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Synthesis and characterization of tin(II) selenide nanocrystalline by electron beam irradiation method
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Colloids and Surfaces A: Physicochem. Eng. Aspects 313–314 (2008) 40–42
Synthesis and characterization of tin(II) selenide nanocrystalline by electron beam irradiation method Zhen Li, Zheng Jiao, Minghong Wu ∗ , Qing Liu, Haijian Zhong, Xiang Geng Shanghai Applied Radiation Institute, Shanghai University, Shanghai 201800, China Received 23 October 2006; accepted 23 April 2007 Available online 31 May 2007
Abstract A novel method has been developed by electron beam irradiation to prepare nanocrystalline tin(II) selenide with an orthorhombic phase. Two megaelectron volt 10 mA GJ-2-II electronic accelerator is applied as radiation resource. SnCl2 , Se react under 350 kGy radiation dose, and the optimal experiment condition is studied. Nanocrystalline SnSe is prepared rapidly at room temperature under atmospheric pressure, without any kind of toxic reagents. The structure and morphology of prepared SnSe nanocrystalline are analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM). The results show that the as-prepared SnSe is of high quality. TEM images reveal that the product was comprised of homogeneous and spherical grains and that the average grain size is about 50 nm. The optical properties of prepared SnSe nanocrystalline are characterized by using UV–vis–NTR spectroscopy and photoluminescence spectroscopy. The prepared SnSe nanoparticles show blue shift compare to the bulk material, and the band gap energy of SnSe nanocrystalline is obtained by using the extrapolation. The possible mechanism of the SnSe grain growth by electron beam method is proposed. © 2007 Elsevier B.V. All rights reserved. Keywords: Tin(II) selenide; Nanocrystalline; Electron beam irradiation
1. Introduction Nanostructured materials are expected to play a crucial role in the future technological advance in electronics, optoelectronics and memory devices [1]. Recently, the synthesis and characterization of selenides have attracted considerable attention due to their interesting properties and potential applications. Tin(II) selenide is an IV–VI semiconductor, and has an energy gap of about 1.0 eV. SnSe has been widely used as thermoelectric cooling materials, optical recording materials, solar cell materials, sensors and laser materials [2–5]. Tin(II) selenide has been prepared by various methods such as Bridgman method [6], solvothermal method [7], solid-state reaction [8], vapor–liquid method [9], organometallic precursor method [10] and liquid ammonia method [11]. However, these methods usually require high temperature, and the reaction time is long, or most of organometallic precursors are toxic.
∗
Corresponding author. Tel.: +86 21 6998 2744; fax: +86 21 6998 2749. E-mail address: [email protected] (M. Wu).
0927-7757/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2007.04.069
In this paper, we report an electron beam irradiation route to synthesize nanocrystalline SnSe. This one-step method is simple and convenient, and it is carried out at room temperature. It does not require the preparation of easily hydrolyzed Na(K)2 Se, toxic H2 Se, organometallic precursors, which are usually used to prepare selenides. The prepared SnSe nanocrystalline are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis–NIR spectroscopy and photoluminescence spectroscopy. 2. Experiment SnCl2 ·2H2 O, Se powder and polyvinyl alcohol were used in our experiments. All reagents were analyzed for purity and were produced by Shanghai Chemical Reagents Company. Tin(II) selenide nanoparticles were prepared as follows: firstly 0.2 mol/l SnCl2 ·2H2 O solution 10 ml was dispersed adequately in 5 ml 5 wt% polyvinyl alcohol. Se powder (0.157 g) was put into 25 ml ethylenediamine and dispersed adequately. Subsequently, the compound was added slowly into Sn2+ solution with churning up continuously, and put the mixed solution into sealed plastic bag. A GJ-2-II electronic accelerator (Shanghai Xianfeng Co.
Z. Li et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 313–314 (2008) 40–42
41
Fig. 1. The XRD pattern of as-prepared nanocrystalline SnSe.
