In this paper, we present a tilted fiber Bragg gratings (TFBG) based surface Plasmon resonance (SPR) label-free sensors with boronic acid derivative (ABA-PBA) as receptor molecule to detect glycoprotein with high sensitivity and selectivity. Tilted fiber Bragg gratings (TFBG) as a near infrared wavelengths detecting element can be able to excite a number of cladding modes whose properties can be detected accurately by measuring the variation of transmitted spectra. A 10° TFBG coated by 50nm gold film was manufactured to stimulate surface plasmon resonance on the surface of the sensor. The sensor was loaded with boronic acid derivative as the recognition molecule which has been widely used in various areas for the recognition matrix of diol-containing biomolecules. The proposed TFBG-SPR sensors exhibit good selectivity and repeatability with the protein concentration sensitivity up to 2.867dB/ (mg/ml) and the limit of detection was 2*10<sup>-5</sup>g/ml.
A fiber Bragg grating (FBG) has been utilized in capacitively coupled plasmas (CCP) for thermometry of neutral gas. We studied the effects of high frequency and low frequency power on radial distribution of neutral gas temperature. The result shows that the neutral gas temperature increases with increasing high frequency power. However, the presence of low frequency power will decrease the neutral gas temperature. Particularly, we eliminated the effect of ion bombardment on temperature measurement by studying axial distribution near plasma–sheath boundary. With features of immune to electromagnetic interference, high precision, and spatial resolving power, the FBG is a commendable candidate for CCP or other radio-frequency plasmas thermometry in both laboratory and industry.
In this paper, we propose and demonstrate a novel self-referencing surface plasmon resonance (SPR) fiber-optic sensor which provides a Fabry-Perot (FP) interference referencing signal for temperature compensating. The sensor is fabricated by splicing a capillary partly coated with gold film between multimode fibers. The multimode fibers act as the lead-in and lead-out fibers while the capillary is used as sensing element. Because the FP interference and SPR effects can occur in the capillary simultaneously, the spectrum of the sensor exhibits SPR absorption and FP interference fringes. Due to the FP interference fringe sensitive to temperature while insensitive to refractive index (RI), it can be used as referencing signal and the SPR absorption was used as measuring signal. Experimental results show that this approach we presented can compensate temperature effect and develop this sensor as a practicable high-sensitivity sensing device. Moreover, as a self-referencing fiber-optic SPR sensor, this simple and low-cost element can be used for highly sensitive biosensing for further investigations.
We present a localized surface plasmon resonance fiber optic biosensor based on an intensity interrogation mechanism. A layer of gold nano sphere is deposited on a fiber optic sensor probe which works as the sensing element and is immobilized on the sidewall of an unclad optical fiber via two different immobilization methods (amino silane method and layer by layer self-assembly method). Different self-assembly layers were also respectively investigated by using layer by layer self-assembly method to explore the optimum layer number. Experimental results reveal that PDDA/PSS/PAH layer self-assembly method provides the best LSPR response. We obtain a refractive index sensitivity as 6.57RIU<sup>-1</sup> in a RI range of 1.3266~1.3730. We also conduct real-time and label free monitoring of Ribonuclease B/Con A biomolecular interaction by using this sensor prototype and demonstrate it can perform qualitative and quantitative detection in real-time biomolecular sensing.