Liquid-Phase Cyclic Chemiluminescence for the Identification of Cobalt Speciation.

Accurate discrimination of metal species is a significant analytical challenge. Herein, we propose a novel methodology based on liquid-phase cyclic chemiluminescence (CCL) for the identification of cobalt speciation. The CCL multistage signals (In) of the luminol-H2O2 reaction catalyzed by different cobalt species have different decay coefficients k. Thereby, we can facilely identify various cobalt species according to the distinguishable k values, including the complicated and structurally similar cobalt complexes, such as analogues of [Co(NH3)5X]n+ (X = Cl-, H2O, and NH3), Co(II) porphyrins, and bis(2,4-pentanedione) cobalt(II) derivatives. Especially, the number of substituent atoms also influences the k value greatly, which allows excellent discrimination between complexes that only have a subtle difference in the substituent group. In addition, linear discriminant analysis based on In provides a complementary solution to improve the differentiating ability. We performed density functional theory calculations to investigate the interaction mode of H2O2 over cobalt species. A close negative correlation between the adsorption energy and the k value is observed. Moreover, the calculation of energy evolutions of H2O2 decomposition into a double hydroxide radical shows that a high level of consistency exists between the activation energy barrier and the k value. The results further demonstrate that the decay coefficient of the CCL multistage signal is associated with the catalytic reactivity of the cobalt species. Our work not only broadens the application of chemiluminescence but also provides a complementary technology for speciation analysis.

High-Performance Cataluminescence Sensor Based on Nanosized V2O5 for 2-Butanone Detection.

The development of high-performance sensors is of great significance for the control of the volatile organic compounds (VOCs) pollution and their potential hazard. In this paper, high crystalline V2O5 nanoparticles were successfully synthesized by a simple hydrothermal method. The structure and morphology of the prepared nanoparticles were characterized by TEM and XRD, and the cataluminescence (CTL) sensing performance was also investigated. Experiments found that the as-prepared V2O5 not only shows sensitive CTL response and good selectivity to 2-butanone, but also exhibits rapid response and recovery speed. The limit of detection was found to be 0.2 mg/m3 (0.07 ppm) at a signal to noise ratio of 3. In addition, the linear range exceeds two orders of magnitude, which points to the promising application of the sensor in monitoring of 2-butanone over a wide concentration range. The mechanism of the sensor exhibiting selectivity to different gas molecules were probed by quantum chemistry calculation. Results showed that the highest partial charge distribution, lowest HOMO-LUMO energy gap and largest dipole moment of 2-butanone among the tested gases result in it having the most sensitive response amongst other VOCs.

Covalent organic framework derived Fe3O4 / N co-doped hollow carbon nanospheres modified electrode for simultaneous determination of biomolecules in human serum.

In this work, Fe3O4/N co-doped hollow carbon spheres (Fe3O4@NHCS) as a promising electrocatalysis material had been prepared through carbonizing covalent organic frameworks and ferric irons. The morphology, structure, composition and electrocatalytic performance of Fe3O4@NHCS were characterized by various techniques. The electrode modified with Fe3O4@NHCS (Fe3O4@NHCS/GCE) exhibited excellent electrocatalytic activity for the oxidation of dopamine, uric acid, guanine and adenine. Simultaneous determination of these biomolecules was successfully achieved with Fe3O4@NHCS/GCE. Under the optimum conditions, the linear ranges for the determination of dopamine, uric acid, guanine and adenine were 0.01-40, 0.10-40, 0.50-30 and 0.50-40 µmol/L with the correlation coefficients of 0.9905, 0.9906, 0.9919 and 0.9908, respectively. The detection limits were 6.3, 36.1, 143.2 and 123.5 nmol/L for dopamine, uric acid, guanine and adenine, respectively (S/N = 3). In addition, the modified electrode was also applied to the simultaneous determination of these biomolecules in human serum samples and the recovery were varied from 97.6% to 104.2%. The results demonstrated that the Fe3O4@NHCS modified electrode had the characteristics of high sensitivity, good selectivity and reliability.

A Cataluminescence Sensor Based on NiO Nanoparticles for Sensitive Detection of Acetaldehyde.

