C. Cruz-Vázquez

Electroconducting transparent film of amorphous copper sulfide on polyethylene substrate

The reaction between 1,4,8,11-tetraazacyclotetradecanecopper(II) perchlorate and sodium sulfide gave a transparent amorphous CuS film supported on a polyethylene substrate. The surface electrical resistivity of the film was ca. 10 k Ω□ at 300 K and showed a metal-like temperature dependence down to 250 K.

Tetrathiafulvalene (TTF), tetramethyltetraselenafulvalene (TMTSF), and BIS (ethylenedithio) tetrathiafulvalene (BEDT-TTF) salts of copper halides

Abstract The crystal conductivities of (TTF)2CuCl2 and (TTF)6CuBr4 exhibited metal-like temperature dependence above ca. 200 K. The X-ray analysis of the crystals suggested that the donor molecules form a uniform column without being coordinated to copper, and that the inorganic ions are disordered. The reaction of copper (II) halides with TMTSF and BEDT-TTF yielded (TMTSF)3/2CuCl2 (the powder conductivity was 9 × 10−2 S cm−1 at 300 K), (TMTSF)CuBr2 (7 × 10−4 S cm−1), (BEDT-TTF)2CuCl2 (3 × 10−3 S cm−1), and (BEDT-TTF)7/5CuBr2 (1.7 S cm−1). (TMTSF)CuBr2 was an n-type semiconductor, and others were p-type semiconductors. Magnetic studies showed that the materials can be formulated as (D)n+·CuIX2.

Thermally and optically stimulated luminescence of new ZnO nanophosphors exposed to beta particle irradiation

In this work, we report on the thermoluminescence (TL) and the optically stimulated luminescence (OSL) of ZnO nanophosphors obtained by thermal annealing of ZnS powders synthesized by precipitation in a chemical bath deposition reaction. To obtain nanocrystalline ZnO, ZnS pellet-shaped samples were subjected to a sintering process at 700 °C during 24 h exposed to air at atmospheric pressure. Some samples were exposed to beta particles in the 0.15–10.15 kGy dose range and the integrated TL as a function of dose increased with dose level, with no saturation indication for the tested dose levels. Computerized glow-curve deconvolution of the experimental glow curves in individual peaks revealed a second-order kinetics. In order to test the OSL response, samples were irradiated with beta particles with doses up to 600 Gy, and an increasing intensity as dose increased was observed. We conclude that the new ZnO phosphors under investigation are good candidates to be used as dosimetric materials.

Biocompatibility of crystalline opal nanoparticles

BackgroundSilica nanoparticles are being developed as a host of biomedical and biotechnological applications. For this reason, there are more studies about biocompatibility of silica with amorphous and crystalline structure. Except hydrated silica (opal), despite is presents directly and indirectly in humans. Two sizes of crystalline opal nanoparticles were investigated in this work under criteria of toxicology.MethodsIn particular, cytotoxic and genotoxic effects caused by opal nanoparticles (80 and 120 nm) were evaluated in cultured mouse cells via a set of bioassays, methylthiazolyldiphenyl-tetrazolium-bromide (MTT) and 5-bromo-2′-deoxyuridine (BrdU).Results3T3-NIH cells were incubated for 24 and 72 h in contact with nanocrystalline opal particles, not presented significant statistically difference in the results of cytotoxicity. Genotoxicity tests of crystalline opal nanoparticles were performed by the BrdU assay on the same cultured cells for 24 h incubation. The reduction of BrdU-incorporated cells indicates that nanocrystalline opal exposure did not caused unrepairable damage DNA.ConclusionsThere is no relationship between that particles size and MTT reduction, as well as BrdU incorporation, such that the opal particles did not induce cytotoxic effect and genotoxicity in cultured mouse cells.

Thermally stimulated luminescence of Mg-doped ZnO Nanophosphors

Nanosized ZnO:Mg phosphors were synthesized through a controlled chemical reaction. X-ray diffraction patterns confirmed that Mg entered in a substitutive way in Zn sites. To investigate their thermoluminescence (TL) properties, some samples were exposed to beta-particle irradiation. The results reported here show that Mg doping improves ZnO TL features that are important for TL dosimetry applications, such as the shape of the glow curve, the temperature at which the maximum TL intensity is observed, and the TL fading and reproducibility. No saturation clues of the TL response as a function of the dose is observed for doses below 1600 Gy.

