On the Kinetics of Sol Gel Al:ZnO Thin Films Crystallization on Silicon Substrate

Recently, there is a growing interest in applying ZnO thin films on silicon buffer substrates for p-n junction devices, optical wave guide, etc. A sol gel process is very attractive technique for obtaining oxide thin films, due to easy control of film composition, easy fabrication of large area thin films with low cost and the ability to coat-specific shapes substrates. This paper presents a kinetic investigation of the crystallization (550-650 oC) of high preferential c-axis oriented ZnO thin films on p-type (100) silicon wafer substrate, from XRD data

Photocatalytic Properties of Semiconductive Oxide Nanoparticles. From Fundamentals to Applications

Photocatalysis is a promising technology that demonstrated important applications in environmental systems such as air purification, pollution removal, self-cleaning and antimicrobial. Semiconductive oxides (e.g., ZnO, TiO2, CuO) are important photocatalytic materials that can act as sensitizes for light based redox processes due to their electronic structure, which is characterized by the conduction-band with electrons (good reductants) and the valence band with holes (powerful oxidants). Excitation of electrons from the conduction-band and valenceband holes can react with electron donors and electron acceptors adsorbed on the semiconductor surface and electric double layer around the particles. The band gap value determines the semiconductive behavior of oxide nanoparticles. The absorption of UV-Vis radiation is an important tool for evaluating photocatalytic behavior of the obtained semiconductive nanoparticles. In this paper we present the correlation between the band gap value, particle size and the photocatalytic activity of ZnO nanoparticles prepared via an aqueous solution chemical method

Photocatalytical Activities of Manganese Doped Zinc Oxide Nanoparticles Prepared by Sol-Gel Method

In the last period, ZnO and doped ZnO nanoparticles are intensively investigated for their photocatalytic properties. This paper reports on ZnO and Mndoped ZnO nanoparticles obtained by modified sol-gel method. Were studied the structural and optical properties by using x-ray diffraction (XRD) data and visible absorbtion spactra. The photocatalytic activity of nanoparticles was investigated based on the degradation of the Methylene Blue (MB) dye solution. The results showed that Mn doping enhanced the photocatalytic activity of ZnO nanoparticles

Low-Temperature and UV Irradiation Effect on Transformation of Zirconia -MPS nBBs-Based Gels into Hybrid Transparent Dielectric Thin Films

Bottom-up approaches in solutions enable the low-temperature preparation of hybrid thin films suitable for printable transparent and flexible electronic devices. We report the obtainment of new transparent PMMA/ZrO2 nanostructured -building blocks (nBBs) hybrid thin films (61–75 nm) by a modified sol-gel method using zirconium ethoxide, Zr(OEt)4, and 3-methacryloxypropyl trimethoxysilane (MPS) as a coupling agent and methylmethacrylate monomer (MMA). The effect of low-temperature and UV irradiation on the nBBs gel films is discussed. The thermal behaviors of the hybrid sols and as-deposed gel films were investigated by modulated thermogravimetric (mTG) and differential scanning calorimetry (DSC) analysis. The chemical structure of the resulted films was elucidated by X-ray photoelectron (XPS), infrared (IR) and Raman spectroscopies. Their morphology and crystalline structure were observed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and grazing incidence X-ray diffraction. The cured films show zirconia nanocrystallites of 2–4 nm in the hybrid matrix and different self-assembled structures for 160 °C or UV treatment; excellent dielectric behavior, with dielectric constant values within 6.7–17.9, depending on the Zr(OEt)4:MMA molar ratio, were obtained

A Chitosan–Agarose Polysaccharide-Based Hydrogel for Biomimetic Remineralization of Dental Enamel

Developing multifunctional systems for the biomimetic remineralization of human enamel is a challenging task, since hydroxyapatite (HAP) rod structures of tooth enamel are difficult to replicate artificially. The paper presents the first report on the simultaneous use of chitosan (CS) and agarose (A) in a biopolymer-based hydrogel for the biomimetic remineralization of an acid-etched native enamel surface during 4–10-day immersion in artificial saliva with or without (control group) fluoride. Scanning electron microscopy coupled with energy-dispersive X-ray spectrometry, Fourier transform infrared and Raman spectroscopies, X-ray diffraction, and microhardness tests were applied to investigate the properties of the acid-etched and remineralized dental enamel layers under A and CS-A hydrogels. The results show that all biomimetic epitaxial reconstructed layers consist mostly of a similar hierarchical HAP structure to the native enamel from nano- to microscale. An analogous Ca/P ratio (1.64) to natural tooth enamel and microhardness recovery of 77.4% of the enamel-like layer are obtained by a 7-day remineralization process in artificial saliva under CS-A hydrogels. The CS component reduced carbonation and moderated the formation of HAP nanorods in addition to providing an extracellular matrix to support growing enamel-like structures. Such activity lacked in samples exposed to A-hydrogel only. These data suggest the potential of the CS-A hydrogel in guiding the formation of hard tissues as dental enamel

