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Phospholipid-assisted synthesis of size-controlled gold nanoparticles
Materials Research Bulletin 42 (2007) 1310–1315 www.elsevier.com/locate/matresbu
Phospholipid-assisted synthesis of size-controlled gold nanoparticles Peng He a,*, Xinyuan Zhu b,** a
b
Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA Instrumental Analysis Center, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai 200030, PR China Received 5 March 2006; received in revised form 9 July 2006; accepted 8 October 2006 Available online 29 November 2006
Abstract Morphology and size control of gold nanoparticles (AuNPs) by phospholipids (PLs) has been reported. It was found that gold entities could form nanostructures with different sizes controlled by PLs in an aqueous solution. During the preparation of 1.5 nm gold seeds, AuNPs were obtained from the reduction of gold complex by sodium borohydride and capped by citrate for stabilization. With the different ratios between seed solution and growth solution, which was composed by gold complex and PLs, gold seeds grew into larger nanoparticles step by step until enough large size up to 30 nm. The main discovery of this work is that common biomolecules, such as PLs can be used to control nanoparticle size. This conclusion has been confirmed by transmission electron micrographs, particle size analysis, and UV–vis spectra. # 2006 Elsevier Ltd. All rights reserved. Keywords: A. Nanostructures; A. Surface; B. Chemical synthesis; B. Crystal growth
1. Introduction In the past few years, a number of studies have been conducted on the formation and morphology control of gold nanoparticles (AuNPs) with different sizes [1–8]. One of the most attractive properties of AuNPs is their capability of size-controlled structures, which may have potentially biomedical and molecular biology applications [9,10]. Different experimental conditions and reaction systems have been utilized to control the formation and morphology of gold nanostructures [11–18]. Although the formation and transformation of gold nanostructures into different sizes and shapes are determined by numerous factors, the selection of stabilizing agents plays a very important role [19–22]. For example, with the aid of cationic surfactants, AuNPs with a 5 nm diameter are formed at the initial stage in an aqueous solution, and then the particles grow into 40 nm gradually [19]. Similarly, when AuNPs are mixed with sodium dodecyl sulfate (SDS), one kind of anionic surfactants, nanoparticles with different sizes are generated in a water system. Furthermore, these entities are able to transform into different-shaped nanocrystals consisting of highly faceted pentagonal- or hexagonal-morphology [20]. In the context of the previous studies, a couple of experiments have been proposed to induce gold nanostructure formation based on different reaction conditions. The primary driving force for controlling particle size comes from the combination of the spontaneous particle aggregations and the particle-size restrictive properties of stabilizer [23,24]. Although such considerations provide grounds for chemical stabilizing agents, the biological surfactants * Corresponding author. Tel.: +1 919 515 4691. ** Corresponding author. Tel.: +86 21 62932997; fax: +86 21 62932067. E-mail addresses: [email protected] (P. He), [email protected] (X. Zhu). 0025-5408/$ – see front matter # 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.materresbull.2006.10.014
P. He, X. Zhu / Materials Research Bulletin 42 (2007) 1310–1315
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leading to size-controlled AuNPs are not fully accessed. Our studies focused on the in situ transient step-growth of AuNPs controlled by phospholipids (PLs) in an aqueous phase, which led to the formation of gold nanostructures with stimuli–responsive characteristics. Moreover, the transient effects occurring during AuNPs formation were also examined by using transmission electron microscopy (TEM), particle size analysis, and UV–vis spectroscopy. 2. Experimental 2.1. Materials 1,2-Bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine PL was purchased from Avanti Polar Lipids, Inc. Au(III) chloride trihydrate HAuCl43H2O, trisodium citrate, sodium borohydride NaBH4, and ascorbic acid were purchased from Aldrich Chemical Inc. 2.2. Preparation of seed solution A 20 mL aqueous solution containing 2.5 10 4 M HAuCl4 (2 mg) and 2.5 10 4 M trisodium citrate (1.5 mg) was prepared in a conical flask. Then, the ice-cold, freshly prepared 0.1 M NaBH4 (0.6 mL, 2.3 mg) was added into the solution under stirring. The solution turned pink immediately after the addition of NaBH4, indicating particle formation. The particles in this solution were used as 1.5 nm Au seeds within 2–5 h after preparation. Here, citrate serves only as a capping agent since it cannot reduce the gold salt at room temperature (25 8C). 2.3. Preparation of growth solution A 50 mL aqueous solution of 2.5 10 4 M HAuCl4 (5 mg) was prepared in a conical flask. Then, 46 mg solid 1,2bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine PL (0.001 M final concentration) was added into the solution, and the mixture was heated until the solution turned a clear purple color. Finally, the solution was cooled to room temperature and used as a stock growth solution. 