Sensitive and selective detection of harmful gas is an important task in environmental monitoring. In this work, a gas sensor based on cataluminescence (CTL) for detection of acetaldehyde was designed by using nano-NiO as the sensing material. The sensor shows sensitive response to acetaldehyde at a relatively low working temperature of 200 °C. The linear range of CTL intensity versus acetaldehyde concentration is 0.02-2.5 mg/L, with a limit of detection of 0.006 mg/L at a signal-to-noise ratio of three. Mechanism study shows that electronically excited CO2 is the excited intermediate for CTL emission during the catalytic oxidation of acetaldehyde on the NiO surface. The proposed sensor has promising application in monitoring acetaldehyde in residential buildings and in the workplace.

Rapid chiral analysis based on liquid-phase cyclic chemiluminescence.

Rapid chiral analysis has become one of the important aspects of academic and industrial research. Here we describe a new strategy based on liquid-phase cyclic chemiluminescence (CCL) for rapid resolution of enantiomers and determination of enantiomeric excess (ee). A single CCL measurement can acquire multistage signals that provide a unique way to examine the intermolecular interactions between chiral hosts and chiral guests, because the lifetime (τ) of the multistage signals is a concentration-independent and distinguishable constant for a given chiral host-guest system. According to the τ values, CCL allows discrimination between a wide range of enantiomeric pairs including chiral alcohols, amines and acids by using only one chiral host. Even the chiral systems hardly distinguished by nuclear magnetic resonance and fluorescence methods can be distinguished easily by CCL. Additionally, the τ value of a mixture of two enantiomers is equal to the weighted average of each enantiomer, which can be used for the direct determination of ee without the need to separate the chiral mixture and create calibration curves. This is extremely crucial for the cases without readily available enantiomerically pure samples. This strategy was successfully applied to monitoring of the Walden inversion reaction and analysis of chiral drugs. The results were in good agreement with those obtained by high-performance liquid chromatography, indicating the utility of CCL for routine quick ee analysis. Mechanism study revealed that the τ value is possibly related to the activity of the chiral substance to catalyze a luminol-H2O2 reaction. Our research provides an unprecedented and general protocol for chirality differentiation and ee determination, which is anticipated to be a useful technology that will find wide application in chirality-related fields, particularly in asymmetric synthesis and the pharmaceutical industry.

Synthesis of Nano-Praseodymium Oxide for Cataluminescence Sensing of Acetophenone in Exhaled Breath.

In this work, we successfully developed a novel and sensitive gas sensor for the determination of trace acetophenone based on its cataluminescence (CTL) emission on the surface of nano-praseodymium oxide (nano-Pr6O11). The effects of working conditions such as temperature, flow rate, and detecting wavelength on the CTL sensing were investigated in detail. Under the optimized conditions, the sensor exhibited linear response to the acetophenone in the range of 15-280 mg/m3 (2.8-52 ppm), with a correlation coefficient (R2) of 0.9968 and a limit of detection (S/N = 3) of 4 mg/m3 (0.7 ppm). The selectivity of the sensor was also investigated, no or weak response to other compounds, such as alcohols (methanol, ethanol, n-propanol, iso-propanol, n-butanol), aldehyde (formaldehyde and acetaldehyde), benzenes (toluene, o-xylene, m-xylene, p-xylene), n-pentane, ethyl acetate, ammonia, carbon monoxide, carbon dioxide. Finally, the present sensor was applied to the determination of acetophenone in human exhaled breath samples. The results showed that the sensor has promising application in clinical breath analysis.

Multistage Signals Based on Cyclic Chemiluminescence for Decoding Complex Samples.

Identification of complex samples presents a difficult challenge for modern analytical techniques, and the differentiation among closely similar mixtures often remains indeterminate. In this article, we designed a simplified cyclic chemiluminescence (CCL) system that is able to measure multistage signals in a single sample injection. The system was used to investigate the CCL reactions of the binary, ternary, and multicomponent mixtures. Results showed that each mixture has a unique exponential decay equation (EDE) with a constant decay coefficient (k-value) to describe the change law of its multistage signals. Further studies found that different brands of liquor, beer, toner, and baby powder have different k-values, and the same brand of the commodities between different batches have the same k-values, which allows facile identification of these complex samples. We then used different catalysts to design digital codes of the k-value for further improving the identifying ability of CCL. Moreover, the multistage signals are like fingerprints and could be used for linear discriminate analysis, which provides another complementary approach for identification of complex samples. Finally, we demonstrated that CCL shows potential applications in certification and quality assurance according to the change of the k-values of the sample. This work demonstrates that excellent discrimination ability of CCL for the identification of complex samples and provides a promising technology for quality assurance.

