Formaldehyde gas sensor based on silver-and-yttrium-co doped-lithium iron phosphate thin film optical waveguide
Introduction
The evaluation of indoor air quality is a serious environmental issue that needs to be addressed urgently. Formaldehyde (CHOH) is one of the harmful volatile organic compounds (VOCs) emitted by building materials, interior decoration materials, wood furniture, carpets, and so on. Formaldehyde gas irritates human eyes and noses at concentrations higher than 200 ppb, causes breathing difficulties above concentrations of 5 ppm, and has been known to be a carcinogen since 1980 [1], [2]. The World Health Organization (WHO) has established a concentration of 0.08 ppm, averaged over 30 min, as a standard for long-term exposure to formaldehyde vapors [3], while the Chinese Environmental Protection Agency (EPA) established 0.06 ppm as the standard [4].
Several sensors have been reported for formaldehyde detection. These include enzyme-based biosensors [5], metal-oxides-based gas sensors [6], piezoelectric sensors [7], and optical fiber sensors [8]. Among the various kinds of sensors, optical chemical sensors have been shown to be safe for use in an explosive environment, in addition to be applicable in unusual or extreme conditions [9]. The optical waveguide (OWG) sensor [10], [11] is of particular interest owing to its high sensitivity, fast response time, low cost, and intrinsically safe detection.
A simple planar OWG consists of a substrate, a thin top layer (waveguide layer) with a refractive index greater than that of the substrate (onto this, a sensitive covering material is deposited to detect the analyte), and the covering material (usually air). In this study, LiFePO4 co doped with Ag and Y (LiFe1−0.01xY0.005xAg0.005xPO4) was used as the sensing element for a formaldehyde gas sensor. LiFePO4, which has an olivine structure, has attracted great interest as the cathode material in rechargeable lithium-ion batteries because of its high energy density, low cost, low toxicity, excellent thermal stability, and safety [12], [13], [14]. So far, a number of experimental studies on LiFePO4 have appeared that have improved its electrochemical properties through doping with other elements [15], [16], prepared LiFePO4 thin film electrodes [17], and used it lithium-ion sensors [18]. However, there is almost no report on its optical properties as well as the gas sensing applications.
After enormous experiment confirm that, LiFePO4 thin film exhibited excellent optical transparency [19], [20], [21], easy fabricated, high refractive index, good response to pollutant gases, and was a qualitative candidate for optical waveguide gas sensor.
In semiconductor gas sensor, the gas-sensitivity has been improved by introducing dopants or decreasing particle size of sensing materials [22]. Previously [20], [21], the sensitivity and selectivity of LiFePO4 thin film OWG were improved by doping Ag and Y, separately. In this study, in order to get more sensitive material, both Ag and Y were selected as dopants.
Herein, we report the development of a LiFe1−0.01xY0.005xAg0.005xPO4-thin-film/tin-diffused glass-based OWG sensor and its application in formaldehyde gas detection. Our research focused on the effect that the concentrations of the dopants, Ag and Y, used to fabricate the LiFe1−0.01xY0.005xAg0.005xPO4 thin film, had on the gas sensing properties of the sensor with respect to formaldehyde gas.
