Nitrogen-doped TiO2 nanotubes with enhanced visible light photocatalytic activity have been synthesized using commercial titania P25 as raw material by a facile P25/urea co-hydrothermal method. Morphological and microstructual characteristics were conducted by transmission electron microscopy, powder X-ray diffraction, and nitrogen adsorption/desorption isotherms; chemical identifications were performed using X-ray photoelectron spectroscopy, and the interstitial nitrogen linkage to the TiO2 nanotubes is identified. The photocatalytic activity of all nitrogen-doped TiO2 nanotubes synthesized by different urea content, evaluated by the decomposition of rhodamine B dye solution under visible light using UV¡VVis absorption spectroscopy, is found to exhibit higher degradation rate than that of P25. Factors affecting the photocatalytic activity of RB were analyzed and a possible mechanism of photodegradation was also proposed. The high photocatalytic activity was attributed to the process of two different mechanisms, one was the direct degradation of the chromophoric system and the other was successive deethylation of the four ethyl groups.

Photocatalysis is an advanced oxidation process for the purification and remediation of contaminated waters and wastewaters, and is advantageous over conventional treatment technologies due to its ability to degrade emerging and recalcitrant pollutants. In addition, photocatalytic disinfection is less chemical-intensive than other methods such as chlorination, and can inactivate even highly resistant microorganisms with good efficacy. Process sustainability and cost-effectiveness may be improved by utilizing solar irradiation as the source of necessary photons for photocatalyst excitation. However, solar-induced activity of the traditionally-used titania is poor due to its inefficient visible light absorption, and recombination of photo-excited species is problematic. Additionally, mass transfer limitations and difficulties separating the catalyst from the post-treatment slurry hinder conversions and efficiencies obtainable in practice. In this research, various strategies were explored to address these issues using novel visible light active photocatalysts. Two classes of carbon-enhanced photocatalytic materials were studied: activated carbon adsorbent photocatalyst composites, and carbon-doped TiO2. Adsorbent photocatalyst composites based on activated carbon and plasmonic silver/silver chloride structures were synthesized, characterized, and experimentally investigated for their photocatalytic activity towards the degradation of model organic pollutants (methyl orange dye, phenol) and the inactivation of a model microorganism (Escherichia coli K-12) under visible light. The adsorptive behaviour of the composites towards methyl orange dye was also studied and described according to appropriate models. Photocatalytic bacterial inactivation induced by the prepared composites was investigated, and the inactivation mechanisms and roles of incorporated antimicrobial silver on disinfection were probed and discussed. These composites were extended towards magnetic removal strategies for post-use separation through the incorporation of magnetic nanoparticles to prepare Ag/AgCl-magnetic activated carbon composites, and the effect of nanoparticles addition on the properties and photoactivities of the resulting materials was explored. Another silver/silver halide adsorbent photocatalyst composite based on activated carbon and Ag/AgBr exhibiting visible light absorption due to both localized surface plasmon resonance and optical band gap absorption was synthesized and its photocatalytic activity towards organics degradation and microbial inactivation was studied. Carbon-doped mixed-phase titania was also prepared and experimentally investigated.

Photocatalysis is an advanced oxidation process for the purification and remediation of contaminated waters and wastewaters, and is advantageous over conventional treatment technologies due to its ability to degrade emerging and recalcitrant pollutants. In addition, photocatalytic disinfection is less chemical-intensive than other methods such as chlorination, and can inactivate even highly resistant microorganisms with good efficacy. Process sustainability and cost-effectiveness may be improved by utilizing solar irradiation as the source of necessary photons for photocatalyst excitation. However, solar-induced activity of the traditionally-used titania is poor due to its inefficient visible light absorption, and recombination of photo-excited species is problematic. Additionally, mass transfer limitations and difficulties separating the catalyst from the post-treatment slurry hinder conversions and efficiencies obtainable in practice. In this research, various strategies were explored to address these issues using novel visible light active photocatalysts. Two classes of carbon-enhanced photocatalytic materials were studied: activated carbon adsorbent photocatalyst composites, and carbon-doped TiO2. Adsorbent photocatalyst composites based on activated carbon and plasmonic silver/silver chloride structures were synthesized, characterized, and experimentally investigated for their photocatalytic activity towards the degradation of model organic pollutants (methyl orange dye, phenol) and the inactivation of a model microorganism (Escherichia coli K-12) under visible light. The adsorptive behaviour of the composites towards methyl orange dye was also studied and described according to appropriate models. Photocatalytic bacterial inactivation induced by the prepared composites was investigated, and the inactivation mechanisms and roles of incorporated antimicrobial silver on disinfection were probed and discussed. These composites were extended towards magnetic removal strategies for post-use separation through the incorporation of magnetic nanoparticles to prepare Ag/AgCl-magnetic activated carbon composites, and the effect of nanoparticles addition on the properties and photoactivities of the resulting materials was explored. Another silver/silver halide adsorbent photocatalyst composite based on activated carbon and Ag/AgBr exhibiting visible light absorption due to both localized surface plasmon resonance and optical band gap absorption was synthesized and its photocatalytic activity towards organics degradation and microbial inactivation was studied. Carbon-doped mixed-phase titania was also prepared and experimentally investigated.

