Optical Properties and Colloidal Stability Mechanism of Bismuth Nanoparticles Prepared by Q-switched Nd:Yag Laser Ablation in Liquid

Available online at www.sciencedirect.com

ScienceDirect Procedia Materials Science 11 (2015) 679 – 683

5th International Biennial Conference on Ultrafine Grained and Nanostructured Materials, UFGNSM15

Optical Properties and Colloidal Stability Mechanism of Bismuth Nanoparticles Prepared by Q-Switched Nd:Yag Laser Ablation in Liquid S. Dadashia, H. Delavaria, R. Poursalehi a,* a

Nanomaterials group, Department of Materials Engineering, Tarbiat Modares University, Tehran, 14115-143, Iran

Abstract Bismuth is semimetal with unique properties such as magnetoresistance and thermoelectric behaviors due to high electron mobility, low carrier density and highly anisotropic Fermi surface. In addition, bismuth NPs undergoes a semimetal to semiconductor transition due to size induced quantum confinement effect. Therefore, bismuth NPs are potentially useful for optical and electro optical devices. In addition, bismuth NPs are interesting as green lubricant and thermoelectric materials. Recently, laser ablation is extensively employed to synthesis of metal NPs by laser target interaction in liquid environment. The aim of this work is the synthesis of stable bismuth colloidal NPs by Q-switched laser ablation in acetone. A Q-switched Nd:YAG laser with the fundamental wavelength at 1064 nm ,energy of 118 mJ/pulse and 12 ns pulse duration was employed for bismuth target ablation. The laser was operated for 5 min at repetition rate of 10 Hz. Colloidal stability, particle size, crystal structure and optical properties of the NPs were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectroscopy respectively. The bismuth NPs were rather spherical and with the particle size of 27±9 nm. The XRD pattern of NPs was consistent with a bismuth rhombohedral crystal structure. Colloidal bismuth NPs in acetone is in light brown color. UV-Visible spectra were measured in 6 months shows perfect stability of colloidal samples without any precipitation. Optical extinction without plasmon resonance pick in visible wavelengths is the optical characteristic of bismuth NPs and reveal perfect dispersion of NPs without agglomeration or coupling of NPs in liquid. According to the FT-IR result as the stability of NPs is related to the large dipole moment of acetone molecule and acetone enolate formation on the surface of bismuth NPs. © 2015 2015Published The Authors. Published by Elsevier © by Elsevier Ltd. This is an openLtd. access article under the CC BY-NC-ND license Peer-review under responsibility of the organizing committee of UFGNSM15. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of UFGNSM15

* Corresponding author. Tel.: +98-021-82883997; fax: +98-021-82884390. E-mail address: [email protected]

2211-8128 © 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of UFGNSM15 doi:10.1016/j.mspro.2015.11.027

680

S. Dadashi et al. / Procedia Materials Science 11 (2015) 679 – 683

Keywords: Bismuth nanoparticles; laser ablation; optical properties; colloidal stability.

