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1.
Ultrason Sonochem ; 67: 105164, 2020 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-32417625

RESUMO

In modern approaches for nanomaterials synthesis, ultrasonication plays an important role in providing the larger surface area and smaller crystalline size properties that are favorable to electrochemical techniques. Herein, we report the tin (IV) oxide on graphene oxide nanoparticles were synthesized (SnO2@GO NPs) by ultrasonic methodology (UZ SONOPULS HD 3400 Ultrasonic homogenizer) with the total power of 400 W and the (frequency of 20 kHz; 140 W/dm3). The formation of as-prepared SnO2@GO NPs and its surface morphology were scrutinized over XRD, XPS, TEM, and FESEM. Besides, the sonochemically prepared SnO2@GO NPs were employed for the determination of environmental hazardous mercury (Hg). As a result, the modified electrode acquired a very low-level detection limit of 1.2 nM with a wider range of 0.01-10.41-µM and 14.52-225.4-µM for the detection of Hg. Finally, the practical applicability of SnO2@GO NPs in spiked human blood serum and tuna fish samples shows appreciable found and recovery values. .

2.
Spectrochim Acta A Mol Biomol Spectrosc ; 231: 118131, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32062514

RESUMO

A novel method for turn-off sensing 1,1-diamino-2,2-dinitroethylene (FOX-7) in aqueous medium was first proposed based on the inner filter effect (IFE) of FOX-7 on the fluorescence of molybdenum disulfide quantum dots (MoS2 QDs). Water-soluble MoS2 QDs as the fluorophore were prepared by the simple hydrothermal method. The morphology, structure, composition and optical properties of the prepared MoS2 QDs were characterized by Transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), UV-vis absorption and photoluminescence spectra. The results showed that the MoS2 QDs had good water dispersibility and emitted strong photoluminescence with a particle size of 2 nm. Under the optimal experimental conditions, the fluorescence signal of MoS2 QDs was quenched in the concentrations range of FOX-7 (0.5-100 µM) and the limit of detection (LOD) of the sensor was 0.19 µM. The method had been applied to analyze the real water samples with good selectivity and stability. Moreover, the quenching mechanism was studied systematically by the Fourier transform infrared (FT-IR), UV-vis absorption spectra, fluorescence lifetime, and Stern-Volmer equation, which had been proved to be static quenching. The fluorescence quenching mechanism is mainly IFE and electron transfer.

3.
Ultrason Sonochem ; 58: 104647, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31450323

RESUMO

In this work, lanthanum tungstate (La2(WO4)3) nanoparticles (NPs) were synthesized by facile sonochemical method (elmasonic P, under-sonication 37/100 kHz, ~60 W energy) and utilized as an electrode material for the selective and sensitive electrochemical determination of anti-scald inhibitor diphenylamine (DPA). The synthesized La2(WO4)3 NPs were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDAX), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses. The results revealed that the sonochemically synthesized La2(WO4)3 nanoparticles were with high crystallinity and uniformly distributed nanoparticles like structure. The as-prepared lanthanum tungstate NPs exhibited an excellent electrocatalytic behavior for DPA determination with the lowest detection limit of 0.0024 µM, wide linear range response of 0.01-58.06 µM and a remarkable sensitivity of 1.021 µA µM-1 cm-2. Furthermore, La2(WO4)3 NPs showed a good recovery to DPA in apple juice sample. Besides, the electrochemical mechanism of the DPA oxidation reaction was provided in detail.

4.
J Mater Chem B ; 7(33): 5065-5077, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31432868

RESUMO

The current study reports a new, simple and fast method using a flake-like dysprosium molybdate (Dy2MoO6; FL-DyM) nanostructured material to detect the antibiotic drug metronidazole (METZ). This nanocomposite material was employed on the surface of a glassy carbon electrode (GCE) to develop the electrode (FL-DyM/GCE). Further, the synthesized FL-DyM was systematically characterized by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray diffraction (EDS), elemental mapping, X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analyses. Cyclic (CV) and differential pulse voltammetry (DPV) techniques were used to study the electrochemical properties. The FL-DyM/GCE-based sensor demonstrated excellent selectivity and sensitivity for the detection of the drug METZ, which could be attributed to the strong affinity of FL-DyM towards the -NO2 group in METZ, and the good electrocatalytic activity and conductivity of FL-DyM. The fabrication and optimization of the working electrode were accomplished with CV and DPV obtained by scan rate and pH studies. Compared to the bare GCE and other rare-earth metal molybdates, the FL-DyM/GCE sensor displayed a superior electrocatalytic activity response for METZ detection. The sensor demonstrated a good linear relationship over the concentration range of 0.01-2363 µM. The quantification and detection limits were found to be 0.010 µM and 0.0030 µM, respectively. The FL-DyM/GCE sensor displayed excellent selectivity, repeatability, reproducibility, and stability for the detection of METZ in human urine and commercial METZ tablet samples, which validates the new technique for efficient drug sensing in practical applications.

