RESUMO
Retraction of 'Aqueous aerobic oxidation of alkyl arenes and alcohols catalyzed by copper(II) phthalocyanine supported on three-dimensional nitrogen-doped graphene at room temperature' by Mojtaba Mahyari et al., Chem. Commun., 2014, 50, 7855-7857, https://doi.org/10.1039/C4CC01406E.
RESUMO
[This corrects the article DOI: 10.1039/C3RA44696D.].
RESUMO
Achieving an efficient catalyst in the ATRP system with a simple design, preparation from available materials, and high recyclability is a significant challenging issue. To attain the goal, herein, we used chitosan (CS)-modified cellulose filter paper (FP) as a green support for the synthesis of dip catalyst. The preparation of this catalyst involved surface treatment of the FP strips by CS coating through a dipping method, which increased the affinity of the substrate for adsorbing copper ions in the next step. The Cu@CS-FP catalyst was prepared without the requirement of any ligands. The synthesized dip-catalyst, in the form of the strips, was employed for the first time in the ATRP reaction of methyl methacrylate to assay catalytic activity. Catalytic insertion/ removal (ON/OFF) experiments were carried out during the polymerization. A reasonable control over the molecular weight with high conversion (68%) and polydispersity index of 1.32 under mild reaction conditions were obtained. Significantly, because of the facile separation of the catalyst, the amount of copper that remained in the polymer was very low (2.7 ppm). Also, the recyclability of the catalyst was investigated for five runs. The conversion in the final run was 64% without a loss of catalyst efficiency.
RESUMO
A novel ammonia (NH3) chemical sensor is presented with ultra-high response, good selectivity, fast response, and long-term stability using detecting layer of polyaniline/cupric oxide nanoparticles supported on three-dimensional nitrogen-doped graphene-based frameworks (PANI/CuO@3D-NGF) nanocomposite. The NH3 gas sensing response of the PANI/CuO@3D-NGF nanocomposite was studied by resistivity method in low concentration range of 50 ppb-100 ppm at room temperature. The PANI/CuO@3D-NGF nanocomposite was prepared through in situ polymerization of PANI on the CuO@3D-NGF with a high surface area. Morphological and structural analysis revealed that the ultrathin 3D interconnected graphene substrate maximizes the surface area. It is also shown that the CuO nanoparticles offer active adsorption sites for free NH3 molecule. The PANI/CuO@3D-NGF nanocomposite gas sensor shows the response of 930% to 100 ppm NH3 with an outstanding low detection limit of 50 ppb and an average response time of 30 s at room temperature. The excellent sensing performance of the PANI/CuO@3D-NGF nanocomposite was attributed to 3D interconnected porous structure, remarkable enhancement of charge carriers as a result of CuO@3D-NGF, and modified π-interactions between molecules. Graphical abstract.
RESUMO
In this paper, we presented the fabrication and properties of new ammonia (NH3) sensors with sensitive layer of nickel nanoparticles decorated on three-dimensional nitrogen-doped graphene-based frameworks/polyaniline (NiNPs@3D-(N)GFs/PANI) hybrid. The hybrid are synthesized through in-situ oxidative polymerization on flexible thin substrate. Synergetic behavior between both components manifested outstanding sensitivity (750.2 at 1000â¯ppm NH3) and quick response (95â¯s) and recovery (25â¯s) times and a lower limit of detection (~â¯45â¯ppb) at room temperature. The sensitivity of NiNPs@3D-(N)GFs/PANI hybrid sensor was shown to be about 14 times more than its of pure PANI sensor at 1000â¯ppm of NH3. The excellent sensitivity of the as-prepared hybrid is mainly originated from the substantial rise of hole-like carriers by NiNPs@3D-(N)GFs as well as improved inter-molecule interactions via π- π electron networks. The obtained results revealed significant advantages for the synthesized hybrid sensor, making it a suitable choice for real-world applications of NH3 detection.
RESUMO
Introducing a new class of chiral selectors is an interesting work and this issue is still one of the hot topics in separation science and chirality. In this study, for the first time, sulfated maltodextrin (MD) was synthesized as a new anionic chiral selector and then it was successfully applied for the enantioseparation of five basic drugs (amlodipine, hydroxyzine, fluoxetine, tolterodine, and tramadol) as model chiral compounds using CE. This chiral selector has two recognition sites: a helical structure and a sulfated group which contribute to three corresponding driving forces; inclusion complexation, electrostatic interaction, and hydrogen binding. Under the optimized condition (buffer solution: 50 mM phosphate (pH 3.0) and 2% w/v sulfated MD; applied voltage: 18 kV; temperature: 20°C), baseline enantioseparation was observed for all mentioned chiral drugs. When instead of sulfated MD neutral MD was used under the same condition, no enantioseparation was observed which means the resolution power of sulfated MD is higher than neutral MD due to the electrostatic interaction between sulfated groups and protonated chiral drugs. Also, the countercurrent mobility of negatively charged MD (sulfated MD) allows more interactions between the chiral selector and chiral drugs and this in turn results in a successful resolution for the enantiomers. Furthermore, a higher concentration of neutral MD (approximately five times) is necessary to achieve the equivalent resolution compared with the negatively charged MD.
