Huge enhancement in two-photon photoluminescence of Au nanoparticle clusters revealed by single-particle spectroscopy.

Aggregated metal nanoparticles have been known to display significantly enhanced two-photon photoluminescence (TPPL) compared to nonaggregated nanoparticles, which could be utilized to develop platforms for two-photon sensing and imaging applications. Here we have conducted single-particle spectroscopic studies on gold (Au) nanoparticle clusters of different sizes to understand the enhancement mechanisms and explore the limit of maximum achievable enhancement. Our studies show that the TPPL intensity of Au nanoparticle clusters significantly increases from monomer to trimer. The averaged intensity of the Au nanosphere dimers and linear trimers is ~7.8 × 10(3) and ~7.0 × 10(4) times that of Au nanosphere monomers, respectively. A highest enhancement of 1.2 × 10(5) folds was obtained for the linear trimer. The TPPL spectra of these single Au nanosphere clusters closely resemble their corresponding scattering spectra, suggesting strong correlation between their TPPL with plasmon resonance. The scattering spectra of dimers and linear trimers displayed cos(2) dependence on the detection polarization, while their TPPL displayed cos(4) dependence on the excitation polarization, which are very similar to Au nanorods. These results suggest that two-photon excitation of dimer and linear trimer is strongly coupled to their longitudinal plasmon resonance modes. These studies help to provide insight on fundamental understanding of the enhancement mechanisms as well as development of biomedical and photonic applications.

[1]  Marco Finazzi,et al.  Dependence of the two-photon photoluminescence yield of gold nanostructures on the laser pulse duration , 2009 .

[2]  Philip S Low,et al.  In vitro and in vivo two-photon luminescence imaging of single gold nanorods. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[3]  Jianfang Wang,et al.  Nanonecklaces assembled from gold rods, spheres, and bipyramids. , 2007, Chemical communications.

[4]  P. Nordlander,et al.  Plasmons in strongly coupled metallic nanostructures. , 2011, Chemical reviews.

[5]  Emil Prodan,et al.  Plasmon Hybridization in Nanoparticle Dimers , 2004 .

[6]  E. Coronado,et al.  The Optical Properties of Metal Nanoparticles: The Influence of Size, Shape, and Dielectric Environment , 2003 .

[7]  P. Prasad,et al.  Multiphoton absorbing materials: molecular designs, characterizations, and applications. , 2008, Chemical Reviews.

[8]  Younan Xia,et al.  Isolating and probing the hot spot formed between two silver nanocubes. , 2009, Angewandte Chemie.

[9]  Jianfang Wang,et al.  Plasmon–molecule interactions , 2010 .

[10]  Qinghua Xu,et al.  Biocompatible glutathione capped gold clusters as one- and two-photon excitation fluorescence contrast agents for live cells imaging. , 2011, Nanoscale.

[11]  Weihai Ni,et al.  pH-Controlled reversible assembly and disassembly of gold nanorods. , 2008, Small.

[12]  H. Ehrenreich,et al.  Optical Properties of Ag and Cu , 1962 .

[13]  Coupled nanoantenna plasmon resonance spectra from two-photon laser excitation. , 2010, Nano letters.

[14]  Hongyu Chen,et al.  Measuring ensemble-averaged surface-enhanced Raman scattering in the hotspots of colloidal nanoparticle dimers and trimers. , 2010, Journal of the American Chemical Society.

[15]  Qing-Hua Xu,et al.  Size-dependent two-photon excitation photoluminescence enhancement in coupled noble-metal nanoparticles. , 2012, ACS applied materials & interfaces.

[16]  Zongfu Yu,et al.  Large single-molecule fluorescence enhancements produced by a bowtie nanoantenna , 2009 .

[17]  C. Noguez.  Surface Plasmons on Metal Nanoparticles: The Influence of Shape and Physical Environment , 2007 .

[18]  Younan Xia,et al.  Bright three-photon luminescence from gold/silver alloyed nanostructures for bioimaging with negligible photothermal toxicity. , 2010, Angewandte Chemie.

[19]  Rongchao Jin,et al.  Correlating second harmonic optical responses of single Ag nanoparticles with morphology. , 2005, Journal of the American Chemical Society.

[20]  Three-dimensional orientation sensors by defocused imaging of gold nanorods through an ordinary wide-field microscope. , 2011, ACS nano.

[21]  Hiromi Okamoto,et al.  Plasmon mode imaging of single gold nanorods. , 2004, Journal of the American Chemical Society.