5.
Carbohydr Polym ; 222: 115017, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31320078

RESUMO

Water purification has always being an imperative but challenging issue of our times. Here, we used an organic-inorganic material, i.e. bacterial cellulose (BC) and Ca-montmorillonite (Ca-MMT) composites to treat complex wastewater. The surface and inside of the BC/Ca-MMT was a microporous structure capable of providing abundant adsorption sites. We demonstrated the BC/Ca-MMT has superior removal efficiency towards methylene blue (MB) and tetracycline (TC). Typically, the sample showed significant uptake ability towards MB and TC with uptake characteristics of pseudo-second-order model and Langmuir isotherm model. More interestingly, in MB-TC binary system, the removal of the two contaminative species was hardly affected by other coexisting components. Meanwhile, the sample was ease of regeneration and kept stable reusability through consecutive four recycles. With more virtues, such as low cost and wide range of resources of the two raw materials, the BC/Ca-MMT is expected to be a promising versatile water purifier in sewage treatment.


Assuntos
Antibacterianos/isolamento & purificação , Bentonita/química , Celulose/química , Corantes/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Antibacterianos/química , Cálcio/química , Corantes/química , Gluconacetobacter xylinus/química , Concentração de Íons de Hidrogênio , Cinética , Azul de Metileno/química , Azul de Metileno/isolamento & purificação , Tetraciclina/química , Tetraciclina/isolamento & purificação , Poluentes Químicos da Água/química , Purificação da Água/métodos
6.
Carbohydr Polym ; 220: 170-175, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31196537

RESUMO

It's long been understood that antimicrobial properties are one of the most important function in the field of biomedicine. In this thesis, we introduce a new technique to functionalize bacterial cellulose (BC) with antimicrobial properties by in situ method. We design a series of experiments on hydrolyzing mulberry leaves and exploring the methods of fermenting and purifying to obtain a BC complex with antimicrobial properties. Meanwhile, the anti-bacterial performances of MH-BC (fermented by the mulberry leaves acid hydrolysate fermentation medium) were evaluated with Escherichia coli and Staphylococcus aureus, and the experimental results showed that the MH-BC have excellent anti-bacterial activities. Considering the excellent biocompatibility of MH-BC towards hMSCs, we expect that this antibacterial functional BC composite will find potential applications in biomedicine and regenerative medicine.


Assuntos
Antibacterianos/farmacologia , Materiais Biocompatíveis/farmacologia , Celulose/farmacologia , Escherichia coli/efeitos dos fármacos , Gluconacetobacter xylinus/metabolismo , Células-Tronco Mesenquimais/efeitos dos fármacos , Staphylococcus aureus/efeitos dos fármacos , Fermentação , Humanos , Hidrólise , Teste de Materiais/métodos , Células-Tronco Mesenquimais/citologia , Morus/microbiologia , Folhas de Planta/microbiologia
7.
Anal Chim Acta ; 1073: 22-29, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31146832

RESUMO

An electrochemical sensor based on a glassy carbon electrode (GCE) modified by three-dimensional graphene (3D-GE) and polyglutamic acid (PGA) was developed to quantitatively detect Amoxicillin (AMX), a worldwide used antibiotic. AMX response at PGA/3D-GE/GCE involving the transfer of one electron and an equal number of protons were determined using electrochemical approaches. Density functional theory simulations were performed to give insights on the reaction mechanism of AMX on the surface of the modified electrode. When the optimization of the experimental conditions was completed, the linear range of AMX was 2-60 µM. Besides, the detection limit was calculated as 0.118 µM (S/N = 3). And the modified electrode could detect the concentration of the AMX in human urine samples. Overall, the developed PGA/3D-GE/GCE for determination of AMX shows great potentials in practice.


