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Synthesis of gold nanoparticles using N,N-dimethylacetoacetamide: Size and shape control by the reaction temperature
Current Applied Physics 6 (2006) 216–218 www.elsevier.com/locate/cap www.kps.or.kr
Synthesis of gold nanoparticles using N,N-dimethylacetoacetamide: Size and shape control by the reaction temperature Jae Hee Song a, Yeong-Joon Kim
b,* ,
Ji-Soo Kim
c
a
Department of Chemistry, Sunchon National University, Suncheon 540-742, Republic of Korea Department of Chemistry, Chungnam National University, Daejeon 305-764, Republic of Korea Division of Nanomaterial and Environmental Sciences, Korea Basic Science Institute, Daejeon 305-333, Republic of Korea b
c
Received 28 January 2005 Available online 12 September 2005
Abstract Uniform Au nanoparticles were synthesized by a simple process, mixing HAuCl4 and N,N-dimethylacetoacetamide. These nanoparticles were characterized by UV–Vis, TEM, and EDX. N,N-dimethylacetoacetamide was effectively used as a reducing agent and stabilizing agent as well. The reaction temperature played an important role in the size-selective and shape-selective Au nanoparticle formation. The Au spherical nanoparticles obtained at room temperature had diameters of 100 nm whereas the spherical, triangle, square, and hexagonal shape mixtures were obtained at 100 C with diameter range of 20 nm. 2005 Elsevier B.V. All rights reserved. Keywords: Au nanocrystals; N,N-dimethylacetoacetamide
1. Introduction Nanosized materials have been an important subject in basic science research as well as in technological applications, since they have their own characteristic optical, electronic, magnetic, and catalytic properties different from the bulk materials. And these characteristic properties of nanomaterials often depend critically not only on particle size but also on particle shape [1– 3]. Therefore, considerable effort has focused on size and shape selective nanocrystal growth using a variety of synthetic methods, including electrochemistry [4,5], templating [6,7], photochemistry [8,9], and seeding [10,11]. Very recently, it has been reported that Au nanoparticles with controlled-shapes were synthesized by introducing acetylacetone and several related ligands [12]. Hexadecylaniline was used for the synthesis of organically dispersible gold nanoparticles where the *
Corresponding author. Tel.: +82 42 821 5476. E-mail address: [email protected] (Y.-J. Kim).
1567-1739/$ - see front matter 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2005.07.043
spontaneous reduction of aqueous HAuCl4 solution results in variable shapes of nanoparticles [13]. In this paper, we are reporting that N,N-dimethylacetoacetamide is used as a reducing agent and a stabilizing agent as well for the synthesis of gold nanoparticles at various temperatures. By tuning the reaction temperature, the shape and size of the resulting Au nanocrystals were controlled.
2. Experimental N,N-dimethylacetoacetamide (0.5 ml) was dissolved in 0.5 ml of deionized water. They were mixed very well and used as a stock solution. In a clean beaker, 5 ml of HAuCl4 aqueous solution (1.6 · 104 M) was mixed with 200 ll of N,N-dimethylacetoacetamide stock solution (final concentration 0.08 M) under vigorous stirring at various temperatures (20, 40, and 100 C). The solution turned pink in several minutes. After 30 min, absorption spectra of the Au nanoparticle dispersions
J.H. Song et al. / Current Applied Physics 6 (2006) 216–218
were taken using a Cary 3 UV–Vis spectrophotometer. One drop of the resulting solution was dropped on the carbon-coated copper grid for transmission electron microscopy (TEM) analysis.
217
0.6
3. Results and discussion Fig. 1a shows the UV–Vis spectra of Au nanocrystals that were produced after the reduction process with N,N-dimethylacetoamide at 20 C. The color of 5 ml of 1.6 · 104 M HAuCl4 solution was light yellow. The color of the solution changed to pink with a red tint as 200 ll of N,N-dimethylacetoacetamide stock solution (final concentration 0.08 M) was added to the stirred HAuCl4 solution. As the reaction time increased, a new absorption band appeared at around 585 nm, which corresponds to the known surface plasmon absorption band of Au nanocrystals. N,N-dimethylacetoacetamide is clearly used as a reducing agent for making gold nanoparticles like other b-diketones such as acetylacetone þ [12]. Initially, HAuCl4 turns to Auðb-diketonateÞ2 chelate and then the Au(III) b-diketonates are decomposed to produce gold nanoparticles. b-Diketones are oxidized
Absorbance
0.4
c 0.2
b a
0.0
400
500
600
700
800
900
Wavelength (nm) Fig. 1. UV–Vis spectrum of Au nanocrystals produced at (a) 20 C, (b) 40 C, and (c) 100 C.
to chlorinated b-diketones. It can be also used as a stabilizing reagent since there is a strong interaction between Au(0) surface and b-diketones through oxygen chelation. This is probably the reason why the Au
Fig. 2. TEM images of Au nanoparticle prepared at (a) 20 C, (b) 40 C, and (c) 100 C.
