Multi-parametric surface plasmon resonance (MP-SPR) is based on surface plasmon resonance (SPR), an established real-time label-free method for biomolecular interaction analysis, but it uses a different optical setup, a goniometric SPR configuration. While MP-SPR provides same kinetic information as SPR (equilibrium constant, dissociation constant, association constant), it provides also structural information (refractive index, layer thickness). Hence, MP-SPR measures both surface interactions and nanolayer properties.
The goniometric SPR method was researched alongside focused beam SPR and Otto configurations at VTT Technical Research Centre of Finland since 1980s by Dr. Janusz Sadowski. The goniometric SPR optics was commercialized by Biofons Oy for use in point-of-care applications. Introduction of additional measurement laser wavelengths and first thin film analyses were performed in 2011 giving way to MP-SPR method.
The MP-SPR optical setup measures at multiple wavelengths simultaneously (similarly to spectroscopic SPR), but instead of measuring at a fixed angle, it rather scans across a wide range of θ angles (for instance 40 degrees). This results in measurements of full SPR curves at multiple wavelengths providing additional information about structure and dynamic conformation of the film.
The measured full SPR curves (x-axis: angle, y-axis: reflected light intensity) can be transcribed into sensograms (x-axis: time, y-axis: selected parameter such as peak minimum, light intensity, peak width). The sensograms can be fitted using binding models to obtain kinetic parameters including on- and off-rates and affinity. The full SPR curves are used to fit Fresnel equations to obtain thickness and refractive index of the layers. Also due to the ability of scanning the whole SPR curve, MP-SPR is able to separate bulk effect and analyte binding from each other using parameters of the curve.
While QCM-D measures wet mass, MP-SPR and other optical methods measure dry mass, which enables analysis of water content of nanocellulose films.
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Surface plasmons (SPs) are coherent delocalized electron oscillations that exist at the interface between any two materials where the real part of the dielectric function changes sign across the interface (e.g. a metal-dielectric interface, such as a metal sheet in air). SPs have lower energy than bulk (or volume) plasmons which quantise the longitudinal electron oscillations about positive ion cores within the bulk of an electron gas (or plasma). The charge motion in a surface plasmon always creates electromagnetic fields outside (as well as inside) the metal.
Surface plasmon resonance (SPR) is a phenomenon that occurs where electrons in a thin metal sheet become excited by light that is directed to the sheet with a particular angle of incidence, and then travel parallel to the sheet. Assuming a constant light source wavelength and that the metal sheet is thin, the angle of incidence that triggers SPR is related to the refractive index of the material and even a small change in the refractive index will cause SPR to not be observed.
In physics, a plasmon is a quantum of plasma oscillation. Just as light (an optical oscillation) consists of photons, the plasma oscillation consists of plasmons. The plasmon can be considered as a quasiparticle since it arises from the quantization of plasma oscillations, just like phonons are quantizations of mechanical vibrations. Thus, plasmons are collective (a discrete number) oscillations of the free electron gas density. For example, at optical frequencies, plasmons can couple with a photon to create another quasiparticle called a plasmon polariton.
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Elsevier Sci Ltd2024
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We report on deep-to-near-UV transient absorption spectra of core-shell Au/SiO2 and Au/TiO2 nanoparticles (NPs) excited at the surface plasmon resonance of the Au core, and of UV-excited bare anatase TiO2 NPs. The bleaching of the first excitonic transitio ...