Assuntos
Amoxicilina/química , Teoria da Densidade Funcional , Grafite/química , Simulação de Dinâmica Molecular , Ácido Poliglutâmico/química , Técnicas Eletroquímicas , Eletrodos , Tamanho da Partícula , Propriedades de Superfície
8.
Chem Commun (Camb) ; 55(18): 2692-2695, 2019 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-30747934

RESUMO

Nb2O5@carbon/reduced graphene oxide (M-Nb2O5@C/rGO) composites are fabricated by annealing the precursor of graphene oxide supported Nb-based metal organic frameworks for the first time. The lithium ion capacitor using M-Nb2O5@C/rGO as the anode and activated carbon as the cathode delivers a high energy density of 71.5 W h kg-1 and excellent cycling stability.

9.
Spectrochim Acta A Mol Biomol Spectrosc ; 212: 300-307, 2019 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-30660062

RESUMO

A novel fluorescent sensor based on g-C3N4 nanofibers for the sensitive detection of dopamine (DA) has been proposed. We synthesized g-C3N4 nanofibers by directly hydrolyzing bulk g-C3N4 in the alkaline atmosphere (3 M NaOH). The obtained ultrathin g-C3N4 nanofibers were verified by characterizations of Transmission electronic microscope (TEM), X-ray diffractometer (XRD), Fourier transformation-infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). It was found that the fluorescence intensity of g-C3N4 nanofibers was obviously quenched by DA. Fluorescence resonance energy transfer (FRET) between DA and g-C3N4 nanofibers led to the fluorescence reduction of g-C3N4 nanofibers. The fluorescent probe based on g-C3N4 nanofibers exhibits linear responses to the concentration of DA in the range from 0 to 4 µM and 4 to 20 µM, the limit of detection is 17 nM. The fluorescent probe shows excellent stability, good selectivity with its application in serums.


Assuntos
Dopamina/análise , Corantes Fluorescentes/química , Grafite/química , Nanofibras/química , Compostos de Nitrogênio/química , Espectrometria de Fluorescência/métodos , Dopamina/sangue , Humanos , Concentração de Íons de Hidrogênio , Nanofibras/ultraestrutura , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
10.
Anal Chim Acta ; 1042: 29-36, 2018 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-30428985

RESUMO

The sensing performance of a Langmuir-Blodgett monolayer was significantly improved by controlling the film organization at the air-water interface. Cellulose acetate (CA) and 4-tert-butylcalix [6]arene (calix) were co-spread and formed a Langmuir film, which was efficiently transferred onto a preoxidized gold electrode, Auox. The modified gold electrode was applied as a fast, highly sensitive electrochemical sensing platform for the quantitative determination of a model molecule, dopamine (DA). The modified gold electrode, CA-calix/Auox, demonstrated better recognition and sensing ability towards dopamine as compared with electrodes modified by a single component. Under the optimized conditions, the reduction peak currents at the CA-calix/Auox increased linearly within the concentration range of dopamine from 5 to 100 and 100-7500 nM, and exhibited a very low limit of detection (LOD) of 2.54 nM (S/N = 3). These results suggest a simple, superior and efficient approach for the controllable rearrangement of Langmuir-Blodgett monolayers on a molecular level. The electroanalytical performance was optimized from the perspective of the electrode-electrolyte interface.

11.
ChemSusChem ; 11(5): 907-915, 2018 03 09.
Artigo em Inglês | MEDLINE | ID: mdl-29388379

RESUMO

The incorporation of spacers between graphene sheets has been investigated as an effective method to improve the electrochemical performance of graphene papers (GPs) for supercapacitors. Here, we report the design of free-standing GP@NiO and GP@Ni hybrid GPs in which NiO nanoclusters and Ni nanoparticles are encapsulated into graphene sheets through electrostatic assembly and subsequent vacuum filtration. The encapsulated NiO nanoclusters and Ni nanoparticles can mitigate the restacking of graphene sheets, providing sufficient spaces for high-speed ion diffusion and electron transport. In addition, the spacers strongly bind to graphene sheets, which can efficiently improve the electrochemical stability. Therefore, at a current density of 0.5 A g-1 , the GP@NiO and GP@Ni electrodes exhibit higher specific capacitances of 306.9 and 246.1 F g-1 than the GP electrode (185.7 F g-1 ). The GP@NiO and GP@Ni electrodes exhibit capacitance retention of 98.7 % and 95.6 % after 10000 cycles, demonstrating an outstanding cycling stability. Additionally, the GP@NiO∥GP@Ni delivers excellent cycling stability (93.7 % after 10 000 cycles) and high energy density. These free-standing encapsulated hybrid GPs have great potential as electrode for high-performance supercapacitors.


