Since the highly cited paper by Purcell postulating the “Scallop theorem” almost 50 years ago, asymmetry is an unavoidable part of micromotors. It is frequently induced by self-shadowing or self-masking, resulting in so-called Janus colloids. This strategy works very reliably, but turns into a bottleneck once up-scaling becomes important. Herein, existing alternatives are discussed and a novel synthetic pathway yielding active swimmers in a one-pot synthesis is presented. To understand the resulting mobility from a single material, the geometric asymmetry is evaluated using a python based algorithm and this process is automated in an open access tool.

This article presents nano composite TiO2.Fe2O3/laterite materials, which were successfully prepared by hydrometallurgical method. The materials were modified using urea as the nitrogen source. The particles size of the materials is from 20-30 nanometers. The obtained materials can not only absorb arsenic compounds but also enhance the ability of converting As (III) or As (V) into Aso, which is removed from solution. Arsenic removal efficiency of these materials is high. Using sunlight in a hydraulic retention time, about 180 minutes, the arsenic value at the inflow was about 10 mg/L but the outflow was negligible. Covering TiO2.Fe2O3 nano on laterite have brought high economical efficiency, on one hand, it saved material and on the other hand, it can be continuously operated without the centrifugal separation of the nano material. / Bài báo này giới thiệu về phương pháp điều chế vật liệu nano TiO2.Fe2O3 biến tính nitơ được phủtrên đá ong bằng phương pháp thủy luyện. Vật liệu nano thu được có kích thước 20-30 nm. Vật liệu thu được không những có khả năng hấp phụ các hợp chất của asen mà còn có khả năng khử As (III) hoặc As (V) thành Asokhi được chiếu sáng. Sử dụng ánh sáng mặt trời chiếu vào hệ thống xử lý trong thời gian 180 phút có thể loại bỏ được gần như hoàn toàn asen ra khỏi nước mặc dù hàm lượng đầu vào là 10 mg/l. Việc phủ vật liệu TiO2.Fe2O3 nano lên đá ong đã mang lại hiệu quả kinh tế cao, một mặt nó tiết kiệm được vật liệu, mặt khác, vật liệu có thể sử dụng một cách liên tục mà không cần phải tách bằng phương pháp ly tâm.

No description available.

[ES] En la última década, las crecientes necesidades de protección del medio ambiente han estimulado la investigación en el campo de la fotocatálisis. La contaminación del agua por productos químicos orgánicos, tintes textiles y productos farmacéuticos constituye un peligro cada vez más dañino para el medio ambiente, la salud humana y la vida acuática. Para solucionar este problema y luchar contra la contaminación del agua, varios grupos de investigación han demostrado la utilidad del uso de dióxido de titanio TiO2 como un prometedor fotocatalizador no tóxico y de bajo coste para la fotodegradación de contaminantes. Obviamente, como cualquier otro material, el TiO2 tiene limitaciones en varias áreas de aplicación debido a su ancho de banda prohibida, que limita su rango de absorción a los rayos UV. Esto nos incita a asociarlo a semiconductores de banda prohibida baja como PbS. En este trabajo se asociaron nanopartículas de PbS a nanotubos de TiO2 (NTs) para mejorar su actividad fotocatalítica en el visible. Comenzamos nuestro trabajo optimizando la deposición de micro/nanoestructuras de PbS mediante el método hidrotermal mientras estudiamos la influencia de los parámetros de deposición en las propiedades morfológicas y estructurales de las micro/nanoestructuras de PbS de diferentes formas. Inicialmente, la atención se centró en optimizar los parámetros para sintetizar nanopartículas de PbS a partir de microestructuras mediante un simple cambio del precursor aniónico (fuente de S2-). Posteriormente, se realizó un estudio sobre el efecto de la concentración del precursor en la calidad de las nanopartículas de PbS. A continuación, se estudió la influencia de la decoración de las NP de PbS en las propiedades físicas, ópticas y estructurales de las NT de TiO2. Demostramos la efectividad de la técnica SILAR para la realización de heteroestructuras {NPs PbS}n - NTs TiO2, que son adecuadas para la integración en dispositivos fotocatalíticos. Hemos