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Ya-Ping Sun

Publications and source records attributed to Ya-Ping Sun.

At least 19 recordsLinked to original sources
PubMed2006

Alternatively modified bingel reaction for efficient syntheses of C60 hexakis-adducts.

It was found that the C60 hexakis-adduct (Th) bearing 12 electron-donating N,N-dimethylaniline moieties could not be synthesized by the Bingel-Hirsch method with either classical or deviated experimental parameters in a one-pot reaction. A different modification to the original Bingel reaction without the use of any templating agent was necessary for high-yield synthesis of the compound. The generalization of this alternatively modified Bingel method to the preparation of other C60 hexakis-adducts is demonstrated. [structure: see text].

Journal Article↗
PubMed2006

Unique aggregation of anthrax (Bacillus anthracis) spores by sugar-coated single-walled carbon nanotubes.

There has been significant interest in the binding of anthrax spores by molecular species, but with only limited success. Proteins and more recently peptides were used. However, despite the known presence of carbohydrates on the spore surface, carbohydrate-carbohydrate interactions have hardly been explored likely because of the lack of required specific platform for synthetic carbohydrates. We report the successful use of single-walled carbon nanotubes as a truly unique scaffold for displaying multivalent monosaccharide ligands that bind effectively to anthrax spores with divalent cation mediation to cause significant spore aggregation. The work should have far-reaching implications in development of countermeasure technologies.

Animals↗
PubMed2006

Efficient quenching of photoluminescence from functionalized single-walled carbon nanotubes by nitroaromatic molecules.

The photoluminescence from functionalized single-walled carbon nanotubes was found to be highly sensitive to the presence of nitroaromatic compounds such as nitrobenzene, 4-nitrotoluene, and 2,4-dinitrotoluene. The strong luminescence quenching in solution was at the upper limit of diffusion-control and also showed significant static quenching contributions. Mechanistic implication of the results and potential applications are discussed.

Dinitrobenzenes↗
PubMed2006

An expeditious enantioselective total synthesis of valilactone.

The title compound was synthesized through an expeditious route using Crimmins aldolization to establish the two key stereogenic centers and a hydroxyl group activation (HGA) protocol to construct the anti alpha,beta-disubstituted beta-lactone from the corresponding syn aldol.

Cyclization↗
PubMed2006

Synthesis of nonactin and the proposed structure of trilactone.

[reaction: see text] An efficient enantioselective route to nonactin using a novel beta-inversion of an Evans syn aldol to construct the THF ring is presented. Through total synthesis, the structure for trilactone proposed in the literature is shown likely to be incorrect.

Anti-Bacterial Agents↗
PubMed2006

Quantum-sized carbon dots for bright and colorful photoluminescence.

We report that nanoscale carbon particles (carbon dots) upon simple surface passivation are strongly photoluminescent in both solution and the solid state. The luminescence emission of the carbon dots is stable against photobleaching, and there is no blinking effect. These strongly emissive carbon dots may find applications similar to or beyond those of their widely pursued silicon counterparts.

Carbon↗
PubMed2006

Luminescence polarization spectroscopy study of functionalized carbon nanotubes in a polymeric matrix.

Single-walled carbon nanotubes (SWNTs) were well-functionalized for a study of their defect-derived luminescence properties. The soluble nanotube sample was homogeneously dispersed in poly(vinyl alcohol) (PVA) films via solution-phase mixing and then wet-casting. The PVA films embedded with the functionalized SWNTs were strongly luminescent according to spectroscopic and confocal microscopic results. The luminescence from the films was highly polarized, with the observed anisotropy value approaching the limit for collinear absorption and emission dipole moments. The films were mechanically stretched to align the embedded nanotubes, and results from luminescence measurements of the stretched films suggested that the excitation was strongly in favor of the direction along the nanotube axis. Mechanistic implications of the polarization spectroscopy results for the luminescent functionalized nanotubes in the polymeric matrix with and without the mechanic alignment are discussed.

Journal Article↗
PubMed2005

Visible luminescence of carbon nanotubes and dependence on functionalization.

Strong luminescence emissions over a broad wavelength region were detected from well-dispersed carbon nanotubes in most functionalized samples, even with excitation wavelengths into the near-IR. Apparently, the better dispersion and functionalization of the nanotubes resulted in more intense luminescence emissions. These emissions may logically be attributed to the trapping of excitation energy by defect sites in the nanotube structure, which are passivated upon the appropriate functionalization of the nanotubes. Better functionalization improves not only the nanotube dispersion (thus diminishing the quenching due to intertube interactions) but also the surface passivation to make the energy trapping sites more emissive, leading to stronger luminescence emissions. Because of such high sensitivity, the visible luminescence emissions may prove valuable in the evaluation of dispersion in functionalized carbon nanotube samples and related nanocomposite materials.

