A simple and straightforward approach was used to prepare Fe2O3/graphene nanocomposites with different temperature conditions. The nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and photoluminescence (PL).
Trang 1EFFECT OF TEMPERATURE ON THE STRUCTURE AND
SYNTHESIZED BY HYDROTHERMAL METHOD
Tran Van Khai1, 2, * Nguyen Quang Vinh1, Le Van Thang1, 2, Mai Thanh Phong3
1
Faculty of Materials Technology, Ho Chi Minh City University of Technology,
Vietnam National University Ho Chi Minh City, 268 Ly Thuong Kiet street,
Ward 14, District 10, Ho Chi Minh City
2
Material Technologies Laboratory, Ho Chi Minh City University of Technology, Vietnam National University Ho Chi Minh City, 268 Ly Thuong Kiet street,
Ward 14, District 10, Ho Chi Minh City
3
Ho Chi Minh City University of Technology, Vietnam National University Ho Chi Minh City,
268 Ly Thuong Kiet street, Ward 14, District 10, Ho Chi Minh City
* Email: tvkhai1509@hcmut.edu.vn
Received: 5 August 2019, Accepted for publication: 30 September 2019
Abstract A simple and straightforward approach was used to prepare Fe2O3/graphene
nanocomposites with different temperature conditions The nanocomposites were characterized
by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning microscopy
(FE-SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and
photoluminescence (PL) The results show that Fe2O3 nanoparticles with size in range of 60-100
nm are anchored on the surface and filled between the graphene nanosheets at hydrothermal
reaction The PL spectrum exhibits the emission peaks appeared at ~ 650 nm and ~ 720 nm
Keywords: Fe2O3/graphene, nanocomposite, graphene, hydrothermal method
Classification numbers: 2.1.1, 2.4.4, 2.9.4
1 INTRODUCTION
Over the past few years, a lot of carbon-based materials have been synthesized and
investigated for potential applications [1-3] Graphene, a single layer of carbon atoms densely
packed into a two-dimensional (2D) honeycomb sp2 carbon lattice, has attracted a great deal of
research attention due to its unique electrical, physical, and chemical properties [4, 5] It has
unmatched thermal conductivity (~ 5000 W/mK), very high electron mobility (μ ~ 200,000 cm2
V-1.s-1), a theoretical specific surface area (~ 2630 m2/g) as well as excellent mechanical
properties (Young’s modulus ~ 1.1 TPa), which makes it promising for applications in various
fields such as solar-cells, energy storage, field effect transistors, catalyst support, sensors,
supercapacitors, electrodes, separation and nanocomposites [6-9] Up to now, a number of facile
and low-cost methods have been used to prepare graphene in bulk quantities [10] Among the
many methods proposed, most people produced graphene sheets by chemical reduction of
exfoliated graphene oxides [11] Many graphene nanocomposites based on the hybridization
with nanoparticles fabricated are of highly versatile in electronics [12], photonics [13], energy
Trang 2storage [14, 15], sensors [16], catalysis [17] and bioapplication [18] Although these exciting results concerning the graphene based materials in these fields, there are still some issues remained for further consideration
Recently, transition metal oxides have been widely studied in various fields to constitute composite materials with graphene in order to enhance its properties in application Among the various transition metal oxides, such as ZnO [19], TiO2 [20], Fe3O4 [21], CuO [22], SnO2 [23]; Fe2O3 is one of the most common oxides in the natural world Due to its low cost, environmental friendliness, chemical stability and nontoxic, Fe2O3 has been extensively studied in lithium batteries [24], catalysis [25], sensors [16], magnetic materials [26], biological and medical fields [27] It has been differently synthesized dimensional nanostructures (1D), such as nanorods [28], nanobelts [29], nanowires [30], nanotubes [31], porous structures) [32], core–shell structures [33], and so on In terms of Fe2O3, several ways, including precipitation methods [34], hydrothermal methods [35], solvothermal methods [36], hydrolysis [37], microwave methods [38], were utilized in preparation of its graphene composites
