Sirtuin 3 (SIRT3) improves sevoflurane-induced postoperative cognitive impairment by regulating mitochondrial oxidative stress.

One of the most prevalent co-operative disorders is postoperative cognitive dysfunction (POCD), however, its pathogenesis remains unclear. Thus, the aim of this work was to evaluate SIRT3's impact on cognitive decline in aged mice under anesthesia. Adeno-associated virus SIRT3 vector (AAV-SIRT3) or empty vector (AAV-VEH) was injected into the hippocampal region of aged mice after sevoflurane induction in order to upregulate the expression of SIRT3. The expression levels of SIRT3, pro-inflammatory cytokines, and apoptotic factors in hippocampus tissues were identified by PCR, Western blotting, TUNEL staining, and enzyme-linked immunosorbent assay (ELISA), and the cognitive function of mice was assessed. The SIRT3 expression was down-regulated in the hippocampal tissue of anesthetized mice. SIRT3 overexpression can improve the learning and memory ability, reduce the escape latency, and increase the residence time in the platform and platform crossing ability of mice. The overexpression of SIRT3 in hippocampus can reduce the oxidative stress response and inflammatory response induced by anesthesia in mice, increase the superoxide dismutase (SOD) expression level, and decrease the expression level of MDA and inflammatory factors in hippocampus. In addition, SIRT3 overexpression can also reduce anesthetic-induced hippocampal cell apoptosis. By reducing the hippocampus mitochondrial oxidative stress response, SIRT3 plays a significant role in the pathophysiology of POCD in mice and is a potential target for POCD treatment and diagnosis.

Ultra-large electromechanical deformation in lead-free piezoceramics at reduced thickness.

Lead-free piezoceramics with large controllable deformations are highly desirable for numerous energy converter applications ranging from consumer electronics to medical microrobots. Although several new classes of high-performance ferroelectrics have been discovered, a universal strategy to enable various piezoceramics to realize large electromechanical deformations is still lacking. Herein, by gradually reducing the thickness from 0.5 mm to 0.1 mm, we discover that a large nominal electrostrain of ∼11.49% can be achieved in thin 0.937(Bi0.5Na0.5)TiO3-0.063BaTiO3 (BNT-BT) ceramics with highly asymmetric strain-electric field curves. Further analyses of the polarization switching process reveal that the boosted strain curves originate from the bending deformation driven by asymmetric ferroelastic switching in the surface layers. Based on this, one monolayer BNT-BT was designed to realize digital displacement actuation and a scanning mirror application with a maximum mirror deflection angle of 44.38°. Moreover, the surface effect-induced bending deformation can be extended to other piezoceramics, accompanied by derived shape retention effects. These discoveries raise the possibility of utilizing thickness engineering to design large-displacement actuators and may accelerate the development of high-performance lead-free piezoceramics.

Ordered growth of metal oxides in patterned multi-angle microstructures.

Herein, we report a facile method combining top-down patterning transfer and bottom-up nanorod growth for preparing large-area and ordered TiO2 nanorod arrays. Pre-crystallization seeding was patterned with nanostructured morphologies via interfacial tension-driven precursor solution scattering on various types and period templates. This is a widely applicable strategy for capillary force-driven interfacial patterns, which also shows great operability in complex substrate morphologies with multiple-angle mixing. Moreover, the customized patterned lithographic templates containing English words, Arabic numerals, and Chinese characters are used to verify the applicability and controllability of this hybrid method. In general, our work provides a versatile strategy for the low-cost and facile preparation of hydrothermally growable metal oxide (e.g., ZnO and MnO2) nanostructures with potential applications in the fields of microelectronic devices, photoelectric devices, energy storage, and photocatalysis.

Space-Confined seeding and growth of ordered arrays of TiO2 hierarchical nanostructures.

Here, we report a facile approach to fabricate large area ordered arrays of TiO2 hierarchical nanostructures through space-confined seeding and growth on inverted pyramid templates. The mechanisms of space-confined seeding and growth have been systematically explored and studied. The drying TiO2 seed precursor solution prefers to accumulate on the narrow structures including the centre and edges of the inverted pyramid structures, which facilitates to reduce the free energy of the precursor solution surface and form crystal seeds. Followed by hydrothermal treatment, selective growth of TiO2 hierarchical nanostructures on desirable locations, such as only on the centre, only on the edges, or on the entire surface of the inverted pyramid templates, can be achieved. In addition, the growth temperature, duration and solvents affect the morphology of TiO2 hierarchical nanostructures. This work may provide a universal approach to obtain ordered arrays of metal oxide (e.g. ZnO and MnO2, etc.) nanostructures for applications in optics, electrics, energy, and catalysis.

