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Zibo, China

Yang P.,University of Jinan | Zhang L.,Wan Jie Group Co. | Li X.,University of Jinan | Zhang Y.,University of Jinan | And 2 more authors.
Journal of Non-Crystalline Solids

Multi hydrophobic CdSe/ZnS or CdSe/Cd xZn 1 - xS quantum dots were encapsulated into SiO 2 beads through a three-step sol-gel procedure. First, the quantum dots were transferred from toluene to water phase via silanization using tetraethyl orthosilicate. The control of ligand exchange (partially hydrolyzed tetraethyl orthosilicate instead of organic amine) resulted in the quantum dots retaining their initial photoluminescence efficiencies after the phase transfer. Second, the assembly of the quantum dots occurs by the hydrolysis and condensation of tetraethyl orthosilicate to form seeds. The amount of 3-mercaptopropyltrimethoxysilane during incorporation plays an important role in controlling the quantum dot number per seed. Third, the seeds are coated with a SiO 2 shell by a subsequent Stöber process. The resulting SiO 2 beads with a controlled number of hydrophobic quantum dots revealed high photoluminescence efficiency. The SiO 2 beads were functionalized with amine, carboxyl, and thiol-terminated biolinkers for surface modification. To confirm the surface modification by carboxyl groups, the SiO 2 beads were conjugated with amino functional polystyrene beads. The silica beads introduced here represent a new platform for nanoparticulate multimodality bioanalysis. © 2012 Elsevier B.V. Source

Zhang Y.,University of Jinan | Yang P.,University of Jinan | Zhang L.,Wan Jie Group Co.
Materials Chemistry and Physics

We developed a facile method (a polyol synthesis) to prepare uniform silver nanostructures with various morphologies using ethylene glycol (EG) reduction of silver nitrate at 120 °C in the presence of poly(vinyl pyrrolidone) (PVP) and NaCl. Ag rods were fabricated by simply aging the freshly prepared AgNO3 solution with PVP, EG, and NaCl under ambient atmosphere without changing other parameters. The formation and degradation of the rods were systematically investigated. The result indicates that twinned-crystal seeds play an important role for the growth of anisotropic Ag rods. The NaCl concentration in solutions affected the formation of the rod. The rod was degraded subsequently via an etching process of O2/Cl (NaCl), resulting in the formation of Ag nanostructures with various shapes. Twinned Ag seeds in solutions were etched by increasing the concentration of NaCl, yielding uniform Ag cubes. Regular Ag cubes were fabricated under optimal preparation conditions. Ag cubes with various sizes (150-600 nm) were created by adjusting PVP concentrations in solutions. © 2013 Elsevier B.V. All rights reserved. Source

Yang F.,University of Jinan | Yang P.,University of Jinan | Zhang L.,Wan Jie Group Co.

We exploited the synthesis of near-infrared (NIR) emitting ternary-alloyed CdTeSe and quaternary-alloyed CdZnTeSe quantum dots (QDs) with rod and tetrapod morphologies, which have tunable emission in the NIR electromagnetic spectrum. The morphologies of the QDs depended strongly on their growth kinetics, probably due to the coordinating ligands used in the preparation. Using oleic acid, stearic acid and hexadecylamine as ligands and keeping the same reaction parameters, QDs with tetrapod and rod morphologies were created. Not only had the capping ligands influenced the morphologies of QDs, but also they influenced the optical properties of QDs. The molar ratios of Cd/Zn and Te/Se upon preparation were adjusted for investigating the effect of composition on the properties of resulting QDs. By varying the composition of QDs, the photoluminescence (PL) wavelength of QDs was tuned from 650 nm to 800 nm. To enhance PL efficiency and stability, QDs were coated with a CdZnS shell. As NIR PL has numerous advantages in biological imaging detection, these QDs hold great potential for application. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd. Source

Zhang L.,Wan Jie Group Co. | Zhang L.,Shandong University of Technology | Yu X.,Shandong University of Technology | Zhang H.,Shandong University of Technology | And 2 more authors.
Journal of Radioanalytical and Nuclear Chemistry

In this work, a naturally occurring illite was characterized by using FT-IR and XRD technique to determine its surface functional groups and crystal structure. Sorption of 60Co(II) on illite as a function of contact time, pH, ionic strength, foreign ions, humic substances and temperature was studied under ambient condition using batch technique. The results indicated that the sorption of 60Co(II) on illite is strongly affected by pH values (2-9) and ionic strength. A positive effect of humic substances on 60Co(II) sorption was found at pH < 7.0, whereas a negative effect was observed at pH > 7.0. At low pH, the sorption of 60Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na +/H+ on illite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir and Freundlich models were used to simulate the sorption isotherms of 60Co(II) at three different temperatures of 298.15, 323.15 and 343.15 K. The thermodynamic parameters (ΔH 0, ΔS 0 and ΔG 0) calculated from the temperature dependent sorption isotherms indicated that the sorption process of 60Co(II) on illite was endothermic and spontaneous. © 2012 Akadémiai Kiadó, Budapest, Hungary. Source

Yang P.,University of Jinan | Wang Y.,University of Jinan | Zhang L.,Wan Jie Group Co.
Journal of Nanoscience and Nanotechnology

Luminescent CdSe/Cd0.5Zn0.5S quantum dots (QDs) with narrow size distribution and high photoluminescence (PL) efficiency were fabricated via a two-step organic synthesis. The QDs were coated with a SiO 2 shell by a reverse micelle route. The thickness of SiO2 shell on the QDs was adjusted for investigating the effect of the porous structure of SiO2 matrix on the stability of the QDs. When the shell thickness of SiO2 shells is less than 5 nm, the pores of SiO 2 shell are type II (cylindrical pores). In contrast, the pores of SiO2 shell are type IV (one-neck-flask-shaped pores) while the shell thickness is 10 nm. The stability of SiO2-coated QDs was investigated in phosphate-buffered saline (PBS, pH ~ 7.4) buffer solutions using various phosphate concentrations. The QDs coated with a SiO2 shell with type IV pores revealed high stability compared with those with type II pores. This is ascribed that cylindrical pores (type II) accelerated the transfer of ions in SiO2 shells compared with type IV pores. Copyright © 2013 American Scientific Publishers. Source

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