碳点(CD)表面结构的复杂性质阻碍了对其发射行为的全面理解。在这项研究中,我们使用两种通过酸碱处理产生的CD,一种是表面质子化,另一种是表面去质子化,目的是使用超快光谱技术研究这些表面改性对载体行为的影响。TEM,XRD,FTIR和拉曼光谱证明了CD的结构,具有石墨核和丰富的表面官能团。XPS证实了通过质子化和去质子化对CD的成功表面改性。超快瞬态吸收(TA)光谱表明,去质子化修饰可能会减缓弛豫过程,从而增加可见PL量子产率(PLQY)。相反,由于诱导的低能吸收带,质子化可以加速弛豫过程,导致自我吸收和降低PLQY。此外,对不同比例乙醇的混合溶剂中的CD进行TA分析,表明乙醇在减缓松弛过程中的有益作用。导致去质子化CD的PLQY增加33.7%,质子化CD的PLQY增加22.1%。这项研究阐明了CD中表面去质子化/质子化修饰与载体行为之间的复杂关系,为不同应用的高亮度CD的设计提供了一个潜在的途径。
The intricate nature of the surface structure of carbon dots (CDs) hinders a comprehensive understanding of their emission behavior. In this study, we employ two types of CDs created through acid-alkali treatments, one with surface
protonation and the other with surface deprotonation, with the objective of investigating the impact of these surface modifications on carrier behavior using ultrafast spectroscopy techniques. TEM, XRD, FTIR and Raman spectra demonstrate the CDs\' structure, featuring graphitic core and abundant surface functional groups. XPS confirms the successful surface modifications of CDs via
protonation and deprotonation. Ultrafast transient absorption (TA) spectroscopy reveals that deprotonation modification may decelerate the relaxation process, thereby increasing the visible PL quantum yields (PLQY). Conversely,
protonation may accelerate the relaxation process due to the induced low-energy absorption band, resulting in self-absorption and reduced PLQY. Furthermore, TA analysis of CDs in mixed solvents with different proportions of ethanol shows the beneficial effect of ethanol in decelerating the relaxation process, leading to an increased PLQY of 33.7 % for deprotonated CDs and 22.1 % for protonated CDs. This study illuminates the intricate relationship between surface deprotonation/
protonation modifications and carrier behavior in CDs, offering a potential avenue for the design of high-brightness CDs for diverse applications.