Competition of the roles of π-conjugated domain between emission center and quenching origin in the photoluminescence of carbon dots depending on the interparticle separation

Abstract The π-conjugated domain, which is one of frequently-suggested fluorescence origin of carbon dots (CDs), can also act as fluorescence quenching origin in aggregated state. This dual role of the π-conjugated domain in CDs offers a challenge to prediction of photoluminescence (PL) characteristics in solid-state. Here, we focus on the effect of π-conjugated domain on the PL phenomenon for different interparticle separation using three types of CDs with different degree of carbonization. The degree of carbonization was controlled by selecting three alcoholic solvent species for solvothermal reaction, which can influence carbonization of CDs. In dilute dispersion, CDs from three different solvents possessed two emissive centers originated from surface- and core-state with different relative intensities depending on the degree of carbonization. With the increase in concentration of CDs, the higher contents of π-conjugated domain changed the dominant PL center from surface- to core-state due to the greater reduction of surface-derived emission. In aggregated state, the emission from surface-state was totally suppressed, and the π-conjugated domain contents influenced the emission efficiency of core-state. Based on PL decay results, we proposed the PL mechanism of the CDs for different interparticle separation, which would extend the boundary in the interpretation of PL properties of CDs.