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1.
J Colloid Interface Sci ; 562: 224-234, 2020 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-31838358

RESUMO

The increasing demand of rare earth elements in agriculture and industry raises the potential environmental pollution with their inevitable toxicity and biological accumulation. It is necessary to develop an efficient and low-cost technique to effectively remove rare earth elements. N-doped carbon dots (CDs) were green-synthesized using one-pot domestic microwave oven and novel alginate composite (ALG@CDs) beads were fabricated by embedding the N-doped CDs into pure alginate hydrogel beads. The synthetic materials were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and zeta potential measurement. The ALG@CDs beads could effectively adsorb rare earth elements from aqueous solutions. Taking the adsorption of rare earth element Gd (III) as an example, initial concentration, adsorbent dosage, pH, temperature and contact time were optimized. The adsorption isotherms and kinetics fitted to Langmuir isotherm model (R2 > 0.9991) and pseudo-second-order kinetic model (R2 = 0.9918), respectively. The adsorption capacity of ALG@CDs-3 (201.21 mg/g) for Gd (III) was much higher than that of bare ALG beads (124.38 mg/g) according to the maximum theoretical adsorption capacity of Langmuir model. Competitive adsorption results indicated that ALG@CDs beads had stronger affinity to Gd (III) than to Al (III), Co (II), Ni (II), Zn (II), and Mg (II). The adsorbent could be easily collected and reused for five adsorption-regeneration cycles. The results indicated that the fabricated ALG@CDs beads are the promising materials for adsorption or enrichment of rare earth elements from waste water.

2.
Chirality ; 31(11): 917-922, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31456270

RESUMO

A three-dimensional molecularly imprinted overoxidized polypyrrole/MnO2 /carbon felt (MIOPPy/MnO2 /CF) composites were fabricated, which results in increased active area of the surface of the molecularly imprinted polymers film and greatly improved electrochemical chiral recognition effect for tryptophan isomers. The composites were characterized by field emission scanning electron microscope, transmission electron microscope, X-ray diffractometer, UV-visible spectra, N2 adsorption-desorption isotherms, and electrochemical methods. The manuscript provides a proof of concept and shows promising potential of the prepared composites for chiral recognition.

3.
Talanta ; 202: 520-525, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31171216

RESUMO

A rapid, cost-effective and quencher-free fluorescence-based analytical method for sensitive detection of l-cysteine (Cys) based on 2-aminopurine (2-AP) labeled DNA probe and exonuclease I (Exo I) activity was developed. 2-AP labeled DNA probe includes two thymine (T)-T mismatches, which can bind with Hg2+ to form T-Hg2+-T pairing bases, resulting in stable hairpin with five base pairs in its stem. The target Cys can remove Hg2+ from the stem of the hairpin probe based on the high affinity of Cys with Hg2+, leading to the unfolding of the hairpin probe. At last, by adding Exo I, the resulted single-stranded DNA (ssDNA) will be digested to release free 2-AP with strong fluorescence. Under the optimal conditions, the sensing system exhibited a good and wider linear range from 0.4 to 400 nM (R2 = 0.997) and a detection limit as low as 0.16 nM for Cys. Furthermore, other amino acids without reductive sulfur group did not generate obvious change in fluorescence signals. Finally, the sensor can be used in diluted real samples with a good recovery rate, showing promising application in food, environmental and medical analysis.


Assuntos
2-Aminopurina/química , Cisteína/análise , Sondas de DNA/química , Fluorescência , Conformação de Ácido Nucleico
4.
ACS Appl Mater Interfaces ; 11(3): 2840-2848, 2019 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-30584765

RESUMO

A new molecularly imprinted SiO2 (MISiO2) film on the surface of indium tin oxide (ITO) electrode was prepared by the sol-gel method and was then applied successfully in the electrochemical chiral recognition of tryptophan (Trp) isomers. Owing to the high chemical stability, excellent rigidity, and low cost, the resultant sol-gel SiO2 is a good matrix material for molecular imprinting. Nonionic surfactant cicosaethylene glycol hexadecyl ether (Brij58) arranged directionally on the surface of the hydrophobic ITO electrode possesses a large amount of oxygen-containing functional groups and may induce the accumulation of template molecules (L-Trp) on the surface of ITO, resulting in L-MISiO2/ITO after the removal of L-Trp templates by calcination. The characterizations of the L-MISiO2/ITO reveal that the L-Trp templates could be successfully removed from the matrix, producing complementary cavities within the L-MISiO2/ITO. The resultant L-MISiO2/ITO exhibits greatly higher affinity toward L-Trp than D-Trp due to the three-point interaction mechanism, and therefore it exhibits good chiral recognition ability for the Trp isomers. In addition, the as-prepared L-MISiO2/ITO or D-MISiO2/ITO (D-Trp as the templates) can predict the ratio of L- and D-isomers in racemic mixture. Last, the MISiO2 films exhibited quick binding kinetics and good recognition reproducibility.