Ltd.) was used to generate electron beams, worked at 2 MeV 10 mA conditions. The prepared solutions were irradiated under electron beam at different doses. After irradiation, the suspension colloids were kept for several hours to allow precipitation. A black-gray precipitate was collected and washed with anhydrous ethanol and then distilled water to remove by-products. The final product was dried in vacuum at 80 ◦ C for 1 h. The X-ray powder diffraction (XRD) pattern was recorded on a Rigaku D/max ␥A X-ray diffractometer using Cu K␣ radi˚ employing a sampling width of 0.02◦ in ation (λ = 1.5418 A), the 2θ range from 0◦ to 100◦ . The crystallite size was calculated from the X-ray diffraction spectrum using the Scherrer equation. To examine the morphology and particle size of the products, transmission electron microscopy (TEM) images were taken on a Hitachi H-800, using an acceleration voltage of 200 kV. UV–vis–NIR spectroscopy (JASCO V-570) and photoluminescence spectroscopy (Shanghai Analysis Instrument Plant 970CRT) were used to observe the optical properties. 3. Results and discussion Through experiment we found that the optimal experiment condition was arrived when radiation dose was 350 kGy. Fig. 1 shows the XRD pattern of as-prepared nanocrystalline SnSe. The XRD peaks is at 2θ = 26.02◦ , 29.76◦ , 30.68◦ , 31.24◦ , 38.12◦ , 43.78◦ , 49.80◦ and 54.88◦ . All peaks correspond to the reflections of the orthorhombic structure of SnSe (JCPDS 32-1382). The cell constants (a = 1.148 nm, b = 0.413 nm, c = 0.439 nm) calculated from the XRD pattern of as-prepared nanocrystalline SnSe are consistent with reported values (a = 1.142 nm, b = 0.419 nm, c = 0.446 nm). The grain size of the sample, which calculated from the half-width of the diffraction peaks using the Scherrer equation, is about 48 nm. The transmission electron microscopy (TEM) micrograph gives the morphology of the nanocrystallites. Fig. 2 shows that nanocrystallites of SnSe are homogeneous and spherical. The sample is agglomerate slightly. The grain sizes are between 40 and 60 nm, and the average diameter of these nanoparticles is about 50 nm.
Fig. 2. The TEM morphology of as-prepared nanocrystalline SnSe.
Semiconductor nanoparticles generally exhibit threshold energy in the optical absorption measurement due to the sizedependent band gap structure, which is reflected by the blue shifting of the absorption edge with decreasing particle size. The UV–vis–NIR absorption spectrum of as-prepared nanocrystalline SnSe dispersed in deionized water is shown in Fig. 3.
Fig. 3. The UV–vis–NIR absorption spectrum of as-prepared nanocrystalline SnSe.
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Z. Li et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 313–314 (2008) 40–42
solution. Therefore, the activity of Sn2+ is increased, and the nucleation of SnSe is controlled. 4. Conclusion
Fig. 4. The photoluminescence spectra of as-prepared nanocrystalline SnSe.
The spectrum shows a long tail near the absorption edge, which makes the precise observation of the band gap difficult. Fig. 4 shows the photoluminescence spectra of as-prepared nanocrystalline SnSe dispersed in anhydrous ethanol. The spectrum shows the emission spectrum under PL excitation at 260 nm with the range of 380–500 nm at the scan rate of 50 nm/min. The PL peak of as-prepared SnSe is around 415 nm, and the band gap energy of sample is 3.03 eV according to the calculation [12]. The widening of band gap energy of as-prepared SnSe compare to bulk SnSe materials (1.97 eV [13]) is due to the effect of size quantization. The possible mechanism of the SnSe grain growth by electron beam method is described as following: irradiation of water by electronic accelerator produces the hydrated electrons e− aq [14]. Because the standard electrochemical potential of hydrated electron is −2.77 V and the standard potential of Se2− /Se is −0.77 V, the reactions take place as follows: 2− Se + 2e− aq → Se
(1)
Sn2+ + Se2− → SnSe ↓
(2)
Ethylenediamine as solvent plays an important role in the nucleation of nanocrystalline SnSe. Because its N-chelating makes it a strong donor ligand, ethylenediamine is chosen as solvent. Ethylenediamine binds with Sn2+ and the chelate compound is formed, which makes Sn2+ disperse adequately in the
