ABSTRACT
Rapid discrimination of compounds with similar structures and properties is a hot topic in analytical chemistry. In this study, a cyclic chemiluminescence (CCL) system was designed by using nano-magnesium oxide as catalyst. The effects of reactant concentration, reaction temperature and detection wavelength on CCL analysis were studied. It was found that the CCL signal satisfied the first order exponential decay law. Each reaction had an exponential decay equation (EDE) describing its signal change law. The initial variable A was proportional to the reactant concentration. The decay-coefficient k was a characteristic constant that was independent of the reactant concentration. For iso-butanol, it's A-values versus concentration was linear in 0. 89-14. 24 mg / L, the average of k-value in this range was 32. 0 with a RSD of 2. 2% . Thus, qualitative and quantitative analysis could be conducted according to the A and k values. The system was used to analyze eight kinds of alcohol compounds, and it was found that there were significant differences in the k-values for different alcohols. For example, the k-values for n-butanol, iso-butanol and sec-butanol were 27. 2 ±0. 2, 32. 0±0. 8 and 19. 5±0. 1, respectively.
ABSTRACT
Based on the plasma activation and the sensing ability of cataluminescence, a low temperature plasma-assisted cataluminescence sensor was developed for ethylene detection using the low-cost and abundant alkaline-earth oxides of MgO nanomaterials as the sensing materials.Taking advantage of the high activity of the plasma, the working temperature of this method was greatly decreased than that of traditional detection method (300-500℃), and the sensing of ethylene was realized at room temperature without any heating device.This ethylene cataluminescence sensor gave a linear range of 112-4997 ng/mL (90-3998 ppm, R=0.97669) with a detection limit of 37 ng/mL (30 ppm).Besides, the sensor showed good selectivity and stability in ethylene detection.Due to the absence of the heating element, the present sensor was simple, rapid, low-cost, low energy-consumption and stable for ethylene sensing.This study improved the applicability of cataluminescence sensors and might promote the development of cataluminescence sensors.
ABSTRACT
A novel method based on cross sensitivity of cataluminescence (CTL) on nano-Ti3CeY2O11 was proposed for simultaneous determination of formaldehyde, benzene and sulfur dioxide in air.The relations between the concentrations of formaldehyde, benzene and sulfur dioxide and their CTL intensities were respectively ascertained at three wavelengths.The accurate concentrations of formaldehyde, benzene and sulfur dioxide can be calculated by superimposed total CTL intensities.The three analysis wavelengths are 420 nm, 535 nm and 680 nm.The surface temperature of the sensitive materials is 280℃.The carrier gas flow rate is 130 mL/min.The detection limits (3σ) are 0.04 mg/m3 for formaldehyde, 0.05 mg/m3 for benzene and 0.10 mg/m3 for sulfur dioxide, respectively.The linear ranges of CTL intensity versus analyte concentration are 0.08-75.60 mg/m3 for formaldehyde, 0.1-101.40 mg/m3 for benzene and 0.3 to 115.00 mg/m3 for sulfur dioxide.The recoveries of 12 testing standard samples by this method are 96.4%-103.7% for formaldehyde, 97.8%-102.5% for benzene and 97.2%-103.3% for sulfur dioxide.Common coexisting substances, such as acetaldehyde, toluene, hydrogen sulfide, ammonia, methanol, ethanol and carbon dioxide, do not disturb the determination.The relative deviation of CTL signals of continuous 200 h detection for gaseous mixture containing formaldehyde, benzene and sulfur dioxide is less than 2%, which shows the longevity of the nanometer composite oxide to formaldehyde, benzene and sulfur dioxide.This method makes full use of the cross sensitive phenomenon, and can realize the on-line analysis of formaldehyde, benzene and sulfur dioxide in air.
ABSTRACT
CeO2-Co3 O4 composite nanofibers were prepared by the double jets electrospinning method. The nanofibers were then deposited onto the surface of a ω-type heating coil as cataluminescence material to prepare a new cataluminescence ( CTL ) type formaldehyde gas sensor. The crystalline phase and microstructure of CeO2-Co3 O4 composite nanofibers were characterized by X-ray diffraction ( XRD) and scanning electron microscope (SEM), and the cataluminescence mechanism and electrochemical characteristic of formaldehyde on the surface of CeO2-Co3 O4 nanofibers were analyzed by H2 temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). Under the optimal conditions (500 nm of wavelength, 0. 2 L/ min of flow rate and 550℃), there was a good relationship between the CTL intensity of this formaldehyde gas sensor (Ce30) and formaldehyde concentration in the range of 1. 2 -50 μg / m3 , the sensitivity was 40. 04 a. u. / (μg / m3 ), the detection limit was 1. 2 μg / m3 , the dynamic response time and recover time of formaldehyde gas were 2. 4 s and 3. 5 s, respectively. The formaldehyde sensor was successfully applied to the determination of formaldehyde in the automotive exhaust, with relative errors of 0. 39% -1. 07% and relative standard deviations of less than 3% .