Utilization of chitosan-based sensor thin films for the detection of lead ion by surface plasmon resonance optical sensor

Chitosan-based sensor thin films were fabricated to detect trace amounts of lead ion using surface plasmon resonance (SPR) optical sensor. The gold surface used for SPR measure- ments was modified with chitosan and chitosan-tert- butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide) (chitosan-BCAT). Both chitosan and chitosan-BCAT layers were deposited on the gold surface by spin coating technique. The experiment has been carried out to monitor the SPR signals for lead ion with sensitive enhancement by chitosan and chitosan-BCAT layers. For both layers, the change in resonance angle (δθ) is directly proportional to the concentration of lead ion solution. The higher amounts of (δθ) were obtained for chitosan-BCAT film due to a specific binding of BCAT with lead ion. The chitosan-BCAT film enhanced the sensitivity of detection down to 0.03 ppm. Data analysis also has been done by Matlab software using Fresnel formula for multilayer system

Characterization of the optical properties of heavy metal ions using surface plasmon resonance technique.

The aim of this research is to characterize the optical properties of heavy metal ions (Hg2+, Cu2+, Pb2+ and Zn2+) using surface plasmon resonance (SPR) technique. Glass cover slips, used as substrates were coated with a 50 nm gold film using sputter coater. The measurement was carried out at room temperature using Kretchmann SPR technique. When the air medium outside the gold film is changed to heavy metal ions solution, the resonance angle shifted to the higher value for all samples of heavy metal ions solution. By our developed fitting program (using Matlab software), the experimental SPR curves were fitted to obtain the refractive index of Hg2+, Cu2+, Pb2+ and Zn2+ ions solution with different concentrations. Both the real and imaginary part of refractive index of the heavy metal ions solution increased with the concentration. The results give the basic idea such that the SPR technique could be used as an alternative optical sensor for detecting heavy metal ions in solution

Optical characterization of multi layer thin films using surface plasmon resonance method: from electromagnetic theory to sensor application

Surface plasmon resonance (SPR) is a quantum electromagnetic phenomenon arising from the interaction of light with free electrons at a metal-dielectric interface. SPR has emerged as a powerful optical sensor based on the sensing of the change in refractive index of a medium adjacent to the metal surface layer. In the present work, the data analysis in SPR method which involves determination of optical constants and thicknesses of multi layer thin films was investigated based on Kretschmann configuration. The SPR experimental results (reflectance versus incident angle plots) were analyzed by using Maxwell's and Fresnel's equations. The calculations involve transfer matrix method where the unknown optical parameters were obtained by fitting experimental SPR plots to calculated theoretical results. The utility of this transfer matrix has also been demonstrated for recently reported SPR experiment on sensor application

Study of PFS and PAC coagulation effect on Pi River water

Using poly-aluminum chloride (PAC) and poly-ferric sulfate (PFS) as coagulants, the effects of the dosage of PAC and PFS on the removal of turbidity, chromaticity and UV254* in water were investigated by using the method of enhanced coagulation. The results show that when the raw water is neutral and the turbidity is less than 20NTU, and the pH value does not decrease much after coagulation and sedimentation, PAC and PFS are separately added to 7.5mg/l, 35mg/l. The removal rate of turbidity and chromaticity in the water sample can reach 83.75% and 48.47%, respectively, but the removal rate of UV254* is less than 30%, the mass ratio of PAC to PFS is 1:1 to 6:1, the removal efficiency of turbidity and Chroma increased by about 10%, but the removal efficiency of UV254* did not change or even decreased, both PFS and PAC can effectively remove the turbidity and Chroma in the micro polluted Pi River, but the removal effect of UV254* is not good, and the removal effect of PAC is better than PFS

Linear-Parameter-Varying Antiwindup Compensation for Enhanced Flight Control Performance

Actuator saturation is one of the major issues of flight control in the high angle-of-attack region. This paper presents a saturation control scheme for linear parameter varyjing (LPV) systems from an antiwindup control perspective. The proposed control approach is advantageous from the implementation standpoint because it can be thought of as an augmented control algorithm to the existing control system. Moreover, the synthesis condition for an antiwindup compensator is formulated as a linear matrix inequality (LMI) optimization problem and can be solved efficiently. We have applied te LPV antiwindup controller to an F-16 longitudinal autopilot control system design and compared it with the thrust vectoring control scheme. The nonlinear simulations show that an LPV antiwindup controller improves flight quality and offers advantages over thrust vectoring in a high angle-of-attack region

Surface plasmon resonance optical sensor for detection of essential heavy metal ions with potential toxicity: copper, zinc and manganes.

