Haesol Jung

Preparation and Exceptional Lithium Anodic Performance of Porous Carbon-Coated ZnO Quantum Dots Derived from a Metal–Organic Framework

Hierarchically porous carbon-coated ZnO quantum dots (QDs) (~3.5 nm) were synthesized by a one-step controlled pyrolysis of the metal-organic framework IRMOF-1. We have demonstrated a scalable and facile synthesis of carbon-coated ZnO QDs without agglomeration by structural reorganization. This unique microstructure exhibits outstanding electrochemical performance (capacity, cyclability, and rate capability) when evaluated as an anode material for lithium ion batteries.

Preparation of a freestanding, macroporous reduced graphene oxide film as an efficient and recyclable sorbent for oils and organic solvents

In this work, we report the preparation of reduced graphene oxide (rGO)-based freestanding recyclable oil adsorbents via an environmentally friendly one-step low-temperature thermal reduction process. The heating rate was adjusted to successfully control the macroporosity of the rGO films (rGOFs), thereby modulating the adsorption behaviors. The adsorption capacities for a variety of organic solvents and oil species, measured as the percentage weight gain, were measured. Adsorption capacities up to 4500% of the initial rGOF weight were achieved. The films displayed excellent stability over 10 cycles of use and regeneration without incurring significant structural damage or a decrease in the oil adsorption properties. These results suggested that the rGOF-based oil adsorbents may potentially be useful as next-generation oil adsorbent materials for the remediation of the maritime ecosystem in the wake of a massive oil spill.

Highly reproducible thermocontrolled electrospun fiber based organic photovoltaic devices.

In this work, we examined the reasons underlying the humidity-induced morphological changes of electrospun fibers and suggest a method of controlling the electrospun fiber morphology under high humidity conditions. We fabricated OPV devices composed of electrospun fibers, and the performance of the OPV devices depends significantly on the fiber morphology. The evaporation rate of a solvent at various relative humidity was measured to investigate the effects of the relative humidity during electrospinning process. The beaded nanofiber morphology of electrospun fibers was originated due to slow solvent evaporation rate under high humidity conditions. To increase the evaporation rate under high humidity conditions, warm air was applied to the electrospinning system. The beads that would have formed on the electrospun fibers were completely avoided, and the power conversion efficiencies of OPV devices fabricated under high humidity conditions could be restored. These results highlight the simplicity and effectiveness of the proposed method for improving the reproducibility of electrospun nanofibers and performances of devices consisting of the electrospun nanofibers, regardless of the relative humidity.