Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 217
Filtrar
1.
Adv Mater ; : e1907112, 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-32020715

RESUMO

Electrochemical conversion of nitrogen (N2 ) into value-added ammonia (NH3 ) is highly desirable yet formidably challenging due to the extreme inertness of the N2 molecule, which makes the development of a robust electrocatalyst prerequisite. Herein, a new class of bullet-like M-Te (M = Ru, Rh, Ir) glassy porous nanorods (PNRs) is reported as excellent electrocatalysts for N2 reduction reaction (NRR). The optimized IrTe4 PNRs present superior activity with the highest NH3 yield rate (51.1 µg h-1 mg-1 cat. ) and Faraday efficiency (15.3%), as well as long-term stability of up to 20 consecutive cycles, making them among the most active NRR electrocatalysts reported to date. Both the N2 temperature-programmed desorption and valence band X-ray photoelectron spectroscopy data show that the strong chemical adsorption of N2 is the key for enhancing the NRR and suppressing the hydrogen evolution reaction of IrTe4 PNRs. Density functional theory calculations comprehensively identify that the superior adsorption strength of IrTe4 adsorptions originates from the synergistic collaboration between electron-rich Ir and the highly electroactive surrounding Te atoms. The optimal adsorption of both N2 and H2 O in alkaline media guarantees the superior consecutive NRR process. This work opens a new avenue for designing high-performance NRR electrocatalysts based on glassy materials.

2.
Nano Lett ; 2020 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-32052980

RESUMO

Spin engineering provides a powerful strategy for manipulating the interaction between electrons in d-orbital and oxygen-containing adsorbates, while little endeavor was performed to understand whether such strategy can make a prosperous enhancement for fuels electrooxidations. Herein, we demonstrate that spin engineering of trimetallic Pd-Fe-Pt nanomeshes (NMs) can achieve superior enhancement for fuels electrooxidations. Magnetization characterizations reveal that Pd59Fe27Pt14 NMs own the highest number of polarized spins (µb = 0.85 µB/f.u), playing an important role on facilitating the adsorption of OHads to promote the oxidation of COads, as confirmed by theoretical results. Consequently, the optimized Pd59Fe27Pt14 NMs exhibit excellent methanol oxidation reaction activity and stability with mass activity of 1.61 A mgPt-1, 2.6-fold and 7.3-fold larger than those of PtRu/C and Pt/C. Such catalysts also present exceptional performances in ethanol oxidation and formic acid oxidation reactions. Our work highlights a new strategy for designing efficient electrocatalysts for fuels electrooxidations and beyond.

3.
World J Gastroenterol ; 26(1): 21-34, 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31933512

RESUMO

BACKGROUND: Phosphatidylinositol-3,4,5-trisphosphate dependent Rac exchange factor 1 (PREX1) was reported to be overexpressed in some cancers and involved in cancer development, but its expression and significance in gastric cancer remain unclear. AIM: To evaluate the expression of PREX1 in gastric cancer and its significance in the development of gastric cancer, especially to evaluate the potential mechanism of PREX1 in gastric cancer. METHODS: Bioinformatic analysis was performed in order to examine the expression of PREX1 in gastric cancer. The relationship between the survival rate of gastric cancer patients and PREX1 expression was assessed by Kaplan Meier portal. The Gene Set Enrichment Analysis and the correlation between PREX1 and transforming growth factor (TGF) ß1 pathway-related mediators were evaluated by cBioPortal for Cancer Genomics. Western blotting and reverse transcriptase polymerase chain reaction assay were used to test the role of TGFß1 on the expression of PREX1. Western blotting and dual-luciferase reporter system was used to evaluate the effect of PREX1 on the activation of TGFß1 pathway. Wound healing and Transwell assay were used to assess the effect of PREX1 on the metastasis activity of gastric cancer cells. RESULTS: PREX1 was overexpressed in the gastric tumors, and the expression levels were positively associated with the development of gastric cancer. Also, the high expression of PREX1 revealed poor prognosis, especially for those advanced and specific intestinal gastric cancer patients. PREX1 was closely involved in the positive regulation of cell adhesion and positively correlated with TGFß1-related mediators. Furthermore, TGFß1 could induce the expression of PREX1 at both the protein and mRNA level. Also, PREX1 could activate the TGFß1 pathway. The induced PREX1 could increase the migration and invasion activity of gastric cancer cells. CONCLUSION: PREX1 is overexpressed in gastric cancer, and the high level of PREX1 predicts poor prognosis. PREX1 is closely associated with TGFß signaling and promotes the metastasis of gastric cancer cells.

