Showing papers by "Galen D. Stucky published in 2003"
TL;DR: Mesoporous WO3 films with a lamellar structure have been synthesized by electrodeposition using sodium dodecyl sulfate (SDS) as a templating agent as mentioned in this paper.
Abstract: Mesoporous WO3 films with a lamellar structure (see Figure) have been synthesized by electrodeposition using sodium dodecyl sulfate (SDS) as a templating agent. Compared to non-porous WO3 prepared with isopropanol instead of SDS, lamellar phase mesoporous WO3 showed higher photocatalytic activity and greater current density for hydrogen intercalation, probably due to the larger surface area of mesoporous WO3 and more facile charge transport.
449 citations
TL;DR: It is shown that the highly ordered mesostructured metal phosphates can be moulded into morphologies of choice, and that they show interesting physicochemical properties.
Abstract: Although the chemical diversity of ordered composite mesoporous materials has been expanding during the past decade, progress has been limited by the need for a general synthetic approach that is predictive and makes use of well developed fundamental chemical principles. Researchers have previously used the interaction of organic-inorganic (OI) species that are present during the nucleation of the composite phase, and several synthesis pathways, such as direct surfactant-inorganic interaction (S+I-, S-I+, S0I0) and mediated interaction (S+X-I+, S-X+I-), have been proposed. Here we describe a new perspective in which the self-adjusted inorganic-inorganic (II) interplay between two or more inorganic precursors is guided by acid-base chemistry considerations, and in this simple way we produce an overall 'framework' for the sophisticated combination of synergic inorganic acid-base precursor pairs. We propose several new routes and demonstrate their versatility and validity through the successful syntheses of a wide variety of highly ordered, large-pore, homogeneous, stable and multicomponent mesostructured minerals, including metal phosphates and metal borates, as well as various metal oxides and mixed metal oxides. We show that the highly ordered mesostructured metal phosphates can be moulded into morphologies of choice, and that they show interesting physicochemical properties.
417 citations
TL;DR: In this paper, a block copolymer was used as a structure-directing agent to fill a titania polysilicon film with a semiconducting polymer and showed that 33% of the total volume of the film can be filled with the polymer.
Abstract: Interpenetrating networks of organic and inorganic semiconductors are attractive for photovoltaic cells because electron transfer between the two semiconductors splits excitons. In this paper we show that films of titania with a uniform distribution of pore sizes can be made using a block copolymer as a structure-directing agent, and that 33 % of the total volume of the film can be filled with a semiconducting polymer.
413 citations
TL;DR: In this article, the authors demonstrate that highly crystalline, monodisperse maghemite nanoparticles, synthesized in organic solvents, can be effectively transferred into an aqueous medium using an ammonium salt and stabilized at neutral pH.
Abstract: We demonstrate that highly crystalline, monodisperse maghemite (γ-Fe2O3) nanoparticles, synthesized in organic solvents, can be effectively transferred into an aqueous medium using an ammonium salt and stabilized at neutral pH. The nanoparticles remain monodisperse, as characterized by TEM and XRD, as well as superparamagnetic, as determined by SQUID magnetometry. When the aqueous maghemite is combined with the block copolypeptide poly(EG2-lys)100-b-poly(asp)30, the nanoparticles assemble into uniform clusters comprised of approximately 20 nanoparticles, resulting in a water soluble block copolypeptide−nanoparticle composite structure.
281 citations
TL;DR: In this paper, the mesoporous titania thin films, which have a well-ordered pore structure and two-phase walls made of amorphous titania and TiO 2 nanocrystallites, were doped with up to 8 millmol% lanthanide ions, and the ordered structure of the material was preserved.
222 citations
TL;DR: Transmission electron microscopy of whole mounts and thin sections confirmed that bacteria are able to extract Cd and Se from QDs in a fashion dependent upon the QD surface conjugate, suggesting that there is breakup or dissolution of the QDs.