A composite prepared from gold nanoparticles and a metal organic framework (type MOF-74) for determination of 4-nitrothiophenol by surface-enhanced Raman spectroscopy.

Core-shell nanoparticles (NPs) consisting of a gold core and a metal-organic framework shell (type MOF-74) were synthesized via one-pot synthesis. The NPs exhibit highly sensitive and stable SERS activity for the detection of 4-nitrothiophenol, with a specific band at 1337 cm-1. The method has a linear response in 0.10-10 µmol·L-1 analyte concentration range and a lower detection limit of 69 nmol·L-1. The potential application of this novel SERS substrate was evaluated by two model reactions involving 4-nitrothiophenol. The first involves in-situ SERS monitoring of the surface plasmon-induced nitration of aromatic rings without adding conventional acid catalyst. The second involves the photocatalytic reduction of 4-nitrothiophenol to 4-thioaminophenol in the presence of Au/MOF-74 under 785-nm laser irradiation. The plasmon-assisted dimerization of 4-nitrothiophenol to form 4,4'-dimercaptoazobenzene can also be monitored simultaneously. Graphical abstract Schematic presentation of a nanoparticle SERS substrate consisting of gold core and MOF-74 shell, which was applied to detection of 4-nitrothiophenol. The Au/MOF-74 was successfully used for in-situ monitoring of two model reactions involving 4-nitrothiophenol by SERS.

Cataluminescence sensor for highly sensitive and selective detection of iso-butanol.

In this paper, a gaseous sensor was described for detection of iso-butanol on the basis of its strong cataluminescence (CTL) emission on nano-MgO surface. The sensor showed high sensitivity and specificity to iso-butanol with response time less than 1 s and recovery time less than 18 s. A good linearly relationship between CTL intensity and the concentration of iso-butanol was observed in the range of 7.6-3350 mg/m3 (r = 0.9992), the limit of detection was 2.5 mg/m3. The proposed CTL sensor exhibits good specificity to iso-butanol against other compounds including common alcohols. The possible reaction paths of iso-butanol on the MgO surface were investigated in detail. Results shows that the hydrogen atom abstraction of iso-butanol to form ß-Riso following consumption via Waddington mechanism possible is a major reaction channel for CTL emission. The sensor was applied to analyze iso-butanol in spiked samples, satisfactory recoveries were obtained in the range of 96.6-112.8% and the RSDs were 5.0-10.1%, indicating that the proposed sensor is a promising candidate for rapid analysis of iso-butanol.

Carbon dot-decorated porous organic cage as fluorescent sensor for rapid discrimination of nitrophenol isomers and chiral alcohols.

Isomers discrimination plays a vital role in modern chemistry, and development of efficient and rapid method to achieve this aim has attracted a great deal of interest. In this work, a novel carbon dot-decorated chiral porous organic cage hybrid nanocomposite (CD@RCC3) was prepared and used to fabricate fluorescent sensor. The resultant CD@RCC3 was characterized by using a range of techniques, finding that CD@RCC3 possesses strong and stable fluorescent property in common organic solvents, especially it exhibits chiral property. The potential application of CD@RCC3 in fluorescence sensing was demonstrated by isomers discrimination. The designed sensor was successfully used to rapid discriminate nitrophenol isomers. Meanwhile, it exhibited differentiation ability towards phenylalaninol and phenylethanol enantiomers. Our work enriches the type of synthetic materials for fluorescence sensing, and provides a simple method for distinguishing structural isomers and chiral isomers.

Ozone-induction coupled with plasma assistance to enhance cataluminescence for monitoring of volatile organic compounds.

