Ligia Todan

TiO2-based Nanomaterials with Photocatalytic Properties for the Advanced Degradation of Xenobiotic Compounds from Water. A Literature Survey

In recent years, the photochemistry of nano-semiconductor particles has been one of the fastest growing research areas in the physical chemistry field. TiO2 is considered as the most thoroughly investigated semiconductor in the literature, due to its photocatalytic activity, excellent functionality, thermal stability, and non-toxicity. It seems to be the most promising for the photocatalytic destruction of organic pollutants. The challenge for scientific materials is to find a processing method in which the crystalline phase as well as the size and morphology of TiO2 nanocrystals can be controlled. The concept of the present paper consists of a comprehensive study regarding the level of knowledge in the synthesis of TiO2-based nanopowders and their application in the advanced degradation of aromatic nitrocompounds. The objectives are related to: critical analysis of the synthesis techniques of the TiO2-based nanopowders, underlining the importance of using the sol–gel method evaluation of the morphological and structural specific characterization of these techniques; and a comprehensive study of the operational parameters of the pollutant photocatalytic degradation. The relative simple sol–gel method is the most widely used, being considered as a versatile means of developing catalytic materials, as well as an important experimental tool in understanding their physical and chemical properties. In order to enhance TiO2 photocatalysis and to extend the response into the visible domain, titanium has been doped with metals, nonmetals, and ionic components. A recent literature survey concerning some transition metals-doping (Fe, Co, and Ni) of TiO2 nanopowders by the sol–gel method was also included.

A way for improving the stability of the essential oils in an environmental friendly formulation.

The essential oils (EOs) possess amazing properties explaining the interest for their applications in many essential domains. They also present the disadvantage of their chemical instability in the presence of air, light, moisture, and high temperatures. The paper focuses on two of the most known and used EOs, lavender and mint, respectively. The idea of the study was to protect them using the encapsulated systems. The originality of the work consists in the combination between the advantages of the molecular encapsulation of the EOs by cyclodextrins (CD) with the advantages offered by the sol-gel process. Original formulations have been processed by entrapping these essential oils in silica matrices obtained from a colloidal silica sol by the aqueous route of the sol-gel method. Another non-toxic ingredient, β-cyclodextrin, able to form inclusion complexes (ICs) with the essential oils has been used. The characterization methods (chromatography, UV-vis, IR, and NMR spectroscopies) have evidenced the presence of the mentioned inclusion complexes. Due to their formation, which modifies the water solubility of the EOs, the chromatographic analysis was possible using water as solvent, which is a novelty in EOs determinations. Protected from both the cyclodextrin and silica matrix, the essential oils became more resistant versus the effects of the environment factors. Thus, the resulted powders can find applications in domains as agriculture, food industries, cosmetics, pharmaceutical, and medicine.

Thermal behavior of silicophosphate gels obtained from different precursors

Phosphosilicate glasses are of great interest in important fields, such as optical active systems, energy generating systems, humidity sensors, and as materials for biomedical applications. Many studies were accomplished to establish the influence of different reaction parameters on the evolution and final structure of sol–gel prepared phosphosilicate gels. In the present work, we studied the thermal behavior of the silicophosphate gels obtained starting with different phosphorous precursors, the influence of these precursors on the composition and structure of the resultant gels, and their evolution with thermal treatment. By Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and thermodifferential analysis (DTA/TG), and Differential Scanning calorimetry coupled with Mass Spectrometry (DSC-MS), it was established that the type of the precursors essentially influences the composition and structure and consequently the thermal behavior of the obtained gels. In the case of triethylphosphate precursor, all used methods of investigation have shown that the ester is trapped in the silica matrix and it is eliminated during the thermal treatment. Triethylphosphite partially hydrolizes and reacts with the silica network during post-preparation thermal treatment. Only in the case of H3PO4, an interaction with TEOS takes place and leads to Si–O–P bond formation. By thermal treatment, the gels with different composition and structure lead to materials with different properties.