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Chiral glutamide-derived lipids form self-assembled fibrous molecular gels that can be used as HPLC organic phases. In this study, HPLC separation efficiency was improved through the addition of branched amphiphilic glutamide lipids to the side chains of a terminally immobilized flexible polymer backbone. Poly(4-vinylpyridine) with a trimethoxysilyl group at one end was grafted onto the surface of porous silica particles (Sil−VP15, polymerization degree = 15), and the pyridyl side chains were quaternized with a glutamide lipid having a bromide group (BrG). Elemental analysis indicated that the total amount of the organic phase of the prepared stationary phase (Sil−VPG15) was 38.0 wt%, and the quaternization degree of the pyridyl groups was determined to be 32.5%. Differential scanning calorimetric analysis of a methanol suspension of Sil−VPG15 indicated that the G moieties formed a highly ordered structure below the phase transition temperature even on the silica surface, and the ordered G moieties exhibited a gel-to-liquid crystalline phase transition. Compared with a commercially available octadecylated silica column, the Sil−VPG15 stationary phase showed high selectivity toward polycyclic aromatic hydrocarbons, and particularly excellent separations were obtained for geometrical and positional isomers. Sil−VPG15 also showed highly selective separation for phenol derivatives, and bio-related molecules containing phenolic groups such as steroids were successfully separated. These separation abilities are probably due to multiple interactions between the elutes and the highly ordered functional groups, such as the pyridinium and amide groups, on the highly ordered molecular gel having self-assembling G moieties.

Two new copolymer-grafted silica stationary phases were prepared and employed in hydrophilic interaction chromatography (HILIC). 2-(Dimethylamino)ethyl methacrylate (DMAEMA) are copolymerized with itaconic acid (IA) and acrylic acid (AA) respectively, via thiol-ene click reaction on silica surface with deep eutectic solvents (DES) as new solvents. The obtained poly(DMAEMA-co-itaconic acid)-grafted silica (Sil-PDM-PIA) and poly(DMAEMA-co-acrylic acid)-grafted silica (Sil-PDM-PAA) were characterized by Fourier transform infrared spectroscopy, elemental analysis and solid-state 13C NMR spectra. Their hydrophilic interaction performances were evaluated by separating nucleosides, nucleobases, saccharides, and amino acids. Compared with previous reported poly(itaconic acid)-grafted silica (Sil-PIA) and poly(acrylic acid)-grafted silica (Sil-PAA) stationary phases, these two new copolymer-grafted silica performed higher selectivity and better separation for polar analytes in HILIC.

In this study, a new stationary phase based on poly(itaconic acid)-grafted silica (Sil-PIA) were synthesized in deep eutectic solvents (DESs) and characterized in detail. Itaconic acid was homopolymerized on silica via surface radical chain-transfer reaction using DESs as a new kind of green solvents. Sil-PIA were obtained and characterized by Fourier transform infrared spectroscopy, elemental analysis and scanning electron microscopy. The retention changes of nucleosides and nucleobases on the columns was studied under different chromatographic conditions including salt concentration, acetonitrile content, mobile phase pH, and column temperature. Compared with previous reported poly(acrylic acid)-grafted silica (Sil-PAA) stationary phase, Sil-PIA possesses shorter retention time but similar or higher selectivity for the separation of most polar compounds such as bases, nucleosides, amino acids, and saccharides in hydrophilic interaction chromatography. Most importantly, Sil-PIA presents very good performance at the separation of eleven ginsenosides using isocratic elution in hydrophilic chromatography.

Microflowers made of interconnected MnO2 nanosheets have been successfully synthesized in a microwave reactor through a hydrothermal reduction of KMnO4 with aqueous HCl at elevated temperatures in the presence of superparamagnetic Fe3O4@SiO2 core–shell nanoparticles. Due to the chemical compatibility between SiO2 and MnO2, the heterogeneous reaction leads to the spontaneous encapsulation of the Fe3O4@SiO2 core–shell nanoparticles in the MnO2 microflowers. The resulting hybrid particles exhibit multiple properties including high surface area associated with the MnO2 nanosheets and superparamagnetism originated from the Fe3O4@SiO2 core–shell nanoparticles, which are beneficial for applications requiring both high surface area and magnetic separation.

