A facile and novel synthetic method for the preparation of hydroxyl capped fluorescent carbon nanoparticles

A new type of fluorescent carbon based nanomaterial has drawn considerable attention due to their unique physicochemical properties. Carboxyl functionalized carbon nanoparticles are well documented in the literature. However, the carbonyl moiety in the carboxyl group considerably reduces the photoluminescence quantum yield. In this study, we present a direct, simple and novel synthetic route to produce hydroxyl functionalized fluorescent carbon nanoparticles derived from candle soot using organic base and surfactant which could be readily scaled up. The functionalization of carbon nanoparticle was confirmed by various spectroscopic techniques. 1H NMR and FTIR measurements have been used to confirm the presence of sp2 carbon in the form of aryl and hydroxyl moieties. MALDI-TOF Mass and TGA measurements further confirmed the functionalization. Structural characterization of these particles by Raman spectroscopy showed characteristic peaks located at 1333 and 1583 cm−1 corresponding to diamond-like (D) and graphite-like (G) bands of the carbon allotropes respectively. The minimum grain size of 7.3 nm was calculated using Raman spectra of the functionalized carbon nanoparticles which corroborate well with the results of dynamic light scattering (DLS) and TEM studies. UV–vis spectroscopic measurements displayed an absorption band at ca. 245 nm, which was consistent with the optical characteristics of functionalized carbon nanoparticles. PL measurements confirmed that the functionalized carbon nanoparticles have characteristic emission peak and shows fluorescence under blue light excitation. With a combination of free dispersion in water and attractive PL properties, these functionalized carbon nanoparticles hold promise for application in nanotechnology.