基于新型二氧化锰-碳纳米管复合材料的高灵敏过氧化氢传感器

本文以多壁碳纳米管(MWCNTs)和KMnO4为原料,通过直接氧化还原反应合成了一种新型MnO2-C纳米复合材料,将其滴涂在玻碳(GC)电极表面,成功制备出一种非酶型H2O2传感器。采用循环伏安法和计时电流法研究了该传感器对H2O2的电催化氧化行为。实验结果表明,与GC电极和MWCNTs修饰电极相比,该电极对H2O2氧化显示出更好的催化活性。实验对影响电极性能的各种参数,包括pH值、工作电位及MnO2-C修饰量进行了探讨。在最佳实验条件下,传感器对H2O2响应的线性范围为5.0×10-7～0.2mol·L-1,检测限(S/N=3)为1.4×10-7 mol·L-1。该传感器选材新颖,制备方法简单,重现性好,稳定性和抗干扰能力强。     

Preparation of Core–Shell Nanofibers with Selectively Localized CNTs from Shish Kebab‐like Hierarchical Composite Micelles

A novel and facile bottom‐up strategy for preparing core‐shell nanofibers with selectively localized carbon nanotubes is developed using hierarchical composite micelles of crystalline‐coil copolymer and carbon nanotubes as the building blocks. An amphiphilic di‐block copolymer of poly (p‐dioxanone) (PPDO) and PEG (polyethylene glycol) functionalized with pyrene moieties at the chain ends of PPDO blocks (Py‐PPDO‐b‐PEG) is designed for constructing composite micelles with multiwalled carbon nanotubes (MWCNTs). The self‐assembly of Py‐PPDO‐b‐PEG and MWCNTs is co‐induced by the crystallization of PPDO blocks and the π–π stacking interactions between pyrene moieties and MWCNTs, resulting in composite micelles with “shish kebab”‐like nanostructure. A mixture of composite micelles and polyvinyl alcohol (PVA) water solution is then used as the spinning solution for preparing electrospun nanofibers. The morphologies of the nanofibers with different composition are investigated by SEM and TEM. The results suggest that the MWCNTs selectively localized in the core of the nanofibers of MWCNTs/Py‐PPDO‐b‐PEG/PVA. The alignment and interfusion of composite micelles during the formation of nanofibers may confine the carbon nanotubes in the hydrophobic core region. In contrast, the copolymer without pyrene moieties cannot form composite micelles, thus these nanofibers show selective localization of MWCNTs in the PVA shell region.

     

Adsorption of TCDD molecule onto CNTs and BNNTs: Ab initio van der Waals density-functional study

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCCD) is one of the most dangerous compounds that infect the environment and hence its removal is crucial for safety in human life. In this work, we have investigated the interaction of TCDD with boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs) by using the density functional theory (DFT) calculations. Our first-principles results have been validated by experiment and also other theoretical values for the similar system. The adsorption energies for TCDD molecule on the BNNTs and CNT are calculated. It was found that TCDD adsorption ability of BNNT is slightly stronger than that of CNT and TCDD molecule prefers to be adsorbed on BNNTs with molecular axis parallel to the tube axis. The results obtained indicate that TCDD is weakly bound to the outer surface of all the considered nanotubes and the obtained adsorption energy values and binding distance are typical for the physisorption. We also evaluated the influence of curvature and introduced defects on the TCDD adsorption ability of BNNTs. Furthermore, we have analyzed the electronic structure and charge population for the energetically most favorable complexes and the results indicate that no significant hybridization between the respective orbitals of the two entities was accomplished.     

钛基底的纳米金刚石掺混纳米碳管的场发射特性

在纳米金刚石场发射的基础上, 研究了纳米金刚石掺混纳米碳管的场发射特性。采用电泳沉积法形成了纳米金刚石与纳米碳管的复合涂层, 经热处理后制备出阴极样品, 然后进行微观表征, 再进行场发射特性测试与发光测试。结果表明, 与未掺混的纳米金刚石阴极样品相比, 复合涂层阴极样品的场发射开启电场明显减小, 场发射电流提高, 在较低的电场下阳极表面荧光粉就可以发光, 但发光不均匀, 出现了"边沿发光"的现象。分析了纳米金刚石掺混纳米碳管场发射性能提高的机理, 是由于纳米碳管掺入之后, 涂层的电子输运能力得到增强, 涂层中有效发射体的数目增加。最后, 解释了"边沿发光"现象的成因。     

Development and application of carbon nanotubes assisted electromembrane extraction (CNTs/EME) for the determination of buprenorphine as a model of basic drugs from urine samples

In this work carbon nanotubes assisted electromembrane extraction (CNTs/EME) coupled with capillary electrophoresis (CE) and ultraviolet (UV) detection was developed for the determination of buprenorphine as a model of basic drugs from urine samples. Carbon nanotubes reinforced hollow fiber was used in this research. Here the CNTs serve as a sorbent and provide an additional pathway for solute transport. The presence of CNTs in the hollow fiber wall increased the effective surface area and the overall partition coefficient on the membrane; and lead to an enhancement in the analyte transport. For investigating the influence of the presence of CNTs in the SLM on the extraction efficiency, a comparative study was carried out between EME and CNTs/EME methods. Optimization of the variables affecting these methods was carried out in order to achieve the best extraction efficiency. Optimal extractions were accomplished with NPOE as the SLM, with 200 V as the driving force, and with pH 2.0 in the donor and pH 1.0 in the acceptor solutions with the whole assembly agitated at 750 rpm after 25 min and 15 min for EME and CNTs/EME, respectively.     

