Self-cleaning of modified cotton textiles by TiO2 at low temperatures under daylight irradiation

Recent advances in cotton fabric-based photocatalytic composites for the degradation of organic contaminants

Cotton is one of the oldest and most widely used natural fibers in the world. It enables a wide range of applications due to its excellent moisture absorption, thermal insulation, heat resistance, and durability. Benefiting from current developments in textile technology and materials science, people are constantly seeking more comfortable, more beautiful and more versatile cotton fabrics. As the second skin of body, clothing not only provides the basic needs of wear but also increases the protection of body against different environmental stimuli. In this article, a comprehensive review is proposed regarding research activities of systematically summarise the development and research of cotton fabric-based photocatalytic composites for the degradation of organic contaminants in the area of self-cleaning, degradation of gaseous contaminants, pathogenic bacteria or viruses, and chemical warfare agents. Specifically, we begin with a brief exposition of the background and significance of cotton fabric-based photocatalytic composites. Next, a systematical review on cotton fabric-based photocatalytic composites is provided according to their mechanisms and advanced applications. Finally, a simple summary and analysis concludes the current limitations and future directions in these composites for the degradation of organic contaminants.

Innovative textiles treated with TiO2-AgNPs with succinic acid as a cross-linking agent for medical uses

Silver and titanium-silver nanoparticles have unique properties that make the textile industry progress through the high quality of textiles. Preparation of AgNPs and TiO2-Ag core-shell nanoparticles in different concentrations (0.01% and 0.1% OWF) and applying it to cotton fabrics (Giza 88 and Giza 94) by using succinic acid 5%/SHP as a cross-linking agent. Ultra-violet visible spectroscopy (UV-Vis), X-ray diffraction (XRD), dynamic light scattering (DLS), zeta potential, transmission electron microscopy (TEM), scanning electron microscopy/energy-dispersive X-ray (SEM-EDX) are tools for AgNPs and TiO2-AgNPs characterization and the treated cotton. The resulting AgNPs and TiO2-AgNPs were added to cotton fabrics at different concentrations. The antimicrobial activities, UV protection, self-cleaning, and the treated fabrics' mechanical characteristics were investigated. Silver nanoparticles and titanium dioxide-silver nanoparticles core-shell were prepared to be used in the treatment of cotton fabrics to improve their UV protection properties, self-cleaning, elongation and strength, as well as the antimicrobial activities to use the produced textiles for medical and laboratory uses and to increase protection for medical workers taking into account the spread of infection. The results demonstrated that a suitable distribution of prepared AgNPs supported the spherical form. Additionally, AgNPs and TiO2-AgNPs have both achieved stability, with values of (- 20.8 mV and - 30 mV, respectively). The synthesized nanoparticles spread and penetrated textiles' surfaces with efficiency. The findings demonstrated the superior UV protection value (UPF 50+) and self-cleaning capabilities of AgNPs and TiO2-AgNPs. In the treatment with 0.01% AgNPs and TiO2-AgNPs, the tensile strength dropped, but the mechanical characteristics were enhanced by raising the concentration to 0.1%. The results of this investigation demonstrated that the cotton fabric treated with TiO2-AgNPs exhibited superior general characteristics when compared to the sample treated only with AgNPs.

Chitosan and TiO2 functionalized polypropylene nonwoven fabrics with visible light induced photocatalytic antibacterial performances

Chitosan/TiO2 functionalized polypropylene (CS/TiO2/PP) nonwoven fabrics were fabricated through crosslinking of chitosan with glutaraldehyde followed by loading of TiO2 nanoparticles. The functionalized CS/TiO2/PP has super hydrophilicity and excellent visible light induced photocatalytic antibacterial properties owing to the synergistic effects of CS and TiO2. The photocatalytic degradation performance was determined by assessing the degradation of methyl blue under simulated visible light irradiation and its recyclability was also evaluated. In addition, SEM images demonstrated that TiO2 nanoparticles were distributed evenly on the surface of the 2 g/L CS/TiO2/PP. Meanwhile, the polypropylene surface showed a significant increase in hydrophilicity after being treated with chitosan and TiO2. The photocatalytic degradation results revealed that CS/TiO2/PP had higher photocatalytic properties than those of pure PP under visible light, and the degradation rate of methylene blue reached 96.4 % after 90 min of light exposure. Compared to pure PP, the antibacterial properties of CS/TiO2/PP significantly increased, and the bacterial reduction percentages were increased to 98.7 % and 96.3 %, against E. coli and S. aureus, respectively. The functionalized CS/TiO2/PP composites exhibited promising potential in environmentally friendly antibacterial materials.