We demonstrate the fabrication of magnetically assembled one-dimensional chain-like photonic nanostructures with significantly high photonic stability. The key lies in the use of agarose hydrogel to prevent coagulation of the magnetic assemblies. When exposed to an external magnetic field, negatively charged Fe3O4@SiO2 particles can effectively assemble in the hydrogel matrix into one-dimensional chains with internal periodicity and display a fast, fully reversible, and tunable photonic response to the changes in the external field. The steric hindrance and the hydrogen bonding from the agarose network effectively limit the migration of the Fe3O4@SiO2 particles and their chain-like assemblies. As a result, the system shows remarkable stability in photonic response under external magnetic fields of large gradients, something which has previously been a challenge. The ability to stabilize the magnetic particle assemblies over a long period represents a major stride toward practical applications of such field-responsive photonic materials.

We report that fully alloyed Ag/Au nanospheres with high compositional homogeneity ensured by annealing at elevated temperatures show large extinction cross sections, extremely narrow bandwidths, and remarkable stability in harsh chemical environments. Nanostructures of Ag are known to have much stronger surface plasmon resonance than Au, but their applications in many areas have been very limited by their poor chemical stability against nonideal chemical environments. Here we address this issue by producing fully alloyed Ag/Au nanospheres through a surface-protected annealing process. A critical temperature has been found to be around 930 °C, below which the resulting alloy nanospheres, although significantly more stable than pure silver nanoparticles, can still gradually decay upon extended exposure to a harsh etchant. Nanospheres annealed above the critical temperature show a homogeneous distribution of Ag and Au, minimal crystallographic defects, and the absence of structural and compositional interfaces, which account for the extremely narrow bandwidths of the surface plasmon resonance and may enable many plasmonic applications with high performance and long lifetime, especially for those involving corrosive species.

This paper reports the synthesis of hierarchical assemblies of Au nanocrystals (and AgI nanocrystals) in the Fe 3 O 4 –SiO 2 –Au–Ag–AgI composite particles through the use of AuI 4 − ions as the critical precursor in a wet chemical approach. Both the reduction of AuI 4 − ions by ascorbic acid and the galvanic replacement reaction between AuI 4 − ions and Ag domains occur simultaneously during the synthetic process to ensure the formation of hierarchical assembly of small Au nanocrystals with high surface areas. In combination with the strong absorption of visible light corresponding to the surface plasmon resonances (SPRs), these composite particles exhibit enhanced photocatalytic performance under visible illumination in comparison to the Au or Ag nanoparticles without the hierarchical morphologies. This study indicates that carefully engineering the morphology and assembly configuration of plasmonic nanocrystals to expose high surface areas can improve their photocatalytic activities toward the utilization of visible light.

Synthesis of a class of exotic interfaced dimers with high asymmetries in terms of composition, morphology, structure (solid versus hollow), and dimension of the individual nanoscale components in the dimers is successfully accomplished. Typical examples include the interfaced dimers made of solid Au nanoparticles and hollow bimetallic nanoshells with different compositions, such as Au/Ag, Pt/Ag, and Pd/Ag. The success of the synthesis relies on the combination of asymmetric overgrowth of Ag nanodomains on the partially passivated Au nanoparticles and a following galvanic replacement reaction between the Ag nanodomains and appropriate noble metal precursors. The entire synthesis is processed on the unique superparamagnetic colloidal substrates that offer many advantages, such as time-efficiency, scalability, and high yield. The Au nanoparticle and the bimetallic nanoshell in each interfaced dimer are in direct contact, resulting in the possible strong coupling between them as well as novel properties that cannot be observed in either the nanoparticle or the nanoshell. For example, dimers made of Au nanoparticles and Pd/Ag nanoshells exhibit enhanced catalytic performance toward Suzuki coupling reactions under illumination of visible light because the strong surface plasmon resonances in the Au nanoparticles can influence the catalytic activity of the Pd/Ag nanoshells through coupling between the nanoparticles and the nanoshells.

