Synthesis, characterization and electrochemical properties of different morphological ZnO anchored on graphene oxide sheets

Accepted Manuscript Synthesis, characterization and electrochemical properties of different morphological ZnO anchored on graphene oxide sheets Linlin Zhong, Monica Samal, Kyusik Yun PII:

S0254-0584(17)30851-9

DOI:

10.1016/j.matchemphys.2017.10.062

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MAC 20101

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Materials Chemistry and Physics

Please cite this article as: Linlin Zhong, Monica Samal, Kyusik Yun, Synthesis, characterization and electrochemical properties of different morphological ZnO anchored on graphene oxide sheets, Materials Chemistry and Physics (2017), doi: 10.1016/j.matchemphys.2017.10.062 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Synthesis, Characterization and Electrochemical Properties of Different Morphological ZnO Anchored on Graphene Oxide Sheets

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Linlin Zhong1, Monica Samal*2, and Kyusik Yun*1 1 Department of Bionanotechnology, Gachon University, GyeonggiDo 13120, Republic of Korea 2 Department of Material Science and Engineering, North Carolina State University, Raleigh 27606, USA # Address corresponding authors to Kyusik Yun , [email protected] and Monica Samal, [email protected] *Present address: Department of Bionanotechnology, Gachon University, GyeonggiDo 13120, Republic of Korea

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Abstract

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In this study, we reported an optimized facile method to synthesize ZnO particles of three kinds of morphologies, flower-like, rod-like and sphere. Although ZnO grew along the a- and c-axes, however, the anisotropic crystal growth mechanism of ZnO particles was investigated by the ratio of precursor and temperature of the reaction. The characterizations of three ZnO

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particles were measured by Field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy and X-ray diffraction. In addition, ZnO with three shapes was fixed on gold-printed circuit board to detect their electrochemistry property in a 3% H2O2/phosphate

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buffer, while ZnO/GO (graphene oxide) composite was obtained by organic linking which showed the different electrochemical results compare to that of ZnO. electron-transfer distance

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and speed have been changed between the products and support due to the combination of ZnO and GO. The exploration of ZnO of different shape and ZnO/GO composites on their features and properties would provide significant evidence for their application as sensors in extensive fields.

Keywords: ZnO; Graphene oxide; Composite; Characterization

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1.

Introduction

ZnO is a development semiconductor with a wide band-gap (3.37 eV) and high exciton binding

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energy (60 meV), and received extensive attention depending on its unique performance in electronics, optics and photonics[1-3]. Amount of methods have been developed to synthesize ZnO particles of different morphologies, such as hydrothermal methods, thermal evaporation,

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metal-organic chemical vapor deposition, pulsed laser deposition and atomic layer deposition[4-6]. The hydrothermal method is a gentle and simple process that occurs under facile conditions,

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while it is beneficial for ZnO crystal growth along the a- and c-axes[7-9]. Forming ZnO particles with a variety of morphologies enable to control the ratio of the precursor, solution pH, reaction time and temperature. ZnO nanosparticles with numerous shapes have been reported, including nanowires, nanobelts, nanorods, nanospheres and nanoplates[10-12]. As indicated in many reports,

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ZnO is regarded as an excellent functional material due to the abundant active sites on its surface, which can be efficiently bonded with other materials such as graphene oxide (GO), carbon nanotubes, and polymers[13].The combining between ZnO and GO is expected to lead to its

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improved electrochemical activity and, consequently, the development of high-sensitivity components for next-generation detection systems[14].

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Since the isolation of free-standing graphene in 2004, graphene has got much research interest because of its high specific surface area, good charge-carrier mobility, great thermal and electrical conductivity[15-17]. However, GO sheet stack easily attribute to strong π-π interactions and van der Waals forces, which not only decreases the surface area of the GO, but also hinders the penetration of electrolyte ions[18]. Thus, metal oxide particles have been used as spacers to prevent this stacking of GO[19, 20]. Anchoring ZnO particles to the surface of GO mitigates the

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problems of ZnO agglomeration and the stacking of GO[21]. Meanwhile, intercalative structures in the composites increase the interface area and afford a novel way to modulate the electron transfer, resulting in improved electron conductivity[22, 23]. In this regard, ZnO/GO composites

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have become highly researched materials for electrodes owing to their large electrolyte contact interface and nanoscale morphology, which can greatly shorten the ion-diffusion path[24]. Owing to the synergistic effect of the ZnO/GO components, electrodes fabricated by this composite

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exhibit good electrochemical properties [25-27]. Nowadays more efforts are made by researchers on environmental pollution and its association with the safety of daily life and people’s health . This has led to an interest in the developed of ZnO/GO composites for the detection of

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[28-30]

environmental contamination through electrochemical method which is increasingly important analytical tools owing to their intrinsic advantages, such as good portability, low cost, and high sensitivity. [31, 32]

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The objective of this article is to describe the ZnO of different nanostructure that has been grown in various condition and electrochemical property for hydrogen peroxide(H2O2) compare to that of their composites with GO[33, 34]. It would be helpful to provide meaningful evidence for

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application[35].

