Qu-Quan Wang

The biocompatibility of quantum dot probes used for the targeted imaging of hepatocellular carcinoma metastasis

Semiconductor quantum dots (QDs) have several photo-physical advantages over organic dyes making them good markers in biomedical application. We used CdSe/ZnS QDs with maximum emission wavelength of 590nm (QD590) linked to alpha-fetoprotein (AFP) monoclonal antibody (Ab) to detect AFP in cytoplasm of human hepatocellular carcinoma (HCC) cell line HCCLM6. For the in vivo studies, we used QD-AFP-Ab probes for targeted imaging of human HCC xenograft growing in nude mice by injecting them into the tail vein. In addition, the cytotoxicity in vitro, the acute toxicity in vivo, the hemodynamics and tissue distribution of these probes were also investigated. The results in vitro and in vivo indicate that our QD-based probes have good stability, specificity and biocompatibility for ultrasensitive fluorescence imaging of molecular targets in our liver cancer model system.

Nucleation and growth study of atomic layer deposited HfO2 gate dielectrics resulting in improved scaling and electron mobility

HfO2 films have been grown with two atomic layer deposition (ALD) chemistries: (a) tetrakis(ethylmethylamino)hafnium (TEMAHf)+O3 and (b) HfCl4+H2O. The resulting films were studied as a function of ALD cycle number on Si(100) surfaces prepared with chemical oxide, HF last, and NH3 annealing. TEMAHf+O3 growth is independent of surface preparation, while HfCl4+H2O shows a surface dependence. Rutherford backscattering shows that HfCl4+H2O coverage per cycle is l3% of a monolayer on chemical oxide while TEMAHf+O3 coverage per cycle is 23% of a monolayer independent of surface. Low energy ion scattering, x-ray reflectivity, and x-ray photoelectron spectroscopy were used to understand film continuity, density, and chemical bonding. TEMAHf+O3 ALD shows continuous films, density >9g∕cm3, and bulk Hf–O bonding after 15 cycles [physical thickness (Tphys)=1.2±0.2nm] even on H-terminated Si(100). Conversely, on H-terminated Si(100), HfCl4+H2O requires 50 cycles (Tphys∼3nm) for continuous films and bulk Hf–O bonding. ...

Fano resonances in dipole-quadrupole plasmon coupling nanorod dimers

We theoretically investigate the plasmon coupling in metallic nanorod dimers. A pronounced dip is found in the extinction spectrum due to plasmonic Fano resonance, which is induced by destructive interference between the bright dipole plasmon of a short nanorod and the dark quadrupole plasmon of a long nanorod. This Fano interference can also be explained as the coupling between the bright and dark modes both supported by the whole dimer. The Fano resonance can be tuned by adjusting the spatial or spectral separation between two nanorods in the dimer.

Neurotoxin-conjugated upconversion nanoprobes for direct visualization of tumors under near-infrared irradiation

We report the development of neurotoxin-mediated upconversion nanoprobes for tumor targeting and visualization in living animals. The nanoprobes were synthesized by preparing polyethylenimine-coated hexagonal-phase NaYF(4):Yb,Er/Ce nanoparticles and conjugating them with recombinant chlorotoxin, a typical peptide neurotoxin that could bind with high specificity to many types of cancer cells. Nanoprobes that specifically targeted glioma cells were visualized by laser scanning upconversion fluorescence microscopy. Good probe biocompatibility was displayed with cellular and animal toxicity determinations. Animal studies were performed using Balb-c nude mice injected intravenously with the nanoprobes. The obtained high-contrast images demonstrated highly specific tumor binding and direct tumor visualization with bright red fluorescence under 980-nm near-infrared irradiation. The high sensitivity and high specificity of the neurotoxin-mediated upconversion nanoprobes and the simplification of the required optical device for tumor visualization suggest an approach that may help improve the effectiveness of the diagnostic and therapeutic modalities available for tumor patients.

