Highly luminescent carbon-nanoparticle-based materials: Factors infl uencing photoluminescence quantum yield

Abstract

Unravelling the factors infl uencing photoluminescence (PL) quantum yield of the carbon nanoparticles (CNPs) is the prerequisite for preparing highly luminescent CNP-based materials. In this work, an easy and effective method is reported for preparing highly luminescent CNP-based materials. Water-soluble luminescent CNPs (CNP-Cs) with large size distribution (1-60 nm) with PL quantum yields of 22% are synthesized through a microwave pyrolysis approach. Energy transfer (ET) is confi rmed to occur from small size CNPs (CNP-Ss:1-7 nm, blue emitters) to large size CNPs (CNP-Ls:10-60 nm, green emitters). Further centrifugally separating CNP-Cs resulted in an enhancement of the PL quantum yield up to 39% of CNP-Ss aqueous solution. The PL quantum yield of CNP-Ss could even be further improved in high-viscosity solvents. PL quantum yield higher than 90% is achieved in fi lms of commercial glue water embedded with the CNP-Ss at embedding ratio lower than 3 wt%. By contrast, the yield is greatly decreased in the CNP-C-embedding fi lms with embedding ratio higher than 1 wt%, which is due to self-absorption, as well as enhanced ET between CNP-Ss and CNP-Ls. High-viscosity solvents and polymer matrix are proposed to act as surface passivation reagents to enhance PL quantum yield of CNPs.