Thermal and plasma enhanced atomic layer deposition of ultrathin TiO2 on silicon from amide and alkoxide precursors: growth chemistry and photoelectrochemical performance.

Due to its low cost and suitable band gap, silicon has been studied as a photoanode material for some time. However, as a result of poor stability during the oxygen evolution reaction (OER), Si still remains unsuitable for any extended use. Ultra-thin titanium dioxide (TiO2) films have been used as protective coatings and are shown to enhance Si photoanode lifetime with added solar to hydrogen (STH) performance improvements through distancing the oxidation reaction away from the Si photoanode surface and improved charge transport through the anode. This study details the nucleation, growth chemistry, and performance of TiO2 thin films prepared via thermal and plasma enhanced atomic layer deposition (ALD) using both titanium isopropoxide (TTIP) and Tetrakis(dimethylamido)titanium (TDMAT) as the precursor material. The effect of post ALD treatments of plasma and air annealing was also studied. Films were investigated using photoelectrochemical cell testing to evaluate photoelectrochemical performance, and in-vacuum cycle-by-cycle x-ray photoelectron spectroscopy (XPS) was used as the primary characterisation technique to study nucleation mechanisms and film properties contributing to improvements in cell performance. TiO2 grown by plasma enhanced ALD results in cleaner films with reduced carbon incorporation. However, despite increased carbon incorporation, thermally grown films showed improved photocurrent as a result of oxygen vacancies in these films. Post deposition annealing in a H2 ambient is shown to further improve photocurrent in all cases, while annealing in atmosphere leads to uniform film chemistry and enhanced photocurrent stability in all cases.

Isotopic carbon turnover in pig hoof and rib

The objective of this study was to evaluate the behavior of carbon incorporation and turnover in hoof and ribs of pigs at different periods of development in the search for tissues that reflect longer the former diet. We used 132 commercial hybrids (barrows and females), weaned at an average age of 21 days, distributed in a completely randomized design with four treatments on different days of substitution of corn (C4 cycle plant grain) diets with broken rice (C3 cycle plant grain) at 21, 42, 63 and 110 days of age to change the carbon-13 isotope signal. By means of isotopic dilution curves, we observed that animals whose C4 diet was replaced with C3 diet at 21, 42, 63 and 110 days of age, for hoof and rib, reached a new level of isotope equilibrium. Bone samples are better choices to reflect the former diet, due to conservation of the isotopic signal for longer.

Sonochemically synthetized ZnO-Graphene nanohybrids and its characterization

The paper presents the morphological, structural and compositional properties of the sonochemically prepared ZnO-1.4wt% Graphene (Z-G) nanocomposites as a function of pH value of suspension varying from 8.5 to 14 and thermal annealing at 450°C in nitrogen or air ambient. The SEM analysis of the Z-G hybrids dried at 150°C in air has shown a nano-flower like nanostructure for a pH value of 14. The XRD analysis of dried Z-G hybrids revealed a crystallite size increase from 3.5 nm to 18.4 nm with pH increase, and this result was explained in terms of colloids zeta potential evolution with pH value. The Raman and EDS spectroscopy have shown a split of the G band (1575 cm−1) of graphene into two bands (1575 cm−1 and 1605 cm−1), an increased height of D (1323 cm−1) band, and an additional amount of carbon due to CO2 absorption from the air, respectively. The carbon incorporation increased with the decrease of pH, and was associated with a hydrozincite phase, Zn5(CO3)2(OH)6. The formation of dried Z-G nanocomposite was clearly demonstrated only at a pH value equal to 14, where two ZnO Raman active bands at 314.9 cm−1 and 428.2 cm−1 appeared. This result may indicate the sensitivity of the Raman spectroscopy to the nanoflower-like nanostructure of dried Z-G hybrids prepared at pH=14. The thermal treatment of Z-G hybrids in N2at 450°C has increased the number of ZnO Raman bands as a function of pH value, it has decreased the amount of additional carbon by conversion of hydrozincite to ZnO and preserved the graphene profile. The thermal treatment in air at 450°C has increased the crystalline symmetry and stoichiometry of the ZnO as revealed by high and narrow Raman band from 99 cm−1 specific to Zn optical phonons, but it has severely affected the graphene profile in the Z-G hybrid, due to combustion of graphene in oxygen from the ambient.