Presence Of Nitrogen Dioxide Research Articles

Optical Oxygen Sensors Show Reversible Cross-Talk and/or Degradation in the Presence of Nitrogen Dioxide.

A variety of luminescent dyes including the most common indicators for optical oxygen sensors were investigated in regard to their stability and photophysical properties in the presence of nitrogen dioxide. The dyes were immobilized in polystyrene and subjected to NO2 concentrations from 40 to 5500 ppm. The majority of dyes show fast degradation of optical properties due to the reaction with NO2. The class of phosphorescent metalloporphyrins shows the highest resistance against nitrogen dioxide. Among them, palladium(II) and platinum(II) complexes of octasubstituted sulfonylated benzoporphyrins are identified as the most stable dyes with almost no decomposition in the presence of NO2. The phosphorescence of these dyes is reversibly quenched by nitrogen dioxide. Immobilized in various polymeric matrices, the sulfonylated Pt(II) benzoporphyrin demonstrates about one order of magnitude more efficient quenching by NO2 than by molecular oxygen. Our study demonstrates that virtually all commercially available and reported optical oxygen sensors are likely to show either irreversible decomposition in the presence of nitrogen dioxide or reversible luminescence quenching. They should be used with extreme caution if NO2 is present in relatively high concentrations or it may be generated from other species such as nitric oxide. As an important consequence of nearly anoxic systems, production of nitrogen dioxide or nitric oxide may be therefore erroneously interpreted as an increase in oxygen concentration.

Nitrous acid production and uptake by Zea mays plants in growth chambers in the presence of nitrogen dioxide

Nitrous acid (HONO) photolysis is an important atmospheric reaction that leads to the formation of hydroxyl radicals (OH), the main diurnal atmospheric oxidants. The process of HONO formation remains unclear, and comparisons between field measurements and model results have highlighted the presence of unknown HONO sources. HONO production on plant surfaces was recently suggested to contribute to atmospheric HONO formation, but there is limited information on the quantification of HONO production and uptake by plants. To address this gap in the existing knowledge, the current study investigated HONO exchange on living Zea mays plants. Experiments were conducted in growth chambers under controlled experimental conditions (temperature, relative humidity, NO2 mixing ratio, light intensity, CO2 mixing ratio) at temperatures ranging between 283 and 299 K. To investigate the effect of drought on HONO plant-atmosphere exchanges, experiments were carried out on two sets of Zea mays plants exposed to two different water supply conditions during their growth: optimal watering (70% of the field capacity) and water stress (30% of the field capacity). Results indicated that the uptake of HONO by control Zea mays plants increased linearly with ambient temperature, and was correlated with CO2 assimilation for temperatures ranging from 283 to 299 K. At 299 K, HONO production on the leaves offset this uptake and Zea mays plants were a source of HONO, with a net production rate of 27 ± 7 ppt h-1. Deposition velocities were higher for HONO than CO2, suggesting a higher mesophyll resistance for CO2 than HONO. As water stress reduced the stomatal opening, it also decreased plant-atmosphere gas exchange. Thus, climate change, which may limit the availability of water, will have an impact on HONO exchange between plants and the atmosphere.

Catalyzing heavy haze

Air Pollution Intense regional haze events periodically affect many heavily polluted urban areas, causing adverse effects on human health and possibly affecting local climate. The reasons that these episodes occur are not entirely clear. Zhang et al. present a combination of field measurements, laboratory experiments, and model simulations to show that black carbon particles are central components of haze development. They demonstrate that the frequency of heavy haze events declines significantly with the reduction of sulfur dioxide and that sulfur dioxide oxidation is efficiently catalyzed on black carbon particles in the presence of nitrogen dioxide and ammonia. This unexpected finding implies that reduction of sulfur dioxide alone will not reduce the frequency of heavy-haze events in these environments. Proc. Natl. Acad. Sci. U.S.A. 117 , 3960 (2020).

Photooxidation of Di-tert-butyl Malonate in the Presence and Absence of Nitrogen Dioxide.

