Monodisperse Surface-Charge-Controlled Black Nanoparticles for Near-Infrared Shielding

Abstract

A simple and quick preparation of black polymer nanoparticles by the microwave-assisted polymerization of 1,5-dihydroxynaphthalene and 1,3,5-trimethyl-1,3,5-triazinane under high temperature and pressure was demonstrated. The average diameter of the nanoparticles ranged from 20 to 700 nm, depending on the preparation conditions such as reaction solvent, monomer concentrations, and monomer ratio in the seed mixture. The surface charge of the nanoparticles was also determined by the monomer ratio used in the seed mixture. The nanoparticles could be dispersed in polar solvents such as water, methanol, and ethanol, probably because the phenolic hydroxyl groups and primary/secondary amine groups remained on the surface of the nanoparticles. The reflectance spectroscopic measurements from 200 to 2200 nm showed that the nanoparticles expressed selective reflectivity of NIR wavelengths. The absorption and reflectance properties could be tuned by microwave-assisted wet calcination of the nanoparticles. The particl...