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the ZnO of different shape and ZnO/GO composites as suitable materials on sensor

2. Experimental

2.1 Chemicals and materials Precursor reagents and graphite powder, zinc acetate dihydrate, zinc nitrate hexahydrate, sodium hydroxide, dimethyl sulfoxide, 3-aminopropyl triethoxysilane (APTS), and dimethyl formamide were obtained from Sigma-Aldrich (St Louis, Mo, USA). A Live/Dead BacLight kit

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was supplied by Sigma Co. from Molecular Probes, Invitrogen, Carlsbad, California, and used according to the manufacturer’s protocol. Potassium permanganate and hydrogen peroxide were obtained from Junsei Chemical Co., Ltd., Japan. Sulfuric acid and hydrochloric acid were

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obtained from Dae Jung Chemicals and Metal Co., Ltd. (Siheung, Gyonggi-do, Korea). Milli-Q water with a resistance greater than 18 MΩ was used in all experiments. All chemical reagents

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were of analytical grade and used without further purification. 2.2 Preparation of three types ZnO

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For the synthesis of different ZnO structures, co-precipitation was used which method reported in our previous study.[36] Zinc acetate dehydrates and zinc nitrate hexahydrate (0.125 M, 2.2 g) was continuously stirred in methanol solution or aqueous solution until solution change to clear. Sodium hydroxide (0.25 M, 0.6 g) was dropped into above solution with drastically stirring

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by using a syringe pump (flow rate of 330µL/min). Controlling pH of mixture solution through adding the extra NaOH solution and reaction temperature determine that the white precipitate would be obtained. The detail experimental parameters of synthesizing different morphology

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ZnO particles summarized in Table 1. The final ZnO products were collected by centrifugation and repeated washing with ethanol and deionized water and then dried in an oven 60 °C for 24 h.

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2.3 Synthesis of ZnO/GO composites The pristine ZnO would be embedded on the surface of graphene oxide which was synthesized by modified Hummers’ method.[37, 38] In brief, graphite (2.0 g) was dissolved in sulfuric acid (98%, mass percent) under stirring for 1 h, and then potassium permanganate (6.0 g) was added gently. The mixture was diluted with distilled water and hydrogen peroxide (30%). The dark brown solution was filtered and washed with 5% hydrochloric acid to remove metal ions.

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Graphene oxide powder was gotten after washing with distilled water and drying in the hot oven. The prepared ZnO (1.0 g) was dissolved in 15 mL dimethyl sulfoxide and ultrasonicated for 1h. APTS (15 mL) was added to the solution and sonicated for 1 h to complete the reaction. The

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amino-functionalized ZnO was separated from the solution via centrifugation, washed with absolute ethanol, and dried in an oven. Fig. 1 describes the synthesis process of ZnO/GO composites using APTS as a linker to combine amino groups on ZnO-APTS with the carbonyl

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groups of GO. Brown powder prepared was washed with deionized and dried in an oven. All the

2.4 Characteristic measurement

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samples were compared for electrochemical detection in a phosphate buffer/3% H2O2 electrolyte.

The ultrasonic system and injection pump used in this study were a VCX 505 Sonics and a KDS101 syringe pump, respectively (KD Scientific). Morphological characteristics were studied

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with a conventional field-emission scanning electron microscope (FE-SEM; JEOL JSM-7500F, 15 kV) and a biological atomic force microscope (Bio-AFM; Nanowizard II, JPK) in intermittent air mode. Ultraviolet-visible (UV-Vis) spectra were recorded with an Optical 3220

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spectrophotometer. X-ray diffraction (XRD; Scintag-SDS 2000) was performed at40 kV voltage and 30mA current in continuous can mode. Fourier transform infrared (FT-IR) spectra of the

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samples were recorded at room temperature with a TENSOR 27 instrument (Bruker) in the 650-4000 cm-1 region.

