Photochromic wool fabrics from a hybrid silica coating

In this work, a photochromic wool fabric has been prepared by applying a photochromic-dye hybrid silica sol-gel onto the surface of fabric. The photochromic fabric was found to have a very quick optical response. Two types of silica were used as the matrix material, and the type of silica had a small effect only on the photochromic performance, the fabric washing fastness, and water contact angle, but affected the fabric handle property considerably. The silica from a precursor containing a long alkyl chain showed very little influence on the fabric handle and better photochromic performance than that containing a phenyl group.

Photochromic wool fabrics with enhanced durability and photochromic performance

In our previous work, we have produced a photochromic wool fabric by applying a thin layer of hybrid silica-photochromic dye onto the wool surface. The coating showed a very fast optical response, but had little influence on the fabric handle, however durability was low. In this context, we reported that durability of the hybrid layer can be improved by introducing epoxy groups into the silica matrix via co-hydrolysis and co-condensation of an alkyl trialkoxysilane (ATAS) and 3-glycidoxypropyltrimethoxysilane (GPTMS). The presence of epoxy groups in the silica enhanced both washing and abrasion durabilities. Also, the optical response speed was slightly increased as well. Effects of the type of alkyl silane and the GPTMS:alkyl silane ratio on the coating durability, fabric handle and optical response were examined.

Fast response photochromic textiles from hybrid silica surface coating

In this study, a hybrid silica sol-gel embedded with a photochromic dye has been applied to wool fabric to form a photochromic coating. The treated wool fabrics showed very quick photochromic response. Five different silanes have been used as the silica precursor, and the resultant coating showed slight differences in photochromic performance, fabric washing fastness, and surface hydrophilicity. However, the silica type had a considerable influence on fabric handle property. The silica matrix from the silane containing a long alkyl chain had a very little influence on the fabric handle and better photochromic performance than those from other different silane precursors.

Photochromic coloration of wool fabric

A method has been developed for producing photochromic wool fabric by applying a layer of hybrid silica containing a photochromic dye onto wool fibres. A number of different hybrid silicas were prepared by the sol-gel technique involving co-hydrolysis and co-condensation of alkyltrialkoxysilanes together with 3-glycidoxypropyltrimethoxysilane. With the dye Photorome II, it was possible to obtain a photo chromic coating which showed fast optical response. The coating had only a slight effect on the fabric handle. The durability of the coating appeared to be acceptable, at least for fashion wear.

Photochromic textiles from hybrid silica coating with improved photostability

Photochromic surface coating on textiles may create new fashion opportunities. It also enhances the ultraviolet (UV) protection ability of the coated products. In this study, a spirooxazine dye and a silane that bears a long alkyl chain have been used to produce hybrid photochromic silica coatings on wool fabrics. Four stabilisers are added separately to the photochromic silica coatings to examine their influence on photostability and photochromic behaviour. It is found that the addition of UV stabilisers slightly reduces the photochromic response speed and photochromic absorption. However, the addition of UV stabilisers to the photochromic coating considerably improves the photochromic lifetime. Among the four UV stabilisers studied, the quencher results in the best improvement to photostability with the lowest reduction in photochromic absorption.

Photochromic fabrics from hybrid silica surface coatings

In this study, hybrid silica prepared by a sol-gel technique and doped with a photochromic dye was used to produce photochromic coatings on fabric surfaces. The coated fabrics showed a strong photochromic effect with very fast optical response speed. Good coating adhesion was obtained on wool fabrics. The photostability of the photochromic fabrics was improved by three different processes: adding a photo stabilizer, adjusting the surface wettability and sealing off the dye-containing pores with additional silica coating. Four UV stabilizers were added separately to the photochromic silica coatings to investigate their influence on the photostability and photochromic behaviour. The addition of UV stabilizers retarded the photochromic response and reduced photochromic absorption, but increased photochromic lifetime. Among the four UV stabilizers studied, the quencher resulted in the best improvement to the photostability with minimal reduction in the photochromic absorption. Increasing the hydrophobicity of the coating, and sealing-off the dye-containing pores were also found to improve photostability.

Photochromic wool fabric by sol-gel coating and photochromism

The application of photochromism in textiles has potential to create new opportunities to develop fancy colour-changing effects in fashionable textiles, as well as smart garments capable of protecting wearers from the effects of UV irradiation and responding to environmental changes. This book presents a coating method for achieving quick and obvious photochromic effects on wool fabrics using conventional photochromic dyes and hybrid silicas. It covers details about fabricating different types of photochromic dye-silica coatings, measuring their optical performance, assessing some physical characterisations of the coatings, and measuring the effects of the coatings on fabric performance.

Photochromic fabrics with improved durability and photochromic performance

Previously, we have reported a method for producing photochromic wool fabric by applying a thin layer of hybrid silica-photochromic dye onto the wool surface. While the photochromic coating showed a very fast optical response and had little influence on the fabric handle, its durability was poor. In this study, the durability of the photochromic coating layer was improved by introducing epoxy groups into the silica matrix via co-hydrolysis and co-condensation of an alkyl trialkoxysilane compound (ATAS) and 3-glycidoxypropyltrimethoxysilane (GPTMS). The presence of epoxy groups in the silica enhanced both washing and abrasion durability or fastness. In addition, the optical response speed was slightly increased as well. Effects of the type of alkyl silane and the GPTMS/alkyl silane ratio on the coating durability, fabric handle and optical response were examined.

