Enhanced Biosensing Activity of Bimetallic Surface Plasmon Resonance Sensor

Abstract

Surface plasmon resonance (SPR) sensors present a challenge when high sensitivity and small FWHM (full width at half maximum) are required to be achieved simultaneously. FWHM is defined by the difference between the two extreme values of the independent variable at which the value of the dependent variable is equal to half of its maximum. A smaller value of FWHM indicates better accuracy of SPR measurements. Theoretically, many authors have claimed the possibility of simultaneously achieving high sensitivity and small FWHM, which in most of the cases has been limited by experimental validation. In this report, an experimental study on the improved surface plasmon resonance (SPR) characteristics of gold over silver bimetallic sensor chips of different film thicknesses is presented. A comparative study of antigen–antibody interaction of the bimetallic chip using a custom-made, low-cost, and portable SPR device based on an angular interrogation scheme of Kretschmann configuration is performed. Pulsed direct current (DC) magnetron-sputtered bimetallic films of gold over silver were used in the construction of the SPR chip. The FWHM and sensitivity of the bimetallic sensors were firstly characterized using standard solutions of known refractive index which were later immobilized with monoclonal anti-immunoglobulin G (IgG) in the construction of the SPR biochip. Spectroscopic measurements such as ultraviolet–visible light spectroscopy (UV–Vis) and Fourier-transform infrared spectroscopy (FTIR) were used for the confirmation of the immobilization of the antibody. The performance of the bimetallic SPR biochip was investigated by exposing the sensor to various concentrations of the target protein. The results indicated that the bimetallic sensors of silver/gold had a 3.5-fold reduced FWHM compared to pure gold-based sensors, indicating a higher detection accuracy. In addition, they exhibited a significant shift in resonance angle as high as 8.5 ± 0.2 due to antigen–antibody interaction, which was ~1.42-fold higher than observed for pure silver-based sensors.

Sensitivity Enhanced Refractive Index Fiber Sensor Based on Long-Range Surface Plasmon Resonance in SiO2-Au-TiO2 Heterostructure

“…Their average sensitivities within the RI range from 1.33 to 1.39, as the linearly fitting curves show in Figure 7b, are about 11,586 nm/RIU and 10,639 nm/RIU, respectively. The corresponding average resolutions are about 8.63 × 10 −7 RIU and 9.40 × 10 −7 RIU, respectively, based on Equation (6).…”

“…For further enhancing their performance and functions, SPR-based devices with multilayer heterostructures arouse researchers' considerable interest. For example, bimetallic layers are widely proposed to improve the sensitivity and stability of SPR biosensors [5][6][7]. A layer made of metal oxide, such as indium tin oxide (ITO) [8], tin oxide (SnO 2 ) [9], titanium dioxide (TiO 2 ) [10], hafnium oxide (HfO 2 ) [11], tantalum oxide (Ta 2 O 5 ) [12], and so forth, is commonly used as an adhesive layer to strengthen the attachment of a metal film on a substrate, or deposited on top of the metal layer to protect metal from oxidization.…”

Improving the Detection Accuracy of an Ag/Au Bimetallic Surface Plasmon Resonance Biosensor Based on Graphene

“…However, SPR sensors with only an Au layer provide high sensitivity with low of detection accuracy and quality factor, while that with only an Ag film ameliorates the sensor's detection accuracy and quality factor at a cost of low sensitivity. Therefore, bimetallic structures consisting of Ag/Au films are considered as a compromise between two single metal based sensors [12][13][14][15][16][17].…”

Optical Characterization of Ultra-Thin Films of Azo-Dye-Doped Polymers Using Ellipsometry and Surface Plasmon Resonance Spectroscopy

“…SPs and localized surface plasmons (LSPs) were reported long ago [6,7], and their use is of the utmost importance in, for example, the field of bio-sensing [8][9][10], enhanced spectroscopies [11], dye-sensitized solar cells [12], and photocatalysis [13]. Important reviews summarize the developments in the field [9,[14][15][16][17][18][19].…”