2.4. Preparation of size-controlled gold nanoparticles Three sets of 25 mL conical flask were labeled A, B, and C, respectively. In set A, 7.5 mL growth solution was mixed with freshly prepared 0.1 M ascorbic acid solution (0.05 mL, 1 mg). Then, 2.5 mL seed solution was added under stirring. Stirring continued for 10 min after the solution turned reddish purple. Particles prepared by this way were spherical with a diameter of 10 nm. Similarly, 9 mL growth solution and 0.1 M ascorbic acid solution (0.05 mL, 1 mg) were mixed as set B, and 1.0 mL seed solution was added under vigorously stirring. Stirring continued for 10 min. The solution’s final color was ruby purple. Particles prepared by this way were spherical with a diameter of 17 nm. The particles prepared here were used as seeds in set C. In set C, 9 mL growth solution was mixed with 0.1 M ascorbic acid solution (0.05 mL, 1 mg), and then 1.0 mL solution from set B was added under stirring vigorously. Stirring was continued for 10 min. The final color of the solution was deep purple. Particles prepared by this way were roughly spherical with a diameter of 30 nm. 2.5. Characterizations Transmission electron micrographs were acquired on a Zeiss EM 109T microscope using an accelerating voltage of 50 kV. Liquid specimens were diluted in deionized water by a factor of 100, followed by casting onto Formvar-coated copper grids (T. Pella, Inc.). Particle size analysis was performed using a Microtrac Particle Size Analyzer model UPA250. UV–vis absorption spectra were recorded using a Cary 500 Scan UV–vis near-IR spectrophotometer (Varian). Specimens were dissolved in double deionize (DDI) water. 3. Results and discussion AuNPs are known to form unique sizes and shapes which are primarily a function of their chemical and physical features as well as preparation conditions. Although there have been a number of studies that focused on size- and
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Fig. 1. Scheme of preparation of phospholipid-assisted size-controlled gold nanoparticles.
Fig. 2. TEM images of gold nanoparticles with different sizes in diameter: (a) 1.5 nm, (b) 10 nm, (c) 17 nm, and (d) 30 nm.
P. He, X. Zhu / Materials Research Bulletin 42 (2007) 1310–1315
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shape-controlled AuNPs and showed that these species might be generated in an aqueous phase with the aid of chemical agents, biological stabilizers leading to size-controlled AuNPs formation are not well established. Here, we propose to use the biomolecules PLs to control the size of nanoparticles. As illustrated in Fig. 1, three steps to show biomolecular control for particle size are involved: (1) the formation of gold seeds produced by NaBH4 reduction and stabilized by citrate; (2) the preparation of growth agents formed by HAuCl4 and PL mixture; (3) the size-controlled synthesis of AuNPs with different ratios between seed solution and growth solution. To provide evidences that the size of AuNPs could be adjusted readily by such an approach, the TEM measurements were performed. Fig. 2a–d gives TEM images of AuNPs formed by pure seeds, growth/seeds 3:1 (A step), growth/ seeds 9:1 (B step), and growth/B step 9:1 (C step), respectively. It can be found that the particle sizes change from 1.5 nm (A) to 10 nm (B), 17 nm (C), and 30 nm (D). The 10 and 17 nm particles were achieved by one-step seeding and adjusting the ratio between gold seeds and gold complex. The 30 nm size particles were obtained by stepwise seeding where 17 nm particles were employed as seeds in the growth process. When the nanoparticles were gradually produced during the size enlargement, the fraction of nonspherical-shaped particles increased. The formation of these highly nonspherical nanoparticles may be related to the ineffective capping interactions between the lamellar micelle structures formed by the PL molecules and the nanoparticles. Fig. 3 shows the evolution of the gold nanoparticle size as a function of different ratios of seed/growth solution. The particle size data are interpreted in terms of a classical nucleation/diffusional growth model. Here, the initially formed gold atoms self-nucleate to form a determined number of seeds during the first stage of the reaction, and particles then continue to grow by diffusion-driven deposition of gold atoms reduced from growth solution onto these existing seeds. The UV–vis spectra are shown in Fig. 4 and the particle plasmon absorption bands at 512 nm become blunt and broad with increasing particle size from 1.5 to 30 nm. The absorbance band at 512 nm is the characteristic feature of gold plasmon resonance. The plasmon bands take red shifts from 512 to 550 nm for particle sizes from 1.5 to 30 nm. The absorbance increase is due to the progressive growth in particle size and large molar extinction coefficient from
Fig. 3. Particle size analysis of gold nanoparticles with different sizes in diameter: (a) 1.5 nm, (b) 10 nm, (c) 17 nm, and (d) 30 nm.
