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This dissertation aims to develop methods for statistical predictions based on various types of data from different areas. We focus on applications from reliability and spatial epidemiology. Chapter 1 gives a general introduction of statistical predictions. Chapters 2 and 3 investigate the photodegradation of an organic coating, which is mainly caused by ultraviolet (UV) radiation but also affected by environmental factors, including temperature and humidity. In Chapter 2, we identify a physically motivated nonlinear mixed-effects model, including the effects of environmental variables, to describe the degradation path. Unit-to-unit variabilities are modeled as random effects. The maximum likelihood approach is used to estimate parameters based on the accelerated test data from laboratory. The developed model is then extended to allow for time-varying covariates and is used to predict outdoor degradation where the explanatory variables are time-varying. Chapter 3 introduces a class of models for analyzing degradation data with dynamic covariate information. We use a general path model with random effects to describe the degradation paths and a vector time series model to describe the covariate process. Shape restricted splines are used to estimate the effects of dynamic covariates on the degradation process. The unknown parameters of these models are estimated by using the maximum likelihood method. Algorithms for computing the estimated lifetime distribution are also described. The proposed methods are applied to predict the photodegradation path of an organic coating in a complicated dynamic environment. Chapter 4 investigates the Lyme disease emergency in Virginia at census tract level. Based on areal (census tract level) count data of Lyme disease cases in Virginia from 1998 to 2011, we analyze the spatial patterns of the disease using statistical smoothing techniques. We also use the space and space-time scan statistics to reveal the presence of clusters in the spatial and spatial/temporal distribution of Lyme disease. Chapter 5 builds a predictive model for Lyme disease based on historical data and environmental/demographical information of each census tract. We propose a Divide-Recombine method to take advantage of parallel computing. We compare prediction results through simulation studies, which show our method can provide comparable fitting and predicting accuracy but can achieve much more computational efficiency. We also apply the proposed method to analyze Virginia Lyme disease spatio-temporal data. Our method makes large-scale spatio-temporal predictions possible. Chapter 6 gives a general review on the contributions of this dissertation, and discusses directions for future research. / Ph. D.

The design of biomaterials, historically initiated and developed by physicians and engineers, in the last decades has slowly shifted toward a more biochemical based approach. For the replacement, repair and regeneration of tissues scientists are now focusing on materials that stimulate specific biological response at the molecular level. These biomaterials have already shown interesting applications in cell proliferation, differentiation, and extracellular matrix production and organization when the material modifications are designed to elicit specific interactions with cell integrins. In the present work we propose the application of this strategy for the development of blood-compatible materials. We first identified, in the coagulation cascade a key enzyme that constitute a valuable biological target for the development of anti-thrombogenic compounds. Piperazinyl-amide derivatives of N-alfa-(3-trifluoromethyl-benzenesulfonyl)-L-arginine were synthesized as graftable thrombin inhibitors. These inhibitors provided a spacer arm for surface grafting and a fluorine tag for XPS (X-ray photoelectron spectroscopy) detection. The possible disturbance of biological activity due to a variable spacer-arm fixed on the N-4 piperazinyl position was evaluated in vitro against human alfa-thrombin, in silico by molecular modelling and via X-ray diffraction study. Selected inhibitors, having inhibition potency in the mM range, were grafted on polyesters surface via wet chemistry and photochemical activation treatments. Wet chemistry surface grafting was performed by specific hydroxyl chain-ends activation and resulted in bioactive molecules fixation of 20-300pmol/cm2. The photochemical grafting was performed using a molecular clip providing an aromatic azide, for nitrene insertion into a polymer, and an activated ester for grafting of tag compounds. This grafting technique resulted in a dramatic increase in fixed bioactive signals (up to nmol/cm2). The material blood-compatibilization induced by the surface fixation of the inhibitors, was measured by a static blood clot weight measurement test. The wet chemistry grafting technique resulted in moderate blood-compatibilization while by the photochemical grafting method important decrease in surface blood clot formation was observed. In the latter case, the blood response to material contact was found to be strongly affected by the polyester surface photo-degradation induced by the activation treatment.

