Scientific Papers in SCI

Transition metal diborides (TMB₂), such as ZrB₂ and HfB₂, are a class of ultra-high-temperature ceramics (UHTCs) that have attracted considerable attention due to their performance in extreme environments. Their implementation is burdened by the high energetic requirement of traditional synthetic procedures. Here, we report a novel methodology, termed as Flash Joule Heating-Boro/Carbothermal Reduction (FJH-BCTR), for the instantaneous synthesis of phase-pure sub-micron powders of several TMB₂ and composite within seconds and without any external source of heating. The immediate synthesis is attributed to the Joule heat generated by the current, enabling extremely fast heating and cooling rates and, therefore, avoiding excessive grain growth. The advantages of FJH-BCTR are thoroughly displayed and can be summarized as; highly efficient, it allows a dramatic drop in terms of energy and time; universal, several TMB₂ and composite can be prepared; and flexible, different experimental parameters can be tuned to achieve the desired phase.

The oxidative carbonylation of methanol to synthesize dimethyl carbonate (DMC) has been extensively studied over Cu-based catalysts, but the activity and selectivity are not high. The Co catalysts exhibit high DMC selectivity, but the difficulty in recycling homogeneous Co catalyst and the low conversion of heterogeneous Co catalyst limit the application of Co catalysts. Here, the core–shell ZIFs materials were synthesized and carbonized to obtain solid core–shell cobalt catalysts, and then the catalytic performance for methanol conversion to DMC was investigated. The CoNC@NC catalyst, carbonized from Z67@Z8 with Z67 as the core and Z8 as the shell, shows that the carbonized NC shell effectively suppressed the aggregation of Co NPs and the Co NPs were only 15.4 nm, which was much smaller than those of NC@CoNC (34.5 nm) and CoNC (48.1 nm) catalysts. Compared with the CoNC catalyst, CoNC@NC significantly improved the pulse chemisorption of CH₃OH and CO, leading to a significant increase in methanol conversion from 6.9% to 17.1%. Furthermore, the deactivation rate of the CoNC@NC catalyst (22.8%) was much lower than that of CoNC (59.4%) after five reaction cycles. The results of this work provide a new strategy for the design and preparation of solid cobalt catalysts for the oxidative carbonylation of methanol to DMC.

Glycerol is a by-product in biodiesel production (in the range of g·L⁻¹), so its photoreforming by photocatalysis is a way of valorising it. TiO₂ in photocatalysis has been widely studied, although its efficiency is limited by the high energy band gap, and the electron-hole recombination. Its combination with different semiconductors should improve charge separation, extending also the absorption from UV to visible light. Cu and Ni oxides are two of the most efficient low-cost transition metal oxide catalysts. Experiments were carried out in a 25 L pilot plant connected to a compound parabolic solar collector. Different combinations of the three semiconductors, based on the concentration of each metal on TiO₂ (Me, 5%, 7.2% and 10%) were evaluated. Evonik P25-TiO₂, CuO and NiO were combined by mechanical mixing. Hydrogen was quantified by a micro gas chromatograph, and copper and nickel leaching by ICP-MS. The best hydrogen production (0.060 mMol kJ⁻¹) was attained with a proportion of 10:1 of TiO₂:MeO, that corresponds to a total metal concentration of 7.2 wt%, being Cu and Ni in the same proportion. Metal content in solution increased as the reaction progressed, but Ni lixiviation of <0.012 mg L⁻¹ was not significant. Significant Cu leaching (>1 mg L⁻¹) was observed. This article presents novel results, in a solar pilot plant, for determining which ternary mixture can give better results, as well as metal leaching into water. Handling relevant volume of water in anoxic conditions can help to understand the application of this technology for the production of hydrogen.

MoS₂ nanosheets belong to an emerging family of nanomaterials named bidimensional transition metal dichalcogenides (2D TMDCs). The use of such promising materials, featuring outstanding chemical and physical properties, is expected to increase in several fields of science and technology, with an enhanced risk of environmental dispersion and associated wildlife and human exposures. In this framework, the assessment of MoS₂ nanosheets toxicity is instrumental to safe industrial developments. Currently, the impact of the nanomaterial on the nervous tissue is unexplored. In this work, we use as in vivo experimental model the early-stage zebrafish, to investigate whether mechano-chemically exfoliated MoS₂ nanosheets reach and affect, when added in the behavioral ambient, the nervous system. By high throughput screening of zebrafish larvae locomotor behavioral changes upon exposure to MoS₂ nanosheets and whole organism live imaging of spinal neuronal and glial cell calcium activity, we report that sub-acute and prolonged ambient exposures to MoS₂ nanosheets elicit locomotor abnormalities, dependent on dose and observation time. While 25 μg mL⁻¹ concentration treatments exerted transient effects, 50 μg mL⁻¹ ones induced long-lasting changes, correlated to neuroinflammation-driven alterations in the spinal cord, such as astrogliosis, glial intracellular calcium dysregulation, neuronal hyperactivity and motor axons retraction. By combining integrated technological approaches to zebrafish, we described that MoS₂ 2D nanomaterials can reach, upon water (i.e. ambient) exposure, the nervous system of larvae, resulting in a direct neurological damage.