Assuntos
Eletroforese Capilar/métodos , Preparações Farmacêuticas/análise , Preparações Farmacêuticas/química , Polissacarídeos/química , Anlodipino/análise , Ânions , Compostos Benzidrílicos/análise , Soluções Tampão , Cresóis/análise , Eletroforese Capilar/instrumentação , Fluoxetina/análise , Concentração de Íons de Hidrogênio , Hidroxizina/análise , Fenilpropanolamina/análise , Fosfatos , Espectroscopia de Infravermelho com Transformada de Fourier , Estereoisomerismo , Sulfatos/química , Temperatura , Tartarato de Tolterodina , Tramadol/análiseRESUMO
We are introducing graphene oxide modified with amine groups as a new solid phase for extraction of heavy metal ions including cadmium(II), copper(II), nickel(II), zinc(II), and lead(II). Effects of pH value, flow rates, type, concentration, and volume of the eluent, breakthrough volume, and the effect of potentially interfering ions were studied. Under optimized conditions, the extraction efficiency is >97 %, the limit of detections are 0.03, 0.05, 0.2, 0.1, and 1 µg L(-1) for the ions of cadmium, copper, nickel, zinc, and lead, respectively, and the adsorption capacities for these ions are 178, 142, 110, 125, and 210 mg g(-1). The amino-functionalized graphene oxide was characterized by thermogravimetric analysis, transmission electron microscopy, scanning electron microscopy, and Fourier transform infrared spectrometry. The proposed method was successfully applied in the analysis of environmental water and food samples. Good spiked recoveries over the range of 95.8-100.0 % were obtained. This work not only proposes a useful method for sample preconcentration but also reveals the great potential of modified graphene as an excellent sorbent material in analytical processes.
Assuntos
Monitoramento Ambiental , Poluentes Ambientais/análise , Metais Pesados/análise , Cádmio/análise , Cobre/análise , Análise de Alimentos/métodos , Contaminação de Alimentos/estatística & dados numéricos , Grafite/química , Microscopia Eletrônica de Transmissão , Níquel/análise , Extração em Fase Sólida/métodos , Espectrofotometria Atômica , Poluentes Químicos da Água/análiseRESUMO
Copper(ii) tetrasulfophthalocyanine supported on three-dimensional nitrogen-doped graphene-based frameworks was synthesized and introduced as a bifunctional catalyst for selective aerobic oxidation of alkyl arenes and alcohols to the corresponding carbonyl compounds. The ease of catalyst separation, high turnover, low catalyst loading and recyclability could potentially render it applicable in industrial setting.
RESUMO
The ordered carbohydrate-derived porous carbons (OC-DPCs) were first functionalized with thiol groups (-SH) and then immobilized with gold nanoparticles (AuNPs). The Au-SH-OC-DPCs were characterized by CHN analysis, transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD). The Au-SH-OC-DPCs were applied for the fabrication of a new electrochemical sensor. The electrocatalytic capabilities of the new sensor were tested by the oxidation of nicotinamide adenine dinucleotide (NADH) in a 0.1 M Robinson buffer solution (pH 7.0) using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and differential pulse voltammetry (DPV). The Au-SH-OC-DPCs showed a good voltammetric performance in the electrochemical detection of NADH with a low detection limit (1.0 nM), high sensitivity (4.934 µA/µM), and wide linear concentration range (5.0 nM-10 µM).
Assuntos
Carbono/química , Técnicas Eletroquímicas/instrumentação , Ouro/química , Nanopartículas Metálicas/química , NAD/análise , Técnicas Biossensoriais/instrumentação , Eletrodos , Limite de Detecção , Oxirredução , PorosidadeRESUMO
Graphene oxide-cobalt phthalocyanine (GO-PcCo) hybrid material as a new electrocatalyst was synthesized and used successfully to fabrication of new biosensor for the electrooxidation of l-cysteine (CSH) in aqueous media. Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) images revealed that cobalt phthalocyanine is covalently attachment on graphene oxide sheets as single layers GO-PcCo. Cyclic voltammetric studies showed that the GO-PcCo/glassy carbon electrode (GO-PcCo/GCE) improves electrochemical behavior of CSH oxidation, as compared to the GO and PcCo. In addition, the results indicated that GO and PcCo have a synergic effect in the electrooxidation of CSH. The catalytic oxidation responses were studied and the reaction mechanisms were discussed. The electrocatalytic behavior is further developed as a new detection scheme for CSH by chronoamperometry method and under optimized conditions, excellent analytical features, including high sensitivity and selectivity, low detection limit and satisfactory dynamic range, were achieved.
Assuntos
Técnicas Biossensoriais/métodos , Cisteína/isolamento & purificação , Grafite/química , Óxidos/química , Carbono/química , Cisteína/química , Eletroquímica , Indóis/química , Limite de Detecção , Compostos Organometálicos/química , Oxirredução , Água/químicaRESUMO
A Passerini-type condensation for the synthesis of α-acyloxycarboxamides starting from simple and readily available inputs, including an isocyanide, aldehydes and water in the presence of trimethylsilyl azide as a catalyst under reflux conditions in toluene in good yields, is described.
Assuntos
Amidas/síntese química , Amidas/química , Ácidos Carboxílicos/química , Cromatografia Gasosa-Espectrometria de Massas , Espectroscopia de Ressonância MagnéticaRESUMO
In this work, two novel isocyanide-based multicomponent reactions of 1,2-diamine compounds with diketene have been developed as efficient strategies for the synthesis of 2,3,4,5-tetrahydro-1H-benzo[b][1,4]diazepine-2-carboxamides with regiochemical control and 1,6-dihydropyrazine-2,3-dicarbonitriles in good to excellent yields at ambient temperature.