Thermosensitive gold nanoparticles were fabricated by conjugating Au with a thiol-terminated poly(N-isopropylacrylamide) or PPA; this polymer stabilizer exhibits a temperature transition while undergoing a hydrophilic to hydrophobic transformation. The introduction of PPA onto gold nanoparticles has sensitized Au nanoparticles with unique temperature dependence. At low temperature (25 degrees C), the solutions containing PPA-functionalized gold nanoparticles are transparent, whereas higher temperatures (30 degrees C) lead to opaque suspensions. The thermosensitive property of PPA-functionalized Au nanoparticles is reversible, and the clear-opaque suspensions can be repeated many times.
We present a dynamic molecular self-assembly system, driven mostly by π−π molecular orbital interactions. The formation of such selforganized dynamic systems is characterized with absorption, fluorescence, and NMR spectroscopies as well as dynamic light scattering. Our results demonstrate that proper design of molecules can promote self-organization in solution. As a result, we observed distinct red, orange, yellow, and green photoluminescence from different initial concentrations while exciting the system at the same wavelength.
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