Stable Room-Temperature Phosphorescence from MXene-Derived Carbon Dots: Ultralong Afterglow Emission without an External Matrix

Abstract

Herein, we synthesized highly defined carbon dots (CDs) from two-dimensional delaminated MXene through a solution-based acid etching method. The as-synthesized CDs show blue fluorescence emission in the solution phase upon neutralization with excess alkali. However, after solidification, the solid powder of CDs shows strong bright green room-temperature phosphorescence/afterglow emission for up to 5 s without using any further external matrix. The fundamental photophysical properties of the CDs are further correlated with the structural and elemental features. It suggests that the rigidity of the surface emissive states due to the slow modification of the exterior surface of CDs facilitates the afterglow emission. Temperature-dependent photoluminescence study and the systematic interconversion between room-temperature phosphorescence and prompt fluorescence depict the possible thermally activated delayed fluorescence at high temperatures. It is further correlated with the low-temperature phosphorescence studies (up to 90 K). The solid powder of CDs has been further utilized directly as a sustainable smart material for anticounterfeiting and information protection applications.

Waste Polyethylene-Derived Carbon Dots: Administration of Metal-Free Oxidizing Agents for Tunable Properties and Photocatalytic Hyperactivity

“…In addition, medium-intense peaks in CD 1 and CD 4 and more intense peaks in CD 2 and CD 3 are present at ∼1720 cm –1 due to carbonyl functional groups. A prominent peak corresponding to the −CC– bonds is observed in the 1620–1650 cm –1 region. ,,, In addition, in all samples, asymmetric and symmetric stretchings of −SO 3 groups are present at ∼1150 and ∼1017 cm –1 , respectively, originating from an H 2 SO 4 attack on the polymer backbone, and another peak at ∼860 cm –1 corresponds to the C–C ring and −CH 2 deformations. ,,, Notably, an additional peak (∼1265 and ∼730 cm –1 in CD 2 ) corresponds to the N–O stretching and out-of-plane wagging deformations originating from the nitric acid attack on the preformed char. , Thus, the FTIR analysis revealed that all CDs contain graphitic domains and surface functional groups, while NO 2 groups are introduced upon nitric acid treatment.…”