Gold nanoparticle I and nanoparticle II protected by 10-(1-pyrenyl)-6-oxo-decanethiol and 17-(1-pyrenyl)-13-oxo-heptadecanethiol, respectively, were prepared and characterized by 1 H NMR, FT-IR, XPS, UV-vis and fluorescence spectroscopies and TEM and elemental analysis. Their compositions were determined to be (C25H27OS)225•Au1601 and (C32H41OS)120•Au1052, respectively. Unusual fluorescence enhancement was observed for the aged solutions of nanoparticle I and nanoparticle II, and a possible explanation for this phenomenon was also discussed. This experimental finding provides further evidence for the chain density gradient and the motion of termini groups of alkanethiolates adsorbed onto the surface of gold nanoparticle.

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A new bis(rhodamine)-based fluorescent probe 4 was synthesized, and it exhibited high selectivity for Fe3+ over other commonly coexistent metal ions in both 50% ethanol and Tris–HCl buffer. Upon the addition of Fe3+, the spirocyclic ring of 4 was opened and a significant enhancement of visible color and fluorescence in the range of 500–600 nm was observed.Electronic supplementary materialThe online version of this article (doi:10.1007/s10895-011-1022-0) contains supplementary material, which is available to authorized users.