Fabrication and applications of multifunctional nanostructured TiO2

Nanomaterials development is a rapidly emerging field of research with enormous potential for societal and economic benefits. In agro and food industries dimension-dependent properties or phenomena of nanomaterials may be used for various functional effects such as increased bioavailability or decreased toxicity of products, better detection of pathogens, improved food packaging materials, or improved delivery of nutrients. Since these effects may derive from altered or unique characteristics of materials in the nanoscale range that are not normally observed or expected in larger-scale materials with the same chemical composition, such changes raise questions about the safety, effectiveness, performance, quality or public health impact of nanotechnology products. In this article, we have reviewed the fabrication, properties, and selected applications of nanostructured TiO2 based materials. Special attention has been paid to TiO2 nanoparticles and nanotubes fabrication perspectives and applications in agriculture. We have shown that high photocatalytic disinfection and photobiological effects of nanostructured TiO2 coupled with its low price, nontoxicity, and stable performance especially provide new approaches for solving environmental pollution and pesticide residue problems in agriculture.Paper: [https://hdl.handle.net/21.15107/rcub_dais_5121

Photocatalytic activity of N-TiO2 nanotubes decorated with CdS QD

The negative consequences of the modern world are environmental pollution. To decrease it, a lot of research is focused on finding solution for its remediation. Photoactive materials have ability to utilize solar energy for the degradation of organic and inorganic pollutants. Among different photoactive material TiO2 has advantages due to its non-toxicity, chemical stability and corrosion resistance. The aim of this study was to investigate the synergetic effect of nitrogen incorporation into crystal structure of TiO2 and deposition of CdS onto amelioration of the photocatalytic degradation of methylen orange compared to the pristine TiO2. For that purpose TiO2 nanotubes were obtained by anodization of titanium foil in HF containing electrolyte. To achieve crystal structure and at the same time to introduce nitrogen in TiO2, the samples were annealed in ammonia atmosphere at 450 °C, for different time of annealing. The highest amount of nitrogen was achieved for the shortest time of annealing (30 min). Beside that, it was observed that the highest level of interstitial nitrogen was also achieved for the shortest time of annealing. Further, CdS quantum dots (QDs) were deposited on the nitrogen doped TiO2 nanotubes via an ex-situ method (using binding reagent). According to the FESEM micrographs, a partial agglomeration of CdS QDs on some domaines on top of the nanotubes was observed. By performing the DRS, the improvement of the optical response after nitrogen doping and deposition of CdS was demonstrated. The sample with the highest amount of total nitrogen and interstitial nitrogen in combination with deposition CdS QDs exhibited the highest photocatalytic efficiency

ToF-ERDA/RBS analysis of annealed TiO2 nanotubes grown onto FTO glass

Different semiconductors have been studied as photoanode material for solar cells. Among them, TiO2 has been shown to be the best material due to its chemical stability and good charge transport capability. It is usually deposited onto FTO glass (F-SnO2), and then heated at high temperature in order to obtain inter-crystalline electric contact for improving electron conductivity. The focus of this research was chemical analysis of the TiO2 nanotubes (NTs) obtained by anodization of titanium film on FTO glass using NH4F in ethylene glycol electrolyte. There are only few studies suggesting that the electrolyte is a source of N dopant in TiO2, but also Sn diffusion from FTO support was reported. This study aims to show the chemical distribution of elements of interest along the nanotubes depth. For that purpose the time-of-flight elastic recoil detection analysis (ToF-ERDA) and Rutherford backscattering (RBS) methods were used as complementary techniques for chemical analysis of both light, such is N, and heavy elements, such is Sn. The TiO2 NTs films were annealed at different temperatures (450– 630 °C) and the impact of the heating temperature on the chemical distribution was followed

