We report a new paradigm for the synthesis of metal−organic framework (MOF) crystals with controlled thickness by utilizing interfacial self-assembly of frameworks on metal ion-doped polymer precursors. The approach involves preparation of metal ion-doped polymer precursors through ion-exchange reactions and synthesis of MOF crystals by immersion into solutions containing organic ligands. The thickness of the resulting MOF crystals can be readily controlled by the number of doped-metal ions in the polymer precursors. MOF crystals could be very important and potentially useful for applications, and the present approach based on interfacial self-assembly could significantly advance MOF crystal preparation techniques.

Fluorescence enhancement of CdTe nanocrystals through energy transfer to Ag nanocrystals is described, enabling us to fabricate highly luminescent quartz substrate. By immobilization of CdTe nanocrystals on Ag nanocrystals linked by dithiol molecules, fluorescence of CdTe nanocrystals is enhanced as compared to that of only CdTe nanocrystals. For example, the CdTe/Ag nanocrystals film linked by 1,5-pentanedithiol molecules exhibits ca. 3-fold fluorescence intensity of CdTe nanocrystals without Ag nanocrystals. Importantly, the fluorescence lifetime of this film decreased by complexation with Ag nanocrystals, indicating that the mechanism of fluorescence enhancement may be caused by energy transfer from CdTe to Ag nanocrystals. This effect depends on both distance between CdTe and Ag nanocrystals and types of metal nanocrystals. Fundamental understanding of enhancement effect by plasmonic nanocrystals paves the way toward the development of light-emitting devices, sensors, and energy conversion devices.

We report a novel approach for fabricating Au nanocrysltas/porous coorodination polymers (PCPs) heterostructured composite based on preferential self-assembly of frameworks on nanocrystal surface. This approach involves the synthesis of carboxylic acid-fucntionalized Au nanocrystals and preferential growth of frameworks consisting of Zn 2+ ions and benzene-1,4-dicarboxylate (bdc) on nanocrystals. Here, the key is to use Au nanocrystals stabilized with mercaptoacetic acid molecules bearing carboxylic acid groups that have strong interaction between metal ions of PCP precursors. During solvothermal reaction for construction of PCP frameworks, Au nanocrystals can be act as scaffolds for self-assembly of framework component. This approach allows us to synthesize Au nanocrystals dispersed in PCP crystals and will be extended to other types of nanocompoiste such as metal oxides and semiconductors.