Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 287
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Biomaterials ; 255: 120167, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32540756

RESUMO

In vivo chemical reactions activated by the tumor microenvironment (TME) are particularly promising for antitumor treatments. Herein, employing Cu2-xSe-Au Janus nanoparticles (NPs), photothermal conversion-coordinated Fenton-like and photocatalytic reactions are demonstrated in vitro/vivo. The amorphous form of Cu2-xSe and the catalytic effect of Au benefit the OH generation, and the photo-induced electron‒hole separation of the Janus NPs produces additional OH. The plasmonic electrons of Au facilitate the conversion from Cu2+ to Cu+. Both Cu2-xSe and Au contributes to the efficient photothermal conversion, further promoting the reactions. As a result, the H2O2 utilization rate is largely increased, and remarkable generation of reactive oxygen species is achieved by cell endogenous H2O2in vitro/vivo. A competent tumor inhibition effect is afforded, with high-contrast multimodal imaging. This work opens up the route synergistically integrating photothermal therapy with chemodynamic therapy and photocatalytic therapy into tri-combination antitumor therapy, simply by heterojunction of semiconductor and noble metal.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32516498

RESUMO

Developing graphene-like two-dimensional materials naturally possessing a band gap has sparked enormous interest. Thanks to the inherent wide band gap and high mobility in the 2D plane, covalent organic frameworks containing triazine rings (t-COFs) hold great promise in this regard, whilst the synthesis of single-layer t-COFs remains highly challenging. Herein, we present the fabrication of a well-defined graphene-like t-COF on Au(111). Instead of single/multiple-step single-type reactions commonly applied for on-surface synthesis, distinct stepwise on-surface reactions, including alkynyl cyclotrimerization, C-O bond cleavage, and C-H bond activation, are triggered on demand, leading to product evolution in a controlled step-by-step manner. Aside from the precise control in sophisticated on-surface synthesis, this work proposes a single-atomic-layer organic semiconductor with a wide band gap of 3.41 eV.

3.
Nat Commun ; 11(1): 1379, 2020 03 13.
Artigo em Inglês | MEDLINE | ID: mdl-32170166

RESUMO

Bioelectricity generation, by Shewanella oneidensis (S. oneidensis) MR-1, has become particularly alluring, thanks to its extraordinary prospects for energy production, pollution treatment, and biosynthesis. Attempts to improve its technological output by modification of S. oneidensis MR-1 remains complicated, expensive and inefficient. Herein, we report on the augmentation of S. oneidensis MR-1 with carbon dots (CDs). The CDs-fed cells show accelerated extracellular electron transfer and metabolic rate, with increased intracellular charge, higher adenosine triphosphate level, quicker substrate consumption and more abundant extracellular secretion. Meanwhile, the CDs promote cellular adhesion, electronegativity, and biofilm formation. In bioelectrical systems the CDs-fed cells increase the maximum current value, 7.34 fold, and power output, 6.46 fold. The enhancement efficacy is found to be strongly dependent on the surface charge of the CDs. This work demonstrates a simple, cost-effective and efficient route to improve bioelectricity generation of S. oneidensis MR-1, holding promise in all relevant technologies.


Assuntos
Fontes de Energia Bioelétrica , Carbono/metabolismo , Shewanella/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Materiais Biocompatíveis , Biotecnologia , Eletricidade , Técnicas Eletroquímicas , Transporte de Elétrons , Shewanella/genética , Shewanella/ultraestrutura
4.
ChemSusChem ; 13(1): 260-266, 2020 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-31444854