[22]  Prashant K. Jain,et al.  Surface Plasmon Coupling and Its Universal Size Scaling in Metal Nanostructures of Complex Geometry: Elongated Particle Pairs and Nanosphere Trimers , 2008 .

[23]  Qing-Hua Xu,et al.  Two-photon ratiometric sensing of Hg2+ by using cysteine functionalized Ag nanoparticles. , 2011, Nanoscale.

[24]  Mustafa Yorulmaz,et al.  Luminescence quantum yield of single gold nanorods. , 2012, Nano letters.

[25]  Qing-Hua Xu,et al.  Separation distance dependent fluorescence enhancement of fluorescein isothiocyanate by silver nanoparticles. , 2007, Chemical communications.

[26]  Muthu Kumara Gnanasammandhan,et al.  Plasmon enhanced upconversion luminescence of NaYF4:Yb,Er@SiO2@Ag core-shell nanocomposites for cell imaging. , 2012, Nanoscale.

[27]  Paul Mulvaney,et al.  Plasmon coupling of gold nanorods at short distances and in different geometries. , 2009, Nano letters.

[28]  Lukas Novotny,et al.  Continuum generation from single gold nanostructures through near-field mediated intraband transitions , 2003 .

[29]  G. Wiederrecht,et al.  Surface plasmon characteristics of tunable photoluminescence in single gold nanorods. , 2005, Physical review letters.

[30]  G S Kino,et al.  Improving the mismatch between light and nanoscale objects with gold bowtie nanoantennas. , 2005, Physical review letters.

[31]  O. Martin,et al.  Resonant Optical Antennas , 2005, Science.

[32]  Qing-Hua Xu,et al.  Enhanced two-photon emission in coupled metal nanoparticles induced by conjugated polymers. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[33]  Yuqiang Jiang,et al.  Bioimaging with Two‐Photon‐Induced Luminescence from Triangular Nanoplates and Nanoparticle Aggregates of Gold , 2009 .

[34]  P. Nordlander,et al.  A Hybridization Model for the Plasmon Response of Complex Nanostructures , 2003, Science.

[35]  J. Lakowicz,et al.  Metal-enhanced fluorescence from CdTe nanocrystals: a single-molecule fluorescence study. , 2006, Journal of the American Chemical Society.

[36]  Federico Capasso,et al.  Self-Assembled Plasmonic Nanoparticle Clusters , 2010, Science.

[37]  S. Link,et al.  Characterizing Plasmons in Nanoparticles and Their Assemblies with Single Particle Spectroscopy , 2011 .

[38]  Luis M Liz-Marzán,et al.  Molecular thinking for nanoplasmonic design. , 2012, ACS nano.

[39]  Jianfang Wang,et al.  Experimental evidence of plasmophores: plasmon-directed polarized emission from gold nanorod-fluorophore hybrid nanostructures. , 2011, Nano letters.

[40]  Steven R. Emory,et al.  Probing Single Molecules and Single Nanoparticles by Surface-Enhanced Raman Scattering , 1997, Science.

[41]  Neus G Bastús,et al.  Kinetically controlled seeded growth synthesis of citrate-stabilized gold nanoparticles of up to 200 nm: size focusing versus Ostwald ripening. , 2011, Langmuir : the ACS journal of surfaces and colloids.

[42]  P. Mulvaney,et al.  Surface plasmon resonances in strongly coupled gold nanosphere chains from monomer to hexamer. , 2011, Nano letters.

[43]  Harry A. Atwater,et al.  Local detection of electromagnetic energy transport below the diffraction limit in metal nanoparticle plasmon waveguides , 2003, Nature materials.

[44]  Logan K. Ausman,et al.  Methods for describing the electromagnetic properties of silver and gold nanoparticles. , 2008, Accounts of chemical research.

[45]  M. El-Sayed,et al.  The `lightning' gold nanorods: fluorescence enhancement of over a million compared to the gold metal , 2000 .

[46]  Jianfang Wang,et al.  Plasmon coupling in clusters composed of two-dimensionally ordered gold nanocubes. , 2009, Small.

[47]  Otto L. Muskens,et al.  Quantitative Absorption Spectroscopy of a Single Gold Nanorod , 2008 .

[48]  Petru Ghenuche,et al.  Spectroscopic mode mapping of resonant plasmon nanoantennas. , 2008, Physical review letters.

[49]  Na Zhou,et al.  Band-selective coupling-induced enhancement of two-photon photoluminescence in gold nanocubes and its application as turn-on fluorescent probes for cysteine and glutathione. , 2012, ACS applied materials & interfaces.