4.
Bioresour Technol ; 300: 122623, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31927344

RESUMO

Microbial fuel cell is a green and sustainable bio-electrochemical system that can harvest bioelectricity from organic matter conversion by bacteria in wastewater, but weak electrochemical activity and poor biocompatibility between electro-active bacteria and anode limit its scale-up application. In the present, the biomass carbon derived from mango wood was prepared via one-step carbonization method for anode materials in microbial fuel cell. A desirable anode C/1050 with large electrochemical active surface area (75.3 cm2), low electron transfer resistance (4.36 Ω), and benign biocompatibility were developed, achieving power density up to 589.8 mW·m-2. This study provides a low-cost and high-performance biomass carbon used as anode material in microbial fuel cell for practical application.


Assuntos
Fontes de Energia Bioelétrica , Mangifera , Biomassa , Carbono , Eletricidade , Eletrodos , Madeira
5.
Ann Biomed Eng ; 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31916125

RESUMO

Irreversible electroporation (IRE) is an emerging technology for non-thermal ablation of solid tumors. This study sought to integrate electrodes into microporous poly(caprolactone) (PCL) scaffolds previously shown to recruit metastasizing cancer cells in vivo in order to facilitate application of IRE to disseminating cancer cells. As the ideal parallel plate geometry would render much of the porous scaffold surface inaccessible to infiltrating cells, numerical modeling was utilized to predict the spatial profile of electric field strength within the scaffold for alternative electrode designs. Metal mesh electrodes with 0.35 mm aperture and 0.16 mm wire diameter established electric fields with similar spatial uniformity as the parallel plate geometry. Composite PCL-IRE scaffolds were fabricated by placing cylindrical porous PCL scaffolds between two PCL dip-coated stainless steel wire meshes. PCL-IRE scaffolds exhibited no difference in cell infiltration in vivo compared to PCL scaffolds. In addition, upon application of IRE in vivo, cells infiltrating the PCL-IRE scaffolds were successfully ablated, as determined by histological analysis 3 days post-treatment. The ability to establish homogeneous electric fields within a biomaterial that can recruit metastatic cancer cells, especially when combined with immunotherapy, may further advance IRE technology beyond solid tumors to the treatment of systemic cancer.

6.
Dig Dis Sci ; 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31897898

RESUMO

BACKGROUND: Emerged as important regulators in cancer progression, circular RNAs have been tested to participate in diverse biological processes. Former studies have suggested that circular RNA_LARP4 (circLARP4) exerts indispensable function on the development of different cancers such as gastric cancer and ovarian cancer. Nonetheless, the specific role of circLARP4 has not been discovered in ESCC. AIMS: The aim of this study is to explore the biological function and regulatory mechanism of circLARP4 in ESCC. METHODS: CircLARP4, miR-1323, and PTEN expression levels were quantified by RT-qPCR. CCK-8, EdU, caspase-3 activity, wound healing, transwell, and western blot assays were chosen to assess ESCC cell growth. Luciferase reporter, RIP, and RNA pull-down assays were performed to examine the interaction between miR-1323 and circLARP4 (or PTEN). RESULTS: CircLARP4 expression was observably downregulated in ESCC cell lines, and overexpressed circLARP4 restrained cell proliferation and migration whereas boosted cell apoptosis in ESCC. Molecular mechanism experiments revealed that circLARP4 could act as a sponge for miR-1323 and negatively modulated miR-1323 expression in ESCC. Interestingly, the repression of miR-1323 was correlated with inhibitive cell proliferation, migration, and promotive apoptosis. Besides, miR-1323 bound with PTEN, and PTEN expression was negatively regulated by miR-1323 whereas positively regulated by circLARP4 in ESCC. Moreover, rescue assays testified that miR-1323 overexpression or PTEN deficiency could countervail the function of circLARP4 overexpression on ESCC progression. More importantly, circLARP4 played an inhibitory role in PI3K/AKT pathway. CONCLUSIONS: CircLARP4 sponges miR-1323 and hampers tumorigenesis of ESCC through modulating PTEN/PI3K/AKT pathway.