The rate constant for the reaction of di-tert-butyl malonate (DTBM) with chlorine atoms in the gas phase was measured using cyclohexane and pentane as references. The measurements lead to a value of (1.5 ± 0.1) × 10-10 cm3 molecule-1 s-1. The subsequent photo-oxidation mechanism of DTBM in the absence and presence of nitrogen dioxide was investigated. The main carbonated products identified in the first case were acetone, formic acid, carbon monoxide, and carbon dioxide. The addition of nitrogen dioxide lead besides to the formation of (CH3)3CC(O)OONO2 and (CH3)3CONO2. The proposed photo-oxidation mechanism was supported both experimentally and computationally. The results reveal that the (CH3)3COC(O)CH2C(O)OC(CH3)2O• radical formed reacts according to two competitive reactions: decomposition to yield acetone and (CH3)3COC(O)CH2C(O)O• radical 55 ± 2%, and migration of the H atom of the methylene group to the terminal oxygen atom 40 ± 3%.

Aerobic carbon-carbon bond cleavage of alkenes to aldehydes catalyzed by first-row transition-metal-substituted polyoxometalates in the presence of nitrogen dioxide.

A new aerobic carbon-carbon bond cleavage reaction of linear di-substituted alkenes, to yield the corresponding aldehydes/ketones in high selectivity under mild reaction conditions, is described using copper(II)-substituted polyoxometalates, such as {α2-Cu(L)P2W17O61}(8-) or {[(Cu(L)]2WZn(ZnW9O34)2}(12-), as catalysts, where L = NO2. A biorenewable-based substrate, methyl oleate, gave methyl 8-formyloctanoate and nonanal in >90% yield. Interestingly, cylcoalkenes yield the corresponding epoxides as products. These catalysts either can be prepared by pretreatment of the aqua-coordinated polyoxometalates (L = H2O) with NO2 or are formed in situ when the reactions are carried with nitroalkanes (for example, nitroethane) as solvents or cosolvents. Nitroethane was shown to release NO2 under reaction conditions. (31)P NMR shows that the Cu-NO2-substituted polyoxometalates act as oxygen donors to the C-C double bond, yielding a Cu-NO product that is reoxidized to Cu-NO2 under reaction conditions to complete a catalytic cycle. Stoichiometric reactions and kinetic measurements using {α2-Co(NO2)P2W17O61}(8-) as oxidant and trans-stilbene derivatives as substrates point toward a reaction mechanism for C-C bond cleavage involving two molecules of {α2-Co(NO2)P2W17O61}(8-) and one molecule of trans-stilbene that is sufficiently stable at room temperature to be observed by (31)P NMR.

Investigation of iso-octane combustion in a homogeneous charge compression ignition engine seeded by ozone, nitric oxide and nitrogen dioxide

The homogeneous charge compression ignition (HCCI) engine is well known as an alternative engine which could replace conventional engines (spark ignition (SI) and combustion ignition (CI) engines) in order to meet pollutant requirements and reduce fuel consumption. However, controlling this kind of combustion remains difficult and represents a real challenge. The present investigation focussed on the use of different oxidizing chemical species (ozone, nitric oxide and nitrogen dioxide) which can modify the chemical kinetic governing HCCI combustion. Experiments were conducted on a single cylinder HCCI engine fuelled with iso-octane, for constant engine parameters and for oxidizing species concentrations varying from 0 up to 100ppm. These experimental results are coupled with kinetic analyses in a homogeneous constant volume reactor performed with a detailed kinetic mechanism. The effects of ozone, nitric oxide and nitrogen dioxide were initially studied and compared when they separately seed the intake of the engine. Results showed that all the molecules improve HCCI iso-octane combustion. The highest effect on CA50 phasing was observed for ozone while the lowest was for nitrogen dioxide. These results were confirmed and explained by a kinetic interpretation. HCCI experiments were then carried out with ozone and nitric oxide injected together in the intake of the engine. Experimental results show a combustion enhancement when these two molecules are present but a delay in CA50 phasing was observed for low ozone concentrations and a constant nitric oxide concentration until the ozone concentration becomes higher. A kinetic interpretation, through two-step computations, showed that there is a strong oxidizing reaction between nitric oxide and ozone, yielding nitrogen dioxide. Therefore, the presence of nitrogen dioxide can explain the CA50 delay observed due to its low effect among all the oxidizing chemical species studied.

