The Erratic Emission of Pyrene on Gold Nanoparticles

Abstract

Gold nanoparticles functionalized with chromophores are known to present unpredictable fluorescence as a function of their structure. Odd-even effects, based on the number of methylene units of the chain to which the fluorophore is attached, and the nature of the anchoring group on the gold surface have, in the past, been suggested to be responsible for the behavior. Here we investigate the fluorescence processes of two newly synthesized pyrene derivatives bound to gold nanoparticles. Two structurally identical ligands, differing only in the nature of the anchoring group (a thiolate in one case and an amine in the other), were newly synthetized and attached to the gold nanoparticles. The same changes in the fluorescence properties, namely, a red spectral shift with a moderate increase of the quantum yield and a shortening of the excited-state lifetime, are observed in the two cases and ascribed to the proximity of the gold core. By comparison with the results reported for other pyrene derivatives, it has been possible to draw the conclusions that (i) the nature of the binding group does not affect the fluorescence properties of the fluorophores attached to the nanoparticle surface and (ii) much stronger fluorescence is observed in the case of pyrene separated from the gold by short alkyl chain. The unusual behavior is explained in simple terms of competing chain-chain and chromophore-chromophore interactions and by means of proper energy diagrams.

Size‐ and Distance‐Dependent Nanoparticle Surface‐Energy Transfer (NSET) Method for Selective Sensing of Hepatitis C Virus RNA

“…The net luminescence can either decrease or increase depending on how the gold particle affects the chromophores excitation rate R exc , and the radiative and nonradiative decay rates of its excited state, R rad and R nonrad , which together determine the observed luminescence emission rate R emiss . [14,[18][19][20][21][22][23][24][25][26][27][28][46][47][48] Figure 2 demonstrates the quenching behavior of 5'-Cy3-modified 5'-(Cy3) UGUACUCACCGGUUCCGCAGAC-CAC' À3' RNA as a function of 45 nm gold nanoparticle concentration ( % 10 À11 m). The Stern-Volmer relationship [47] between quencher concentration and fluorescence intensity is given by Equation (1) in which f 0 and F 0 are quantum yield and emission intensity in the absence of quencher, respectively; f and F are the same parameters in the presence of quencher; k q , k e , and k d are the rates of quenching, emission, and deactivation, respectively; K SV is the Stern-Volmer quenching constant for collisional deactivation; and C Q is the concentration of nanoparticle quencher.…”

“…The limitations of FRET can be overcome with a dynamic molecular method based on the distance-dependent plasmon coupling of metal nanoparticles. Recently several groups including ours [14,[18][19][20][21][22][23][24][25][26][27][28][35][36][37][38][39][40][41] have reported that nanoparticle surface-energy transfer (NSET) is a technique capable of measuring distances nearly twice as far as FRET in which energy transfer from a donor molecule to a nanoparticle surface follows a predictable distance dependence. Like FRET, [44,45] the interaction for NSET is dipole-dipole in nature, but is geometrically different beAbstract: We report size-and distancedependent surface-energy transfer (SET) properties of gold nanoparticles for recognizing hepatitis C virus (HCV) RNA sequence sensitively and selectively (single-base mutations) in a homogeneous format.…”

Tunable Aminooxy‐Functionalized Monolayer‐Protected Gold Clusters for Nonpolar and Aqueous Oximation Reactions

“…Comparison of the fluorescence emission spectra of 1‐pyrenecarboxaldehyde with the corresponding derivatized Au(C 6 S)( AOT ‐pyrene) MMPCs with the same pyrene concentration shows the fluorescence is quenched when bound to the Au cluster ( Figure ). The quenching of fluorophores by metal nanoparticles is well established, and serves in this case as an indication of successful coupling of fluorophores through oximation.…”

Luminescent gold nanoclusters as biocompatible probes for optical imaging and theranostics

“…[45][46][47][48][49][50] Au 3+ is partially reduced to Au + by subsequent addiction of a thiol, with the simultaneous formation of Au(I) thiolate oligomers, composed by alternating thiolates and Au + atoms (figure 2). [43,51] The addition of a strong reductant as NaBH 4 , or weaker reducing agents, [24,[52][53][54][55] causes Au + conversion to Au 0 .…”