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Rapid synthesis of long silver nanowires by controlling concentration of Cu2+ ions
Author’s Accepted Manuscript Rapid synthesis of long silver nanowires by controlling concentration of Cu2+ ions Shang Wang, Yanhong Tian, Su Ding, Yilong Huang www.elsevier.com
PII: DOI: Reference:
S0167-577X(16)30283-X http://dx.doi.org/10.1016/j.matlet.2016.02.124 MLBLUE20413
To appear in: Materials Letters Received date: 10 December 2015 Revised date: 3 February 2016 Accepted date: 23 February 2016 Cite this article as: Shang Wang, Yanhong Tian, Su Ding and Yilong Huang, Rapid synthesis of long silver nanowires by controlling concentration of Cu2+ ions, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2016.02.124 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Rapid synthesis of long silver nanowires by controlling concentration of Cu 2+ ions Shang Wang, Yanhong Tian*, Su Ding, Yilong Huang State Key Lab of Advanced Welding and Joining, Harbin Institute of Technology, Harbin, China, 150001. * Corresponding author. Tel. /fax: +86 0451 86412359/86416186 E-mail address: [email protected] Abstract Long silver nanowires (AgNWs) with mean length of 49.4 μm were synthesized by a rapid one-step polyol method within only 30 minutes. The relationship between Cu 2+ and the size of AgNWs had been studied. AgNWs were longer at higher concentration of Cu 2+ because the presence of Cu+ (reduced from Cu 2+) could increase the absorption rate of silver atoms (Ag0). By simply controlling the concentration of Cu 2+ in reaction process, the diameter of AgNWs ranging from 31 nm to 57 nm could also be adjusted. This rapid method improved the production efficiency of long AgNWs and could be applied to high performance transparent electrodes. Keywords: Silver nanowires; Copper ions; Rapid synthesis; Microstructure; Electronic materials 1 Introduction In the recent years, novel nanomaterials such as carbon nanotubes (CNTs), graphene, and metal nanowires are developed to substitute indium tin oxide (ITO) in transparent electrodes field [1]. Among them, AgNWs based transparent electrodes, which are always applied on touch screen, solar cell and LED, are considered to be one of the most promising candidates of commercial used ITO due to their simple solution process and high conductivity, such as polyol method [2-5]. Also, it has been reported that transparent electrodes fabricated with longer silver nanowires could achieve a higher electrical conductivity since more inter-nanowire junctions
1
improved the number of conductive paths compared to the shorter ones [2, 6]. Therefore, synthesis of ultra-long silver nanowires is highly desirable. The key issue to successfully synthesize long nanowires is to control the nucleation progress of seeds and the deposition speed of Ag 0 [7, 8]. Xia and his co-workers [9] had found that uniform nanowires could be obtained in presence of Cu 2+, which could be reduced to Cu + by EG. The Cu+ ions would react with atomic oxygen (Oa) that suppressed the etching of five-twinned seeds. Pirooz et, al. also found that the Cu 2+/Cu+ redox pair could reduce the concentration of oxygen in solution [10]. Nevertheless, the existence of Cu2+ is seldom considered during the growth process of nanowires. Moreover, it will take about 1-12h to grow long silver nanowires [11, 12]. In this study, a modified polyol method was used to synthesize long AgNWs with mean length of 49.4±24.3 μm in a large scale within only 30 minutes. The initial ratio between Ag + and CuCl2 was adjusted carefully to generate AgNWs with various diameter and length by controlling nucleation and growth of AgNWs. 2 Materials and experiments In a typical synthesis process, 20 ml Ethylene Glycol (EG) (TianjingFuyu Fine Chemical Co.,Ltd) in a glass vial was pre-heated in an oil bath at temperature of 160℃ for 5 min to remove the water. To achieve long AgNWs, 2 mL of 4 mM CuCl2·H2O(99.0%, Tianjin Zhiyuan Chemical Reagent Co., Ltd) was added into the solution which was much more than previous reports. After another ten minutes, 20 ml of the mixture of 0.2 g AgNO3(99.8%, Tianjin Dongjulong Chemical Reagent Co., Ltd) and 0.4 g PVP (avg Mw ~55 000, Aldrich) were injected into the solution. The total reaction took about 30 min.
