Hyper-Rayleigh scattering of gold nanorods and their relationship with linear assemblies of gold nanospheres

Abstract

The surface plasmon enhanced hyper-Rayleigh scattering light collected from an aqueous solution of gold nanorods is reported. A non negligible part of the signal is attributed to a photoluminescence background attributed to the electron-hole recombination following multiphoton excitation of d-valence band electrons into the sp-conduction band. This radiative relaxation process is likely favored by the presence of the organic species adsorbed at the surface of the nanorods. The absolute value for the hyperpolarisability of nanorods is also compared by the external reference method to that of para-nitroaniline and found to be rather large although an absolute value cannot be given because the exact number density of the gold nanorods is unaccessible. This value is however compared with values reported for linear assemblies of gold spherical nanoparticles and further support the simple model of gold metal ellipsoids to describe the hyper-Rayleigh light intensities. The polarisation analysis of the hyper-Rayleigh scattering light is also determined for gold nanorods and compared to the expected one for gold nanospheres. For the latter spheres, the weakness of the signal intensities precludes a definite comparison with the model. On the opposite, for the nanorods, the polarisation dependence of the hyper-Rayleigh scattered light clearly deviates from the one expected for nanospheres.

Label-free detection of single base-mismatch DNA hybridization on gold nanoparticles using hyper-Rayleigh scattering technique: studies on size-dependent properties

“…The HRS technique [19][20][21][22][23][24][25][26][27][28][29][30] is based on light scattering. The intensity of the Rayleigh scattering is linearly dependent on the number density and the impinging laser intensity, and quadratically on the linear polarizability α.…”

“…This enhancement factor is comparable with the SERS signal enhancement [1][2][3][4] . In fact, it has been shown that [19][20][21][22][23][24][25][26] the HRS technique is considerably more sensitive than 1) the normal Rayleigh scattering, the typical spectroscopic technique to monitor nanoparticle aggregate size and 2) the absorption spectroscopy, because it responds to the to the formation of smaller particle aggregates; thus the onset of the HRS enhancement should be observable before any visible color change occurs. Therefore, one can use this HRS technique to probe target molecules coated onto nanoparticles.…”

“…Diagnostic of olegonucleotide sequence using unmodified DNA remains attractive due to simplify sample preparation, decrease assay cost and eliminate potential artifacts from modification. In this paper, we demonstrate for the first time that the hyper-Rayleigh scattering (HRS) technique [20][21][22][23][24][25][26][27][28][29][30] , which has emerged over the past decade as a powerful method to determine the microscopic non-linear optical (NLO) properties of species in solution, can be used to achieve the ultra-sensitive detection of single base-pair mismatch in oligonucleotide strands without any modification of DNA.…”

“…This is a second harmonic generation experiment in which the light is scattered in all directions rather that as a narrow coherent beam. It is now reported [19][20][21][22][23][24][25][26] that metallic nanoparticles, such as gold, silver, platinum and copper exhibits enormous HRS response, showed their potential to be excellent nonlinear scatters. The HRS technique has emerged as a method for the solution phase nonlinear optical property measurements in the last twelve years [20][21][22][23][24][25][26][27][28][29][30] .…”

“…The HRS experiment's unique characteristics allow interrogation of particle/solution interface [19][20][21][22][23][24][25][26] that is invisible to conventional SHG measurements. The intense HRS signal from gold nanoparticles in solution has potential applicability for the detection of extremely small amount of materials [18][19][20][21][22][23][24][25] . Recently, the HRS technique has been used to study the gold, silver and cadmium nanoparticle suspensions and Vance et al 19 have shown that the HRS intensity enhanced by a factor up to 10 5 in nanocrystalline gold particle suspensions.…”