Abstract
Label-free measurements of small-molecule binding interactions are of high interest to researchers across multiple scientific disciplines. Label-free optical sensors based on surface plasmon resonance (SPR) have been widely used for detecting various targets including toxic heavy metals in solutions. In this research, an SPR optical sensor enhanced with a 4-(2-pyridylazo)-resorcinol (PAR)-based composite layer was employed for the detection of the cobalt ion (Co2+). A binding analysis study was conducted by monitoring the interaction between Co2+ and the sensing layer thin film. In our experiment, there were no changes in SPR angle for a gold layer in contact with Co2+ of different concentrations, whereas the enhanced SPR sensor produced a maximum SPR angle shift of 0.328°. From the relationship between the angle shift and the concentration of Co2+, the sensor had a sensitivity of 0.2375° ppm−1 for concentrations of less than 1 ppm, 0.0044° ppm−1 for concentrations of 1 to 10 ppm, and 0.00069° ppm−1 for concentrations from 10 to 100 ppm. Further analysis was also carried out by calculating the full width at half maximum (FWHM), detection accuracy (DA), and signal-to-noise ratio (SNR). In the binding analysis, the experimental results were fitted with Langmuir, Freundlich, and Sips isotherm equations. It was found that the Sips isotherm equation most closely fitted the experimental data with an R2 value of 0.96716 and a binding affinity of 1.649 ppm−1.
Highlights
In recent years, the scientific community has been focusing on monitoring and improving public health and welfare through the advancement of sensor technology for the detection of ISSN 0914-4935 © MYU K.K. https://myukk.org/Sensors and Materials, Vol 32, No 9 (2020)materials hazardous to the human body, such as viruses, bacterial agents, gases, toxic heavy metals, and other toxic materials
Several sensing methods, which can be categorized into label and label-free methods, have been developed.(1) When applying a label-free sensor, the targeted molecules do not undergo any physical modification due to a reactive label, such as a fluorescence or radioactive dye used in the label method.(2) Over the past few decades, a variety of label-free optical sensors have become well established, including surface plasmon resonance (SPR).(3,4) This can be used in a versatile label-free optical sensor for detecting molecular interactions.(5–7) The basic principle of an SPR sensor is that changes in resonance angle are observed, where the binding of a targeted molecule on a sensor layer adjacent to the metal layer causes a change in refractive index near the metal surface
Has been receiving continuous attention from the scientific community owing to its advantages and for its use in the analysis of binding properties.(14–16) As well as label-free measurement, SPR sensors have the advantages of a simple preparation process, cost efficiency, high sensitivity, and fast and real-time analysis.(17,18) one major drawback of these sensors is that the metal layer alone is insufficient as a sensing layer for binding analysis.(19–25) To overcome this hindrance, active layers have been developed as the sensing element to improve the performance of SPR optical sensors.(26–30) SPR optical sensors have been developed by introducing novel materials as the sensing layer to sense various analytes including heavy metals in the biomedical and environment fields.(31–34) In this study, the potential of a
Summary
The scientific community has been focusing on monitoring and improving public health and welfare through the advancement of sensor technology for the detection of ISSN 0914-4935 © MYU K.K. https://myukk.org/Sensors and Materials, Vol 32, No 9 (2020)materials hazardous to the human body, such as viruses, bacterial agents, gases, toxic heavy metals, and other toxic materials. Several sensing methods, which can be categorized into label and label-free methods, have been developed.(1) When applying a label-free sensor, the targeted molecules do not undergo any physical modification due to a reactive label, such as a fluorescence or radioactive dye used in the label method.(2) Over the past few decades, a variety of label-free optical sensors have become well established, including surface plasmon resonance (SPR).(3,4) This can be used in a versatile label-free optical sensor for detecting molecular interactions.(5–7) The basic principle of an SPR sensor is that changes in resonance angle are observed, where the binding of a targeted molecule (analyte) on a sensor layer adjacent to the metal layer causes a change in refractive index near the metal surface This changes the resonance angle, which is the angle with minimum reflectance.(8–13) Over the past decade, SPR has been receiving continuous attention from the scientific community owing to its advantages and for its use in the analysis of binding properties.(14–16) As well as label-free measurement, SPR sensors have the advantages of a simple preparation process, cost efficiency, high sensitivity, and fast and real-time analysis.(17,18) one major drawback of these sensors is that the metal layer alone is insufficient as a sensing layer for binding analysis.(19–25) To overcome this hindrance, active layers have been developed as the sensing element to improve the performance of SPR optical sensors.(26–30) SPR optical sensors have been developed by introducing novel materials as the sensing layer to sense various analytes including heavy metals in the biomedical and environment fields.(31–34) In this study, the potential of a. In its compound form, it appears as a white crystalline compound with a weak odor and a bittersweet taste.(44) The reaction of resorcinol with 2-pyridylazo led to the synthesis of PAR for the first time in 1959.(45) Since PAR has been widely used as a chromogenic reagent for the detection of mainly metal ions.(46,47) Owing to its remarkable sensitivity towards a wide selection of metal ions, PAR has been integrated with other materials to improve the performance of sensors.(48,49)
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