2.5 Electrochemical measurement CV measurements were recorded with a VersaSTAT 3 potentiostat (Princeton Applied Research, USA) using a standard three-electrode configuration. The gold printed circuit board (Au-PCB) working electrode used in the cyclic voltammetry (CV) study was made from a conventional

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Au-PCB chip. CV experiments were performed with a conventional three-electrode cell comprising an Au-PCB working electrode, a Pt wire auxiliary electrode, and an Ag/AgCl reference electrode. As a crucial component in Au-PCB electrodes, the role of the material used

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to modify them is generally present to facilitate electron transfer from the external circuit and complete electron transfer from the working electrode to the electrolyte.

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3. Results and Discussion 3.1 Mechanism of ZnO growth

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ZnO has polar surfaces, the most common of which is the basal plane. The oppositely charged ions produce positively charged Zn and negatively charged O surfaces, resulting in a normal dipole moment and spontaneous polarization along the c-axis, as well as a divergence in surface energy. To maintain stable structures, polar surfaces generally have facets or exhibit extensive

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surface reconstruction; however, ZnO surfaces are atomically flat, stable, and exhibit no reconstruction. In our study, sodium hydroxide is used to supply OH- ions to the solution, which play a crucial role in ZnO formation [39]. For the reactions at higher pH, the nucleation rate is low

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and the crystal growth is relatively fast. Due to the presence of fewer nuclei and more growth units, the complex [Zn(OH)4]2- connects with the surface at different sites on a single ZnO crystal.

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In a short time, every site may act as a new nucleation center for the growth of the branching structure. Thus, [Zn(OH)4]2- growth units begin to incorporate into the ZnO along the c-axis at different sites. We also found evidence supporting the idea that the growth surface of the ZnO crystal is mainly on the interior of the Zn(OH)2 phase. The Zn(OH)2 complex further reacts with excess OH- ions to form [Zn(OH)4]2- ions. During heating, dehydration of [Zn(OH)4]2- occurs, eventually forming ZnO.

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3.2 Characterization of the particles Morphological analysis of the three types of ZnO and ZnO/GO composites was conducted using

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SEM. As is apparent from the SEM images collected at low and high resolution shown in Fig. 2 (a) and (b), the micro-sized flower-like ZnO particles are composed of several branch-like nanostructures that extend radially from the center, which related to the principle of anisotropy growth. Flower-like structures for ZnO have already been reported by Han et al., although these

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comprised different structural designs and subunits to those reported here.[40, 41] Rod-like ZnO

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particles with 1.0 µm and 0.1 µm in length and width were formed attribute to the vertical growth along the c axis was faster than the lateral growth. As can be seen from SEM image in Fig.2 (c) and (d), the rod-like ZnO particles have a smooth top surface and rough sides. The spherical ZnO display in Fig. 2 (e) and (f) consists of packed nano-grain that unstable nanosized

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particles tend to aggregate into stable sphere shape in much larger scale. GO sheets displayed corrugation and scrolling comprise a basal plane covered mainly with epoxy and hydroxyl groups, while carbonyl and carboxyl groups are located at the edges. The

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oxygen containing groups act as anchoring sites, enabling the in situ formation of nanostructures on the surfaces and edges of the GO sheets. GO sheets also provide numerous negatively charged

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sites, which potentially attract more positively charged Zn2+ ions. When GO is introduced into the hybrids, a ZnO/GO structure where the GO sheets are uniformly encrusted with ZnO particles of various structures is observed, as shown clearly in Fig. 3. The inset images exhibit the magnified morphology of ZnO/GO composites. The purification of hybrids was manifested by EDX spectrum, peaks ascribed to Zn, O, and C elements are observed for the ZnO/GO composites, and no peaks from other elements are detected.

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XRD patterns obtained from three kinds of ZnO particles in order to confirm the phase purity and wurtzite structure of ZnO. Characteristic peaks are shown in Fig. 4, corresponding to the (100), (002), (101), and (102) planes, respectively, which can be indexed to hexagonal [42, 43]

. There is no other pattern besides those from the ZnO particles, which

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wurtzite ZnO

confirms that they are highly pure and in a single ZnO phase. The intensities and narrow widths of the diffraction peaks also indicate that the products have excellent crystalline structures. A

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small (100)/(002) ratio indicates that the ZnO particles are oriented along the c-axis, while a larger (100)/(002) ratio indicates shortening along the c-axis. These results are in agreement with

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those previously reported [44]. Among the three types of ZnO particles, the flower-type ZnO particles show the smallest (100)/(002) ratio, which is related to the formation of eight branches that grow along the c-axis. Conversely, the largest (100)/(002) ratio for spherical ZnO indicates growth around the original nucleus rather than along the c-axis.