1. Introduction Nanoparticles (NPs) have special and different properties compared with their bulk size due to their small size and large specific surface area. In past decade preparation, characterizations and application of the NPs have received great attention. Metal NPs have unique properties such as optical, magnetic, catalytic and these effects are related to their shapes and small size, Müller (2015), ArboledaMuñetón et al. (2015). Bismuth is a semimetal with a rhombohedral structure with direct band gap, high carrier motilities, anisotropic Fermi surface and small electron effective mass, small energy overlap between valance and conduction band, Verma et al. (2013), Wang et al. (2005), high reflective index, Kumari et al. (2007). A broad range of techniques from chemistry and physics have been combined to synthesis of bismuth. The fabrication technique has great effects on the properties of NPs therefore numerous physical and chemical methods have been employed in the preparation of nanoparticles, Tilaki et al. (2006). The laser ablation widely have been used for nanostructured materials processing because of its many advantage such as easy transferring of target material composition in to product at a low working temperature, fast, suited for further functionalization, high purity for synthesized NPs, Hahn (2008) and the potential absence of any surfactant however it can added to ablation media. Furthermore synthesized NPs by laser ablation have been used for biological or biochemical application, Briand and Burford (1999), Itina and Gouriet (2004). Acetone is an appropriate liquid media of laser ablation to prepare ultrafine pure stable NPs with stoichiometry same as target. In addition optical properties, colloidal stability of bismuth crystal structure and stability mechanism of colloidal bismuth NPs were investigated. 2. Experimental Bismuth NPs were prepared by pulsed laser ablation of bismuth target in acetone. The target was washed with ethanol and several time with acetone using an ultrasonic cleaner. The target is located in solution and then was ablated by the first harmonic (1064 nm) of a Nd:YAG laser operated at 10 Hz with a pulse duration of 12 ns and was focused by a set of optical components supplied at normal incident to the surface of the bismuth target and scanned over it manually for avoiding the decrease of energy density. The laser was irradiated at energy of 118 mJ/pulse and 1 mm spot size for 3. The setup for the experiments carried out in liquid media is shown in (Fig. 1) The prepared colloid solution was completely transparent and stable for more than one week without aggregation, The optical properties of the obtained colloidal solutions were measured, immediately, after laser ablation, by a UV-Vis (SPUV26) – spectrophotometer. Crystal structure analyzed by X-ray diffraction (XRD) (XPert Pro MPD- PANalytical), with Cu – Kα (λ= 1.54 Å) radiation. A scanning electron microscopy (SEM), MIRA ESCAN was used to perform information about the morphology and size distribution of bismuth NPs. In addition Fourier transform infrared spectroscopy (FTIR) spectrum of the colloidal solution was measured by NEXUS-670 from 400-4000 cm-1.

Fig. 1. Experimental setup of laser ablation in liquid media.

681

S. Dadashi et al. / Procedia Materials Science 11 (2015) 679 – 683

3. Results and discussion 3.1. Size and morphology of bismuth NPs Morphology and size distributions of colloidal bismuth NPs in acetone were characterized by scanning electron microscopy. The observed bismuth NPs are rather spherical or the aspect ratio is nearly one. (Fig. 2) a shows a typical SEM images of bismuth NPs prepared in acetone and (Fig. 2) b shows size distribution of bismuth NPs. As can be clearly seen, no aggregation, NPs welding, cross linking or welded NPs networks took place and the size distribution is narrow with an average size of 27±9 nm. 14

a

b

12

size=27nm Gaussian fit

count

10 8 6 4 2 0 15

20

25

30

35

40

size(nm)

Fig. 2. (a) SEM image of bismuth NPs prepared by laser ablation in acetone ; (b) Size distribution of bismuth NPs.

3.2. Crystal structure of bismuth NPs

(012)

The investigations of bismuth NPs crystal structure are performed by XRD spectrum of bismuth. The XRD pattern of bismuth NPs prepared by laser ablation is shown in (Fig. 3) There are seven different peaks, can be indexed based on rhombohedral cell with a = 4.5350 Å, b = 4.5350 Å and c = 11.8140 Å and α= β = 90◦ and γ = 120◦. Bismuth NPs have reflection from (003), (101), (012), (104), (110), (015), (006), (202), (024), (205), (122), planes. In addition planes at 2θ° = 22.56° and 2θ ° = 46.06 ° have very low intensity and also could be indexed at (003) and (006) planes of bismuth rhombohedral crystal structure NPs (code: 01-085-1330).

10

15

20

25

30

35

40

45

50

55

(205) (122)

(024)

(003) (101)

(015) (006) (202)

(104) (110)

Intensity(a.u)

Reference code:01-085-1330

60

65

70

2 (degree)

3.3. Optical

properties of Fig. 3. XRD pattern of bismuth NPs prepared by laser ablation in acetone.