Modification of Cotton and Leather Surfaces Using Cold Atmospheric Pressure Plasma and TiO2-SiO2-Reduced Graphene Oxide Nanopowders

Surface modification of textile fabrics and leathers is very versatile and allows the products quality improvement. In this work, cotton and leather substrates were pre-treated with cold atmospheric pressure plasma (CAPP) and further coated with TiO₂-SiO₂-reduced graphene oxide composites in dispersion form. By using a Taguchi scheme, this research evaluated the effect of three significant parameters, i.e., the pre-treatment with CAPP, organic dispersion coating and TiO₂-SiO₂-reduced graphene oxide (TS/GR) composites, that may affect the morpho-structural properties and photocatalytic activity of modified cotton and leather surfaces. The characteristics of cotton/leather surfaces were evaluated by morphological, structural, optical and self-cleaning ability using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), X-ray powder diffraction (XRD), attenuated total reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR) and UV-Vis spectroscopy. The self-cleaning performance of the obtained cotton and leather samples was evaluated by photocatalytic discoloration of berry juice surface stains under UV light irradiation for 12 h. The successfulness of coating formulations was proven by the SEM analysis and UV-Vis spectroscopy. The XRD patterns and ATR-FTIR spectra revealed the cellulose and collagen structures as dominant components of cotton and leather substrates. The CAPP treatment did not damage the cotton and leather structures. The photocatalytic results highlighted the potential of TiO₂-SiO₂-reduced graphene oxide composites in organic dispersion media, as coating formulations, for further use in the fabrication of innovative self-cleaning photocatalytic cotton and leather products.

Morphological Structures and Self-Cleaning Properties of Nano-TiO2 Coated Cotton Yarn at Different Washing Cycles

Titanium dioxide (TiO₂) has an extraordinary photocatalytic activity and it effectively provides self-cleaning properties for cotton products. With the presence of succinic acid, it helps the adherence of the TiO₂ nanoparticles on cotton surfaces. However, the ability of succinic acid to keep the TiO₂ adhered on cotton after washing is not yet fully understood. Therefore, this study aimed to investigate the effects of washing cycles on nano-TiO₂ coated cotton yarn with the aid of succinic acid on the morphological structures and self-cleaning properties. In this study, the nano-TiO₂ was synthesized using a hydrothermal method. The cotton yarn was coated with succinic acid and was later dipped in a nano-TiO₂ nanoparticles suspension. The nano-TiO₂ coated yarn samples then underwent the 5^th, 10^th, 15^th, and 20^th wash cycles and were tested for morphological structures and self-cleaning. The self-cleaning properties of the nano-TiO₂ coated yarn were determined using the depth of colour stain. The depth of the colour stain was presented as K/S value, where K and S are corresponded to the absorption and scattering coefficients of the stained fabric, respectively. From the analysis, our synthesized nano-TiO₂ had a size of 20-50 nm range with a band gap of 3.06 eV. After coating, the nano-TiO₂ coated cotton yarn changed in its morphological structure at 5^th, 10^th, 15^th, and 20^th wash cycles, respectively. At the 20^th wash cycle, the weight (%) of the Ti element continued to decrease up to 4.45%, reducing the photocatalytic activity with the K/S value close to the stained yarn, which was about 0.4. The 5^th wash cycle maintained a good photocatalytic activity with the K/S value of 0.06 near to the K/S value of the unstained cotton yarn. The presence of succinic acid in the nano-TiO₂ coated cotton yarn provided good self-cleaning properties up to the 15^th wash cycle. By undertaking this study, an enhanced cotton property has been developed that will benefit the textile and clothing industry. This nano-TiO₂ coated cotton the has potential to be used for daily apparel and sportwear.