RESUMO

Transition metal selenides (TMSs) with excellent electrochemical activity and high intrinsic electrical conductivity have attracted considerable attention owing to their potential use in energy storage devices. However, the low energy densities of the reported TMSs, which originate from the small active surface area and poor electrolyte ion mobility, substantially restrict their application potential. In this work, porous ultrathin nickel selenide nanosheet networks (NiSe NNs) on nickel foam are fabricated by using a novel, facile method, that is, selenylation/pickling of the pre-formed manganese-doped α-Ni(OH)2 . Removal of Mn resulted in NNs with a highly porous structure. The 3D framework of the NNs and the inherent nature of the NiSe affords high ion mobility, abundant accessible activated sites, vigorous electrochemical activity, and low resistance. One of the highest specific capacities of TMSs ever reported, that is, 443 mA h g-1 (807 µAh cm-2 ) at 3.0 A g-1 , is achieved with the NNs as electrodes. The assembled NiSe NNs//porous carbon hybrid supercapacitor delivers a high energy density of 66.6 Wh kg-1 at a power density of 425 W kg-1 , with excellent cycling stability. This work provides a new strategy for the production of novel electrode materials that can be applied in high-performance hybrid supercapacitors, and a fresh pathway towards commercial applications of hybrid supercapacitors based on TMS electrodes.

5.
Nanoscale ; 11(41): 19334-19340, 2019 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-31423505

RESUMO

Charge transfer at interfaces plays a critical role in the performance of graphene based electronic devices. However, separate control of the charge transfer process in the graphene/SiO2 system is still challenging. Herein, we investigate the effects of the trapped interfacial icelike water layer on the charge transfer between graphene and the SiO2/Si substrate through recording the surface potential changes induced by partial removal of the interfacial icelike water layer upon in situ heating. The scanning Kelvin probe microscopy surface potential mapping shows that the graphene is electronically modified by the icelike water layer as the electron density transfers from graphene to the icelike water layer, resulting in hole-doping of graphene, which was also confirmed by the graphene field effect transistor electrical transport measurements. In addition, the density functional calculations provide in-depth insight into the electronic contributions of the icelike water layer to graphene and the charge transfer mechanism. This research will improve our ability to manipulate graphene's electronic properties for diverse applications, such as humidity sensing.

6.
J Phys Chem Lett ; 10(18): 5381-5386, 2019 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-31448921

RESUMO

Solar-driven production of renewable energy (e.g., H2) has been investigated for decades. To date, the applications are limited by low efficiency due to rapid charge recombination (both radiative and nonradiative modes) and slow reaction rates. Tremendous efforts have been focused on reducing the radiative recombination and enhancing the interfacial charge transfer by engineering the geometric and electronic structure of the photocatalysts. However, fine-tuning of nonradiative recombination processes and optimization of target reaction paths still lack effective control. Here we show that minimizing the nonradiative relaxation and the adsorption energy of photogenerated surface-adsorbed hydrogen atoms are essential to achieve a longer lifetime of the charge carriers and a faster reaction rate, respectively. Such control results in a 16-fold enhancement in photocatalytic H2 evolution and a 15-fold increase in photocurrent of the crystalline g-C3N4 compared to that of the amorphous g-C3N4.

7.
Nanoscale ; 11(30): 14322-14329, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31323078

RESUMO

Development of fluorescence enhancement (FE) platforms based on ZnO nanorods (NRs) has sparked considerable interest, thanks to their well-demonstrated potential in chemical and biological detection. Among the multiple factors determining the FE performance, high-order waveguide modes are specifically promising in boosting the sensitivity and realizing selective detection. However, quantitative experimental studies on the influence of the NR diameter, substrate, and surrounding medium, on the waveguide-based FE properties remain lacking. In this work, we have designed and fabricated a FE platform based on patterned and well-defined arrays of vertical, hexagonal prism ZnO NRs with six distinct diameters. Both direct experimental evidence and theoretical simulations demonstrate that high-order waveguide modes play a crucial role in FE, and are strongly dependent on the NR diameter, substrate, and surrounding medium. Using the optimized FE platform, a significant limit of detection (LOD) of 10-16 mol L-1 for Rhodamine-6G probe detection is achieved. Especially, a LOD as low as 10-14 g mL-1 is demonstrated for a prototype biomarker of carcinoembryonic antigen, which is improved by one order compared with the best LOD ever reported using fluorescence-based detection. This work provides an efficient path to design waveguiding NRs-based biochips for ultrasensitive and highly-selective biosensing.


