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Selective growth of silver nanoparticles on ~100 nm thick silica patterns produced by nanoimprint method has been successfully demonstrated using either (1) thermo-induced reduction or (2) room temperature electroless deposition (ELD) without removing the ~25 nm thick residual layer left by nanoimprint process. This selectivity was achieved by silane additive, (3-mercaptopropyl)trimethoxysilane (3-MTS), which was added to the silica matrix to control nucleation and growth of silver. The presence of silver nanoparticles was confirmed by EDX and UV-vis spectrum, and the density, distribution, and size of silver particles were examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Silica film heat-treated between 400 and 600 °C resulted in silver particles of 100-120 nm diameter with a linear density of 2.63-3.36 μm(-1), while the film treated by room temperature ELD produced silver particles of 67 nm diameter with a linear density of 5.65 μm(-1). The selective growth ratio based on particle density on pattern area versus residual layer is 12.92 and 20.31 for high- and room-temperature processes, respectively, whereas the samples without 3-MTS shows low selective growth ratio of 1.22 and 1.04. These results prove that both approaches are fast and effective, suggesting their potential to produce other type of nanoparticle arrays directly on nanoimprinted patterns.

Growth of AgCl cubic crystals at the surface of sol–gel silica films containing AgCl nanocrystals and poly(ethylene glycol)/ethylene glycol as diffusion-controlled media has been successfully demonstrated. Crystals were grown during the shrinking of the film when it was exposed to air at room temperature, and both size and shape of the crystals were found to be dependent on the film thickness. When the film thickness was in the range of 70–250 nm, cubic shaped crystals with size between 120 and 250 nm were produced. These cubes exhibited predominant {200} facets as indicated by the electron beam diffraction patterns. Spherical crystals with size and height between 200 and 400 nm were observed when film thickness was in the range of 250–400 nm, while elliptical crystals were found on films thicker than 400 nm. Crystals were not grown when the film thickness was

An interconnected silver network composed of grain boundary layers with each layer about 100 nm thick was spontaneously formed inside a silica matrix when a sol–gel sample containing silver ion and polyethylene glycol was dried and heat-treated. The minimum spacing of the silver structure was ≈15 µm and the density of the silver structure was related to the drying rate, which can be controlled by either drying temperature or vacuum drying time. It was found that the shrinkage-induced stress during the drying process results in microcracks where the crack surfaces serve as a 3D template for silver to develop into interconnected network when the sample is annealed at 160 °C. The ability to control the density of microcracks and to utilize the microcracks as silver template suggests that this method can be utilized to (1) create interconnected silver network of desired density in silica materials, (2) visualize the microcracks of sol–gel materials, and (3) reinforce and repair the defects after microcracks have formed.

The activity of core–shell nanoparticles (NCs) in electrooxidation of methanol (MOR) was found to be dependent on the crystalline structure of the core and the lattice strain at the core–shell interface. Ru-core and Pt-shell NCs delivered 6.1-fold peak MOR current density at −135 mV than Pt NCs, while the Co-core and Pt-shell NCs showed a 1.4-fold peak MOR current density at 280 mV. The current density is improved by the compressive lattice strain of the surface that is caused by the lattice mismatch between the Pt shell and the Ru core. For Co-core NCs, the enhancement results from the ligand effect at surface Pt sites. In addition, the Ru-core NCs maintained a steady current density of 0.11 mA cm–2 at 500 mV in a half-cell system for 2 h, which is 100-fold higher than that of Pt NCs and Co-core NCs. These results provide mechanistic information for the development of fuel cell catalysts along with reduced Pt utilization and programmable electrochemical performance.

To synthesize long and uniform vertically aligned carbon nanotube (VACNT) arrays, it is essential to use catalytic nanoparticles (NPs) with monodisperse sizes and to avoid NP agglomeration at the growth temperature. In this work, VACNT arrays were grown on chemically synthesized Fe(3)O(4) NPs of diameter 6 nm by chemical vapor deposition. Coating the NPs with a thin layer of Al(2)O(3) prior to CNT growth preserves the monodisperse sizes, resulting in uniform, thick and dense VACNT arrays. Comparison with uncoated NPs shows that the Al(2)O(3) coating effectively prevents the catalyst NPs from sintering and coalescing, resulting in improved control over VACNT growth.