Assuntos
Capacitância Elétrica , Grafite/química , Nanoestruturas/química , Eletrodos , Transporte de Elétrons , Níquel/química , Eletricidade Estática
12.
ACS Appl Mater Interfaces ; 10(4): 3549-3561, 2018 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-29297668

RESUMO

In this work, we synthesized the hierarchical ZnO@C@NiO core-shell nanorods arrays (CSNAs) grown on a carbon cloth (CC) conductive substrate by a three-step method involving hydrothermal and chemical bath methods. The morphology and chemical structure of the hybrid nanoarrays were characterized in detail. The combination and formation mechanism was proposed. The conducting carbon layer between ZnO and NiO layers can efficiently enhance the electric conductivity of the integrated electrodes, and also protect the corrosion of ZnO in an alkaline solution. Compared with ZnO@NiO nanorods arrays (NAs), the NiO in CC/ZnO@C@NiO electrodes, which possess a unique multilevel core-shell nanostructure exhibits a higher specific capacity (677 C/g at 1.43 A/g) and an enhanced cycling stability (capacity remain 71% after 5000 cycles), on account of the protection of carbon layer derived from glucose. Additionally, a flexible all-solid-state supercapacitor is readily constructed by coating the PVA/KOH gel electrolyte between the ZnO@C@NiO CSNAs and commercial graphene. The energy density of this all-solid-state device decreases from 35.7 to 16.0 Wh/kg as the power density increases from 380.9 to 2704.2 W/kg with an excellent cycling stability (87.5% of the initial capacitance after 10000 cycles). Thereby, the CC/ ZnO@C@NiO CSNAs of three-dimensional hierarchical structure is promising electrode materials for flexible all-solid-state supercapacitors.

13.
Chemistry ; 24(8): 1844-1852, 2018 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-29027721

RESUMO

The large-scale, low-cost preparation of Pt-based catalysts with high activity and durability for the methanol oxidation reaction is still challenging. The key to achieving this aim is finding suitable supporting materials. In this paper, N-doped carbon nanofibrous networks are prepared by annealing a gel containing two inexpensive and ecofriendly precursors, that is, bacterial cellulose and urea, for the loading of Pt nanoparticles. An undoped analogue is also prepared for comparison. Meanwhile, the effect of the annealing temperature on the performance of the catalysts is evaluated. The results show that the N doping and higher annealing temperature can improve the electron conductivity of the catalyst and provide more active sites for the loading of ultrafine Pt nanoparticles with a narrow size distribution. The best catalyst exhibits a remarkably high electrocatalytic activity (627 mA mg-1 ), excellent poison tolerance, and high durability. This work demonstrates an ideal Pt supporting material for the methanol oxidation reaction.


Assuntos
Celulose/química , Nanopartículas Metálicas/química , Metanol/química , Nanofibras/química , Platina/química , Carbono/química , Catálise , Microscopia Eletrônica de Varredura , Nitrogênio/química , Oxirredução , Espectroscopia Fotoeletrônica
14.
Nanotechnology ; 28(31): 315403, 2017 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-28635618

RESUMO

Strongly coupled boron and nitrogen co-doped graphene (BN-G) hybrids with nickel cobaltite (NiCo2O4) nanosheets (NCO/BN-G) were fabricated by a facile soft-chemical method for asymmetric supercapacitors with high-performance. The strong interaction between BN-G and NiCo2O4 nanosheets are explored by various techniques. The effect of heteroatom doping on electrochemical properties of the hybrids is systematically investigated. The strong synergistic effect between NiCo2O4 and BN-G leads to a specific capacitance of 106.5 mA h g-1 at the current density of 0.5 A g-1 and capacitance retention of 96.8% after 10 000 cycles at 5 A g-1, much better than those of the pure NiCo2O4 and its hybrid with N-doped graphene. Moreover, an asymmetric supercapacitor device, assembled with NCO/BN-G and activated carbon (NCO/BN-G//AC), exhibits a maximum energy density of 45.6 Wh kg-1 and an excellent cycling stability. The improved electrochemical performance of the NCO/BN-G hybrid is attributed to the good conductivity of BN-G and the synergistic effect between NiCo2O4 nanosheets and BN-G combined together through a plane-to-plane contact mode.