A simple and robust strategy is reported in this Article for the synthesis of stable magnetic surface-enhanced Raman scattering (SERS) hot spots in superparamagnetic, raspberry-shaped, mesoscopic gold particles that are composed of superparamagnetic Fe3O4 cores, amorphous SiO2 mediation shells, and outer individual Au nanoparticles. The average interparticle gaps between the Au nanoparticles can be finely tuned by controlling the synthesis conditions, resulting in the formation of adequate SERS hot spots. The magnetic cores provide the capability to concentrate solution analytes adsorbed on the surfaces of the composite particles with the assistance of an external magnetic field, leading to ultrasensitive SERS detection of target species with concentration as low as femtomolar.

Derjaguin-Landau-Verwey-Overbeek (DLVO) theory fails in explaining the superior stability of colloid particles in aqueous suspensions under conditions of high ionic strengths where electrostatic forces are effectively screened. Accumulating evidence shows that the formation of a thin rigid layer of solvent molecules in the vicinity of a colloidal particle surface provides an additional repulsive interaction when the interparticle distance is reduced to several nanometers. The effective determination of the thickness of the solvation layer however remains a challenge. Here, we demonstrate a simple yet powerful magnetophotonic technique that can be used to study the thickness of the solvation layers formed on the colloidal silica surface in various polar solvents. A relationship between the hydrogen-bonding ability of the solvents and the thickness of solvation layer on colloidal silica surfaces has been identified; this observation is found to be consistent with the previously proposed hydrogen-bonding origin of the solvation force.

Interparticle magnetic dipole force has been found to drive the formation of dynamic superparamagnetic colloidal particle chains that can lead to the creation of photonic nanostructures with rapidly and reversibly tunable structural colors in the visible and near-infrared spectrum. Although most studies on magnetic assembly utilize simple permanent magnets or electromagnets, magnetic fields, in principle, can be more complex, allowing the localized modulation of assembly and subsequent creation of complex superstructures. To explore the potential applications of a magnetically tunable photonic system, we study the assembly of magnetic colloidal particles in the complex magnetic field produced by a nonideal linear Halbach array. We demonstrate that a horizontal magnetic field sandwiched between two vertical fields would allow one to change the orientation of the particle chains, producing a high contrast in color patterns. A phase transition of Fe(3)O(4)@SiO(2) particles from linear particle chains to three-dimensional crystals is found to be determined by the interplay of the magnetic dipole force and packing force, as well as the strong electrostatic force. While a color pattern with tunable structures and diffractions can be instantly created when the particles are assembled in the form of linear chains in the regions with vertical fields, the large field gradient in the horizontal orientation may destabilize the chain structures and produces a pattern of 3D crystals that compliments that of initial chain assemblies. Our study not only demonstrates the great potential of magnetically responsive photonic structures in the visual graphic applications such as signage and security documents but also points out the potential challenge in pattern stability when the particle assemblies are subjected to complex magnetic fields that often involve large field gradients.

Magnetically responsive photonic nanochains that have been produced by inducing chaining of uniform magnetic particles during their silica coating process and then allowing additional deposited silica to wrap entire structures. The optical diffraction of these nanochains can be switched on and off by applying magnetic fields.

Copper(I) sulfide (Cu(2)S) nanodisks with controllable size and aspect ratio have been synthesized by using a one-pot colloidal process, in which no pre-prepared organometallic precursors are required. The reaction involves the injection of dodecanethiol into a hot solution containing copper salt, surfactants, and a high boiling-point organic solvent. Copper thiolate forms at the beginning of the reaction which effectively acts as a precursor whose decomposition leads to further nucleation and growth of Cu(2)S nanocrystals. The nanocrystals begin as small nanodots in the early stages of the reaction, gradually turning into nanodisks with aspect ratios (average disk diameter divided by thickness) up to 2.0, while the band gap of the nanocrystals decreases accordingly. As the growth of nanocrystals follows the monomer addition mechanism, the diameter, thickness, aspect ratio, and optical property of the Cu(2)S nanodisks can be tuned systematically by changing the reaction time, the amount of surfactants, and the concentration of the precursors. This synthesis provides a simple and highly reproducible method for the preparation of Cu(2)S nanocrystals that may find potential applications in the fabrication of photovoltaic devices.

