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1.
Chem Sci ; 13(38): 11320-11329, 2022 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-36320582

RESUMO

Rechargeable Zn batteries hold great practicability for cost-effective sustainable energy storage but suffer from irreversibility of the Zn anode in aqueous electrolytes due to parasitic H2 evolution, corrosion, and dendrite growth. Herein, we report a non-flammable, dilute, and hydrous organic electrolyte by dissolving low-cost hydrated Zn(ClO4)2·6H2O in trimethyl phosphate (TMP), which homogenizes plating/stripping and enables in situ formation of a Zn3(PO4)2-ZnCl2-rich interphase to stabilize the Zn anode. A dilute 0.5 m Zn(ClO4)2·6H2O/TMP electrolyte featuring a H2O-poor Zn2+-solvation sheath and low water activity enables significantly enhanced Zn reversibility and a wider electrochemical window than the concentrated counterpart. In this formulated electrolyte, the Zn anode exhibits a high efficiency of 99.5% over 500 cycles, long-term cycling for 1200 h (5 mA h cm-2 at 5 mA cm-2) and stable operation at 50 °C. The results would guide the design of hydrous organic electrolytes for practical rechargeable batteries employing metallic electrode materials.

2.
Nano Lett ; 22(11): 4333-4339, 2022 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-35584407

RESUMO

Achieving metal nanocrystals with metastable phase draws much attention due to their anticipated fascinating properties, wheras it is still challenging because their polymorphism nature and phase transition mechanism remain elusive. Here, phase stability of face-centered cubic (fcc) Pd nanocrystals was studied via in situ spherical aberration (Cs)-corrected transmission electron microscopy (TEM). By constructing a well-defined Pd/C composite structure, Pd nanocrystals encapsulated by graphite, the dispersion process of fcc Pd was observed through a nucleation and growth process. Interestingly, Cs-corrected scanning TEM analysis demonstrated that the newly formed Pd nanocrystals could adopt a metastable hexagonal phase, which was considered challenging to obtain. Accordingly, formation mechanism of the hexagonal Pd nanocrystals was proposed, which involved the combined effect of two factors: (1) templating of graphite and (2) size effect. This work is expected to offer new insight into the polymorphism of Pd nanocrystals and pave the way for the future design of metastable metal nanomaterials.


Assuntos
Grafite , Nanopartículas Metálicas , Nanoestruturas , Nanopartículas Metálicas/química , Microscopia Eletrônica de Transmissão , Nanoestruturas/química , Transição de Fase
3.
Appl Opt ; 61(10): 2490-2496, 2022 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-35471313

RESUMO

Spectral filters with polarimetric character in short-wave infrareds are urgently needed because of their broad applications in optic-fiber communications, polarimetric detections, and imaging. Based on our earlier progress in developing polarimetric devices in infrared wavelengths, in this work, a plasmonic-metasurface-based polarization-dependency multi-channel narrowband filter in short-wave infrareds was developed. To meet the requirement by the developing trend of polarimetric detection/spectral imaging in short-wave infrareds, a resonant cavity in the form of the Au hat/elliptical Si/SiO2 pillars/Au layer as the filters was proposed. Numerical simulations by finite-difference time-domain (FDTD) show resonant and polarized transmissions of the designed devices to infrared light in short wavelengths, and the peak positions are relevant to the structural dimensions. Optical characteristics of the filters, fabricated by electron beam lithography/dry-etch technique, agree well with the simulated behavior. To enhance the transmission efficiency to the applicable level, nanoprocessing of the filters still needs to be optimized. Nevertheless, the progress reported is promising for this new type of spectral filters based on modern metasurfaces.

4.
Nat Commun ; 12(1): 5770, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34599160

RESUMO

Metal/oxide interface is of fundamental significance to heterogeneous catalysis because the seemingly "inert" oxide support can modulate the morphology, atomic and electronic structures of the metal catalyst through the interface. The interfacial effects are well studied over a bulk oxide support but remain elusive for nanometer-sized systems like clusters, arising from the challenges associated with chemical synthesis and structural elucidation of such hybrid clusters. We hereby demonstrate the essential catalytic roles of a nanometer metal/oxide interface constructed by a hybrid Pd/Bi2O3 cluster ensemble, which is fabricated by a facile stepwise photochemical method. The Pd/Bi2O3 cluster, of which the hybrid structure is elucidated by combined electron microscopy and microanalysis, features a small Pd-Pd coordination number and more importantly a Pd-Bi spatial correlation ascribed to the heterografting between Pd and Bi terminated Bi2O3 clusters. The intra-cluster electron transfer towards Pd across the as-formed nanometer metal/oxide interface significantly weakens the ethylene adsorption without compromising the hydrogen activation. As a result, a 91% selectivity of ethylene and 90% conversion of acetylene can be achieved in a front-end hydrogenation process with a temperature as low as 44 °C.

