Solution reduction synthesis of surface stabilized silicon nanoparticles

This paper describes the preparation of air and moisture stable octanol derivatized crystalline silicon nanoparticles by room temperature sodium naphthalenide reduction of silicon halides.     

Biocompatible nanoparticles and gadolinium complexes for MRI applications

Performances of double-emulsion techniques (W/O/W and W/O/O) and ionotropic gelation process were compared to achieve encapsulation of gadolinium MRI contrast agents (GdCAs) into biocompatible polymeric nanoparticles (NPs) with high Gd-loadings. The better approach proved to be ionotropic gelation with H[Gd(DOTA)] as GdCA. Relaxometry evaluation of H[Gd(DOTA)]?NPs efficiency demonstrated that incorporation of H[Gd(DOTA)] inside an hydrogel matrix highly improved H[Gd(DOTA)] relaxivity. Particle efficacy as MR contrast agents was further demonstrated on a 3 T clinical imager: a significant improvement of T₁- and T₂- MR signals was obtained at doses much lower than the currently used.     

Structural insights on nanoparticles containing gadolinium complexes as potential theranostic

Nanostructures are gaining interest in drug release applications. Amphiphilic molecules can give, in water solution, a variety of nanostructures as well as thermodynamically stable mesophases three-dimensional inverse cubic structures. These mesophases are attractive candidates for biomedical applications containing extensive water channel networks and could act as very efficient delivery systems of drugs or contrast agents. In order to discover, optimize, and develop these systems, we have performed a deep physicochemical characterization by dynamic light scattering and small-angle neutron scattering of nanoparticles of monoolein (MO) and Pluronic PF127, containing different amounts (1, 5, 10, and 20 %) of the synthetic amphiphilic gadolinium complex (C18)₂DTPA(Gd). Nanoparticle size is found in the 70–400 nm range for all investigated systems; the morphology of the aggregates is driven by the main constituents MO/PF127 and is a mixture of multilayer vesicles and bicontinuous aggregates. Nanostructures are also able to encapsulate doxorubicin (drug-loading content between 70 and 90 % for the different systems) acting as a potential theranostic for simultaneous cancer therapy and MRI visualization.     

Obtaining gadolinium nanoparticles and studying their properties in a helium flow

A method for obtaining Gd nanoparticles with diameters of 89 to 18 nm upon metal evaporation both in a flow of pure helium and with the addition of 0.5% of oxygen is described. It is found that the addition of O₂ does not affect the size of the particles, their structure, or the Curie temperature, though the magnetization is reduced. Particles with sizes of 18 nm have cubic lattice symmetry (fcc) and remain paramagnetic below T_c; with an increase in the size of nanoparticles, the proportion of the hexagonal (hcp) phase, which coincides with the gadolinium structure, also grows, and below T_c such particles become ferromagnetic. Oxygen impurities seem to have no effect on magnetic and structural transitions in nanoparticles.     

Vapor-phase synthesis of nanoparticles

An overview of methods for preparing nanoparticles in the vapor phase is given, and recent advances are reviewed. Developments in instrumentation for monitoring vapor-phase synthesis of nanoparticles and in modeling these processes are also included. The most important developments relate to improved control and understanding of nanoparticle aggregation and coalescence during synthesis, and to methods for producing multi-component nanoparticles.     

Fine tuning of gadolinium doped ceria electrolyte nanoparticles via reverse microemulsion process

Gadolinium doped ceria (Gd–CeO₂) nanoparticles have been synthesized by an reverse microemulsion system using cyclohexane as the oil phase, a non-ionic surfactant Igepal CO 520 and their mixed aqueous solutions of gadolinium III nitrate hexahydrate and cerium III nitrate hexahydrate as the water phase. The control of particle size was achieved by varying the water to surfactant molar ratio. The synthesized and calcined powders were characterized by thermogravimetry-differential thermal analysis (TGA-DTA), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The XRD results show that all the samples calcined at 700 °C were single phase cubic fluorite structure. The average size of the particle was found to increase with increase in water to surfactant molar ratio (R). The mean diameter of the particle for various value of R varies between 8–15 nm (SEM) and 7.5–11 nm (TEM), respectively. EDS confirm the presence of gadolinia and ceria phase in the nanopowder calcined at 700 °C. FTIR analysis was carried to monitor the elimination of residual oil and surfactant phases from the microemulsion-derived precursor and calcined powder. Raman spectroscopy and DTA evidenced the formation of a solid solution of gadolinium doped ceria at room temperature.     

