Schulich Faculty of Chemistry , Technion-Israel Institute of Technology , Haifa 3200003 , Israel.
School of Chemistry , Tel Aviv University , Tel Aviv 6997801 , Israel.
J Am Chem Soc. 2019 Sep 25;141(38):15413-15422. doi: 10.1021/jacs.9b08071. Epub 2019 Sep 10.
Carbon dots (C-Dots) are promising new materials for the development of biocompatible photosensitizers for solar-driven catalysis and hydrogen production in aqueous solution. Compared to common semiconducting quantum dots, C-Dots have good physicochemical, as well as photochemical stability, optical brightness, stability and nontoxicity, while their carbon based source results in tunable surface chemistry, chemical versatility, low cost, and biocompatibility. Herein we show that doping the C-Dots with phosphate or boron significantly influences their excited-state dynamics, which is observed by the formation of a unique long-lived photoproduct as a function of the different dopants. To probe the photosensitizing capabilities of the C-Dots, we followed the photoreduction of methyl viologen (MV), which acts as a molecular redox mediator (electron acceptor) to the C-Dots (the photosensitizer, i.e., electron donor) in aqueous solution, using steady-state and time-resolved fluorescence and absorption spectroscopic techniques as well as electrochemical measurements. We show that ultrafast electron transfer to MV and slow charge recombination results in a high quantum yield of MV photoreduction, while the doping drastically influences this quantum yield of MV radical. Our findings contribute to the photophysical understanding of this intriguing and relatively new carbon-based nanoparticle and can improve the design and development of efficient photosensitizers over commonly used heterogeneous catalysts in photocatalytic systems by increasing the efficiency of radical generation.
碳点 (C-Dots) 是一种很有前途的新型材料，可用于开发适用于太阳能驱动催化和水溶液中制氢的生物相容性光催化剂。与常见的半导体量子点相比，C-Dots 具有良好的物理化学稳定性和光化学稳定性、光学亮度、稳定性和非毒性，而其碳基来源则导致可调的表面化学、化学多功能性、低成本和生物相容性。本文表明，用磷酸盐或硼掺杂 C-Dots 会显著影响其激发态动力学，这可以通过不同掺杂剂形成独特的长寿命光产物来观察到。为了研究 C-Dots 的光敏能力，我们通过稳态和时间分辨荧光和吸收光谱技术以及电化学测量，研究了 C-Dots（光敏剂，即电子供体）在水溶液中对甲紫精 (MV) 的光还原反应。MV 作为分子氧化还原介体（电子受体）。我们表明，超快电子转移到 MV 和缓慢的电荷复合导致 MV 光还原的量子产率很高，而掺杂则极大地影响了 MV 自由基的量子产率。我们的研究结果有助于理解这种引人入胜且相对较新的碳基纳米粒子的光物理性质，并通过提高自由基生成效率，改善光催化体系中常用的多相催化剂的设计和开发，提高光催化剂的效率。
