Sonochemically synthesized mesoporous cobalt oxide nanoparticles for luminol-enhanced chemiluminescence sensing.

In recent years, mesoporous cobalt oxides have attracted more attention due to their exceptional physical and chemical properties and their important applications in various fields. The synthesis of cobalt oxides of various sizes, morphologies, and porosity is still a challenging process. In this report, mesoporous Co3O4NPs with different porosity were synthesized through facile, one-step, and cost-effective routes, without using any complicated materials or instruments, via the sonochemical process. X-ray powder diffraction (XRD), BET, and transmission electron microscopy (TEM) were used to characterize the as-synthesized NPs. XRD technique was used to determine the crystal structure and phase of the NPs, BET to describe the porous nature of the NPs, and TEM to investigate the structure and morphology of the NPs. Next, the effect of as-synthesized Co3O4NPs as a catalyst for the luminol-H2O2chemiluminescence system was studied. Co3O4NPs were chosen since they have nanoscale size, high specific surface area, and mesoporous nature. Therefore, these NPs can form more active sites and thus show unique catalytic activity than common ionic catalysts such as Co2+, Fe3+, Cu2+used in the luminol-H2O2CL system. Finally, this system was used to detect and measure H2O2and glucose under optimal conditions. A good linear relationship was observed between the chemiluminescence intensity of the designed system and the concentration of H2O2and glucose. A linear range like 0.25-10 pM for H2O2and 1-30 nM for glucose was obtained. The excellent LOD of the proposed method for measuring H2O2was about 0.07 pM, and for measuring glucose was about 0.14 nM.

Nanoporous TiO2 nanoparticle assemblies with mesoscale morphologies: nano-cabbage versus sea-anemone.

We report the novel synthesis of nanoporous TiO2 nanoparticle ensembles with unique mesoscale morphologies. Constituent nanoparticles evolved into multifaceted assemblies, exhibiting excellent crystallinity and enhanced photocatalytic activity compared with commercial TiO2. Such materials could be exploited for applications, like organic pollutant degradation.

Bright luminescent, colloidal stable silica coated CdSe/ZnS nanocomposite by an in situ, one-pot surface functionalization.

In this article, a systematic study of the design and development of surface-modification schemes for silica coated nanocomposite via an in situ, one-pot way is presented. Silica coated CdSe/ZnS nanoparticles were prepared in a water-in-oil microemulsion and subsequently surface modified via addition of various organosilane reagents to the microemulsion system. The resulting functionalized composite nanoparticles were characterized by different techniques like Transmission Electron Microscopy (TEM), photoluminescence spectroscopy and zeta-potential measurements. The results demonstrate that depending on the sequence of addition of silica precursors and organosilanes the product can show bright luminescence or considerable colloidal stability. The organosilanes molecules which are used here, act both as a stabilizer of the microemulsion system (regarding the charge compensation) and as a functional group the final product on top of silica shell. Using these surface-modification process, silica coated nanoparticles can be more readily conjugated with biomolecules and used as highly luminescent, sensitive, and reproducible labels in bioanalytical applications. Most importantly such surface functionalization could pave the way for controlled multi-mixed nanoparticles encapsulation (for example magnetic and QD nanoparticles).

A facile synthesis method to silica coated CdSe/ZnS nanocomposites with tuneable size and optical properties.

A facile method for the preparation of single Quantum Dots (QDs) in silica spheres with tunable size and optical property has been developed. A time interval addition of silica precursor method has been used to increase the size of the silica shell and in parallel tuning the photoluminescence property. The resulting CdSe/ZnS/SiO(2) nanocomposites were characterized by transmission electron microscopy, photoluminescence spectroscopy and zeta-potential measurements. Since for different applications of silica coated core-shell nanoparticles, control over the thickness of the shell in parallel with tuning on the optical property of the final product required, these study could pave the way for the application of this nanocomposites in different fields like photonic crystals, biolabeling, etc.

A four-color colloidal multiplexing nanoparticle system.

Any labeling with multicolor markers can be affected by the autofluorescence of biological tissue due to the UV or blue light excitation sources, or the results are affected by fluorescence resonance energy transfer. In this work, we present novel IR-to-vis upconverting nanoparticles of different rare earth metal dopants. With a single excitation source of 980 nm, four different colors of nanocrystals can be spectrally separated under multiplexing conditions. The particles were phase transferred into polar solvents by means of silica encapsulation and were characterized by transmission electron microscopy, X-ray diffraction, and photoluminescence spectroscopy.

Au-silica nanoparticles by "reverse" synthesis of cores in hollow silica shells.

Core-silica shell nanoparticles were prepared in a "reverse" manner by nucleation and growth of Au cores within hollow silica nanospheres.

Silica encapsulation of hydrophobically ligated PbSe nanocrystals.

Spherical PbSe@SiO2 nanoparticles have been successfully synthesized within reverse micelles via metal alkoxide hydrolysis and condensation within a microemulsion system. These core-shell nanoparticles were characterized by transmission electron microscopy (TEM), NIR absorption spectroscopy, energy-dispersive X-ray analysis, and TEM electron diffractions. It shows that the obtained core-shell structures have a spherical shape with narrow size distribution (average size approximately 35 nm) and smooth surfaces. The size of the particles and the thickness of the shells can be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethoxysilane (TEOS) within the microemulsion.

One-pot synthesis of YF3@silica core/shell nanoparticles.

A new one-pot synthetic method for preparing core/shell YF3@SiO2 nanoparticles with different morphologies, from spherical to elongated structures ("pearl necklace"), is described; absorbance and photoluminescence spectroscopy reveals intrinsic but no extrinsic defects in the YF3.

Silica coated, water dispersible and photoluminescent Y (V,P)O(4):Eu(3+),Bi(3+) nanophosphors.

We propose an approach for silica encapsulation of YV((0.7))P((0.3))O(4):Eu(3+), Bi(3+) nanophosphors through a microemulsion process. The resulting YV((0.7))P((0.3))O(4):Eu(3+), Bi(3+)@SiO(2) core-shell nanophosphors were characterized by transmission electron microscopy, UV/vis absorption and photoluminescence spectroscopy, energy-dispersive x-ray analysis (EDAX), selected area electron diffraction and zeta-potential measurements. The obtained nanocomposites have quite a uniform spherical shape and diameters of about 15 nm. Zeta-potential measurements show that coated particles are stable at high volume fractions and can endure large variations in pH and electrolyte concentration without coalescence. These core-shell nanophosphors could also be used as ultrasensitive biological labels, because they are obtained in nanoscale and well dispersible in water.