Elsevier

Applied Surface Science

Volume 256, Issue 14, 1 May 2010, Pages 4661-4666
Applied Surface Science

Spectroscopic characterization approach to study surfactants effect on ZnO2 nanoparticles synthesis by laser ablation process

https://doi.org/10.1016/j.apsusc.2010.02.068Get rights and content

Abstract

Zinc peroxide nanoparticles having grain size less than 5 nm were synthesized using pulsed laser ablation in aqueous solution in the presence of different surfactants and solid zinc target in 3% H2O2. The effect of surfactants on the optical and structure of ZnO2 was studied by applying different spectroscopic techniques. Structural properties and grain size of the synthesized nanoparticles were studied using XRD method. The presence of the cubic phase of zinc peroxide in all samples was confirmed with XRD, and the grain sizes were 4.7, 3.7, 3.3 and 2.8 nm in pure H2O2, and H2O2 mixed with SDS, CTAB and OGM respectively. For optical characterization, FTIR transmittance spectra of ZnO2 nanoparticles prepared with and without surfactants show a characteristic ZnO2 absorption at 435–445 cm−1. FTIR spectrum revealed that the adsorbed surfactants on zinc peroxide disappeared in case of CTAB and OGM while it appears in case of SDS. This could be due to high critical micelles SDS concentration comparing with others which is attributed to the adsorption anionic nature of this surfactant. Both FTIR and UV–vis spectra show a red shift in the presence of SDS and blue shift in the presence of CTAB and OGM. The blue shift in the absorption edge indicates the quantum confinement property of nanoparticles. The zinc peroxide nanoparticles prepared in additives-free media was also characterized by Raman spectra which show the characteristic peaks at 830–840 and 420–440 cm−1.

Introduction

Material in nanoscale exhibit physical properties distinctively different from that of bulk due to the number of surface atoms and surface energy. The surface area to volume ratio (S/V) of a system is inversely proportional to particle size and increase drastically for particles less than 100 nm in diameter [1], [2], [3]. Nanometer-size materials like nanoparticles or nanowires can be produced in different methods. It has been reported that ZnO nanoparticles and Zn(OH)2 multilayer ultrathin films were prepared by layer-by-layer (LBL) self-assembly method on glass substrate [4]. Recently, Szabó and co-workers [5], [6] reported the preparation of zinc peroxide and zinc oxide nanoparticles by self-assembled hybrid nanolayers generated on the surface of silicon wafers using the layer silicate hectorite and PSS (sodium polystyrene-sulfonate) as an anionic polyelectrolyte. Preparation of ZnO2/poly (acrylic acid) sandwich structures were also reported [7] by layer-by-layer (LbL) self-assembly method where the structure and optical behavior of the hybrid films were controlled by changing the surface charge and conformation of the poly(acrylic acid).

In general there are two approaches to fabricate nanomaterials: top-down and bottom-up. In the top-down approach nanoparticles etching of smaller structures from larger ones, laser ablation and milling are typical examples of top-down approach in fabrication of nanoparticles. On the other hand, bottom-up approach refers to the build-up of a material from the bottom: atom-by-atom, molecule-by-molecule, or cluster-by-cluster [8]. The pulsed laser ablation (PLA) technique in liquid medium has been proven an effective and simple technique for preparing metal, metal oxide, metal peroxide nanoparticles [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20]. PLA technique for synthesis of nanostructured materials from a solid target in liquid media has many advantages. Firstly, this method is simple so it does not require costly chambers and high vacuum pumps and considered as clean method. Most importantly, it has been demonstrated that size of synthesized material can be controlled by changing different parameters such as: laser wavelength, pulse laser duration, changing the pH of the solution, adding surfactants and changing the temperature of solution [12], [21], [22], [23], [24]. These parameters not only change the size and shape of the nanoparticles but at same time they also change the optical and electronic properties. Zinc peroxide ZnO2 is a widely used semiconductor with band gab energy 4.20 eV. ZnO2 has been applied in many applications including: photo-catalysis [25], rubber technology [26], therapeutic [27] and synthesis ZnO [28], [29], [30].

Section snippets

Experimental

A schematic diagram of the laser based set-up for synthesis of nanoparticles is depicted in Fig. 1. A Q-switched Nd-YAG laser (Spectra physics Model GCR 100) operating at 355 nm wavelength using third harmonic generator was employed as an excitation source. It can deliver maximum pulse energy of 300 mJ with a pulse width of 8 ns and operates at a 10 Hz pulse repetition rate. The collimated beam at 355 nm is tightly focused on the target sample using a convex lens to create a spark or breakdown in

Analytical measurements

A variety of analytical techniques were applied for the characterization of products. X-ray diffraction (XRD) (Shimadzu XRD Model 6000) was employed to determine crystalline phases and average crystalline size. The AFM measurements were performed using a Digital Instrument's Nanoscope Dim 3100 microscope in tapping mode, with commercial silicon tips MikroMasch NSC35/AlBS having a typical tip curvature radius of less than 10 nm. The BET surface areas were determined using a flow absorption

Results and discussion

The particle size and morphology of nano-ZnO was characterized using XRD and AFM techniques.

Fig. 2 shows the XRD spectra of the ZnO2 nanoparticles synthesized in powder form using the pulsed laser ablation. Here the laser energy was kept at 100 mJ and the laser irradiation time was 45 min. The XRD spectrum as depicted in Fig. 2 clearly shows the crystalline structure of the nanoparticles and various peaks of zinc peroxide (ZnO2). The main dominant peaks for ZnO2 were identified at 2θ = 31.61,

Conclusion

In this work, Zinc peroxide nanoparticles were synthesized using pulsed laser ablation in aqueous solution in the presence of different surfactants using solid zinc target in 3% H2O2 aqueous solution. The effect of surfactants on the structure of ZnO2 nanoparticles was studied by employing different spectroscopic techniques. The grain sizes measured were 4.7, 3.7, 3.3 and 2.8 nm in pure H2O2 and H2O2 mixed with SDS, CTAB and OGM respectively. Raman spectra showed characteristic peaks at 830–840

Acknowledgments

The support by the Laser Reaserch Group under Physics Departments, Deanship of Scientific Research at King Fahd University of Petroleum & Minerals for funding different projects and special support by KACST under project # 28-40 is gratefully acknowledged. One of the authors (Q. Drmosh) is thankful to Government of Yemen for finacial support for his master work. He is also thankful to KFUPM for its hospitality and permission to work at its research facilties.

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