Self-cleaning wool: effect of noble metals and silica on visible-light-induced functionalities of nano TiO2 colloid

© 2014 The Textile Institute. This study intends to enhance the functionality of titanium dioxide (TiO2) nanoparticles applied to wool fabrics under visible light. Herein, TiO2, TiO2/SiO2, TiO2/Metal, and TiO2/Metal/SiO2 nanocomposite sols were synthesized and applied to wool fabrics through a low-temperature sol–gel method. The impacts of three types of noble metals, namely gold (Au), platinum (Pt), and silver (Ag), on the photoefficiency of TiO2 and TiO2/SiO2 under visible light were studied. Different molar ratios of Metal toTiO2 (0.01, 0.1, 0.5, and 1%) were employed in synthesizing the sols. Photocatalytic efficiency of fabrics was analyzed through monitoring the removal of red wine stain and degradation of methylene blue under simulated sunlight and visible light, respectively. Also, the antimicrobial activity against Escherichia coli (E. coli) bacterium and the mechanical properties of fabrics were investigated. Through applying binary and ternary nanocomposite sols to fabrics, an enhanced visible-light-induced self-cleaning property was imparted to wool fabrics. It was concluded that the presence of silica and optimized amount of noble metals had a synergistic impact on boosting the photocatalytic and antimicrobial activities of coated samples. The fabrics were further characterized using attenuated total reflectance, energy-dispersive X-ray spectrometry, and scanning electron microscopy images.

Synthesis and preliminary analytical evaluation of the chemiluminescence from (4-[4-(dichloromethylsilanyl)-butyl]-4`-methyl-2,2`-bipyridyl)bis(2,2`-bipyridyl)ruthenium(II) covalently bonded to silica particles

This paper describes, for the first time, a simple and effective synthetic route for covalently bonding the chemiluminescence reagent, (4-[4-(dichloromethylsilanyl)-butyl]-4’-methyl-2,2’-bipyridyl)bis(2,2’-bipyridyl)ruthenium(II) onto silica particles. The subsequent preparation of chemically regeneratable detection cells and their preliminary analytical evaluation with both sequential injection analysis and flow injection analysis are also reported. Unoptimised analytical figures of merit were established for standard solutions of codeine and sodium oxalate with detection limits calculated from three times the standard deviation of the blank signal, of 1 × 10^–8 M and 3 × 10^–7 M respectively. The chemically immobilised reagent exhibited some intriguing solvent and kinetic effects, which are also briefly discussed.

Characterization of conductive polyprrole coated wool yarns

Wool yarns were coated with conducting polypyrrole by chemical synthesis methods. Polymerization of pyrrole was carried out in the presence of wool yarn at various concentrations of the monomer and dopant anion. The changes in tensile, moisture absorption, and electrical properties of the yarn upon coating with conductive polypyrrole are presented. Coating the wool yarns with conductive polypyrrole resulted in higher tenacity, higher breaking strain, and lower initial modulus. The changes in tensile properties are attributed to the changes in surface morphology due to the coating and reinforcing effect of conductive polypyrrole. The thickness of the coating increased with the concentration of p-toluene sulfonic acid, which in turn caused a reduction in the moisture regain of the wool yarn. Reducing the synthesis temperature and replacing p-toluenesulfonic acid by anthraquinone sulfonic acid resulted in a large reduction in the resistance of the yarn.

Effect of synthesis parameters on the electrical conductivity of polypyrrole-coated poly(ethylene terephthalate) fabrics

The effects of pyrrole, anthraquinone-2-sulphonic acid (AQSA) and iron(III) chloride (FeCl3) concentrations, reaction time and temperature on the electrical conductivity of polypyrrole (PPy) - coated poly(ethylene terephthalate) (PET) fabrics were investigated. With an increase in both the AQSA and FeCl3 concentrations, resistivity decreased to a point beyond which higher concentrations led to increased surface resistivity. Erosion of the polymer coating, in dynamic synthesis from continual abrasion, manifested as an exponential increase in the resistance of the coated textile substrate. This was not encountered in static synthesis conditions. Temperature affected the degree of surface and bulk polymerisation. The effect of polymerisation temperature on conductivity was negligible. Conductive polymer coating on textiles through chemical polymerisation enabled a smooth coherent film to encase individual fibres, which did not affect the tactile properties of the host substrate. The optimum FeCl3/pyrrole and AQSA FeCl3/pyrrole molar ratios were found to be 2.22 and 0.40 respectively.

