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.     

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.     

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.     

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.     

Nanosized gamma-Al2O3 + Nd2O3-based cataluminescence sensor for ethylene dichloride.

A gas-sensor utilizing cataluminescence (CTL) on nanosized gamma-Al2O3 + Nd2O3 for measuring low concentrations of gaseous ethylene dichloride (EDC) was developed. The results showed that gamma-Al2O3 nanoparticles as a catalyst offered high sensitivity and selectivity in the detection of EDC. The addition of a small quantity of Nd2O3 increased the intensity of CTL more than two-fold. Quantitative analysis was performed at a wavelength of 400 nm and at an optimal temperature of 279 degrees C, and the optimal flow rate of carrier gas was 320 mL/min. Under the optimized conditions, the linear range of CTL intensity vs. concentration is 6-5000 ppm (R = 0.9996; n = 7), with a detection limit of 2 ppm. The response time is <5 s. No interference or only very low levels of significant interference were observed when substances such as formaldehyde, n-hexane, methyl benzene, carbon tetrachloride, chloroform and benzene were passed through the sensor.     

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.     

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.     

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.     

A novel fluorescent sensor based on electrosynthesized benzene sulfonic acid‐doped polypyrrole for determination of Pb(II) and Cu(II)

To develop conducting organic polymers (COPs) as luminescent sensors for determination of toxic heavy metals, a new benzene sulfonic acid‐doped polypyrrole (PPy‐BSA) thin film was electrochemically prepared by cyclic voltammetry (CV) on flexible indium tin oxide (ITO) electrode in aqueous solution. PPy‐BSA film was characterized by FTIR spectrometry, X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The optical properties of PPy‐BSA were investigated by ultraviolet (UV)‐visible absorption and fluorescence spectrometry in dimethylsulfoxide (DMSO) diluted solutions. PPy‐BSA fluorescence spectra were strongly quenched upon increasing copper(II) ion (Cu²⁺) and lead(II) ion (Pb²⁺) concentrations in aqueous medium, and linear Stern–Volmer relationships were obtained, which indicated the existence of a main dynamic fluorescence quenching mechanism. BSA‐PPy sensor showed a high sensitivity for detection of both metallic ions, Cu²⁺ and Pb²⁺, with very low limit of detection values of 3.1 and 18.0 nM, respectively. The proposed quenching‐fluorimetric sensor might be applied to the determination of traces of toxic heavy metallic ions in water samples.     

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.     

Novel fluorescent sensor using molecularly imprinted silica microsphere‐coated CdSe@CdS quantum dots and its application in the detection of 2,4,6‐trichlorophenol from environmental water samples

In this study, a high fluorescence sensitivity and selectivity, molecularly imprinted nanofluorescent polymer sensor (MIP@SiO₂@QDs) was prepared using a reverse microemulsion method. 2,4,6‐Trichlorophenol (2,4,6‐TCP) was detected using fluorescence quenching. Tetraethyl orthosilicate (TEOS), quantum dots (QDs) and 3‐aminopropyltriethoxysilane (APTS) were used as cross‐linker, signal sources and functional monomer respectively. The sensor (MIP@SiO₂@QDs) and the non‐imprinted polymer sensor (NIP@SiO₂@QDs) were characterized using infra‐red (IR) analysis, X‐ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The selectivity of MIP@SiO₂@QDs was examined by comparing 2,4,6‐TCP with other similar functional substances including 2,4‐dichlorophenol (2,4‐DCP), 2,6‐dichlorophenol (2,6‐DCP) and 4‐chlorophenol (4‐CP). Results showed that MIP@SiO₂@QDs had better selectivity for 2,4,6‐TCP than the other compounds. Fluorescence quenching efficiency displayed a good linear response at the 2,4,6‐TCP concentration range 5–1000 μmol/L. The limit of detection (LOD) was 0.9 μmol/L (3σ, n = 9). This method was equally applicable for testing actual samples with a recovery rate of 98.0–105.8%. The sensor had advantages of simple pretreatment, good sensitivity and selectivity, and wide linear range and could be applied for the rapid detection of 2,4,6‐TCP in actual samples.     

