O2-Responsive Chemical Sensors Based on Hybrid Xerogels that Contain Fluorinated Precursors (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...
Stable Sensors with Tunable Sensitivities Based on Class II Xerogels
Analytical Chemistry, 2006
We report on the analytical figures of merit for O 2responsive sensor arrays and films formed by sequestering tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) within class II organically modified silicates that are composed of tetramethoxysilane or tetraethoxysilane and monoalkylsiloxanes of the form (C n H 2n+1 )-Si-(OR) 3 (n ) 1-12, R ) Me or Et). These sensors exhibit a reasonably linear response to gaseous and dissolved O 2 (r 2 > 0.99), and the sensor responses are stable for over 2 years. Sensor sensitivity can be tuned continuously by adjusting n. For gas-phase O 2 detection, changes in the sensor sensitivity depend primarily on the O 2 diffusion coefficient within the xerogel phase. The O 2 solubility coefficient within the xerogel phase is also a factor but to a lesser degree. For dissolved O 2 detection, changes in the sensor sensitivity depend on the O 2 diffusion coefficient and the O 2 solubility coefficient within the xerogel phase. A linear correlation also exists between the sensor sensitivity and the polarity within these xerogels. Finally, the feature size of pin-printed sensor elements was found to depend linearly on pin velocity. The results of these experiments demonstrate a new strategy for creating xerogel-based sensor arrays consisting of diversified sensor elements for the same target analyte.
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.
Chemistry of Materials, 2004
The title compounds were synthesized by Sonogashira coupling reactions of appropriate Ru(II) complexes with the electron acceptors. Characterization was conducted in solution and in frozen matrixes. Finally, the title compounds were evaluated as dopants of sol-gel materials. It was found that the intramolecular quenching efficiency of 4-benzoyl-Nmethylpyridinium cation in solution depends on the solvent: photoluminescence is quenched completely in CH 3 CN, but not in methanol or ethanol. On the other hand, intramolecular emission quenching by 4-benzyl-N-methyl viologen is complete in all solvents. The difference between the two quenchers is traced electrochemically to the solvation of the 4-benzoyl-Nmethylpyridiniums by alcohol. In frozen matrixes or adsorbed on the surfaces of silica aerogel, both Ru(II) complex/electron acceptor dyads of this study are photoluminescent, and the absence of quenching has been traced to the environmental rigidity. When doped aerogels are cooled at 77 K, the emission intensity increases by ∼4×, and the spectra shift to the blue, analogous to what is observed with Ru(II) complexes in solutions undergoing fluidto-rigid transition. However, in contrast to frozen solutions, the luminescent moieties in the bulk of aerogels kept at low temperatures are still accessible to gas-phase quenchers diffusing through the mesopores, leading to more sensitive platforms for sensors than other room-temperature configurations. Thus, the photoluminescence of our Ru(II) complex dyads adsorbed on aerogel is quenchable by O 2 both at room temperature and at 77 K. Furthermore, it was also found that O 2 modulates the photoluminescence of aerogels doped with 4-benzoyl-N-methylpyridinium -based dyads over a wider dynamic range compared with aerogels doped with either our viologen-based dyads or with Ru(II) tris(1,10-phenanthroline) itself.
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
Sensors and Actuators B: Chemical, 2010
A new method for enhancement of luminescence from sol-gel based sensors is demonstrated, utilising the quenching effect and filtering effect of a gold film. Ruthenium (4,7-diphenyl-1,10-phenanthroline) 3 Cl 2 is encapsulated in a trimethoxysilane (TEOS) xerogel and spin-coated to an approximate thickness of less than 100 nm. Using off axis illumination of the xerogel film, luminescence was collected using a photodiode below the plane of the gold and doped thin film. The gold had the effect of improving all sensor figures of merit via two mechanisms. Firstly, the transmission spectrum of the gold film peaks at 520 nm but allows poor transmission of excitation light at 450 nm reducing stray light interference in addition to a 550 nm cut-on filter. Secondly, and more, importantly relatively insensitive luminophores within approximately 10 nm of the gold film are quenched resulting in a significant noise reduction by removal of insensitive residual metal ion-ligand complex luminescence. It is questioned whether an element of radiative-decay-engineering of luminescence is occurring with luminophore emission coupling to the gold film and initiating plasmonic emission from the underside of the film, but no evidence either in terms of solely p-polarisation or increased intensity of luminescence was evidenced. This confirms that the sensor enhancement mechanism is primarily the function of metal quenching as evidenced by reduced background intensity as noise and improved response time to oxygen quenching indicating that only the most sensitive luminophores are available to be dynamically quenched by formation of the ruthenium:oxygen charge transfer complex. This simple sensor geometry improves a basic oxygen sensor luminophore:matrix combination and stands comparison with more complex combinations such as those achieved with fluorinated sol-gel matrices.
