Ultrasensitive BOD Detection of Fiber Integrated With Nb2CTX MXene for Water Pollution

Two-dimensional (2D) Nb
₂
CT
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MXene has outstanding physicochemical properties and great potential in biochemical sensing applications. Here, we proposed and designed an ultrasensitive microfiber sensor integrated with Nb
₂
CT
_X
nanosheets and tested its BOD detection power. The Nb
₂
CT
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nanosheets were coated on the microfiber surfaces to enhance BOD sensing performance. The Nb
₂
CT
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nanosheets have a sheet-like structure, large specific surface area, and hydrophilic surface functional groups that significantly increase light-matter interactions and refractive index modulation around the microfiber. The transmission spectrum red shift significantly increases with BOD concentration whereas the transmission spectrum blue shift significantly increases with external temperature. An ultrasensitivity value of 34.98 nm/mg/mL and a detection limit of 0.00057 mg/mL were obtained. These values were more than twice those obtained using the bare sensor. The temperature sensitivity was -0.41 nm/°C. The device had inverse spectral responses to BOD concentration and temperature. For this reason, we achieved temperature compensation by demodulating the shifts in the various transmission dips. As the proposed microfiber sensor is ultrasensitive and has temperature compensation, it is a novel and promising design for biosensing and environmental pollution monitoring.