Abstract
A reagent-less pH sensor based on disposable and low cost carbon fibre cloth (CFC) is demonstrated for the first time, where tungsten oxide nanoparticles were grown directly onto the CFC substrate. For comparison purpose, tungsten oxide nanoparticle modified glassy carbon electrode (GCE) was also fabricated as a pH sensor, where hydrothermally synthesized tungsten oxide nanoparticles were drop casted onto the GCE surface. The corresponding equilibrium potential using tungsten oxide/CFC as a pH sensor was measured using open circuit potential (OCP), and was found to be linear over the pH range of 3–10, with a sensitivity of 41.38 mVpH−1, and response time of 150 s. In the case of tungsten oxide/GCE as a pH sensor, square wave voltammetry (SWV) was used to measure the shifts in peak potential and was found to be linear with a pH range of 3–11, and a sensitivity of 60 mVpH−1 with a potential drift of 2.4–5.0% after 3 hour of continuous use. The advantages of tungsten oxide/CFC and tungsten oxide/GCE as pH sensing electrode have been directly compared with the commercial glass probe based electrode, and validated in real un-buffered samples. Thereby, tungsten oxide nanoparticles with good sensitivity and long term stability could be potentially implemented as a low cost and robust pH sensor in numerous applications for the Internet of Things (IoT).
Highlights
Gate FET with Layer-by-Layer Films of Dendrimers/TiO2 Nanoparticles[17]
As the requirement for pH sensors is essential in multi-purpose applications, a different design with enhanced flexibility is required, which cannot be provided by conventional solid state-type electrodes28. pH sensors based on silicon nitride films[29], paper[30] and polyimide surfaces[13] are reported to be flexible
The intense diffraction peaks located at 23.06°, 24.87°, 28.12°, 30.42°, 33.82°, 36.7°and 39.5° correspond to the tungsten oxide anorthic phase (JCPDS No 32–1395)
Summary
Gate FET with Layer-by-Layer Films of Dendrimers/TiO2 Nanoparticles[17] Among these oxide materials, WO3 is found to be a promising material for sensing pH because of its good catalytic activity, low cost, appropriate physical structure and morphologic control of the nano-structures, stability, reversible conductivity change with highly sensitive, selectivity and biocompatible characteristics[4,5,18]. The sensing capabilities of both systems were investigated and validated in respect of static and dynamic properties such as calibration, stability, response time, as well as sensitivity in oxygenated and deoxygenated environment. We have found both WO3/CFC (direct growth) and WO/GCE exhibit an excellent linearity with better sensitivity and stability in both acidic and alkaline environment
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