Top-down and bottom-up approaches to transparent, flexible and luminescent nitrogen-doped carbon nanodot-clay hybrid films

Two easy approaches are successfully employed for the preparation of nitrogen-doped carbon nanodot (NCND)-clay hybrids (bulk solids and thin films). Fluorescent and small NCNDs are intercalated within the interlayer space of LAPONITE® clay with a simple ion exchange reaction in bulk or embedded between functionalized LAPONITE® sheets by combining a layer-by-layer approach with a self-assembly process. In both cases, homogeneous hybrids with 2D-ordered NCNDs (accounting for >20 wt%) are produced, with the NCND optoelectronic properties preserved. Drop casting of suspensions or self-assembly on flexible substrates allows the fabrication of luminescent flexible films. The transparency of the films is found to be adjustable either by controlling the concentration of the drop-cast suspensions or by the number of layers in the self-assembly procedure. The prepared films are stable over time: the inert LAPONITE® platelets not only guide the highly ordered 2D assemblies of NCNDs in the interlayer space but also protect them from external agents, which could affect their surfaces and thus alter their optoelectronic properties.