Efficient White Electrochemiluminescent Emission From Carbon Quantum Dot Films

Abstract

Carbon quantum dots (CQDs) were manufactured from citric acid and urea in a gram-scale synthesis with a controlled size range between 1. 5 and 23.8 nm. The size control was realized by varying volume of the precursor solution in a hydrothermal synthesis method. The prepared CQDs were investigated using electrochemiluminescence (ECL) spectroscopy at interfaces of their electrode films and electrolyte solution containing coreactants rather than conventional optoelectronic tests, providing an in-depth analysis of light-emission mechanisms of the so-called half-cells. ECL from the CQD films with TPrA and K 2 S 2 O 8 as coreactants provided information on the stability of the CQD radicals in the films. It was discovered that CQD •− has a powerful electron donating nature to sulfate radical to generate ECL at a relative efficiency of 96% to the Ru(bpy) 3 Cl 2 /K 2 S 2 O 8 coreactant system, indicating a strong performance in light emitting applications. The smaller the CQD particle sizes, the higher the ECL efficiency of the film interface, most likely due to the increased presence of surface states per mass of CQDs. Spooling ECL spectroscopy of the system revealed a potential-dependent light emission starting from a deep red color to blue-shifted intensity maximum, cool bright white emission with a correlated color temperature of 3,200 K. This color temperature is appropriate for most indoor lighting applications. The above ECL results provide information on the performance of CQD light emitters in films, permitting preliminary screening for light emitting candidates in optoelectronic applications. This screening has revealed CQD films as a powerful and cost-effective light emitting layer toward lighting devices for indoor applications.

Highly sensitive Ni2+ sensors based on polyurethane‐derived, label‐free carbon dots with high adsorption capacity

“…To further investigate the inner filter effect, the optical band gaps (E g ) of carbon dots and Ni 2+ were estimated from Tauc plot (Figure 5e and f) [57] . The Tauc plot showed that the optical band gaps of carbon dots and Ni 2+ are 5.3 and 3.8 eV, respectively, which are close the literature values [58–59] . The larger optical band gap of carbon dots confirmed that the emission energy after energy absorption was sufficient to be absorbed by Ni 2+ (Figure 5g), which is in consistency with the overlapped carbon dot emission and Ni 2+ absorption in Figure 5d.…”

“…[57] The Tauc plot showed that the optical band gaps of carbon dots and Ni 2 + are 5.3 and 3.8 eV, respectively, which are close the literature values. [58][59] The larger optical band gap of carbon dots confirmed that the emission energy after energy absorption was sufficient to be absorbed by Ni 2 + (Figure 5g), which is in consistency with the overlapped carbon dot emission and Ni 2 + absorption in Figure 5d. Moreover, we believed that the functional groups of carbon dots, such as carbonyl, hydroxyl, and carboxylate groups, induced Ni 2 + via electrostatic attraction leading to effective inner filter effect.…”

Red, green, and blue light-emitting carbon dots prepared from o-phenylenediamine

“…The CDs with visible spectral emission can be obtained through a one pot pyrolysis method by adjusting the precursor or reaction conditions. [6][7][8][9][10] Lin et al 11 developed a variety of colored uorescent CDs using different precursors, and differences in particle size and nitrogen content were proposed to result in red-shied emission. The emission wavelength of CDs changed from 426 to 603 nm by changing the precursors from (o-, m-, p-) phenylenediamine, and tricolour CDs were prepared.…”

Film Electrochemiluminescence Controlled by Interfacial Reactions Along with Aggregation‐, Matrix‐Coordination‐, and Crystallization‐Induced Emissions

“…Adsetts and Ding et al. performed a CQD size dependent study on the CQD film AIECL and interfacial properties to understand CQD emission mechanisms [48] . The CQD sample series featured a range of sizes from 1.5 to 23.8 nm where the smallest (1.5 nm) and largest (23.8 nm) CQDs were covered in detail and referred to as CQD3 and CQD4 in this subsection.…”