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UV-Vis absorption spectrum of GO, as well as those of the as-prepared flower-like ZnO, rod-like ZnO, spherical ZnO and their GO composites are shown in Fig 5. The spectra of the flower-like ZnO, rod-like ZnO, and spherical ZnO exhibit characteristic peaks with their

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fundamental absorption at around 360 nm, confirming the presence of highly crystalline ZnO. As

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previously reported, GO has an absorption peak centered at 235 nm and a shoulder at 300 nm, which can be attributed to ð→ð* transitions in the aromatic C-C bonds and n→ð* transitions in the C=O bonds, respectively[36]. The spectra of the hybrids show an absorption peak at ~360nm, attributed to the absorption of surface-attached ZnO particles. However, the absorption peak of GO at 235 nm is shifted to 225 nm in the of spherical-ZnO/GO composites compared to the flower-like-ZnO/GO and rod-like-ZnO/GO composites, which is consistent with data reported

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elsewhere in the literature. The blue shift of the peak is evidence for rapid electron transfer between the ZnO particles and GO sheets.

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FT-IR spectroscopy was used to ascertain the presence or absence of the various vibrational modes present in synthesized particles. Figure 6 (a) shows the characteristic absorption peaks of Zn-O are nearer to 525 cm-1 from three type ZnO samples. A small peak at 1425 cm-1 existed in flower-like ZnO which from zinc nitrate hexahydrate is corresponding to N-O band. A weak

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carbonyl band at 1636 cm-1 present in rod-like ZnO and spherical ZnO, which is attributed to

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C=O groups from residual incompletely reacted zinc acetate. The FTIR spectra of GO shows characteristic bands at 1050, 1350 and 2820 cm-1 in Fig. 5 (b), which are attributed to the C-O, C-C, and C-H stretching vibration, respectively

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. In addition, the broad band at 3343 cm-1 is

assigned to the O-H stretching vibration. Such red shift of the FTIR spectrum in three types ZnO/GO composites are due to the conjugation between ZnO and GO surface, which the peaks

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at 1050 and 2820 cm-1 shift to 1075 and 2855 cm-1 are corresponding to the C-O and C-H stretching vibration from GO. The bands at 1425 and 1610 cm-1 can be attributed to the stretching of N-H and C=O groups. The broad peak at 3300 cm-1 relates to the O-H or N-H

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stretching vibration. Therefore, the FT-IR spectral features are well matched with reported

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stretching frequency values and further indicate the intense interaction between ZnO and GO. 3.2 Electrochemical investigation for detecting hydrogen peroxide Electrochemical testing performed with a conventional three-electrode cell comprising an Au-PCB working electrode, a Pt wire auxiliary electrode, and an Ag/AgCl reference electrode. The three types of ZnO and their composites were used to drop on the surface of Au-PCB electrodes, which were then utilized to detect hydrogen peroxide (H2O2) at low concentration. To

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evaluate the abilities of the modified electrodes for H2O2 detection, their electrochemical signals were compared in the absence and presence of 3% H2O2.The bare Au-PCB electrode was treated

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with oxygen plasma before modification in order to adhere the materials. The electrochemical behaviors of the three shapes of ZnO were investigated over a potential range of 0 to 1.0 V by CV at a constant scan rate of 50 mV/s. As shown in Fig. 7 (a), no obvious

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peak is observed with the bare Au-PCB electrode and pure ZnO-modified electrodes in the PBS solution. However, the three different ZnO/GO composites replaced pure ZnO to modified

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Au-PCB working electrode that presents distinct oxidation peaks at 0.9 V with different current densities, as shown in Fig. 7 (b). This is because the HPO42- and H2PO4- ions in the PBS react with the hydroxyl groups of the GO, leading to oxidation. Furthermore, the spherical ZnO particles represent the best sensitivity compared to the flower-like and rod-like particles due to

graphene oxide.

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larger surface-volume ratio, more activity electrons transfer from ZnO particles to surface of

The ZnO particles modified electrodes present current responses in 3% H2O2, as shown in Fig.

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8 (a). There is one large peak and one smaller peak, indicating that oxidation occurs twice. Firstly, ZnO is oxidized by H2O2 to ZnO2 and H2O2 is hydrolyzed to form O2 and H2O at 0.2 V.