682

S. Dadashi et al. / Procedia Materials Science 11 (2015) 679 – 683

bismuth NPs The optical properties of bismuth NPs were studied by optical transmission measurements of liquids that contained bismuth NPs. (Fig. 4) shows optical transmission spectra of bismuth NPs in acetone in the range of 300 to 1100 nm. The uniform ascending spectrum presents no substantial absorption peaks at visible wavelengths because of the size and dielectric function of the bismuth NPs. Generally the small size bismuth NPs exhibit a peak below 300 nm however due to the opacity of acetone below 300 nm this peak is undetectable by transmission measurement, Wang et al. (2005). In acetone optical transmission of metallic nanoparticles prepared by pulsed laser ablation could be remain unchanged even after several months, Tilaki et al. (2007). In this research bismuth NPs synthesized via pulsed Nd:YAG laser ablation in acetone show a light brown color and the optical transmission intensity exhibited stability of colloidal solution without any precipitation even after 11 days. However after 21 days few precipitation was observed. Optical transmission spectra of metal NPs have a peak at specific wavelength due to surface plasmon resonance. According to the Mie theory of absorption and scattering of light by small particles, the wavelength of the maximum optical transmission and the shape of the spectra depends on the dielectric function of the medium, size, shape and material type of the nanoparticles, Tilaki et al. (2007). The position of the optical transmission peak is related to the size and aggregation of bismuth NPs and also the nature of surrounding liquid. 3.4. Surface properties and stability of bismuth NPs To study surface chemistry of the NPs and chemical compounds on the NPs surface, FT-IR is used and the FT-IR spectrum of colloidal bismuth NPs in acetone is shown in (Fig. 5) The observed peaks in range of 3600-3800 cm-1 are dependent to C-H bond. Frequency of available peak in pure acetone is 1737 cm-1 concerning to the C=O stretched bond mode and O- H causes the appearance of a broad peak. The weak absorption at 1200 cm-1 can be due to stretched mode of C-C bond. Therefore, taking absorption spectrum of colloid bismuth nanoparticles in acetone into account, it can be concluded that the peak of C=O stretched bond at 1737 cm -1 has transferred toward lower frequencies and also its intensity is reduced too. This is indicating that sample of synthesized colloid bismuth NPs caused replacement of the frequency and reveal production of other compounds. Observed adsorption spectrum at 1634 cm-1 can be related to enolate ions that can be absorb on bismuth NPs surfaces. The mentioned ions cannot be in form of free ions in acetone but can only form and adsorb on the surface of NPs. Acetone enolate can be characterized specially through C=C bond which does not exist in pure acetone, Giorgetti et al. (2012), Wang et al. (2005). The formation of enolate with C=O bond can transform maximum absorption to lower frequencies which is compatible with FT-IR spectrum at 1600 up to 1650 cm-1. As a result this frequency shift could be attributed to stretching bot of C=O and C=C modes. In addition presence of enolate acetone in infrared spectrum has been accepted for various metal oxide and even noble metal such as gold nanoparticles, Giorgetti et al. (2012). Due to the interaction of liquid environment molecules and charged nanoparticles, electrical double layers surround the surface of the NPs. The rate of aggregation depends on the interaction of the liquid environment molecules with surface atoms and nanoparticle- nanoparticle interaction, Tilaki et al. (2006). To describe the surface interaction between NPs-NPs, repulsive and attractive forces have been considered. Van der Waals attraction would result in the formation of agglomeration of the NPs and repulsive electrostatic forces would result in more stability due to overlapping of electrical double layers, Tilaki et al. (2006). As mentioned above, in acetone because of the high dipole moment of surrounding molecules, and acetone enolate formation on bismuth NPs surface the overlapping of strong electrical double layers creates sufficient electrostatic repulsive force between NPs. For this reason, no aggregation and precipitation takes place and the colloidal solution is stable. Mechanism of stability of bismuth NPs can be attributed to enolate ion which like a surfactant surrounds the bismuth NPs, and prevents their aggregation.

