The surface chemistry of Au colloids and their interactions with functional amino acids
The surface chemistry of Au colloids and their interactions with functional amino acids
复制标题
DOI：
10.1021/jp037056a
复制
发表时间：
2004-04-01
影响因子：
3.3
通讯作者：
Gedanken, A
中科院分区：
文献类型：
--
作者：
Zhong, ZY;Patskovskyy, S;Gedanken, A
这里报道的工作描述了纳米级Au胶体和两种主要类型的有机官能团之间的相互作用，即，烷硫醇和氨基酸。颗粒Au的表面化学主要由与其（负）表面电荷相关的电动因素决定。广义多粒子Mie计算被用来模拟Au粒子的光吸收特性，存在于单独或在不同程度的聚集。标准（单分散）Au胶体的实验证实了理论预测的一个新的峰出现在较长的波长，增强和位移进一步从原始峰的颗粒尺寸的增加，增加聚集体的大小，或更短的颗粒间的间距。通过明智地选择端基组成（单端或双端）、烷基链长度和pH敏感基团（如羧酸根）的存在来控制烷硫醇中的聚集度。在氨基酸中，发现α-胺（与-COOH相邻）的反应性是pH依赖性的。通过α-胺的连接在低pH下被激活，但在中等和高pH下由于Au表面与带电羧酸酯基团或甚至酰胺中的（形式上中性的）极性羰基之间的静电排斥力而被抑制。然而，二元氨基酸仍然可以用于在高pH下交联Au胶体。pH不敏感的（远程）胺将氨基酸结合到每个颗粒上，留下突出的α-胺对，其可以通过对称的连接分子如戊二醛（通过其亲电中心）桥接。这提供了一种新的方式来组织Au纳米粒子到扩展的架构和功能材料在很宽的pH范围内。Au胶体识别和确定二元氨基酸的基础上的光学吸收变化的潜力进行了简要评估。对于较大（40 nm）的Au颗粒，半胱氨酸的检测限较高（1.2 μ g/mL）。
The work reported here describes interactions between nanoscale Au colloids and two main types of organic functional groups, viz., alkanethiols and amino acids. The surface chemistry of particulate Au is dominated by electrodynamic factors related to its (negative) surface charge. Generalized multiparticle Mie calculations were used to model the optical absorption characteristics of Au particles, existing either singly or in varying degrees of aggregation. Experiments with standard (monodisperse) Au colloids confirm the theoretical prediction of a new peak appearing at longer wavelength that intensifies and shifts further from the original peak with increasing particle size, increasing aggregate size, or shorter interparticle spacing. Control of aggregation degree in alkanethiols is achieved by judicious selection of terminal group composition (single- or double-ended), alkyl chain length, and the presence of pH sensitive groups such as carboxylates. In amino acids, the reactivity of the alpha-amine (adjacent to -COOH) is found to be pH-dependent. Linking via the alpha-amine is activated at low pH but suppressed at intermediate and high pH due to electrostatic repulsive forces between the Au surface and the charged carboxylate group or even the (formally neutral) polar carbonyl group in amides. However, dibasic amino acids can still be used to cross-link Au colloids at high pH. The pH insensitive (remote) amine binds amino acids to each particle, leaving protruding pairs of alpha-amines that can be bridged by a symmetrical linker molecule like glutaraldehyde (via its electrophilic centers). This offers a new way to organize Au nanoparticles into extended architectures and functional materials over a wide range of pH. The potential of Au colloids to recognize and determine dibasic amino acids based on optical absorption changes is briefly assessed. A higher detection limit for cysteine (1.2,mug/mL) was found for larger (40 nm) Au particles.