Customizing nanotubular titania for photocatalytic activity

Semiconductor TiO2 photocatalysis is a heterogeneous catalysis, where the photons of the sun or artificial light source are activating the catalyst that enters in reactions. The targeted real-world applications are in environmental protection and remediation such as wastewater treatment, air purification and decomposition of harmful organic pollutants. In this talk, I present the synthesis of nanotubular, thin TiO2 coatings with altered morphology and crystallinity made by anodization technique. The influence of the anodization parameters and post-synthesis annealing conditions on the photocatalytic methyl orange dye decomposition was assessed. Different morphology, crystallinity and introducing a dopant into lattice increase electron transport and electron lifetime which further improve photocatalytic activity

TiO2 nanotubes film/FTO glass interface: Thermal treatment effects

Pure Ti films deposited by radio-frequency magnetron sputtering on FTO glass were anodized to fabricate TiO2 nanotubes (NTs) arrays. The TiO2 NTs/FTO samples were sintered at 450, 550 and 630°C, in ambient air. The thermal treatment did not influence the crystal phase composition, preserving in all cases the anatase single phase. As expected, the crystalline anatase quality improved with the annealing temperature. Nevertheless, slight differences in nanotubular morphology, such as the appearance of grains inside the walls, were observed in the case of the sample sintered at 630°C. Chemical analysis by X-ray Photoelectron Spectroscopy of annealed samples revealed the presence of Sn inside TiO2 NTs, due to diffusion of Sn from the substrate to TiO2. For the substrate was used FTO glass whose top layer consists of SnO2 doped with F. Rutherford Backscattering Spectrometry and Time-of-Flight Elastic Recoil Detection Analysis were carried out to study the elemental depth profile of the films. It was found that the temperature of sintering controls the Sn diffusion inside TiO2 film. Sn atoms diffuse towards the TiO2 NTs surface for the samples annealed at 450 and 550°C. The diffusion is however hindered in the case of the heat treatment at 630°C. Besides, the Ti diffusion into the SnO2 underlayer was observed, together with the formation of TiO2/SnO2 interfaces. One then expected but not a great difference in absorption between samples, since all contained anatase phase, as confirmed by Diffuse Reflectance Spectroscopy. A higher amount of Sn was however detected for the sample annealed at 550°C, which accounts for a slight red absorption shift. The importance of controlling the annealing parameters of the anodized TiO2/FTO structures was highlighted through the formation of TiO2-SnO2 interfaces and the Sn insertion from FTO, which can play an essential role in increasing the photoperformances of TiO2 NTs/FTO based structures of photovoltaic cells

PRIMENA NANOČESTICA SEPIOLITA ZA DOBIJANJE PAPIRA POBOLJŠANIH MEHANIČKIH SVOJSTAVA

Tehničko rešenje koje se odnosi na primenu nanočestičnog sepiolita za poboljšanje mehaničkih svojstava papira proizvedenog u Fabrici Hartije Beograd je uspešno realizovano kroz laboratorijska ispitivanja i industrijsku probu. U laboratorijskim uslovima praćenjem promene viskoznosti disperzija skroba sa različitim udelom sepiolita utvrđeno je da dodatak sepiolita menja prirodu disperzije od dilatantnog, preko njutnovskog do pseudoplastičnog fluida. Skenirajuća elektronska mikroskopija je pokazala da su sepiolitska nanovlakna homogeno dispergovana na površini papira. Prisustvo sepiolita je uticalo na povećanje gramature papira. Ispitivanjem mehaničkih svojstava uzoraka papira utvrđeno je da se sa povećanjem sadržaja sepiolita u disperziji skroba povećava vrednosti otpornosti na pucanje i otpornosti na pritisak. U industrijskim uslovima takođe dolazi do poboljšanja mehaničkih svojstava papira što otvara mogućnost primene nanočestičnog sepiolita u proizvodnji ambalažnog papira u Fabrici Hartije Beograd.Tehničko rešenj

