中文摘要：

研究了两性离子配体修饰的金纳米颗粒在酸性和碱性溶液中的稳定性和可逆聚集性．测量了金溶胶在不同条件下的UV-Vis吸收光谱，通过光谱的变化揭示其稳定性和可逆聚集性．结果表明：经配体修饰的金纳米颗粒在酸性和碱性溶液中的稳定性有了很大的提高：强酸性条件可诱导金溶胶失稳聚沉，回调pH值又可使其重新分散．利用这种pH依赖的可逆聚集特性，可以将稀溶胶浓缩成浓溶胶或固体保存，一旦需要又可加水恢复到分散的状态．

英文摘要：

In this work, the stability and reversible aggregation properties of zwitterion-modified Au nanoparticles （Au NPs） were studied under acidic and alkaline conditions. The UV-Vis spectra of the Au colloids were measured under different conditions, and the stability and reversible aggregation properties of the Au colloids were revealed through the spectral changes. The results showed that the modification with zwitterionic ligands largely improved the stability of the Au NPs under both acidic and alkaline conditions. Under strongly acidic conditions, the modified Au NP colloids lost stability and aggregated, but the aggregated colloids could be redispersed once the pH of the colloids was returned to an appropriate value. By exploiting their pH-dependent reversible aggregation properties, dilute Au NP colloids were concentrated to give concentrated Au NP colloids or solid Au NP aggregates; these systems could be preserved for long periods of time, and if needed, could be recovered to give well-dispersed dilute dispersions simply by adding water.