Micropollutants, or emerging pollutants, consist of many natural and anthropogenic substances, present in trace concentrations, mainly in wastewater. These pollutants influence the activity of natural substances in living organisms (as occurs with certain hormones). These substances, called endocrine disruptors, can manifest effects at very low concentrations and they are difficult to eliminate by conventional treatments^[1].

Photodegradation using classic photocatalysts, such as TiO₂, have the drawback that they only absorb in the UV region and have very low efficiencies due to rapid electron-hole recombination. However, the addition of sub-nanometric clusters (metal molecules) has proved capable of modifying TiO₂ bandgap, resulting in enhanced light absorption and a reduction effect on the recombination rate of electron-hole pairs^[2].

In this work, SnO₂/TiO₂ hybrid nanomaterials have been synthesized by the sol-gel method and characterized for later use in photocatalytic reactions as substrates of clusters. The clusters deposition method was incipient wetness impregnation. Then, they were studied by UV-Vis spectroscopy and diffuse reflectance spectroscopy to check how the deposition process improves the optical properties of the materials, increasing visible light absorption through the appearance of midgaps, which make these nanomaterials very interesting for photocatalytic reactions^[2].

The photocatalytic activity of these hybrid nanomaterials has been studied by photodegrading methylene blue in water using a solar simulator. The results confirm the improvement in photocatalytic efficiency, achieved thanks to the deposition of clusters. In addition, different parameters relevant to photocatalysis were optimized, such as the deposition of silver clusters, the catalyst concentration, or the shelf-life of the catalyst.