Fluorescence-based sensing is a straightforward and powerful technique with high sensitivity for the detection of a wide range of chemical and biological analytes. Integrating the high sensing capabilities of fluorescent probes with wireless navigation systems can enable the extension of their operational range, even in challenging scenarios with limited accessibility or involving hazardous substances. This study presents the development of molecularly engineered magneto-fluorescent microrobots based on the push-pull quinonoids by incorporating magnetic nanoparticles using a reprecipitation approach with the aim of detecting high-energy explosives and antibiotics in aqueous environments. The magnetic components in the microrobots offer remotely controlled navigability toward the intended target areas under the guidance of external magnetic fields. Upon interactions with either explosives (picric acid) or antibiotics (tetracycline), the microrobots' intrinsic fluorescence switches to a "fluorescence off" state, enabling material-based intelligence for sensing applications. The molecular-level interactions that underlie "on-off" fluorescence state switching upon engagement with target molecules are elucidated through extensive spectroscopy, microscopy, and X-ray diffraction analyses. The microrobots' selectivity toward target molecules is achieved by designing microrobots with amine functionalities capable of intermolecular hydrogen bonding with the acidic hydroxyl group of picric acid, leading to the formation of water-soluble charge transfer picrate complexes through proton transfer. Similarly, proton transfer interactions play a key role in tetracycline detection. The selective fluorescence switching performance of microrobots in fluidic channel experiments illustrates their selective sensing intelligence for target molecules in an externally controlled manner, highlighting their promising characteristics for sensing applications in real-world scenarios.

• Keywords
• charge transfer complexes, environmental monitoring, fluorescence sensing, magnetic microrobots, organic pollutants,
• MeSH
• Anti-Bacterial Agents * analysis   MeSH
• Fluorescent Dyes * chemistry   MeSH
• Magnetite Nanoparticles * chemistry   MeSH
• Tetracycline * analysis   MeSH
• Water chemistry   MeSH
• Explosive Agents * analysis   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents * MeSH
• Fluorescent Dyes * MeSH
• Magnetite Nanoparticles * MeSH
• picric acid MeSH Browser
• Picrates MeSH
• Tetracycline * MeSH
• Water MeSH
• Explosive Agents * MeSH

Ammonia (NH₃) production is a critical industrial process, as ammonia is a key component in fertilizers, essential for global agriculture and food production. However, the current method of synthesizing ammonia, the Haber-Bosch process, is highly energy-intensive, and relies on fossil fuels, contributing substantially to greenhouse gas emissions. Moreover, the centralized nature of the Haber-Bosch process limits its accessibility in remote or resource-limited areas. Photochemical synthesis of ammonia, provides an alternate lower energy, carbon-free pathway compared to the prevailing industrial methods. The photoconversion of nitrate anions, often present in wastewater, offers a greener, more sustainable, and energy-efficient route for both ammonia-generation and wastewater treatment. Photochemical and chemical synthesis of ammonia requires intensive mass-transfer processes, which limits the efficiency of the method. To change the game, in this work, a key new technology of ammonia-generation, a catalytic ammonia generation (AmmoGen) microrobot, which converts nitrate to ammonia using renewable light energy is reported. The magnetic propulsion of the AmmoGen microrobots significantly enhances mass-transfer, and expedites the photosynthesis of ammonia. Overall, this "proof-of-concept" study demonstrates that microrobots can aid in catalytic small molecule activation and generation of value-added products; and are envisaged to pave the way toward new sustainable technologies for catalysis.

• Keywords
• ammonia, magnetically driven, microrobots, nitrate reduction, photosynthesis,
• Publication type
• Journal Article MeSH