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

The pi-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 pi-conjugated domain in CDs offers a challenge to prediction of photoluminescence (PL) characteristics in solid-state. Here, we focus on the effect of pi-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 pi-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 pi-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. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study investigates the impact of the pi-conjugated domain on the photoluminescence (PL) phenomenon of carbon dots (CDs) under different interparticle separation conditions, using three types of CDs with varying degrees of carbonization achieved by solvothermal reactions in different alcoholic solvents. At low dispersion, CDs from different solvents exhibit two emissive centers with varying relative intensities based on the degree of carbonization. The higher pi-conjugated domain content in CDs leads to a shift in the dominant PL center from surface- to core-state as CD concentration increases.