Assuntos
Bioensaio/métodos , Corantes Fluorescentes/química , Nanotubos/química , Biomarcadores/análise , Antígeno Carcinoembrionário/análise , Humanos , Imunoensaio/métodos , Limite de Detecção , Neoplasias/diagnóstico , Rodaminas/química , Óxido de Zinco/química
8.
Ultramicroscopy ; 204: 34-48, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31128412

RESUMO

Research and development of lithium-ion batteries (LIBs) require powerful characterization approaches. Atomic force microscopy (AFM) is a multifunctional method that allows investigation of the topography, the electrochemical reactions, the ion transport phenomena, and the surface potential of samples at high resolution. Thus, this technique plays an increasingly important role in the study of LIBs. Herein, the progresses made in the application of AFM for the study of LIBs are reviewed and discussed.

9.
Angew Chem Int Ed Engl ; 58(19): 6265-6270, 2019 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-30737874

RESUMO

The selective oxidation of primary alcohols to aldehydes by O2 instead of stoichiometric oxidants (for example, MnVII , CrVI , and OsIV ) is an important but challenging process. Most heterogeneous catalytic systems (thermal and photocatalysis) require noble metals or harsh reaction conditions. Here we show that the Bi24 O31 Br10 (OH)δ photocatalyst is very efficient in the selective oxidation of a series of aliphatic (carbon chain from C1 to C10 ) and aromatic alcohols to their corresponding aldehydes/ketones under visible-light irradiation in air at room temperature, which would be challenging for conventional thermal and light-driven processes. High quantum efficiencies (71 % and 55 % under 410 and 450 nm irradiation) are reached in a representative reaction, the oxidation of isopropanol. We propose that the outstanding performance of the Bi24 O31 Br10 (OH)δ photocatalyst is associated with basic surface sites and active lattice oxygen that boost the dehydrogenation step in the photo-oxidation of alcohols.

10.
Ultramicroscopy ; 196: 24-32, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30273806

RESUMO

Charge transfer plays fundamental roles in information transmission in cells, especially in neurons. To date, direct observation of charge propagation in neurons at nanometer level has not been achieved yet. Herein, a combined charge injection and Electrostatic Force Microscopy (EFM) detection approach is applied to directly study charge propagation and distribution at nanometer resolution in spines and synapses of hippocampal neurons. Charge density, charge mobility and membrane potential in neural signal transmission process through the spines of axons and dendrites of hippocampal neurons were investigated quantitatively. Postsynaptic densities (PSD) in spines of axons and dendrites were revealed and studied. The methods and results from present work provide insights into physiological activities and processes related with electrical properties in nervous system and other biological samples.

11.
J Am Chem Soc ; 140(48): 16711-16719, 2018 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-30394730

RESUMO

Photocatalytic organic conversions involving a hydrogen transfer (HT) step have attracted much attention, but the efficiency and selectivity under visible light irradiation still needs to be significantly enhanced. Here we have developed a noble metal-free, basic-site engineered bismuth oxybromide [Bi24O31Br10(OH)δ] that can accelerate the photocatalytic HT step in both reduction and oxidation reactions, i.e., nitrobenzene to azo/azoxybenzene, quinones to quinols, thiones to thiols, and alcohols to ketones under visible light irradiation and ambient conditions. Remarkably, quantum efficiencies of 42% and 32% for the nitrobenzene reduction can be reached under 410 and 450 nm irradiation, respectively. The Bi24O31Br10(OH)δ photocatalyst also exhibits excellent performance in up-scaling and stability under visible light and even solar irradiation, revealing economic potential for industrial applications.

