InP/ZnS–graphene oxide and reduced graphene oxide nanocomposites as fascinating materials for potential optoelectronic applications† Monica Samal, a Priyaranjan Mohapatra, b Ramesh Subbiah, c Chang-Lyoul Lee, d Benayad Anass, e Jang Ah Kim, f Taesung Kim f and Dong Kee Yi * g Our recent studies on metal–organic nanohybrids based on alkylated graphene oxide (GO), reduced alkylated graphene oxide (RGO) and InP/ZnS core/shell quantum dots (QDs) are presented. The GO alkylated by octadecylamine (ODA) and the QD bearing a dodecane thiol (DDT) ligand are soluble in toluene. The nanocomposite alkylated-GO–QD (GOQD) is readily formed from the solution mixture. Treatment of the GOQD composite with hydrazine affords a reduced-alkylated-GO–QD (RGOQD) composite. The structure, morphology, photophysical and electrical properties of GOQDs and RGOQDs are studied. The micro-FTIR and Raman studies demonstrate evidence of the QD interaction with GO and RGO through facile intercalation of the alkyl chains. The field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) images of the GOQD composite show heaps of large QD aggregates piled underneath the GO sheet. Upon reduction to RGOQDs, the QDs become evenly distributed on the graphene bed and the size of the clusters significantly decreases. This also facilitates closer proximity of the QDs to the graphene domains by altering the optoelectronic properties of the RGOQDs. The X-ray photoelectron spectroscopy (XPS) results confirm QDs being retained in the composites, though a small elemental composition change takes place. The XPS and the fluorescence spectra show the presence of an In(Zn)P alloy while the X-ray diffraction (XRD) results show characteristics of the tetragonal indium. The photoluminescence (PL) quenching of QDs in GOQD and RGOQD films determined by the time correlated single photon counting (TCSPC) experiment demonstrates almost complete fluorescence quenching in RGOQDs. The conductance studies demonstrate the differences between GOQDs and RGOQDs. Investigation on the metal–oxide–semiconductor field-effect transistor (nMOSFET) characteristics shows the composite to exhibit p-type channel material properties. The RGOQD exhibits much superior electrical conductance as a channel material compared to the GOQD due to the close proximity of the QDs in the RGOQD to the graphene surface. The transfer characteristics, memory properties, and on/off ratios of the devices are determined. A mechanism has been proposed with reference to the Fermi energies of the composites estimated from the ultraviolet photoelectron spectroscopy (UPS) studies. 1 Introduction The superior electrical conductivity and the exible atom-thin 2D features of graphene 1–3 make it an excellent electron-trans- port matrix compared to the carbon nanotube. Chemical modication of graphene and graphene oxide (GO) 4,5 so as to tune the graphene sheet properties has been an important area of research for this new class of materials for diverse applica- tions. A polystyrene–graphene composite 6 has a conductivity of 0.1 S m 1 , sufficient for many electrical applications. 7 Electro- responsive characteristics of silica–GO hybrid particles, 8 high performance photocatalytic properties of TiO 2 nanocrystals and layered MoS 2 –graphene hybrids, 9 CoO– and Fe 2 O 3 –graphene, a-MnO 2 –RGO, polymer–graphene composites as electrodes in Li ion batteries, 10–12 electrically conductive and thermally stable a Department of Bionano Technology, GBRI, Gachon Bionano Institute, Gachon University, Seongnam 460-701, South Korea b Department of Chemistry, Veer Surendra Sai University of Technology, Burla 768018, India c Center for Biomaterials, Korea Institute of Science and Technology (KIST), Seoul 136- 791, South Korea d Advanced Photonics Research Institute (APRI), Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, South Korea e Samsung Advanced Institute of Technology, Yongin 446-712, South Korea f SKKU Advanced Institute of NanoTechnology, Department of Mechanical Engineering, Sungkyunkwan University, Suwon 440-746, South Korea g Department of Chemistry, Myongji University, Yongin 449-728, South Korea. E-mail: dongkeeyi@gmail.com † Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr02333h Cite this: DOI: 10.1039/c3nr02333h Received 7th May 2013 Accepted 1st August 2013 DOI: 10.1039/c3nr02333h www.rsc.org/nanoscale This journal is ª The Royal Society of Chemistry 2013 Nanoscale Nanoscale PAPER Published on 02 August 2013. Downloaded by Korea Institute of Science and Technology / KIST on 22/08/2013 03:33:45. View Article Online View Journal