15.
Mikrochim Acta ; 185(1): 39, 2017 12 08.
Artigo em Inglês | MEDLINE | ID: mdl-29594453

RESUMO

Porous graphitic carbon nitride (g-C3N4) was prepared by a one-step acid etching and ultrasonication process. It is found that the strong blue fluorescence of g-C3N4 (with excitation/emission maxima at 320/400 nm) is fairly selectively quenched by uric acid (UA). The morphology and chemical structure of the nanoporous g-C3N4 were characterized by XRD, TEM and FTIR. Quenching studies and Stern-Volmer plots reveal two UA concentration ranges of different quenching efficiency. The first extends from 50 to 500 nM, the other from 0.5 to 10 µM. The limit of detection is 8.4 nM. The two quenching processes are attributed to both dynamic and static quenching. The porous g-C3N4 probes were applied to the determination of UA in (spiked) human serum and human plasma, and the results were as good as those obtained with UA standard solutions. These data illustrate that g-C3N4 can be used to selectively and sensitively quantify trace levels of UA even in a complex environment. Graphical abstract Porous graphite nitride carbon (g-C3N4) is shown to be a viable fluorescent probe for uric acid (UA) via both dynamic and static quenching. The electron transfer of carbon nitride is represented by the arrows; hν is the incident light; PL is the fluorescence emission.

16.
ACS Omega ; 2(3): 1063-1073, 2017 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-31457489

RESUMO

An effective strategy was developed to enhance the adaptability of graphene/silicone matrices under external stimuli by embedding nanoscale SiO2 into the graphene/silicone interfaces as a buffer layer. Chemically reduced graphene (rGE) was first covered by SiO2 using an in situ preparation, forming sandwichlike rGE/SiO2 (rGES). Then, rGES was integrated into methyl vinyl polysiloxane, followed by vulcanization, producing the final rGES/silicone rubber (SR) nanocomposite. Such interfacial modification actually built a rigid-flexible SiO2 buffer layer between rGE and polysiloxane. Obvious improvements were seen in both thermal and mechanical properties due to improved interfacial interaction. In a vulcanized rGES/SR system, the addition of 30 wt % rGES (3 wt % rGE) yielded a tensile strength of 6.13 MPa (up to 25 times that of the unmodified rGE in filled SR), a tear strength of 18.08 kN/m, and an elongation at break of 267%, several times higher than those of an rGE/SR nanocomposite. Thermal analysis results indicated that the initial decomposition temperature of rGES/SR containing 5 wt % rGES (0.5 wt % rGE) increased by more than 98 and 288 °C compared to that of SiO2/SR and rGE/SR, respectively. The rGES/polysiloxane matrices showed a tensile shear adhesive strength of 1.78 MPa when used as an adhesive for aluminum sheets, which is higher than that of the rGE/polysiloxane matrix (0.93 MPa).

17.
Se Pu ; 34(2): 130-9, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27382716

RESUMO

The optical absorption detector is one of the most commonly used detectors for high performance liquid chromatography (HPLC). As a core part of this kind of detector, the designs of flow cells, where light passes through samples for acquiring samples information, will affect the performance of a detector. In order to enhance the signal to noise ratio of detectors and reduce the bands broadening that come from flow cells, it is necessary to design a flow cell with a longer optical path length and a less cell volume while maintaining the luminous flux. However the limitations of the machining capacity make it difficult to increase the optical path length, reduce the cell volume and keep or increase the luminous flux simultaneously. It is a challenge to optimize the designing and machining of flow cells so as to improve the performance of detectors. This review discusses the development of designing flow cells based on the detection principle in some aspects of increasing the optical path length, reducing the cell volume, taking the advantages of total reflection and so on. At the same time, some of the designs are illustrated in detail. These various ideas and structures are significant references for designing flow cells and developing optical absorption detectors.

