Chemiluminescence Emission Intensity Research Articles

Nonlinear dynamics of attenuation behavior in combustion oscillations in a swirl-stabilized combustor

We experimentally examine the attenuation behavior in combustion oscillations from the perspective of symbolic dynamics, dynamical systems theory, complex networks, and machine learning. The periodicity of combustion oscillations gradually decreases with increasing amount of air steadily injected into flame base, maintaining a nearly in-phase synchronized state between pressure and OH* chemiluminescence emission intensity fluctuations. Both the dynamic behaviors of pressure and OH* chemiluminescence emission intensity fluctuations in the attenuation regime close to well-suppressed combustion oscillations exhibit pseudo-periodic oscillations with deterministically nonperiodic intercycle dynamics. They lead to noisy chaotic oscillations and exhibit a desynchronized state during well-suppressed combustion oscillations.

Chemiluminescence reaction of graphene oxide – luminol – dissolved oxygen and its application for determination of isoniazid and paracetamol

A new and sensitive CL method was proposed for determination of paracetamol (PCM) and isoniazid (IND) in pharmaceutical preparations. The CL method is based on enhancing effect of IND and also decreasing effect of PCM on the graphene oxide (GO)-luminol-dissolved oxygen (DO) chemiluminescence (CL) reaction in a strongly alkaline medium. GO was synthesized by using improved hummer method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR) methods. The effects of various chemical reagents, involved in the CL reaction, on the CL emission intensity were also investigated and optimized. Under the optimum conditions, a linear relationship was obtained between the CL intensity and the concentration of PCM and IND in the range of 7.0 × 10−6–5.0 × 10−5 mol L−1 and 1.0 × 10−7–1.0 × 10−4 mol L−1 with limit of detections of 8.7 × 10−7 and 7.9 × 10−8 mol L−1, respectively. The mechanism of CL system was also discussed, briefly.

Ultrasensitive chemiluminescence assay for cimetidine detection based on the synergistic improving effect of Au nanoclusters and graphene quantum dots.

A novel and sensitive chemiluminescence (CL) procedure based on the synergetic catalytic effects of gold nanoclusters (Au NCs) and graphene quantum dots (GQDs) was developed for the reliable measurement of cimetidine (CM). The initial experiments showed that the KMnO4 -based oxidation of alkaline rhodamine B (RhoB) generated a very weak CL emission, which was intensively enhanced in the simultaneous presence of Au NCs and GQDs. CL intermediates can be adsorbed and gathered on the surface of Au NCs, becoming more stable. GQDs participate in the energy transferring processes and facilitate them. These improving effects were simultaneously obtained by adding both Au NCs and GQDs into the RhoB-KMnO4 reaction. Consequently, the increasing effect of the Au NCs/GQDs mixture was more than that of pure Au NCs or GQDs, and a new nano-assisted powerful CL system was achieved. Furthermore, a marked quenching in the emission of the introduced CL system was observed in the presence of CM, so the system was examined to design a sensitive sensor for CM. After optimization of influencing parameters, the linear lessening in CL emission intensity of KMnO4 -RhoB-Au NCs/GQDs was verified for CM concentrations in the range 0.8-200ngml-1 . The limit of detection (3Sb /m) was 0.3ngml-1 . Despite being a simple CL method, good sensitivity was obtained for CM detection with reliable results for CM determination in human urine samples.

Simplex optimization of the variables influencing the determination of pefloxacin by time-resolved chemiluminescence

A new chemiluminescence (CL) detection system combined with flow injection analysis (FIA) for the determination of Pefloxacin is proposed. The determination is based on an energy transfer from Pefloxacin to terbium (III). The metal ion enhances the weak CL signal produced by the KMnO4/H2SO3/Pefloxacin system. A modified simplex method was used to optimize chemical and instrumental variables. The influence of the interaction of the permanganate, Tb (III), sodium sulphite and sulphuric acid concentrations, flow rate and injected sample volume was thoroughly investigated by using a modified simplex optimization procedure. The results revealed a strong direct relationship between flow rate and CL intensity throughout the studied range that was confirmed by a gamma test. The response factor for the CL emission intensity was used to assess performance in order to identify the optimum conditions for maximization of the response. Under such conditions, the CL response was proportional to the Pefloxacin concentration over a wide range. The detection limit as calculated according to Clayton's criterion 13.7μgL−1. The analyte was successfully determined in milk samples with an average recovery of 100.6±9.8%.

