Extent Of Photodegradation Research Articles

Quantifying Photodegradation of Peatland‐Derived Dissolved Organic Carbon in the Coastal Ocean of Southeast Asia

AbstractSoutheast Asia's peatlands are a globally significant source of terrigenous dissolved organic carbon (tDOC) to the ocean, and field observations show that this tDOC is extensively remineralized within the shelf sea. Yet the processes that drive this remineralization remain unclear. Here, we combined incubation experiments and model simulations to quantify the rate and extent of photodegradation of tDOC in the Sunda Shelf Sea. During laboratory photodegradation experiments, 26%–74% of the peatland tDOC was photomineralized, but realistic in situ rates of photodegradation have not yet been estimated in this region. Based on spectrally resolved apparent quantum yields for tDOC remineralization calculated from experiments, modeled in situ solar irradiance, and measured in‐water inherent optical properties, we simulated peatland tDOC photomineralization for two coastal regions of the Sunda Shelf Sea. These simulations show that sunlight can directly remineralize 25 ± 9% of the tDOC input over its maximum 2‐year residence time in the Sunda Shelf Sea, accounting for 38% of the total tDOC remineralization. We also found that photobleaching can remove 54 ± 4% of colored dissolved organic matter over this time‐scale. We further derived a simplified photochemical decay constant ∅ref of 0.016 day−1 for Southeast Asia's peatland‐derived tDOC, which can be used to parameterize the recently proposed UniDOM model. We conclude that direct photodegradation may be a greater sink for tDOC in Southeast Asia's coastal ocean compared to higher latitudes, although it is insufficient to account for the total tDOC remineralization observed in the Sunda Shelf Sea.

Mercury Sources and Fate in a Large Brackish Ecosystem (the Baltic Sea) Depicted by Stable Isotopes.

Identifying Hg sources to aquatic ecosystems and processes controlling the levels of monomethylmercury (MMHg) is critical for developing efficient policies of Hg emissions reduction. Here we measured Hg concentrations and stable isotopes in sediment, seston, and fishes from the various basins of the Baltic Sea, a large brackish ecosystem presenting extensive gradients in salinity, redox conditions, dissolved organic matter (DOM) composition, and biological activities. We found that Hg mass dependent fractionation (Hg-MDF) values in sediments mostly reflect a mixing between light terrestrial Hg and heavier industrial sources, whereas odd Hg isotope mass independent fractionation (odd Hg-MIF) reveals atmospheric inputs. Seston presents intermediate Hg-MDF and odd Hg-MIF values falling between sediments and fish, but in northern basins, high even Hg-MIF values suggest the preferential accumulation of wet-deposited Hg. Odd Hg-MIF values in fish indicate an overall low extent of MMHg photodegradation due to limited sunlight exposure and penetration but also reveal large spatial differences. The photodegradation extent is lowest in the central basin with recurrent algal blooms due to their shading effect and is highest in the northern, least saline basin with high concentrations of terrestrial DOM. As increased loads of terrestrial DOM are expected in many coastal areas due to global changes, its impact on MMHg photodegradation needs to be better understood and accounted for when predicting future MMHg concentrations in aquatic ecosystems.

Investigating the sustainability of agricultural plastic products, combined influence of polymer characteristics and environmental conditions on microplastics aging

