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排序方式: 共有155条查询结果,搜索用时 281 毫秒
71.
This paper reports a novel method for the rapid determination of vitamin B(12) concentration in a continuous-flow lab-on-a-chip system. This new method is based on luminol-peroxide chemiluminescence (CL) assays for the detection of cobalt(II) ions in vitamin B(12) molecules. The lab-on-a-chip device consisted of two passive micromixers acting as microreactors and a double spiral microchannel network serving as an optical detection region. This system could operate in two modes. In the first mode, samples are acidified and evaluated directly in the microchip. In the second mode, samples are treated externally by acidification prior to detection in the microchip. In the first mode, the linear range obtained was between 1.00 ng ml(-1) to 10 μg ml(-1), R(2) = 0.996, with a relative standard deviation (RSD) of 1.23 to 2.31% (n = 5) and a limit of detection (lod) of 0.368 pg ml(-1). The minimum sample volume required and the analytical time were 30 μl and 3.6 s, respectively. In the second mode, the linear range obtained was between 0.10 ng ml(-1) to 10 μg ml(-1), R(2) = 0.994, with the RSD of 0.90 to 2.32% (n = 6) and a lod of 0.576 pg ml(-1). The minimum sample and the analytical time required were 50 μl and 6 s, respectively. The lab on a chip working in mode II was successfully used for the determination of vitamin B(12) concentrations in nutritional supplemental tablets and hen egg yolks.  相似文献   
72.
Water scarcity and pollution rank equal to climate change as the most urgent environmental turmoil for the 21st century. To date, the percolation of textile effluents into the waterways and aquifer systems, remain an intricate conundrum abroad the nations. With the renaissance of activated carbon, there has been a steadily growing interest in the research field. Recently, the adoption of titanium dioxide, a prestigious advanced photo-catalyst which formulates the new growing branch of activated carbon composites for enhancement of adsorption rate and discoloration capacity, has attracted stern consideration and supports worldwide. Confirming the assertion, this paper presents a state of art review of titanium dioxide/activated carbon composites technology, its fundamental background studies, and environmental implications. Moreover, its major challenges together with the future expectation are summarized and discussed. Conclusively, the expanding of activated carbons composites material represents a potentially viable and powerful tool, leading to the plausible improvement of environmental conservation.  相似文献   
73.
A new ternary compound, Ce2PdGa10, has been synthesized using Ga flux and characterized by single-crystal X-ray diffraction. Ce2PdGa10 adopts a tetragonal structure in the I4/mmm space group and is isostructural to Ce2NiGa10. Lattice parameters are , , , and Z=2. The compound is metallic (dρ/dT>0), with the resistance decreasing roughly linearly with temperature from 300 to 175 K. The magnetic susceptibility of Ce2PdGa10 is consistent with local-moment paramagnetism and no long-range magnetic ordering occurs down to 2 K. A large positive magnetoresistance over 200% is observed at 2 K for fields of 9 T. In this paper, we present the structure and physical properties of Ce2PdGa10 and compared them to CePdGa6.  相似文献   
74.
Over the past couple of years, the resurgence of placing an effective and sustainable amendment to combat against the auxiliary industrial entities, remains a highly contested agenda from a global point. With the renaissance of activated carbon, there has been a steadily growing interest in the research field. Recently, the adoption of zeolite composite, a prestigious advanced catalyst which formulates the enhancement of adsorption rate and hydrogen storage capability, has fore fronted to be a new growing branch in the scientific community. Confirming the assertion, this paper presents a state of art review of activated carbon/zeolite composite technology, its fundamental background studies, and environmental implications. Moreover, its major challenges together with the future expectation are summarized and discussed. Conclusively, the expanding of activated carbon/zeolite composite represents a potentially viable and powerful tool, leading to the plausible improvement of environmental preservation.  相似文献   
75.
The synthesis and characterisation of a series of new rod-shaped liquid crystal (LC), 2-(4-alkyloxybenzylidenamino)benzothiazoles possessing even number of carbon atoms at the alkyloxy chain (CnH2n?+?1O-, n = 2, 4, 6, 8, 10, 12, 14, 16, 18) are reported. The molecular structures of title compounds were elucidated using FTIR and nuclear magnetic resonance spectroscopic techniques. The phase behaviour of these new compounds was characterised and studied by differential scanning calorimetry and polarising optical microscopy. Lower members (n = 2, 4 and 6) did not exhibit mesophase. Octyloxy derivative was monotropic LC. Enantiotropic smectic A phase was observed from n-decyloxy derivatives onward to the last homologous synthesised.  相似文献   
76.