7.
Bioresour Technol ; 296: 122319, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31689612

RESUMO

A kind of reduced graphene oxide decorated with titanium-based (RGO/TiO2) composites are successfully synthesized and employed in this current study as a novel nonprecious metal catalyst for enhancing bioelectricity generation and cathodic oxygen reduction reaction (ORR) in single chamber microbial fuel cells (MFCs). Compared with commercial Pt/C, RGO/TiO2 shows obviously enhanced oxygen reduction reaction activity due to the appropriately-permeated, large electrochemical active area, enough exposure of electrocatalytic active sites of RGO/TiO2. The air-cathode MFC with RGO/TiO2-1 cathode achieves 1786.7 mW m-3 of power density, 86.7% ±â€¯1.2% of COD removal and 31.6% ±â€¯1.1% of CE, which are higher than commercial Pt/C. Moreover, RGO/TiO2-1 cathode exhibits high-effective electrocatalytic activity, and the power density of RGO/TiO2-1 can keep a stable level and only has a minor decline (5.35%) during 30-cycles operation. These results indicate that RGO/TiO2-1 is a potential cathode catalyst, markedly enhancing cathode ORR, wastewater treatment efficiency, and bioelectricity generation of MFC.


Assuntos
Oxigênio , Titânio , Eletrodos , Características da Família , Grafite
8.
J Am Chem Soc ; 142(2): 962-972, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31852179

RESUMO

The pursuit of efficient hydrogenation nanocatalysts with a desirable selectivity toward intricate substrates is state-of-the-art research but remains a formidable challenge. Herein, we report a series of novel PdCdx nanocubes (NCs) for ultraselective hydrogenation reactions with flexible tuning features. Obtaining a desirable conversion level of the substrates (e.g., 4-nitrophenylacetylene (NPA), 4-nitrobenzaldehyde (NBAD), and 4-nitrostyrene (NS)) and competitive selectivity for all potential hydrogenation products have been achieved one by one under optimized hydrogenation conditions. The performance of these PdCdx NCs displays an evident dependence on both the composition and the use of Cd and a need for a distinct hydrogen source (H2 or HCOONH4). Additionally, for the selectivity of hydrogen to be suitably high, the morphology of the NCs has a very well-defined effect. Density functional theory calculations confirmed the variation of adsorption energy for the substrate and hydrogenation products by carefully controlled introduction of Cd, leading to a desirable level of selectivity for all potential hydrogenation products. The PdCdx NCs also exhibit excellent reusability with negligible activity/selectivity decay and structural/composition changes after consecutive reactions. The present study provides an advanced strategy for the rational design of superior hydrogenation nanocatalysts to achieve a practical application for desirable and selective hydrogenation reaction efficiency.

9.
Nat Commun ; 10(1): 5692, 2019 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-31831748

RESUMO

Pursuing active and durable water splitting electrocatalysts is of vital significance for solving the sluggish kinetics of the oxygen evolution reaction (OER) process in energy supply. Herein, theoretical calculations identify that the local distortion-strain effect in amorphous RuTe2 system abnormally sensitizes the Te-pπ coupling capability and enhances the electron-transfer of Ru-sites, in which the excellent inter-orbital p-d transfers determine strong electronic activities for boosting OER performance. Thus, a robust electrocatalyst based on amorphous RuTe2 porous nanorods (PNRs) is successfully fabricated. In the acidic water splitting, a-RuTe2 PNRs exhibit a superior performance, which only require a cell voltage of 1.52 V to reach a current density of 10 mA cm-2. Detailed investigations show that the high density of defects combine with oxygen atoms to form RuOxHy species, which are conducive to the OER. This work offers valuable insights for constructing robust electrocatalysts based on theoretical calculations guided by rational design and amorphous materials.

