new chemiluminescent set-up screens the light generated from luminol oxidation by horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H₂O₂). The pollutant concentrations in real water samples were calculated by studying the effect of metal ions on chemiluminescence signal. Owing to its simplicity, portability and low cost, this approach presents a real alternative to classical optical methods. It is constructed with simple materials: a black box containing a cuvette and a micro-camera. When the enzymatic reaction takes place, the luminescence is captured by the camera placed in upright position. The image can be saved automatically in a computer for further analysis using a MATLAB interface. The RGB diagram is then established to determine the analyte concentrations in the tested samples. This method was successfully applied for the determination of mercury (Hg), lead (Pb) and cadmium (Cd) in lake and field water samples. In these experiments, three concentrations of each analytes were tested (5, 25 and 50 µg/L). We noted a good proportionality between the analyte concentration and the chemiluminescent detection intensity. Detection of binary and tertiary combinations of heavy metals has been also investigated. The developed biosensor showed low detection limits for the tested heavy metals: 1, 0.7 and 0.02 for Hg²⁺, Pb²⁺ and Cd²⁺, respectively. Finally, excellent recoveries ranging from 98% to 104% were obtained for the HRP-inhibition assay.     

An unusual conformational similarity of two peptide folds featuring sulfonamide and carboxamide on the backbone

Two folded peptides featuring carboxamide and sulfonamide at the core of the peptide fold have been shown to possess almost similar conformational features, despite the well-known fact that carboxamides and sulfonamides have strikingly different hydrogen-bonding and geometrical preferences.     

PbS quantum dot sensitized anatase TiO2 nanocorals for quantum dot-sensitized solar cell applications

Lead sulphide (PbS) quantum dot (QD) sensitized anatase TiO(2) nanocorals (TNC) were synthesized by SILAR and hydrothermal techniques. The TNC, PbS and PbS-TNC samples were characterized by optical absorption, XRD, FT-IR, FESEM and XPS. The results show that PbS QDs are coated on the TNCs, the optical absorption is found to be enhanced and the band edge is shifted to ~693 nm as compared with plain TNCs at 340 nm. The PbS-TNC sample exhibits an improved photoelectrochemical performance with a maximum short circuit current (J(sc)) of 3.84 mA cm(-2). The photocurrent density was found to be enhanced 2 fold, as compared with those of the bare PbS photoelectrode. The total power conversion efficiency of the PbS-TNC electrodes is 1.23%.     

A novel fluoride selective optical chemosensor based on internal charge transfer signaling

A new internal charge transfer probe, NAPH-1, synthesized by incorporating photoemitive naphthalimide core with an acidic imidazolium ring, offers highly selective colorimetric and ratiometric ‘off-on’ signaling for targeting F⁻, while Cl⁻, Br⁻, I⁻, , SCN⁻, AcO⁻, and do not appreciably perturb the photophysical properties of the probe even at relatively higher concentrations than the F⁻. Deprotonation of the imidazolium ring, supported by the ¹H NMR and theoritical studies, seems to cause the spectral modulations.