We report a solution-phase rapid-injection-based route for the synthesis of calcium molybdate (CaMoO4) microstructures with well-defined shape and size. This ternary metal oxide material has been widely used as phosphors, scintillator, and laser materials for a long time because of its attractive luminescence property. Complex three-dimensional structures, mainly doughnut-shaped microparticles with highly controllable size and aspect ratio, can be obtained at 100 °C by controlling the reaction conditions including the concentration of reactants, molar ratio between reactants, molybdenum source, pH, and the volume ratio of the mixed solvents. Other shapes such as spindles, nanosheets, and microspheres can also be produced by pushing the reaction conditions away from those optimal for doughnuts. X-ray diffraction, scanning electron microscopy, transmission electronic microscopy, and X-ray energy dispersive spectrometer were used to characterize the obtained samples. The photoluminescence spectra of the CaMo...

force associated with the expansion of the film, we show that the blown film method can be used to biaxially deform the embedded spherical polymer colloids into disk-shaped ellipsoids in a uniform manner. Figure 1 schematically outlines the procedure. In the first step, monodispersed polystyrene (PS) microspheres are dispersed in a diluted aqueous solution of polyvinyl alcohol (PVA). [34] A thin composite PS/PVA film is obtained by slowly evaporating the solvent. The film is then mounted on top of the wide opening of a ceramic filtering funnel, and sealed with a steel clamp. To improve the sealing, a polyethylene film, such as those used to package food, may be sandwiched between the funnel and the composite film. The system is then immersed into a hot silicon oil bath at � 1608C. The composite film softens and becomes deformable at this temperature, which is much higher than the Tgs of both PVA (� 858C) and PS (� 958C). Air is then injected into the system through the small opening at the end of the funnel using a syringe, allowing the film to blow into a dome-like shape. The funnel is removed from the oil bath and allowed to cool in air with the pressure maintained so that the stretched PVA films do not show apparent shrinkage upon cooling. The softened PS colloids experience a uniform 2D stretching force because of their small sizes compared to the PVA film, and eventually evolve into disk-shapes during the bubble expansion. It has been suggested that the transformation of the embedded particles is facilitated by the strong adhesion arising from the hydrogen bonding between the hydroxyl groups on the PVA and the surface groups on the latex particle surface. [25,29] The deformed shapes are locked in place when the particles are cooled below their Tg. Finally, dissolving the PVA film in isopropanol/water at 608C releases the stretched PS particles which can be collected by centrifugation. The transformation from spherical colloids to disks can be controlled by the extent of bubble expansion, which can be simply represented by the ratio of the height of the bubble (H) to the original film size (D), which is the diameter of the funnel opening. Practically, the height of the bubble can be controlled by the amount of air injected into the funnel through the syringe. As shown in the scanning electron microscopy (SEM) images in Figure 2, PS spheres with radius R0 of � 290nm can be uniformly transformed into disk-shaped spheroids with the major axis (Rd )o f� 350nm, � 450nm, and eventually � 575nm at different H/D ratios. Along with the expansion in the major axis, the dimension in the minor axis decreases during the stretching, as clearly demonstrated in the insets of Figure 2. Because very few particles are standing in a perfectly vertical orientation, it is difficult to survey many of them to accurately obtain the average value of the minor axis. We therefore only determined the average value of the major axis by measuring

tence of a large number of silicate species and their rich chemical interactions makes the dissolution and growth of silica challenging to study. However, this complexity also provides enormous opportunities for the development of materials with new structures and functionalities. For example, systematic investigation of the dissolution and formation of silica nanoparticles has made it possible to control the nucleation and growth, and subsequently the crystal size and shape, of zeolite materials. [4–6] Herein, we report that amorphous silica colloids, when dispersed in an aqueous solution of NaBH4, undergo a spontaneous morphology change from solid to hollow spheres. Concurrent but separate coredissolution and shell-growth processes appear to be responsible to the formation of the hollow structures. Besides the interesting fundamental aspects of this spontaneous process, this work also provides an effective self-templated route for the preparation of hollow silica nanostructures, which may find immediate applications in fields such as catalysis and drug delivery. [7–12] Since silica can coat many nanostructures through simple sol–gel processes, our discovery also allows convenient transformation of core–shell particles into yolk– shell structures, which are promising for use as nanoscale reactors and controlled-release vehicles. Compared to widely adopted methods using polymer beads and micelle and

We describe a modified polyol process for the synthesis of silver nanocrystals with uniform sizes ranging from several nanometers to ∼20 nm. The use of polyacrylic acid, in place of polyvinylpyrrolidone in the conventional polyol process, significantly limits the growth of silver nanocrystals, prevents the interparticle aggregation and fusion, and leads to a uniform population of samples with high water solubility. The size of nanocrystals can be conveniently tuned by controlling the reaction time, the concentration and chain length of the polymeric surfactants, and the reaction temperature. Uniform silver nanocrystals within sizes below 20 nm are preferred candidates over larger particles for applications where high density of optical absorption is required, for example, for photothermal conversion in cancer therapy.