The accelerated use of plastic products for agricultural practices has raised global concern regarding their negative impacts on soil health. This study aims to better understand the combined influence of polymer characteristics and environmental conditions on microplastic photodegradation within the agricultural soil system. For this purpose, the photodegradation behavior of low density polyethylene (LDPE) microplastics was studied through accelerated UVA radiation experiments under two different relative humidity (RH10 and RH70) and soil deposition conditions. The variations of plastics' surface physiochemistry due to the accelerated photodegradation were studied using Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), and Field Emission Scanning Electron Microscopy (FE-SEM). The carbonyl and vinyl indices were calculated using the ATR-FTIR information to compare the degree of microplastics' photodegradation. The plastics' bulk characteristics, including the percentage of crystallinity and molecular weight distributions, were examined using the Differential Scanning Calorimetry (DSC) and Gel Permeation Chromatography (GPC). Furthermore, the extent of UVA light interaction with the microplastics was studied by determining spectral quantum yield. The results demonstrated that new LDPE microplastics with a lower molecular weight (Mw = 233 kD) were subjected to a greater extent of photodegradation than those with greater molecular weight (Mw = 515 kD). Elevated relative humidity (RH70) limited the photooxidation process of microplastics and consequently reduced the surface chemistry alterations. Deposition of soil particles with respect to the plastic particles impacted the photodegradation behavior. The microplastics covered by soil particles were not degraded, unlike those deposited next to the soil particles. The knowledge developed through this study could encourage the farmers and agricultural stakeholders to apply more efficient practices to remove plastic residuals after harvesting and conduct proper plastic disposal practices to protect soil health.

Photo‐protective effect of cuttlefish ink melanin on human hair

AbstractThe photoprotective properties of exogenous melanin extracted from cuttlefish ink on human hair was assessed. Melanin extracted from cuttlefish ink was applied on black hair and irradiated using a solar simulator. The extent of photodegradation was determined by microstructural, morphological and mechanical testing. The UV–Vis spectra of melanin extracted from cuttlefish ink indicated strong absorption at UV region and moderate absorption in visible region. The melanin‐coated samples indicated significant protection to hair cuticle against UV radiations, as indicated by microscopic images (SEM). Conversely, visible cracks were evident on uncoated hair shafts, when exposed to UV‐radiations. Also, the melanin‐coated hair samples indicated negligible alterations in disulfide linkages, free sulfhydryl group content, water retention index and swelling index on UV exposure, as compared to that of uncoated samples. Similarly, the mechanical strength of the uncoated hair fibers was far compromised by UV irradiation compared to that of melanin‐coated hair fibers. The observations of the present study postulate cuttlefish melanin as a potential photoprotective agent in hair‐care formulations, which is otherwise considered as a process discard from cephalopod processing industry.

Effect of water and light on the stability of transition metal nitroprussides

Transition metal nitroprussides form an interesting family of coordination polymers with a 3D porous framework and appropriate properties for energy conversion and storage, photocatalysis, electrochemical devices, gas separation and storage, among other many potential applications. The stability of sodium nitroprusside in aqueous solution in the presence of light has been intensively studied related to its medical applications as a potent hypotensive agent. The stability of the corresponding transition metal salts in environmental conditions, where water molecules and light are always present, remains undocumented, and it is relevant for such potential applications as functional materials. In this contribution, we are reporting the results of a study on the effect of water and light on the stability of these solids in aqueous suspension under illumination and in the darkness, and in environmental conditions. The degradation process in water suspension was monitored from pH measurements and the recovered solid fractions were characterized by IR and and Mössbauer spectroscopies. The observed behavior evidences that the metal linked at the N end of CN ligands in the nitroprusside building block plays a relevant role in the extent of photodegradation. A metal with a high ability to subtract electron density from the nitroprusside ion generates a higher photostability for this last one.

A Z-scheme g-C3N4/Ag3PO4 nanocomposite: Its photocatalytic activity and capability for water splitting

