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Laser-driven structural transformations in dextran- <i>graft</i> -PNIPAM copolymer/Au nanoparticles hybrid nanosystem: the role of plasmon heating and attractive optical forces
摘要： Laser induced structural transformations in a dextran grafted-poly(N-isopropylacrylamide) copolymer/Au nanoparticles (D-g-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-g-PNIPAM/AuNPs macromolecules accompanied by their shrinking and aggregation. The hysteresis non-reversible character of the structural transformation in D-g-PNIPAM/AuNPs system has been observed at the decrease of laser intensity, i.e. 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.
关键词： Plasmon heating,Attractive optical forces,LCST phase transition,Au nanoparticles,Laser induced structural transformations,Dextran-graft-PNIPAM copolymer
更新于2025-11-19 16:56:42
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2-D Silver-thiocyanate Layers Directed by Viologens: Structural Transformations upon Low Pressure Stimuli, Piezochromic Luminescence, Photocurrent Responses and Photocatalytic Properties
摘要： The reactions of AgSCN with excess KSCN in presence of linear viologens templates afford seven new hybrids, {(MV)[Ag4(SCN)6]}n (1), {(MV)[Ag2(SCN)4]}n (2), {(EV)[Ag4(SCN)6]}n (3), {(EV)[Ag2(SCN)4]}n (4), {(BV)[Ag4(SCN)6]}n (5), {(CMV)[Ag2(SCN)4]}n (6) and {(BMPE)[Ag2(SCN)4]}n (7), (MV2+=methyl viologen, EV2+=ethyl viologen, BV2+=benzyl viologen, CMV2+=cyanomethyl viologen, BMPE2+=1,2-bis(N-methylpyridiniim-4-yl)ethane). The silver-thiocyanate skeletons with formula of [Ag4(SCN)6]n 2n- and [Ag2(SCN)4]n 2n- are the scarce representative examples of the 2-D polypseudorotaxane arrays penetrated (for 1-6) or intercalated (for 7) by viologen dications. Upon the external low pressure stimulus, the 2-D silver-thiocyanate layers penetrated by cations exhibit loser packing with longer Ag-S(N) bond lengths, weaker CT interactions and larger cavities, but the contrary trend can be found on compound with intercalated organic cations. Due to the strong CT interactions between viologens and silver-thiocyanate skeletons, the charge transfers can occur at room temperature. Interestingly, 7 represents typical reversible piezochromic luminescence behaviour. In addition, they show excellent photocurrent responses and efficient photocatalytic degeneration performances on organic dyes. Finally, their band structures and density of states before and after compression based on DFT calculations were executed to correlate their properties.
关键词： Piezochromic Luminescence,Viologens,Silver-thiocyanate,Photocurrent Responses,Photocatalytic Properties,Structural Transformations
更新于2025-09-10 09:29:36