Influence of Synthesis Parameters on Structure of 1-D TiO2 nanostructures

The influence of electrochemical conditions and the heat treatment on the crystal structure and the microstructure evolution of TiO2 based nanotubes synthesized by the self-ordering anodization process is investigated in this work. The electrochemical anodization was performed at room temperature, for 30 minutes under 15, 20 and 25 V, with stirring. The as-anodized Ti foils were annealed in air at 450, 600, 650 and 700 °C for 30 minutes. The structure and the lattice dynamics of the samples has been studied by using XRD and Raman spectroscopy methods. The microstructure development of the 1-D TiO2 nanostructures has been analyzed by FESEM

Influence of Synthesis Parameters on Structure of 1-D TiO2 nanostructures

The influence of electrochemical conditions and the heat treatment on the crystal structure and the microstructure evolution of TiO2 based nanotubes synthesized by the self-ordering anodization process is investigated in this work. The electrochemical anodization was performed at room temperature, for 30 minutes under 15, 20 and 25 V, with stirring. The as-anodized Ti foils were annealed in air at 450, 600, 650 and 700 °C for 30 minutes. The structure and the lattice dynamics of the samples has been studied by using XRD and Raman spectroscopy methods. The microstructure development of the 1-D TiO2 nanostructures has been analyzed by FESEM

Poboljšanje apsorpcionih svojstava fotoanode na bazi nanocevi titan(IV)-oksida deponovanjem kadmijum-sulfida različitim tehnikama

In recent decades, many scientific studies have been focused on alternative energy sources due to the growing energy needs of the world's population. Solar energy can cover the entire energy consumption of the world population and meet the future energy needs. Although commercial solar cells based on silicon have the efficiency over 20%, the production costs of this type of solar cells are very high. Therefore, in recent years the great efforts of researchers have been focused on the development of a new and cheaper type of solar cells. Among the studied structures there are solar cells sensitized with quantum dots, whose role is to improve the absorption properties of TiO2 photoanode. Compared to organic dyes as sensitizers, quantum dots are cheaper, more stable and show the multiple exciton generation effect. These cells consist of nanoporous TiO2, whose absorption onset is shifted to longer wavelengths by depositing of nanoparticles of selenium and tellurium compounds on the surface of TiO2. Cadmium sulfide (CdS) has a conduction band edge 0.5 eV lower than the conduction band edge of TiO2, which allows the transfer of the excited electrons from CdS to TiO2, preventing the recombination of electrons with photogenerated holes. Since for the effective electron transfer, the direct contact between the TiO2 and sensitizersis essential, thus it is necessary to provide a large specific surface available for sensitization. Among the investigated TiO2nanostructures, that meet the required criteria, it has been shown that nanotubes allow better performance of the final solar cell compared to TiO2 nanoparticle. Onedimensional nanotubes allow rapid transport of excited electrons and reduce the electron energy loss that happens at nanoparticles interfaces...Poslednjih decenija mnoga naučna istraživanja su fokusirana na alternativne izvore energije usled sve većih potreba svetske populacije za energijom. Solarna energija može pokriti celokupnu energetsku potrošnju svetske populacije i zadovoljiti buduće energetske potrebe. Iako komercijalne solarne ćelije na bazi silicijuma imaju efikasnost i preko 20 %, troškovi proizvodnje ovog tipa solarne ćelije su veoma visoki. Zbog toga su veliki napori naučnika poslednjih godina usmereni na razvoj novog i jeftinijeg tipa solarne ćelije. Među izučavanim strukturama su solarne ćelije sa kvantnim tačkama kao senzivatorima, čija je uloga poboljšanje apsorpcionih svojstava fotoanode na bazi TiO2. U poređenju sa organskim bojama kao senzivatorima, kvantne tačke su jeftinije, stabilnije i pokazuju efekat višestrukog pobuđivanja elektrona. Ove ćelije se sastoje od nanoporoznog TiO2, čija je apsorpciona granica pomerena ka većim talasnim dužinama deponovanjem nanočestica jedinjenja halkogenih elemenata na površini TiO2. Kadmijum-sulfid (CdS) ima granicu provodne zone nižu za 0,5 eV od granice provodne zone TiO2, što omogućava transfer pobuđenih elektrona iz CdS u TiO2, sprečavajući rekombinaciju elektrona sa fotogenerisanim šupljinama. S obzirom na to da je za transfer elektrona bitan direktan kontakt između senzivatora i TiO2 neophodno je da se obezbedi velika specifična površina TiO2 dostupna za depoziciju senzivatora. Od izučavanih nanostruktura TiO2, koji zadovoljavaju traženi kriterijum, dokazano je da nanocevi omogućavaju bolje performanse konačne solarne ćelije u odnosu na nanočestični TiO2. Jednodimenzionalnost nanocevi omogućava ubrzan transport..