Dynamic Restructuring of Coordinatively Unsaturated Copper Paddle Wheel Clusters to Boost Electrochemical CO2 Reduction to Hydrocarbons.

The electrochemical reduction of CO2 to hydrocarbons involves a multistep proton-coupled electron transfer (PCET) reaction. Second coordination sphere engineering is reported to be effective in the PCET process; however, little is known about the actual catalytic active sites under realistic operating conditions. We have designed a defect-containing metal-organic framework, HKUST-1, through a facile "atomized trimesic acid" strategy, in which Cu atoms are modified by unsaturated carboxylate ligands, producing coordinatively unsaturated Cu paddle wheel (CU-CPW) clusters. We investigate the dynamic behavior of the CU-CPW during electrochemical reconstruction through the comprehensive analysis of in situ characterization results. It is demonstrated that Cu2 (HCOO)3 is maintained after electrochemical reconstruction and that is behaves as an active site. Mechanistic studies reveal that CU-CPW accelerates the proton-coupled multi-electron transfer (PCMET) reaction, resulting in a deep CO2 reduction reaction.

A redox-active support for the synthesis of Au@SnO2 core-shell nanostructure and SnO2 quantum dots with efficient photoactivities.

A defect pyrochlore-type Sn1.06Nb2O5.59F0.97 (SnNbOF) nano-octahedron is used as a redox-active support for fabricating Au@SnO2 core-shell and SnO2 quantum dots at room temperature without the use of organic species or foreign reducing reagents. Gold (Au) and SnO2 components were obtained through an in situ redox reaction between the HAuCl4 and reductive Sn2+ ions incorporated in SnNbOF. The composition and morphology of the resulting nanocomposites (denoted as Au-SnNbOF) could be controlled by adjusting the Au/SnNbOF ratio. The Au-SnNbOF nanocomposites exhibited efficient photoactivities for methyl orange (MO) degradation under the visible light irradiation (λ > 420 nm), during which the MO was almost completely degraded within 8 min. Among all the samples, the 5wt% Au-SnNbOF nanocomposite had the highest rate constant (0.43 min-1), which was 40 times higher than that of the blank SnNbOF.

Core-Shell Au@SnO2 Nanostructures Supported on Na2Ti4O9 Nanobelts as a Highly Active and Deactivation-Resistant Catalyst toward Selective Nitroaromatics Reduction.

Catalysis using gold (Au) nanoparticles has become an important field of chemistry. However, activity loss caused by aggregation or leaching of Au nanoparticles greatly limits their application in catalytic reaction. Herein, we report a facile and green synthesis of a core-shell Au@SnO2 nanocomposite, exhibiting excellent activity toward selective nitroaromatics reduction under mild conditions. The core-shell Au@SnO2 nanocomposite (Au size = ∼50 nm; shell thickness = ca. 16 nm) is conceived and validated by a direct redox reaction between HAuCl4 and SnF2. Optimization of the core size, shell thickness, and dispersion of Au@SnO2 has been introduced by an alkaline surface supported by negatively charged metal oxide Na2Ti4O9. The as-obtained Au-Sn-Na2Ti4O9 catalyst with much smaller Au cores (ca. 5 nm) and thinner SnO2 nondensed shells (ca. 4 nm) exhibits highly improved catalytic activities for nitro reduction compared to most of the known Au-based catalysts. Moreover, the core-shell Au@SnO2 structure inhibits the leaching and agglomeration of Au nanoparticles and thus leads to superior catalytic durability.

Anomalous Photovoltaic Effect in Centrosymmetric Ferroelastic BiVO4.

The anomolous photovoltaic (APV) effect is an intriguing phenomenon and rarely observed in bulk materials that structurally have an inversion symmetry. Here, the discovery of such an APV effect in a centrosymmetric vanadate, BiVO4, where noticeable above-bandgap photovoltage and a steady-state photocurrent are observed in both ceramics and single crystals even when illuminated under visible light, is reported. Moreover, the photovoltaic voltage can be reversed by the stress modulation, and a sine-function relationship between the photovoltage and stress directional angle is derived. Microstructure and strain-field analysis reveal localized asymmetries that are caused by strain fluctuations in bulk centrosymmetric BiVO4. On the basis of the experimental results, a flexoelectric coupling via a strain-induced local polarization mechanism is suggested to account for the APV effect observed. This work not only allows new applications for BiVO4 in optoelectronic devices but also deepens insights into the mechanisms underlying the APV effect.

A New Defect Pyrochlore Oxide Sn1.06Nb2O5.59F0.97: Synthesis, Noble Metal Hybrids, and Photocatalytic Applications.