Abstract: Biologically conjugated quantum dots (QDs) have shown great promise as multiwavelength fluorescent labels for on-chip bioassays and eukaryotic cells. However, use of these photoluminescent nanocrystals in bacteria has not previously been reported, and their large size (3 to 10 nm) makes it unclear whether they inhibit bacterial recognition of attached molecules and whether they are able to pass through bacterial cell walls. Here we describe the use of conjugated CdSe QDs for strain- and metabolism-specific microbial labeling in a wide variety of bacteria and fungi, and our analysis was geared toward using receptors for a conjugated biomolecule that are present and active on the organism's surface. While cell surface molecules, such as glycoproteins, make excellent targets for conjugated QDs, internal labeling is inconsistent and leads to large spectral shifts compared with the original fluorescence, suggesting that there is breakup or dissolution of the QDs. Transmission electron microscopy of whole mounts and thin sections confirmed that bacteria are able to extract Cd and Se from QDs in a fashion dependent upon the QD surface conjugate.
212 citations
TL;DR: In this article, Zhao et al. synthesized SBA-15 mesoporous materials using the method reported by Zhao et. al. They removed surfactant from as-made materials by means of different techniques: thermal treatment under air atmosphere, solvent washing at different temperatures, and supercritical CO2 extraction in the presence and absence of cosolvents.
Abstract: SBA-15 mesoporous materials were synthesized using the method reported by Zhao et al. Surfactant was removed from as-made materials by means of different techniques: thermal treatment under air atmosphere, solvent washing at different temperatures, and supercritical CO2 extraction in the presence and absence of cosolvents. The structure of resulting materials was characterized using conventional techniques: nitrogen and argon adsorption measurements, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared spectroscopy (FT-IR), and 29Si MAS NMR. The efficiency of surfactant removal using CO2 under supercritical conditions is similar to that obtained by means of solvent washing under reflux but shows some improvements in the presence of cosolvents. Mesoscopic properties of mild-temperature solvent extracted SBA-15 materials depend on the efficiency of the surfactant removal and the use of supercritical CO2 as solvent. Likewise, the size and volume of the complementary microporosity dete...
167 citations
TL;DR: It is shown that the local hardness and stiffness of the jaws correlate with the local zinc concentration, pointing toward a structural role for zinc, and a direct coordination of zinc and chlorine to the protein is hypothesized.
Abstract: Higher animals typically rely on calcification to harden certain tissues such as bones and teeth. Some notable exceptions can be found in invertebrates: The fangs, teeth, and mandibles of diverse arthropod species have been reported to contain high levels of zinc. Considerable quantities of zinc also occur in the jaws of the marine polychaete worm Nereis sp. High copper levels in the polychaete worm Glycera dibranchiata recently were attributed to a copper-based biomineral reinforcing the jaws. In the present article, we attempt to unravel the role of zinc in Nereis limbata jaws, using a combination of position-resolved state-of-the-art techniques. It is shown that the local hardness and stiffness of the jaws correlate with the local zinc concentration, pointing toward a structural role for zinc. Zinc always is detected in tight correlation with chlorine, suggesting the presence of a zinc-chlorine compound. No crystalline inorganic phase was found, however, and results from x-ray absorption spectroscopy further exclude the presence of simple inorganic zinc-chlorine compounds in amorphous form. The correlation of local histidine levels in the protein matrix and zinc concentration leads us to hypothesize a direct coordination of zinc and chlorine to the protein. A comparison of the role of the transition metals zinc and copper in the jaws of two polychaete worm species Nereis and Glycera, respectively, is presented.
148 citations
TL;DR: In this article, a new method to prepare thin mesoporous platinum films by coupling potential-controlled self-assembly of surfactant-inorganic aggregates and electrodeposition processes was developed.
Abstract: A new method to prepare thin mesoporous platinum films by coupling potential-controlled self-assembly of surfactant-inorganic aggregates and electrodeposition processes was developed. This method uses extremely dilute surfactant solutions to generate films with accessible pores and thermally stable frameworks. Thus, the resulting films possess high surface areas that lead to enhanced electrocatalytic properties towards methanol oxidation compared to those of non-mesoporous platinum films.
