Activating One/Two‐Photon Excited Red Fluorescence on Carbon Dots: Emerging n→π Photon Transition Induced by Amino Protonation

• Published in: Advanced science Vol. 10; no. 11; pp. e2207566 - n/a
• Main Authors: Zhang, Qing, Wang, Fengqing, Wang, Ruoyu, Liu, Junlan, Ma, Yupengxue, Qin, Xiaoru, Zhong, Xiaoxia
• Format: Journal Article
• Language: English
• Published: Germany John Wiley & Sons, Inc 01.04.2023; John Wiley and Sons Inc; Wiley
• Subjects: Carbon; carbon quantum dots; Investigations; Lasers; molecular state; Morphology; Nitrogen; Optical properties; Particle size; photoluminescence mechanism; reaction sediments; Sediments; Spectrum analysis; Transmission electron microscopy; photoluminescence mechanism; molecular state; reaction sediments; carbon quantum dots
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.202207566

Due to the complicated nature of carbon dots (CDs), fluorescence mechanism of red fluorescent CDs is still unrevealed and features highly controversial. Reliable and effective strategies for manipulating the red fluorescence of CDs are urgently needed. Herein, CDs with one‐photon excited (622 nm, QYs ≈ 17%) and two‐photon (629 nm) excited red fluorescence are prepared by acidifying o‐phenylenediamine‐based reaction sediments. Systematic analysis reveals that the protonation of amino groups increases the particle surface potential, disperse the bulk sediments into nano‐scale CDs. In the meanwhile, amino protonation of pyridinic nitrogen (–N=) structure inserts numerous n orbital energy levels between the π → π* transition, narrows the gap distance for photon transition, and induces red fluorescence emission on CDs. Present research reveals an effective pathway to activate CDs reaction sediments and trigger red emission, thus may open a new avenue for developing CDs with ideal optical properties and promising application prospects. Due to the advantages of long wavelength emission, near‐infrared (NIR) fluorescent Carbon Dots (CDs) attract broad interest. However, strategies for manipulating NIR fluorescence of CDs are urgently needed. Here, the authors reveal an effective pathway to activate one‐photon and two‐photon NIR emission on CDs, providing a new avenue for developing CDs with ideal optical properties.