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Synthesis of silver particles with different sizes and morphologies
Materials Letters 63 (2009) 1266–1268
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Synthesis of silver particles with different sizes and morphologies G.A. Martínez-Castañón a,⁎, N. Niño-Martínez b, J.P. Loyola-Rodríguez a, N. Patiño-Marín a, J.R. Martínez-Mendoza b, Facundo Ruiz b a b
Maestria en Ciencias Odontológicas, Facultad de Estomatología, UASLP, Av. Manuel Nava 2, Zona Universitaria, San Luis Potosí, S. L. P., México Facultad de Ciencias, UASLP, Álvaro Obregón 64, Col. Centro, San Luis Potosí, S. L. P., México
a r t i c l e
i n f o
Article history: Received 12 January 2009 Accepted 28 February 2009 Available online 9 March 2009 Keywords: Metals and alloys Crystal growth
a b s t r a c t In this work, using a simple templateless, surfactantless, chemical reduction method, we synthesized micronsized silver particles with different sizes and morphologies by simply changing the reaction conditions, specifically, the amount of ascorbic acid added to a silver nitrate aqueous solution, the Ag+:Ascorbic Acid molar ratios used were 1:1, 1:2, 1:3 and 1:4. The morphologies obtained were polyhedrons and dendrites. The sizes of the particles ranged from 1.5 μm to 15 μm. The principal driven force which produces the changes in the morphology of the Ag particles could be the variations in the electrochemical potential aroused from the changes in the amount of ascorbic acid used in the reaction. © 2009 Elsevier B.V. All rights reserved.
1. Introduction
3. Results and discussion
In the last years, many studies have been made in order to synthesize silver colloids by chemical methods [1–8]. Most of them give very small particles which could be used as SERS surfaces [9–13]. Just few of these studies are devoted to micron-sized silver particles [1,14] although these particles have interesting applications on catalyst and electronics. The most common morphology obtained when one synthesize metal particles by chemical methods is, by thermodynamic reasons, the spherical one, and it is a challenge to obtain particles with different sizes and morphologies [15]. To date, much effort has been made to prepare particles with well-defined sizes, shapes and cristallinity [16–18]. In this work we synthesize silver micron-particles with different sizes and morphologies using a simple templateless, surfactantless, chemical reduction method. The morphologies obtained are polyhedrons and dendrites.
In order to determine the composition of the particles an X-ray diffraction analysis was made using the dried powders. X-ray diffraction patterns were recorded on a GBC-Difftech MMA model, with Cu Kα irradiation at λ = 1.54 Å. Fig. 1 shows the diffraction pattern of the sample with dendritic morphology (Sample C), the rest of the samples present a similar pattern. All samples obtained are elemental silver with a unit cell parameter being a = b = c = 4.085 Å and they agree with the published data (JCPDS 04-0783). The refined crystallite size for this sample is 166.3 nm. The peak intensity ratios of the (111) to (200) diffractions and the (200) to (220) diffractions, 2.63 and 1.58, are close to the values from a polycrystalline Ag with randomly distributed grains, 2.5 and 1.6 [19]; although, it is in general accepted that dendrites are formed by preferential growth along particular crystal directions, these results indicate that dendrites are probably not formed by particles with a strong preferred orientation, it is, we cannot establish, using this technique, the actual direction in which dendrites are growing. The morphology of the Ag particles was observed using a XL-30 scanning electron microscope (Phillips, Netherlands). Fig. 2a, b, c and d show images of the silver particles synthesized with different Ag+:
2. Experimental In a normal synthesis, a silver nitrate solution was prepared by dissolving 1 mmol of the salt in 100 mL of 0.1 M nitric acid, this solution was placed in a 400 mL reaction vessel and, under magnetic stirring, a specific amount of ascorbic acid (AA) dissolved en 10 mL of deionized water was rapidly added (see Table 1 for more details). The reaction took place at ambient conditions and the particles appeared after 5 min of reaction. After 1 h of aging, the particles formed were settled, washed two times with water, two times with acetone and dried at room temperature.