18.
Nanomaterials (Basel) ; 6(10)2016 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-28335305

RESUMO

A novel, simple and selective electrochemical method was investigated for the simultaneous detection of dopamine (DA) and uric acid (UA) on a poly(l-lysine)/graphene oxide (GO) modified glassy carbon electrode (PLL/GO/GCE) by differential pulse voltammetry (DPV). The electrochemically prepared PLL/GO sensory platform toward the oxidation of UA and DA exhibited several advantages, including high effective surface area, more active sites and enhanced electrochemical activity. Compared to the PLL-modified GCE (PLL/GCE), GO-modified GCE and bare GCE, the PLL/GO/GCE exhibited an increase in the anodic potential difference and a remarkable enhancement in the current responses for both UA and DA. For the simultaneous detection of DA and UA, the detection limits of 0.021 and 0.074 µM were obtained, while 0.031 and 0.018 µM were obtained as the detection limits for the selective detection of UA and DA, using DPV in the linear concentration ranges of 0.5 to 20.0 and 0.5 to 35 µM, respectively. In addition, the PLL/GO/GCE demonstrated good reproducibility, long-term stability, excellent selectivity and negligible interference of ascorbic acid (AA). The proposed modified electrode was successfully implemented in the simultaneous detection of DA and UA in human blood serum, urine and dopamine hydrochloride injection with satisfactory results.

19.
Small ; 11(43): 5833-43, 2015 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-26390018

RESUMO

Catalysts with low-cost, high activity and stability toward oxygen reduction reaction (ORR) are extremely desirable, but its development still remains a great challenge. Here, a novel magnetically separable hybrid of multimetal oxide, cobalt ferrite (CoFe2O4), anchored on nitrogen-doped reduced graphene oxide (CoFe2O4/NG) is prepared via a facile solvothermal method followed by calcination at 500 °C. The structure of CoFe2O4/NG and the interaction of both components are analyzed by several techniques. The possible formation of Co/Fe-N interaction in the CoFe2O4/NG catalyst is found. As a result, the well-combination of CoFe2O4 nanoparticles with NG and its improved crystallinity lead to a synergistic and efficient catalyst with high performance to ORR through a four-electron-transfer process in alkaline medium. The CoFe2O4/NG exhibits particularly comparable catalytic activity as commercial Pt/C catalyst, and superior stability against methanol oxidation and CO poisoning. Meanwhile, it has been proved that both nitrogen doping and the spinel structure of CoFe2O4 can have a significant contribution to the catalytic activity by contrast experiments. Multimetal oxide hybrid demonstrates better catalysis to ORR than a single metal oxide hybrid. All results make the low-cost and magnetically separable CoFe2O4/NG a promising alternative for costly platinum-based ORR catalyst in fuel cells and metal-air batteries.

20.
Nanoscale ; 7(32): 13619-28, 2015 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-26205788

RESUMO

Nowadays, biologically oxidizing graphitic materials is of great importance for practical applications as an eco-friendly and low-cost method. In this work, a bacterial strain is isolated from the contaminated soil in a graphite mine and its ability to oxidize graphite, graphene oxide (GO) and reduced graphene oxide (RGO) is confirmed. After being cultivated with bacteria, graphite is inhomogeneously oxidized, and moreover oxidized sheets exfoliated from graphite are detected in the medium. RGO shows a higher degree of oxidation compared to graphite owing to more original defects, while GO breaks into small pieces and becomes full of holes. Both the holes in GO and the exfoliated sheets from graphite caused by bacteria have a size of below 1 µm, in agreement with the size of bacterial cells. Besides, the preliminary mechanism of the bacterial oxidation is explored, suggesting that the contact between bacterial cells and materials promotes the oxidation of graphitic materials. The ability of naphthalene-degrading bacteria to oxidize and degrade the graphitic materials shows the potential for producing GO in an eco-friendly way and degrading carbon nanomaterials in the environment.


Assuntos
Bactérias/metabolismo , Grafite/química , Grafite/metabolismo , Nanoestruturas/química , Naftalenos/metabolismo , Biodegradação Ambiental , Desenho de Equipamento , Conformação Molecular , Nanoestruturas/ultraestrutura , Oxirredução , Microbiologia do Solo
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