A general approach to synthesize asymmetric hybrid nanoparticles by interfacial reactions

Asymmetric multicomponent nanoparticles (AMNPs) offer new opportunities for new-generation materials with improved or new synergetic properties not found in their individual components. There is, however, an urgent need for a synthetic strategy capable of preparing hybrid AMNPs with fine-tuned structural and compositional complexities. Herein, we report a new paradigm for the controllable synthesis of polymer/metal AMNPs with well-controlled size, shape, composition, and morphology by utilizing interfacial polymerization. The hybrid AMNPs display a new level of structural-architectural sophistication, such as controlled domain size and the number of each component of AMNPs. The approach is simple, versatile, cost-effective, and scalable for synthesizing large quantities of AMNPs. Our method may pave a new route to the design and synthesis of advanced breeds of building blocks for functional materials and devices.     

A general approach to mesoporous metal oxide microspheres loaded with noble metal nanoparticles

Catalytic microspheres: A general approach is demonstrated for the facile preparation of mesoporous metal oxide microspheres loaded with noble metal nanoparticles (see TEM image in the picture). Among 18 oxide/noble metal catalysts, TiO(2)/0.1?mol?% Pd microspheres showed the highest turnover frequency in NaBH(4) reduction of 4-nitrophenol (see picture).     

A facile route to synthesize silver nanoparticles in polyelectrolyte capsules

We are reporting a novel green approach to incorporate silver nanoparticles (NPs) selectively in the polyelectrolyte capsule shell for remote opening of polyelectrolyte capsules. This approach involves in situ reduction of silver nitrate to silver NPs using PEG as a reducing agent (polyol reduction method). These nanostructured capsules were prepared via layer by layer (LbL) assembly of poly(allylamine hydrochloride) (PAH) and dextran sulfate (DS) on silica template followed by the synthesis of silver NPs and subsequently the dissolution of the silica core. The size of silver nanoparticles synthesized was 60±20 nm which increased to 100±20 nm when the concentration of AgNO(3) increased from 25 mM to 50 mM. The incorporated silver NPs induced rupture and deformation of the capsules under laser irradiation. This method has advantages over other conventional methods involving chemical agents that are associated with cytotoxicity in biological applications such as drug delivery and catalysis.     

A general route to synthesize supported isolated oxide and mixed-oxide nanoclusters at sizes below 5 nm

A simple and efficient route to prepare supported nanocrystalline oxides is presented. The synthesis procedure, i.e. in situ autocombustion of a glycine complex, allows the production of nanocrystals in a porous matrix presenting larger pore size. An example of successful formation of 2-5 nm nanocrystals is given for a single oxide (Fe(2)O(3)), a mixed-oxide structure (LaCoO(3) perovskite-type) and a nickel-doped oxide.     

A simple route to synthesize carbon-nanotube/cadmium-sulfide hybrid heterostructures and their optical properties

Multi-walled carbon nanotube/cadmium sulfide hybrid heterostructures were easily synthesized by employing a thermal decomposition of thioacetamide as a sulfide-ion source in an aqueous regime. The resulting cadmium-sulfide phase is comprised of a zinc-blende structure of spherical polycrystalline nanoparticles (cadmium-sulfide nanoclusters) with the subunits of ca. 15 nm, deposited on the nanotube surface. The formation of the cadmium-sulfide nanoparticles with zinc-blende structure (cubic crystal) suggests that the local concentrations of reacting ion species in the vicinity of the nanotube surface are different from those in the reaction solution. The cadmium-sulfide nanoparticles are comprised of a stoichiometrically ideal chemical-composition ratio (cadmium: sulfur=1:1.02) of cadmium and sulfur with the valence states of +2 and −2, respectively. The optical responses of the cadmium-sulfide phase for ultraviolet-visible light and photoluminescence spectroscopes show the proper size-effect and inherent optical properties of the cadmium-sulfide nanoparticles.     

A new way to synthesize ZnS nanoparticles

ZnS nanoparticles were prepared with normal ZnO and Na2S by solid-liquid chemical reaction under ultrasonic condition andcharacterized by XRD,TEM,SEM,IR and TG-DTG.The results showed that these particles were good crystal cubic zinc blendedwith average size of 50 nm,possess good IR transmittance in the range of 400-4000 cm and good thermal stability.     