10.
Artigo em Inglês | MEDLINE | ID: mdl-31765075

RESUMO

Crystal phase engineering is a powerful strategy for regulating the performance of electrocatalysts towards many electrocatalytic reactions, while its impact on the nitrogen electroreduction has been largely unexplored. Herein, we demonstrate that structurally ordered body-centered cubic (BCC) PdCu nanoparticles can be adopted as active, selective, and stable electrocatalysts for ammonia synthesis. Specifically, the BCC PdCu exhibits excellent activity with a high NH3 yield of 35.7 µg h-1 mg-1 cat , Faradaic efficiency of 11.5 %, and high selectivity (no N2 H4 is detected) at -0.1 V versus reversible hydrogen electrode, outperforming its counterpart, face-centered cubic (FCC) PdCu, and most reported nitrogen reduction reaction (NRR) electrocatalysts. It also exhibits durable stability for consecutive electrolysis for five cycles. Density functional theory calculation reveals that strong orbital interactions between Pd and neighboring Cu sites in BCC PdCu obtained by structure engineering induces an evident correlation effect for boosting up the Pd 4d electronic activities for efficient NRR catalysis. Our findings open up a new avenue for designing active and stable electrocatalysts towards NRR.

11.
Front Microbiol ; 10: 2489, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31749783

RESUMO

Staphylococcus aureus is a bacterial pathogen that causes food poisoning, various infections, and sepsis. Effective strategies and new drugs are needed to control S. aureus associated infections due to the emergence and rapid dissemination of antibiotic resistance. In the present study, the antibacterial activity, potential mode of action, and applications of flavonoids from licorice were investigated. Here, we showed that glabrol, licochalcone A, licochalcone C, and licochalcone E displayed high efficiency against methicillin-resistant Staphylococcus aureus (MRSA). Glabrol, licochalcone A, licochalcone C, and licochalcone E exhibited low cytotoxicity without hemolytic activity based on safety evaluation. Glabrol displayed rapid bactericidal activity with low levels of resistance development in vitro. Meanwhile, glabrol rapidly increased bacterial membrane permeability and dissipated the proton move force. Furthermore, we found that peptidoglycan, phosphatidylglycerol, and cardiolipin inhibited the antibacterial activity of glabrol. Molecular docking showed that glabrol binds to phosphatidylglycerol and cardiolipin through the formation of hydrogen bonds. Lastly, glabrol showed antibacterial activity against MRSA in both in vivo and in vitro models. Altogether, these results suggest that glabrol is a promising lead compound for the design of membrane-active antibacterial agents against MRSA and can be used as a disinfectant candidate as well.

12.
J Immunol Res ; 2019: 7024905, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31737687

RESUMO

Objective: Asthma is a syndrome that incorporates many immune phenotypes. The immunologic effects of subcutaneous immunotherapy (SCIT) exerts on allergic asthma remain still largely unknown. Here, we investigated the effects of SCIT on cytokine production and peripheral blood levels of lymphocyte subtypes in children with mite-induced moderate and severe allergic asthma. Methods: The study included 60 kids with mite-induced allergic asthma from 5 to 10 years old. All subjects had received antiasthmatic pharmacologic for 3 months at baseline. Half of the children were treated with SCIT combined with pharmacologic treatment named the SCIT group and the other half only with pharmacologic therapy named the no-SCIT group. Total asthma symptom score (TASS) and total medication score (TMS) were recorded. Flow cytometry was used to identify lymphocyte subtypes: type 2 innate lymphocytes (ILC2s), type 1 (Th1) and type 2 (Th2) helper T cells, T helper 17 (Th17) cells, and regulatory T (Treg) cells. ELISA, flow cytometry, and cytometric bead array were used to assess cytokines IL-13, IFN-γ, IL-4, IL-17, and TGF-ß, at baseline and 3 and 6 months after study treatment in both groups of patients. Results: Both groups can significantly improve clinical symptoms in children with asthma. SCIT can significantly reduce asthma medication after 6 months of treatment. SCIT induced a significantly higher and progressive reduction in ILC2 percentage and IL-13 levels after 3 and 6 months of treatment compared with baseline and compared with no-SCIT patients. Significant differences were detected in the Th1/Th2 cell ratio and IFN-γ/IL-4 cytokine ratio between groups after 6 months of treatment. Similarly, the Th17/Treg ratio and IL-17/TGF-ß ratio in the SCIT group were much lower than those in the no-SCIT group after 3-6 months of treatment. Conclusion: SCIT is a promising option to reduce the percentage of ILC2 and regulate Th1/Th2 and Th17/Treg immune balance in the peripheral blood of children with asthma.