demostrado que la calidad de la estructura cristalina, el tamaño de los cristales y las propiedades ópticas de los sistemas fabricados dependen del número de ciclos SILAR "n" y de la distribución y tamaño de las NP de PbS depositadas por SILAR. Finalmente, se presentó el estudio cinético de la actividad fotocatalítica de NTs de TiO2 puras y decoradas con NPs de PbS para la fotodegradación de antibióticos (tetraciclina) bajo irradiación UV. Primero, encontramos que el sistema PbS NPs/TiO2 NTs es efectivo para la fotodegradación de tetraciclina (TC), con una degradación óptima para un número de ciclo SILAR de deposición de PbS igual a 5. Segundo, estudiamos la actividad fotocatalítica de TiO2 NTs puros en una solución acuosa de TC bajo luz ultravioleta. Después de optimizar las condiciones experimentales, logramos una fotodegradación de aproximadamente el 99% de la tetraciclina después de 5 horas de irradiación. Además, hemos demostrado que el fotocatalizador es estable y podría usarse con éxito durante al menos cinco ciclos sucesivos sin una pérdida significativa de rendimiento. Estos resultados sugieren que el fotocatalizador PbS NPs/TiO2 NTs es un sistema efectivo y prometedor para la purificación de agua. Además, con base en los resultados de las pruebas de atrapamiento, propusimos un mecanismo de fotodegradación que muestra que la capacidad de las NT de TiO2 para oxidar el antibiótico se debe principalmente a los agujeros fotogenerados, así como a los radicales hidroxilo (OH), que se consideran como agentes oxidantes primarios que actúan no solo en la superficie sino también en solución. / [CA] A la darrera dècada, les creixents necessitats de protecció del medi ambient han estimulat la recerca en el camp de la fotocatàlisi. La contaminació de l'aigua per productes químics orgànics, tints tèxtils i productes farmacèutics constitueix un perill cada cop més nociu per al medi ambient, la salut humana i la vida aquàtica. Per solucionar aquest problema i lluitar contra la contaminació de l'aigua, diversos grups de recerca han demostrat la utilitat de l'ús de diòxid de titani TiO2 com un prometedor fotocatalitzador no tòxic i de baix cost per a la fotodegradació de contaminants. Òbviament, com qualsevol altre material, el TiO2 té limitacions en diverses àrees d'aplicació a causa de la seva amplada de banda prohibida, que limita el seu rang d'absorció als raigs UV. Això ens incita a associar-ho a semiconductors de banda prohibida baixa com a PbS. En aquest treball es van associar nanopartícules de PbS a nanotubs de TiO2 (NTs) per millorar la seva activitat fotocatalítica en l'espectre visible. Comencem el nostre treball optimitzant la deposició de micro/nanoestructures de PbS mitjançant el mètode hidrotermal mentre estudiem la influència dels paràmetres de deposició en les propietats morfològiques i estructurals de les micro/nanoestructures de PbS de diferents formes. Inicialment, l'atenció es va centrar a optimitzar els paràmetres per sintetitzar nanopartícules de PbS a partir de microestructures mitjançant un simple canvi del precursor aniònic (font de S2-). Posteriorment, es va fer un estudi sobre l'efecte de la concentració del precursor en la qualitat de les nanopartícules de PbS. A continuació, es va estudiar la influència de la decoració de les NP de PbS a les propietats físiques, òptiques i estructurals de les NT de TiO2. Hem demostrat l'efectivitat de la tècnica SILAR per a la realització d'heteroestructures {NPs PbS}n - NTs TiO2, que són adequades per a la integració en dispositius fotocatalítics. Hem demostrat que la qualitat de l'estructura cristal´lina, la mida dels cristals i les propietats òptiques dels sistemes aconseguits depenen del nombre de cicle SILAR "n" i la distribució de mida de les NP de PbS dipositades per SILAR. Finalment, es presenta un estudi cinètic de l'activitat fotocatalítica de NTs de TiO2 pures i decorades amb NPs de PbS per a la fotodegradació d'antibiòtics (tetraciclina) sota irradiació UV. Primer, trobem que el sistema PbS NPs/TiO2 NTs és efectiu per a la fotodegradació de tetraciclina (TC), amb una degradació òptima per a un nombre de cicle SILAR de deposició de PbS igual a 5. Segon, estudiem l'activitat fotocatalítica