Colored Coating Materials with Spectrally Selective Reflectance for Woodland Camouflage Textile Fabrics

The camouflage effect aims to reproduce natural or artificial surroundings in terms of color, [...

Carbon Nanomaterials from Biomass Wastes

Biomass represents carbon that has been sequestered from the environment by plants through photosynthesis and nutrition [...

Modeling the Properties of Curcumin Derivatives in Relation to the Architecture of the Siloxane Host Matrices

Research in the field of natural dyes has constantly focused on methods of conditioning curcumin and diversifying their fields of use. In this study, hybrid materials were obtained from modified silica structures, as host matrices, in which curcumin dyes were embedded. The influence of the silica network structure on the optical properties and the antimicrobial activity of the hybrid materials was monitored. By modifying the ratio between phenyltriethoxysilane:diphenyldimethoxysilane (PTES:DPDMES), it was possible to evaluate the influence the organosilane network modifiers had on the morphostructural characteristics of nanocomposites. The nanosols were obtained by the sol–gel method, in acid catalysis. The nanocomposites obtained were deposited as films on a glass support and showed a transmittance value (T measured at 550 nm) of around 90% and reflectance of about 11%, comparable to the properties of the uncovered support. For the coatings deposited on PET (polyethylene terephthalate) films, these properties remained at average values of T550 = 85% and R550 = 11% without significantly modifying the optical properties of the support. The sequestration of the dye in silica networks reduced the antimicrobial activity of the nanocomposites obtained, by comparison to native dyes. Tests performed on Candida albicans fungi showed good results for the two curcumin derivatives embedded in silica networks (11–18 mm) by using the spot inoculation method; in comparison, the alcoholic dye solution has a spot diameter of 20–23 mm. In addition, hybrids with the CA derivative were the most effective (halo diameter of 17–18 mm) in inhibiting the growth of Gram-positive bacteria, compared to the curcumin derivative in alcoholic solution (halo diameter of 21 mm). The results of the study showed that the presence of 20–40% by weight DPDMES in the composition of nanosols is the optimal range for obtaining hybrid films that host curcumin derivatives, with potential uses in the field of optical films or bioactive coatings

Preparation of Transparent Sol-Gel Modified Silica Hydrophobic Coatings on Plastic Substrates

Transparent hydrophobic or super-hydrophobic thin films prepared on plastic substrates haveattracted attention in recent years because they can be suited to optical applications such as lenses [...

Fluorescent Silica Hybrid Film-Forming Materials Based on Salicylaldazine

Fluorescent film-forming materials were obtained by embedding salicylaldazine (SAA) in silica hybrids generated by sol–gel processes from different silane precursors in acid catalysis. Tuned local environments for the fluorophore were generated in the hosting network by modifying silica sols with organic groups through the co-condensation of tetraethylortosilicate (TEOS) and different alkoxysilanes hydrolysis products. The photophysical properties of the luminescent hybrid films were studied in direct relationship with structural, textural, and surface properties and based on interactions between SAA species and the silica hosting network. Film-forming materials were studied in order to determine differences in absorption and fluorescence emission due to the environments around the fluorophore. The variations recorded in the fluorescence emission spectra of the hybrid films were related to interactions established between the fluorophore species and their sterically hindered surroundings of the host hybrid silica, where free molecular motions are restricted. The influence of the type and amount of network modifier and of the fluorophore loading on the transparency of the films and fluorescence intensity was also investigated. The study carried out led to the elucidation of the necessary conditions for obtaining luminescent film-forming materials with high luminescence intensity and transparency useful for the design of new light concentrators

Physicochemical and Morphological Properties of Hybrid Films Containing Silver-Based Silica Materials Deposited on Glass Substrates

The main goal of this study was to present a facile and inexpensive approach for the preparation of hybrid coatings by the deposition under ambient air conditions of silver-based silica materials on glass substrates, which can be used to improve solar cells’ performance. The silica materials containing silver nanoparticles (AgNPs) were synthesized by the hydrolytic condensation of tetraethylorthosilicate (TEOS), triethoxymethylsilane (MTES), and trimethoxyhexadecylsilane (HDTMES), under acidic conditions, at room temperature (25 ± 2 °C). The silver nitrate solution (AgNO3, 0.1 wt. %) was used as a source of Ag+ ions. The final samples were investigated through Fourier Transform Infrared Spectroscopy–Attenuated Total Reflectance (FTIR–ATR), Transmission Electron Microscopy equipped with energy dispersive X–ray (TEM–EDX), UV–Vis spectroscopy, Atomic Force Microscopy (AFM), and Raman Spectroscopy (RS). The TEM images confirmed the formation of AgNPs and were found to be around 3 nm. It was observed that AgNPs were embedded in the silica matrix. EDX also confirmed the presence of the resulting AgNPs within the silica material. AFM images demonstrated that the morphology of the hybrid films’ surfaces can be changed as a function of sol–gel composition. RS analysis indicated that silanol groups were significantly present on the silver-based silica film surface. The UV–Vis spectra revealed that the hybrid coatings presented a reflectance of ~8%, at 550 nm. This study will enhance the value of nanocoating technology in optoelectronics, particularly in the development of nanostructures that improve the performance in thin-film solar cells

Effect of Modified Silica Materials on Polyvinyl Chloride (PVC) Substrates to Obtain Transparent and Hydrophobic Hybrid Coatings

In this research, we report a simple and inexpensive way to prepare transparent and hydrophobic hybrid coatings through deposition of different silica materials on polyvinyl chloride (PVC) substrates. The silica materials were prepared using an acid-catalyzed sol–gel method at room temperature (25 ± 2 °C), using alkoxysilanes: tetraethoxysilane (TEOS), as the silica source, and ethoxydimethylvinylsilane (DMVES), triethoxyoctylsilane (OTES), and trimethoxyhexadecylsilane (HDTMES), as modifier agents. The obtained materials were characterized (either as powders or as thin films) by Fourier-transform infrared spectroscopy (FTIR), UV/Vis spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and water contact-angle measurements. UV/Vis spectra showed that the PVC substrate coated with the silica material containing TEOS/DMVES/OTES had a transmittance of about 90% in the wavelength range of 650–780 nm. The water contact angles increased from 83° for uncoated PVC substrate to ~94° for PVC substrates coated with the sol–gel silica materials. These PVC films with hybrid silica coatings can be used as the materials for outdoor applications, such as energy-generating solar panel window blinds or PVC clear Windmaster outdoor blinds