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排序方式: 共有379条查询结果,搜索用时 15 毫秒
1.
    
The simultaneous promotion in mechanical and electrical properties of rigid polyurethane (RPU) is an important task for expanding potential application. In this work, carbon fibers (CFs) reinforced RPU composites were prepared with the goal of improving mechanical and electrical properties. Metallized CFs meet our performance requirements and can be easily achieved via electrodeposition. However, the weak bonding strength in fiber‐metal‐RPU interface restricts their application. Inspired by the reducibility and wonderful adhesion of dopamine (DA), we proposed a new and efficient electrochemical method to fabricate metallized CFs, where DA polymerization was simultaneously integrated coupled with the reduction of metal ions (Ni2+). The characterization results helped us to gain insight about the reaction mechanism, which was never reported as far as we know. Compared with pure RPU, the tensile, interlaminar shear and impact strength of polydopamine (PDA)‐nickel (Ni) modified CFs/RPU composites were improved by 11.2%, 21.0%, and 78.0%, respectively, which attributed to the strong interfacial adhesion, including mechanical interlocking and chemical crosslinking between treated CFs and RPU. In addition, the PDA‐Ni surface treatment method also affected the dispersion of short CFs in the RPU, which increased the possibility of conductor contact and reduced insulator between fibers networks, resulting in higher electrical conductivity.  相似文献   
2.
    
Dopamine (DA) plays an essential role in the central nervous, renal, hormonal and cardiovascular systems. Various modified carbon nanotubes (CNT)-based dopamine sensors have been reported, but inexpensive, highly sensitive plain CNT-based ones are seldom studied. In this work, a facile and inexpensive CNT-based DA sensor is made by rich-defect multi-walled carbon nanotubes (RD-CNT) via an ultrasound method. The defect and elemental states of the RD-CNT are systematically studied by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), Raman spectroscopy, X-ray powder diffraction (XRD) and X-ray-photoelectron spectroscopy (XPS). Results show that massive holes and cracks exist in RD-CNT. The level of defects increases from the additional exposed edges. The electrochemical characterizations indicate that the electrochemical sensor has the highest sensitivity of 438.4 μA/(μM ⋅ cm2) among all carbon materials-based DA sensors while well meeting the clinically required detection range and selectivity. The DA sensor was further used to detect live healthy human serum and live PC12 cells with satisfactory results, thus holding great promise for an inexpensive but sensitive DA sensor in practical applications of clinical diagnosis and biological research.  相似文献   
3.
    
One-dimensional Ni/Au/PPy-COOH nanowires with multiple segments were synthesized in this study. Smooth surfaces and magnetic properties of nanowires were investigated by scanning transmission electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), and Electron Spin Resonance (ESR) techniques. The nanowires were used to modify the screen-printed electrode surface and as a micro-environment for Trametes versicolor laccase. The ability of this enzyme biosensor to detect dopamine change in human biological samples was demonstrated by a wide linear range (0.01–50 μM) and a low LOD (2.265 nM). In addition, the biosensor exhibited excellent selectivity allowing the detection of dopamine in the presence of ascorbic acid, uric acid, L-Cys, serotonin, and glucose, with high sensitivity of reduction currents obtained at −0.2 V (vs. Ag/AgCl). The proposed biosensor allowed the detection of dopamine in commercial serum and artificial urine with recovery values close to 100 %. It also demonstrated reproducibility, reusability, and long-term storage stability. The sensitivity, Kmapp, and Imax values of the biosensor were determined as 2.05 μM and 1.03 μA, respectively. The LAC-Ni/Au/PPy-COOH/NAF/SPE biosensor is a reliable design for detecting dopamine with a wide linear range.  相似文献   
4.
    
