Sensitive and selective system of benzene detection based on a cataluminescence sensor

Au/La₂O₃ nanomaterials were prepared through calcining Au‐modified La(OH)₃ precursors. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X‐ray diffractometry (XRD) were employed to characterize the as‐prepared samples. Benzene, a common volatile organic compound, was selected as a model to investigate the cataluminescence (CTL)‐sensing properties of the Au/La₂O₃ nanomaterials. Results indicated that the as‐prepared Au/La₂O₃ exhibited outstanding CTL properties such as stable intensity, high signal‐to‐noise values, and short response and recovery times. Under optimized conditions, the benzene assay exhibited a broad linear range of 1–4000 ppm, with a limit of detection of 0.7 ppm, which was below the standard permitted concentrations. Furthermore, the gas sensor system showed outstanding selectivity for benzene compared with seven other types of common volatile organic compounds (VOCs). The proposed gas sensor showed good characteristics with high selectivity, fast response time and long lifetime, which suggested the promising application of the Au/La₂O₃ nanomaterials as a novel highly efficient CTL‐sensing material. Copyright © 2013 John Wiley & Sons, Ltd.     

Zeolite-based cataluminescence sensor for the selective detection of acetaldehyde.

The reactions of acetaldehyde with O atoms in the cages of large-pore zeolites have been discovered to result in light emission. The luminescence characteristics of acetaldehyde vapours passing through the surface of chosen zeolites were studied using a cataluminescence-based detection system. To demonstrate the feasibility of the method, the detection of acetaldehyde using catalysts was studied systematically and a linear response of 0.06-31.2 microg/mL acetaldehyde vapour was obtained. Methanol, ethanol, isopropanol, methylbenzene, chloroform, dichlormethane and acetonitrile did not interfere with the determination of acetaldehyde. Acetaldehyde vapour could also be distinguished from some homologous series such as formaldehyde, cinnamaldehyde, glutaraldehyde and benzaldehyde on this catalyst, possibly due to the stereoselectivity of the zeolite and its specific reaction mechanism. Moreover, acetaldehyde was quantified without detectable interference from formaldehyde in four artificial samples. Thus, this kind of cataluminescence-based sensor could be potentially extended to the analysis of volatile organic compounds in air, and the simple and portable properties of cataluminescence-based sensors could also make them beneficial in many areas of analytical science.     

Development of a cataluminescence sensor for detecting benzene based on magnesium silicate hollow spheres

A novel and sensitive gas sensor was developed for the determination of benzene based on its cataluminescence (CTL) by oxidation in air on the surface of hollow magnesium silicate spheres. Luminescence characteristics and optimum conditions were investigated. Results indicated that the as‐prepared magnesium silicate hollow spheres exhibited outstanding CTL properties such as stable intensity, high signal/noise values, and short response and recovery times. Under optimized conditions, benzene exhibited a broad linear range of 1–4500 ppm, with a correlation coefficient of 0.9946 and a limit of detection (signal‐to‐noise ratio (S/N) = 3) of 0.6 ppm, which was below the standard permitted concentration. The relative standard deviation (RSD) for 100 ppm benzene was 4.3% (n = 6). Furthermore, the gas sensor system showed outstanding selectivity for benzene compared with nine other common volatile organic compounds (VOCs). The proposed gas sensor showed good characteristics of high selectivity, fast response time and long lifetime, which suggested the promising application of magnesium silicate hollow spheres as a novel highly efficient CTL sensing material. The mechanism for the improved performance was also discussed based on the experimental results. Copyright © 2014 John Wiley & Sons, Ltd.     

A novel gaseous dimethylamine sensor utilizing cataluminescence on zirconia nanoparticles

A novel cataluminescence (CTL) sensor using ZrO₂ nanoparticles as the sensing material was developed for the determination of trace dimethylamine in air samples based on the catalytic chemiluminescence (CL) of dimethylamine on the surface of ZrO₂ nanoparticles. The CTL characteristics and the different factors on the signal intensity for the sensor, including nanomaterials, working temperature, wavelength and airflow rate, were investigated in detail. The CL intensity on ZrO₂ nanoparticles was the strongest among the seven examined catalysts. This novel CL sensor showed high sensitivity and selectivity to gaseous dimethylamine at optimal temperature of 330°C. Quantitative analysis was performed at a wavelength of 620 nm. The linear range of CTL intensity vs concentration of gaseous dimethylamine was 4.71 × 10^?3 to 7.07 × 10^?2 mg L^?1 (r = 0.9928) with a detection limit (3σ) of 6.47 × 10^?4 mg L^?1. No or only very low levels of interference were observed while the foreign substances such as benzene, hydrochloric acid, methylbenzene, chloroform, n‐hexane and water vapor were passing through the sensor. The response time of the sensor was less than 50 s, and the sensor had a long lifetime of more than 60 h. The sensor was successfully applied to the determination of dimethylamine in artificial air samples, and could potentially be applied to analysis of nerve agents such as Tabun (GA). Copyright © 2009 John Wiley & Sons, Ltd.     