12.
Nano Lett ; 18(11): 6778-6788, 2018 11 14.
Artigo em Inglês | MEDLINE | ID: mdl-30288978

RESUMO

Development of stimuli-responsive theranostics is of great importance for precise cancer diagnosis and treatment. Herein, bovine serum albumin (BSA) modified bismuth nanoraspberries (Bi-BSA NRs) are developed as cancer theranostic agents for multimodal imaging and chemo-photothermal combination therapy. The Bi-BSA NRs are synthesized in aqueous phase via a facile reduction method using Bi2O3 nanospheres as the sacrificial template. The morphology, biocompatibility, photothermal effect, drug loading/releasing abilities, chemotherapy effect, synergistic chemo-photothermal therapy efficacy, and multimodal imaging capacities of Bi-BSA NRs have been investigated. The results show that the NRs possess multiple unique features including (i) raspberry-like morphology with high specific surface area (∼52.24 m2·g-1) and large cavity (total pore volume ∼0.30 cm3·g-1), promising high drug loading capacity (∼69 wt %); (ii) dual-stimuli responsive drug release, triggered by acidic pH and NIR laser irradiation; (iii) infrared thermal (IRT), photoacoustic (PA) and X-ray computed tomography (CT) trimodality imaging with the CT contrast enhanced efficiency as high as ∼66.7 HU·mL·mg-1; (iv) 100% tumor elimination through the combination chemo-photothermal therapy. Our work highlights the great potentials of Bi-BSA NRs as a versatile theranostics for multimodal imaging and combination therapy.


Assuntos
Meios de Contraste , Diagnóstico por Imagem , Hipertermia Induzida , Nanopartículas Metálicas , Neoplasias , Fototerapia , Nanomedicina Teranóstica/métodos , Bismuto , Meios de Contraste/química , Meios de Contraste/farmacologia , Células HeLa , Humanos , Nanopartículas Metálicas/química , Nanopartículas Metálicas/uso terapêutico , Neoplasias/diagnóstico por imagem , Neoplasias/metabolismo , Neoplasias/terapia , Soroalbumina Bovina/química , Soroalbumina Bovina/farmacologia
13.
Angew Chem Int Ed Engl ; 57(49): 16015-16019, 2018 12 03.
Artigo em Inglês | MEDLINE | ID: mdl-30334357

RESUMO

By reacting with NaCl on Au(111), the formation of hypoxanthine (HX) tetrads is demonstrated at the atomic scale in real space. These results directly demonstrate that alternative purine tetrads can be formed in both planar and non-planar configuration, and that ionic bonding plays a crucial role for the formation and planar-to-stereo transformation of the tetrads, providing deeper insight for constructing artificial DNA/RNA quadruplexes. Moreover, both the tilted HXs and Na show strong charge transfer with the substrate in the non-planar phase. The insights gained by this work also open up new routes to tune the electrostatic nature of metal-organic interfaces and design stereo-nanostructures on surfaces.

14.
Nanoscale ; 10(38): 18178-18185, 2018 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-30255900

RESUMO

Two-dimensional (2D) van der Waals (vdW) materials with strong in-plane chemical bonds and weak interaction in the out-of-plane direction have been acknowledged as a basic building block for designing dimensional materials in 0D, 1D, 2D and 3D forms. Compared to the explosive research on 2D vdW materials, quasi-one-dimensional (quasi-1D) vdW materials have received rare attention, despite the fact that they also present rich physics in electronics and engineering implications. Herein, quasi-1D MoS2 nanoscrolls are directly fabricated from CVD-grown 2D triangular MoS2 sheets. The formation, stability and electronic properties of quasi-1D MoS2 nanoscrolls are studied experimentally and theoretically. The formation of a nanoscroll always starts from the edge of a triangular MoS2 sheet along its armchair orientation. The electronic properties of MoS2 nanoscrolls are systemically studied with optical spectroscopy and electrical transport together with density-functional theory (DFT) calculations. Surprisingly, the carrier mobility and contact properties of MoS2 nanoscroll based field effect transistors (FETs) are distinct from that of 2D MoS2 sheets. The transition from a 2D semiconductor MoS2 sheet to a 1D metallic MoS2 nanoscroll is successfully achieved. It is expected that this method of fabricating MoS2 nanoscrolls will attract wide interest for 1D transition metal dichalcogenides with novel physical and chemical properties.