5.
Angew Chem Int Ed Engl ; 60(41): 22339-22344, 2021 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-34352928

RESUMO

The strong metal-support interaction (SMSI) is widely used in supported metal catalysts and extensive studies have been performed to understand it. Although considerable progress has been achieved, the surface structure of the support, as an important influencing factor, is usually ignored. We report a facet-dependent SMSI of Pd-TiO2 in oxygen by using in situ atmospheric pressure TEM. Pd NPs supported on TiO2 (101) and (100) surfaces showed encapsulation. In contrast, no such cover layer was observed in Pd-TiO2 (001) catalyst under the same conditions. This facet-dependent SMSI, which originates from the variable surface structure of the support, was demonstrated in a probe reaction of methane combustion catalyzed by Pd-TiO2 . Our discovery of the oxidative facet-dependent SMSI gives direct evidence of the important role of the support surface structure in SMSI and provides a new way to tune the interaction between metal NPs and the support as well as catalytic activity.

6.
Nano Lett ; 21(17): 7309-7316, 2021 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-34410724

RESUMO

Understanding surface reconstruction of nanocrystals is of great importance to their applications, however it is still challenging due to lack of atomic-level structural information under reconstruction conditions. Herein, through in situ spherical aberration corrected scanning transmission electron microscopy (STEM), the reconstruction of nanocrystalline SnO2 (110) surface was studied. By identifying the precise arrangements of surface/subsurface Sn and O columns through both in situ bright-field and high-angle annular dark-field STEM images, an unexpected added Sn2O model was determined for SnO2 (110)-(1 × 2) surface. The protruded Snδ+ of this surface could act as the active sites for activating O2 molecules according to our density functional theory (DFT) calculations. On the basis of in situ observation of atomic-level reconstruction behaviors and DFT calculations, an energy-driven reconstruction process was also revealed. We anticipate this work would help to clarify the long-standing debate regarding the reconstruction of SnO2 (110) surface and its intrinsic property.

7.
Chem Commun (Camb) ; 57(35): 4319-4322, 2021 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-33913950

RESUMO

We demonstrate that the capacity decay and voltage drop issues of the Li3V2(PO4)3 cathode are significantly addressed by using a concentrated aqueous electrolyte based on Zn and Li salts. The resultant aqueous Zn//Li3V2(PO4)3 battery achieves a high output voltage of 1.75 V and a long lifespan with 82.3% capacity retention over 2000 cycles. Joint structural and spectroscopic characterizations reveal that this battery operates through Li+ (de)intercalation into the cathode along with Zn2+ plating/stripping at the anode.

8.
Science ; 371(6528): 517-521, 2021 01 29.
Artigo em Inglês | MEDLINE | ID: mdl-33510028

RESUMO

The interface between metal catalyst and support plays a critical role in heterogeneous catalysis. An epitaxial interface is generally considered to be rigid, and tuning its intrinsic microstructure with atomic precision during catalytic reactions is challenging. Using aberration-corrected environmental transmission electron microscopy, we studied the interface between gold (Au) and a titanium dioxide (TiO2) support. Direct atomic-scale observations showed an unexpected dependence of the atomic structure of the Au-TiO2 interface with the epitaxial rotation of gold nanoparticles on a TiO2 surface during carbon monoxide (CO) oxidation. Taking advantage of the reversible and controllable rotation, we achieved in situ manipulation of the active Au-TiO2 interface by changing gas and temperature. This result suggests that real-time design of the catalytic interface in operating conditions may be possible.

