Detection of ammonia in the ppt range based on a composite optical waveguide pH sensor

Optical Fibre Long-Period Gratings Functionalised with Nano-Assembled Thin Films: Approaches to Chemical Sensing

“…The assessment of the cross sensitivity to other amine containing compounds is in progress. When compared with other ammonia optical sensors [46] the developed LPG device shows similar detection levels to coulorometric [47] and absorption spectroscopy [48] devices. In particular, the current LPG optical fibre sensor modified with a mesoporous thin film offers unique advantages such as versatile chemical infusion of various chemicals into the mesopores, fast response time owing to the easy analyte penetration and robustness.…”

Optical Waveguide BTX Gas Sensor Based on Yttrium-Doped Lithium Iron Phosphate Thin Film

“…We have found that the LiFe 0.99 Y 0.01 PO 4 film refractive index and thickness for the OWG BTX gas sensor were 1.899 and 104 nm, respectively. The cutoff thickness for the TE 0 mode in a thin film waveguide on glass substrate and sensitivity of thin film OWG were calculated with Runge-Kutta method [9], and the results are as shown in Figure 4. The theoretical calculation indicated that when a LiFe 0.99 Y 0.01 PO 4 film of a 100-120 nm thickness was coated onto the surface of the Tin-diffused glass, the resulting OWG was capable of supporting a TE 0 mode-guided wave, and the relative sensitivity reached its maximum limit of 12809-13988 times/cm (n = 1.899).…”

“…In comparison, the optical waveguide (OWG) sensors [7][8][9] are small in size, of high sensitivity, of fast response time, monitored at room temperature, and of intrinsically safe detection. Furthermore, they suffer little or no interference in the waveguide element of the sensor and can be made at a very low cost.…”

A new sensor for ammonia based on cyanidin-sensitized titanium dioxide film operating at room temperature

“…There is an increasing need to detect low concentrations of air pollutants such as ammonia, which are frequently encountered in every day life, such as in agriculture where the ammonia are used in fertilizers, or in waste water where ammonia result from the surfactant, pharmaceutical and dye manufacturing industries [1,2]. Ammonia has characteristic odors [3,4].…”

“…Occupational safety and health administration (OSHA) has set a 15 min exposure limit for gaseous ammonia by a volume of 35 ppm in environmental air. In the past decade, many kinds of ammonia sensors have been developed based on different sensing mechanisms [1,2,[5][6][7][8][9]. These include electrical [10], mass [11], or optical-based methods [12].…”