Graphene oxide coated flower-shaped ZnO nanorods: Optoelectronic properties
Graphical abstract
Introduction
Recently, interest in graphene-based materials hasexploded due to many important applications in diverse fields of nanotechnology, because of their unique electric, thermal, mechanical properties and high theoretical specific surface area [1]. In particular, graphene oxide (GO), which can be prepared from graphite powder by a modified Hummers’ method [2], has attracted considerable interest as a promising building block for the fabrication of functional carbon-based nanomaterials, because of its significant advantages such as low cost, easy preparation, and good solubility [3]. In addition, GO is highly oxygenated by hydroxyl and epoxide functional groups at their basal planes, acting as nucleation centres to anchor active nanomaterials at the surface of GO [4]. Especially, incombination with ZnO nanostructures, the delocalized conjugated π systems of GO enable high mobility of charge carriers and relatively low recombination rate of graphene oxide [5,6].
Due to their excellent properties, wide band gap (3.37 eV), high exciton binding energy (60 meV), low cost and easy synthesis, one-dimensional ZnO nanostructures display a huge application potentialin solid-state device technology (optoelectronic devices, sensors, solar cells, and supercapacitors) [7]. A number of methods has been developed to synthesize ZnO nanostructures with different morphologies, such as hydrothermal technique, thermal evaporation, metal-organic chemical vapor deposition, pulsed laser deposition and atomic layer deposition [[8], [9], [10]]. The hydrothermal synthesis implies a simple process that occurs under easy conditions, while it is beneficial for ZnO crystal growth along the a and c axes [[11], [12], [13]]. Furthermore, the formation of ZnO nanostructures with a wide variety of morphologies involves control of the ratio of precursors, pH solution, reaction time and temperature [[14], [15], [16]].
In recent times, the conversion of one dimensional nanostructures on high-surface area substrates has attracted much attention in virtue of their exceptional and enhanced properties, due to synergistic interactions, size effects and abundant active sites on its surface [17], which can be efficiently used for linking with other materials such as graphene derivatives, carbon nanotubes, and polymers [18]. In particular, the combination of ZnO nanostructures and GO is expected to lead to improved performances in the case of photocatalysts [19], biosensors, batteries [20], supercapacitors [21]. To date, severalworks on the synthesis of GO coated ZnO nanostructures have been reported. Thuanet al. [22] synthesized ZnO quantum dots with different diameters, linked to the surface of GO, by using the sol-gel method. Kumar et al. [23] investigated the optical properties of ZnO decorated graphene oxide and of reduced graphene oxide synthesized by the hydrolysis approach. In our previous work [24] we successfully synthesized GO/ZnO NRs/GO sandwich structures via a simple hydrothermal method and investigated their photoluminescence (PL) mechanisms.
In this work, we report the preparation of ZnO NRs and ZnO NRs:GO nanocomposites by hydrothermal method and drop coating, respectively. The structural, morphological, vibrational, optical and luminescence properties of ZnO NRs and ZnO NRs:GO nanocomposites were investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), as well as micro-Raman, FTIR, UV–Vis–NIR (ultraviolet–visible–near infrared) and PL spectroscopies. Our results indicate that the addition of graphene oxide significantly contributes to the growth of high quality ZnO nanorods and improves their photocatalytic performance, together with their application potential in low-cost optoelectronic devices.
Section snippets
Synthesis of ZnO NRs and ZnO NRs:GO nanocomposite
The procedure to fabricate high quality ZnO nanorods is shown in Fig. 1(a). Initially, appropriate amounts of zinc nitrate hexahydrate (0.1 M, 73 ml), hexamethylenetetramine (0.1 M, 73 ml) and NaOH (73 mg, 10 ml) aqueous solutions were separately prepared in deionized water. Then NaOH solution was dripped into the mixture solution under constant stirring. After that, the mixed solution was added in a 200 ml teflon-sealed autoclave and hydrothermally grown at 90 °C for 24 h, then cooled to room
Structural analysis
Fig. 2 illustrates the XRD patterns of as-synthesized ZnO NRs and ZnO NRs:GO nanocomposite. The sharp diffraction peaks indicated high crystallinity of ZnO NRs based samples. The diffraction lines of ZnO NRs at 31.8°, 34.5°, 36.3°, 47.6°, 56.6°, 62.9°, 66.4°, 68.0°, 69.1°, 72.6° and 77.0°, can be assigned to (100), (002), (101), (102), (110), (103), (200), (112), (201), (004) and (202) planes, respectively, of the hexagonal (wurtzite) structure of ZnO (JCPDS Card no. 36-1451) with P63mc space
Conclusion
ZnO NRs and ZnO NRs:GO nanocomposite have been successfully prepared via the hydrothermal method and drop coating process, respectively. The effect of GO on the structural and optical properties of ZnO nanorods was investigated. The formation of the hexagonal crystal structure of ZnO without any other impurity phases was observed in the prepared samples. SEM images revealed that ZnO nanorods were covered by graphene oxide layers. Optical transmission and reflectance of GO coated ZnO NRs were
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
Special thanks to the Africa Graphene Center, University of South Africa, Department of Physics, and Alexandru Ioan Cuza University of Iasi, Faculty of Physics (Romania).
