S. J. Lee

The physicochemical properties of polyindole / thiol composites

We synthesized the polyindole (PI) and poly(2,5-dimercapto-1,3,4-thiadiazole) (pDMcT) by chemical oxidation method. The polymerization of PI and pDMcT was confirmed by FT-IR. We have measured the electrochemical properties of the unit cell both before and after charge/discharge experiment. It showed the plateau region around 3.0V in discharge curves behavior. The specific discharge capacity value of these compositions was saturated after 10th cycle as ∼75mAh/g. We have tried to explain the reaction in PI/thiol composites with various methods. The intensity of the ESR signal increases after charging and the σ dc of these composites increases by charging. From the results, it could be found that the formation of unpaired electrons at nitrogen site in PI is confirmed in this system.

Fabrication and physical properties of conductive polyacrylonitrile-polyaniline derivative fibers

Spinning solutions were prepared by dissolving polyacrylonitrile (PAN) and sulfonated polyaniline (SPAN) in methyl sulfoxide (DMSO) solution. Polyacrylonitrile-sulfonated polyaniline fibers were fabricated by wet spinning method. The fibers were elongated more than 5 times during the spinning process. All of the fibers are conductive without additional acid doping process. The characterization of fibers has been studied by XRD, electrical conductivity, and tensile properties.

Surface enhanced Raman scattering effect of CdSe/ZnS quantum dots hybridized with Au nanowire

Functionalized CdSe/ZnS quantum dots (QDs) were attached to the surface of Au nanowire (NW). Analysis of optical absorption spectra disclosed surface plasmon bands of Au NWs at 562 and 627u2009nm and showing an overlap with the QD absorption band. Micro Raman spectra (λexu2009=u2009514u2009nm) of the QDs/Au single NW exhibited surface enhanced Raman scattering (SERS) peaks at 180, 205, and 277u2009cm−1, corresponding to surface, longitudinal, and transverse optical phonon modes, respectively. From time-resolved fluorescence spectra, the exciton lifetime of QDs decreased after hybridization with Au NW due to the energy transfer, supporting the SERS effect.

Nanoscale luminescence characteristics of CdSe/ZnS quantum dots hybridized with organic and metal nanowires: Energy transfer effects

Hybrid nanosystems comprising functionalized CdSe/ZnS core–shell quantum dots (QDs) on the surface of light-emitting poly(3-hexylthiophene) (P3HT), metallic copper (Cu), and insulating polystyrene (PS) nanowires (NWs) are fabricated. Using high-resolution scanning transmission electron microscopy, we observe that the QDs are attached to the surface of the NWs. The nanoscale photoluminescence (PL) characteristics of the hybrid QD/P3HT, QD/Cu, and QD/PS single NWs are investigated using laser confocal microscopy (LCM) with high spatial resolution. For the hybrid QD/P3HT single NW, the LCM PL intensity from the P3HT NW increases considerably, while that of the QDs decreases due to Forster resonance energy transfer. Hybridization affects the nanoscale PL characteristics of both the P3HT NW and the QDs. The LCM PL intensity of the hybrid QD/Cu NW is three times higher than that of the QD/PS NW, because of surface plasmon resonance coupling energy transfer between the QDs and the Cu NW. Time-resolved PL spectra reveal that the exciton lifetimes of the QDs drastically decrease after the hybridization with P3HT or Cu NWs, due to energy transfer effects. The nanoscale PL efficiency of the QDs can be controlled by hybridization with NWs having distinct properties.

Effects of chemical etching with hydrochloric acid on a glass surface

Glass slides were chemically etched with hydrochloric acid using three different methods. We investigated the effects of chemical etching treatments on such properties as chemical composition, surface roughness, and relative transmittance of the glass. Sodium, calcium, and aluminum atoms at the glass surface were effectively reduced by chemical etching with hydrochloric acid. Boiling the glass in a 36% hydrochloric acid solution for 30 min was more effective in reducing sodium, calcium, and aluminum atoms at the surface of the glass than any of the other etching methods using hydrochloric acid. Surface morphology of the glass was very different with chemical etching treatments with hydrochloric acid etchant. Root-mean-square surface roughness of the bare glass was 0.58 nm, but the roughness of the glass etched with hydrochloric acid ranged from 5.4 to 6.8 nm. The sodium concentration at the glass surface was greatly reduced, from 2.7% to 0.2%. The depth that was affected by chemical etching with hydrochlo...

Gate-dependent photoconductivity of single layer graphene grafted with metalloporphyrin molecules

We present the gate-dependent photoconductivity measurements of single layer graphene ribbons grafted with zinc porphyrin molecules Zn(OEP). The Zn(OEP)-graphene showed a maximum 610% increase in its photo-sensitivity compared to the bare graphene samples. Furthermore, the measured photocurrent exhibited strong dependence on the gate bias, light power, and light wavelength. These dependences showed clear evidence of the excitation of the carriers in Zn(OEP) and their energy transfer to graphene.