Xia Pan, Huang Zhiyuan, Li Xin, Romero Juan J, Vullev Valentine I, Pau George Shu Heng, Tang Ming Lee
Materials Science & Engineering Program, University of California, Riverside, Riverside, CA 92521, USA.
Department of Chemistry, University of California, Riverside, Riverside, CA 92521, USA.
Chem Commun (Camb). 2017 Jan 19;53(7):1241-1244. doi: 10.1039/c6cc08229g.
The effect of isomeric substitutions on the transmitter for triplet energy transfer (TET) between nanocrystal (NC) donor and molecular acceptor is investigated. Each isomeric acceptor is expected to bind in a unique orientation with respect to the NC donor. We see that this orbital overlap drastically affects the transmission of triplets. Here, two functional groups, the carboxylic acid and dithiocarbamate, were varied between the 1-, 2- and 9-positions of the anthracene ring to give three ACA and three ADTC isomers. These six anthracene isomers served as transmitters for triplets between CdSe NC sensitizers and 9,10-diphenylanthracene annihilators for photon upconversion. The photon upconversion quantum yield (QY) is the highest for 9-ACA (12%), lowest for 9-ADTC (0.1%), around 3% for both 1-ACA and 1-ADTC, and about 1% for the 2-isomers. These trends in QYs are reflected in the rates of TET given by ultrafast transient absorption spectroscopy where a maximum of 3.8 × 10 s for 9-ACA was measured. Molecular excited state energy levels were measured both in solution and polymer hosts to correlate structure to TET. This work confirms that anthracene excited states levels are very sensitive to molecular substitution, which in combination with orbital overlap, critically affect Dexter-based TET.
研究了异构体取代对纳米晶体（NC）供体与分子受体之间三线态能量转移（TET）的供体的影响。预计每个异构体受体相对于NC供体以独特的取向结合。我们发现这种轨道重叠极大地影响了三线态的传输。在此，在蒽环的1、2和9位之间改变了两个官能团，即羧酸和二硫代氨基甲酸盐，得到三种ACA和三种ADTC异构体。这六种蒽异构体用作CdSe NC敏化剂和用于光子上转换的9,10-二苯基蒽湮灭剂之间三线态的供体。光子上转换量子产率（QY）对于9-ACA最高（12%），对于9-ADTC最低（0.1%），对于1-ACA和1-ADTC两者约为3%，对于2-异构体约为1%。超快瞬态吸收光谱给出的TET速率反映了这些QY趋势，其中测量到9-ACA的最大值为3.8×10 s。在溶液和聚合物主体中测量了分子激发态能级，以将结构与TET相关联。这项工作证实蒽激发态能级对分子取代非常敏感，这与轨道重叠相结合，严重影响基于德克斯特的TET。