A general method to synthesis of amphiphilic colloidal nanoparticles of CdS and noble metals

Amphiphilic colloids of CdS and noble metal nanoparticles, which can be dispersed both in water and organic solvents such as ethanol, N,N-dimethylformamide, chloroform, and toluene, are studied. The amphiphilic colloidal nanoparticles are synthesized by grafting the amphiphilic and thermoresponsive polymer of thiol-terminated poly(N-isopropylacrylamide) to CdS and noble metal nanoparticles. The size and morphology of the PNIPAM-grafted colloidal nanoparticles of CdS@PNIPAM can be tuned by changing the molar ratio of PNIPAM/CdS. The size of CdS@PNIPAM nanoparticles slightly decreases first from 5.5 to 4.4 nm then slightly increases from 4.4 to 6.1 nm with the decrease in the molar ratio from 1/1 to 1/10. Spherical nanoparticles of CdS@PNIPAM are synthesized at a higher molar ratio and worm-like nanoparticles are obtained at a lower molar ratio. The resultant PNIPAM-grafted colloidal nanoparticles of CdS@PNIPAM, Au@PNIPAM, Pd@PNIPAM, and Ag@PNIPAM are thermoresponsive in water and show a cloud-point temperature at about 32.5 degrees C.     

Ultrasmall water-soluble metal-iron oxide nanoparticles as T1-weighted contrast agents for magnetic resonance imaging

Using an improved hydrolysis method of inorganic salts assisted with water-bath incubation, ultrasmall water-soluble metal-iron oxide nanoparticles (including Fe(3)O(4), ZnFe(2)O(4) and NiFe(2)O(4) nanoparticles) were synthesized in aqueous solutions, which were used as T(1)-weighted contrast agents for magnetic resonance imaging (MRI). The morphology, structure, MRI relaxation properties and cytotoxicity of the as-prepared metal-iron oxide nanoparticles were characterized, respectively. The results showed that the average sizes of nanoparticles were about 4 nm, 4 nm and 5 nm for Fe(3)O(4), ZnFe(2)O(4) and NiFe(2)O(4) nanoparticles, respectively. Moreover, the nanoparticles have good water dispersibility and low cytotoxicity. The MRI test showed the strong T(1)-weighted, but the weak T(2)-weighted MRI performance of metal-iron oxide nanoparticles. The high T(1)-weighted MRI performance can be attributed to the ultrasmall size of metal-iron oxide nanoparticles. Therefore, the as-prepared metal-iron oxide nanoparticles with good water dispersibility and ultrasmall size can have potential applications as T(1)-weighted contrast agent materials for MRI.     

Novel route to synthesize CuO nanoplatelets

A new synthesis route to obtain high-purity cupric oxide, CuO, using the hydrothermal reaction of copper sulfide and a NaOH solution in an oxygen atmosphere has been developed. The synthesized products showed nanoplatelet-like morphologies with rectangular cross-sections and dimensions at the nanometric scale. Variations in the oxygen partial pressure and synthesis temperature produced changes in size and shape, being found that the proliferation of nanoplatelet structures occurred at 200 °C and 30 bar.     

A general phase transfer protocol for synthesizing alkylamine-stabilized nanoparticles of noble metals

The ethanol-mediated phase transfer protocol was extended herein to prepare alkylamine-stabilized nanoparticles of several noble metals by transferring them from aqueous environment into toluene. This method relies on the use of ethanol as a mediator to provide and maintain adequate contact between dodecylamine and metal nanoparticles during the transfer process and involves first mixing the metal hydrosols and an ethanol solution of dodecylamine and then extracting the dodecylamine-stabilized metal nanoparticles into toluene. Alkylamine-stabilized Ag, Pd, Rh, Ir and Os nanoparticles with 7.09, 3.45, 6.89, 2.42 and 4.52 nm in diameter, respectively, could be prepared this way. The self-assembly of dodecylamine-stabilized Ag and Rh nanoparticles was also detected by transmission electron microscopy (TEM).     

Nanorods of transition metal oxalates: A versatile route to the oxide nanoparticles

A versatile route has been explored for the synthesis of nanorods of transition metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates using reverse micelles. Transmission electron microscopy shows that the as-prepared nanorods of nickel and copper oxalates have diameter of 250 nm and 130 nm while the length is of the order of 2.5 μm and 480 nm, respectively. The aspect ratio of the nanorods of copper oxalate could be modified by changing the solvent. The average dimensions of manganese, zinc and cobalt oxalate nanorods were 100 μm, 120 μm and 300 nm, respectively, in diameter and 2.5 μm, 600 nm and 6.5 μm, respectively, in length. The aspect ratio of the cobalt oxalate nanorods could be modified by controlling the temperature.The nanorods of metal (Cu, Ni, Mn, Zn, Co and Fe) oxalates were found to be suitable precursors to obtain a variety of transition metal oxide nanoparticles. Our studies show that the grain size of CuO nanoparticles is highly dependent on the nature of non-polar solvent used to initially synthesize the oxalate rods. All the commonly known manganese oxides could be obtained as pure phases from the single manganese oxalate precursor by decomposing in different atmospheres (air, vacuum or nitrogen). The ZnO nanoparticles obtained from zinc oxalate rods are ～55 nm in diameter. Oxides with different morphology, Fe₃O₄ nanoparticles faceted (cuboidal) and Fe₂O₃ nanoparticles (spherical) could be obtained.     