Assemble-Electrodeposited Ultrathin Conducting Poly(Azure A) at a Carbon Nanotube-Modified Glassy Carbon Electrode, and its Electrocatalytic Properties to the Reduction of Nitrite

A new type of ultrathin conducting polymer/carbon nanotubes (UCP/CNTs) nanomaterials with high catalytic surface area was proposed in this work. The electrode covered with an ultrathin layer of poly(azure A)/carbon nanotubes nanomaterials was fabricated by two steps: firstly, the single-wall carbon nanotubes (SCNTs) modified glassy carbon (GC) electrode was immersed in an azure A solution to assemble a thin azure A monomer film. Secondly, the assembled AA was electropolymerized in a phosphate buffer solution by cyclic voltammetry (CV). The electrocatalytic activity of the obtained ultrathin conducting poly(azure A)/carbon nanotubes (UCPAA/CNTs) nanomaterials was tested using sodium nitrite. The results showed thus prepared electrode exhibited excellent electrocatalytic behavior to the reduction of nitrite and facilitates the detection of nitrite at an applied reduction peak potential of 0.1 V. A linear range from 3.0 μM to 4.5 mM for the detection of sodium nitrite has been observed with fast response (within 3 s) and a detection limit of 1.0 μM based on a signal-to-noise ratio of 3.     

A new cataluminescence gas sensor based on SiO2 nanotubes fabricated using carbon nanotube templates

In the present work, two morphologies of SiO₂ nanomaterials (SiO₂ nanotubes and nanoparticles) have been successfully synthesized in supercritical fluids (SCFs). The cataluminescence (CTL) features of the two SiO₂ nanomaterials to some common harmful gases were compared, and the results showed that SiO₂ nanotubes had better CTL sensing characteristic to some common harmful gases. The SiO₂ nanotubes not only had uniform size and shape with a high specific surface area, but also exhibited superior sensitivity and selectivity to ethyl acetate vapor. Using the SiO₂ nanotubes as sensing material, a CTL sensor for ethyl acetate vapor was developed. The proposed sensor showed high sensitivity and specificity to ethyl acetate at optimal temperature of 293 °C, a wavelength of 425 nm and a flow rate of 345 mL/min. With a detection limit of 0.85 ppm, the linear range of CTL intensity versus concentrations of ethyl acetate vapor was 2.0-2000 ppm. None or only very low levels of interference were observed while the foreign substances such as acetone, acetaldehyde, acetic acid, formaldehyde, ammonia, ethanol, benzene and methanol were passing through the sensor. This method allows rapid determination of gaseous ethyl acetate at workshop.     

Laboratorial diagnosis of paracoccidioidomycosis and new insights for the future of fungal diagnosis

Paracoccidioidomycosis (PCM) is the most prevalent mycosis in Latin-America. As for other mycosis, its importance of has been largely underestimated, partially due to the limited geographical distribution of the etiologic fungal agent (Paracoccidioides brasiliensis). However, the advent of AIDS and other immune suppressing conditions is creating an emergent need for improved diagnostic tests envisaging simpler, cheaper, faster and more sensitive and accurate detection of pathogenic fungi, especially those causing systemic and opportunistic diseases. Routine laboratorial diagnosis of PCM disease relies mainly on direct observation of the fungus. However, culture growing is slow and, too often, definite diagnosis can only be obtained at later growing stages. Immunodiagnosis is also widely employed, although usually cumbersome and complex. Enzyme-based immunoassays are more amenable to automation for high-throughput testing, but may lead to cross-reactivity with other fungi. Plus, molecular diagnosis relying on polymerase-chain reaction (PCR) and nucleic-acid hybridization, although still at early stages of application to routine diagnosis of P. brasiliensis, has triggered the development of techniques for its improved specific detection, thus contributing for epidemiological studies as well. In the future, microarrays and newer biosensing technologies, coupled to new bionanotechnological tools, will certainly improve diagnosis of PCM and other mycosis through very specific and sensitive pathogen biomolecular detection.     

Temperature and carbon source effects on methane–air flame synthesis of CNTs

We have conducted experimental and numerical studies on flame synthesis of carbon nanotubes (CNTs) to investigate the effects of three key parameters – selective catalyst, temperature and available carbon sources – on CNT growth. Two different substrates were used to synthesize CNTs: Ni-alloy wire substrates to obtain curved and entangled CNTs and Si-substrates with porous anodic aluminum oxide (AAO) nanotemplates to grow well-aligned, self-assembled and size-controllable CNTs, each using two different types of laminar flames, co-flow and counter-flow methane–air diffusion flames. An appropriate temperature range in the synthesis region is essential for CNTs to grow on the substrates. Possible carbon sources for CNT growth were found to be the major species CO and those intermediate species C₂H₂, C₂H₄, C₂H₆, and methyl radical CH₃. The major species H₂, CO₂ and H₂O in the synthesis region are expected to activate the catalyst and help to promote catalyst reaction.