de TiO2 NTs purs en una solució aquosa de TC sota llum ultraviolada. Després d'optimitzar les condicions experimentals, aconseguim una fotodegradació d'aproximadament el 99% de la tetraciclina després de 5 hores d'irradiació. A més, hem demostrat que el fotocatalitzador és estable i es podria fer servir amb èxit durant almenys cinc cicles successius sense una pèrdua significativa de rendiment. Aquests resultats suggereixen que el fotocatalitzador PbS NPs/TiO2 NT és un sistema efectiu i prometedor per a la purificació d'aigua. A més, amb base en els resultats de les proves de captura, vam proposar un mecanisme de fotodegradació que mostra que la capacitat de les NT de TiO2 per oxidar l'antibiòtic es deu principalment als forats fotogenerats, així com als radicals hidroxil (OH), que es consideren .com a agents oxidants primaris que actuen no només a la superfície sinó també en solució. / [EN] The increasing needs for environmental protection have strongly stimulated research in the field of photocatalysis in recent years. Contamination of water by organic chemicals, textile dyes and pharmaceuticals constitute an increasingly harmful hazard to the environment, human health, and aquatic life. To solve this problem and fight water pollution, several research groups have demonstrated the usefulness of using titanium dioxide TiO2 as a promising low-cost non-toxic photocatalyst for the photodegradation of contaminants. Obviously, like any other material, TiO2 has limitations in several areas of application because of its wide band gap, which limits its absorption range to UV. This incites us to associate it to low band gap semicondors such as PbS. In this work, PbS nanoparticles were associated to TiO2 nanotubes (NTs) to improve their photocatalytic activity in the visible. We started our work by optimizing the deposition of PbS micro-nanostructures by the hydrothermal method while studying the influence of deposition parameters on the morphological and structural properties of the different shaped PbS micro-nanostructures. Initially, the focus was on optimizing parameters to synthesize PbS nanoparticles from microstructures by a simple change of the anionic precursor (source of S2-). Subsequently, a study was conducted on the effect of the precursor concentration on the quality of PbS nanoparticles. Next, we also studied the influence of PbS NPs decoration on the physical, optical and structural properties of TiO2 NTs. We demonstrated the effectiveness of the SILAR technique for the realization of {NPs PbS}n - NTs TiO2 heterostructures, which are suitable for integration into photocatalytic devices. We have shown that the quality, crystal structure, crystallite size and optical properties of the achieved systems depend on the SILAR cycle number ''n'' and the size distribution of the SILAR-deposited PbS NPs. Finally, the kinetic study of the photocatalytic activity of pure TiO2 NTs and decorated with PbS NPs for the photodegradation of antibiotics (tetracycline) under UV irradiation was presented. First, we found that the PbS NPs/TiO2 NTs system is effective for the photodegradation of tetracycline (TC), with an optimum degradation for a SILAR cycle number of PbS deposition equal to 5. Second, we studied the photocatalytic activity of pure TiO2 NTs in an aqueous TC solution under UV light. After optimizing the experimental conditions, we achieved a photodegradation of approximately 99% of tetracycline after 5 hours of irradiation. In addition, we have shown that the photocatalyst is stable and could be used successfully for at least five successive cycles without any significant loss of performance. These results suggest that the PbS NPs/TiO2 NTs photocatalyst is an effective and promising system for water purification. In addition, based on the results of the trapping tests, we proposed a photodegradation mechanism that shows that the ability of the TiO2 NTs to oxidize the antibiotic is mainly due to the photogenerated holes as well as the hydroxyl (OH) radicals, which are considered as primary oxidizing agents acting not only on the surface but also in solution. / Jemai, S. (2022). Élaboration et étude optoélectronique des nanotubes d'oxydes métalliques décorés par des nanoparticules de PbS et/ou CdS pour applications environnementales et photovoltaïques [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191332

