Recovery of nanoparticles produced in phosphatidylcholine-based template phases

This paper focuses on the characterization and use of polymer-modified phosphatidylcholine (PC)/sodium dodecyl sulfate (SDS)-based inverse microemulsions as a template phase for BaSO4 nanoparticle formation. The area of the optically clear inverse microemulsion phase in the isooctane/hexanol/water/PC/SDS system is not significantly changed by adding polyelectrolytes, i.e., poly(diallyldimethylammonium chloride) (PDADMAC), or amphoteric copolymers of diallyldimethylammonium chloride and maleamid acid to the SDS-modified inverse microemulsion. Shear experiments show non-Newtonian flow behavior and oscillation experiments show a frequency-dependent viscosity increase (dilatant behavior) of the microemulsions. Small amounts of bulk water were identified by means of differential scanning calorimetry. One can conclude that the macromolecules are incorporated into the individual droplets, and polymer-filled microemulsions are formed. The polymer-filled microemulsions were used as a template phase for the synthesis of BaSO4 nanoparticles. After solvent evaporation the nanoparticles were redispersed in water and isooctane, respectively. The polymers incorporated into the microemulsion are involved in the redispersion process and influence the size and shape of the redispersed BaSO4 particles in a specific way. The crystallization process mainly depends on the type of solvent and the polymer component added. In the presence of the cationic polyelectrolyte PDADMAC the crystallization to larger cubic crystals is inhibited, and layers consisting of polymer-stabilized spherical nanoparticles of BaSO4 (6 nm in size) will be observed.     

Modification of gold nanoparticle composite nanostructures using thermosensitive core-shell particles as a template

We report the formation of novel thermosensitive hybrid core-shell particles via in situ synthesis of gold nanoparticles using thermosensitive core-shell particles as a template. The template core-shell particles, with cores composed mainly of poly(glycidyl methacrylate) (GMA) and shells composed mainly of poly(N-isopropylacrylamide) (PNIPAM), were synthesized in aqueous medium, and functional groups such as thiol groups were incorporated into each particle. We found that these particles containing thiol groups were effective for the in situ synthesis of gold nanoparticles in long-term storage. The obtained hybrid particles exhibited a reversible color change from red to purple, which originated from the surface plasmon resonance of gold nanoparticles and which was temperature-dependent in the range of 25-40 degrees C. In addition to their thermosensitive property, the hybrid particles exhibited the unique characteristic of uniform distribution on a solid substrate. The particles obtained by this approach have potential thermosensitive applications such as in sensors and photonic or electronic devices.     

Gold nanoparticle localization at the core surface by using thermosensitive core-shell particles as a template

We report novel thermosensitive hybrid core-shell particles via in situ gold nanoparticle formation using thermosensitive core-shell particles as a template. This method for the in situ synthesis of gold nanoparticles with microgel interiors offers the advantage of eliminating or significantly reducing particle aggregation. In addition, by using thermosensitive microgel structures in which the shell has thermosensitive and gel properties in water--whereas the core itself is a water-insoluble polymer--we were able to synthesize the gold nanoparticles only at the surface of the core, which had reactive sites to bind metal ions. After the gold nanoparticles were synthesized, electroless gold plating was carried out to control the thickness of the gold nanoshells. The dispersions of the obtained hybrid particles were characterized by dynamic light scattering and UV-vis absorption spectroscopy, and the dried particles were also observed by electron microscopy. Adaptation of the technique shown here will create a number of applications as optical, electronic, and biomedical functional materials.     

模板法组装纳米有序阵列的研究进展

由金属、半导体、碳纳米管、聚苯胺等组成的纳米有序阵列体系,在能量存储或转换、传感等方面具有广阔的应用前景。模板法组装纳米有序阵列体系是以具有特定微孔结构的材料为模板,通过电化学沉积、溶胶-凝胶沉积和化学气相沉积等手段,让纳米单元在模板提供的受控环境中原位生成,形成纳米有序阵列体系。模板法具有可控性好、工艺简便、能耗低等优点。本文综述了模板法组装纳米有序阵列体系的研究进展,并对纳米有序阵列体系的应用前景作了展望。     

Co-Pt and Fe-Pt bimetallic nanoparticles in a carbon matrix are prepared by a plasma arc process

Nanoparticle ensembles in Co-Pt and Fe-Pt systems embedded in a carbon matrix are prepared by a plasma-arc method. Two-phase samples based on disordered FCC solid solutions are prepared in both systems. In the Co-Pt system, the solid solujtions are mixed within one ensemble; in the Fe-Pt system, they are spatially separated. A magnetization hysteresis curve from Co-Pt nanoparticles (3–12 nm) fully coincides with a magnetization curve from a single-phase disordered solid solution Co_0.50Pt_0.50 (7–9 nm) prepared at 325°C by thermolysis of the precursor double complex salt (DCS). Metal ratios, solid solution structures, and particle sizes being the same, the magnetic response is dictated exclusively by the amount of a magnetic phase of mixed and interacting particles and is independent of the distribution of the magnetic phase over the solid solution phases.     