Structure, light absorption properties and photocatalytic activity of carbon-containing titania nanocomposites synthesized via a facile sol-gel method

Facile and green sol–gel method was used to synthesize carbon-containing titania nanopowder, and diethanolamine (DEA) was used as the in situ carbon source. The titania gel was heat treated at temperatures ranging from 300 to 700 °C. X-ray diffraction (XRD), thermal analysis, and Raman spectroscopy reported no crystalline phase at <325 °C. Crystallization of the anatase phase with traces of brookite phases was observed at T > 325 °C, followed by a transformation to anatase/rutile in the range of 400 °C < T ≤ 650 °C. Finally, the complete phase transformation to the rutile phase occurs at temperatures of T > 650 °C. High-resolution electron microscopy (HREM) micrographs confirm the coexistence of anatase and rutile nanocrystals and amorphous carbon clusters in the composite samples. Chemical element analysis via X-ray photoelectron spectroscopy (XPS) indicated nonstoichiometry in the O/Ti ratio, the presence of (Ti³⁺) oxidation state, and elemental carbon. Thermogravimetric (TG) measurements are the most accurate method to measure the carbon content in samples. UV-vis spectroscopy demonstrated considerable enhancement in the optical absorption properties and electronic structure of prepared samples compared to the pure anatase and rutile. This enhancement is strongly correlated with the structure and composition of prepared samples and consequently depends on the preparation method as well as conditions. Innovative features such as self-cleaning action was demonstrated in carbon containing titanate nanocomposite.

Overview of the Influence of Silver, Gold, and Titanium Nanoparticles on the Physical Properties of PEDOT:PSS-Coated Cotton Fabrics

Metallic nanoparticles have been of interest to scientists, and they are now widely used in biomedical and engineering applications. The importance, categorization, and characterization of silver nanoparticles, gold nanoparticles, and titanium nanoparticles have been discussed. Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) is the most practical and reliable conductive polymer used in the manufacturing of conductive textiles. The effects of metallic nanoparticles on the performance of PEDOT:PSS thin films are discussed. The results indicated that the properties of PEDOT:PSS significantly depended on the synthesis technique, doping, post-treatment, and composite material. Further, electronic textiles known as smart textiles have recently gained popularity, and they offer a wide range of applications. This review provides an overview of the effects of nanoparticles on the physical properties of PEDOT:PSS-coated cotton fabrics.

Metal Content in Textile and (Nano)Textile Products

Metals, metallic compounds, and, recently, metallic nanoparticles appear in textiles due to impurities from raw materials, contamination during the manufacturing process, and/or their deliberate addition. However, the presence of lead, cadmium, chromium (VI), arsenic, mercury, and dioctyltin in textile products is regulated in Europe (Regulation 1907/2006). Metal determination in fabrics was performed by inductively coupled plasma-mass spectrometry (ICP-MS) after microwave-assisted acid digestion. The ICP-MS procedure has been successfully validated; relative standard deviations were up to 3% and analytical recoveries were within the 90-107% range. The developed method was applied to several commercial textiles, and special attention has been focused on textiles with nanofinishing (fabrics prepared with metallic nanoparticles for providing certain functionalities). Arsenic content (in textile T4) and lead content (in subsamples T1-1, T1-2, and T3-3) were found to exceed the maximum limits established by the European Regulation 1907/2006. Although impregnation of yarns with mercury compounds is not allowed, mercury was quantified in fabrics T1-2, T5, and T6. Further speciation studies for determining hexavalent chromium species in sample T9 are necessary (hexavalent chromium is the only species of chromium regulated). Some textile products commercialised in Europe included in this study do not comply with European regulation 1907/2006.

Photocatalytic oxidation of nitric oxide over AgNPs/TiO2-loaded carbon fiber cloths

Series of AgNPs/TiO₂-loaded carbon fiber cloth (CFC) composites were prepared by incorporation of pristine TiO₂ and three AgNPs-modified TiO₂ additives onto the surface of four commercial CFCs. AgNPs/TiO₂ photocatalysts were synthesized by the wet impregnation method, including NaBH₄ reduction of silver ions. The silver content in the modified photocatalyst was assessed by inductively coupled plasma optical emission spectrometry (ICP-OES) as well as XRD analysis. It can be indicated that silver was successfully reduced to Ag nanoparticles what was confirmed by UV-Vis/DRS as well as XRD methods. The photocatalytic activity of the AgNPs/TiO₂-loaded CFCs was evaluated during the photocatalytic oxidation (PCO) tests of nitric oxide (NO) acting as a model air contaminant under UV light. It was found that the highest NO removal rate was observed for the AgNPs/TiO₂-loaded CFC material containing 3.70 wt% of AgNPs. Modification of TiO₂ with AgNPs stabilized the photocatalytic efficiency of the composites during 5 as well as 24 consecutive NO photooxidation cycles. It was also concluded that the presence of AgNPs was a key factor responsible for hindering NO₂ formation.