Herein, we adopted one-step hydrothermal method to synthesize Fe2O3/graphene nanocomposites with different temperature condition Under the hydrothermal condition, graphene oxide (GO) is simultaneously reduced to graphene along with the homogeneous precipitation of Fe2O3 nanoparticles Compared to GO and reduced graphene oxide (rGO), Fe2O3/graphene composites can be easily separated from the solution after adsorption
2 EXPERIMENTS 2.1 Materials
All chemicals used in this study were purchased from Xilong Scientific Co., Ltd., including graphite flakes (~5 μm, 99.8 %), H2SO4 (98 %), H3PO4 (85 %), KMnO4 (98 %), H2O2 (30 wt
%), FeCl3.6H2O and CO(NH2)2 The starting GO nanosheets were prepared by modified Hummors method
2.2 Synthesis of Fe 2 O 3 /graphene nanocomposites
The Fe2O3/graphene nanocomposites were prepared via a one-pot hydrothermal method First, 0.41 g of FeCl3.6H2O and 1.55 g of CO(NH2)2 were added into 10 mL of a 1.825 mg/mL graphene oxide (GO) aqueous solution while stirring for 30 min at room temperature, and the above mixture was sonicated for 20 min to obtain a uniform suspension After adding distilled water to about 90 mL, the mixture solution was transferred to a 100 mL Teflon-lined stainless steel autoclave and maintained for 8 h at several different temperatures in an electric oven After being cooled to room temperature naturally, the resulting black product was centrifuged and washed with distilled water and ethanol several times, and Fe2O3/graphene composites were finally dried at 35 °C for 3 h
2.3 Characterization
The X-ray diffraction (XRD) patterns were recorded using a D8 advance (Bruker-AXS) diffractometer with Cu Kα radiation (λ= 0.1546 nm) The morphologies of the as-prepared products were observed by field emission scanning electron microscopy (FESEM Hitachi
Trang 3S-JEOL JEM-100CX II) at 100 kV TEM specimens were prepared by drop casting the dispersions
on a carbon-coated copper grid, followed by drying under vacuum for 24 h at 50 °C Raman
measurements were carried out using Horiba XploRA One spectrometer equipped with an
Olympus BX50 microscope attachment to focus the laser beam on a 180×120 μm2
selected area
of the sample, a 15 mW green argon laser (λ = 532 nm) were used as an excitation source with
exposition time of 15 s along with a 900 lines per mm grating monochromator with liquid
nitrogen-cooled CCD The room-temperature photoluminescence (PL) used a He-Cd laser line
with the excitation source of 325 nm
3 RESULTS AND DISCUSSION
The Fe2O3 nanoparticles are grown on the surfaces of the graphene nanosheets through a
reduction process of the pristine GO to reduce graphene under a hydrothermal treatment Urea
can release CO2 and OH- when the temperature of the solution exceeds 80°C, as a result,
Fe(OH)3 particles anchor onto the surfaces of GO sheets uniformly The formation of
Fe2O3/graphene composite under the action of urea can be represented as following:
CO(NH2)2 + 3H2O 2NH3.H2O + CO2 NH3.H2O NH4++ OH−
Fe3+ + 3OH− Fe(OH)3 2Fe(OH)3 Fe2O3 + 3H2O
Figure 1 FE-SEM images of Fe2O3/graphene composites grown at different temperatures: (a) 120 °C, (b) 150 °C, (c) 180 °C, (d) 210 °C, (e) 240 °C for 8 h and (g) EDS analyses of the composites
The morphologies and structure of the Fe2O3/graphene composites grown at different