⁎ Corresponding author. Tel./fax: +52 444 8262361. E-mail address: [email protected] (G.A. Martínez-Castañón). 0167-577X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2009.02.061
Table 1 Experimental conditions used in the method reported in this work. Sample label
Ag+:AA molar ratio
Morphology achieved
Sample Sample Sample Sample
1:1 1:2 1:3 1:4
Polihedrons Polihedrons Dendrites Dendrites
A B C D
G.A. Martínez-Castañón et al. / Materials Letters 63 (2009) 1266–1268
Fig. 1. Diffraction pattern of the sample with dendritic morphology. The refined cell parameter is a = b = c = 4.085 Å and the crystallite size is 166.3 nm.
AA molar ratios. Using Ag+:AA molar ratios of 1:1 and 1:2 we can obtain polyhedron particles with a decrease in the size of the particles when the amount of AA was increased, 3 μm for the Ag+:AA molar ratio 1:1 (Fig. 2a) and 1.5 μm for the Ag+:AA molar ratio 1:2. The polyhedrons present a hexagonal plate structure with two (111) bases with laterally exposed {100} and {111} facets [19]. Using Ag+:AA molar ratios of 1:3 and 1:4 we can obtain dendritic particles (Fig. 2c, Ag+:AA
1267
molar ratio 1:3 and d, Ag+:AA molar ratio 1:4 respectively). There is a high yield for each morphology in all samples, that is, no mixture exists among polyhedron and dendrites. The transition from polyhedron to dendritic structures was reported by Gu and Zhang [19], they obtained particles with similar morphologies using an electrochemical method varying the applied potential. In this work when we added different amounts of ascorbic acid we varied the electrochemical potential in the reaction, this could be the reason why the particles change their morphology. Fig. 3 shows individual particles of samples C and D, the overall length of the dendrites are 10 μm and 15 μm respectively. Particles in sample D are ticker and bigger than particles in sample C and present sub-branches; but, according to Rietveld analysis (results not shown) both samples are formed by individual particles with sizes about 150 nm. Dendritic Ag structures have aroused the interest of many researchers due to the excellent connectivity between the different parts of the structures [18]. This dendritic structure represents a sort of growth (Diffusion-Limited Aggregation) where one particle is formed after another and then it diffuses sticking the growing structure [8,16,20]. In order to obtain dendrites, it is necessary to reduce a large number of silver ions and form ultrafine particles which diffuse and built the final structure. This morphology dependence on the reactions conditions is still unknown and need more studies. Absorption measurements were obtained with an Ocean Optics S2000UV-VIS fiber optic spectrometer. In order to get the uv–vis spectra, the powders were redispersed in deionized water. Fig. 4 shows the spectra of the sample A, it has a maximum on 440 nm, it corresponds well to the silver plasmon [21], all sample present the same optical features. These results confirm the idea that silver
Fig. 2. SEM images of the four samples synthesized with different Ag+:AA molar ratio, a) 1:1; b) 1:2; c) 1:3 and d) 1:4.
1268
G.A. Martínez-Castañón et al. / Materials Letters 63 (2009) 1266–1268
Fig. 4. Uv–vis spectra of the sample with polyhedron morphology (Sample A).
Autónoma de San Luis Potosí (UASLP). The authors want to thanks to Dra. Ma. Guadalupe Sánchez-Loredo. References
Fig. 3. Individual particles of samples C and D.
