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Qun Huo

Publications and source records attributed to Qun Huo.

11 recordsLinked to original sources
PubMed2006

Extinction coefficient of gold nanoparticles with different sizes and different capping ligands.

Extinction coefficients of gold nanoparticles with core size ranging from approximately 4 to 40 nm were determined by high resolution transmission electron microscopy analysis and UV-vis absorption spectroscopic measurement. Three different types of gold nanoparticles were prepared and studied: citrate-stabilized nanoparticles in five different sizes; oleylamide-protected gold nanoparticles with a core diameter of 8 nm, and a decanethiol-protected nanoparticle with a diameter of around 4 nm. A linear relationship between the logarithms of extinction coefficients and core diameters of gold particles was found independent of the capping ligands on the particle surface and the solvents used to dissolve the nanoparticles. This linear relation may be used as a calibration curve to determine the concentration or average size of an unknown nanoparticle or nanoparticle-biomolecule conjugate sample.

Gold↗
PubMed2006

Polymerization of a cysteinyl peptidolipid Langmuir film.

The surface pressure-area isotherm of a cysteinyl peptidolipid on a pure water subphase (pH 5.8) was compared with that on a water subphase saturated with oxygen and buffered with ammonium bicarbonate (pH 7.8). A reduction of the limiting molecular area was observed for the isotherm measured on the subphase saturated with oxygen. Hysteresis in the compression-decompression cycles of the Langmuir film was also observed. Taking into consideration the chemical structure of the peptidolipid, we rationalized that the free sulfhydryl groups of the peptidolipid were oxidized in the presence of oxygen in the alkaline subphase to form intermolecular disulfide bonds at the air-water interface. The surface topography of the peptidolipid Langmuir film was observed by epi-fluorescence microscopy and the Langmuir-Blodgett film by environmental scanning electron microscopy (ESEM). The micrographs showed evidence of the polymerization of the cysteinyl peptidolipid at the air-water interface. Furthermore, the XPS spectra of the Langmuir-Blodgett films also proved the existence of disulfide bonds. The control peptidolipid C(18)-Ser-Gly-Ser-OH showed identical surface pressure-area isotherms in the presence or absence of an oxygen-saturated subphase.

Lipoproteins↗
PubMed2006

Kinetic study of gold nanoparticle growth in solution by Brust-Schiffrin reaction.

Nanoparticle growth in solution is a rather complicated process governed by many thermodynamic and kinetics factors. A better understanding of nanoparticle growth kinetics is of primary importance leading to a better control on the nanoparticle size and size distribution. In this work we conducted both experimental and theoretical study on the kinetics of Brust-Schiffrin reaction for the synthesis of gold nanoparticles. Using an excessive amount of thiol ligands, the nanoparticle growth was stopped at different intermediate stages. Our study revealed and confirmed that the reproducibility of Brust-Schiffrin reaction for the synthesis of gold nanoparticles with diameters around 2 nm is rather poor due to the intrinsic complexity of this two-phase reaction. The analysis results of each intermediate product by TEM showed that nanoparticles grew very rapidly at the early stage of reaction and reached a maximum value of 2.6 nm at reaction time of around 10 minutes. Further increase of reaction time led to a decrease of nanoparticle size. In addition to the experimental study, we proposed a kinetic model for nanoparticle growth in solution by assuming that the nanoparticle core expands through incremental addition of gold atoms to the existing nanoparticle nuclei. This model not only gave a relatively good fitting to the experimental data, but also provided further insight into the nucleation and core expansion stage of the nanoparticle growth, which had not been revealed in previous modeling studies.

Computer Simulation↗
PubMed2005

Optical limiting of a covalently bonded gold nanoparticle/polylysine hybrid material.

The optical limiting performance of a covalently bonded gold nanoparticle (approximately 2 nm)/polylysine hybrid material (AuNP-PLL) was investigated using 4.1 ns laser pulses at 532 nm. The hybrid material exhibits enhanced optical limiting in comparison to individual nanoparticles, presumably due to the interparticle electromagnetic interactions between particles in close proximity. Reverse saturable absorption and/or free carrier absorption were found to be the dominant contributor(s) to the optical limiting of the hybrid material.

Journal Article↗
PubMed2005

A "nanonecklace" synthesized from monofunctionalized gold nanoparticles.

Gold nanoparticles with a single carboxylic acid group on the surface were prepared from a solid phase place exchange reaction and then coupled to polylysine using an in situ activation agent, diisopropylcarbodiimide (DIPCDI). The covalent amide bond linkage between the nanoparticles and polylysine and the ring closure of the polylysine chain have led to the formation of a nanoparticle/polymer hybrid material with "nanonecklace" structures.

Carbodiimides↗
PubMed2004

Comparison study of the solution phase versus solid phase place exchange reactions in the controlled functionalization of gold nanoparticles.

Gold nanoparticles offer tremendous potential in the areas of nanoelectronics, bio- and chemosensors, and catalysis. However, before these applications are realized, the surface functionality of nanoparticles must be better controlled. Our lab has recently reported a novel synthetic approach for making monofunctionalized nanoparticles through a solid phase place exchange reaction. Monofunctionalized gold nanoparticles may also be prepared through a solution phase place exchange reaction. In this study, we compared the efficiency of these two separate approaches toward controlled functionalization of gold nanoparticles by (1)H NMR, Fourier transform infrared (FT-IR), and transmission electron microscopy (TEM) analysis. We found that the solid phase place exchange approach is much more efficient at producing monofunctionalized gold nanoparticles. (1)H NMR data were used to give a semiquantitative count of substituted bifunctional ligands, and FT-IR spectra supported these findings. Furthermore, we used a diamine coupling reaction of nanoparticles to show the presence of single or multiple functional groups on the nanoparticle surface by TEM analysis.

Diamines↗
PubMed2004

Synthesis and supramolecular self-assembly study of a novel porphyrin molecule in Langmuir and Langmuir-Blodgett films.

The self-assembly and supramolecular engineering of porphyrins into ordered arrays have recently attracted much interest because of their promising application potential in molecular and electronic devices, spintronics, energy harvesting and storage, catalysis, and sensor development. We herein report the synthesis and supramolecular self-assembly study of a novel porphyrin molecule, 2Por-TAZ, in Langmuir and Langmuir-Blodgett films. The 2Por-TAZ molecule contains two porphyrin macrocycles attached to a triaminotriazine headgroup. Triaminotriazines are known to form a highly ordered linear supramolecular self-assembly through complementary hydrogen bonding with barbituric acid molecules at the air-water interface. Surface pressure-area isotherm measurements and polarized UV-vis absorption spectroscopic studies indicate that the 2Por-TAZ molecules adopted an edge-on orientation at the air-water interface. Polarized UV-vis absorption study also revealed that the 2Por-TAZ molecules formed linear supramolecular networks on pure water and barbituric acid subphase with porphyrin flat planes facing toward the compression direction. The binding of barbituric acid with 2Por-TAZ molecules was observed from the expansion of the Langmuir monolayer film. Compared to the transferred LB film from pure water subphase, both the UV-vis absorbance and fluorescence emission intensity of the LB film transferred from barbituric acid subphase increased significantly.

Hydrogen Bonding↗