Afterwards, acetone and ethanol were used to wash the
2
precipitate with centrifugation of 2000 rpm for 5 min. All of these materials were used as received without further purification. SEM images were collected using a Helios Nanolab 600i with an acceleration voltage of 20 kV. TEM images were collected using a JEM 2100 microscope with an acceleration voltage of 200 kV. XRD patterns were collected on D8-ADVANCE X-ray diffractometer with Cu Kα radiation (λ=1.5418 Å) at 40 kV and 40 mA. 3 Results and discussion Fig.1 shows the SEM images of AgNWs synthesized under different concertation of Cu2+ and the corresponding length distribution of AgNWs. When there were no Cu2+ in solution, the total reaction took about 1.5 h. A mixture of particles and wires with length around 8.2±3.7 μm were produced as shown in Fig. 1(a). With the concentration of Cu2+ increasing to 0.19 mM, the average length of AgNWs was improved to 12.6±6.6 μm with some short silver bars as shown in Fig. 1(b). It is worth to mention that the reaction time was declined to 40 minutes meanwhile. Continuously increasing the concentration of Cu 2+, the product was almost AgNWs and the length was further increased to 49.4±24.3 μm and even more than 70 μm as shown in Fig. 1(c), which was superior to normal polyol method and the total reaction took only 30 minutes. It was found that the length of AgNWs was improved as the increasing concentration of Cu 2+. The high concertation Cu2+ would be induced into Cu+ by EG, which could remove the Oa on the surface of AgNWs and decrease the etching rate of Ag0 by Cl- [9]. In contrary, when the nanowires prepared by NaCl instead of CuCl2, the nanocrystal was etched quickly and was hard to grow larger without presence of Cu2+. Thus, AgNWs could growth more quickly and longer when more Cu2+ was present in solution, and long AgNWs were obtained by this modified polyol method. 3
Fig.1 SEM images and length distribution of AgNWs synthesized with a), d) 0.38 mM NaCl, b), e) 0.19 mM and c), f) 0.36 mM CuCl 2, respectively.
Fig.2 a) TEM image, and b) corresponding selected area diffraction pattern (SAED) of single silver nanowire. Inset picture in Fig. 2a shows the direction of electron beam.
4
Moreover, the diffraction pattern of AgNWs to confirm the crystal structure, as shown in Fig. 2. The as-prepared AgNWs were with twinned structure as reported by previous papers [13]. When the e-beam was directed to one side face of AgNW as inset picture in Fig. 2a shown. There were two sets of diffraction patterns with zone axis of [111] and [011] as shown in Fig. 2b, which confirmed the five twinned structure.
Fig.3 TEM images of AgNWs prepared at 160℃ with a) 0.38 Mm NaCl, b) 0.19 mM and c) 0.36 mM CuCl2. d) is the statistic diameter of AgNWs under different condition. In previous reports [14], AgNWs always grew thicker when the desirable long nanowires were obtained at high reaction temperatures and high concentration of silver. In this study, the diameter of AgNWs was also studied by changing the addition of CuCl 2 due to the Cu2+ could affect the size of Ag seeds. Fig. 3 shows TEM images of AgNWs at different concentration of Cu2+. The mean diameter of Fig. 3a, 3b and 3c were 48±7 nm, 49±14 nm and 72±13 nm, respectively. It was obviously that the diameter of AgNWs increased when the concentration of Cu2+ was improved 5
even when the reaction time was reduced as Fig. 3d shows. As mentioned above, due to the high concentration of Cu2+ in solution, there were more Cu + that prevented the Oa etching of Ag atoms [12]. Ag0 could adopt on the surface of silver seeds even in a relatively short time. This process may lead to larger seeds and then thicker wires.
