Yongxiu Li

Controlled growth and field emission properties of CuS nanowalls

Vertically oriented CuS nanowalls supported on a copper substrate have been synthesized through a facile method involving an inorganic vapour–solid phase reaction. The CuS nanowalls were well connected to form an extended network. The shapes of the CuS nanostructures could be controlled by adjusting the reaction conditions such as the reaction temperature and the flow rate of argon gas. The crystallinity of the nanowalls was investigated by XRD and their morphological features were characterized by FESEM. Both TEM and SAED analyses revealed that the nanowalls are single-crystalline. The field emission properties of the CuS nanowalls were investigated. The turn-on field and current density of the CuS nanowalls are comparable to those of many other semiconductor nanomaterials, which suggests that the CuS nanowalls may have potential applications in the vacuum microelectronics industry.

A new type of silica-coated Gd2(CO3)3:Tb nanoparticle as a bifunctional agent for magnetic resonance imaging and fluorescent imaging

We report a new type of dual modal nanoprobe to combine optical and magnetic resonance bioimaging. A simple reverse microemulsion method and coating process was introduced to synthesize silica-coated Gd(2)(CO(3))(3):Tb nanoparticles, and the particles, with an average diameter of 16 nm, can be dispersed in water. As in vitro cell imaging of the nanoprobe shows, the nanoprobe accomplishes delivery to gastric SGC7901 cancer cells successfully in a short time, as well as NCI-H460 lung cancer cells. Furthermore, it presents no evidence of cell toxicity or adverse affect on kidney cell growth under high dose, which makes the nanoprobes optical bioimaging modality available. The possibility of using the nanoprobe for magnetic resonance imaging is also demonstrated, and the nanoprobe displays a clear T(1)-weighted effect and could potentially serve as a bimodal T(1)-positive contrast agent. Therefore, the new nanoprobe formed from carbonate nanoprobe doped with rare earth ions provides the dual modality of optical and magnetic resonance imaging.

Synthesis of Nano-sized Yttria via a Sol-Gel Process Based on Hydrated Yttrium Nitrate and Ethylene Glycol and Its Catalytic Performance for Thermal Decomposition of NH4ClO4

Abstract Nano-sized yttria particles were synthesized via a non-aqueous sol-gel process based on hydrated yttrium nitrate and ethylene glycol. The effects of the molar ratio of ethylene glycol to yttrium ion and calcination temperature on crystallite size of the products were studied. The catalytic performance of the as-prepared yttria for the ammonium perchlorate (AP) decomposition was investigated by differential scanning calorimetry (DSC). The results indicate that the nano-sized cubic yttria particles with less than 20 nm in average crystallite size can be obtained after 2 h reflux at 70 °C, dried at 90 °C, forming xerogel, and followed by annealing of xerogel for 2 h, and that the addition of the nano-sized yttria to AP incorporates two small exothermic peaks of AP in the temperature ranges of 310 ∼ 350 °C and 400 ∼ 470 °C into a strong exothermic peak of AP and increases the apparent decomposition heat from 515 to over 1110 J·g −1 . It is also clear that the temperature of AP decomposition exothermic peak decreases and the apparent decomposition heat of AP increases with the increase of the amount of nano-sized yttria. The fact that the addition of the 5% nano-sized yttria to AP decreases the temperature of AP exothermic peak to 337.7 °C by reduction of 114.6 °C and increases the apparent decomposition heat from 515 to 1240 J·g −1 , reveals that nano-sized yttria shows strong catalytic property for AP thermal decomposition.

Novel Salt-Assisted Combustion Synthesis of High Surface Area Ceria Nanopowders by An Ethylene Glycol-Nitrate Combustion Process

A novel salt-assisted combustion process with ethylene glycol as a fuel and nitrate as an oxidant to synthesize high surface area ceria nanopowders was reported. The effects of various tunable conditions, such as fuel-to-oxidant ratio, type of salts, and amount of added salts, on the characteristics of the as-prepared powders were investigated by X-ray diffraction, transmission electron microscopy and BET surface area measurement. A mechanism scheme was proposed to illustrate the possible formation processes of well-dispersed ceria nanoparticles in the salt-assisted combustion sunthesis. It was verified that the simple introduction of leachable inert inorganic salts as an excellent agglomeration inhibitor into the redox mixture precursor leads to the formation of well-dispersed ceria particles with particle size in the range of 4 ∼ 6 nm and a drastic increase in the surface area. The presence of KCl results in an over ten-fold increment in specific surface area from 14.10 m2·g−1 for the produced ceria powders via the conventional combustion synthesis process to 156.74 m2·g−1 for the product by the salt-assisted combustion synthesis process at the same molar ratio of ethylene glycol-nitrate.