132 citations
TL;DR: It is proposed that the formation of charge-stabilized hydrogen bonds between the positively charged amines of the homopolymer polyelectrolytes and the negatively charged citrate molecules stabilizing the quantum dots is responsible for the macroscopic phase separation in this completely aqueous system.
Abstract: Nanoparticle vesicles were spontaneously assembled from homopolymer polyamine polyelectrolytes and water-soluble, citrate-stabilized quantum dots. The further addition of silica nanoparticles to a solution of quantum dot vesicles generated stable micrometer-sized hollow spheres whose walls were formed of a thick, inner layer of close-packed quantum dots followed by an outer layer of silica. The method employed here to assemble both the nanoparticle vesicles and the hollow spheres is in direct contrast to previous syntheses that use either tailored block copolymers or oil-in-water emulsion templating. We propose that the formation of charge-stabilized hydrogen bonds between the positively charged amines of the homopolymer polyelectrolytes and the negatively charged citrate molecules stabilizing the quantum dots is responsible for the macroscopic phase separation in this completely aqueous system. The ease and processibility of the present approach gives promise for the production of a diverse array of mate...
123 citations
TL;DR: Well-ordered mesostructured/mesoporous silica nanofibers have been synthesized in a quiescent dilute aqueous cationic surfactant/silica precursor reaction mixture under strong acidic conditions and exhibit either a circular architecture with the pore channels running in a circular direction around the fiber axis or a longitudinal architecture.
Abstract: Well-ordered mesostructured/mesoporous silica nanofibers have been synthesized in a quiescent dilute aqueous cationic surfactant/silica precursor reaction mixture under strong acidic conditions. These nanofibers have diameters ranging from 50 to 300 nm and lengths up to millimeters. Transmission electron microscopy (TEM) studies show that the nanofibers exhibit either a circular architecture with the pore channels running in a circular direction around the fiber axis or a longitudinal architecture with the pore channels running parallel to the fiber axis. The pore channels in both arrangements are hexagonally packed. The circular or longitudinal architecture can be selectively obtained during synthesis by varying reaction temperature or using inorganic salts as additives.
TL;DR: In this article, five commercial poly(ethylene oxide)/poly(butylene oxide) (PEO/PBO) triblock copolymer surfactants were utilized as structure-directing agents to synthesize mesoporous silica under acidic conditions.
Abstract: Five commercial poly(ethylene oxide)/poly(butylene oxide) (PEO/PBO) triblock copolymer surfactants were utilized as structure-directing agents to synthesize mesoporous silica under acidic conditions. The structures of these materials were characterized by using powder X-ray diffraction (XRD), nitrogen adsorption analysis, and transmission electron micrographs (TEM). The relationship between the pore sizes of silica mesostructures and hydrophobic block weight as well as block architecture of their block copolymer templates was discussed. From the comparison of the critical micelle concentration (CMC) values of these PEO−PBO copolymers and the resultant silica mesostructures, it is proposed that the CMC of block copolymers correlates to the final silica mesostructures and can be used as an important criterion for the rational design of ordered mesoporous materials especially when they are synthesized as precipitates from solutions. Such conclusions are useful to fabricate ordered and large pore mesoporous m...
TL;DR: The characteristics of these natural adhesives produced by these unicellular organisms to adhere to other cells or the substratum are revealed that might be of use in designing man‐made analogues that function in wet environments.
Abstract: Summary We present the first in vivo study of diatoms using atomic force microscopy (AFM). Three chain-forming, benthic freshwater species ‐ Eunotia sudetica, Navicula seminulum and a yet unidentified species ‐ are directly imaged while growing on glass slides. Using the AFM, we imaged the topography of the diatom frustules at the nanometre range scale and we determined the thickness of the organic case enveloping the siliceous skeleton of the cell (10 nm). Imaging proved to be stable for several hours, thereby offering the possibility to study long-term dynamic changes, such as biomineralization or cell movement, as they occur. We also focused on the natural adhesives produced by these unicellular organisms to adhere to other cells or the substratum. Most man-made adhesives fail in wet conditions, owing to chemical modification of the adhesive or its substrate. Diatoms produce adhesives that are extremely strong and robust both in fresh- and in seawater environments. Our phase-imaging and force-pulling experiments reveal the characteristics of these natural adhesives that might be of use in designing man-made analogues that function in wet environments. Engineering stable underwater adhesives currently poses a major technical challenge.
