Microchimica Acta - A highly sensitive thin-film pH micro-sensor has been fabricated by deposition of lead dioxide (β-PbO2) nanoparticles (NPs) on a planar gold electrode. The resulting pH... 相似文献
A novel method for the determination of Pb2+ with bismuth film electrodes (BFEs) based on magneto-voltammetry was investigated. In the presence of a 0.6?T external magnetic field, square wave voltammetry of Pb2+ was performed with BFEs. A high concentration of Fe3+ was added to the analytes to generate a large cathodic current during the preconcentration step. A Lorentz force from the flux of net current through the magnetic field resulted in convection. Then, more Pb2+ deposited onto the electrode and larger stripping peak currents were observed. BFEs that were prepared by simultaneously depositing the bismuth and Pb2+ on an electrode offered a mercury-free environment for this determination. This method exhibits a high sensitivity of 4.61?µA?µM?1 for Pb2+ over the 1?×?10?8 to 1?×?10?6?M range. A detection limit as low as 8.5?×?10?10?M was obtained with only 1-min preconcentration. The method was successfully applied to determine Pb2+ in real water samples. 相似文献
The arrays of gold nanoparticles (AuNPs) were fabricated on flexible and transparent single-walled carbon nanotube (SWCNT) films using the electrochemical deposition method, and the patterned nanotubes were then used as electrodes for hydroxylamine detection. The sizes and densities of the AuNPs could easily be controlled by varying the amount of charge deposited, and the gold-deposited area showed a homogeneous distribution on the exposed SWCNT film surface. X-ray diffraction analysis of the AuNPs shows a face-centered cubic structure that is dominated by the lowest energy {111} facets. The oxidation of the hydroxylamine on the AuNP-deposited SWCNT films depended strongly on the solution pH, and the maximum catalytic current was observed at a pH of 9.0. A linear electrical response was observed for concentrations ranging from 0.016 to 0.210 mM, and the detection limit and the sensitivity were 0.72 μM and 165.90 μAmM?1 cm?2, respectively. Moreover, the amperometric response in hydroxylamine showed a stable response for a long time (300 s), during which time it retained 94% of its initial value. In the long-term storage stability test, the current response to hydroxylamine decreased slightly, with only 17% leakage after 30 days. 相似文献
We report a route for synthesizing patterned carbon nanotube (CNT) catalysts through the microcontact printing of iron-loaded poly(styrene-block-acrylic acid) (PS-b-PAA) micellar solutions onto silicon wafers coated with thin aluminum oxide (Al(2)O(3)) layers. The amphiphilic block copolymer, PS-b-PAA, forms spherical micelles in toluene that can form quasi-hexagonal arrays of spherical PAA domains within a PS matrix when deposited onto a substrate. In this report, we dip a poly(dimethylsiloxane) (PDMS) molded stamp into an iron-loaded micellar solution to create a thin film on the PDMS features. The PDMS stamp is then put in contact with a substrate, and uniaxial compressive stress is applied to transfer the micellar thin film from the PDMS stamp onto the substrate in a defined pattern. The polymer is then removed by oxygen plasma etching to leave a patterned iron oxide nanocluster array on the substrate. Using these catalysts, we achieve patterned vertical growth of multiwalled CNTs, where the CNTs maintain the fidelity of the patterned catalyst, forming high-aspect-ratio standing structures. 相似文献
A carbon paste electrode that was chemically modified with multiwall carbon nanotubes and p-aminophenol was used as a selective electrochemical sensor for the simultaneous detection of hydroxylamine (HX) and phenol. Cyclic voltammetry, double potential-step chronoamperometry, square wave voltammetry (SWV), and electrochemical impedance spectroscopy were used to investigate the use of p-aminophenol in the carbon nanotubes paste matrixes as a mediator for the electrocatalytic oxidation of HX and phenol in aqueous solution. The coefficient of electron transfer and catalytic reaction rate constant were determined using the electrochemical methods. Under optimized conditions, the electrocatalytic oxidation current peaks for HX and phenol increased linearly with concentration in the range of 0.5-180.0 and 10.0-650.0 μmol/L for HX and phenol, respectively. The detection limits for HX and phenol were 0.15 and 7.1 μmol/L, respectively. The anodic potential peaks of HX and phenol were separated by 0.65 V in SWV. Because of good selectivity and sensitivity, the present method provides a simple method for the selective detection of HX and phenol in practical samples such as water samples. 相似文献
Monoshaped and monosized copper nanostructured particles have been prepared by potentiostatic electrochemical deposition on an ultrathin polypyrrole (PPY) film, electrochemically grown on a Si(100) substrate sputter-coated with a thin gold film or gold-film electrode (GFE). The crystal size and the number density of the copper nanocrystals have been examined by varying several deposition parameters, including the thickness of the gold film, the PPY film thickness, the applied potential, and the Cu2+ and the electrolyte concentrations for copper deposition. Optimal conditions for uniform growth ofnanocrystals well-dispersed on the GFE have been determined, along with insight into the mechanism of crystal growth. A minimum gold film thickness of 80 nm is required to eliminate the effects of the gold-silicon interface. The PPY film thickness and homogeneity principally affect the shape uniformity of the nanocrystals, while the copper deposition potential could be used to regulate the size and number density of the nanocrystals. Both the Cu2+ and electrolyte concentrations are also found to play important roles in controlling the electrodeposition of nanocrystal growth. 相似文献
