A cheap, effective, and recyclable nanomaterial that can not only detect but also eradicate heavy metals from water, especially cadmium and lead. This is the result of a collaboration between scientists from CATRIN at Palacký University, VSB-TUO and IT4Innovations, and the Catalan Institute of Nanoscience and Nanotechnology (ICN2) in Barcelona.

The so-called graphene dots, derived from the Nobel Prize-winning material graphene, have already been used by researchers to prepare a paper detector. A simple test will show the presence of dangerous heavy metals without expensive equipment in about 30 minutes.

Wastewater contamination caused by industrial activity is an urgent problem today, with lead and cadmium, along with mercury, among the most toxic heavy metals ever. Their discharge into the environment causes extensive damage to aqueous ecosystems and contamination of agricultural crops. In humans, prolonged exposure to these heavy metals can lead to serious failure of organs and vital functions, and their carcinogenic effects have been demonstrated.

"It is very important to have inexpensive technology that can detect these highly harmful substances in the water even in small quantities and at the same time remove them elegantly and quickly. The newly developed material can do both - in the form of a paper sensor it reliably identifies cadmium or lead and then in the form of nanoparticles it removes these metals with record efficiency. This is the direction that modern technologies are now taking. A similar approach is being taken in medicine, for example, where the same substance in the body diagnoses a disease and subsequently cures it," said one of the authors of the research, Radek Zbořil, who also works at the Nanotechnology Centre, one of the components of the Centre for Energy and Environmental Technologies at VSB-TUO. The results of the research have been published in the professional Small journal and the scientists have already applied for patent protection for the discovery.

Graphene dots have, among other exceptional properties, the photoluminescence ability - that is, they glow when irradiated. This property played an important role in the research.

"We found that if cadmium or lead is bound to the surface of our sensor, the photoluminescence is quenched. This allows us to detect the metal. This is in very small quantities, many times lower than the limits allowed by the European Union for the content of these elements in drinking water," said David Panáček from CATRIN, the first author of the work. The disadvantage of existing technologies used for heavy metal determination is the need for special and expensive technical equipment and trained personnel. To avoid this complication, the scientists developed a unique paper detector. "The basis is a cheap chromatographic paper on which we have deposited the nanomaterial. Such a detector is extremely cheap and easy to use. After dipping the paper into water, we can tell with the naked eye whether heavy metals are present in the water or not," explained Panáček.

The new material has a number of advantages compared to already available materials that are also able to detect heavy metals in water. The most important is the ability to not only detect but also destroy heavy metals in water. "The developed material is reusable and recyclable. In addition, it is a carbon material that is non-toxic to the environment and there is no problem in producing it on a large scale. It could find application, for example, in the form of filters to prevent contamination of water with dangerous lead or cadmium," added another of the authors, Michal Otyepka from CATRIN and IT4Innovations at VSB-TUO.