temperatures were observed by FE-SEM As can be seen in Figure 1(a-e), the Fe2O3
nanoparticles are uniformly anchored on the surface and filled between the graphene nanosheets
Furthermore, there are no free or independent Fe2O3 nanoparticles outside the graphene sheets,
demonstrating that all of the nanoparticles are completely attached to the almost transparent
c )
Trang 4graphene sheets Figure 1(g) confirms the presence of C, O and Fe elements in the products, proving the formation of Fe2O3/graphene composites again
TEM images (Figure 2) illustrate the presence of interface between Fe2O3 particles and graphene with good size distribution The almost transparent graphene sheets are fully decorated with Fe2O3 particles with average diameters of 60 nm Even after a long duration of sonication during the preparation of the TEM specimen, Fe2O3 particles are still adsorbed on the surface of graphene nanosheets, proving the formation of Fe2O3/graphene composites again Most carboxyl and hydroxyl groups, which can act as anchor sites, are decorated on the edges of GO, leading to
in situ formation of Fe2O3 nanoparticles attached on the edges of GO sheets [34] Similar to the dopamine molecule, GO has a large quantity of phenolic hydroxyl groups that can coordinate with Fe2O3 nanoparticles [40] Herein, the nanoparticles directly disperse on the surface and alternate between graphene sheets, which could efficiently prevent from agglomerating of graphene sheets
Figure 2 TEM images of Fe2O3/graphene composites grown at 180°C for 8h at different scales
XRD diffraction patterns of GO, reduced graphene oxide (rGO) and Fe2O3/graphene nanocomposites are shown in Figure 3 In the case of GO (Figure 3a), a strong diffraction peak
at 2θ of 11.2°, which is associated with (002), showing the complete oxidation of graphite to the graphite oxide due to the introduction of oxygen-containing functional groups on the graphite sheets [41,42] For the XRD pattern of rGO, after reduction, the peak located at 11.2° disappears, while a broad diffraction peak (002) appears at 25° The basal spacing of rGO is a little larger than that of GO, revealing the great reduction of GO and exfoliation of layered graphene sheets For Fe2O3/graphene nanocomposites, the XRD pattern is shown in Figure 3b
Trang 5peaks at 2θ value of 24.2, 33.2, 35.5, 40.9, 43.5, 49.5, 54.1, 57.6, 62.4, and 64.0° can be indexed
as (012), (104), (110), (113), (202), (024), (116), (018), (214) and (330) crystal planes of
hexagonal iron oxide, respectively The strong and sharp diffraction peaks show that the
obtained products are well crystallized The disappearance of GO peak is attributed that the
regular layer stacking of GO can be destroyed by the ultrasonic process and the crystal growth of
Fe2O3 during the hydrothermal reaction, leading to the exfoliation of GO sheets On the other
hand, as reported previously in many literatures, GO sheets can be reduced under hydrothermal
conditions [43] and the obtained graphene sheets can be further exfoliated by decorating Fe2O3
nanoparticles, resulting in the disappearance of diffraction peak of GO
Figure 3 XRD patterns of a) GO and rGO, b) Fe2O3/graphene composites synthesized at
120, 150, 180, 210 and 240 oC for 8 h.
The Raman spectra of GO, rGO and Fe2O3/graphene nanocomposites are presented in
Figure 4 In the case of GO, there are two peaks observed at 1330 and 1590 cm-1, corresponding
to the disorder band associated with structural defects, amorphous carbon created in graphene
(D-band) and well ordered scattering of the E2g phonon of sp2 C atoms of graphene (G-band),
respectively [44] The intensity of D-band is stronger than that of G-band, meaning the presence
of high density of defects and structure disorder in GO Moreover, the ID/IG intensity ratio, as a