Development of highly sensitive sensor system for methane utilizing cataluminescence

A gaseous sensor system was developed for the detection of methane based on its cataluminescence emission. Cataluminescence characteristics and optimal conditions were studied in detail under optimized experimental conditions. Results showed that the methane cataluminescence sensor system could cover a linear detection range from 10 to 5800 ppm (R = 0.9963, n = 7) and the detection limit was about 7 ppm (S/N = 3), which was below the standard permitted concentration. Moreover, a linear discriminant analysis method was used to test the recognizable performance of the methane sensor. It was found that methane, ethane, propane and pentane could be distinguished clearly. Its methane sensing properties, including improved sensitivity, selectivity, stability and recognition demonstrated the TiO₂/SnO₂ materials to be promising candidates for constructing a cataluminescence‐based gas sensor that could be used for detecting explosive gas contaminants. Copyright © 2015 John Wiley & Sons, Ltd.     

A cataluminescence gas sensor for ammonium sulfide based on Fe3O4–carbon nanotubes composite

In the present work, Fe₃O₄–carbon nanotubes (CNTs) composite was explored as a sensing material candidate for ammonium sulfide. Intense chemiluminescence emission can be observed during the catalytic oxidation of ammonium sulfide on the surface of Fe₃O₄–CNTs composite. Based on this phenomenon, a selective and sensitive gas sensor for the determination of ammonium sulfide was demonstrated. Under the optimized conditions, the linear range of cataluminescence intensity vs concentration of ammonium sulfide gas was 1.4–115 µg mL^?1 (R = 0.998) with a limit of detection (S/N = 3) of 0.05 µg mL^?1. The relative standard deviation (n = 5) for 14.3 µg mL^?1 ammonium sulfide was 1.9%. There was no response to common foreign substances, such as sulfur dioxide, toluene, aether, ethanol, acetone, hydrogen sulfide, carbon bisulfide, benzene and ammonia. The proposed sensor was successfully applied for the determination of ammonium sulfide in artificial air samples. Copyright © 2009 John Wiley & Sons, Ltd.     

A 1,2‐propylene oxide sensor utilizing cataluminescence on CeO2 nanoparticles

A simple and sensitive gas sensor was proposed for the determination of 1,2‐propylene oxide (PO) based on its cataluminescence (CTL) by oxidation in the air on the surface of CeO₂ nanoparticles. The luminescence characteristics and optimal conditions were investigated in detail. Under optimized conditions, the linear range of the CTL intensity versus the concentration of PO was 10–150 ppm, with a correlation coefficient (r) of 0.9974 and a limit of detection (S/N = 3) of 0.9 ppm. The relative standard deviation for 40 ppm PO was 1.2% (n = 7). There was no or only weak response to common foreign substances including acetone, formaldehyde, ethyl acetate, acetic acid, chloroform, propanol, carbon tetrachloride, ether and methanol. There was no significant change in the catalytic activity of the sensor for 100 h. The proposed method was simple and sensitive, with a potential of detecting PO in the environment and industry. Copyright © 2014 John Wiley & Sons, Ltd.     

An ethyl acetate sensor utilizing cataluminescence on Y2O3 nanoparticles

A cataluminescence (CTL) sensor using Y₂O₃ nanoparticles as the sensing materials was proposed for the determination of ethyl acetate. This ethyl acetate sensor showed high sensitivity and specificity at the optimal temperature of 264°C. Quantitative analysis was performed at a wavelength of 425 nm. The linear ranges of CTL intensity vs ethyl acetate concentrations were 2.0–250 ppm (r = 0.9965) and 250–6500 ppm (r = 0.9997) with a detection limit (3σ) of 0.5 ppm. There was no response or weak response when foreign substances such as formic acid, n‐hexane, toluene, acetic acid, benzene, and formaldehyde passing through the surface of Y₂O₃ nanoparticles. The sensor had a long lifetime more than 80 h with 3600 ppm ethyl acetate. It had been applied successfully to determine ethyl acetate in artificial air samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Detection of hydrogen sulphide using cataluminescence sensors based on alkaline-earth metal salts