Noble metal nanoparticles have attracted considerable attention due to their useful capabilities as heterogeneous catalysts. However, they are usually prepared using various organic stabilizing agents that negatively affect their catalytic activities. Herein, we report a facile, clean, and effective method for synthesizing supported ultrafine noble metal nanoparticles by utilizing the reductive property of a new pyrochlore oxide: Sn1.06Nb2O5.59F0.97 (SnNbOF). Ultrafine Au, Pd, and Pt nanoparticles or clusters are homogeneously distributed on the SnNbOF surface. In addition, the atomic cavities and ion-exchange properties of pyrochlore-type SnNbOF can facilitate the synthesis of atomic Ag dispersed within the framework of SnNbOF. Noble metal-SnNbOF hybrids can be obtained in one step at room temperature, and no foreign reducing agents or stabilizing organics are required for the synthesis. We also show that the fabricated hybrids exhibit promising photocatalytic properties for ethylene oxidation and CO2 reduction.

Photocatalytic oxidation of methane over SrCO3 decorated SrTiO3 nanocatalysts via a synergistic effect.

Because of the high C-H bond energy as well as the non-polar feature of CH4 molecules, oxidation of methane under mild conditions remains a challenging task for both C1 utilization and atmospheric environmental cleansing. Here we report that by using a sol-gel method SrCO3 decorated SrTiO3 nanocatalysts (SrTiO3-S) with an average particle size of ∼25 nm can be readily prepared, which surprisingly show efficient performance for photocatalytic oxidation of methane with the activity close to fourfold of P25, a benchmark photocatalyst. Further investigation revealed a synergistic effect between SrCO3 and SrTiO3 when combined together into a composite material as both of which are totally inactive for methane oxidation if used alone. Gas adsorption characterization disclosed that the SrCO3 can adsorb methane and cannot adsorb carbon dioxide, whereas the SrTiO3 will preferentially adsorb CO2 instead of CH4. Photocurrent and photoluminescence measurements indicate that SrCO3 exhibits a negligible photocurrent response relative to the SrTiO3 semiconductor under simulated solar light illumination but the formation of the SrCO3/SrTiO3 junction structure (SrTiO3-S) helps reduce surface recombination of the photogenerated electrons and holes. All these results refer to the synergistic mechanism in which the SrCO3 acts as a trapping agent to adsorb methane and weaken its C-H bond while the SrTiO3 acts as a photocatalyst to activate and oxidize methane under light illumination. The underlying photooxidation mechanism is further investigated with the aid of in situ electron paramagnetic resonance and infrared spectroscopy.

Photocatalytic oxidation of methane over silver decorated zinc oxide nanocatalysts.

The search for active catalysts that efficiently oxidize methane under ambient conditions remains a challenging task for both C1 utilization and atmospheric cleansing. Here, we show that when the particle size of zinc oxide is reduced down to the nanoscale, it exhibits high activity for methane oxidation under simulated sunlight illumination, and nano silver decoration further enhances the photo-activity via the surface plasmon resonance. The high quantum yield of 8% at wavelengths <400 nm and over 0.1% at wavelengths ∼470 nm achieved on the silver decorated zinc oxide nanostructures shows great promise for atmospheric methane oxidation. Moreover, the nano-particulate composites can efficiently photo-oxidize other small molecular hydrocarbons such as ethane, propane and ethylene, and in particular, can dehydrogenize methane to generate ethane, ethylene and so on. On the basis of the experimental results, a two-step photocatalytic reaction process is suggested to account for the methane photo-oxidation.

Defective, Porous TiO2 Nanosheets with Pt Decoration as an Efficient Photocatalyst for Ethylene Oxidation Synthesized by a C3N4 Templating Method.

We report herein a C3N4 templating method for successfully synthesizing defective, porous TiO2 nanosheets with Pt decoration as an efficient photocatalyst for C2H4 oxidation. During the synthetic procedure, C3N4 not only acts as a 2D template to direct synthesize porous TiO2 nanosheets (TiO2-NS) but also facilitates oxygen vacancy formation on TiO2. The resultant TiO2-NS shows enhanced UV and visible-light photoactivities toward C2H4 oxidation as compared to blank TiO2 (TiO2-B) prepared without C3N4 template. Subsquently, Pt nanoparticles are homogeneously decorated onto the surface of TiO2-NS. The as-obtained Pt-TiO2-NS exhibits efficient photocatalytic activity and stability toward ethylene oxidation.

Graphene Oxide Regulated Tin Oxide Nanostructures: Engineering Composition, Morphology, Band Structure, and Photocatalytic Properties.