10.
Science ; 367(6476): 428-430, 2020 01 24.
Artigo em Inglês | MEDLINE | ID: mdl-31974251

RESUMO

Imaging a reaction taking place at the molecular level could provide direct information for understanding the catalytic reaction mechanism. We used in situ environmental transmission electron microscopy and a nanocrystalline anatase titanium dioxide (001) surface with (1 × 4) reconstruction as a catalyst, which provided highly ordered four-coordinated titanium "active rows" to realize real-time monitoring of water molecules dissociating and reacting on the catalyst surface. The twin-protrusion configuration of adsorbed water was observed. During the water-gas shift reaction, dynamic changes in these structures were visualized on these active rows at the molecular level.

11.
Angew Chem Int Ed Engl ; 59(6): 2171-2180, 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-31298462

RESUMO

The shape of metal nanoparticles (NPs) is one of the key factors determining their catalytic reactivity. Recent in situ TEM observations show that dynamic reshaping of metal NPs occurs under the reaction conditions, which becomes a major hurdle for fully understanding catalytic mechanisms at the molecular level. This Minireview provides a summary of the latest progress in characterizing and modeling the equilibrium shape of metal NPs in various reactive environments through the joint effort of state-of-the-art in situ environmental transmission electron microscopy experiments and a newly developed multiscale structure reconstruction model. The quantitative agreement between the experimental observations and theoretical modeling demonstrate that the fundamental mechanism of the reshaping phenomenon is driven by anisotropically changed surface energies under gas adsorption. The predictable reshaping of metal NPs paves the way for the rational design of truly efficient nanocatalysts in real reactions.

12.
Adv Mater ; 31(42): e1903719, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31475404

RESUMO

Nitrogen oxides are one of the major sources of air pollution. To remove these pollutants originating from combustion of fossil fuels remains challenging in steel, cement, and glass industries as the catalysts are severely deactivated by SO2 during the low-temperature selective catalytic reduction (SCR) process. Here, a MnOX /CeO2 nanorod catalyst with outstanding resistance to SO2 deactivation is reported, which is designed based on critical information obtained from in situ transmission electron microscopy (TEM) experiments under reaction conditions and theoretical calculations. The catalysts show almost no activity loss (apparent NOX reaction rate kept unchanged at 1800 µmol g-1 h-1 ) for 1000 h test at 523 K in the presence of 200 ppm SO2 . This unprecedented performance is achieved by establishing a dynamic equilibrium between sulfates formation and decomposition over the CeO2 surface during the reactions and preventing the MnOX cluster from the steric hindrance induced by SO2 , which minimized the deactivation of the active sites of MnOX /CeO2 . This work presents the ultralong lifetime of catalysts in the presence of SO2 , along with decent activity, marking a milestone in practical applications in low-temperature selective catalytic reduction (SCR) of NOX .

13.
Nano Lett ; 19(6): 4205-4210, 2019 06 12.
Artigo em Inglês | MEDLINE | ID: mdl-31145634

RESUMO

Layer-by-layer growth played a critical role in the fine design of novel materials and devices. Although it has been widely studied during materials synthesis, the atomic mechanism of the growth remains unclear due to the lack of direct observation at the atomic scale. Here, we report a new mode in layer-by-layer growth via surface reconstruction on MoO2 (011) by environmental transmission electron microscopy and density functional theory calculations. Our in situ environmental transmission electron microscopy results demonstrate that the layer-by-layer growth of MoO2 experiences two steps that occur in an oscillatory manner: (1) the formation of an atomic ledge by transforming a section of the reconstructed layer to the intrinsic surface layer and then (2) the spontaneous reconstruction of the newly formed intrinsic surface section. Thus, the surface reconstruction can be considered as an intermediated phase during the layer-by-layer growth of MoO2. A similar phenomenon was also observed in the MoO2 dissolution procedure.

14.
Phys Chem Chem Phys ; 21(6): 3134-3139, 2019 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-30675619

RESUMO

Bimetallic core-shell nanoparticles have received considerable attention for their unique optical, magnetic and catalytic properties. However, these properties will be dramatically modified under ambient conditions by their structure and/or composition change. Thus, it is of primary importance to study the complex transformation pathway of core-shell nanoparticles at an elevated temperature. In this work, by using an aberration-corrected scanning transmission electron microscope equipped with an energy dispersive X-ray mapping system, the complete transformation process from a well-designed Pd@Au core-shell nanoparticle to a uniform alloy particle was visualized. It is revealed that this transformation process went through three steps, i.e., surface refacetting, particle resphering and complete alloying. Combining with a developed atomic kinetic Monte Carlo simulation, we found that surface energy is the driving force for shape variation, and the different atomic activation barriers of surface diffusion and bulk migration result in the multistep transformation pathway. Our results offered important information for understanding the structure evolution of bimetallic core-shell nanoparticles, which is beneficial for the rational design of nanoparticles with kinetic stability.

