Precursor-dependent structural diversity in luminescent carbonized polymer dots(CPDs):the nomenclature

Carbon dots(CDs)have received immense attention in the last decade because they are easy-to-prepare,nontoxic,and tailorable carbon-based fluorescent nanomaterials.CDs can be categorized into three subgroups based on their morphology and chemical structure:graphene quantum dots(GQDs);carbon quantum dots(CQDs),and carbonized polymer dots(CPDs).The detailed structures of the materials can vary significantly,even within the same category.This property is particularly predominant in chemically synthesized CPDs,as their formation proceeds via the polymerization-carbonization of molecules or polymer precursors.Abundant precursors endow CPDs with versatile structures and properties.A wide variety of carbon nanomaterials can be grouped under the category of CPDs because of their observed diversity.It is important to understand the precursor-dependent structural diversity observed in CPDs.Appropriate nomenclature for all classes and types of CPDs is proposed for the better utilization of these emerging materials。

Confined-domain crosslink-enhanced emission effect in carbonized polymer dots

Revealing the photoluminescence(PL)origin and mechanism is a most vital but challenging topic of carbon dots.Herein,confined-domain crosslink-enhanced emission(CEE)effect was first studied by a well-designed model system of carbonized polymer dots(CPDs),serving as an important supplement to CEE in the aspect of spatial interactions.The“addition-condensation polymerization”strategy was adopted to construct CPDs with substituents exerting different degrees of steric hindrance.The effect of confined-domain CEE on the structure and luminescence properties of CPDs have been systematically investigated by combining characterizations and theoretical calculations.Such tunable spatial interactions dominated the coupling strength of the luminophores in one particle,and eventually resulted in the modulated PL properties of CPDs.These findings provide insights into the structural advantages and the PL mechanism of CPDs,which are of general significance to the further development of CPDs with tailored properties.

Highly efficient solid-state luminescence of carbonized polymer dots without matrix

Development of high-performance solid state luminescent carbon-based nanomaterials remains challenging.Here,strong blue-green fluorescent carbonized polymer dots(CPDs)from o-aminobenzenethiol and thiosalicylic acid(o ABT-TSA-CPDs)with an absolute photoluminescence quantum yield(PLQY)of 76%in solid state without matrix were synthesized.Through adjusting the reaction temperature and time,the PL centers were proved to be carbon core state and surface state associated to carbonyl group which was the source of strong fluorescence emission in solid state.The mechanism of the unique phenomenon of enhanced emission from ethanol solution(PLQY=7%)to powder(PLQY=76%)was investigated by analyzing the chemical properties and structures of o ABT-TSA-CPDs at different temperatures and o ABT-TSACPDs/PVC composites,and was confirmed as fixation of PL centers.

A combined experimental and theoretical investigation of donor and acceptor interface in efficient aqueous-processed polymer/nanocrystal hybrid solar cells

As a route to improving the energy conversion of organic-inorganic hybrid-solar cells, we have tested the performance of poly(phenylene vinylene)(PPV), poly(2,5-thienylene vinylene)(PWTV) polymers and CdTe nanocrystal devices produced via aqueous-processing. It is found that small differences in the conformation of the sensitizer lead to dramatic effects on the solar cell efficiency. Using a combination of UV-Vis absorption spectroscopy and first-principles non-adiabatic molecular dynamics(NAMD) based on time-dependent density-functional theory(TDDFT), PPV is found to have a longer electron injection and recombination time despite seeming to have a better energy alignment with the substrate, which leads to a higher devices performance than PWTV. The present results shed new light on the understanding of organic-inorganic hybrid-solar cells and will trigger further experimental and theoretical investigations.