Films consisting of pristine multi-walled carbon nanotubes (MWCNTs) and nitrogen-doped MWCNTs (N-MWCNTs) were fabricated by means of chemical vapor deposition and chemically decorated with gold nanoparticles (AuNPs). Optical microscopy and image analysis reveal that the deposited AuNPs have diameters of 50–200 nm and 100–400 nm, respectively. The AuNP-modified films of MWCNTs and of N-MWCNTs were initially investigated with respect to their response to the ferro/ferricyanide redox system. The N-MWCNTs/AuNPs exhibit lower detection limit (0.345 μM) for this redox system compared to that of MWCNTs/AuNPs (0.902 μM). This is probably due to the presence of nitrogen that appears to enhance the electrocatalytic activity of MWCNTs. The findings demonstrate that the electrochemical responses of both films are distinctly enhanced upon deposition of AuNPs on their surfaces. The detection limits of MWCNTs/AuNPs and N-MWCNTs/AuNPs systems are lower by about 43 % and 27 %, respectively, compared to films not modified with AuNPs. The electrocatalytic activity of the films towards the oxidation of ascorbic acid (AA), uric acid (UA), and dopamine (DA) was studied. The findings reveal that N-MWCNTs/AuNPs represent a powerful analytical tool that enables simultaneous analysis of AA, UA, and DA in a single experiment.
Figure
Films consisting of pristine and nitrogen-doped multi-walled carbon nanotubes were fabricated, decorated with gold nanoparticles, and their electrocatalytic activity towards oxidation of ascorbic acid, uric acid, and dopamine was investigated. An enhanced electrocatalytic activity was observed on modified nitrogen-doped carbon nanotubes, where all biomolecules can be simultaneously analyzed. 相似文献
Three different forms of carbon, i.e., multi-walled carbon nanotubes (CNTs), single-walled CNTs, and soot, were decorated
with gold nanoparticles by a new method. In this method C10H8− ions transfer electrons to the CNTs or soot. These electrons on the carbon surface can then reduce Au3+ species to form supported Au nanoparticles with a narrow particle size distribution. Thermogravimetric/differential thermal
analyses (TG/DTA), XRD, Raman, and TEM show that naphthalene molecules remain trapped inside the Au nanoparticles and can
only be removed by treatment at ca. 300 °C. Remarkable effect of the Au nanoparticles on the oxidation of carbon by O2 is also observed by TG/DTA, i.e., on-set oxidation temperature and activation energy (Ea). It is shown that as the Au particle size decreases from 25 to 2 nm a linear decrease of the oxidation temperature is observed.
Au particles larger than 25 nm do not produce any significant effect on carbon oxidation. These results are discussed in terms
of spillover catalytic effect where Au nanoparticles activate O2 molecules to produce active oxygen species which oxidize the different carbon supports. 相似文献
A novel glassy carbon electrode (GCE) modified with a composite film of poly (4-vinylpyridine) (P4VP) and multiwalled carbon nanotubes (P4VP/MWCNT GCE) was used for the voltammetric determination of paracetamol (PCT). This novel electrode displayed a combined effect of P4VP and MWCNT on the electro-oxidation of PCT in a solution of phosphate buffer at pH 7. Hence, conducting properties of P4VP along with the remarkable physical properties of MWCNTs might have combined effects in enhancing the kinetics of PCT oxidation. The P4VP/MWCNT GCE has also demonstrated excellent electrochemical activity toward PCT oxidation compared to that with bare GCE and MWCNT GCE. The anodic peak currents of PCT on the P4VP/MWCNT GCE were about 300 fold higher than that of the non-modified electrodes. By applying differential pulse voltammetry technique under optimized experimental conditions, a good linear ratio of oxidation peak currents and concentrations of PCT over the range of 0.02–450 μM with a limit of detection of 1.69 nM were achieved. This novel electrode was stable for more than 60 days and reproducible responses were obtained at 99% of the initial current of PCT without any influence of physiologically common interferences such as ascorbic acid and uric acid. The application of this electrode to determine PCT in tablets and urine samples was proposed. 相似文献
Binding of gold nanoparticles (Au-NP) at amine-functionalised multi-walled carbon nanotubes (MWNTs) is proposed. The MWNTs are functionalised with acylchloride groups, which further react with ethylenediamine to form amine-functionalised MWCNTs. These amines are able to bind preformed colloidal Au-NPs. The Au/MWNT composite material facilitates electron-transfer reactions with free-diffusing redox compounds. 相似文献