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Fig. 4. UV–vis spectra of gold nanoparticles with different sizes in diameter: (a) 1.5 nm, (b) 10 nm, (c) 17 nm, and (d) 30 nm.
large particle, indicating the aggregation of gold seeds triggered by growth solution. The absorbance increase for 30 nm size particles was not distinct since some of the gold complex was reduced to aggregate to form nonspherical particles, which decreased the total surface of gold particles. Based on these experimental data which combine both morphological and spectroscopic measurements, the distinguished advantages of biological surfactants leading to size-controlled AuNPs are constructed. Generally speaking, surface derivatization of AuNPs is often essential to control their self-assembly and physical properties. This can be achieved by ligand exchange reactions of alkanethiol-capped AuNPs with other functionalized thiol derivatives, leading to particle aggregation during the process. In comparison with the surface derivatization approach, the biological surfactant stabilization for size-controlled AuNPs displays several merits in this respect: first, the particle stabilization does not contain the strong gold–thiol bonding connection, which benefits the easy removal of surfactants; second, the presence of surfactants can homogeneously disperse the AuNPs that are originally insoluble in an aqueous solution; third, the size growth is a continuous process in which the current AuNPs can be used as catalysts for upcoming growth according to the diffusional growth mechanism [25]; fourth, size-controlled AuNPs are manipulated by PLs, one of the main components of cell membrane, which induces a potential biocompatible probe applied into the drug delivery in live cells. 4. Conclusions A new approach to control the size of gold nanoparticles (AuNPs) by the biomolecules phospholipids (PLs) has been developed. Our studies illustrate that the synthesis of size-controlled AuNPs is determined by several factors, including the different ratios of seed solution/growth solution and the composition of seed solution and growth solution. Furthermore, the growth process of different-sized nanoparticles is in situ tracked by morphological and spectroscopic techniques, which demonstrates the advantages of PLs as biological surfactants to control nanoscale size. With increasing the ratio of growth solution/seed solution, the size of AuNPs enlarges from 1.5 to 30 nm. In the meantime, the morphology of correspondent AuNPs changes from spherical shape into nonspherical shape. Acknowledgments This work was financially supported by the National Natural Science Foundation of China (Nos. 20574044 and 20104004) and by Shanghai Rising-Star Program (06QA14029). References [1] M.C. Daniel, D. Astruc, Chem. Rev. 104 (2004) 293. [2] T. Yonezawa, M. Sutoh, T. Kunitake, Chem. Lett. 26 (1997) 619.
