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Biomedical subjects

Yuehe Lin

Publications and source records attributed to Yuehe Lin.

At least 37 records · Page 2Linked to original sources
PubMed2005

Platinum/Carbon nanotube nanocomposite synthesized in supercritical fluid as electrocatalysts for low-temperature fuel cells.

Carbon nanotube (CNT)-supported Pt nanoparticle catalysts have been synthesized in supercritical carbon dioxide (scCO(2)) using platinum(II) acetylacetonate as metal precursor. The structure of the catalysts has been characterized with transmission electron micrograph (TEM) and X-ray photoelectron spectroscopy (XPS). TEM images show that the platinum particles' size is in the range of 5-10 nm. XPS analysis indicates the presence of zero-valence platinum. The Pt-CNT exhibited high catalytic activity both for methanol oxidation and oxygen reduction reaction. The higher catalytic activity has been attributed to the large surface area of carbon nanotubes and the decrease in the overpotential for methanol oxidation and oxygen reduction reaction. Cyclic voltammetric measurements at different scan rates showed that the oxygen reduction reaction at the Pt-CNT electrode is a diffusion-controlled process. Analysis of the electrode kinetics using Tafel plot suggests that Pt-CNT from scCO(2) provides a strong electrocatalytic activity for oxygen reduction reaction. For the methanol oxidation reaction, a high ratio of forward anodic peak current to reverse anodic peak current was observed at room temperature, which implies good oxidation of methanol to carbon dioxide on the Pt-CNT electrode. This work demonstrates that Pt-CNT nanocomposites synthesized in supercritical carbon dioxide are effective electrocatalysts for low-temperature fuel cells.

Journal Article↗
PubMed2005

Enzyme nanoparticles-based electronic biosensor.

A simple and effective method to prepare an enzyme electronic biosensor by immobilizing enzyme nanoparticles directly onto the gold electrode surface is described; prepared horseradish peroxidase nanoparticles have been successfully used to develop reagentless electronic biosensors for H2O2 detection without promoters and mediators and offer great potential to develop enzyme-based electronic biosensors.

Biosensing Techniques↗
PubMed2005

Ultrasensitive voltammetric detection of trace heavy metal ions using carbon nanotube nanoelectrode array.

We describe an ultrasensitive voltammetric detection of trace heavy metal ions using nanoelectrode arrays (NEAs) that are based on low-site density carbon nanotubes (CNTs). The NEAs were prepared by sealing the side-walls of CNTs with an epoxy passive layer that reduces the current leakage and eliminates the electrode capacitance, leading to a low background current. This provides a high signal-to-noise ratio. The CNTs-NEAs coated with a bismuth film were used successfully for voltammetric detection of trace cadmium(II) and lead(II) at the sub-ppb level. The detection limit of 0.04 microg L(-1) was obtained under optimum experimental conditions. The attractive behavior of the new carbon NEA sensing platform holds great promise for onsite environmental monitoring and biomonitoring of toxic metals.

Electrochemistry↗
PubMed2005

Novel hybrid materials with high stability for electrically switched ion exchange: carbon nanotube-polyaniline-nickel hexacyanoferrate nanocomposites.

A novel and stable carbon nanotube-polyaniline-nickel hexacyanoferrate nanocomposite film has been synthesized by the electrodeposition method, and the feasibility for removing radioactive caesium through an electrically switched ion exchange process using the nanocomposite film has been evaluated in a mixture containing NaNO3 and CsNO3.

Journal Article↗
PubMed2005

Incorporation of hydroxypyridinone ligands into self-assembled monolayers on mesoporous supports for selective actinide sequestration.

In this study, three isomers of hydroxypyridinones (1,2-HOPO, 3,2-HOPO, and 3,4-HOPO) were attached to self-assembled monolayers on mesoporous silica (SAMMS). The HOPO-SAMMS materials have superior solid adsorbents properties: they do not suffer from solvent swelling; their rigid, open pore structure allows rapid sorption kinetics; their extremely high surface area enables the installation of high functional density; and being silica-based, they are compatible with vitrification into a final vitreous waste form. Kinetics, equilibrium, and selectivity of the adsorptions of actinide on the HOPO-SAMMS at various pH values and in the presence of other metal cations, anions, and competing ligands are reported. Rapid sequestration of U(VI), Np(V), and Pu(IV) was observed. Very little competition from transition metal cations and common species was observed.

