Green and facile sol-gel synthesis of the mesoporous SiO2-TiO2 catalyst by four different activation modes

Titania-mediated stabilization of fluorescent dye encapsulation in mesoporous silica nanoparticles

Mesoporous silica nanoparticles hosting guest molecules are a versatile tool with applications in various fields such as life and environmental sciences. Current commonly applied pore blocking strategies are not universally applicable and are often not robust enough to withstand harsh ambient conditions (e.g. geothermal). In this work, a titania layer is utilized as a robust pore blocker, with a test-case where it is used for the encapsulation of fluorescent dyes. The layer is formed by a hydrolysis process of a titania precursor in an adapted microemulsion system and demonstrates effective protection of both the dye payload and the silica core from disintegration under otherwise damaging external conditions. The produced dye-MSN@TiO2 particles are characterized by means of electron microscopy, elemental mapping, ζ-potential, X-ray diffraction (XRD), nitrogen adsorption, Thermogravimetric analysis (TGA), fluorescence and absorbance spectroscopy and Fourier Transform Infrared Spectroscopy - Total Attenuated Reflectance (FT-IR ATR). Finally, the performance of the titania-encapsulated MSNs is demonstrated in long-term aqueous stability and in flow-through experiments, where owing to improved dispersion encapsulated dye results in improved flow properties compared to free dye properties. This behavior exemplifies the potential advantage of carrier-borne marker molecules over free dye molecules in applications where accessibility or targeting are a factor, thus this encapsulation method increases the variety of fields of application.

Immobilized mesoporous materials for carvacrol delivery to the germination and early growth of tomato plants (Solanum Lycopersicum)

The immobilization of TiO₂-SiO₂ (TSO) materials on seed mats stands as a practical way to help the germination and early growth of tomato plants (Solanum Lycopersicum). Mesoporous materials are functionalized with triethanolamine (TEA) and loaded with the biocide molecule of carvacrol (CAR). The effect of CAR on the parameters of germination percentage, germination time, root, shoot length, and chlorophyll content of seeds and/or tomato seedlings are investigated. The germination experiments were carried out using seed mats coated with the TSO materials, also TSO powdered materials were put directly on the tomato seeds to study their effect on germination. Direct deposition of TSO composites achieved the complete germination and longer shoots due to the cooperative interactions among nanomaterials, carvacrol, and the tomato seed. However, the handling of the seeds and the detrimental effect of powder in the germination system made difficult the application with agricultural purposes. The plastic seed mats provide a practical system with lower germination, but more homogenous growth of root/shoot is possible. Surprisingly, in this methodology the carvacrol presents a detrimental effect on germination due to less interaction with the seeds. The handling of seeds and recover of the nanomaterials and its reuse are advantages of the plastic seed mats, which together with less wastage of seeds suggest a potential use in agriculture. The as-synthetized TSO NPs, together with the functionalization of triethanolamine and carvacrol used to promote the health germination of the seeds, allows the control of the time for seed germination, germination %, and length for the root/shoot of seed tomato germination. The immobilization of mesoporous materials results in an alternative to help the germination and early growth of agricultural plants searching to avoid the lixiviation of nanomaterials to the environment.

Green Chemistry Metrics, A Review

Attending both the United Nations Decade of Education for Sustainable Development (2005–2014) and the United Nations 2030 Agenda for Sustainable Development, this review is presented, bearing in mind that green chemistry is essential to contribute to sustainability. This work has compiled all the information relating to green chemistry metrics, so that stakeholders can select an appropriate model, under the Green Chemistry Protocol, to evaluate how much green is a process. The review was organized considering the following convenient sections: the mass valuation, the recognition of the human health and environmental impact, metrics using computational programs (software and spreadsheets), and finally global metrics. This review was developed by consulting the principal databases, since the appearance of the first green chemistry textbook in 1998. A massive number of references were attained involving the keywords proposed below, with six languages observed, highlighted by the English language. It is important to emphasize that the 12 Principles of Green Chemistry are conceptual and offer little quantitative information. In addition, almost all the reported metric green propositions do not consider the 12 principles and few papers offer how to obtain an appropriate evaluation about the greenness of a research. In this sense, it is convenient to note that only in the Spanish literature are there two metrics that consider all the principles. Finally, to our knowledge, and after a deep search in the literature, it is the first review that covers the different features of green chemistry: mass, environment/human health. and in some cases, the use of computational programs.

Synthesis, Characterization and Photocatalytic Behavior of SiO2 @nitrized-TiO2 Nanocomposites Obtained by a Straightforward Novel Approach

We report on the facile synthesis of SiO2 @nitrized-TiO2 nanocomposite (NST) by calcination of TiO2 xerogel with OctaAmmonium POSS® (N-POSS; POSS=polyhedral oligomeric silsesquioxanes). The as-obtained nanoporous mixed oxide is constituted by uniformly distributed SiO2 and nitrized-TiO2 , where the silica component is present in an amorphous state and TiO2 in an anatase/rutile mixed phase (92.1 % vs. 7.9 %, respectively) with very small anatase crystallites (3.7 nm). The TiO2 lattice is nitrized both at interstitial and substitutional positions. NST features a negatively charged surface with a remarkable surface area (406 m2  g-1 ), endowed with special adsorption capabilities towards cationic dyes. Its photocatalytic behavior was tested by following the degradation of standard aqueous methylene blue and methyl orange solutions under UV and visible light irradiation, according to ISO 10678:2010. For comparison, analogous investigations were carried out on a silica-free N-TiO2 , obtained by using NH4 Cl as nitrogen source.