Photodegradation

The application of physics to art history, art conservation and archaeology is currently a growing area of research. Astronomy and astrophysics have made significant contributions to imaging science which has in turn contributed to the developments of many other fields ranging from biological science to the study of art history, archaeology and art conservation. This paper will discuss how knowledge traditionally associated with astrophysics have made impact on the
study of cultural heritage. Examples will be drawn from recent research carried out in my research group.

A complete set of platinum(II) solketal substituted phthalocyanines has been synthesized and characterized. To evaluate their potential as Type II photosensitizers for photodynamic therapy, comparative studies of their photophysical and photochemical properties with analogous zinc(II) series have been achieved: electronic absorption, fluorescence quantum yields, lifetimes, and fluorescence quenching by benzoquinone, as well as singlet oxygen generation and photodegradation. It appears that platinum(II) phthalocyanines are worth being used as Type II photosensitizers, as they exhibit good singlet oxygen generation and appropriate photodegradation.

Various biotic or abiotic factors influence the fate of pesticides in the natural environment, of which ultraviolet (UV) component in the sunlight is one of the most powerful forces. Studies on the photodegradation of pesticides have not only significance from the point of view of environmental science, but also very important in researching and developing new, safer, and effective pesticides. Previously we have studied the photodegradation of triazine- and urea-type herbicides in details. This paper is intended to outline the photodegradation pattern of some commonly used N-containing herbicides that belong to the groups of the mentioned triazines (atrazine, cyanazine, terbuthylazine, terbutryn) and ureas (chloroxuron, methabenzthiazuron, diuron, fenuron), as well as thiolcarbamates (butylate, cycloate, EPTC, molinate, vernolate), in order to gain information about their possible fate and derivatives in the environment.The most significant processes of photodegradation of triazines are the partial or complete loss of side-chains, or rather the substitution of the heteroatom-containing side-chain to hydroxyl-group. The chemical characteristics of the side chains determines basically the speed of the degradation. It can be concluded that the C–S bond breaks down much easier than C–Cl bond, and the chlorine atom remaining on the triazine-ring promotes the loss of alkyl-chains to a higher extent than that the hydroxy-group. In the case of ureas, the chemical properties of groups in both the N and N′ position can influence the degradation process. It could be stated the proximity of large aryl-substituent and methyl-group in the N position is unfavorable and instabilizing, promoting the further degradation of compound, at the same time, loss of these groups is the preferred degradation route. In the case of thiolcarbamates, the most frequent processes are the α- and β-oxidation of alkyl-groups connecting to the nitrogen atom. In the most cases, the N-formyl and N-dealkylated products were identified in the degradation mixture. The thioalkyl-group showed fair stability under the circumstances of photodegradation. Its partly or completely degraded products cannot be detected, and represent only very small part of the mixture.

Las bolsas plásticas son de uso desechable y se liberan al medio ambiente en cantidades crecientes. Por esta razón muchos fabricantes las están produciendo a base de materiales poliméricos degradables, como por ejemplo, los polihidroxialcanoatos y los polilactatos. En este trabajo se evaluó la degradabilidad por exposición al ambiente de bolsas plásticas declaradas como degradables por sus fabricantes, y se compararon con las convencionales. Se estudiaron tres parámetros como son pérdida de masa, absorción de agua y resistencia mecánica. Los resultados mostraron que las bolsas llamadas degradables presentaron mayor pérdida de masa, mayor absorción de agua, y menor resistencia mecánica antes y después de la exposición al ambiente que las bolsas convencionales, demostrando que las modificaciones químicas realizadas por los fabricantes realmente favorecen su degradación.

Polythiophene (PTh) has been the subject of considerable interest because of its good environmental stability, unique redox electrical behavior, stability in doped or neutral states, ease of synthesis, and wide range of applications in many fields. Apart from its applications in the electrical or electronic field, PTh has shown promising applications in photocatalytic degradation. The fabrication of a catalyst, metal oxides with PTh, extends the absorption range of the modified composite system, thereby enhancing the photocatalytic activity under UV or visible light irradiation. Substituted PTh, such as alkyl substitution, modifies the electronic properties of the polymer, thereby enlarging the potential for industrial applications. PTh or substituted PTh when combined with metal, metal oxide or a combination of both, can exhibit tailorable photocatalytic properties. This review focuses on the chemistry of the band gap engineering of PTh or PTh based systems and the mechanism of photocatalytic degradation. The major developments in the field of UV and visible light-assisted photocatalysis are discussed in terms of the parameters that affect the photocatalytic efficiency. On the other hand, some challenges still needs to be investigated experimentally, which are mentioned as the scope for future studies. For simplicity, the review has been classified under a major subheading depending on the type of composite system used for photocatalysis.

Polymeric composites for automotive window seal applications are generally exposed to complex service environment conditions. The fundamental physico-chemical processes that control the durability of such composite systems on a micro and macroscopic level were evaluated in the present case using thermal analysis (TA), elemental mapping and microscopy. Five different EPDM rubber compounds (control, three bulk modified and one surface modified),

Photodegradation of a phenol wastewater sample with ZnO–TiO2 supported on
nano-clinoptilolite particles (NCP) was studied. NCP were obtained by planetary ball mill.
The proposed catalyst was obtained via ion exchanging of NCP with Zn(NO3)2∙6H2O and
C4H10N2O10Ti∙H2O (0.2 M) aqueous solutions for 12 h followed by calcination at 450°C for
12 h. XRD, FT-IR, and TEM were used for characterization of samples. The best degradation
efficiency was related to the catalyst containing both ZnO and TiO2. The optimum values
were 0.1 g L−1 of photocatalyst, 100 times diluted wastewater solution, and pH of 3.0 in
photodegradation studies.

We have synthesized two mononuclear complexes, Mn-hq and Co-hq, to serve as sustainable catalysts (for degrading dyes from organic pollutant) and as biocatalysts (for promoting oxidation of catechol to quinone). The two complexes have been characterized by various spectroscopic tools, and with the assistance of single-crystal X-ray diffraction data, their molecular structures were established. The present complexes were exploited for the catalytic activity, i.e., enzymatic activity and pho-tocatalytic property. In methanolic solution, Mn-hq and Co-hq were examined for catecholase-like activity and Mn-hq particularly catalyzes the oxidation of 3,5-di-tert-butyl catechol to analogous quinone with a K cat value of 835.2 h −1. Additionally, Mn-hq and Co-hq demonstrated remarkable photocatalytic activity for the degradation of methylene blue (MB) in the aqueous medium beneath visible light. Co-hq shows excellent stability and recyclability toward MB. Further, trapping experiment along with degradation pathways is also explored. Thus, the present research throws light on the excellent catalytic properties of simply designed complexes and this activity can be tuned for desired efficiencies in future prospects.

In this work, a facile enhanced property of Ag3PO4 photocatalyst using H2O2 for methylene blue photodegradation has been conducted. Ag3PO4 photocatalyst was synthesized using the coprecipitation method. Then, the photocatalytic activity and stability of Ag3PO4 were tested in the methylene blue degradation under the addition of an H2O2 30% solution. According to the results, the prolonged photocatalysis reaction led to a decrease in the catalysis ability of the Ag3PO4 photocatalyst. Meanwhile, the addition of 5 mL of H2O2 (AH-10% sample) tends to enhance the stability of Ag3PO4 photocatalyst with the dye removal percentage and recycling test were up to 90.3% and three recycle runs, respectively. The low stability of Ag3PO4 might be due to the catalyst photo-corrosion through Ag + reduction. This research suggests that H2O2 is beneficial to inhibit the photo-corrosion of Ag3PO4 photocatalyst, even though released Ag ions that were caused by the excess addition of H2O2 oxidizing agent should be considered.

Preparation, characterization and utilization of TiO2-SiO2 as photocatalyst for methyl violet (MV) decolorization has been conducted. In this research, preparation of TiO2-SiO2 was developed based on natural renewable silica source; rice husk ash (RHA) via a sol-gel technique. The composite was formed by the dispersing of titanium isopropoxide as titania precursor into the gel of silica followed by aging, drying and calcination. The TiO2-SiO2 sample was characterized by powder X-ray diffraction (XRD), diffuse reflectance-UV Visible spectrophotometric analysis (DRUV-Vis), gas sorption analyzer and Scanning electron micrograph (SEM) before its utilization as photocatalyst in methyl violet photooxidation. As comparison to the physicochemical character study, the synthesis of TiO2-SiO2 by using tetraethyl ortosilicate (TEOS) was performed as a confirmation. Result showed that prepared TiO2-SiO2 has the character similar to TiO2-SiO2 as synthesized by TEOS precursor. The formation of cry...

The photocatalytic degradation of p-aminobenzoic acid was studied using C-doped ZnO nanorods as the catalyst synthesized through a low cost and simple precipitation method. The as-synthesized nanorods were fully characterized by SEM, TEM, XRD, BET and XPS. The photocatalytic degradation of p-aminobenzoic acid was carried out under sunlight irradiation. Optimal experimental conditions were determined for C-doped ZnO nanorods with a catalyst dosage of 0.5 g/L in a p-aminobenzoic acid solution, and 97% degradation was obtained. The results showed that the C-doped ZnO nanorods can be reusable and retain good photodegradation efficiency. A pseudo first order reaction was found to provide the best correlations, with a constant rate of 0.028 min −1 .

In this work, a one-dimensional (1-D) cobalt(II)-based coordination polymer, [Co(SCN) 2 (peol)] n (H 4 peol = pentaerythritol and NCS À = thiocyanate), was synthesized under solvothermal conditions. Elemental, FTIR, UV-Visible, PXRD, TGA, magnetic and single-crystal X-ray diffraction analyses characterized the polymer (Co-CP). Further, scanning electron microscopy (SEM) was employed to understand the outer morphology of Co-CP. The material importance of Co-CP was investigated by studying its magnetic and photodegradation properties. Variable temperature magnetic data of Co-CP unveiled the existence of strong antiferromagnetic interactions coupled with anisotropy in the system, with parameters C = 2.71 cm 3 K mol À1 and h = À6.43 K. Furthermore, Co-CP has been effectively used as a photocatalyst for the degradation of organic pollutants methylene blue (MB) and rhodamine-B (Rh-B) in the aqueous phase, with good recyclability. Co-CP exhibits unusual photocatalytic activity toward the degradation of the solid organic dyes. Based on a scavenging investigation, a plausible mechanism for the photocatalytic activity has also been proposed.