The design of biomaterials, historically initiated and developed by physicians and engineers, in the last decades has slowly shifted toward a more biochemical based approach. For the replacement, repair and regeneration of tissues scientists are now focusing on materials that stimulate specific biological response at the molecular level. These biomaterials have already shown interesting applications in cell proliferation, differentiation, and extracellular matrix production and organization when the material modifications are designed to elicit specific interactions with cell integrins. In the present work we propose the application of this strategy for the development of blood-compatible materials. We first identified, in the coagulation cascade a key enzyme that constitute a valuable biological target for the development of anti-thrombogenic compounds. Piperazinyl-amide derivatives of N-alfa-(3-trifluoromethyl-benzenesulfonyl)-L-arginine were synthesized as graftable thrombin inhibitors. These inhibitors provided a spacer arm for surface grafting and a fluorine tag for XPS (X-ray photoelectron spectroscopy) detection. The possible disturbance of biological activity due to a variable spacer-arm fixed on the N-4 piperazinyl position was evaluated in vitro against human alfa-thrombin, in silico by molecular modelling and via X-ray diffraction study. Selected inhibitors, having inhibition potency in the mM range, were grafted on polyesters surface via wet chemistry and photochemical activation treatments. Wet chemistry surface grafting was performed by specific hydroxyl chain-ends activation and resulted in bioactive molecules fixation of 20-300pmol/cm2. The photochemical grafting was performed using a molecular clip providing an aromatic azide, for nitrene insertion into a polymer, and an activated ester for grafting of tag compounds. This grafting technique resulted in a dramatic increase in fixed bioactive signals (up to nmol/cm2). The material blood-compatibilization induced by the surface fixation of the inhibitors, was measured by a static blood clot weight measurement test. The wet chemistry grafting technique resulted in moderate blood-compatibilization while by the photochemical grafting method important decrease in surface blood clot formation was observed. In the latter case, the blood response to material contact was found to be strongly affected by the polyester surface photo-degradation induced by the activation treatment.

This study aims at tackling some of the problems often encountered in photostability testing and liquid formulation development. Three anti-cancer drugs will be employed as models; Dacarbazine (DBZ) has well established photostability issues, Axitinib (AXI) and Sunitinib (SUT) are two new drugs only commercially available in solid dosage forms. In ethanol, the photokinetics of these drugs were well described by the newly proposed Φ-order kinetic mathematical model. This has confirmed the photoreversible character of AXI and SUT’s and unimolecular photoreaction of DBZ’s photodegradations. Also, the Φ-order kinetics is proven to describe them better than the usually used classic thermal reaction orders. In aqueous solution, the drugs were found to undergo thermal and photochemical complex degradations, involving at least 3 photoproducts. A new photokinetic approach has been proposed in this work to solving and unravelling the attributes of such complex mechanisms. For the first time, the quantum yields (QY) of the three drugs were determined and found to increase with irradiation wavelength. SUT’s QY were comparable in ethanol and water (QY460 = 0.02), DBZ was found to be more photoefficient in water (QY330 = 0.04 and 0.1, respectively) and AXI in water (QY330 = 0.06 and 0.03). Φ-order kinetics’ potential for the development of reliable actinometers of the three drugs, without prior knowledge of unknown reaction parameters, has also been established. A general equation to describe the isotherm of a (Gn:Hm) guest-host multicomponent complex was proposed in this work to palliate the lack of a strategy for characterising nanosponge-drug complexes. It provides information on both stiochiometry and association constant of the complex. The results indicate that hydrophobic AXI forms a 1:0.8 complex, indicating the possibility of multiple association sites and/or different types of binding. The newly developed AXI/nanosponge liquid formulation has significantly increased solubility (5000-fold) and thermal stability. Furthermore, the photostability of DBZ and SUT were considerably improved by using a strategy based on light-absorption competitors. Their initial velocities reduced from 10 and 3 s-1 (respectively) to 1 and 0.13 s-1. The successful application of these methods to the model anti-cancer drugs has set out new approaches that might be found useful for future treatments of photodegradation data, development of drug-actinometers and liquid formulations of drugs.

