In the ~150 years comprised between the discovery of yttrium (1794) and promethium (1947), the rare earth metals were an incomplete chapter and a stone in the shoe of the periodic classification of the chemical elements. This group of 17 elements with remarkable chemical similarity raised confusion on many brilliant scientists, including Mendeleev, and led to the consolidation of many theories in Chemistry, from atomic spectroscopy to quantum theory. Nowadays we know that the special properties of these elements arise from filling 4f orbitals, which results in unique spectroscopic, magnetic and catalytic behavior. Such properties make rare earths essential elements on optical devices, lasers, telecommunications and magnetic materials for sustainable energy. The importance of rare earths far exceeds the science and technology domains, reaching the same level of other strategic materials for energy and defense. Hence, this work presents a brief discussion about the historical path of the rare earth elements in the Periodic Table and about the exploration of these resources in Brazil, detailing some of the extractive activities since the 19th century and some perspectives for future activities concerning this group of elements in Brazil.

Light and rare earths (RE) have a long lived relationship that dates from the discoveries of these elements in the nineteenth century. Since then, the increasing comprehension of their spectroscopic properties conducted to a wide and alluring literature about light absorption and emission by this particular and fascinating group. For more than 50 years, RE-containing solid-state optical materials have undoubtfully been an important subject for the development of more efficient lighting, visualization, communication and health everyday applications. Therefore, this review introduces the spectroscopic properties of rare earth materials and their applications, with a brief discussion of the main mechanisms of light absorption and emission from a 4f elements inorganic physical chemistry perspective. Special attention is devoted to the use of these elements in systems concerning photoprotection and to the fundamentals of visible light generation for lighting and visualization.

<p>Catalytic combustion of soot was performed over ZnO:CeO₂ catalysts obtained via a non‑alkoxide sol-gel route. Different kinetics parameters were calculated through thermal analyses, thus, enabling the correlation between the experimental data and the decomposition mechanisms probably associated with the soot decomposition in each case.</p>

<p>Liquid phase synthesis techniques are commonly preferred for the preparation of nanosized inorganic solids due to several advantages over other methodologies, such as low energy consumption, safety, possibility of reactant recovery and, mainly, the homogeneity of the precursors and control of particle sizes and morphologies through bottom-up approaches. In this regard, Colloidal Chemistry plays a key role in the controlled production of different classes of nanoparticles, thus being a subject of growing interest in several fields of Materials, Inorganic, and Physical-Chemistry. Therefore, this article sought to present an introductory outline of Colloidal Chemistry, with a focus on the preparation of inorganic nanoparticles. Given the broadness of this subject, special attention was devoted to nanoparticles based on Rare Earth compounds, due to their current importance in several fields. Therefore, the work presents the principles involved in the most commonly applied methodologies for the liquid phase synthesis of nanoparticles, such as coprecipitations and hydro/solvothermal techniques, as well as precipitations into nanoreactors based on reverse microemulsions, with a brief survey of the main advances in these fields in recent years.</p>

This contribution introduces a brief discussion about the properties and applications of the rare earth elements, with a focus on their current status in Brazil. The general chemical properties, main applications and historical background of the chemistry of these elements are presented, and special attention is devoted to the development of the exploitation and both academic and industrial activities involving rare earths in Brazil. A discussion of the current world scenario ensues and some perspectives regarding the prospection, market and government policy concerning the rare earth elements in Brazil are given.

CeO2 and mixed CeO2-ZrO2 nanopowders were synthesized and efficiently deposited onto cordierite substrates, with the evaluation of their morphologic and structural properties through XRD, SEM, and FTIR. The modified substrates were employed as outer heterogeneous catalysts for reducing the soot originated from the diesel and diesel/biodiesel blends incomplete combustion. Their activity was evaluated in a diesel stationary motor, and a comparative analysis of the soot emission was carried out through diffuse reflectance spectroscopy. The analyses have shown that the catalyst-impregnated cordierite samples are very efficient for soot oxidation, being capable of reducing the soot emission in more than 60%.