Influence of non-hydrolysable groups in silane precursor on pore dimension and photochromic properties of sol-gel silica embedded with a spirooxazine dye

In this work, silica embedded with a spirooxazine dye was prepared by hydrolysis of silanes that bear a nonhydrolyzable group of different structures through a sol-gel route in the presence of a spirooxazine dye, and the pore dimension and photochromic properties of photochromic silica coatings on fabric were studied. The pore dimension in the silica was examined by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and nitrogen adsorption porosimetry. The SAXS results revealed that the distance between pores was in the range between 0.8 nm and 1.9 nm and it increased with increasing the size of the non-hydrolyzable group. Pore size measured by nitrogen adsorption porosimetry was in the range of 2.1-2.7 nm. The photochromic optical absorption was influenced mainly by the hydrophobicity of the non-hydrolyzable groups, while the color changing rates were influenced by the steric effect of the non-hydrolyzable groups and their interaction with the dye.

A study on the photostability of photochromic fabrics from hybrid organosilica coatings

Photochromic fabrics were prepared using a coating solution containing photochromic dyes and silica sol-gel. The photochromic effect was rapid. The effect of three different post treatments on the optical and durability of the photochromic fabrics was evaluated. These included incorporating a UV stabilizer, increasing the surface hydrophobicity by fluorinating the pores, and blockading the dye-containing pores with additional silica coating. All the treatments improved photostability, without significantly affecting response/fading speeds.

Photocatalytic degradation of dye effluent by titanium dioxide pillar pellets in aqueous solution

Photocatalytic oxidation (PCO) process is an effective way to deal with organic pollutants in wastewater which could be difficult to be degraded by conventional biological treatment methods. Normally the TiO2 powder in nanometre size range was directly used as photocatalyst for dye degradation in wastewater. However the titanium dioxide powder was arduous to be recovered from the solution after treatment. In this application, a new form of TiO2 (i.e. pillar pellets ranging from 2.5 to 5.3 mm long and with a diameter of 3.7 mm) was used and investigated for photocatalytic degradation of textile dye effluent. A test system was built with a flat plate reactor (FPR) and UV light source (blacklight and solar simulator as light source respectively) for investigating the effectiveness of the new form of TiO2. It was found that the photocatalytic process under this configuration could efficiently remove colours from textile dyeing effluent. Comparing with the TiO2 powder, the pellet was very easy to recovered from the treated solution and can be reused in multiple times without the significant change on the photocatalytic property. The results also showed that to achieve the same photocatalytic performance, the FPR area by pellets was about 91% smaller than required by TiO2 powder. At least TiO2 pellet could be used as an alternative form of photocatalyst in applications for textile effluent treatment process, also other wastewater treatment processes.

Polypyrrole nanoparticles and dye absorption properties

Polypyrrole (PPy) nanoparticles were prepared by using microemulsion polymerization processes at 3 °C. Particle characterization was performed by using FTIR, elementary analysis, UV–vis spectra and scanning electron microscope (SEM). The size of the nanoparticles varied from about 50 to 100 to 100 to 200 nm with the change in concentration of surfactant from 0.8 to 0.44 M. Polypyrrole nanoparticles were dedoped by a 10% NaOH solution, followed by a redoping process using a nuclear fast red kernechtrot dye, which has a sulfonate group. Dedoping changed the optical absorption properties of the nanoparticles.

Photocatalytic decolorization of lanasol blue CE dye solution using a flat-plate reactor

This paper reports the effectiveness of the photocatalysis TiO₂ in degrading Lanasol Blue CE. A flat-plate reactor (FPR) with a reactor area of 0.37 m² and ultraviolet (UV) light source of six 36 W blacklight lamps was used in the study. Operating variables including dosage of the photocatalyst, flow rates through the FPR, UV intensity, and tilted angle of the reactor were investigated to degrade Lanasol Blue CE. Results showed that the photocatalytic process can efficiently remove the color in textile dyeing effluent. The degradation process was approximated using first-order kinetics. The photocatalytic apparent reaction rate increased with the increasing UV intensity received by the photocatalyst TiO₂ in slurry. The liquid flow rate and tilted angle influenced the film thickness. The apparent reaction rate constant was mainly determined by the liquid film thickness, UV intensity, and the dosage of the photocatalyst. The findings of this research can be utilized as preliminary input for potential solar photocatalytic applications on color removal from dye solutions.

The effects of dye dopants on the conductivity and optical absorption properties of polypyrrole

Ten anionic compounds, including four acidic dyes, were used to dope polypyrrole powder. The effects of the dopants on density, optical absorption and conductivity of the polypyrroles were studied. The presence of the dopant in the conducting polymer matrix was verified by ATR-FTIR spectroscopy. Density function theory (DFT) simulation was used to understand the effect of the dopants on the solid structure, optical absorption and energy band structures. Anthraquinone-2-sulfonic acid-doped polypyrrole yielded the highest conductivity. The dye-doped polypyrrole showed an enhancement in its UV–vis optical absorption.