Ultrasensitive chemiluminescent biosensor for the detection of cholesterol based on synergetic peroxidase-like activity of MoS2 and graphene quantum dots

Developing a novel non-enzyme mimetic in biosensors is of great significance. Here, a synergetic peroxidase-like activity was disclosed for mixed MoS2 quantum dots (MoS2 QDs) and graphene quantum dots (GQDs). The high catalytic effect of this mixture was studied on the chemiluminescence system. It was observed that the simultaneous presence of MoS2 QDs and GQDs had a powerful enhancing effect on the chemiluminescence (CL) emission of rhodamine B (RB)-H2O2 reaction. MoS2 QDs and GQDs mixture (prepared with a ratio of 3:2) showed a superior catalytic activity when compared to each of the constituents. A linear relationship was acquired between the CL emission intensity and H2O2 concentration in the range of 1.5–460nmolL−1. On the other hand, since the enzymatic oxidation of cholesterol leads to the production of H2O2; the offered CL system was examined to detect cholesterol after its oxidation by cholesterol oxidase (ChOx) enzyme. Herein, a further improvement was achieved by MoS2 nanosheets. The MoS2 nanosheets increased the performance of ChOx in cholesterol oxidation process. The obtained results confirmed a highly selective and sensitive determination of cholesterol concentration in a linear dynamic range of 0.08–300µmolL−1, with a detection limit (3S) of 35nmolL−1. The developed method was successfully applied for the detection of cholesterol level in human serum samples.

Real-Time Observation of Hydrogen Peroxide Transport through the Oil Phase in a W/O/W Double Emulsion with Chemiluminescence Emission

The evaluation of the transport rates of hydrophilic substances is important in agricultural and pharmaceutical chemistry and in the cosmetics and food-processing industries. Although there are some estimation methods focusing on the diffusion of the substances through the oil phase of the W/O/W core-shell double emulsions (oil microcapsules), all of them take several hours or days. This long-time measurement has a risk of rupture of the oil microcapsules, which causes significant errors. If it were possible to measure the transport rate of substances in the oil phase of the oil microcapsules in real time, the risk of rupture could be reduced. Here, we propose a new estimation method for the transport rates of hydrogen peroxide (H2O2) in the oil phase of an oil microcapsule for real-time estimation by means of chemiluminescence (CL) emission of the luminol reaction. We theoretically give the relationship among the CL emission intensity, diffusion coefficient, microcapsule size, and experimental time and successfully estimate the diffusion coefficient of H2O2 in the oil phase of the oil microcapsule from the experimental data. Moreover, we discuss the dependence of the permeation of H2O2 through the oil phase on the concentration of the oil-soluble surfactant; the difference in the permeation rate is likely to be attributed not to the diffusion coefficient but to the partition coefficient of H2O2 in the oil microcapsule.

A novel and sensitive chemosensor based on a KMnO4-rhodamine B-CdS quantum dot chemiluminescence system for meropenem detection.

A sensitive and simple flow injection chemiluminescence (CL) system was constructed for the determination of meropenem, in which the CL intensity of the KMnO4-rhodamine B (Rh B) reaction was enhanced in the presence of CdS quantum dots (QDs). A CL resonance energy transfer (CRET) occurs between CdS QDs as a donor and Rh B as an energy acceptor. Based on the strong specific quenching effect of meropenem on the CL intensity, a novel chemosensor for meropenem sensing was developed. Under the optimized conditions, the quenched CL emission intensity was proportional to the concentration of meropenem in the range of 0.002-10.0 mg L-1 with a detection limit (3σ) of 0.8 μg L-1 Moreover, the feasibility of the induced CL system was studied via the meropenem determination in environmental water samples.