In summary, nanocrystalline SnSe has been prepared through a reaction between a selenium ethylenediamine solution and Se powder by electron beam irradiation method. This one-step route is carried out quickly under room temperature. XRD, TEM results reveal that the obtained particles by electron beam irradiation method are orthorhombic tin(II) selenide, and have spherical shape morphology, 40–60 nm diameters and welldegree of dispersion. The UV–vis–NTR absorption spectrum and photoluminescence spectra show the blue shifting of the absorption edge, which are due to small size effects of nanocrystalline SnSe. This novel method may be extended to prepare other metal selenides. Acknowledgments This work was supported by Shanghai Committee of Education (project 04AB42) and Shanghai Leading Academic Disciplines (T0105). References [1] R. Waser, Nanoelectronics and Information Technology: Materials, Processes, Devices, Wiley, New York, 2002. [2] Y. Xie, H.L. Su, B. Li, Y.T. Qian, Mater. Res. Bull. 35 (2000) 459. [3] S.E. Lehman, G.L. Schimek, J.M. Cusick, J.W. Kolis, Inorg. Chim. Acta 260 (1997) 173. [4] J.L. Morales, L. Sanchez, J. Santos, J. Solid Chem. 148 (1999) 513. [5] A. Agarwal, J. Cryst. Growth 183 (1998) 347. [6] A. Agnihotri, A.K. Jain, B.K. Gupta, J. Cryst. Growth 46 (4) (1979) 491. [7] W.Z. Wang, Y. Geng, Y.T. Qian, C. Wang, X.M. Liu, Mater. Res. Bull. 34 (3) (1999) 403. [8] S.S. Siddiqui, C.F. Desai, Cryst. Res. Technol. 28 (8) (1993) 1169. [9] N. Erdem, S. Onurlu, J. Mater. Sci. Lett. 8 (4) (1989) 483. [10] P. Boudjouk, S. Seidder, Chem. Mater. 6 (11) (1994) 2108. [11] G. Henshaw, I.P. Parkin, G. Shaw, J. Chem. Soc. Chem. Commun. (1996) 1095. [12] J. Bardeen, F.J. Blatt, L.H. Hall, Proceedings of the Photoconductivity Conference of Atlantic City, New York, 1956, pp. 146–150. [13] B.I. Evans, R.A. Hazelwood, J. Mater. Sci. Lett. 2 (1969) 891. [14] R.J. Woods, A.K. Pikaev, Applied Radiation Chemistry, Radiation Processing, John Wiley Sons Inc., New York, 1994, pp. 165–171.
Colloids and Surfaces A: Physicochem. Eng. Aspects 313–314 (2008) 40–42
Synthesis and characterization of tin(II) selenide nanocrystalline by electron beam irradiation method Zhen Li, Zheng Jiao, Minghong Wu ∗ , Qing Liu, Haijian Zhong, Xiang Geng Shanghai Applied Radiation Institute, Shanghai University, Shanghai 201800, China Received 23 October 2006; accepted 23 April 2007 Available online 31 May 2007
Abstract A novel method has been developed by electron beam irradiation to prepare nanocrystalline tin(II) selenide with an orthorhombic phase. Two megaelectron volt 10 mA GJ-2-II electronic accelerator is applied as radiation resource. SnCl2 , Se react under 350 kGy radiation dose, and the optimal experiment condition is studied. Nanocrystalline SnSe is prepared rapidly at room temperature under atmospheric pressure, without any kind of toxic reagents. The structure and morphology of prepared SnSe nanocrystalline are analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM). The results show that the as-prepared SnSe is of high quality. TEM images reveal that the product was comprised of homogeneous and spherical grains and that the average grain size is about 50 nm. The optical properties of prepared SnSe nanocrystalline are characterized by using UV–vis–NTR spectroscopy and photoluminescence spectroscopy. The prepared SnSe nanoparticles show blue shift compare to the bulk material, and the band gap energy of SnSe nanocrystalline is obtained by using the extrapolation. The possible mechanism of the SnSe grain growth by electron beam method is proposed. © 2007 Elsevier B.V. All rights reserved. Keywords: Tin(II) selenide; Nanocrystalline; Electron beam irradiation
1. Introduction Nanostructured materials are expected to play a crucial role in the future technological advance in electronics, optoelectronics and memory devices [1]. Recently, the synthesis and characterization of selenides have attracted considerable attention due to their interesting properties and potential applications. Tin(II) selenide is an IV–VI semiconductor, and has an energy gap of about 1.0 eV. SnSe has been widely used as thermoelectric cooling materials, optical recording materials, solar cell materials, sensors and laser materials [2–5]. Tin(II) selenide has been prepared by various methods such as Bridgman method [6], solvothermal method [7], solid-state reaction [8], vapor–liquid method [9], organometallic precursor method [10] and liquid ammonia method [11]. However, these methods usually require high temperature, and the reaction time is long, or most of organometallic precursors are toxic.
