Semiconductors based on transition metal oxides represent an important class of materials used in emerging technologies. For this, the performance of these materials strongly depends on the size and morphology of particles, surface charge characteristics, and the presence of bulk and surface defects that are influenced by the synthesis method and the experimental conditions the materials are prepared. In this context, the present review aims to report the importance of choosing the synthesis methods and experimental conditions to modify structural, morphological, and electronic characteristics of semiconductors, more specifically, tin oxide (SnO₂), since these parameters may be a determinant for better performance in various applications, including photocatalysis. SnO₂ is an n-type semiconductor with a band gap between 3.6 and 4.0 eV, whose intrinsic characteristics are responsible for its electrical conductivity, good optical characteristics, high thermal stability, and other qualities. Such characteristics have provided excellent results in advanced oxidative processes, i.e., heterogeneous photocatalysis applications. This process involves semiconductors in the production of hydroxyl radicals via activation by light absorption, and it is considered as an emerging and promising technology for domestic-industrial wastewater treatment. In our review article, we focused on the photodegradation of different organic dyes and types of persistent organic pollutants using SnO₂-based photocatalysts, and how the efficiency of these materials can be impacted by synthesis methods and experimental conditions employed to prepare them.

The study aimed to utilize MoO₃ catalysts, produced on a pilot scale via combustion reaction, to produce biodiesel from residual oil. Optimization of the process was conducted using a 2³ experimental design. Structural characterization of the catalysts was performed through X-ray diffraction, fluorescence, Raman spectroscopy, and particle size distribution analyses. At the same time, thermal properties were examined via thermogravimetry and differential thermal analysis. Catalytic performance was assessed following process optimization. α-MoO₃ exhibited a monophasic structure with orthorhombic phase, whereas α/h-MoO₃ showed a biphasic structure. α-MoO₃ had a larger crystallite size and higher crystallinity, with thermal stability observed up to certain temperatures. X-ray fluorescence confirmed molybdenum oxide predominance in the catalysts, with traces of iron oxide. Particle size distribution analyses revealed polymodal distributions attributed to structural differences. Both catalysts demonstrated activity under all conditions tested, with ester conversions ranging from 93% to 99%. The single-phase catalyst had a long life cycle and was reusable for six biodiesel production cycles. The experimental design proved to be predictive and significant, with the type of catalyst being the most influential variable. Optimal conditions included α-MoO₃ catalyst, oil/alcohol ratio of 1/15, and a reaction time of 60 min, resulting in high biodiesel conversion rates and showcasing the viability of MoO₃ catalysts in residual oil biodiesel production.

Gallium, a trace metal not found in its elemental form in nature, has garnered significant interest as a biocide, given its ability to interfere with iron metabolism in bacteria. Consequently, several gallium compounds have been developed and studied for their antimicrobial properties but face challenges of poor solubility and formulation for delivery. Organizing the metal into three-dimensional, hybrid scaffolds, termed metal-organic frameworks (MOFs), is an emerging platform with potential to address many of these limitations. Gallium MOFs show improved solubility and antibacterial potency relative to the free metal due to their ability to coload antibiotics and functional biomolecules. Synthetic strategies are equally versatile, with several rapid, cost-effective, and scalable methods available. In this review, we present the advantages and disadvantages of these various synthetic strategies with respect to their antibacterial efficiency, product purity, and reaction control. The activity of gallium-based MOFs against Gram-positive and Gram-negative pathogens in mono- and combinatorial therapeutic settings is discussed in the context of their mechanisms of action and structure-function-performance relationships collated from recent studies. While gallium MOF development as antibacterials is still in its nascent stages, the examples discussed here highlight their potential as a novel class of therapeutics poised to impact the fight against pan-drug-resistant bacterial pathogens.

The search for environmentally correct fuels has been gaining momentum/prominence in scientific research, for example, using oils or fats of animal/vegetable origin and commercial/residual oils. These oils consist primarily of free fatty acids with high energy power and can be converted into fatty acid esters (biodiesel) using highly efficient and recyclable heterogeneous catalysts. Among the heterogeneous catalysts most used in the conversion of biodiesel, two are worth mentioning: MoO₃ and ferrospinels. The first is because it contains in its structure, especially the orthorhombic, acidic active sites of Lewis and Brönsted-Lowry, and the second is because they have high specific surface areas and adequate magnetic characteristics that allow the recovery of the medium. Another interesting point is the use of residues for catalysis that has been highlighted, as they are materials that contain metals such as Fe, K, Si, Mg, Na, and Ti in their composition, which accelerate reactions. Thus, in this sense, this article proposes to carry out a bibliographical survey of the literature in experimental scientific papers and published reviews on the use of MoO₃ and ferrospinels as heterogeneous catalysts supported on waste from cut ornamental rocks (granite/marble) for the production of biodiesel, which is the core of this search, on the online data platforms Science Direct (Elsevier) and Web of Science covering the period from 2016 to April 2023, using the Start software (State of the Art through Systematic Review). The results revealed a quantitative of 223 articles in general, in which 62 were accepted, and 161 were rejected. While in the review extraction stage, 22 papers were accepted, and 40 were rejected. In addition, the review revealed that most of the catalysts and catalytic supports used for the production of biodiesel with oils are oxides, nothing specifically informing the use of waste from cuts of ornamental rocks (granite/marble) as a host material (support) for the catalysts MoO₃ and ferrospinels aiming the production of biodiesel. Therefore, meaning that it is not possible to use this type of residue as a support for catalysts, but rather that there may be a lack of research investigating this application.