Chemiluminescence of Lucigenin–Allantoin and Its Application for the Detection of Allantoin

Allantoin has been reported as a promising biomarker for monitoring of oxidative stress in humans and widely utilized in a variety of topical pharmaceuticals and cosmetics. Currently, the detection of allantoin is achieved by using chromatographic coupled techniques, which needs sample pre-extraction, derivatization, complex matrixes, and expensive instrumentation. Herein we report both the intense chemiluminescence of allantoin with lucigenin and the chemiluminescent detection of allantoin for the first time. The lucigenin-allantoin system demonstrated chemiluminescence emission intensity 17 times higher than that of the classic lucigenin-hydrogen peroxide system. Based on this fascinating phenomenon, a novel chemiluminescence method has been developed for the sensitive and selective allantoin determination with the combination of flow injection analysis. This method shows a linear calibration curve in the range 0.1-3000 μM with a detection limit (3σ/s) of 0.03 μM. Moreover, it was successfully utilized for the determination of allantoin in human eye drop and real urine samples after simple dilution with water. It shows excellent recoveries in the range 94.0-101.7%, and each measurement takes a very short time. This method exhibits potential advantages in the form of simplicity, rapidity, sensitivity, selectivity, and low cost. Allantoin could be an effective candidate for constructing new chemiluminescence systems, and it may provide a broad range of sensing applications.

Flow Injection Chemiluminescence Determination of Acetylsalicylic Acid in Pharmaceutical Formulations

A simple and sensitive flow injection chemiluminescence method was proposed for the determination of acetylsalicylic acid (aspirin) in pharmaceutical formulations. The method was based on inhibition effect of acetylsalicylic acid on the chemiluminescence reaction of luminol–hydrogen peroxide and potassium hexacyanoferrate. Different experiment parameters affecting the chemiluminescence intensity were carefully studied and incorporated into the procedure. The detection limit was 0.5 μg/mL of acetylsalicylic acid, and chemiluminescence emission intensity was correlated with the drug concentration in the range 2.5-125 μg/mL with correlation coefficient of 0.9985 and analytical frequency of 75 determinations per hour. The results obtained for the assay of pharmaceutical formulations were compared well with those obtained by the official method in British Pharmacopoeia and demonstrated good accuracy and precision.

Determination of Montelukast in Plasma Using β-Cyclodextrins Coated on CoFe2O4 Magnetic Nanoparticles in Luminol-H2O2 Chemiluminescence System Optimized by Doehlert Design.

A novel chemiluminescence method using β-cyclodextrins coated on CoFe2O4 magnetic nanoparticles is proposed for the chemiluminometric determination of montelukast in plasma. The effect of coated β-cyclodexterinon CoFe2O4 magnetic nanoparticles in the chemiluminescence of luminol-H2O2 system was investigated. It was found that β-cyclodexterin coated on CoFe2O4 magnetic nanoparticles could greatly enhance the chemiluminescence of the luminol-H2O2 system. Doehlert design was applied in order to optimize the number of experiments to be carried out to ascertain the possible interactions between the parameters and their effects on the chemiluminescence emission intensity. This design was selected because the levels of each variable may vary in a very efficient way with few experiments. Doehlert design and response surface methodology have been employed for optimization pH and concentrations of the components. Results showed under the optimized experimental conditions, the relative CL intensity (ΔI) is increased linearly in the concentration range of 0.003-0.586 μgml(-1) of montelukast with limit of detection (LOD) 1.09×10(-4) μgml(-1) at S/N ratio of 3, limit of quantitative (LOQ) 3.59×10(-4) μgml(-1) and the relative standard deviation 2.63%. The method has been successfully applied to the determination of montelukast in plasma of human body. Results specified that relative chemiluminescence intensity (ΔI) has good proportional with the montelukast concentration with R(2)=0.99979. The test of the recovery efficiency for known amounts of montelukast was also performed, the recoveries range obtained from 98.2 to 103.3%, with RSDs of <4% indicated that the proposed method was reliable.