A novel route to obtain metal and oxide nanoparticles co-existing on a substrate

In this work we present a novel route to cover large surfaces with metal and oxide nanoparticles (NPs) by growing and annealing of metallic bilayers. We have used this method to fabricate ensembles of Au and α-Fe₂O₃ NPs on silica substrates from Fe/Au bilayers. The morphology of the hybrid nanostructures and the presence of defects and disorder can be tuned through the processing parameters as the initial film thickness and the annealing conditions. The proximity effects between both types of NPs alter their physical properties. In particular, we observe that the presence of α-Fe₂O₃ NPs modifies the surface plasmon resonance of Au NPs.     

A general thermal process for the one-step preparation of well-stable noble metal nanoparticles

Heating sodium 3-thiophenemalonic acid-noble metal salt aqueous solution at 100°C, without the extra step of introducing other reducing agents and protective agents, results in the formation of well-stable noble metal that includes Au, Ag, Pt, or Pd nanoparticles. As-formed colloidal solutions were characterized by UV-vis absorption spectra and transmission electron microscopy and the nanoparticle formation process was also traced by time-dependent UV-vis absorption spectra. The text was submitted in English by the author.     

A general route to 5-aminotetrazoles

Various di- and trisubstituted (benzotriazolyl)carboximidamides were used for the preparation of N,N-di- and 1,N,N-trisubstituted 5-aminotetrazoles 3a-e and 6a-d under mild conditions in good to excellent yields.     

A general route to 11-deoxyanthracyclines

Diels-Alder type cycloaddition of unsaturated ketene acetal $\text{5}$ with various naphtoquinones affords a short and regiospecific access to tetracyclic ketones, key intermediates for the further synthesis of 11-deoxyanthracyclines.     

A general route to five-coordinate hydridosilicates

Five-coodinate potassium hydridosilicates, [HSi(OR)₄]⁻ K⁺ (R  Et, i-Pr, Ph), have been obtained in good yield from the reaction of a trialkoxy- or triarylox-silane with the corresponding potassium alkoxide or aryloxide, and characterized spectroscopically. Reaction of the hydrosilicates with an excess of Grignard reagent gives the corresponding triorganosilanes.     

A general nonaqueous route to binary metal oxide nanocrystals involving a C-C bond cleavage

A widely applicable solvothermal route to nanocrystalline iron, indium, gallium, and zinc oxide based on the reaction between the corresponding metal acetylacetonate as metal oxide precursor and benzylamine as solvent and reactant is presented. Detailed XRD, TEM, and Raman studies prove that, with the exception of the iron oxide system, where a mixture of the two phases magnetite and maghemite is formed, only phase pure materials are obtained, gamma-Ga(2)O(3), zincite ZnO, and cubic In(2)O(3). The particle sizes lie in the range of 15-20 nm for the iron, 10-15 nm for the indium, 2.5-3.5 nm for gallium, and around 20 nm for zinc oxide. GC-MS analysis of the final reaction solution after removal of the nanoparticles showed that the composition is rather complex consisting of more than eight different organic compounds. Based on the fact that N-isopropylidenebenzylamine, 4-benzylamino-3-penten-2-one, and N-benzylacetamide were the main species found, we propose a detailed formation mechanism encompassing solvolysis of the acetylacetonate ligand, involving C-C bond cleavage, as well as ketimine and aldol-like condensation steps.     

A general chemical route to polyaniline nanofibers

Uniform polyaniline nanofibers readily form using interfacial polymerization without the need for templates or functional dopants. The average diameter of the nanofibers can be tuned from 30 nm using hydrochloric acid to 120 nm using perchloric acid as observed via both scanning and transmission electron microscopy. When camphorsulfonic acid is employed, 50 nm average diameter fibers form. The measured Brunauer-Emmett-Teller surface area of the nanofibers increases as the average diameter decreases. Further characterization including molecular weight, optical spectroscopy, and electrical conductivity are presented. Interfacial polymerization is shown to be readily scalable to produce bulk quantities of nanofibers.