The authors describe a strategy for ozone-induction coupling with plasma assistance (O3-I/PA) to enhance cataluminescence (CTL) based sensing of volatile organic compounds (VOCs). A homemade O3-I/PA CTL sensor system was constructed based on this strategy. O3-I/PA can significantly enhance the CTL response to many compounds that were hardly detectable previously with adequate sensitivity. Without any preconcentration, the limits of detection (for S/N = 3) are 20 µg.m-3 (= 5 ppbv) for toluene and 8 µg.m-3 (6.4 ppbv) for formaldehyde. VOCs including benzene, alkanes, halohydrocarbons, alkenes alcohols, aldehydes, ketones and ethers are found to produce a strong response when using this sensor system. Mechanistic studies showed that the synergistic effect of ozone-induction and plasma assistance promote the oxidation of the VOCs under formation of CO2. This strongly favors CTL emission. The sensor system can be used as a direct-reading detector for on-line and real-time monitoring of total VOCs. It also can be used as a detector in gas chromatography for the identification of individual VOCs. It is perceived that this work paves the way to both a new kind of vapor sensor and to a detection scheme in gas chromatography. Graphical abstract The synergistic effect of ozone-induction and plasma assistance promote the deep oxidation of the VOCs into CO2, which strongly favors cataluminescence emission.

Noninvasive Strategy Based on Real-Time in Vivo Cataluminescence Monitoring for Clinical Breath Analysis.

The development of noninvasive methods for real-time in vivo analysis is of great significant, which provides powerful tools for medical research and clinical diagnosis. In the present work, we described a new strategy based on cataluminescence (CTL) for real-time in vivo clinical breath analysis. To illustrate such strategy, a homemade real-time CTL monitoring system characterized by coupling an online sampling device with a CTL sensor for sevoflurane (SVF) was designed, and a real-time in vivo method for the monitoring of SVF in exhaled breath was proposed. The accuracy of the method was evaluated by analyzing the real exhaled breath samples, and the results were compared with those obtained by GC/MS. The measured data obtained by the two methods were in good agreement. Subsequently, the method was applied to real-time monitoring of SVF in exhaled breath from rat models of the control group to investigate elimination pharmacokinetics. In order to further probe the potential of the method for clinical application, the elimination pharmacokinetics of SVF from rat models of control group, liver fibrosis group alcohol liver group, and nonalcoholic fatty liver group were monitored by the method. The raw data of pharmacokinetics of different groups were normalized and subsequently subjected to linear discriminant analysis (LDA). These data were transformed to canonical scores which were visualized as well-clustered with the classification accuracy of 100%, and the overall accuracy of leave-one-out cross-validation procedure is 88%, thereby indicating the utility of the potential of the method for liver disease diagnosis. Our strategy undoubtedly opens up a new door for real-time clinical analysis in a pain-free and noninvasive way and also guides a promising development direction for CTL.

Simple and Excellent Selective Chemiluminescence-Based CS2 On-Line Detection System for Rapid Analysis of Sulfur-Containing Compounds in Complex Samples.

To study the interesting chemical reaction phenomenon can greatly contribute to the development of an innovative analytical method. In this paper, a simple CL reaction cell was constructed to study the chemiluminescence (CL) emission from the thermal oxidation of carbon disulfide (CS2). We found that the CL detection of CS2 exhibits unique characteristics of excellent selectivity and rapid response capacity. Experimental investigations together with theoretical calculation were performed to study the mechanism behind the CL reaction. The results revealed that the main luminous intermediates generated during the thermal degradation of CS2 are SO2* and CO2*. Significantly, this CL emission phenomenon has a wide application due to many sulfur-containing compounds that can convert to CS2 under special conditions. On the basis of this scheme, a CS2-generating and detection system was developed for rapid measurement of CS2 or other compounds that can convert to CS2. The usefulness of the system was demonstrated by measuring dithiocarbamate (DTC) pesticides (selected mancozeb as a representative analyte) based on the evolution of CS2 in spiked agricultural products. Results showed that the system allows online and large volume detection of CS2 under nonequilibrium condition, which greatly reduces the analytical time. The concentrations of mancozeb in the spiked samples were well-quantified with satisfied recoveries of 76.9-97.3%. The system not only addresses the urgent need for rapid in-field screening of DTC residues in foodstuffs but also opens a new opportunity for the fast, convenient, and cost-effective detection of CS2 and some other sulfur-containing compounds in complex samples.

Development of a cyclic system for chemiluminescence detection.

