Synthesis And Applications Of Ellipsoidal Polydopamine Capsules And N-doped Carbon Nanocapsules

Bioinspired oxidative self-polymerization of dopamine can coat any surface with a layer of polydopamine(PDA)coating and therefore has attracted wide interest.Other material morpholies of PDA such as nanoparticles and capules are expected to further expand its applications in other fields.In this work,we used polystyrene ellipsoids with various sizes and aspect ratios as the templates for PDA coating and prepared hybrid PS@PDA ellipsoidal particles.Proper conditions have been found to coat the PS ellipsoids with a conformal PDA layers,regardless of their sizes and surface curvatures.Followed by the removal of the PS template particles with tetrahydrofuran,we prepared polydopamine capsules with an ellipsoidal shape.We also prepared N-doped carbon nanocapsules with an ellipsoidal shape,through one-pot carbonization of PDA coated PS ellipsoids,excluding the necessity of subsequent templates removal.The ellipsoidal capsules and carbon materials were fully characterized by scanning electron microscope,transmission electron microscope,X-ray photoelectron spectroscopy,thermogravimetric,infrared spectra,Raman spectroscopy,X-ray diffraction and BET specific surface area test.Polydopamine capsules and N-doped carbon nanocapsules obtained from PS@PDA with one-time polydopamine coating often collapse or break seriously.Iterating PDA coating of PS ellipsoids leads to three dimensional structures with increased wall thickness and mechanical strength.Due to a large number of chemical groups and strong adhesion,polydopamine capsules can be fluorescently labeled.Compared with many kinds of adsorbents,polydopamine capsules have strong adsorption property of methylene blue,with the adsorption capacity up to 210 mg/g after two hours.N-doped carbon nanocapsules have many unique properites and might be used as electrode materials of super capacitors.