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1.
J Colloid Interface Sci ; 566: 265-270, 2020 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-32007738

RESUMO

Downsizing copper nanoparticles (Cu NPs) can effectively improve their catalytic activity, but simultaneously ensuring the structural stability is always a challenge. In this study, by laser ablating a Cu target in graphene oxide (GO) solution along with a reduction treatment, pure Cu NPs (2.0 ± 0.4 nm) are evenly scattered on reduced graphene oxide (rGO). As-prepared Cu/rGO nanocomposites (NCs) are applied as catalysts for 4-nitrophenol (4-NP) reduction, which display high values of mass-normalized rate constant (k/m, 3.118 s-1 mgCu-1) and turnover frequency (TOF, 2.987 × 10-4 mmol mgCu-1 s-1), over those of most reported Cu catalysts. In addition, owing to the stable conjugation between ultrafine Cu NPs and rGO, the Cu/rGO catalysts reveal good catalytic stability that the conversion efficiency of 4-NP is still over 92.0% even after 10 successive cycles.

2.
J Colloid Interface Sci ; 566: 284-295, 2020 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-32007739

RESUMO

For the potential use of Au nanoparticles (NPs) in photothermal therapy, it is important and effective to achieve the uniaxial assembly of Au NPs to allow enhanced absorption in the near infrared (NIR) region. Herein, we first presented the construction of amorphous selenium encapsulated gold (Se@Au) chain-oligomers by successive laser ablation of Au and Se targets in sodium chloride solution without other toxic precursors, stabilizers, or templating molecules. Se@Au chain-oligomers showed evidently enhanced NIR absorption and excellent photothermal transduction efficiency (η), which was higher than 47% at 808 nm. After being stored for 1 year, the Se@Au colloids still exhibited outstanding photothermal performance. The cytotoxicity assay demonstrated that there is negligible toxicity of Se@Au chain-oligomers in cells, but cell viability declined to only 1% in phototherapeutic experiments that were implemented in vitro. In intracellular Reactive Oxygen Species (ROS) generation measurements, Se@Au chain-oligomers could trigger a 35.9% increment of ROS upon laser irradiation. The possible synergetic effects between the anticancer function of Se and photothermal behaviors of Se@Au oligomers were intended to increase ROS level in cells. Therefore, such designed Se@Au chain-oligomers of high stability exhibit promising potential for their use as in vivo photothermal therapeutic agents.

3.
Sci Rep ; 8(1): 1359, 2018 01 22.
Artigo em Inglês | MEDLINE | ID: mdl-29358720

RESUMO

Agglomeration-triggered deactivation of supported platinum electrocatalysts markedly hinders their application in methanol oxidation reaction (MOR). In this study, graphene-supported nickel-iron layered double hydroxide (NiFe-LDH/rGO), in which Fe3+ was introduced to replace Ni2+ partially in the Ni(OH)2 lattice to provide stronger metal-support bonding sites, was utilized to immobilize Pt nanoparticles (NPs). Given the optimized metal-support interfacial contact (Fe3+-O(H)-Pt) between Pt NPs and NiFe-LDH/rGO nanosheets for Pt/NiFe-LDH/rGO electrocatalysts, the Pt/NiFe-LDH/rGO electrocatalysts displayed dramatically enhanced durability than that of Pt/Ni(OH)2/rGO counterpart as well as commercial Pt/C, and 86.5% of its initial catalytic activity can be maintained even after 1200 cycles of cyclic voltammetry (CV) tests during MOR. First-principle calculations toward the resultant M-O(H)-Pt (M = Fe3+, Ni2+) interfacial structure further corroborates that the NiFe-LDH nanosheets can provide stronger bonding sites (via the Fe3+-O(H)-Pt bonds) to immobilize Pt NPs than those of Ni(OH)2 nanosheets (via the Ni2+-O(H)-Pt bonds).

4.
J Colloid Interface Sci ; 514: 165-171, 2018 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-29253758

RESUMO

Loading of noble metal nanoparticles (NPs) on the surfaces of semiconductor oxides to form a hybrid nanostructure is an effective strategy to improve gas-sensing performance. In this study, WO3 nanoplatelets decorated with Au NPs were prepared by laser ablation in liquids (LAL) with subsequent aging and annealing treatments. Results indicated that Au NPs with an average size of 7.8 ±â€¯2.5 nm were highly dispersed on the surface of WO3 nanoplatelets. As gas-sensing materials, the obtained Au-decorated WO3 nanoplatelets showed lower operating temperature of 320 °C and higher response value of 3.5-fold in detecting ethanol molecules compared with pure WO3 nanoplatelets. Moreover, Au-decorated WO3 nanoplatelets displayed good selectivity toward ethanol compared with other tested vapors and excellent stability within several cycled measurements. These results can be ascribed to the supported Au NPs, which promote the adsorption and dissociation of oxygen species, eventually resulting in accelerated electron depletion on the surface of Au-WO3 hybrids.