Molecule-coated nanoparticles are hybrid materials which can be engineered with novel properties. The molecular coating of metal nanoparticles can provide chemical functionality, enabling assembly of the nanoparticles that are important for applications, such as biosensing devices. Herein, we report a new self-assembly of core-satellite gold nanoparticles linked by a simple amino acid l-Cysteine for biosensing of Cu2+. The plasmonic properties of core-satellite nano-assemblies were investigated, a new red shifted absorbance peak from about 600 to 800 nm was found, with specific wavelength depending on ratios with assembly of large and small gold nanoparticles. The spectral features obtained using surface-enhanced Raman spectroscopy (SERS) provided strong evidence for the assembly of the Cu2+ ions to the L-Cysteine molecules leading to the successful formation of the core-satellite Cu(l-Cysteine) complex on the gold surfaces. In addition, a linear relationship between the concentration of mediating Cu2+ and absorbance of self-assembled gold nanoparticles (GNPs) at 680 nm was obtained. These results strongly address the potential strategy for applying the functionalized GNPs as novel biosensing tools in trace detections of certain metal ions. 相似文献
Carbon nanotube-supported gold nanoparticles of different sizes (diameter of 3 or 20 nm) were evaluated as catalysts in four selected organic transformations. The nanohybrids were shown to efficiently catalyze the investigated reactions, regardless of the size of the supported gold nanoparticles. However, some differences were observed as regards turnover frequency values although size effect turned out to be less significant when only gold surface atoms were considered. 相似文献
The electrooxidation of carbon monoxide and methanol on Pt-coated Au nanoparticles attached to 3-aminopropyl trimethoxysilane-modified indium tin oxide electrodes was examined as a function of Pt film thickness and Au particle coverage. For the electrodes with medium and high Au particle coverages, the CO stripping peak position shifts to more negative values with increasing Pt film thickness, from ca. 0.8 V (vs Ag/AgCl) at 1 ML to 0.45 V at 10 ML. Accompanying this peak potential shift is the sharpening of the peak width from more than 150 to 65 mV. For the electrode with low Au particle coverage, similar peak width narrowing was also observed, but the peak potential shift is much smaller, from 0.85 V at 1 ML of Pt to 0.65 V at 10 ML. These observations are compared with the CO oxidation on bulk Pt electrodes and on Pt films deposited on bulk Au electrodes. The film-thickness-dependent CO oxidation is explained by d band theory in terms of strain and ligand effects, the particle size effect, and the particle aggregation induced by Pt film growth. Corresponding to the increasing CO oxidation activity, the current density of methanol oxidation grows with the Pt film thickness. The peak potential and current density reach the same values as those obtained on a polycrystalline bulk Pt electrode when more than 4 ML of Pt is deposited on the Au particle electrodes with a particle coverage higher than 0.25. These results suggest that it is feasible to reduce Pt loading in methanol fuel cells by using Pt thin films as the anode catalyst. 相似文献
Field-effect transistors were fabricated using high-density single-walled carbon nanotube (SWNT) thin films directly grown on suitable substrates. Such approach eliminated the variations of device behaviors in individual SWNT devices by utilizing a large number of SWNTs in each device. We have found that the behaviors of such devices are closely related to the surface charge densities around SWNTs in aqueous solutions. Adsorption of ionic surfactants on the surface could significantly modulate the device characteristics, which could be detected by measuring the conductance of the devices. The devices could be tuned to be sensitive to either anionic or cationic surfactants by tailoring the surface properties of SiO(2) substrates around SWNTs. This effect could be potentially used to design chemical and biological sensors. 相似文献
We report the implementation of three dimensionally cross-linked, organic nanodielectric multilayers as ultrathin gate dielectrics for a type of thin film transistor device that uses networks of single-walled carbon nanotubes as effective semiconductor thin films. Unipolar n- and p-channel devices are demonstrated by use of polymer coatings to control the behavior of the networks. Monolithically integrating these devices yields complementary logic gates. The organic multilayers provide exceptionally good gate dielectrics for these systems and allow for low voltage, low hysteresis operation. The excellent performance characteristics suggest that organic dielectrics of this general type could provide a promising path to SWNT-based thin film electronics. 相似文献
A method based on use of functionalized gold nanoparticles on polyethylenimine film has been developed for colorimetric detection of immunoglobulin G (IgG). The immunogold nanoparticles were immobilized on quartz slides by recognition between antibody and antigen, with the antigen chemically adsorbed on the polyethylenimine film. By measurement of the UV–visible spectra of the immobilized immunogold, detection of h-IgG was achieved. The detection limit for h-IgG by use of this method can be as low as 0.01 μg mL−1. This method is quite promising for numerous applications in immunoassay.
