STM Imaging of Cyanine Dye J-Aggregates Formed on Carboxyl-Terminated Self-Assembled Monolayers
STM Imaging of Cyanine Dye J-Aggregates Formed on Carboxyl-Terminated Self-Assembled Monolayers
复制标题
在羧基封端的自组装单层上形成的花青染料 J-聚集体的 STM 成像
作者：
Robert W. Owens and;D. A. Smith
报道了1，1‘-二乙基-2，2’-花菁(PIC)染料在11-巯基十一酸(HS-−(CH_2)10-−)自组装单分子膜上J-聚集体的制备和扫描电子显微镜成像。反射吸收测量证实了在COOH表面形成了J-聚集体；然而，分子集合体与SAM的结合不够强，不足以承受STM成像过程中施加的侧向力。我们发现，在使用PIC染料溶液之前，用1 mM的AgNO3溶液对COOH表面进行预处理，可以极大地提高J-聚集体的稳定性。我们认为这是由于SAM的羧基与银络合物的形成，从而允许随后从染料溶液中吸附溴离子。反离子单分子层的形成已被证明是形成稳定的J-聚集体的重要因素。这些样品的STM图像显示出长长的、本质上线性的聚集体(具有类似于PRR的堆积结构)。
We report on the preparation and STM imaging of J-aggregates of 1,1‘-diethyl-2,2‘-cyanine (PIC) dye formed on a self-assembled monolayer of 11-mercaptoundecanoic acid (HS−(CH2)10−COOH). The formation of J-aggregates on the COOH surface was verified by reflection absorption measurements; however, the molecular assemblies were not bound strongly enough to the SAM to withstand the lateral forces applied during STM imaging. We found that pretreating the COOH surface with a solution of 1 mM AgNO3 before application of the PIC dye solution greatly improved the stability of the J-aggregates. We suggest that the reason for this is the formation of a silver chelate with the carboxyl head groups of the SAM which permits the subsequent adsorption of bromide counterions from the dye solution. The formation of a counterion monolayer has been shown to be important in the formation of stable J-aggregates. STM images of these samples revealed long, essentially linear aggregates (with a packing structure similar to the pr...