Joaquim A. O. Carneiro

Enhancement in the photocatalytic nature of nitrogen-doped PVD-grown titanium dioxide thin films

Nitrogen-doped titanium dioxide semiconductor photocatalytic thin films have been deposited by unbalanced reactive magnetron physical vapor deposition on glass substrates for self-cleaning applications. In order to increase the photocatalytic efficiency of the titania coatings, it is important to enhance the catalysts absorption of light from the solar spectra. Bearing this fact in mind, a reduction in the titania semiconductor band-gap has been attempted by using nitrogen doping from a coreactive gas mixture of N2:O2 during the titanium sputtering process. Rutherford backscattering spectroscopy was used in order to assess the composition of the titania thin films, whereas heavy-ion elastic recoil detection analysis granted the evaluation of the doping level of nitrogen. X-ray photoelectron spectroscopy provided valuable information about the cation-anion binding within the semiconductor lattice. The as-deposited thin films were mostly amorphous, however, after a thermal annealing in vacuum at 500 °C the ...

Synthesis of iron-doped TiO2 nanoparticles by ball-milling process : the influence of process parameters on the structural, optical, magnetic, and photocatalytic properties

Titanium dioxide (TiO2) absorbs only a small fraction of incoming sunlight in the visible region thus limiting its photocatalytic efficiency and concomitant photocatalytic ability. The large-scale application of TiO2 nanoparticles has been limited due to the need of using an ultraviolet excitation source to achieve high photocatalytic activity. The inclusion of foreign chemical elements in the TiO2 lattice can tune its band gap resulting in an absorption edge red-shifted to lower energies enhancing the photocatalytic performance in the visible region of the electromagnetic spectrum. In this research work, TiO2 nanoparticles were doped with iron powder in a planetary ball-milling system using stainless steel balls. The correlation between milling rotation speeds with structural and morphologic characteristics, optical and magnetic properties, and photocatalytic abilities of bare and Fe-doped TiO2 powders was studied and discussed.

Self-cleaning smart nanocoatings

Abstract: This chapter describes the major features of current smart, self-cleaning photocatalytic materials. These materials include semiconductor materials such as titanium dioxide (TiO2). This chapter focuses on TiO2-based materials because they are most widely studied. Characteristics such as low toxicity, high chemical stability, availability and low cost make TiO2 the ideal candidate for industrial applications.

Structural and Morphological Characterization of Magnetron Sputtered Nanocrystalline Vanadium Oxide Films for Thermochromic Smart Surfaces

Nanocrystalline vanadium oxide thin films have been deposited by reactive DC magnetron sputtering onto glass substrates under different processing conditions. Structural analysis and phase identification have been carried out by means of X-ray diffractometry (XRD). The surface morphologies of the different films have been examined by both scanning electron microscopy (SEM) and atomic force microscopy (AFM). The XRD results revealed single and multiple phase oxides such as VO2(B), VO2(M), V2O5, etc. with considerable differences concerning to surface morphologies, as observed by SEM and AFM. The effects the O2/Ar flow ratio, DC current, and working pressure on the phases formed and growth rates is discussed. Moreover, VO2(M) films exhibited different morphologies concerning to grain size and shape as well as dissimilar preference in crystal orientation, as a result of the processing conditions. The optical/thermochromic response of the VO2(M) specimens deposited under different growth rate conditions was evaluated by optical spectrophotometry and related to the respective structural characteristics.

Visible light induced enhanced photocatalytic degradation of industrial effluents (Rhodamine B) in aqueous media using TiO 2 nanoparticles

In recent years, new textile materials have been developed through the use of nanotechnology-based tools. The development of textile surfaces with self-cleaning properties has a large combined potential to reduce the environmental impact related to pollution. In this research work, three types of textiles substrates (cotton, Entretela, and polylactic acid (PLA)) were functionalized with titanium dioxide nanoparticles (TiO2) using chemical and mechanical processes (padding). During the functionalization process, two different methods were used, both of which allowed a good fixation of nanoparticles of TiO2 on textile substrates. The samples were examined for morphology and for photocatalytic properties under visible light irradiation. A study aimed at evaluating the effect of pH of the aqueous solution of TiO2 nanoparticles was performed in order to promote interaction between TiO2 and the dye solution rhodamine B (Rh-B). The TiO2 nanoparticles were characterized by X-ray diffraction (XRD). The measurement of the zeta potential of the TiO2 nanoparticle solution proved to be always positive and have low colloidal stability. Chromatography (HPLC and GC-MS) analyses confirm that oxalic acid is the intermediate compound formed during the photodegradation process.

