Guokui Liu

Effects of phonon confinement on the luminescence dynamics of Eu3+ in Gd2O3 nanotubes

The effects of phonon confinement on the excited state dynamics of Eu3+ in Gd2O3 nanotubes are investigated. Anomalous thermalization appears due to elimination of low-energy phonon modes in this highly efficient nanophosphor of many potential applications. It is observed that in the low-temperature excitation spectrum hot bands with fine structures originate from the lowest sublevel of 7F1 at 217?cm?1 above the ground state. The intensity of the hot bands hardly changes below 50?K, but it increases and exhibits normal Boltzmann thermalization above 50?K. The fluorescence lifetime of 5D0 (2.19?ms at 10?K) is found to be unusually longer than that of the bulk counterparts, indicating a small filling factor of 0.55 for the nanotubes. These luminescent properties are attributed to the morphology and to the lack of low-energy phonon modes in the nanotubes.

Quantum dot conjugated hydroxylapatite nanoparticles for in vivo imaging

Hydroxylapatite (HA) nanoparticles were conjugated with quantum dots (QDs) for in vivo imaging. The surface structures of HA nanoparticles with conjugated quantum dots (HA-QD) were studied by transmission electron microscopy (TEM) and laser fluorescent spectroscopy. The TEM data showed that the quantum dots were well conjugated on the HA nanoparticle surfaces. The laser fluorescent spectroscopy results indicated that the HA-QD exhibited promising luminescent emission in vitro. The initial in vivo experiments revealed clear images of HA-QD from the hypodermic injected area at the emission of 600xa0nm. Furthermore, the optimized in vivo images of HA-QD with near-infrared emission at 800xa0nm were visualized after intravenous injection. These luminescent HA-QD nanoparticles may find important applications as biodegradable substrates for biomarkers and in drug delivery.

Luminescent hydroxylapatite nanoparticles by surface functionalization

Hydroxylapatite (HA) nanoparticles were functionalized by depositing rare-earth-doped Y2O3 nanoparticles on the surface, and the structural evolutions of both HA and Y2O3 phases at different annealing temperatures were investigated by x-ray diffraction and transmission electron microscopy. Laser spectroscopy indicated that the surface functionalized HA nanoparticles exhibited strong visible emissions. No visible emissions were observed from rare-earth-doped Y2O3 without any substrate, suggesting a doping-induced environmental change of optically active rare-earth elements in the functionalized HA nanoparticles. The luminescent hydroxylapatite nanoparticles may find important applications as a biodegradable substrate for biomarking and drug delivery.

Crystallization, phase transition and optical properties of the rare-earth-doped nanophosphors synthesized by chemical deposition

The structural and electronic properties of Eu3+-doped Y2O3 films coated on spherical alumina nanoparticles are studied using transmission electron microscope, x-ray diffraction, and laser spectroscopic techniques. It is observed that the coated films crystallize at temperatures higher than 600°C and may be completely converted into a cubic Y2O3 nanocrystalline layer at 750°C. At 900°C, phase transition occurs between the outer coating layer and the inner core, and different types of crystalline nanophase can be obtained. In the materials that we prepared and studied, all possible crystallographic phases, including two of solid-state laser media, YAlO3 (YAP), and Y3Al5O12 (YAG), may be formed in the pseudo-binary Al2O3–Y2O3 nanosystem by controlling thermal annealing procedures from 600 to 900°C, a temperature region far below the conventional solid-state reaction temperature. The spectroscopic properties of Eu3+ in all the nanophases are characterized in comparison with those of their bulk counterparts.

Conjugation of quantum dots and Fe3O4 on carbon nanotubes for medical diagnosis and treatment

Quantum dots (QDs) and Fe3O4 nanoparticles were conjugated onto the surfaces of carbon nanotubes (CNTs) for medical diagnosis and treatment. The nanoassembly was designed to meet the specific needs in cancer in vivo imaging and simultaneous treatment. The key functionalities needed for clinical applications were integrated, including CNT surface functionalization for attachment of biological molecules in targeting, drug storage capabilities, fluorescent emissions near the infrared range, and magnetic hyperthermia. CNT-QD-Fe3O4 developed exhibited a strong fluorescence near the infrared region for noninvasive optical in vivo imaging. Magnetization measurements showed nearly reversible hysteresis curves from CNT-QD-Fe3O4 nanoassembly. Fe3O4 conjugated CNT was found to experience hyperthermia heating under alternating electromagnetic field.Quantum dots (QDs) and Fe3O4 nanoparticles were conjugated onto the surfaces of carbon nanotubes (CNTs) for medical diagnosis and treatment. The nanoassembly was designed to meet the specific needs in cancer in vivo imaging and simultaneous treatment. The key functionalities needed for clinical applications were integrated, including CNT surface functionalization for attachment of biological molecules in targeting, drug storage capabilities, fluorescent emissions near the infrared range, and magnetic hyperthermia. CNT-QD-Fe3O4 developed exhibited a strong fluorescence near the infrared region for noninvasive optical in vivo imaging. Magnetization measurements showed nearly reversible hysteresis curves from CNT-QD-Fe3O4 nanoassembly. Fe3O4 conjugated CNT was found to experience hyperthermia heating under alternating electromagnetic field.

Deposition of ultrathin rare-earth doped Y2O3 phosphor films on alumina nanoparticles

Ultrathin films of Eu 3+ doped Y2O3 were deposited onto alumina nanoparticles using a unique solution synthesis method. The surface structure, composition, and morphology of the thin films deposited were analysed using high resolution transmission electron microscopy (TEM) and high angle annular dark field scanning TEM imaging and energy dispersive x-ray measurements. The films deposited were extremely thin, on the order of 3–5 nm, and uniformly covered all the alumina nanoparticles. X-ray diffraction was used to investigate the phases and structures of the thin films deposited. At the heat treatment temperature of 600 ◦ C, cubic Y2O3 nanocrystals were found in the film while as-coated layers exhibited mainly amorphous features. As the heat treatment temperature increased to 750 ◦ C, the amorphous thin film became well crystallized. Optical properties of Eu 3+ doped Y2O3 films were characterized by fluorescence spectroscopy. Strong photoluminescence was observed in the sample annealed at 750 ◦ C, from the fluorescence of Eu 3+ ions in a well-crystallized film, consistent with the

Deposition of rare-earth doped nanophosphors on multi-wall carbon nanotube surfaces - a new approach in cancer diagnosis

In biomedical science and nanotechnology, it often requires surface multi funcationalization of a nanoparticle or a nanotube. In cancer diagnosis for instance, not only does the nanoparticle need a cavity structure for storage and delivery of drugs, but also be luminescent for diagnosis. Europium doped Y2 O3 were deposited on the multi wall carbon nanotube (MWCNTs) surface by a novel solution method. High resolution transmission electron microscopy (HRTEM) experiments were carried out to study the surface morphologies of the deposited rare-earth doped nanophosphors on MWCNTs. The crystal lattice structures of the surface deposits were identified by using selected area electron diffraction. The optical properties of the surface functionalized MWCNTs were characterized by using a fluorescent spectrometer.Copyright