Preparation and characterization of degradable oxidized bacterial cellulose reacted with nitrogen dioxide

Bacterial cellulose (BC) is regarded as one of the most attractive and promising biomaterials in medical applications owing to its high purity and mechanical properties and excellent biocompatibility. In this study, a new kind of degradable oxidized bacterial cellulose (OBC) was prepared by oxidizing BC in the presence of nitrogen dioxide (NO2), which could be used as a scaffold for tissue engineering and tissue regeneration. The chemical structures, micromorphology, and in vitro degradability of OBC were characterized. The results demonstrated that the oxidation reaction was controllable for tailoring the degree of degradation of BC. After oxidation, the degradation of BC was accelerated, depending on the oxidation time. In the case of oxidation for 12 days, the mass loss rate of OBC increased sharply, up to 45% after being immersed in phosphate buffered saline (PBS) for 60 days, compared with only 10% for original BC in the same condition. The oxidation did not affect the crystal structure of BC, however, changed the morphology of its network. The original dense microfibril network of BC could be gradually degraded and disappeared within a desirable period of time in vitro through controlling the degree of the selective oxidation.

First-Principles Study of Adsorption Properties of NO<sub>2</sub> on Boron-Doped Silicon Carbide Nanotube

To explore a novel sensor to detect the presence of nitrogen dioxide (NO2), we investigate reactivity of boron-doped (B-doped) single-walled (8,0) silicon carbide nanotube (SiCNT) with NO2. Based on density functional theory, the structure and electronic properties of the B-doped SiCNT with and without the adsorption of NO2 molecule have been calculated. Results show that a stable adsorption between the nanotube and the gas molecule is formed and the conductivity of the SiCNT is improved obviously. B-doped SiCNT is expected to be a potential candidate for detecting the presence of NO2.

Computer-assisted study of characteristics of water clusters in the presence of nitrogen dioxide

; however, only two of them, nitrogen(II) oxide and nitrogen(IV) oxide, are stable under ordinary conditions and actively participate in the natural and industrial nitro� gen cycles. Nitrogen oxides ( ) are of great impor� tance for many atmospheric reactions. radical is the most reactive of them; it is formed in the dark and is regulated by the chemical reactions occurring in the night atmosphere. When interacting with water, nitro� gen oxides form nitric acid ( ), which is not only the main component of acid rain, but also governs the main process of removing nitrogen oxides from atmo� sphere. Nitric acid plays the key role in the chemistry of polar stratosphere. It is involved in the formation of ozone holes. Nitrogen oxides directly participate in the formation and decomposition of the tropospheric ozone. Under the action of sunlight, nitrogen dioxide is transformed into monoxide NO, which, in turn, forms by interacting with oxygen. Ozone and peroxide radicals are also involved in this cycle. The physical properties of nitrous oxide ( ), which is one of the most prevailing greenhouse gases, has been studied in greatest detail. The dielectric properties and IR spectra of water clusters interacting with nitrous oxide molecules ( ) were investigated in [1, 2]. The uptake of nitrogen monoxide (NO) mol� ecules by water clusters and their structure and stabil� ity were considered in [3], while the absorption, reflection, and emission spectra were studied in [4, 5]. 2 NO ,NO, 23 NO , 2 NO , 25 NO

Spectral characteristics of water clusters in the presence of nitrogen dioxide

The absorption of NO2 molecules by a water cluster containing 25 molecules was studied by molecular dynamics. The calculated dielectric characteristics of a system of (NO2)i(H2O)25 clusters (1 ≤ i ≤ 6) were compared with similar data for a cluster system of pure water. The ability of the disperse water system that trapped NO2 molecules to absorb IR radiation increased, and the rate of the absorbed energy emission decreased. The Raman spectrum of the disperse system that absorbed NO2 molecules changed most significantly in the low-frequency range. The emission time of cluster-generated radiation was much smaller than the lifetime of the clusters.

Chromatographic Analysis of Adsorption: Chemisorption and/or Physisorption

Eight systems namely the C6H6 /Fe2O3, C6H6/NO2/Fe2O3, C6H5CH3/Fe2O3, C6H5CH3/NO2/Fe2O3, C6H6/ZnO, C6H6/NO2/ZnO, C6H5CH3/ZnO, C6H5CH3/NO2/ZnO are examined through a version of inverse gas chromatography and six physicochemical adsorption quantities are determined for each heterogeneous system. Thus, the reversed flow—(inverse) gas chromatography is used for the investigation and study of adsorption phenomena taking place on these heterogeneous solid surfaces. In the case of iron oxide the presence of nitrogen dioxide facilitates the chemisorption. This is not obvious in the case of zinc oxide. However, nitrogen dioxide facilitates the adsorption of benzene and toluene through van der Waals forces in both oxides. Through the experimental local quantities determined and the detailed time-resolved analysis, useful information for the nature and the strength of the adsorbate–adsorbent as well as the adsorbate–adsorbate interactions have been extracted giving an insight into the topography of the active sites and the nature of the surface bonds.