vital parameter to evaluate disorder and defects of carbon materials, presents a negative
correlation with the degree of ordering in the carbon materials The ID/IG of GO is about 1.07
After hydrothermal reduction, the ID/IG of rGO is increased to 1.25, indicating the presence of
localized sp3 defects with the sp2 carbon network after a reduction in the exfoliated rGO For the
Fe2O3/graphene composites (180 oC), the Raman spectrum shows the typical peaks of hematite
and the D and G bands of graphene, which implies the formation of Fe2O3/graphene composite
Moreover, the Raman peaks at about 220 cm-1 is assigned to the A1g mode and 285 cm-1 can be
ascribed to the Eg mode of Fe2O3, suggesting the combination of Fe2O3 nanoparticles with the
graphene layer The calculated ID/IG ratios of Fe2O3/graphene composite with different
temperature condition 120 °C, 150 °C, 180 °C, 210 °C, 240 °C are 1.22, 1.27, 1.27, 1.28 and
1.25, respectively No other features corresponding to different iron oxide phases were detected,
indicative of high purity of the products
Trang 6Figure 4 Raman spectra of a) GO and rGO, b) Fe2O3/graphene composites
Figure 5 Photoluminescence spectrum of Fe2O3/graphene composite synthesized at 180 oC for 8 h
Photoluminescence (PL) spectrum is a well known technique to study of the interface charge carrier transfer as well as the recombination process involving the electron-hole pairs in semiconductor particles [45] and PL emission results from the radiative recombination of excited electrons and holes Figure 5 shows the PL spectrum of Fe2O3/graphene composites at the excitation wavelength of 448 nm The emission of Fe2O3 is positioned at 650 nm and 720
nm, assigned to 6A1 4T2 (4G) ligand filed transitions of Fe3+ [46] Furthermore, by using the
formula E g = 1240/λ, the Fe2O3/graphene nanocomposites provide band gap of around 1.7 eV
and 1.9 eV
Trang 74 CONCLUSSION
In summary, Fe2O3/graphene nanocomposites have been successfully prepared by a one-step hydrothermal method with different temperature condition The structure and morphologies
of the Fe2O3/graphene nanocomposites are well investigated and provided some positive achievements to any further applications In these different temperature conditions, the experiment was prepared at a temperature of 180°C for 8 h, giving the best results Specifically, through the analysis by SEM and TEM, the results show that Fe2O3 nanoparticles with sizes of
60 nm are homogeneously anchored on the surface and filled between the graphene nanosheets
at hydrothermal reaction It also proves that Fe2O3 effectively prevented graphene sheets from agglomerating Future work should concentrate on improving fabrication approach of nanocomposites and advancing our understanding of nanocomposites toxicity, then realizing their wide applications in our daily life
Acknowledgement This work was supported by Vietnam National University Ho Chi Minh City
(VNU-HCM) under grant number C2018-20-16
REFERENCES
1 Kroto H W., Heath J R., Obrien S C., Curl R F., Smalley R E - C60 Buckminster
fullerene, Nature 318 (1985) 162-163
2 Iijima S - Helical microtubules of graphitic carbon, Nature 354 (1991) 56–58
3 Novoselov K S., Geim A K., Morozov S V., Jiang D., Zhang Y., Dubonos S V., Grigorieva I V., Firsov A A - Electric field effect in atomically thin carbon films,
Science 306 (2004) 666–669
4 Choi W., Lee J - Graphene: Synthesis and Applications, in Nanomaterials and their applications, CRC press, 2012
5 Sharon M., Sharon M., Tiwari A - Graphene: An Introduction to the Fundamentals and Industrial Applications, John Wiley & Sons, 2015
6 Ramanathan T., Abdala A., Stankovich S., Dikin D., Herrera-Alonso M., Piner R., Adamson D., Schniepp H., Chen, Ruoff R - Functionalized graphene sheets forpolymer