P. He, X. Zhu / Materials Research Bulletin 42 (2007) 1310–1315 [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25]
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B.L. Cushing, V.L. Kolesnichenko, C.J. O’Connor, Chem. Rev. 104 (2004) 3893. Y. Sun, Y. Xia, Science 298 (2002) 2176. E. Katz, I. Willner, Angew. Chem. Int. Ed. 43 (2004) 6042. R. Wang, J. Yang, Z. Zheng, M.D. Carducci, J. Jiao, S. Seraphin, Angew. Chem. Int. Ed. 40 (2001) 549. I. Hussain, S. Graham, Z. Wang, B. Tan, D.C. Sherrington, S.P. Rannard, A.I. Cooper, M. Brust, J. Am. Chem. Soc. 127 (2005) 16398. C.H. Walker, J.V.S. John, P. Wisian-Neilson, J. Am. Chem. Soc. 123 (2001) 3846. A.J.S. Venkataraman, C. Subramaniam, R.R. Kumar, S. Priya, T.R.S. Kumar, R.V. Omkumar, A. John, T. Pradeep, Langmuir 21 (2005) 11562. W. Lu, W. Wang, Y. Su, J. Li, L. Jiang, Nanotechnology 16 (2005) 2582. T. Shimizu, T. Teranishi, S. Hasegawa, M. Miyake, J. Phys. Chem. B 107 (2003) 2719. Y. Liu, L. Lin, W. Chiu, J. Phys. Chem. B 108 (2004) 19237. J.P. Sylvestre, A.V. Kabashin, E. Sacher, M. Meunier, J.H. Luong, J. Am. Chem. Soc. 126 (2004) 7176. L.O. Brown, J.E. Hutchison, J. Am. Chem. Soc. 121 (1999) 882. J.P. Wilcoxon, P.P. Provencio, J. Am. Chem. Soc. 126 (2004) 6402. J. Deng, C. Wu, C. Yang, C. Mou, Langmuir 21 (2005) 8947. M. Mandal, S.K. Ghosh, S. Kundu, K. Esumi, T. Pal, Langmuir 18 (2002) 7792. D.A. Fleming, M.E. Williams, Langmuir 20 (2004) 3021. N.R. Jana, L. Gearheart, C.J. Murphy, Langmuir 17 (2001) 6782. C. Kuo, T. Chiang, L. Chen, M.H. Huang, Langmuir 20 (2004) 7820. C. Kuo, M.H. Huang, Langmuir 21 (2005) 2012. H. Hiramatsu, F.E. Osterloh, Chem. Mater. 16 (2004) 2509. K.R. Brown, D.G. Walter, M.J. Natan, Chem. Mater. 12 (2000) 306. J. Wagner, J.M. Kohler, Nano Lett. 5 (2005) 685. X. Peng, J. Wickham, A.P. Alivisatos, J. Am. Chem. Soc. 120 (1998) 5343.
Phospholipid-assisted synthesis of size-controlled gold nanoparticles Peng He a,*, Xinyuan Zhu b,** a
b
Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA Instrumental Analysis Center, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai 200030, PR China Received 5 March 2006; received in revised form 9 July 2006; accepted 8 October 2006 Available online 29 November 2006
Abstract Morphology and size control of gold nanoparticles (AuNPs) by phospholipids (PLs) has been reported. It was found that gold entities could form nanostructures with different sizes controlled by PLs in an aqueous solution. During the preparation of 1.5 nm gold seeds, AuNPs were obtained from the reduction of gold complex by sodium borohydride and capped by citrate for stabilization. With the different ratios between seed solution and growth solution, which was composed by gold complex and PLs, gold seeds grew into larger nanoparticles step by step until enough large size up to 30 nm. The main discovery of this work is that common biomolecules, such as PLs can be used to control nanoparticle size. This conclusion has been confirmed by transmission electron micrographs, particle size analysis, and UV–vis spectra. # 2006 Elsevier Ltd. All rights reserved. Keywords: A. Nanostructures; A. Surface; B. Chemical synthesis; B. Crystal growth
1. Introduction In the past few years, a number of studies have been conducted on the formation and morphology control of gold nanoparticles (AuNPs) with different sizes [1–8]. One of the most attractive properties of AuNPs is their capability of size-controlled structures, which may have potentially biomedical and molecular biology applications [9,10]. Different experimental conditions and reaction systems have been utilized to control the formation and morphology of gold nanostructures [11–18]. Although the formation and transformation of gold nanostructures into different sizes and shapes are determined by numerous factors, the selection of stabilizing agents plays a very important role [19–22]. For example, with the aid of cationic surfactants, AuNPs with a 5 nm diameter are formed at the initial stage in an aqueous solution, and then the particles grow into 40 nm gradually [19]. Similarly, when AuNPs are mixed with sodium dodecyl sulfate (SDS), one kind of anionic surfactants, nanoparticles with different sizes are generated in a water system. Furthermore, these entities are able to transform into different-shaped nanocrystals consisting of highly faceted pentagonal- or hexagonal-morphology [20]. In the context of the previous studies, a couple of experiments have been proposed to induce gold nanostructure formation based on different reaction conditions. The primary driving force for controlling particle size comes from the combination of the spontaneous particle aggregations and the particle-size restrictive properties of stabilizer [23,24]. Although such considerations provide grounds for chemical stabilizing agents, the biological surfactants * Corresponding author. Tel.: +1 919 515 4691. ** Corresponding author. Tel.: +86 21 62932997; fax: +86 21 62932067. E-mail addresses: [email protected] (P. He), [email protected] (X. Zhu). 0025-5408/$ – see front matter # 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.materresbull.2006.10.014