A Practical Alternative to Chemiluminescence-Based Detection of Nitrogen Dioxide: Cavity Attenuated Phase Shift Spectroscopy

We present results obtained from a greatly improved version of a previously reported nitrogen dioxide monitor (Anal Chem. 2005, 77, 724-728) that utilizes cavity attenuated phase shift spectroscopy (CAPS). The sensor, which detects the optical absorption of nitrogen dioxide within a 20 nm bandpass centered at 440 nm, comprises a blue light emitting diode, an enclosed stainless steel measurement cell (26 cm length) incorporating a resonant optical cavity of near-confocal design and a vacuum photodiode detector. An analog heterodyne detection scheme is used to measure the phase shift in the waveform of the modulated light transmitted through the cell induced by the presence of nitrogen dioxide within the cell. The sensor, which operates at atmospheric pressure, fits into a 19 in.-rack-mounted instrumentation box, weighs 10 kg, and utilizes 70 W of electrical power with pump included. The sensor response to nitrogen dioxide (calculated as the cotangent of the phase shift) is demonstrated to be linear (r2 > 0.9999) within +/- 1 ppb over a range of 0-320 ppb (by volume). The device exhibits a detection limit (3sigma precision) of less than 60 parts per trillion (0.060 ppb) with 10 s integration, a value derived from measurements at NO2 concentration levels of both 0 and 20 ppb; the detection limit improves as the integration time is increased to several hundred seconds. The observed baseline drift is less than +/- 0.5 ppb overthe course of a month. An intercomparison of measurements of ambient NO2 concentrations over several days using this sensor with a quantum cascade laser-based infrared absorption spectrometer and a standard chemiluminescence-based NOx analyzer is presented. The data from the CAPS sensor are highly correlated (r2 > 0.99) with the other two instruments. The absolute agreement between the CAPS and each of the two other instruments is within the expected statistical noise associated with the infrared laser-based absorption spectrometer (+/- 0.3 ppb with 10 s sampling) and chemiluminescence analyzer (+/- 0.4 ppb with 60 s averaging). The major limitation concerning accuracy is a direct spectral interference with phototchemically produced 1,2-dicarbonyl species (e.g., glyoxal, methylglyoxal). However, this interference can be readily removed by shifting the detection band to a slightly longer wavelength and ensuring that the lower edge of the detection band is greater than 455 nm.

Comparison of measurements of peroxyacyl nitrates and primary carbonaceous aerosol concentrations in Mexico City determined in 1997 and 2003

Abstract. The concentrations of peroxyacetyl nitrate (PAN) in ambient air can be a good indicator of air quality and the effectiveness of control strategies for reducing ozone levels in urban areas. As PAN is formed by the oxidation of reactive hydrocarbons in the presence of nitrogen dioxide (NO2), it is a direct measure of the peroxyacyl radical levels produced from reactive organic emissions in the urban air shed. Carbon soot, known as black carbon (BC) or elemental carbon (EC), is a primary atmospheric aerosol species and is a good indicator of the levels of combustion emissions, particularly from diesel engines, in major cities. Mexico City is the second largest megacity in the world and has long suffered from poor air quality. Reported here are atmospheric measurements of PAN and BC obtained in Mexico City during the Mexico Megacity 2003 field study. These results are compared with measurements obtained earlier during the Investigación sobre Materia Particulada y Deterioro Atmosférico – Aerosol and Visibility Research (IMADA-AVER) campaign in 1997 to obtain an estimate of the changes in emissions in Mexico City and the effectiveness of control strategies adopted during that time. Concentrations of PAN in 1997 reached a maximum of 34 ppb with an average daily maximum of 15 ppb. The PAN levels recorded in 2003 were quite different, with an average daily maximum of 3 ppb. This dramatic reduction in PAN levels observed in 2003 indicate that reactive hydrocarbon emissions have been reduced in the city due to controls on olefins in liquefied petroleum gas (LPG) and also due to the significant number of newer vehicles with catalytic converters that have replaced older higher emission vehicles. In contrast, black/elemental carbon levels were similar in 1997 and 2003 indicating little improvement likely due to the lack of controls on diesel vehicles in the city. Thus, while air quality and ozone production have improved, Mexico City and other megacities continue to be a major source of black carbon aerosols, which can be an important species in determining regional radiative balance and climate.