Capabilities and limitations of 3D flame measurements based on computed tomography of chemiluminescence

This work investigated the fundamental capabilities and limitations of three-dimensional (3D) combustion measurements based on computed tomography of chemiluminescence (CTC). Experimental, computational, and analytical studies were conducted to map out the fundamental relationship of several parameters important to 3D measurements, including the achievable spatial resolution, the dimension of the measurement volume, and the signal level. The spatial resolution was analyzed both from the Fourier Slice Theorem (FST) and from linear algebraic (LA) considerations, and two limits (the FST and LA limits) were obtained to predict the achievable spatial resolution in tomographic measurements. The achievable signal level and measurement volume were also analyzed under different conditions. These results suggest that it is advantageous to implement tomographic diagnostic such that the projection image fills the camera chip completely. Under such an implementation, the average signal level increases linearly with respect to the size of the measurement volume, and the spatial resolution under the LA limits degrades linearly with respect to the measurement volume if the chemiluminescence emission intensity remains constant. We expect these results to be valuable not only for CTC, but also for tomography diagnostics based on other types of signals because the mathematical formulation in this work is not specific to chemiluminescence signals.

Enzymeless determination of total sugar by luminol–tetrachloroaurate chemiluminescence on chip to analyze food samples

Chemiluminescence (CL) emission from luminol-tetrachloroaurate ([AuCl(4)](-)) system studied in presence of monosaccharide sugars such as glucose and fructose was investigated on a microfluidic chip fabricated by the soft lithography technique. CL emission from the luminol-[AuCl(4)](-) system at 430 nm was intensified remarkably by the catalytic activity of glucose and fructose at room temperature. Under optimized conditions, the CL emission intensity of the system was found to be linearly related to the concentration of the sugars. Based on this observation, nonenzymatic determination of total sugar (glucose, fructose, or hydrolyzable sucrose) was performed in a rapid and sensitive analytical method. The results revealed that the linearity ranged from 9 to 1,750 μM for glucose and 80 to 1,750 μM for fructose, with a limit of detection of 0.65 and 0.69 μM, respectively. The relative standard deviations determined at 250 μM based on six repetitive injections were 1.13 and 1.15% for glucose and fructose, respectively. The developed method was successfully applied for determination of the total sugar concentration in food and beverages.

Abstracts of the 17th International Symposium on Bioluminescence and Chemiluminescence ‐ (ISBC 2012)

WARNING : The light-emitting molecular structures responsible for the chemiluminescence and fluorescence phenomena are not necessarily the same!

Chemiluminescent Determination of Vitamin B12 Using Charge Coupled Device (CCD)

A method was developed for the determination of vitamin B12 based on the enhancement of cobalt (II) on the chemiluminescence (CL) reaction between luminol and percarbonate (powerful source of hydrogen peroxide). The release of cobalt (II) from the vitamin B12 was reached by a simple and fast microwave digestion (20 s microwave digestion time and a mix of nitric acid and hydrogen peroxide). A charge coupled device (CCD) photodetector, directly connected to the cell, coupled with a simple continuous flow system was used to obtain the full spectral characteristics of cobalt (II) catalyzed luminol-percarbonate reaction. The optima experimental conditions were established: 8.0 m mol L−1 luminol in a 0.075 mol L−1 carbonate buffer (pH 10.0) and 0.15 mol L−1 sodium percarbonate, in addition to others experimental parameters as 0.33 mL s−1 flow rate and 2 s integration time, were the experimental conditions which proportionate the optimum CL emission intensity. The emission data were best fitted with a second-order calibration graph over the cobalt (II) concentration range from 4.00 to 300 µ g L−1 (r2 = 0.9990), with a detection limit of 0.42 µ g L−1. The proposed method was successfully applied to the determination of vitamin B12 in pharmaceuticals.