Detection of hydrogen sulphide (H₂S) was conducted based on cataluminescence (CTL) sensors, using alkaline‐earth metal carbonates as catalysts. Optimal working conditions, analytical characteristics and the response properties of the sensor were investigated. CTL intensity examination showed that sensors fabricated with CaCO₃, SrCO₃ or BaCO₃ could be used to detect H₂S gas sensitively. The optimal sensing temperature was about 320 °C. Under the sensing conditions with temperature at ca. 320 °C and gas flow rate in the range 180–200 mL/min, the linear range of CTL intensity vs H₂S concentration was 25–500 ppm, with a detection limit of 2 ppm. The response and recovery times of the sensor were within 5 and 25 min, respectively. Also, the sensor had the property of high selectivity to H₂S with very weak or no obvious response to 14 other gases, such as NO₂, NH₃, hydrocarbons and alcohol. Copyright © 2011 John Wiley & Sons, Ltd.     

Fe-doped MOF-derived N-rich porous carbon nanoframe for H2S cataluminescence sensing

Metal-doped porous carbon matrix composites are considered as outstanding H₂S cataluminescence sensing materials for their good sulfur tolerance and high cataluminescence activity. In this work, an Fe-doped MOF-derived N-rich porous carbon nanoframe was successfully fabricated using the pyrolysis of Fe-doped ZIF-8 in an Ar atmosphere at a temperature of 900°C, and used for H₂S cataluminescence sensing. Along with zinc volatilization, the obtained porous carbon nanoframe not only had high specific surface area and abundant voids, but also had well dispersed Fe species doped in the skeleton. Compared with Fe₂O₃/ZnO composites derived from the same precursor but different pyrolysis terms, this as-prepared Fe-doped N-rich porous carbon presented a three times increase in the cataluminescence intensity towards H₂S, attributed to the porous carbon skeleton that is indispensable for dispersing catalytic active sites and providing more absorptive surface and voids. Comparably, this proposed sensor demonstrated high sensitivity and good selectivity, with the detection range of 1.57–19.58 μg·ml⁻¹ and detection limit of 0.13 μg·ml⁻¹ towards H₂S. This work may provide a new pathway for preparing catalysts for cataluminescence sensing with better metal distribution, higher specific surface area, and richer pores than ever before.     

Sensitive and selective cataluminescence‐based sensor system for acetone and diethyl ether determination

A three‐dimensional hierarchical CdO nanostructure with a novel bio‐inspired morphology is reported. The field emission scanning electronic microscopy, transmission electron microscopy and X‐ray diffractometer were employed to characterize the as‐prepared samples. In gas‐sensing measurements, acetone and diethyl ether were employed as target gases to investigate cataluminescence (CTL) sensing properties of the CdO nanostructure. The results show that the as‐fabricated CdO nanostructure exhibited outstanding CTL properties such as stable intensity, high signal/noise values, short response and recovery time. The limit of detection of acetone and diethyl ether was ca. 6.5 ppm and 6.7 ppm, respectively, which was below the standard permitted concentrations. Additionally, a principal components analysis method was used to investigate the recognizable ability of the CTL sensor, and it was found that acetone and diethyl ether can be distinguished clearly. The performance of the bio‐inspired CdO nanostructure‐based sensor system suggested the promising application of the CdO nanostructure as a novel highly efficient CTL sensing material. Copyright © 2014 John Wiley & Sons, Ltd.     

Research on benzene,toluene and dimethylbenzene detection based on a cataluminescence sensor

We present a sensitive and quick way to determine benzene, toluene and dimethylbenzene (BTEX) in air, applying a cataluminescence (CTL) sensor based on a nano‐sized composite material, γ‐Al₂O₃/PtO₂. The factors that affect the sensor's performance were studied, including the sensing material, temperature, rate of air carrier and wavelength. It was shown that when Pt accounted for 0.2% of the sensing material, the rate of the air carrier that carries target gas was 450 mL/min, the determination wavelength was 400 nm and temperature was 236°C, this sensor showed the best CTL intensity to BTEX. In addition, the CTL intensity had a high linear relation with the concentration of BTEX, with a linear range from 0.5 to 100 mL/m³, and a detection limit 0.22 mL/m³. This nano‐sized material had a quick response within 1.5 s, short recovery time within 1 min and a long lifetime, showing good potential for a variety of applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Detection of volatile organic compounds released by wood furniture based on a cataluminescence test system