The identification of the hydrolysis and photodegradation products of flexible polyurethane foams (PUFs) with addition of biooriginated and biodegradable additive was the first topic of this dissertation work. Separation of polyurethane foam hydrolysis degradation products, designed for ecotoxicological tests, was managed by high-performance liquid chromatography coupled with mass spectrometry (HPLC/MS). The degradations product structure was elucidated by tandem mass spectrometry (MSn). PUF photodegradation products were obtained by exposure of materials by irradiation at 254 nm. Semi-volatile degradation products were isolated from the exposed polyurethane by n-hexane extraction; volatile compounds were collected by solid phase microextraction (SPME). Gas chromatography with mass spectrometry (GC/MS) and complete orthogonal tandem gas chromatography with mass spectrometry (GCxGC/TOF MS) was used for separation and identification of photodegradation products. The influence of the bio-filler on the character of degradation products and the possible effect of PUF degradation products on the environment was discussed at the end of this section. The determination of isoprostanes – markers of oxidative stress in tissues of beadlet anemone (Actinia equina) was the subject of the second topic. F2-isoprostanes were synthesized from the arachidonic acid. With thereby prepared isoprostanes the method of determination by liquid chromatography with tandem mass spectrometry (HPLC/MS/MS) was developed and optimized. The isoprostane isolation process from the Actinia equina tissues was optimized with solid phase extraction (SPE). The resulting methodology was used to quantify isoprostanes in tissues of anemones, which were exposed to both moderate and high temperature changes. The temperature changes were used to initiate the oxidative stress in organisms. In addition, concentration levels of unknown compounds were also monitored. These unknown compounds were extracted from tissues together with F2-isoprostanes and their identity is discussed in this dissertation work too. The possibility of using isoprostane levels in the Anthozoa tissues for the oxidative stress monitoring is discussed in the conclusion of this work.

Les déchets plastiques s'accumulent depuis plusieurs décennies dans les océans où ils se fragmentent en particules appelés microplastiques lorsque leur taille est inférieure à 5 mm. Ces microplastiques sont retrouvés dans toutes les eaux du globe, dans les sédiments ainsi que dans de nombreux organismes marins. Le devenir physicochimique à long terme de ces particules et leur possible fragmentation en nanoplastiques sont complexes, encore peu documentés et nécessitent des études en laboratoire.Afin de comprendre les processus liés à la photodégradation et à la fragmentation des polymères dans l’environnement, mais également dans le but d’'appréhender l’évolution des fragments générés au cours de l’irradiation, un protocole de vieillissement accéléré en milieu abiotique a été mis en place sur des polymères modèles. Le suivi de l’oxydation et de la fragmentation des deux polymères étudiés,polyéthylène basse densité et polypropylène, a été mené à l’aide de techniques spectroscopiques (infrarouge, Raman), DSC, angles de contact, et microscopiques (lumière polarisée, MEB, AFM…).Ce travail a permis de mettre en évidence l’influence significative de l’environnement et de la morphologie initiale des polymères sur leurs cinétiques de vieillissement et leurs mécanismes de fissuration. Ainsi des distributions en nombres, tailles et formes de fragments très différentes ont été obtenues pour les deux polymères selon la présence d’eau. Enfin, après un long temps d’irradiation, des produits de dégradation ont pu être détectés mais la production significative de nanoplastiques n’a pas été démontrée. L'hypothèse d'une taille limite de fragmentation devrait être envisagée. / Plastic wastes have been accumulating for several decades in the oceans where they break up into particles called microplastics when their size is less than 5 mm. These microplastics are found in all earth’s waters, in sediments and in many marine organisms. Their long-term physico-chemical fate and their possible fragmentation into nanoplastics are complex, still poorly documented and require laboratory studies.In order to understand the processes related to photodegradation and fragmentation of polymers, but also in order to understand the evolution of these fragments during irradiation, an accelerated aging protocol in abiotic conditions has been set up. The oxidation and fragmentation of two model polymers, low density polyethylene and polypropylene, were monitored using spectroscopic techniques (InfraRed, Raman), DSC, contact angles and microscopic technics (light microscopy, polarized light, SEM, AFM ...).This work has demonstrated a significant influence of the environment and the initial morphology of the polymers on their kinetics of aging and cracking mechanisms. This lead to significantly different distributions in numbers, sizes and shapes of the generated fragments. Moreover, after a long time of irradiaiton, other degradation products could be detected but the significant production of nanoplastics has not been demonstrated. The possibility of a size limit below which the fragmentation rate of plastics would strongly decrease should be considered.