Advances in photocatalytic self-cleaning, superhydrophobic and electromagnetic interference shielding textile treatments

The use of nanomaterials in textiles provides many new opportunities and advantages for users and manufacturers; however, it comes with some of its downsides and challenges which need to be understood and overcome for enhancing the applicability of these products. This review article discusses the recent progress in developing self-cleaning and conductive textiles as two of the leading research fields of smart textiles. In particular, different aspects of fabricating nanocoatings for photocatalytic self-cleaning, superhydrophobic and electromagnetic interference (EMI) shielding effect will be brought to light. The theoretical concepts, mechanisms, latest fabrication methods along with their potential applications will be discussed. Moreover, the current drawbacks of these fields will be underlined and some recommendations for future research trajectories in terms of performance, current limitations, sustainability and safety will be proposed. This review article provides a comprehensive review on the state-of-the-art achievements in the field, which will be a valuable reference for researchers and decision makers.

Development of photocatalytic paint based on TiO2 and photopolymer resin for the degradation of organic pollutants in water

While the use of TiO2 nanoparticles in the form of slurry/suspension requires energy-intensive separation processes, its immobilization in solid support may open new opportunities in the area of sustainable water treatment technologies. In this study, a novel method for the development of photocatalytic paint based on TiO₂ nanoparticles and acrylate-based photopolymer resin is reported. The paint (TiO₂@polymer) was applied on substrates such as plastic petri dish and glass jar, which was polymerized/solidified by ultraviolet light irradiation. The painted petri dish and glass jar were used for the photocatalytic degradation of model organic pollutants viz. methyl orange (MO), methylene blue (MB), and indole in deionized water, simulated fresh drinking water, and tap water matrices. The photocatalytic degradation studies were performed under sunlight and UV-B light were used for. The sunlight-assisted photocatalytic degradation of MO and MB was found to be faster and more efficient than the UV-B light-assisted ones. Under UV-B light irradiation, it took 120 min to degrade about 80% of 6 ppm MB solution, whereas under sunlight irradiation it took 60 min to degrade about 90% of the same MB solution. The photocatalytic paint generated hydroxyl radical (·OH) under the UV-B and sunlight irradiation, which was studied by the terephthalic acid fluorescence tests. Further, the potential release of TiO₂ during the exposure to UV irradiation was studied by single particle ICP-MS analysis.

Carbon/Graphene-Modified Titania with Enhanced Photocatalytic Activity under UV and Vis Irradiation

Laser synthesis was used for one-step synthesis of titania/graphene composites (G-TiO₂ (C)) from a suspension of 0.04 wt% commercial reduced graphene oxide (rGO) dispersed in liquid titanium tetraisopropoxide (TTIP). Reference titania sample (TiO₂(C)) was prepared by the same method without graphene addition. Both samples and commercial titania P25 were characterized by various methods and tested under UV/vis irradiation for oxidative decomposition of acetic acid and dehydrogenation of methanol (with and without Pt co-catalyst addition), and under vis irradiation for phenol degradation and inactivation of Escherichia coli. It was found that both samples (TiO₂(C) and G-TiO₂(C)) contained carbon resulting from TTIP and C₂H₄ (used as a synthesis sensitizer), which activated titania towards vis activity. The photocatalytic activity under UV/vis irradiation was like that by P25. The highest activity of TiO₂(C) sample for acetic acid oxidation was probably caused by its surface enrichment with hydroxyl groups. G-TiO₂(C) was the most active for methanol dehydrogenation in the absence of platinum (ca. five times higher activity than that by TiO₂(C) and P25), suggesting that graphene works as a co-catalyst for hydrogen evolution. High activity under both UV and vis irradiation for decomposition of organic compounds, hydrogen evolution and inactivation of bacteria suggests that laser synthesis allows preparation of cheap (carbon-modified) and efficient photocatalysts for broad environmental applications.