∗
Corresponding author. Tel.: +86 21 6998 2744; fax: +86 21 6998 2749. E-mail address: [email protected] (M. Wu).
0927-7757/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2007.04.069
In this paper, we report an electron beam irradiation route to synthesize nanocrystalline SnSe. This one-step method is simple and convenient, and it is carried out at room temperature. It does not require the preparation of easily hydrolyzed Na(K)2 Se, toxic H2 Se, organometallic precursors, which are usually used to prepare selenides. The prepared SnSe nanocrystalline are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis–NIR spectroscopy and photoluminescence spectroscopy. 2. Experiment SnCl2 ·2H2 O, Se powder and polyvinyl alcohol were used in our experiments. All reagents were analyzed for purity and were produced by Shanghai Chemical Reagents Company. Tin(II) selenide nanoparticles were prepared as follows: firstly 0.2 mol/l SnCl2 ·2H2 O solution 10 ml was dispersed adequately in 5 ml 5 wt% polyvinyl alcohol. Se powder (0.157 g) was put into 25 ml ethylenediamine and dispersed adequately. Subsequently, the compound was added slowly into Sn2+ solution with churning up continuously, and put the mixed solution into sealed plastic bag. A GJ-2-II electronic accelerator (Shanghai Xianfeng Co.
Z. Li et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 313–314 (2008) 40–42
41
Fig. 1. The XRD pattern of as-prepared nanocrystalline SnSe.
Ltd.) was used to generate electron beams, worked at 2 MeV 10 mA conditions. The prepared solutions were irradiated under electron beam at different doses. After irradiation, the suspension colloids were kept for several hours to allow precipitation. A black-gray precipitate was collected and washed with anhydrous ethanol and then distilled water to remove by-products. The final product was dried in vacuum at 80 ◦ C for 1 h. The X-ray powder diffraction (XRD) pattern was recorded on a Rigaku D/max ␥A X-ray diffractometer using Cu K␣ radi˚ employing a sampling width of 0.02◦ in ation (λ = 1.5418 A), the 2θ range from 0◦ to 100◦ . The crystallite size was calculated from the X-ray diffraction spectrum using the Scherrer equation. To examine the morphology and particle size of the products, transmission electron microscopy (TEM) images were taken on a Hitachi H-800, using an acceleration voltage of 200 kV. UV–vis–NIR spectroscopy (JASCO V-570) and photoluminescence spectroscopy (Shanghai Analysis Instrument Plant 970CRT) were used to observe the optical properties. 3. Results and discussion Through experiment we found that the optimal experiment condition was arrived when radiation dose was 350 kGy. Fig. 1 shows the XRD pattern of as-prepared nanocrystalline SnSe. The XRD peaks is at 2θ = 26.02◦ , 29.76◦ , 30.68◦ , 31.24◦ , 38.12◦ , 43.78◦ , 49.80◦ and 54.88◦ . All peaks correspond to the reflections of the orthorhombic structure of SnSe (JCPDS 32-1382). The cell constants (a = 1.148 nm, b = 0.413 nm, c = 0.439 nm) calculated from the XRD pattern of as-prepared nanocrystalline SnSe are consistent with reported values (a = 1.142 nm, b = 0.419 nm, c = 0.446 nm). The grain size of the sample, which calculated from the half-width of the diffraction peaks using the Scherrer equation, is about 48 nm. The transmission electron microscopy (TEM) micrograph gives the morphology of the nanocrystallites. Fig. 2 shows that nanocrystallites of SnSe are homogeneous and spherical. The sample is agglomerate slightly. The grain sizes are between 40 and 60 nm, and the average diameter of these nanoparticles is about 50 nm.
Fig. 2. The TEM morphology of as-prepared nanocrystalline SnSe.
Semiconductor nanoparticles generally exhibit threshold energy in the optical absorption measurement due to the sizedependent band gap structure, which is reflected by the blue shifting of the absorption edge with decreasing particle size. The UV–vis–NIR absorption spectrum of as-prepared nanocrystalline SnSe dispersed in deionized water is shown in Fig. 3.