Te를 이용한 상온 동작형 NO2센서 제작 및 감응 특성

The characteristic of tellurium thin films was studied for detecting nitrogen dioxide gas at room temperature. The film was deposited on <TEX>$Al_{2}O_{3}$</TEX> substrate by using thermal evaporator. The subsequent process was heat treatment by several conditions. (temperature, flowed gases) Surface and grain boundary was investigated using SEM. The results showed that resistance of the tellurium film decreases reversibly in the presence of nitrogen dioxide. The sensitivity of this device depends on the gas concentration and detect lower concentrations less than 10 ppm.

Mechanism of stable radical generation in aromatic polyamides on exposure to nitrogen dioxide

By using the example of poly- m-phenylene isophthalamide, the mechanism of generation of stable nitrogen-containing radicals in aromatic polyamides in the presence of nitrogen dioxide is considered. The proposed mechanism is based on the reactions of dimers of nitrogen dioxide in the form of nitrosyl nitrate. As a result of a primary reaction of electron transfer from donor functional groups of macromolecules to nitrosyl nitrate, macromolecular radical cations and nitric oxide are formed. Amide groups and phenyl rings can act as electron donors. In the subsequent reactions with participation of radical cations, nitric oxide and nitrogen dioxide oximes, nitroso compounds and nitrites are formed. Generation of stable iminoxyl radicals occurs by reactions of oximes with nitrogen dioxide. Thermolysis of the polymer nitration products gives iminoxyl and acylarylaminoxyl radicals. The structure of iminoxyl radicals and features of dynamics of their formation have been confirmed by ab initio quantum-chemical calculations.

The electronic properties of carbon nanotubes studied by high resolution photoemission spectroscopy

High resolution photoemission spectroscopy was used to follow the modification of the electronic properties of single wall carbon nanotubes determined by the interaction with adsorbed electron donor and acceptor species. Valence band, C1s and adsorbate core level spectra were monitored to reveal the adsorption and to follow the Fermi level shift induced by the charge exchange between C lattice and dopants. In the presence of nitrogen dioxide, a considerable charge withdrawal from C atoms takes place, which is revealed by the binding energy shift of the C1s peak. On the contrary, adsorbed H 2O does not appear to interact with nanotubes. For Li doping, the occurrence of an efficient electron injection into the tube structure is demonstrated by the evidence of Li ionisation, by the enhancement of the density of states near the Fermi level and by the partial conduction band filling, which originates a rigid shift of all C spectral structures.

Nitration and Photonitration of Naphthalene in Aqueous Systems

The nitration of naphthalene was studied in aqueous solution to gain insight into the processes leading to the nitration of aromatic compounds in atmospheric hydrometeors. Reactants used were nitric acid, nitrogen dioxide and peroxynitrous acid in the dark, nitrate, and nitrite/nitrous acid under illumination. Naphthalene nitration can lead to two possible isomers, 1- and 2-nitronaphthalene. The former nitrocompound preferentially forms upon electrophilic processes and in the presence of nitrogen dioxide. Electrophilic nitration of naphthalene takes place in the presence of concentrated nitric acid, but nitration with nitric acid and oxidants (charge-transfer nitration) occurs under much milder conditions than with nitric acid alone. Charge-transfer nitration may have some environmental significance in particular cases, e.g. in acidic aerosols in the presence of HNO3 and oxidants. Nitrogen dioxide is thought to have a role in PAH nitration in the Antarctic particulate matter. In previous papers we have found that nitration induced by peroxynitrous acid, HOONO, can follow two pathways, the former electrophilic (leading for instance to the formation of nitrophenols from phenol) and the latter probably involving HOONO itself (accounting for the formation of nitrobenzene from benzene). In the case of naphthalene and HOONO the electrophilic pathway mainly leads to 1-nitronaphthalene, while the other one preferentially yields 2-nitronaphthalene. The nitration of naphthalene in the presence of nitrite/nitrous acid under irradiation leads to both nitroisomers in similar ratios, and the process is not inhibited by hydroxyl scavengers. This excludes nitrogen dioxide as reactive species for nitration and marks a difference with phenol photonitration and a similarity with the behavior of benzene under comparable conditions. Nitrite photochemistry (and nitrite-induced photonitration as well) is expected to be relevant in fog and cloudwater in polluted areas. An important difference with the gas-phase nitration is that the radicals OH and NO3 are unlikely to play a relevant role in the nitration of naphthalene in aqueous solution.

