Synthesis of graphene on Zno substrate by chemical vapor deposition

Chemistry and Environment 
 N.M.Tuong, “Synthesis of graphene on ZnO substrate by chemical vapor deposition.” 
116 
SYNTHESIS OF GRAPHENE ON ZnO SUBSTRATE BY 
CHEMICAL VAPOR DEPOSITION 
Nguyen Manh Tuong* 
Abstract: Graphene was synthesized by chemical vapor deposition (CVD) 
method on the ZnO catalyst substrate thin plate form at 550oC in the time periods 
of 5 min; 10 min and 30 min. ZnO substrates were fabricated by hydrothermal 
method at 125oC in 10 hours. Material structures are characterized by XRD, TEM, 
SEM and TGA. The obtained ZnO substrate was a thin plate form and uniform. 
Graphene was grown on ZnO substrate with thicknesses in the range 7-10 nm, 
number of layers 10-15. 
Keywords: Nanocomposite, CVD method, Graphene, Absorbance wavelength. 
1. INTRODUCTION 
Graphene is known as a single layer structure sp2 – bonded carbon atoms arranged in a 
two dimensional lattice, with outstanding physical and chemical properties. It has great 
surface area, good thermal conductivity, and high transparent and electron mobility [1]. In 
recently, graphene has attracted many scientists because of various applications such as 
transistors, nano-electronic devices and sensors [2, 3]. Additionally, in graphene-based 
nanocomposites, hybrid of metal oxide (MnO2, TiO2, ZnO,) and graphene are widely 
investigated, but ZnO combined graphene is the most popular. They have various 
application in different fields. 
Chen et al. successfully synthesized of graphene-zinc oxide nano-walls composite by 
one-step co-electrodeposition, graphene oxide was electrochemically reduced and zinc 
oxide was electrodeposited simultaneously. The obtained products presented superior 
electrochemical activity [4]. Zhang et al. also prepared composite of graphene – zinc oxide 
through a spontaneous reduction of graphene oxide via zinc slice in one-spot approach at 
room temperature, and used to modify glassy carbon electrode for developing of electrode 
sensor, used to detect ascorbic acid, dopamine and uric acid [5]. Pahari et al. studied ZnO 
coating amorphous graphene with vary thickness, graphene affects the optical and 
hydrophobic properties of zinc oxide. It is seen that with increase coating optical gap has 
been decrease [6].Park et al. synthesized ZnO/G from ZnO nanorod and graphene thin 
layer has high electrical conduction and good optical properties [7]. Fan et al. prepared 
ZnO/G by hydrothermal method, powder GO was added into solution contain ZnO sol. 
Under UV radiation, composite presented higher effective ability than usual [8]. 
In this work, we investigated the synthesis process of graphene/ZnO nano-composite 
by CVD method. This is an effective method for preparing high quality graphene film, 
large surface area and suitable to industrial scaling at low cost [9]. Owing to method’s 
advantages and exceptional application of ZnO and graphene nano-composite, this work 
opened new approaches in graphene as well as zinc nano-materials. 
2. EXPERIMENT 
2.1. Chemicals 
Research 
Journal of Military Science and Technology, Special Issue, No.48A, 5 - 2017 117 
Chemicals were used in this work such as: Zinc sulfate heptahydrated solid 
ZnSO4.7H2O, sodium hydroxide solid NaOH, cyclohexan, and nitrogen. 
2.2. Synthesis of ZnO substrate 
The starting material used was ZnSO4.7H2O solid available (28.7g). It was dissolved 
in a 400mL- beaker by deionized water then heat to 70oC and stir constantly on magnetic 
stirring machine. Then,gradually add 52ml 0.4M NaOH solution to beaker and remain 
temperature in 2 hours. After that, place it to deposit and remove water, the remained 
mixture was transfer to 2 tubes to centrifugate 3 or 4 times. The white solid was obtained 
having pH medium. The Zn(OH)2 were transferred into a Teflon-lined stainless steel 
autoclave of 60 ml capacity and sealed. The autoclave was maintained at 125 ◦C for 10h. 
After cooling down to room temperature naturally, the white product was collected. The 
product was centrifuged, filtered out and washed with de-ionized water and alcohol for 
several times, and then dried at 60◦C in air. Finally, Zn(OH)2 was dehydrated at 550
oC in 2 
hour to transform ZnO. 
2.3. Synthesis of graphene on ZnO 
The CVD system was presented as below 
Figure 1. CVD system. 
Catalyst ZnO was placed on the silica boat. It was loaded on a substrate holder of CVD 
system. Then, cyclohexane and N2 gases wear dried and adjusted (velocity and flow rate) 
to get the desire graphene before they came into the system. Set up temperature at 600oC 
and take reaction in 5, 10, 30 minutes. The excess gases were burned to avoid polluting. 
After that, cooling the product to room temperature. 
2.4. Characterization of materials 
The morphologies and the microstructure of the synthetic products were analyzed 
using transmission electron microscope (TEM) technique (Tecnai G2 20 S-TWIN/FEI), 
Scanning electron microscopy (SEM).). X-ray diffraction was used to investigate 
crystalline structure of ZnO. The thermal analysis method (TGA) indicated the ratio 
G:ZnO in the sample. The optical absorption properties were investigated using an 
UV−vis diffuse reflectance spectrophotometer. 
Chemistry and Environment 
 N.M.Tuong, “Synthesis of graphene on ZnO substrate by chemical vapor deposition.” 
118 
3. RESULTS AND DISCUSSION 
The typical XRD patterns of the ZnO are shown in Fig. 2 and table 1. 