Fig.4 TEM images of samples after 6 min reaction with a) 0.19 mM and b) 0.36 mM CuCl2, respectively. To confirm the relationship between size of seeds and diameter of AgNWs, some early formed seeds were taken from solution reacted after about 6 minutes. Fig. 4a shows these seeds with 0.19 mM CuCl2 in solution, there were some short bars with small multiple twined seeds with the size varying from 31 nm to 57 nm. Particles in Fig. 4b, which added 0.36 mM CuCl 2 in solution, were larger than those in Fig. 3a. Due to higher Ag0 adopting speed, these particles could even grow to 112 nm in diameters. Once these seeds had formed, they could evolve into suitable wires with a diameter similar to the seeds [14]. Higher the concentration of Cu 2+ was, thicker nanowires were. Therefore, we can not only control the length but also the diameter of AgNWs by controlling the concentration of Cu 2+. 4 Conclusions In conclusion, a rapid polyol method was used to synthesize long AgNWs with mean length of 49.4±24.3 μm at 160℃ within only 30 minutes. The Cu2+ present in solution could be reduced to 6
Cu+ by ethylene glycol, so the size of AgNWs could be adjusted. The Cu+ could not only reduce the Oa etching of Ag seeds during the nucleation process, but also increase the adopt rate of Ag0 on the surface of AgNWs during the growth process. Hence, by simply varying the concentration of Cu2+, AgNWs with different size could be produced. Acknowledgements The authors are grateful for financial support from the National Natural Science Found ation of China (Grant No. 51522503) and support from Program for New Century Excellent Talents in University (NCET-13-0175). References [1] Hecht DS, Hu LB, Irvin G. Emerging Transparent Electrodes Based on Thin Films of Carbon Nanotubes, Graphene, and Metallic Nanostructures. Adv Mater. 2011;23:1482-513. [2] Lee J, Lee P, Lee HB, Hong S, Lee I, Yeo J, et al. Room-Temperature Nanosoldering of a Very Long Metal Nanowire Network by Conducting-Polymer-Assisted Joining for a Flexible Touch-Panel Application. AdvFunct Mater. 2013;23:4171-6. [3] Zhang KL, Du YG, Chen SM. Sub 30 nm silver nanowire synthesized using KBr as co-nucleant through one-pot polyol method for optoelectronic applications. Org Electron. 2015;26:380-5. [4] Lee J, Lee P, Lee H, Lee D, Lee SS, Ko SH. Very long Ag nanowire synthesis and its application in a highly transparent, conductive and flexible metal electrode touch panel. Nanoscale. 2012;4:6408-14. [5] S. Murali, T. Xu, B. D. Marshall, M. J. Kayatin, K. Pizarro, V. K. Radhakrishnan, D. Nepal, V. A. Davis, Lyotropic Liquid Crystalline Self-Assembly in Dispersions of Silver Nanowires and Nanoparticles, Langmuir, 26, 11176-11183 (2010). [6] Mutiso RM, Sherrott MC, Rathmell AR, Wiley BJ, Winey KI. Integrating Simu-lations and Experiments To Predict Sheet Resistance and Optical Transmittance in Nanowire Films for Transparent Conductors. Acs Nano. 2013;7:7654-63. [7] Johnson CJ, Dujardin E, Davis SA, Murphy CJ, Mann S. Growth and form of gold nanorods prepared by seed-mediated, surfactant-directed synthesis. J Mater Chem. 2002;12:1765-70. 7
[8] Wiley B, Sun YG, Mayers B, Xia YN. Shape-controlled synthesis of metal nano-structures: The case of silver. Chem-Eur J. 2005;11:454-63. [9] Korte KE, Skrabalak SE, Xia YN. Rapid synthesis of silver nanowires through a CuCl- or CuCl2mediated polyol process. J Mater Chem. 2008;18:437-41. [10] Amirjani A, Fatmehsari DH, Marashi P. Interactive effect of agitation rate and oxidative etching on growth mechanisms of silver nanowires during polyol process. J ExpNanosci. 2015;10:1387-400. [11] Wiley B, Herricks T, Sun YG, Xia YN. Polyol synthesis of silver nanoparticles: Use of chloride and oxygen to promote the formation of single-crystal, truncated cubes and tetrahedrons. Nano Lett. 2004;4:1733-9. [12] Araki T, Jiu JT, Nogi M, Koga H, Nagao S, Sugahara T, et al. Low haze transparent electrodes and highly conducting air dried films with ultra-long silver nanowires synthesized by one-step polyol method. Nano Res. 2014;7:236-45. [13] Staleva H, Skrabalak SE, Carey CR, Kosel T, Xia YN, Hartland GV. Coupling to light, and transport and dissipation of energy in silver nanowires. Phys Chem Chem Phys. 2009;11:5889-96. [14] Coskun S, Aksoy B, Unalan HE. Polyol Synthesis of Silver Nanowires: An Extensive Parametric Study. Cryst Growth Des. 2011;11:4963-9.
