Photodecomposition Rate Research Articles

Cysteine assisted synthesis of Bi2S3/BiOBr nanocomposites for photocatalytic decomposition of rhodamine B

Novel Bi2S3/BiOBr nanocomposites (NCs) were prepared via L-Cysteine-assisted hydrothermal avenue as efficient photocatalysts to degrade rhodamine B (RhB). As a result, the obtained Bi2S3/BiOBr NCs exhibited the slice-like microstructure with the average diameters of ca. 100 nm. The elemental analysis of X-ray photoelectron spectroscopy indicates that the nanocomposites were combined by Bi2S3 and BiOBr. Then, the photo-induced degradation of RhB was performed with a Xenon lamp to simulate the sunlight ([Formula: see text] 400 nm) and the photo-decomposition rate was calculated. The following results showed that the Bi2S3/BiOBr NCs possessed excellent photocatalytice performance, which was better than that of other samples as control. Thus, this avenue provides a new reference for the facile synthesis of photocatalysts with low cost and high efficiency.

Metal-Free C60-Doped Mesoporous Carbon Nitride Drives Red-Light Photocatalysis.

The pursuit of novel strategies for synthesizing high-performance nanostructures of graphitic carbon nitride (g-C3N4) has garnered increasing scholarly attention in the field of photocatalysis. Herein, we have successfully designed a metal-free photocatalyst by integrating mesoporous carbon nitride (mpg-C3N4) and C60 through a straightforward and innovative method, marking the first instance of such an achievement. Under red light, the C60/mpg-C3N4 composite exhibited a significantly accelerated rhodamine B (RhB) photodecomposition rate, surpassing bulk g-C3N4 by more than 25.8 times and outperforming pure mpg-C3N4 by 7.8 times. The synergistic effect of C60 and the mesoporous structure significantly enhanced the photocatalytic performance of g-C3N4 by adjusting its electronic structure, broadening the light absorption range, increasing the active sites, and reducing the recombination of photogenerated carriers. This work presents a promising avenue for harnessing a metal-free, stable, efficient photocatalyst driven by red light, with potential for enhancing solar energy utilization in environmental remediation.

Water film-mediated photocatalytic oxidation of oxalate on TiO2

Water films on minerals under humid environment can be photocatalytic hotspots when exposed to sunlight or artificial sources of ultraviolet (and visible) radiation. In this study, we resolved the water film-mediated photocatalysis of oxalate adsorbed on TiO2 using in situ infrared spectroscopy. We found that 0.5 to 4 monolayer- (ML) thick water films enhanced the photodecomposition rates of oxalate under 21 kPa O2. We explained this through the combined actions of direct hole transfer, ligand-to-metal-charge transfer, as well as the production of hydroxyl radicals and reactive oxygen species. Rates were, however, substantially slower in the absence of O2 because charge recombination, together with water film-mediated charge localization, disrupted hole transfer and hydroxyl radical production. Our work adds insight into the impact of humidity on controlling important photocatalytic processes in nature (drying soils, atmospheric aerosols), and technology (water and air treatment).

Enhanced photocatalytic activity of Er doped ZnO nanospindles and nanorods for degradation of organic pollutants

Rare earth doping in ZnO is an efficient way to improve the photocatalytic performance. In the present work, Er doped ZnO nanospindles and nanorods were prepared through a simple cost effective wet chemical approach and were thoroughly characterized by FESEM, XRD, Raman spectroscopy, UV–vis-DRS, UV–vis absorption and PL spectroscopy. Nanospindle and nanorod-like morphologies of the fabricated samples were revealed by FESEM. XRD analyses revealed hexagonal wurtzite structure of Er doped ZnO nanostructures and confirmed Er doping into ZnO. PL studies showed increased defect concentration in ZnO nanostructures doped with Er ions. The photodegradation ability of nanostructures was investigated using cationic and anionic dyes and photodecomposition rate of 0.042 min−1 was achieved for MB decolorization using 0.5 % Er doped ZnO sample upon 32 min of solar light illumination. The probable photodecomposition mechanism supported by in-situ radical trapping experiments and repeatability test have also been discussed and results suggest that Er doped ZnO photocatalyst exhibit potential for use as commercial solar-active photocatalysts.