Immunofluorescence detection with quantum dot bioconjugates for hepatoma in vivo

The use of highly specific and highly sensitive immunofluorescent probes is a promising approach for biomedical imaging in living tissue. We focus on immunofluorescence with quantum dot bioconjugates for hepatoma detection in vivo. We synthesized specific immunofluorescent probes by linking quantum dots to AFP (alpha-fetoprotein) antibody for specific binding AFP-an important marker for hepatocellular carcinoma cell lines. In in vivo studies, the characteristic quantum dot (QD) fluorescent property is exhibited by the QDs-Anti-AFP probes in tumor and they demonstrate active tumor targeting and spectroscopic hepatoma imaging with an integrated fluorescence imaging system. We investigate the inhomogeneous distribution of the QDs-Anti-AFP probes in tumor by using a site-by-site measurement method to test their ability for distribution studies of cancer cells. These results demonstrate the practicality of QD bioconjugates as attractive fluorescent probes for biomedical detection.

Tuning Gold Nanorod-Nanoparticle Hybrids into Plasmonic Fano Resonance for Dramatically Enhanced Light Emission and Transmission

We investigate the optical response of a gold nanorod array coupled with a semicontinuous nanoparticle film. We find that, as the gold nanoparticle film is adjusted to the percolating regime, the nanorod-film hybrids are tuned into plasmonic Fano resonance, characterized by the coherent coupling of discrete plasmonic modes of the nanorod array with the continuum band of the percolating film. Consequently, optical transmission of the percolating film is substantially enhanced. Even more strikingly, electromagnetic fields around the nanorod array become much stronger, as reflected by 2 orders of magnitude enhancement in the avalanche multiphoton luminescence. These findings may prove instrumental in the design of various plasmonic nanodevices.

Coherent exciton-plasmon interaction in the hybrid semiconductor quantum dot and metal nanoparticle complex

We studied theoretically the exciton coherent dynamics in the hybrid complex composed of CdTe quantum dot (QDs) and rodlike Au nanoparticles (NPs) by the self-consistent approach. Through adjusting the aspect ratio of the rodlike Au NPs, the radiative rate of the exciton and the nonradiative energy transfer rate from the QD to the Au NP are tunable in the wide range 0.05-4 ns(-1) and 4.4 x 10(-4) to 2.6 ns(-1), respectively; consequently, the period of Rabi oscillations of exciton population is tunable in the range 0.6 pi-9 pi.

Low-temperature chemical vapor deposition and scaling limit of ultrathin Ru films

Thermal chemical vapor deposition at temperatures as low as 423 K, using Ru3(CO)12 with no accompanying reactive gas, forms pure, uniform, and smooth Ru films on Ta and low-resistivity films on SiO2. A 2.5-nm-thick Ru film fully covers the underlying Ta and the Ru film is thermally stable up to 573 K. Unlike Ta, Ru films exhibit excellent wetting by Cu even when the Ru surface is contaminated with small amounts of oxygen.

Surface functionalization of ZnO nanotetrapods with photoactive and electroactive organic monolayers.

Two strategies have been explored for organic functionalizations of ZnO nanotetrapods via anchoring groups of carboxylate and phosphonate. With these methods, oleyl chains were assembled on the surfaces of the ZnO nanotetrapods, significantly enhancing their solubility in nonpolar solvents, such as chloroform and toluene. The surface functionalization strategies have been extended to electroactive and photoactive molecules such as protoporphyrin and C(60) on the ZnO nanotetrapods. The surface-modified ZnO nanotetrapods were characterized comprehensively, revealing a uniform, covalently linked monolayer assembled on the surface. This work opens a broad perspective for the application of the organically functionalized nanotetrapods in optoelectronics and biomedicine.

Controlled Synthesis and Upconverted Avalanche Luminescence of Cerium(III) and Neodymium(III) Orthovanadate Nanocrystals with High Uniformity of Size and Shape

We report on controlled synthesis of uniform LnVO4 (Ln = Ce and Nd) nanocrystals (NCs) with square-plate and H-shaped morphologies in nanosized reverse microemulsion reactors, via a facile solvo/hydrothermal strategy. The NCs were thoroughly characterized by X-ray diffraction, transmission electron microscopy (TEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDS), infrared absorption spectroscopy, and photoluminescence. Possible mechanisms of the rare-earth orthovanadate NC growth and size and shape evolution are proposed. A unique upconverted avalanche luminescence property pertaining to the NCs has been discovered, systematically studied, and mechanistically discussed. Our work combines synthetic and optical studies of the NCs and lays a foundation for reinventing their applications in optoelectronics among others.