Photoluminescence Switching in Quantum Dots Connected with Carboxylic Acid and Thiocarboxylic Acid End-Group Diarylethene Molecules.

We contrast the switching of photoluminescence (PL) of PbS quantum dots (QDs) cross-linked with photochromic diarylethene molecules with different end groups, 4,4'-(1-cyclopentene-1,2-diyl)bis[5-methyl-2-thiophenecarboxylic acid] () and 4,4'-(1-cyclopentene-1,2-diyl)bis[5-methyl-2-thiophenethiocarboxylic acid] (). Our results show that the QDs cross-linked with the carboxylic acid end group molecules () exhibit a greater amount of switching in photoluminescence intensity compared to QDs cross-linked with the thiocarboxylic acid end group (). We also demonstrate that regardless of the molecule used, greater switching amounts are observed for smaller quantum dots.

Synthesis of Bis-Thioacid Derivatives of Diarylethene and Their Photochromic Properties.

Diarylethenes (DAEs) are an important class of photoswitchable compounds that typically undergo reversible photochemical conversions between the open and closed cyclized forms upon treatment with UV light or visible light. In this study, we introduced thioacid functional groups to several photochromic dithienylethene (DTE) derivatives and established a method that can be used to prepare these photoswitchable thioacids. Four thioacid-functionalized diarylethene derivatives were synthesized through the activation of carboxylic acids with -hydroxysuccinimide, followed by reactions with sodium hydrosulfide with yields over 90%.

Photoluminescence switching in quantum dots connected with fluorinated and hydrogenated photochromic molecules.

We investigate switching of photoluminescence (PL) from PbS quantum dots (QDs) crosslinked with two different types of photochromic diarylethene molecules, 4,4'-(1-cyclopentene-1,2-diyl)bis[5-methyl-2-thiophenecarboxylic acid] (1H) and 4,4'-(1-perfluorocyclopentene-1,2-diyl)bis[5-methyl-2-thiophenecarboxylic acid] (2F). Our results show that the QDs crosslinked with the hydrogenated molecule (1H) exhibit a greater amount of switching in photoluminescence intensity compared to QDs crosslinked with the fluorinated molecule (2F). With a combination of differential pulse voltammetry and density functional theory, we attribute the different amount of PL switching to the different energy levels between 1H and 2F molecules which result in different potential barrier heights across adjacent QDs.