Photoinduced Chemiluminescence Research Articles

Antibacterial Superhydrophobic Cotton Fabric with Photothermal, Self-Cleaning, and Ultraviolet Protection Functionalities.

Cotton fabrics with superhydrophobic, antibacterial, UV protection, and photothermal properties were developed using Ag/PDMS coatings, and the role of coating formulations on the obtained functionalities was studied. Specific attention was paid to understanding the relationships between the fabrics' superhydrophobicity and antibacterial activity against Escherichia coli (E. coli) bacteria. UV protection performance of Ag/PDMS coatings was thoroughly evaluated based on the variation of UV transmission rate through coated fabrics and photoinduced chemiluminescence spectra. Moreover, the effect of silver nanoparticles (Ag NPs) and PDMS on developing a photothermal effect on fabrics was discussed. It was found that the content of Ag NPs and PDMS played critical roles in determining the water contact angle (WCA) on modified fabrics. The largest WCA was 171.31°, which was durable even after numerous accelerated wash cycles and abrasions. Antibacterial activity of fabrics showed the positive effect of pure PDMS in bacterial growth inhibition. Moreover, it was found that the antibacterial performance was greatly affected by the content of Ag NPs loaded on fabrics rather than their superhydrophobic status. Moreover, increasing the content of Ag NPs boosted the UV protection level of fabrics, improved fabrics photostability, and reduced the UV transmission rate through fabrics. Testing the photothermal effect confirmed that the content of Ag NPs and PDMS both played prominent roles, where Ag acted as a photothermal agent and PDMS determined the NIR reflection rate from the coated surface. The modified fabrics were characterized using TGA, SEM, FTIR, and XRD techniques, and it was confirmed that using a higher amount of PDMS increased the amount of Ag NPs deposition on fabrics.

Synergetic adsorption-photocatalysis process of titania-silica photocatalysts and their immobilization on PEEK nonwoven filter for VOC removal

Studying the synergistic mechanisms of removing volatile organic compounds (VOCs) in an adsorption-photocatalytic oxidation process, remains a major challenge. This study explores the synergistic effects of SiO2 nanoparticles and anatase TiO2 nanocomposites in removing ethyl acetate, as a VOC test model, under solar irradiation in a photo-reactor. The physiochemical properties of the synthesized TiO2/SiO2 nanocomposites (70/30 and 50/50, molar ratio) and pure TiO2 nanoparticles were systematically characterized. It was found that the TiO2/SiO2 nanocomposite with 30% SiO2 showed the best synergistic adsorption and photocatalytic activity for the elimination of ethyl acetate among the tested samples. The integrated adsorption-photocatalytic mechanisms of TiO2/SiO2 nanocomposites were revealed by inverse gas chromatography (IGC), electron paramagnetic resonance (EPR), photoluminescence (PL) techniques and kinetic analysis. Moreover, a facile ambient-temperature immobilization method was successfully developed to load photocatalysts onto poly-ether ether-ketone (PEEK) nonwoven. In addition, the photo-induced chemiluminescence (PICL) analysis confirmed that the TiO2/SiO2 coating prevented the photodegradation of PEEK substrate under UVA radiation and improved its photostability. These results provided new understanding on designing highly adsorptive photocatalysts which are commercially applicable on filter materials for efficient VOC removal and air purification.

K+ Ion-Doped Mixed Carbon Nitride: A Daylight-Driven Photocatalyst and Luminophore for Enhanced Chemiluminescence.