Titanium dioxide(TiO2) is a stable, effective and well-known photocatalyst for degradation of pollutants. However, its practical applications are limited due to the need for energy higher than 3.2 eV, or a wavelength lower than 390 nm (high frequency waves, ultraviolet and above) hindering its ability to effectively work in the visible light region (about 400 nm to 700 nm). Nitrogen-doped TiO2 (N-TiO2) has garnered some attention as a photocatalyst as it appears to work even in the visible light region. This could allow the utilization of a larger part of the solar spectrum. This thesis presents the results of photocatalytic degradation of methylene blue (MB) carried out under simulated visible light by using TiO2 and N-TiO2(doped in the lab) to evaluate and compare their efficiencies under similar conditions.

No description available.

TiO2 nanoparticles are one of the most suitable materials for photocatalysis, specifically for water and air treatment and removal of a wide variety of organic pollutants such as dyes, aromatic compounds, and chlorinated aromatic compounds. Methods of synthesis of TiO2 are generally categorized in two main classes of wet chemical, and dry methods. Wet chemical methods generally provide a better control over size, size distribution, and shape; all of which significantly affect photocatalytic performance of the produced nanoparticles. Despite its advantages over other semiconductor photocatalysts, wide band-gap of titania restrains its photocatalytic activity to only UV light, which only makes up to 5% of the light reaching surface of the earth. To induce visible-light activity, titania has been doped by different dopants, including transition metal-dopants such as Fe, and Co and non-metal dopants such as N, and C. Nitrogen has been shown to be a better dopant, providing a suitably placed energy state within the band-gap of TiO2, and not suffering from issues related to transition-metal dopants such as low thermal and physical stability and high electron-hole recombination rates. To dope titania with nitrogen, one could add the nitrogen source together with other precursors during synthesis, referred to as wet chemical doping methods, or anneal the synthesized titania nanoparticles under a flow of ammonia at high temperatures, referred to as dry doping methods. While different doping methods have been studied individually, the author maintains that there has been an absence of research comparing the effectiveness of these methods, on photocatalytic performance of N-doped TiO2 within a consistent experiment. In this research TiO2 nanoparticles were synthesized by a facile, inexpensive sol-gel method, and doping was done by wet chemical methods, dry methods, and a combination of both these methods. Visible-light photocatalytic activity of these nanoparticles was evaluated by their efficiency in degradation of methyl orange. The results show wet doping methods increase the efficiency of titania nanoparticles more than dry doping, or combination of both. Further investigation showed that the main reason for higher activity of wet chemically doped nanoparticles is due to their higher available surface area of 131.7 m2.g-1. After normalizing the available surface area, measured by the BET method, it was shown that a combination of wet chemical doping, and dry doping at 600 °C result in the most active nanoparticles, but high temperature dry doping severely decreases the surface area, lowering the overall efficiency of the product. Additionally, N-doped TiO2 nanoparticles were synthesized using a simple hydrothermal method, in which the nitrogen source was used not only to dope, but also to control shape, size, size distribution, and morphology of the titania nanoparticles, and to induce aqueous colloidal stability. It was shown that addition of triethylamine during the synthesis, results in ultra-small, colloidally stable, cubic TiO2 nanoparticles, while using triethanolamine results in formation of TiO2 pallets, assembled into spherical, rose-like structures. The synthesized nanoparticles show impressive efficiency in visible-light removal of phenol, 4-chlorophenol, and pentachlorophenol, achieving 100% degradation of a 100-ppm phenol solution in 90 min, more than 98% degradation of a 20-ppm 4-chlorophenol solution in 90 min, and 97% degradation of a 10-ppm pentachlorophenol in 180 min with 500 ppm loading of the catalyst in all cases. Moreover, synthesized nanoparticles showed no sign of deactivation after 5 consecutive runs, removing 4-chlorophenol, showing their reusability. / Graduate