Metallic nanoparticles containing single and binary components have been known for their catalytic properties to grow carbon nanotube (CNT) arrays. In this paper, an intermetallic catalyst consisting of iron and zirconium was used to grow millimeter long, well aligned arrays. The Fe–Zr catalysts enabled the growth of 1.7 mm-long carbon nanotube arrays in 45 min. A comparison with pure iron catalyst indicated that adding Zr to iron can stabilize the Fe catalyst at the CNT growth temperature and moderate its reactivity. SEM images showed the different growth behaviors for Fe–Zr and Fe catalysts. The long, uniform CNT arrays grown here have potential applications in many advanced composites.

Nanodiamonds (NDs) with modified surface functional groups and surface characteristics are an attractive model to understand adsorption mechanisms of molecules on substrates. The research described in this paper illustrates the binding mechanisms of fluorescent dyes to ND surfaces as these interactions are extremely useful in many biomedical ND applications. A thorough study of binding and release mechanisms was completed using an assortment of carbon based nanoparticles, including NDs, onion-like carbon, and single-wall nanohorns. Surface charge interactions were studied in combination with surface areas, configurations, and modifications in order to determine which is responsible for the largest adsorption capacity and strongest binding. Adsorption studies were carried out using UV–Vis measurements followed by maximum binding capacity determination using the Langmuir isotherm and related transform equations. Langmuir and transform calculations further reveal the specific surface area covered by adsorbents for select nanocarbon materials. In addition, cyclic voltammetry measurements confirm that dye adsorbed onto NDs exhibits equal electrochemical properties as in its unbound state.

Silver-nanoparticle-embedded aminosilica colloids synthesized via aminosilane-induced spontaneous reduction reaction exhibit selective adhesion properties on hydrophobic surfaces and have been utilized as a simple and one-step procedure to create patterned nanocomposite film with silver to aminosilica mole ratio at 0.9:1. Substrates that enable self-assembly of the colloids include silicon wafer, polydimethylsiloxane, and microscope slide, where patterns of hydrophilic surface were either created using oxygen plasma treatment or stamped with chemical ink using microcontact printing. Upon substrates being immersed in a solution containing silver-aminosilica colloids, particles attach to hydrophobic surfaces and continuously self-assemble onto the deposited film, allowing us to fabricate nanocomposite patterns with controllable thickness (approximately 200 nm).

Colloidal stability is one of the critical factors for the use of nanodiamonds as potential enterosorbents. Although nanodiamonds are believed to be a promising enterosorbent, colloidal stability in hydrosols of raw polydispersed nanodiamonds produced by detonation is typically low. Surface modification and fractionation significantly improves colloidal stability of nanodiamond suspensions within the physiological pH range. The modification of nanodiamonds can be completed either by physical means, i.e., plasma treatments, or by chemical methods. In the current paper an analysis of the colloidal stability of detonation nanodiamonds hydrosols, which have undergone different surface modifications, is presented based on zeta potential measurements and titration experiments.

We report a rapid and spontaneous metallization process associated with sol–gel reaction of aminosilane that can be utilized to synthesise silver embedded silica nanocomposite without involving additional reducing agents. The reduction reaction induced by bis[3-(trimethoxysilyl)propyl]ethylenediamine (enTMOS) involves amine functional moieties, which drive the reduction reaction with presence of water. Cyclic voltammetry was used to investigate the redox potential of enTMOS and its relation to chemical environment. It was found that the oxidation potential of enTMOS depending on the amount of water (water:enTMOS (v/v) = 8:1–0:1) ranges from 0.48 to 0.68 V versus Ag/AgCl electrode in methanol. The oxidation potential of aminosilane decreases with water content and becomes more negative than that of Ag, suggesting the aminosilane acts as a silver reducing agent while serving as a matrix to encapsulate silver nanoparticles after reacting with water. This process has been utilized to produce evenly dispersed silver nanoparticles with sizes ranging from 5 to 20 nm in both liquid and solid forms of aminosilane, allowing us to prepare silver nanoparticles doped silica nanocomposite that exhibits enhanced electrochemical properties.