Master of Science / Department of Chemistry / Jun Li / With the increasing consumption of energy and the depletion of fossil fuels, finding an alternative energy source is critical. Solar energy is one of the most promising energy sources and solar cells are the devices that convert solar radiation into electricity. Currently, the most widely used solar cell is based on p-n junction formed with crystalline silicon materials. While showing high efficiency, the high fabrication cost limits its broad applications. Dye sensitized solar cell (DSSC) is a promising low-cost alternative to the Si solar cell, but its efficiency is much lower. Improvements in materials and interfaces are needed to increase the DSSC efficiency while maintain the low cost. In this thesis, three projects were investigated to optimize the DSSC efficiency and reduce the cost. The first project is to optimize the TiO[subscript]2 barrier layers on Fluorine-doped Tin Dioxide (FTO) surface. Two preparation methods, i.e. TiCl[subscript]4 solution treatment and thermal oxidation of sputtered Ti metal films, were employed and systematically studied in order to minimize electron-hole recombination and electron backflow during photovoltaic processes of DSSCs. TiCl[subscript]4 solution treatment method was found to create a porous TiO[subscript]2 barrier layer. Ti sputtering method created a very compact TiO[subscript]2 blocking layer. Two methods showed different characteristics and may be used for different DSSC studies. The second project is to reduce the DSSC cost while maintaining the efficiency by replacing the expensive Pt counter electrode with a novel vertically aligned carbon nanofiber (VACNF) electrode. A large specific electrode surface area (~125 cm[superscript]2 over 1 cm[superscript]2 geometric area) was obtained by using VACNFs. The relatively high surface area, good electric conductivity and the large numbers of active graphitic edges existed in cone-like microstructure of VACNFs were employed to improve redox reaction rate of I[subscript]3[superscript]-/I[superscript]- mediators in the electrolyte. Faster electron transfer and good catalytic activities were obtained with such counter electrodes. The third project is to develop a metal organic chemical vapor deposition (MOCVD) method to coat TiO[subscript]2 shells on VACNF arrays as potential photoanodes in the DSSC system in order to improve the electron transfer. Fabrication processes were demonstrated and preliminary materials were characterized with scanning electron microscopy and transmission electron microscopy. MOCVD at 300 mTorr vapor pressure at 550° C for 120 min was found to be the optimal condition.

Les matériaux composites sont utilisés dans beaucoup de domaines pour leurs propriétés mécaniques spécifiques, leur mise en forme facile et leur bas coût. Cependant, lorsque les composites pétro-sourcées sont en fin de vie, le traitement des déchets a un fort impact environnemental. C’est pour cette raison que les industriels se tournent vers des matériaux bio-sourcés. Ils souhaitent ainsi abaisser le coût des matières premières mais aussi se donner une image plus « verte » grâce à l’utilisation de matériaux renouvelables et/ou compostables. Le projet présenté s’inscrit dans dans cette optique où il est question d’élaborer de nouveaux composites à renfort et matrices bio-sourcés et tout particulièrement des composites fibre de lin/acide polylactique (PLA). Ces derniers sont généralement appelés bio-composites. L’originalité de cette étude réside dans le traitement des fibres de lin afin de les compatibilité avec la matrice PLA. Le traitement consiste au greffage de dioxyde de titane sur la surface de fibres de lin fonctionnalisée par oxydation au TEMPO. Ces fibres longues sont ensuite utilisées comme renfort sous forme de tissu unidirectionnel dans la matrice PLA. Le comportement mécanique en traction, flexion et la résistance à l’impact de ces biocomposites sont étudiés afin d’analyser l’influence du traitement des fibres sur leur performances.