Facile synthesis Cu2O nanomaterials via hydrothermal method: Effect of precursors ratio on structural and morphological characteristics

The single phase Cu2O nanomaterials had been fabricated via facile hydrothermal method using non-toxic precursors of CuSO4.5H2O and Na2SO3 (then, the CuSO4 0.3M and Na2SO3 0.3M solution are mixed with volume ratios of 1:5, 1:6, 1:7 and 1:10, respectively). The observed materials were characterized using fine analysis methods such as X-ray diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy, and UV-Vis spectroscopy. The fabricated Cu2O samples had flower-like morphology which was assembled from octahedral. The samples had an average crystalline size of ~20.1-23.3 nm and a narrow bandgap of ~1.98 eV. The photocatalytic activity of samples was investigated via Congo red (CR) dye photodecomposition experiment, the catalyst dose and the concentration of CR values were studied as the factors affecting the photocatalytic efficiency. The results showed that the fabricated Cu2O samples had good photocatalytic ability in decomposing the CR solution in the visible region. The Cu2O (M­1-6) sample had the best degradation efficiency of the CR solution was the (reached 91.3% after 300 min under visible light radiation of the 150W Led lamp at the CR concentration of 20 ppm). The photo-decomposition rate constant of M­1-6 sample reached 0.00774 min-1.

Photodegradation of free base and zinc porphyrins in the presence and absence of oxygen

Comparison of photostability in degassed and aerated toluene solutions is reported for 5,10,15,20-tetraphenylporphyrin, 5,10,15-tri(p-tolyl)porphyrin, and their zinc analogues. After degassing, quantum yields of photodegradation are higher, but the photodecomposition rates decrease. Lower stability in deoxygenated solutions is due to much longer triplet lifetimes: 200–300 microseconds, compared to 200–360 ns in non-degassed toluene. For the zinc porphyrins, the LC–MS results show that the initial photoproduct contains two oxygen atoms. Based on electronic absorption and calculations, it is assigned to dehydrated zinc biladienone structure, relatively stable in toluene, but readily demetallated in dichloromethane. A similar species is formed also in the case of free bases, but it then undergoes hydration due to traces of water present in the solvent. Zinc derivatives were found to form biladienones even in degassed solutions. To explain this observation, we postulate formation of a complex with remaining oxygen or oxygen-containing species which is not removed by freeze–thaw procedure. This hypothesis is confirmed by MS results and by the analysis of photodegradation products obtained when zinc porphyrin is complexed with dimethylsulfoxide (DMSO). Under these circumstances, changes in absorption are the same as in the absence of DMSO when non-degassed toluene is used, but irradiation of deoxygenated solutions leads to a different photoproduct. For both degassed and non-degassed solvents, complexation with DMSO results in the enhancement of photostability.Graphical abstract

Photo Stabilizing Efficiency Of Poly(methyl methacrylate) Based On Metal Ion Complexes Of Saccharine

The photostabilization of poly(methyl methacrylate) (PMMA) films having saccharine complexes of Zn(II), Cd(II), Hg(II), Fe(III), Ni(II) and Cu(II) complexes was investigated. The production of PMMA films containing such complexes (0.5% by weight) was carried out by the casting method using THF. The photostabilization activities of the compounds were determined by monitoring the carbonyl and hydroxyl index with irradiation time. Evaluation of stabilizing efficiency of PMMA by ultra-violet spectroscopy to investigate photodecomposition rate constant (kd) for PMMA films in the absence and presence of saccharine complexes. The changes in the viscosity average molecular weight of PMMA with irradiation time were evaluated. The rate of photostabilization for PMMA in the presence of the additives was found to follow the order Ni(sac) > Cu(sac) > Zn(sac) > Cd(sac) > Hg(sac) > Fe(sac). Depending on the structure of the additive, such as a peroxide decomposer, UV absorption or a radical scavenger for the photostabilizer. Keywords: Photodegradation, UV stabilizers, PMMA, Saccharine.