Photodegradation of Rifampin (Rf) was evaluated by g-C3N4/Ag3PO4 nanocomposite (NC) under the visible-light irradiation. The samples were characterized by XRD, SEM-EDX, and X-Ray mapping, FTIR, and DRS. The XRD patterns showed the body-centered cubic phase for Ag3PO4 with an average size of 21.4 ± 3.8 nm and 20 nm for the NC by the Scherrer and Williamson-Hall equations, respectively. The pHpzc values about 10.7, 9.7, and 6.9 and the bandgap energies of 2.39, 2.97, and 2.90 eV were respectively for the as-synthesized Ag3PO4, g-C3N4, and g-C3N4/Ag3PO4 samples. The absorbencies of Rf solutions at maximum wavelengths of 330 and 470 nm were used to estimate the Rf photodegradation extent. Greater degradation extents were obtained by the absorbencies recorded at 470 nm. The percentage of the composite components varied the photodegradation efficiency, and the composite containing 60% g-C3N4 (G60) showed the highest activity. The best photodegradation results obtained at CRf: 2 ppm, solution pH: 5.5, catalyst dose: 1 g/L, irradiation time: 10 min. The solutions with degradation extents of 96 and 97% showed the mineralization extents of 96.4 and 98.2%, calculated from the COD results. The photodegradation pathway obeyed the direct Z-Scheme mechanism. This mechanism pathway was theoretically evaluated for the probable ability of the composite for the hydrogen production and water splitting. The potential of the CB positions (Ag3PO4: −1.08 V, g-C3N4: 0.21 V) confirms that the accumulated electrons in CB-Ag3PO4 position are stronger reducing agent than that of g-C3N4 for the reduction of dissolved oxygen to the superoxide radicals and they are also capable of reducing water molecules or protons to hydrogen molecules.

A novel quadripartite Cu2O-CdS-BiVO4-WO3 visible-light driven photocatalyst: Brief characterization and study the kinetic of the photodegradation and mineralization of sulfasalazine

A novel quadripartite Cu2O-CdS-BiVO4-WO3 nanocomposite (NC) was prepared by mechanical mixing of the individual semiconductor nanoparticles (NPs). The work focused on the kinetic study of the photodegradation and photo mineralization processes of sulfasalazine (SZ) by the quadripartite NC. XRD patterns showed the cubic phase of CdS and WO3 crystals, the monoclinic BiVO4, and the hexagonal CdS crystals in the composite, which relatively also confirmed by SEM and TEM images. The average crystallite sizes of about 28 nm and 22.5 nm were obtained for the NC by the Scherrer and Williamson-Hall equations, respectively. Photoluminescence (PL) spectra showed the lowest intensity for the composite. Both the lowest PL intensity and the highest photocatalytic activity were achieved when the moles of Cu2O in the composite was 3 times greater than the other components. Diffuse reflectance spectroscopy (DRS) results also showed a relative enhancement in the band gap energy of the composite especially for WO3 NPs alone. The photodegraded SZ solutions were subjected to the COD experiment to estimate the mineralization extent of SZ molecules or its degradation intermediates. Kinetic of both processes obeyed the Hinshelwood kinetic model and the rate constants of 0.0265 min−1 (t1/2 of 26.2 min) and 0.0323 min−1 (t1/2 of 21.5 min) were respectively obtained for the photodegradation and mineralization processes of SZ molecules, confirming that the mineralization of SZ is about 1.23 times faster than its photodegradation extent.

A comprehensive study on the mechanism pathways and scavenging agents in the photocatalytic activity of BiVO4/WO3 nano-composite

The BiVO4-WO3 nano-composite (NC) was synthesized, characterized by the x-ray diffraction (XRD), scanning electron microscope (SEM), diffuse reflectance spectroscopy (DRS), and the photoluminescence spectroscopy (PL), Transmission electron microscope (TEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and N2 adsorption-desorption (for the BET surface area determination) and used in the photodegradation of sulfasalazine (SFSZ) aqueous solution. Band gap energy and potential positions of the conduction and valence bands of the semiconductors were estimated. The composite with a mole ratio of 1:4 of BiVO4:WO3 showed the best photodegradation efficiency under visible light irradiation. The results confirmed a relatively smaller mineralization extent for SFSZ molecules than its photodegradation extent. The kinetic results showed k-values of 0.041 min−1 and 0.022 min−1 for the degradation and mineralization extents of SFSZ molecules that correspond to t1/2 values of 17.1 and 31.5 min, respectively, confirming that photodegradation extent of SFSZ is about 1.85 times greater than its mineralization extent. Effects of the scavenging agents were studied and the results showed superoxide radicals, the photogenerated holes, OH radicals, and the photogenerated electrons have the important roles in SFSZ photodegradation, respectively. Among the type II-heterojunction and Z-scheme mechanisms, the latter case had the most important role in the photodegradation of SFSZ.