5.
Food Chem ; 256: 358-366, 2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-29606460

RESUMO

In this study, magnetic zeolitic imazolate framework-8 (Fe3O4@ZIF-8) was successfully synthesized by a typical hydrothermal method. The facile magnetic solid-phase extraction (MSPE) based on Fe3O4@ZIF-8 was proposed for concentrating polymer additives (antioxidants and ultraviolet absorbers). The conditions of MSPE process were optimized. An analytical method of magnetic solid-phase extraction followed by high performance liquid chromatography (MSPE-HPLC) was successfully established for the simultaneous determination of seven polymer additives in drinks and foods packed with plastic. The established method showed good precision, reproducibility, stability, and accuracy with the low limits of detection (0.03-0.15 ng/mL) and limits of quantification (0.08-0.50 ng/mL). The results of this study indicated the Fe3O4@ZIF-8 coupled with HPLC provided an efficient enrichment and determination method for polymer additives in drinks and foods.


Assuntos
Bebidas/análise , Cromatografia Líquida de Alta Pressão/métodos , Embalagem de Alimentos/instrumentação , Magnetismo/métodos , Plásticos/análise , Polímeros/análise , Extração em Fase Sólida/métodos , Iogurte/análise , Contaminação de Alimentos/análise , Plásticos/isolamento & purificação , Polímeros/isolamento & purificação , Reprodutibilidade dos Testes , Zeolitas/química
6.
ACS Appl Mater Interfaces ; 9(4): 3677-3685, 2017 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-28071045

RESUMO

Novel Bi2Te3/graphene quantum dots (Bi2Te3/GQDs) hybrid nanosheets with a unique structure that GQDs are homogeneously embedded in the Bi2Te3 nanosheet matrix have been synthesized by a simple solution-based synthesis strategy. A significantly reduced thermal conductivity and enhanced powder factor are observed in the Bi2Te3/GQDs hybrid nanosheets, which is ascribed to the optimized thermoelectric transport properties of the Bi2Te3/GQDs interface. Furthermore, by varying the size of the GQDs, the thermoelectric performance of Bi2Te3/GQDs hybrid nanostructures could be further enhanced, which could be attributed to the optimization of the density and dispersion manner of the GQDs in the Bi2Te3 matrix. A maximum ZT of 0.55 is obtained at 425 K for the Bi2Te3/GQDs-20 nm, which is higher than that of Bi2Te3 without hybrid nanostrucure. This work provides insights for the structural design and synthesis of Bi2Te3-based hybrid thermoelectric materials, which will be important for future development of broadly functional material systems.

7.
Phys Chem Chem Phys ; 17(9): 6406-14, 2015 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-25656925

RESUMO

Metal nanoparticles embedded in hollow materials are important due to their wide applications in catalysis. In this work, we disclosed a nontraditional synthetic pathway to prepare silica hollow nanospheres by hydrothermal treatment in the presence of compressed CO2. Especially, the silica hollow nanospheres with an outer diameter of about 16 nm and an inner pore size of 7 nm were obtained using 1.0 MPa CO2. The formation mechanism of silica hollow nanospheres induced by CO2 was investigated by high-pressured UV/Vis spectroscopy. Moreover, gold nanoparticles (2.5 nm) embedded in the silica hollow nanospheres were prepared by a one-pot synthesis using HAuCl4 as a precursor. The current synthetic route of nano-catalysts was simple and facile, in which no etching agent was needed in the process of the hollow material preparation. Besides, this nano-catalyst showed an excellent catalytic performance in epoxidation of styrene with high conversion (82.2%) and selectivity (90.2%) toward styrene oxide, as well as in the selective oxidation of ethylbenzene with good conversion (26.6%) and selectivity (87.8%) toward acetophenone. Moreover, the Au nanoparticles (AuNPs) embedded in silica hollow nanospheres exhibited an excellent recyclability in both the oxidation reactions.


Assuntos
Dióxido de Carbono/química , Ouro/química , Nanopartículas Metálicas , Dióxido de Silício/química , Catálise , Microscopia Eletrônica de Transmissão , Oxirredução
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