Studying the photodecomposition rate constant and morphology properties of modified poly(vinyl chloride) with novel Schiff's bases

AbstractThe photodegradation of a poly(vinyl chloride) (PVC) film filled with Schiff bases in its structure was investigated and studied by comparing it with a blank PVC film. A PVC film containing novel Schiff's bases was synthesized and used as a photostabilizer for PVC. PVC was exposed to ultraviolet light and underwent harmful changes, where the photostabilization effect differed before and after filling aromatic Schiff bases within the structure. After 300 h of UV irradiation, the photodecomposition rate constants were calculated to identify the impact of Schiff bases on PVC films. In order to evaluate the impact of adding Schiff bases as photo‐stabilizers, the evolution of different functional groups during irradiation was monitored using FTIR spectra. Also, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were exploited to examine the surface morphology of produced polymers. These investigations showed that filling novel Schiff bases inside the polymers performed much better photostabilization than plain PVC. Hence, the photodecomposition rate constant, on the other hand, was calculated alongside the irradiation time.

Ceramic ZnO-SnO2-Fe2O3 Powders and Coatings -Effective Photogenerators of Reactive Oxygen Species

Ceramic ZnO-SnO2-Fe2O3 powders and transparent coatings on glasses prepared using the non-isothermal polymer-salt method demonstrate a strong ability to generate chemically active oxygen species under UV and visible irradiation. Crystal structures and morphologies of these materials were studied using the XRD and the SEM analysis. It was found that there are significant differences in the crystal structure of ceramic powders and thin coatings. The powders consist of randomly oriented oxide nanocrystals of size ~47 nm. The strong orientation of the ZnO nanocrystals due to their interaction with the glass substrate is observed in the coating structure. Experimental data show that thin ceramic coatings are transparent (~90%) in the visible spectral range and the band gap of the ceramic material is 3.44 eV. The band gap value of this multi-component ceramic material is described sufficiently using Verlag’s law. Ceramic powders and coatings demonstrate the intensive photogeneration of reactive oxygen species, both in liquid and air. High photocatalytic activity of ZnO-SnO2-Fe2O3 ceramic coatings and powders was observed upon the oxidation of the diazo dye, Chicago Sky Blue. In the presence of transparent photocatalytic coating, the value of the constant rate of the dye photodecomposition was high (k = 0.056 min−1). It was found that, in spite of their short life time, photogenerated reactive oxygen species demonstrate the ability to decompose dye molecules located up to a distance of 0.5 mm from the surface of ceramic coating. Obtained experimental results suggest that the prepared ceramic materials are promising for different practical applications of the photocatalytic materials.

Enhancement of Photostabilization of Poly(Vinyl Chloride) in the Presence of Tin-Cephalexin Complexes.

Poly(vinyl chloride), PVC, has many attractive properties, including low cost of manufacture, resistance to acid and alkali corrosion, and ease of molding. However, PVC suffers from aging in harsh conditions, leading to the shortening of its useful life. Stability to irradiation, for example, can be improved through the incorporation of additives to PVC. The design, synthesis, and application of new stabilizers continue to attract attention. The current work investigates the effect of three tin-cephalexin complexes on the stability of PVC on irradiation with ultraviolet (UV) light (λ = 313 nm) at 25 °C for a long duration. The PVC was blended with tin-cephalexin complexes at low concentrations (0.5% by weight), and thin films (around 40 µm) were made from the mixed materials. Various methods, including weight loss, infrared spectroscopy, and surface inspection of irradiated films were used to investigate the role played by these additives in the inhibition of PVC photodecomposition. The results confirmed that the additives led to a significant reduction in the rate of photodecomposition of the PVC blends. Tin-cephalexin complexes can absorb harmful radiation, deactivate hydrogen chloride, and scavenge high-energy species such as peroxides, therefore acting as stabilizers for PVC.

Supramolecular porphyrin as an improved photocatalyst for chloroform decomposition.