<p>Ispitana je kinetika i mehanizam fotokatalitičke&nbsp;razgradnje herbicida kvinmeraka i klomazona u prisustvu&nbsp;UV/TiO₂&nbsp; Degussa P25, odnosno piklorama i&nbsp; klopiralida&nbsp;<br />primenom UV/TiO₂&nbsp; Wackherr pri različitim&nbsp;eksperimentalnim uslovima. Praćena je i kinetika&nbsp;razgradnje odabranih herbicida direktnom fotolizom uz&nbsp;primenu sunčevog, UV i vidljivog zračenja, kao i u&nbsp;odsustvu svetlosti. Pored toga, upoređena je efikasnost&nbsp;<br />UV/TiO₂&nbsp; Degussa P25, odnosno UV/TiO₂&nbsp; Wackherr sa&nbsp;vidljivim zračenjem, kao i direktnom fotolizom u&nbsp;prisustvu pomenutih izvora svetlosti.&nbsp; U cilju procene&nbsp;<br />citotoksičnosti klomazona i klopiralida, kao i sme&scaron;e&nbsp;klomazona i klopiralida i njihovih intermedijera nastalih&nbsp;tokom fotokatalitičke razgradnje ispitan je&nbsp; in vitro&nbsp; rast&nbsp;<br />ćelijskih linija&nbsp; MRC-5 i H-4-II-E.&nbsp; Nakon ispitivanja&nbsp;fotokatalitičke razgradnje odabranih herbicida u dvaput&nbsp;destilovanoj vodi, praćena je njihova razgradnja i u&nbsp;prirodnim vodama. Takođe, ispitan je uticaj dodatka&nbsp;hidrogenkarbonata i huminske kiseline na efikasnost&nbsp;razgradnje odabranih herbicida. Fotokatalitička razgradnja&nbsp;klomazona, piklorama i mekopropa je ispitivana i u&nbsp;prisustvu UV/TiO₂&nbsp; nanocevi. Aktivnost katalizatora TiO_2&nbsp;Wackherr&nbsp; i TiO₂&nbsp; nanocevi je upoređena sa TiO₂&nbsp; Degussa&nbsp;P25.</p> / <p>The kinetics and mechanism of photocatalytic degradation&nbsp;of the herbicides quinmerac and clomazone in the&nbsp;presence of UV/TiO₂&nbsp; Degussa P25, and of picloram and&nbsp;clopyralid using UV/TiO₂&nbsp; Wackherr under different&nbsp;experimental conditions were studied. The kinetics of&nbsp;degradation of selected herbicides by direct photolysis&nbsp;using sunlight, UV and visible radiation, and in the&nbsp;absence of light were followed. In addition, the&nbsp;efficiencies of UV/TiO₂&nbsp; Degussa P25 and UV/TiO_2&nbsp;Wackherr &nbsp;were compared with visible radiation and direct&nbsp;photolysis in the presence of the above mentioned light&nbsp;sources. In order to evaluate the cytotoxicity of clomazone&nbsp;<br />and clopyralid alone and in their mixture with&nbsp;intermediates formed during the photocatalytic&nbsp;degradation, in vitro growth of cell lines, MRC-5 and H-4-II-E was followed. After examining&nbsp; the photocatalytic&nbsp;degradation of selected herbicides in double distilled&nbsp;water, their decomposition in natural waters was also&nbsp;followed. Also, the influence of hydrogencarbonate and&nbsp;humic acid addition on the efficiency of degradation of&nbsp;selected herbicides was studied. Photocatalytic&nbsp;degradations of clomazone, picloram and mecoprop were&nbsp;investigated in the presence of UV/TiO_2&nbsp;nanotubes. Activities of the catalysts TiO₂&nbsp; Wackherr and TiO_2&nbsp;nanotubes were compared to TiO₂ Degussa P25.</p>