15.
Angew Chem Int Ed Engl ; 57(51): 16827-16831, 2018 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-30397982

RESUMO

Preventing sintering of supported nanocatalysts is an important issue in nanocatalysis. A feasible way is to choose a suitable support. However, whether the metal-support interactions promote or prevent the sintering has not been fully identified. Now, completely different sintering behaviors of Au nanoparticles on distinct anatase TiO2 surfaces have been determined by in situ TEM. The full in situ sintering processes of Au nanoparticles were visualized on TiO2 (101) surface, which coupled the Ostwald ripening and particle migration coalescence. In contrast, no sintering of Au on TiO2 anatase (001) surface was observed under the same conditions. This facet-dependent sintering mechanism is fully explained by the density function theory calculations. This work not only offers direct evidence of the important role of supports in the sintering process, but also provides insightful information for the design of sintering-resistant nanocatalysts.

16.
Chem Commun (Camb) ; 54(62): 8587-8590, 2018 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-29972158

RESUMO

We demonstrate an unexpected refacetting process of Pd nanoparticles, induced by N2 under atmospheric pressure at elevated temperatures, by in situ TEM observations. The morphology changes, with a notable increase in the fraction of Pd{110} facets, were visualized by atomic-scale TEM images and further explained by theoretical calculations. Firm evidence and rational understanding revealed that the "inert" gas N2 has the ability to modify the structure of metal nanoparticles. This surprising effect should be considered seriously in vast chemical applications that use N2 as a carrier gas or protective atmosphere.

17.
Angew Chem Int Ed Engl ; 57(35): 11344-11348, 2018 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-29979826

RESUMO

Acquiring the kinetics of gas-nanoparticle fast reactions under ambient pressure is a challenge owing to the lack of appropriate in situ techniques. Now an approach has been developed that integrates time-resolved in situ electron diffraction and an atmospheric gas cell system in transmission electron microscopy, allowing quantitative structural information to be obtained under ambient pressure with millisecond time resolution. The ultrafast oxidation kinetics of Ni nanoparticles in oxygen was vividly obtained. In contrast to the well-accepted Wagner and Mott-Cabrera models (diffusion-dominated), the oxidation of Ni nanoparticles is linear at the initial stage (<0.5 s), and follows the Avrami-Erofeev model (n=1.12) at the following stage, which indicates the oxidation of Ni nanoparticles is a nucleation and growth dominated process. This study gives new insights into Ni oxidation and paves the way to study the fast reaction kinetics of nanoparticles using ultrafast in situ techniques.

18.
PLoS Genet ; 14(4): e1007275, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29621232

RESUMO

To identify genetic contributions to type 2 diabetes (T2D) and related glycemic traits (fasting glucose, fasting insulin, and HbA1c), we conducted genome-wide association analyses (GWAS) in up to 7,178 Chinese subjects from nine provinces in the China Health and Nutrition Survey (CHNS). We examined patterns of population structure within CHNS and found that allele frequencies differed across provinces, consistent with genetic drift and population substructure. We further validated 32 previously described T2D- and glycemic trait-loci, including G6PC2 and SIX3-SIX2 associated with fasting glucose. At G6PC2, we replicated a known fasting glucose-associated variant (rs34177044) and identified a second signal (rs2232326), a low-frequency (4%), probably damaging missense variant (S324P). A variant within the lead fasting glucose-associated signal at SIX3-SIX2 co-localized with pancreatic islet expression quantitative trait loci (eQTL) for SIX3, SIX2, and three noncoding transcripts. To identify variants functionally responsible for the fasting glucose association at SIX3-SIX2, we tested five candidate variants for allelic differences in regulatory function. The rs12712928-C allele, associated with higher fasting glucose and lower transcript expression level, showed lower transcriptional activity in reporter assays and increased binding to GABP compared to the rs12712928-G, suggesting that rs12712928-C contributes to elevated fasting glucose levels by disrupting an islet enhancer, resulting in reduced gene expression. Taken together, these analyses identified multiple loci associated with glycemic traits across China, and suggest a regulatory mechanism at the SIX3-SIX2 fasting glucose GWAS locus.