In this paper, we described a new concept of cyclic chemiluminescence (CCL) detection, and a homemade system was designed to realize such detection. The direction of the carrier in the CCL system is in a state of periodical change that can trigger a succession of chemiluminescence (CL) reactions in a single sample injection. Therefore, in contrast to the traditional CL detection, which only records a single signal, CCL allows us to obtain multistage signals. To evaluate the new method, the cataluminescence (CTL) reaction of the volatile organic compounds (VOCs) on a nanosized catalyst was selected as the analytical model. We found that each CCL reaction has a unique exponential decay equation (EDE) to describe the change law of its multistage signals. Further study showed that the initial amount (A) of the EDE is linear with the analyte concentration, while the decay coefficient (k) is a characteristic constant for a given reaction. The formation mechanism of the exponential function and the determinants of the decay coefficient were discussed in detail. As a distinct application, CCL is capable of rapidly discriminating various analytes and even structural isomers.

Development of a simple cataluminescence sensor system for detecting and discriminating volatile organic compounds at different concentrations.

The detection and identification of volatile organic compounds (VOCs) is one of the most serious subjects in the field of chemical sensing, but it remains an enormous challenge. Usually, during the sensing of gases involved in chemical reactions, the residual gas of that reaction (including undecomposed analytes and reaction products) are considered waste gases and released into the air. Here, a novel cataluminescence (CTL) sensing method based on detection of the luminescent intensities of both the analyte (I(A)) and its products (I(R)) was developed and used to identify VOCs at different concentrations. After the analyte gas passed through the first sensing material, the product gas was treated as a new reactant and passed through the second sensing material (which could be the same as or different from the first material). The luminescent signals of I(A) and I(R) were recorded over a short period of time using one photomultiplier. We found the ratio of I(A) to I(R) (I(A)/I(R)) to be a unique characteristic of a given analyte within a wide range of concentrations. To illustrate the new method, 11 kinds of organic gases were successfully identified using I(A)/I(R) values. The most distinct feature of this method is that it allows the user to obtain many more luminescent signals from the sensing materials than common methods. It does so by allowing different flow channels of the analyte gas. This simple method here was used to discriminate different species, homologous series, and isomers in different concentrations. This method could be applied to chemical sensing arrays to increase the discrimination ability or decrease the number of sensing units required.

A new method for identifying compounds by luminescent response profiles on a cataluminescence based sensor.

Rapid identification of different compounds has been proven to be one of the most dynamic fields in analytical chemistry. Herein, a very simple cataluminescence-sensor-based (CTL-based) method suitable for rapid identification of compounds is reported. The oxidation of analytes was catalyzed in a closed reaction cell (CRC) containing enough air to facilitate complete luminescent response profiles with several peaks. The multipeaked response profiles are characteristic of analytes and can be used for identifying compounds. In existing CTL-based sensors, CTL reactions take place in an airstream flow reaction cell (AFRC) in which a continuous airstream carries the analytes flow across the catalyst's surface. The luminescent response profiles obtained are transitory and lack characteristic features, so they cannot be used to identify different compounds. To illustrate the new method, 12 medicines and 4 organic gases were examined in CRC sensors. Results showed that these compounds could be successfully identified through their unique luminescent response profiles. The response was rapid and the system was inexpensive and easy to handle. We believe that it has great potential for real-world use.

A highly sensitive and selective dimethyl ether sensor based on cataluminescence.

A sensor for detecting dimethyl ether was designed based on the cataluminescence phenomenon when dimethyl ether vapors were passing through the surface of the ceramic heater. The proposed sensor showed high sensitivity and selectivity to dimethyl ether at an optimal temperature of 279 degrees C. Quantitative analysis were performed at a wavelength of 425 nm, the flow rate of carrier air is around 300 mL/min. The linear range of the cataluminescence intensity versus concentration of dimethyl ether is 100-6.0x10(3) ppm with a detection limit of 80 ppm. The sensor response time is 2.5 s. Under the optimized conditions, none or only very low levels of interference were observed while the foreign substances such as benzene, formaldehyde, ammonia, methanol, ethanol, acetaldehyde, acetic acid, acrolein, isopropyl ether, ethyl acetate, glycol ether and 2-methoxyethanol were passing through the sensor. Since the sensor does not need to prepare and fix up the granular catalyst, the simple technology reduces cost, improves stability and extends life span. The method can be applied to facilitate detection of dimethyl ether in the air. The possible mechanism of cataluminescence from the oxidation of dimethyl ether on the surface of ceramic heater was discussed based on the reaction products.