Dibbell Rachel S, Soja Gregory R, Hoth Ruth M, Watson David F
Department of Chemistry, University at Buffalo, The State University of New York, Buffalo, NY 14260-3000, USA.
Langmuir. 2007 Mar 13;23(6):3432-9. doi: 10.1021/la063161a. Epub 2007 Feb 17.
A novel photochemical mechanism is reported for the site-selective deposition of quantum dots onto nanocrystalline TiO2 films. The patterning mechanism involves the combination of surfactant-mediated self-assembly and monolayer photolithography. In the self-assembly process, CdS and CdSe quantum dots were attached to TiO2 surfaces through bifunctional mercaptoalkanoic acid (MAA) linkers. MAAs were adsorbed to the TiO2 surface as the deprotonated carboxylates, primarily through monodentate coordination to Ti4+ sites. CdSe quantum dots were bound to the terminal thiol groups of surface-adsorbed MAAs, with a surface adduct formation constant, Kad, of (2.1 +/- 0.7) x 104 M-1. The color and optical density of the quantum dot-functionalized TiO2 films were tunable. Monolayer photopatterning involved the TiO2-catalyzed oxidative degradation of surface-adsorbed mercaptohexadecanoic acid (MHDA). A mechanism is proposed wherein MHDA degradation occurs through both oxidative decarboxylation and the formation of interchain disulfides. These MHDA photodegradation processes regulate the extent to which CdSe quantum dots adsorb onto the TiO2 surface. Illumination through a photomask yielded optically patterned, quantum dot-functionalized TiO2 films that were characterized by scanning electron microscopy and energy-dispersive X-ray analysis.
报道了一种用于将量子点选择性沉积到纳米晶TiO₂薄膜上的新型光化学机制。图案化机制涉及表面活性剂介导的自组装和单层光刻技术的结合。在自组装过程中，硫化镉（CdS）和硒化镉（CdSe）量子点通过双功能巯基链烷酸（MAA）连接体附着到TiO₂表面。MAA以去质子化的羧酸盐形式吸附到TiO₂表面，主要通过单齿配位作用于Ti⁴⁺位点。CdSe量子点与表面吸附的MAA的末端巯基结合，表面加合物形成常数Kad为(2.1±0.7)×10⁴ M⁻¹。量子点功能化的TiO₂薄膜的颜色和光密度是可调的。单层光图案化涉及TiO₂催化的表面吸附的巯基十六烷酸（MHDA）的氧化降解。提出了一种机制，其中MHDA的降解通过氧化脱羧和链间二硫化物的形成来发生。这些MHDA光降解过程调节了CdSe量子点吸附到TiO₂表面的程度。通过光掩膜进行光照产生了光学图案化的、量子点功能化的TiO₂薄膜，通过扫描电子显微镜和能量色散X射线分析对其进行了表征。