218
J.H. Song et al. / Current Applied Physics 6 (2006) 216–218
colloidal solution generated by N,N-dimethylacetoacetamide remains stable for days. This method is simple and uses a mild reaction condition compared to the conventional method using surfactants and harsh reductants. An absorption peak at 573 nm (Fig. 1b) was observed when 5.0 ml of 1.6 · 104 M HAuCl4 solution was mixed with 200 ll of N,N-dimethylacetoacetamide at 40 C. Since the absorption band appears at different wavelength, it indicates that the reaction temperature of HAuCl4 with N,N-dimethylacetoacetamide is closely related to the size of Au nanoparticles prepared. Fig. 1c shows the absorption peak at 548 nm when 5.0 ml of 1.6 · 104 M HAuCl4 solution was mixed with 200 ll of N,N-dimethylacetoacetamide at 100 C. As the reaction temperature was elevated, the size and shape of resulting Au nanoparticles were varied, indicating that the morphology of Au nanocrystals can be controlled via this simple one step reaction. One drop of the reaction mixture was placed on a carbon-coated copper grid for transmission electron microscopy (TEM) analysis. TEM images were obtained from samples prepared after the reaction of HAuCl4 with N,N-dimethylacetoacetamide was completed at three different temperatures. The TEM images were taken without any further separation procedure like centrifugation. Fig. 2a shows TEM image of Au nanoparticles prepared by mixing 5.0 ml of HAuCl4 (1.6 · 104 M) with 200 ll N,N-dimethylacetoacetamide at 20 C. High yields of spherical Au nanoparticles were produced, with diameters of 100 nm. TEM image of Au nanoparticles produced at 40 C is shown in Fig. 2b. Unlike the TEM image of Fig. 2a, the diameters of Au nanoparticles were in the range of 30 nm. At 100 C, the Au nanoparticles with diameters of
Fig. 3. EDX spectrum recorded on Au nanoparticles.
20 nm were produced (Fig. 2c). Spherical, triangle, square, and hexagonal shape mixtures were obtained. These results clearly show that by varying the reaction temperature, using the same concentration ratio of AuCl 4 to N,N-dimethylacetoacetamide, the size and shape of Au nanoparticles can be readily tuned. Fig. 3 shows EDX spectrum recorded on synthesized Au nanoparticles and only Au was detected. Cu and C signals are from the TEM grid.
4. Conclusion N,N-dimethylacetoacetamide is a good reducing agent in the synthesis of Au nanoparticles from HAuCl4 in aqueous solution. It stabilizes resulting gold nanoparticles so that the solution remains stable for days. By tuning the reaction temperature, the shape and size of the resulting Au nanocrystals were controlled.
Acknowledgments This work was supported by the Ministry of Science and Technology of Korea through Proton Accelerator User Program (No. M202AK010021-04A1101-02117) and by non-directed research funds at Chungnam National University in 2004.
References [1] Y.W. Cao, R. Jin, C.A. Mirkin, J. Am. Chem. Soc. 123 (2001) 7961. [2] S. Link, M.A. El-Sayed, J. Phys. Chem. B 103 (1999) 8410. [3] J.A. Creighton, D.G. Eadon, J. Chem. Soc. Faraday Trans. 87 (1991) 3881. [4] S. Chang, C. Shih, C. Chen, W. Lai, C.R.C. Wang, Langmuir 15 (1999) 701. [5] Y. Yu, S. Chang, C. Lee, C.R.C. Wang, J. Phys. Chem. B 101 (1997) 6661. [6] J. Yu, J.Y. Kim, S. Lee, J.K.N. Mbindyo, B.R. Martin, T.E. Mallouk, Chem. Commun. 24 (2000) 2445. [7] M. Wirtz, C.R. Martin, Adv. Mater. 15 (2003) 455. [8] F. Kim, J.H. Song, P. Yang, J. Am. Chem. Soc. 124 (2002) 14316. [9] K. Esumi, K. Matsuhisa, K. Torigoe, Langmuir 11 (1995) 3285. [10] C.J. Murphy, N.R. Jana, Adv. Mater. 14 (2002) 80. [11] B.D. Busbee, S.O. Obare, C.J. Murphy, Adv. Mater. 15 (2003) 414. [12] S. Kundu, A. Pal, S.K. Ghosh, S. Nath, S. Panigrahi, S. Praharaj, T. Pal, Inorg. Chem. 43 (2004) 5489. [13] P.R. Selvakannan, S. Mandal, R. Pasricha, M. Sastry, J. Colloid Interface Sci. 279 (2004) 124.
