Jianchun Yang

Non-enzymatic electrochemical sensors for the detection of hydrogen peroxide based on Cu2O/Cu nanocomposites

In this article, Cu2O/Cu NC nanocomposite catalysts on glass carbon electrodes have been synthesized by electrochemical deposition at −0.2 V versus silver/silver chloride and used to construct an electrochemical sensor for detection of hydrogen peroxide. The effects of deposition time and pH were investigated in detail. In 0.1 M phosphate buffer saline (PBS, pH = 6.5), the Cu2O/Cu NC modified electrode exhibits a wide linear dependence (R = 0.996) at a concentration of H2O2 from 4.0 × 10−7 M to 1.0 × 10−2 M, a high sensitivity of 870.4 μA mM−1 cm−2 and a detection limit of 2.0 × 10−7 M. Additionally, the sensor was applied for the determination of H2O2 in milk, showing its potential for practical applications.

An optical fiber methane gas sensing film sensor based on core diameter mismatch

An optical fiber evanescent wave methane gas sensor based on core diameter mismatch is reported. The sensor consists of a multimode fiber in which a short section of standard single-mode fiber, coated with the inclusion of cryptophane molecules E in a transparent polysiloxane film, is inserted. The sensing principle is analyzed by optical waveguide theory. For different sensing film thicknesses and interaction lengths, the sensor signal is investigated within the methane concentration range of 0-14.5% (v/v). It is shown that the sensor signal with the thickness of 5 \mu m and the interaction length of 3 mm strengthens linearly with the increasing concentration of methane, with a slope of 0.0186. The best detection limit of the sensor for methane is 2.2% (v/v) with a response time of 90 s. This sensor is suitable for the detection of methane concentration below the critical value of 5%.

High-sensitivity photonic crystal fiber long-period grating methane sensor with cryptophane-A-6Me absorbed on a PAA-CNTs/PAH nanofilm

A high-sensitivity photonic crystal fiber long-period grating (PCF-LPG) methane sensor with cryptophane-A-6Me absorbed on a poly(acrylic acid)-carbon nanotubes/ polypropylene amine hydrochloride (PAA-CNTs/PAH) nanofilm was investigated. The sensing film was coated onto the internal surface of a photonic crystal fiber cladding air holes by an electrostatic self-assembly technique. Based on a finite element method and the coupled local-mode theory, the effects of the sensing films refractive index (RI) and thickness on the resonant wavelength were theoretically and numerically analyzed. When the sensing film RI decreases from 1.55 to 1.53, and the thickness increases from 100 nm to 200 nm, the resonant wavelength has a blue shift. A higher RI sensitivity with 1.075 × 103 nm RIU-1 is observed for the film thickness of 200 nm. The PCF-LPG methane sensor was fabricated by a pressurized injection method. The sensing experimental result shows that the resonant wavelength of the transmission spectra has a blue shift when the methane concentration increases from 0.0% to 3.5% by volume. The sensor has a good sensitivity of 1.078 nm%-1 and a low detection limit of 0.18% for a film thickness of 210 nm.

An in-line Mach-Zehnder Interferometer Using Thin-core Fiber for Ammonia Gas Sensing With High Sensitivity

Ammonia is an important indicator among environmental monitoring parameters. In this work, thin-core fiber Mach-Zehnder interferometer deposited with poly (acrylic acid) (PAA), poly (allyamine hydrochloride) (PAH) and single-walled carbon nanotubes (SWCNTs-COOH) sensing film for the detection of ammonia gas has been presented. The thin-core fiber modal interferometer was made by fusion splicing a small section of thin-core fiber (TCF) between two standard single mode fibers (SMF). A beam propagation method (BPM) is employed for the design of proposed interferometer and numerical simulation. Based on the simulation results, interferometer with a length of 2 cm of thin-core fiber is fabricated and experimentally studied. (PAH/PAA)2 + [PAH/(PAA + SWCNTs-COOH)]8 film is deposited on the outer surface of thin-core fiber via layer-by-layer (LbL) self-assembly technique. The gas sensor coated with (PAH/PAA)2 + [PAH/(PAA + SWCNTs-COOH)]8 film towards NH3 gas exposure at concentrations range from 1 to 960 ppm are analyzed and the sensing capability is demonstrated by optical spectrum analyzer (OSA). Experimental results show that the characteristic wavelength shift has an approximately linear relationship in the range 1–20 ppm, which is in accordance with the numerical simulation. Thus, this paper reveals the potential application of this sensor in monitoring low concentration NH3 gas.

Photonic crystal fiber modal interferometer for refractive index sensing of glycerine solution

A photonic crystal fiber sensor was prepared for refractive index sensing. Based on modal interferometer theory, the relationships between the refractive index of glycerine solution and resonant wavelength shift of the sensor are analyzed by numerical simulation. A fiber optical device was designed to operate the sensing experiment. The sensing experiment shows that the resonant wavelength blued-shift for the sensor with refractive index in the range of 1.33~1.41 happens when increasing glycerine solution from 0.0% to 50.0% (v/v). The experimental results are approximately consistent with theory.

A novel sensor for detecting PM2.5 concentration based on refractive index sensing of a photonic crystal fiber

A novel sensor for detecting particulate matter 2.5 (PM2.5, particles with a diameter smaller than 2.5 μm) concentration in environment air is presented by using modal interference in a photonic crystal fiber (PCF). The sensor is composed of a single mode-multimode-PCF-multimode-single mode optical fiber, and the corresponding polypyrrole (PPy) sensing nanofilm with a light-inducing characteristic is synthesized onto the outside surface of a PCF in-situ by an interfacial ploymerization method. The experimental result shows that the thickness of the sensing film is within the range of 100~150 nm by a scanning electron microscope. When the sensor is placed in PM2.5 air flow, the PM2.5 particles are absorbed onto the surface of a PPy sensing film due to a light-inducing electrostatic effect, resulting in the refractive index (RI) change of a sensing film. For PM2.5 air flow with a concentration of 55 μg/m3 and a sampling time of 30 min, the characteristic wavelength of the interference spectra has a blue shift with 1 nm. After turning off the light source, the characteristic wavelength of the sensor is back to the initial value owing to no light-inducing electrostatic effect and the PM2.5 particles desorbing. The sensor has a good reversibility.

Thin-core fiber modal interferometer for ammonia sensing

A ammonia sensor depositing with a polyelectrolyte thin film composed of poly(acrylic acid) (PAA) and poly(allyamine hydrochloride) (PAH) via the layer-by-layer (LbL) self-assembly technique, is demonstrated with a thin-core fiber modal interferometer (TCFMI).