Anisotropic polydopamine capsules with an ellipsoidal
shape that can tolerate harsh conditions: efficient adsorbents for organic dyes
and precursors for ellipsoidal hollow carbon particles
Yang, L (Yang, Lu)[ 1 ] ; Wang, C (Wang, Cong)[ 1 ] ; Ye, ZH (Ye, Zihan)[ 2 ] ; Zhang, PJ (Zhang, Pengjiao)[ 2 ] ; Wu, SH (Wu, Songhai)[ 1 ] ; Jia, SY (Jia, Shaoyi)[ 1 ] ; Li, ZY (Li, Zhanyong)[ 2 ] ; Zhang, ZK (Zhang, Zhenkun)[ 2 ]
RSC ADVANCES, 2017, 7(35): 21686-21696
DOI: 10.1039/c7ra02235b
WOS:000399810800041
Abstract
Polymeric capsules often buckle, collapse or even break
when being processed in the dried state into other materials under high
temperature and pressure due to moderate mechanical rigidity. In the case of
non-spherical capsules, to keep their precious anisotropic morphology intact
under harsh conditions is even more challenging since the whole surface of such
kinds of capsules does not experience the same stress or strain due to the
different surface curvatures. In the current work, we reported a strategy to
prepare polydopamine (PDA) capsules with an ellipsoidal shape and enhanced
mechanical rigidity using polystyrene ellipsoids as the sacrificial anisotropic
templates. Bio-inspired oxidation induced self-polymerization of dopamine can
form conformal PDA coatings on polystyrene ellipsoids of various aspect ratios
and sizes. Several strategies have been exploited to increase the thickness of
the PDA shell, among which, iterating PDA coating produces ellipsoidal PDA
capsules with a thick and robust shell. These ellipsoidal PDA capsules can
survive carbonization at temperatures as high as 800 degrees C and were
directly turned into N-doped carbon capsules with a well-defined ellipsoidal
shape, excluding the necessity of removing the sacrificial templates after carbonation.
Furthermore, the rigid PDA ellipsoidal capsules are efficient adsorbents for
organic dyes in contaminated water and have impressive adsorption efficiencies
as high as 200 mg g(-1).