A novel chemiluminescence sensor for the determination of indomethacin based on sulfur and nitrogen co‐doped carbon quantum dot–KMnO4 reaction

We report on a simple and sensitive sulfur and nitrogen co‐doped carbon quantum dot (S,N‐CQD)‐based chemiluminescence (CL) sensor for the determination of indomethacin. S,N‐CQDs were prepared by a hydrothermal method and characterized by fluorescence spectra, Fourier transform infrared spectroscopy and transmission electron microscopy. To obtain the best CL system for determination of indomethacin, the reaction of S,N‐CQDs with some common oxidants was studied. Among the tested systems, the S,N‐CQD–KMnO₄ reaction showed the highest sensitivity for the detection of indomethacin. Under optimum conditions, the calibration plot was linear over a concentration range of 0.1–1.5 mg L^?1, with a limit of detection (3σ) of 65 μg L^?1. The method was applied to the determination of indomethacin in environmental and biological samples with satisfactory results.     

Cataluminescence‐based sensors: principle,instrument and application

The cataluminescence (CTL)‐based sensor is a new promising type of chemical transducer, and has attracted much attention of researchers for its potential versatile applications in public safety, emission control and environmental protection. In this review, we briefly introduce the development history of CTL‐based sensors and summarize existing explanations of the CTL reaction mechanism as well as three research strategies for mechanism the CTL mechanism. In the following, all the function units of a typical CTL‐based sensor system are described and the investigation of the sensor materials. CTL‐based sensor arrays, are discussed in detail. We classify the recent novel hyphenated techniques based on CTL coupled to other analysis techniques into the preconcentration‐CTL hyphenated technique, nebulization‐CTL hyphenated technique, plasma‐assisted CTL technique and tandem CTL technique according to the type of analysis combined with CTL and provide a detailed account of novel hyphenated techniques. Owing to the appearance of these novel techniques, the application range of CTL has been expanded as well as the sensitivity and selectivity of CTL system has been greatly improved. Finally, the applications of CTL‐based sensor and sensor arrays in the last several years are classified and summarized. Copyright © 2014 John Wiley & Sons, Ltd.     

A sensitive fluorescent nanosensor for chloramphenicol based on molecularly imprinted polymer‐capped CdTe quantum dots

A novel fluorescent nanosensor using molecularly imprinted silica nanospheres embedded CdTe quantum dots (CdTe@SiO₂@MIP) was developed for detection and quantification of chloramphenicol (CAP). The imprinted sensor was prepared by synthesis of molecularly imprinting polymer (MIP) on the hydrophilic CdTe quantum dots via reverse microemulsion method using small amounts of solvents. The resulting CdTe@SiO₂@MIP nanoparticles were characterized by fluorescence, UV–vis absorption and FT‐IR spectroscopy and transmission electron microscopy. They preserved 48% of fluorescence quantum yield of the parent quantum dots. CAP remarkably quenched the fluorescence of prepared CdTe@SiO₂@MIP, probably via electron transfer mechanism. Under the optimal conditions, the relative fluorescence intensity of CdTe@SiO₂@MIP decreased with increasing CAP by a Stern–Volmer type equation in the concentration range of 40–500 µg L^–1. The corresponding detection limit was 5.0 µg L^–1. The intra‐day and inter‐day values for the precision of the proposed method were all <4%. The developed sensor had a good selectivity and was applied to determine CAP in spiked human and bovine serum and milk samples with satisfactory results. Copyright © 2015 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.     

Preparation of co‐Co3O4/carbon nanotube/carbon foam for glucose sensor

Co‐Co₃O₄/carbon nanotube/carbon foam (Co‐Co₃O₄/CNT/CF) nanocomposites were prepared by soaking melamine foam into a solution of Co(NO₃)₂·6H₂O, followed by calcination in N₂ and air in sequence. The obtained Co‐Co₃O₄/CNT/CF nanocomposites were characterized with scanning electron microscopy and cyclic voltammetry. It was found that Co₃O₄ nanoparticles were grown on the external of CF successfully, while CNTs were grown on the surfaces of CF in a large amount, which further improved the electrical conductivity of the. The prepared Co‐Co₃O₄/CNT/CF nanocomposites were then used to construct nonenzymatic sensor to detect glucose in alkaline solution. The sensor showed detection range from 1.2 μM to 2.29 mM with a detection limit of 0.4 μM (S/N =3) and a high sensitivity of 637.5 μA^?1 cm^?2. The developed sensor also showed an instant response, favorable reproducibility, and high selectivity. The results attest that Co‐Co₃O₄/CNT/CF composites have great potential in the development of nonenzymatic sensors for glucose.     