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Then, ZnO on the surface of the electrode continues to respond to O2, so a second weak oxidation occurs. The functionalization of the graphene surface leads to the formation of defects or oxygen-containing functional groups located at its edge sites, which play a crucial role in providing active sites for reduction. The electrons move from the ZnO to the surface of the GO sheets by fast charge transfer, the improved speed of which is attributed to the short distance between the ZnO and the GO. Herein, we see an apparent redox peak at 0.9 V when the modified electrodes are dipped in 3% H2O2, attributed to ZnO oxidation and GO reduction. Therefore, the

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redox peak presented by the ZnO/GO-modified electrode indicates that its electrochemical activity is more sensitive toward low concentrations of H2O2 than that of the bare gold-PCB electrode. This redox sensitivity to H2O2 is ascribed to the high surface-to-volume ratio of the

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nanocomposite and the synergistic effect of ZnO and GO[46]. The structure of ZnO particles didn’t show obvious distinct reaction between it and GO surface in the 3% H2O2. However, sensitivity property of different structure ZnO/ GO compoaites for same concentration H2O2

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compared to another two structure composites.

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presented in Fig 8 (b). Rod-like ZnO/GO composite displayed more sensitivity for H2O2

Conclusions

In this work, we successfully synthesized ZnO particles of three types. Although all of ZnO grew along the a- and c-axes, however, anisotropic crystal growth mechanism leading to the

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form of flower-like, rod-like and spherical ZnO was related to the ratio of precursor and temperature of the reaction. Anchored the ZnO particles to the surface of GO used a simple method due to a number of carboxyl groups of GO. The prepared three types of ZnO and GO

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were characterized with UV-Vis spectrophotometry, FT-IR spectroscopy, and X-ray diffraction. Working electrodes modified with ZnO and ZnO/GO composites showed different behaviors in

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CV experiments. ZnO/GO composites exhibited sensitivity to low concentrations of H2O2, ascribed to the synergistic effect between the ZnO and GO sheets. Acknowledgements

This work was supported by National Research Foundation of Korean (NRF) grant funded by the Korea Government (MSIP)(No. 2017R1A2B4004700). Conflicts of Interest: The authors declare no conflict of interest. This article does not contain any studies with human participants or animals performed by any of the authors.

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References

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[1] J. Qin, R. Li, C. Lu, Y. Jiang, H. Tang, X. Yang, Ag/ZnO/graphene oxide heterostructure for the removal of rhodamine B by the synergistic adsorption–degradation effects, Ceram. Int.41(3) (2015) 4231-4237. [2] S. Xu, L. Fu, T.S.H. Pham, A. Yu, F. Han, L. Chen, Preparation of ZnO flower/reduced graphene oxide composite with enhanced photocatalytic performance under sunlight, Ceram. Int.41(3) (2015) 4007-4013. [3] Y. Zeng, X. Pan, W. Dai, Y. Chen, Z. Ye, The enhancement of a self-powered UV photodetector based on vertically aligned Ag-modified ZnO nanowires, RSC Adv. 5(82) (2015) 66738-66741. [4] Z. Zhang, S.J. Wang, T. Yu, T. Wu, Controlling the growth mechanism of ZnO nanowires by selecting catalysts., J. Phys. Chem. C 111(47) (2007) 17500-17505. [5] D.J.R. Ye Sun, and Michael N. R. Ashfold, Mechanism of ZnO Nanotube Growth by Hydrothermal Methods on ZnO Film-Coated Si Substrates, J. Phys. Chem. B 110 (2006) 15186-15192. [6] A. Di Mauro, M. Cantarella, G. Nicotra, V. Privitera, G. Impellizzeri, Low temperature atomic layer deposition of ZnO: Applications in photocatalysis, Appl. Catal. B Environ. 196 (2016) 68-76. [7] N.J. Nicholas, G.V. Franks, W.A. Ducker, The mechanism for hydrothermal growth of zinc oxide, Cryst.Eng. 14(4) (2012) 1232-1240. [8] M.J. Limo, R. Ramasamy, C.C. Perry, ZnO Binding Peptides: Smart Versatile Tools for Controlled Modification of ZnO Growth Mechanism and Morphology, Chem. Mater. 27(6) (2015) 1950-1960. [9] T.J. Athauda, P. Hari, R.R. Ozer, Tuning physical and optical properties of ZnO nanowire arrays grown on cotton fibers, ACS Appl. Mater. 5(13) (2013) 6237-46. [10] J.X. Hu Wang, Kangping Yanand Ming Duan, Growth Mechanism of Different Morphologies of ZnO Crystals prepared by hydrothermal method, J. Mater. Sci. Technol. 27(2) (2010) 153-158. [11] Z.L. Wang, Zinc oxide nanostructures: growth, properties and applications, J. Phys.: Condens. Matter 16(25) (2004) R829-R858. [12] V. Baranwal, A. Zahra, P.K. Singh, A.C. Pandey, Starch assisted growth of dumbbell-shaped ZnO microstructures, J. Alloys Compd. 646 (2015) 238-242. [13] J. Du, R. Zhao, S. Chen, H. Wang, J. Li, Z. Zhu, Self-assembly of gridlike zinc oxide lamellae for chemical-sensing applications, ACS Appl Mater Interfaces 7(10) (2015) 5870-8. [14] Y.W. Wang, A. Cao, Y. Jiang, X. Zhang, J.H. Liu, Y. Liu, H. Wang, Superior antibacterial activity of zinc oxide/graphene oxide composites originating from high zinc concentration localized around bacteria, ACS Appl. Mater. 6(4) (2014) 2791-8. [15] N. Kumar, A.K. Srivastava, H.S. Patel, B.K. Gupta, G.D. Varma, Facile Synthesis of ZnO-Reduced Graphene Oxide Nanocomposites for NO2Gas Sensing Applications, Eur. J. Inorg. Chem. 2015(11) (2015) 1912-1923. [16] G. Sun, L. Zhang, Y. Zhang, H. Yang, C. Ma, S. Ge, M. Yan, J. Yu, X. Song, Multiplexed enzyme-free electrochemical immunosensor based on ZnO nanorods modified reduced graphene oxide-paper electrode and silver deposition-induced signal amplification strategy, Biosens. Bioelectron. 71 (2015) 30-6. [17] H.L. Zou, B.L. Li, H.Q. Luo, N.B. Li, A novel electrochemical biosensor based on hemin functionalized graphene oxide sheets for simultaneous determination of ascorbic acid, dopamine and uric acid, Sens. Actuators. 207 (2015) 535-541. [18] M. Saranya, R. Ramachandran, F. Wang, Graphene-zinc oxide (G-ZnO) nanocomposite for electrochemical supercapacitor applications, Journal of Science: Advanced Materials and Devices 1(4) (2016) 454-460.

