Photoluminescent carbon quantum dots as a directly film-forming phosphor towards white LEDs

Abstract

Photoluminescent organosilane-functionalized carbon quantum dots (CQDs), 3.0-3.5 nm in diameter, were synthesized via a facile hydrothermal method using citric acid monohydrate as a precursor and N-(3-(trimethoxysilyl) propyl) ethylenediamine as a coordinating and passivation agent. The optical properties of the as-obtained CQDs were investigated in detail. The CQD aqueous solution emits bright blue-white light under ultraviolet (UV) illumination with a quantum yield of 57.3% and high red-green-blue (RGB) spectral composition of 60.1%, and in particular the CQDs exhibit excitation-independent photoluminescence. The CQDs have a narrow size distribution around 3.1 nm and good film-forming ability through simple heat-treatment. By virtue of these excellent optical characteristics and good film-forming ability, a white light-emitting device (LED) was fabricated by combining a UV-LED chip with a single CQD phosphor film, which exhibited cool white light with a CIE coordinate of (0.31, 0.36), a color rendering index of 84 and a correlated color temperature of 6282 K. In addition, the white LED exhibits good optical stability under various working currents and for different working time intervals. Moreover, the interaction between the carbogenic core and surface groups was discussed using the DMol(3) program based on density functional theory. This research suggests the great potential of CQDs for solid-state lighting systems and reveals the effect of the surface state on the photoluminescent mechanism of CQDs.

Investigation on the chirality mechanism of chiral carbon quantum dots derived from tryptophan

“…3(d)). 23,24 These results demonstrate that as-prepared L-CQDs contain lots of functional groups on their surface. The chemical compositions of D-CQDs are similar to those of L-CQDs, as shown in Fig.…”

Polymer composite fluorescent hydrogel film based on nitrogen‐doped carbon dots and their application in the detection of Hg2+ ions

“…The fluorescence intensity of the N‐CDs and the hydrogel films decreased slightly under 365 nm UV light over 400 min as shown in Figure (a). The results show that the N‐CDs and the hydrogel films have good anti‐photobleaching ability, which is attributed to the high QY of the N‐CDs and the passive nature of N ‐(2‐hydroxyethyl) ethylenediamine . The reduction level of the fluorescence intensity of the hydrogel films is slightly lower than that of the N‐CDs.…”

Quenching‐Resistant Polymer Carbon Dot Preserving Emission Color Consistency in Solid‐State

“…The center of emission spectra of PCD‐based LED was located at 434 nm for 1 wt% and at 484 nm for 50 wt% that are blue region (Figure S15, Supporting Information). The red‐shift with concentration increase may be due to the inner filter effect or energy transfer, which is arising from additional emissive states formed during sonication and annealing. While PCD‐based LED showed almost same blue emission irrespective of loading amounts of PCD, RCD‐based LED showed obvious color change from blue to red as the loading fraction increased.…”