Fabrication of multifunctional microcapsules containing n-eicosane core and zinc oxide shell for low-temperature energy storage, photocatalysis, and antibiosis

In this study, a novel type of multifunctional microcapsules based on an n-eicosane phase change material (PCM) core and a ZnO shell were designed not only for latent heat storage but also for photocatalytic and antibacterial activities. A series of microcapsule samples were synthesized through an in-situ precipitation reaction of Zn(CH3COO)(2)center dot 2H(2)O and NaOH in an O/W emulsion templating system followed by a long-term aging process. The formation of the ZnO shell was monitored by X-ray powder diffraction to identify a phase transition from epsilon-Zn(OH)(2) to ZnO. The chemical composition and surface elemental distribution of the resultant microcapsules were characterized by Fourier-transform infrared, energy-dispersive X-ray, and X-ray photoelectron spectroscopy. Morphologic investigation denionstrated that the microcapsules presented regular spheres with a well-defined core-shell structure. Differential scanning calorimetry analysis indicated that the phase change performance and encapsulation efficiency of the microcapsules were determined by the weight ratio of n-eicosane/Zn(CH3COO)(2)center dot 2H(2)O loaded in the synthesis. Moreover, the microcapsules achieved an excellent energy storage capability and a high working reliability. Most of all, the multifunctional microcapsules gained high photocatalytic and antibacterial activities and especially revealed a high antimicrobial effectiveness against Staphylococcus aureus. With such a multifunctional feature, the microcapsules developed in this work highlight their potential applications in environmental protection and biomedical fields. (C) 2015 Elsevier Ltd. All rights reserved.