Exploring the Properties of NiO Nanoparticles Prepared by Reflux Method10

Mechanics, Materials Science & Engineering, May 2017

ISSN 2412-5954

Exploring the Properties of NiO Nanoparticles Prepared by Reflux Method10 A. Dhayal Raj1,a, A. Albert Irudayaraj1, A. Reenaarul Vani1 1

Department of Physics, Sacred Heart College, Tirupattur, India

a

dhayalraj03@gmail.com DOI 10.2412/mmse.25.82.979 provided by Seo4U.link

Keywords: NiO nanostructures, pH, SEM, XRD, reflux method.

ABSTRACT. Admirable nanoparticles of nickel oxide have been synthesized by Reflux method. Required amount of nickel nitrate was dissolved in 200ml of Ethylene Glycol (EG).To the above solution 50ml of PEG was added and stirred well. The pH of the solution was adjusted as 8, 10 and 12 using HCl in order to investigate the effect of pH on the properties of the prepared NiO nanoparticles. The precipitate was collected, washed several times and was calcinated at 500oC for 1 hr. The samples were subjected to various characterizations such asXRD, SEM, UV and FTIR, inorder to study its structure, morphology, optical properties and functional group. The results show that pH plays a key role in the synthesis of NiO nanostructures. The morphology of the prepared samples holds substantial promise for applying NiO as a potential gas sensing material.

Introduction. Nickel oxide (NiO) nanoparticles have been received considerable attention due to their wide range of applications in various fields included the fabrication of catalysis [1-4], electro chromic films [4-6], fuel cell electrode and gas sensors [6-9], battery cathodes [10-11], magnetic materials [12-13], photovoltaic devices and electrochemical super capacitors, smart windows and dye-sensitized photocathodes [14]. Therefore, NiO became one of the most important transition metal oxides. However, most of these applications require particles with a small size and a narrow size distribution. The reduction in size leads to the volume effect, the quantum size effect and the surface effect which in turn improves the properties of NiO nanoparticles.

One of the major challenges, the world recently facing is energy consumption and demand. To meet the energy requirements of this modern generation, an ideal energy storage device is needed at present to provide high energy in short time. Especially, the device should store more power and deliver high energy output for various applications. Among all energy storage devices, electrochemical capacitors exhibit high power density than other electrochemical devices, such as batteries, photo-voltaic devices, etc. and high energy density than conventional capacitors because of unique charge storage mechanisms. Transition metal oxides have been studied to obtain high specific capacitance and high charge/discharge ability in electro-chemical capacitors. Among the transitional metal oxides available, nickel oxide is an attractive material in electrochemical devices. In this research work, nanocrystalline nickel oxide nanoparticles have been prepared by reflux method. The prepared samples are found to have uniform particle size distribution and excellent morphological characteristics. The obtained results were discussed and presented in this research article.

Experimental. Required amount of nickel nitrate was added to 200ml of ethylene glycol. To the above solution 50 ml of PEG was added and stirred well. The pH of the resultant solution was altered to the required value (10 and 12) using dilute HCL. The final solution was refluxed for 5 hours under constant stirring. The precipitate was collected, washed several times with double distilled water and ethanol. Then it was 10

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Mechanics, Materials Science & Engineering, May 2017

ISSN 2412-5954

characterizations in order to investigate the effect of pH on the properties of the prepared NiO nanoparticles.

Results and Discussion. Structural Analysis

Fig. 1. XRD pattern for the NiO nanoparticles a) pH10 b) pH12.

Fig. 1 (a - b) shows the XRD pattern for the NiO nanoparticles prepared by reflux method. The sharp peaks obtained in the XRD patterns show the crystalline behavior of the materials due to high temperature hea reported standard JCPDS data for NiO (JCPDS card No: 89-7131). The XRD patterns obtained for -crystallized single phase face centered cubic (FCC) geometry as reported. The XRD patterns of each sample exactly agree with the JCPDS data without any collateral peaks, indicating high purity of the prepared samples. The crystallite size of the particles, determined with Sc -20 nm.

3.2 Morphological Analysis

a

b

Fig. 2. HR-SEM images for the NiO nanoparticles a) ph 10, b) ph 12.

The SEM images of the NiO nanoparticles prepared by reflux method are shown in Fig. 2 (a and b).

From the SEM images, it was understood that all NiO grains are spherical in shape. From the Fig.s, it was found that the grains are present in the range of 22nm and 34 nm for the samples prepared with MMSE Journal. Open Access www.mmse.xyz

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Mechanics, Materials Science & Engineering, May 2017

ISSN 2412-5954

pH values 10 and 12 respectively. However, the presence of bigger grains in the samples may be due to the high temperature treatment procedure adopted during calcination.

Functional group analysis. Spectra of the pH10 and pH12 products NiO nanoparticles after calcination. A narrow and strong band at 3420 cm 1 relating to the (OH) stretching vibration. The broad and intense band centered at 2919cm 1 is assigned to the O H stretching vibration of the interlayer water molecules and of the H bound OH group. The peak observed at 1644 cm 1 is assigned to the bending vibration of water molecules. Calcination, the FT-IR spectra of NiO nanoparticles shows strong band at 425 to 800 cm 1 corresponds to the vibration of Ni O bond. It could be seen from Fig. 2 that the broad absorption band attributable to the band O H stretching vibrations, due to the fact that the calcined powders tend to physically absorption of water due to KBr (Fig. 3).

Fig. 3. Transmittance vs. wavenumber.

Optical analysis. Spectra of pH 10 and pH 12 NiO nanoparticles are shown in Fig. 4. The Fig. 4 shows that the broad and less symmetric absorption peaks were observed at 350nm, due to blue shifted as compared to the bulk material. The blue shifting of effects are caused due to the quantum size effect where as the broadening and as symetricity are due to the huge size distribution of synthesized materials and it was also conformed to our SEM results. The band gap energy (Eg) of the nano particles was calculated using the formula Eg= . This absorption spectrum of chosen nanomaterial gives the good relation between the particle and band gap obtain value of particle size is 3.37eV and 3.55eV respectively (Fig. 4).

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Fig. 4. Absorption vs. wavelength.

Summary. The NiO nanoparticles have successfully prepared by reflux method with different pH values. The phase and purity of both the samples was confirmed by X-ray diffraction analysis. The size of the nano-crystallites was 10nm and 20 nm, as evaluated by the wellfor samples prepared with pH values 10 and 12 respectively. SEM revels that the samples show spherical morphology as shown and the size has been increased with increasing the pH value. It is clear show that pH is plays a vital role in controlling the size of the particle. From the FTIR spectra irrational peaks around 743cm-1 and 828cm-1 to confirm the formation of NiO. The band gap of NiO was calculated from the absorption spectra and was found to be 3.1eV and 3.4eV respectively.

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