The demand for rechargeable batteries has rapidly grown due to the increasing gap between limit amount of fossil fuel and rapid growth of energy consumption. Rechargeable battery which known as electrochemical energy storage device was a major focus for academic and industrial research. Sulfur (S) has been regarded as one of the most promising candidates for high specific energy cathode materials due to its high abundance, low toxicity, high theoretical specific capacity, and low density. Owing to the high theoretical specific capacity and low redox potential, lithium (Li) is the most promising anode material which raises most research attention. Researcher also interested in magnesium (Mg) metal anode due to its high natural abundance, good safety and high theoretical volumetric energy. The cathode electrolyte interfacial process in Li-S batteries under lean electrolyte condition was studied with the most widely used electrolyte The interfacial processes on the sulfur cathode under the lean electrolyte condition was probed using operando electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT). The operando EIS reveals a significant and rapid increase in charge transfer resistance during the transition from high-order polysulfides to low-order ones under a low E/S ratio, which is induced by a kinetic bottleneck at the interphase due to Li-ion mass transfer limitation. The GITT results confirm the kinetic bottleneck by revealing a large discharge overpotential during the transition phase. The understanding of Li-S reactions under lean electrolyte condition is then applied to a carboranyl ionic liquid electrolyte system. Such novel ionic electrolyte was first synthesized and reported in this paper with good chemically and electrochemically stability with Li anode and S cathode as well as polysulfide. High specific energy Li-S battery can be achieved via sparingly dissolving pathway during discharging in carboranyl ionic liquid electrolyte. Mg-S batteries in magnesium monocarborane (Mg(CB11H12)2) in tetraglyme (G4) electrolyte was first studied by our group. Understanding of cathode electrolyte interface reveal that sulfur is unstable under oxidation in the Mg(CB11H12)2 electrolyte. With the X-ray Photoelectron Spectroscopy (XPS) data of pristine sulfur cathode after charging, we propose a novel explanation of the overcharge behavior for Mg-S

Terahertz waves can be used for many potential applications including security screening, chemical sensing and medical diagnosis. However, the practical applications are limited by the size, cost and complexity of terahertz systems. This is due to the lack of monolithically integrated terahertz optoelectronic devices. During my doctoral studies, I have extensively explored the possibility of using quantum well structures as a platform for monolithic integration of terahertz optoelectronics. Based on a GaAs/AlGaAs quantum well structure operating at ~800 nm wavelength, high performance SOA-integrated terahertz photomixers are demonstrated and characterized as both terahertz transmitter and receiver. An in-depth theoretical model is given to predict the performance of the fabricated terahertz transmitter and receiver prototypes, accounting for the optical absorption, RC parasitics and ultrafast carrier dynamics. Terahertz transmitters with radiation power levels of –10, –20, –26, and -35 dBm are demonstrated at 140, 310, 400, and 500 GHz and show record-high optical-to-terahertz conversion efficiencies of 2% at 140 and 230 GHz. With the same device structure, terahertz receivers with noise equivalent power levels of 2.3, 8.1, 13.7, 15.1, and 93 pW/Hz0.5 are demonstrated at 140, 250, 310, 400 and 500 GHz, which are equivalent or better than the state-of-the-art room temperature terahertz receivers. The wafer structure can be modified to further improve the device performance. The presented scheme is compatible with photonic integrated system foundry processes, e.g., InP based processes, which could enable fabrication of compact, low-cost, scalable terahertz systems with high volumes.

The relationship between social media use and mental health has long puzzled communication and psychology scholars. There have been attempts to explain their relationship (e.g., examining the effects of different social media activities and employing novel measurement strategies). This project adds to the literature by testing priming effects in the context of social media research and advocates for the meaningfulness of measurement strategies by showing how self-reported mental health is subject to survey structure and language. We collected data from participants for three experimental studies (n=571, n=581, and n=656, respectively). Our results demonstrated that presenting the addiction scale first in the survey elicited higher self-reported depression than other conditions placing the depression scale first, but the order of the addiction scale did not alter participants' perceived self-esteem. Notably, results also indicate that the wording of questionnaire items can affect participants' mental health, such that participants in conditions where mental health scales contained mixed wording (i.e., a scale that contains positive and negative descriptions designed to measure the same construct), tended to report lower self-esteem and depression. Furthermore, our results imply that reading an article focusing on the pros of social media resulted in higher self-esteem and lower depression than reading an article highlighting the cons of social media. These findings have implications for future research germane to how social media impacts our mental health.