particles prepared in this work (polyhedron and dendrites) are formed by the attachment of ultrafine particles which are the responsible of the optical properties. 4. Conclusions In summary, we synthesized micro-sized silver particles with different sizes and with polyhedron and dendritic morphologies by simply changing the reaction conditions, specifically, the amount of ascorbic acid added to the reaction. No template is needed and the particles are elemental silver. Acknowledgements This work was partially supported by Consejo Nacional de Ciencia y Tecnología (CONACYT), Programa de Mejoramiento del Profesorado (PROMEP) Fondo de Apoyo a la Investigación (FAI) of Universidad
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
Velikov K, Zegers GE, van Blaaderen A. Langmuir 2003;19:1384. Seo W, Kim T, Sung J, Song K. Korean Chem Eng Res 2004;42:78. Maillard M, Huang P, Brus L. Nano Lett 2003;3:1611. Sun Y, Gates B, Mayers B, Xia Y. Nano Lett 2002;2:165. Rivas L, Sanchez-Cortes S, García-Ramos JV, Morcillo G. Langmuir 2001;17:574. Bell WC, Myrick ML. J Colloid Interface Sci 2001;242:300. Sun Y, Riggs JE, Rollins HW, Guduru R. J Phys Chem B 1999;103:77. Zhou Y, Yu SH, Wang CY, Li XG, Zhu YR, Chen ZY. Adv Mater 1999;11:850. Iliescu T, Irimie F, Bolboaca M, Paiz Cs, Kiefer W. Vib Spectrosc 2002;29:251. Muñiz-Miranda M. Vib Spectrosc 2002;29:229. Shin H, Yang H, Jung Y, Kim S. Vib Spectrosc 2002;29:79. Arenas JF, López-Tocón I, Centeno SP, Soto J, Otero J. Vib Spectrosc 2002;29:147. Constantino C, Lemma T, Antunes P, Aroca R. Spectrochim Acta Part A 2002;58:403. Xiong L, Yong C, Fu-bin T, Zhi-tao W. Thermochim Acta 1995;253:285. Jana NR, Gearheart L, Murphy CJ. Adv Mater 2001;13:1389. Zhang X, Wang G, Liu X, Wu H, Fang B. Cryst Growth Des 2008;8:1430. Fang J, You H, Kong P, Yi Y, Song X, Ding B. Cryst Growth Des 2007;7:864. Rashid MH, Mandal TK. J Phys Chem C 2007;111:16750. Gu C, Zhang TY. Langmuir 2008;24:12010. Wen X, Xie YT, Mak WC, Cheung KY, Li XY, Renneberg R, et al. Langmuir 2006;22:4836. [21] Martínez-Castañón GA, Niño-Martínez N, Martínez-Gutiérrez F, Martínez-Mendoza JR, Ruiz Facundo. J Nanopart Res 2008;10:1343.
Contents lists available at ScienceDirect
Materials Letters j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m a t l e t
Synthesis of silver particles with different sizes and morphologies G.A. Martínez-Castañón a,⁎, N. Niño-Martínez b, J.P. Loyola-Rodríguez a, N. Patiño-Marín a, J.R. Martínez-Mendoza b, Facundo Ruiz b a b
Maestria en Ciencias Odontológicas, Facultad de Estomatología, UASLP, Av. Manuel Nava 2, Zona Universitaria, San Luis Potosí, S. L. P., México Facultad de Ciencias, UASLP, Álvaro Obregón 64, Col. Centro, San Luis Potosí, S. L. P., México
a r t i c l e
i n f o
Article history: Received 12 January 2009 Accepted 28 February 2009 Available online 9 March 2009 Keywords: Metals and alloys Crystal growth
a b s t r a c t In this work, using a simple templateless, surfactantless, chemical reduction method, we synthesized micronsized silver particles with different sizes and morphologies by simply changing the reaction conditions, specifically, the amount of ascorbic acid added to a silver nitrate aqueous solution, the Ag+:Ascorbic Acid molar ratios used were 1:1, 1:2, 1:3 and 1:4. The morphologies obtained were polyhedrons and dendrites. The sizes of the particles ranged from 1.5 μm to 15 μm. The principal driven force which produces the changes in the morphology of the Ag particles could be the variations in the electrochemical potential aroused from the changes in the amount of ascorbic acid used in the reaction. © 2009 Elsevier B.V. All rights reserved.
1. Introduction
3. Results and discussion
In the last years, many studies have been made in order to synthesize silver colloids by chemical methods [1–8]. Most of them give very small particles which could be used as SERS surfaces [9–13]. Just few of these studies are devoted to micron-sized silver particles [1,14] although these particles have interesting applications on catalyst and electronics. The most common morphology obtained when one synthesize metal particles by chemical methods is, by thermodynamic reasons, the spherical one, and it is a challenge to obtain particles with different sizes and morphologies [15]. To date, much effort has been made to prepare particles with well-defined sizes, shapes and cristallinity [16–18]. In this work we synthesize silver micron-particles with different sizes and morphologies using a simple templateless, surfactantless, chemical reduction method. The morphologies obtained are polyhedrons and dendrites.
