Development of Photonic Crystal Fiber Based Gas/ Chemical Sensors

The development of highly-sensitive and miniaturized sensors that capable of real-time analytes detection is highly desirable. Nowadays, toxic or colorless gas detection, air pollution monitoring, harmful chemical, pressure, strain, humidity, and temperature sensors based on photonic crystal fiber (PCF) are increasing rapidly due to its compact structure, fast response and efficient light controlling capabilities. The propagating light through the PCF can be controlled by varying the structural parameters and core-cladding materials, as a result, evanescent field can be enhanced significantly which is the main component of the PCF based gas/chemical sensors. The aim of this chapter is to (1) describe the principle operation of PCF based gas/ chemical sensors, (2) discuss the important PCF properties for optical sensors, (3) extensively discuss the different types of microstructured optical fiber based gas/ chemical sensors, (4) study the effects of different core-cladding shapes, and fiber background materials on sensing performance, and (5) highlight the main challenges of PCF based gas/ chemical sensors and possible solutions

Evanescent field exposed microstructure fibers for optical sensing / Ng Wee Lit

In this work, a modified photonic crystal fiber (PCF) that we refer to as Sunny PCF is proposed. The Sunny PCF with triangular interstitial air holes surrounding the core region increases the interaction of guided modes with the surrounding media. Full-vectorial finite element method (FEM) with perfectly matched layer boundary condition is used to design and simulate the evanescent field exposure and confinement loss characteristics of the proposed Sunny PCF. By adding sunny structure to a conventional PCF with air-filling ratio of 0.9, the highest achievable evanescent field exposure with negligible confinement loss can be significantly increased to 21.23% from 15.83% (for a comparative non-Sunny PCF) at the operating wavelength of 1550 nm. A preliminary Sunny PCF has been fabricated to prove the feasibility of the proposed structure. In the second part of this work, a new microstructured optical fiber (MOF) which can provide large cavities besides high evanescent field exposure and low confinement loss has been proposed, named Diamond Ring Fiber (DRF). Large cavities ease the infiltration of analyte and allow material coating for certain sensing applications. A silica core is supported by a thin ring in the middle of DRF, forming two large air holes in this fiber. Silica core surrounded by air allows high exposure of guided mode into the air with low confinement loss. 3 DRFs with different parameters have been fabricated using stack and draw method. An experiment has been carried out to study the beam profile of guided mode in different sizes of DRFs. Full-vectorial FEM with perfectly matched layer boundary condition is used to simulate the performance of the fibers using Scanning Electron Microscope (SEM) cross sectional images obtained. DRF with the core size of 0.8 μm can achieve high evanescent field exposure of 39.56% with low confinement loss of 0.027 dB/m at the wavelength of 1550 nm while providing two large cavities with the diameter of 4.2 μm and 10.8 μm respectively. This work is part of a larger effort in using surface plasmon resonance (SPR) for biosensing where the long term target is to adopt fiber technologies as a substrate as opposed to silicon based fabrication. A highly sensitive DRF based SPR sensor for refractive index sensing is then simulated. Chemically-active plasmonic material (gold) layer is coated inside the large cavity of DRF, and the analyte is infiltrated directly through the fiber. The light guiding properties and sensing performances are numerically investigated using FEM. The proposed sensor shows a maximum wavelength and amplitude interrogation sensitivity of 6,000 nm/RIU and 508 RIU-1, respectively over the refractive index range of 1.33-1.39. Additionally, it also shows a sensor resolution of 1.67×10-5 RIU and 1.97×10-5 RIU by following the wavelength and amplitude interrogation methods, respectively

A Novel Diamond Ring Fiber-Based Surface Plasmon Resonance Sensor

We propose a highly sensitive novel diamond ring fiber (DRF)-based surface plasmon resonance (SPR) sensor for refractive index sensing. Chemically active plasmonic material (gold) layer is coated inside the large cavity of DRF, and the analyte is infiltrated directly through the fiber instead of selective infiltration. The light guiding properties and sensing performances are numerically investigated using the finite element method (FEM). The proposed sensor shows a maximum wavelength and amplitude interrogation sensitivity of 6000 nm/RIU and 508 RIU−1, respectively, over the refractive index range of 1.33–1.39. Additionally, it also shows a sensor resolution of 1.67 × 10−5 and 1.97 × 10−5 RIU by following the wavelength and amplitude interrogation methods, respectively. The proposed diamond ring fiber has been fabricated following the standard stack-and-draw method to show the feasibility of the proposed sensor. Due to fabrication feasibility and promising results, the proposed DRF SPR sensor can be an effective tool in biochemical and biological analyte detection

Anti-Hyperuricemic Effect of Ethyl Acetate Sub-Fractions from Chrysanthemum morifolium Ramat. Dried Flowers on Potassium Oxonate-Induced Hyperuricemic Rats

Xanthine oxidase (XO) plays an important role in purine degradation in humans. The study aimed to determine the XO inhibitory potential of Chrysanthemum morifolium dried flower ethyl acetate sub-fractions and its anti-hyperuricemic effect in rat models. Bioassay-guided fractionation based on XO inhibitory assay was employed to obtain bioactive fractions and sub-fractions. In vitro cytotoxicity and cellular antioxidant capacity of the sub-fraction and its mode of XO inhibition were also investigated. The anti-hyperuricemic effect of the bioactive sub-fraction was investigated using rat models via oral consumption, and followed by an XO mRNA gene expression study. The compounds in the bioactive sub-fractions were identified putatively using HPLC-Q-TOF-MS/MS. Ethyl acetate (EtOAc) fraction exhibited the highest XO inhibition among the fractions. It was further fractionated into 15 sub-fractions. F10 exhibited high XO inhibitory activity, cellular pro-proliferative effect, and intracellular antioxidant activity among the sub-fractions tested. This sub-fraction was non-cytotoxic at 0.1–10 µg/mL, and very effective in lowering serum and urine uric acid level in rat models upon oral consumption. A total of 26 known compounds were identified and seven unknown compounds were detected via HPLC-Q-TOF–MS/MS analysis. The possible mechanisms contributing to the anti-hyperuricemic effect were suggested to be the non-competitive inhibition of XO enzyme, XO gene expression down-regulation, and the enhancement of uric acid excretion

Impact of the COVID-19 Pandemic on Door-to-Balloon Time for Primary Percutaneous Coronary Intervention - Results From the Singapore Western STEMI Network -

10.1253/circj.CJ-20-0800CIRCULATION JOURNAL852139-14