No abstract

TiO 2 thin films were synthesized using Low Pressure Chemical Vapour Deposition (LPCVD) onto glass substrates. Titanium isopropoxide (TTIP) and N 2 gas were used as the precursor and carrier gas respectively. The effects of reaction temperature, carrier gas flow rate and deposited area were studied. SEM, TEM, powder XRD and UV-Vis and Raman spectroscopy were employed to characterize the phase and morphology of the synthesized materials. The results show that a dual phase (sodium-doped TiO 2 (B) and anatase) nanocrystalline thin film was successfully prepared by LPCVD with needle-and polygonal plate-shape crystallites respectively. At the interface with the substrate, the thin film deposit exhibited a preferr ed orientation of TiO 2 (B) needles in the [001] direction of average crystallite size 50-80 nm in length and 5-10 nm in width, whilst the crystallite size of anatase polygonal-plates was around 200 nm. The optimal LPCVD condition for preparing this mixed ph ase of TiO 2 was 550 o C (actual temperature) with a 1 mL/s N 2 flow rate. A possible mechanism for the mixed-phase formation by LPCVD on the glass substrates is described as well as the implications for the production of selfcleaning structures.

We present a universal synthesis method for mixed phase TiO2(B)/anatase thin films on any substrate.

An anion-controlled synthesis of a new three-dimensional (3D) “racemate”, an enantiomorphic twofold interpenetrated 3D zinc­(II) coordination polymer containing bridging glutarate (glu) and 4,4′-bipyridine (4,4′-bipy) ligands, {[Zn4(H2O)2(4,4′-bipy)4(glu)3]­(NO3)2} n , 1 (P21/c), with ligand substitution-induced single-crystal-to-single-crystal (SCSC) transformation and photocatalysis for dye degradation was studied. The influence of a counteranion in zinc­(II) starting materials and synthetic techniques upon the phase formation were explored. The complex 1 was successfully synthesized from zinc­(II) nitrate salt via microwave-assisted techniques as well as the conventional hydrothermal technique, whereas the employment of zinc­(II) acetate or sulfate salt yielded a two-dimensional coordination polymer, [Zn­(4,4′-bipy)­(glu)] n , 2 (P1̅), and the use of zinc­(II) chloride led to a one-dimensional (1D) zigzag chain, [Zn­(4,4′-bipy)­Cl2] n 3 (C2/c). The synthetic-method-dependent formation was illustrated as the microwave-assisted techniques and conventional hydrothermal technique enabled the formation of crystalline-phase pure 1, while the sonochemical synthesis provided mixed crystalline-phases of 1 and 2. In the structure of 1, the 4,4′-bipy ligand links dinuclear Zn­(II) building units into 1D chains along the [1̅01] direction. The glu2– ligand acts as tethering linkers expanding the structure into a cationic 3D coordination polymer that interpenetrates with its enantiomer to give a 3D solid-state “racemate”. Powder X-ray diffraction revealed that the ligand substitution-induced SCSC transformation of the twofold interpenetrated 3D framework, 1 (P21/c), which was triggered by chloride, led to a 1D zigzag chain, 3 (C2/c), whereas the bromide-triggered reaction led to a mixed crystalline phase between the isostructural 1D zigzag chain, [Zn­(4,4′-bipy)­Br2] n , 4 (C2/c), and its polymorph, [Zn­(4,4′-bipy)­Br2] n , 5 (P212121). The photocatalysis for the methyl orange degradation of 1 was studied.