Synthesis of gold nanoparticles using N,N-dimethylacetoacetamide: Size and shape control by the reaction temperature Jae Hee Song a, Yeong-Joon Kim
b,* ,
Ji-Soo Kim
c
a
Department of Chemistry, Sunchon National University, Suncheon 540-742, Republic of Korea Department of Chemistry, Chungnam National University, Daejeon 305-764, Republic of Korea Division of Nanomaterial and Environmental Sciences, Korea Basic Science Institute, Daejeon 305-333, Republic of Korea b
c
Received 28 January 2005 Available online 12 September 2005
Abstract Uniform Au nanoparticles were synthesized by a simple process, mixing HAuCl4 and N,N-dimethylacetoacetamide. These nanoparticles were characterized by UV–Vis, TEM, and EDX. N,N-dimethylacetoacetamide was effectively used as a reducing agent and stabilizing agent as well. The reaction temperature played an important role in the size-selective and shape-selective Au nanoparticle formation. The Au spherical nanoparticles obtained at room temperature had diameters of 100 nm whereas the spherical, triangle, square, and hexagonal shape mixtures were obtained at 100 C with diameter range of 20 nm. 2005 Elsevier B.V. All rights reserved. Keywords: Au nanocrystals; N,N-dimethylacetoacetamide
1. Introduction Nanosized materials have been an important subject in basic science research as well as in technological applications, since they have their own characteristic optical, electronic, magnetic, and catalytic properties different from the bulk materials. And these characteristic properties of nanomaterials often depend critically not only on particle size but also on particle shape [1– 3]. Therefore, considerable effort has focused on size and shape selective nanocrystal growth using a variety of synthetic methods, including electrochemistry [4,5], templating [6,7], photochemistry [8,9], and seeding [10,11]. Very recently, it has been reported that Au nanoparticles with controlled-shapes were synthesized by introducing acetylacetone and several related ligands [12]. Hexadecylaniline was used for the synthesis of organically dispersible gold nanoparticles where the *
Corresponding author. Tel.: +82 42 821 5476. E-mail address: [email protected] (Y.-J. Kim).
1567-1739/$ - see front matter 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2005.07.043
spontaneous reduction of aqueous HAuCl4 solution results in variable shapes of nanoparticles [13]. In this paper, we are reporting that N,N-dimethylacetoacetamide is used as a reducing agent and a stabilizing agent as well for the synthesis of gold nanoparticles at various temperatures. By tuning the reaction temperature, the shape and size of the resulting Au nanocrystals were controlled.
2. Experimental N,N-dimethylacetoacetamide (0.5 ml) was dissolved in 0.5 ml of deionized water. They were mixed very well and used as a stock solution. In a clean beaker, 5 ml of HAuCl4 aqueous solution (1.6 · 104 M) was mixed with 200 ll of N,N-dimethylacetoacetamide stock solution (final concentration 0.08 M) under vigorous stirring at various temperatures (20, 40, and 100 C). The solution turned pink in several minutes. After 30 min, absorption spectra of the Au nanoparticle dispersions
J.H. Song et al. / Current Applied Physics 6 (2006) 216–218
were taken using a Cary 3 UV–Vis spectrophotometer. One drop of the resulting solution was dropped on the carbon-coated copper grid for transmission electron microscopy (TEM) analysis.
217
0.6
3. Results and discussion Fig. 1a shows the UV–Vis spectra of Au nanocrystals that were produced after the reduction process with N,N-dimethylacetoamide at 20 C. The color of 5 ml of 1.6 · 104 M HAuCl4 solution was light yellow. The color of the solution changed to pink with a red tint as 200 ll of N,N-dimethylacetoacetamide stock solution (final concentration 0.08 M) was added to the stirred HAuCl4 solution. As the reaction time increased, a new absorption band appeared at around 585 nm, which corresponds to the known surface plasmon absorption band of Au nanocrystals. N,N-dimethylacetoacetamide is clearly used as a reducing agent for making gold nanoparticles like other b-diketones such as acetylacetone þ [12]. Initially, HAuCl4 turns to Auðb-diketonateÞ2 chelate and then the Au(III) b-diketonates are decomposed to produce gold nanoparticles. b-Diketones are oxidized
Absorbance
0.4
c 0.2
b a
0.0
400
500
600
700
800
900
Wavelength (nm) Fig. 1. UV–Vis spectrum of Au nanocrystals produced at (a) 20 C, (b) 40 C, and (c) 100 C.
to chlorinated b-diketones. It can be also used as a stabilizing reagent since there is a strong interaction between Au(0) surface and b-diketones through oxygen chelation. This is probably the reason why the Au
Fig. 2. TEM images of Au nanoparticle prepared at (a) 20 C, (b) 40 C, and (c) 100 C.