Photodegradation enhancement of 2-chlorophenol using ZnO–CdS@CS nanocomposite under visible light

A facile micro-emulsion method used to prepare zinc oxide–cadmium sulfide (ZnO–CdS). Then, chitosan (CS) is utilized as a polymer matrix. Fourier-transform infrared spectroscopy, X-ray diffraction spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, dynamic light scattering, and photoluminescence is applied to evaluate the chemical structure, surface morphology, and the optical properties. Thermal gravimetric analysis is done to estimate the stability of the prepared nanomaterials. The photocatalytic activity of the synthesized nanoparticles was investigated via high-performance liquid chromatography analysis toward 2-chlorophenol degradation under visible light. Obviously, the spectrum of UV–visible for ZnO–CdS@CS nanostructure demonstrates a shift to longer wavelength (red shift) than the other prepared materials with the lowest band gap energy (2.10 eV). Also, the photocatalytic degradation of ZnO, ZnO@CS, ZnO–CdS, and ZnO–CdS@CS is 80%, 84%, 88%, and 98%, consecutively. The pseudo-first-order rate constant (K) for ZnO, ZnO@CS, ZnO–CdS, and ZnO–CdS@CS is 0.0039 min−1, 0.0048 min−1, 0.0058 min−1, and 0.0108 min−1, respectively. The CdS NPs and CS matrix (carbon and nitrogen “C–N”) introduce supplementary energy levels for excitation that causing a decrease in the band gap, increasing the extent of photodegradation in the visible region and assist for electron–hole separation. The reusability studied ZnO–CdS@CS manifested degradation under the same condition.

Photocatalytic activity of Ni0.5Zn0.5Fe2O4@polyaniline decorated BiOCl for azo dye degradation under visible light - integrated role and degradation kinetics interpretation.

Herein, we demonstrated the excellent improvement in photocatalytic degradation performance of BiOCl upon facile heterogeneous decoration with an integrated Ni0.5Zn0.5Fe2O4@polyaniline nanocomposite for an organic pollutant, methyl orange dye (MO), under visible light irradiation. The physico-chemical nature of the heterogeneous nanocomposite was characterized by XRD, FTIR, HRTEM-EDX and XPS analyses. The tuning of the band gap and optical sensitivity of BiOCl using Ni0.5Zn0.5Fe2O4@polyaniline were measured by DRS, PL and EIS techniques. To validate the transformation of the BiOCl photocatalyst to a visible light active photocatalyst due to the incorporation of Ni0.5Zn0.5Fe2O4@polyaniline and to gain insight into the origin of the synergistic effect for dye degradation by the heterostructured nanocomposite, we explored the effects of process parameters such as catalyst dosage, initial dye concentration, pH and the presence of inorganic anions on the extent of photo degradation. To get more details about reaction kinetics, a kinetic model using non-liner regression analysis was developed and the validity of the model was tested by comparing the experimental values with the calculated data. Based on the intermediate product formation, identified by GC-MS, a probable degradation pathway and a mechanism based on the electrochemical behaviour of the developed catalyst and trapping experiments were also proposed.

Nanostructured boron carbide (B4C): A bio-compatible and recyclable photo-catalyst for efficient wastewater treatment

Carbides have noteworthy manifold properties, solely adjusted to the requirements of different users. Nanostructured Boron Carbide (B4C) is one of them which possess unique characteristics to move towards industrial wastewater treatment from its traditional uses. Present work deals with the first photocatalytic study of biocompatible nanostructured B4C for organic (Methylene blue, MB) as well as industrial (Synazol yellow, SY) dye. The textile industry excretes non-biodegradable waste into water bodies, so effective and economical catalyst for the removal of industrial pollutants is the need of the hour. B4C shows remarkable results for the degradation of MB and SY dyes. The high degradation efficiency of 91.09% and 76.04% was achieved with 0.5 g/L catalyst for SY and MB dyes respectively loading due to the presence of defect states in the material. The effect of concentration of catalyst loading on the extent of photo-degradation has been considered for this study. As the concentration of B4C catalyst increases, the number of active sites on the surface of catalyst also increased which leads to improvement in degradation of dyes. Reusability of the same catalyst showed good results for its cost-effective use. The toxicity assessment revealed superior biocompatibility of B4C nanostructures upto the concentration ∼800 ppm. These findings indicate that B4C nanostructures may have potential to become a safer and promising photocatalyst for industrial wastewater treatment.

Synthesis, photodegradable and antibacterial properties of polystyrene-cinnamaldehyde copolymer film

Copolymerization of styrene (St) and different ratios of Cinnamaldehyde (Cin) from cinnamon oil and synthetic cinnamaldehyde were carried out by free radical polymerization, and were characterized by Fourier Transform Infrared (FTIR) spectroscopy, Thermo Gravimetric Analysis (TGA), Differential Scanning Calorimetric (DSC) analysis, and Gel Permeation Chromatography (GPC). Photodegradation of cinnamaldehyde incorporated copolymer (Poly (St-co-Cin)) films have been studied at outdoor weathering and under direct ultraviolet (UV) radiation. The extent of photodegradation was assessed by FTIR spectroscopy, percentage weight loss, surface analysis, average molecular weights and polydispersity indices. FTIR analysis confirms the photodegradable mechanisms of the copolymer films as Norrish Type I, Norrish Type II and photo-oxidation. Extreme weight loss was observed at outdoor weathering with 36.76% weight loss for 75% (w/w) cinnamaldehyde (natural-from cinnamon oil) incorporated copolymer (Poly(St-co-N-Cin)), and 45.58% weight loss for 75% (w/w) cinnamaldehyde (synthetic) incorporated copolymer (Poly(St-co-S-Cin)) with respect to 2.5% weight loss for polystyrene (PS) homopolymer for the period of 100 days. The average molecular weights of Poly(St-co-Cin) copolymers after outdoor weathering have drastically reduced compared to polystyrene. Scanning Electron Microscope (SEM) images clearly depict the fracture generation on Poly(St-co-Cin) films upon degradation. Embrittlement and color developments of the copolymer films with aging were noticeably evident. Furthermore, copolymers were tested positive for antibacterial activity against both gram negative and gram positive bacteria.

Synergistic effects of copper oxide-zeolite nanoparticles composite on photocatalytic degradation of 2,6-dimethylphenol aqueous solution

Due to hazardous effects of the phenolic compounds for body life, an effective catalyst based on the supporting of CuO onto the nanoparticles of clinoptilolite (NC) was constructed. The NC powder was prepared via mechanical ball-mill technique and ion exchanged in Cu(II) aqueous solution. The exchanged Cu(II)-NC was calcined at 450°C for 12h for the preparation of CuO-NC catalyst. The resulted CuO-NC catalyst was then used in the photocatalytic degradation of 2,6-dimethyl phenol (DMP) aqueous solution, as a hazardous member of the phenolic compounds, under Hg-lamp irradiation. The used CuO-NC is simple, effective and cheap. The samples were characterized by X-ray Diffraction (XRD), Fourier Transformation Infrared (FT-IR), Ultra Violet-Visible Diffuse Reflectance Spectroscopy (UV–Vis DRS) and Transmission Electron Microscope (TEM) techniques. After the study of the effects of some key operating factors influencing the degradation extent of DMP pollutant, the best photodegradation extent was obtained at 0.25gL−1 of CuO-NC catalyst and 30ppm DMP solution at pH5.5. The degradation process was monitored during the experimental runs through UV/Vis absorption spectroscopy and the degradation extent of DMP molecules was confirmed by the Chemical Oxygen Demand (COD) and High Performance Liquid Chromatography (HPLC) methods. The degradation process obeyed from the first–order kinetics.

Novel NiWO4-ZnO-NRGO Ternary Nanocomposites with Enhanced Photocatalytic Activity

A novel NiWO4-ZnO-NRGO ternary nanocomposite was efficiently synthesized via a facile, fast and easy microwave irradiation technique and its capability to photodegrade organic dye in aqueous solution was investigated. The products were characterized through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, photoluminescence spectroscopy (PL), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS) techniques. The photocatalytic activity was evaluated by estimating the extent of photodegradation of methylene blue (MB) under irradiation of visible light source, which showed 9 times enhancement for the ternary composites compared to that for pure NiWO4. The outcomes reveal that the novel NiWO4-ZnO-NRGO ternary nanocomposite could be a highly efficient visible light photocatalyst for the removal of environmental contaminants in wastewater

Correlating chemical and physical changes of photo-oxidized low-density polyethylene to the activation energy of water release

Understanding and quantifying the effect of degradation on the chemical and physical properties of LDPE films is crucial for maintaining high quality of recycled LDPE products. Thermal gravimetric analysis coupled with mass spectroscopy (TGA-MS), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry and electron microscopy combined with modulated TGA (MTGA) were used to evaluate LDPE films that sustained natural and accelerated weathering. Cross-referencing the chemical changes occurring to the LDPE samples during the weathering process with the dynamic results of MTGA provided a strong correlation between the release of caged water from the bulk of the LDPE and a specific energy value (E′), termed here as ‘volitalization energy’. The E′ value and the temperature at which it is measured are shown, for the first time, to be descriptors for the extent of photo-degradation. The data for accelerated- and naturally-induced degradation show a similar trend with respect to the effect of UVA radiation. A strong correlation is shown between the extent degradation determined by the traditional carbonyl index and the rate of water evaporation at the E′ temperature.

The challenges in lifetime prediction of oxodegradable polyolefin and biodegradable polymer films

The service lifetime of polymer films is controlled by the chemical reactions leading to chain scission and the mediating environmental factors. For application as agricultural cropping film, controlled accelerated degradation is required. For a photo-sensitive linear low density polyethylene (LLDPE) + 1% nano-titania (as the anatase/rutile mixed phase P25), the environmental factors are not only UV dose and temperature but also soil parameters such as moisture and organic material content. This provides a challenge in predicting the useful lifetime from laboratory accelerated ageing studies. To enhance degradation when the (LLDPE + 1% P25) is buried, UV-C pre-irradiation has been shown to accelerate strength loss but the rate of embrittlement is not sufficient for the application as crop propagation film. Biodegradable poly(butylene adipate-co-terephthalate) or PBAT has a higher rate of degradation when buried outdoors in soil than when buried under laboratory conditions: The elongation at break fell from 900% to 70% in one month in the field while similar changes required 6 months in the laboratory. The small changes in Mn¯ for embrittlement in the field suggests that the loss of mechanical properties was not linked to bulk property changes but rather to surface morphology (cracks and holes) as seen by SEM. This suggests that even in thin films, enzyme-mediated hydrolysis of PBAT is surface controlled. DNA analysis of the soil around the buried films after 35 days ageing outdoors showed fungi play a more dominant role in PBAT biodegradation compared to bacteria. UV degradation of PBAT film is controlled by the photochemistry of the terephthalate moiety in the polymer and the development of fluorescence is a useful indicator of the extent of photo-degradation.