Synthesis and characterization of magnetic oxide nanoparticles and corresponding thin films for wastewaters treatment

Industrial wastewater can be properly treated using nanotechnologies and nanomaterials. This paper presents the synthesis and characterization of three series of magnetic nanoparticles (MNPs) and corresponding thin films, used for the degradation of organic compounds and removal of heavy metals from industrial wastewater. The samples were obtained by co-precipitation from a ferric (Fe3+) and ferrous (Fe2+) ions solution in a molar ratio of 2:1, at temperatures between 80-95 °C. The characterization of the samples was performed by scanning electron microscopy (SEM), and X-ray diffraction (XRD) methods. The magnetic nanoparticles were deposited on glass substrates by the centrifugal coating technique and the optical and magneto-optical activity was investigated by UV-Vis spectroscopy and magnetic circular dichroism technique (MCD). The effect of the investigated samples on the decomposition under UV irradiation of organic dyes was monitored by UV-Vis spectroscopy. Our preliminary results have shown that the magnetite and maghemite MNPs can be effective in UV degradation of methylene blue (MB) dye

Low-Temperature and UV Irradiation Effect on Transformation of Zirconia -MPS nBBs-Based Gels into Hybrid Transparent Dielectric Thin Films

Bottom-up approaches in solutions enable the low-temperature preparation of hybrid thin films suitable for printable transparent and flexible electronic devices. We report the obtainment of new transparent PMMA/ZrO2 nanostructured -building blocks (nBBs) hybrid thin films (61–75 nm) by a modified sol-gel method using zirconium ethoxide, Zr(OEt)4, and 3-methacryloxypropyl trimethoxysilane (MPS) as a coupling agent and methylmethacrylate monomer (MMA). The effect of low-temperature and UV irradiation on the nBBs gel films is discussed. The thermal behaviors of the hybrid sols and as-deposed gel films were investigated by modulated thermogravimetric (mTG) and differential scanning calorimetry (DSC) analysis. The chemical structure of the resulted films was elucidated by X-ray photoelectron (XPS), infrared (IR) and Raman spectroscopies. Their morphology and crystalline structure were observed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and grazing incidence X-ray diffraction. The cured films show zirconia nanocrystallites of 2–4 nm in the hybrid matrix and different self-assembled structures for 160 °C or UV treatment; excellent dielectric behavior, with dielectric constant values within 6.7–17.9, depending on the Zr(OEt)4:MMA molar ratio, were obtained

Magnetic Core-Shell Iron Oxides-Based Nanophotocatalysts and Nanoadsorbents for Multifunctional Thin Films

In recent years, iron oxides-based nanostructured composite materials are of particular interest for the preparation of multifunctional thin films and membranes to be used in sustainable magnetic field adsorption and photocatalysis processes, intelligent coatings, and packing or bio-medical applications. In this paper, superparamagnetic iron oxide (core)-silica (shell) nanoparticles suitable for thin films and membrane functionalization were obtained by co-precipitation and ultrasonic-assisted sol-gel methods. The comparative/combined effect of the magnetic core co-precipitation temperature (80 and 95 °C) and ZnO-doping of the silica shell on the photocatalytic and nano-sorption properties of the resulted composite nanoparticles were investigated by ultraviolet-visible (UV-VIS) spectroscopy monitoring the discoloration of methylene blue (MB) solution under ultraviolet (UV) irradiation and darkness, respectively. The morphology, structure, textural, and magnetic parameters of the investigated powders were evidenced by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET) measurements, and saturation magnetization (vibrating sample magnetometry, VSM). The intraparticle diffusion model controlled the MB adsorption. The pseudo- and second-order kinetics described the MB photodegradation. When using SiO2-shell functionalized nanoparticles, the adsorption and photodegradation constant rates are three–four times higher than for using starting core iron oxide nanoparticles. The obtained magnetic nanoparticles (MNPs) were tested for films deposition