Determination of fluvoxamine maleate in human urine and human serum using alkaline KMnO4–rhodamine B chemiluminescence

The flow‐injection chemiluminescence (FI‐CL) behavior of a gold nanocluster (Au NC)–enhanced rhodamine B–KMnO₄ system was studied under alkaline conditions for the first time. In the present study, the as‐prepared bovine serum albumin‐stabilized Au NCs showed excellent stability and reproducibility. The addition of trace levels of fluvoxamine maleate (Flu) led to an obvious decline in CL intensity in the rhodamine B–KMnO₄–Au NCs system, which could be used for quantitative detection of Flu. Under optimized conditions, the proposed CL system exhibited a favorable analytical performance for Flu determination in the range 2 to 100 μg ml^?1. The detection limit for Flu measurement was 0.021 μg ml^?1. Moreover, this newly developed system revealed outstanding selectivity for Flu detection when compared with a multitude of other species, such as the usual ions, uric acid and a section of hydroxy compounds. Additionally, CL spectra, UV–visible spectroscopes and fluorescence spectra were measured in order to determine the possible reaction mechanism. This approach could be used to detect Flu in human urine and human serum samples with the desired recoveries and could have promising application under physiological conditions.     

Analysis of 2‐propanol in exhaled breath using in situ enrichment and cataluminescence detection

We report a simple gaseous sensor for the sensitive detection of trace 2‐propanol in exhaled breath using in situ enrichment and cataluminescence detection method on the surface of nanomaterials. The influences of heating voltage and absorption time on the CTL intensity were discussed, respectively. In the selected conditions, the linear range of 2‐propanol concentration is 60–600 ppbv and the detection of limit is 11 ppbv. Moreover, the lifetime and selectivity of the sensor were also investigated. It has the potential to diagnostic volatile organic compounds in human breath. Copyright © 2010 John Wiley & Sons, Ltd     

A molecularly imprinted nanofilm‐based quartz crystal microbalance sensor for the real‐time detection of pirimicarb

This study aimed to prepare a novel quartz crystal microbalance (QCM) sensor for the detection of pirimicarb. Pirimicarb‐imprinted poly (ethylene glycol dimethacrylate‐N‐metacryloyl‐(l )‐tryptophan methyl ester) [p (EGDMA‐MATrp)] nanofilm (MIP) on the gold surface of a QCM chip was synthesized using the molecular imprinting technique. A nonimprinted p (EGDMA‐MATrp) nanofilm (NIP) was also synthesized using the same experimental technique. The MIP and NIP nanofilms were characterized via Fourier transform infrared spectroscopy attenuated total reflectance spectroscopy, contact angle, atomic force microscopy, and an ellipsometer. A competitive adsorption experiment on the sensor was performed to display the selectivity of the nanofilm. An analysis of the QCM sensor showed that the MIP nanofilm exhibited high sensitivity and selectivity for pirimicarb determination. A liquid chromatography‐tandem mass spectrometry method was prepared and validated to determine the accuracy and precision of the QCM sensor. The accuracy and precision of both methods were determined by a comparison of six replicates at three different concentrations to tomato samples extracted by using a Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method. The limit of detection of the QCM sensor was found to be 0.028 nM. In conclusion, the QCM sensor showed good accuracy, with recovery percentages between 91 and 94%. Also, the pirimicarb‐imprinted QCM sensor exhibited a fast response time, reusability, high selectivity and sensitivity, and a low limit of detection. Therefore, it offers a serious alternative to the traditional analytical methods for pesticide detection in both natural sources and aqueous solutions.     

Uncertainty for Data with Non-Detects: Air Toxic Emissions from Combustion

Air toxic emission factor datasets often contain one or more points below a single or multiple detection limits and such datasets are referred to as “censored.” Conventional methods used to deal with censored datasets include removing non-detects, replacing the censored points with zero, half of the detection limit, or the detection limit. However, the estimated means of the censored dataset by conventional methods are usually biased. Maximum likelihood estimation (MLE) and bootstrap simulation have been demonstrated as a statistically robust method to quantify variability and uncertainty of censored datasets and can provide asymptotically unbiased mean estimates. The MLE/bootstrap method is applied to 16 cases of censored air toxic emission factors, including benzene, formaldehyde, benzo(a)pyrene, mercury, arsenic, cadmium, total chromium, chromium VI and lead from coal, fuel oil, and/or wood waste external combustion sources. The proportion of censored values in the emission factor data ranges from 4 to 80%. Key factors that influence the estimated uncertainty in the mean of censored data are sample size and inter-unit variability. The largest range of uncertainty in the mean was obtained for the external coal combustion benzene emission factor, with 95 confidence interval of the mean equal to minus 93 to plus 411%.