Stable Sensors with Tunable Sensitivities Based on Class II Xerogels (original) (raw)
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O2-Responsive Chemical Sensors Based on Hybrid Xerogels that Contain Fluorinated Precursors
Applied Spectroscopy, 2006
We report the development and analytical figures of merit associated with several new O2-responsive sensor materials. These new sensing materials are formed by sequestering the luminophore tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) ([Ru(dpp)3]2+) within hybrid xerogels that are composed of two of the following methoxysilanes: tetramethoxysilane, n-propyl-trimethoxysilane, 3,3,3-trifluoropropyl-trimethoxysilane, phenethyl-trimethoxysilane, and pentafluorophenylpropyl-trimethoxysilane. Steady-state and time-resolved luminescence measurements are used to investigate these hybrid xerogel-based sensor materials and elucidate the underlying reasons for the observed performance. The results show that many of the [Ru(dpp)3]2+-doped composites form visually uniform, crack-free xerogel films that can be used to construct O2 sensors that have linear calibration curves and excellent long-term stability. To the best of our knowledge, the [Ru(dpp)3]2+-doped fluorinated hybrid xerogels al...
O2-Responsive Chemical Sensors Based on Hybrid Xerogels that Contain Fluorinated Precursors
Appl Spectrosc, 2006
We report the development and analytical figures of merit associated with several new O 2-responsive sensor materials. These new sensing materials are formed by sequestering the luminophore tris(4,7-diphenyl-1,10phenanthroline)ruthenium(II) ([Ru(dpp) 3 ] 2þ) within hybrid xerogels that are composed of two of the following methoxysilanes: tetramethoxysilane, n-propyl-trimethoxysilane, 3,3,3-trifluoropropyl-trimethoxysilane, phenethyl-trimethoxysilane, and pentafluorophenylpropyl-trimethoxysilane. Steady-state and time-resolved luminescence measurements are used to investigate these hybrid xerogel-based sensor materials and elucidate the underlying reasons for the observed performance. The results show that many of the [Ru(dpp) 3 ] 2þ-doped composites form visually uniform, crackfree xerogel films that can be used to construct O 2 sensors that have linear calibration curves and excellent long-term stability. To the best of our knowledge, the [Ru(dpp) 3 ] 2þ-doped fluorinated hybrid xerogels also exhibit the highest O 2 sensitivity of any reported [Ru(dpp) 3 ] 2þ-based sensor platform.
The Analyst, 2006
The objective of this research is to develop arrays of tuned chemical sensors wherein each sensor element responds to a particular target analyte in a unique manner. By creating sol-gel-derived xerogels that are co-doped with two luminophores at a range of molar ratios, we can form suites of sensor elements that can exhibit a continuum of response profiles. We trained an artificial neural network (ANN) to ''learn'' to identify the optical outputs from these xerogel-based sensor arrays. By using the ANN in concert with our tailored sensor arrays we obtained a 5-10 fold improvement in accuracy and precision for quantifying O 2 in unknown samples. We also explored the response characteristics of these types of sensor elements after they had been contacted with rat plasma/blood. Contact with plasma/blood caused y15% of the luminophore molecules within the xerogels to become non-responsive to O 2 . This behavior is consistent with rat albumin blocking certain pore sub-populations within the mesoporous xerogel matrix thereby limiting O 2 access to the luminophores.
Analytica Chimica Acta, 2010
This paper describes the fabrication and performance of a range of highly sensitive luminescence-based oxygen sensor films based on the fluorinated sol-gel precursor 3,3,3-trifluoropropyltrimethoxysilane (TFP-TMOS). The oxygen-sensitive ruthenium complex [Ruthenium(II)-tris(4,7-diphenyl-1,10phenanthroline)] dichloride, [Ru(dpp) 3 ] 2+ was entrapped in a wide range of ORMOSILs (organically modified silicates) matrices composed of alkyl and TFP-TMOS sol-gel precursors in different relative ratios. The influence of TFP-TMOS on sensor sensitivity, humidity-sensitivity and long-term stability was investigated and performance was compared to that of similar but non-fluorinated films. The optimum limit of detection was found to be 0.002% of oxygen for the propyltriethoxysilane (PTEOS)/TFP-TMOS-derived film compared to 0.09% for PTEOS-derived films reported previously. Photobleaching of the luminescent complex in fluorinated and non-fluorinated matrices was also investigated. It was established that photobleaching was reduced but not eliminated in fluorinated films. All films produced in this study exhibit very good reproducibility, reversibility, enhanced sensitivity, humidity-insensitivity and long-term stability.
Novel sol-gel derived films for luminescence-based oxygen and pH sensing
2000
A range of both sol-gel and polymer derived sensor films have been developed for optical oxygen and pH sensing. Oxygen sensing is based on the luminescence quenching of the ruthenium complex (Ru(II)-tris( 4,7-diphenyl-1,10-phenanthroline))dichloride, ((Ru(dpp)3) 2+ ), which is entrapped in the sol-gel matrix. The oxygen-dependent luminescence is detected using the principle of phase fluorometry, which facilitates indirect monitoring of the
Optical Sol-Gel-Based Dissolved Oxygen Sensor: Progress Towards a Commercial Instrument
Journal of Sol-gel Science and Technology - J SOL-GEL SCI TECHNOL, 1998
A dissolved oxygen sensor based on fluorescence quenching of the oxygen-sensitive ruthenium complex, [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline]2+, which has been immobilized in a porous silica sol-gel-derived film, is reported. Ormosil sensing films were fabricated using modified silica precursors such as methyltriethoxysilane (MTEOS) and ethyltriethoxysilane (ETEOS) and were dip-coated onto planar glass substrates. Tailoring of the films for dissolved oxygen (DO) sensing is described whereby sensor response is optimized by maximizing film hydrophobicity by the use of the modified precursors. Sensor performance parameters such as limit of detection and sensor resolution are reported. Issues such as dye leaching and photobleaching are discussed. Progress towards a commercial instrument is reported.