In this work, the outlying decoration of the free-base meso-(4-tetra) pyridyl porphyrin (H2TPyP) with the RuCl(dppb)(5,5'-Me-bipy) ruthenium complex (here named Supra-H2TPyP) is observed as an improved molecular photocatalyst for dye-mediated chloroform (CHCl3) decomposition via one-photon absorption operating in the visible spectral range (532 nm and 645 nm). Supra-H2TPyP offers a better option for CHCl3 photodecomposition when compared to the same process mediated by pristine H2TPyP, which requires either excited-state- or UV absorption. The chloroform photodecomposition rates for Supra-H2TPyP as well as its excitation mechanisms are explored as a function of distinct laser irradiation conditions.

Effect of TiO2 Additives on the Stabilization of h-YbFeO3 and Promotion of Photo-Fenton Activity of o-YbFeO3/h-YbFeO3/r-TiO2 Nanocomposites.

Nanostructured hexagonal rare-earth orthoferrites (h-RfeO3, R = Sc, Y, Tb-Lu) are well known as a highly effective base for visible-light-driven heterojunction photocatalysts. However, their application is limited by metastability, leading to difficulties in synthesis due to the irreversible transformation to a stable orthorhombic structure. In this work, we report on a simple route to the stabilization of h-YbFeO3 nanocrystals by the synthesis of multiphase nanocomposites with titania additives. The new I-type heterojunction nanocomposites of o-YbFeO3/h-YbFeO3/r-TiO2 were obtained by the glycine-nitrate solution combustion method with subsequent heat treatment of the products. An increase in the mole fraction of the h-YbFeO3 phase in nanocomposites was found with the titanium addition, indicating its stabilizing effect via limiting mass transfer over heat treatment. The complex physicochemical analysis shows multiple contacts of individual nanocrystals of o-YbFeO3 (44.4-50.6 nm), h-YbFeO3 (7.5-17.6 nm), and rutile r-TiO2 (~5 nm), confirming the presence of the heterojunction structure in the obtained nanocomposite. The photocatalytic activity of h-YbFeO3/o-YbFeO3/r-TiO2 nanocomposites was evaluated by the photo-Fenton degradation of the methyl violet under visible light (λ ≥ 400 nm). It was demonstrated that the addition of 5 mol.% of TiO2 stabilizes h-YbFeO3, which allowed us to achieve a 41.5 mol% fraction, followed by a three-time increase in the photodecomposition rate constant up to 0.0160 min-1.

Comprehensive spectral analysis of reaction of three aldehydes with ammonium sulfate and glycine

Light-absorbing brown carbon (BrC), a major contributor to global climate change, is widely studied. Comparative analysis showed that methylglyoxal (MG) tended to form a greater amount of aqueous BrC with AS/Gly/AS-Gly in a relatively short time, whereas 1,4-dioxane-2,5-diol (DD) tended to form darker BrC in the same reaction time. The absorption Ångström exponent (Åabs) over 250–400 nm and 400–480 nm in the absorption spectra combined with the index of recent autochthonous contribution (BIX), fluorescence index (FI), and humification index (HIX) in the fluorescence spectra, provided more information on the source of aqueous BrC. The absorbance intensity order and the fluorescence intensity order were MG-AS-Gly > DD-AS-Gly > GX-AS-Gly and GX-AS-Gly > MG-AS-Gly > DD-AS-Gly, respectively. The reaction rate (K) of H2O2 oxidation and photodecomposition gradually increased from ultraviolet (UV) to visible (Vis) region. The short lifetime of aldehyde-amine mixtures indicates that imine BrC is photochemically unstable and easily dissolves under sunlight. The absorbance and light decomposition rates were lowest in the GX-AS-Gly reaction system, indicating that the small amount of BrC formed by this system was more stable. The unsaturated double bonds gradually lengthened or shortened in the Maillard-type browning or aldol condensation reactions to form different numbers of product molecules. Furthermore, as these BrC reactions are strongly pH-dependent, it is necessary to measure (or control) the pH in the specific BrC system. Extensive laboratory spectroscopic comparative studies on these aqueous BrCs can be used to better understand the evolution of atmospheric BrC and its effects on climate.