Morphology- and Crystalline Composition-Governed Activity of Titania-Based Photocatalysts: Overview and Perspective

Titania photocatalysts have been intensively examined for both mechanism study and possible commercial applications for more than 30 years. Although various reports have already been published on titania, including comprehensive review papers, the morphology-governed activity, especially for novel nanostructures, has not been reviewed recently. Therefore, this paper presents novel, attractive, and prospective titania photocatalysts, including zero-, one-, two-, and three-dimensional titania structures. The 1D, 2D, and 3D titania structures have been mainly designed for possible applications, e.g., (i) continuous use without the necessity of particulate titania separation, (ii) efficient light harvesting (e.g., inverse opals), (iii) enhanced activity (fast charge carriers’ separation, e.g., 1D nanoplates and 2D nanotubes). It should be pointed out that these structures might be also useful for mechanism investigation, e.g., (i) 3D titania aerogels with gold either incorporated inside the 3D network or supported in the porosity, and (ii) titania mesocrystals with gold deposited either on basal or lateral surfaces, for the clarification of plasmonic photocatalysis. Moreover, 0D nanostructures of special composition and morphology, e.g., magnetic(core)–titania(shell), mixed-phase titania (anatase/rutile/brookite), and faceted titania NPs have been presented, due to their exceptional properties, including easy separation in the magnetic field, high activity, and mechanism clarification, respectively. Although anatase has been usually thought as the most active phase of titania, the co-existence of other crystalline phases accelerates the photocatalytic activity significantly, and thus mixed-phase titania (e.g., famous P25) exhibits high photocatalytic activity for both oxidation and reduction reactions. It is believed that this review might be useful for the architecture design of novel nanomaterials for broad and diverse applications, including environmental purification, energy conversion, synthesis and preparation of “intelligent” surfaces with self-cleaning, antifogging, and antiseptic properties.

Recent Advances in TiO2 Films Prepared by Sol-gel Methods for Photocatalytic Degradation of Organic Pollutants and Antibacterial Activities

Photocatalysis has recently emerged as an advanced, green, and eco-friendly process for the treatment of wastewater and air, and antimicrobial disinfection applications. In this context, TiO2 nanostructures have been shown to be the prominent photocatalyst candidates due to their low cost, non-toxicity, and ease of fabrication. This review highlights the investigation and development of TiO2 photocatalyst film by sol-gel method with special emphasis on the photodecolorization of synthetic dyes and antibacterial activities. Furthermore, various synthesis methods for the preparation of TiO2 films and their advantages, as well as limitations, are summarized. Finally, recent advances in TiO2 films by sol-gel method for dye degradation and antibacterial activities, challenges, and future perspective are discussed.

Rate-Limiting Steps of Dye Degradation over Titania-Silica Core-Shell Photocatalysts

In this work, we employed a step-by-step sol-gel process to controllably deposit ultra-thin layers of SiO2 on anatase nanoparticles in the range between 0 and 1 nm. The deposition was confirmed by TEM, EDX, and ATR-FTIR (e.g., Ti-O-Si band at 960 cm-1). Zeta potential measurements unravelled a continuous change in surface charge density with increasing silica shell thickness. The photocatalysts were evaluated towards adsorption and degradation of positively-charged and negatively-charged dyes (methylene blue, methyl orange) under UV illumination. The growth mechanism follows the Stranski–Krastanov model with three thickness regimes: (a) Flat islands (first step), (b) mono/bilayers (second/third step), and (c) regular thick films (fourth/fifth step). The results suggest different rate limiting processes for these regimes: (a) For the thinnest scenario, acidic triple-phase boundaries (TPBs) increase the activity for both dyes with their accessibility being the rate limiting step; (b) for continuous mono/bilayers, dye adsorption on the negatively-charged SiO2 shells becomes the rate liming step, which leads to a stark increase in activity for the positively-charged MB and a decrease for MO; (c) for thicker shells, the activity decreases for both dyes and is limited by the charge transport through the isolating shells.

In-situ synthesis of rGO-ZnO nanocomposite for demonstration of sunlight driven enhanced photocatalytic and self-cleaning of organic dyes and tea stains of cotton fabrics

Recently, research activities are focused on development of 2D reduced graphene oxide (rGO) based semiconductor nanocomposite materials for boosting up its catalytic applications. In this work, a rarely reported green synthesis approach has been envisioned to synthesize in-situ 2D rGO-ZnO (rGZn) nanocomposites from Apple juice and zinc acetate. Also the composition of the samples has been optimized to achieve high photocatalytic and self-cleaning properties by the formation of reactive oxidation species. The samples are characterized for their microstructural, optical absorption and photoluminescence properties. It has been tested that rGZn nanocomposites are capable of removing a test dye, namely methylene blue (MB) from water and achieved the highest dye degradation efficiency of ∼91% within only 60 min under UV-vis light irradiation. A smart cotton fabric (CF) coated with rGZn has been prepared and demonstrated its photocatalytic self-cleaning property by degradation of MB, rhodamine B dyes and tea stains on it even under sunlight irradiation, which is scarcely available in the literature. Therefore, this work may open a new avenue of research for low cost and easy synthesis of rGO-semiconductor nanocomposites with high photocatalytic properties for industrial applications as well as for development of rGO based smart fabric for real-life applications.

