Fluorescent nanocomposites of Ag nanoclusters grown in anionic polymer layers grafted to plastic substrate: Preparation, characterization and evaluation in Hg 2+ sensing and white light generation

Fluorescent noble metal nanoclusters (NCs) are emerging optical nanomaterials with properties similar to those of quantum dots. Their applications can be expanded by combining them with polymer matrices to obtain flexible and transparent light‐emitting nanocomposites. However, achieving highly fluorescent nanocomposites of this type remains challenging due to phase separation and aggregation of NCs in polymer hosts leading to a strong reduction in fluorescence efficiency. We address this key issue by covalently grafting a layer of a specifically selected matrix polymer onto a transparent plastic film and photochemically synthesizing the fluorescent metal NCs directly in the grafted layer. The surface‐grafted matrix polymer effectively captures the noble metal (Ag) ions, photo‐reduces them to atoms, acts as a capping ligand for the growing Ag NCs, and immobilizes them on the substrate surface. The Ag NCs were produced by both wet and dry synthesis, and effects of synthesis method, reaction time, and matrix polymer layer thickness on the fluorescence properties of the resulting nanocomposites were investigated and discussed. Importantly, the fluorescence intensity of these nanocomposite films is sensitive to submicromolar concentrations of aqueous Hg 2+ that makes them useful as fluorescent sensing materials for selective and ultrasensitive detection of Hg 2+ ions in water. Besides, the nanocomposite films obtained by the dry synthesis of NCs exhibit an intensive emission covering the whole green to red range of the visible spectrum and, hence, produce bright white light under illumination with a blue LED that makes them attractive as down‐conversion materials in one‐phosphor‐converted white LEDs.