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

[19] W.H. Nam, B.B. Kim, S.G. Seo, Y.S. Lim, J.Y. Kim, W.S. Seo, W.K. Choi, H.H. Park, J.Y. Lee, Structurally nanocrystalline-electrically single crystalline ZnO-reduced graphene oxide composites, Nano Lett. 14(9) (2014) 5104-9. [20] T. Yang, M. Chen, Q. Kong, X. Wang, X. Guo, W. Li, K. Jiao, Shape-controllable ZnO nanostructures based on synchronously electrochemically reduced graphene oxide and their morphology-dependent electrochemical performance, Electrochim. Acta. 182 (2015) 1037-1045. [21] J. Wang, T. Tsuzuki, B. Tang, X. Hou, L. Sun, X. Wang, Reduced graphene oxide/ZnO composite: reusable adsorbent for pollutant management, ACS Appl. Mater. Interfaces 4(6) (2012) 3084-90. [22] A. Ramadoss, S.J. Kim, Facile preparation and electrochemical characterization of graphene/ZnO nanocomposite for supercapacitor applications, Mater. Chem. Phys. 140(1) (2013) 405-411. [23] H.Y. Abbasi, A. Habib, M. Tanveer, Synthesis and characterization of nanostructures of ZnO and ZnO/Graphene composites for the application in hybrid solar cells, J Alloys Compd. 690 (2017) 21-26. [24] D. Chen, Y. Zhao, Y. Chen, B. Wang, H. Chen, J. Zhou, Z. Liang, One-step chemical synthesis of ZnO/graphene oxide molecular hybrids for high-temperature thermoelectric applications, ACS Appl. Mater. 7(5) (2015) 3224-30. [25] L. Jiang, S. Gu, Y. Ding, F. Jiang, Z. Zhang, Facile and novel electrochemical preparation of a graphene-transition metal oxide nanocomposite for ultrasensitive electrochemical sensing of acetaminophen and phenacetin, Nanoscale. 6(1) (2014) 207-14. [26] A. Chakraborty, A. Agresti, R. Pizzoferrato, F.D. Matteis, A. Orsini, P.G. Medaglia, Study of Structural and Optical Properties of Low temperature photo-activated ZnO-rGO composite thin film, Mater. Res. Bull. (2017). [27] Y.-Z. Liu, Y.-F. Li, Y.-G. Yang, Y.-F. Wen, M.-Z. Wang, A one-pot method for producing ZnO–graphene nanocomposites from graphene oxide for supercapacitors, Scripta Mater. 68(5) (2013) 301-304. [28] W. Xia, C. Mei, X. Zeng, G. Fan, J. Lu, X. Meng, X. Shen, Nanoplate-Built ZnO Hollow Microspheres Decorated with Gold Nanoparticles and Their Enhanced Photocatalytic and Gas-Sensing Properties, ACS Appl. Mater. 7(22) (2015) 11824-32. [29] E.R. Ezeigwe, M.T.T. Tan, P.S. Khiew, C.W. Siong, One-step green synthesis of graphene/ZnO nanocomposites for electrochemical capacitors, Ceram. Int. 41(1) (2015) 715-724. [30] S. Abdolhosseinzadeh, H. Asgharzadeh, S. Sadighikia, A. Khataee, UV-assisted synthesis of reduced graphene oxide–ZnO nanorod composites immobilized on Zn foil with enhanced photocatalytic performance, Res. Chem. Intermed. 42(5) (2015) 4479-4496. [31] L. Fu, Y. Zheng, A. Wang, W. Cai, B. Deng, Z. Zhang, An Electrochemical Sensor Based on Reduced Graphene Oxide and ZnO Nanorods-Modified Glassy Carbon Electrode for Uric Acid Detection, AJSE-Engineering. (2015). [32] M. Veerapandian, M.-H. Lee, K. Krishnamoorthy, K. Yun, Synthesis, characterization and electrochemical properties of functionalized graphene oxide, Carbon 50(11) (2012) 4228-4238. [33] S.A. Hosseini, S. Babaei, Graphene Oxide/Zinc Oxide (GO/ZnO) Nanocomposite as a Superior Photocatalyst for Degradation of Methylene Blue (MB)-Process Modeling by Response Surface Methodology (RSM), J. Braz. Chem. Soc. (2016). [34] E. Salih, M. Mekawy, R.Y.A. Hassan, I.M. El-Sherbiny, Synthesis, characterization and electrochemical-sensor applications of zinc oxide/graphene oxide nanocomposite, JNSC. 6(2) (2016) 137-144. [35] V. Kumar, K.-H. Kim, J.-W. Park, J. Hong, S. Kumar, Graphene and its nanocomposites as a platform for environmental applications, Chem. Eng. J. 315 (2017) 210-232. [36] L. Zhong, K. Yun, Graphene oxide-modified ZnO particles: synthesis, characterization, and antibacterial properties, Int J Nanomedicine 10 (2015) 79-92. [37] E. Rokhsat, O. Akhavan, Improving the photocatalytic activity of graphene oxide/ZnO nanorod films by UV irradiation, Appl. Surf. Sci. 371 (2016) 590-595.

