Effect of heat treatment on the structure and morphology of ZnO nanorod array and its composite with titania precursor

ABSTRACT

Effects of the elevated temperature on the structure evolution of the ZnO nanorod array (ZNA) and their hybrid nanocomposite with layered (tetramethyl)ammonium titanate (LTMAT) prepared by the liquid phase deposition were investigated. The vertically oriented ZnO nanorods were deposited on a quartz plate by a chemical bath deposition method and then they were penetrated by the LTMAT using the dip-coating method from the water solution. As a result of such an experimental procedure, an assembly composed of the ZNA with LTMAT was obtained and called hybrid nanocomposite. Since the LTMAT converts to TiO₂ upon subsequent sintering at 350 °C, it can be regarded as TiO₂ precursor for the thermal treatment experiments. The experiments with ZNA and their hybrid nanocomposite at the elevated temperature revealed coalescence of the deposited ZnO nanorods and crystallization of zinc titanate with Zn₂TiO₄ stoichiometry.     

Shaping metal–organic framework (MOF) powder materials for CO2 capture applications—a thermogravimetric study

Journal of Thermal Analysis and Calorimetry - The paper presents the effect of the tabletting pressure and time on the chemical structure and crystallinity of the CuBTC and MIL-53(Al)...     

Switching the Switch: Ligand Induced Disulfide Formation in HDAC8

Human histone deacetylase 8 is a well-recognized target for T-cell lymphoma and particularly childhood neuroblastoma. PD-404,182 was shown to be a selective covalent inhibitor of HDAC8 that forms mixed disulfides with several cysteine residues and is also able to transform thiol groups to thiocyanates. Moreover, HDAC8 was shown to be regulated by a redox switch based on the reversible formation of a disulfide bond between cysteines Cys₁₀₂ and Cys₁₅₃. This study on the distinct effects of PD-404,182 on HDAC8 reveals that this compound induces the dose-dependent formation of intramolecular disulfide bridges. Therefore, the inhibition mechanism of HDAC8 by PD-404,182 involves both, covalent modification of thiols as well as ligand mediated disulfide formation. Moreover, this study provides a deep molecular insight into the regulation mechanism of HDAC8 involving several cysteines with graduated capability to form reversible disulfide bridges.     

Thermodynamic model and Raman spectra of MgO–P2O5 glasses

Journal of Thermal Analysis and Calorimetry - The structure of binary glasses xMgO·(1?x)P2O5 (x?=?0.30, 0.35, 0.40, 0.45, 0.50, and 0.55) was studied by thermodynamic model...     

Spatiotemporal Studies of the One-Dimensional Coordination Polymer [Fe(ebtz)2(C2H5CN)2](BF4)2: Tug of War between the Nitrile Reorientation Versus Crystal Lattice as a Tool for Tuning the Spin Crossover Properties**

Reaction of 1,2-di(tetrazol-2-yl)ethane (ebtz) with Fe(BF₄)₂⋅6 H₂O in different nitriles yields one-dimensional coordination polymers [Fe(ebtz)₂(RCN)₂](BF₄)₂⋅nRCN (n=2 for R=CH₃ ( 1 ) and n=0 for R=C₂H₅ ( 2 ) C₃H₇ ( 3 ), C₃H₅ ( 4 ), CH₂Cl ( 5 )) exhibiting spin crossover (SCO). SCO in 1 and 3 – 5 is complete and occurs above 160 K. In 2 , it is shifted to lower temperatures and is accompanied by wide hysteresis (T_1/2^↓=78 K, T_1/2^↑=123 K) and proceeds extremely slowly. Isothermal (80 K) time-resolved single-crystal X-ray diffraction studies revealed a complex nature for the HS→LS transition in 2 . An initial, slow stage is associated with shrinkage of polymeric chains and with reduction of volume at 77 % (in relation to the difference between cell volumes V_HS−V_LS) whereas only 16 % of iron(II) ions change spin state. In the second stage, an abrupt SCO occurs, associated with breathing of the crystal lattice along the direction of the Fe–nitrile bonds, while the nitriles reorient. HS→LS switching triggered by light (808 nm) reveals the coupling of spin state and nitrile orientation. The importance of this coupling was confirmed by studies of [Fe(ebtz)₂(C₂H₅CN/C₃H₇CN)₂](BF₄)₂ mixed crystals ( 2 a , 2 b ), showing a shift of T_1/2 to higher values and narrowing of the hysteresis loop concomitant with an increase of the fraction of butyronitrile. This increase reduces the capability of nitrile molecules to reorient. Density functional theory (DFT) studies of models of 1 – 5 suggest a particular possibility of 2 to adopt a low (140–145°) value of its Fe-N-C(propionitrile) angle.     

