Controlled Synthesis of Gold Nanostars by Using a Zwitterionic Surfactant
Controlled Synthesis of Gold Nanostars by Using a Zwitterionic Surfactant
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DOI：
10.1002/chem.201201024
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发表时间：
2012-07-01
影响因子：
4.3
通讯作者：
Pallavicini, Piersandro
中科院分区：
文献类型：
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作者：
Casu, Alberto;Cabrini, Elisa;Pallavicini, Piersandro
在经典的晶种生长法中，用十二烷基磺基甜菜碱（LSB）表面活性剂取代十六烷基三甲基溴化铵（CTAB），得到了单晶金纳米星（m-NS）和五元金不对称纳米星（a-NS）。在所有合成条件下的主要产物是α-NS，其具有高纵横比（AR）的分支，从而导致在750 - 1150 nm范围内的LSPR吸收。m-NS相对于a-NS的百分比、a-NS分支的纵横比以及因此它们的LSPR吸收的位置可以简单地通过调节还原剂的浓度、表面活性剂的浓度或催化Ag+阳离子的浓度来精细地调节。m-NS具有更短和更大的分支，其AR受合成条件的影响很小，并显示位于700 nm左右的LSPR。的生长机制，涉及的LSB的硫酸根部分的纳米物体的表面上的直接接触提出，从而意味着优先涂层的{111} Au面与弱相互作用。与此一致，我们还观察到LSB表面活性剂从纳米星表面直接完全置换。这是通过在水溶液中简单地加入硫醇以产生极其稳定的涂覆的a-NS和m-NS来获得的，所述a-NS和m-NS耐受高度酸性、碱性并且在类似于体内条件下。
By replacing cetyltrimethylammonium bromide (CTAB) with the zwitterionic lauryl sulfobetaine (LSB) surfactant in the classical seed-growth synthesis, monocrystalline gold nanostars (m-NS) and pentatwinned gold asymmetric nanostars (a-NS) were obtained instead of nanorods. The main product under all synthetic conditions was a-NS, which have branches with high aspect ratios (AR), thus leading to LSPR absorptions in the 7501150 nm range. The percentage of m-NS versus a-NS, the aspect ratio of the a-NS branches, and consequently the position of their LSPR absorption can be finely tuned simply by regulating the concentration of reductant, the concentration of surfactant, or the concentration of the catalytic Ag+ cation. The m-NS have instead shorter and larger branches, the AR of which is poorly influenced by synthetic conditions and displays an LSPR positioned around 700 nm. A growth mechanism that involves the direct contact of the sulfate moiety of LSB on the surface of the nano-object is proposed, thereby implying preferential coating of the {111} Au faces with weak interactions. Consistent with this, we also observed the straightforward complete displacement of the LSB surfactant from the surface of the nanostars. This was obtained by the simple addition of thiols in aqueous solution to yield extremely stable coated a-NS and m-NS that are resistant to highly acidic, basic, and in similar to in vivo conditions.