Wood furniture is an important source of indoor air pollution. To date, the detection of harmful substances in wood furniture has relied on the control of a single formaldehyde component, therefore the detection and evaluation of pollutants released by wood furniture are necessary. A novel method based on a cataluminescence (CTL) sensor system generated on the surface of nano‐3TiO₂–2BiVO₄ was proposed for the simultaneous detection of pollutants released by wood furniture. Formaldehyde and benzene were selected as a model to investigate the CTL‐sensing properties of the sensor system. Field emission scanning electronic microscopy (FESEM), transmission electron microscopy (TEM) and X‐ray diffraction (XRD) were employed to characterize the as‐prepared samples. The results showed that the as‐prepared test system exhibited outstanding CTL properties such as stable intensity, a high signal‐to‐noise ratio, and short response and recovery times. In addition, the limit of detection for formaldehyde and benzene was below the standard permitted concentrations. Moreover, the sensor system showed outstanding selectivity for formaldehyde and benzene compared with eight other common volatile organic compounds (VOCs). The performance of the sensor system will enable furniture VOC limit emissions standards to be promulgated as soon as possible. Copyright © 2015 John Wiley & Sons, Ltd.     

A new infra-red gas analyser and portable photosynthesis meter

The new infra-red gas analyser for measurement of CO₂ concentration described uses a focussed, dual optical path. The 2W radiation source is a heated alumina bead and a cooled lead selenide photoconductive detector measures the difference in radiation absorption at 4.26 m by the gas in sample and reference tubes. Radiation is chopped alternately between these tubes at 120 Hz. The signal from the detector is processed through an a.c. coupled amplifier, phase sensitive detector and low pass filter. Incorporated into the photosynthesis meter, the sample tube of the analyser is connected to a leaf chamber and circulating pump forming a closed gas circuit. As a leaf in the chamber removes carbon dioxide from the air in the closed circuit, the decrease in its concentration is sensed by the analyser. The time taken for the concentration to decrease by a predetermined amount (typically 30 ppm) is displayed and rate of net photosynthesis can be calculated from this and the volume of the closed circuit. A measurement of the light-saturated rate of net photosynthesis of a healthy flag leaf of wheat can be made in 10–15 seconds. The system is fully portable and has been used intensively in the field for two summers.     

A research on determination of explosive gases utilizing cataluminescence sensor array.

In this paper, we propose a model of a sensor array system, which consists of three cataluminescence sensors based on nanosized SrCO3, gamma-Al2O3 and BaCO3 as catalysts, for quantitative analysis of the explosive gases of propane, n-butane and iso-butane in a mixture. Six linear regression equations of the cataluminescence intensity vs. the gas concentrations in the range 2000-10,000 ppm were established from the sensor array system at two working temperatures, as the explosive gases show different sensitivity to the three sensors. The least squares method was employed for solving the simultaneous equations and quantifying the concentrations of the three components. The detection limits (3sigma) of propane, n-butane and iso-butane on SrCO3, gamma-Al2O3 and BaCO3 sensors are 50, 40 and 20 ppm, 80, 60 and 40 ppm, and 20, 10 and 5 ppm, respectively. The concentrations of two artificial samples containing the tertiary mixture were analysed with satisfactory results.     

An all-solid-state amperometric ethanol sensor

An all-solid-state pellet electrode for ethanol determination has been developed and compared with the membrane-layered sensor. It is found that the new pellet electrodes have reliable responses (current vs. concentration) to ethanol from 0.1 to 10 m with response times of about 2 min. The current response decreases about 10% h⁻¹ during continuous operation, compared with a drop of 50% h⁻¹ with normal membrane electrodes. Fresh electrodes can be stored in a freezer for 2 weeks without apparent activity loss. The measurement procedure is convenient and it is probable that reproducible, disposable electrodes can be made at low cost. This format is general and can easily be extended to many other systems with β-NAD⁺/NADH as coenzyme.     

