Seminar Prof. Juwon Oh [Kyungpook Nat'l Univ.] - Emissive Properties of NIR Semiconducting Nanoparticles
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Date: 2025/11/13 (THU) 5pm
Venue: Science Hall B131
Abstract:
Semiconducting nanoparticles (NPs) have advantageous physical and chemical properties,such as tunable emission, high absorption coefficients, high photochemical stability and durability. In bottom-up approaches, the NPs are synthesized from molecular precursors, in which small particles with 1~2 nm size, called as nanocluster (NC), are isolated. The NCsshow atomically-precise control and distinct properties from nanoparticles. As a representative semiconducting NP and NC, InP NP and NC were investigated. InP NC shows less-ordered structure with polytwistane structure, where In-P bonds exhibit various bondlengths and angles. This leads to negligible quantum confinement effect, which is characterized as a nanomolecule. Highly-ordered zinc-blend structure was observed in InPNP, where photoinduced stark effect well demonstrates its quantum confinement effect.
This electronic evolution from molecular-like to quantum-dot-like nature provides an insightinto highly NIR emissive materials. The quantum confinement leads to collective atomicinteraction in NPs (or quantum dots), which brings out the low-frequency phonon with a suppression of high frequency localized vibrations. Because the overtones of high frequencyvibrations (C-H and N-H etc.) are observed up to 1000 nm, small band-gap semiconductingNPs can be a candidate for highly NIR emissive materials. In this regard, NIR PL nature of Ag2S NP, which is known as non-toxic and environmental benign materials), wereinvestigated.