Study of zinc thiocarbamide chloride,a single-source precursor for zinc sulfide thin films by spray pyrolysis

Thermal decomposition of the title compound, Zn(tu)₂Cl₂ (tu=thiourea), was studied up to 1200°C in dynamic inert (N₂) and oxidative (air) atmospheres using simultaneous TG/DTA techniques. In addition, XRD and IR were employed ex situ to resolve the reaction mechanism and products. Cubic ZnS (sphalerite) is formed below 300°C in both atmospheres and is observed until 760°C, whereafter it transforms in nitrogen to the hexagonal ZnS (wurtzite). EGA by FTIR revealed the complexity of the decomposition reactions involving also the evolution of H₂NCN, which reacts to form hexagonal ZnCN₂ as revealed by an XRD analysis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal decomposition study of HAuCl4·3H2O and AgNO3 as precursors for plasmonic metal nanoparticles

Thermal decomposition of HAuCl₄·3H₂O and AgNO₃, as precursors for Au and Ag nanoparticles, respectively, was monitored by coupled TG–DTA with TG/EGA–FTIR and EGA–MS techniques in a flowing 80 %Ar + 20 %O₂ and Ar atmospheres in the temperature range of 30–600 °C. The intermediate and final products of thermal decomposition were analysed by ex situ XRD and FTIR techniques. The thermal degradation of HAuCl₄·3H₂O starts immediately after melting at 75 °C and takes place in three steps in the temperature range of 75–320 °C with total mass loss of 49.4 and 49.7 % in artificial air and Ar atmospheres, respectively. EGA by MS and FTIR revealed a simultaneous release of H₂O and HCl in the temperature range of 75–235 °C. EGA by MS revealed a release of Cl₂ at around 225 °C and in the interval of 250–320 °C. According to the XRD analysis, the main solid product in the end of the first decomposition step at 190 °C is AuCl₃; in the end of the second decomposition step at 240 °C is AuCl and the final product at 320 °C is Au. The thermal decomposition of AgNO₃ takes place in a single step in the temperature range of 360–515 °C with a total mass loss of 39.0 and 37.8 % in flowing artificial air and Ar atmospheres, respectively. According to EGA–MS and EGA–FTIR the main evolved gases are NO₂, NO and O₂. The final product of the thermal decomposition at 600 °C is Ag irrespective of the atmosphere.     

Thermoanalytical study of precursors for In<Subscript>2</Subscript>S<Subscript>3</Subscript> thin films deposited by spray pyrolysis

Thermal decomposition of precursors for In₂S₃ thin films obtained by drying aqueous solutions of InCl₃ and SC(NH₂)₂ at the In:S molar ratios of 1:3 (1) and 1:6 (2) was monitored by simultaneous TG/DTA/EGA-FTIR measurements in the dynamic 80%Ar + 20%O₂ atmosphere. XRD and FTIR were used to identify the dried precursors and products of the thermal decomposition. The precursors 1 and 2 are complex compounds, while in 2 free SC(NH₂)₂ is also present. The thermal degradation of 1 and 2 in the temperature range of 30–900 °C consists of four mass loss steps, the total mass loss being 89.1 and 78.5%, respectively. According to XRD, In₂S₃ is formed below 300 °C, crystalline In_2.24(NCN)₃ is detected only in 1 above 520 °C and In₂O₃ is the final decomposition product at 900 °C. The gaseous species evolved include CS₂, NH₃, H₂NCN, HNCS, which upon oxidation yield also COS, SO₂, HCN and CO₂.     

Thermal behaviour of precursors for CuInS2 thin films deposited by spray pyrolysis

The thermal decomposition of precursors for copper indium disulphide (CuInS₂) thin films obtained by drying aqueous solutions of copper chloride (CuCl₂), indium chloride (InCl₃) and thiourea (SC(NH₂)₂) at the Cu:In:S molar ratios of 1:1:3 (1) and 1:1:6 (2) was monitored by simultaneous thermogravimetry /differential thermal analysis/ evolved gas analysis-mass spectrometry (TG/DTA/EGA-MS) measurements in a dynamic 80 %Ar + 20 %O₂ atmosphere. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to characterise the dried precursors and products of the thermal decomposition. The precursors 1 and 2 are mixtures of copper and indium chloride thiourea complex compounds, whilst 1 can also contain unreacted InCl₃. The thermal degradation of 1 and 2 in the temperature range of 30–800 °C consists of six steps with a total mass loss of 71.5 and 89.8 %, respectively. According to XRD, CuInS₂ is formed below 300 °C. Decomposition of 1 and 2 is completed at 620 and 600 °C, respectively. The final decomposition product of 1 at 800 °C consists of a mixture of In₂O₃ and CuO phases, whilst 2 consists of In₂O₃, CuO and Cu₂In₂O₅ phases. EGA by MS revealed the release of CS₂, NH₃, H₂NCN and HNCS, which upon their oxidation also yield COS, SO₂, HCN and CO₂.     

Novel nonsecosteroidal vitamin D mimics exert VDR-modulating activities with less calcium mobilization than 1,25-dihydroxyvitamin D3.

BACKGROUND: The secosteroid 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) acts through the vitamin D receptor (VDR) to elicit many activities that make it a promising drug candidate for the treatment of a number of diseases, including cancer and psoriasis. Clinical use of 1,25(OH)2D3 has been limited by hypercalcemia elicited by pharmacologically effective doses. We hypothesized that structurally distinct, nonsecosteroidal mimics of 1,25(OH)2D3 might have different activity profiles from vitamin D analogs, and set out to discover such compounds by screening small-molecule libraries. RESULTS: A bis-phenyl derivative was found to activate VDR in a transactivation screening assay. Additional related compounds were synthesized that mimicked various activities of 1,25(OH)2D3, including growth inhibition of cancer cells and keratinocytes, as well as induction of leukemic cell differentiation. In contrast to 1, 25(OH)2D3, these synthetic compounds did not demonstrate appreciable binding to serum vitamin D binding protein, a property that is correlated with fewer calcium effects in vivo. Two mimics tested in mice showed greater induction of a VDR target gene with less elevation of serum calcium than 1,25(OH)2D3. CONCLUSIONS: These novel VDR modulators may have potential as therapeutics for cancer, leukemia and psoriasis with less calcium mobilization side effects than are associated with secosteroidal 1,25(OH)2D3 analogs.     

CuInS2 solar cell absorber plasmonically modified by gold nanoparticles

Thin CuInS₂ light-absorbing layer prospective for the solar cell applications is modified by gold nanoparticles. Theoretical and experimental possibilities of placement nanoparticles over or under the CuInS₂ coating were tested. It was revealed that placement of nanoparticles under the CuInS₂ layer is better in terms of spray pyrolysis technique. It results in more effective plasmon-enhanced light absorption in the CuInS₂ layer at the visible/near infrared 650–700 nm spectral range.