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The acid-base properties of surfaces significantly influence catalytic and (photo)electrochemical processes. Estimation of acid dissociation constants (p K a values) for colloids is commonly performed through electroanalytical techniques or spectroscopic methods employing label molecules. Here, we show that polarimetric angle-resolved second harmonic scattering (AR-SHS) can be used as an all-optical, label-free probe of colloid surface p K a values. We apply AR-SHS to dispersions of 100 nm anatase TiO 2 particles to extract surface potential and surface susceptibility, a measure of interfacial water orientation, as a function of pH. The surface potential follows changes in surface charge density, while the interfacial water orientation inverts at pH ∼4.8, ∼6, and ∼7.6. As the variation in bulk pH modifies the populations of Ti-OH 2 + , Ti-OH, and Ti-O - interfacial groups, a change in water orientation reports on the ratio of protonated/deprotonated species. Such observation allows for p K a evaluation from plots of surface susceptibility versus pH. A Nerstian trend in the surface potential is additionally demonstrated.

Mesoporous silica nanoparticles (MSNs) have drawn attention as efficient nanocarriers for drug delivery systems owing to their unique physiochemical properties. However, systemically controlling the kinetics of drug release from the nanocarriers and in situ monitoring of the drug release are still challenging. Here, we report surface-capped MSNs used for controlled drug release and demonstrate label-free in situ Raman monitoring of released drugs based on the molecule-specific spectral fingerprints. By capping the surface of MSNs with amine moieties, gold nanoparticles, and albumin, we achieved high loading efficiencies (up to 97%) of doxorubicin and precisely controlled drug release stimulated by changing pH value. Moreover, we monitored in real-time drug release profile and visualized cellular distribution of the delivered drug at nanoscale based on its intrinsic Raman peak. Finally, we evaluated drug responses in cancer cells and normal cells to investigate whether capped-dMSNs exhibit selective drug release. Our findings would be beneficial for designing smart drug carriers and directly monitoring the release behavior of drugs in actual cellular environments., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A template-mediated process for the preparation of mesoporous carbon shells with high surface area, dual-pore structure, and excellent performance in the adsorption of humic acid is reported. Their synthesis involves templating phenolic resin against wrinkled silica nanospheres, subsequent carbonization under Ar atmosphere, and final release of dual-pore mesoporous carbon shells by etching the silica templates. An additional silica layer was used to protect the phenolic resin from aggregation during carbonization, and its subsequent removal gives the carbon shells a hydrophilic surface, which significantly improves their dispersity in aqueous media. When used as adsorbents for humic acid removal, the as-prepared dual-pore mesoporous carbon shells show superior adsorption performance to activated carbon. [ABSTRACT FROM AUTHOR]

Coating titania shells onto sub-micron sized particles has been widely studied recently, with success mainly limited to objects with sizes above 50 nm. Direct coating on particles below this size has been difficult to attain especially with good control over properties such as thickness and crystallinity. Here we demonstrate that titanium-glycolate formed by reacting titanium alkoxide and ethylene glycol is an excellent precursor for coating titania on aqueous nanoparticles. The new coating method is particularly useful for its ability to coat materials lacking strong polymers or ligands which are frequently needed to facilitate typical titania coatings. We demonstrate the effectiveness of the process of coating titania on metal nanoparticles ranging from citrate-stabilized gold and silver spheres to gold nanorods and silver nanoplates, and larger particles such as SiO2 microspheres and polymer spheres. Further the thickness of these coatings can be tuned from a few nanometers to ∼40 nm through sequential coatings. These coatings can subsequently be crystallized into TiO2 through refluxing in water or by calcination to obtain crystalline shells. This procedure can be very useful for the production of TiO2 coatings with tunable thickness and crystallinity as well as for further study on the effect of TiO2 coatings on nanoparticles. [ABSTRACT FROM AUTHOR]

Mesoporous hollow colloidal particles with well-defined characteristics have potential use in many applications. In liquid-phase catalysis, in particular, they can provide a large active surface area, reduced diffusion resistance, improved accessibility to reactants, and excellent dispersity in reaction media. Herein, we report the tailored synthesis of sulfated ZrO2 hollow nanostructures and their catalytic applications in the dehydration of fructose. ZrO2 hollow nanoshells with controllable thickness were first synthesized through a robust sol-gel process. Acidic functional groups were further introduced to the surface of hollow ZrO2 shells by sulfuric acid treatment followed by calcination. The resulting sulfated ZrO2 hollow particles showed advantageous properties for liquid-phase catalysis, such as well-maintained structural integrity, good dispersity, favorable mesoporosity, and a strongly acidic surface. By controlling the synthesis and calcination conditions and optimizing the properties of sulfated ZrO2 hollow shells, we have been able to design superacid catalysts with superior performance in the dehydration of fructose to 5-hydroxymethyfurfural than the solid sulfated ZrO2 nanocatalyst. [ABSTRACT FROM AUTHOR]

Abstract: A platinum precursor (H2PtCl6) was reduced to platinum nanoparticles using sodium alkoxide in the presence of a carbon support. Various electrolytes such as H2O, HCl, and NaCl were used in order to deposit platinum nanoparticles on the carbon support. In the case of H2O and NaCl, Pt nanoparticles were not successfully supported on the carbon. However, HCl was found to be efficient for the deposition of Pt nanoparticles on the carbon support. The supported Pt catalysts with various Pt loadings (40–80wt.%) were prepared and characterized by comparison with commercially available carbon-supported Pt catalysts. It was revealed that the prepared Pt catalysts showed a better catalytic performance than the commercial catalysts in the electro-oxidation of methanol, due to the enhanced active metal surface areas of the prepared Pt catalysts. [Copyright &y& Elsevier]

Abstract: A carbon-supported Pt catalyst (40wt.% loading) is prepared by a modified ethylene glycol reduction method (Pt–EG-complex). In this procedure, a complex produced by reacting ethylene glycol with sodium borohydride (NaBH4), serves as a reducing agent for the Pt precursor and as a stabilizer for preventing the growth of Pt particles. For purposes of comparison, two types of carbon-supported Pt catalyst (40wt.% loading) are also prepared by a NaBH4 reduction method, in which the Pt precursor is reduced in a ethylene glycol solution (Pt–EG–NaBH4) and in de-ionized water (Pt–H2O–NaBH4). Analysis by X-ray diffraction and transmission electron microscopy reveal that the Pt–EG-complex catalyst is comprised of highly-dispersed Pt nanoparticles with a uniform size (2.9–3.1nm) on the carbon support, while large Pt particles are observed in the Pt–EG–NaBH4 (3.3–3.6nm) and Pt–H2O–NaBH4 (5.7–6.2nm) catalysts. The Pt–EG-complex catalyst has the highest electrochemical surface area and shows the highest catalytic performance for methanol electro-oxidation. [Copyright &y& Elsevier]

Abstract: We describe a method tuning the band-gap energy (E g) of visible light sensitive TiO2-x C x nanoparticle. E g tends to become smaller with the increase in the amount of carbon dopant in TiO2-x C x nanoparticle due to the increase in excess electrons. Photo-catalytic oxidative activity, however, did not depend on only the value of E g, but also the energy level of valence band. TiO1.96C0.04 nanoparticle having E g of 2.6eV showed outstanding performance in oxidative decomposition of phenol under the irradiation of visible light. [Copyright &y& Elsevier]