Adsorption↗
PubMed2005

Actinide sequestration using self-assembled monolayers on mesoporous supports.

Surfactant templated synthesis of mesoporous ceramics provides a versatile foundation upon which to create high efficiency environmental sorbents. These nanoporous ceramic oxides condense a huge amount of surface area into a very small volume. The ceramic oxide interface is receptive to surface functionalization through molecular self-assembly. The marriage of mesoporous ceramics with self-assembled monolayer chemistry creates a powerful new class of environmental sorbent materials called self-assembled monolayers on mesoporous supports (SAMMS). These SAMMS materials are highly efficient sorbents whose interfacial chemistry can be fine-tuned to selectively sequester a specific target species, such as heavy metals, tetrahedral oxometalate anions, and radionuclides. Details addressing the design, synthesis, and characterization of SAMMS materials specifically designed to sequester actinides, of central importance to the environmental cleanup necessary after 40 years of weapons-grade plutonium production, as well as evaluation of their binding affinities and kinetics are presented.

Actinoid Series Elements↗
PubMed2005

Carbon nanotubes (CNTs) for the development of electrochemical biosensors.

Carbon nanotube (CNT) is a very attractive material for the development of biosensors because of its capability to provide strong electrocatalytic activity and minimize surface fouling of the sensors. This article reviews our recent developments of oxidase- and dehydrogenase-amperometric biosensors based on the immobilization of CNTs, the co-immobilization of enzymes on the CNTs/Nafion or the CNT/Teflon composite materials, or the attachment of enzymes on the controlled-density aligned CNT-nanoelectrode arrays. The excellent electrocatalytic activities of the CNTs on the redox reactions of hydrogen peroxide, nicotinamide adenine dinucleotide (NADH), and homocysteine have been demonstrated. Successful applications of the CNT-based biosensors reviewed herein include the low-potential detections of glucose, organophosphorus compounds, and alcohol.

Alcohols↗
PubMed2005

Hydroxypyridinone functionalized self-assembled monolayers on nanoporous silica for sequestering lanthanide cations.

1,2-Hydroxypyridinone (1,2-HOPO) ligands were installed as self-assembled monolayers on nanoporous silica (MCM-41) to create a superior class of sorbent materials for lanthanide cations. Lanthanides were used as a model system for the radioactive, expensive, and highly hazardous actinides in preliminary screening studies. The ligand properties of the 1,2-HOPO ligand field and the extremely large surface area of MCM-41, coupled with the dense monolayer coating, contribute to the extremely high lanthanide binding capacity of the 1,2-HOPO nanoporous sorbent. At pH 4-5.9, the mass-weighted partition coefficients (Kd) for La, Nd, Eu, and Lu were 354,000, 344,000, 210,800, and 419,800, respectively. The rigid, open pore structure of the silica also allows for very rapid sorption. Being silica-based, the sorbent is compatible with vitrification processing into a final glasseous waste form, for subsequent disposition in a deep geological repository.

Cations↗
PubMed2005

Supercritical fluid attachment of palladium nanoparticles on aligned carbon nanotubes.

Nanocomposite materials consisting of Pd nanoparticles deposited on aligned multi-walled carbon nanotubes have been fabricated through hydrogen reduction of palladium-beta-diketone precursor in supercritical carbon dioxide. The supercritical fluid processing allowed deposition of high-density Pd nanoparticles (approximately 5-10 nm) on both as-grown (unfunctionalized) and functionalized (using HNO3 oxidation) nanotubes. However, the wet processing for functionalization results in pre-agglomerated, bundle-shaped nanotubes, thus significantly reducing the effective surface area for Pd particle deposition, although the bundling provides more secure, lock-in-place positioning of nanotubes and Pd catalyst particles. The nanotube bundling is substantially mitigated by Pd nanoparticle deposition on the unfunctionalized and geometrically separated nanotubes, which provides much higher catalyst surface area. Such nanocomposite materials utilizing geometrically secured and aligned nanotubes can be useful for providing much enhanced catalytic activities to chemical and electrochemical reactions (e.g., fuel cell reactions), and eliminate the need for tedious catalyst recovery process after the reaction is completed.

Adsorption↗
PubMed2005

A renewable electrochemical magnetic immunosensor based on gold nanoparticle labels.

