2020, Vol.30, No.1

Carbon Letters 2023 KCI Impact Factor : 1.35 KCI-WoS Impact Factor : 6.04

pISSN : 1976-4251 / eISSN : 2233-4998
https://journal.kci.go.kr/carbon

Polyaniline–graphene quantum dots (PANI–GQDs) are considered as an important candidate for applications in photovoltaic cells. In this work, GQDs were prepared using sono-Fenton reagent from reduced graphene oxide (rGO). PANI–GQD hybrid was also synthesized using the chemical in situ polymerization method. The synthesized materials were characterized using UV–visible (UV–Vis) spectroscopy, photoluminescence (PL) spectroscopy, current–voltage (I–V) characteristic, thermal gravimetric analysis (TGA), Raman spectroscopy, and X-ray difraction (XRD). Dynamic light scattering was also used to estimate the lateral size of GQDs. The enhanced visible-light absorbance in the hybrid was confrmed by UV–Vis analysis and the decrease in intensity around 3461 cm−1 in FT-IR spectra was due to the interaction between functional groups of PANI with GQDs. This led to improved thermal stability and conductivity as observed from TGA and I–V analysis, respectively. Moreover, the Raman spectrum for PANI–GQDs showed a decrease in the peak at ~1348 and ~1572 cm−1 as compared to PANI and GQDs. Similarly, from the XRD profle of PANI–GQDs, a shift in peak was observed due to an alteration in the microstructure. A sandwich device with cell structure glass/ITO/PANI–GQDs/Al was fabricated and its application was tested. Current density–voltage (J–V) curve of the device was measured with a Keithley SMU 2400 unit under an illumina�tion intensity of 100 Wm−2 simulating the AM 1.5 solar spectrum. The hybrid exhibited photovoltaic properties, and 0.857% efciency was observed in response to the applied voltage. This work suggests that PANI can be used as an alternative material for photovoltaic cells.

Chemical incorporation of epoxy-modifed graphitic layers in epoxy/novolac phenolic resin matrices was carried out through co-curing of epoxy and novolac resins using triphenylphosphine as catalyst. First, (3-glycidyloxypropyl) trimethoxysilane (GPTMS) was grafted on graphene oxide (GO) surface to obtain epoxidized GO layers. Then epoxy resin and GPTMS-mod�ifed GO were incorporated into thermosetting reaction using novolac resin in the presence of triphenylphosphine. Covalent attachment of GPTMS-modifed GO to the resin matrices resulted in a hybrid composite with high thermal characteristics. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis (TGA), X-ray dif�fraction, and Raman spectroscopy were used for approving modifcation of GO with GPTMS. The images resulted from scanning and transmission electron microscopies exhibited GO layers with lots of creases turning to smooth layers with a few thin ripples after modifcation with GPTMS. TGA results showed that thermal characteristics of resins were improved by the addition of GPTMS-modifed GO. Char residue of the hybrid composites containing 0.5 and 1 wt% of GPTMS-modifed GO reached 28.1 and 34.3%, respectively. Also, their maximum thermal degradation temperature was also increased by the incorporation of GPTMS-modifed GO.

In this paper, we report graphene composite membranes prepared by transfer of a layer of chemical vapor deposition graphene onto porous anodic alumina (AA) substrates with nominal pore size 20 and 30 nm, referred as 20AA and 30AA. The coated and uncoated substrates were characterized using optical and electron microscopy techniques. The bare substrates exhibited a smooth surfaces with a well-organized array of hexagonal pores, displaying an average pore size of 17±3 (20AA) and 23±3 nm (30AA). The scanning electron microscopy and atomic force microscopy analyses confrmed the successful transfer of graphene layer onto the target substrates. The molecular transport study was performed by introducing 0.5 M potassium chloride (KCl) and deionized water in a Side-bi-Side Franz difusion cell. The graphene/20AA specimen blocked 66% ions transport, and graphene/30AA membrane about 64%. The ions blockage exceeded 90%, near the characteristics of defect�free graphene when the defects of the transferred graphene were sealed with Nylon 6,6. The results of this study suggest the potential use of graphene on AA substrates for water desalination and gas purifcation applications.