Miniaturized planar room temperature ionic liquid electrochemical gas sensor for rapid multiple gas pollutants monitoring (original) (raw)
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CMOS Monolithic Electrochemical Gas Sensor Microsystem Using Room Temperature Ionic Liquid
IEEE Sensors Journal, 2018
The growing demand for personal healthcare monitoring requires a challenging combination of performance, size, power, and cost that is difficult to achieve with existing gas sensor technologies. This paper presents a new CMOS monolithic gas sensor microsystem that meets these requirements through a unique combination of electrochemical readout circuits, post-CMOS planar electrodes, and room temperature ionic liquid (RTIL) sensing materials. The architecture and design of the CMOS-RTIL-based monolithic gas sensor are described. The monolithic device occupies less than 0.5 mm 2 per sensing channel and incorporates electrochemical biasing and readout functions with only 1.4 mW of power consumption. Oxygen was tested as an example gas, and results show that the microsystem demonstrates a highly linear response (R 2 = 0.995) over a 0-21% oxygen concentration range, with a limit of detection of 0.06% and a 1 s response time. Monolithic integration reduces manufacturing cost and is demonstrated to improve limits of detection by a factor of five compared to a hybrid implementation. The combined characteristics of this device offer an ideal platform for portable/wearable gas sensing in applications such as air pollutant monitoring.
Electroanalysis, 2004
A novel solid-state amperometric O 2 gas sensor based on the supported 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF 4) porous polyethylene membrane-coated electrodes has been proposed with its characterization. By electrochemical impedance technique, the ionic conductivity of the supported EMIBF 4 membrane was estimated to be ca. 0.6 S m À1 , indicating that the supported EMIBF 4 membrane (the thickness: 50 mm) can be used as a solid state ionic conductor at room temperature. The cyclic voltammograms obtained for the one-electron redox reaction of O 2 / O 2 À. (O 2 À. : superoxide ion) couple at high scan rates (> 100 mV s À1) showed a couple of usual redox peaks, while at low scan rates (< 30 mV s À1) S-shaped steady-state voltammograms similar to those obtained by rotating disk voltammetry were obtained. These results were explained on the basis of the mass transport of O 2 at the supported EMIBF 4 membrane-coated electrode system. The transient and steady-state reduction currents for the reduction of O 2 to O 2 À. as well as the transient oxidation current for the reoxidation of O 2 À. to O 2 , which were obtained by potentialstep chronoamperometry, could be used to measure the change of O 2 concentration in O 2-N 2 mixed gas stream. The present O 2 gas sensor demonstrated a wide detection range, a high sensitivity and an excellent reproducibility.
Sensors and actuators. B, Chemical, 2017
Intense study on gas sensors has been conducted to implement fast gas sensing with high sensitivity, reliability and long lifetime. This paper presents a rapid amperometric method for gas sensing based on a room temperature ionic liquid electrochemical gas sensor. To implement a miniaturized sensor with a fast response time, a three electrode system with gold interdigitated electrodes was fabricated by photolithography on a porous polytetrafluoroethylene substrate that greatly enhances gas diffusion. Furthermore, based on the reversible reaction of oxygen, a new transient double potential amperometry (DPA) was explored for electrochemical analysis to decrease the measurement time and reverse reaction by-products that could cause current drift. Parameters in transient DPA including oxidation potential, oxidation period, reduction period and sample point were investigated to study their influence on the performance of the sensor. Oxygen measurement could be accomplished in 4 s, and th...
The electrochemical reduction of oxygen (O 2) has been studied on commercially-available integrated Pt thin-film electrodes (TFEs). Chemically reversible (but electrochemically quasi-reversible) cyclic voltammetry was observed in the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C 2 mim][NTf 2 ]), showing superior behaviour of TFEs compared to screen-printed electrodes for oxygen sensing. As a step towards the preparation of robust gas sensors, the RTIL was mechanically stabilised on the TFE surface by the addition of poly(methyl methacrylate) (PMMA). At a PMMA concentration in the RTIL of ca. 50% mass, electrolyte flow was not evident. O 2 reduction peak currents were found to decrease systematically with increasing PMMA content, reflecting the higher viscosity of the electrolyte medium. Linear calibration graphs were obtained for 0–100% vol. oxygen at all PMMA–RTIL mixtures studied. The sensitivities decreased as [PMMA] increased, but the limits of detection were relatively unchanged. Mechanical stability of the sensors was tested in different orientations (flat, upside down, sideways) with both the neat RTIL and 50% mass electrolyte. Whilst the electrochemical responses were dramatically changed for the neat RTIL, the responses in the PMMA– RTIL mixture were independent of electrode orientation. Additionally, the oxygen response in the PMMA–RTIL mixture was less affected by atmospheric impurities and moisture, compared to the neat RTIL. This suggests that these low-cost miniaturised devices can successfully be used for oxygen sensing applications in field situations, especially where portability is essential.
?-Sensors: A new concept for advanced solid-state ionic gas sensors
Applied Physics A Solids and Surfaces, 1992
A new principle of solid state electrochemical sensors based on the kinetics of controlled chemical reactions of the gas with the electroactive species of a solid electrolyte is presented and demonstrated for the measurement of CO2 partial pressures. The reaction may be for many gases modified by the formation of intermediate product phases.
Commercially available Pt screen printed electrodes (SPEs) have been employed as possible electrode materials for methylamine (MA) and hydrogen chloride (HCl) gas detection. The room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2]) was used as a solvent and the electrochemical behaviour of both gases was first examined using cyclic voltammetry. The reaction mechanism appears to be the same on Pt SPEs as on Pt microelectrodes. Furthermore, the analytical utility was studied to understand the behaviour of these highly toxic gases at low concentrations on SPEs, with calibration graphs obtained from 10 to 80 ppm. Three different electrochemical techniques were employed: linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV), with no significant differences in the limits of detection (LODs) between the techniques (LODs were between 1.4 to 3.6 ppm for all three techniques for both gases). The LODs achieved on Pt SPEs were lower than the current Occupational Safety and Health Administration Permissible Exposure Limit (OSHA PEL) limits of the two gases (5 ppm for HCl and 10 ppm for MA), suggesting that Pt SPEs can successfully be combined with RTILs to be used as cheap alternatives for amperometric gas sensing in applications where these toxic gases may be released.
Successive ionic layer deposition: possibilities for gas sensor applications
Journal of Physics: Conference Series, 2005
In this paper we discuss results of research related to design of successive ionic layer deposition (SILD) technology for both preparing porous nano-structured SnO 2 films, and surface modification of SnO 2 films deposited by spray pyrolysis. This new method of metal oxide deposition has exited high interest, because of this method simplicity, cheapness, and ability to deposit thin nano-structured films on rough surfaces. Method of successive ionic layer deposition (SILD) consists essentially of repeated successive treatments of the conductive or dielectric substrates by solutions of various salts, which form on the substrate surface poorly soluble compounds. It was shown that SILD technology is effective method for above mentioned purposes.
Electrochemical Sensing of Oxygen Gas in Ionic Liquids
The work presented in this thesis aimed to investigate the potentiality of screen printed electrodes (SPEs), when used in conjunction with non-volatile room temperature ionic liquids (RTILs), for the amperometric sensing of gases. O 2 was selected as the model gas for these studies. Cyclic voltammetry (CV) and amperometry techniques were employed for these investigations. Experiments were conducted with an inert background atmosphere of N 2 gas.