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[38] A.A.A. LEILA SHAHRIARY, Graphene Oxide Synthesized by using Modified Hummers Approach, IJEEE 02 (2014). [39] G. Mondragón-Galicia, C. Gutiérrez-Wing, M. Eufemia Fernández-García, D. Mendoza-Anaya, R. Pérez-Hernández, Ag nanowires as precursors to synthesize Ag–ZnO nanostructured brushes, RSC Adv. 5(53) (2015) 42568-42571. [40] H.J. Kim, M.K. Joshi, H.R. Pant, J.H. Kim, E. Lee, C.S. Kim, One-pot hydrothermal synthesis of multifunctional Ag/ZnO/fly ash nanocomposite, Colloids Surf.A. s 469 (2015) 256-262. [41] N. Ait Ahmed, H. Hammache, L. Makhloufi, M. Eyraud, S. Sam, A. Keffous, N. Gabouze, Effect of electrodeposition duration on the morphological and structural modification of the flower-like nanostructured ZnO, Vacuum. 120 (2015) 100-106. [42] M. Ahmad, E. Ahmed, Z.L. Hong, N.R. Khalid, W. Ahmed, A. Elhissi, Graphene–Ag/ZnO nanocomposites as high performance photocatalysts under visible light irradiation, J. Alloys Compd. 577 (2013) 717-727. [43] B. Li, T. Liu, Y. Wang, Z. Wang, ZnO/graphene-oxide nanocomposite with remarkably enhanced visible-light-driven photocatalytic performance, J. Colloid Interface Sci. 377(1) (2012) 114-21. [44] T.V.-S. Anna Mclaren, Guoqiang Li, and Shik Chi Tsang, Shape and Size Effects of ZnO Nanocrystals on Photocatalytic Activity, J. AM. CHEM. SOC 131 (2009) 12540–12541. [45] Y.-L. Chen, C.-E. Zhang, C. Deng, P. Fei, M. Zhong, B.-T. Su, Preparation of ZnO/GO composite material with highly photocatalytic performance via an improved two-step method, Chin. Chem. Lett. 24(6) (2013) 518-520. [46] S. Palanisamy, S.-M. Chen, R. Sarawathi, A novel nonenzymatic hydrogen peroxide sensor based on reduced graphene oxide/ZnO composite modified electrode, Sens. Actuators.B. 166-167 (2012) 372-377.