Influence of alkali metal cations on the photoactivity of crystalline and exfoliated amorphous WO3 – photointercalation phenomenon

In order to investigate the effect of photointercalation on photoelectrochemical properties, two types of WO3-based photoanodes, bulk and exfoliated have been prepared and investigated. An aqueous exfoliation method is introduced for the simple fabrication of amorphous and hydrated WO3 nanomaterial using commercial bulk WO3 precursor. The comparison of obtained material with bulk WO3 was performed using Raman, UV–vis, and XPS as well as scanning and transmission electron microscopies. The photoelectrochemical and photocatalytic performances of bulk and exfoliated WO3 were compared. Generally, the proposed exfoliation procedure led to the preparation of photo(electro)catalyst characterized by better performance measured as a photocurrent of water oxidation and rate of methylene blue photodecomposition. The main aim of this research was to investigate the influence of alkali metal cations (Li+,Na+,K+,Cs+) presence in electrolyte on the photocatalytic and photo(electro)catalytic activity of the samples in a form of suspended powder and thin layer on transparent-conductive substrate (FTO), respectively.

Photochemical transformation of fentanyl under the simulated solar radiation – Enhancement of the process by heterogeneous photocatalysis and in silico analysis of toxicity

In this study the photochemical transformation of fentanyl—a very potent opioid drug—under simulated solar radiation was investigated for the first time. This pharmaceutical is frequently detected in various environment samples at concentrations that should be regarded as potentially harmful. Nevertheless, to date, no drug phototransformation products (TPs) have been reported. Considering fentanyl's exceptionally high toxicity, knowledge of the properties of these potential TPs is essential in order to properly assess its pollution impact. In this study, all photolytic experiments were performed using a xenon lamp (D65 filter) and RP-UHPLC coupled with the ESI-high-resolution tandem mass spectrometry. The phototransformation of fentanyl in natural river water and the application of heterogeneous photocatalysis as a possible way of decontaminating water were also investigated. Fentanyl turned out to be photostable, but twenty-six previously unreported TPs (formed mainly as a consequence of hydroxylation and oxidation) were found and characterized. The applied catalysts—TiO2 and ZnO—showed very high effectiveness, and the presence of the natural water matrix further increased the photodecomposition rate (up to 600 times) relative to direct photolysis. Importantly, the almost complete degradation of the parent compound as well as its TPs after 16 min of irradiation indicated that heterogeneous photocatalysis can be considered an efficient way of treatment of fentanyl-contaminated water. The computational analysis of toxicity showed that fentanyl may be more harmful to rodents and aquatic species than its TPs. However, some of these products are probably more mutagenic and developmentally toxic. Additionally, one product in particular may be a strong estrogenic compound, proving the importance of assessing TPs' toxic properties. The evaluation of bioaccumulation, bioconcentration and biodegradability revealed that fentanyl possesses unfavorable properties compared to TPs.

Plasmonics-Enhanced UV Photocatalytic Water Purification

Titanium dioxide (TiO2) is commonly used for photocatalytic decomposition of organic contaminants for the purpose of water purification. One promising method to enhance TiO2 photocatalysis is the incorporation of surface plasmon resonance on its surface where photocatalytic reactions take place. Herein, a novel methodology using plasmonically tuned aluminum nanostructures to enhance the rate of photodecomposition of aqueous methyl orange is demonstrated. These nanostructures are tuned to the TiO2 band gap in the UV regime and patterned on TiO2-coated substrates using nanosphere lithography. Compared to a blank TiO2 film, the plasmonics is found to enhance the initial TiO2 photocatalytic rate by up to 10 times, and further enhancement is possible upon refinement of the plasmonic technology.