A particle-based renewable electrochemical magnetic immunosensor was developed by using magnetic beads and gold nanoparticle labels. Anti-IgG antibody-modified magnetic beads were attached to a renewable carbon paste transducer surface by magnet that was fixed inside the sensor. Gold nanoparticle labels were capsulated to the surface of magnetic beads by sandwich immunoassay. Highly sensitive electrochemical stripping analysis offers a simple and fast method to quantify the capatured gold nanoparticle tracers and avoid the use of an enzyme label and substrate. The stripping signal of gold nanoparticles is related to the concentration of target IgG in the sample solution. A transmission electron microscopy image shows that the gold nanoparticles were successfully capsulated to the surface of magnetic beads through sandwich immunoreaction events. The parameters of immunoassay, including the loading of magnetic beads, the amount of gold nanoparticle conjugate, and the immunoreaction time, were optimized. The detection limit of 0.02 microg ml(-1) of IgG was obtained under optimum experimental conditions. Such particle-based electrochemical magnetic immunosensors could be readily used for simultaneous parallel detection of multiple proteins by using multiple inorganic metal nanoparticle tracers and are expected to open new opportunities for disease diagnostics and biosecurity.

Biosensing Techniques↗
PubMed2005

Nanostructured electrochemical sensors based on functionalized nanoporous silica for voltammetric analysis of lead, mercury, and copper.

We have successfully developed electrochemical sensors based on functionalized nanostructured materials for voltammetric analysis of toxic metal ions. Glycinylurea self-assembled monolayers on mesoporous silica (Gly-UR SAMMS) were incorporated in carbon paste electrodes for the detection of toxic metal ions such as lead, copper, and mercury based on adsorptive stripping voltammetry (AdSV). The electrochemical sensor yields a linear response at a low ppb level of Pb2+ (i.e., 2.5-50 ppb) after a 2-min preconcentration period, with reproducible measurements (%RSD = 3.5, N = 6) and an excellent detection limit (1 ppb). By exploiting the interfacial functionality of Gly-UR SAMMS, the sensor is selective for the target species, does not require the use of a mercury film, and can be easily regenerated in dilute acid solution. The rigid, open, parallel pore structure, combined with suitable interfacial chemistry of SAMMS, also results in fast analysis times (2-3 min). The nanostructured SAMMS materials enable the development of miniature sensing devices that are compact and low cost, have low energy consumption, and are easily integrated into field-deployable units.

Copper↗
PubMed2005

Deposition of platinum nanoparticles on carbon nanotubes by supercritical fluid method.

Carbon nanotube-supported platinum nanoparticles with a 5-15 nm diameter size range can be synthesized by hydrogen reduction of platinum(ll) acetylacetonate in methanol modified supercritical carbon dioxide. X-ray photoelectron spectroscopy and X-ray diffraction spectra indicate that the carbon nanotubes contain zero-valent platinum metal and high-resolution transmission electron microscopy images show that the visible lattice fringes of platinum nanoparticles are crystallites. Carbon nanotubes synthesized with 25% by weight of platinum nanoparticles exhibit a higher activity for hydrogenation of benzene compared with a commercial carbon black platinum catalyst. The carbon nanotube-supported platinum nanocatalyst can be reused at least six times for the hydrogenation reaction without losing activity. The carbon nanotube-supported platinum nanoparticles are also highly active for electrochemical oxidation of methanol and for reduction of oxygen suggesting their potential use as a new electrocatalyst for proton exchange membrane fuel cell applications.

Benzene↗
PubMed2004

Composition-controlled synthesis of bimetallic gold-silver nanoparticles.

This paper reports findings of an investigation of the synthesis of monolayer-capped binary gold-silver (AuAg) bimetallic nanoparticles that is aimed at understanding the control factors governing the formation of the bimetallic compositions. The synthesis of alkanethiolate-capped AuAg nanoparticles was carried out using two related synthetic protocols using aqueous sodium borohydride as a reducing agent. One involves a two-phase reduction of AuCl(4)(-), which is dissolved in organic solution, and Ag(+), which is dissolved in aqueous solution. The other protocol involves a two-phase reduction of AuCl(4)(-) and AgBr(2)(-), both of which are dissolved in the same organic solution. AuAg nanoparticles of 2-3 nm core sizes with different compositions in the range of 0-100% Au have been synthesized. The two synthetic routes were compared in terms of bimetallic composition and size properties. Our new findings have allowed us to establish the correlation between synthetic feeding of metals and metal compositions in the bimetallic nanoparticles, which have important implications to the exploration of gold-based bimetallic nanoparticles for constructing sensing and catalytic nanomaterials.