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Graphic

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Schematic of electrochemical reaction on ZnO and ZnO/GO composites modified Au-PCB electrode, respectively. Insert image is rod-like ZnO particles and rod-like ZnO/GO composites.

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ZnO Morphology

Zinc precursor (M)

NaOH(M)

Solvent

Temperature °C

pH

0.25

Water

90

11

0.25

Methanol

0.125 Zn(CH3COO)2

Rod-like ZnO

0.25 Zn(CH3COO)2

0.25

Methanol

9

65

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The experimental parameter of synthesizing different morphology ZnO particles.

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Table1.

0.125

65

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Spherical ZnO

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Flower-like ZnO

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Zn(NO3)2.6H2O

Figure 1. Schematic of synthetic procedure (a) Preparation of ZnO-APTS (b) Fabrication of ZnO/GO composites

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Figure 2. SEM images of different morphology ZnO particles. (a) (b) Flower-like ZnO particles with eight branches (c) (d) Rod-like ZnO which its length is about 4.5 µm (e) (f) Spherical ZnO consist

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uniform secondary ZnO nanocrystals

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Figure 3. SEM images of ZnO/GO composites represent graphene oxide sheet was fully covered by dispersion ZnO particles (a) Flower-like ZnO/GO composites (c) Rod-like ZnO/GO composites (d)

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Spherical ZnO/GO composites. (Figure insets are the magnification SEM images of ZnO/GO morphology) EDX pattern (b, d, f) demonstrates three types of ZnO/GO composites only include three elements,

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carbon, oxygen and zinc.

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Figure 4. XRD patterns of flower-like ZnO, rod-like ZnO and spherical ZnO. Characteristic peaks of

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three ZnO structures are almost similar corresponding to (100), (002), (101), (102) plane, respectively.

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(100)/(002) ratios are different due to their growth along the c axis.

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Figure 5. UV-visible spectra of three shape ZnO particles. (a) Exhibit ZnO characteristic spectrum at

around 360 nm and graphene oxide gives an absorption peak at 235 nm and a shoulder at 300 nm. (b) The

peak.

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absorption peak of ZnO/GO composites show original peak existing in graphene oxide and weaken ZnO

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Flower-like ZnO Rod-like ZnO

N-O

O-H

Zn-O

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Transmittance% (T)

Spherical ZnO

C=O

Zn-O

O-H C=O

Zn-O

4000

3500

3000

2500

2000

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O-H

1500

1000

500

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Wavenumber (cm-1)

GO Flower-like ZnO/GO Rod-like ZnO/GO Spherical ZnO/GO

O-H

C-O

C-H

N-H

C=O

Zn-O

C=O N-H

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Transmittance% (T)

C-C

Zn-O C=O N-H

C-H

4000

3500

3000

2500

Zn-O

2000

1500

1000

500

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-1 Wavenumber (cm )

Figure 6. FTIR spectrum of (a) Three kinds of ZnO particles with the special peak at 525 cm-1

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corresponding to ZnO-O band. (b) ZnO/GO composites shows the peaks relation to C-O stretching vibration, C-C, C-H and O-H stretching vibration from GO, and the Zn-O band is also presented.

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Figure 7. Cyclic voltammetry (CV) curves were detected in PBS solution (pH=7.0) (a) Bare Au-PCB and

three shapes ZnO modified Au-PCB electrode. (c) (d)ZnO/GO composites modified Au-PCB electrode show distinct oxidation peak at 0.9 V. Scan rate is constant at 50 mV/s.

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Figure 8. Cyclic voltammetry (CV) curves were carried on with modified Au-PCB electrode in 3% H2O2

solution. (a) Three shapes ZnO particles modified Au-PCB electrodeand ZnO/GO modified Au-PCB electrode in 3% H2O2.

(b) Different structure ZnO particles combined graphene oxide to modify bare

Au-PCB electrode for detecting H2O2. Apparent redox peak occurred at 0.9 V. Scan rate is constant at 50 mV/s.

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Highlights 1. Three types of ZnO particles are synthesized successfully by facile method. 2. The mechanism of ZnO growth in the aqueous solution is proposed. 3. The ZnO particles were decorated on the surface of graphene oxide sheets. 4. ZnO and ZnO/GO composites can be applied in analyzation of H2O2.