Mario Urso

Abstract Nanoplastic pollution, the final product of plastic waste fragmentation in the environment, represents an increasing concern for the scientific community due to the easier diffusion and higher hazard associated with their small sizes. Therefore, there is a pressing demand for effective strategies to quantify and remove nanoplastics in wastewater. This work presents the “on-the-fly” capture of nanoplastics in the three-dimensional (3D) space by multifunctional MXene-derived oxide microrobots and their further detection. A thermal annealing process is used to convert Ti 3 C 2 T x MXene into photocatalytic multi-layered TiO 2 , followed by the deposition of a Pt layer and the decoration with magnetic γ-Fe 2 O 3 nanoparticles. The MXene-derived γ-Fe 2 O 3 /Pt/TiO 2 microrobots show negative photogravitaxis, resulting in a powerful fuel-free motion with six degrees of freedom under light irradiation. Owing to the unique combination of self-propulsion and programmable Zeta potential, the microrobots can quickly attract and trap nanoplastics on their surface, including the slits between multi-layer stacks, allowing their magnetic collection. Utilized as self-motile preconcentration platforms, they enable nanoplastics’ electrochemical detection using low-cost and portable electrodes. This proof-of-concept study paves the way toward the “on-site” screening of nanoplastics in water and its successive remediation.

Abstract The increasing use of polymers has led to an uncontrollable accumulation of polymer waste in the environment, evidencing the urgent need for effective and definitive strategies to degrade them. Here, self‐propelled light‐powered magnetic field‐navigable hematite/metal Janus microrobots that can actively move, capture, and degrade polymers are presented. Janus microrobots are fabricated by asymmetrically depositing different metals on hematite microspheres prepared by low‐cost and large‐scale chemical synthesis. All microrobots exhibit fuel‐free motion capability, with light‐controlled on/off switching of motion and magnetic field‐controlled directionality. Higher speeds are observed for bimetallic coatings with respect to single metals. This is due to their larger mixed potential difference with hematite as indicated by Tafel measurements. As a model for polymers, the total degradation of high molecular weight polyethylene glycol is demonstrated by matrix‐assisted laser desorption/ionization mass spectrometry. This result is attributed to the active motion of microrobots, enhanced electrostatic capture of polymer chains, improved charge separation at the hematite/metal interface, and catalyzed photo‐Fenton reaction. This work opens the route toward the degradation of polymers and plastics in water using light.

Abstract The growing use of plastic materials has led to the continuous accumulation of wastes in marine environments, which fragment into hazardous micro‐and nanoplastics. These plastic particles absorb toxic organic pollutants on their surface, support bacterial biofilms growth, and propagate through the food chain, posing serious risks for human health. Therefore, nano/microplastics pollution has become a global issue, making their definitive elimination compulsory. Self‐propelled nano/microrobots have demonstrated efficient removal of nano/microplastics from water, combining enhanced physicochemical properties of nano/microscale materials and active motion. During the last year, the potential of this technology to degrade nano/microplastics has been investigated. Here, the most advanced strategies for nano/microplastics capture and subsequent degradation by autonomous nano/microrobots are critically reviewed. A short introduction to the main propulsion mechanisms and experimental techniques for studying nano/microplastics degradation is also provided. Forthcoming challenges in this research field are discussed proactively. This perspective inspires future nano/microrobotic designs and approaches for water purification from nano/microplastics and other emerging pollutants.

Abstract Bacterial biofilms are multicellular communities firmly attached to solid extracellular substrates. They are considered the primary cause of huge economic losses, from medicine due to medical implants’ failure to large infrastructure due to enhanced pipe corrosion. Therefore, their eradication is highly desirable. Here, the preparation of ZnO self‐propelled micromotors is reported, programming their morphology and motion properties through Ag doping. The ZnO:Ag micromotors actively move upon light irradiation via a self‐electrophoretic mechanism, showing excellent light‐controlled on/off switching motion. At the same time, the rapid and effective removal of both gram‐positive and gram‐negative bacteria biofilms from the solid surface is demonstrated, exploiting the well‐known antibacterial activity of both Ag and ZnO as well as the enhanced diffusion of the micromotors. The new concept for the low‐cost and scalable preparation of chemically programmable Ag‐doped ZnO micromotors here illustrated opens a new route toward the formulation of a new class of light‐driven semiconducting self‐propelled micromotors for environmental applications.