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Graphene oxide (GO) with different oxidation degrees is prepared by a modified Hummers' method varying KMnO4 amount from 0.5 to 6.0 g. X‐ray powder diffraction (XRPD), micro–Raman, thermogravimetric analysis, X‐ray photoeelectron spectroscopy, Boehm titrations, high–resolution transmission electron microscopy, and, finally, positron annihilation lifetime spectroscopy (PALS) are exploited to assess the properties of GO. Results show that increasing oxidant species can tune the interlayer gap between GO sheets up to a maximum value in the case of 4.0 g KMnO4 content. Moreover, these results validate the two‐component‐based model of GO in which, at low oxidation degree, there are unsplit/isolated graphene planes, instead at higher oxidant amounts, a five‐layer sandwiched configuration occurs comprising graphene planes having functional groups decorating the edges (bwGO), hydrated oxidative debris (OD) and "empty" spaces (revealed by PALS as the distance between (bwGO + OD) two‐component layers). In addition, by XRPD analysis, the total gap between two sheets is easily computed. In order to correlate these findings to pollutant removal capability, planar o‐toluidine adsorption is studied. Since this molecule diffuses in an aqueous environment, the obtained adsorption percentages are compared to the thickness of the hydrated OD grafted onto bwGO. A strict connection between the pollutant removal efficacy and the variation of the hydrated interlayer distance is found. [ABSTRACT FROM AUTHOR]

Abstract Nanocrystalline TiO2samples were prepared by promoting the growth of a sol–gel precursor, in the presence of water, under continuous (CW), or pulsed (PW) ultrasound. All the samples turned out to be made of both anatase and brookite polymorphs. Pulsed US treatments determine an increase in the sample surface area and a decrease of the crystallite size, that is also accompanied by a more ordered crystalline structure and the samples appear to be more regular and can be considered to contain a relatively low concentration of lattice defects. These features result in a lower recombination rate between electrons and holes and, therefore, in a good photocatalytic performance toward the degradation of NO x in air. The continuous mode induces, instead, the formation of surface defects (two components are present in XPS Ti 2p3/2region) and consequently yields the best photocatalyst. The analysis of all the characterization data seems to suggest that the relevant parameter imposing the final features of the oxides is the ultrasound total energypervolume (E tot/V) and not the acoustic intensity or the pulsed/continuous mode.

A library of alkyl galactosides was synthesized to provide the "polar head" of sugar fatty acid esters to be tested as non‐ionic surfactants. The enzymatic transglycosylation of lactose resulted in alkyl β‐D‐galactopyranosides, whereas the Fischer glycosylation of galactose afforded isomeric mixtures of α‐ and β‐galactopyranosides and α‐ and β‐galactofuranosides. n‐Butyl galactosides from either routes were enzymatically esterified with palmitic acid, used as the fatty acid "tail" of the surfactant, giving the corresponding n‐butyl 6‐O‐palmitoyl‐galactosides. Measurements of interfacial tension and emulsifying properties of n‐butyl 6‐O‐palmitoyl‐galactosides revealed that the esters of galactopyranosides are superior to those of galactofuranosides, and that the enantiopure n‐butyl 6‐O‐palmitoyl‐β‐D‐galactoside, prepared by the fully enzymatic route, leads to the most stable emulsion. These results pave the way to the use of lactose‐rich cheese whey as raw material for the obtainment of bio‐based surfactants. [ABSTRACT FROM AUTHOR]

Sensitivity and selectivity are the two major parameters that should be optimized in chemiresistive devices with boosted performances towards Volatile Organic Compounds (VOCs). Notwithstanding a plethora of metal oxides/VOCs combinations that have been investigated so far, a close inspection based on theoretical models to provide guidelines to enhance sensors features has been scarcely explored. In this work, we measured experimentally the sensor response of a WO3 chemiresistor towards gaseous acetone and toluene, observing a two orders of magnitude higher signal for the former. In order to gain insight on the observed selectivity, Density Functional Theory was then adopted to elucidate how acetone and toluene molecules adsorption may perturb the electronic structure of WO3 due to electrostatic interactions with the surface and hybridization with its electronic structure. The results of acetone adsorption suggest the activation of the carbonyl group for reactions, while an overall lower charge redistribution on the surface and the molecule was observed for toluene. This, combined with acetone's higher binding energy, justifies the difference in the final responses. Notably, the presence of surface oxygen vacancies, characterizing the nanostructure of the oxide, influences the sensing performances. [ABSTRACT FROM AUTHOR]

Featured Application: Reconstruction of chemical images of solid objects revealed in human fingerprints, using nanoparticles to assist MALDI imaging. Commercially available UV-adsorbent TiO2 nanoparticles were used to assist laser/desorption ionization in the course of matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI). Titanium nano-powders proved extremely stable and efficient for small molecule ionization, with negligible background noise in the low mass region (m/z < 500 Da). Validation steps were carried out, assessing detection limits and comparing the results to those of the established DESI/Orbitrap technique. The new analytical method was used to reveal the molecular distribution of endogenous (lipids) and exogenous (analgesics and antipyretics) compounds in latent finger marks (LFMs). The detection limits of endogenous fatty acids and small molecules such as caffeine were in the range of fmol/mm2 on LFMs. The technique separated overlapping latent finger marks, exploiting the differences in lipid expression of human skin. Finally, the method was used to prove contact between skin and objects contaminated by different substances, such as credit cards and paper clips, with chemical images that maintain the shape of the objects on the LFM. [ABSTRACT FROM AUTHOR]

Nanocomposites are at the heart of the present nanotechnology revolution in several strategic fields, including Green Chemistry, sensors and pollutant remediation. The promising and extensively examined nanotitania photocatalysts have performances hampered by the rapid recombination of photogenerated charge carriers. To better understand these materials, here we generalize the 2D-heterojunctions physics to 3D patchworks of intimately associated anatase and brookite mixed crystallites, i.e. multi-phase polymorphs, MPPs. The synthesized composite material is fully characterized experimentally and by simulations. We demonstrate that the anatase–brookite interphase behaves as a ground-state nano-diode containing an almost ideal nanocapacitor, associated with a net migration of electrons from anatase to brookite. Implications of the direct observation of a polarized interphase on the understanding of nanotitania photocatalysts at the atomic scale are discussed. [ABSTRACT FROM AUTHOR]

Sugar fatty acid esters are a relevant class of surfactants. Base catalyzed transesterification of lower esters may be carried out on an industrial level. Direct esterification of fatty acids with sugars over heterogeneous catalysts should be more environmental friendly, however this approach is quite challenging. The activity of montmorillonites has been investigated in the acylation of d‐glucose with palmitic acid and the number of Lewis acid sites on the catalyst surface measured through FTIR of adsorbed pyridine. The use of a ketone, namely acetylacetone, as solvent allows the formation of an acetal between the sugar and the solvent itself, increasing the solubility of the substrate, with a maximum of conversion when using FeIII exchanged montmorillonite K10 as the catalyst. The main reaction product was the dipalmitate ester with an acetal group at the 1,2 position of d‐glucose. This product with a hydrophilic lipophilic balance (HLB) of 4.9 shows interesting properties as surfactant with a CMC value close to 0.036% wt/v measured in sunflower oil. [ABSTRACT FROM AUTHOR]