Highly Luminescent Carbon-​Nanoparticle-​Based Materials: Factors Influencing Photoluminescence Quantum Yield

Unravelling the factors influencing photoluminescence (PL) quantum yield of the carbon nanoparticles (CNPs) is the prerequisite for prepg. highly luminescent CNP-​based materials. In this work, an easy and effective method is reported for prepg. highly luminescent CNP-​based materials. Water-​sol. 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 confirmed 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 sepg. CNP-​Cs resulted in an enhancement of the PL quantum yield up to 39​% of CNP-​Ss aq. soln. 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 films of com. 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 films 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.