Polarity, intramolecular charge transfer, and hydrogen bond co-mediated solvent effects on the optical properties of graphene quantum dots

Comprehensive advances in the synthesis, fluorescence mechanism and multifunctional applications of red-emitting carbon nanomaterials

“…The energy difference between the ground and excited states as well as the orientation polarizability of solvents are both inuenced by interactions between the solvent and carbon core. 293,294 For polar solvents, there is a hypsochromic shi with decrease in the polarity of the solvents and the shi is bathochromic with increase in the polarity of the solvent. The nonradiative charge recombination on the surface of FCNMs can be prevented by increasing the protonation capacity of the solvent and decreasing the viscosity of the FCNM solution, which will increase the ability to absorb and emit light in the red or near infrared region.…”

Identification of Chinese baijiu from the same brand based on a graphene quantum dots fluorescence sensing array

“…From a chemical point of view, it can be concluded that GQDs are aromatic substances with electron donating and electron absorbing groups. 34 This provides the possibility for the occurrence of intramolecular charge transfer (ICT) processes. 43,44 Hydrogen bonding also becomes more important in the interaction of GQDs with solvents due to the presence of protonating groups such as nitrogen-containing substances.…”

“…Due to a combination of polarity effects, intramolecular charge transfer and hydrogen bonding, the organic molecules cause changes in the fluorescence of the GQDs. 34 In addition, many types of Wuliangye brand baijiu were well characterized.…”

Detection of Extreme Acidity Based on Carbon Dots: One‐Step Gram‐Scaled Syntheses, Ratiometric Emission Photoluminescent Probe, and Hand‐Held Visual Detection

“…Under high acidity, the oxygencontaining functional groups on the surface of CDs are deprotonated, which further changed the aggregation state, charge density, and energy gap of CDs, resulting in the variation of the PL properties. [36,52,55,56] Figure 5c displayed the FIIR spectra of CDs and CDs + [H + ], respectively. The vibration peak of ─OH was shifted (Δ𝛿 = 33 cm −1 ) from 3425 cm −1 (CDs) to 3392 cm −1 (CDs + [H + ]).…”

“…At the same time, the formation of hydrogen bonds inhibits the rotation of the oxygen-containing functional groups on the surface of CDs, thus suppressing the non-radiative leap channels to improve fluorescence efficiency. [36,[59][60][61] The hydrogen network of CDs tends to be formed under high acidity. Therefore, the PL properties of CDs were sensitive to high [H + ], which exhibited great potential to detect extreme acidity.…”