Nanotubes (inner diameter of 8nm and outer diameter of 10nm with a length of up to several hundred nm) and nanowires (diameter 20 – 50nm and up to several μm in length) of TiO₂-B have been synthesised and characterised for the first time. These exhibit excellent properties as a host for lithium intercalation and are able to accommodate lithium up to a composition of Li₀.₉₈TiO₂-B for the nanotubes and Li₀.₈₉TiO₂-B for the nanowires. Following some irreversible capacity on the first cycle, which could be reduced to 4% for the nanowires, capacity retention for the nanowires is 99.9% and for the nanotubes is 99.5% per cycle. In both cases, the cycling occurs at ~1.6V versus lithium. The cycling performance was compared with other forms of bulk and nano-TiO₂, all of which were able to intercalate less lithium. Nanowires of VO₂-B (50 – 100nm in diameter and up to several μm in length) were synthesised by a hydrothermal reaction and characterised. By reducing the pressure inside the hydrothermal bomb, narrower VO₂-B nanowires with a diameter of 2 – 5nm and length of up to several hundred nm were created - some of the narrowest nanowires ever made by a hydrothermal reaction. These materials are isostructural with TiO₂-B and were also found to perform well in rechargeable lithium ion batteries, being able to intercalate 0.84Li for the ultra-thin nanowires and 0.57Li for the standard nanowires. The standard VO₂-B nanowires have a capacity retention of 99.8% and the ultra-thin nanowires have 98.4% per cycle after some irreversible capacity on the first cycle. This was found to improve markedly when different electrolytes were used. Macroporous Co₃O₄ (pore size 400nm with a surface area of 208m²/g) was prepared and cycled in rechargeable lithium cells with capacities of 1500mAh/g being achieved. The structure was found to break down on the first cycle and after this the material behaved in the manner of Co₃O₄ nanoparticles. Finally a new candidate for next generation rechargeable lithium batteries was examined; Li/O₂ cells. The cathode is composed of porous carbon in which Li⁺, e⁻ and O₂ meet to form Li₂O₂ on discharge. The reaction is reversible on charge. Capacities of 2800mAh/g can be achieved when 5%mole of αMnO₂ nanowires catalyst is used. Fade is high at 3.4% per cycle meaning that there is much work to do to develop these into a commercial prospect.

<p>   Contamination of surface and ground water from industrial wastes and anthropogenic activities represents one of the greatest challenges to the sustainable development of human society. Heterogeneous photocatalysis, a kind of advanced oxidation process characterized by the production of highly oxidative hydroxyl radicals, is a relatively novel subject with tremendous potential in water treatment applications.</p><p>    The purpose of this research was first to develop feasible hydroxyl radical detection methods, which can be used to evaluate efficiency of photocatalytic process, and second to prepare immobilized TiO2 films with high photocatalytic activities by the sol gel method.</p><p>    The feasibility of Indigo carmine and phthalic hydrazide as OH-radical probes was investigated. The organic dye Indigo carmine absorbs visual light strongly at 610 nm and its destruction can be monitored conveniently in a spectrophotometer. Results showed that both ^·OH and HO₂^·can bleach Indigo carmine, and the bleaching yield of ^·OH was pH independent. The photocatalytic dye bleaching in black light UV illuminated Degussa P25 TiO2 aerated suspensions was then investigated. A strong pH dependency of the bleaching yield was found.  This implies that the quantum yield of OH radical at pH 3 is one fourth compared to that at pH 10. The reaction of the OH radical with phthalic hydrazide will form strongly chemiluminescent 3-hydroxyphthalic hydrazide. Using the more specific phthalic hydrazide as OH radical probe, an even stronger pH dependent quantum yield of OH radical was found. At pH 10 the quantum yield reached the same magnitude as that obtained by using Indigo carmine, whereas the quantum yields at acidic pH were close to zero. However it was found that the addition of phosphate and fluoride anions can substantially enhance the OH radical yield at acidic pH by blocking the adsorption of phthalic hydrazide onto the TiO2 surfaces. Hence the adsorption of phthalic hydrazide to TiO2 is an important factor to consider when this method is used. <em></em></p><p>    Photocatalytic TiO2 films coated on metal plates were prepared by a sol gel method using titanium isopropoxide as TiO2 precursor and isopropanol as solvent. The photocatalytic activity of the obtained films was evaluated by bleaching of indigo carmine at pH 9 under black light UV irradiation. The effect of the molar ratio of isopropanol, water and hydrochloric acid to titanium isopropoxide was studied. It was also shown that the activities of TiO2 films are considerably influenced by calcination temperature, coating cycles and the supporting materials.