683

S. Dadashi et al. / Procedia Materials Science 11 (2015) 679 – 683

100 100

95 90

90

2 1 1 8 .8 5

85 80

80 T %

T%

75 70 65

2 9 7 0 .2 8

5 2 7 .7 1 1 2 6 1 .9 8 1 2 2 8 .9 8 1 3 6 5 .6 2

70 60

1 6 3 4 .4 6

60 Bismuth NPs in acetone as prepared Bismuth NPs in acetone after 3 day Bismuth NPs in acetone after 11 day Bismuth NPs in acetone after 21 day

55 50

1 7 3 7 .0 8

50 40 3 4 4 5 .7 2

45 400

500

600

700

800

900

1000 1100

Wavelength (nm)

Fig. 4. UV-Visible spectra of bismuth NPs.

4000

3500

3000

2500

2000

1500

1000

500

-1

W a v e n u m b e r (C m )

Fig. 5. FT-IR spectrum of bismuth NPs.

4. Conclusion In summary, stable and pure bismuth NPs have been synthesized by laser ablation in acetone without the presence of any surfactant with an average size of 27±9 nm and high stability and single phase purity. The composition and structural analysis by SEM, XRD UV-Visible photo spectroscopy and FT-IR confirmed the stable bismuth NPs synthesis. The optical properties of bismuth NPs were studied by optical transmission measurements of liquids that contained bismuth NPs in the range of 300-1100 nm. According to the results the stability is related to the dipole moment of acetone molecules and adsorption of acetone on the bismuth NPs surface and enolate ion formation. This method can be used for generation of ultrapure NPs for drug delivery, drug targeting and bioresponse application.

References ArboledaMuñetón, D., M.J.M. Santillán, Herrera, L.J.M., Raap, M.V., Zélis, M., Muraca, D., Schinca, D., Scaffardi, L.B., 2015. Synthesis of Ni Nanoparticles by Femtosecond Laser Ablation in Liquids: Structure and Sizing. J. Phys. Chem. C 119, 13184–13193. Briand, G.G., Burford, N., 1999. Bismuth compounds and preparations with biological or medicinal relevance. Chem. Rev. 99, 2601–58. Giorgetti, E., Muniz-Miranda, M., Marsili, P., Scarpellini, D., Giammanco, F., 2012. Stable gold nanoparticles obtained in pure acetone by laser ablation with different wavelengths. J. Nanoparticle Res. 14. Hahn, A., 2008. Influences on Nanoparticle Production during Pulsed Laser Ablation. J. Laser Micro/Nanoengineering 3, 73–77. Itina, T., Gouriet, K., 2004. Mechanisms of Nanoparticle Formation by Laser Ablation. Kumari, L., Lin, J.-H., Ma, Y.-R., 2007. Nanohooks: Synthesis, Characterization and Optical Properties. J. Phys. Condens. Matter 19, 406204. Müller, M.T., 2015. Production of supported gold and gold–silver nanoparticles by supercritical fluid reactive deposition: Effect of substrate properties. J. Supercrit. Fluids 96, 287–297. Tilaki, R.M., Iraji zad, a., Mahdavi, S.M., 2007. Size, composition and optical properties of copper nanoparticles prepared by laser ablation in liquids. Appl. Phys. A 88, 415–419. Tilaki, R.M., Iraji zad, a., Mahdavi, S.M., 2006. Stability, size and optical properties of silver nanoparticles prepared by laser ablation in different carrier media. Appl. Phys. A 84, 215–219. Verma, R.K., Kumar, K., Rai, S.B., 2013. Near infrared induced optical heating in laser ablated Bi quantum dots. J. Colloid Interface Sci. 390, 11–16. Wang, Y.W., Hong, B.H., Kim, K.S., 2005. Size control of semimetal bismuth nanoparticles and the UV-visible and IR absorption spectra. J. Phys. Chem. B 109, 7067–7072.