With their unique ability to differentiate into all cell types, embryonic stem (ES) cells hold great therapeutic promise. To improve the efficiency of embryoid body (EB)-mediated ES cell differentiation, we studied murine EBs on the basis of their size and found that EBs with an intermediate size (diameter 100–300 μm) are the most proliferative, hold the greatest differentiation potential, and have the lowest rate of cell death. In an attempt to promote the formation of this subpopulation, we surveyed several biocompatible substrates with different surface chemical parameters and identified a strong correlation between hydrophobicity and EB development. Using self-assembled monolayers of various lengths of alkanethiolates on gold substrates, we directly tested this correlation and found that surfaces that exhibit increasing hydrophobicity enrich for the intermediate-size EBs. When this approach was applied to the human ES cell system, similar phenomena were observed. Our data demonstrate that hydrophobic surfaces serve as a platform to deliver uniform EB populations and may significantly improve the efficiency of ES cell differentiation.

Sol-gel immobilization of soluble proteins has proven to be a viable method for stabilizing a wide variety of proteins in transparent inorganic matrices. The encapsulation of membrane-bound proteins has received much less attention, although work in this area suggests potential opportunities in microarray technology and high-throughput drug screening. The present paper describes a liposome/sol-gel architecture in which the liposome provides membrane structure and protein orientation to two transmembrane proteins, bacteriorhodopsin (bR) and F(0)F(1)-ATP synthase; the sol-gel encapsulation converts the liposomal solution into a robust material without compromising the intrinsic activity of the incorporated proteins. Here we report on two different proteoliposome-doped gels (proteogels) whose properties are determined by the transmembrane proteins. Proteogels containing bR proteoliposomes exhibit a stable proton gradient when irradiated with visible light, whereas proteogels containing proteoliposomes with both bR and F(0)F(1)-ATP synthase couple the photo-induced proton gradient to the production of ATP. These results demonstrate that materials based on the liposome/sol-gel architecture are able to harness the properties of transmembrane proteins and enable a variety of applications, from power generation and energy storage to the powering of molecular motors, and represent a new technology for performing complex chemical synthesis in a solid-state matrix.

The growth kinetics of crystals of bis(imidazolium 2,6-dicarboxypyridine) M (II) dihydrate, where M = Cu, Ni, Co, Zn, and Mn, were studied in situ using atomic force microscopy. The aspect ratios of specific crystal facets were found to vary systematically with changes in the total concentration of the three components in this crystal system, which can be explained in terms of the growth kinetics at the (100) and (011) faces. Furthermore, inclusion of chemical additives in the growth solutions altered both the habit and faceting of these crystals. Crystallographic analysis of the molecular packing revealed a mechanism by which changes in the habit and faceting occur in the presence of chemical additives. This mechanism was exploited to facet selectively the (001) face for epitaxial studies between crystals containing different metal (II) ions. Epitaxial deposition of crystalline layers containing one metal (II) ion onto the (001) face of a crystal substrate containing a different metal (II) ion was found ...

The supramolecular chemistry and crystal structures of five bis(2-methylimidazolium 2,6-dicarboxypyridine) M(II) complexes, where M = Zn, Cu, Ni, Co, and 7:3 Mn/Cu (1−5, respectively), are reported. These complexes form building blocks with nearly identical molecular structures that crystallize in the same packing pattern. Anions of 2,6-dicarboxypyridine and cations of 2-methylimidazole form N−H···O and O−H···O hydrogen bonds that dominate crystal packing by forming linear ribbons of molecules. Thus, complexes 1−5 form an isomorphous series with a single robust crystalline architecture that accommodates five different transition metals without altering molecular packing. The growth of crystals from solutions that contain two different metal complexes produces mixed crystals in which mixtures of the different metal complexes are incorporated in the same relative molar ratio present in solution. This technique was used to grow crystals of 5 with Mn and Cu complexes in a 7:3 molar ratio. Complexes 1−5 form c...