P. He, X. Zhu / Materials Research Bulletin 42 (2007) 1310–1315
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leading to size-controlled AuNPs are not fully accessed. Our studies focused on the in situ transient step-growth of AuNPs controlled by phospholipids (PLs) in an aqueous phase, which led to the formation of gold nanostructures with stimuli–responsive characteristics. Moreover, the transient effects occurring during AuNPs formation were also examined by using transmission electron microscopy (TEM), particle size analysis, and UV–vis spectroscopy. 2. Experimental 2.1. Materials 1,2-Bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine PL was purchased from Avanti Polar Lipids, Inc. Au(III) chloride trihydrate HAuCl43H2O, trisodium citrate, sodium borohydride NaBH4, and ascorbic acid were purchased from Aldrich Chemical Inc. 2.2. Preparation of seed solution A 20 mL aqueous solution containing 2.5 10 4 M HAuCl4 (2 mg) and 2.5 10 4 M trisodium citrate (1.5 mg) was prepared in a conical flask. Then, the ice-cold, freshly prepared 0.1 M NaBH4 (0.6 mL, 2.3 mg) was added into the solution under stirring. The solution turned pink immediately after the addition of NaBH4, indicating particle formation. The particles in this solution were used as 1.5 nm Au seeds within 2–5 h after preparation. Here, citrate serves only as a capping agent since it cannot reduce the gold salt at room temperature (25 8C). 2.3. Preparation of growth solution A 50 mL aqueous solution of 2.5 10 4 M HAuCl4 (5 mg) was prepared in a conical flask. Then, 46 mg solid 1,2bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine PL (0.001 M final concentration) was added into the solution, and the mixture was heated until the solution turned a clear purple color. Finally, the solution was cooled to room temperature and used as a stock growth solution. 2.4. Preparation of size-controlled gold nanoparticles Three sets of 25 mL conical flask were labeled A, B, and C, respectively. In set A, 7.5 mL growth solution was mixed with freshly prepared 0.1 M ascorbic acid solution (0.05 mL, 1 mg). Then, 2.5 mL seed solution was added under stirring. Stirring continued for 10 min after the solution turned reddish purple. Particles prepared by this way were spherical with a diameter of 10 nm. Similarly, 9 mL growth solution and 0.1 M ascorbic acid solution (0.05 mL, 1 mg) were mixed as set B, and 1.0 mL seed solution was added under vigorously stirring. Stirring continued for 10 min. The solution’s final color was ruby purple. Particles prepared by this way were spherical with a diameter of 17 nm. The particles prepared here were used as seeds in set C. In set C, 9 mL growth solution was mixed with 0.1 M ascorbic acid solution (0.05 mL, 1 mg), and then 1.0 mL solution from set B was added under stirring vigorously. Stirring was continued for 10 min. The final color of the solution was deep purple. Particles prepared by this way were roughly spherical with a diameter of 30 nm. 2.5. Characterizations Transmission electron micrographs were acquired on a Zeiss EM 109T microscope using an accelerating voltage of 50 kV. Liquid specimens were diluted in deionized water by a factor of 100, followed by casting onto Formvar-coated copper grids (T. Pella, Inc.). Particle size analysis was performed using a Microtrac Particle Size Analyzer model UPA250. UV–vis absorption spectra were recorded using a Cary 500 Scan UV–vis near-IR spectrophotometer (Varian). Specimens were dissolved in double deionize (DDI) water. 3. Results and discussion AuNPs are known to form unique sizes and shapes which are primarily a function of their chemical and physical features as well as preparation conditions. Although there have been a number of studies that focused on size- and
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P. He, X. Zhu / Materials Research Bulletin 42 (2007) 1310–1315
Fig. 1. Scheme of preparation of phospholipid-assisted size-controlled gold nanoparticles.