Electrochemical detection of arsenic on a gold nanoparticle array

The detection of As(III) was investigated on a gold nanoparticle array. At the first stage, gold nanoparticles were synthesized on glassy carbon microspheres. The resulting hybrid material was characterized by SEM and the sizes of the nanoparticles were found to be in the range 20–200 nm. At the second stage, glassy carbon microspheres decorated with Au nanoparticles were abrasively attached to the surface of a basal-plane pyrolytic electrode. The resulting gold nanoarray was characterized by the reduction of surface gold oxides. Furthermore, it was found to have good characteristics for the sensing of arsenic via anodic stripping voltammetry with a limit of detection of 0.8 μM and a sensitivity of 0.91 C M⁻¹. The text was submitted by the authors in English.     

Efficient electrocatalyst utilization: electrochemical deposition of Pt nanoparticles using nafion membrane as a template

We deposit Pt particles electrochemically on an electrode covered with a Nafion membrane. Platinum ions travel through the hydrophilic channels of the membrane, and platinum deposits are formed at the place where the channels make contact with the planar electrode. This procedure deposits the catalyst only at the end of the hydrophilic channels that cross the membrane; no catalyst is placed under the hydrophobic domains, where it would not be in contact with the electrolyte. By performing a series of cyclic voltammograms with this system, we show that deposition of the platinum through the membrane achieves better platinum utilization than deposition of platinum on the naked electrode followed by the placement of the membrane on top.     

Lanthanum zirconate nanoparticles and ceramics produced using a nitrate-modified alkoxide synthesis route

Fine lanthanum zirconate powder was prepared by thermally decomposing a nitrate-alkoxide-based precursor derived from dehydrated lanthanum nitrate, zirconium n-butoxide and 2-methoxyethanol. Upon heating, the decomposition of the organic groups was promoted by the nitrate groups, yielding a porous powder that crystallized into a pyrochlore phase at 800 °C. The powder that was heat treated at 900 °C for 1 h was composed of friable agglomerates of approximately 60-nm-sized nanoparticles. The ceramics obtained from the powder heat treated at 900 °C and milled for 30 min reached a relative density of 97.9 % after sintering at 1,400 °C for 10 h, which is at least 100 °C lower than the typically reported temperatures for this material.     

Hetero-assembly of gold nanoparticles on a DNA origami template

Hetero-assembling of spherical building blocks with well-defined spatial distribution holds great significance in developing chiral nanostructures. Herein, a strategy for hetero-assembling of gold nanoparticles(Au NPs) was demonstrated using rigid bifacial DNA origami as templates. By tuning the sizes and the fixed location of Au NPs on DNA origami, right-handed and left-handed Au NPs nanostructures were respectively constructed. Gel electrophoresis indicated the formation of the DNA origami-Au NPs complex and transmission electron microscopy(TEM) visually displayed the arrangement of Au NPs in these two chiral structures. The spatial configuration and 3D geometry of Au NPs were further illustrated by the stereographic TEM with tilting angles from ?30° to 30°. This strategy provides a universal approach to construct the asymmetrical 3D geometries, which may have potential applications in biomimicking and nanophotonics.     

Double template electrosynthesis of ZnO nanodot array

This communication describes the preparation of highly-ordered nanodot arrays of ZnO, a technologically important material, by the double template approach developed by Bartlett and co-workers. Colloidal polystyrene spheres were used as the primary template, and electrodeposited polypyrrole was used as the secondary template in this study. The ZnO nanodot arrays were prepared on a polycrystalline Au substrate by electrodeposition using the pyrrole secondary template after making it insulating by potentiodynamically deactivating it. The ZnO nanodot array was characterized by scanning electron microscopy, energy-dispersive X-ray analyses, and laser Raman spectroscopy.     

Simultaneous patterning of nanoparticles and polymers using an evaporation driven flow in a vapor permeable template

Nanoparticles and polymers have great potential for lowering cost and increasing functionality of printed sensors and electronics. However, creation of practical devices requires that many of these materials be patterned on a single substrate, and many current patterning processes can only handle a single material at a time, necessitating alignment of serial processing steps. Higher throughput and lower cost can be achieved by patterning multiple materials simultaneously. To this end, the microfluidic molding process is adapted to pattern various nanoparticle and polymer inks simultaneously, in a completely additive manner, with three-dimensional control and high relative positional accuracy between the different materials. A differential template distortion observed in channels containing different inks is analyzed and found to result from pressure force in the template due to flow of a highly viscous and highly concentrated ink in small channels. The resulting optimization between patterning speed and dimensional fidelity is discussed.     