Electrochemical anodizing, structural and mechanical characterization of nanoporous alumina templates

Highly ordered Anodic Aluminum Oxide (AAO) structures produced from aluminum by using an electrochemical anodizing method were developed towards its application for the next generation of micro/nanomedical and energy devices. In addition of analyzing the anodizing current profile, the surface morphology was characterized by using Scanning Electron Microscopy (SEM), the crystalline structure by X-Ray Diffraction (XRD) and the mechanical properties by nanoindentation experiments. The anodizing time and applied potential determines the nanopores regularity and their size, although the effect of the potential is more pronounced than the effect of temperature in the transformation from crystalline alumina to amorphous alumina. Optimum pore growth was achieved with an applied potential of 17 V which led to a pore fraction - P(f) - of about 17.5%. The experimental Berkovich nanoindentation method was used to determine the AAO hardness as a function of the indenter depth, during the loading stage, using mechanical response and deformation behaviour of the nanopores structure. From the experimental data of the load-displacement curves, this method allows the calculation of the indenter contact depth at each reloading point, thus leading to the estimation of the materials hardness. The results reveal that the hardness depends on the processing conditions used for the production of the AAO samples that also strongly influences the organization and pore size uniformity.

Deposition of ITO Thin Films onto PMMA Substrates for Waveguide Based Biosensing Devices

Biosensors’ research filed has clearly been changing towards the production of multifunctional and innovative design concepts to address the needs related with sensitivity and selectivity of the devices. More recently, waveguide biosensors, that do not require any label procedure to detect biomolecules adsorbed on its surface, have been pointed out as one of the most promising technologies for the production of biosensing devices with enhanced performance. Moreover the combination of optical and electrochemical measurements through the integration of transparent and conducting oxides in the multilayer structures can greatly enhance the biosensors’ sensitivity. Furthermore, the integration of polymeric substrates may bring powerful advantages in comparison with silicon based ones. The biosensors will have a lower production costs being possible to disposable them after use (“one use sensor chip”). This research work represents a preliminary study about the influence of substrate temperature on the overall properties of ITO thin films deposited by DC magnetron sputtering onto 0,5 mm thick PMMA sheets.

High barrier plastics using nanoscale inorganic films

Abstract: Packaging materials for food containers need to fulfil extremely tight standards towards the fresh-like quality maintenance of packed products. Even though polymers are normally preferred for the production of packaging systems, their permeability to gases, water vapour and odours remains a concern. In this sense, new approaches using nanoscale effects are under development to design, create or model gas-barrier nanocoatings with significantly optimized properties. It is generally agreed that the final barrier performances of the deposited inorganic materials are strongly coupled with mechanical and morphological properties. Basically, a good barrier system should have a dense morphology without cracks, good adhesion to the substrate, low stress, uniform thickness and reproducibility. At the moment, researchers aim for development of cost effective mass production techniques.

Smart self-cleaning coatings for corrosion protection

Abstract: Self-cleaning surfaces have attracted significant attention in recent years for their potential in both fundamental research and practical applications. Under the scope of self-cleaning smart coatings, this chapter explores the principal features of materials that can be used as protective coatings with an emphasis on the photocatalytic materials that have been developed to date. The chapter also highlights the importance of using titanium dioxide (TiO 2 ) as a semiconductor material in industrial applications since it can act as a photoanode for metal cathodic protection.

Development of photocatalytic ceramic materials through the deposition of TiO2 nanoparticles layers

Urbanism and communities centralization enlarges atmospheric pollution that affects both human beings as well as their constructed buildings. Different scientific and technological studies are being conducted, both in academic and construction industry, aiming the development of new construction materials with properties that can decrease visual pollution of cities, reducing also the number of cleanings required. The present research work aims the study and the production of self-cleaning ceramic surfaces in an economical and viable way without changing aesthetical aspect of material substrates used. The use of TiO2 nanoparticles (TiO2-NNPs) represents an attractive way to generate self-cleaning surfaces, therefore promoting the degradation of pollutant agents and reducing cleaning maintenance costs. In order to impart self-cleaning properties to ceramic surfaces, TiO2-NNPs based layers were deposited on different ceramic material substrates using the dip-coating method. The Photocatalytic activity (degradation of pollutants adsorbed on the surface) of the TiO2-NNPs based layers was characterized via the decomposition rate of an aqueous solution of Methylene blue (MB) under UV light irradiation. Colourless layers were successfully produced onto gray and white ceramic substrates using this sol-gel technique, without changing their aesthetical appearance. It was observed that the best photocatalytic activity was exhibited by the most porous ceramic substrate (gray); nevertheless, all the TiO2-NNPs coated ceramic surfaces showed good photocatalytic efficiency.