In this study, we examine the noncovalent interactions that occur between the cyclic dipeptide of glycine (GLYDKP) and a carboxylic acid guest. This study complements our earlier studies on the cyclic dipeptide of aspartic acid by exploring further the possibility of using hydrogen-bonded tapes comprised of molecules of GLYDKP, as a scaffold with which to control the location of guest molecules in a crystalline lattice. On the basis of the 11 cocrystals of GLYDKP reported herein, we conclude that guest molecules will be positioned between tapes of GLYDKP if the guest molecules meet the following criteria. First, the width of the guest molecule should be between 4.5 and 8.5 A. Second, interactions between adjacent guest molecules should be stronger than a van der Waals contact. Third, a hydrogen-bond donor (hydroxyl group) and a hydrogen-bond acceptor (carbonyl group) should be present in the structure of the guest with their separation no greater than two bonds between the carbon atom of the carbonyl grou...

The crystal structures of three cyclic thioureas (4,5-disubstituted benzimidazolene-2-thiones) are reported. Each compound forms a tape motif in the solid state. Two of the three compounds assemble into tapes via N−H- - -S hydrogen bonds. These tapes pack into planar sheets. The third compound assembles into tapes via C−H- - -Br hydrogen bonds. These tapes pack at angles relative to each other, generating puckered sheets. The patterns of packing of these three cyclic thioureas are compared to those observed in the crystalline solids of cyclic ureas that have analogous molecular structures. The patterns of packing adopted by cyclic thioureas are rationalized in terms of molecular structure, solvent of crystallization, and energies and efficiencies of packing.

A molecular building block, (S,S)-3,6-dicarboxymethyl-2,5-diketopiperazine (ASPDKP), was designed to assemble into hydrogen-bonded tapes, a one-dimensional motif in the solid state. Tapes made with ASPDKP possess pendant carboxylic acid groups that can be used to position guest molecules at well-defined intervals along the backbone of the tapes. Guest molecules can be used to control the spacing between adjacent tapes and the topology of layers composed of tapes. Several derivatives of pyridine were cocrystallized with ASPDKP, and the resulting molecular solids were characterized. Eight crystalline solids are described. These structures reveal both the strengths and limitations of hydrogen-bonded tapes to function as scaffolds with which to engineer crystalline architecture. The strengths of tapes to function as scaffolds are made evident by the six solids in which tapes are present. First, hydrogen-bonded tapes are tolerant to the presence of other functional groups capable of forming hydrogen bonds such...

Nanodiamond (ND) and other nanocarbon particles are popular platforms for the immobilization of molecular species. In the present research, factors affecting adsorption and desorption of propidium iodide (PI) dye, chosen as a charged molecule model, on ND and sp 2 carbon nanoparticles were studied, with a size ranging from 75 to 4,305 nm. It was found that adsorption of PI molecules, as characterized by ultra- violet-visible spectroscopy, on ND particles is strongly influenced by sorbent-sorbate electrostatic interactions. Different types of NDs with a negative zeta potential were found to adsorb positively charged PI molecules, while no PI adsorption was observed for NDs with a positive zeta potential. The type and density of surface groups of negatively charged NDs greatly influenced the degree and capacity of the PI adsorbed. Ozone-purified NDs had the highest capacity for PI adsorption, due to its greater density of oxygen containing groups, i.e., acid anhydrides and carboxyls, as assessed by TDMS and TOF-SIMS. Single wall nanohorns and carbon onion particles were found to adsorb PI regardless of their zeta potential; this is likely due to p bonding between the aromatic rings of PI and the graphitic surface of the materials and the internal cavity of the horns.