Superparamagnetic Fe(3)O(4) colloids with highly charged surfaces have been assembled into ordered structures in water in response to external magnetic fields. The colloids form chainlike structures with regular interparticle spacings of a few hundred nanometers along the direction of the external field so that the system strongly diffracts visible light. The balance between attractive (in this case, magnetic) and repulsive (electrostatic) forces dictates interparticle spacing and therefore optical properties. By changing the relative strength of these two forces, one can tune the peak diffraction wavelength over the entire visible spectrum. We were able to optimize the diffraction intensity and the tuning range through studying their dependence on variables such as the size distribution and concentration of the Fe(3)O(4) colloids or ionic strength of the solutions. The fast, reversible response and the feasibility for miniaturization impart these photonic materials great potential in applications such as optoelectronic devices, sensors, and color displays.

Hydrophobic inorganic nanocrystals have been transferred from organic solvent to aqueous solution through a robust and general ligand exchange procedure. Polyelectrolytes such as poly(acrylic acid) and poly(allylamine) are used to replace the original hydrophobic ligands on the surface of nanocrystals at an elevated temperature in a glycol solvent and eventually render the nanocrystals highly water soluble. The physical properties of the nanocrystals, such as superparamagnetism, photocatalytic activity, and photoluminescence, are maintained or improved after ligand exchange.

A self-templated approach has been developed for the synthesis of TiO2 microcapsules with tunable size and wall thickness by heating sol-gel derived TiO2 microspheres with poly(acrylic acid) (PAA) in a diethylene glycol (DEG) solution. PAA plays a crucial role in the formation of microcapsules by crosslinking the surface TiO2 nanoparticles and preventing them from dissolution by DEG. Hollow microcapsules form when DEG molecules penetrate the outer layer and remove the core materials by forming soluble titanium glycolate.

Creating novel structures by self-assembly processes and fixing the resultant assemblies are both critical to the design and fabrication of functional materials through bottom-up approaches. We demonstrate magnetically induced self-assembly of 2D photonic labyrinth structures and their solidification through a sol–gel method. The photonic labyrinth structures can be patterned into more regular arrangements using nonmagnetic substrates. This work may provide a platform for fabricating novel materials and devices with complex morphologies and spatial configurations.

Controlled assembly of nanoparticles into asymmetric configurations is of great interest due to their novel properties and promising applications. In this Article, we report a generic strategy for the synthesis of dimer nanoclusters and asymmetric nanoassemblies by using magnetic colloidal substrates, on which tailored surface modification and controlled physical confinement are applied. The modularity of our approach facilitates the fabrication of asymmetric nanostructures with varying sizes, shapes, compositions, surface chemistry, and surface hydrophobicity. Success in the syntheses sheds a light on the versatility of our strategy in rationally designing and synthesizing asymmetric nanostructures with tailored properties and functionalities.

Charged superparamagnetic colloidal Fe(3)O(4)@SiO(2) core-shell particles were chosen as model dipolar soft spheres to study their crystallization and magnetically induced phase transition in suspensions. The 3D colloidal crystals feature excellent magnetically responsive photonic properties with strong diffraction, fast response and wide tunability.

A one-pot solution process has been devised to synthesize colloidal Bi2Te3-Te heterogeneous nanostructures (HNs) that comprise Bi2Te3 nanoplates and Te nanorods. By controlling the reaction kinetics, the reaction of TeO3(2-) and Bi(3+) in the presence of hydrazine first produces uniform Te nanorods and then grows Bi2Te3 nanoplates on the tips and surfaces of these Te nanorods, forming various shapes including "nails", "barbells", "syringes", and "accordions". The specific topological arrangement realized arises from the peculiar anisotropic reactivity of the first formed Te nanorods, whose tips are subsequently exploited to seed the heterogeneous nucleation of Bi2Te3 as enabled by the similar crystal structure and the small lattice mismatch between Te and Bi2Te3. Three important processes, heterogeneous nucleation of Bi2Te3 on the tips and/or surface of Te nanorods, homogeneous nucleation of Bi2Te3, and the direct reaction of a Bi precursor and Te nanorods to form hollow structures via the Kirkendall Effect, occur under various conditions. The manipulation of these processes provides a robust means for the fine shape control of Bi2Te3-Te HNs. It is envisioned that the tailored synthesis of Bi2Te3-Te HNs may promise unique opportunities for producing thermoelectric materials with greatly enhanced performance.

