Singlet Delta Oxygen Production Research Articles

Singlet delta oxygen production in a 2D micro-discharge array in air: effect of gas residence time and discharge power

The production of singlet delta oxygen (O2(a1Δg)) is of growing interest for many applications. We report on the measurement of O2(a1Δg) and ozone (O3) in a room temperature atmospheric pressure discharge in dry air. The plasma source is a 2D array of micro-discharges generated by an alternating current voltage at 20 kHz. The study focuses on the effect of gas flow through the discharge. The maximum investigated flow rate allows reducing the gas residence time in the discharge zone to half the discharge period. Results indicate that the residence time and discharge power have a major effect on the O2(a1Δg) production. Different O2(a1Δg) density dependencies on power are observed for different flow rates. Effects of collisional quenching on the as-produced and measured O2(a1Δg) densities are discussed. The flow rate also allows for control of the O2(a1Δg) to O3 density ratio in the effluent from 0.7 to conditions of pure O3.

Pressure Effects in the Spatial Development of Microcathode Sustained Discharges in Rare-Gas Oxygen Mixtures

It has been recently demonstrated that microcathode sustained discharges (MCSD) are very efficient for the production of large fluxes of singlet delta oxygen (SDO). In this paper, a comparison between MCSD operation in Ar/O2 and in He/O2 mixtures is done. It is shown that, even if SDO production efficiency is theoretically much higher in Ar/O2 mixtures, atmospheric pressure operation is only possible in He-based mixtures.

Cold atmospheric pressure plasma jets as sources of singlet delta oxygen for biomedical applications

Absolute densities of singlet delta oxygen (SDO) molecules were measured using infrared optical emission spectroscopy in the flowing effluents of two different atmospheric-pressure plasma jets (APPJs): a capacitively coupled radio-frequency-driven jet (rf-APPJ) and a lower frequency kilohertz-driven dielectric barrier discharge jet. The plasma jets were operated in helium, with small admixtures of molecular oxygen (O2 < 2%). High absolute SDO densities of up to 6.2 × 1015 cm−3 were measured at approximately 10 cm downstream. The rf-APPJ seems to be much more efficient in producing SDO. The influence of different parameters, such as gas flows and mixtures and power coupled to the plasmas, on the production of SDO by the two APPJs has been investigated. Despite the considerable differences between the two plasma jets (excitation frequency, electric field direction, inter-electrode distance, plasma propagation), similar dependencies on the oxygen admixture and on the dissipated power were found in both APPJs. However, opposite trends were observed for the gas flow dependence. The results presented in this paper show that the control of the external operating conditions of each APPJ enables the tailoring of the SDO composition of both plasma effluents. This provides scope to tune the plasma jets for desired applications, e.g., in biomedicine.

DNA oxidation by singlet delta oxygen produced by atmospheric pressure microdischarges

Arrays of microcathode sustained discharges were developed for the production of singlet delta oxygen (SDO) at atmospheric pressure. SDO densities higher than 3.5×1016 cm−3 have been efficiently produced and transported over distances longer than 50 cm. These arrays appear to be an ideal tool for examining the reactivity of SDO with biological components. Experiments were performed indicating that SDO is able to oxidize 2′-deoxyguanosine, a DNA constituent. It is shown that the 4-OH-8-oxodGuo formation is proportional to the number of SDO molecules while other reactive species could also be involved in the production of the nucleosides dSp and dZ.

Influence of nitrogen oxides NO and NO2 on singlet delta oxygen production in pulsed discharge

The influence of nitrogen oxides NO and NO2 on the specific input energy (SIE) and the time behaviour of singlet delta oxygen (SDO) luminescence excited by a pulsed e-beam sustained discharge in oxygen were experimentally and theoretically studied. NO and NO2 addition into oxygen results in a small increase and decrease in the SIE, respectively, the latter being connected with a large energy of electron affinity to NO2. The addition of 0.1–0.3% nitrogen oxides was experimentally and theoretically demonstrated to result in a notable enhancement of the SDO lifetime, which is related to a decrease in the atomic oxygen concentration in afterglow. It was experimentally demonstrated that to get a high SDO concentration at the gas pressure 30–60 Torr for a time interval of less than ∼0.5 s one needs to add not less than 0.2% nitrogen oxides into oxygen. The temperature dependence of the relaxation constant for SDO quenching by unexcited oxygen was estimated by using experimental data on the time behaviour of SDO luminescence.

Measurement of singlet oxygen concentrations in a fast flow dc discharge in oxygen–argon mixtures

Production of singlet delta oxygen (SO) by a dc glow discharge in flowing O2 : Ar mixtures has been investigated. SO concentrations have been measured with dilution of oxygen up to O2 : Ar = 5 : 95 at a pressure up to 14 Torr and specific power load in the discharge up to 50 J mmol−1. The largest relative SO concentrations achieved in experiments exceeded 9%. This is sufficient to obtain population inversion and laser gain in the oxygen–iodine medium.It was found that for the mixtures with large Ar content stray spectral lines appear near the SO 1268 nm band that is used to determine the SO concentration. These are the Ar I lines and their intensities increase relative to the SO band with Ar content. To estimate their contribution it is suggested to normalize their intensities on the intensity of the 1280 nm line.

