Photoluminescent Honeycomb Films Templated by Microwater Droplets

The europium polyoxometalate anion, [EuW10O36]9−, can be transferred from an aqueous phase into a chloroform phase through encapsulation by dioctadecyldimethylammonium (DODMA+). The formed (DODMA)9[EuW10O36] complexes can self-assemble into ordered, uniform porous honeycomb films by using a simple solvent-evaporation method at the air/water interface without any extra moist airflow. TEM, SEM, and AFM observations show porous morphologies with pores having a diameter of about 2 μm and a wall depth of about 0.8 μm. The microlamellar structure and crystalline nanoaggregates of (DODMA)9[EuW10O36] complexes in films are characterized by XRD measurements and high-resolution TEM observations. During self-assembly into porous honeycomb films, it is speculated that the cooled microwater droplets that are induced by the quick evaporation of chloroform act as the templates for pores and that (DODMA)9[EuW10O36] complexes are deposited around pores. Because of the intrinsic fluorescence of [EuW10O36], the photoluminescent porous honeycomb films of (DODMA)9[EuW10O36] complexes can emit fluorescence when they are excited by UV light. It is expected that this will meet more requirements of new materials for fluorescence, separation membranes, microstructured electrode surfaces, containers, and reactors.