In order to determine the composition of the particles an X-ray diffraction analysis was made using the dried powders. X-ray diffraction patterns were recorded on a GBC-Difftech MMA model, with Cu Kα irradiation at λ = 1.54 Å. Fig. 1 shows the diffraction pattern of the sample with dendritic morphology (Sample C), the rest of the samples present a similar pattern. All samples obtained are elemental silver with a unit cell parameter being a = b = c = 4.085 Å and they agree with the published data (JCPDS 04-0783). The refined crystallite size for this sample is 166.3 nm. The peak intensity ratios of the (111) to (200) diffractions and the (200) to (220) diffractions, 2.63 and 1.58, are close to the values from a polycrystalline Ag with randomly distributed grains, 2.5 and 1.6 [19]; although, it is in general accepted that dendrites are formed by preferential growth along particular crystal directions, these results indicate that dendrites are probably not formed by particles with a strong preferred orientation, it is, we cannot establish, using this technique, the actual direction in which dendrites are growing. The morphology of the Ag particles was observed using a XL-30 scanning electron microscope (Phillips, Netherlands). Fig. 2a, b, c and d show images of the silver particles synthesized with different Ag+:
2. Experimental In a normal synthesis, a silver nitrate solution was prepared by dissolving 1 mmol of the salt in 100 mL of 0.1 M nitric acid, this solution was placed in a 400 mL reaction vessel and, under magnetic stirring, a specific amount of ascorbic acid (AA) dissolved en 10 mL of deionized water was rapidly added (see Table 1 for more details). The reaction took place at ambient conditions and the particles appeared after 5 min of reaction. After 1 h of aging, the particles formed were settled, washed two times with water, two times with acetone and dried at room temperature.
⁎ Corresponding author. Tel./fax: +52 444 8262361. E-mail address: [email protected] (G.A. Martínez-Castañón). 0167-577X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2009.02.061
Table 1 Experimental conditions used in the method reported in this work. Sample label
Ag+:AA molar ratio
Morphology achieved
Sample Sample Sample Sample
1:1 1:2 1:3 1:4
Polihedrons Polihedrons Dendrites Dendrites
A B C D
G.A. Martínez-Castañón et al. / Materials Letters 63 (2009) 1266–1268
Fig. 1. Diffraction pattern of the sample with dendritic morphology. The refined cell parameter is a = b = c = 4.085 Å and the crystallite size is 166.3 nm.
AA molar ratios. Using Ag+:AA molar ratios of 1:1 and 1:2 we can obtain polyhedron particles with a decrease in the size of the particles when the amount of AA was increased, 3 μm for the Ag+:AA molar ratio 1:1 (Fig. 2a) and 1.5 μm for the Ag+:AA molar ratio 1:2. The polyhedrons present a hexagonal plate structure with two (111) bases with laterally exposed {100} and {111} facets [19]. Using Ag+:AA molar ratios of 1:3 and 1:4 we can obtain dendritic particles (Fig. 2c, Ag+:AA
1267
molar ratio 1:3 and d, Ag+:AA molar ratio 1:4 respectively). There is a high yield for each morphology in all samples, that is, no mixture exists among polyhedron and dendrites. The transition from polyhedron to dendritic structures was reported by Gu and Zhang [19], they obtained particles with similar morphologies using an electrochemical method varying the applied potential. In this work when we added different amounts of ascorbic acid we varied the electrochemical potential in the reaction, this could be the reason why the particles change their morphology. Fig. 3 shows individual particles of samples C and D, the overall length of the dendrites are 10 μm and 15 μm respectively. Particles in sample D are ticker and bigger than particles in sample C and present sub-branches; but, according to Rietveld analysis (results not shown) both samples are formed by individual particles with sizes about 150 nm. Dendritic Ag structures have aroused the interest of many researchers due to the excellent connectivity between the different parts of the structures [18]. This dendritic structure represents a sort of growth (Diffusion-Limited Aggregation) where one particle is formed after another and then it diffuses sticking the growing structure [8,16,20]. In order to obtain dendrites, it is necessary to reduce a large number of silver ions and form ultrafine particles which diffuse and built the final structure. This morphology dependence on the reactions conditions is still unknown and need more studies. Absorption measurements were obtained with an Ocean Optics S2000UV-VIS fiber optic spectrometer. In order to get the uv–vis spectra, the powders were redispersed in deionized water. Fig. 4 shows the spectra of the sample A, it has a maximum on 440 nm, it corresponds well to the silver plasmon [21], all sample present the same optical features. These results confirm the idea that silver
Fig. 2. SEM images of the four samples synthesized with different Ag+:AA molar ratio, a) 1:1; b) 1:2; c) 1:3 and d) 1:4.
