Assembly Of Novel Mineral-based Photofunctional Thin Films Via Layer-by-layer Self-Assemble Method

Two-dimensional layered materials, due to their nanosheets’ unique anisotropic and molecular level thickness, cause extensive interest of scientists and show the powerful potential-application on a new nanoscale assembly in nano-materials research. In this paper, we select oppositely-charged inorganic nanosheets to form electronic microenvironment(EME), and control the composition of inorganic nanosheets in order to generate magnetic field(MF), and finally explore the effects on optical property of organic chromophores in the interlayer. The main contents are listed as follow:(1) Luminescent multilayer thin films(MTFs) based on montmorillonite(MMT) nanosheets and non-magnetic layered double hydroxides(LDHs) nanosheets intercalating luminescent π-conjugated anionic polymer were fabricated via LBL method. According to results of obtained samples, we confirmed that electronic microenvironment(EME) formed by oppositely-charged inorganic nanosheets can prolong the lifetimes of MTFs containing anionic polymer more than 2.5 times compared to the pristine solution’s. Above all, the novel concept is successfully verified that EME can affect the conjugate structure of anionic chromophores, and then we firstly propose the novel mechanisms of elevating fluorescence lifetime.(2) In order to verify the double coupling effect of EME and MF generated by the inorganic nanosheets, we choose Ni Fe-LDHs, MMT and organic luminescent material to construct the optical functional MTFs by LBL method. We found that, due to the double coupling effect of EME and MF, lifetimes of MTFs containing cationic chromophores are prolonged over 45-fold, and those of MTFs containing anionic chromophores are also promoted to about three times. Thus we confirmed that EME can affect the different ionic chromophores, and MF can also produce beneficial effects on the luminescent lifetimes.(3) To test universality of EME and MF, we transform different transition metal to synthesize the different LDHs, and then fabricated MTFs via the same methods. Due to the double coupling effect of EME and MF, the lifetimes of MTFs regardless of cationic or anionic chromophores between the interlayer, the luminescent lifetimes have been improved dramatically. We confirm that the EME and MF exist the extensively influence on the optical property of the luminescent MTFs, which can provide a novel method to fabricate mineral-based thin films and open a new direction for the further research of optical materials.