Eui Jung Kim

We report an effective method for producing graphene sheets using solvothermal-assisted exfoliation of graphite in a mixed solvent of toluene and oleylamine. The mixed solvent of toluene and oleylamine produces higher yield of graphene than its constituents, oleylamine and toluene. The oleylamine molecules with its long chain enwrap the graphene sheets efficiently, while toluene helps the oleylamine molecules become more flexible and easily intercalate into the edge of graphite. The prepared graphene sheets have a high quality, and the concentration of graphene in the dispersion is as high as 0.128 mg mL−1. The high-quality graphene sheets obtained in this work make them suitable for application in many fields such as energy-storage materials and polymer composites.

We report the fast synthesis of thermally reduced graphene oxide : platinum (TRGO : Pt) nanohybrids by simply spraying a GO:Pt ⁴⁺ solution on a hot plate.

A new method of inserting an eco-sustainable hydrophilic system into an anti-reflection (AR) system was developed and its applicability to photovoltaic systems was determined. We created a TiO₂ nanoparticle composite with a densely multi-layered AR system top layer to demonstrate its eco-sustainable, hydrophilic performance and to act as a low refractive index material, which is essential for AR. The hydrophilic system displayed the lowest reflectance and a remarkable contact angle reduction to 0 degrees under UV light irradiation. The annealed hydrophilic system (the eco-sustainable system) exhibited the highest photodecomposition activity of 100% within 90 min by effective separation of electron–hole pairs using SiO_x nanoparticles inside the TiO₂ layer as trap levels. The successful AR, hydrophilic, and eco-sustainable characteristics of the simplified system composed of only two materials, TiO₂ and SiO_x, are anticipated to contribute to the enhancement of photovoltaic system efficiency.

The electronic structure of Zn(OH)₂ has been studied by first-principles calculations using the local density approximation + Hubbard U (LDA+U) scheme. Based on the LDA+U calculations of ZnO and Zn(OH)₂, a principle for the correct assignment of the U values has been established. The assigned U values should assure an appropriate overlap of the Zn 3d and O 2p states. Both theoretical calculations and experimental investigations have determined an energy band gap of 5.65 eV for Zn(OH)₂. We also report abnormal yellow luminescence of Zn(OH)₂ resembling that of ZnO. Characterizations of cathodoluminescence, UV-Vis absorption and X-ray photoelectron spectroscopy reveal that ZnO of several atomic layers in thickness covers the surface of Zn(OH)₂, which gives rise to the intense yellow luminescence observed for Zn(OH)₂.

Texture engineering of thin films with controlled crystalline orientation is essential in tuning their properties. We have successfully prepared ZnO:In thin films via chemical bath deposition (CBD), with the preferred orientation of the films varying from [002] to [100] and [110] by simply altering the solvent composition. Growth mechanism of the preferred crystallite orientation in ZnO:In thin films have been systematically investigated. It is found that the variation in the preferred orientation in the films obeys the principle of evolutionary selection, that is, the fastest‐growing crystallographic direction determines the preferred orientation of the films. The tunable crystallite orientation indicates no epitaxial relationship has been established between the crystallites and the seeds. XPS analysis reveals the successful incorporation of indium in the ZnO:In thin films and the oxygen desorption upon reductive annealing. CBD, thus, is demonstrated to produce transparent conductive oxide thin films with tunable textures.

We report an effective method for producing graphene sheets using solvothermal-assisted exfoliation of graphite in a mixed solvent of toluene and oleylamine. The mixed solvent of toluene and oleylamine produces higher yield of graphene than its constituents, oleylamine and toluene. The oleylamine molecules with its long chain enwrap the graphene sheets efficiently, while toluene helps the oleylamine molecules become more flexible and easily intercalate into the edge of graphite. The prepared graphene sheets have a high quality, and the concentration of graphene in the dispersion is as high as 0.128 mg mL−1. The high-quality graphene sheets obtained in this work make them suitable for application in many fields such as energy-storage materials and polymer composites.