Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 8 de 8
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Proc Natl Acad Sci U S A ; 117(17): 9194-9201, 2020 04 28.
Artigo em Inglês | MEDLINE | ID: mdl-32295882

RESUMO

Promotion of C-C bonds is one of the key fundamental questions in the field of CO2 electroreduction. Much progress has occurred in developing bulk-derived Cu-based electrodes for CO2-to-multicarbons (CO2-to-C2+), especially in the widely studied class of high-surface-area "oxide-derived" copper. However, fundamental understanding into the structural characteristics responsible for efficient C-C formation is restricted by the intrinsic activity of these catalysts often being comparable to polycrystalline copper foil. By closely probing a Cu nanoparticle (NP) ensemble catalyst active for CO2-to-C2+, we show that bias-induced rapid fusion or "electrochemical scrambling" of Cu NPs creates disordered structures intrinsically active for low overpotential C2+ formation, exhibiting around sevenfold enhancement in C2+ turnover over crystalline Cu. Integrating ex situ, passivated ex situ, and in situ analyses reveals that the scrambled state exhibits several structural signatures: a distinct transition to single-crystal Cu2O cubes upon air exposure, low crystallinity upon passivation, and high mobility under bias. These findings suggest that disordered copper structures facilitate C-C bond formation from CO2 and that electrochemical nanocrystal scrambling is an avenue toward creating such catalysts.

2.
J Am Chem Soc ; 2020 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-32299212

RESUMO

Carrier recombination is a crucial process governing the optical properties of a semiconductor. Although various theoretical approaches have been utilized to describe carrier behaviors, a quantitative understanding of the impact of defects and interfaces in low dimensional semiconductor systems is still elusive. Here, we develop a model system consisting of chemically tunable, highly luminescent halide perovskite nanocrystals to illustrate the role of carrier diffusion and material dimensionality on the carrier recombination kinetics and luminescence efficiency. Our advanced synthetic methods provide a well-controlled colloidal system consisting of nanocrystals with different aspect ratios, halide compositions, and surface conditions. Using this system, we reveal the scaling laws of photoluminescence quantum yield and radiative lifetime with respect to the aspect ratio of nanocrystals. The scaling laws derived herein are not only a phenomenological observation but proved a powerful tool disentangling the carrier dynamics of microscopic systems in a quantitative and interpretable manner. The investigation of our model system and theoretical formulation bring to light the dimensionality, as a hidden constraint on carrier dynamics, and identify the diffusion length as an important parameter that distinguishes nanoscale and macroscale carrier behaviors. The conceptual distinction in carrier dynamics in different dimensionality regimes informs new design rules for optical devices where complex microstructures are involved.

3.
Nano Lett ; 2020 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-32348146

RESUMO

Because of the toxicity of lead, searching for a lead-free halide perovskite semiconducting material with comparable optical and electronic properties is of great interest. Rare-earth-based halide perovskite represents a promising class of materials for this purpose. In this work, we demonstrate the solution-phase synthesis of single-crystalline CsEuCl3 nanocrystals with a uniform size distribution centered around 15 nm. The CsEuCl3 nanocrystals have photoluminescence emission centered at 435 nm, with a full width at half-maximum of 19 nm. Furthermore, CsEuCl3 nanocrystals can be embedded in a polymer matrix that provides enhanced stability under continuous laser irradiation. Lead-free rare-earth cesium europium halide perovskite nanocrystals represent a promising candidate to replace lead halide perovskites.

4.
ACS Appl Mater Interfaces ; 9(9): 8201-8210, 2017 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-28207233

RESUMO

The increase of surface area and the functionalization of catalyst are crucial to development of high-performance semiconductor metal oxide (SMO) based chemiresistive gas sensors. Herein, nanoscale catalyst loaded Co3O4 hollow nanocages (HNCs) by using metal-organic framework (MOF) templates have been developed as a new sensing platform. Nanoscale Pd nanoparticles (NPs) were easily loaded on the cavity of Co based zeolite imidazole framework (ZIF-67). The porous structure of ZIF-67 can restrict the size of Pd NPs (2-3 nm) and separate Pd NPs from each other. Subsequently, the calcination of Pd loaded ZIF-67 produced the catalytic PdO NPs functionalized Co3O4 HNCs (PdO-Co3O4 HNCs). The ultrasmall PdO NPs (3-4 nm) are well-distributed in the wall of Co3O4 HNCs, the unique structure of which can provide high surface area and high catalytic activity. As a result, the PdO-Co3O4 HNCs exhibited improved acetone sensing response (Rgas/Rair = 2.51-5 ppm) compared to PdO-Co3O4 powders (Rgas/Rair = 1.98), Co3O4 HNCs (Rgas/Rair = 1.96), and Co3O4 powders (Rgas/Rair = 1.45). In addition, the PdO-Co3O4 HNCs showed high acetone selectivity against other interfering gases. Moreover, the sensor array clearly distinguished simulated exhaled breath of diabetics from healthy people's breath. These results confirmed the novel synthesis of MOF templated nanoscale catalyst loaded SMO HNCs for high performance gas sensors.


