Colloidal Stable Quantum Dots Modified by Dual Functional Group Polymer for Inkjet Printing
Quantum dots(QDs) with unique fluorescence properties have been applied in a variety of applications. Here, we report an effective method to prepare water dispersible QDs which have remarkable colloidal stability and could be used in inkjet printing. A new set of dual functional group polymers, mercaptopropionic polyethylenimine (MPPEI), as ligands combines thiol of 3-mercaptopropionic acid (MPA) and amine of polyethylenimine (PEI) , for the surface functionalization of CdSe/CdS/ZnS quantum dots(QDs) . These ligands reduce issues of thiol oxidation and weak binding affinity on amino. Ligation with these polymers provides fluorescent QDs with excellent acid resistance, base resistance, photostability and thermostability since the branched structure of MPPEI could provide QDs very effective protection. We use this stable QDs as security inks and get the fluorescent pattern invisible under ambient light.