Hybrid gadolinium oxide nanoparticles: multimodal contrast agents for in vivo imaging

Luminescent hybrid nanoparticles with a paramagnetic Gd2O3 core were applied as contrast agents for both in vivo fluorescence and magnetic resonance imaging. These hybrid particles were obtained by encapsulating Gd2O3 cores within a polysiloxane shell which carries organic fluorophores and carboxylated PEG covalently tethered to the inorganic network. Longitudinal proton relaxivities of these particles are higher than the positive contrast agents like Gd-DOTA which are commonly used for clinical magnetic resonance imaging. Moreover these particles can be followed up by fluorescence imaging. This study revealed that these particles suited for dual modality imaging freely circulate in the blood vessels without undesirable accumulation in lungs and liver.     

Radiation synthesis of seroalbumin nanoparticles

Synthesis of small polymeric particles can be achieved by ionizing radiation technology via intramolecular crosslinking by gamma rays onto soluble polymer molecules in random coil conformation. Differently soluble globular proteins are naturally densely packed structures. Fragmentation and aggregation processes have been reported for irradiated globular proteins solutions with ionizing radiations.In this work we describe protein-based nanoparticles prepared by gamma irradiation of a soluble and globular protein, such as seroalbumin, as the basic building blocks keeping its original conformational shape. Protein nanoparticles in the range 20–40 nm were detected after gamma irradiation of the aqueous protein solution in the presence of polar organic solvents. Nanoparticles were characterized by DLS, fluorescence, and UV and CD spectroscopy, showing that the protein molecules keep their general three-dimensional structure into the created nanoparticle.     

Electrochemical synthesis of polyaniline nanoparticles

Polyaniline nanoparticles were prepared on a highly oriented pyrolytic graphite (HOPG) surface from dilute polyaniline acidic solution (1 mM aniline+1 M HClO₄) using a pulsed potentiostatic method. Electrochemistry, Fourier transform infrared external reflection spectroscopy (FT-IR-ERS), X-ray photoelectron spectroscopy (XPS) and tapping-mode atomic force microscopy (TMAFM) were used to characterize the composition and structure of the polyaniline nanoparticles. FT-IR-ERS and XPS results revealed that the polyaniline was in its emeraldine form. TMAFM measurement showed that the electropolymerized polyaniline nanoparticles dispersed on the HOPG surface with a coverage of about 10¹⁰ cm⁻². These nanoparticles were disk-shaped having a height of 10–30 Å and an apparent diameter varying from 200 to 600 Å. The particle dimensions increased with the electropolymerization charge (Q) over the interval from 5.7 to 19.3 μC cm⁻².     

Polyelectrolyte-templated synthesis of bimetallic nanoparticles

Bimetallic nanoparticles (NPs) are known to exhibit enhanced optical and catalytic properties that can be optimized by tailoring NP composition, size, and morphology. Galvanic deposition of a second metal onto a primary metal NP template is a versatile method for fabricating bimetallic NPs using a scalable, solution-based synthesis. We demonstrate that the galvanic displacement reaction pathway can be controlled through appropriate surface modification of the NP template. To synthesize bimetallic Au-Ag NPs, we used colloidal Ag NPs modified by layer-by-layer (LBL) assembled polyelectrolyte layers to template the reduction of HAuCl(4). NPs terminated with positively and negatively charged polyelectrolytes yield highly contrasting morphologies and Au surface concentrations. We propose that these charged surface layers control galvanic charge transfer by controlling nucleation and diffusion at the deposition front. This surface-directed synthetic strategy can be advantageously used to tailor both overall NP morphology and Au surface concentrations.     

Size-controlled synthesis of magnetite nanoparticles

Monodisperse magnetite nanoparticles have been synthesized by high-temperature solution-phase reaction of Fe(acac)3 in phenyl ether with alcohol, oleic acid, and oleylamine. Seed-mediated growth is used to control Fe3O4 nanoparticle size, and variously sized nanoparticles from 3 to 20 nm have been produced. The as-synthesized Fe3O4 nanoparticles have inverse spinel structure, and their assemblies can be transformed into gamma-Fe2O3 or alpha-Fe nanoparticle assemblies, depending on the annealing conditions. The reported procedure can be used as a general approach to various ferrite nanoparticles and nanoparticle superlattices.     