A novel BOD sensor based on bacterial luminescence

A reagent-type BOD sensor with a new principle employing a luminous bacterium, Photobacterium phosphoreum, was developed. The increased intensity of luminescence resulting from the cellular assimilation of organic compounds in wastewater was detected by a photodiode. The BOD response of the bacterial reagent could be obtained within 15 min with +/-7% error. The temperature condition for optimal BOD response was 18 degrees to 25 degrees C at pH 7 to 8, indicating that it is possible to measure BOD at room temperature without having to stabilize the temperature of the measuring system. For practical use, two procedures for long-term preservation of the bacterial reagent, vacuum drying method and freezing method, are suggested. The metabolic characteristics of employed luminous bacteria were investigated by comparing the BOD values for several pure organic substrates estimated by the BOD sensor with conventional 5-day BOD values. In comparison with the 5-day measurement for some wastewater samples, BOD values estimated by the sensor showed comparatively good agreement with those measured by the 5-day method. (c) 1993 Wiley & Sons, Inc.     

A novel hydrogen peroxide sensor based on immobilization of haemoglobin on nano-TiO2/DTAB composite film

Abstract

The direct electron transfer of immobilized haemoglobin (Hb) on nano-TiO₂ and dodecyltrimethylammonium bromide (DTAB) film modified carbon paste electrode (CPE) and its application as a hydrogen peroxide (H₂O₂) biosensor were investigated. On nano-TiO₂/DTAB/Hb/CPE, Hb displayed a rapid electron transfer process with participation of one proton and with an electron transfer rate constant which estimated as 0.29 s^??1. Thus, the proposed biosensor exhibited a high sensitivity and excellent electrocatalytic activity for the reduction of H₂O₂. The catalytic reduction current of H₂O₂ was proportional to H₂O₂ concentration in the range of 0.2–4.0 mM with a detection limit of 0.07 mM. The apparent Michaelis–Menten constant (K_m^app) of the biosensor was calculated to be 0.127 mM, exhibiting a high enzymatic activity and affinity. This sensor for H₂O₂ can potentially be applied in determination of other reactive oxygen species as well.     

A novel colorimetric fluoride sensor based on a semi‐rigid chromophore controlled by hydrogen bonding

A novel semi‐rigid latent chromophore E1, containing an amide subunit activated by an adjacent semi‐rigid intramolecular hydrogen‐bonding (IHB) unit, was designed for the detection of fluoride ion by the ‘naked‐eye’ in CH₃CN. Comparative studies on structural analogs (E2, E3, and E4) provided significant insight into the structural and functional role of the amide N–H and IHB segment in the selective recognition of fluoride ions. The deprotonation of the amide N–H followed by the enhancement of intramolecular charge transfer (ICT) induced the colorimetric detection of E1 for fluoride ion. Copyright © 2015 John Wiley & Sons, Ltd.     

Effects of protein sources on concentrations of hydrogen sulphide in the rumen headspace gas of dairy cows

Two Latin square design experiments investigated the relationship between hydrogen sulphide concentration in the rumen headspace gas of dairy cows and the early stages of protein degradation in the rumen. In Expt 1, three protein sources differing in rumen N (nitrogen) degradability (maize gluten feed (MGF); sunflower meal (SFM); and soyabean meal (SBM)) were used, whereas in Expt 2 four different batches of the same feed (MGF) differing in colour (CIE L*, a*, b* (CIELAB) scale) were used. After allowing the concentration of hydrogen sulphide in rumen gas to decline close to zero, a fixed amount of protein sources was offered to cows and the concentrations of hydrogen sulphide were recorded in rumen headspace gas at 30-min intervals. In Expt 1, the concentration of hydrogen sulphide showed considerable variation between protein sources, with MGF having the highest concentration followed by SFM and SBM resulting in very low concentrations. The N wash losses (zero time measurements with nylon bags) ranked the feeds in the same way, from MGF (highest; 61%) to SBM (lowest; 26%). There were marked differences in the degradation of cystine and methionine between protein sources, although the degradation of cystine was always higher than for methionine. MGF (Expt 2) led to increased concentrations of hydrogen sulphide, with peak concentrations achieved between 1 and 2 h after feeding. The concentrations of hydrogen sulphide were higher for MGF1, intermediate for MGF2 and lower for MGF3 and MGF4, agreeing with colour scale. Differences in the early stages of dietary sulphur degradation corresponded with differences in hydrogen sulphide concentrations in rumen gas. The results suggest that hydrogen sulphide concentrations in the rumen headspace gas could be useful to evaluate nutritional parameters not measured by the in sacco technique, contributing to a better understanding of the response of dairy cows to different protein supplements.