Figure 相似文献
DNA oligonucleotides were covalently immobilized to prepatterned single-walled carbon nanotube (SWNT) multilayer films by amidation. SWNT multilayer films were constructed via consecutive condensation reactions creating stacks of functionalized SWNT layers linked together by 4,4'-oxydianiline. Aminated- or carboxylated-DNA oligonucleotides were covalently immobilized to the respective carboxylated or aminated SWNT multilayer films through amide bond formation using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride. UV-vis-NIR spectroscopic analysis indicated that the SWNT film surface density increased uniformly according to the number of reaction cycles. Scanning electron microscopy and contact angle measurements of the SWNT multilayer film revealed a uniform coverage over the substrate surface. The covalent attachment of DNA oligonucleotides to the SWNT multilayer films and their subsequent hybridization with complementary oligonucleotides were verified using X-ray photoelectron spectroscopy and fluorescence-based measurements. This is the first report demonstrating that DNA oligonucleotides can be covalently attached to immobilized SWNT multilayer films. The anchored DNA oligonucleotides were shown to exhibit excellent specificity, realizing their potential in future biosensor applications. 相似文献
The effects of oxygen reactive ion etching (RIE) on the surface wettability of aligned carbon nanotube (CNT) films have been systematically investigated. It was found that 3 s of RIE treatment could change the surface of CNT films from hydrophobic to more hydrophilic. The degree of modification in the surface wettability of the film could be controlled by the flow rate of O2 gas during the RIE process. It is proposed that such a surface hydrophobicity change is related to the opened structure and functionalized tip of as-treated CNTs by oxygen reactive ions. More importantly, after the RIE treatment, focused laser pruning was utilized to trim the surface layer of treated CNTs and revert them back to a hydrophobic surface. Combined with the laser pruning technique and O2 RIE treatment, CNT templates with interlaced wettability surfaces in a stripe pattern have been fabricated. It has been demonstrated that this interlaced and structured wettability pattern can be used to selectively assemble microspheres or quantum dots on the aligned CNT films with desired patterns. 相似文献
The authors describe a method for the fabrication of a nanohybrid composed of carbon dots (C-dots) and gold nanoparticles (AuNPs) by in-situ reduction of C-dots and hydroauric acid under alkaline conditions. The process does not require the presence of surfactant, stabilizing agent, or reducing agent. The hybrid material was deposited in a glassy carbon electrode (GCE), and the modified GCE exhibited good electrocatalytic activity toward the oxidation of nitrite due to the synergistic effects between carbon dots and AuNPs. The findings were used to develop an amperometric sensor for nitrite. The sensor shows a linear response in the concentration range from 0.1 μmol?L-1 to 2 mmol?L-1 and a low detection limit of 0.06 μmol?L-1 at the signal-to-noise ratio of 3.
Graphical abstract Fabrication, characterization and electrochemical behavior of a glassy carbon electrode modifid with carbon dots and gold nanoparticles for sensing nitrite in lake water.
We report on a carbon nanotube (CNT) fiber microelectrode coated with palladium nanoparticles (PdNPs) and enabling electrochemical sensing of hydrogen peroxide (H2O2). The synergistic effects of the CNT fibers (good mechanical strength and large surface area) and of the PdNPs (high electrocatalytic activity) result in a microelectrode for H2O2 that exhibits a 2-s response time, a detection limit as low as 2 μM, a sensitivity of 2.75 A cm?2 M?1, and a linear response range from 2 μM to 1.3 mM (R?=?0.9994). The sensor is also selective and not interfered by potentially competing species in biological fluids, thus representing an inexpensive but highly sensitive and selective microsensor for H2O2.
Figure
Images ofthe palladium nanoparticle-coated carbon nanotube (PdNP/CNT) fiber microelectrode (left) and its amperometric response to hydrogen peroxide (H2O2) with different concentrations (right) 相似文献
A sensitive electrochemical sensor has been fabricated to detect ultratrace nitroaromatic explosives using ordered mesoporus carbon (OMC). OMC was synthesized and characterized by scanning electron microscopy, transmission electron microscopy and nitrogen adsorption/desorption measurements. Glassy carbon electrodes functionalized with OMC show high sensitivity of 62.7 μA cm−2 per ppb towards 2,4,6-trinitrotoluene (TNT). By comparison with other materials such as carbon nanotubes and ordered mesoporous silica, it is found that the high performance of OMC toward sensing TNT is attributed to its large specific surface area and fast electron transfer capability. As low as 0.2 ppb TNT, 1 ppb 2,4-dinitrotoluene and 1 ppb 1,3-dinitrobenzene can be detected on OMC based electrodes. This work renders new opportunities to detect ultratrace explosives for applications of environment protections and home securities against chemical warfare agents. 相似文献
We present a soft-lithography based method to fabricate plastic thin film fluidic devices on glass and plastic substrates. Principles of soft-lithography and spin casting were used to generate the films. The thickness of these films is controllable and the patterns we have generated have submicron scale dimensions. By using commercially available compact disc (CD) components as molds, we have been able to generate parallel line and cross patterns on these thin films. These patterned films could be lifted from the substrates and further folded into rolls. 相似文献