Photocatalytic production of reactive oxygen species from O2 at the interface of the photocatalyst is significant to convert luminous energy like daylight into chemical energy and could be momentous for a reactive oxygen species-based chemiluminescence system. Herein, we synthesized a novel K+ ion-doped tri-s-triazine/triazine mixed carbon nitride (MCN), in which K+ ions were intercalated into the layers in a bridging manner. After a mild daylight treatment for 30 min, the MCN suspension could produce long-lifetime reactive oxygen species and further directly produce intense and stable chemiluminescence emission in the presence of luminol. In particular, the chemiluminescence intensity was 780 times that of H2O2-luminol, and MCN could be recycled several times in the chemiluminescence system. The mechanism results revealed a large number of reactive oxygen species that were generated from O2 on the surface of MCN through a temperate photocatalytic process. In the theoretical calculation, the charge density of N interacting with K+ ions was significantly more negative than that at the corresponding position in graphitic carbon nitride, which was beneficial to the adsorption and activation of oxygen, and the narrower band gap suggested that the doping of K+ ions was conducive to the intramolecular charge transfer interaction. Then, the long-lifetime reactive oxygen species triggered the conversion of luminol into an excited-state intermediate, which further transferred energy to MCN, producing strong chemiluminescence emission. The K+ ion-doped MCN might conduct as an efficient photocatalyst for reactive oxygen species generation, recyclable catalysts, and luminophores in the photoinduced chemiluminescence system.

Study on photofading of two natural dyes sodium copper chlorophyllin and gardenia yellow on cotton

The light fastness of fabrics dyed with natural dyes is not satisfactory, which limits their applications in the textile industry. So far, the detailed photofading mechanism of natural dyes remains unclear. To improve the light fastness of cotton fabrics dyed with two natural dyes (sodium copper chlorophyllin and gardenia yellow), two additives ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) and sodium citrate were used to treat the dyed cotton fabrics via the dipping-padding method. The performance results showed that both the two additives had good effects on inhibiting the photofading of the dyed fabrics. The photofading mechanism of the two natural dyes was also investigated. The results from 1,1-Diphenyl-2-picrylhydrazyl free radical (DPPH) scavenging assay and cyclic voltammetry tests demonstrated very limited antioxidant properties of the two dyes. Singlet oxygen and hydroxyl radical were detected in the photosensitizing process of the two dyes by electron paramagnetic resonance method. The photo-induced chemiluminescence (PICL) tests confirmed that the color changes of the dyed cotton fabrics were reduced because the reactivities of the two dyes to react with reactive oxygen species were dramatically reduced in the presence of EDTA-2Na and sodium citrate. End products generated in the photofading of the two dyes were detected by high-performance liquid chromatography-mass spectrometry (HPLC–MS). Based on the comprehensive analysis of above results, possible degradation pathways of the two dyes were proposed. The mechanism study in this research may help shed light on proposing universal solutions to the poor light fastness of most natural dyes on cotton.

Waste-Hair-Derived Natural Melanin/TiO2 Hybrids as Highly Efficient and Stable UV-Shielding Fillers for Polyurethane Films

Melanin is a ubiquitous natural pigment that protects living organisms from intense sunlight. Although synthetic melanin with different sizes and morphologies has been developed for UV-shielding polymers, studies can rarely be found regarding their natural counterparts. In this study, the natural melanin (NM) granules were isolated from conventional textile scraps such as yak and alpaca hair wastes and well characterized. This was followed by integrating them with TiO2 nanoparticles through hydrogen bonding using a simple physical mixing method, and the resultant NM/TiO2 hybrids were embedded in polyurethane (PU) films. Our results suggested that the PU films containing 2.5 wt % NM/TiO2 hybrids possessed highly efficient UV-shielding ability, improved photostability, and well-maintained transparency. The ultraviolet protection factor (UPF) values of the 2.5 wt %-NM/TiO2/PU composite films were approximately four times higher than those of the 2.5 wt %-TiO2/PU composite films. Moreover, although the 2.5 wt %-NM/TiO2/PU and 1.25 wt %-NM/PU composite films shared a similar UPF value, the transmittance at 550 nm of 2.5 wt %-NM/TiO2/PU was ∼2.5 times higher. Most importantly, the photoinduced chemiluminescence tests proved the excellent photostability of the NM/TiO2/PU composite films. Owing to the abundant natural source of NM, the commercial availability of TiO2, as well as the simple preparation protocol of the NM/TiO2 hybrids, this work highlights the potential of hair-derived NM-based UV-shielding fillers for various polymeric materials.

