About this Abstract |
| Meeting |
MS&T25: Materials Science & Technology
|
| Symposium
|
2025 Undergraduate Student Poster Contest
|
| Presentation Title |
SPU-34: Ligand Shell Density Controls Photoinduced Detachment in Colloidal CdSe Quantum Dots |
| Author(s) |
Jacob Cho, McKenna Grega, John Asbury |
| On-Site Speaker (Planned) |
Jacob Cho |
| Abstract Scope |
The dynamic interactions between colloidal nanocrystals and their organic ligand shells remain poorly understood despite their central role in stability, photophysics, and interfacial charge transfer. Here we use nanosecond mid-infrared transient absorption spectroscopy to directly observe photoinduced ligand detachment from CdSe quantum dots passivated by oleic acid in solution. Following band-edge excitation, we detect the rapid appearance of a vibrational feature at ~1700 cm⁻¹ characteristic of free oleic acid, demonstrating that surface-bound carboxylates undergo photoinduced detachment and protonation. NMR measurements establish ligand shell densities, and corresponding free acid kinetics demonstrate that denser shells (OA:Cd ≥ 6:1) suppress ligand escape and promote reattachment, in contrast to sparsely covered shells that favor long-lived detachment. These results identify ligand shell density as a key parameter governing both photochemical detachment and vibrational–electronic coupling, and suggest design rules for balancing surface passivation with accessible sites for photocatalysis and charge transfer. |