Figure Captions Fig.1 SEM images and length distribution of AgNWs synthesized with a), d) 0.38 mMNaCl, b), e) 0.19 mM and c), f) 0.36 mM CuCl2, respectively Fig.2 a) TEM image, and b) corresponding selected area diffraction pattern (SAED) of single silver nanowire. Inset picture in Fig. 2a shows the direction of electron beam. Fig.3 TEM images of AgNWs prepared at 160℃ with a) 0.38 mMNaCl, b) 0.19 mM and c) 0.36 mM CuCl2. d) is the statistic diameter of AgNWs under different condition. Fig.4 TEM images of samples after 6 min reaction with a) 0.19 mM and b) 0.36 mM CuCl 2, respectively.
Highlights AgNWs with mean length of 49.4 μm have been synthesized within only 30 min. 8
Longer AgNWs were achieved at higher concentration of Cu 2+ in shorter reaction time.
By adjusting the concentration of Cu2+, the diameter of AgNWs could be adjusted.
9
PII: DOI: Reference:
S0167-577X(16)30283-X http://dx.doi.org/10.1016/j.matlet.2016.02.124 MLBLUE20413
To appear in: Materials Letters Received date: 10 December 2015 Revised date: 3 February 2016 Accepted date: 23 February 2016 Cite this article as: Shang Wang, Yanhong Tian, Su Ding and Yilong Huang, Rapid synthesis of long silver nanowires by controlling concentration of Cu2+ ions, Materials Letters, http://dx.doi.org/10.1016/j.matlet.2016.02.124 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Rapid synthesis of long silver nanowires by controlling concentration of Cu 2+ ions Shang Wang, Yanhong Tian*, Su Ding, Yilong Huang State Key Lab of Advanced Welding and Joining, Harbin Institute of Technology, Harbin, China, 150001. * Corresponding author. Tel. /fax: +86 0451 86412359/86416186 E-mail address: [email protected] Abstract Long silver nanowires (AgNWs) with mean length of 49.4 μm were synthesized by a rapid one-step polyol method within only 30 minutes. The relationship between Cu 2+ and the size of AgNWs had been studied. AgNWs were longer at higher concentration of Cu 2+ because the presence of Cu+ (reduced from Cu 2+) could increase the absorption rate of silver atoms (Ag0). By simply controlling the concentration of Cu 2+ in reaction process, the diameter of AgNWs ranging from 31 nm to 57 nm could also be adjusted. This rapid method improved the production efficiency of long AgNWs and could be applied to high performance transparent electrodes. Keywords: Silver nanowires; Copper ions; Rapid synthesis; Microstructure; Electronic materials 1 Introduction In the recent years, novel nanomaterials such as carbon nanotubes (CNTs), graphene, and metal nanowires are developed to substitute indium tin oxide (ITO) in transparent electrodes field [1]. Among them, AgNWs based transparent electrodes, which are always applied on touch screen, solar cell and LED, are considered to be one of the most promising candidates of commercial used ITO due to their simple solution process and high conductivity, such as polyol method [2-5]. Also, it has been reported that transparent electrodes fabricated with longer silver nanowires could achieve a higher electrical conductivity since more inter-nanowire junctions
1
