Applied to anti-counterfeiting and flexible composite utilizing photoluminescence properties of CdSe/ZnS nanocrystal quantum dots via hot-injection

Quantum dots with excellent luminescence properties are being studied in a wide range of fields, such as displays, sunlight, and bio-imaging; although quantum dots are the same material, unlike bulk materials, as their size decreases their optical and electrical properties change due to the quantum confinement effect. In this study, CdSe quantum dots were synthesized by a well-known hot-injection method and a ZnS shell layer was formed on the surface of the CdSe quantum dot core to enhance the properties, thereby synthesizing the CdSe/ZnS core/shell structure. At this time, the quantum yield increased more than twice, and the emission line width decreased. When anti-counterfeiting ink was made using quantum dots with enhanced luminescence characteristics and applied to a bank note, it was impossible to check with the naked eye, but letters and emblems could be confirmed under UV light. In addition, a composite made by mixing with a silicon-based polymer showed excellent flexibility; and, when applied on a blue LED chip, a single wavelength and bright light peculiar to quantum dots were realized.