Impact of Laser Energy on Synthesis of Iron Oxide Nano-particles in Liquid Medium

doi:10.4236/wjnse.2011.14014

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World Journal of Nano Science and Engineering, 2011, 1, 89-92

doi:10.4236/wjnse.2011.14014 Published Online December 2011 (http://www.SciRP.org/journal/wjnse)

Impact of Laser Energy on Synthesis of Iron Oxid e

Nanoparticles in Liquid Medium

Alemu Kebede1, Ashok V. Gholap1, Awadhesh K. Rai2*

1Department of Physics , Addis Ababa University, Addis Ababa, Ethiopia

2Laser Spectroscopy Research Laboratory, University of Allahabad, Allahabad, India

E-mail: [email protected], *[email protected]

Received May 30, 201 1; revised November 10, 2011; accepted November 20, 2011

Abstract

We present echofriendly laser ablation technique of Synthesizing iron oxide nanoparticle in pure water and

discuss the impact of laser energy on the size, shape and morphology of the nanoparticle. The synthesized

nanoparticle was characterized by UV/Visible absorption spectroscopy and morphological study was per-

formed by scanning electron microscope (SEM). Intensity and wave length of the absorption peak of the

colloidal nanoparticle prepared in water are dependent on the laser energy. Red-shift in the absorption band

was observed at increasing laser energy. The intensity of absorption peak also changed when ablating laser

energy was increased. The spherical natures of the nanoparticle is lost as the laser energy gradually increases

and finally triangular shaped structures is observed as the laser energy increases from 9.3 mJ to 75 mJ.

Keywords: Laser, Ablation, SEM, UV/Visible, Nanoparticle, Iron Oxide

1. Introduction

The electronic and optical properties and the chemical

reactivity of small clusters/nanoparticles are completely

different from the known property of each component in

the bulk or at extended surfaces. The interaction forces

crucially determine the properties of individual and col-

lective nanoparticles. This interaction between nanopar-

ticles resulting in aggregates may influence on their be-

havior [1]. Iron nanoparticles are of great interest due to

their unique physicochemical properties and have been

used for the development of imaging, purifying agents,

magnetic and electrical applications. The structure and

properties of the nanoparticle have been more investi-

gated [1-6]. Much work on the synthesis of iron oxide

nanoparticles have been done on bottom-up method in

which chemicals are required for its synthesis [6,7]. But

these methods are not echo friendly and may result in

pollution of the environment. In addition to this there is

possibility of the presence of impurities which create

hindrance in using composites of the nanoparticle for

medical purposes.

The laser ablation of a solid target immersed in a liq-

uid environment has become an increasingly important

top-down method for fabricating nano-structured materi-

als [8,9] which are free from chemicals. The physical

approach was originally used to produce noble metal

nanoparticles with bare surfaces, which cannot be achieved

with wet chemical methods. Recently, Abhimanyu K. et

al. [8] used pulsed laser ablation in liquid medium to

synthesized and characterize noble metal nanoparticles.

In this paper, we present an efficient and chemical-free

method of preparation of colloidal iron oxide nanoparti-

cle in water using laser ablation, and its characterization.

The synthesized iron oxide colloidal nanoparticle loaded

with insulin have been used for oral delivery in diabetic

management.

2. Experimental Details

Iron slug (99.95% pure), 9.5 mm dia × 9.5 mm length

and 10 g mass was purchased from Alfa Aesar, USA.

Ultra pure de-ionized water (HPLC grade) was pur-

chased from Merck, Germany. Laser ablation of iron

oxide nano-particle in pure water was performed by us-

ing Nd:YAG, pulsed laser (Continuum Surelite III-10,

USA), using its second harmonic, (532 nm) wavelength,

and having 4Hz pu lse repetition rate. The n anoparticle of

iron oxide was synthesized at three different laser ener-

gies: 25.8 m, 75 mJ and 255 mJ. A long focal length lens,

300 mm was use to focus th e laser beam on to the mate-

rial (Iron slug) emersed in 10 ml ultra pure water. Abla-

A. KEBEDE ET AL.

tion was made for 30 minutes. The experimental set-up

for synthesis of iron oxide nanoparticle in water is shown

in Figure 1.

3. Results and Discussion

Three different laser energies; 9.3 mJ, 25.8 mJ, 75 mJ at

4 Hz pulse repetition rate have been used for ablation

purpose of iron slug immersing into 10 ml pure water

(Figure 1). The color of the solutions has gradually

changed to dark brown (Figure 2) after ablation of the

slug for 30 minutes which clearly indicates the formation

of iron oxide colloidal nanoparticles.