</p> / <p>    Förorening av yt- och grundvatten från industrier och humana aktiviteter utgör en av de största utmaningarna för en hållbar utveckling av det mänskliga samhället. Heterogen fotokatalys, en slags avancerad oxidations process som kännetecknas av att starkt oxidativa hydroxylradikaler produceras, är en relativt ny teknik med stor potential för vattenrening.</p><p>    Ett syfte med detta licentiatarbete var först att utveckla och genomföra olika metoder för att detektera bildningen av hydroxylradikaler såväl i laboratoriet som i tekniska miljöer. Det andra syftet med arbetet var att syntetisera immobiliserade TiO2 filmer med hög fotokatalytisk effektivitet med en sol-gel metod.</p><p>    Möjligheten att använda indigokarmin och ftalhydrazid som OH-radikalprob undersöktes. Det organiska färgämnet indigokarmin absorberar synligt ljus starkt vid 610 nm vilket gör att dess nedbrytning lätt kan följas i en spektrofotometer. Resultaten av gammaradiolys visade att båda ^•OH och HO₂^• kan bleka indigokarmin och att den blekning som härrör från ^•OH var oberoende av pH. Fotokatalytisk blekning av indigokarmin med blacklight UV bestrålning av  Degussa P25 TiO2 suspensioner undersöktes sedan. Ett starkt pH-beroende av blekningsutbytet erhölls vilket tolkas som att kvantutbytet av OH-radikaler vid pH 3 är en fjärdedel jämfört med det vid pH 10.</p><p>    När ftalhydrazid reagerar med OH-radikaler bildas starkt kemiluminiscent 3-hydroxy-ftalhydrazid. Med denna  specifika OH-radikalprob, erhölls ett ännu starkare pH beroende. Vid pH 10 var kvantutbytet i paritet med det som erhölls med indigokarmin, medan kvantutbytet vid lågt pH var nära noll. Tillsats av fosfat-  och fluoridjoner visade sig avsevärt öka OH-radikalutbytet vid lågt pH-värde genom att blockera adsorption av ftalhydrazid på TiO2 ytorna. Adsorptionen av ftalhydrazid på TiO2 är således en viktig faktor när denna metod används.</p><p>    Fotokatalytiskt verksamma TiO2-filmer på metallplattor framställdes med sol-gel metoden med titan-isopropoxide som TiO2-prekursor och isopropanol som lösningsmedel. Den fotokatalytiska aktiviteten av TiO2-belagda plattor utvärderades genom blekning av indigokarmin vid pH 9 under blacklight UV-bestrålning. Effekten av olika proportioner mellan isopropanol, vatten och saltsyra till titan isopropoxide undersöktes. Det visade sig att denfotokatalytiska aktiviteten av TiO2-plattorna i hög grad påverkades av kalcineringstemperatur, beläggningscykler och materialet i plattorna.</p>

This work presents a new low-temperature fabrication process of metal oxide nanostructures that allows high-aspect ratio zinc oxide (ZnO) and titanium dioxide (TiO2) nanowires and nanotubes to be readily integrated with microelectronic devices for sensor applications. This process relies on a new method of forming a close-packed array of self-assembled high-aspect-ratio nanopores in an anodized aluminum oxide (AAO) template in a thin (2.5 µm) aluminum film deposited on a silicon and lithium niobate substrate (LiNbO3). This technique is in sharp contrast to traditional free-standing thick film methods and the use of an integrated thin aluminum film greatly enhances the utility of such methods. We have demonstrated the method by integrating ZnO nanowires, TiO2 nanowires, and multiwall TiO2 nanotubes onto the metal gate of a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), and the delay line of a surface acoustic wave (SAW) device to form an integrated ChemFET (Chemical Field-Effect Transistor) and a orthogonal frequency coded (OFC) SAW gas sensor. The resulting metal oxide nanostructures of 1-1.7 µm in height and 40-100 nm in diameter offer an increase of up to 220X the surface area over a standard flat metal oxide film for sensing applications. The metal oxide nanostructures were characterized by SEM, EDX, TEM and Hall measurements to verify stoichiometry, crystal structure and electrical properties. Additionally, the electrical response of ChemFETs and OFC SAW gas sensors with ZnO nanowires, TiO2 nanowires, and multiwall TiO2 nanotubes were measured using 5-200 ppm ammonia as a target gas at room temperature (24ºC) showing high sensitivity and reproducible testing results.

Titanium dioxide (TiO2) attracts extensive attention due to its widespread technological and environmental applications. This study seeks to investigate the surface charging behavior of the two TiO2 polymorphs, anatase and rutile, using Flow Adsorption Microcalorimetry (FAMC). FAMC allows direct quantitative measurement of the heat of a surface reaction; these calorimetric heats are directly proportional to the surface charge. Determining the magnitude of positive and negative charges at the surface over a range of pHs allows for the determination of the point of zero net charge (PZNC) via a unique calorimetric method that removes many of the shortcomings related to the other analytical techniques used for such measurements.