金属石墨结构D型光纤SPR生物传感器设计与模拟

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"D-shaped光纤光学表面等离子体共振生物传感器基于金属石墨烯结构的研究" 在光学传感领域，D-shaped光纤表面等离子体共振（Surface Plasmon Resonance, SPR）生物传感器因其高灵敏度和实时监测能力而备受关注。本文详细介绍了利用金属石墨烯层设计的一种新型D-shaped光纤SPR生物传感器，并通过有限元方法对其进行了模拟研究。首先，这种D-shaped光纤结构的独特设计允许光在光纤核心与外部环境之间进行有效交互。D-shaped光纤的横截面形状类似于字母"D"，其中一侧被切割，使得光纤内部的光能够与外部介质直接接触。这种设计极大地提高了传感器对环境变化的敏感性。文章指出，金属石墨烯层是传感器的核心组成部分，它能够产生表面等离子体振荡（Surface Plasmon Oscillation）。金属石墨烯具有优异的电学性能和光学特性，其导电性和可调谐性使得它成为理想的选择用于感应外部环境的折射率变化。在实验中，研究者模拟了当外部环境折射率从1.33变化到1.36时的SPR效应。通过有限元方法的模拟，结果显示金属石墨烯层在特定的偏振状态下可以与光有效地耦合，触发强烈的等离子体振荡。这种耦合效应使得传感器能够对微小的折射率变化作出响应，因此，它可以用来检测生物分子如蛋白质、核酸或其他化学物质的存在和浓度，这些变化通常伴随着环境折射率的变化。此外，金属石墨烯的使用还带来了其他优势，比如低损耗、高稳定性和生物兼容性，这些特性对于构建高性能生物传感器至关重要。该工作不仅提供了一种新的传感器设计方案，也为开发更高效、更灵敏的生物检测技术开辟了新路径。这篇研究论文深入探讨了D-shaped光纤SPR生物传感器的工作原理，强调了金属石墨烯层在提高传感器性能方面的重要性，并展示了通过模拟方法优化传感器设计的潜力。这一研究对于未来在生物医学、环境监测以及食品安全等领域实现高精度的检测技术具有重要意义。

COL 11(11), 110607(2013) CHINESE OPTICS LETTERS November 10, 2013

D-shaped fiber optic SPR biosensors based on a

metal-graphene structure

Dejun Feng (

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, Guanxiu Liu (

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, Maosen Zhang (

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, and Dongfang Jia (

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School of Information Science and Engineering, Shandong University, Jinan 250100, China

College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China

∗

Corresponding author: dejunfeng@sdu.edu.cn

Received July 18, 2013; accepted October 17, 2013; posted online November 8, 2013

We design a D-shaped fiber optic biosensor based on the surface plasmon resonance (SPR) of a metal-

graphene layer and simulate this SPR using the finite element method. Using a metal-graphene layer as the

sensing material, surface plasma resonance is simulated as the refractive index of the external environment

ranges from 1.33 to 1.36. Simulation results show that a metal-graphene layer attached to the D-shaped

optical fiber core can couple with light under a specific polarization state and excite strong plasma os-

cillations on the layer surface. Calculated transmission coefficients show that the resonance wavelength

obviously moves toward longer wavelengths as the refractive index of the test medium increases, and a sen-

sitivity of 5400 nm/RIU is obtained. Because of its large surface volume ratio and good biocompatibility,

graphene may be utilized in many applications in the field of biosensing.

OCIS codes: 060.0060, 060.2370, 170.0170.

doi: 10.3788/COL201311.110607.

Rapid developments in modern electronics and biotech-

nology have a llowed the emergence of fiber optic biosen-

sor technology as an independent high-tech field

[1]

. Fiber

optic biosensors can be divided into evanescent wave

[2]

ﬂuorescence labeled

[3]

, and surface plasmon resona nce

[4]

(SPR) sensors according to the operating principle. SPR

technology is widely used in optical biosensors because

it features a dvantages such as absence of marking, high

sensitivity, high specificity, and real-time results

[5]

Graphene film is a monolayer of carbon atoms packed

into a dense honeycomb crystal structure that ca n be

viewed as an individual atomic plane extracted from

graphite. As a novel material with unique optical and

electrical pr operties, graphene has been extensively stud-

ied in a number of areas

[6,7]

. It pos sesses advantages of

large surface volume ratio and good biocompatibility

and thus allows fixing of large amounts of biomolecules.

Biosensors bas e d on graphene are known to have wide lin-

ear ranges and low detection thresholds. Thus, gra phene

provides a good platform from which to build a variety

of biosensors

[8]

Each carbon atom of graphene features an unfilled e lec-

tron structure. As such, graphene is a typical zero-band

gap semi-metallic material that can replace traditional

precious metals to produce SPR

[9]

. Pradeep Kumar

Maharana et al. developed a chalcogenide prism and

graphene multilayer-based SPR biosensor in 2012

[10]

Graphene increases the absorption of biomolecules,

thereby improving the sensitivity of the resulting biosen-

sor. Jang Ah Kim et al. reported an SPR based fiber op-

tic sensor coated with graphene

[11]

. When streptavidin-

biotin and double-cross DNA are combined, the refractive

index increases and the resona nce wavelength at 7.726

nm moves toward longer wavelengths.

While combining graphene biosensor technology

with optical fibers shows good prospects for sensing

applications

[12]

, domestic research on graphene-based

optical biosensors is fairly limited. Traditional opti-

cal fiber sensors have advantages of large transmission

capacity, rapid measurement, anti-electromagnetic inter-

ference, and miniaturization. Thus, this letter designs a

fiber optic biosensor based on the SPR effect on a metal-

graphene layer. The resulting sensor is expected to be

widely used in the chemical, biomedical, environmental

safety, and food safety industries as well as in many other

aspects.

Surface plasmon polaritons (SPPs) are electromagnetic

waves excited by the interaction between light and free

electrons on a metal surface typically presenting in the

interface of a metal and dielectric layer

[13]

. Given their

high sensitivity depending on the surface environment,

SPPs are widely used in biosensors.

Figure 1 shows the interface of the metal-dielectric.

The incident light is decomposed into s-polarized light

(TE wave ) whose electric vector E is perpendicular to the

incident plane, and p-polarized light (TM wave) whose

E is in the incident plane. Since the s-polarized E is

parallel to the direction of the interface, it does not hin-

der the movement of electrons and cannot excite surface

plasmon waves (SPWs); thus, SPR phenomena cannot

occur. In p-polarized light, the E has a component in the

vertical direction of the interface, and electrons around

the nucleus vibrate perpendicular to the interface driven

by the electric field of light. On the metal surface, the

transverse movement (perpendicular to the interface) of

electrons is blocked by the surface to form a gradient dis-

tribution of the electron conce ntration. This distribution

causes plasma oscillation or SPWs on the metal surface.

SPPs are non-radiative electromagnetic waves con-

strained to the surface of a conductor. Generally, surface

plasmons ar e accompanied by a longitudinal (TM or p-

polarized) electric field, which decays exponentially in

metal as well as in dielectrics. Because o f the exponential

decay of the field intensity, the field has its maximum

at metal-dielectr ic interface itself. High losses in the

metal cause SPWs to propagate with high attenuation in

the visible and near-infrared spectral regions, eventually

depleting SPWs within a limited range of propagation

1671-7694/2013/110607(4) 110607-1

 2013 Chinese Optics Letters

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