The effects of structural design parameters on the performance of nano-replicated photonic crystal (PC) label-free biosensors were examined by the analysis of simulated reflection spectra of PC structures. The grating pitch, duty, scaled grating height and scaled TiO2 layer thickness were selected as the design factors to optimize the PC structure. The peak wavelength value (PWV), full width at half maximum of the peak, figure of merit for the bulk and surface sensitivities, and surface/bulk sensitivity ratio were also selected as the responses to optimize the PC label-free biosensor performance. A parametric study showed that the grating pitch was the dominant factor for PWV, and that it had low interaction effects with other scaled design factors. Therefore, we can isolate the effect of grating pitch using scaled design factors. For the design of PC-label free biosensor, one should consider that: (1) the PWV can be measured by the reflection peak measurement instruments, (2) the grating pitch and duty can be manufactured using conventional lithography systems, and (3) the optimum design is less sensitive to the grating height and TiO2 layer thickness variations in the fabrication process. In this paper, we suggested a design guide for highly sensitive PC biosensor in which one select the grating pitch and duty based on the limitations of the lithography and measurement system, and conduct a multi objective optimization of the grating height and TiO2 layer thickness for maximizing performance and minimizing the influence of parameter variation. Through multi-objective optimization of a PC structure with a fixed grating height of 550 nm and a duty of 50%, we obtained a surface FOM of 66.18 RIU−1 and an S/B ratio of 34.8%, with a grating height of 117 nm and TiO2 height of 210 nm.
Metal-enhanced fluorescence (MEF) is a powerful technology to improve the sensitivity of fluorescence analysis by allowing fluorophores to interact with enhanced electromagnetic fields generated by the localised surface plasmon resonance effects of metallic nanostructures. To apply MEF technology to disposable DNA or protein microarray analysis, metallic nanostructures need to be fabricated on the full area of a glass slide at low cost. In this reported work an oblique angle deposition process was used to fabricate Ag nanorods on the whole area of a 25 × 75 mm 2 glass slide to serve as an inexpensive and large-area MEF substrate. To examine the feasibility of the proposed substrate and maximise signal enhancement, Ag nanorods with different lengths were deposited on glass slides. Different concentrations of streptavidin-conjugated Cy5 in phosphate buffered saline were spotted onto the Ag nanorods and bare glass substrates, and the fluorescence signals were measured and compared. Longer Ag nanorods improved the fluorescence enhancement factor because of a higher surface plasmon resonance effect and the large surface area of the nanostructure with a high aspect ratio. A maximum enhancement factor of −23 was obtained from Ag nanorods that were 1000 nm long with comparable uniformity with the glass substrate.
Photonic-crystal (PC) structures are used as biosensors that detect the changes in the surrounding refractive index due to biomolecular interactions. In this study, a method of modeling a PC structure that considers the sidewall deposition effect during high-index layer deposition was proposed to precisely predict the performance of a label-free PC biosensor. A PC composed of nanoreplicated grating and a TiO2 high-index layer was fabricated. To replicate nanograting, a silicon mold with a 450 nm pitch and a 100 nm grating height was fabricated via photolithography and reactive ion etching. A mold cavity was coated with a self-assembled monolayer, and UV replication was performed. To realize the PC structure, a TiO2 high-index layer was deposited using the E-beam evaporation system. To design the simulation model considering the sidewall deposition effect, the cross-sectional surface profile of each PC layer was measured. Finally, the changes in the transmission spectrum of the fabricated PC structure with different buffer solutions were measured and compared with the simulated results obtained from rigorous coupled wave analysis to examine the prediction accuracy of the proposed simulation model.
Bi3+, Eu3+, Dy3+ activated Y2O3 phosphors were prepared through the sol-gel process. X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, and photoluminescence (PL) spectra were used to characterize the resulting phosphors. The XRD patterns show the refined crystal structure of Y2O3. The energy transfer processes of Bi(3+)-Eu3+ occurred in the host lattices. The thermal stability of Y2O3:Bi3+, Eu3+, Dy3+ phosphors was studied. Under short wavelength UV excitation, the phosphors show excellent characteristic red, blue, and yellow emission with medium intensity.
A bilayer wire grid polarizer (B-WGP) composed of UV-replicated nanograting and deposited aluminum layer was designed, fabricated, and evaluated as a simpler and less costly reflective polarizer. To design the B-WGP structure, a parametric study of structural design factors on the simulated performance was conducted using rigorous coupled wave analysis. A durable electroformed nickel stamp was fabricated using a lithographed photo resist master pattern having a nanograting with a pitch of 110 nm, a line width of 65 nm, and a height of 80 nm. A polymer grating was fabricated by the UV replication process, and an aluminum layer with a thickness of 50 nm was deposited by electron-beam evaporation. To examine the performance of the fabricated bilayer wire-grid polarizer, the transmission spectra of p- and s-polarized light, and the extinction ratio spectra were measured and compared with the simulated values. The measured transmittance of p-polarized light and the extinction ratio of the fabricated bilayer wire grid polarizer were ∼40% and ∼103 in whole visible ranges, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.