Despite all the attempts to create advanced hemoglobin (Hb)‐based oxygen carriers (HBOCs) employing an encapsulation platform, major challenges including attaining a high Hb loading and long circulation times still need to be overcome. Herein, the fabrication, for the first time, of nanoparticles fully made of Hb (Hb‐NPs) employing the electrospray technique is reported. The Hb‐NPs are then coated by antioxidant and self‐polymerized poly(dopamine) (PDA) to minimize the conversion of Hb into nonfunctional methemoglobin (metHb). The PDA shell is further functionalized with poly(ethylene glycol) (PEG) to achieve stealth properties. The results demonstrate that the as‐prepared Hb‐NPs are hemo‐ and biocompatible while offering antioxidant protection and decreasing the formation of metHb. Additionally, decoration with PEG results in decreased protein adsorption onto the Hb‐NPs surface, suggesting a prolonged retention time within the body. Finally, the Hb‐NPs also preserve the reversible oxygen‐binding and releasing properties of Hb. All in all, within this study, a novel HBOCs with high Hb content is fabricated and its potential as an artificial blood substitute is evaluated.  相似文献   
5.
A set of integrated end-column amperometric detection system has been developed,onto which an electrophoresis microchip can be conveniently integrated.Finely machined by a piece of transparent organic glass,the system consists of an electrophoresis microchip platform and an amperometric detection reservoir,in which the microchip can be fixed onto the platform by microchip grooves and with stainless steel fixture.Each detection electrode can be directly fixed in the amperometric detection reservoir by screws...  相似文献   
6.
2-巯基乙醇自组装膜电极对多巴胺电催化氧化及其分析应用   总被引:12,自引:0,他引:12  
张修华  王升富 《分析化学》2002,30(11):1312-1315
在裸金电极上制备了 2 巯基乙醇自组装膜电极 (ME AuSAMs) ,研究了多巴胺 (DA)在ME AuSAMs上的电化学行为 ,发现该膜电极对DA的氧化具有良好的电催化作用 ,氧化过电位降低了 3 94mV ,测得DA的扩散系数D为 9.1 4 5× 1 0 - 7cm2 s,初步探讨了电催化机理。采用水平衰减全反射 傅里叶变换红外光谱 (ATR FTIR)技术对ME AuSAMs进行了表征 ;方波伏安法 (squarewavevoltammetry ,SWV)测定DA ,其氧化峰电流与DA浓度在 2 .0 0× 1 0 - 6 ~ 1 .0 0× 1 0 - 4 mol L范围内呈线性关系 ;相关系数为 0 .9998,检出限为 4 .0 0× 1 0 - 7mol L。该电极用于DA药物针剂的测定 ,结果满意  相似文献   
7.
Summary Methylphenidate (MP) binds to the cocaine binding site on the dopamine transporter and inhibits reuptake of dopamine, but does not appear to have the same abuse potential as cocaine. This study, part of a comprehensive effort to identify a drug treatment for cocaine abuse, investigates the effect of choice of calculation technique and of solvent model on the conformational potential energy surface (PES) of MP and a rigid methylphenidate (RMP) analogue which exhibits the same dopamine transporter binding affinity as MP. Conformational analysis was carried out by the AM1 and AM1/SM5.4 semiempirical molecular orbital methods, a molecular mechanics method (Tripos force field with the dielectric set equal to that of vacuum or water) and the HF/6-31G* molecular orbital method in vacuum phase. Although all three methods differ somewhat in the local details of the PES, the general trends are the same for neutral and protonated MP. In vacuum phase, protonation has a distinctive effect in decreasing the regions of space available to the local conformational minima. Solvent has little effect on the PES of the neutral molecule and tends to stabilize the protonated species. The random search (RS) conformational analysis technique using the Tripos force field was found to be capable of locating the minima found by the molecular orbital methods using systematic grid search. This suggests that the RS/Tripos force field/vacuum phase protocol is a reasonable choice for locating the local minima of MP. However, the Tripos force field gave significantly larger phenyl ring rotational barriers than the molecular orbital methods for MP and RMP. For both the neutral and protonated cases, all three methods found the phenyl ring rotational barriers for the RMP conformers/invertamers (denoted as cte, tte, and cta) to be: cte, tte> MP > cta. Solvation has negligible effect on the phenyl ring rotational barrier of RMP. The B3LYP/6-31G* density functional method was used to calculate the phenyl ring rotational barrier for neutral MP and gave results very similar to those of the HF/6-31G* method.  相似文献   
8.
A glassy carbon electrode (GCE) was modified with electropolymerized films of amidosulfonic acid in pH 7.0 phosphate buffer solution (PBS) by cyclic voltammetry (CV). The modified electrode showed an excellent electrocatalytical effect on the oxidation of dopamine (DA). In pH 7.0 PBS, the anodic peak current increased linearly with the concentration of DA in the range of 5.0×10–7 1.0×10–4moldm–3, with a correlation coefficient of 0.9932, and a detection limit (S/N=3) of 1.0× 10–7moldm–3. The relative standard deviation of 10 successive scans was 2.5% for 1.0×10–6moldm–3 DA. The interference of ascorbic acid (AA) with the determination of DA could be eliminated because of the very distinct attracting interaction between DA cations and the negatively poly(amidosulfonic acid) film in pH 7.0 PBS. The proposed method exhibited good recovery and reproducibility.  相似文献   
9.
A facile, economic and green one‐step hydrothermal synthesis route using dopamine as source towards photoluminescent carbon nanoparticles (CNPs) is proposed. The as‐prepared CNPs have an average size about 3.8 nm. The emission spectra of the CNPs are broad, ranging from approximately 380 (purple) to approximately 525 nm (green), depending on the excitation wavelengths. Due to the favorable optical properties, the CNPs can readily enter into A549 cells and has been used for multicolor biolabeling and bioimaging. Most importantly, the as‐prepared CNPs contain distinctive catechol groups on their surfaces. Due to the special response of catechol groups to Fe3+ ions, we further demonstrate that such wholly new CNPs can serve as a very effective fluorescent sensing platform for label‐free sensitive and selective detection of Fe3+ ions and dopamine with a detection limit as low as 0.32 μM and 68 nM , respectively. The new “mix‐and‐detect” strategy is simple, green, and exhibits high sensitivity and selectivity. The present method was also applied to the determination of Fe3+ ions in real water samples and dopamine in human urine and serum samples successfully.  相似文献   
10.
《Analytical letters》2012,45(5):311-321
Abstract

The catecholamines and related biological amines have been converted to trimethylsilyl ether-amide derivatives through a two-step reaction sequence. All hydroxyl groups (phenolic and alcohol) were converted to TMSi ethers by reaction with TSIM. N-acylimidazole was added to the reaction mixture to effect the acylation of primary and secondary amines. TMSi-Ac (trimethylsilyl ether-acetyl) and TMSi-HFB (trimethylsilyl ether-heptafluorobutyryl) derivatives were studied. The HFB derivatives had excellent GLC properties. It is proposed to compare the sensitivity of detection of these and related compounds by flame ionization and by electron capture detection systems.  相似文献   
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