Semiconductors are a class of materials essential for the electronics industry. They have intermediate properties between conductors and insulators, which can be modified by doping with different chemical elements or by the application of electric fields or light. Black phosphorus is a stable form of phosphorus whose crystalline structure is composed by stacking two-dimensional, one atom thick, thin layers. This material has immense potential to be used in electronic devices at the nanoscale due to its semiconductor properties, which can be adjusted by the number of atomic layers according to the need.

The hydrogen gas ($\rm H_2$) is one of the best alternatives to fossil fuels because its combustion has as final product only water vapor. However, several technological challenges still need to be overcome in order to make it economically viable. One way to produce hydrogen is by breaking down water molecules $\rm H_2O$, with formation of $\rm H_2$ molecules. The main reaction in this process is the Hydrogen Evolution Reaction (HER) in which the protons in an acid medium are reduced and form hydrogen gas by electrons passed through catalysts.

Synthetic dyes are in constant use in a wide variety of industries, from textile to cosmetics. Both the production and use of these substances can lead to environmental problems if they are not properly degraded or removed from industrial effluents. Among the many physical, chemical or biological processes that can be used for the treatment of such wastes, the adsorption processes are noteworthy for combining low cost and high removal rates.

The search for clean, renewable and cheap energy sources has intensified in recent years with the growing consensus that the rise in the planet's average temperature, and the consequent intensification of extreme weather events, is caused by human action. Hydrogen ($\rm H_2$) is one of the best alternatives to fossil fuels, especially because its combustion has only water vapor as final product. However, the economic viability of the production, storage and distribution of hydrogen for power generation still requires solutions for several technological challenges.

Lactose is the main carbohydrate present in milk. To be digested and absorbed by the body, it must be broken down into its constituents: glucose and galactose. The breakdown is catalyzed by an enzyme called lactase, produced in the small intestine of young mammals especially for the digestion of the maternal milk.

In internal combustion engines, various toxic substances - such as $ \rm CO$, $\rm NO_2 $ - are produced due to the incomplete breakdown of fuels. By decreasing the activation energy required for complete combustion to occur, catalysts aid in transforming these products into less toxic gases - such as carbon dioxide ($\rm CO_2 $), methane ($\rm CH_4 $).

Though initially described as a mild version of dengue fever, the Zika virus (ZIKV) outbreak in the Americas unexpectedly revealed major neurological impacts as fetal microcephaly or other congenital brain injuries when women are infected during pregnancy and Guillain-Barre´ syndrome (a disorder in which the body's immune system damages the nerves) in adults. It can be transmitted both by the insect vector and sexual contact. Its outbreak became a global health threat of complex epidemiology and devastating neurological impacts, therefore requiring urgent efforts towards the development of novel efficacious and safe antiviral drugs.

Everything we know about the organisms that lived thousands of years ago comes from the fossils they left behind. The formation of fossils is an extremely rare phenomenon. It depends on the burial of the organism, the chemical processes responsible for its conservation and the non-destruction of the resulting fossil by later geological processes.

In 2016, the concentration of carbon dioxide ($\rm CO_2$) in the atmosphere has exceeded 400 ppm (parts per million), and has increased year by year since the beginning of the industrial revolution, when human activity began to inject more carbon into the atmosphere than the what the environment is capable of absorbing. The increase in the concentration of both $\rm CO_2$ and other greenhouse gases in the atmosphere is currently considered the main cause of the rise in the average temperature of the planet, which leads to the intensification of extreme climatic events.

The study of the embryonic development of the human brain and the distribution of nutrients during this phase was for a long time limited to animal models and dead human tissues. Much has changed with the so-called organoids: mini-organs created in vitro in the laboratory, from a few cells of the organ themselves, from embryonic stem cells or from pluripotent cells. These organoids present a three-dimensional micro-anatomy similar to the real organ but more simplified.