A Thin Silica-Polymer Shell for Functionalizing Colloidal Inorganic Nanoparticles

Highly Efficient and Thermally Stable QD-LEDs Based on Quantum Dots-SiO2-BN Nanoplate Assemblies

Silica encapsulation effectively elevates the resistance of quantum dots (QDs) against water and oxygen. However, QDs-SiO₂ composites present low thermal conductivity and strong thermal accumulation, leading to considerable fluorescence quenching of QDs in optoelectronic devices at high power. Here, a sandwich structural QDs-SiO₂-BN nanoplate assembly material (QDs-SiO₂-BNAs) is developed to reduce the thermal quenching and enhance the stability of QDs in LEDs. The QDs-SiO₂-BNAs is fabricated by embedding QDs-SiO₂ into the interlayer of layer-by-layer assembled BN nanoplates, and the BN nanoplates are pretreated by SiO₂ encapsulation to strengthen the interaction with QDs-SiO₂. This assembly structure endows the QDs with fast heat dissipation and double surface protection against air. The medium power QDs-converted LEDs (QD-LEDs) fabricated by direct on-chip packaging of the QDs-SiO₂-BNAs gain 44.2 °C temperature reduction at 0.5 W in comparison with conventional QD-LEDs. After aging, the resulting QD-LEDs present degradation of only 1.2% under sustained driving for 250 h. The QD-LEDs also pass the 1 week reliability test at 85 °C/85% RH with <±0.01 shift of the color coordinates, demonstrating the profound potential of the QDs-SiO₂-BNAs in LED lighting and display applications.

Core/shell quantum dots encapsulated in biocompatible oil-core nanocarriers as two-photon fluorescent markers for bioimaging

Highly fluorescent quantum dots (QDs)-loaded nanocapsules, intended for fluorescent cell imaging, were prepared via an emulsification/solvent-evaporation method. CdSe/ZnS core/shell quantum dots were applied as cargo; Poloxamer 403 as the polymer component; Cremophor EL as the nonionic surfactant; and mineral oil, oleic acid, or silicone oil were applied as the oil phases. Transmission electron microscopy, atomic force microscopy, dynamic light scattering, and zeta potential measurements were used to characterize the novel QDs-labeled nanoparticles by particle size, distribution, and morphology, as well as by ζ-potential and physical stability. The fabricated long-lasting nanocapsules exhibit good luminescence properties upon both one-photon and two-photon excitation. The potential of the encapsulated QDs for fluorescent imaging was evaluated in cytotoxicity studies as well as in imaging of intracellular localization, accumulation, and distribution of QDs delivered to well-characterized human cancer cell lines--doxorubicin-sensitive breast (MCF-7/WT) and alveolar basal epithelial (A549)--as well as on normal human umbilical vein endothelial (HUVEC) cells, as investigated by confocal laser scanning microscopy (CLSM). The colloidal CdSe/ZnS-loaded nanocapsules are shown to exhibit strong two-photon-induced luminescence upon excitation in the NIR optical transmission window spectral range, making them ideal markers for bioimaging application. The total two-photon cross section of a single nanocapsule was determined to be about 4.1 × 10(6) GM at 800 nm.

Synthesis and Phase Transfer of Monodisperse Iron Oxide (Fe3O4) Nanocubes

Cube-shaped magnetic iron oxide nanoparticles were synthesised and studied with the aim to achieve superior magnetic properties. This study describes a straightforward and simple synthesis method for preparing monodisperse 11–14-nm superparamagnetic iron oxide nanocubes via an ‘effective monomer’ growth mechanism. The as-synthesised nanoparticles are insoluble in water. However, substitution of the non-polar ligands of the particles using a new method that involved an ionic compound generated colloidally stable and water dispersible cube-shaped particles with a very small hydrodynamic diameter. The cubes displayed superior magnetic properties over spherical particles.

Polymer-coated quantum dots

Quantum Dots (QDs) are semiconductor nanocrystals with distinct photophysical properties finding applications in biology, biosensing, and optoelectronics. Polymeric coatings of QDs are used primarily to provide long-term colloidal stability to QDs dispersed in solutions and also as a source of additional functional groups used in further chemical derivatization of the nanoparticles. We review the coating methods, including multidentate and amphiphilic polymeric coatings, and grafting-to and grafting-from approaches. We highlight the most commonly used polymers and discuss how their chemical structure influences the coating properties.

Controllable synthesis of highly conductive polyaniline coated silica nanoparticles using self-stabilized dispersion polymerization

Highly conductive silica/polyaniline (PANi) core/shell nanoparticles (NPs) were synthesized in various diameters (from 18 to 130 nm) using self-stabilized dispersion polymerization. The polymerization was carried out in an aqueous/organic liquid system at -30 °C. In this system, the organic phase plays a key role in directing para-direction oriented polymerization of the PANi on the surface of silica NPs. Because of its para-direction polymerized structure, the synthesized silica/PANi core/shell NPs exhibited enhanced electrical conductivity (25.6 S cm(-1)) compared with NPs (1.4 S cm(-1)) prepared by homogeneous polymerization. The conductivities and BET surface areas were 25.6 S cm(-1)/170 m(2) g(-1) (18 nm in diameter), 22.5 S cm(-1)/111 m(2) g(-1) (35 nm in diameter), 18.3 S cm(-1)/78 m(2) g(-1) (63 nm in diameter), and 16.4 S cm(-1)/53 m(2) g(-1) (130 nm in diameter). In this series, increased para-coupling along the polymer backbone was elucidated using several characterization techniques, including Fourier transform infrared (FTIR), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) spectroscopy. As-prepared silica/PANi core/shell NPs exhibited capacitance as high as 305 F g(-1).