Here, the synthesis of water-dispersible naked gold nanoclusters (AuNC ) is reported by a simple reduction of HAuCl with NaOH at room temperature, and it is shown that they are non-luminescent. They are then easily passivated with different thiols and adenosine monophosphate, leading to luminescent NCs. This is an important finding because the photoluminescence of the passivated NCs can now be clearly attributed to the ligand-AuNC surface interaction. These results are also highly relevant from the point of view of the preparation of luminescent NCs from the same NC batch. This strategy can be valuable for the preparation of a broad range of nano(bio)composites.

Reduction of Au3+ in the presence of just AMP and HEPES, combined with light exposure, gives rise to luminescent, water-soluble Au+ nanoclusters. Their photoluminescence is considerably enhanced by adding Y3+ or Yb3+, which leads to Au+/Y3+ and Au+/Yb3+ NCs, respectively.

A water-dispersible, biocompatible, fluorescent ratiometric pH nanosensor over a broad pH range is reported.

Sewage sludge from the galvanic industry represents a problem to the environment, due to its high metal content that makes it a hazardous waste and must be treated or disposed of properly. This study aimed to evaluate the sludge from three galvanic industries and determine its possible use as catalysts for the synthesis of materials. Catalyst was obtained from a thermal process based on dried between 100–120 °C and calcination of sludges between 400 to 700 °C. The physical–chemical properties of the catalyst were analyzed by several techniques as physisorption of N2 and chemisorption of CO of the material. Catalytic activity was analyzed by thermogravimetric analysis of a thermo-catalytic decomposition of crude oil. The best conditions for catalyst synthesis were calcination between 400 and 500 °C, the temperature of reduction between 750 and 850 °C for 15 min. The catalytic material had mainly Fe as active phase and the specific surface between 17.68–96.15 m2·g−1, the catalysts promote around 6% more weight-loss of crude oil in the thermal decomposition compared with assays without the catalyst. The results show that the residual sludge of galvanic industries after thermal treatment can be used as catalytic materials due to the easiness of synthesis procedures required, the low E-factor obtained and the recycling of industrial waste promoted.