Solvent: A Key in Digestive Ripening for Monodisperse Au Nanoparticles

Nanoscale Research Letters, Jan 2017

This work has mainly investigated the influence of the solvent on the nanoparticles distribution in digestive ripening. The experiments suggested that the solvents played a key role in digestive ripening of Au nanoparticles (Au NPs). For the benzol solvents, the resulting size distribution of Au NPs was inversely related to the solvent polarity. It may be interpreted by the low Gibbs free energy of nanoparticles in the high polarity medium, which was supposedly in favor of reducing the nanoparticles distribution. Through digestive ripening in the highly polar benzol solvent of p-chlorotoluene, monodisperse Au NPs with relative standard deviation (RSD) of 4.8% were achieved. This indicated that digestive ripening was an effective and practical way to prepare high-quality nanoparticles, which holds great promise for the nanoscience and nanotechnology. Graphical Abstract The polarity of benzol solvent plays significant role in obtaining high-quality monodisperse Au nanoparticles.

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Solvent: A Key in Digestive Ripening for Monodisperse Au Nanoparticles

Wang et al. Nanoscale Research Letters Solvent: A Key in Digestive Ripening for Monodisperse Au Nanoparticles Peng Wang 0 Xuan Qi 0 Xuemin Zhang 0 Tieqiang Wang 0 Yunong Li 0 Kai Zhang 0 Shuang Zhao 0 Jun Zhou 0 1 Yu Fu 0 0 College of Sciences, Northeastern University , Shenyang 110004 , China 1 School of Materials Science and Engineering, Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University , Shenyang 110004 , China This work has mainly investigated the influence of the solvent on the nanoparticles distribution in digestive ripening. The experiments suggested that the solvents played a key role in digestive ripening of Au nanoparticles (Au NPs). For the benzol solvents, the resulting size distribution of Au NPs was inversely related to the solvent polarity. It may be interpreted by the low Gibbs free energy of nanoparticles in the high polarity medium, which was supposedly in favor of reducing the nanoparticles distribution. Through digestive ripening in the highly polar benzol solvent of p-chlorotoluene, monodisperse Au NPs with relative standard deviation (RSD) of 4.8% were achieved. This indicated that digestive ripening was an effective and practical way to prepare high-quality nanoparticles, which holds great promise for the nanoscience and nanotechnology. Solvent polarity; Digestive ripening; Au nanoparticles; Monodispersity - Background Au nanoparticles (Au NPs) and their self-assemblies have drawn intense attentions due to their unique properties and potential applications [1, 2], such as catalysts [3], electronic and optoelectronic nanodevices [4], biosensors [5], and biomedicine [6]. For fully implementing the functions of Au NPs, the uniform size distribution is of key significance. The monodisperse nanoparticles (relative standard deviation less than 5.0%) show unique properties and higher performances compared with the corresponding polydisperse ones [7, 8]. Unfortunately, it is hard to prepare monodisperse Au NPs with simple synthesis process and common starting materials [9–11]. Therefore, a great deal of effort has been made to obtain monodisperse Au NPs [12]. One main strategy is direct alteration of the synthesis method, including selection of special metal sources and reduction agents, introduction of nanoparticle seeds, addition of surfactants, and so on. However, although the monodisperse Au NPs have been achieved by direct synthesis [13], it suffers from high-cost of starting materials, tedious separation and unsatisfied repeatability. An alternative approach to preparing monodisperse Au NPs is post-treatment of the prepared ones, which could detour the issue. Digestive ripening, discovered by Lin [14], is an effective post-treatment method. It is carried on by refluxing a nanoparticle suspension with an excess amount of capping agents (called as digestive ripening agents (DRA)), which could cause the shrink of large particles and the growth of small particles to achieve an equilibrium size at a stable state [11, 12]. A distinct feature of digestive ripening is that it can obtain high reproducibility and yield with fine control [15]. The effect factors on digestive ripening, including capping agent, temperature, refluxing time, field effect, and the length of digestive ripening agent, have been explored [11, 16–20]. Solvent is an important participant in digestive ripening. Moreover, the study has shown the solvent plays a vital role in the synthesis process, which implied the effect of the solvent on digestive ripening would be remarkable. However, the related work has been rarely reported. In addition, thus far the monodisperse Au nanoparticles obtained by digestive ripening mainly came from the system reported by Lin [11]. In that system, the original Au nanoparticles were synthesized by a surfactantassisted method. Its process was tedious and the yield © The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. was low, that substantially weakened the advantage of digestive ripening. Based on the above consideration, digestive ripening of Au NPsin different solvents was investigated in this work. The experiments showed that there was no obviously development in size distribution of Au NPs in the solvents of linear hydrocarbon. However, there was a dramatic change when benzol solvents were used. Moreover, the distribution was closely related with the solvent polarity. The higher the polarity of the used solvent is, the lower the RSD of the resulting nanoparticles is. When a highly polar benzol of p-chlorotoluene was used as the reflux solvent, RSD of the Au NPs (...truncated)


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Peng Wang, Xuan Qi, Xuemin Zhang, Tieqiang Wang, Yunong Li, Kai Zhang, Shuang Zhao, Jun Zhou, Yu Fu. Solvent: A Key in Digestive Ripening for Monodisperse Au Nanoparticles, Nanoscale Research Letters, 2017, pp. 25, Volume 12, Issue 1, DOI: 10.1186/s11671-016-1797-7