L'extinction de fluorescence dans des assemblages de chromophores organiques et nanoparticules d'or

Transcription

1 L'extinction de fluorescence dans des assemblages de chromophores organiques et nanoparticules d'or Martinus H. V. Werts, Raïssa Praho, Nicolas Nerambourg, Mireille-Blanchard-Desce équipe Photonique Moléculaire et upramoléculaire UMR6510 (E), Université de Rennes 1, CNR Daniel Thomas Interactions Cellulaires et Moléculaires, UMR6026, Rennes Grégory chneider and Gero Decher Institut Charles adron, trasbourg

2 effects of noble metal nanostructures on molecular fluorescence enhancement e.g dyes on silver nanoparticle fractal clusters or 1 % 99 % + quenching Au Au quantitative spectroscopic studies of AuNP effects on fluorescence intensities and lifetimes in dilute, limpid solutions

3 tratégie métal nanostructuré: ex. nanoparticule, soluble en milieu organique nm et plus exaltation du champ électromagnétique ( fois) hν transfert d'énergie et/ou d'électrons molécule photoactive << 10 nm

4 putting fluorophores onto metal nanoparticles by ligand exchange ~ 15 Å H = H H = H N N 2 n-dodecanethiol "NN039" Au gold nanoparticle 4 nm diameter protected by a AM ~600 thiol ligands H thiol-functionalised fluorophore Au fluorophore-nanoparticle assembly ("doping level": 1, 2, 5, 10%) H (toluene solutions) Langmuir 2007, 23, 5563

5 Au H Au H remaining fluorescence from free and bound chromophores

6 Analysis of ligand exchange equilibrium: relative brightness of fluorophores on nanoparticles Au K eq + H Au + H C 6 H 13 N I I bound = free 0.21 N C 6 H 13 I N n-hex I I bound = free N I I bound = free 0

7 Functionalised nanoparticles by layer-by-layer deposition 13 nm "citrate"- stabilised gold polyelectrolyte metal (+) nanoparticle polyelectrolyte (-) functionalities in water! Decher et al, Thin olid Films 1992, 210, 831 Decher, cience 1997, 277, 1232 chneider et al, Nano Lett. 2004, 4, 1833 collaboration G. chneider/g. Decher, trasbourg

8 Distance dependent fluorescence quenching Nano Letters 2006, 6, 530

9 Influence of gold NP on molecular fluorescence Dissolution of the gold core by cyanide etch fluorescéine 1 2Au H2 + 4KCN 2K[Au(CN) 2] + 2K 2 1 mm KCN

10 quenching efficiency (lower values = more quenching)

11 two-photon excited fluorescence set-up

12 effect of gold particle on two-photon excited fluorescence fluorescein chromophore 10 spacer layers (same ratio as 1-photon) excitation at 940 nm (fs pulses) lock-in detection using PMT by the way: no luminescence from gold nanoparticles detected

13 Back to AMs: hydrophilic protected AuNPs Choice of ligands Alkyl chain: order near the surface Water-solubility H H NH 2 N C C 2 H Functionalisation (fluorophores, biomolecules) H

14 Functionalisation with fluorophores Gold nanoparticle 13 nm H H ,8 éq. 16 0,2 éq. eau Millipore 8h H MP-AuNP + 1M NaCl = 15 2 = N H N H 16 2 Au-citrate Au-citrate + NaCl

15 Removal of free ligands purification through repeated centrifugation, followed by ephadex size-exclusion chromatography Analysis: size-exclusion chromatography before last ephadex column: presence of free fluorophores after last ephadex column: solution free of unbound fluorophores Int. J. Nanotechnol. (special issue), in press

16 Liberation of fluorophores mercaptoethanol does the trick H H H excès (1000 éq.) H H H H H H H H + H + H H + ratio of fluorescence intensities of bound and free chromophores comparable to "LbL" architecture quantitative comparison of fluorescence intensities and decay times between free and bound fluorophores

17 Merci Nicolas Nerambourg Raïssa Praho Marina Charlot aid Gmouh livier Mongin Mireille Blanchard-Desce and all Daniel Thomas (TEM, Rennes) Gero Decher (trasbourg) Grégory chneider (trasbourg -> Harvard) ponsors Rennes Métropole Région Bretagne MENER