Silver nanoplates with an extremely high aspect ratio (up to over 400) and a widely tunable surface plasmon resonance (SPR) band have been successfully synthesized by combining the concepts of selective ligand adhesion and seeded growth. Citrate ligands are used as the sole surfactant to effectively block overgrowth on the basal {111} facets and only allow growth in the lateral direction. By slowing down the reaction rate using Ag-citrate complex as precursor, the thin nature of Ag nanoplates is maintained with the edge length grown up to 4 μm, which ensures the high aspect ratio and the widely tunable SPR band. We also observe a size distribution focusing effect that helps to produce uniform nanoplates as well as narrow SPR bands over a wide range, which is important in many practical applications.

We report the rapid formation of photonic crystal structures by assembly of uniform nonmagnetic colloidal particles in ferrofluids using external magnetic fields. Magnetic manipulation of nonmagnetic particles with size down to a few hundred nanometers, suitable building blocks for producing photonic crystals with band gaps located in the visible regime, has been difficult due to their weak magnetic dipole moment. Increasing the dipole moment of magnetic holes has been limited by the instability of ferrofluids toward aggregation at high concentration or under strong magnetic field. By taking advantage of the superior stability of highly surface-charged magnetite nanocrystal-based ferrofluids, in this paper we have been able to successfully assemble 185 nm nonmagnetic polymer beads into photonic crystal structures, from 1D chains to 3D assemblies as determined by the interplay of magnetic dipole force and packing force. In a strong magnetic field with large field gradient, 3D photonic crystals with high reflectance (83%) in the visible range can be rapidly produced within several minutes, making this general strategy promising for fast creation of large-area photonic crystals using nonmagnetic particles as building blocks.

Protein phosphorylation plays a key role in most cellular processes. Studying phosphopeptides in complex biological samples has been a great challenge due to their low abundance as well as the coexistence of excessive amounts of salts or surfactants. In this work we demonstrate a general approach for selective separation of phosphopeptides using a class of novel mesoporous nanostructured materials. TiO(2) nanocrystals are first self-assembled into submicrometer clusters containing relatively uniform mesoscale pores and then stabilized by coating with a thin layer of silica. Calcination of the materials at high temperatures connects the neighboring nanocrystals together and enhances the mechanical stability of the clusters and at the same time removes the organic surfactants and makes the TiO(2) surface fully accessible to phosphopeptides. By coating the nanocrystal clusters with a layer of silica before calcination and removing it afterward through chemical etching, we have been able to make the cluster surface hydrophilic and negatively charged, thus enhancing the water dispersibility of the clusters and eventually their accessibility to phosphopeptides. The high selectivity and capacity of these mesoporous TiO(2) clusters have been demonstrated by effectively enriching phosphopeptides from digests of phosphoprotein (alpha- or beta-casein), protein mixtures of beta-casein and bovine serum albumin, milk, and human serum samples. We also demonstrate that the self-assembly process brings the flexibility of incorporation of multiple components, such as superparamagnetic nanocrystals, to further facilitate the peptide separation.

We demonstrate a water-based etching strategy for converting solid silica shells into porous ones with controllable permeability. It overcomes the challenges of the alkaline-based surface-protected etching process that we previously developed for the production of porous and hollow silica nanostructures. Mild etching around the boiling point of water partially breaks the imperfectly condensed silica network and forms soluble monosilicic acid, eventually producing mesoscale pores in the silica structures. With the surface protection from poly(vinyl pyrrolidone) (PVP), it is possible to maintain the overall shape of the silica structures while at the same time to create porosity inside. By using bulky PVP molecules which only protect the near-surface region, we are able to completely remove the interior silica and produce hollow particles. Because the etching is mild and controllable, this process is particularly useful for treating small silica particles or core-shell particles with very thin silica shells for which the alkaline-based etching method has been difficult to control. We demonstrated the precise control of the permeation of the chemical species through the porous silica shells by using a model reaction which involves the etching of Ag encapsulated inside Ag@SiO(2) by a halocarbon. It is expected that the water-based surface-protected etching method can be conveniently extended to the production of various porous silica shells containing functional materials whose diffusion to outside and/or reaction with outside species can be easily controlled.