Figure 2. XRD pattern of ZnO. 
Table 1. The peaks 2 θ and crystalline plans of ZnO. 
Peaks 2 θ 31.7 34.4 36.2 47.5 56.6 62.9 66.3 67.9 69.2 77.0 
Crystalline 
planes 
(1 0 
0) 
(0 0 
2) 
(1 0 
1) 
(1 0 
2) 
(1 1 
0) 
(1 0 
3) 
(2 0 
0) 
(1 1 
2) 
(2 0 
1) 
(2 0 
2) 
It shows that there are ten main peaks at 2 which correspond to the crystalline 
planes of ZnO, respectively, with an average size of 35 nm according to Scherer’s 
formula. 
Fig.3a and 3b show SEM of ZnO and G/ZnO 5min. It has seen that ZnO particles 
quite distributed equally. By comparing figure a and b, clearly that graphene was grown on 
the surface of zinc oxide. The formation is uniform and smooth. 
Research 
Journal of Military Science and Technology, Special Issue, No.48A, 5 - 2017 119 
(a) (b) 
(c) (d) 
Figure 3. Representative SEM images of ZnO (a) substrates and G/ZnO 5 min (b); 
 TEM images of ZnO (c) and G/ZnO 5min (d). 
TEM images (Fig. 3c and d) show clearly that graphene were grown on ZnO 
substrate, but the formation is not uniform on all ZnO particles. Graphene also has sheet 
plate forms with 7-10 nm in thickness, and 10 -15 layers. The ratio of carbon in materials 
increase with more time interval of ZnO in CVD system (Table 2). This ratio was 
determined by Thermal gravity analysis method. The mass loss around 600oC is the 
percentage of carbon in material. 
Table 2. Percentage of carbon in sample vs. time. 
Reaction time 
(min) 
5 10 30 
G (%) 4.8 9.7 15 
Chemistry and Environment 
 N.M.Tuong, “Synthesis of graphene on ZnO substrate by chemical vapor deposition.” 
120 
Figure 4. Thermal analysis of G/ZnO 10 min. 
UV-vis spectroscopy was used to evaluate the absorbance wavelength of materials. 
Figure 5. UV-vis spectroscopy (quality and unit in vertical axis). 
The UV-vis spectroscopy (Fig.5) show that the presence as well as ratio of of 
graphene affects significantly to the absorbance wavelength of Zinc oxide. Graphene 
coated on zinc oxide decrease the band gap of ZnO semiconductor and enhance the 
absorbace intensity of materials 
4. CONCLUSION 
Graphene on ZnO substrate was successfully synthesize by chemical vapor deposition 
method from cyclohexane as a starting material. The SEM and TEM images proved the 
formation of graphene on the surface of zinc oxide with 7-10 nm thickness, number of 
Furnace temperature /°C0 100 200 300 400 500 600 700
 TG/%
-8
-6
-4
-2
0
2
4
6
8
HeatFlow/µV
-20
-10
0
10
20
Mass variation: -9.07 %
Peak :649.38 °C
Figure:
08/11/2015 Mass (mg): 32.84
Crucible:PT 100 µl Atmosphere:AirExperiment:10' G-ZnO
Procedure: RT ----> 800C (10 C.min-1) (Zone 2)Labsys TG
Exo
ZnO 
G/ZnO 5m 
G/ZnO 10m 
G/ZnO 30m 
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Journal of Military Science and Technology, Special Issue, No.48A, 5 - 2017 121 
layers 10 -15. The ratio of graphene in composite depends on reaction time in CVD 
system. Since the band gap of obtained materials are narrower than ZnO pure, it has 
potential application for photocatalysis. 
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interconnected graphene-zinc oxide nanowall via one-step co-electrochemical 
deposition”, Materials Letters 138 (2015) 124-127. 
[5]. X.Zhang, Y.C. Zhang, L.X.Ma, “One-spot facile fabrication of graphene-zinc oxide 
composite and its enhanced sensitivity for simultaneous electrochemical detection of 
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[6]. D. Pahari, N.S. Das, B. Das, K.K. Chattopadhyay, D. Banerjiee, “Tailoring the optical 
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[7]. J.M. Lee, Y.B. Pyun, J. Yi, J.W. Choung, W.I. Park, “ ZnO nanorod− graphene 
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TÓM TẮT 
NGHIÊN CỨU TỔNG HỢP GRAPHENEN 
BẰNG PHƯƠNG PHÁP CVD TRÊN XÚC TÁC ZnO 
Graphen hình thành trên xúc tác ZnO dạng phiến mỏng ở 550oC trong các 
khoảng thời gian 5,10 và 30 phút. ZnO được điều chế bằng phương pháp thuỷ 
nhiệt ở 125oC trong 10 giờ. Cấu trúc và tính chất của vật liệu được xác định 
bằng các phương pháp XRD, TEM, SEM và TGA. ZnO tổng hợp được có cấu 
trúc phiến mỏng, đồng đều. Graphen trên nền ZnO có chiều dày trong khoảng 7 
- 10 nm và có số lớp từ 10 -15 tùy thuộc vào thời gian phản ứng. 
Từ khóa: Vật liệu xúc tác quang, Hiệu suất xử lý, G/ZnO, CVD. 
Received date, 16th February 2017 
Revised manuscript, 28th March 2017 
Published on 26th April 2017 
Author affiliations: 
Insitute for Chemistry - Material, Academy of Military Science and Technology; 
*Corresponding author: manhtuong74@gmail.com.