13.
ACS Appl Mater Interfaces ; 11(43): 39722-39727, 2019 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-31609103

RESUMO

Electrochemical CO2 reduction (ECR) to highly value-added products is regarded as a promising way to capture and utilize atmospheric CO2. While the large overpotential and low selectivity largely hinder its practical application, it is highly desirable to design promising catalysts for efficient ECR catalysis. Herein, we have designed a series of core/shell Ag/(Amorphous-Sn(IV)) (Ag/(A-Sn(IV))) nanoparticles (NPs) as highly active and selective catalysts for ECR. Precise amorphous shell tuning of Ag/(A-Sn(IV)) NPs reveals that Ag/(A-Sn(IV)) NPs exhibit volcano-like activity and selectivity toward ECR as a function of the thickness of amorphous shells. The ultrathin amorphous shell not only effectively suppressed the hydrogen evolution reaction (HER) to increase the ECR activity but also converted the ECR product from CO to HCOOH as the applied voltage increased. As a consequence, the optimized core/shell Ag75/(A-Sn(IV))25 NPs show outstanding performance with a CO faradaic efficiency (FE) of 88.0% and a partial current density of 7.9 mA/cm2 at -0.7 V and a HCOOH FE of 75.1% and a partial current density of 13.4 mA/cm2 at -0.9 V. It also exhibited negligible change in current density and FE of the main products after a 12 h reaction. Theoretical calculation further confirmed that the regulation of the shell thickness effectively inhibited the HER and enhanced ECR with a 0.6 nm shell thickness of Ag/(A-Sn(IV)) NPs exhibiting the best activity.

14.
PLoS One ; 14(9): e0223228, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31557269

RESUMO

Chloroplast plays an important role in the plant life cycle. However, the details of its development remain elusive in rice. In this study, we report the fine-mapping of a novel rice gene wpb1 (white panicle branch 1), which affects chloroplast biogenesis, from a tropical japonica variety that results in an albino panicle branches at and after the heading stage. The wpb1 variety was crossed with Nipponbare to generate the F2 and BC1F2 populations. Green and white panicle branch phenotypes with a 3:1 segregation ratio was observed in the F2 population. Bulked segregant analysis (BSA) based on whole genome resequencing was conducted to determine the wpb1 locus. A candidate interval spanning from 11.35 to 23.79M (physical position) on chromosome 1 was identified. The results of BSA analysis were verified by a 40K rice SNP-array using the BC1F2 population. A large-scale F2 population was used to pinpoint wpb1, and the locus was further narrowed down to a 95-kb interval. Furthermore, our results showed that the expression levels of the majority of the genes involved in Chl biosynthesis, photosynthesis and chloroplast development were remarkably affected in wpb1 variety and in F2 plants with a white panicle branch phenotype. In line with the results mentioned above, anatomical structural examination and chlorophyll (Chl) content measurement suggested that wpb1 might play an important role in the regulation of chloroplast development. Further cloning and functional characterization of the wpb1 gene will shed light on the molecular mechanism underlying chloroplast development in rice.