Talanta, 2003
In this article, an emission based, simple and fast method is proposed for the determination of gaseous oxygen. A newly synthesized fluorophore, dichloro-{2,6-bis[1-(4-dimethylamino-phenylimino) ethyl]pyridine}ruthenium(II) has been used for oxygen sensing together with oxygen carrier perfluorochemicals (PFCs) in silicon matrix. It should be noted that the solubility of oxygen in fluorocarbons is about three to ten times large as that observed in the parent hydrocarbons or in water, respectively. Employed PFCs are chemically and biochemically inert, have high dissolution capacities for oxygen, and, once doped into sensing film, considerably enhance the response of sensing agent. #
The Analyst, 1993
A simple, low-cost technique for the fabrication of optical sensors for oxygen is described and preliminary results obtained using these sensors are reported. The technique is based on coating a declad portion of an optical fibre with a microporous glass film prepared by the sol-gel process. A ruthenium complex [Rut'-tris-(2,2'-bipyridine) or Ru~~-tris(4,7-diphenyl-l,1O-phenanthroline)] is trapped in the nanometre-scale cage-like structure of the porous film. In this sensor configuration the complex is excited by the evanescent field of the 488 nm radiation guided by the optical fibre. The luminescence from such complexes is known t o be quenched by oxygen and the sensors exhibit repeatable quenching behaviour when exposed t o various concentrations of oxygen. The ratio R = lo/lloo where lo and llo0 represent the detected signals from a sensor exposed t o 100% nitrogen and 100% oxygen, respectively, is used as a measure of the sensitivity of the sensor. Sensors based on the diphenylphenanthroline complex exhibit greater sensitivity than those based o n the bipyridine complex, in accordance with theoretical predictions. More importantly, however, the design potential of the sol-gel process for sensor fabrication is demonstrated by the achievement of a substantial increase in R when the process parameters are adjusted t o increase the pore volume.
A dissolved oxygen sensor based on composite fluorinated xerogel doped with platinum porphyrin dye
Luminescence, 2009
A new functional fl uorinated material taking n-propyltrimethoxysilicane (n-propyl-TriMOS) and 3,3,3trifl uoropropyltrimethoxysilicane (TFP-TriMOS) as precursors was applied to construct a novel dissolved oxygen sensing fi lm. The sensing fi lm was fabricated by dip-coating the functional fl uorinated material-doped [meso-tetrakis(pentafl uorophenyl) porphyinato] platinum(II) (PtF 20 TPP) onto a glass slide. The oxygen sensing fi lm exhibited a good linear relationship, fast response time, long stability and high sensitivity to dissolved oxygen. In the developed optical oxygen sensor, an LED and a photodiode were composed to construct a back-detection optical system not needing an optical fi ber based on fl uorescence intensity detection. The smart optical oxygen sensor based on the PtF 20 TPP fl uorescence quenching possesses the advantages of portability and low cost and can be applied to the dissolved oxygen in situ monitoring in seawater.
Optimisation of sol-gel-derived silica films for optical oxygen sensing
Journal of Sol-Gel Science and Technology, 1997
Sol-gel-derived silica films were fabricated by dip-coating onto planar and optical fibre substrates. The films were pre-doped with the oxygen-sensitive ruthenium complex [Ru(II)-tris(4,7-diphenyl-1,10-phenanthroline)], whose fluorescence is quenched in the presence of oxygen. The structure and behaviour of sol-gel films is related to the fabrication parameters. In order to optimise the films for oxygen sensing in gaseous and in aqueous media, the quenching behaviour was monitored as a function of dip-speed and water : precursor ratio. By adjusting the above parameters, film properties can be tailored to optimise oxygen quenching in particular concentration ranges and environments.