15.
Proc Natl Acad Sci U S A ; 115(34): 8517-8522, 2018 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-30082405

RESUMO

Filamentous Desulfobulbaceae bacteria were recently discovered as long-range transporters of electrons from sulfide to oxygen in marine sediments. The long-range electron transfer through these cable bacteria has created considerable interests, but it has also raised many questions, such as what structural basis will be required to enable micrometer-sized cells to build into centimeter-long continuous filaments? Here we dissected cable bacteria cells in vitro by atomic force microscopy and further explored the interior, which is normally hidden behind the outer membrane. Using nanoscale topographical and mechanical maps, different types of bacterial cell-cell junctions and strings along the cable length were identified. More important, these strings were found to be continuous along the bacterial cells passing through the cell-cell junctions. This indicates that the strings serve an important function in maintaining integrity of individual cable bacteria cells as a united filament. Furthermore, ridges in the outer membrane are found to envelop the individual strings at cell-cell junctions, and they are proposed to strengthen the junctions. Finally, we propose a model for the division and growth of the cable bacteria, which illustrate the possible structural requirements for the formation of centimeter-length filaments in the recently discovered cable bacteria.


Assuntos
Fenômenos Fisiológicos Bacterianos , Deltaproteobacteria/fisiologia , Microbiologia da Água , Transporte Biológico Ativo/fisiologia
16.
Chem Commun (Camb) ; 54(64): 8845-8848, 2018 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-30039145

RESUMO

Using a combination of UHV-STM and molecular mechanics calculations, we investigate the surface self-assembly of a complex multi-component metal-molecule system with synergistic non-covalent interactions. Hydrogen bonding between three-dimensional Lander-DAT molecules and planar PTCDI molecules, adsorbed closer to the surface, is found to be facilitated by electrostatic interactions between co-adsorbed Ni adatoms and the flexible molecular DAT groups.

17.
Angew Chem Int Ed Engl ; 57(33): 10666-10671, 2018 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-29900645

RESUMO

Phase transition from WO3 to sub-stoichiometric WO2.9 by a facile method has varied the typical semiconductor to be quasi-metallic with a narrowed band gap and a shifted Femi energy to the conduction band, while maintaining a high crystallinity. The resultant WO2.9 nanorods possess a high total absorption capacity (ca. 90.6 %) over the whole solar spectrum as well as significant photothermal conversion capability, affording a conversion efficiency as high as around 86.9 % and a water evaporation efficiency of about 81 % upon solar light irradiation. Meanwhile, the promising potential of the nanorods for anticancer photothermal therapy have been also demonstrated, with a high photothermal conversion efficiency (ca. 44.9 %) upon single wavelength near-infrared irradiation and a high tumor inhibition rate (ca. 98.5 %). This study may have opened up a feasible route to produce high-performance photothermal materials from well-developed oxides.