15.
Opt Express ; 27(16): 23422-23431, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31510618

RESUMO

A new type of electrically controlled liquid-crystal microlens matrix (EC-LCMM) with a nested electrode array for efficiently tuning and swinging focus, which means that the focus position can be adjusted in three dimensions, is proposed. The EC-LCMM is constructed by a 10 × 10 arrayed annular-sector-shaped aluminum electrode with a central microhole of 140µm diameter and three annular-sectors of 210µm external diameter and the period length of 280µm. To the arrangement of the patterned electrode, both the 10 × 10 LC microlens array based on the annular-sector-shaped aluminum electrode and the 9 × 9 LC microlens array based on an arrayed quasi-quadrilateral-ring-shaped electrode can be obtained. The 9 × 9 LC microlens array is formed by matching adjacent four annular-sector-shaped sub-electrodes in the 10 × 10 LC microlenses. The developed EC-LCMM can be used to electrically tune focus along the optical axis and also swing focus over a focal plane selected. The typical performances include: electrically tunable focusing in a driving voltage range of 3~7Vrms, the focal length in a range of 2~0.6mm, and the maximum focus swing distance being 16µm. For effectively describing the focus swing efficiency, the parameters of SF and SA are defined, which are the ratios between the focus swinging distance and the current focal length along the optical axis, and between the focus swinging extent and the external diameter of a single annular-sector-shaped aluminum electrode, respectively. The SF and SA of the EC-LCMM are ~16‰ and ~7.6%, respectively. It can be expected that the complex wavefront can be more efficiently measured and adjusted according to the EC-LCMM-based Shack-Hartmann wavefront measuring and adjusting architecture.

16.
Nano Lett ; 19(10): 6894-6903, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31547661

RESUMO

The defect engineering of noble metal nanostructures is of vital importance because it can provide an additional yet advanced tier to further boost catalysis, especially for one-dimensional (1D) noble metal nanostructures with a high surface to bulk ratio and more importantly the ability to engineer the defect along the longitudinal direction of the 1D nanostructures. Herein, for the first time, we report that the defect in 1D noble metal nanostructures is a largely unrevealed yet essential factor in achieving highly active and stable electrocatalysts toward fuel cell reactions. The detailed electrocatalytic results show that the Pd-Sn nanowires (NWs) exhibit interesting defect-dependent performance, in which the defect-rich Pd4Sn wavy NWs display the highest activity and durability for both the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR). Density functional theory (DFT) calculations reveal that a large number of surface vacancies/agglomerated voids are the driving forces for forming surface grain boundaries (GBs) within Pd4Sn WNWs. These electronic active GB regions are the key factors in preserving the number of Pd0 sites, which are critical for minimizing the intrinsic site-to-site electron-transfer barriers. Through this defect engineering, the Pd4Sn WNWs ultimately yield highly efficient alkaline ORR and MOR. The present work highlights the importance of defect engineering in boosting the performance of electrocatalysts for potentially practical fuel cells and energy applications.

17.
ACS Nano ; 13(10): 11303-11309, 2019 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-31532626

RESUMO

Although the water gas shift (WGS) reaction has sparked intensive attention for the production of high-purity hydrogen, the design of cost-efficient catalysts with noble metal-like performance still remains a great challenge. Here, we successfully overcome this obstacle by using Se-incorporated MoS2 with a 1T phase. Combining the optimized electronic structure, additional active sites from edge sites, and a sulfur vacancy based on the 1T phase, as well as the high surface ratio from the highly open structure, the optimal MoS1.75Se0.25 exhibits superior activity and stability compared to the conventional 2H-phase MoS2, with poor activity, large sulfur loss, and rapid inactivation. The hydrogen production of MoS1.75Se0.25 is 942 µmol, which is 1.9 times higher than MoS2 (504 µmol) and 2.8 times higher than MoSe2 (337 µmol). Furthermore, due to the lattice stabilization via Se-incorporation, MoS1.75Se0.25 exhibited excellent long-term stability without obvious change in more than 10 reaction rounds. Our results demonstrate a pathway to design efficient and cost-efficient catalysts for WGS.