M.Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / To replace the conventional wastewater treatment technology, photocatalysis has the best potential due to its utilization of visible light to photodegrade organic and inorganic contaminants. However, agglomeration of nanoparticles leads to serious decrease in photocatalytic performance when applied in slurry form, due to hindrance effect. TiO2 semiconductor photocatalyst mediated advanced oxidation process is referred to as one of the most efficient technologies to degrade organic pollutants in water. However, TiO2 semiconductor for water purification hinders large scale applicability due to poor activity under visible light and the recombination of photogenerated electron and hole pairs. The modification of TiO2 semiconductor photocatalyst with carbon dots (CDs) is of high importance due to low toxicity, aqueous stability, enhanced surface area, economic feasibility, good biocompatibility and chemical inertness of CDs. Herein, strategies are highlighted to improve the activity of TiO2 semiconductor photocatalyst by coupling it with CDs and Fe2O3. In this study, we study the morphological influence of TiO2 nanostructures on photocatalytic degradation of tetracycline hydrochloride present in industrial wastewater. TiO2 nanostructures, nanotubes, nanospheres and nanofibers were Synthesized using the hydrothermal technique. TiO2 nanotubes, nanofibers and nanospheres were prepared by the hydrothermal treatment of TiO2 nanoparticles with different NaOH concentrations (5, 10 and 12 N) at 120 and 140 ˚C; afterwards, HCl was added until it reached pH 2. Both the crystalline phase and coordination of the TiO2 nanotubes, nanofibers and nanospheres were composed principally. Likewise, the surface area, pore volume and pore size of the TiO2 nanotubes, nanofibers and nanospheres changed with the NaOH rinsing treatment. The photocatalytic activity for tetracycline degradation were strongly enhanced by the nanofibers and nanotubes in the basic and acid media, respectively, showing a relationship between their structure and the medium. TiO2 nanostructures and the composite material were characterized by scanning electron microscope\SEM), X-Ray Diffraction (XRD), transmission electron microscope (TEM) and Fourier transform infrared (FTIR). BET surface area analysis was carried out using nitrogen adsorption desorption curves. The results show that TiO2 morphology had great influence on photocatalytic degradation of tetracycline hydrochloride due to difference in specific surface area and pore volume of nanostructures. The photocatalytic degradation experiments were carried out for three hours under visible-LED light. TiO2 nanofibers show better degradation performance than nanotubes and nanospheres due to presence of large surface area for reaction, higher porosity with dispersion of active sites at different length scales of pores and presence of oxygen vacancies. Agricultural biomass pine bark serves as a carbon source and was doped into TiO2-nanofibers (TNF) to fabricate the composite material (CD-TNF). CD-TNF composite nanofibers were prepared via a facile hydrothermal method. This study revealed that the photocatalytic efficiency of tetracycline (TC) under visible light irradiation of the composite nanofiber is higher than that of pure TiO2-nanofiber. The anchored CDs can both enhance the light absorption and suppress photogenerated electron hole recombination which results in the enhancement of catalytic and antibacterial properties. The CDs can better capture and transfer photogenerated electrons through the Ti-O-C and Fe-O-C bonds. Moreover, CDs can improve the utilization of photogenerated electrons and the electrons in CDs are captured by O2 to produce O2•- radicals and the role of O2•- radicals in the photocatalytic process is significantly improved. A new efficient photocatalyst consisting of TiO2/CD/Fe2O3 composite material was Synthesized