218
J.H. Song et al. / Current Applied Physics 6 (2006) 216–218
colloidal solution generated by N,N-dimethylacetoacetamide remains stable for days. This method is simple and uses a mild reaction condition compared to the conventional method using surfactants and harsh reductants. An absorption peak at 573 nm (Fig. 1b) was observed when 5.0 ml of 1.6 · 104 M HAuCl4 solution was mixed with 200 ll of N,N-dimethylacetoacetamide at 40 C. Since the absorption band appears at different wavelength, it indicates that the reaction temperature of HAuCl4 with N,N-dimethylacetoacetamide is closely related to the size of Au nanoparticles prepared. Fig. 1c shows the absorption peak at 548 nm when 5.0 ml of 1.6 · 104 M HAuCl4 solution was mixed with 200 ll of N,N-dimethylacetoacetamide at 100 C. As the reaction temperature was elevated, the size and shape of resulting Au nanoparticles were varied, indicating that the morphology of Au nanocrystals can be controlled via this simple one step reaction. One drop of the reaction mixture was placed on a carbon-coated copper grid for transmission electron microscopy (TEM) analysis. TEM images were obtained from samples prepared after the reaction of HAuCl4 with N,N-dimethylacetoacetamide was completed at three different temperatures. The TEM images were taken without any further separation procedure like centrifugation. Fig. 2a shows TEM image of Au nanoparticles prepared by mixing 5.0 ml of HAuCl4 (1.6 · 104 M) with 200 ll N,N-dimethylacetoacetamide at 20 C. High yields of spherical Au nanoparticles were produced, with diameters of 100 nm. TEM image of Au nanoparticles produced at 40 C is shown in Fig. 2b. Unlike the TEM image of Fig. 2a, the diameters of Au nanoparticles were in the range of 30 nm. At 100 C, the Au nanoparticles with diameters of
Fig. 3. EDX spectrum recorded on Au nanoparticles.
20 nm were produced (Fig. 2c). Spherical, triangle, square, and hexagonal shape mixtures were obtained. These results clearly show that by varying the reaction temperature, using the same concentration ratio of AuCl 4 to N,N-dimethylacetoacetamide, the size and shape of Au nanoparticles can be readily tuned. Fig. 3 shows EDX spectrum recorded on synthesized Au nanoparticles and only Au was detected. Cu and C signals are from the TEM grid.
4. Conclusion N,N-dimethylacetoacetamide is a good reducing agent in the synthesis of Au nanoparticles from HAuCl4 in aqueous solution. It stabilizes resulting gold nanoparticles so that the solution remains stable for days. By tuning the reaction temperature, the shape and size of the resulting Au nanocrystals were controlled.
Acknowledgments This work was supported by the Ministry of Science and Technology of Korea through Proton Accelerator User Program (No. M202AK010021-04A1101-02117) and by non-directed research funds at Chungnam National University in 2004.
References [1] Y.W. Cao, R. Jin, C.A. Mirkin, J. Am. Chem. Soc. 123 (2001) 7961. [2] S. Link, M.A. El-Sayed, J. Phys. Chem. B 103 (1999) 8410. [3] J.A. Creighton, D.G. Eadon, J. Chem. Soc. Faraday Trans. 87 (1991) 3881. [4] S. Chang, C. Shih, C. Chen, W. Lai, C.R.C. Wang, Langmuir 15 (1999) 701. [5] Y. Yu, S. Chang, C. Lee, C.R.C. Wang, J. Phys. Chem. B 101 (1997) 6661. [6] J. Yu, J.Y. Kim, S. Lee, J.K.N. Mbindyo, B.R. Martin, T.E. Mallouk, Chem. Commun. 24 (2000) 2445. [7] M. Wirtz, C.R. Martin, Adv. Mater. 15 (2003) 455. [8] F. Kim, J.H. Song, P. Yang, J. Am. Chem. Soc. 124 (2002) 14316. [9] K. Esumi, K. Matsuhisa, K. Torigoe, Langmuir 11 (1995) 3285. [10] C.J. Murphy, N.R. Jana, Adv. Mater. 14 (2002) 80. [11] B.D. Busbee, S.O. Obare, C.J. Murphy, Adv. Mater. 15 (2003) 414. [12] S. Kundu, A. Pal, S.K. Ghosh, S. Nath, S. Panigrahi, S. Praharaj, T. Pal, Inorg. Chem. 43 (2004) 5489. [13] P.R. Selvakannan, S. Mandal, R. Pasricha, M. Sastry, J. Colloid Interface Sci. 279 (2004) 124.