18.
Chemistry ; 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31483074

RESUMO

Amorphous oxides have attracted special attention as advanced electrocatalysts owing to their unique local structural flexibility and attractive electrocatalytic properties. With abundant randomly oriented bonds and surface-exposed defects (e.g., oxygen vacancies) as active catalytic sites, the adsorption/desorption of reactants can be optimized, leading to superior catalytic activities. Amorphous oxide materials have found wide electrocatalytic applications ranging from hydrogen evolution and oxygen evolution to oxygen reduction, CO2 electroreduction and nitrogen electroreduction. The amorphous oxide electrocatalysts even outperform their crystalline counterparts in terms of electrocatalytic activity and stability. Despite of the merits and achievements for amorphous oxide electrocatalysts, there are still issues and challenges existing for amorphous oxide electrocatalysts. There are rarely reviews specifically focusing on amorphous oxide electrocatalysts and therefore it is imperative to have a comprehensive overview of the research progress and to better understand the achievements and issues with amorphous oxide electrocatalysts. In this minireview, several general preparation methods for amorphous oxides are first introduced. Then, the achievements in amorphous oxides for several important electrocatalytic reactions are summarized. Finally, the challenges and perspectives for the development of amorphous oxide electrocatalysts are outlined.

19.
Appl Opt ; 58(24): 6611-6617, 2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31503592

RESUMO

An electrically controlled arc-electrode liquid-crystal microlens array (AE-LCMLA), with tuning and swing focus, is proposed, which can be utilized to replace the traditional mechanically controlled microlenses and also cooperate with photosensitive arrays to solve the problems of measuring and further adjusting a strong distortion wavefront. The top patterned electrode of a single LC microlens is composed of three arc-electrodes distributed symmetrically around a central microhole for constructing the key controlling structures of the LC cavity in the AE-LCMLA. All the arc-electrodes are individually controlled, and then the focal spot of each microlens can be moved freely in a three-dimensional fashion including along the optical axial direction and over the focal plane by simply adjusting the driving signal voltage applied over each arc-electrode, independently. The featured performances of the AE-LCMLA in a wavelength range of ∼501-561 nm are the driving signal voltage being relatively low (less than ∼11 Vrms), the focal length tuning range being from ∼2.54 mm to ∼3.50 mm, the maximum focus swing distance being ∼52.92 µm, and the focus swing ratio K being ∼20‰.

20.
Acc Chem Res ; 52(12): 3384-3396, 2019 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-31397995

RESUMO

The development of renewable energy storage and conversion has been greatly promoted by the achievements in platinum (Pt)-based catalysts, which possess remarkable catalytic performance. However, the high cost and limited resources of Pt have hindered the practical applications and thus stimulated extensive efforts to achieve maximized catalytic performance with minimized Pt content. Low dimensional Pt-based bimetallic nanomaterials (such as nanoplates and nanowires) hold enormous potential to realize this target owing to their special atomic arrangement and electronic structures. Recent achievements reveal that strain engineering (e.g., the compressive or tensile strain existing on the Pt skin), surface engineering (e.g., high-index facets, Pt-rich surface, and highly open structures), and interface engineering (e.g., composition-segregated nanostructures) for such nanomaterials can readily lead to electronic modification, more active sites, and strong synergistic effect, thus opening up new avenues toward greatly enhanced catalytic performance. In this Account, we focus on recent advances in low dimensional Pt-based bimetallic nanomaterials as promising catalysts with high activity, long-term stability, and enhanced selectivity for both electrocatalysis and heterogeneous reactions. We begin by illustrating the important role of several strategies on optimizing the catalytic performance: (1) regulated electronic structure by strain effect, (2) increased active sites by surface modification, and (3) the optimized synergistic effect by interfacial engineering. First of all, a difference in atomic bonding strength can result in compressive or tensile force, leading to downshift or upshift of the d-band center. Such effects can be significantly amplified in low-dimensionally confined nanostructures, producing optimized bonding strength for improved catalysis. Furthermore, a high density of high-index facets and a Pt-rich surface in shape-controlled nanostructures based on surface engineering provide further enhancement due to the increased Pt atom utilization and optimal adsorption energy. Finally, interfacial engineering of low dimensional Pt-based bimetallic nanomaterials with high composition-segregation can facilitate the catalytic process due to a strong synergetic effect, which effectively tunes the electronic structure, modifies the coordination environment, and prevents catalysts from serious aggregation. The rational design of low dimensional Pt-based bimetallic nanomaterials with superior catalytic properties based on strain, surface, and interface engineering could help realize enhanced catalysis, gain deep understanding of the structure-performance relationship, and expand access to Pt-based materials for general communities of materials science, chemical engineering, and catalysis in renewable energy research fields.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA