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PubMed2005

Holographic manipulation of nanoparticle distribution morphology in nanoparticle-dispersed photopolymers.

We report on experimental verification of mass transfer of nanoparticles during holographic recording in nanoparticle-dispersed photopolymers. Through direct observations of the microscopic structure of recorded holograms as well as optical measurements of the phase shift between the light interference pattern and a recorded hologram we find that holographic exposure causes nanoparticles to be redistributed from bright to dark regions, leading to periodic assembly of nanoparticles and thereby to formation of high-contrast holograms.

Journal Article↗

PubMed2006

Two-dimensional imaging of atomic distribution morphology created by holographically induced mass transfer of monomer molecules and nanoparticles in a silica-nanoparticle-dispersed photopolymer film.

We report an electron-probe microanalysis of a hologram recorded in a silica-nanoparticle-dispersed photopolymer film. We used S and Si atoms as label elements to identify formed polymer and nanoparticle species, respectively. It is found that the periodic density distributions of S and Si atoms are out of phase with each other, indicating that those of the formed polymer and nanoparticles are out of phase each other. This result shows decisive evidence of the mutual diffusion of monomer molecules and silica nanoparticles in the film under holographic two-beam interference exposure.

Journal Article↗

PubMedDate not supplied

The preparation of CdTe nanoparticles and CdTe nanoparticle-labelled microspheres for biological applications.

Different sizes of CdTe semiconductor nanoparticles were prepared in aqueous solution. These nanoparticles exhibit narrow fluorescence with full width at half-maximum (FWHM) of 35-45 nm that spans the visible spectrum, and they also have high PL quantum yield with high resistance to photodegradation. In addition, CdTe quantum dot (QD)-labelled microspheres, comprising polystyrene (PS) cores and CdTe/polyelectrolyte (PE) shells, were also prepared by the layer-by-layer technique in this paper. The optical properties of the CdTe nanoparticles and CdTe-labelled microspheres were investigated by UV-Visible absorption and luminescence spectroscopy, and fluorescence microscopy was employed for microscopic identification behaviour of the luminescent microspheres.

Animals↗

PubMed2005

Gold nanoparticle-cytochrome C complexes: the effect of nanoparticle ligand charge on protein structure.

We report the effect of nanoparticle ligand charge on the structure of a covalently, site-specifically linked protein. Au nanoparticles with positive, negative, and neutral ligands were appended to a specific cysteine, C102, of Saccharomyces cerevisiae cytochrome c. Conjugates were purified by HPLC or gel electrophoresis. Circular dichroism spectroscopy shows that changing the nanoparticle ligand dramatically influences the attached cytochrome c structure. The protein retains its structure with neutral ligands but denatures in the presence of charged species. This is rationalized by the electrostatic interaction of amino acids in the local vicinity of C102 with the endgroups of the ligand.

Chromatography, High Pressure Liquid↗

PubMed2005

Novel polyelectrolyte carboxymethyl konjac glucomannan-chitosan nanoparticles for drug delivery. I. Physicochemical characterization of the carboxymethyl konjac glucomannan-chitosan nanoparticles.

Carboxymethyl konjac glucomannan-chitosan (CKGM-CS) nanoparticles, which are well dispersed and stable in aqueous solution, were spontaneously prepared under very mild conditions via polyelectrolyte complexation. The physicochemical properties of the nanoparticles were identified by Zetasizer 3000 and Fourier transform infrared. It was found that at various CKGM and CS concentrations the particles ranged in size from approximately 50 to 1200 nm, and the zeta potential from 15 to 45 mV. By changing pH value of the medium and increasing the concentration of salt, the mean size of the particles increased and the zeta potential decreased. Also, investigations on the encapsulation efficiency of the bovine serum albumin loaded CKGM-CS nanoparticles were also undertaken. This nanoparticulate system driven by complex formation shows potential as an advanced drug delivery system for water-soluble drugs.

Chitosan↗

PubMed2006

Co-Pt alloy nanoparticles produced using a template of nanoparticle array.

A monolayer of Co-Pt alloy nanoparticles in the nanometer-size regime was fabricated using a nanotemplate approach. 1.7-nm-thick Co46Pt54 film was deposited onto a preexisting array of Ni seed particles embedded in a polyimide film. During subsequent annealing, the deposited Co46Pt54 film coalesced onto the seed particles to produce a monolayer of Co-Pt alloy particles. Deposition and annealing were repeated to increase both average particle size and volume fraction of the alloy particles. It was also shown that the annealing temperature was critical in controlling the particle size distribution and the final composition of the nanoparticles. This method of forming a single layer of vertically aligned nanoparticles can be easily extended to a large area as well as to produce a different combination of alloy particles on a polymer film.

Journal Article↗

PubMed2005

Synthesis of amorphous carbon nanoparticles and carbon encapsulated metal nanoparticles in liquid benzene by an electric plasma discharge in ultrasonic cavitation field.

A newly-developed method permits an electric plasma discharge to occur with relatively low electric power in insulating organic solutions due to the presence of an ultrasonic cavitation. A stable electric plasma could be generated in an ultrasonic cavitation field containing a thousand tiny activated bubbles, in which the electric conductivity could be improved due to formed radicals and free electrons, using copper electrodes and a titanium ultrasonic horn. This method allowed us to synthesize pyrolytic amorphous carbon nanoparticles smaller than about 30 nm in diameter from benzene liquid. In addition, we synthesized TiC nanoparticles about 50-150 nm in size, and copper nanoparticles smaller than 10 nm, which were encapsulated in multilayered graphite cages. Finally, we used GC-MS and MALDI-TOF-MS to observe and analyze the polymerized compounds and the degree of polymerization of the benzene liquid after the plasma treatment.

Benzene↗

PubMed2003

Metathetical conversion of Nd2O3 nanoparticles into NdS2 polysulfide nanoparticles at low temperatures using boron sulfides.

A new simple metathetical sulfidation method using boron sulfides has been developed to prepare nanoparticles of NdS(2) via conversion of ca. 50-nm-sized nanoparticles of Nd(2)O(3) at 450 degrees C, in which boron and sulfur powders form boron sulfides in situ and evaporate to sulfidize the oxide. The X-ray powder diffraction analysis revealed that the products were purely NdS(2), and the atomic absorption spectrometric analysis confirmed nonexistence of boron in the products after washing with water. The detailed TEM studies showed that the NdS(2) nanoparticles maintained the original size of the oxide particles without fusion during the low-temperature sulfidation process.

Journal Article↗

PubMed2005

Environmentally responsive "hairy" nanoparticles: mixed homopolymer brushes on silica nanoparticles synthesized by living radical polymerization techniques.

This article reports on the preparation of environmentally responsive "hairy" nanoparticles by growth of mixed poly(tert-butyl acrylate) (PtBA)/polystyrene (PS) brushes from silica particles using living radical polymerization techniques and subsequent hydrolysis of PtBA to produce amphiphilic mixed poly(acrylic acid) (PAA)/PS brushes. Silica particles were synthesized by the Stober process and were functionalized with an asymmetric difunctional initiator-terminated monolayer. Surface-initiated atom transfer radical polymerization of tBA was carried out in the presence of a free initiator. Kinetics study showed that the polymerization was well controlled. By cleaving PtBA off the particles, the molecular weights of the grafted and free polymers were found to be essentially identical. Mixed PtBA/PS brushes were obtained by the nitroxide-mediated radical polymerization of styrene from PtBA particles. The M(n) of the grafted PS was found to be the same as that of the free PS formed in the solution from the free initiator. Amphiphilic mixed PAA/PS brush-coated nanoparticles were synthesized from mixed PtBA/PS particles by hydrolysis of PtBA with iodotrimethylsilane. Tyndall scattering experiments and (1)H NMR study showed that the mixed PAA/PS particles can be dispersed and form a stable suspension in CHCl(3), a selective solvent for PS, and also in CH(3)OH, a selective solvent for PAA, demonstrating the capability of these hairy nanoparticles to undergo chain reorganization in response to environmental changes.

Journal Article↗

PubMed1995

Evaluation of poly(isobutylcyanoacrylate) nanoparticles for mucoadhesive ocular drug delivery. I. Effect of formulation variables on physicochemical characteristics of nanoparticles.

A factorial design was applied to evaluate the effect of formulation variables on physicochemical properties of poly(isobutylcyanoacrylate) nanoparticles. Formulation variables were dextran T40 or T70 and Pluronic F68 or Tween 20 acting as stabilizer and surfactant respectively, and three pH levels (2, 4 and 7). Nanoparticles possessed unimodal particle size distribution with significant effect of dextran, surfactant and pH. A wide range of molecular weight distribution was observed with significant effect of pH and dextran on average molecular weight. NMR studies revealed the presence of dextran, monomer and surfactants in the nanoparticles. Solid state surface analysis using X-ray photoelectron spectroscopy confirmed the presence of three chemical environments to the carbon envelope, O-C = O, C-O/C identical to N and C-C.

Chromatography, Gel↗

PubMed2003

Physicochemical investigations on solid lipid nanoparticles and on oil-loaded solid lipid nanoparticles: a nuclear magnetic resonance and electron spin resonance study.

PURPOSE: Recently, colloidal dispersions made of mixtures from solid and liquid lipids have been described to combine controlled-release characteristics with higher drug-loading capacities than solid lipid nanoparticles (SLNs). It has been proposed that these nanostructured lipid carriers (NLCs) are composed of oily droplets that are embedded in a solid lipid matrix. The present work investigates the structure and performance of NLCs. METHODS: Colloidal lipid dispersions were produced by high-pressure homogenization and characterized by laser diffraction, photon correlation spectroscopy, wide-angle x-ray scattering, and differential scanning calorimetry. Proton nuclear magnetic resonance spectroscopy and electron spin resonance experiments were performed to investigate the mobility of the components and the molecular environment of model drugs. Furthermore, a nitroxide reduction assay with ascorbic acid was conducted to explore the accessibility of the lipid model drug from the outer aqueous phase. RESULTS: Proton nuclear magnetic resonance spectra clearly demonstrate that NLC nanoparticles differ from nanoemulsions and from SLNs by forming a liquid compartment that is in strong interaction to the solid lipid. The electron spin resonance model drug was found to be accommodated either on the particle surface with close water contact (SLN) or additionally in the oil (NLC). The oil compartment must be localized on the particle surface, because it can be easily reached by ascorbic acid. CONCLUSION: Neither SLN nor NLC lipid nanoparticles showed any advantage with respect to incorporation rate or retarded accessibility to the drug compared with conventional nanoemulsions. The experimental data let us conclude that NLCs are not spherical solid lipid particles with embedded liquid droplets, but they are rather solid platelets with oil present between the solid platelet and the surfactant layer.

Calorimetry, Differential Scanning↗

PubMed2006

Synthesis of small palladium nanoparticles stabilized by bisphosphine BINAP bearing an alkyl chain and their palladium nanoparticle-catalyzed carbon-carbon coupling reactions under room-temperature.

A new bisphosphine ligand, C8-BINAP, and C8-BINAP-stabilized palladium nanoparticles have been prepared; C8-BINAP was found to be an effective protecting ligand for preparing and stabilizing palladium nanoparticles with very small core size and narrow size distribution and the C8-BINAP-Pd nanoparticles behave as an efficient catalyst for carbon-carbon coupling reactions at room temperature.

Journal Article↗

PubMed2005

Scanning transmission electron microscopy and its application to the study of nanoparticles and nanoparticle systems.

Scanning transmission electron microscopy (STEM) techniques can provide imaging, diffraction and spectroscopic information, either simultaneously or in a serial manner, of the specimen with an atomic or a sub-nanometer spatial resolution. High-resolution STEM imaging, when combined with nanodiffraction, atomic resolution electron energy-loss spectroscopy and nanometer resolution X-ray energy dispersive spectroscopy techniques, is critical to the fundamental studies of importance to nanoscience and nanotechnology. The availability of sub-nanometer or sub-angstrom electron probes in a STEM instrument, due to the use of a field emission gun and aberration correctors, ensures the greatest capabilities for studies of sizes, shapes, defects, crystal and surface structures, and compositions and electronic states of nanometer-size regions of thin films, nanoparticles and nanoparticle systems. The various imaging, diffraction and spectroscopy modes available in a dedicated STEM or a field emission TEM/STEM instrument are reviewed and the application of these techniques to the study of nanoparticles and nanostructured catalysts is used as an example to illustrate the critical role of the various STEM techniques in nanotechnology and nanoscience research.

