Multiresponsive, easy-reversible, and dual-visual Pt(II) salt nanostructures for advanced anti-counterfeiting application

Smart materials that integrate multi-stimuli response, full reversibility, and dual-visual read-out channel are highly desired for anti-counterfeiting and information encryption applications. Herein, we developed a multiresponsive perchlorate terpyridyl Pt(II) nano complex which could undergo fully reversible conversion between three forms stimulated by water or formaldehyde molecule due to the extent of Pt–Pt interaction. Meanwhile, a dual-visual channel, i.e., the colorimetric channel changed from yellow to orange or red and the corresponding luminescent channel from orange to orange-red or red, has also been found. The weak and equivalent strength of ion-dipole interaction and hydrogen bond that generated between formaldehyde/water and Pt(II) salt result in the easy-control reversibility between the three forms. Furthermore, by introducing different polymer matrices, 1Cl·ClO₄@PMMA (1Cl·ClO₄:[Pt(tpy)Cl]·ClO₄, tpy: 2,2':6',2''-terpyridine), PMMA: poly(methyl methacrylate)) and 1Cl·ClO₄@PVA (PVA: polyvinyl alcohol) are successfully constructed, which exhibit different reversible behaviors since the PMMA and PVA matrix exert different influences on the strength of hydrogen-bond. Those smart Pt(II) salt nanostructures present great potential for high-security-level anticounterfeiting application.