In this work, surface plasmon resonance (SPR) spectroscopy had been studied for detection of essential heavy metal ions with potential for toxicity: copper, zinc and manganese ions (Cu2+, Zn2+ and Mn2+). The sensitivity of SPR optical sensor had been enhanced by introducing a thin crosslinked chitosan layer on a gold film. Crosslinked chitosan solution was synthesized by homogeneous reaction of medium molecular weight chitosan in aqueous acetic acid solution with glutaraldehyde as crosslinking agent. It was deposited on gold film by spin coating. From the results we found that the change in the resonance angle (Δθ) is directly proportional to the concentration of heavy metal ions solution (0.5-100 ppm). The sensitivity of this optical sensor for the studied heavy metal ions are in following order: Cu2+ > Zn2+ > Mn2+. The gold/chitosan interface in SPR technique is highly sensitive for these heavy metal ions with detection limit as low as 0.5 ppm

Analysis of Pb(II) ion sensing by crosslinked chitosan thin film using surface plasmon resonance spectroscopy

The crosslinked chitosan thin film had been studied as a sensor element of surface plasmon resonance (SPR) optical sensor. Crosslinked chitosan solution was synthesized by homogeneous reaction of medium molecular weight chitosan in aqueous acetic acid solution with glutaraldehyde as crosslinking agent. It was deposited on gold film by spin coating. Using SPR technique, the optical properties of crosslinked chitosan thin film before and after contacting with different concentration of Pb(II) ion in a range of 0.5–100 ppm had been obtained by fitting. The resonance angle shifted to lower value as the Pb(II) ion concentration increased. Changes in the resonance angle (Δθ) are directly proportional to the concentration of Pb(II) ion solution. X-ray photoelectron spectroscopy (XPS) had been employed to confirm chemical elements and their bonding of the thin film prior to adsorption, as well as chemical interactions involved between Pb(II) ion and the thin film

Immobilization of tetrabutyl thiuram disulfide in chitosan thin film for sensing zinc ion using surface plasmon resonance spectroscopy

Tetrabutyl thiuram disulfide (TBTDS) immobilized in chitosan thin film has been studied as a sensor element for zinc ion, Zn2+, using surface plasmon resonance (SPR). The TBTDS-immobilized chitosan thin film, which acts as an active layer, was coated on a gold film by spin coating. Zn2+ can be detected by measuring the SPR signal when TBTDS-immobilized chitosan thin film contacts with Zn2+ in solution. The sensor produced a linear response for Zn2+ ranging from 0.1 to 1 ppm with a sensitivity of 0.0317 degrees ppm(-1). Using immobilized TBTDS as an active layer, the Zn2+ can also be selectively detected when present in mixtures of heavy metal ions

Detection of mercury and copper ions using surface plasmon resonance optical sensor.

Mercury and copper ions, Hg2+ and Cu2+, can be detected by measuring surface plasmon resonance signals with a thin chitosan layer deposited on a gold film. An amount of 0.55 ml of chitosan cross-linked glutaraldehyde solution was spin coated onto a glass cover slip at 6000 rev./min for 30 s. Changes in the resonance angle (Δθ) are directly proportional to the concentration of heavy metal ions in solution (0.5–100 ppm). The sensitivities to Hg2+ and Cu2+ are 0.00743 and 0.00654 ppm−1, respectively. The gold/chitosan interface is highly sensitive to Hg2+ and Cu2+ with detection limits as low as 500 ppb

Development of surface plasmon resonance spectroscopy for metal ion detection

Surface plasmon resonance (SPR) spectroscopy has emerged as an optical sensor for sensing a variety of analytes, including metal ions. However, despite its numerous advantages, which include very high sensitivity, simple sample preparation, low cost, fast measurement capability, no requirement for reference solution, high reproducibility, ability to monitor kinetic behaviour, label-free detection, and nondestructiveness, the SPR optical sensor has to compete with existing methods especially in terms of sensitivity and selective detection. A critical review of the use of SPR in metal ion detection is presented. It describes the instrument and different developments on active layers or recognition molecules for sensitivity and selectivity improvements. In conclusion, progress in SPR optical sensor technology will further expand SPR detection abilities and allow SPR sensing to be used widely including in environmental monitoring as an effective metal ion sensor in the future