Photoprotective properties of alpaca fiber melanin reinforced by rutile TiO2 nanoparticles: A study on wool fabric

Melanin/titanium dioxide (TiO2) composite systems are introduced as efficient UV absorbers. Natural melanin particles were extracted from the pigmented alpaca fibers and the spindle-like rutile TiO2 nanoparticles were synthesized through a two-step sol-gel method at room temperature. The composites of melanin/TiO2 were prepared via electrostatic attraction force. In order to understand the UV absorption features of melanin and melanin/TiO2 composite systems, the prepared particles were applied to the surface of wool fabrics. Then, the UV protection and photostability of functionalized fabrics were assessed based on photoinduced chemiluminescence (PICL) emission, UV reflectance spectra, photoyellowing and ultraviolet protection factor (UPF). It was observed that the photostability of treated fabrics enhanced significantly, implying the generation of less free polymeric radicals in the substrate under UV irradiation. Among different synthesized composites, the proportion of melanin/TiO2 1/4 was the most efficient ratio inducing 80% reduction in the PICL emission peak intensity compared with untreated wool samples. The presence of melanin particles significantly enhanced the UPF values of fabrics where 30% increment was observed for wool samples after treating with melanin/TiO2 1/4 compared with pure TiO2. Having some advantages such as nontoxicity, eco-friendly and feasible synthesis approach, the prepared bio-organic/inorganic composite structures can be of some potential applications in photoprotecting and free radical quenching purposes.

Selective determination of nitrite/nitrate based on photo-induced redox activity of titanium dioxide.

Given its unique photocatalytic and structural properties, titanium dioxide was used as a sensitizer for the quantification of nitrite and nitrate contents by high-performance liquid chromatography with ultraviolet/nano-titanium dioxide photo-induced chemiluminescence detection. The photo-induced chemiluminescence signal was enhanced after the introduction of titanium dioxide. Ethylenediaminetetraacetic acid, as a positive hole scavenger, considerably improved the signal. The peak area of the chemiluminescence signal was enhanced 85 times after ethylenediaminetetraacetic acid was added to 1×10-6 mol/L of nitrite. The detection limits of nitrite and nitrate were 9.0×10-9 and 1.4×10-7 mol/L, respectively. Our method was applied for the determination of nitrite and nitrate contents in water samples. In contrast to other methods, our method is simple and environmentally friendly and enables the simultaneous determination of nitrite and nitrate.

Antioxidant homeostasis is disturbed in fetuses with leptin-resistant genotypes: A cross-sectional study

Leptin resistance is associated with lower reproductive efficiency, with deficiencies in embryo viability and growth leading to low prolificacy and high incidence of intrauterine growth restriction. We aimed to investigate the underlying mechanisms of the leptin-resistance, evaluating the antioxidant homeostasis of leptin-resistant and lean swine fetuses. The study included 70 plasma samples from fetuses at day 62 of gestation (mid-pregnancy), from breeds with (Iberian breed; n=35) and without leptin resistance (25% Large White x 25% Landrace x 50% Pietrain; n=35). The antioxidant status of the plasma samples was determined by photoinduced chemiluminescence whilst systemic oxidative stress was assessed determining plasma hydrogen peroxide concentration by enzimoimmunoassay. Plasma total antioxidant capacity was significantly lower in leptin-resistant fetuses (p=0.003), whilst systemic oxidative stress was increased (p=0.02). Our results indicate key differences in the antioxidant status in pregnancies affected by leptin resistance.