Synthesis of dissymmetrical nanoparticles with a new hybrid silica template

An easy, novel route to prepare Janus nanoparticles and nano-bowls with tunable shapes has been developed. This approach uses a new kind of monodisperse vinyl-silica nanoparticles as templates to obtain large amounts of uniform Janus particles and nano-bowls (several grams). The efficient method adopts water-based hydrolysis-condensation and seed-emulsion polymerization. The uniform Janus nanoparticles and nano-bowls will display wide potential applications in many fields, such as: chemical sensors, construction of complex superstructures and nano-bioreactors.     

Enhancing cell recognition by scrutinizing cell surfaces with a nanoparticle array

We report a dual-ligand nanoparticle array approach for discerning cells that have different surface receptor profiles surrounding a common primary receptor expressed at high or low levels. The achieved differentiation provides nanoparticles the ability for potential applications in treatment of patients at a personalized medicine level for drug delivery and radiation therapy with a much better safety profile.     

Ordered nanopore boring in silicon: Metal-assisted etching using a self-aligned block copolymer Au nanoparticle template and gravity accelerated etching

Metal-assisted etching into Si (1 0 0) surfaces can be performed in a highly defined and regular arrangement using self-organized patterns of single-size gold catalyst particles that are block polymer templated on Si surfaces. We show that small size catalyst particles (diameter ≈10 nm) can be forced to maintain straight etch tracks perpendicular to the surface using adequate centrifugal gravity force. This allows the creation of highly ordered uniform and synchronized pore boring into the substrate with single pore diameters in the 10 nm range.     

Controlled synthesis of highly dispersed TiO2 nanoparticles using SBA-15 as hard template

Highly dispersed TiO2 nanoparticles were successfully synthesized by a wet impregnation method using SBA-15 as hard template for confining the growth of TiO2 nanocrystals, and then calcined at 550 degrees C in muffle furnace for 2 h. The as-synthesized samples were characterized with Fourier transform infrared spectra (FTIR), Raman spectroscopy, diffuse reflectance UV-visible spectroscopy (UV-vis), powder X-ray diffraction (XRD), small-angle X-ray diffraction (SAXRD), nitrogen adsorption, transmission electron microscopy (TEM) and photoluminescence spectra (PL). It was found that SBA-15 contained abundant silanol groups after removal of triblock copolymers by ethanol extraction and could easily adsorb a great number of titanium alkoxide via chemisorption. After subsequent hydrolysis of the anchored Ti complexes and calcination of the amorphous TiO2, anatase TiO2 nanocrystals with spherical shape and uniform particle diameter of about 6 nm were formed. A blue shift was observed in UV-vis absorption spectra due to the quantum size effect of TiO2 nanoparticles. Moreover, the as-prepared TiO2 nanoparticles showed a high PL intensity due to an increase in the recombination rate of photogenerated electrons and holes under UV light irradiation.     

Ascorbic acid as a mediator and template for assembling metallic nanoparticles

In this paper we report the results on the use of L-ascorbic acid (AA) in assembling metal nanoparticles (NPs) into three-dimensional fibrous structures. The degradation product of AA leads to the formation of fibrous structures, which has been used as a template for deposition of metal NPs such as Au, Pt, and Ag. We also report that AA can be used as the reducing agent in generating Au NPs. The spontaneous fiber formation and formation of Au NPs by AA have been coupled to generate fibers made up of composite of Au NPs and the polymer from the degradation products of AA. These fibers appear in the form of a fiber bundle with branched structures having overall dimensions on the order of several millimeters. They have typical widths of 1-4 microm with length of each segment of fiber bundle on the order of 40 microm. The composite fiber bundle has been found to be electrically conducting with surface resistivity on the order of 2.16x10(3) Omegacm. UV-vis spectroscopy, X-ray diffraction, transmission and scanning electron microscopic measurements were used to establish the formation of fibrous structures in the medium.     

Molecular sensors using a resonance Raman template

The potential use of resonance Raman spectroscopy as a molecular sensing tool is illustrated using a metalloporphyrin template and pyridine as an analyte. The equilibrium binding constant for the axial binding of pyridine to zinc tetraphenylporphyrin has been measured using resonance Raman spectroscopy. Although no new peaks are observed and the porphyrin peaks do not shift position, the quantification is made possible by the selective resonance enhancement of the template vibrations. The value for log k was determined by resonance Raman to be 3.65 +/- 0.32, which compares well with previously published values estimated using absorption data. Values for log k were determined for a series of related compounds, the picolines, and these also compare favourably with those previously reported.     

Direct synthesis of a macroscopic array of naked Ag nanoparticles

A 2-D array of naked Ag nanoparticles has been synthesized through interfacial reduction of Ag(+) under hydrothermal conditions. The process bestows the synthesis, nucleation, growth and self-assembly of the nanoparticles in a simple one-pot reaction and makes use of no additive or capping agent. The resulting macroscopic liquid silver mirror is highly stable and composed of tightly packed naked Ag nanoparticles (17 (3) nm diameter, with interparticle gaps of 1.3 (1.0) nm) which can be easily transferred to a given substrate for application.