Towards Red Emissive Systems Based on Carbon Dots

Abstract

Carbon dots (C-dots) represent an emerging class of nontoxic nanoemitters that show excitation wavelength-dependent photoluminescence (PL) with high quantum yield (QY) and minimal photobleaching. The vast majority of studies focus on C-dots that exhibit the strongest PL emissions in the blue/green region of the spectrum, while longer wavelength emissions are ideal for applications such as bioimaging, photothermal and photodynamic therapy and light-emitting diodes. Effective strategies to modulate the PL emission of C-dot-based systems towards the red end of the spectrum rely on extensive conjugation of sp2 domains, heteroatom doping, solvatochromism, surface functionalization and passivation. Those approaches are systematically presented in this review, while emphasis is given on important applications of red-emissive suspensions, nanopowders and polymer nanocomposites.

Searching for the true origin of the red fluorescence of leaf-derived carbon dots

“…These properties have shown promising potential for applications in drug delivery, 2 bioimaging, 3,4 fluorescent sensing, 5 optoelectronic devices, [6][7][8][9] photocatalysis, 10 electrocatalysis 11 and information encryption. [12][13][14] In addition, due to the unique optical and photoelectric properties of red-emitting CDs in the red/near infrared region, these interesting CDs can be used as an important building block for applications ranging from bioimaging 15,16 and LEDs 17 to photophysics. [18][19][20] Conventional synthesis methods of CDs usually require toxic chemicals or organic solvents as precursors, thus increasing environmental and energy consumption issues.…”

Ultrafast insights into full-colour light-emitting C-Dots

“…The following equation was used for the multiexponential decays to calculate the average lifetime from the fitted data,where τ i represents the excited-state lifetime having the 9–12,29 relative amplitude of A i for each component.…”

“…where τ i represents the excited-state lifetime having the [9][10][11][12]29 relative amplitude of A i for each component.…”

“…Moreover, different degrees of dehydration and carbonization play important roles in controlling the size of the sp 2 -conjugated domains within the prepared C-Dots. [27][28][29][30] Some recent reviews have suggested that the oxygen-containing functional groups act as emissive surface states as well as trap states of C-Dots. Carbonyl groups of carboxylic acid, esters, and aldehyde groups play an important role regarding the tuning of band gap, whereby it has been suggested that the band gap becomes narrower with the increase in -CvO groups in the surface state.…”

One-Pot Synthesis of Dual Color-Emitting CDs: Numerical and Experimental Optimization towards White LEDs

“…Such one-pot methods are capable of drastically reducing the number of steps required in the overall nanocomposite fabrication process; however, controlling the properties of the final white light is harder with such approaches. For example, for some one-pot synthesized CDs, the lack of a sufficiently intense red component in the total spectrum results in cool white light with low CRI [ 43 , 44 ]. Moreover, problems related to an excessively low photoluminescence quantum yield (PLQY), or to aggregation-induced quenching of the fluorescence of CDs in the nanocomposites, can hinder the attainment of high color-converting performances [ 30 , 35 , 40 , 42 ].…”