Assuntos
Glicemia/genética , Diabetes Mellitus Tipo 2/genética , Inquéritos Epidemiológicos , China , Jejum , Feminino , Estudo de Associação Genômica Ampla , Humanos , Ilhotas Pancreáticas/metabolismo , Masculino , Mutação de Sentido Incorreto , Inquéritos Nutricionais , Locos de Características Quantitativas
19.
J Pediatr ; 191: 158-163.e3, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-29173301

RESUMO

OBJECTIVE: To identify causal mutations in certain genes in children with acute recurrent pancreatitis (ARP) or chronic pancreatitis (CP). STUDY DESIGN: After patients were enrolled (CP, 55; ARP, 14) and their clinical characteristics were investigated, we performed next-generation sequencing to detect nucleotide variations among the following 10 genes: cationic trypsinogen protease serine 1 (PRSS1), serine protease inhibitor, Kazal type 1 (SPINK1), cystic fibrosis transmembrane conductance regulator gene (CFTR), chymotrypsin C (CTRC), calcium-sensing receptor (CASR), cathepsin B (CTSB), keratin 8 (KRT8), CLAUDIN 2 (CLDN2), carboxypeptidase A1 (CPA1), and ATPase type 8B member 1 (ATP8B1). Mutations were searched against online databases to obtain information on the cause of the diseases. Certain novel mutations were analyzed using the SIFT2 and Polyphen-2 to predict the effect on protein function. RESULTS: There were 45 patients with CP and 10 patients with ARP who harbored 1 or more mutations in these genes; 45 patients had at least 1 mutation related to pancreatitis. Mutations were observed in the PRSS1, SPINK1, and CFTR genes in 17 patients, the CASR gene in 5 patients, and the CTSB, CTRC, and KRT8 genes in 1 patient. Mutations were not found in the CLDN, CPA1, or ATP8B1 genes. We found that mutations in SPINK1 may increase the risk of pancreatic duct stones (OR, 11.07; P = .003). The patients with CFTR mutations had a higher level of serum amylase (316.0 U/L vs 92.5 U/L; P = .026). CONCLUSION: Mutations, especially those in PRSS1, SPINK1, and CFTR, accounted for the major etiologies in Chinese children with CP or ARP. Children presenting mutations in the SPINK1 gene may have a higher risk of developing pancreatic duct stones.


Assuntos
Marcadores Genéticos , Predisposição Genética para Doença , Mutação , Pancreatite/genética , Análise de Sequência de DNA/métodos , Doença Aguda , Adolescente , Criança , Pré-Escolar , China , Feminino , Humanos , Lactente , Modelos Logísticos , Masculino , Pancreatite Crônica/genética , Recidiva , Estudos Retrospectivos
20.
ACS Appl Mater Interfaces ; 9(37): 31853-31860, 2017 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-28850214

RESUMO

A facile confined solid-state seed-mediated alloying strategy is applied for the rational synthesis of supported Au-Ni bimetallic nanoparticles (BMNPs). The method sequentially deposits nickel salts and AuNP seeds into the ordered array of extra-large mesopores (EP-FDU-12 support) followed by a high-temperature annealing process. The size, structure, and composition of the AuNi BMNPs can be well tuned by varying the AuNP seeds, annealing temperature, and feeding ratio of metal precursors. Kinetic studies and DFT calculations suggest that the introduction of the Ni component can significantly prompt the O2 activation on AuNPs, which is critical for the selective alcohol oxidation using molecular O2 as the oxidant. The optimal Au-Ni BMNP catalyst showed the highest turnover frequency (TOF) (59 000 h-1, 240 °C) and highest space-time yield (STY) of benzyl aldehyde (BAD) productivity (9.23 kg·gAu-1·h-1) in the gas-phase oxidation of benzyl alcohol (BA), which is at least about 5-fold higher than that of other supported Au catalysts.

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