Although quantum dot (QD), a semiconductor nanocrystal (NC) exhibits excellent photophysical properties such as boad absorption bands, tunable emission bands and good photostabilities, its toxic heavy metal component (cadmium, selenium or tellurium) have limited its biological applications. Thus, diverse approaches have been reported to synthesize the high performance heavy metal-free fluorescence nanocrystals, for example, InP, InP/ZnS, CuInS2, AgInS2 and ZnS-AgInS2 (ZAIS). In particular, ZAIS has excellent properties including long fluorescence lifetime and higher brightness than QDs without photoblinking. Moreover, its emission wavelength can be controlled by the composition ratio without size-dependent bandgap change, different from QD. Here, we applied the sonochemical approach to the synthesis of (ZnxAgyInz)S2 (ZAIS) NC, which is simple, rapid, and efficient to create a library of ZAIS containing the information of fluorescence colors and intensities according to ratios of each component – Zn, Ag, In. However, several sonochemical parameters such as ultrasonic power, temperature and reaction time are still not well established in detail for the high performance ZAIS synthesis. Therefore, we investigated these controlling factors to find out optimal reaction conditions of ZAIS synthesis. In addition, we observed the effects of ligands as a solvent, stabilizer and capping reagent on the synthesis of ZAIS. Dodecylamine, Tri-Octyl Phosphine Oxide(TOPO), Tri-Octyl Phosphine(TOP), Dodecanoic acid and Oleylamine were used to analyze its role for the fluorescence intensity and wavelength shift, as well as the long-term stability. Especially, we showed that dodecylamine and oleylamine contributed to the high performance and stability of ZAIS NC. As the ligand length is longer, the emission wavelength tends to shift to the longer wavelength. We further showed how the ligand structure with / without unsaturated carbon affect the feature of ZAIS NC.

Analysis of sonochemical parameters and various ligands effects on (ZnxAgyInz)S2 synthetic mechanism

256th National Meeting (2018)

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