5.
Chemphyschem ; 18(9): 1133-1139, 2017 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-28097772

RESUMO

Laser melting in liquids (LML) is one of the most effective methods to prepare bimetallic alloys; however, despite being an ongoing focus of research, the process involved in the formation of such species remains ambiguous. In this paper, we prepared two types of Pt-based bimetallic alloys by LML, including Pt-Au alloys and Pt-iron group metal (iM=Fe/Co/Ni) alloys, and investigated the corresponding mechanisms of alloying process. Detailed component and structural characterizations indicate that laser irradiation induced a quite rapid formation process (not exceeding 10 s) of Pt-Au alloy nanospheres, and the crystalline structures of Pt-Au alloys is determined by the monometallic constituents with higher content. For Pt-iM alloys, we provide direct evidence to support the conclusion that FeOx /CoOx /NiOx colloids can be reduced to elementary Fe/Co/Ni particles by ethanol molecules during laser irradiation, which then react with Pt colloids to form Pt-iM sub-microspheres. These results demonstrate that LML provides an optional route to prepare Pt-based bimetallic alloy particles with tunable size, components, and crystalline phase, which should have promising applications in biological and catalysis studies.

6.
Sci Rep ; 6: 32631, 2016 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-27599448

RESUMO

Understanding the thermodynamic behavior and growth kinetics of colloidal nanoparticles (NPs) is essential to synthesize materials with desirable structures and properties. In this paper, we present specific uncapped Te colloidal NPs obtained through laser ablation of Te in various protic or aprotic solvents. At ambient temperature and pressure, the uncapped Te NPs spontaneously exhibited analogous evolution and growth of "nanoparticle-nanochain-agglomerate-microsphere" in different solvents. The distinctive growth kinetics of the formation of nanochains strongly depended on the polarity and dielectric constant of solvent molecules. The growth rate of agglomerates and microspheres was closely related to the zeta potential of the colloidal solution of Te nanochains and the average size of Te agglomerates. Furthermore, the resulting uncapped Te NPs and Te nanochains displayed a prominent size-dependent and structure-inherited chemical reductive ability. These findings provide insights into the growth of active uncapped nanoparticles in various dispersion media. This study also provides an alternative route in designing novel nanostructures of alloys, telluride, and functional composites using Te as a unique reactive precursor.

7.
Phys Chem Chem Phys ; 18(32): 22503-8, 2016 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-27465699

RESUMO

Incorporating noble metal nanoparticles on the surface or the inner side of semiconductors to form a hybrid nanostructure is an effective route for improving the gas sensing performance of the semiconductors. In this study, we present novel Au-decorated ZnO nanospheres (Au-ZnO NSs) obtained by the laser irradiation of liquids. Structural characterization indicated that the Au-ZnO NSs consisted of single crystalline ZnO NSs with a few Au nanoparticles decorated on their surfaces and abundant encapsulated Au nanoparticles with relatively small sizes. Laser irradiation-induced heating-melting-evaporating processes are responsible for the formation of unique Au-ZnO NSs. The gas sensing properties of the Au-ZnO NSs, as gas sensing materials, were investigated and compared with those of pure ZnO NSs. The former showed a lower working temperature, higher sensitivity, better selectivity, and good reproducibility. The response values of the Au-ZnO NS and pure ZnO NS sensors to ethanol of 100 ppm were 252 and 75 at a working temperature of 320 °C and 360 °C, respectively. Significant enhancements in gas sensing performance should be attributed to the electronic sensitization induced by the depleted layers between the encapsulated Au nanoparticles and ZnO and chemical sensitization originating from the catalytic effects of Au nanoparticles decorated on the surfaces that dissociated molecular oxygen.

8.
ACS Appl Mater Interfaces ; 7(41): 22935-40, 2015 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-26435201

RESUMO

We report a simple and environmentally friendly route to prepare platinum/reduced graphene oxide (Pt/rGO) nanocomposites (NCs) with highly reactive MnOx colloids as reducing agents and sacrificial templates. The colloids are obtained by laser ablation of a metallic Mn target in graphene oxide (GO)-containing solution. Structural and morphological investigations of the as-prepared NCs revealed that ultrafine Pt nanoparticles (NPs) with an average size of 1.8 (±0.6) nm are uniformly dispersed on the surfaces of rGO nanosheets. Compared with commercial Pt/C catalysts, Pt/rGO NCs with highly electrochemically active surface areas show remarkably improved catalytic activity and durability toward methanol oxidation. All of these superior characteristics can be attributed to the small particle size and uniform distribution of the Pt NPs, as well as the excellent electrical conductivity and stability of the rGO catalyst support. These findings suggest that Pt/rGO electrocatalysts are promising candidate materials for practical use in fuel cells.

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