The effectiveness of modified nanodiamonds (NDs) for the adsorption of mycotoxins, aflatoxin B1 (AfB1) and ochratoxin A (OTA), are investigated in this paper. Binding and release mechanisms of the mycotoxins were addressed using an assortment of NDs modified by different surface treatments, including carboxylation, hydrogenation and hydroxylation, followed by isolating NDs of different sizes. Results indicate that AfB1 adsorption on NDs is directly related to aggregate size, whereas OTA adsorption is primarily centered upon electrostatic interactions that depend on the types of surface functional groups on the ND. Findings show that modified NDs with small aggregation sizes (~40 nm) have greater adsorption capacities for AfB1 than yeast cells walls and untreated NDs from various vendors, but comparable to activated charcoal. In OTA studies, positively charged NDs outperformed clay minerals, which are well-known and efficient sorbents for mycotoxins. Furthermore, ND adsorption capacities can be preserved in a wide range of pH.

Hydroxyapatite-gelatin modified siloxane (GEMOSIL) nanocomposite was developed by coating, kneading and hardening processes to provide formable scaffolding for alloplastic graft applications. The present study aims to characterize scaffolding formability and mechanical properties of GEMOSIL, and to test the in vitro and in vivo biocompatibility of GEMOSIL. Buffer Solution initiated formable paste followed by the sol–gel reaction led to a final hardened composite. Results showed the adequate coating of aminosilane, 11–19 wt%, affected the cohesiveness of the powders and the final compressive strength (69 MPa) of the composite. TGA and TEM results showed the effective aminosilane coating that preserves hydroxyapatite-gelatin nanocrystals from damage. Both GEMOSIL with and without titania increased the mineralization of preosteoblasts in vitro. Only did titania additives revealed good in vivo bone formation in rat calvarium defects. The scaffolding formability, due to cohesive bonding among GEMOSIL particles, could be further refined to fulfill the complicated scaffold processes.

In this research, core-shell electrocatalysts comprising a Ru core covered with precisely controlled 1.5-3.6 atomic layers (ALs)-thick Pt atoms are synthesized. The sample with 1.5 ALs shows a 3.2-fold improvement in CO-tolerance and 2.4-fold current enhancement at the conventional battery operation potential (I 300 , at 300 mV vs Ag/AgCl) during methanol oxidatign as compared with conventional all-Pt nanoparticles. The origin of the enhanced performance and the atomic structure of the core-shell nanoparticles are elucidated to be mainly dominated by the lattice strain (possibly some slight effect of heteroatomic interactions) then by the combination of ligand effects and bifunctional mechanisms when the shell crystal is thicker than 2.7 ALs.

Aminosilane has been explored as an alternative chemical linker to facilitate the binding and solidification of hydroxyapatite-gelatin nanocomposite at room temperature, which was synthesized using co-precipitation method in the presence of gelatin. This aminosilane treatment was found effective at low concentration (~25 μL/mL) and the solidification and dehydration of hydroxyapatite-gelatin slurry completes within hours depending on the amount of aminosilane. The resulting sample exhibits compressive strength of 133 MPa, about 40% higher than glutaraldehyde treated samples, and shows good biocompatibility based on cell adhesion, proliferation, alkaline phosphate synthesis, and mineralization studies.

Nanodiamonds (NDs) have desirable chemical, physical and biological properties that lend them to a wide range of applications. ND’s facile surface chemistry, for example, can be used to create a high affinity for adsorbing various biological molecules. However, NDs, which are commercially available from multiple vendors, show inconsistencies with surface groups, aggregate sizes and impurity contents that may limit adsorption. We explore adsorption mechanisms of molecules to NDs in efforts to expand ND applications to drug delivery agents, bio-labels and enterosorbents. In doing so, several types of NDs and modification methods are evaluated to increase adsorption capacity and selectivity of propidium iodide and aflatoxin B1. Capacities and binding strengths of target molecules are assessed by Langmuir isotherms and transform calculations. UV-Vis spectroscopy shows our modification treatments are successful in increasing ND adsorption capacities. Additionally, cyclic voltammetry measurements, used to monitor in-situ adsorption, show electrochemical detection even after binding.