Extruded polymer films pigmented with a heterogeneous ion-pair based lumophore for O2 sensing
The Analyst, 2013
A novel approach to polymeric Ru(II)-diimine luminescent O 2 sensors is described. The Ru(II)-diimine, tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) dichloride ([Ru(dpp) 3 ] 2+), is first ion-paired to the surface of heterogeneous TiO 2 particles, rendered negatively charged due to the alkali nature of the aqueous solution, to produce an O 2 sensitive pigment with a strikingly high oxygen sensitivity (i.e. PO 2 (S ¼ 1/2) ¼ 0.002 atm, where PO 2 (S ¼ 1/2) is defined as the amount of oxygen required to reduce the initial, oxygen free luminescence by 50%), and a rapid response to oxygen. The pigment is extruded in low density polyethylene (LDPE) to produce a thin (60 mm), flexible, O 2 sensing plastic film, with an O 2 sensitivity (PO 2 (S ¼ 1/2) ¼ 0.84 atm) comparable to the more traditional homogeneous lumophore ionpair based O 2 sensor ink films reported in the literature.
Chemistry of Materials, 2010
A new oxygen sensor, compound 2, was synthesized through a chemical modification of a popularly used oxygen sensor of platinum(II)-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin (PtTFPP). The new sensor compound 2 possesses four crosslinkable methacrylate functional moieties, enabling it to be polymerized and crosslinked with other monomers for polymer sensing film (also called membrane) preparation. Using this characteristic, compound 2 was covalently bonded to hydrophilic poly(2-hydroxyethyl methacrylate)-co-polyacrylamide (referred to as PHEMA to simplify) and hydrophobic polystyrene (PS) films. To better understand the advantages and disadvantages of chemical crosslinking approaches and the influence of polymer matrices on sensing performance, PtTFPP was physically incorporated into the same PHEMA and PS matrices to compare. Response to dissolved oxygen (DO), leaching of the sensor molecules from their matrices, photostability of the sensors, and response time to DO changes were studied. It was concluded that the chemical crosslinking of the sensor compound 2 in polymer matrices: (i) alleviated the leaching problem of sensor molecules which usually occurred in the physically doped sensing systems and (ii) significantly improved sensors' photostability. The PHEMA matrix was demonstrated to be more suitable for oxygen sensing than PS, because for the same sensor molecule, the oxygen sensitivity in PHEMA film was higher than that in PS and response time to DO change in the PHEMA film was faster than that in PS. It was the first time oxygen sensing films were successfully prepared using biocompatible hydrophilic PHEMA as a matrix, which does not allow leaching of the sensor molecules from the polymer matrix, has a faster response to DO changes than that of PS, and does not present cytotoxicity to human lung adenocarcinoma epithelial cells (A549). It is expected that the new sensor compound 2 and its similar compounds with chemically crosslinking characteristics can be widely applied to generate many interesting oxygen sensing materials for studying biological phenomena.
Microchemical Journal, 2013
An optical sensing membrane was prepared to detect oxygen, temperature, and pH simultaneously. Optimum amounts of the fluorescence indicators (tris(4,7-diphenyl-1,10-phenanthroline) ruthenium complex (Rudpp)doped silica nanoparticles (RudppSi) for oxygen, 8-hydroxypyrene-1,3,6-trisulfonate (HPTS)-doped silica particles (HPTSSi) for pH, and CdSeTe quantum dots (QDs) for temperature) in a sensing membrane were identified using response surface methodology (RSM). The difference in fluorescence intensity between 0% DO (dissolved oxygen) and 100% DO, the difference in fluorescence intensity between pH 5 and pH 8, and the difference in fluorescence intensity between 15°C and 45°C in the sensing membrane were employed as statistical model responses. Optimum concentrations of fluorescence indicators in the sensing membrane were 5.68 mg RudppSi/ml sol-gel solution, 18.0 mg HPTSSi/ml sol-gel solution, and 1.98 mg CdSeTe QDs/ml sol-gel solution. Several optical sensing membranes were prepared based on the RSM analysis results, and tested experimentally on the sensitivity and performance. The membrane enabled triple detection of DO, pH, and temperature very well and could be used to monitor a variety of microbiological and medical applications.
Optical oxygen sensor based on metallo-organic compound immobilized by sol-gel technique
Biotechnology Techniques, 1995
Opfical sensors suitable for moniforing of O2 in wafer medium were prepared by immobilization of mefallo-organic complexes in xerogels created by sol-gel technique and applied fo optical fibre fip or glass slides by dipping. Tris (I, IO-phenanfhroline)rufhenium (II) chloride was immobilized on fhe tip of opfical fibre. The fluorescence spectra of the complex were sensitive to O2 in wafer solufion. The sensifivify of absorption spectra of bis(histidinafo)cobalf (II ) to O2 and pH was examinafed bofh in fhe solution of precursors of silica sol-gel glasses and in fhe complex-confaining coating of glass slides.