improved the number of conductive paths compared to the shorter ones [2, 6]. Therefore, synthesis of ultra-long silver nanowires is highly desirable. The key issue to successfully synthesize long nanowires is to control the nucleation progress of seeds and the deposition speed of Ag 0 [7, 8]. Xia and his co-workers [9] had found that uniform nanowires could be obtained in presence of Cu 2+, which could be reduced to Cu + by EG. The Cu+ ions would react with atomic oxygen (Oa) that suppressed the etching of five-twinned seeds. Pirooz et, al. also found that the Cu 2+/Cu+ redox pair could reduce the concentration of oxygen in solution [10]. Nevertheless, the existence of Cu2+ is seldom considered during the growth process of nanowires. Moreover, it will take about 1-12h to grow long silver nanowires [11, 12]. In this study, a modified polyol method was used to synthesize long AgNWs with mean length of 49.4±24.3 μm in a large scale within only 30 minutes. The initial ratio between Ag + and CuCl2 was adjusted carefully to generate AgNWs with various diameter and length by controlling nucleation and growth of AgNWs. 2 Materials and experiments In a typical synthesis process, 20 ml Ethylene Glycol (EG) (TianjingFuyu Fine Chemical Co.,Ltd) in a glass vial was pre-heated in an oil bath at temperature of 160℃ for 5 min to remove the water. To achieve long AgNWs, 2 mL of 4 mM CuCl2·H2O(99.0%, Tianjin Zhiyuan Chemical Reagent Co., Ltd) was added into the solution which was much more than previous reports. After another ten minutes, 20 ml of the mixture of 0.2 g AgNO3(99.8%, Tianjin Dongjulong Chemical Reagent Co., Ltd) and 0.4 g PVP (avg Mw ~55 000, Aldrich) were injected into the solution. The total reaction took about 30 min.
Afterwards, acetone and ethanol were used to wash the
2
precipitate with centrifugation of 2000 rpm for 5 min. All of these materials were used as received without further purification. SEM images were collected using a Helios Nanolab 600i with an acceleration voltage of 20 kV. TEM images were collected using a JEM 2100 microscope with an acceleration voltage of 200 kV. XRD patterns were collected on D8-ADVANCE X-ray diffractometer with Cu Kα radiation (λ=1.5418 Å) at 40 kV and 40 mA. 3 Results and discussion Fig.1 shows the SEM images of AgNWs synthesized under different concertation of Cu2+ and the corresponding length distribution of AgNWs. When there were no Cu2+ in solution, the total reaction took about 1.5 h. A mixture of particles and wires with length around 8.2±3.7 μm were produced as shown in Fig. 1(a). With the concentration of Cu2+ increasing to 0.19 mM, the average length of AgNWs was improved to 12.6±6.6 μm with some short silver bars as shown in Fig. 1(b). It is worth to mention that the reaction time was declined to 40 minutes meanwhile. Continuously increasing the concentration of Cu 2+, the product was almost AgNWs and the length was further increased to 49.4±24.3 μm and even more than 70 μm as shown in Fig. 1(c), which was superior to normal polyol method and the total reaction took only 30 minutes. It was found that the length of AgNWs was improved as the increasing concentration of Cu 2+. The high concertation Cu2+ would be induced into Cu+ by EG, which could remove the Oa on the surface of AgNWs and decrease the etching rate of Ag0 by Cl- [9]. In contrary, when the nanowires prepared by NaCl instead of CuCl2, the nanocrystal was etched quickly and was hard to grow larger without presence of Cu2+. Thus, AgNWs could growth more quickly and longer when more Cu2+ was present in solution, and long AgNWs were obtained by this modified polyol method. 3
Fig.1 SEM images and length distribution of AgNWs synthesized with a), d) 0.38 mM NaCl, b), e) 0.19 mM and c), f) 0.36 mM CuCl 2, respectively.