TL;DR: In this paper, a cooperative assembly of cadmium selenide (CdSe) QDs and silica nanoparticles into 3-dimensional microcavities with a high QD volume fraction is presented.
Abstract: Quantum dot (QD) resonators for microcavity lasing applications were successfully synthesized by a single system diblock copolypeptide mediated process. Using specifically tailored block peptides and nanoparticles, we present here the cooperative assembly of cadmium selenide (CdSe) QDs and silica nanoparticles into 3-dimensional microcavities with a high QD volume fraction. These hollow QD microspheres are a perfect combination of both quantum and optical confinement, in which the electronic states of the 3-dimensional confined semiconductor nanocrystals are coupled to the photonic states of the spherical microcavity. We show that the specific interaction between the mode properties of the cavity with the emission of its QD building blocks leads to room-temperature microcavity lasing without the use of additional mirrors, substrate spheres, or gratings.
TL;DR: In this article, trimethoxysilylpropyl methacrylate (TMSPM) and methyl methacelate (MMA) with varied composition and molecular weight were prepared as building blocks for transparent organic−inorganic hybrid materials.
Abstract: Copolymers of trimethoxysilylpropyl methacrylate (TMSPM) and methyl methacrylate (MMA) with varied composition and molecular weight were prepared as building blocks for transparent organic−inorganic hybrid materials. Thermally and chemically induced condensation of these network precursors after solvent evaporation results in optically clear coatings as thick as 1.0 mm with extremely low lateral shrinkage. Many interacting variables such as acid catalyst concentration, polymer molecular weight, polymer composition, and thermal treatment combine to produce materials having controllable shrinkage, hardness, transparency, and thermal stability. By selectively defining these variables, the syntheses of these materials are optimized such that silsesquioxane-cross-linked acrylic polymers are produced that exhibit desirable properties such as low optical loss in the visible spectrum, low lateral shrinkage, high scratch hardness, and no glass transition temperature. The available combinations, interrelationships,...
TL;DR: The partial oxidation of alkanes via bromination followed by the reaction with solid metal oxide mixtures is shown to give an array of products that can be tuned by varying the MO and the reaction conditions.
TL;DR: In this article, a series of 5 ms bipolar current pulses were used to construct large-scale electrically continuous Au thin films with 10-30 nm in thickness and approximately 0.25 cm2 in area by pulsed galvanostatic electrodeposition.
Patent•
19 Nov 2003TL;DR: In this article, a reactant selected from the group consisting of alkanes, alkenes, alkynes, dienes, and aromatics is reacted with a halide selected from a group including chlorine, bromine, and iodine to form a first reaction product.
Abstract: A reactant selected from the group consisting of alkanes, alkenes, alkynes, dienes, and aromatics is reacted with a halide selected from the group including chlorine, bromine, and iodine to form a first reaction product. The first reaction product is reacted with a solid oxidizer to form a product selected from the group including olefins, alcohols, ethers, and aldehydes, and spent oxidizer. The spent oxidizer is oxidized to form the original solid oxidizer and the second reactant which are recycled.
Patent•
27 Feb 2003TL;DR: Alcohols, ethers, aldehydes, and olefins are manufactured from alkanes by mixing an alkane and a halogen selected from the group including chlorine, bromine, and iodine in a reactor to form alkyl halide and hydrogen halide as discussed by the authors.
Abstract: Alcohols, ethers, aldehydes, and olefins are manufactured from alkanes by mixing an alkane and a halogen selected from the group including chlorine, bromine, and iodine in a reactor to form alkyl halide and hydrogen halide. The alkyl halide only or the alkyl halide and the hydrogen halide are directed into contact with metal oxide to form an alcohol and/or an ether, or an olefin and metal halide. The metal halide is oxidized to form original metal oxide and halogen, both of which are recycled.
