Zhang Bohan, Wang Bingzhe, Ushakova Elena V, He Bingchen, Xing Guichuan, Tang Zikang, Rogach Andrey L, Qu Songnan
Joint Key Laboratory of the Ministry of Education, Institute of Applied Physics and Materials Engineering, University of Macau, Taipa, Macau SAR, 999078, P. R. China.
Center of Information Optical Technologies, ITMO University, Saint Petersburg, 197101, Russia.
Small. 2023 Aug;19(31):e2204158. doi: 10.1002/smll.202204158. Epub 2022 Oct 10.
It is important to reveal the luminescence mechanisms of carbon dots (CDs). Herein, CDs with two types of optical centers are synthesized from citric acid in formamide by a solvothermal method, and show high photoluminescence quantum yield reaching 42%. Their green/yellow emission exhibits pronounced vibrational structure and high resistance toward photobleaching, while broad red photoluminescence is sensitive to solvents, temperature, and UV-IR. Under UV-IR, the red emission is gradually bleached due to the photoinduced dehydration of the deprotonated surface of CDs in dimethyl sulfoxide, while this process is hindered in water. From the analysis of steady-state and time-resolved photoluminescence and transient absorption data together with density functional theory calculations, the green/ yellow emission is assigned to conjugated sp -domains (core state) similar to organic dye derivatives stacked within disk-shaped CDs; and the broad red emission-to oxygen-containing groups bound to sp -domains (surface state), whereas energy transfer from the core to the surface state can happen.
揭示碳点（CDs）的发光机制很重要。在此，通过溶剂热法由柠檬酸在甲酰胺中合成了具有两种光学中心的碳点，并显示出高达42%的高光致发光量子产率。它们的绿色/黄色发射表现出明显的振动结构和高抗光漂白性，而宽的红色光致发光对溶剂、温度和紫外-红外光敏感。在紫外-红外光下，由于二甲基亚砜中碳点去质子化表面的光致脱水，红色发射逐渐被漂白，而此过程在水中受到阻碍。通过对稳态和时间分辨光致发光以及瞬态吸收数据的分析，并结合密度泛函理论计算，绿色/黄色发射归因于类似于堆叠在盘状碳点内的有机染料衍生物的共轭sp -域（核心态）；而宽的红色发射归因于与sp -域结合的含氧基团（表面态），并且可能发生从核心到表面态的能量转移。