nanocomposites, Nat Nanotechnol 3 (2008) 327–331
7 Stoller M D., Park S., Zhu Y., An J., Ruoff R S - Graphene-based ultracapacitors,
Nano Lett 8 (2008) 3498–3502
8 Liu C., Yu Z., Neff D., Zhamu A., Jang B Z - Graphene-based supercapacitor with an
ultrahigh energy density, Nano Lett 10 (2010) 4863–4868
9 Khai T V., Thu L V., Ha L T T, Thanh V M., Lam T D - Structural, optical and gas sensing properties of vertically well-aligned ZnO nanowires grown on graphene/Si
substrate by thermal evaporation method, Mater Charact 141 (2018) 296-317
10 Xu Y., Bai H., Lu G., Li C., Shi G - Flexible graphene films via the filtration of
water-soluble noncovalent functionalized graphene sheets, J Am Chem Soc 130 (2008)
5856–5857
11 Xu Y., Sheng K., Li C., Shi G - Self-assembled graphene hydrogel via a one-step
hydrothermal process, ACS Nano 4 (2010) 4324–4330
Trang 812 Eda G., Chhowalla M - Graphene-based composite thin films for electronics, Nano Lett
9 (2009) 814–818
13 Bao Q., Zhang H., Yang J., Wang S., Tang D.Y., Jose R., Ramakrishna S., Lim C.T., Loh K.P - Graphene–Polymer Nanofiber Membrane for Ultrafast Photonics, Adv Funct
Mater 20 (2010) 782–791
14 Peng C., Chen B., Qin Y., Yang S., Li C., Zuo Y., Liu S., Yang J - Facile ultrasonic
synthesis of CoO quantum dot/graphene nanosheet composites with high lithium storage
capacity, ACS Nano 6 (2012) 1074–1081
15 Kuhn L., Gorji N E - Review on the graphene/nanotube application in thin film solar
cells, Mater Lett 171 (2016) 323–326
16 Liang S M., Zhu J W., Wang C., Yu S T., Bi H P., Liu X H., Wang X - Fabrication of alpha Fe2O3@graphene nanostructures for enhanced gas sensing property to ethanol,
Appl Surf Sci 292 (2014) 278–284
17 Yuan Y., Jiang W., Wang Y., Shen P., Li F., Li P., Zhao F., Gao H - Hydrothermal preparation of Fe2O3/graphene nanocomposite and its enhanced catalytic activity on the
thermal decomposition of ammonium perchlorate, Appl Surf Sci 303 (2014) 354–359
18 Gollavelli G., Ling Y.C - Multi-functional graphene as an in vitro and in vivo imaging
probe, Biomaterials 33 (2012) 2532–2545
19 Cho P.S., Kim K.W., Lee J.H - NO2 sensing characteristics of ZnO nanorods prepared by
hydrothermal method, J Electroceram 17 (2006) 975–978
20 Lv X., Zhang G., Fu W - Highly efficient hydrogen evolution using TiO2/graphene
composite photocatalysts, Procedia Eng 27 (2012) 570–576
21 Lian P., Zhu X., Xiang H., Li Z., Yang W., Wang H - Enhanced cycling performance of Fe3O4–graphene nanocomposite as an anode material for lithium-ion batteries,
Electrochim Acta 56 (2010) 834–840
22 Wang H., Liang Q Q., Wang W J., An Y.R., Li J H., Guo L - Preparation of flower-like SnO2 nanostructures and their applications in gas-sensing and lithium storage, Cryst
Growth Des 11 (2011) 2942–2947
23 Ba N N., Zhu L J., Zhang G.Z., Li J F., H J Li H J - Facile synthesis of 3D CuO nanowire bundle and its excellent gas sensing and electrochemical sensing properties,
Sens Actuators B 227 (2016) 142–148
24 NuLi Y., Zeng R., Zhang P., Guo Z., H Liu H - Controlled synthesis of α-Fe2O3 nanostructures and their size-dependent electrochemical properties for lithium-ion
batteries, J Power Sources 184 (2008) 456–461
25 Sivula K., Zboril R., Formal F.L., Robert R., Weidenkaff A., Tucek J., Frydrych J., Graetzel M - Photoelectrochemical Water Splitting with Mesoporous Hematite Prepared
by a Solution-Based Colloidal Approach, J Am Chem Soc 132 (2010) 7436–7444
26 Dyal A., Loos K., Noto M., Chang S.W., Spagnoli C., Shafi, K.V Ulman A., Cowman M., Gross R.A - Activity of Candida rugosa lipase immobilized on α-Fe2O3 magnetic
nanoparticles, J Am Chem Soc 125 (2003) 1684–1685
Trang 927 Kulal P M., Dubal D P., Lokhande C D., Fulari V J - Chemical synthesis of Fe2O3 thin