Letter↗
PubMed2005

Derivatized fullerenes bearing multiple electron donors: synthesis and charge transfer properties.

A series of methano-C60 adducts bearing up to six electron donating N,N-dimethylaniline units (denoted as D compounds), along with their analogues without the dimethylamino groups as references (R compounds), were synthesized. The redox properties of the D compounds in solutions were evaluated spectroscopically in reference to the R compounds. According to UV/vis absorption results, there are obviously ground-state intramolecular charge-transfer complexes in the D series, and the charge-transfer effects apparently become saturated with only two donor units in the molecule. The photoinduced intramolecular electron-transfer properties of the D compounds were investigated via fluorescence measurements. The emission from intramolecular exciplexes can be found only in the D molecule with two electron donor units. Throughout the D series, the fluorescence properties are highly sensitive to the solvent polarity, with the emission completely quenched for all of the molecules in a polar solvent like methylene chloride. Mechanistic implications of the results are discussed.

Journal Article↗
PubMed2005

Solubilization of boron nitride nanotubes.

A successful attempt in the functionalization and solubilization of boron nitride nanotubes is reported, and a functionalization mechanism based on interactions of amino functional groups with nanotube surface borons is proposed.

Journal Article↗
PubMed2005

NMR detection of single-walled carbon nanotubes in solution.

The detection of nanotube carbons in solution by (13)C NMR is reported. The highly soluble sample was from the functionalization of (13)C-enriched single-walled carbon nanotubes (SWNTs) with diamine-terminated oligomeric poly(ethylene glycol) (PEG(1500N)). The ferromagnetic impurities due to the residual metal catalysts were removed from the sample via repeated magnetic separation. The nanotube carbon signals are broad but partially resolved into two overlapping peaks, which are tentatively assigned to nanotube carbons on semiconducting (upfield) and metallic (downfield) SWNTs. The solid-state NMR signals of the same sample are similarly resolved. Mechanistic and practical implications of the results are discussed.

Journal Article↗
PubMed2005

Direct conjugation of semiconductor nanoparticles with proteins.

Nanocrystalline CdS particles directly conjugated with bovine serum albumin (BSA) protein were prepared by applying the supercritical fluid processing technique, rapid expansion of a supercritical solution into a liquid solvent. The direct conjugation takes advantage of the unique features of the process for nanoparticle formation. The BSA-conjugated CdS nanoparticles in stable aqueous suspension or in the solid state were characterized by using microscopy, X-ray diffraction, and optical spectroscopy methods. The results show that well-dispersed CdS nanoparticles are coated with BSA in a core-shell-like arrangement and that the protein species associated with the nanoparticles remain functional according to the modified Lowry assay. These BSA-conjugated CdS nanoparticles are also strongly luminescent, with the luminescence spectrum contributed to primarily by the exciton emission.

Animals↗
PubMed2005

Polymeric nanoparticles from rapid expansion of supercritical fluid solution.

In this concept paper we highlight applications of supercritical fluid technology in particle formation and production, especially some recent advances in the rapid expansion of supercritical solutions (RESS) processing technique. We also highlight the simple but significant modification to the traditional RESS by using a liquid solvent or solution at the receiving end of the supercritical solution expansion, or the rapid expansion of a supercritical solution into a liquid solvent (RESOLV), and applications of the technique to the preparation of nanoparticles. In particular, successes and challenges in the use of RESOLV for nanoscale (<100 nm) polymeric particles and the subsequent protection of the suspended nanoparticles from agglomeration are discussed.

Journal Article↗
PubMed2005

Visualizing adhesion-induced agglutination of Escherichia coli with mannosylated nanoparticles.

Polymeric nanoparticles covalently functionalized with derivatized D-mannose molecules were synthesized and characterized. These nanoparticles have an average size of approximately 160 nm in diameter, thus bearing a large number of surface-tethered mannose moieties for multivalent interactions with adhesins on bacterial cells. Specifically, the mannosylated nanoparticles bind strongly with Escherichia coli, allowing the convenient visualization of adhesion interactions under a conventional electron microscope. Since a single nanoparticle is capable of binding more than one cell, the adhesion interactions result in significant nanoparticle-mediated cell agglutination according to electron microscopy imaging. Potential applications of the mannosylated nanoparticles in the inhibition of enteropathogenic infections are discussed.

Adhesins, Escherichia coli↗