RESUMO
Surface plasmon resonance (SPR) sensors based on a silver film suffer from signal degradation due to silver oxidation in aqueous sensing environments. To overcome this limitation, we fabricated the planar plasmonic substrate employing an atomic MoS2 layer on a silver surface. Successful production of a large-area MoS2 monolayer blocks the penetration of oxygen and water molecules. In addition, we theoretically and experimentally found that MoS2 layer on the silver film can improve the SPR sensitivity and stability significantly. In this study, the proposed SPR substrate has the potential to provide highly enhanced sensor platforms for surface-limited molecular detections.
RESUMO
We demonstrated an enhanced surface plasmon resonance (SPR) detection by incorporating a nanoporous gold film on a thin gold substrate. Nanoscale control of thickness and roughness of the nanoporous layer was successfully accomplished by oblique angle deposition. In biosensing experiments, the results obtained by biotin-streptavidin interaction showed that SPR samples with a nanoporous gold layer provided a notable sensitivity improvement compared to a conventional bare gold film, which is attributed to an excitation of local plasmon field and an increased surface reaction area. Imaging sensitivity enhancement factor was employed to estimate an overall sensor performance of the fabricated samples and an optimal SPR structure was determined. Our approach is intended to show the feasibility and extend the applicability of the nanoporous gold film-mediated SPR biosensor to diverse biomolecular binding events.
RESUMO
We experimentally demonstrate that introduction of a dielectric film can prevent the surface plasmon resonance (SPR) curve from being shifted to a smaller angle, called negative shift, which occurs unpredictably when metallic nanostructures deposited on a metal film are exposed to an adsorption of binding analytes. From parylene coating experiments, we find that the proposed reflection-type SPR system with a low refractive index MgF2 film and gold nanorods can provide an enhanced sensitivity by more than 6 times as well as a reliable positive shift. It is due to the fact that use of a dielectric film can contribute to the compensation of an anomalous dispersion relation and the prevention of a destructive interaction of propagating surface plasmons with multiple localized plasmon modes. Our approach is intended to show the feasibility and extend the applicability of the proposed SPR system to diverse biomolecular reactions.
Assuntos
Nanopartículas Metálicas/química , Fenômenos Ópticos , Ressonância de Plasmônio de Superfície/métodos , Ouro/química , Nanopartículas Metálicas/ultraestrutura , Nanotubos/química , Nanotubos/ultraestrutura , Polímeros/química , Fatores de Tempo , Xilenos/químicaRESUMO
In this study, we investigated the performance improvement of a localized surface plasmon resonance (LSPR) biosensor by incorporating a metal-dielectric-metal (MDM) stack structure and subwavelength metallic nanograting. The numerical results showed that the LSPR substrate with a MDM stack can provide not only a better sensitivity by more than five times but also a notably improved signal quality. While the gold nanogratings on a gold film inevitably lead to a broad and shallow reflectance curve, the presence of a MDM stack can prevent propagating surface plasmons from interference by locally enhanced fields excited at the gold nanogratings, finally resulting in a strong and deep absorption band at resonance. Therefore, the proposed LSPR structure could potentially open a new possibility of enhanced detection for monitoring biomolecular interactions of very low molecular weights.
Assuntos
Biopolímeros/análise , Técnicas Biossensoriais/instrumentação , Ouro/química , Nanopartículas Metálicas/química , Refratometria/instrumentação , Ressonância de Plasmônio de Superfície/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Teste de Materiais , Espalhamento de Radiação , Razão Sinal-RuídoRESUMO
An optical process by which transmission wavelengths can be divided selectively by changing a resonance condition of surface plasmons (SPs) is demonstrated. When white light is incident to an SP resonance substrate with a dielectric grating, SP waves are excited at resonance and transmitted into the air via diffraction by a large-area grating pattern fabricated by nanoimprint lithography. While only a limited range of certain wavelengths is allowed to transmit, the peak transmission wavelength can be tuned continuously in the visible band. We also show that multiple wavelengths are transmitted into different directions simultaneously by using a wedge-shaped white light.
Assuntos
Lentes , Refratometria/instrumentação , Ressonância de Plasmônio de Superfície/instrumentação , Cor , Desenho de Equipamento , Análise de Falha de Equipamento , Luz , Espalhamento de RadiaçãoRESUMO
Although subwavelength dielectric gratings can be employed to achieve a high sensitivity of the surface plasmon resonance (SPR) biosensor, the plasmonic interpretation verifying the resulting sensitivity improvement remains unclear. The aim of this study is to elucidate the effects of the grating's geometric parameters on the amplification of SPR responses and to understand the physical mechanisms associated with the enhancement. Our numerical results show that the proposed SPR substrate with a dielectric grating can provide a better sensitivity due to the combined effects of surface reaction area and field distribution at the binding region. An influence of adhesion layer on the sensor performance is also discussed. The obtained results will be promising in high-sensitivity plasmonic biosensing applications.
Assuntos
Cromo/química , Ressonância de Plasmônio de Superfície/métodos , Algoritmos , Desenho de Equipamento , Ouro/química , Nanopartículas Metálicas/química , Análise Numérica Assistida por Computador , Ressonância de Plasmônio de Superfície/instrumentaçãoRESUMO
We investigated the near-field enhancement of a localized surface plasmon resonance (LSPR) structure based on gold nanograting pairs with a nanosized gap. The results calculated by finite-difference time-domain and rigorous coupled-wave analysis methods presented that the nanogap enclosed by two neighboring nanogratings produced significant confinement and enhancement of electromagnetic fields and allowed a sensitive detection in sensing of surface binding events. Gold gratings with a narrow gap distance less than 10 nm showed enhanced refractive index sensitivity due to the intensified optical field at the nanogap, outperforming the LSPR structure with noninteracting nanogratings. Also, we analyzed the effectiveness of using an overlap integral (OI) between analyte and local plasmon field to estimate the detection sensitivity. We found a strong correlation of field-analyte OI with far-field sensor sensitivity.
Assuntos
Nanopartículas Metálicas , Ouro , Nanotecnologia , Fenômenos Ópticos , Ressonância de Plasmônio de Superfície/instrumentação , Ressonância de Plasmônio de Superfície/métodos , Ressonância de Plasmônio de Superfície/estatística & dados numéricos , Propriedades de SuperfícieRESUMO
We demonstrated an enhanced surface plasmon resonance (SPR) detection by incorporating subwavelength SiO2 gratings built on a thin silver film. Large-area SiO2 gratings were fabricated by nanoimprint lithographic technique and dry etching processes and used to sense a surface-limited biomolecular interaction. Numerical results based on rigorous coupled-wave analysis method exhibited that the dielectric gratings can provide a notable sensitivity improvement by 2 times, which is attributed to an increase in surface reaction area. As another possible application of the fabricated plasmonic substrate, experimental data of imaging the cell morphology were also presented. This study was intended to show the feasibility and extend the applicability of a large-area grating-based SPR substrate to diverse optical bioengineering fields.