Characterization of Tetrol I-1 and (±)-anti-BPDE-DNA Adducts with Solid-Matrix Fluorescence Quenching

The solid-matrix fluorescence (SMF) quenching of (±)-anti-benzo[a]pyrene-trans-7,8-dihydrodiol-9,10-epoxide (BPDE)-DNA adducts and a hydrolysis product of the DNA adducts, tetrol I-1, were investigated by using thallium nitrate and sodium iodide to quench the SMF. Several fluorescence quenching models were evaluated for both (±)-anti-BPDE-DNA adducts and tetrol I-1. The SMF quenching phenomena were quite different with the two salts for the (±)-anti-BPDE-DNA adducts and tetrol I-1. Generally, with thallium nitrate as a quencher, a two-site model with two independent quenching sites was applicable to both the (±)-anti-BPDE-DNA adducts and tetrol I-1 data. However, with sodium iodide, the SMF quenching data for tetrol I-1 were fit to the sphere of action model, but the (±)-anti-BPDE-DNA adducts SMF quenching data were qualitatively related to a BET isotherm. From the SMF quenching data, unique information was acquired for the quasi-intercalated BPDE-DNA adducts and the external form of the BPDE-DNA adducts. In addition, insights were obtained on how the adsorbed salts interacted with the solid matrix and with the (±)-anti-BPDE-DNA adducts and tetrol I-1.

OPTICAL AND ELECTRICAL PROPERTIES OF THALLIUM SULPHIDE AND TlxMySz (M=Cu,Bi,Sb) thin films

Tl2S thin films (0.05μm-1μm) were deposited from chemical bath containing thallium nitrate and thiourea. These films possess an indirect optical band gap of about 1 eV. Multi-layer films: Tl2S-CuS , Tl2S-Bi2S3 and Tl2S-Sb2S3 films were prepared, which when annealed at 300°C led to the formation of CuTlS2 (tetragonal, E g.dir = 1.25 eV), Bi2Tl4S5 (orthorhombic, E g.dir = 2.05 eV), TlSbS2 (triclinic, E g.dir = 1.92 eV), as confirmed by XRD. Optical band gap of 1.4 eV - 2 eV suggests possible application as absorber materials in solar cell.