Electronic Transitions in Different Redox States of Trinuclear 5,6,11,12,17,18-Hexaazatrinaphthylene-Bridged Titanium Complexes: Spectroelectrochemistry and Quantum Chemistry

Multinuclear transition metal complexes bridged by ligands with extended π-electronic systems show a variety of complex electronic transitions and electron transfer reactions. While a systematic understanding of the photochemistry and electrochemistry has been attained for binuclear complexes, much less is known about trinuclear complexes such as hexaphenyl-5,6,11,12,17,18-hexaazatrinaphthylene-tristitanocene [(Cp₂Ti)₃HATN(Ph)₆]. The voltammogram of [(Cp₂Ti)₃HATN(Ph)₆] shows six oxidation and three reduction waves. Solution spectra of [(Cp₂Ti)₃HATN(Ph)₆] and of the electrochemically formed oxidation products show electronic transitions in the UV, visible and the NIR ranges. Density functional theory (DFT) and linear response time-dependent DFT show that the three formally titanium(II) centers transfer an electron to the HATN ligand in the ground state. The optically excited transitions occur exclusively between ligand-centered orbitals. The charged titanium centers only provide an electrostatic frame to the extended π-electronic system. Complete active self-consistent field (CASSCF) calculation on a structurally simplified model compound, which considers the multi-reference character imposed by the three titanium centers, can provide an interpretation of the experimentally observed temperature-dependent magnetic behavior of the different redox states of the title compound in full consistency with the interpretation of the electronic spectra.     

Prospects of Observing Ionic Coulomb Blockade in Artificial Ion Confinements

Nanofluidics encompasses a wide range of advanced approaches to study charge and mass transport at the nanoscale. Modern technologies allow us to develop and improve artificial nanofluidic platforms that confine ions in a way similar to single-ion channels in living cells. Therefore, nanofluidic platforms show great potential to act as a test field for theoretical models. This review aims to highlight ionic Coulomb blockade (ICB)—an effect that is proposed to be the key player of ion channel selectivity, which is based upon electrostatic exclusion limiting ion transport. Thus, in this perspective, we focus on the most promising approaches that have been reported on the subject. We consider ion confinements of various dimensionalities and highlight the most recent advancements in the field. Furthermore, we concentrate on the most critical obstacles associated with these studies and suggest possible solutions to advance the field further.     

Examining the possibilities of applying high pressure to preserve yoghurt supplemented with probiotic bacteria

Natural yoghurt was subject to pressures of 200 and 250 MPa/4 and 18°C/15 min, after which milk-activated inocula of Lactobacillus acidophilus and Bifidobacterium sp. were added. The yoghurts were stored for 4 weeks at refrigeration temperature. After preparation and each week of storage, the count of bacteria, acidity, antibacterial property and an organoleptic assessment was determined. The highest survival rate was demonstrated by the bacteria of Lactobacillus delbrueckii ssp. bulgaricus, Streptococcus thermophilus and Bifidobacterium sp. in the yoghurt pressurised 200 MPa/15min at 4°C. Acidity increases in the control yoghurts were higher than in the pressurised ones. Pressurised yoghurts demonstrated weaker antibacterial effect in comparison to control yoghurts. Slight changes in the smell and taste were observed after pressurisation. Yoghurts pressurised at 18°C were characterised by more favourable organoleptic properties. Better conciseness of the curd and lower whey seep out were observed in pressurised yoghurt.