Effects of graphene on thermal oxidation of isotactic polypropylene

Nanocomposites containing graphene nanoplateletes (GNP) and isotactic polypropylene (PP) were obtained by in situ polymerization. The kinetics of peroxyl radical termination in the obtained nanocomposites was measured by decay of photoinduced chemiluminescence of PP. The concentration of peroxyl radicals was found to decrease significantly, and the rate of their decay was found to increase substantially in the presence of GNP. This shows that GNP is able to inhibit radical processes. At the same time, the additives of GNP were found to act as an effective catalyst, significantly decreasing oxidation induction times and increasing the rates of nanocomposite thermal oxidation. The treatment of GNP by ultrasound can reduce the catalytic activity of GNP, as a result of which the inhibitory effect of GNP becomes predominant. Possible mechanisms of catalysis and inhibition involving GNP are discussed.

Determination of carbamates in soils by liquid chromatography coupled with on-line postcolumn UV irradiation and chemiluminescence detection

In this study, high performance liquid chromatography (HPLC) coupled with a simple and fast sample pre-treatment based on the use of the UV-irradiation in a simple continuous flow system for the chemiluminescent quantification of pesticide carbamates in soils was developed and validated. HPLC was used to separate thiodicarb, bendiocarb and carbaryl in soil extracts. The eluates emerging from the column tail were mixed with an alkaline solution of Co2+ in EDTA and irradiated with UV light to induce photolysis of the carbamates, in order to obtain free radicals and other reactive species capable of oxidizing luminol and producing photoinduced chemiluminescence (PICL) as a result. Measurements of CL intensity were plotted as a function of time to obtain chromatographic peaks. Under the optimum operating conditions for the combined HPLC-PICL system, CL peak areas were linearly related to analyte concentrations. The limit of detection were 0.05 mg L−1 for thiodicarb, 0.09 mg L−1 for bendiocarb and 0.17 mg L−1 for carbaryl. A simple extraction procedure using 98% methanol as solvent ensured complete dissolution of the analytes in spiked soils with recoveries from 87 to 120%. The proposed method is a simple, fast, accurate choice for quantifying the target pesticides in soils.

Chemiluminescence and reactivity of the composites based on blends of polypropylene and polyamide

The effect of the composition of blends based on isotactic polypropylene (PP) and aliphatic polyamide 6/66-4 (PA) on the rate of photo-oxidation of their mixtures in air at room temperature has been studied. The decay of photoinduced chemiluminescence was studied to determine the kinetics of peroxyl radical termination in composites and the rate constants of this process depending on the composition of the mixtures. In the presence of PA, the rate of photo-oxidation of mixtures is much higher than the rates of photo-oxidation of separately taken components, PP and PA. Thus, the kinetics of photo-oxidation of mixtures differs from the simple sum of photo-oxidation kinetics of PP and PA, which should be expected in the absence of chemical and physical interaction of the components of the mixture. A decrease in the rate constants due to PA additives indicates a decrease in the mobility of molecules in the composites and explains the observed increase in photo-oxidation of mixtures.

Determination of Antioxidant Activity of Brandy and Other Aged Beverages by Electrochemical and Photochemiluminescence Methods

The discovery of the impact of antioxidant compounds on health has led to the development of several methods based on different physiochemical processes for quantifying the antioxidant activity of samples. However, when comparing the antioxidant activity of samples, the use of alternative methods may lead to conflicting results. The aim of this study is to evaluate the antioxidant capacity of brandies, old wines and sweet wines by two methods: the first electrochemical method and the second based on photo-induced chemiluminescence, using various statistical approaches: correlation of data, the Bland-Altman test and FREML regression. The results obtained show that these two methods for evaluating antioxidant activity are not comparable. Only no commercial brandy shows statistically similar results, at a probability of 95 %, for the two methods.

Development of a Photoinduced Chemiluminescent Method for the Determination of the Herbicide Quinmerac in Water.

A new, simple, and sensitive method, based on photoinduced chemiluminescence, was developed for the determination of quinmerac. The photoproduct, obtained after ultraviolet irradiation in basic medium, was mixed with sodium sulfite (sensitizer), and Ce(IV) (oxidant) in acid medium. A wide linear dynamic range (2-600 ng mL(-1)) and a limit of detection of 0.6 ng mL(-1) were obtained without any pretreatment (0.08 ng mL(-1) after solid-phase extraction). The determination was performed using a flow-injection manifold, which allowed a high throughput (144 h(-1)). The interday reproducibility was 5.6% (n = 5), and the intraday repeatability was 3.9 and 2.9% for 20 and 200 ng mL(-1) of quinmerac, respectively (n = 21). Finally, the method was applied to surface water and groundwater, with recoveries ranging from 78.1 to 94.5%.