UV/Visible spectroscopic technique has been used to

verify the formation of iron oxide nanoparticles. The

UV-Visible absorption spectrum of synthesized nanopar-

ticle were recorded using Perkin Elmer Lambda-35 UV/

Vis spectrometer. Our experimental results clearly dem-

onstrates that the position of absorption band and peaks

(Figure 3) depends up on the laser energy which had

been used to synthesize th e iron oxide colloidal nanopar-

ticles. The peak of the iron oxide colloidal nanoparticles

shifted from 205 nm to 215 nm as the laser energy

changed from 9.3 mJ to 75 mJ (Figure 3 and Table 1).

The change in position of absorption peak of the iron

oxide colloidal nanoparticles may be due to the change in

the size of the colloidal nanoparticles. Our experimental

results clearly reveales that smaller size nanoparticles are

synthesized using lower laser energy 9.3 mJ (Figure

4(a)), and a tendency of agglomeration/cementation was

also seen at higher laser energy 75 mJ (Figure 4(b)).

This may cause a decrease in the reactivity of the nanoparti-

cle as suggested by Paul G. et al. [10]. Further, it was ob-

served tht the shape of the nanoparticles is changing with

the laser energy, i.e., when the laser energy is increased

the shape of the nanoparticlesit changes from spherical

nature to triangular nature (Figure 4(c)). Therefore one

may conclude that the spherical nanoparticles may be

synthesized at lower laser energy. The other difficulty in

synthesizing iron oxide nanoparticles at higher laser en-

ergy is associated with mechanical difficulties because

because increasing laser energy resulted in the propaga-

tion of shock waves throughout the liquid medium and it

is found difficult to control the rod at a fixed position

during the ablation. At very high energy of the laser

beam splashing of water from the container takes place

and water from the container jumps out and collects at

the surface of the focusing lens which prevents the

transmission of the laser beam and finally stopped the

ablation and this needs frequent cleaning of the focusing

lens and there would also be loss of nanoparticles along

with water splashing out of the container. The high local

temperature of plasma during ablation of the nanoparti-

cles in liquid solution may also have an impact on de-

termining the optical properties of th e nanoparticles.

Figure 1. Experimental set up of laser ablation of iron oxide

nanoparticle in water, 1: Laser source; 2: Laser light; 3:

Right angled prism; 4: Converging lense; 5: Glass; 6: Water;

7: Iron slug; 8: Plasma.

Figure 2. Iron oxide nanoparticle synthe sized in water.

Figure 3. UV/Visible spectra of iron oxide nanoparticle in

water.

A. KEBEDE ET AL.

(a) (b) (c)

Figure 4. SEM image of colloidal iron oxide nanoparticles in water synthesized by laser ablation at (a) 25.8 mJ; (b) cementa-

tion of nanoparticles 75 mJ; (c) shape of nanoparticles (at the edge of a slide) at 75 mJ.

Table 1. Dependence wave length and absorbance on laser

energy.

Absorbance Wave length

(nm) Laser energy

(mJ)

0.425 205 9.3

1.717 210 25

1.729 215 75

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4. Conclusions

Iron oxide nanoparticles of different sizes and surface

morphology have been successfully synthesized ul-

trapure water. The particle morphology showed depend-

ence of shape and size of the nanoparticles on the laser

energy which was further confirmed by the red shift in

the absorbance peak.

[4] H.-Y. Huang, Y.-T. Shieh, C.-M. Shieh and Y.-K. Twu,

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Composite Platform for Mismatch-Discriminating DNA

Hybridization for Neisseria gonorrhoeae Detection Caus-

ing Sexually Transmitted Disease,” Biosenceors and Bio-

electronics, Vol. 26, No. 6, 2011, pp. 2967-2974.

5. Acknowledgements

I would like to acknowledge National Center for Ex-

perimental Mineralogy and Petrology, Allahabad Uni-

versity, for service they rendered me with scaning elec-

tron microscopic (SEM) image of the nanoparticles. I am

thankful to Rohit Kumar, Abhimanyu K. Singh, Neeraj

Giri and Ashok K. Pathak for their assistance and help.

My special thanks goes to Prof. Ram Kripal for his as-

sistance and provision of UV/Vis absorption spectrome-

ter. Addis Ababa University, post graduate program, de-

serves acknowledgement for its financial assistance.

[6] R. Sarkar, P. Pal, M. Mahato, T. Kamilya, A. Chaudhuri

and G. B. Talapatra “On the Origin of Iron-Oxide Nano-

particle Formation Using Phospholipid Membrane Tem-

plate,” Colloids and Surface B: Biointerface, Vol. 79, No.

12, 2010, pp. 384-389.

doi:10.1016/j.colsurfb.2010.04.023

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der Elst and N. Muller, “Magnetic Iron Oxide Nanoparti-

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