Preparation and Characterization of Porous Yttrium Oxide Powders with High Specific Surface Area

Abstract The porous cubic yttrium oxides with high specific surface area were prepared by the explosive decomposition of yttrium nitrate and its complex formed with methyl salicylate. The specific surface area and properties of powders synthesized at various temperatures were characterized using BET, X-ray diffraction (XRD), infrared spectra (IR), and scanning electron microscopy (SEM). The results indicate that the highest specific surface area is found to be 65.37 m 2 ·g −1 at the calcination temperature of 600 °C, and then decreases to 20.33 m 2 ·g −1 with the calcination temperature rising from 600 to 900 °C. The powders show strong surface activity for adsorping water and carbon dioxide in air, which also decreases with the rising calcination temperature. The drop both on the surface area and surface activity of samples at higher temperatures may be due to pore-narrowing(sintering) effects.

Preparation of La(OH)3 and La2O3 with Rod Morphology by Simple Hydration of La2O3

Lanthanum hydroxide with rod-like morphology was synthesized with simple hydration processing via the hydration of its bulk oxide in normal water solution at boiling temperature. An XRD pattern shows the formation of the hexagonal phase of La(OH)3, indicating that the hydration process is very rapid. The as-prepared La(OH)3 is almost entirely with a needle- or rod-like shape with a width of 2 ∼ 3 μm and a length of 5 ∼ 8 μm. The mechanism of the formation of La(OH)3 with rod-like morphology was preliminarily presented. It is easier to expand the simple hydration process on a large scale than the hydrothermal process.

Mesoporous silica coated Gd2(CO3)3:Eu hollow nanospheres for simultaneous cell imaging and drug delivery

In the present work, mesoporous silica coated Gd2(CO3)3:Eu hollow nanospheres (Gd2(CO3)3:Eu@mSiO2 HNSs) were successfully synthesized via a facial route and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM) infrared spectrometer (IR), energy dispersive X-ray spectrum (EDS) and Brunauer–Emmet–Teller (BET) surface area analysis. The results indicate that the prepared monodispersed nanoparticles are hollow spheres with a 400 nm sphere core and 30 nm thick shell and have a narrow size distribution. In vitro cell imaging of the hollow nanosphere shows Gd2(CO3)3:Eu@mSiO2 HNSs were able to enter NCI-H460 lung cancer cells rapidly. The possibility of using the synthesized hollow nanospheres for magnetic resonance imaging was also demonstrated, and the hollow nanosphere displays a clear T1-weighted effect and could potentially serve as a bimodal T1-positive contrast agent. The drug loading and controlled release performance of Gd2(CO3)3:Eu@mSiO2 HNSs was evaluated with doxorubicin hydrochloride (DOX) as a model drug at different pH values (pH = 7.4, 5.8). The Gd2(CO3)3:Eu@mSiO2 HNSs showed sustainable pH dependent drug release property. Furthermore, the in vitro cytotoxic effect against NCI-H460 lung cancer cells of the DOX-loaded carriers was investigated in detail. In all, the Gd2(CO3)3:Eu@mSiO2 HNSs as a new type of theragnostic (imaging and treatment) agent can provide new opportunities in cancer treatment.

Searching for a high efficiency and environmental benign reagent to leach ion-adsorption rare earths based on the zeta potential of clay particles

To overcome the serious water pollution and landslides that occur in response to in situ ion-adsorption rare earths (IAREs) leaching, it is essential to identify highly efficient and environmentally benign leaching reagents. Therefore, the leaching efficiency (LE) of IAREs by different inorganic electrolytes at different concentrations was compared, and the landslides and ion releasing performance of tailings driven by water rinsing were evaluated based on the zeta potential of clay particles (CPs). It was found that the LE increased as the concentration increased for all electrolytes. A linear relationship existed between the LE of IAREs and the zeta potential of CPs for every electrolyte, but the slope values of the linear relationships differed among the electrolytes. Moreover, the LE of IAREs by aluminum sulfate solution was the highest and the slope of the linear relationship was positive. However, the zeta potential of CPs and the slope of the linear relationship for electrolytes of bivalent metal ions became negative. According to the double electric layer model, the negative zeta potential is a result of cation migration from the Stern layer to the diffusion layer, meaning that the residual electrolytes in tailings can be washed out by rain and produce a large amount of wastewater. Additionally, the high zeta potential can increase the repulsive force between particles, leading to landslides. Therefore, aluminum sulfate as a leaching agent of IAREs not only has a high LE but also can reduce the amount of wastewater and the risk of landslides.