Intramolecular Hydrogen Bonds Quench Photoluminescence and Enhance Photocatalytic Activity of Carbon Nanodots

Abstract

Understanding the photoluminescence (PL) and photocatalytic properties of carbon nanodots (CNDs) induced by environmental factors such as pH through surface groups is significantly important to rationally tune the emission and photodriven catalysis of CNDs. Through adjusting the pH of an aqueous solution of CNDs, it was found that the PL of CNDs prepared by ultrasonic treatment of glucose is strongly quenched at pH 1 because of the formation of intramolecular hydrogen bonds among the oxygen-containing surface groups. The position of the strongest PL peak and its corresponding excitation wavelength strongly depend on the surface groups. The origins of the blue and green emissions of CNDs are closely related to the carboxyl and hydroxyl groups, respectively. The deprotonated COO(-) and CO(-) groups weaken the PL peak of the CNDs and shift it to the red. CNDs alone exhibit photocatalytic activity towards degradation of Rhodamine B at different pH values under UV irradiation. The photocatalytic activity of the CNDs is the highest at pH 1 because of the strong intramolecular hydrogen bonds formed among the oxygen-containing groups.

Enhanced Biological Photosynthetic Efficiency Using Light‐Harvesting Engineering with Dual‐Emissive Carbon Dots

“…The chemical compositions and bonds of CDs are further characterized. As shown in the Fourier transform infrared (FT‐IR) spectrum (Figure e), the broad absorption band at 3050–3700 cm −1 corresponding to the stretching vibrations of COOH, OH, and NH . The characteristic absorption bands at 3289, 1620, and 1668 cm −1 can be attributed to the stretching vibrations of NH of the porphyrin ring, aromatic CC, and CN vibrations of pyrrole, respectively .…”

“…Recently, CDs have been reported to display tunable PL emissions because of the prior interaction between the solvent molecules or the existence of various surface trap states with different solvent polarity . The QYs of CDs mentioned above also see a decline in water, which may be attributed to the nonradiative PL quenching caused by the hydrogen bonds formed between oxygen‐related groups and water molecules . A highly positive ζ‐potential of CDs in water has been found, +36.2 ± 1.8 mV; normally, a large magnitude of ζ‐potential suggests a stable colloid system.…”

Smart Utilization of Carbon Dots in Semiconductor Photocatalysis

“…The original CDs contained CO and COOH groups, which induced high upward band bending, and facilitated the separation of the photocarriers, leading to higher photocatalytic activity. [3d] The intramolecular hydrogen bonds that were formed among the oxygen‐containing groups on the CDs enhanced the band‐bending effect, facilitating the separation and stabilization of the photocarriers, all of which serve to enhance the photocatalytic performance …”

In Situ Time‐Dependent and Progressive Oxidation of Reduced State Functionalities at the Nanoscale of Carbon Nanoparticles for Polarity‐Driven Multiscale Near‐Infrared Imaging

“…For further assessing the surface chemistry of CNPs, Raman, Fourier transform infrared (FT‐IR), 1 H‐NMR spectroscopy studies, and X‐ray photoelectronic (XPS) spectroscopic studies were undertaken ( Figure 3 A–C; Figure 4 ; and Figure S8, Supporting Information, respectively). Raman spectra of these amorphous materials are characterized by the presence of “G” ( graphitic , sp 2 hybridized) and “D” bands ( disordered graphitic , sp 3 hybridized) bands at 1367 cm −1 and a G band at 1529 cm −1 , which corresponds to disordered structures and graphitic structures, respectively . The intensity of I D / I G was found to increase from 0.89 to 1.12 from CNP BI1 to CNP BI6 which could be attributed that the amorphous structures of CNPs are closely correlated to the red shift in PL emission .…”