The surge of Dengue cases around the globe has intensified the demand for a reliable diagnostic method. The work demonstrates, to the best of our knowledge, the first label-free optical based sensor for detection of Dengue II E proteins. This was achieved by utilizing tapered optical fiber that has been functionalized with complementary recombinant antibodies. The fundamental concept of the sensor relies on the interaction between strong evanescent waves resulting from the dimensional change of the fiber and immune complex formed on the surface of the fiber when the virus is present. Sensitivity and detection limit values obtained with the sensor setup are 5.02 nm/nM and 1 pM, respectively, with a standard deviation value of no more than ±0.4. The compact and rapid sensor is a viable alternative for label-free and quantitative assessment of the infection, which may assist in providing better clinical management and understanding of the disease.
We have proposed a study on single-mode tapered optical fiber for temperature sensing application. A theoretical analysis and its experimental validation were carried out to study the taper profile for highly sensitive temperature sensor. Experiments were performed to observe a wavelength shift of transmission spectra with different taper profiles. The effects of taper profiles on the sensitivity of the sensor were also investigated. Our results indicate that the tapered fiber-based temperature sensor has sensitivity in the range of 0.01143 to 0.03406 nm/ • C. The findings also demonstrate that the sensor sensitivity can be adjusted with variation to the taper profile.
We examine and demonstrate a biosensor using single-mode tapered fiber that has been immobilized with biorecognition molecules to sense targeted proteins. Interaction of evanescent waves with the external medium surrounding the tapered region produces an interferometric-patterned spectrum, which shifts correspondingly to any changes of refractive index (RI) in the external medium. The proposed setup managed to obtain an RI sensitivity and concentration sensitivity of 2526.8 nm/RIU and 20.368 nm=M, respectively, which, to our knowledge, is highly sensitive when compared with previous studies. The dynamic performance, good specificity, and high sensitivity of the proposed method highlight an immensely beneficial choice for immunological diagnostics.
Carbon nanotubes (CNTs) and graphene are carbon-based materials with great potential for electrochemical sensing in various applications such as for the environmental, biological, and physical sensors. For environmental applications, the sensor used to detect heavy metals such as cadmium (Cd), lead (Pb), mercury (Hg), iron (Fe), and other heavy metals that present in the water qualitatively and at the lowest limit of detection value. The uniqueness of their structures and chemical properties has attracted many researchers to develop carbon-based electrochemical sensors for environmental applications. These carbon materials are low-dimensional, thus providing the elevated aspect ratios and subsequently able to increase the sensitivity of the sensor probe. In the meantime, the graphene has its advantages in terms of its large surface area per unit volume to absorb and trap the molecules on the surface. In theory, the carbon atom is in the mid-range of electronegativity and can thus form a stable covalent bond with other molecules. These two materials are therefore consistent to bond with other functional groups such as amine, aldehyde, carboxyl, and thiol groups. All these functional groups can be functionalized with specific ligands or receptors for that particular heavy metal to provide specific and sensitive detection. Convenience in terms of their functionality, making them the center of attention as versatile platforms for functionalizing and designing an electrochemical sensor probe based on applications of concern. This paper focuses on reviewing carbon-based electrochemical sensors development to detect heavy metal in water for real-time monitoring of water quality, thus providing a brief overview of the sensor design reported previously.
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