Chlorinated hydrocarbons are among the most persistent contaminants in groundwater reserves – aquifers – worldwide. The problem is characteristic of industrialized regions, where substances were widely used, until the 1980s, as solvents, degreasers, in enamels for car painting and in dry cleaning, among other applications. Very small amounts of these pollutants are enough to make these waters unfit for human consumption, as they cause damage to the kidneys and liver, and cancer.

The understanding of light and its interaction with materials was, in the last century, an important way for scientific discoveries. A prominent example is the photoelectric effect: the emission of electrons by materials when subjected to the incidence of light at certain wavelengths. Wave theories already explained the behavior of light in many optical phenomena, but were not able to fully explain the characteristics of the photoelectric effect. The explanation for this phenomenon, as proposed by Einstein, required that the energy associated with light could only assume well-defined values, said to be discrete or quantized, that is, light should also have properties normally associated with particles.

Polysaccharides are molecules ubiquitous in nature, serving as a natural barrier for plants, energy sources for algae, and making up the cell wall of fungi. The deconstruction or modification of these polysaccharides is of great industrial interest, as in the textile and paper industry, as well as for the generation of biofuels and renewable chemical intermediates. Currently, the use of these polysaccharides in by-products of industrial interest requires the use of chemical reagents that generate environmental impacts or is carried out by industrial enzymes that are still not very efficient.

For decades, scientists have been using fossils of microorganisms to better understand the origin and evolution of life on Earth, but this branch of palaeobiology has taken a great leap forward with the development of novel imaging techniques. Historically, the study of the earliest traces of life on Earth has been surrounded by a lot controversy and technical challenges. Sometimes it is even difficult to tell out if a structure is really a fossil or… just an artefact.

The search for clean and renewable energy sources has intensified in recent years, due to the continuous increase in the concentration of greenhouse gases in the atmosphere, such as carbon dioxide. Also part of this search is the development of new systems to store and supply energy for various applications, from electric cars and buses to portable electronics. Thus, devices such as lithium batteries, flow batteries and supercapacitors are studied to meet these new demands.

Antibiotic resistance is a very pressing public health issue. Drug resistant bacteria are on the rise, and the number of antibiotics available to fight them are not enough. Infections by drug resistant bacteria is especially a serious problem for people with compromised immune systems, such as cancer and AIDS patients.

Antibiotic resistant bacteria are one of the most alarming public health problems, causing approximately 700,000 fatalities each year. The emergence of new resistant bacteria and the lack of effective drugs are some of the challenges in this complex medical landscape. If nothing is done, this number is estimated to rise to around 10 million deaths by 2050. The administration of multiple cycles of antibiotics stimulates the emergence of resistant bacteria, and multidrug-resistant pathogens force patients into prolonged hospital stays, also increasing the costs associated with treatment.

The search for clean and renewable energy sources has intensified in recent years, including, for example, the conversion of sunlight into electricity through photovoltaic cells. Simply put, sunlight incident on these devices is absorbed by electrons in the material. They are expelled from the atoms or molecules to which they were associated, forming the electric current that will be used to charge a battery or to operate other electric devices.

A galaxy is a gravitationally bound system made up of stars, gases – mainly hydrogen and helium – and, to a lesser extent, other heavier chemical elements. The visible universe is estimated to house trillions of galaxies and each galaxy is estimated to contain from a few hundred million ($ \rm 10^8 $) to one hundred trillion ($ \rm 10^{14} $) stars. The galaxy where we are located is called the Milky Way and our Sun orbits the galactic center at a distance of 27,000 light-years (one light-year is the distance light travels in a year, approximately 10 trillion kilometers).

Nanoparticles, clusters of atoms typically between 1 and 100 nanometers in size, have been investigated across a wide range of fields of knowledge. The properties of these tiny particles can be controlled by their composition, size and shape. This way, they are adaptable to virtually every kind of application. For example, multipurpose nanomaterials, combining properties such as optical and magnetic properties, are promising in a variety of biotechnological applications such as cancer treatment, diagnosis, screening, among others.