Room-temperature single-photon emitters in titanium dioxide optical defects

Fluorescence properties of crystallographic point defects within different morphologies of titanium dioxide were investigated. For the first time, room-temperature single-photon emission in titanium dioxide optical defects was discovered in thin films and commercial nanoparticles. Three-level defects were identified because the g(2) correlation data featured prominent shoulders around the antibunching dip. Stable and blinking photodynamics were observed for the single-photon emitters. These results reveal a new room-temperature single-photon source within a wide bandgap semiconductor.

Innovative Self-Cleaning and Biocompatible Polyester Textiles Nano-Decorated with Fe-N-Doped Titanium Dioxide

The development of innovative technologies to modify natural textiles holds an important impact for medical applications, including the prevention of contamination with microorganisms, particularly in the hospital environment. In our study, Fe and N co-doped TiO₂ nanoparticles have been obtained via the hydrothermal route, at moderate temperature, followed by short thermal annealing at 400 °C. These particles were used to impregnate polyester (PES) materials which have been evaluated for their morphology, photocatalytic performance, antimicrobial activity against bacterial reference strains, and in vitro biocompatibility on human skin fibroblasts. Microscopic examination and quantitative assays have been used to evaluate the cellular morphology and viability, cell membrane integrity, and inflammatory response. All treated PES materials specifically inhibited the growth of Gram-negative bacilli strains after 15 min of contact, being particularly active against Pseudomonas aeruginosa. PES fabrics treated with photocatalysts did not affect cell membrane integrity nor induce inflammatory processes, proving good biocompatibility. These results demonstrate that the treatment of PES materials with TiO₂-1% Fe–N particles could provide novel biocompatible fabrics with short term protection against microbial colonization, demonstrating their potential for the development of innovative textiles that could be used in biomedical applications for preventing patients’ accidental contamination with microorganisms from the hospital environment.

Significant Improvement in Thermal and UV Resistances of UHMWPE Fabric through in Situ Formation of Polysiloxane-TiO2 Hybrid Layers

Anatase nanocrystalline titanium dioxide coatings were produced on ultrahigh molecular weight polyethylene (UHMWPE) fabric by radiation-induced graft polymerization of γ-methacryloxypropyl trimethoxysilane (MAPS) and subsequent cohydrolysis of the graft chains (PMAPS) with tetrabutyl titanate, followed by boiling water treatment for 180 min. The resulting material was coded as UHMWPE-g-PMAPS/TiO2 and characterized by attenuated total reflection infrared spectrometry, differential scanning calorimetry, X-ray diffraction, thermal gravimetry, and ultraviolet absorption spectroscopy, among others. The predominant form of TiO2 in the thin film was anatase. The coating layer was composed of two sublayers: an inner part consisting of an organic-inorganic hybrid layer to prevent photocatalytic degradation of the matrix by TiO2 film, and an outer part consisting of anatase nanocrystalline TiO2 capable of UV absorption. This UHMWPE-g-PMAPS/TiO2 composite exhibited much better thermal resistance than conventional UHMWPE fabric, as reflected by the higher melting point, decreased maximum degradation rate, and higher char yield at 700 °C. Compared with UHMWPE fabric, UHMWPE-g-PMAPS/TiO2 exhibited significantly enhanced UV absorption and excellent duration of UV illumination. Specifically, the UV absorption intensity was 2.4-fold higher than that of UHMWPE fabric; the retention of the break strength of UHMWPE-g-PMAPS/TiO2 reached 92.3% after UV irradiation. This work provides an approach for addressing the issue of self-degradation of TiO2-coated polymeric materials due to the inherent photoactivity of TiO2.

