Nanostructured Au Chips with Enhanced Sensitivity for Sensors Based on Surface Plasmon Resonance (original) (raw)
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Enhancing Surface Plasmon Resonance Detection Using Nanostructured Au Chips
Nanoscale Research Letters, 2016
The increase of the sensitivity of surface plasmon resonance (SPR) refractometers was studied experimentally by forming a periodic relief in the form of a grating with submicron period on the surface of the Au-coated chip. Periodic reliefs of different depths and spatial frequency were formed on the Au film surface using interference lithography and vacuum chalcogenide photoresists. Spatial frequencies of the grating were selected close to the conditions of Bragg reflection of plasmons for the working wavelength of the SPR refractometer and the used environment (solution of glycerol in water). It was found that the degree of refractometer sensitivity enhancement and the value of the interval of environment refractive index variation, Δn, in which this enhancement is observed, depend on the depth of the grating relief. By increasing the depth of relief from 13.5 ± 2 nm to 21.0 ± 2 nm, Δn decreased from 0.009 to 0.0031, whereas sensitivity increased from 110 deg./RIU (refractive index unit) for a standard chip up to 264 and 484 deg./RIU for the nanostructured chips, respectively. Finally, it was shown that the working range of the sensor can be adjusted to the refractive index of the studied environment by changing the spatial frequency of the grating, by modification of the chip surface or by rotation of the chip.
Science and innovation, 2017
An innovative project on the development of a method for manufacturing sensor chips with enhanced sensitivity for biosensors based on surface plasmon resonance (SPR) operating in the Kretschmann scheme has been completed. An increase in sensitivity of such sensor has been achieved by forming high-frequency periodic grating on the sensor chip surface using the interference photolithography technique. All processes have been optimized. A pilot sample of modernized SPR refractometer as well as a pilot batch of nanostructured sensor chips with spatial frequencies up to 3400 mm-1 have been manufactured and tested. The use of nanostructured chips has resulted in a 4.7-time increase in the SPR refractometer sensitivity.
High-sensitivity integrated devices based on surface plasmon resonance for sensing applications
Photonics Research, 2017
A metallic nanostructured array that scatters radiation toward a thin metallic layer generates surface plasmon resonances for normally incident light. The location of the minimum of the spectral reflectivity serves to detect changes in the index of refraction of the medium under analysis. The normal incidence operation eases its integration with optical fibers. The geometry of the arrangement and the material selection are changed to optimize some performance parameters as sensitivity, figure of merit, field enhancement, and spectral width. This optimization takes into account the feasibility of the fabrication. The evaluated results of sensitivity (1020 nm/RIU) and figure of merit (614 RIU −1) are competitive with those previously reported.
High sensitivity surface plasmon resonance (SPR) refractive index sensor in 1.5 μm
Materials Express, 2017
We have chemically modified metal nanoslit array surfaces with alkanethiol self-assembled monolayers and have characterized the resulting spectral shift of optical transmission. Adsorption of a self-assembled monolayer ͑1.5 nm thick͒ on a silver nanoslit array ͑slit width of 30-50 nm and grating period of 360 nm͒ is found to cause an 11 nm redshift of the main transmission peak. Strong confinement of optical fields in the narrow slit region allows sensitive transduction of surface modification into a shift of surface plasmon resonance wavelength.
Sensitivity enhancement of nanoplasmonic sensors in low refractive index substrates
Optics express, 2009
Metal films perforated by nanoholes constitute a powerful platform for surface plasmon resonance biosensing. We find that the refractive index sensitivity of nanohole arrays increases if their resonance is red-shifted by increasing the separation distance between holes. However, an additional sensitivity enhancement occurs if the nanohole sensors are manufactured on low index substrates, despite the fact such substrates significantly blue-shift the resonance. We find a approximately 40% higher bulk refractive index sensitivity for a system of approximately 100 nm holes in 20 nm gold films fabricated on Teflon substrates (n=1.32) compared to the case when conventional glass substrates (n=1.52) are used. A similar improvement is observed for the case when a thin layer of dielectric material is deposited on the samples. These results can be understood by considering the electric field distribution induced by the so-called antisymmetric surface plasmon polariton in the thin gold films.