Absorption properties enhancement of the photoanode with titanium dioxide nanotubes by deposition of cadmium sulfide via different techniques

Poslednjih decenija mnoga naučna istraživanja su fokusirana na alternativne izvore energije usled sve većih potreba svetske populacije za energijom. Solarna energija može pokriti celokupnu energetsku potrošnju svetske populacije i zadovoljiti buduće energetske potrebe. Iako komercijalne solarne ćelije na bazi silicijuma imaju efikasnost i preko 20 %, troškovi proizvodnje ovog tipa solarne ćelije su veoma visoki. Zbog toga su veliki napori naučnika poslednjih godina usmereni na razvoj novog i jeftinijeg tipa solarne ćelije. Među izučavanim strukturama su solarne ćelije sa kvantnim tačkama kao senzivatorima, čija je uloga poboljšanje apsorpcionih svojstava fotoanode na bazi TiO2. U poređenju sa organskim bojama kao senzivatorima, kvantne tačke su jeftinije, stabilnije i pokazuju efekat višestrukog pobuđivanja elektrona. Ove ćelije se sastoje od nanoporoznog TiO2, čija je apsorpciona granica pomerena ka većim talasnim dužinama deponovanjem nanočestica jedinjenja halkogenih elemenata na površini TiO2. Kadmijum-sulfid (CdS) ima granicu provodne zone nižu za 0,5 eV od granice provodne zone TiO2, što omogućava transfer pobuđenih elektrona iz CdS u TiO2, sprečavajući rekombinaciju elektrona sa fotogenerisanim šupljinama. S obzirom na to da je za transfer elektrona bitan direktan kontakt između senzivatora i TiO2 neophodno je da se obezbedi velika specifična površina TiO2 dostupna za depoziciju senzivatora. Od izučavanih nanostruktura TiO2, koji zadovoljavaju traženi kriterijum, dokazano je da nanocevi omogućavaju bolje performanse konačne solarne ćelije u odnosu na nanočestični TiO2. Jednodimenzionalnost nanocevi omogućava ubrzan transport...In recent decades, many scientific studies have been focused on alternative energy sources due to the growing energy needs of the world's population. Solar energy can cover the entire energy consumption of the world population and meet the future energy needs. Although commercial solar cells based on silicon have the efficiency over 20%, the production costs of this type of solar cells are very high. Therefore, in recent years the great efforts of researchers have been focused on the development of a new and cheaper type of solar cells. Among the studied structures there are solar cells sensitized with quantum dots, whose role is to improve the absorption properties of TiO2 photoanode. Compared to organic dyes as sensitizers, quantum dots are cheaper, more stable and show the multiple exciton generation effect. These cells consist of nanoporous TiO2, whose absorption onset is shifted to longer wavelengths by depositing of nanoparticles of selenium and tellurium compounds on the surface of TiO2. Cadmium sulfide (CdS) has a conduction band edge 0.5 eV lower than the conduction band edge of TiO2, which allows the transfer of the excited electrons from CdS to TiO2, preventing the recombination of electrons with photogenerated holes. Since for the effective electron transfer, the direct contact between the TiO2 and sensitizersis essential, thus it is necessary to provide a large specific surface available for sensitization. Among the investigated TiO2nanostructures, that meet the required criteria, it has been shown that nanotubes allow better performance of the final solar cell compared to TiO2 nanoparticle. Onedimensional nanotubes allow rapid transport of excited electrons and reduce the electron energy loss that happens at nanoparticles interfaces..