Fig. 2. TEM images of gold nanoparticles with different sizes in diameter: (a) 1.5 nm, (b) 10 nm, (c) 17 nm, and (d) 30 nm.
P. He, X. Zhu / Materials Research Bulletin 42 (2007) 1310–1315
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shape-controlled AuNPs and showed that these species might be generated in an aqueous phase with the aid of chemical agents, biological stabilizers leading to size-controlled AuNPs formation are not well established. Here, we propose to use the biomolecules PLs to control the size of nanoparticles. As illustrated in Fig. 1, three steps to show biomolecular control for particle size are involved: (1) the formation of gold seeds produced by NaBH4 reduction and stabilized by citrate; (2) the preparation of growth agents formed by HAuCl4 and PL mixture; (3) the size-controlled synthesis of AuNPs with different ratios between seed solution and growth solution. To provide evidences that the size of AuNPs could be adjusted readily by such an approach, the TEM measurements were performed. Fig. 2a–d gives TEM images of AuNPs formed by pure seeds, growth/seeds 3:1 (A step), growth/ seeds 9:1 (B step), and growth/B step 9:1 (C step), respectively. It can be found that the particle sizes change from 1.5 nm (A) to 10 nm (B), 17 nm (C), and 30 nm (D). The 10 and 17 nm particles were achieved by one-step seeding and adjusting the ratio between gold seeds and gold complex. The 30 nm size particles were obtained by stepwise seeding where 17 nm particles were employed as seeds in the growth process. When the nanoparticles were gradually produced during the size enlargement, the fraction of nonspherical-shaped particles increased. The formation of these highly nonspherical nanoparticles may be related to the ineffective capping interactions between the lamellar micelle structures formed by the PL molecules and the nanoparticles. Fig. 3 shows the evolution of the gold nanoparticle size as a function of different ratios of seed/growth solution. The particle size data are interpreted in terms of a classical nucleation/diffusional growth model. Here, the initially formed gold atoms self-nucleate to form a determined number of seeds during the first stage of the reaction, and particles then continue to grow by diffusion-driven deposition of gold atoms reduced from growth solution onto these existing seeds. The UV–vis spectra are shown in Fig. 4 and the particle plasmon absorption bands at 512 nm become blunt and broad with increasing particle size from 1.5 to 30 nm. The absorbance band at 512 nm is the characteristic feature of gold plasmon resonance. The plasmon bands take red shifts from 512 to 550 nm for particle sizes from 1.5 to 30 nm. The absorbance increase is due to the progressive growth in particle size and large molar extinction coefficient from
Fig. 3. Particle size analysis of gold nanoparticles with different sizes in diameter: (a) 1.5 nm, (b) 10 nm, (c) 17 nm, and (d) 30 nm.
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Fig. 4. UV–vis spectra of gold nanoparticles with different sizes in diameter: (a) 1.5 nm, (b) 10 nm, (c) 17 nm, and (d) 30 nm.
