Polarization interferometry (PI) techniques, which are able to improve surface plasmon resonance (SPR) sensing performance and reduce restrictions on allowable parameters of SPR-supporting metal films, have been experimentally realized only in SPR sensors using monochromatic light as a source. Wavelength-interrogation SPR sensors modulated by PI techniques have not been reported due to the wavelength-sensitive characterization of PI phase compensators. In this work we develop a specially designed rhombic prism for phase compensating which is totally insensitive to wavelength. For the first time we successfully apply PI technique to a wavelength-interrogation SPR imager. This imager is able to offer two-dimensional imaging of the whole array plane. As a result of PI modulation, resolutions of 1.3×10−6 refractive index unit (RIU) under the normal condition and 3.9×10−7 RIU under a more time-consuming condition are acquired. The application of this imager was demonstrated by reading microarrays for identification of bacteria, and SPR results were confirmed by means of fluorescence imaging.
Surface plasmon resonance (SPR) is an optical label-free sensing technique with high sensitivity and has been widely
used in biological and chemical studies. Recently, there are many reports about sensing DNA microarrays with
two-dimensional surface plasmon resonance imaging (SPRi) technique. However, the relations between the SPR
refractive index response and the conditions of DNA immobilization are still not well known. This impedes the
development of SPR bio-sensing.
In this paper, we use a SPR imaging technique which we have previously reported-parallel scan spectral SPR
imaging-to study the equivalent refractive index of the DNA probes (Bacterial 16S rDNA universal primer)
immobilized on gold surface of the SPR sensing module. We change the immobilization conditions including types of
the buffer solution, the incubation time and the concentrations of probe, obtain the equivalent refractive index of these
biochemical molecules on the gold surface. From the relations of the equivalent refractive index and these conditions,
we finally conclude with the optimal conditions of the DNA immobilization. These results are useful for further DNA
microarray studies base on SPR.
In this paper, a new parallel scan spectral surface plasmon resonance (SPR) 2D sensing system is presented. With a lineshaped
light illumination, an image acquired with area CCD detector provides both SPR wavelength information and 1D
spatial distribution. Thus, 2D distribution of refractive index of the entire sensing plane can be obtained with 1D optical
line parallel scan. A refractive index distribution model and a manually dotted DNA array are measured with this system.
The technology shows advantages of both high sensitivity and high throughput in these results, and could have potential
applications in biochips analysis.
In a SPR sensor, a glass slide is coated with a metal film, whose thicknesses, density and dielectric constant deadly affect
the measurement sensitivity and precision in bio-detection. The optimum thickness of gold film used in SPR is between
40nm and 50nm without adhesive film, according to calculations based on multilayer reflection model cited in large
numbers of literatures. But experimental study on the optimum film parameters are still lacking attribute to the limitation
of film coating technology and high-precision thickness measurement technology. The optimum gold film thickness is
not 45nm observed in our SPR bio-detection, and the property of adhesive film which is needed for enhancing the
adhesion of metal film affects the SPR responsive bandwidth and minimum reflectivity. The experiment study on the
sensor gold film and the property of adhesive film for SPR sensor are described in this paper using high precision SPR
detection system, X-ray diffraction and magnetron sputtering technology. The optimum thickness for single gold film is
44nm and is 42nm for gold film with 2.4nm Cr adhesive layer. A new estimating factor is proposed to evaluate the
quality and resolution of metallic film.
In this paper, a new Surface Plasmon Resonance (SPR) sensor for refractive index (RI) based on polarization
interferometry and phase modulation is presented. Its sensitivity is not a direct function on intensity variations(δr/δn),
nor on phase variations(δφ/δn), but on ((δr/δn)▵φ+r(δφ/δn)) (here r and φ represent the amplitude and the
phase of reflectivity; n represents the refractive index). According to our theoretical calculation, the dynamic range of
this kind of SPR sensor is much wider than that of sensors based on either variations of intensity or variations of phase.
This sensor can also provide very high resolution comparable with SPR sensors base on phase variations which has the
highest sensitivities till now.
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