Improved Photodegradation of Organic Contaminants Using Nano-TiO2 and TiO2 -SiO2 Deposited on Portland Cement Concrete Blocks

The photocatalytic activity of TiO2 nanoparticles (nano-TiO2 ) and its hybrid with SiO2 (nano-TiO2 -SiO2 ) for degradation of some organic dyes on cementitious materials was studied in this work. Nanohybrid photocatalysts were prepared using an inorganic sol-gel precursor and then characterized using XRD, SEM and UV-Vis. The grain sizes were estimated by Scherrer's equation to be around 10 nm. Then, a thin layer was applied to Portland cement concrete (PCC) blocks by dipping them into nano-TiO2 and nano-TiO2 -SiO2 solution. The efficiency of coated PCC blocks for the photocatalytic decomposition of two dyes, Malachite Green oxalate (MG) and Methylene Blue (MB), was examined under UV and visible irradiation and then monitored by the chemical oxygen demand tests. The results showed that more than 80% and 92% of MG and MB were decomposed under UV-Vis irradiation using blocks coated with nano-TiO2 -SiO2 . TiO2 /PCC and TiO2 -SiO2 /PCC blocks showed a significant ability to oxidize dyes under visible and UV lights and TiO2 -SiO2 /PCC blocks require less time for dye degradation. Based on these results, coated blocks have increased photocatalytic activity which can make them commercially accessible photocatalysts.

Functional Application of Noble Metal Nanoparticles In Situ Synthesized on Ramie Fibers

Different functions were imparted to ramie fibers through treatment with noble metal nanoparticles including silver and gold nanoparticles. The in situ synthesis of silver and gold nanoparticles was achieved by heating in the presence of ramie fibers in the corresponding solutions of precursors. The unique optical property of synthesized noble metal nanoparticles, i.e., localized surface plasmon resonance, endowed ramie fibers with bright colors. Color strength (K/S) of fibers increased with heating temperature. Silver nanoparticles were obtained in alkaline solution, while acidic condition was conducive to gold nanoparticles. The optical properties of treated ramie fibers were investigated using UV-vis absorption spectroscopy. Scanning electron microscopy (SEM) was employed to observe the morphologies of silver and gold nanoparticles in situ synthesized on fibers. The ramie fibers treated with noble metal nanoparticles showed remarkable catalytic activity for reduction of 4-nitrophenol (4-NP) by sodium borohydride. Moreover, the silver nanoparticle treatment showed significant antibacterial property on ramie fibers.

TiO₂ Nanosols Applied Directly on Textiles Using Different Purification Treatments

Self-cleaning applications using TiO₂ coatings on various supporting media have been attracting increasing interest in recent years. This work discusses the issue of self-cleaning textile production on an industrial scale. A method for producing self-cleaning textiles starting from a commercial colloidal nanosuspension (nanosol) of TiO₂ is described. Three different treatments were developed for purifying and neutralizing the commercial TiO₂ nanosol: washing by ultrafiltration; purifying with an anion exchange resin; and neutralizing in an aqueous solution of ammonium bicarbonate. The different purified TiO₂ nanosols were characterized in terms of particle size distribution (using dynamic light scattering), electrical conductivity, and ζ potential (using electrophoretic light scattering). The TiO₂-coated textiles’ functional properties were judged on their photodegradation of rhodamine B (RhB), used as a stain model. The photocatalytic performance of the differently treated TiO₂-coated textiles was compared, revealing the advantages of purification with an anion exchange resin. The study demonstrated the feasibility of applying commercial TiO₂ nanosol directly on textile surfaces, overcoming problems of existing methods that limit the industrial scalability of the process.

Antibacterial surfaces based on functionally graded photocatalytic Fe3O4@TiO2 core–shell nanoparticle/epoxy composites

Functionally graded epoxy composites with various concentration profiles of Fe₃O₄@TiO₂ core–shell nanoparticles (NPs) were synthetized and characterized, with focus on their antibacterial properties.

Effect of dicarboxylic acid chain length on the self-cleaning property of Nano-TiO2-coated cotton fabrics

In this study, the effect of dicarboxylic acid chain length on the amount of TiO2 nanoparticles (TiO2NPs) adsorption-produced self-cleaning property and washing durability on cotton fabrics were investigated. First, cotton fabric samples were treated with three kinds of dicarboxylic acids--oxalic, succinic, and adipic acids--and then dipped in TiO2NP solution with a certain concentration. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to investigate bonds formation between dicarboxylic acid groups and hydroxyl groups of cellulose, and a scanning electron microscope (SEM) was applied for the analysis of surface morphology in specimens. Drop absorbency time was determined for samples using the AATCC TM 79:2000. Washing stability and the amount absorption of TiO2NPs were determined by weighing and absorption spectrophotometry procedures, and the stain removal evaluation was conducted to assess the self-cleaning property. Results showed that all of the dicarboxylic acids used in this experiment improved the amount of TiO2NPs absorbed onto cotton samples and their durability to washing. In addition, color variation of samples treated with oxalic acid after 180 min of UV irradiation and drop absorbency time for samples treated with succinic acid were significantly increased by about 126 and 600%, respectively. The best durability was obtained from adipic acid, while a better self-cleaning property was obtained from oxalic acid.

