In this study, we experimentally confirmed the sensitivity enhancement by the nanowire-based surface plasmon
resonance (SPR) sensor structure. Gold nanowire samples with a period of 500 nm were fabricated by interference
lithography on a gold-SF10 glass substrate. Sensitivity enhancement compared to a conventional SPR structure was
measured to be 31% when evaluated using a varied concentration of ethanol at a dielectric surrounding layer. This result
is consistent with numerical data of rigorous coupled-wave analysis. Rough surfaces of thin gold film and gold
nanowires are deemed to induce the sensitivity degradation by more than 10%. More significant sensitivity improvement
can be achieved by implementing finer nanowires.
In this study, we investigated the impact of surface roughness on the sensitivity of conventional and nanowire-based
surface plasmon resonance (SPR) biosensors. The theoretical research was conducted using rigorous coupled-wave
analysis with Gaussian surface profiles of gold films determined by atomic force microscopy. The results suggest that,
when surface roughness ranges 1 nm, the sensitivity of a conventional SPR system is not significantly affected regardless
of the correlation length. For a nanowire-based SPR biosensor, however, we found that the sensitivity degrades
substantially with a decreasing correlation length. Particularly, at a correlation length smaller than 100 nm, random
rough surface may induce destructive coupling between excited localized surface plasmons, which can lead to prominent
reduction of sensitivity enhancement.
In this study, we investigate the impact of the cross sectional profile of an array of metallic nanowires on the feasibility of a localized surface plasmons resonance (LSPR) biosensor. Calculations were performed using rigorous coupled wave analysis with an emphasis on the extinction properties of the LSPR structure. It was confirmed that the resonance spectrum strongly depends on the nanowire period and profile. Our numerical results indicate that the nanowire structure, particularly that of a T-profile, delivers extremely linear sensing performance over a wide range of target refractive index with much enhanced sensitivity. The extinction-based LSPR structure also involves relatively large dimension and thus is expected to provide a feasible biosensor using current semiconductor technology.
In this study, localized surface plasmon resonance (SPR) biosensors with gold nanowires regularly patterned on a gold film are considered for sensitivity enhancement. The theoretical investigation was conducted using rigorous coupled wave analysis (RCWA) in terms of various design metrics, such as the resonance angle shift, the SPR curve angular width (SPR CAW), and the minimum reflectance at resonance (MRR). Especially, when LSP modes couple resonantly, broad SPR CAW and shallow MRR as well as a large shift of the resonance angle can be observed due to absorptive damping and localized coupling. The results show that, in general, nanowires of a T-profile present more effective sensitivity enhancement than an inverse T-profile. The sensitivity enhancement mediated by the presence of nanowires has been clarified qualitatively based on the dispersion relation between metal film involving nanowires and surrounding dielectric medium. Moreover, optimal design parameters of nanowires are determined based on quantitative metrics that measure the sensor performance and the fabrication reliability.
It is well known that the use of noble metal nanoparticles can considerably enhance the sensitivity of conventional surface plasmon resonance (SPR) biosensors. In our study, we theoretically investigate this sensitivity enhancement effect using rigorous coupled-wave analysis. It is based on the assumption that the enhancement of localized plasmons can be demonstrated by the coupling phenomenon between the periodic noble metal structures and the incident light with an appropriate polarization. It is shown that the rigorous coupled-wave method can be applied to calculating a SPR structure that includes metallic nanoparticles of rectangular-like geometry, where the presence of nanoparticles induces significant changes in the position of reflectivity minimum. The influence of the nanoparticle period on the sensitivity enhancement is also confirmed. In the calculation, Au nanoparticles deposited on an Au film or adsorbed on a SAM layer are modified to regularly patterned one-dimensional nanowires. When the period is less than 300 nm, the calculated sensitivity enhancement of the nanoparticle-based SPR structure is more than ten-fold compared with that of a conventional SPR biosensors configuration.
KEYWORDS: Simulation of CCA and DLA aggregates, Imaging systems, Analog electronics, Optical components, Resistance, Modulators, Cancer, Toxicity, Animal model studies, Luminescence
An integrated cytometric fluorescent imaging system is developed for characterizing chemical concentration and
cellular status in microscale cell culture analog (μCCA) devices. A μCCA is used to evaluate the potential toxicity and
efficacy of proposed pharmaceutical treatment of animals or humans. The imaging system, based on discrete optical
components, not only provides a robust and compact tool for real-time measurements, but the modularity of the system
also offers flexibility to be applicable to various μCCA structures that may be appropriate to various animal or human
models. We investigate the dynamics of doxorubicin, a chemotherapeutic agent, on cultured cells in a μCCA using the
integrated cytometric fluorescent imaging system. This study incorporates two uteran cancer cell lines representing a
sensitive cell type and a multi-drug resistant (MDR) derivative cell line. The ultimate goal is to test the effect of MDR
modulators in combination with doxorubicin to kill cancer cells while not causing undue harm to normal cells.
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