by the hydrothermal treatment and applied in the photodegradation of 5 mg/L tetracycline hydrochloride (TC) under visible-LED light. The CDs/TiO2/Fe2O3 composite showed enhanced photocatalytic performance for tetracycline photodegradation when compared with TiO2/CDs and pure TiO2 under the visible light irradiation. The mechanism of the improved photocatalytic activity over CDs/TiO2/Fe2O3 was also investigated. The influence of the interface formation between Fe2O3 and TiO2/CDs affects severely the charges separation efficiency and enhances the electron transfer to keep on the existence of Fe3+/Fe2+ moieties that take significant role in the reaction mechanism.

[pt] Os nanomateriais sensíveis à luz visível baseados em TiO2 são amplamente estudados para aplicações fotocatalíticas sob radiação UV-Vis. Entre os mecanismos de sensibilização à luz visível, vacâncias de oxigênio extrínsecas foram introduzidas em TiO2 e complexos de transferência de carga (CTCs) foram formados entre ligantes quelantes, como acetilacetona, e TiO2 nanocristalino ( TiO2-ACAC). Por outro lado, foi encontrado na literatura que o ácido glutárico acoplado à anatase nanocristalina (TiO2-GA) apresenta alta eficiência fotocatalítica sob UV devido à sua alta área superficial. No entanto, a influência das vacâncias de oxigênio extrínsecas no desempenho fotocatalítico dos CTCs à base de TiO2 é desconhecida e a sensibilização do TiO2 à luz visível por funcionalização com ácido glutárico (TiO2-GA) e seu desempenho fotocatalítico sob radiação de luz visível ainda não foram investigados. Neste trabalho, vacâncias de oxigênio extrínsecas de superfície/volume foram introduzidas em TiO2-ACAC através de calcinação a 270 °C sob ar estático, atmosferas de Ar e H2 e nanomateriais de TiO2-GA sensíveis à luz visível foram sintetizados via sol-gel e calcinados sob ar estático a 270 °C. Os CTCs de TiO2-ACAC e TiO2-GA foram caracterizados pelas técnicas de XRPD, FTIR, TGA, DRS, PL, EPR e XPS. Os resultados de FTIR comprovaram a formação do CTC através da interação quelante bidentada entre TiO2 e GA. Os CTCs de TiO2-GA calcinados a 270 °C sob ar estático exibiram uma longa cauda de absorção no espectro de luz visível devido à formação de centros F+ e defeitos Ti3+. A fotodegradação da tetraciclina (TC) usando sequestrantes e a correlação com EPR-spin trapping destacaram o papel fundamental do radical superóxido na degradação da TC pelos CTCs de TiO2-ACAC e TiO2- GA sob radiação de luz visível de baixa potência. O aumento da concentração de vacâncias de oxigênio extrínsecas não foi benéfico para o desempenho fotocatalítico dos CTCs de TiO2-ACAC, uma vez que as vacâncias de oxigênio extrínsecas no volume também atuam como centros de recombinação. De fato, o CTC de TiO2-ACAC com a menor concentração de vacâncias de oxigênio extrínsecas exibiu o maior desempenho fotocatalítico para degradação da TC devido a uma distribuição adequada de vacâncias de oxigênio extrínsecas no volume, o que fez com que os elétrons aprisionados sofressem saltos repetidos, reduzindo as taxas de recombinação e melhorando a eficiência na produção de radicais superóxido. Por outro lado, o alto teor de molécula orgânica de GA ineficientemente ligada à superfície do TiO2 não foi benéfica para o desempenho fotocatalítico dos CTCs de TiO2-GA, uma vez que a molécula orgânica que não é efetivamente ligada à superfície do TiO2 reduziu os sítios ativos na nanoestrutura de