films for supercapacitor application, J Alloys Compd 509 (2011) 2567-5271
28 Pradhan G K., Parida K M - Fabrication, growth mechanism, and characterization of α-Fe2O3 nanorods, ACS Appl Mater Interfaces 3 (2011) 317–323
29 Wang H Z., Zhang X T., Liu B., Zhao H L., Li Y C., Huang Y B., Du Z L - Synthesis and characterization of single crystal α-Fe2O3 nanobelts, Chem Lett 34 (2005) 184–185
30 Chueh Y L., Lai M W., Liang J Q., Chou L J., Wang Z L - Systematic study of the growth of aligned arrays of α-Fe2O3 and Fe3O4 nanowires by a vapor-solid process, Adv
Funct Mater 16 (2006) 2243–2251
31 Mohapatra S K., John S E., Banerjee S., Misra M - Water photo oxidation by smooth and ultrathin α-Fe2O3 nanotube arrays, Chem Mater 21 (2009) 3048–3055
32 Yan W., Fan H., Zhai Y., Yang C., Ren P., Huang L - Low temperature solution-based synthesis of porous flower-like α-Fe2O3 superstructures and their excellent gas-sensing
properties, Sens Actuators B 160 (2011) 1372–1379
33 Yu Q., Zhu J., Xu Z., Huang X - Facile synthesis of α-Fe2O3@SnO2 core–shell
heterostructure nanotubes for high performance gas sensors, Sens Actuators B 213
(2015) 27–34
34 Zhu X., Zhu Y., Murali S., Stoller M D., R S Ruoff R S - Nanostructured reduced graphene oxide/Fe2O3 composite as a high-performance anode material for lithium ion
batteries, ACS Nano 5 (2011) 3333–3338
35 Wang G., Liu T., Luo Y., Zhao Y., Ren Z., Bai J., Wang H - Preparation of Fe2O3/graphene composite and its electrochemical performance as an anode material for
lithium ion batteries, J Alloys Comp 509 (2011) L216–L220
36 Zhu J., Zhu T., Zhou X., Zhang Y., Lou X.W., Chen X., Zhang H., Hng H.H., Yan Q - Facile synthesis of metal oxide/reduced graphene oxide hybrids with high lithium storage
capacity and stable cyclability, Nanoscale 3 (2011) 1084–1089
37 Chen D., W Wei W., Wang R., Zhu J., L Guo L - α-Fe2O3 nanoparticles anchored on
graphene with 3D quasi-laminated architecture: in situ wet chemistry synthesis and
enhanced electrochemical performance for lithium ion batteries, New J Chem 36 (2012)
1589–1596
38 Zou Y., Kan J., Wang Y - Fe2O3-graphene rice-on-sheet nanocomposite for high and fast
lithium ion storage,” J Phys Chem C 115 (2011) 20747–20753
39 Xu C., Wang X., Zhu J., Yang X., Lu L - Deposition of Co3O4 nanoparticles onto
exfoliated graphite oxide sheets, J Mater Chem 18 (2008) 5625-5629
40 Liu J., Bai H., Wang Y., Liu Z., Zhang X., Sun D.D - Self-assembling TiO2 nanorods on large graphene oxide sheets at a two-phase interface and their anti-recombination in
photocatalytic applications, Adv Funct Mater 20 (2010) 4175-4181
41 Khai T V., Na H G., Kwak D S., Kwon Y J., Ham H., K B Shim K.B and Kim H W
- Significant enhancement of blue emission and electrical conductivity of N-doped
graphene, J Mater Chem 22 (2012) 17992-18003
42 Khai T V., Na H G., Kwak D S., Kwon Y J., Ham H., Shim K B., H W Kim H W - Influence of N-doping on the structural and photoluminescence properties of graphene
oxide films, Carbon 50 (2012) 3799–3806
Trang 1043 Xu C., Wang X., J W Zhu J W - Graphene-metal particle nanocomposites, J Phys
Chem C 112 (2008) 19841–19845
44 L W Zhang L W., H B Fu H.B., Zhu Y F - Efficient TiO2 photocatalysts from surface hybridization of TiO2 particles with graphite‐like carbon, Adv Funct Mater 18 (2008) 2180-2189
45 Haldar K K., Sinha G., Lahtinen J., Patra A - Hybrid colloidal Au-CdSe pentapod heterostructures synthesis and their photocatalytic properties, ACS Appl Mater Interfaces
4 (2012) 6266-6272
46 Mitra S., Das S., Mandal K., Chaudhuri S - Synthesis of a α-Fe2O3 nanocrystal in its different morphological attributes: Growth mechanism, optical and magnetic properties,
Nanotechnology 18 (2007) 275608