Multifunctional Au nanoshells with tunable optical properties and fast magnetic response have been fabricated through a sequence of sol-gel, surface-protected etching, and seed-mediated growth processes. The use of a porous silica layer enhances the uniformity of nanoshell growth, the reproducibility of the synthesis, and the structural and optical stability of the products.

Core-shell structured Fe(3)O(4)/SiO(2)/TiO(2) nanocomposites with enhanced photocatalytic activity that are capable of fast magnetic separation have been successfully synthesized by combining two steps of a sol-gel process with calcination. The as-obtained core-shell structure is composed of a central magnetite core with a strong response to external fields, an interlayer of SiO(2), and an outer layer of TiO(2) nanocrystals with a tunable average size. The convenient control over the size and crystallinity of the TiO(2) nanocatalysts makes it possible to achieve higher photocatalytic efficiency than that of commercial photocatalyst Degussa P25. The photocatalytic activity increases as the thickness of the TiO(2) nanocrystal shell decreases. The presence of SiO(2) interlayer helps to enhance the photocatalytic efficiency of the TiO(2) nanocrystal shell as well as the chemical and thermal stability of Fe(3)O(4) core. In addition, the TiO(2) nanocrystals strongly adhere to the magnetic supports through covalent bonds. We demonstrate that this photocatalyst can be easily recycled by applying an external magnetic field while maintaining their photocatalytic activity during at least eighteen cycles of use.

The size and shape of it: The optical properties of Ag nanoplates can be precisely tuned in a wide range through a UV-light-induced reconstruction process in which the morphology of the nanoparticles is changed from thin triangular plates to thick round plates (see picture). This unconventional "backward tuning" strategy is a practical route to stable silver nanoplates that display a wide range of plasmon wavelengths.

Polydimethylsiloxane (PDMS) rubber can be thermally decomposed in air to produce silica vapor species which can deposit on porous anodic aluminum oxide (AAO) templates to produce silica nanotubes with a smooth surface and highly controllable thickness.

We report the synthesis of magnetically responsive hierarchical assemblies of silica colloids that can be used as recoverable supports for nanocatalysts. Each assembly is composed of a central magnetite/silica composite core and many small satellite silica spheres. The two regions are held together as a stable unit by a polymer network of poly(N-isopropylacrylamide). The central magnetite particles are superparamagnetic at room temperature with strong magnetic response to external fields, thus providing a convenient means for separating the entire assembly from the solution. The satellite silica particles provide large surface areas for loading nanocatalysts through the well-developed silane chemistry. As an example, we demonstrate the use of such magnetically responsive hierarchical assemblies as recoverable supports for Au nanocatalysts for the reduction of 4-nitrophenol with NaBH4.

A high-temperature solution-phase hydrolysis approach has been developed for the synthesis of colloidal magnetite nanocrystals with well-controlled size and size distribution, high crystallinity, and high water solubility. The synthesis was accomplished by the hydrolysis and reduction of iron(III) cations in diethylene glycol with a rapidly injected solution of sodium hydroxide at an elevated temperature. The high reaction temperature allows for control over size and size distribution and yields highly crystalline products. The superior water solubility is achieved by using a polyelectrolyte, that is, poly(acrylic acid) as the capping agent, the carboxylate groups of which partially bind to the nanocrystal surface and partially extend into the surrounding water. The direct synthesis of water-soluble nanocrystals eliminates the need for additional surface modification steps which are usually required for treating hydrophobic nanocrystals produced in nonpolar solvents through the widely recognized pyrolysis route. The abundant carboxylate groups on the nanocrystal surface allow further modifications, such as bioconjugation, as demonstrated by linking cysteamine to the particle surface. The monodisperse, highly water-soluble, superparamagnetic, and biocompatible magnetite nanocrystals should find immediate important biomedical applications.