TL;DR: In this paper, the 2D hexagonal mesostructured silica thin films were made using acidic sol−gel synthesis with poly(ethylene oxide)-b-poly(propylene oxide)-poly(poly(methylene oxide), (EO20PO70EO20) as the structure-directing agent, and the dyes were doped into the synthesis solutions so that they underwent co-assembly with the silica and block copolymer.
Abstract: Energy transfer between the organic laser dyes coumarin 485 and pyrromethene 567 was investigated in mesostructured silica/block copolymer thin films. The 2-D hexagonal mesostructured silica thin films were made using acidic sol−gel synthesis with poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide), (EO20PO70EO20) as the structure-directing agent. The dyes were doped into the film synthesis solutions so that they underwent co-assembly with the silica and block copolymer. At a very low concentration of acceptor, one acceptor molecule for every 20 donor molecules, the donor's emission was drastically quenched, suggesting efficient energy transfer. Investigations into amplified spontaneous emission revealed that the donor/acceptor system resulted in full gain narrowing at significantly lower concentrations than systems without a donor.
TL;DR: CdSe/CdS core-shell quantum dots have been self-assembled onto thiolcarboxylic acid functionalized gold surfaces by hydrogen bonding; control of the pH during deposition allows producing a high coverage photoactive surface for use in a surface sensitized Schottky barrier photovoltaic structure.
Patent•
13 Jan 2003TL;DR: A method of making colloidal sphere templates and the sphere-templated porous materials made from the templates is described in this paper, which is useful in the synthesis of submicron porous, metallic tin-based and other high capacity anode materials with controlled pore structures for application in rechargeable lithium-ion batteries.
Abstract: A method of making colloidal sphere templates and the sphere-templated porous materials made from the templates The templated porous materials or thin films comprise micron and submicron-scaled spheres in ordered, disordered, or partially ordered arrays The invention is useful in the synthesis of submicron porous, metallic tin-based and other high capacity anode materials with controlled pore structures for application in rechargeable lithium-ion batteries The expected benefits of the resulting nanostructured metal films include a large increase in lithium storage capacity, rate capability, and improved stability with electrochemical cycling
TL;DR: Tungsten oxide films were successfully synthesized by electroless deposition on copper substrates from tungsten-peroxo electrolytes as discussed by the authors, where reducing electrons were provided by the copper substrate during oxidation to CuO.
Abstract: Tungsten oxide films were successfully synthesized by electroless deposition on copper substrates from tungsten-peroxo electrolytes. The reducing electrons were provided by the copper substrate during oxidation to CuO. Mesoporous tungsten oxide was also fabricated by this method using SDS as a templating agent. This method can be used to fabricate molybdenum oxide, niobium oxide, zirconium oxide, and titanium oxide from metal-peroxo electrolytes.
TL;DR: In this article, the antiferromagnetic ordering and crystal structure of the clathrate compound was investigated using multitemperature neutron and synchrotron x-ray powder diffraction.