Conventional top-down lithographic processes approach their practical and theoretical limits at dimensional scales less than 100 nm. Alternative bottom-up methods are being investigated to build nanoscale architectures, including the use of biomolecules whose functional groups bind inorganic particles. In this study, the fabrication and alignment of microtubule-based nanowires are investigated. Microtubules (MT) are fibrous proteins found in nearly all eukaryotes. Our work was carried out using polymerized alpha- and beta-tubulins, which were cross-linked with glutaraldehyde to stabilize the protein structure. Ni coated microtubules were fabricated by reducing Ni2+ to Ni0 on Pd activated microtubule surface. Focus Ion Beam was used to write metal contacts on these Ni microtubule nanowires and DC conductivity values were measured. Au deposition on MT was performed by both electroless deposition and electrodeposition, by reducing HAuCl4 onto MT prebound with 2 nm Au colloids. Although most MTs exhibited discontinuous Au binding, a fraction of MTs were covered completely by Au. Preliminary electrical measurements for these materials are reported. Alignment of microtubules was also achieved by injecting MTs into microfluidic devices over amine-coated substrate surfaces. These biotemplating approaches are the first steps towards constructing more complicated 2D and 3D architectures.

Here, we have combined the understanding of density functional theory in relation with lattice strain-to-activity correlation to design a Rucore–Ptshell structured electrocatalyst in a dye-sensitized solar cell (DSC) cathode. This electrocatalyst possesses a compressive lattice strain in the shell region which translocates the Pt valence charge to neighboring atoms to decrease the Pt valence band density of states and thus lower the Pt d-band levels. Consequently, compared with DSCs using Pt nanoparticles (NPs) cathode, the Rucore–Ptshell NPs improves the triiodide to iodide redox reduction activity by 2.11-fold and thus boosts the photovoltaic efficiency of DSCs by ∼30.4%. These results provide mechanistic information for the development of DSCs with reduced Pt utilization and programmable electrochemical performance.

This study investigates how the nucleation sequences of Pt and Ru crystallites affect the structure evolutions along with the methanol electrooxidation activity of bimetallic PtRu nanoparticles (BiNPs). We found that the BiNPs crystallites would transform from cubic to tetrakaidecahedron crystals on increasing the Ru content from 0 to 54 at%. This reduces the particle size and the size distributions during the nucleation-growth of the crystal. In the meantime, the unfilled d state and the heteroatomic intermixing of Pt atoms along with the MOR reactivity of the BiNPs will be enhanced. By increasing Ru >54 at%, the BiNPs would transform into an ellipsoid-like crystallite with a Ru rich core. This is because the Pt anions would replace the metallic Ru atoms and form a discrete sub-nano Pt nuclei at the NPs surface. Consequently, the surface MOR activity of the BiNPs is substantially suppressed.

In this study, we successfully manipulate the heterogeneous junction at Co₃O₄-Pt core-shell cathodic nanocatalysts (C/P CNCs) by controlling the core/shell ratios. Our results indicate the cobalt core atoms would inject their valence charge to the surface Pt atoms due to the presence of extensive lattice strain in the shell region. This charge injection accelerates the redox kinetics at the catalysts surface. Consequently, compared with that using Pt nanoparticle cathode, the C/P CNCs at an optimal Pt/Co atomic ratio of 1, improves the current density and the photovoltaic efficiency of dye-sensitized soar cell (DSSC) by ∼36.3% and ∼22.9%, respectively. By combining structure and electrochemical analysis, we systematically elucidate the effects of Pt/Co (shell/core) ratios, the interplay of Co atoms on the shell structures, and the redox activity of C/P CNCs on the DSSC performance. Hereby, this study provide mechanistic insights in developing electrocatalysts for DSSC with programmable performance and reduced Pt utilization.

A aminosilica nanocomposite layer containing a monolayer of gold nanoparticles (d = 18-22 nm) with a well-defined spacing was spontaneously deposited on an unmodified polystyrene surface via a sol-gel reaction when the reduction reaction was carried out under 1:8 molar ratio (gold(III):aminosilane). The amount of aminosilica and spacing between gold nanoparticles were found to be a function of the aminosilane:water molar ratio, which contributes to the plasmonic property of the films with its absorption wavelength ranging between 701 and 548 nm. Furthermore, the nanocomposite film that consists of a monolayer of nanoparticles in aminosilica has also been deposited on the surface of polystyrene beads. This core-shell structure was found capable of storing electrostatic charges and forming a well-separated 2D array.