Electric generators of singlet delta oxygen for an oxygen-iodine laser

Experimental and theoretical research into electric generators of singlet delta oxygen (SDO) for an oxygen-iodine laser made at the Lebedev Physics Institute and TRINITI is discussed. Breakdown and current-voltage characteristics of self-sustained electric discharge in SDO were studied both experimentally and theoretically, indicating that SDO and pure oxygen have quite different electric features. The electric properties and spectroscopy of an e-beam sustained discharge (EBSD) in oxygen and oxygen gas mixtures were experimentally studied. A comprehensive numerical model describing SDO kinetics in different kinds of discharge was developed. The pulsed EBSD in pure oxygen and its mixtures with noble gases was shown to be very unstable and characterized by low input energy. When adding small amounts of carbon monoxide or hydrogen, the electric stability of the EBSD increases, the specific input energy (SIE) per molecular component being more than order of magnitude higher and coming to 6.5 kJ/(l atm(O2 + CO)) for the gas mixture O2: Ar: CO = 1: 1: 0.1. Theoretical calculations demonstrated that, for an SIE of 6.5 kJ/(l atm), the SDO yield may reach ∼20%, exceeding its threshold value needed for oxygen-iodine laser operation at room temperature. The calibration of the optical scheme for measuring the SDO absolute concentration and yield using the detection of luminescence of the SDO going from a chemical SDO generator was performed. The measurement of the SDO yield demonstrated that it was ∼10.5% for an SIE of ∼3.0 kJ/(l atm(O2 + CO)), which is about 1.5 times less than the results of theoretical calculations for such an SIE. SDO production in RF slab discharge ignited in oxygen gas mixtures was experimentally studied, experimental SDO yield being about 10%. The choice of electrode material was demonstrated to be very important.

Efficient chemical oxygen-iodine laser powered by a centrifugal bubble singlet oxygen generator

Efficient production of singlet delta oxygen in a bubble singlet oxygen generator (BSOG) under the influence of centrifugal acceleration, 136g, has been obtained. An output power of 770W with chemical efficiency of 25.6% has been achieved in a small-scale, supersonic chemical oxygen-iodine laser supplied by the centrifugal BSOG. The ratio of the output power to the basic hydrogen peroxide volumetric flow rate was 4.3KJ∕liter. Efficient chemical oxygen-iodine laser (COIL) operation with the centrifugal BSOG demonstrates the potential for mobile COIL applications.

Non-self-sustained electric discharge in oxygen gas mixtures: singlet delta oxygen production

The possibility of obtaining a high specific input energy in an electron-beam sustained discharge ignited in oxygen gas mixtures O2 : Ar : CO (or H2) at the total gas pressures of 10–100 Torr was experimentally demonstrated. The specific input energy per molecular component exceeded ∼6 kJ l−1 atm−1 (150 kJ mol−1) as a small amount of carbon monoxide was added into a gas mixture of oxygen and argon. It was theoretically demonstrated that one might expect to obtain a singlet delta oxygen yield of 25% exceeding its threshold value needed for an oxygen–iodine laser operation at room temperature, when maintaining a non-self-sustained discharge in oxygen gas mixtures with molecular additives CO, H2 or D2. The efficiency of singlet delta oxygen production can be as high as 40%.

Singlet Delta Oxygen Production from a Gas—Solid Reaction.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Model for oxygen recombination on reaction-cured glass

This article briefly reviews the model for recombination of oxygen on a silicon-dioxide surface presented in detail in a previous paper. Data for oxygen recombination on reaction-cure d glass (RCG), a silicon-dioxid ebased material, is presented and compared with the Si-O2 recombination model. The model is modified slightly to better represent the oxygen-RCG system, but the essential feature of the model, the participation of the oxygen of the surface matrix itself, remains unchanged. The ramifications of the model toward the production of excited molecular oxygen is examined as it may pertain to surface heating during a re-entry. Data indicating that the predicted production of singlet-delta oxygen, and no higher-electronic-state oxygen is given in support of the model.

Nonisothermal analysis of the reaction kinetics for chlorine in basic hydrogen peroxide

The effect of temperature on the reaction kinetics of chlorine with basic hydrogen peroxide (BHP) war investigated for the system of Cl 2 at atmospheric pressure absorbing into 4 M KOH in aqueous hydrogen peroxide for the temperature range of 0-20 o C. This reaction is important for the production of singlet delta oxygen [O 2 ( 1 Δ g )] used in the chemical oxygen-iodine laser (COIL)

Singlet delta oxygen generation for Chemical Oxygen-Iodine Lasers

The development of Chemical Oxygen-Iodine Lasers is based on the generation of singlet delta oxygen. To improve the overall efficiency of these lasers, it is necessary to increase the generator production and yield of singlet delta oxygen at low and high pressure, respectively, for subsonic and supersonic lasers. Furthermore, the water vapor content must be as low as possible. A generator model, based on gas-liquid reaction and liquid-vapor equilibrium theories associated with thermophysical evaluations is presented. From model predictions, operating conditions have been drawn to attain the following experimental results in a bubble-column: by increasing the superficial gas velocity, the production of singlet delta oxygen is largely improved at low pressure; by mixing chlorine with an inert gas before injection in the reactor, this yield is maintained constant up to higher pressure. A theoretical analysis of these experimental results and their consequences for both subsonic and supersonic lasers are presented.

Production of singlet delta oxygen by atmospheric pollutants.

Singlet delta oxygen (1O2) was generated at atmospheric pressure using heterogeneous gas-phase photosensitization. Polycyclic aromatic hydrocarbons (PAH), known constituents of the atmosphere, were found to be efficient sensitizers in the production of singlet delta oxygen under simulated environmental conditions. A novel mechanism involving singlet delta oxygen is proposed in which PAH on particle surfaces are self-activated to form direct-acting mutagens.