Reprint of: Photostability of wool fabrics coated with pure and modified TiO2 colloids

The surface of wool fabrics was coated with TiO2 and TiO2-based nanocomposite colloids and the impact of this coating on the photostability of wool was investigated. TiO2 along with TiO2/Metal and TiO2/Metal/SiO2 sols were synthesized through a low-temperature sol–gel method and applied to fabrics. Composite colloids were synthesized through integrating the silica and three noble metals of silver (Ag), gold (Au) and platinum (Pt) into the synthesis process of sols. Four different molar ratios of Metal to TiO2 (0.01%, 0.1%, 0.5% and 1%) were used to elucidate the role of metal type and amount on the obtained features. Photostability and UV protection features of fabrics were evaluated through measuring the photo-induced chemiluminescence (PICL), photoyellowing rate and ultraviolet protection factor (UPF) of fabrics. PICL and photoyellowing tests were carried out under UVA and UVC light sources, respectively. PICL profiles demonstrated that the presence of pure and modified TiO2 nanoparticles on fabrics reduced the intensity of PICL peak indicating a lower amount of polymer free radicals in coated wool, compared to that of pristine fabric. Moreover, a higher PICL peak intensity as well as photoyellowing rate was observed on fabrics coated with modified colloids in comparison with pure TiO2. The surface morphology of fabrics was further characterized using FESEM images.

Photostability of wool fabrics coated with pure and modified TiO2 colloids

The surface of wool fabrics was coated with TiO2 and TiO2-based nanocomposite colloids and the impact of this coating on the photostability of wool was investigated. TiO2 along with TiO2/Metal and TiO2/Metal/SiO2 sols were synthesized through a low-temperature sol–gel method and applied to fabrics. Composite colloids were synthesized through integrating the silica and three noble metals of silver (Ag), gold (Au) and platinum (Pt) into the synthesis process of sols. Four different molar ratios of Metal to TiO2 (0.01%, 0.1%, 0.5% and 1%) were used to elucidate the role of metal type and amount on the obtained features. Photostability and UV protection features of fabrics were evaluated through measuring the photo-induced chemiluminescence (PICL), photoyellowing rate and ultraviolet protection factor (UPF) of fabrics. PICL and photoyellowing tests were carried out under UVA and UVC light sources, respectively. PICL profiles demonstrated that the presence of pure and modified TiO2 nanoparticles on fabrics reduced the intensity of PICL peak indicating a lower amount of polymer free radicals in coated wool, compared to that of pristine fabric. Moreover, a higher PICL peak intensity as well as photoyellowing rate was observed on fabrics coated with modified colloids in comparison with pure TiO2. The surface morphology of fabrics was further characterized using FESEM images.

Fast determination of thiacloprid by photoinduced chemiluminescence.

A new and sensitive application of chemiluminescence detection has been developed for the determination of the pesticide thiacloprid in water. It was based on the on-line photoreaction of thiacloprid in a basic medium, with quinine acting as the sensitizer of the chemiluminescent response; cerium (IV) in sulfuric acid medium was used as the oxidant. High degrees of automation and reproducibility were achieved using a flow-injection analysis (FIA) manifold. The validation of the method was performed in terms of selectivity, linearity, limit of detection (LOD), precision, and accuracy. Liquid chromatography with ultraviolet (UV) detection was used as reference for mineral, tap, ground, and spring water samples. The proposed method is fast (with a throughput of 130 h(-1)), sensitive (LOD of 0.8 ng mL(-1) without preconcentration steps and of 0.08 ng mL(-1) with solid-phase extraction [SPE]), low cost, and possible to couple with separation methods for the simultaneous determination of other pesticides. The enhanced chemiluminescence intensity was linear with the thiacloprid concentration above the 2-80 and 80-800 ng mL(-1) ranges. A possible reaction mechanism is also discussed.

