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Physics Colloquium - Graduate Oral Presentations

This is a past event.

Thursday, March 28, 2019, 4 pm– 5 pm

This is a past event.

Thursday, March 28 @ 4pm – 139 Fisher Hall

Jinlin Zhang (Advisors: Prof. Jae Yong Suh and Prof. Yoke Khin Yap) will present "Light-matter Interactions in Hybrid Nanostructures of Au Nanorod Arrays with Monolayer WS2". Light-matter interaction systems have attracted intensive researches due to their potential applications in fundamental quantum science, optoelectronics and nonlinear optical devices. In this talk, I will discuss our experimental studies towards plasmon-exciton coupling and nonlinear optical properties (Second harmonic generation) in hybrid nanostructures that consist of Au nanorod arrays and monolayer WS2. An intermediate plasmon-exciton coupling was achieved owing to spectral and spatial overlap with the strong near-field formed around Au nanorods. Rabi splitting of 173 meV was observed in hybrid nanostructures of Au single nanorod array-monolayer WS2 at room temperature. Moreover, we are investigating the second-harmonic generation tuned by the local fields supported by these symmetry-broken hybrid nanostructures.

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Amit Acharya (Advisors: Dr. Yoke Khin Yap and Dr. Dongyan Zhang) will present “Broad Spectra Absorption of Boron Nitride and Molybdenum Disulphide Quantum Dots for Photovoltaic Devices”. After the discovery of semi-metallic graphene, layered materials such as hexagonal Boron Nitride (h-BN) and molybdenum disulphide (MoS2) have attracted a lot of attention. When these materials are scaled down to nano size, they offer unique optical properties like broad spectra absorption bands for effective photoelectron generation for use in QD-sensitized photovoltaic devices. A top-down approach was employed to convert h-BN and MoS2 particles into QDs by using homogenizing, sonication, and heating in Dimethylformamide (DMF). The MoS2 are 2-40 nm in dimension, while the BN QDs are 2-8 nm in dimension. We show that the fluorescent emission from these polydisperse QDs are excitation wavelength dependent. These MoS2 QDs could absorb a wide spectrum range of light from 320-520nm to produce fluorescence emission from 385-569 nm. The h-BN QDs can absorb a broader spectra from 300-580nm with fluorescence emission of 380 nm to 620 nm. The broad absorption wavelength range of these QDs would meet the peak of solar irradiation spectrum to enable effective production of photoelectrons from the sun for the applications of photovoltaic devices. Detailed of these results will be discussed in the presentation.

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