Master of Science / Department of Chemistry / Kenneth J. Klabunde / Although Degussia-Huls P-25 TiO[subscript]2 semiconductor photocatalyst has high photodegradation rate for organic molecules, it works only under ultra-violet (UV) light. Mesoporous metal doped V-MCM-48 silica was synthesized under ambient conditions for use as a visible-light photocatalyst to convert toxic probe molecules to innocuous products: CO[subscript]2 + H[subscript]2O. The synthesis employed a modified Stober metal doped MCM-48 silica method. Powder X-ray diffraction (XRD), diffuse-reflectance-ultra-violet-visible (DR-UV-vis) spectroscopy, and N[subscript]2 adsorption-desorpton analysis characterization methods were completed on V-MCM-48 mesoporous material. These characterization methods indicate V-MCM-48 structure had formed with visible light absorption and mesoporous properties. Photocatalysis studies were completed with V-MCM-48 under dark, visible, and UV-light illumination conditions for the following probe molecules: acetaldehyde, carbon monoxide, ethanol, acetone, 2-propanol, and acetonitrile. Acetaldehyde over V-MCM-48 was converted to CO[subscript]2 under dark, visible, and UV-light conditions. Carbon monoxide photooxidation occurred over V-MCM-48 under visible and UV-light. Ethanol and acetonitrile had smaller photodegradation activity over V-MCM-48. Acetone and 2-propanol had no activity photocatalytically. Under dark and visible light illumination, V-MCM-48 consumed approximately one-half acetaldehyde and produced one-third CO[subscript]2 concentration as compared with the P-25 TiO[subscript]2 under UV-light. V-MCM-48 produced two-thirds of the amount of CO[subscript]2 in comparison to nanoparticle Au/ZnO catalyst under UV-light. The results infer V-MCM-48 might be useful in gas and liquid phase photocatalysis including water-splitting due to a high oxidation state (V[superscript]5+), visible light absorption, and high surface area. In conclusion, an extended literature review has been completed and literature employed extensively throughout the thesis with potential methods to further the research on V-MCM-48/Si-MCM-48 in catalysis, chromatography, adsorption/gas separation, and solar collection/water-splitting.

Microplastics take hundreds to thousands of years to degrade in nature, and pose a threat to the environment. A photocatalytical degradation method have been developed to take advantage of solar light to degrade microplastics, however it takes several months to degrade microplastics with the process. The purpose of this study is to enhance the degradation rate of microplastics by synthesizing a material where photocatalysis is combined with Fenton reaction. A material with zinc oxide nanorods coated with tin oxide and decorated with iron particles (𝑍𝑛𝑂/𝑆𝑛𝑂2/𝐹𝑒0) was synthesized and used to degrade methylene blue, polystyrene and polypropylene. The result show that the degradation rate with a 𝑍𝑛𝑂/𝑆𝑛𝑂2/𝐹𝑒0 – sample is faster than with a 𝑍𝑛𝑂 – sample, and that it can be used to degrade polystyrene and polypropylene.Students’ view on researchers can affect the development of their interest and attitude towards science. Study visits to laboratories have been used to increase students’ interest and give them new experiences. The purpose of this study is to investigate what and how high school students learn during a study visit to a nanotechnology laboratory, and how the study visit affects high school students’ interest and motivation for research and learning. A study visit with 5 stations was organized, and students were given a questionnaire about what they learned during the study visit. Thematic analysis was used to analyze the students’ answers. The result shows that the study visit increased students’ interest in research, and the importance of designing stations so that they are connected to students’ previous knowledge and are within their proximal development zone. / Mikroplaster tar hundratals till tusentals år att bryta ner i naturen och utgör ett hot mot miljön. En fotokatalytisk nedbrytningsprocess har utvecklats där solljus utnyttjas för att bryta ner mikroplaster, dock tar det flera månader att bryta ner mikroplaster med den processen. Syftet med denna studie är att förbättra nedbrytningshastigheten av mikroplaster genom att syntetisera ett material där fotokatalys kombineras med Fenton-reaktion. Ett material med zinkoxid nanorör belagda med tennoxid och dekorerade med järnpartiklar (𝑍𝑛𝑂/𝑆𝑛𝑂2/𝐹𝑒0) syntetiserades och användes för att bryta ner metylenblått, polystyren och polypropen. Resultatet visar att nedbrytningshastigheten med 𝑍𝑛𝑂/𝑆𝑛𝑂2/𝐹𝑒0 – materialet är snabbare än med ett 𝑍𝑛𝑂 – material, och att 𝑍𝑛𝑂/𝑆𝑛𝑂2/𝐹𝑒0 – materialet kan användas för att bryta ned polystyren och polypropen.Elevers syn på forskning och forskare kan påverka utvecklingen av deras intresse och inställning till vetenskap. Studiebesök på laboratorier har använts för att öka elevernas intresse och ge dem nya erfarenheter. Syftet med denna studie är att undersöka vad och hur gymnasieelever lär sig under ett studiebesök i ett nanotekniklaboratorium och hur studiebesöket påverkar gymnasieelevernas intresse och motivation för forskning och lärande. Ett studiebesök med 5 stationer organiserades och eleverna fick ett frågeformulär om vad de lärde sig under studiebesöket. Tematisk analys användes för att analysera elevernas svar. Resultatet visar att studiebesöket ökade elevernas intresse för forskning och vikten av att utforma stationer så att de är kopplade till elevernas tidigare kunskaper och ligger inom deras proximala utvecklingszon.