NH4I has been proven to be a promising cosolvent for cuprous iodide (CuI) single crystal growth from aqueous solutions by the temperature reduction method. In our work, as compared with NH4Cl and NH4Br, NH4I offers more advantages for single crystal growth, such as by remarkably increasing the solubility and growth rate of CuI crystals, effectively reducing the impurity concentration, and enhancing the crystal quality and crystallinity. A regular, centimeter-sized, high optical quality single crystal was successfully obtained using NH4I as a cosolvent. The electronic and optical properties of the as-grown crystal were characterized by Hall-effect measurements and optical transmission and photoluminescence spectra, respectively. The results demonstrated that the CuI crystal is conductive (high p-type mobility of 12.81 cm2 V−1 s−1) and transparent (great transmittance over 80%).

High quality γ-CuI single crystals have been grown using a mild temperature difference method with ammonium halide (NH4X, X = Cl, Br, I) as the co-solvents. The growth habit and optical properties of the crystals obtained using different co-solvents were systematically examined. By changing the type of co-solvent, the crystallites obtained display octahedron or tetrahedron morphology. All the as-grown crystals are of high transmittance (over 70%). Simultaneously, the crystals exhibit a sharp band-edge emission at around 411 nm, indicating that the interband excitonic transition emission occupies a dominant position in the spectrum and the intensity of defect emission is dramatically depressed. The possible mechanisms of how the co-solvent influences the growth habit and luminescence properties of the γ-CuI crystals are discussed. In particular, our results provide valuable clues to improve the luminescence performance of γ-CuI crystals.

The dye of 2, 7-dimethyl-3, 6-diazacyclohepta-1, 6-diene perchlorate (dye 1) and chlorination of 2, 7-dimethyl-3, 6-diazacyclohepta-1, 6-diene perchlorate (dye 2) were prepared and characterized. The dye 2 molecules were introduced into the polyvinyl alcohol (PVA) films to produce solid ultraviolet (UV) filters. UV spectroscopy measurements were carried out to investigate the optical properties of UV filters. The UV filter exhibited high transmittance within solar blind spectral region (240–280 nm) and a strong absorption band occurred between 300 and 375 nm. The detection experiment results of corona discharge show that the UV filter can be used for solar blind detection.

A new crystal material for UV light band-pass filter, ACNSH (ammonium cobalt nickel sulfate hexahydrate) was composed and its crystal structure was studied by X-ray diffraction method. The empirical composition of the title compound is (NH4)2Co0.17Ni0.83(SO4)2 · 6H2O with formula weight 395.15. ACNSH structure belongs to monoclinic space group P2(1)/c, crystal parameters a = 6.2432(3) Å, b = 12.4728(5) Å, c = 9.1967(4) Å, α = γ = 90°, β = 106.9880(10)°, V = 684.90(5) Å3, Z = 2, and Dc = 1.916 g/cm3. Solubility of ACNSH in water was determined and large, dark-green crystals with sizes up to 18 × 19 × 45 mm3 have been grown by cooling solution method. Optical transmission spectra reveals that ACNSH has low band at 450–600 nm. Thermo-gravimetric analysis showed that the dehydration temperature of ACNSH is about 97 °C. The relationship between the structural constituents and optical transmission properties is discussed.

We have designed and grown a large single crystal of Rb2Ni (SO4)2 · 6H2O (RNSH) using traditional temperature reduction method. This single crystal structure was determined using X-ray single crystal diffraction method. The optical transmission spectrum demonstrates the characteristics of ultraviolet filters. RNSH crystal exhibits high thermal stability with dehydration temperature above 100 °C. The growth behaviors and dislocation etching characteristics were detected under atomic force microscopy (AFM).

•Temperature reduction method was developed to grow large CuCl and CuBr crystals.•Transparent, tetrahedral single crystals larger than 6 mm on an edge were obtained.•Structure, stability, composition and optoelectronic properties were characterized.•This study provided useful clues for growing large size water-insoluble crystals.Large transparent tetrahedral CuX (X=Cl, Br) single crystals with over 6 mm on an edge were grown by the temperature reduction method at the range of 40–50 °C. Aqueous HX (X=Cl, Br) were used as solvents. Solubility curves of CuX in 3 mol L−1 HX acid solutions were measured by indirect weight analysis. The crystals were further characterized by X-ray powder diffraction (XRD) measurement, thermal analysis (DTA/TG), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflection spectrum (UVDRS). The results indicate that CuX single crystals have cubic structures with a nearly standard ratio of Cu/X and wide direct band gaps (EgCuCl=3.21 eV, EgCuBr=2.95 eV).