Characterization of conducting polymer coated synthetic fabrics for heat generation

Heat generation in fabrics coated with the conductive polymer polypyrrole was investigated. The PET fabrics were coated by chemical synthesis using four different oxidizing agent–dopant combinations. The samples from the four different dopant systems all show an increase in temperature when a fixed voltage is applied to the fabric. The antraquinone-2-sulfonic acid (AQSA) sodium salt doped polypyrrole coating was the most effective in heat generation whereas the sodium perchlorate dopant system was the least effective. The power density per unit area achieved in polypyrrole coated polyester–Lycra® fabric with 0.027 mol/l of AQSA acting as dopant was 430 W/m². The power density per unit area achieved for the sodium perchlorate system, using the same synthesis conditions, was 55 W/m².

Generating heat from conducting polypyrrole-coated PET fabrics

Heating effects in polypyrrole-coated polyethyleneterephthalate (PET)-Lycra® fabrics were studied. Chemical synthesis was employed to coat the PET fabrics by polypyrrole using ferric chloride as oxidant and antraquinone- 2-sulfonic acid (AQSA) and naphthalene sulfonic acid (NSA) as dopants. The coated fabrics exhibited reasonable electrical stability, possessed high electrical conductivity, and were effective in heat generation. Surface resistance of polypyrrole-coated fabrics ranged from approximately 150 to 500 /square. Different connections between conductive fabrics and the power source were examined. When subjected to a constant voltage of 24 V, the current transmitted through the fabric decreased about 10% in 72 h. An increase in resistance of conductive fabrics subjected to constant voltage was observed

Development of a cooling fabric from conducting polymer coated fibres: proof of concept

It is supposed that there should be a thermal electric effect if a dc current is applied across two dissimilar conducting polymers, similar to so called “Peltier effect” in metals or semiconductors. However, this hypothesis has not been tested on conducting polymers and using these materials to make cooling fabrics has never been attempted before. Polypyrrole coated fabrics were used to test the hypothesis in this preliminary study. Seebeck and the Peltier effects were proven to exist. However, thermoelectricity effect between two conducting polymer coated fabric samples was only about 10 μV/°C. Cooling effect by conductive polymer powder was achieved but performance was unsteady due to electrical degradation of the conducting polymer. Nevertheless, the concept was demonstrated and the development of a cooling fabric is possible.

Frictional and tensile properties of conducting polymer coated wool and alpaca fibers

Wool and alpaca fibers were coated with polypyrrole by vapor-phase polymerisation method. The changes in frictional and tensile properties of the single fibers upon coating with the conductive polymer are presented. Coating a thin layer of polypyrrole on the alpaca and wool fibers results in a significant reduction in the fiber coefficient of friction, as the conducting polymer layer smooths the protruding edges of the fiber scales. It also reduces the directional friction effect of the fibers. Depending on the type of fiber, the coating may slightly enhance the tensile properties of the coated fibers.

The relative absorption of fatty acids in brown trout (Salmo trutta) fed a commercial extruded pellet coated with different lipid sources

The objective of the present study was to investigate the fatty acid absorption capabilities of brown trout (Salmo trutta) fed commercial extruded diets. Five commercial extruded pellets, different only in the lipid sources used for fat coating, were tested on juvenile brown trout for 45 days. The trout were reared in fresh water at 14.6 ± 0.4° C and 7.7 ±
0.3 mg/l, temperature and dissolved oxygen, respectively. The tested lipid sources were fish oil, canola oil, oleine oil, swine fat and poultry fat. After the adaptation period faeces were collected by gently stripping from naesthetized fish. Fatty acid analysis was performed on experimental diets and on collected faeces to evaluate the relative absorption capabilities of the trout digestive system with respect to each detected fatty acid. The use of the relative absorption efficiency (rAE) was opted to evaluate the intrinsic capability of each fatty acid to be absorbed. Brown trout showed a
specific preferential order of absorption of the fatty acids, preferring shorter over longer chain fatty acids and preferring the more unsaturated to the more saturated fatty acids. The fatty acid that showed the best relative absorbability was the C18:4n-3 (rAE = 5.14 ± 0.72), which has a fairly short carbon chain, but at the same time a high unsaturation level, followed by the C18:3n-3 (rAE = 3.38 ± 0.30). The fatty acid that showed the worst relative absorbability (rAE = 0.21 ± 0.02) was C24:1n-9.