1268
G.A. Martínez-Castañón et al. / Materials Letters 63 (2009) 1266–1268
Fig. 4. Uv–vis spectra of the sample with polyhedron morphology (Sample A).
Autónoma de San Luis Potosí (UASLP). The authors want to thanks to Dra. Ma. Guadalupe Sánchez-Loredo. References
Fig. 3. Individual particles of samples C and D.
particles prepared in this work (polyhedron and dendrites) are formed by the attachment of ultrafine particles which are the responsible of the optical properties. 4. Conclusions In summary, we synthesized micro-sized silver particles with different sizes and with polyhedron and dendritic morphologies by simply changing the reaction conditions, specifically, the amount of ascorbic acid added to the reaction. No template is needed and the particles are elemental silver. Acknowledgements This work was partially supported by Consejo Nacional de Ciencia y Tecnología (CONACYT), Programa de Mejoramiento del Profesorado (PROMEP) Fondo de Apoyo a la Investigación (FAI) of Universidad
[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20]
Velikov K, Zegers GE, van Blaaderen A. Langmuir 2003;19:1384. Seo W, Kim T, Sung J, Song K. Korean Chem Eng Res 2004;42:78. Maillard M, Huang P, Brus L. Nano Lett 2003;3:1611. Sun Y, Gates B, Mayers B, Xia Y. Nano Lett 2002;2:165. Rivas L, Sanchez-Cortes S, García-Ramos JV, Morcillo G. Langmuir 2001;17:574. Bell WC, Myrick ML. J Colloid Interface Sci 2001;242:300. Sun Y, Riggs JE, Rollins HW, Guduru R. J Phys Chem B 1999;103:77. Zhou Y, Yu SH, Wang CY, Li XG, Zhu YR, Chen ZY. Adv Mater 1999;11:850. Iliescu T, Irimie F, Bolboaca M, Paiz Cs, Kiefer W. Vib Spectrosc 2002;29:251. Muñiz-Miranda M. Vib Spectrosc 2002;29:229. Shin H, Yang H, Jung Y, Kim S. Vib Spectrosc 2002;29:79. Arenas JF, López-Tocón I, Centeno SP, Soto J, Otero J. Vib Spectrosc 2002;29:147. Constantino C, Lemma T, Antunes P, Aroca R. Spectrochim Acta Part A 2002;58:403. Xiong L, Yong C, Fu-bin T, Zhi-tao W. Thermochim Acta 1995;253:285. Jana NR, Gearheart L, Murphy CJ. Adv Mater 2001;13:1389. Zhang X, Wang G, Liu X, Wu H, Fang B. Cryst Growth Des 2008;8:1430. Fang J, You H, Kong P, Yi Y, Song X, Ding B. Cryst Growth Des 2007;7:864. Rashid MH, Mandal TK. J Phys Chem C 2007;111:16750. Gu C, Zhang TY. Langmuir 2008;24:12010. Wen X, Xie YT, Mak WC, Cheung KY, Li XY, Renneberg R, et al. Langmuir 2006;22:4836. [21] Martínez-Castañón GA, Niño-Martínez N, Martínez-Gutiérrez F, Martínez-Mendoza JR, Ruiz Facundo. J Nanopart Res 2008;10:1343.