Abstract: The antiferromagnetic ordering and crystal structure of the clathrate compound ${\mathrm{Eu}}_{4}{\mathrm{Ga}}_{8}{\mathrm{Ge}}_{16}$ was investigated using multitemperature neutron and synchrotron x-ray powder diffraction. High-resolution low-Q neutron data were measured at long wavelength $(\ensuremath{\lambda}=4.2\AA{})$ between 1.5 and 15 K for an accurate description of the magnetic structure, whereas high-Q diffraction patterns were collected using neutrons of wavelength 1.9 \AA{} at the same temperatures to determine the nuclear structure precisely. The structure orders antiferromagnetically at about 8 K with ferromagnetic chains parallel to the a axis. The intrachain Eu-Eu distance, 4.1216(1) \AA{} at 1.5 K, is significantly shorter than the distance observed in the ferromagnetic clathrates $\ensuremath{\beta}\ensuremath{-}{\mathrm{Eu}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$ (5.23 \AA{}) and $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Eu}}_{8}{\mathrm{Ga}}_{16}{\mathrm{Ge}}_{30}$ (5.56 \AA{}). Antiferromagnetic coupling to the nearest and next-nearest chains at distances of 5.99 and 6.98 \AA{}, respectively, leads to an overall antiferromagnetic structure. A fit to a power law of the temperature dependence of the ordered ${\mathrm{Eu}}^{2+}$ magnetic moment results in a moment of $7.01(7){\ensuremath{\mu}}_{B}$ at 0 K in agreement with the $7{\ensuremath{\mu}}_{B}$ for the free ion value of ${\mathrm{Eu}}^{2+}.$ The temperature dependence of the crystal structure was investigated from 11 K to room temperature using synchrotron x-ray powder diffraction. Analysis of the atomic displacement parameters with Einstein and Debye models gives ${\ensuremath{\Theta}}_{E}=82(3)\mathrm{K}$ for the guest atom and ${\ensuremath{\Theta}}_{D}=266(4)\mathrm{K}$ for the framework atoms. Based on ${\ensuremath{\Theta}}_{D}$ the lattice contribution to thermal conductivity is estimated to be 0.0125 W/cm K.
TL;DR: In this article, the magnetic ordering in the clathrate compound was studied using magnetic susceptibility, M\"ossbauer spectroscopy, and heat-capacity measurements, and the spin-flop phase diagram was established and used to extract the next-neighbor interaction energy.
Abstract: The magnetic ordering in the ${\mathrm{Eu}}_{4}{\mathrm{Ga}}_{8}{\mathrm{Ge}}_{16}$ clathrate compound was studied using magnetic susceptibility, M\"ossbauer spectroscopy, and heat-capacity measurements. Antiferromagnetic ordering is observed at 8 K. M\"ossbauer spectroscopy shows the Eu atoms to exist as ${\mathrm{Eu}}^{2+}$ with strong room-temperature absorption at -11.8 mm/s vs ${\mathrm{EuF}}_{3}.$ The temperature dependence of the Lamb-M\"ossbauer factor can be fitted to an Einstein model with an effective Einstein temperature of 80 K. In combination with heat-capacity measurements, this result suggests that the Eu atoms behave like isolated oscillators that are effectively decoupled from the lattice. The magnetic susceptibility data are interpreted using the Curie-Weiss law for ordering with ${\ensuremath{\mu}}_{\ensuremath{\parallel},\mathrm{eff}}=8.00\ifmmode\pm\else\textpm\fi{}0.03{\ensuremath{\mu}}_{B}/{\mathrm{Eu}}^{2+}$ ion and $\ensuremath{\theta}=4.43\ifmmode\pm\else\textpm\fi{}0.08\mathrm{K}.$ The positive Weiss constant is rationalized by a nearest-neighbor ferromagnetic exchange interaction within an overall antiferromagnetically ordered system. The spin-flop phase diagram is established and used to extract the next-nearest-neighbor interaction energy. The location of the tri-critical point in H,T space is determined. The magnetic heat capacity ${C}_{m}$ is extracted by modeling the lattice contribution using a weighted Debye-Einstein model with fitted Debye temperature ${\ensuremath{\Theta}}_{D}=314\ifmmode\pm\else\textpm\fi{}4\mathrm{K}$ and using a fixed Einstein temperature ${\ensuremath{\Theta}}_{E}=80\mathrm{K}.$ Integration of ${C}_{m}/T$ gave 15.1 J/K mol ${\mathrm{Eu}}^{2+}$ in fair accordance with expectations based on configurational considerations.
TL;DR: Schofield and Nesson as mentioned in this paper showed that the correlation between the element concentration in Glycera jaws and the mechanical properties of the jaw may not reflect the correlations between atacamite mineral content and mechanical properties.
Abstract: Schofield and Nesson ( [1][1] ) express concern that the correlation between the element concentration in Glycera jaws and the mechanical properties of the jaw ( [2][2] ) may not reflect the correlation between atacamite mineral content and mechanical properties. They argue that there may be “