Fig.2 a) TEM image, and b) corresponding selected area diffraction pattern (SAED) of single silver nanowire. Inset picture in Fig. 2a shows the direction of electron beam.
4
Moreover, the diffraction pattern of AgNWs to confirm the crystal structure, as shown in Fig. 2. The as-prepared AgNWs were with twinned structure as reported by previous papers [13]. When the e-beam was directed to one side face of AgNW as inset picture in Fig. 2a shown. There were two sets of diffraction patterns with zone axis of [111] and [011] as shown in Fig. 2b, which confirmed the five twinned structure.
Fig.3 TEM images of AgNWs prepared at 160℃ with a) 0.38 Mm NaCl, b) 0.19 mM and c) 0.36 mM CuCl2. d) is the statistic diameter of AgNWs under different condition. In previous reports [14], AgNWs always grew thicker when the desirable long nanowires were obtained at high reaction temperatures and high concentration of silver. In this study, the diameter of AgNWs was also studied by changing the addition of CuCl 2 due to the Cu2+ could affect the size of Ag seeds. Fig. 3 shows TEM images of AgNWs at different concentration of Cu2+. The mean diameter of Fig. 3a, 3b and 3c were 48±7 nm, 49±14 nm and 72±13 nm, respectively. It was obviously that the diameter of AgNWs increased when the concentration of Cu2+ was improved 5
even when the reaction time was reduced as Fig. 3d shows. As mentioned above, due to the high concentration of Cu2+ in solution, there were more Cu + that prevented the Oa etching of Ag atoms [12]. Ag0 could adopt on the surface of silver seeds even in a relatively short time. This process may lead to larger seeds and then thicker wires.
Fig.4 TEM images of samples after 6 min reaction with a) 0.19 mM and b) 0.36 mM CuCl2, respectively. To confirm the relationship between size of seeds and diameter of AgNWs, some early formed seeds were taken from solution reacted after about 6 minutes. Fig. 4a shows these seeds with 0.19 mM CuCl2 in solution, there were some short bars with small multiple twined seeds with the size varying from 31 nm to 57 nm. Particles in Fig. 4b, which added 0.36 mM CuCl 2 in solution, were larger than those in Fig. 3a. Due to higher Ag0 adopting speed, these particles could even grow to 112 nm in diameters. Once these seeds had formed, they could evolve into suitable wires with a diameter similar to the seeds [14]. Higher the concentration of Cu 2+ was, thicker nanowires were. Therefore, we can not only control the length but also the diameter of AgNWs by controlling the concentration of Cu 2+. 4 Conclusions In conclusion, a rapid polyol method was used to synthesize long AgNWs with mean length of 49.4±24.3 μm at 160℃ within only 30 minutes. The Cu2+ present in solution could be reduced to 6
Cu+ by ethylene glycol, so the size of AgNWs could be adjusted. The Cu+ could not only reduce the Oa etching of Ag seeds during the nucleation process, but also increase the adopt rate of Ag0 on the surface of AgNWs during the growth process. Hence, by simply varying the concentration of Cu2+, AgNWs with different size could be produced. Acknowledgements The authors are grateful for financial support from the National Natural Science Found ation of China (Grant No. 51522503) and support from Program for New Century Excellent Talents in University (NCET-13-0175). References [1] Hecht DS, Hu LB, Irvin G. Emerging Transparent Electrodes Based on Thin Films of Carbon Nanotubes, Graphene, and Metallic Nanostructures. Adv Mater. 