Departement de chimie, Universite de Sherbrooke, Sherbrooke, Quebec, Canada J1K 2R1.
Langmuir. 2010 Jul 20;26(14):12366-70. doi: 10.1021/la101798x.
Gold nanoparticles (AuNPs) coated with a water-soluble polymer displaying a photoswitchable lower critical solution temperature (LCST) were synthesized, and the photoinduced change in the aggregation state of AuNPs was investigated. The photoactivity of AuNPs was conferred by tethering on the surface a random copolymer of N,N-dimethylacrylamide and N-4-phenylazophenyl acrylamide (P(DMA-co-Azo)), whose LCST could be lowered upon the trans-cis photoisomerization of azobenzene groups. It was found that the dispersion of P(DMA-co-Azo)-coated AuNPs in aqueous solution remained stable regardless of temperature and the isomeric form of azobenzene groups. However, with the presence of free P(DMA-co-Azo) chains in the solution, the reversible photoinduced shift of LCST of the polymer could result in a reversible photoswitching between dispersion and aggregation of AuNPs. A stable dispersion could be obtained at T < LCST of the polymer with azobenzene in the trans form (without irradiation), while upon UV irradiation, the lowering of LCST with cis-azobenzene put the solution to above the altered LCST and the insoluble polymer chains led to aggregation of AuNPs; the initial dispersion state could be recovered by visible light irradiation, bringing cis-azobenzene back to the trans form. The use of such a photoresponsive polymer to optically tune the aggregation state of AuNPs allows the surface plasmon resonance (SPR) of AuNPs to be reversibly switched by light at two wavelengths, the extent of which depends on the amount of free polymer chains in the solution.
合成了一种包覆在水溶性聚合物上的金纳米粒子 (AuNPs)，该聚合物具有光致切换的低临界溶液温度 (LCST)，并研究了 AuNPs 聚集状态的光诱导变化。通过在表面键合 N,N-二甲基丙烯酰胺和 N-4-苯偶氮基苯丙烯酰胺 (P(DMA-co-Azo)) 的无规共聚物，赋予 AuNPs 光活性，其 LCST 可以在偶氮苯基团的顺反异构化后降低。结果发现，无论温度和偶氮苯基团的异构形式如何，P(DMA-co-Azo)包覆的 AuNPs 在水溶液中的分散体都保持稳定。然而，在溶液中存在游离的 P(DMA-co-Azo)链的情况下，聚合物 LCST 的可逆光诱导位移可以导致 AuNPs 的分散体和聚集体之间的可逆光切换。在聚合物中含有反式偶氮苯（无辐照）时，T < LCST 可以获得稳定的分散体，而在 UV 辐照下，含顺式偶氮苯的 LCST 降低会使溶液超过改变后的 LCST，不溶性聚合物链导致 AuNPs 聚集；可见光照射可以恢复初始分散状态，使顺式偶氮苯恢复为反式。使用这种光响应聚合物来光学调节 AuNPs 的聚集状态可以使 AuNPs 的表面等离子体共振 (SPR) 在两个波长的光下可逆切换，其程度取决于溶液中游离聚合物链的数量。