    
Pyridinium (the protonated form of pyridine) and related compounds have been proposed to be promising homogenous electrocatalysts in the electrochemical reduction of CO2 to methanol due to the low overpotential required to achieve faradaic yields of about 20 %, although the percentage yields vary dramatically between different research groups. In this study, experimental conditions were varied during the electrolysis of CO2 at a platinum electrode in the presence of pyridinium to determine the reasons for the discrepancies in the yields of methanol reported between different research groups. Two other vitamin-based and environmentally friendly nitrogen-containing heterocyclic compounds (nicotinamide and nicotinic acid) which have structural similarities to the promising but toxic pyridine homogeneous electrocatalyst, were also investigated as alternative electrocatalysts for the reduction of CO2 in aqueous acidic media. Cyclic voltammetry studies suggest that nicotinamide and nicotinic acid (forms of vitamin B3) follow a similar reaction mechanism as pyridine in the reduction of CO2. Relatively low faradaic yields of methanol were obtained during controlled potential electrolysis experiments for all the electrocatalysts (0.4–1.9 %) which can be attributed to the low solubility of CO2 along with the competing hydrogen evolution reaction. It was found that adventitious sources of methanol were responsible for greatly inflating the apparent yields of methanol unless scrupulous care was taken in controlling the experimental conditions. The problem with background methanol is particularly difficult to control due to the electrochemical reactions typically generating products in the parts per million range, considerably lower than normal synthetic reactions.  相似文献   
77.
    
For the advancement of electrochemical energy conversion and storage technologies, bifunctional electrocatalysts are crucial for efficiently driving both the oxygen evolution (OER) and reduction reactions (ORR). Cobalt-based spinel oxides are a class of promising bifunctional electrocatalysts. However their low electrical conductivity and stability may hinder further improvement. A novel composite material composed of NiCo2O4 nanoparticles integrated with emerging two dimensional MXene nanosheets (NiCo2O4/MXene) was developed. The successful integration of NiCo2O4 with MXene brings about a number of attractive structural features. This includes synergistic effects between NiCo2O4 and MXene, highly accessible surface areas, complete exposure of numerous active sites, and excellent electronic conductivity, all of which collectively contribute to the desirability of composite material for OER and ORR. The synthesized NiCo2O4/MXene composite showed extraordinary OER electrocatalytic activity with a lower overpotential of 360 mV at a current density of 10 mA/cm2, and a small Tafel slope of 64 mV/dec compared to NiCo2O4, MXene and NiCo2O4+MXene (physically mixed). Additionally, NiCo2O4/MXene displays an ORR limiting current density of −4 mA/cm2 and exhibited highest onset potential and half wave potential of 0.92 V and 0.72 V vs. RHE, respectively, for the ORR in alkaline media compared to NiCo2O4, MXene and NiCo2O4+MXene (physically mixed).  相似文献   
78.
Foo ML  Horike S  Kitagawa S 《Inorganic chemistry》2011,50(23):11853-11855
The synthesis and characterization of [Ba(HBTB)] is reported. This is the first porous framework synthesized with barium using carboxylate ligands. The framework has robust microporous character (Langmuir surface area of 879 m(2) g(-1)) and possesses unsaturated metal sites when fully desolvated.  相似文献   
79.
Ring borylation of [Me4C2(eta5-C5H4)2CrCO] by B(C6F5)3 affords the zwitterionic complex {Me4(eta5-C5H4)(eta5-C4H3B(C6F5)3)}CrH(CO) (1), the first structurally characterized bent-metallocene complex of Cr(4+). This species decomposes thermally to the zwitterionic species {Me4(eta5-C5H4)(eta5-C4H3B(C6F5)3)}Cr (2) and the ionic species [Me4C2(eta5-C5H4)2CrCO][HB(C6F5)3] (3). The molecular structure of 2 is also described.  相似文献   
80.
CMOS sensors are becoming a powerful tool in the biological and chemical field. In this work, we introduce a new approach on quantifying various pH solutions with a CMOS image sensor. The CMOS image sensor based pH measurement produces high-accuracy analysis, making it a truly portable and user friendly system. pH indicator blended hydrogel matrix was fabricated as a thin film to the accurate color development. A distinct color change of red, green and blue (RGB) develops in the hydrogel film by applying various pH solutions (pH 1–14). The semi-quantitative pH evolution was acquired by visual read out. Further, CMOS image sensor absorbs the RGB color intensity of the film and hue value converted into digital numbers with the aid of an analog-to-digital converter (ADC) to determine the pH ranges of solutions. Chromaticity diagram and Euclidean distance represent the RGB color space and differentiation of pH ranges, respectively. This technique is applicable to sense the various toxic chemicals and chemical vapors by situ sensing. Ultimately, the entire approach can be integrated into smartphone and operable with the user friendly manner.  相似文献   
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