Preparation of Multicolor Photoluminescent Carbon Dots by Tuning Surface States.

Kai Jiang,Yuhui Wang,Congzhong Cai,Xiangyu Feng,Zhongjun Li,Xiaolu Gao,Hengwei Lin

doi:10.3390/nano9040529

Abstract

The achievements of multicolor photoluminescent (PL)-emissive carbon dots (CDs), particularly red to near infrared (NIR), are critical for their applications in optoelectronic devices and bioimaging, but it still faces great challenges to date. In this study, PL emission red-shifts were observed when tartaric acid (TA) was added into m-phenylenediamine (mPD) or o-phenylenediamine (oPD) solutions as carbon sources to prepare CDs, i.e., from blue to green for mPD and from yellow-green to red for oPD. Morphology and structure analyses revealed that the increased surface oxidation and carboxylation were responsible for the red-shifts of emission, indicating that TA played a key role in tuning the surface state of CDs. These factors could be employed as effective strategies to adjust PL emissions of CDs. Consequently, multicolor PL CDs (i.e., blue-, green-, yellow-green- and red-emissive CDs) can be facilely prepared using mPD and oPD in the absence and presence of TA. Particularly, the obtained red-emissive CDs showed a high PL quantum yield up to 22.0% and an emission covering red to NIR regions, demonstrating great potentials in optoelectronic devices and bioimaging. Moreover, multicolor phosphors were further prepared by mixing corresponding CDs with polyvinylpyrrolidone (PVP), among which the blue, green, and red ones could serve as three primary color phosphors for fabricating multicolor and white light-emitting diodes (LEDs). The white LED was measured to show a Commission Internationale de L’Eclairage (CIE) 1931 chromaticity coordinate of (0.34, 0.32), a high color rendering index (CRI) of 89, and a correlated color temperature (CCT) of 5850 K, representing one of the best performances of white LEDs based on CDs.

Highlights

Since the traditional photoluminescent (PL) materials exhibit drawbacks of quick photobleaching, complicated preparation processes, severe toxicity, and/or detrimental effects to humans and the environment, the exploitation of new kinds of PL materials are still highly desirable [1,2,3]
Nanomaterials 2019, 9, 529 displayed a high color rendering index (CRI) of 89 and relatively low correlated color temperature (CCT) of 5850 K, representing one of the best performances of white light-emitting diodes (LEDs) based on carbon dots (CDs)
The CCT and CRI of the white LED were measured and determined to be 5850 K and 89, respectively, representing superior white light emission performances. These results demonstrate potential applications of the as-prepared CDs for the generation of lighting devices

Summary

Introduction

Since the traditional photoluminescent (PL) materials (e.g., semiconductor quantum dots, organic fluorescent dyes, and rare earth-based phosphors) exhibit drawbacks of quick photobleaching, complicated preparation processes, severe toxicity, and/or detrimental effects to humans and the environment, the exploitation of new kinds of PL materials are still highly desirable [1,2,3]. Morphology and structure/composition analyses revealed that the increased surface oxidation and carboxylation should be responsible for the observed red-shifts of emission Such factors could be employed as effective strategies to adjust the PL emission wavelength of CDs. such factors could be employed as effective strategies to adjust the PL emission wavelength of CDs Based on these findings, multicolor PL CDs (i.e., blue, green, yellow-green, and red emissive CDs, abbreviated as b-CDs, g-CDs, y-CDs, and r-CDs, respectively) were facilely prepared using mPD or oPD in the absence and presence of TA. Nanomaterials 2019, 9, 529 displayed a high color rendering index (CRI) of 89 and relatively low correlated color temperature (CCT) of 5850 K, representing one of the best performances of white LEDs based on CDs

Reagents

Procedure

Equipment and Characterization

Findings

Conclusions