Facile synthesis of magnetic fluorescent nanoparticles: Adsorption and selective detection of Hg(II) in water

An adsorbent-chemosensor system based on magnetic fluorescent nanoparticles (MFNPs) was successfully constructed via high-gravity technology and a self-assembly approach, which adopts magnetic Fe₃O₄ nanoparticles as a core, chitosan (CS) as a shell, and carbon quantum dots (CQDs) as a fluorescent probe. The adsorbent-chemosensor possesses an average diameter of 10 nm and a narrow size distribution, as well as superparamagnetic properties, a well-defined pore structure, and superior fluorescence emission intensity. As an adsorbent, the core-shell nanocomposites provide a relatively high adsorption capacity for heavy metal ions and displayed a maximum monolayer adsorption capacity of 110.62 mg Hg(ii) per gram of adsorbent owing to the synergistic interaction due to the high porosity of the core-shell structure and the high affinity of Hg(ii)-Fe₃O₄ or Hg(ii)-CS interactions. As a fluorescent probe, the as-prepared hybrid nanospheres exhibited favorable sensitivity and a low detection limit (12.43 nM) toward Hg(ii). The nanocomposites also demonstrated excellent reusability, with a loss of adsorption of less than 13% and a loss of fluorescence intensity of 5% after five regeneration test cycles. The present work provides a potential approach for the design of a novel and cheap adsorbent-chemosensor for application in the recognition of Hg(ii) and its elimination from water.