A facile, one-step hydrothermal method has been developed to fabricate tin oxide-reduced graphene oxide (Sn-RGO) nanocomposites with tunable composition, morphology, and energy band structure by utilizing graphene oxide (GO) as a multifunctional two-dimensional scaffold. By adjusting the GO concentration during synthesis, a variety of tin oxide nanomaterials with diverse composition and morphology are obtained. Simultaneously, the varying of GO concentration can also narrow the bandgap and tune the band edge positions of the Sn-RGO nanocomposites. As a result, the Sn-RGO nanocomposites with controllable composition, morphology, and energy band structure are obtained, which exhibit efficient photoactivities toward methyl orange (MO) degradation under visible-light irradiation. It is expected that our work would point to the new possibility of using GO for directing synthesis of semiconductor nanomaterials with tailored structure and physicochemical properties.

Enhanced ethylene photodegradation performance of g-C3N4-Ag3PO4 composites with direct Z-scheme configuration.

Photocatalytic oxidation of ethylene continues to be a challenge at the frontier of chemistry. In a previous report, a simple Ag3 PO4 semiconductor material was shown to have strong photooxidative properties and efficiently oxidised water and decomposed organics in aqueous solution under visible-light illumination. Herein, its effects on the photo-oxidation of gaseous C2 H4 were investigated by fabricating graphitic C3 N4-Ag3 PO4 composite semiconductors with direct Z-scheme configuration. It was found that both the ethylene photo-oxidative activity and the stability of Ag3 PO4 are considerably improved by fabrication of Z-scheme composites. Moreover, stable C2 H4 photo-oxidation activity could be obtained by treating the composite at 450 °C for 3 h after long-term operation. From the point of view of environmental pollutant cleanup, the present technique avoids the side reaction of oxidising water and will be valuable for further investigations on both Ag3 PO4 and CH degradation.

Bimetallic alloy nanocrystals encapsulated in ZIF-8 for synergistic catalysis of ethylene oxidative degradation.

Highly dispersed PtPd alloy nanocrystals (NCs) were firstly successfully encapsulated in microporous zeolitic imidazolate framework ZIF-8 (PtPd@ZIF-8) with tunable compositions by a "bottle around ship" approach. The PtPd@ZIF-8 catalyst showed excellent synergistic photocatalytic activity in the transformation of the adsorbed ethylene into CO2 and H2O at room temperature.

Anisotropy in photocatalytic oxidization activity of NaNbO3 photocatalyst.

NaNbO(3) single-crystal films with (100), (110) and (111) oriented crystal planes were grown on LaAlO(3) (100), (110) and (111) substrates by pulsed laser deposition. The NaNbO(3) films exhibit anisotropy in the photocatalytic oxidization activity for Rhodamine B (RhB) degradation. The increasing order of RhB degradation in Ar atmosphere under full arc irradiation of a Xe lamp is (100) < (110) < (111), which is consistent with that of ˙OH generation. The good linear relationship between the activity of RhB degradation and the coercive electric field indicates that the photocatalytic activity is closely related to the ferroelectric property.

K(0.46)Na(0.54)NbO3 ferroelectric ceramics: chemical synthesis, electro-mechanical characteristics, local crystal chemistry and elastic anomalies.

K(0.46)Na(0.54)NbO(3) ceramics have been fabricated via a chemical synthesis route. It was found that 500 °C heat treatment is sufficient to crystallize the niobate powder and the ceramic sintered at 1080 °C in air shows good ferroelectric and piezoelectric properties (P(r) ~ 15 µC cm(-2), d(33) ~ 120 pC N(-1)). Electron diffraction patterns not only determine the space group symmetry of Pcm2(1) for the first time, but also reveal structural disorder in K(0.46)Na(0.54)NbO(3), and 1-D correlated strings of Nb-O atomic displacements are suggested to account for the polar behaviour. Elastic constants such as the bulk and shear moduli as well as their evolution with temperature were also measured using the resonant ultrasound spectroscopy method.

An orthophosphate semiconductor with photooxidation properties under visible-light irradiation.

The search for active semiconductor photocatalysts that directly split water under visible-light irradiation remains one of the most challenging tasks for solar-energy utilization. Over the past 30 years, the search for such materials has focused mainly on metal-ion substitution as in In(1-x)Ni(x)TaO(4) and (V-,Fe- or Mn-)TiO(2) (refs 7,8), non-metal-ion substitution as in TiO(2-x)N(x) and Sm(2)Ti(2)O(5)S(2) (refs 9,10) or solid-solution fabrication as in (Ga(1-x)Zn(x))(N(1-x)O(x)) and ZnS-CuInS(2)-AgInS(2) (refs 11,12). Here we report a new use of Ag(3)PO(4) semiconductor, which can harness visible light to oxidize water as well as decompose organic contaminants in aqueous solution. This suggests its potential as a photofunctional material for both water splitting and waste-water cleaning. More generally, it suggests the incorporation of p block elements and alkali or alkaline earth ions into a simple oxide of narrow bandgap as a strategy to design new photoelectrodes or photocatalysts.