Journal Article↗

PubMed2006

Synthesis of core-shell nanoparticles using organic surface-functionalized gold and Au@SiO2 nanoparticles as multifunctional initiators in atom transfer radical polymerization.

Gold and Au@SiO2 nanoparticles were synthesized and surface-functionalized by initiators for atom transfer radical polymerization (ATRP), either using a thiol or a trialkoxysilane anchor group for the immobilization of the initiating functionality. The thus obtained initiator-capped gold systems were applied in polymerizations of various monomers, such as styrene, methacrylic acid trimethyloxysilyl propylester and isoprene and copolymers thereof. The final inorganic-organic core-shell nanoparticles were characterized applying different techniques such as electron microscopy and light scattering. Kinetic studies of the polymerizations revealed that they were highly controlled and therefore the thickness of the polymer shell could be easily adjusted. The obtained nanoparticles formed stable suspensions in various organic solvents and can therefore be used as building blocks for polymer nanocomposites.

Gold↗

PubMed2001

Nanoparticles in plant extracts--factors which influence the formation of nanoparticles in black tea infusions.

The influence of different factors on the formation of nanoparticles in freshly brewed tea extracts was investigated. A black tea infusion was observed during cooling using photon correlation spectroscopy (PCS). The mean particle size and the number of the nanoparticles increase with decreasing temperature. In the presence of caffeine more particles are formed within the infusion. To study the influence of slight structural differences between methylxanthines, the effect of the addition of caffeine to solutions of freshly prepared decaffeinated tea was compared to that of theophylline and theobromine. In the case of theophylline fewer nanoparticles were formed. Molecular modelling calculations were performed to evaluate the most probable geometries for caffeine-polyphenol complexes. A parallel position and a congruent orientation of the 6-membered ring of caffeine and the aromatic galloyl group is the most probable geometry.

Absorptiometry, Photon↗

PubMed1991

Nanoparticles as drug carriers for vinblastine. Acute toxicity of vinblastine in a free form and associated to polybutylcyanoacrylate nanoparticles.

The possibility of reducing toxicity of Vinblastine by fixing it in polybutyl-2-cyanoacrylate nanoparticles was studied. A significant reduction of mortality of mice was recorded after a single intraperitoneal (i. p.) injection of nanoparticle-associated Vinblastine. A wide range of doses of Vinblastine (1.04-6.25 mg/kg) were used. There was a considerable decrease of leucopenia caused by Vinblastine-loaded polybutyl-2-cyanoacrylate nanoparticles as compared to that induced by free Vinblastine.

Animals↗

PubMed2006

Fabrication of hollow multifunctional spheres containing MCM-41 nanoparticles and magnetite nanoparticles using layer-by-layer method.

Macroscopic mesoporous silica spheres have been fabricated by alternatively depositing preformed MCM-41 nanoparticles and polyelectrolytes onto polystyrene lattices. High surface area hollow mesoporous spheres were obtained by removal of the core by solvent or calcination. Further, the versatility of the layer-by-layer (LBL) method was extended to fabricate magnetite-mesoporous silica composites by depositing magnetite and MCM-41 nanoparticles onto polystyrene beads. Such high surface area composites are important since the mesopores can be used for encapsulation of varied materials like enzymes and drugs while the presence of magnetite ensures application in biocatalysis and separation under magnetic field.

Journal Article↗

PubMed2003

Chiral bisphosphine BINAP-stabilized gold and palladium nanoparticles with small size and their palladium nanoparticle-catalyzed asymmetric reaction.

The reduction of tetrachloroaurate or potassium tetrachloropalladate with sodium borohydride in the presence of optically active 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl [BINAP] gave the chiral (S)- or (R)-BINAP-stabilized gold or palladium nanoparticles which showed the small core (1.7 nm for BINAP-Au and 2.0 nm for BINAP-Pd) with narrow size distribution and remarkably high stability. Asymmetric hydrosilylation of styrene with trichlorosilane in the presence of chiral BINAP-Pd nanoparticles afforded an optically active 1-phenyl-1-trichlorosilylethane which was converted into an optically active 1-phenylethanol (95% enantiomeric excess) by oxidative cleavage of the carbon-silicon bond.

Journal Article↗