large particle, indicating the aggregation of gold seeds triggered by growth solution. The absorbance increase for 30 nm size particles was not distinct since some of the gold complex was reduced to aggregate to form nonspherical particles, which decreased the total surface of gold particles. Based on these experimental data which combine both morphological and spectroscopic measurements, the distinguished advantages of biological surfactants leading to size-controlled AuNPs are constructed. Generally speaking, surface derivatization of AuNPs is often essential to control their self-assembly and physical properties. This can be achieved by ligand exchange reactions of alkanethiol-capped AuNPs with other functionalized thiol derivatives, leading to particle aggregation during the process. In comparison with the surface derivatization approach, the biological surfactant stabilization for size-controlled AuNPs displays several merits in this respect: first, the particle stabilization does not contain the strong gold–thiol bonding connection, which benefits the easy removal of surfactants; second, the presence of surfactants can homogeneously disperse the AuNPs that are originally insoluble in an aqueous solution; third, the size growth is a continuous process in which the current AuNPs can be used as catalysts for upcoming growth according to the diffusional growth mechanism [25]; fourth, size-controlled AuNPs are manipulated by PLs, one of the main components of cell membrane, which induces a potential biocompatible probe applied into the drug delivery in live cells. 4. Conclusions A new approach to control the size of gold nanoparticles (AuNPs) by the biomolecules phospholipids (PLs) has been developed. Our studies illustrate that the synthesis of size-controlled AuNPs is determined by several factors, including the different ratios of seed solution/growth solution and the composition of seed solution and growth solution. Furthermore, the growth process of different-sized nanoparticles is in situ tracked by morphological and spectroscopic techniques, which demonstrates the advantages of PLs as biological surfactants to control nanoscale size. With increasing the ratio of growth solution/seed solution, the size of AuNPs enlarges from 1.5 to 30 nm. In the meantime, the morphology of correspondent AuNPs changes from spherical shape into nonspherical shape. Acknowledgments This work was financially supported by the National Natural Science Foundation of China (Nos. 20574044 and 20104004) and by Shanghai Rising-Star Program (06QA14029). References [1] M.C. Daniel, D. Astruc, Chem. Rev. 104 (2004) 293. [2] T. Yonezawa, M. Sutoh, T. Kunitake, Chem. Lett. 26 (1997) 619.
P. He, X. Zhu / Materials Research Bulletin 42 (2007) 1310–1315 [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25]
1315
B.L. Cushing, V.L. Kolesnichenko, C.J. O’Connor, Chem. Rev. 104 (2004) 3893. Y. Sun, Y. Xia, Science 298 (2002) 2176. E. Katz, I. Willner, Angew. Chem. Int. Ed. 43 (2004) 6042. R. Wang, J. Yang, Z. Zheng, M.D. Carducci, J. Jiao, S. Seraphin, Angew. Chem. Int. Ed. 40 (2001) 549. I. Hussain, S. Graham, Z. Wang, B. Tan, D.C. Sherrington, S.P. Rannard, A.I. Cooper, M. Brust, J. Am. Chem. Soc. 127 (2005) 16398. C.H. Walker, J.V.S. John, P. Wisian-Neilson, J. Am. Chem. Soc. 123 (2001) 3846. A.J.S. Venkataraman, C. Subramaniam, R.R. Kumar, S. Priya, T.R.S. Kumar, R.V. Omkumar, A. John, T. Pradeep, Langmuir 21 (2005) 11562. W. Lu, W. Wang, Y. Su, J. Li, L. Jiang, Nanotechnology 16 (2005) 2582. T. Shimizu, T. Teranishi, S. Hasegawa, M. Miyake, J. Phys. Chem. B 107 (2003) 2719. Y. Liu, L. Lin, W. Chiu, J. Phys. Chem. B 108 (2004) 19237. J.P. Sylvestre, A.V. Kabashin, E. Sacher, M. Meunier, J.H. Luong, J. Am. Chem. Soc. 126 (2004) 7176. L.O. Brown, J.E. Hutchison, J. Am. Chem. Soc. 121 (1999) 882. J.P. Wilcoxon, P.P. Provencio, J. Am. Chem. Soc. 126 (2004) 6402. J. Deng, C. Wu, C. Yang, C. Mou, Langmuir 21 (2005) 8947. M. Mandal, S.K. Ghosh, S. Kundu, K. Esumi, T. Pal, Langmuir 18 (2002) 7792. D.A. Fleming, M.E. Williams, Langmuir 20 (2004) 3021. N.R. Jana, L. Gearheart, C.J. Murphy, Langmuir 17 (2001) 6782. C. Kuo, T. Chiang, L. Chen, M.H. Huang, Langmuir 20 (2004) 7820. C. Kuo, M.H. Huang, Langmuir 21 (2005) 2012. H. Hiramatsu, F.E. Osterloh, Chem. Mater. 16 (2004) 2509. K.R. Brown, D.G. Walter, M.J. Natan, Chem. Mater. 12 (2000) 306. J. Wagner, J.M. Kohler, Nano Lett. 5 (2005) 685. X. Peng, J. Wickham, A.P. Alivisatos, J. Am. Chem. Soc. 120 (1998) 5343.