Photoexcited State Properties of Poly(9-vinylcarbazole)-Functionalized Carbon Dots in Solution versus in Nanocomposite Films: Implications for Solid-State Optoelectronic Devices

Carbon dots (CDots) are small carbon nanoparticles with effective surface passivation accomplished mostly via organic functionalization. In this study, the largely amorphous carbon nanoparticles were copolymerized with N-vinylcarbazole in microwave-assisted radical reactions. The copolymers thus formed are structurally equivalent to the individual carbon nanoparticles each surface-functionalized by multiple poly(N-vinylcarbazole) (PVK) segments, thus denoted as PVK-CDots. Their electronic transitions and photoexcited state properties, including especially the characteristic excitation wavelength dependencies of fluorescence parameters, were found to be essentially the same as those commonly observed in CDots of small organic molecules for surface functionalization. The PVK-CDots were dispersed in neat PVK for polymeric nanocomposite films free from any other foreign materials. The optical absorptions and fluorescence emission properties of PVK-CDots in the solid-state film matrix environment were found to be little changed from those in solution. The significance of the findings and implications to various uses of these nanomaterials in optoelectronics and related fields are highlighted and discussed.