Enhanced degradation efficiency of toluene using titania/silica photocatalysis as a regeneration process

Three kinds of titania/silica pellets were prepared using the sol-gel method with surface areas of 50.4m² g-1, 421.1m².g^-1 and 89.1m².g^-1. An annular reactor was designed and built to determine the degradation efficiency of toluene and to investigate the relationship between the adsorption and desorption-photocatalytic processes. Surface area is an important factor influencing the adsorption-photocatalytic efficiency. Higher surface areas of pellets contribute to high rates of conversion of toluene. Un-reacted toluene and reaction intermediates accumulating on their surface deactivated the titania/silica catalyst. To overcome this problem, the adsorption and regeneration process were alternated in a dual reactor system. Connecting or disconnecting the toluene feed gas enabled one reactor to adsorb toluene, while the second reactor was regenerated by photocatalysis. Using UV irradiation and titania/silica pellets with high BET surface area (421.1 m².g^-1), the alternating adsorption/regeneration processes kept the degradation efficiency of toluene at 90% after 8 hours operation. By improving the adsorption-photocatalysis efficiency, and minimising the generation and accumulation of intermediate on the surface of pellets, the method extended catalyst life and maintained a high degradation efficiency of toluene.

Non-isothermal crystallisation kinetics of self-assembled polyvinylalcohol/silica nano-composite

A novel polyvinylalcohol/silica (PVA/SiO₂) nano-composite is prepared with the self-assembly monolayer (SAM) technique. The SiO₂ nano-particles are homogenously distributed throughout the PVA matrixes as nano-clusters with an average diameter ranged from 15 to 240 nm depending on the SiO₂ contents. Using differential scanning calorimetry (DSC), the non-isothermal crystallisation behaviour and kinetics of the PVA/SiO₂ nano-composites are investigated and compared to those of the pure PVA. There are strong dependences of the degree of crystallinity (X_c), peak crystallisation temperature (T_p), half time of crystallisation (t_1/2), and Ozawa exponent (m) on the SiO₂ content and cooling rate. The crystallisation activation energy (E) calculated with the Kissinger model is markedly lower when a small amount of SiO₂ is added, then gradually increases and finally becomes higher than that of the pure PVA when there is more than 10% SiO₂ in the composite.

Dymanic mechanical analysis of polyvinylalcohol/silica nanocomposite

Polyvinylalcohol/Silica (PVA/SiO₂) nanocomposites with different SiO₂ contents are synthesized by employing a novel self-assembly monolayer (SAM) technique. The influence of the silica on dynamic mechanical properties of the nanocomposites is investigated by conducting dynamic mechanical analysis (DMA) and quasi-thermal mechanical analysis (Q-TMA). It is found that the storage modulus (E′), loss factor (tga), glass transition temperature (T_g), and activation energy (E_a) of prepared nanocomposites all show a strong dependence on the SiO₂ content. The Q-TMA results indicate that under a constant force, the elasticity of nanocomposites decreases with SiO₂ content, and the softening temperature moves to a higher temperature when more SiO₂ is added.

Polypyrrole-coated electrospun nanofibre membranes for recovery of Au(III) from aqueous solution

In this paper, for the first time, polypyrrole-coated electrospun nanofibre mats have been used as separation membranes to electrolessly recover Au from aqueous [Au(III)Cl₄]− solutions, based on a continuous-flow membrane separation process. With a [Au(III)Cl₄]− solution passing through the nanofibre membrane, the Au(III) ions were converted into elemental Au. The gold recovered was deposited on the nanofibre membranes in the form of Au particles, as confirmed by EDX and XPS measurements. It has been found that the polypyrrole-coated electrospun nanofibres are good candidate membrane material for the recovery of Au, and the recovery efficiency is affected by the membrane thickness, the permeate flux rate and the initial [Au(III)Cl₄]− concentration.

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.

Conductive poly(α,ω-bis(3-pyrrolyl)alkanes)-coated wool fabrics

Cross-linked poly(α,ω-bis(3-pyrrolyl)alkanes) were directly applied to woven wool substrates by either chemical, vapour or mist polymerization methods. Choice of dopant could greatly improve the surface resistance. The optimum coating on textiles with the lowest surface resistance, highest colour-fastness and stability was achieved using a mist polymerization method with 1,8-bis(pyrrolyl)octane, iron(III) chloride (FeCl₃) as the oxidant and p-toluene sulfonic acid sodium salt (pTSA) as the dopant.