N-Dopant Site Formulation for White-Light-Emitting Carbon Dots with Tunable Chromaticity

Abstract

Multicolor emissions from carbon dots (CDs) are vital for light-emitting diodes (LEDs), particularly for direct, whitelight emission (WLE), which enables a replacement of rare earth (RE)-doped phosphors. However, the difficulty of synthesizing single-component WLE CDs with full-spectrum emission severely hinders further investigation of their emission mechanisms and practical applications. Here, we demonstrate rational design and synthesis of chromatically tunable CDs with cyan-, orange-, and white-light emission, precisely tunable along the blackbody Planckian locus by controlling the ratio of different nitrogen dopant sites. We adopted 15 N solid-state nuclear magnetic resonance (NMR) spectroscopy and X-ray photoelectron spectroscopy (XPS) to identify and quantify N-dopants in different sites and environments, and we explain their influence on emission properties of these CDs. This study provides guiding principles to achieve spectrally tuned emissions, enabling us to design WLE from CDs. This study also clarifies which chemical reagents and their proportions should be used for solvothermal synthesis to realize well-defined WLE from single-component CDs and adjustable, correlated color temperature (CCT) from 6500 to 3500 K. We also demonstrate a soft lighting device by adopting an optical haze film composed of cellulose fibers with excellent light-tailoring characteristics. The proposed methodology for synthesizing WLE CDs by engineering the N-doping sites will boost the development of lighting devices with readily available materials toward realization of low-cost, environmentally friendly WLEDs, solar cells, UV-blockers, counterfeit inks, and display applications.

Bioinspired Carbonized Polymer Microspheres for Full-Color Whispering Gallery Mode Emission for White Light Emission, Unclonable Anticounterfeiting, and Chemical Sensing Applications

“…The C-1s peak of the CPMs mainly consists of three types of C bonds: C–C/CC, C–N/C–O, and COOH/CONH (Figure d). The N-1s HRXPS results exhibit a peak at 399.0 eV corresponding to C–NH 2 and C–N–C (pyridinic nitrogen) and a peak at 400 eV due to the amide bond, which demonstrates the formation of a pyridinic bond and a large amide bond (Figure e). − In the O-1s region, the two peaks at 531.2 and 532.6 eV attributed to the N–CO and the O–CO bonds, respectively, are consistent with the different O functionalities of the O-1s in the CPMs (Figure f). The deconvolution of the C-1s, N-1s, and O-1s spectra of CPM-B, C also reveals the presence of different functional groups (Figure S10).…”

New Insight into Fluorescent Polymeric Carbon Dots for Solid-State Laser Device

“…Carbon dots (CDs), a new class of carbon-based nanostructures, have generated great interest from the research community due to their unique optical properties, photostability, and low cost. − Since CDs are mostly composed of C, O, and H, and are completely metal-free, many research groups anticipate that CDs will ultimately replace RE-doped phosphors, metal-chalcogenide-based quantum dots, and perovskite quantum dots. Another advantage of CDs compared to other quantum dots is that they can easily be synthesized bottom-up from various organic molecules via chemical methods. − Optical properties of CDs depend strongly on their chemical composition, chemical bonding states, structure, surface functionalization, dopants, etc. Structures of CDs include crystalline, amorphous, molecular assembles, and polymeric structures, − some of which have not been proven to contain graphitic, inorganic carbon.…”