Gold↗
PubMed2004

A direct route toward assembly of nanoparticle-carbon nanotube composite materials.

The preparation of nanocomposite materials from carbon nanotubes (CNTs) and metal or metal oxide nanoparticles has important implications to the development of advanced catalytic and sensory materials. This paper reports findings of an investigation of the preparation of nanoparticle-coated carbon nanotube composite materials. Our approach involves molecularly mediated assembly of monolayer-capped nanoparticles on multiwalled CNTs via a combination of hydrophobic and hydrogen-bonding interactions between the capping/mediating shell and the CNT surface. The advantage of this route is that it does not require tedious surface modification of CNTs. We have demonstrated its simplicity and effectiveness for assembling alkanethiolate-capped gold nanoparticles of 2-5 nm core sizes onto CNTs with controllable coverage and spatially isolated character. The loading and distribution of the nanoparticles on CNTs depend on the relative concentrations of gold nanoparticles, CNTs, and mediating or linking agents. The composite nanomaterials can be dispersed in organic solvent, and the capping/linking shells can be removed by thermal treatment to produce controllable nanocrystals on the CNT surfaces. The nanocomposite materials are characterized using transmission electron microscopy and Fourier transform infrared spectroscopy techniques. The results will be discussed in terms of developing advanced catalytic and sensory nanomaterials.

Gold↗
PubMed2004

Spectroscopic characterizations of molecularly linked gold nanoparticle assemblies upon thermal treatment.

The understanding of surface properties of core-shell type nanoparticles is important for exploiting the unique nanostructured catalytic properties. We report herein findings of a spectroscopic investigation of the thermal treatment of such nanoparticle assemblies. We have studied assemblies of gold nanocrystals of approximately 2 nm core sizes that are capped by alkanethiolate shells and are assembled by covalent or hydrogen-bonding linkages on a substrate as a model system. The structural evolution of the nanoparticle assemblies treated at different temperatures was probed by several spectroscopic techniques, including UV-visible, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). The results show that the capping/linking shell molecules can be effectively removed to produce controllable surface and optical properties. The data further revealed that the thermally induced evolution of the surface plasmon resonance property of gold nanoparticles is dependent on the chemical nature of the linker molecule. The spectral evolution is discussed in terms of changes in particle size, interparticle distance, and dielectric medium properties, which has important implications for controlled preparation and thermal processing of core-shell nanostructured metal catalysts.

Journal Article↗
PubMed2003

Solubilization of carbon nanotubes by Nafion toward the preparation of amperometric biosensors.

The ability to solubilize single-wall and multiwall carbon nanotubes (CNT) in the presence of the perfluorinated polymer Nafion is described. Such use of Nafion as a solubilizing agent for CNT overcomes a major obstacle for creating CNT-based biosensing devices. Their association with Nafion does not impair the electrocatalytic properties of CNT. The resulting CNT/Nafion modified glassy-carbon electrodes exhibit a strong and stable electrocatalytic response toward hydrogen peroxide. The marked acceleration of the hydrogen peroxide redox process is very attractive for the operation of oxidase-based amperometric biosensors, as illustrated for the highly selective low-potential (-0.05 V vs Ag/AgCl) biosensing of glucose. These findings open the door for using CNT in a wide range of chemical sensors and nanoscale electronic devices.

Biosensing Techniques↗
PubMed2003

Templateless assembly of molecularly aligned conductive polymer nanowires: a new approach for oriented nanostructures.

Although oriented carbon nanotubes, oriented nanowires of metals, semiconductors and oxides have attracted wide attention, there have been few reports on oriented polymer nanostructures such as nanowires. In this paper we report the assembly of large arrays of oriented nanowires containing molecularly aligned conducting polymers (polyaniline) without using a porous membrane template to support the polymer. The uniform oriented nanowires were prepared through controlled nucleation and growth during a stepwise electrochemical deposition process in which a large number of nuclei were first deposited on the substrate using a large current density. After the initial nucleation, the current density was reduced stepwise in order to grow the oriented nanowires from the nucleation sites created in the first step. The usefulness of these new polymer structures is demonstrated with a chemical sensor device for H(2)O(2), the detection of which is widely investigated for biosensors. Finally, we demonstrated that controlled nucleation and growth is a general approach and has potential for growing oriented nanostructures of other materials.

Journal Article↗