Structural and Optical Properties of ZnO/PMMA Nanocomposite

A. Aadila1, 2, a, N. A. M. Asib1, 2, b, A. N. Afaah1, 2, c, R. Mohamed4, d,

M. Rusop1, 3, e and Z. Khusaimi1, 2, f

1Nano-SciTech Centre, Institute of Science, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia

2Faculty of Applied Sciences, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia

3NANO-Electronic Centre, Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia

4Faculty of Applied Sciences, Universiti Teknologi MARA Cawangan Pahang, Lintasan Semarak, 26400 Bandar Pusat Jengka, Pahang, Malaysia

aaadilaazizali@gmail.com, bamierahasib@yahoo.com, cafaahabdullah@yahoo.com, druzianamohd@pahang.uitm.edu.my, enanouitm@gmail.com, fzurai142@salam.uitm.edu.my

Keywords: ZnO, solution-immersion method, PMMA, spin coating, nanocomposite

Abstract. UV filter is an interesting and challenging application in industries. Hence, ZnO-PMMA

nanocomposite thin films have been chosen to achieve above mentioned characteristics [1]. In this

study, fabrication of ZnO on PMMA glass substrate successfully prepared by using the solution-

immersion method. Layer by layer of poly (methyl methacrylate) (PMMA) was deposited on a glass

substrate using the spin coating technique by dissolving PMMA in toluene. Various layers of

PMMA were varied to 1, 3, 5 and 7 layers. The structural and optical properties of ZnO/PMMA

nanocomposite were then characterized by Field Emission Scanning Electron Microscope (FESEM)

and Photoluminescene (PL) Spectroscopy. From FESEM result, shape of nanorod unclearly seen as

the layer deposited of PMMA increase and from EDAX show oxygen element have highest atomic

percentage 65.50 %. 7 layer of deposited PMMA show highest intensity compare to other layers in

green region at 577.32 nm for PL measurement.

Introduction

Zinc oxide (ZnO) is very promising semiconductor due to unique properties in near-UV region,

electric conductivity and optical transparency [2]. Among one dimensional (1-D) nanomaterials,

ZnO has received extensive attention due to its large direct band gap semiconductor properties (3.3 ̴

3.4 eV) [3, 4] and large exciton binding energy (60 meV) [4, 5]. ZnO has an optical band gap in the

UV region and makes it an extremely efficient UV absorber. ZnO can be synthesized in various

synthetic paths such hydrothermal and solvothermal methods, mircoemulsion, sol-gel method, and

thermal decomposition of precursors [6].

Polymer is flexible lightweight materials and can be produced into thin films at a low cost. They

can be easily processed and shaped into thin films using different methods such dip-coating, spin-

coating, film-casting and printing [7]. Poly (methyl methacrylate) (PMMA) is a type of polymer

which is an optically clear amorphous thermoplastic [2, 6, 8]. It is frequently preferred because of

its moderate properties, easy handling and processing, and low cost [9]. However, PMMA does not

filter ultraviolet (UV) light. So, to overcome the deficiency, semiconductor nanocrystals with large

band gap such as TiO2, ZnO and ZnS can be introduced to PMMA matrix, which can be applied in

transparent UV-protective coatings or UV-shielding windows [10]. Furthermore, the nano

ZnO/PMMA composites have potential applications in UV protecting sheets and films, transparent

barrier or protective layers, antireflection coatings and as materials with increase thermal stability

[11]. The present study, optical properties of ZnO/PMMA nanocomposite was investigated.

Advanced Materials Research Vol. 832 (2014) pp 602-606Online available since 2013/Nov/21 at www.scientific.net© (2014) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.832.602

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Experimental Method

Zinc nitrate hexahydrate Zn (NO3).6H2O mixed with hexamethylenetetramine (HMTA) (CH4N2O)

where HMTA as a stabilizer. While, PMMA solution were prepared by dissolve in toluene. Both of

the solutions were stirred for 24 hours at 60 °C for 1 hour. 6 nm of platinum was sputter coated for

24 s on glass substrate. Layer by layer of PMMA was deposited on glass substrate using spin

coating technique. Substrate deposited with PMMA was immersed in zinc solution by immersion

method for 4 hours. After immersion, the substrate was annealed for 20 minutes at 120 °C.

Fig. 1, Configuration of deposited PMMA layer on glass substrate

Subsequently, the samples were cooled at room temperature. Then, samples were characterized by

using Field Emission Scanning Electron Microscope (FESEM) and Photoluminescene (PL)

Spectroscopy.