Detecting free radicals in sunscreens exposed to UVA radiation using chemiluminescence

One of the current concerns with the application of nanoparticles in sunscreens, and in particular nano-TiO2 and ZnO, is their potential to photogenerate free radicals and reactive oxygen species (ROS) when they absorb ultraviolet wavelengths from sunlight. Free radicals and ROS are known to be associated with UV-induced skin damage and oxidative stress, from which sunscreens are expected to offer significant protection. Here we describe a simple method, based on chemiluminescence emission, for detecting free radicals generated in commercial sunscreens alone, and when applied to various substrates, following exposure to UVA (320–400nm) radiation. This photo-induced chemiluminescence (PICL) technique could be used to optimise sunscreen formulations so as to minimise free radical photogeneration during exposure to sunlight.

Determination of N-methylcarbamate pesticides using flow injection with photoinduced chemiluminescence detection

A sensitive, economic, rapid and simple method for the determination of four N-methylcarbamate pesticides: methomyl (2.0–80 μg L−1), aldicarb (5.0–50 μg L−1), butocarboxim (2.0–60 μg L−1) and oxamyl (2.0–60 μg L−1); is reported. It relies on the coupling of photoinduced chemiluminescence (PICL) detection with flow injection (FI) methodology. The automation of FI together with the use of light as a reagent decreased the environmental impact of the analysis. The proposed method was based on the oxidation of these pesticides, previously irradiated on-line with UV light, with cerium(IV), using quinine as a sensitiser. Limits of detection below the legal limits (100 ng L−1) established by the European Union for drinking waters were obtained without the need of preconcentration steps. A good inter-day reproducibility (1.6–6.4%, n = 5), repeatability (rsd = 2.7 %, n = 25) and high throughput (123 h−1) were achieved. The method was successfully applied to the determination of methomyl in natural waters with mean recoveries ranging from 90% to 98%.

Simple Modification Measurement of Photodegradability of Polymers by using Photo-induced Chemiluminescence Technique

Polymers and organic materials that are exposed to sunlight undergo photooxidation, which leads to deterioration of their physical properties. To allow adequate performance under outdoor conditions, synthetic polymers require additives such as antioxidants and UV absorbers. A major problem with optimising polymer formulations to maximise their working life span is that accelerated weathering tests are empirical. The conditions differ significantly from real weathering situations, and samples require lengthy irradiation period. Degradation may not be apparent in the early stages of exposure, although this is when products such as hydroperoxides are formed which later cause acceleration of oxidation. A simple way of quantifying the number of free radicals presents in organic materials following exposure to light or heat is by measuring chemiluminescence (CL) emission. Most polymers emit CL when they undergo oxidative degradation, and it originates from the bimolecular reaction of macroperoxy radicals which creates an excited carbonyl.

Simple Modification Measurement of Photodegradability of Polymers by using Photo-induced Chemiluminescence Technique

Polymers and organic materials that are exposed to sunlight undergo photooxidation, which leads to deterioration of their physical properties. To allow adequate performance under outdoor conditions, synthetic polymers require additives such as antioxidants and UV absorbers. A major problem with optimising polymer formulations to maximise their working life span is that accelerated weathering tests are empirical. The conditions differ significantly from real weathering situations, and samples require lengthy irradiation period. Degradation may not be apparent in the early stages of exposure, although this is when products such as hydroperoxides are formed which later cause acceleration of oxidation. A simple way of quantifying the number of free radicals presents in organic materials following exposure to light or heat is by measuring chemiluminescence (CL) emission. Most polymers emit CL when they undergo oxidative degradation, and it originates from the bimolecular reaction of macroperoxy radicals which creates an excited carbonyl.