Graphene near infrared-I/II probe in two-photon excitation- wavelength-independent photoluminescence and photoinactivation

Nitrogen doping and amino-group functionalization through chemical modification can engender enhance electron donation. Using a homemade femtosecond titanium:sapphire laser optical system operated at a low energy and short photoexcitation time [power: 200.0 nJ pixel-1; scanning frequency: 150 scans (~0.80-1.33 s); excitation wavelength: 870, 910, or 970 nm], this study conducted these processes on the large is-conjugated system of graphene quantum dot (GQD)-based materials functioning as electron donors; this improved the efficiency of charge transfer to the prepared amino-NGQDs, resulting in enhanced two-photon absorption, excitation-wavelength-independent photoluminescence (EWI-PL), radiative efficiency, excitation absolute cross section, and excitation from the near-infrared (NIR)-I to the NIR-II region. The lifetime decreased and quantum yield (QY) increased. The sorted amino-N-GQDs exhibited two-photon EWI-PL emissions between the ultraviolet and NIR-I regions, leading to the generation of reactive oxygen species (ROS), which functioned as two-photon photosensitizers for photodynamic therapy (PDT). Increasing the mean lateral size of the particles increased the N-functionality-dependent photochemical and electrochemical activities, which improved the PL QY and thus enhanced the efficiency of two-photon PDT. Additionally, a polystyrene sulfonate (PSS) coating was applied (forming sorted amino-N-GQD-PSS); the sulfur atoms introduced by the PSS induced the radiative recombination of localized electron-hole pairs and then improved the sorted amino-N-GQD surfaces by strengthening the quantum confinement of their emissive energy. Thus, compared with the sorted amino-N-GQDs that were not coated, the PSS-coated materials had superior two-photon properties. No ROS were detected. Accordingly, these materials are suitable for use as two photon contrast probes for analyte tracking and localization.(C) 2022 Elsevier Ltd. All rights reserved.

Automated summary

By chemically modifying graphene quantum dot materials through nitrogen doping and amino-group functionalization, this study improved electron donation efficiency, enhancing absorption, luminescence, radiative efficiency, and other properties.