Control of Elemental Mercury Vapor in Combustion Systems Using Fe2O3 Nanoparticles

The U.S. Environmental Protection Agency (EPA) has proposed initial regulations to control mercury (Hg) emissions from coal-burning utilities, the primary source of airborne Hg emissions in the United States. Promising new techniques in capturing Hg involve transformation of elemental Hg into a product that is much more easily collected using conventional air pollution collection devices. In this study, the removal ability of high surface area iron oxide (Fe2O3) nanoparticles prepared on solid glass beads by a dry mechanical coating process was examined. The experimental results showed different mechanisms responsible for the removal depending on the air composition. In pure air, the Fe2O3 nanoparticles adsorbed and desorbed, while in the presence of nitrogen dioxide (NO2) they took on a catalytic role. The maximum specific capacity observed in this study was 1528 μg Hg/g Fe2O3. This study also identified the effective temperature range (180-320℃) for Hg removal, with the optimal temperature being ~260℃. The study reveals the important role of metal oxides in Hg chemistry in combustion systems through heterogeneous oxidation, and demonstrates the potential of Fe2O3 nanoparticles as an alternative material to traditional control techniques, such as activated carbon for reducing Hg emissions from incinerators.

Peroxynitrite Reaction with Heme Proteins

We have reported that low levels of peroxynitrite (PN) can cause inactivation of the heme-thiolate protein prostacyclin (PGI2)-synthase by nitration of a tyrosine residue. To prove that iron catalysis is involved we studied the interaction of PN with microperoxidase and P450nor, a heme-thiolate protein of known structure. Spectral and kinetic analyses allow to conclude on a ferryl nitrogen dioxide complex as an intermediate which decomposes in the presence of an excess of PN under formation of dioxygen, nitrite, and nitrate. This occurs in a catalytic cycle which was more efficient with P450northan with microperoxidase. If phenol was added to the reaction mixtures of PN and the ferric complexes the ratio of hydroxylated to nitrated phenols decreased compared to the metal-free system. Phenol competed with the formation of dioxygen indicating that the ferryl intermediate was involved in both pathways. One therefore can postulate that the ferryl complex reacts with phenol to give the phenoxyradical which is nitrated in the presence of nitrogen dioxide but does not give hydroxylated products as with metal-free PN. Alternately, the ferryl nitrogen dioxide complex can oxidize a second PN molecule to the radical, ·OONO, which can decompose to dioxygen and NO. The latter forms N2O3with the remaining ·NO2radical. A third pathway consists in the isomerization to nitrate which also is catalyzed by the heme proteins since the ratio of nitrite/nitrate does not change significantly during the catalytic reaction with excess of PN. Our data explain the mechanism of nitration of PGI2-synthase, suggest a role of P450noras a PN scavenger, and favor heme-thiolate complexes for trapping PN.

A new sandwich-type diphthalocyanine as a potential optical transducer for NO 2 detection

Bis(phthalocyaninato)titanium(IV) (Ti(Pc) 2), a sandwich-type metal diphthalocyanine, is used as a chemical transducer for the optical detection of nitrogen dioxide. The optical properties of this chemical transducer after its immobilization on controlled pore glass (CPG) by a casting from a Ti(Pc) 2 solution in α-chloronaphthalene are described. This compound is characterized by three well-defined absorption bands in the visible region ( λ=506, 675 and 720 nm) which undergo spectral changes in the presence of nitrogen dioxide. Two different optodes were manufactured and characterized. A plastic flat reflector is used as a solid support placed in front of an optical fibre bundle, and Ti(Pc) 2 is immobilized on CPG that was previously embedded in the plastic reflector either by casting or by sublimation. The characterization of the developed optodes in terms of sensitivity, reversibility and response time is described.