Titania Nanotubes Grown on Carbon Fibers for Photocatalytic Decomposition of Gas-Phase Aromatic Pollutants

This study aimed to prepare titania (TiO₂) nanotube (TNT) arrays grown on un-activated carbon fibers (UCFs), with the application of different TiO₂ loadings based on the coating-hydrothermal process, and to evaluate their photocatalytic activity for the degradation of sub-ppm levels of aromatic pollutants (benzene, toluene, ethyl benzene, and o-xylene (BTEX)) using a plug-flow photocatalytic reactor. The characteristics of the prepared photocatalysts were determined by scanning electron microscopy (SEM),energy-dispersive X-ray (EDX), transmission electron microscopy (TEM), UV-visible absorption spectroscopy (UV-Vis) and X-ray diffraction (XRD) analyses. Spectral analysis showed that the prepared photocatalysts were closely associated with the characteristics of one-dimensional nanostructured TiO₂ nanotubes for TNTUCFs and spherical shapes for TiO₂-coated UCF (TUCF). The photocatalytic activities of BTEX obtained from TNTUCFs were higher than those obtained from a reference photocatalyst, TUCF). Specifically, the average degradation efficiencies of BTEX observed for TNTUCF-10 were 81%, 97%, 99%, and 99%, respectively, while those observed for TUCF were 14%, 42%, 52%, and 79%, respectively. Moreover, the photocatalytic activities obtained for TNTUCFs suggested that the degradation efficiencies of BTEX varied with changes in TiO₂ loadings, allowing for the optimization of TiO₂ loading. Another important finding was that input concentrations and air flow rates could be important parameters for the treatment of BTEX, which should be considered for the optimization of TNTUCFs application. Taken together, TNTUCFs can be applied to effectively degrade sub-ppm levels of gas-phase aromatic pollutants through the optimization of operational conditions.

Facile production of a large-area flexible TiO2/carbon cloth for dye removal

We successfully produced a large area, flexible and robust TiO₂ nanofiber/carbon fiber sheet with great convenience for water purification.

Galvanostatic Deposition of PT Nanoparticles on TiO2 Nanotube Arrays for Amperometric Detection of Hydrogen Peroxide at Low Overpotentials

Highly ordered TiO2nanotube arrays (NTAs) modified with Pt nanoparticles (Pt/TiO2NTAs) have been prepared by anodization of Ti foils followed by electrochemical deposition and employed to improve the performance of the low-overpotential determination of H2O2in solution. Morphologies of TiO2and Pt/TiO2NTAs were observed by SEM and TEM. The electrochemical behaviors of TiO2and Pt/TiO2NTAs were compared by cyclic voltammograms (CVs) in phosphate buffer solutions in absence and prensence of 10 mM H2O2, which showed that Pt nanoparticles can enhance the electrochemical activities of TiO2NTAs and achieve low-overpotential determination of H2O2. Amperometric method with an applied potential of-100 mV was used for H2O2detemination, which demonstrated a good H2O2sensing with sensitivity of 5.4 μAcm-2mM-1.

Physico-chemical processes and kinetics of sunlight-induced hydrophobic ↔ superhydrophilic switching of transparent N-doped TiO₂ thin films

Sunlight-responsive anatase N-doped TiO2 thin films undergoing reversible and switchable hydrophobic to superhydrophilic transition were synthesized by ultrasonic spray pyrolysis in a single step. Film thickness, roughness, surface morphology, crystal structure, composition, band gap, and wetting properties were studied using surface profilometry, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and water contact angle measurements, respectively. Surface X-ray photoelectron spectroscopy before and after sunlight irradiation revealed the major physicochemical process responsible for the hydrophobic → hydrophilic transition as surface hydroxylation and that responsible for hydrophilic → superhydrophilic transition as destruction of surface adsorbed organic species. The kinetic rates of the hydrophobic → superhydrophilic transition under sunlight and superhydrophilic → hydrophobic transition when kept under dark are found to be 0.215 min(-1) and 2.03 × 10(-4) min(-1), respectively.