Surface Of Silica Optical Fiber Research Articles

Label-Free Ultrasensitive and Environment-Friendly Immunosensor Based on a Silica Optical Fiber for the Determination of Ciprofloxacin in Wastewater Samples.

Emerging contaminants, including pharmaceutical compounds, are receiving research attention as a result of their widespread presence in effluents and wastewater treatment plants (WWTPs). The antibiotic ciprofloxacin (CIP) is extensively employed to treat infections in animal and human medicine. Both CIP and its metabolites are common contaminants found in WWTPs. In this study, a label-free ultrasensitive U-bent optical fiber-based immunosensor for the determination of CIP in wastewater samples was developed using the properties of the conducting polymer polyaniline (PANI). The anti-CIP immunoglobulin G (IgG) was deposited on a silica optical fiber surface previously functionalized with PANI. Scanning electron microscopy and micro-Raman spectroscopy were used to investigate the surface of the immunosensor. The analysis of CIP in wastewater was performed without the use of an organic solvent or sample preparation steps, with only the sample dilution in saline buffer (pH = 7.4). The linear range for CIP was from 0.01 to 10,000 ng L-1. The detection limit was 3.30 × 10-3 ng L-1 and the quantification limit was 0.01 ng L-1. The immunosensor provided a high average recovery of 91% after spiking wastewater samples with CIP at a concentration of 9,100 ng L-1. The method was applied in triplicate to wastewater samples from Quebec (Canada), obtaining concentrations of 549 and 267 ng L-1. A comparison with a reference method showed no significant difference (t-test at 95% confidence). The new technique developed is selective, allowing a quantitative analysis of CIP in wastewater.

Performance Comparison of Two Sensors Based on Surface Plasmon Resonance in a Plastic Optical Fiber

In silica optical fiber Surface Plasmon Resonance (SPR)-based sensors, an increase in fiber core diameter produces a corresponding increase in the sensitivity and Signal to Noise Ratio (SNR). In Plastic Optical Fiber (POF) realized in PMMA there are different influences of design parameters on the performance, as both sensitivity and SNR are concerned. In particular, the SNR, for different refractive index values of the analyte, in a 250 μm diameter POF is greater than the one in 1,000 μm diameter POF. On the other hand, the sensitivity, for the same refractive index values of the analyte, in a 1,000 μm diameter POF is greater than the one in a 250 μm diameter POF. The results of an experimental analysis demonstrating the above behavior are reported.

Detection of lipid bilayer membranes formed on silica fibers by double-long period fiber grating laser refractometry

The formation of lipid bilayer membranes on silica optical fiber surfaces is critical to the development of new optical biosensors based on supported lipid bilayer membrane technology. This paper reports on a new long period fiber grating (LPFG) method using double gratings, one serving as the sensor and another as the reference to correct for environmental factors, to study supported lipid membranes on a silica optical fiber. A method for correcting the effect of the environmental variation on sensor responses is described. The measurements show that formation of eggPC lipid bilayer membranes on the silica optical fiber surface takes place in about 3 min, which is accompanied with about a 500 picometer decrease in the resonance coupling wavelength of the sensor grating. The formation process of eggPC lipid bilayer membranes with and without Gramicidin was measured. It was found that while the presence of Gramicidin does not affect the rate of lipid bilayer membrane formation on the silica fiber, it causes a greater decrease in the resonance coupling wavelength than pure eggPC because of the increased film refractive index. Formation of a lipid bilayer membrane on the silica optical fiber surface was verified by confocal microscopy and through fluorescence recovery after photobleaching (FRAP) analysis, confirming the formation of a single lipid bilayer on the surface of the silica fiber with a diffusion coefficient of 1.2 μ m 2 s −1.

Interferometric inscription of surface relief gratings on optical fiber using azo polymer film

We report the fabrication and characteristics of surface relief grating on the end surface of silica optical fiber with a diameter of 125 μm. One- and two-dimensional gratings were inscribed on the fiber surface covered with azo polymer thin-film layer using interferometric methods. Diffraction beam patterns of the zeroth and the first order due to surface relief gratings were observed using a 635 nm laser, and the relation between the measured diffraction beam pattern and the grating period was also investigated.

Drawing-induced hydrogen-associated defect centers at the silica optical fiber surface

Defect centers in optical fibers induced by drawing were investigated using the electron spin resonance technique. The hydrogen hyperfine (hf) doublet with splitting of 119 G was observed for both GeO2-doped and pure silica optical fibers, which contain few hydroxyl ions. The hf peak intensity was directly proportional to specific surface area of optical fibers. These results indicate that the hf doublet arises from the hydrogen interaction with a drawing-induced germanium defect center at or near the optical fiber surface.