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Azobenzene end-functionalized telechelic POx (Az-POx-Az) was designed for as multimodal stimuliresponsive polymer. Az-POx-Az (0.25 g/L) in physiological saline (150 mM NaCl) phosphate buffered solution (10 mM PBS, pH 7.4) exhibited fully reversible trans−cis photoisomerism upon alternate irradiation with 365 and 254 nm UV light. The photoisomerization of the azobenzene moieties influenced the lower critical solution temperature (LCST), and the cis form exhibited a slightly higher LCST than the trans form. Circular dichroism measurements of Az-POx-Az with cyclodextrins (CDs) exhibited induced circular dichroism at the absorption band of the azobenzene moiety, indicating the formation of host−guest complexes between the azobenzene moieties in Az-POx-Az and the CDs. After formation of host−guest complexes consisting of the azobenzene moieties and the CDs, Az-POx-Az exhibited increased LCSTs. Interestingly, the LCSTs of Az-POx-Az with α-CD and β-CD moved in opposite directions upon photoisomerization. By the changing from the trans to cis form, Az-POx-Az with α-CD exhibited a decreased LCST; however, Az-POx-Az with β-CD exhibited an increased LCST. Using the interconversions between the transparent and turbid states of the Az-POx-Az solution, we could realize two different logic circuit modes using three different external stimuli, i.e., temperature, UV light, and cyclodextrins.

The controlled functionalization of single-walled carbon nanotubes (SWNTs) is a key to using them in high-end applications. We show that nanotube reactivity after covalent diazonium modification is governed by a chirality-specific surfactant binding affinity to SWNTs. Both metallic and semiconducting SWNTs tightly organized by a helical flavin mononucleotide (FMN) assembly exhibit two hundred times slower reactivity toward 4-methoxy benzenediazonium (4-MBD) than those wrapped by sodium dodecyl sulfate and this reactivity enables chirality- and metallicity-specific behaviours to be probed, as confirmed by absorption, Raman, and photoluminescence (PL) spectroscopy. Each reaction kinetic of the two-step SWNT PL decays originating from electron transfer and the covalent reaction of 4-MBD, respectively, is inversely proportional to the binding affinity (Ka) between FMN and the SWNTs. The observed marginally higher reaction rate of the metallic nanotube compared to the semiconducting one results from the weaker Ka value of the metallic nanotubes with FMN. An enrichment demonstration of a few nanotube chiralities using selective and slow covalent diazonium chemistry demonstrates the importance of the binding affinity between the surfactant and the SWNTs. The study provides a handle on chirality-specific covalent chemistry via surfactant-SWNT binding affinity and impacts on future-sensing schemes.

Understanding the heterojunction of a lateral heterostructured transition metal dichalcogenide (hTMD) is important in order to take advantage of the combined optoelectronic properties of individual TMDs for various applications but, however, is hampered by mingled effects from lattice mismatch and substrate interaction. Here, we systematically investigated the strain occurring at lateral hTMDs consisting of molybdenum disulfide (MoS2) and molybdenum diselenide (MoSe2) prepared by chemical vapor deposition. Comparison of homologous TMDs and hTMDs from controlled growth order revealed systematic change in photoluminescence behavior depending on substrate interaction and relative lattice mismatch. Near the heterojunction, a TMD with a larger lattice constant (a) exhibits photoluminescence (PL) red-shift, whereas a TMD with smaller a shows an opposite trend owing to lattice-induced strain. These effects are augmented in a subtractive or additive manner by tensile strain from the substrate interaction. Moreover, comparison of PLs revealed that the shell region grown from the core edges exhibits weak substrate interaction contrasted by that of a shell region independently grown on a shell. This study provides detailed understandings of the heterojunction at a lateral hTMD for various applications.