Metal-free in situ carbon-nanotube-modified mesoporous graphitic carbon nitride nanocomposite with enhanced visible light photocatalytic performance

We synthesized a metal-free photocatalyst comprising mesoporous carbon nitride (mpg-C3N4) and carbon nanotubes (CNT), via a facile method involving polymerization of melamine as the precursor in the presence of CNT in refluxing methanol. Under visible light, the CNT/mpg-C3N4 composite resulted in a greater than 8.6 × faster rhodamine B photodecomposition rate compared with bulk graphitic C3N4, and 1.6 × faster compared with pure mpg-C3N4. We attribute the promoted photocatalytic performance of the composite to the synergistic effects of open-ended CNT and mpg-C3N4. The highly interconnected CNT in mpg-C3N4 effectively enhances the transfer of photo-generated electrons, harvests more incident visible light, and provides specific channels for oxygen adsorption and photoreactions. We propose a possible reaction mechanism and report a scavenger experiment that found that superoxide radical (·O2−) is mainly responsible for dye photodegradation. The CNT/mpg-C3N4 retained good stability after several cycles. This work supplies a promising method of exploiting a stable, metal-free, efficient, and visible light-driven semiconductor to enhance solar energy use for environmental remediation.

Microwave-Assisted Synthesis of TiO2/GO Composite and Its Adsorption-Photocatalysis Property under Visible Light

The photocatalytic performance of low-grade Titanium Dioxide (TiO2) anatase was successfully improved by compositing with graphene oxide (GO) via microwave-assisted, activated by UV and Xe light. The various experimental conditions were conducted. X-ray diffraction (XRD), Particle size analyzer (PSA), Prepared TiO2/GO photocatalyst was characterized by several instruments such as Specific surface area (BET) and Scanning electron microscopy (SEM). Effect of various annealing times (30 to 120 minutes) and temperatures (200-1000°C) were studied to reach the optimum pure TiO2 as a further based material in composite with GO. The result showed that both annealing time and temperature influenced crystallinity and particle size only, not the phase structure of TiO2. A similar phenomenon was founded by adding GO in a small concentration. A comparison of photocatalytic activity under UV and Xe irradiation has been proposed to show the GO effect independently. Under UV irradiation, the presence of GO enhancing the active sites of the catalyst. 1.0 wt% of GO succeeds in decomposing 8ppm of RhB more than 90%. Meanwhile, under Xe irradiation, the efficiency of the degradation of RhB was only 30%, resulted in using 1.2wt% of GO. Interestingly, the photodecomposition rate (k) of TiO2/GO composite under Xe irradiation was 3 times over pure TiO2 higher than that of UV irradiation (1 time). The study present that the small concentration of GO affected not only the active site of the TiO2/GO composite but also the electronic properties, which give different effects under different energy activated.

Ice rock-resembling PHB thin films doped with TiO2 NPs as photocatalyst

This study is to evaluate the performance of TiO2 as a photocatalyst for polyhydroxybutyrate (PHB) in different concentrations. Five different concentrations of TiO2 nanoparticles (0.001–0.005 wt%) have been added to PHB blend to produce modified PHB films. The conducting characterizations using FTIR, UV, SEM and optical microscope confirmed the photocatalytic activity of TiO2 on the surface of PHB films. The SEM analyses after irradiation reports show that the PHB thin films doped with different concentrations of TiO2 nanoparticles have piece of ice rock-resembling structure nature with heterogeneous surface morphology. After irradiation, the photodecomposition rate constant showed the highest value in the presence of TiO2 with concentration (0.005 wt%). Therefore, TiO2 nanoparticles, in particular high concentration (0.005 wt%), are considered as a photocatalyst for PHB films (30 μm thickness) photodegradation.

Morphological and Photodecomposition Rate Constant Study of PVC Films Doped with Sulfadiazine Tin(IV) Complexes

This article focus on the calculation of photodecomposition rate constant of PVC films that containing sulfadiazine tin(IV) complexes 1-3 as photostabilzers during UV radiation exposure. This constant calculated as a method for evaluating the efficiency of sulfadiazine tin(IV) complexes 1-3 when used as a PVC photostabilizers after 300 hours of irradiation. The experimental results showed that sulfadiazine tin(IV) complexes 1-3 have reduced the rate of photodecomposition constant value of PVC films significantly with comparison to PVC (blank).