One-dimensional protonated titanate nanostructures were tested as solid acid catalysts in the condensation reaction between benzaldehyde and cyclohexanone. Two morphologies were prepared, protonated titanate nanotubes and nanoribbons. Both possess Lewis and Brønsted acid sites with medium acid strength, whereas only nanotubes have also strong acid sites. Therefore only protonated titanate nanotubes revealed an efficient catalyst that was also successfully applied to other reaction systems with substituted benzaldehyde derivatives. Recycling studies showed no significant decrease in the catalytic activity of protonated titanate nanotubes in five cycles and even showed an excellent performance in the large scale experiment. In addition, protonated titanate nanotubes did not require any activation prior to the reaction. The mechanism is proposed to describe the condensation process over the catalyst.
COBISS.SI-ID: 30232871
The first recyclable polymer-supported electrophilic fluorinating agent was prepared by reaction of molecular fluorine with the triethylenediamine motif that is grafted onto a poly(4-vinylbenzyl chloride-co-divinylbenzene) polyHIPE material. The resulting polymeric SelectfluorTM-type reagent demonstrated high efficiency in the fluorination of naphthol in the course of repeated sequences of fluorination and regeneration. It also reacted with the enol form of the sodium enolate of 1,3-dicarbonyl compounds.
COBISS.SI-ID: 30090791
An alkoxysilyl-functionalised precursor, 1,3,5,7-tetramethyl-1,3,5,7-tetra-(2-(3-trimethoxysilyl)propylsulfanyl)ethyl-cyclotetrasiloxane was synthesized to produce protective coatings. The addition of bis-endcapped 1,2-bis(trimethoxysilyl)ethane and various alkoxysilanes led to formation of more crosslinked coatings as evidenced by 29Si NMR and IR reflection-absorption spectroscopy. The structural changes during forced anodic polarization were followed using ex situ IR reflection-absorption and in situ Raman spectroelectrochemistry. The former technique shows hydration of coatings and cleavage of some siloxane bonds. In situ Raman bands revealed decrease in intensity, while imaging enabled to follow pit formation. The potentiodynamic polarization, impedance spectroscopy and exposure in salt chamber showed that coating with hexadecyltrimethoxysilane is the most efficient.
COBISS.SI-ID: 6198554
Highlights of the article are the following: (i) novel plasma-assisted route to Fe2O3-TiO2-Au nanosystems on FTO substrates is reported, (ii) pure nanocomposites contain α-Fe2O3, amorphous TiO2 and Au nanoparticles, and (iii) functional tests in photoelectrochemical water splitting and self-cleaning applications were performed.
COBISS.SI-ID: 4528891
Highly transparent thin films of TiO2-ZrO2-SiO2 composites on glass were prepared by sol-gel process, wherein different amounts of zirconia precursor were mixed with titania precursor solution (0–20 mol% Zr with regard to Ti). For better adhesion of the films on glass supports, a silica binder was added to the mixture of alkoxides (27 mol% Si vs. Ti). The prepared samples were characterized by various techniques to obtain information on their structural, optical and surface properties. The presence of anatase titania polymorph as the only crystalline phase was detected. Unexpectedly, the higher loading of Zr promoted the growth of anatase particles with progressive spherical shape and concomitant decrease of specific surface area, which adversely influenced the photocatalytic activity. Decrease of the photodegradation activity with increasing amount of Zr was evidenced by contact angle measurements of a fatty deposit, spectrofluorometrically using terephthalic acid probe and by EPR spectroscopy monitoring indirectly the non-persistent radicals generation. On the other hand, the higher content of Zr improved the mechanical stability of resulting thin films. An optimal Zr content around 10 mol% appears to be a good compromise between photocatalytic activity and mechanical robustness of the films.
COBISS.SI-ID: 4714491