2006
An alternating dielectric multi-layer device was fabricated and tested in the laboratory to show that dielectric mirrors of alternating high/low refractive index materials, based on the design of distributed Bragg reflector (DBR) for vertical cavity surface emission lasers (VCSELs), can be used in designing SPR biochemical sensors. The thickness, number of layers, and other design parameters of the device used were optimized using optical admittance loci analysis. The proof-of-concept device was fabricated with a symmetrical structure using Au/(SiO 2 /TiO 2) 4 /Au. Using a 632 nm-wavelength light source on a BK7 coupling prism, our laboratory tests showed that, under water, there was an 11.5 • shift in resonant peak position towards the critical angle (from 74 • in a conventional single-layer Au film), and a 3.25 times decrease in FWHM (the half-peak width). Our design also resulted in a wider dynamic range of up to a 1.50 refractive index unit (RIU), compared to 1.38 RIU in a conventional single-layer Au film. Using glucose solutions in ddH 2 O, the calculated resolution was 1.28 × 10 −5. The calculated intensity sensitivity was 10 000 a.u./RIU, about twice the improvement over the conventional single-layer Au film.
Journal of the Optical Society of America A, 2012
In this paper, the theoretical sensitivity limit of the localized surface plasmon resonance (LSPR) to the surrounding dielectric environment is discussed. The presented theoretical analysis of the LSPR phenomenon is based on perturbation theory. Derived results can be further simplified assuming quasistatic limit. The developed theory shows that LSPR has a detection capability limit independent of the particle shape or arrangement. For a given structure, sensitivity is directly proportional to the resonance wavelength and depends on the fraction of the electromagnetic energy confined within the sensing volume. This fraction is always less than unity; therefore, one should not expect to find an optimized nanofeature geometry with a dramatic increase in sensitivity at a given wavelength. All theoretical results are supported by finite-difference time-domain calculations for gold nanoparticles of different geometries (rings, split rings, paired rings, and ring sandwiches). Numerical sensitivity calculations based on the shift of the extinction peak are in good agreement with values estimated by perturbation theory. Numerical analysis shows that, for thin (≤10 nm) analyte layers, sensitivity of the LSPR is comparable with a traditional surface plasmon resonance sensor and LSPR has the potential to be significantly less sensitive to temperature fluctuations.
Applied Optics, 2011
We examine the correlation between the plasmon field distribution and the sensitivity enhancement for both reflection-and transmission-type localized surface plasmon resonance (LSPR) biosensors with surface-relief gold nanogratings. In our calculation, the near-field characteristics are obtained from the finite-difference time-domain method and compared with the refractive index sensitivity as a unit target sample moves along the sensor surface. The numerical results show that the highest enhancement of sensitivity is found at the lower grating corners where an interplay between the target sample and the locally enhanced field can occur efficiently. This study suggests that, by localizing biomolecular interactions to the highly enhanced field, we can achieve a significantly improved LSPR detection with high sensitivity and a great linearity in a wide dynamic range.
A surface plasmon resonance biosensor based on gold nanoparticle array
Using the finite-difference time-domain (FDTD) method, optical properties are investigated for a sensor comprising a two-dimensional array of gold cubes placed on quartz pillars on a quartz substrate. Background condition is analyzed for an approximate ideal collective resonance. It is found that the resonance intensity is mainly determined by the quartz etch depth, and the spectra valley position depends mainly on the lattice period. Thickness of the gold film affects the wavelength of the transmission spectra slightly, which gives a low processing tolerance requirement for fabrication. Sensitivity of the biosensor is also discussed, spectral sensitivity as high as 596.7 nm/refractive index unit (RIU) is obtained in the visible light region, making it an excellent candidate for liquid detection.