Poly(ethylene terephthalate) (PET)/multi-walled carbon nanotube (MWCNT) nanocomposites were prepared by three different methods: in-situ polymerization technique (I-S), direct mixing in the melt (DM) and dilution of a 0.5 wt.% masterbatch, synthesized via in-situ polymerization, using melt mixing (MB). The morphology of the resulting nanocomposites was examined using scanning and transmission electron microscopy and their electrical properties were characterized by ac conductivity measurements. The I-S series of samples exhibited an extremely low electrical percolation threshold (pc ≈ 0.06 wt.%), as compared to values of similar systems previously mentioned in literature. The MB series showed a comparable pc value (pc: 0.05-0.10 wt.%), whereas the investigation revealed a higher pc in the DM series (pc: 0.10-0.20 wt.%). Finally, selected concentrations of samples were prepared using OH-functionalized MWCNT, following the I-S procedure. The conductivity of these samples was found to be lower than that of samples with non-functionalized MWCNT. 相似文献
Multiwalled carbon nanotubes with nanosized sputtered gold were used to modify a glassy carbon electrode (GCE). The substrate was characterized by scanning electron microscopy (SEM), X-ray diffraction, cyclic voltammetry and amperometry. SEM micrographs indicated an uniform coverage of the carbon nanotubes with nanosized (poly)crystalline gold. Cyclic voltammetry reveals that peak separation of the unmodified GCE in the presence of 1?mM ferricyanide is 131?mV, but 60?mV only for the modified GCE. In addition, the oxidation of NADH (1?mmol?L?1 solution) begins at negative potentials (around ?100?mV vs. Ag/AgCl), and the anodic peak potential (corresponding to the irreversible oxidation of NADH) is found at +94?mV. The effect of pH on the electrocatalytic activity was studied in the range from 5.4 to 8.0. The relationship between the anodic peak potential and the pH indicated a variation of ?33.5?mV/pH which is in agreement with a two-electron and one-proton reaction mechanism. Amperometry, performed at either ?50 or +50?mV vs. an Ag/AgCl reference electrode, indicates that the modified electrode is a viable amperometric sensor for NADH. At a working potential of +50?mV, the response to NADH is linear in the concentration range from 1 to 100???mol?L?1, with an RSD of 6% (n?=?4).
Figure
Multiwalled carbon nanotubes with nanosized sputtered gold were used to modify a glassy carbon electrode. The oxidation of NADH (1?mmol?L?1) begins at negative potentials (around ?100?mV vs. Ag/AgCl), and the anodic peak potential (corresponding to the irreversible oxidation of NADH) is found at +94?mV. 相似文献
An aromatic azo-polymer, poly(thiourea-azo-sulfone)(PTAS), has been prepared using 4-(4-aminophenylsulfonyl)benzenamine and diazonium salt solution of 2,6-diaminopyridine. PTAS was easily processable using polar solvents and had high molar mass 63 × 103g mol 1according to GPC. Mechanically and thermally stable and electrically conducting polymer/CNTs nano-composites were obtained via melt processing technique. Fine distribution of CNTs in a polymer matrix performed an essential role in the preparation of polymer/CNTs nano-composites based on interfacial interaction between CNTs and polymer matrix. Scanning electron micrographs showed good dispersion of filler and adhesion of matrix on the surface of nanotubes. Accordingly, increasing the amount of CNTs from 0.1 wt% to 5 wt% increased the electrical conductivity from 2.99 S cm 1to 3.56 S cm 1. Mechanical strength of functional nanotubes-based hybrids was enhanced from 43.22 MPa to 65.02 MPa compared with that of hybrids with non-functional filler in matrix 37.21 MPa. A rapport between nanotube loading and thermal stability of the materials was also observed. 10% gravimetric loss temperature was increased from 528 °C to 578 °C, while glass transition was improved from 241 °C to 271 °C. Adding up of small quantity of functional CNTs strongly affected the tensile, electrical and thermal properties of materials. Improvement of the physical properties of CNT-reinforced polymer nano-composites was ascribed to the melt processing technique. 相似文献
A supported carbon material is shown to be a highly efficient, eco-friendly and recyclable solid acid catalyst for the Biginelli reaction of aldehyde, β-ketoester and urea or thiourea under microwave irradiation in the absence of solvent. This method offers significant advantages such as efficiency, the excellent yield, avoidance of the organic solvents, mild reaction conditions, easy separation and simple operation. In addition, because of employing microwave as heating source and reducing use of organic solvents, this novel method emerges as a green-approach leading to less harmful residues. Furthermore, a mechanism was proposed to rationalize the reaction and the role of NiO–MWCNTs was also investigated in these transformations. 相似文献
