Freestanding Luminescent Films of Nitrogen-Rich Carbon Nanodots toward Large-Scale Phosphor-Based White-Light-Emitting Devices

Abstract

In this work, nitrogen-rich carbon nanodots (CNDs) are prepared by the emulsion-templated carbonization of polyacrylamide. The formation mechanism and chemical structure are investigated by infrared, nuclear magnetic resonance, and X-ray photoelectron spectroscopies. Transmission electron microscopy also reveals that the obtained CNDs have well-developed graphitic structure and narrow size distribution without any size selection procedure. We vary the molecular weight of the polymer to control the size of the CNDs and finally obtain the CNDs rendering bright visible light under UV illumination with a high quantum yield of 40%. Given that the CNDs are worth utilizing in phosphor applications, we fabricate large-scale (20 × 20 cm) freestanding luminescent films of the CNDs based on a poly(methyl methacrylate) matrix. The polymer matrix can not only provide mechanical support but also disperse the CNDs to prevent solid-state quenching. For practical application, we demonstrate white LEDs consisting of the films as color-converting phosphors and InGaN blue LEDs as illuminators. Such white LEDs exhibit no temporal degradation in the emission spectrum under practical operation conditions. This study would suggest a promising way to exploit the luminescence from solid-state CNDs and offer strong potential for future CND-based solid-state lighting systems.

One-step synthesis of hollow carbon nanospheres in non-coordinating solvent

“…For example, when the hollow carbon nanospheres are excited at wavelengths from 350 to 500 nm, the corresponding emission maxima shift from 430 to 540 nm. This excitation-dependent emission behavior is due to the presence of multiple surface emissive trap states, and then the radiative recombination of the excitons trapped in these states promotes the emission [16]. The strongest emission peak intensity locates at 510 nm when excited at 450 nm, which agrees with the excitation spectrum with a dominant peak at $450 nm.…”

Solid‐State Carbon Dots with Efficient Cyan Emission towards White Light‐Emitting Diodes

“…[1,2] Studies have demonstrated that fluorescent CDs have ab road range of promising applications in bioimaging, [3][4][5] sensors, [6][7][8] photocatalyst [9,10] andw hite Light-Emitting Diodes (LEDs)e tc. [10][11][12][13][14][15][16][17][18][19] However,u pt on ow,a great number of studies have been focused on the synthesis and applicationso fa queous CDs, few attention wasp aid to solid powder CDs. This because CDs alwayss uffer severe luminescenceq uenching in solid powder form due to aggregation.…”

Understanding the Photoluminescence Mechanism of Nitrogen‐Doped Carbon Dots by Selective Interaction with Copper Ions

“…[8] Doping provides an opportunity to tune the electronic energy levels for desired applications. Numerous synthetic strategies are available for preparingn itrogen-doped CDs from biological sources such as orange peels, [9] milk, [10] plant leaf, [11] cucumber [12] and so on, as well as from non-biological carbon precursors such as quinolone, [13] ammonium citrate, [14] polyacrylamide, [15] and so on. Ta ng et al showed that there is as ignificant change in the energy level structure of CDs doped with nitrogen and thus in their photoluminescence behavior.…”