Chemical synthesis of magnetic nanoparticles

Recent advances in the synthesis of various magnetic nanoparticles using colloidal chemical approaches are reviewed. Typically, these approaches involve either rapid injection of reagents into hot surfactant solution followed by aging at high temperature, or the mixing of reagents at a low temperature and slow heating under controlled conditions. Spherical cobalt nanoparticles with various crystal structures have been synthesized by thermally decomposing dicobalt octacarbonyl or by reducing cobalt salts. Nanoparticles of Fe-Pt and other related iron or cobalt containing alloys have been made by simultaneously reacting their constituent precursors. Many different ferrite nanoparticles have been synthesized by the thermal decomposition of organometallic precursors followed by oxidation or by low-temperature reactions inside reverse micelles. Rod-shaped iron nanoparticles have been synthesized from the oriented growth of spherical nanoparticles, and cobalt nanodisks were synthesized from the thermal decomposition of dicobalt octacarbonyl in the presence of a mixture of two surfactants.     

Sonochemical synthesis of ruthenium nanoparticles

Ruthenium nanoparticles have been prepared by sonochemical reduction of a ruthenium chloride solution using ultrasound frequencies in the range 20–1056 kHz The reduction was monitored by UV-Vis absorption spectrophotometry. Reduction proceeds sequentially from Ru(III) to Ru(II) to Ru(0) and takes almost 13 h. The Ru particles produced by the ultrasound reduction have diameters between 10 and 20 nm as measured by transmission electron microscope image.     

Solid state synthesis of water-dispersible silicon nanoparticles from silica nanoparticles

A solid state synthesis for obtaining nanocrystalline silicon was performed by high temperature reduction of commercial amorphous nanosilica with magnesium powder. The obtained silicon powder contains crystalline silicon phase with lattice spacings characteristic of diamond cubic structure (according to high resolution TEM), and an amorphous phase. In ²⁹Si CP MAS NMR a broad multicomponent peak corresponding to silicon is located at −61.28 to −69.45 ppm, i.e. between the peaks characteristic of amorphous and crystalline Si. The powder has displayed red luminescence while excited under UV illumination, due to quantum confinement within the nanocrystals. The silicon nanopowder was successfully dispersed in water containing poly(vinyl alcohol) as a stabilizing agent. The obtained dispersion was also characterized by red photoluminescence with a band maximum at 710 nm, thus enabling future functional coating applications.     

Sonochemical synthesis of magnetic Janus nanoparticles

The sonochemical synthesis of nanosized surface-dissymmetrical (Janus) particles is described. The Janus particles were composed of silica and polystyrene, with the polystyrene portion loaded with nanosized magnetite particles. It is shown that the Janus particles can be used to form kinetically stable oil-in-water emulsions that can be spontaneously broken on application of an external magnetic field. The one-pot synthetic process used to prepare the Janus particles has several advantages over other conventional methods of producing such particles.     

聚甲基丙烯酸钠辅助的金纳米颗粒的绿色制备

利用聚甲基丙烯酸钠的弱还原性和螯合作用,建立了一种水溶性金纳米颗粒合成的新方法.借助紫外可见分光光度计和透射电子显微镜对金纳米颗粒进行了表征,初步讨论了反应物浓度以及反应温度对产物的影响.     

Photochemical synthesis of cadmium sulfide nanoparticles

The formation of cadmium sulfide nanoparticles upon UV irradiation of aqueous solutions of cadmium thiosulfates was established on the basis of spectroscopic and macroscopic data. The yield and size of the cadmium sulfide nanoparticles depend on the ratio of cadmium to thiosulfate ions in solution, the concentration of the solution, and the irradiation duration. The cadmium sulfide nanoparticles with a diameter of 4 nm were obtained by the photolysis of solutions with a concentration of 10⁻³ mol L⁻¹ at the ratio S₂O₃ ²⁻: Cd²⁺ = 2: 1.     

Platinum-catalyzed synthesis of water-soluble gold-platinum nanoparticles

The ability to control composition and size in the synthesis of bimetallic nanoparticles is important for the exploitation of the bimetallic catalytic properties. This paper reports findings of an investigation of a new approach to the synthesis of gold-platinum (AuPt) bimetallic nanoparticles in aqueous solution via one-phase reduction of AuCl(4-) and PtCl(4)(2-) using a combination of reducing and capping agents. Hydrogen served as a reducing agent for the reduction of Pt(II), whereas acrylate was used as a reducing agent for the reduction of Au(III). The latter reaction was found to be catalyzed by the formation of Pt as a result of the reduction of Pt(II). Acrylate also functioned as capping agent on the resulting nanocrystals. By controlling the feed ratios of AuCl(4-) and PtCl(4)(2-) and the relative concentrations of acrylate, an effective route for the preparation of AuPt nanoparticles with bimetallic compositions ranging from approximately 4 to 90% Au and particle sizes ranging from 2 to 8 nm has been demonstrated. The composition, size, and shell properties were characterized using transmission electron microscopy, direct current plasma-atomic emission spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. Implications of the results to the exploration of bifunctional catalysts are also briefly discussed.