2011;23:1482-513. [2] Lee J, Lee P, Lee HB, Hong S, Lee I, Yeo J, et al. Room-Temperature Nanosoldering of a Very Long Metal Nanowire Network by Conducting-Polymer-Assisted Joining for a Flexible Touch-Panel Application. AdvFunct Mater. 2013;23:4171-6. [3] Zhang KL, Du YG, Chen SM. Sub 30 nm silver nanowire synthesized using KBr as co-nucleant through one-pot polyol method for optoelectronic applications. Org Electron. 2015;26:380-5. [4] Lee J, Lee P, Lee H, Lee D, Lee SS, Ko SH. Very long Ag nanowire synthesis and its application in a highly transparent, conductive and flexible metal electrode touch panel. Nanoscale. 2012;4:6408-14. [5] S. Murali, T. Xu, B. D. Marshall, M. J. Kayatin, K. Pizarro, V. K. Radhakrishnan, D. Nepal, V. A. Davis, Lyotropic Liquid Crystalline Self-Assembly in Dispersions of Silver Nanowires and Nanoparticles, Langmuir, 26, 11176-11183 (2010). [6] Mutiso RM, Sherrott MC, Rathmell AR, Wiley BJ, Winey KI. Integrating Simu-lations and Experiments To Predict Sheet Resistance and Optical Transmittance in Nanowire Films for Transparent Conductors. Acs Nano. 2013;7:7654-63. [7] Johnson CJ, Dujardin E, Davis SA, Murphy CJ, Mann S. Growth and form of gold nanorods prepared by seed-mediated, surfactant-directed synthesis. J Mater Chem. 2002;12:1765-70. 7
[8] Wiley B, Sun YG, Mayers B, Xia YN. Shape-controlled synthesis of metal nano-structures: The case of silver. Chem-Eur J. 2005;11:454-63. [9] Korte KE, Skrabalak SE, Xia YN. Rapid synthesis of silver nanowires through a CuCl- or CuCl2mediated polyol process. J Mater Chem. 2008;18:437-41. [10] Amirjani A, Fatmehsari DH, Marashi P. Interactive effect of agitation rate and oxidative etching on growth mechanisms of silver nanowires during polyol process. J ExpNanosci. 2015;10:1387-400. [11] Wiley B, Herricks T, Sun YG, Xia YN. Polyol synthesis of silver nanoparticles: Use of chloride and oxygen to promote the formation of single-crystal, truncated cubes and tetrahedrons. Nano Lett. 2004;4:1733-9. [12] Araki T, Jiu JT, Nogi M, Koga H, Nagao S, Sugahara T, et al. Low haze transparent electrodes and highly conducting air dried films with ultra-long silver nanowires synthesized by one-step polyol method. Nano Res. 2014;7:236-45. [13] Staleva H, Skrabalak SE, Carey CR, Kosel T, Xia YN, Hartland GV. Coupling to light, and transport and dissipation of energy in silver nanowires. Phys Chem Chem Phys. 2009;11:5889-96. [14] Coskun S, Aksoy B, Unalan HE. Polyol Synthesis of Silver Nanowires: An Extensive Parametric Study. Cryst Growth Des. 2011;11:4963-9.
Figure Captions Fig.1 SEM images and length distribution of AgNWs synthesized with a), d) 0.38 mMNaCl, b), e) 0.19 mM and c), f) 0.36 mM CuCl2, respectively Fig.2 a) TEM image, and b) corresponding selected area diffraction pattern (SAED) of single silver nanowire. Inset picture in Fig. 2a shows the direction of electron beam. Fig.3 TEM images of AgNWs prepared at 160℃ with a) 0.38 mMNaCl, b) 0.19 mM and c) 0.36 mM CuCl2. d) is the statistic diameter of AgNWs under different condition. Fig.4 TEM images of samples after 6 min reaction with a) 0.19 mM and b) 0.36 mM CuCl 2, respectively.
Highlights AgNWs with mean length of 49.4 μm have been synthesized within only 30 min. 8
Longer AgNWs were achieved at higher concentration of Cu 2+ in shorter reaction time.
By adjusting the concentration of Cu2+, the diameter of AgNWs could be adjusted.
9