Assuntos
Acetona/química , Catálise , Cobalto , Gases , Nanopartículas Metálicas , Óxidos , Paládio
5.
ACS Appl Mater Interfaces ; 8(40): 26758-26768, 2016 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-27654303

RESUMO

Controlling structural and morphological features of molybdenum disulfide (MoS2) nanoplates determines anode reaction performance for Li-ion and Na-ion batteries. In this work, we investigate dimensional effects of MoS2 nanoplates randomly embedded in twisted mesoporous carbon nanofibers (MoS2@MCNFs) on Li and Na storage properties. Considering dimensions of the MoS2 nanoplates (e.g., interlayer, lateral distance, and slabs of stacking in number), we controlled thermolysis temperature to synthesize the MoS2 nanoplates with different geometry and optimize them in the hybrid anode for delivering high performance. The MoS2@MCNFs electrode exhibits reversible Li and Na capacities greater than 1000 cycles even at high current density of 1.0 A g-1 (1221.94 mAh g-1 with capacity retention of 95.6% for Li-ion batteries and 447.29 mAh g-1 with capacity retention of 87.11% for Na-ion batteries). We elucidated the insertion, conversion, and interfacial reaction characteristics of the thermosensitive MoS2 nanoplates in the MCNFs, especially associated with a reversible capacity. Our study will hint at rational design of the nanostructured MoS2 electrodes and focus on significance of their dimensional effects on anode performance.

6.
Small ; 12(43): 5989-5997, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27622572

RESUMO

Rational design of nanostructures and efficient catalyst functionalization methods are critical to the realization of highly sensitive gas sensors. In order to solve these issues, two types of strategies are reported, i.e., (i) synthesis of peapod-like hollow SnO2 nanostructures (hollow 0D-1D SnO2 ) by using fluid dynamics of liquid Sn metal and (ii) metal-protein chelate driven uniform catalyst functionalization. The hollow 0D-1D SnO2 nanostructures have advantages in enhanced gas accessibility and higher surface areas. In addition to structural benefits, protein encapsulated catalytic nanoparticles result in the uniform catalyst functionalization on both hollow SnO2 spheres and SnO2 nanotubes due to their dynamic migration properties. The migration of catalysts with liquid Sn metal is induced by selective location of catalysts around Sn. On the basis of these structural and uniform functionalization of catalyst benefits, biomarker chemical sensors are developed, which deliver highly selective detection capability toward acetone and toluene, respectively. Pt or Pd loaded multidimensional SnO2 nanostructures exhibit outstanding acetone (R air /R gas = 93.55 @ 350 °C, 5 ppm) and toluene (R air /R gas = 9.25 @ 350 °C, 5 ppm) sensing properties, respectively. These results demonstrate that unique nanostructuring and novel catalyst loading method enable sensors to selectively detect biomarkers for exhaled breath sensors.


Assuntos
Quelantes/química , Metais/química , Nanotecnologia/instrumentação , Compostos de Estanho/química , Catálise , Nanofibras/química , Nanofibras/ultraestrutura , Nanosferas/química , Nanosferas/ultraestrutura , Platina/química , Povidona/química
7.
ACS Appl Mater Interfaces ; 7(51): 28116-21, 2015 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-26654256

RESUMO

To exploit the benefits of nanostructuring for enhanced hydrogen evolution reaction (HER), we employed coaxial electrospinning to synthesize single-layered WS2 nanoplates anchored to hollow nitrogen-doped carbon nanofibers (WS2@HNCNFs) as efficient electrocatalysts. For comparison, bulk WS2 powder and single layers of WS2 embedded in nitrogen-doped carbon nanofibers (WS2@NCNFs) were synthesized and electrochemically tested. The distinctive design of the WS2@HNCNFs enables remarkable electrochemical performances showing a low overpotential with reduced charge transfer resistance, a small Tafel slope, and excellent durability. The experimental results highlight the importance of nanostructure engineering in electrocatalysts for enhanced HER.

8.
Nanoscale ; 7(28): 11945-50, 2015 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-26119251

RESUMO

Single layers of WS2 nanoplates are uniformly embedded in nitrogen-doped carbon nanofibers (WS2@NCNFs) via a facile electrospinning method. Crystallization of the single-layered WS2 nanoplates and in situ nitrogen doping into the carbon nanofibers were simultaneously accomplished during a two-step heat treatment. The distinctive structure of the WS2@NCNFs enables outstanding electrochemical performances.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA