Résumé
In recent years, carbon quantum dots (CQDs) have attracted much attention as an emerging class among carbon-based dots with superior optical properties and long-term colloidal stability. Due to their biocompatibility, high photostability, and low-cost fabrication, CQDs are extensively explored as promising alternatives for common semiconductor nanostructures.1-2 In particular, triangular CQDs have huge potential in several application fields. Although the significant progress was made in synthesis routes, determination of their non-linear optical (NLO) responses at single laser wavelengths were only roughly studied at single laser wavelengths .We fabricated triangular CQDs of various sizes following the solvothermal method at varying reaction conditions. Phloroglucinol molecules were used as carbon sources.5 Linear optical characteristics of CQDs’ suspensions were studied using steady-state and time-resolved fluorescence spectroscopy. Two-photon absorption (2PA) cross-section values were determined from the two-photon excited fluorescence data (TPEF).6 As-obtained blue-, green- and red-emitting CQDs revealed long-living (~4 ns) and efficient (~50%) emission independent on the excitation wavelength, and with ultranarrow bandwidth (~30 nm), indicating a high color-purity. The estimated normalized 2PA cross-section were in the 0.001-0.004 GM∙mol/g range. To the best of our knowledge, this is the first 2PA evaluation in the wide wavelength range.