Result and Discussion

Field Emission Scanning Electron Microscope (FESEM). The surface morphologies of

ZnO/PMMA nanocomposite on different layer of deposited PMMA substrate were characterized by

FESEM (JEOL JSM-7600F). The samples were taken at accelerating voltage of 5.0 kV. All the

samples were coated with platinum to minimize the charging effect. For Fig. 2(a) 1 layer and 2(b) 3

layers, nanorod of ZnO can be clearly seen compared to (c) 5 layers and (d) 7 layers. As layer of

deposited PMMA increase, shapes of ZnO nanorod started to deform. So, layer of PMMA on

substrate effect the shape of nanorod. The presence of ZnO and PMMA particles was be proven by

using EDAX analysis.

(a) 1 layer PMMA

(b) 3 layers PMMA

Advanced Materials Research Vol. 832 603

(c) 5 layers PMMA

(d) 7 layers PMMA

Fig. 2, FESEM image of ZnO/PMMA nanocomposite on different layer of deposited PMMA; (a) 1

layer PMMA, (b) 3 layer PMMA, (d) 5 layers PMMA and (d) 7 layers PMMA

Fig. 3, Energy Dispersive Analysis X-Ray (EDAX) spectrum of ZnO/PMMA nanocomposite

The Energy Disperse Analysis X-Ray (EDAX) was used to analyze the compositional of

nanocomposite material. Fig. 3 show EDAX spectrum of ZnO/PMMA nanocomposite for 1 layer of

deposited PMMA polymer. From Fig. 3, highest peak showed oxygen element with 65.50 % atomic

weight percentage due to oxygen presence in both ZnO compound and PMMA polymer. While

carbon element represent the structure of PMMA [12] with weight percentage 26.26 %. Pt element

contributed to the sample coating with platinum. While, for Si (4.61 %) and Mg (0.47 %) elements

might be due to the contamination of samples which originated from the furnace during annealing

process. The atomic percentage of significant elements in ZnO/PMMA nanocomposite is

summarized in Table 1.

604 Nanoscience, Nanotechnology and Nanoengineering

Table 1, Energy Disperse Analysis X-Ray (EDAX)

Element Atomic Percentage (%)

Oxygen (O) 65.50

Carbon (C) 26.26

Zinc (Zn) 3.05

Platinum (Pt) 0.12

Photoluminescene (PL) Spectroscopy. Photoluminescence (PL) is a sensitive technique for

examining the sample quality, especially its optical properties [7]. PL spectrum shows a wide and

intense emission band covering the whole 400 - 700 nm visible area with three highest peaks. The

broad PL emission band located in the visible region may be related to induced emission from some

defects such as oxygen vacancies and zinc interstitials [10].

Fig. 4, Intensity versus wavelength of ZnO/PMMA nanocomposite

Fig. 4 shows intensity of ZnO/PMMA nanocomposite with different layer of deposited PMMA on

glass substrate. 7 layer of PMMA show highest intensity compared to other layers which

wavelength at 416.05 nm is due to excitonic transition. The green emission at 577.32 nm (2.16 eV)

has an energy smaller than the band gap of ZnO (3.2eV) which this peak is related to oxygen defect

[13], a result of the recombination of a photogenerated hole with an electron occupying the oxygen

vacancy defect states [4]. While, at 635.71 nm is due to surface electrons and other imperfections

[14]. Therefore, as the deposited layer of PMMA on substrate decrease, the intensity of

ZnO/PMMA nanocomposite increases in visible region.

Conclusion

ZnO/PMMA nanocomposite was successfully prepared by using sol-gel spin coating method. From

FESEM, shape of ZnO nanorod deform as the layer of deposited PMMA increase and EDAX

analysis showed oxygen element have highest atomic percentage due to oxygen presence in both of

ZnO compound and PMMA polymer. From PL measurement, the intense peak was at 577.32 nm in

green region for 7 layer of PMMA which can be concluded that PL intensity increase as the layer of

deposited PMMA polymer decrease.

Advanced Materials Research Vol. 832 605

Acknowledgement

Grateful to Universiti Teknologi MARA for the support and also thanks to Fundamental Research

Grant Scheme 600-RMI/FRGS 5/3 (18/2012) for financial support. Thanks to NANO-Scitech

Centre and NANO-Electronic Centre colleagues for their helpful support and encouragement.

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http://dx.doi.org/10.1021/ma062184t