Oxygen vacancy mediated cubic phase stabilization at room temperature in pure nano-crystalline zirconia films: a combined experimental and first-principles based investigation

Triggering photocatalytic performance of La2CoxMn2-xO6 via heat activation

The La-based perovskite (LaBO3) exhibits excellent optical properties. However, its valence band (VB) potential is not sufficiently positive to reach the oxidation potential required for the cleavage of chemical bonds (such as benzylic C-H), limiting its application in photocatalysis. Herein, we report the unconventional effects of heat activation on the reduction of the dissociation energy of benzylic C-H and aqueous H-O, thereby triggering the photocatalytic activity of La2CoxMn2-xO6 perovskites. Additionally, we demonstrate that photocatalysis is the main contributor to substrate conversion in the selective oxidation of toluene and reduction of CO2. Particularly, La2Co1.5Mn0.5O6 shows excellent performance with a product yield of 550.00 mmol gcat-1 and a toluene conversion of 22,866.67 μmol gcat-1 h-1. To the best of our knowledge, this is the highest reported product yield for the selective oxidation of benzylic C-H bond of toluene. Our findings provide insight into the specific role of heat activation in photocatalysis, which is crucial for breaking and overcoming the VB barrier to realize challenging reactions.

Plasma Surface Modification of 3Y-TZP at Low and Atmospheric Pressures with Different Treatment Times

The efficiency of plasma surface modifications depends on the operating conditions. This study investigated the effect of chamber pressure and plasma exposure time on the surface properties of 3Y-TZP with N2/Ar gas. Plate-shaped zirconia specimens were randomly divided into two categories: vacuum plasma and atmospheric plasma. Each group was subdivided into five subgroups according to the treatment time: 1, 5, 10, 15, and 20 min. Following the plasma treatments, we characterized the surface properties, including wettability, chemical composition, crystal structure, surface morphology, and zeta potential. These were analyzed through various techniques, such as contact angle measurement, XPS, XRD, SEM, FIB, CLSM, and electrokinetic measurements. The atmospheric plasma treatments increased zirconia's electron donation (γ-) capacity, while the vacuum plasma treatments decreased γ- parameter with increasing times. The highest concentration of the basic hydroxyl OH(b) groups was identified after a 5 min exposure to atmospheric plasmas. With longer exposure times, the vacuum plasmas induce electrical damage. Both plasma systems increased the zeta potential of 3Y-TZP, showing positive values in a vacuum. In the atmosphere, the zeta potential rapidly increased after 1 min. Atmospheric plasma treatments would be beneficial for the adsorption of oxygen and nitrogen from ambient air and the generation of various active species on the zirconia surface.

General synthesis strategy of ZrO2 nanofilms with few-atom layered thickness for boosting triethylamine detection

ZrO₂, a traditional inert transition metal oxide (TMO), can be prepared into ZrO₂ nanofilms (NFs) with a single-layer thickness of only 2.5 nm through the generally applicable two-dimensional TMO synthesis strategy reported by us, and has displayed remarkable sensitivity and selectivity properties for triethylamine gas detection.

The effect of charged defects on the stability of implanted helium and yttrium in cubic ZrO2: a first-principles study

The effect of charged defects on the stability of implanted He and Y atoms has been fully investigated to gain insight into the occupation mechanism of defects in cubic ZrO₂ using first-principles calculations. For the intrinsic point defects in ZrO₂, the configurations of V_O²⁺, I_O^2-, V_Zr^4-, and I_Zr⁴⁺ are dominant, which have the lowest formation energy over the widest Fermi level range, respectively. He atoms at neutral Zr vacancies have the lowest incorporation energy (0.438 eV), illustrating that the V_Zr⁰ is probably the most stable trapping site for He atoms. For the Y atoms implanted in ZrO₂, the most stable configuration of Y_Zr^1- is obtained over the widest Fermi level range. In the Y-doped ZrO₂, the incorporation energy of He at the site of Oct₂ interstitial is the lowest (1.058 eV). For He atoms trapped at vacancies, He-V_Zr⁰ has the lowest incorporation energy of 0.631 eV. These results indicate that He atoms preferentially occupy the sites of V_Zr⁰. The state of electric charge plays a significant role in the formation of defects in the ionic compound. The present simulation results provide a theoretical foundation for the effect of charged defects on the stability of He atoms, which contributes to the understanding of the microscopic solution behaviour of He atoms in perfect ZrO₂ and Y-doped ZrO₂.

Mechanical and Magnetic Properties of Double Layered Nanostructures of Tin and Zirconium Oxides Grown by Atomic Layer Deposition

Double layered stacks of ZrO₂ and SnO₂ films, aiming at the synthesis of thin magnetic and elastic material layers, were grown by atomic layer deposition to thicknesses in the range of 20–25 nm at 300 °C from ZrCl₄, SnI₄, H₂O, and O₃ as precursors. The as-deposited nanostructures consisted of a metastable tetragonal polymorph of ZrO₂, and a stable tetragonal phase of SnO₂, with complementary minor reflections from the orthorhombic polymorph of SnO₂. The hardness and elastic modulus of the stacks depended on the order of the constituent oxide films, reaching 15 and 171 GPa, respectively, in the case of top SnO₂ layers. Nonlinear saturative magnetization could be induced in the stacks with coercive fields up to 130 Oe.