Section snippets
Preparation of LiFe1−0.01xY0.005xAg0.005xPO4 powders
LiFe1−0.01xY0.005xAg0.005xPO4 powders were synthesized by a hydrothermal method. Iron (II) sulfate heptahydrate (analytically pure), phosphoric acid (85 wt%; analytically pure) and lithium hydroxide monohydrate (analytically pure) were mixed in a molar ratio of 1:1:3 [23]. In order to simplify the synthesis process, AgNO3, Y (NO3)3·6H2O and 0.1 g of ascorbic acid were added to form LiFe1−0.01xY0.005xAg0.005xPO4 (x = 0.5, 1.0, 2.0). The resulting solution was placed in a hydrothermal reactor having
Characterization of the LiFe1−0.01xY0.005xAg0.005xPO4 powders
Fig. 2 shows the XRD patterns of the LiFe1−0.01xY0.005xAg0.005xPO4 powders. All diffraction peaks are shown to follow the standard crystal structure patterns (JCPDS Nos. 40-1,499; LiFePO4) [12]. Diffraction peaks for Ag and Y were not observed because of their low concentration (≤3 wt%). The fact that the peaks were so similar to the standard ones for LiFePO4 suggested the absence of significant amounts of any by-products in the samples. In addition, the XRD patterns confirmed the existence of
Conclusion
In this study, we report a highly sensitive optical waveguide (OWG) sensor for detecting formaldehyde gas. LiFe1−0.01xY0.005xAg0.005xPO4-film/tin-diffused-glass-based OWG sensors were developed and used in the detection of volatile organic compounds (VOCs). The responses of these sensors to formaldehyde gas were higher compared to other VOCs. The sensitivity of these sensors decreased with an increase in the concentration of the dopants, Y and Ag as well as with an increase in the attenuation
Acknowledgement
The authors would like to acknowledge the National Natural Science Foundation of China for the support of this project under the 20965008 and 21265020 grants.
Patima Nizamidin Doctor, Student of College of Chemistry and Chemical Engineering, Xinjiang University, mainly engaged in nano-thin film and optical waveguide gas sensor.
References (29)
- et al.
Silicon-based micro-gas sensors for detecting formaldehyde
Journal of Sensors and Actuators B
(2009) - et al.
Reagentless amperometric formaldehyde-selective biosensors based on the recombinant yeast formaldehyde dehydrogenase
Journal of Talanta
(2008) - et al.
A self-heating gas sensor with integrated NiO thin-film for formaldehyde detection
Journal of Sensors and Actuators B
(2007) - et al.
The fabrication and characterization of a formaldehyde odor sensor using molecularly imprinted polymers
Journal of Colloid and Interface Science
(2005) - et al.
Biochemical gas sensor (bio-sniffer) for ultrahigh-sensitive gaseous formaldehyde monitoring
Journal of Biosensors and Bioelectronics
(2010) - et al.
Thin film composite optical waveguides for sensor applications: a review
Journal of Talanta
(2005) - et al.
Structural and textural characterization of LiFePO4 thin films prepared by pulsed laser deposition on Si substrates
Journal of Thin Solid Films
(2010) - et al.
Surface modification by silver coating for improving electrochemical properties of LiFePO4
Journal of Solid State Communications
(2004) - et al.
Insights into the potentiometric response behaviour vs Li+ of LiFePO4 thin films in aqueous medium
Journal of Analytica Chimica Acta
(2008) - et al.
Optical properties and sensing applications of lithium iron phosphate thin films
Journal of Thin Solid Films
(2012)
Densification and porosity evaluation of ZrO2–3 mol% Y2O3 sol–gel thin films
Journal of Thin Solid Films
Studies on the influence of lithium incorporation in the photoluminescence of Y2O3:Eu3+ thin films
Journal of Physics and Chemistry of Solids
Real-time detection of formaldehyde by a sensor
Journal of Sensors and Actuators B
Formaldehyde in the door environment
Journal of Chemistry Reviews
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Patima Nizamidin Doctor, Student of College of Chemistry and Chemical Engineering, Xinjiang University, mainly engaged in nano-thin film and optical waveguide gas sensor.
Abliz Yimit Doctor, graduate from Yokohama National University, Japan, in 2003 year. Now work at College of Chemistry and Chemical Engineering, Xinjiang University, mainly engaged in nano-thin film and optical waveguide gas sensor.
Adalat Abdurrahman associate professor. Now work at College of Chemistry and Chemical Engineering, Xinjiang University,mainly engaged in nano-thin film and optical waveguide gas sensor.
Kiminori Itoh Doctor, received his Dr. Eng. degree in Industrial Chemistry from the University of Tokyo, Japan, in 1980, and is now a Professor at the Institute of Environmental Science and Technology, Yokohama National University. Mainly engaged in the chemical application of optical waveguides and the measurement of complicated systems, e.g. soil bacteria, human bodies, and global climate.