Plasmonic inhibition of bacterial adhesion on gold-decorated mesoporous zirconium oxide thin films.

Preventing bacterial development on surfaces is essential to avoid problems caused by biofouling. Surfaces decorated with gold nanoparticles have been shown to thermally kill bacteria under high-intensity NIR illumination. In this study, we evaluated the colonization by E. coli of nanostructured surfaces composed of mesoporous zirconia thin films, both with and without gold nanoparticles embedded into the pores. We studied the effect of the nanostructure and of low intensity visible light excitation of the gold nanoparticles on the colonization process. We found that neither the zirconia, nor the presence of pores, or even gold nanoparticles affect bacterial adhesion compared to the bare glass substrate. Therefore, mesoporous zirconia thin films are biologically inert scaffolds that enable the construction of robust surfaces containing functional nanoparticles that can affect bacterial growth. When the gold containing surfaces are irradiated with light, bacterial adhesion shows a remarkable 96 ± 4% reduction. Our studies revealed that these surfaces affect early colonization steps, prior to biofilm formation, preventing bacterial adhesion without affecting its viability. In contrast to related systems where plasmonic excitation induces membrane damage due to strong local heating, the membrane integrity is preserved, showing that these surfaces have a different working principle.

Ibuprofen molecular aggregation by direct back-face transmission steady-state fluorescence.

Direct back-face transmission steady-state fluorescence was successfully applied to the study of aggregation of ibuprofen and ibuprofenate anion in solution taking advantage of its own fluorescence. The analysis of the experimental data involves the use of the differential reabsorption model to account for re-absorption phenomenon and the closed association model to describe aggregation. The fluorescence quantum yield of ibuprofenate increases when it aggregates in the presence of sodium, but it markedly decreases when 1-butyl-3-methylimidazolium is used as counterion. The proposed methodology allows the accurate determination of the critical aggregation concentrations and the mean aggregation numbers. Results were supported by complementary techniques such as time-resolved fluorescence, 1H-NMR and small-angle neutron and X-ray scattering. The developed technique constitutes a promising strategy to characterize the aggregation of poorly fluorescent surfactants that aggregates at high concentrations and hence at high absorbance values, conditions in which the most common right-angle configuration for fluorescence acquisition is troublesome due to re-absorption.

Gold nanoparticles supported in zirconia-ceria mesoporous thin films: a highly active reusable heterogeneous nanocatalyst.

Gold nanoparticles (NP) trapped in the mesopores of mixed zirconia-ceria thin films are prepared in a straightforward and reproducible way. The films exhibit enhanced stability and excellent catalytic activity in nitro-group reduction by borohydride and electrocatalytic activity in CO and ethanol oxidation and oxygen reduction.

Synthesis and photocatalytic activity of titania monoliths prepared with controlled macro- and mesopore structure.

Herein, we report a one-pot synthesis of crack-free titania monoliths with hierarchical macro-mesoporosity and crystalline anatase walls. Bimodal macroporosity is created through the polymer-induced phase separation of poly(furfuryl alcohol). The cationic polymerization of furfuryl alcohol is performed in situ and subsequently the polymer becomes immiscible with the aqueous phase, which includes titanic acid. Addition of template, Pluronic F127, increases the mesopore volume and diameter of the resulting titania, as the poly(ethylene glycol) block interacts with the titania precursor, leading to assisted assembly of the metal oxide framework. The hydrophobic poly(propylene glycol) micelle core could itself be swollen with monomeric and oligomeric furfuryl alcohol, allowing for mesopores as large as 18 nm. Variations in synthesis parameters affect porosity; for instance furfuryl alcohol content changes the size and texture of the macropores, water content changes the grain size of the titania and Pluronic F127 content changes the size and volume of the mesopore. Morphological manipulation improves the photocatalytic degradation of methylene blue. Light can penetrate several millimeters into the porous monolith, giving these materials possible application in commercial devices.

Growth and branching of gold nanoparticles through mesoporous silica thin films.

Composite materials made of mesoporous oxide thin films containing metallic nanoparticles are of high interest in various fields, including catalysis, biosensing and non-linear optics. We demonstrate in this work the fabrication of such composite materials containing a sub-monolayer of gold nanoparticles (GNPs) of various shapes covered with mesoporous silica thin films. Additionally, the shape of the GNPs (and thus their optical properties) can be modified in situ through seeded growth and branching. Such growth proceeds upon wetting with HAuCl(4) solution, a surfactant (cetyltrimethylammonium bromide, CTAB) and a mild reducing agent (ascorbic acid, AA). The effect of varying several reaction parameters (time and CTAB and AA concentrations) was evaluated, showing that more anisotropic particles are obtained at longer reaction times, lower CTAB concentration and higher AA concentration. The final shape of the GNPs was also found to depend on their initial shape and size, as well as the pore size of the mesoporous film covering them. Because the growth proceeds through the pores of the film, it may lead to shapes that are not easily obtained in solution, such as particles with branches on one side only. Finally, we have confirmed that no damage was induced to the mesoporous silica structure during the growth process and thus the final particles remain well covered by the thin film, which can eventually be used as a filter between the GNPs and the outer medium.

Halogen bonding in 1,2-dibromo-4,5-dimethoxybenzene and 1,2-diiodo-4,5-dimethoxybenzene.

An interesting case of ;halogen-bonding-promoted' crystal structure architecture is presented. The two title compounds, C(8)H(8)Br(2)O(2) and C(8)H(8)I(2)O(2), have almost indistinguishable molecular structures but very different spatial organization, and this is mainly due to differences in the halogen-bonding interactions in which the different species present, i.e. Br and I, take part. The dibromo structure exhibits a pi-bonded columnar array involving all four independent molecules in the asymmetric unit, with intercolumnar interactions governed by C-Br...Br-C links and with no C-Br...O/N interactions present. In the diiodo structure, instead, the C-I...O synthon prevails, defining linear chains, in turn interlinked by C-I...I-C interactions.

A liquid crystal derived from ruthenium(II,III) and a long-chain carboxylate.

The title compound, catena-poly[[tetrakis(mu-decanoato-kappa(2)O:O')diruthenium(II,III)(Ru-Ru)]-mu-octanesulfonato-kappa(2)O:O'], [Ru(2)(C(10)H(19)O(2))(4)(C(8)H(17)O(3)S)], is an octanesulfonate derivative of the mixed-valence complex diruthenium tetradecanoate. The equatorial carboxylate ligands are bidentate, bridging two Ru atoms to form a dinuclear structure. Each of the two independent dinuclear metal complexes in the asymmetric unit is located at an inversion centre. The octanesulfonate anion bridges the two dinuclear units through axial coordination. The alkyl chains of the carboxylate and sulfonate ligands are arranged in a parallel manner. The global structure can be seen as infinite chains of polar moieties separated by a double layer of non-polar alkyl groups, without interdigitation of the alkyl chains.