Assuntos
Antineoplásicos/química , Nanotubos/química , Óxidos/química , Tungstênio/química , Água/química , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Células Endoteliais da Veia Umbilical Humana , Humanos , Raios Infravermelhos , Óxidos/toxicidade , Transição de Fase , Luz Solar , Temperatura , Tungstênio/toxicidade
18.
ChemSusChem ; 11(10): 1678-1685, 2018 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-29508549

RESUMO

Low-cost activated carbons with high capacitive properties remain desirable for supercapacitor applications. Herein, a three-dimensional scaffolding framework of porous carbon nanosheets (PCNSs) has been produced from a typical biowaste, namely, ground cherry calyces, the specific composition and natural structures of which have contributed to the PCNSs having a very large specific surface area of 1612 m2 g-1 , a hierarchical pore size distribution, a turbostratic carbon structure with a high degree graphitization, and about 10 % oxygen and nitrogen heteroatoms. A high specific capacitance of 350 F g-1 at 0.1 A g-1 has been achieved in a two-electrode system with 6 m KOH; this value is among the highest specific capacitance of biomass-derived carbon materials. More inspiringly, a high energy density of 22.8 Wh kg-1 at a power density of 198.8 W kg-1 can be obtained with 1 m aqueous solution of Li2 SO4 , and an ultrahigh energy density of 81.4 Wh kg-1 at a power density of 446.3 W kg-1 is realized with 1-ethyl-3-methylimidazolium tetrafluoroborate electrolyte.

19.
Nat Commun ; 9(1): 60, 2018 01 04.
Artigo em Inglês | MEDLINE | ID: mdl-29302040

RESUMO

Solar-driven photocatalysis has attracted significant attention in water splitting, CO2 reduction and organic synthesis. The syntheses of valuable azo- and azoxyaromatic dyes via selective photoreduction of nitroaromatic compounds have been realised using supported plasmonic metal nanoparticles at elevated temperatures (≥90 °C); however, the high cost, low efficiency and poor selectivity of such catalyst systems at room temperature limit their application. Here we demonstrate that the inexpensive graphitic C3N4 is an efficient photocatalyst for selective syntheses of a series of azo- and azoxy-aromatic compounds from their corresponding nitroaromatics under either purple (410 nm) or blue light (450 nm) excitation. The high efficiency and high selectivity towards azo- and azoxy-aromatic compounds can be attributed to the weakly bound photogenerated surface adsorbed H-atoms and a favourable N-N coupling reaction. The results reveal financial and environmental potential of photocatalysis for mass production of valuable chemicals.

20.
ACS Appl Mater Interfaces ; 10(2): 1605-1615, 2018 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-29272573

RESUMO

High-performance theranostic nanoagents, which integrate multimodal imaging and photothermal therapy for clinical anticancer treatment, are highly desired. Herein, we report the synthesis and bioapplication of a multifunctional theranostic nanoagent based on polyethylene glycol (PEG)-modified polypyrrole (PPy)-coated bismuth (Bi) nanohybrids (referred to as Bi@PPy-PEG NHs) for X-ray computed tomography/photoacoustic (CT/PA) dual-modal imaging and photothermal therapy (PTT). The obtained Bi@PPy-PEG NHs have a distinct core-shell structure with the metallic Bi nanoparticle as the inner core and the PPy-PEG layer as the shell. The Bi@PPy-PEG NHs show excellent physiological stability and compatibility, without noticeable cytotoxicity. Importantly, the NHs exhibit strong NIR absorbance and remarkable photothermal conversion capability and conversion stability, with the photothermal conversion efficiency as high as ∼46.3%. Thanks to the strong PTT effect, highly effective photothermal ablation on cancer cells has been achieved both in vitro and in vivo. Furthermore, a high-contrast in vitro and in vivo CT/PA dual-modal imaging has been realized, showing great potential to provide comprehensive diagnosis information for antitumor treatment. In particular, the CT enhancement efficiency of the NHs is of ∼14.4 HU mM-1, which is ∼3.7-fold that of clinically used iohexol. Therefore, our work highlights the potential of using such core-shell Bi@PPy-PEG NHs as a versatile theranostic nanoplatform for cancer imaging and therapy.


Assuntos
Nanoestruturas , Bismuto , Imagem Multimodal , Fototerapia , Polietilenoglicóis , Polímeros , Pirróis , Nanomedicina Teranóstica
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA