Electronic Structure of Carotenoids in Natural and Artificial Photosynthesis | InTechOpen, Published on: 2017-06-14. Authors: Manuel Flores-Hidalgo, Francisco Torres-Rivas, Jesus Monzon- Bensojo, et

The widespread use of nonsteroidal anti-inflammatory drugs (NSAIDs) has led to their frequent detection in aquatic environments, raising serious concerns due to their persistence, toxicity, and potential to induce antibiotic resistance. Ibuprofen and diclofenac, which are produced at annual scales of approximately 15,000 and 940 metric tons, respectively, are often found in surface, ground, and even drinking water. Conventional wastewater treatments fail to eliminate these micropollutants completely and effectively, which necessitates advanced solutions. Among them, heterogeneous photocatalysis has emerged as a promising approach, although its application is limited by rapid electron‒hole recombination and partial mineralization. The addition of hydrogen peroxide (H₂O₂) has the potential to overcome these challenges by increasing reactive oxygen species generation and reducing charge recombination. Although previous reviews have explored photocatalysis and H₂O₂-based advanced oxidation processes (AOPs) for pharmaceutical degradation, their combined application for NSAIDs has received comparatively limited attention. This review analyzes recent progress in H₂O₂-assisted photocatalytic degradation of NSAIDs, emphasizing photocatalyst synthesis, H₂O₂ dosing, pH effects, and performance in real water matrices. It also examines the toxicity of transformation products and critical aspects, such as photocatalyst stability and reactor configurations. As water scarcity, climate change, and population growth intensify pressure on treatment systems, the development of adaptable and scalable technologies becomes urgent. Future directions, including in situ H₂O₂ production, real-time monitoring, and combined use with oxidants such as peroxymonosulfate, are highlighted as promising paths toward more efficient treatment. This work outlines a roadmap for advancing photocatalytic processes as viable tools for safeguarding water quality in diverse environmental scenarios.

Postsurgical infections are an important cause of implant failure, and biomaterials such as Chitosan can be used as an antimicrobial coating to address this important problem. Characterization of silver distribution was performed by several methods, including Electron scanning microscopy (SEM), Inductively coupled plasma (ICP), and Infrared spectrometry (IR). Antimicrobial activity was tested against Candida albicans ATCC 10231, Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, and Pseudomonas aeruginosa BAA-1744 ATCC 109246. The inhibition assays showed that Chitosan films inhibited 68% of C. albicans growth and 23.5% of E. coli growth; the rest of the microorganisms did not have any statistically relevant inhibition. E. coli, P. aeruginosa, and C. albicans were completely inhibited in films with 0.25 mg/mL of AgNO₃ and inhibited 82.5% of S. aureus. The mechanism of integration and release of silver in the films was analyzed by the Density Functional Theory (DFT), considering this analysis of geometry optimization as well as infrared spectroscopy. DFT analysis showed that AgNO₃ is not trapped by covalence in chitosan, being a more stable system when it is closer to an OH group. Chitosan films functionalized with antimicrobial compounds are a promising antimicrobial coating for use in biomaterials to prevent postsurgical complications.

Anthocyanidins under the effects of solvents water, ethanol, n-hexane, and methanol are interesting due to their suitability as natural dyes for photocatalytic applications. In this chapter, DFT and TDDFT methodologies are used to study their electronic structure. The results displayed include HOMO, LUMO, HOMO-LUMO gap, chemical properties, and reorganization energies for the ground states, and excited state data are also displayed. Malvidin in gas phase has lower gap energy. After addition of solvents, gap energy increases in all cases but malvidin with n-hexane presents narrower gap. Conceptual DFT results show that cyanidin and malvidin may have good charge transfer. Cyanidin presented lower electron reorganization energy (λe) using solvent water; however, ethanol and methanol had similar values. TDDFT is used to calculate excited states, and absorption data show wavelength main peak between 479.1 and 536.4 nm. UV-Vis absorption spectra were generated and solvent effects on each molecule is discussed. Anthocyanidins work well in the visible region with the stronger peak at the green region. These pigments are good options for photocatalysis application and cyanidin and malvidin, in this order, may be the best choices for dye sensitization applications.

Heat effects in photocatalytic reactor applications are discussed and a case study is analyzed where sunlight is used to activate a chemical reaction to degrade water pollutants. Heat is produced in the light-capturing process, and heat effects need to be better understood during the device design process. Radiative transfer equation (RTE) is the guiding equation used to calculate radiation proliferation in participating media, and it is used to describe the balance of radiative energy transport in the participating media including the interactions caused by different processes such as absorption, scattering, and emission, which also are subject to additional phenomena like weakening and magnification. This equation plays an important role in the design process since it may be included in the simulation process to represent the sunlight heat effects in the different photocatalytic reactor components. In this chapter, it is explained how to build a simplified algorithm to incorporate the RTE in a numerical calculation during the design of a photocatalytic reactor using the commercial software ANSYS®. In addition, simplifications are explained that enable the program to coordinate some coefficients such as absorption and dispersion so their effects are included within the numerical calculation. A user-defined function is presented in the end of the chapter as a usable algorithm in ANSYS® program with acceptable results for photocatalytic reactors.