Optical CO2 Sensing with Ionic Liquid Doped Electrospun Nanofibers

Abstract

The first use of electrospun nanofibrous materials as highly responsive fluorescence quenching-based optical CO(2) sensors is reported. Poly(methyl methacrylate) and ethyl cellulose were used as polymeric materials. Sensing slides were fabricated by electrospinning technique. A fiber-optic bundle was used for the gas detection. CO(2) sensors based on the change in the fluorescence signal intensity of ion pair form of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS). The sensor slides showed high sensitivities due to the high surface area-to-volume ratio of the nanofibrous membrane structures. The preliminary results of Stern-Volmer analysis show that the sensitivities of electrospun nanofibrous membranes to detect CO(2) are 24 to 120 fold higher than those of the thin film based sensors. The response times of the sensing reagents were short and the signal changes were fully reversible. The stability of ion pair form of HPTS in the employed matrix materials was excellent and when stored in the ambient air of the laboratory there was no significant drift in signal intensity after 7 months. Our stability tests are still in progress.

Applications of Ionic Liquids for the Development of Optical Chemical Sensors and Biosensors

“…1.3). [74][75][76][77][78][79][80] Polymer/IL composites are obtained either by a simple casting of the liquid sensing cocktail on an appropriate support (commonly a polyester or glass slide) or by electrospinning. The resultant materials are continuous thin and bulk films (the thickness is several and 200 μm, respectively) Fig.…”

“…When a gas analysis is carried out, a sensing material is placed into a flow-cell, where a gas mixture (e.g., analyte CO2 with a regeneration agent N2) is introduced via a diffuser needle under ambient conditions either directly or after humidification of the gas by bubbling through water. 76 The intensity of fluorescence in the absence and presence of a gaseous analyte is often measured and referenced against the luminescence intensity (or decay time) of a second inert and spectrally compatible luminophore (e.g., 4-dicyanomethylene-2-methyl-6-(4-(dimethylamino)styryl)-4H-pyrane, DCM, 75,81 a fluorogenic IL (as in [P6,6,6,14]3HPTS), 49 a special excimer-forming fluorescent microviscosity probe (e.g., 1,3-bis(1-pyrenyl)propane, 1,3-bis(1-pyrenyl)decane, etc.) 52 In the literature, such kind of fluorescent sensing is termed ratiometric sensing.…”

“…Additionally, we have found out some contradictions in interpretation of a role of IL in the process of fabricating CO2 sensing EC-based electrospun nanofibers. Aydogdu et al 76 considered [EMIm]BF4 as a polymer electrolyte though the IL more likely served as a plasticizer that was additional to the classic plasticizer dioctyl phthalate. Sometimes it is difficult to distinguish the roles of ILs as solvents and chemical additives to methanol or ethanol in the course of the preparation of sol-gel materials.…”

“…74 [74][75][76][77][78][79][80] Owing to the use of [EMIm]BF4 in EC and PMMA thin films, the sensitivity of the CO2 sensor increased, the hyperbolic response of the recognition element (HPTS)/(TOA)4 in the working concentration range of CO2 straightened, HPTS photostability was enhanced and the sensor lifetime was prolonged up to 95 days under ambient conditions. 75 Note that IL-free sensors completely lost their sensing capability within 3 days.…”

“…The CO2-sensitive EC and PMMA electrospun fibers provided high porosity, large surface area, and high gas permeability compared to the same parameters of continuous thin films along with high stability (7 months). 76 The electrospinning technique was used for the development of the O2-sensitive fibers of EC and PMMA modified by [Ru(bipy)3] 2+ ( Fig. 3.1).…”