TiO2-GA. Nossas descobertas indicaram que os CTCs de TiO2-ACAC e TiO2-GA são capazes de degradar poluentes via interações com buracos eletrônicos e principalmente radicais superóxido e também forneceram informações fundamentais sobre a influência das vacâncias de oxigênio extrínsecas de superfície/volume no desempenho fotocatalítico, parâmetros de rede, propriedades ópticas e fotoquímicas dos CTCs baseados em TiO2. / [en] TiO2-based visible-light-sensitive nanomaterials are widely studied for photocatalytic applications under UV-Vis radiation. Among the mechanisms of visible light sensitization, extrinsic oxygen vacancies have been introduced into TiO2 and charge transfer complexes (CTCs) have been formed between chelating ligands, such as acetylacetone, and nanocrystalline TiO2 (TiO2-ACAC). On the other hand, it was found in the literature that nanocrystalline anatasecoupled glutaric acid (TiO2-GA) exhibits high photocatalytic efficiency under UV due to its high surface area. However, the influence of extrinsic oxygen vacancies on the photocatalytic performance of TiO2-based CTCs is unknown and the sensitization of TiO2 to visible light by functionalization with glutaric acid (TiO2-GA) and its photocatalytic performance under visible light radiation have not yet been investigated. In this work, surface/bulk extrinsic oxygen vacancies were introduced into TiO2-ACAC through calcination at 270 °C under static air, Ar and H2 atmospheres and visible-light-sensitive TiO2- GA nanomaterials were synthesized via sol-gel and calcined under static air at 270 °C. TiO2-ACAC and TiO2-GA CTCs were characterized by XRPD, FTIR, TGA, DRS, PL, EPR and XPS techniques. FTIR results proved the formation of the CTC through bidentate chelating interaction between TiO2 and GA. TiO2-GA CTCs calcined at 270 °C under static air exhibited a long absorption tail in the visible light spectrum due to the formation of F+ centers and bulk Ti3+ defects. Tetracycline (TC) photodegradation using scavengers and the correlation with EPR-spin trapping highlighted the key role of the superoxide radical in the TC degradation by TiO2-ACAC and TiO2-GA CTCs under low-power visible light radiation. The increased extrinsic oxygen vacancies concentration was not beneĄcial for photocatalytic performance of TiO2-ACAC CTCs, since bulk extrinsic oxygen vacancies additionally acts as recombination centers. In fact, the TiO2-ACAC CTC with the lowest extrinsic oxygen vacancies concentration exhibited the highest photocatalytic performance for TC degradation due to an adequate distribution of extrinsic bulk oxygen vacancies, which led to the trapped electrons undergoing repeated hopping, reducing the recombination rates and improving the efficiency in the superoxide radicals production. On the other hand, the high content of GA organic molecule ineffectively bounded to the TiO2 surface were not beneĄcial for photocatalytic performance of TiO2-GA CTCs, since the organic molecule that is not effectively bounded to the TiO2 surface reduced the active sites in the TiO2-GA nanostructure. Our Ąndings indicated that TiO2-ACAC and TiO2-GA CTCs are able to degrade pollutants via interactions with electronic holes and principally superoxide radicals and also, provided fundamental information about the influence of surface/bulk extrinsic oxygen vacancies on photocatalytic performance, lattice parameters, optical and photochemical properties of TiO2- based CTCs.