Photodegradation of cotrimaxazole by clinoptilolite-supported nickel oxide

Photocatalytic activity of NiO incorporated into clinoptilolite nanoparticles (NiO-NCP) was studied in the photodegradation of cotrimaxazole pharmaceutical capsule (a mixture of trimethoprim and sulfamethoxazole) in aqueous system under medium Hg-lamp irradiation. Samples were characterized by XRD, FT-IR, UV–Vis–DRS, TEM and BET. The effects of some key experimental parameters affecting the photodegradation extent of the pollutant were studied and the best results were obtained at 13.2% NiO loaded onto NCP, 0.2gL−1 of the NiO13.2%-NCP catalyst, 50 folds diluted cotrimaxazole solution at pH 3. COD of the pollutant solution was decreased from its initial value of 1930–700mgL−1 during 4h photodegradation process (corresponds to 64% degradation of cotrimaxazole). The peak area of the main peak in HPLC chromatogram was also decreased during the irradiation process. HPLC and COD results are in accordance with decrease in UV–vis absorbance during the photodegradation process, confirming the degradation of cotrimaxazole into smaller fragments.

Tunable White‐Light Emission from Conjugated Polymer‐Di‐Ureasil Materials

Conjugated polymer (CP)‐di‐ureasil composite materials displaying a tunable emission color from blue to yellow through white have been prepared using a simple sol–gel processing method. The tunability of the emission color arises from a combination of energy transfer between the di‐ureasil and the CP dopant and the excitation wavelength dependence of the di‐ureasil emission. Incorporation of the CP does not adversely affect the bulk or local structure of the di‐ureasil, enabling retention of the structural and mechanical properties of the host. Furthermore, CP‐di‐ureasils display superior thermal and photostability compared to the parent CPs. Thermogravimetric analysis shows that the onset of thermal decomposition can be increased by up to 130 °C for CP‐di‐ureasils, while photostability studies reveal a significant decrease in the extent of photodegradation. Steady‐state photoluminescence spectroscopy and picosecond time‐resolved emission studies indicate that the observed tunable emission arises as a consequence of incomplete energy transfer between the di‐ureasil and the CP dopant, resulting in emission from both species on direct excitation of the di‐ureasil matrix. The facile synthetic approach and tunable emission demonstrate that CP‐di‐ureasils are a highly promising route to white‐light‐emitters that simultaneously improve the stability and reduce the complexity of CP‐based multilayer device architectures.

Photodegradation of a polypropylene filled with lanthanide complexes

This research aims at studying the photodegradation of a polypropylene formulation filled with lanthanide complexes. These complexes can be used as tracers for the identification of polymer materials in order to facilitate an high speed automatic sorting of plastic wastes for an economically efficient recycling. By paying attention to the evolution of carbonyl absorption bands in FTIR spectra, it is observed that the addition of lanthanide complexes into our formulation improves UV stability of polypropylene by reducing the extent of photo-degradation. Furthermore, TG analyses show that the traced blends can maintain better thermal properties, after irradiation. A significant increase of the crystallinity degree and a decrease of the melting temperature are more pronounced for the unfilled UV–irradiated PP. This might result from chemi-crystallization that can occur when chain entanglements are broken as a result of chain scissions. From SEM analyses, it is observed that the severity of surface cracks induced by photo degradation is reduced for filled PP. The mechanical tests are in agreement with this result and show a fundamental change in the behavior of the as-exposed blends from a ductile to a brittle material.

Potential Application of Periwinkle Shell Ash as Photocatalyst for the Heterogeneous Photocatalytic Decolourisation of Congo Red Dye in Aqueous Solution

The potential of locally sourced periwinkle shell ash (PSA) has been explored as an alternative photocatalyst for the photocatalytic decolourisation of Congo red dye. The effect of process parameters such as irradiation time, initial dye concentration, catalyst dosage, pH of the solution and the addition of hydrogen peroxide (H 2 O 2 ) on the extent of photodegradation was investigated. The optimum values of the process parameters were: irradiation time, 50 minutes; initial dye concentration, 10 mg/L; PSA dosage, 7 g/L and pH, 4. The addition of H 2 O 2 enhanced the photodegradation process with almost 100 percent decolourisation achieved. The adsorption equilibrium was well described by the Langmuir isotherm equation (R 2 =0.999) indicating mono layer type adsorption while the diffusion mechanism and kinetics of the process were well described by the intra-particle diffusion and Langmuir-Hinshelwood kinetic models with high R 2 values of 0.998 and 0.999 respectively.