Use of thermally annealed multilayer gold nanoparticle films in combination analysis of localized surface plasmon resonance sensing and MALDI mass spectrometry

Abstract

A self-assembled film of gold nanoparticles (AuNPs) with a raspberry-like morphology was prepared on a glass plate by the layer-by-layer thermal annealing of multilayer films of AuNPs. It was possible to control the morphology of the obtained films of AuNPs by changing the annealing temperature, duration of annealing, and number of layers. On investigating the plasmonic properties of these films, we found that AuNP films with a raspberry-like morphology yielded the highest refractive index unit, which is a critical parameter in localized surface plasmon resonance (LSPR) sensing, as compared to other types of AuNP films. Self-assembled AuNP films with a raspberry-like morphology were subsequently functionalized with 11-mercaptoundecanoic acid (MUA) to enable the binding of lysozyme to the MUA-modified Au surface. The superior limit of detection for the LSPR sensing of lysozyme in a buffer solution was found to be in the picomolar range ($10 À12 M). The high sensitivity observed in the region was attributed to the raspberry-like morphology, where the AuNPs were packed closely together, and the electromagnetic field confinement was most intense (i.e., at hot spots). The MUA-modified, self-assembled AuNP films with a raspberry-like morphology were finally used in the combination analysis of LSPR sensing and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the selective detection and identification of lysozyme in human serum.

Nanoglassified, Optically-Active Monolayer Films of Gold Nanoparticles for in Situ Orthogonal Detection by Localized Surface Plasmon Resonance and Surface-Assisted Laser Desorption/Ionization-MS

“…The calcinated AuNP film displays well-defined absorption spectra and good LSPR sensitivity for spherical nanoparticles, with a bulk sensitivity of 84 ± 10 nm/RIU obtained with different solvents (Figure 2 a), which is equivalent to that of other reported solid-bound AuNP structures. 23 The differential extinction spectrum approach was employed for data analysis so that refractive index sensitivities may be evaluated at any given wavelength, rather than limited at the extinction peaks. 24 For calcinated monolayer AuNPs, we observed that wavelengths higher than the initial peak display higher sensitivities, with the sensitivity of 0.106 NEU/RIU at 570 nm increasing to 0.497 NEU/RIU at 600 nm (Figure 2 b).…”

Nanomaterials as stationary phases and supports in liquid chromatography

“…Several means for incorporating nanomaterials in LC systems were described in Section . These methods included covalent immobilization, adsorption, entrapment, and the synthesis or direct development of nanomaterials as part of a chromatographic support ‐. The direct use of some nanomaterials as LC supports has also been possible in a few situations .…”

“…Another strategy that has been used for charged nanoparticles has been to adsorb them onto a support or surface by means of electrostatic interactions . Immobilization through adsorption is often easier to carry out than covalent immobilization, although it can result in lower stability for the stationary phase and some loss in reproducibility when a column containing such a material is used over long periods of time .…”

“…Another advantage of using adsorption is it can allow multiple layers of nanoparticles to be placed onto a support , which can lead to improved retention and resolution . Adsorption through electrostatic interactions has been used for immobilizing materials such as gold nanoparticles , nanomaterials based on zirconia and titanium oxide , and latex nanoparticles onto silica or organic monoliths . A few specific examples are the adsorption of gold nanoparticles onto silica that has been stabilized with L‐cysteine or L‐cysteine methyl ester and the adsorption of zirconia nanoparticles directly, or through alternating layers of these nanoparticles and sodium dodecyl sulfate, on the surface of silica particles .…”

Optical and sensing properties of various shaped gold nanoplates and highly controlled asymmetric gold nanoplate/nanosphere coupled assemblies.

“…Thermally annealed multilayer Au nanoparticle films were also prepared from Au nanoparticles synthesized in solution. 32 Instead of using interface-assisted assembly, multilayer gold nanoparticle films were formed on substrates using layer-by-layer thermal annealing techniques. The sensing platform built from multilayer Au nanoparticle films reached picomolar detection limits for the LSPR sensing of lysozyme in a buffer solution.…”