Water Pollutants p-Cresol Detection Based on Au-ZnO Nanoparticles Modified Tapered Optical Fiber

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Abstract
In this work, a localized plasmon-based sensor is developed for para-cresol (p-cresol) - a water pollutant detection. A nonadiabatic $40~\mu \text{m}$ of tapered optical fiber (TOF) has been experimentally fabricated and computationally analyzed using beam propagation method. For optimization of sensor’s performance, two probes are proposed, where probe 1 is immobilized with gold nanoparticles (AuNPs) and probe 2 is immobilized with the AuNPs along with zinc oxide nanoparticles (ZnO-NPs). The synthesized metal nanomaterials were characterized by ultraviolet-visible spectrophotometer (UV–vis spectrophotometer) and transmission electron microscope (HR-TEM). The nanomaterials coating on the surface of the sensing probe were characterized by a scanning electron microscope (SEM). Thereafter, to increase the specificity of the sensor, the probes are functionalized with tyrosinase enzyme. Different solutions of p-cresol in the concentration range of $0~\mu \text{M}$ – $1000~\mu \text{M}$ are prepared in an artificial urine solution for sensing purposes. Different analytes such as uric acid, $\beta $ -cyclodextrin, L-alanine, and glycine are prepared for selectivity measurement. The linearity range, sensitivity, and limit of detection (LOD) of probe 1 are $0~\mu \text{M}$ – $700~\mu \text{M}$ , 7.2 nm/mM (accuracy 0.977), and $59.90~\mu \text{M}$ , respectively; and for probe 2 are $0~\mu \text{M}$ – $1000~\mu \text{M}$ , 5.6 nm/mM (accuracy 0.981), and $57.43~\mu \text{M}$ , respectively. Thus, the overall performance of probe 2 is quite better due to the inclusion of ZnO-NPs that increase the biocompatibility of sensor probe. The proposed sensor structure has potential applications in the food industry and clinical medicine.
Funding Information
  • Double-Hundred Talent Plan of Shandong Province
  • National Key Research and Development Program of China (2016YFB0402105)
  • Liaocheng University, China (318051901, 31805180301, 31805180326)
  • Science and Engineering Research Board, India (TAR/2018/000051)
  • Fundação para a Ciência e a Tecnologia (FCT) through the iFish Project (CEECIND/00034/2018)
  • National Funds through the FCT/Ministério da Educação and Ciência (MEC), Project i3N (UIDB/50025/2020, UIDP/50025/2020)

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