Poly(aniline-co- o-anisidine) (P(An-co- o-As)) ionomers and poly(sodium 4-styrenesulfonate) (PSS) were layer-by-layer (LbL) assembled on carboxylic acid-functionalized multiwalled carbon nanotubes (MWNTs). The multilayered polyelectrolyte greatly enhanced the dispersibility and stability of MWNTs in aqueous solutions. More importantly, the nanocomposites showed 3 orders of magnitude of conductivity increase, 4.2 S/cm, compared to that of neat ionomers, 0.004 S/cm. The deposition procedure was monitored with zeta (zeta) potential changes. Fourier transform infrared (FT-IR), ultraviolet-visible (UV-vis), and Raman spectra confirmed charge transfer from the quinoid units of the P(An-co- o-As) to MWNTs, which effectively delocalize the electrons. Further, we explored the pH response of the assembled P(An-co- o-As)/PSS/MWNTs multilayer nanocomposites. The sharp transition of the conductivity in the pH range of 2 to 6 makes the nanocomposites promising candidates for chemical-biological sensing. 相似文献
Biodegradable poly(butylene succinate) (PBSU)/functional multi-walled carbon nanotubes (f-MWNTs) nanocomposite were prepared by melt compounding. Nonisothermal crystallization and subsequent melting behavior, isothermal crystallization kinetics, spherulitic morphology, and crystal structure of neat PBSU and its nanocomposite were studied by differential scanning calorimetry, optical microscopy and wide angle X-ray diffraction in detail. The presence of f-MWNTs has a significant heterogeneous nucleation effect on the crystallization and morphology of PBSU, resulting in that the crystallization is enhanced during both nonisothermal and isothermal crystallization in the nanocomposite. Moreover, the crystal structure of PBSU is not modified by f-MWNTs in the nanocomposite. The thermogravimetric analysis illustrates an improvement in thermal stability of PBSU by around 10 °C in the presence of f-MWNTs compared with that of neat PBSU. 相似文献
Multi-walled carbon nanotube decorated with silver nanoparticles (AgNPs-MWCNT) is used as an effective strategy for modification of the surface of pyrolytic graphite electrode (PGE). This modification procedure improved colloidal dispersion of the decorated MWCNTs in water, affording uniform and stable thin films for altering the surface properties of the working electrode. Robust electrode for sensing applications is obtained in a simple solvent evaporation process. The electrochemical behavior of sumatriptan (Sum) at the bare PGE and AgNPs-MWCNT modified PGE is investigated. The results indicate that the AgNPs-MWCNT modified PGE significantly enhanced the oxidation peak current of Sum. A remarkable enhancement in microscopic area of the electrode together with strong adsorption of Sum on the surface of the modified electrode resulted in a considerable increase in the peak current of Sum. Experimental parameters, such as scan rate, pH, accumulation conditions and amount of the modifier used on the PGE surface are optimized by monitoring the CV responses toward Sum. It is found that a maximum current response can be obtained at pH 7.4 after accumulation at open circuit for 150 s. Further experiments demonstrated that the oxidative peak currents increased linearly with Sum concentration in the range of 8.0 × 10−8-1.0 × 10−4 mol L−1 with a detection limit of 4.0 × 10−8 mol L−1. The modified electrode showed high sensitivity, selectivity, long-term stability and remarkable voltammetric reproducibility in response to Sum. These excellent properties make the prepared sensor suitable for the analysis in pharmaceutical and clinical preparations. The modified electrode was successfully applied for the accurate determination of trace amounts of Sum in pharmaceutical preparations. 相似文献
Gold nanoparticles on the surface of multi-walled carbon nanotubes with glassy carbon electrode were prepared using electrochemical synthesis method. The thin films of gold Nanoparticles/multi-walled carbon nanotubes were characterized by scanning electron microscopy, powder X-ray diffraction, and cyclic voltammetry. Electrochemical behavior of adrenaline hydrochloride at gold nanoparticles/multi-walled carbon nanotube modified glassy carbon electrode was investigated. A simple, sensitive, and inexpensive method for determination of adrenaline hydrochloride was proposed. 相似文献
We describe a nanostructured immunosensor for the cardiovascular biomarker netrin 1. A glassy carbon electrode was consecutively modified with multi-walled carbon nanotubes (MWCNTs), nafion (to retain the MWCNTs), thionine-coated gold nanoparticles (Thi@AuNPs), and monoclonal antibodies against netrin 1. The modified electrode was characterized by transmission electron microscopy, cyclic voltammetry, differential pulse voltammetry, UV-visible spectrophotometry and X-ray diffraction. The presence of Thi@AuNPs warrants direct and convenient immobilization of the antibody. This immunoelectrode enables netrin 1 to be determined, best at a voltage of −300 mV (vs. SCE), with a limit of detection of 30 fg mL−1 (at an S/N ratio of 3) after a 50 min incubation time. The detection range extends from 0.09 to 1800 pg∙mL−1. The method is simple, sensitive, specific and reproducible. We presume this stable and reproducible biosensor to be useful for the early detection of cardiovascular diseases.