Mechanochemistry in Portugal—A Step towards Sustainable Chemical Synthesis

In Portugal, publications with mechanochemical methods date back to 2009, with the report on mechanochemical strategies for the synthesis of metallopharmaceuticals. Since then, mechanochemical applications have grown in Portugal, spanning several fields, mainly crystal engineering and supramolecular chemistry, catalysis, and organic and inorganic chemistry. The area with the most increased development is the synthesis of multicomponent crystal forms, with several groups synthesizing solvates, salts, and cocrystals in which the main objective was to improve physical properties of the active pharmaceutical ingredients. Recently, non-crystalline materials, such as ionic liquids and amorphous solid dispersions, have also been studied using mechanochemical methods. An area that is in expansion is the use of mechanochemical synthesis of bioinspired metal-organic frameworks with an emphasis in antibiotic coordination frameworks. The use of mechanochemistry for catalysis and organic and inorganic synthesis has also grown due to the synthetic advantages, ease of synthesis, scalability, sustainability, and, in the majority of cases, the superior properties of the synthesized materials. It can be easily concluded that mechanochemistry is expanding in Portugal in diverse research areas.

Towards Predictive Synthesis of Inorganic Materials Using Network Science

Accelerating materials discovery is the cornerstone of modern technological competitiveness. Yet, the inorganic synthesis of new compounds is often an important bottleneck in this quest. Well-established quantum chemistry and experimental synthesis methods combined with consolidated network science approaches might provide revolutionary knowledge to tackle this challenge. Recent pioneering studies in this direction have shown that the topological analysis of material networks hold great potential to effectively explore the synthesizability of inorganic compounds. In this Perspective we discuss the most exciting work in this area, in particular emerging new physicochemical insights and general concepts on how network science can significantly help reduce the timescales required to discover new materials and find synthetic routes for their fabrication. We also provide a perspective on outstanding problems, challenges and open questions.

Biosynthesis of gold nanoparticles (AuNPs) and the reducing agents in the process

Metallic nanoparticles (NPs) are being used mainly because they have excellent physical, chemical and biological properties, intrinsic to their size, therefore there is a boom in the use of these nanoparticles in various fields and recently, due to the pandemic about coronavirus. Copper NPs began to be used for use in medical supplies such as face masks. NPs are normally obtained through inorganic synthesis, however, the methodologies used to obtain them are in general terms expensive and involve the use of hazardous chemicals, which has increased the development of sustainable and environmentally friendly alternatives, as one of the main objectives of nanotechnology. Considering that nanoparticle biosynthesis is of greatest importance since it allowed obtaining organic NPs through an environmentally friendly; quick and inexpensive. In this work, the synthesis and characterization of AuNPs of six different plant extracts that in traditional medicine are used for respiratory diseases care, were performed. These NPs can be used in different fields; even they represent a good option to be added to medical supplies. As the AuNPs obtained from chamomile extract that turned out to be spherical, 20 nm in diameter, and well dispersed, these could be applied orally, as nanocapsules that are easily eliminated from the human body, or by aerosol, as a possible treatment for the pneumonia and SARS-CoV-2, in addition later for other nosocomial diseases. And to answer the question of what or which reducing agents are involved in the process? We proposed that, for biological synthesis, malic acid may be acting as a reducing agent and the amino group as a stabilizing agent, so we performed a synthesis with malic acid and obtained stable NPs. However, we do not dismiss other metabolites enzymes and/or proteins that could be involved in the process.

CaSiO3-HAp Structural Bioceramic by Sol-Gel and SPS-RS Techniques: Bacteria Test Assessment

The article presents an original way of getting porous and mechanically strong CaSiO3-HAp ceramics, which is highly desirable for bone-ceramic implants in bone restoration surgery. The method combines wet and solid-phase approaches of inorganic synthesis: sol-gel (template) technology to produce the amorphous xonotlite (Ca6Si6O17·2OH) as the raw material, followed by its spark plasma sintering–reactive synthesis (SPS-RS) into ceramics. Formation of both crystalline wollastonite (CaSiO3) and hydroxyapatite (Ca10(PO4)6(OH)2) occurs “in situ” under SPS conditions, which is the main novelty of the method, due to combining the solid-phase transitions of the amorphous xonotlite with the chemical reaction within the powder mixture between CaO and CaHPO4. Formation of pristine HAp and its composite derivative with wollastonite was studied by means of TGA and XRD with the temperatures of the “in situ” interactions also determined. A facile route to tailor a macroporous structure is suggested, with polymer (siloxane-acrylate latex) and carbon (fibers and powder) fillers being used as the pore-forming templates. Microbial tests were carried out to reveal the morphological features of the bacterial film Pseudomonas aeruginosa that formed on the surface of the ceramics, depending on the content of HAp (0, 20, and 50 wt%).