Yeshchenko Oleg A, Naumenko Antonina P, Kutsevol Nataliya V, Harahuts Iulia I
Physics Department, Taras Shevchenko National University of Kyiv 60 Volodymyrs'ka str. 01601 Kyiv Ukraine
Chemistry Department, Taras Shevchenko National University of Kyiv 60 Volodymyrs'ka str. 01601 Kyiv Ukraine.
RSC Adv. 2018 Nov 14;8(67):38400-38409. doi: 10.1039/c8ra07768a.
Laser induced structural transformations in a dextran grafted-poly(-isopropylacrylamide) copolymer/Au nanoparticles (D--PNIPAM/AuNPs) hybrid nanosystem in water have been observed. The laser induced local plasmonic heating of Au NPs leads to Lower Critical Solution Temperature (LCST) phase transition in D--PNIPAM/AuNPs macromolecules accompanied by their shrinking and aggregation. The hysteresis non-reversible character of the structural transformation in D--PNIPAM/AuNPs system has been observed at the decrease of laser intensity, the aggregates remains in solution after the turn-off the laser illumination. This is an essential difference comparing to the case of usual heating-cooling cycles when there is no formation of aggregates and structural transformations are reversible. Such a fundamental difference has been rationalized as the result of action of attractive optical forces arising due to the excitation of surface plasmons in Au NPs. The attractive plasmonic forces facilitate the formation of the aggregates and counteract their destruction. The laser induced structural transformations have been found to be very sensitive to matching conditions of the resonance of the laser light with surface plasmon resonance proving the plasmonic nature of observed phenomena.
已观察到水中葡聚糖接枝聚（N-异丙基丙烯酰胺）共聚物/金纳米颗粒（D-PNIPAM/AuNPs）杂化纳米系统中的激光诱导结构转变。激光诱导的金纳米颗粒的局部等离子体加热导致D-PNIPAM/AuNPs大分子中的低临界溶液温度（LCST）相变，并伴随着它们的收缩和聚集。在激光强度降低时，观察到D-PNIPAM/AuNPs系统中结构转变的滞后不可逆特性，关闭激光照射后聚集体仍保留在溶液中。这与通常的加热-冷却循环情况有本质区别，在通常情况下不会形成聚集体且结构转变是可逆的。这种根本差异被合理地解释为由于金纳米颗粒中表面等离子体的激发而产生的吸引性光学力作用的结果。吸引性等离子体力促进聚集体的形成并抵消它们的破坏。已发现激光诱导的结构转变对激光与表面等离子体共振的匹配条件非常敏感，这证明了所观察到现象的等离子体性质。