Fig. 3. The UV–vis–NIR absorption spectrum of as-prepared nanocrystalline SnSe.
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Z. Li et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 313–314 (2008) 40–42
solution. Therefore, the activity of Sn2+ is increased, and the nucleation of SnSe is controlled. 4. Conclusion
Fig. 4. The photoluminescence spectra of as-prepared nanocrystalline SnSe.
The spectrum shows a long tail near the absorption edge, which makes the precise observation of the band gap difficult. Fig. 4 shows the photoluminescence spectra of as-prepared nanocrystalline SnSe dispersed in anhydrous ethanol. The spectrum shows the emission spectrum under PL excitation at 260 nm with the range of 380–500 nm at the scan rate of 50 nm/min. The PL peak of as-prepared SnSe is around 415 nm, and the band gap energy of sample is 3.03 eV according to the calculation [12]. The widening of band gap energy of as-prepared SnSe compare to bulk SnSe materials (1.97 eV [13]) is due to the effect of size quantization. The possible mechanism of the SnSe grain growth by electron beam method is described as following: irradiation of water by electronic accelerator produces the hydrated electrons e− aq [14]. Because the standard electrochemical potential of hydrated electron is −2.77 V and the standard potential of Se2− /Se is −0.77 V, the reactions take place as follows: 2− Se + 2e− aq → Se
(1)
Sn2+ + Se2− → SnSe ↓
(2)
Ethylenediamine as solvent plays an important role in the nucleation of nanocrystalline SnSe. Because its N-chelating makes it a strong donor ligand, ethylenediamine is chosen as solvent. Ethylenediamine binds with Sn2+ and the chelate compound is formed, which makes Sn2+ disperse adequately in the
In summary, nanocrystalline SnSe has been prepared through a reaction between a selenium ethylenediamine solution and Se powder by electron beam irradiation method. This one-step route is carried out quickly under room temperature. XRD, TEM results reveal that the obtained particles by electron beam irradiation method are orthorhombic tin(II) selenide, and have spherical shape morphology, 40–60 nm diameters and welldegree of dispersion. The UV–vis–NTR absorption spectrum and photoluminescence spectra show the blue shifting of the absorption edge, which are due to small size effects of nanocrystalline SnSe. This novel method may be extended to prepare other metal selenides. Acknowledgments This work was supported by Shanghai Committee of Education (project 04AB42) and Shanghai Leading Academic Disciplines (T0105). References [1] R. Waser, Nanoelectronics and Information Technology: Materials, Processes, Devices, Wiley, New York, 2002. [2] Y. Xie, H.L. Su, B. Li, Y.T. Qian, Mater. Res. Bull. 35 (2000) 459. [3] S.E. Lehman, G.L. Schimek, J.M. Cusick, J.W. Kolis, Inorg. Chim. Acta 260 (1997) 173. [4] J.L. Morales, L. Sanchez, J. Santos, J. Solid Chem. 148 (1999) 513. [5] A. Agarwal, J. Cryst. Growth 183 (1998) 347. [6] A. Agnihotri, A.K. Jain, B.K. Gupta, J. Cryst. Growth 46 (4) (1979) 491. [7] W.Z. Wang, Y. Geng, Y.T. Qian, C. Wang, X.M. Liu, Mater. Res. Bull. 34 (3) (1999) 403. [8] S.S. Siddiqui, C.F. Desai, Cryst. Res. Technol. 28 (8) (1993) 1169. [9] N. Erdem, S. Onurlu, J. Mater. Sci. Lett. 8 (4) (1989) 483. [10] P. Boudjouk, S. Seidder, Chem. Mater. 6 (11) (1994) 2108. [11] G. Henshaw, I.P. Parkin, G. Shaw, J. Chem. Soc. Chem. Commun. (1996) 1095. [12] J. Bardeen, F.J. Blatt, L.H. Hall, Proceedings of the Photoconductivity Conference of Atlantic City, New York, 1956, pp. 146–150. [13] B.I. Evans, R.A. Hazelwood, J. Mater. Sci. Lett. 2 (1969) 891. [14] R.J. Woods, A.K. Pikaev, Applied Radiation Chemistry, Radiation Processing, John Wiley Sons Inc., New York, 1994, pp. 165–171.