References (52)
Photocatalytic reduction of graphene oxides hybridized by ZnO nanoparticles in ethanol
Carbon
(2011)- et al.
UV-assisted photocatalytic synthesis of ZnO–reduced graphene oxide composites with enhanced photocatalytic activity in reduction of Cr (VI)
Chem. Eng. J.
(2012) - et al.
Low temperature atomic layer deposition of ZnO: applications in photocatalysis
Appl. Catal. B Environ.
(2016) - et al.
Mole-controlled growth of Y-doped ZnO nanostructures by hydrothermal method
Curr. Appl. Phys.
(2014) - et al.
Starch assisted growth of dumbbell-shaped ZnO microstructures
J. Alloys Compd.
(2015) - et al.
Synthesis of ZnO@ Graphene composites as anode materials for lithium ion batteries
Electrochim. Acta
(2013) - et al.
Investigations on optical properties of ZnO decorated graphene oxide (ZnO@ GO) and reduced graphene oxide (ZnO@ r-GO)
J. Alloys Compd.
(2018) - et al.
Graphene oxide/ZnO nanorods/graphene oxide sandwich structure: the origins and mechanisms of photoluminescence
J. Alloys Compd.
(2019) - et al.
Preparation and characterization of GO-ZnO nanocomposite for UV detection application
Opt. Mater.
(2019) - et al.
Electrochemistry and electrocatalysis of myoglobin immobilized in sulfonated graphene oxide and Nafion films
Anal. Biochem.
(2016)
Synthesis and characterization of ZnO NPs/reduced graphene oxide nanocomposite prepared in gelatin medium as highly efficient photo-degradation of MB
Ceram. Int.
Preparation of ZnO/GO composite material with highly photocatalytic performance via an improved two-step method
Chin. Chem. Lett.
Facile synthesis of zinc oxide nanoparticles decorated graphene oxide composite via simple solvothermal route and their photocatalytic activity on methylene blue degradation
J. Photochem. Photobiol. B Biol.
Photoinduced superhydrophilicity and high photocatalytic activity of ZnO–reduced graphene oxide nanocomposite films for self-cleaning applications
Mater. Sci. Semicond. Process.
First principle calculations of the electronic and optical properties of pure and (Mo, N) co-doped anatase TiO2
J. Alloys Compd.
Facile synthesis of ZnO/GO nanoflowers over Si substrate for improved photocatalytic decolorization of MB dye and industrial wastewater under solar irradiation
Mater. Sci. Semicond. Process.
Photoluminescence investigation about zinc oxide with graphene oxide & reduced graphene oxide buffer layers
J. Colloid Interface Sci.
Defect engineering of ZnO nanoparticles by graphene oxide leading to enhanced visible light photocatalysis
J. Mol. Catal. Chem.
Photocatalytic performance of a Ag/ZnO/CCG multidimensional heterostructure prepared by a solution-based method
J. Phys. Chem. C
Preparation of graphitic oxide
J. Am. Chem. Soc.
Graphene chiral liquid crystals and macroscopic assembled fibres
Nat. Commun.
Two dimensional soft material: new faces of graphene oxide
Acc. Chem. Res.
ZnO-microrod/p-GaN heterostructured whispering-gallery-mode microlaser diodes
Adv. Mater.
Controlling the growth mechanism of ZnO nanowires by selecting catalysts
J. Phys. Chem. C
Mechanism of ZnO nanotube growth by hydrothermal methods on ZnO film-coated Si substrates
J. Phys. Chem. B
ZnO binding peptides: smart versatile tools for controlled modification of ZnO growth mechanism and morphology
Chem. Mater.
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