Electrical and spectroscopic properties of amorphous copper sulfide films treated with iodine, lithium iodide and sodium iodide

Chemical modification of amorphous CuS films supported on polyethylene substrate was performed by treatment with I 2 , LiI and Nal in organic solvents. The electrical conductivities of the resulting films exhibited a metal-like temperature dependence down to = 120 K, while the untreated films had a resistance minimum at = 250 K. The X-ray photoelectron spectra showed that the copper atoms were in the Cu(I) state in all of the materials studied. Upon treatment with I 2 , a major part of CuS was converted to Cul, and the co-existence of two chemical species enhanced electrical conduction. In films treated with LiI in acetone, the alkali metal ion was involved in a quasi-stoichiometric manner, The amorphous CuS was chemically active and its chemical modifications gave new materials.

Reaction of tetramethyltetraselenafulvalene (TMTSF) with copper (II) halides and the electrical properties of the products

Abstract The semiconductive compounds [( TMTSF ) 3 2 ] + ·Cu I Cl 2 (room-temperature powder conductivity δRT =9 × 10−2 S cm−1 and activation energy E = 0.07 eV and (TMTSF)+·CuIBr2 (ifδRT = 7× 104 S cm−1 and E = 0.18 eV) were obtained by redox reactions between TMTSF and copper (II) halides. These compounds were characterized with the aid of infrared, electron spin resonance of X-ray photoelectron spectroscopies, and thermoelectric power and magnetic susceptibility measurements. In contrast with common TMTSF and TTF conductors, (TMTSF)CuBr2 had a large negative thermoelectric power. This property can be explained on the basis of the excess electrons produced on TMTSF by the transfer of electrons from CuI to TMTSF+.

Thermoluminescence of novel zinc oxide nanophosphors obtained by glycine-based solution combustion synthesis

High-dose thermoluminescence dosimetry properties of novel zinc oxide nanophosphors synthesized by a solution combustion method in a glycine-nitrate process are presented for the very first time in this work. Sintered particles with sizes ranging between ∼500 nm and ∼2 µm were obtained by annealing the synthesized ZnO at 900°C during 2 h in air. X-ray diffraction patterns indicate the presence of the ZnO hexagonal phase, without any remaining nitrate peaks observed. Thermoluminescence glow curves of ZnO obtained after being exposed to beta radiation consists of two maxima: one located at ∼149°C and another at ∼308°C, the latter being the dosimetric component of the curve. The integrated TL fading displays an asymptotic behavior for times longer than 16 h between irradiation and the corresponding TL readout, as well as a linear behaviour of the dose response without saturation in the studied dose interval (from 12.5 up to 400 Gy). Such features place synthesized ZnO as a promising material for high-dose radiation dosimetry applications.

Thermoluminescence of Tequila-based nanodiamond

Nanodiamond thin films were deposited onto Si (100) substrates using Tequila as precursor by pulsed-liquid injection chemical vapour deposition at 850 degrees C. Some samples were exposed to beta particle irradiation in the dose range from 100 to 1600 Gy, and it was found that the thermoluminescence (TL) response is a linear function of dose. The glow curve displays two maxima centred at 170 and 350 degrees C, which does not shift when dose changes, indicating that first-order kinetics processes are involved. From the results, it is concluded that the new nanodiamond films are promising high-dose TL dosimeters.

New electroconducting transparent films: Amorphous copper sulfide and its iodine-doped derivative

Abstract A reaction between [Cu(cyclam)] 2+ (cyclam: 1,4,8,11-tetraazacyclotetradecane) and sodium sulfide gave a polyethylene-supported CuS film, which was transparent and exhibited metal-like electrical conductivity down to 250 K. An electrode fabricated with this film showed Nerstian behavior versus a Ag/AgCl electrode, for Cu 2+ solutions in the concentration range C Cu = 5·10 −5 −10 −2 M. The CuS film was doped with iodine, the temperature range of its metal-like charge-transport behavior was extended down to 140 K. The X-ray photoelectron spectra showed that CuS coexisted with CuI which was formed upon doping. These results suggest that the CuS film can be used in the fabrication of electrical and electronic devices and that the physical properties of the film can be controlled by doping.