Enhancement of Ultraweak Chemiluminescence from Reaction of Hydrogen Peroxide and Bisulfite by Water-Soluble Carbon Nanodots

In this work, carbon nanodots were synthesized through a novel solvothermal route, and the effects of carbon nanodots on the ultraweak chemiluminescence (CL) reaction of hydrogen peroxide (H2O2) and sodium bisulfite (NaHSO3) were explored for the first time. It was found that the CL emission intensity of H2O2–HSO3– was significantly enhanced by carbon nanodots: about 60-fold increase in the CL intensity was obtained. The enhanced CL was induced by the excited-state carbon nanodots (CD*), which could be produced from the electron-transfer annihilation of positively charged carbon nanodots (CD•+) and negatively charged carbon nanodots (CD•–). Radical scavengers such as nitro blue tetrazolium chloride (NBT), sodium azide, thiourea, 5,5-dimethyl-1-pyrroline N-oxide, and ascorbic acid were used to study the intermediate species. The intermediate radicals generated during the reaction of H2O2 and NaHSO3, such as hydroxide radical (•OH), sulfate anionic radical (SO4•–), superoxide anionic radical (•O2–), and sul...

Reconstruction of Heat Release Response of Partially Premixed Flames

The forced response of a swirl-stabilized, partially premixed flame to inlet velocity and equivalence ratio oscillations was experimentally investigated in a model lean premixed gas turbine combustor. The responses of a premixed flame to three different forcing mechanisms were studied: velocity oscillations, equivalence ratio oscillations, and the combination of velocity and equivalence ratio oscillations. The overall heat release response of the flame was determined from measurements of the CH* chemiluminescence emission intensity from the entire flame, while the response of the spatially distributed heat release was determined from phase-synchronized chemiluminescence images. In addition, simultaneous measurements were made of the inlet velocity and equivalence ratio oscillations using the 2-microphone method and an IR absorption technique, respectively. The results show that in the linear regime, the response of a partially premixed flame to simultaneous velocity and equivalence ratio oscillations can be reconstructed from independent measurements of the flame's response to velocity oscillations and to equivalence ratio oscillations using a vector summation method. This is the first experimental demonstration of a 2-input 1-output model of a swirl-stabilized partially premixed flame. It suggests that the response of a partially premixed flame is governed by four physical parameters (i.e., the oscillation frequency, the amplitude of velocity oscillation, the amplitude of equivalence ratio oscillation, and the phase difference between the two oscillations). As a result, the heat release response of a partially premixed flame can be amplified or damped, depending on the phase difference between the velocity and equivalence ratio oscillations at the combustor inlet.

Experimental Investigation of the Nonlinear Response of Swirl-Stabilized Flames to Equivalence Ratio Oscillations

The nonlinear response of a swirl-stabilized flame to equivalence ratio oscillations was experimentally investigated in an atmospheric-pressure, high-temperature, lean-premixed model gas turbine combustor. To generate high-amplitude equivalence ratio oscillations, fuel was modulated using a siren-type modulating device. The mixture ratio oscillations at the inlet of the combustion chamber were measured by the infrared absorption technique, and the flame’s response, i.e., the fluctuation in the flame’s rate of heat release, was estimated by CH∗ chemiluminescence emission intensity. Phase-resolved CH∗ chemiluminescence images were taken to characterize the dynamic response of the flame. Results show that the amplitude and frequency dependence of the flame’s response to equivalence ratio oscillations is qualitatively consistent with the flame’s response to inlet velocity oscillations. The underlying physics of the nonlinear response of the flame to equivalence ratio oscillations, however, is associated with the intrinsically nonlinear dependence of the heat of reaction and burning velocity on the equivalence ratio. It was found that combustion cannot be sustained under conditions of high-amplitude equivalence ratio oscillations. Lean blowoff occurs when the normalized amplitude of the equivalence ratio oscillation exceeds a threshold value. The threshold value is dependent on the mean equivalence ratio and modulation frequency.

β−cyclodextrins-based inclusion complexes of CoFe 2O 4 magnetic nanoparticles as catalyst for the luminol chemiluminescence system and their applications in hydrogen peroxide detection

β−cyclodextrins ( β−CD)-based inclusion complexes of CoFe 2O 4 magnetic nanoparticles (MNPs) were prepared and used as catalysts for chemiluminescence (CL) system using the luminol–hydrogen peroxide CL reaction as a model. The as-prepared inclusion complexes were characterized by XRD (X-ray diffraction), TGA (thermal gravimetric analysis) and FT-IR. The oxidation reaction between luminol and hydrogen peroxide in basic media initiated CL. The effect of β−CD-based inclusion complexes of CoFe 2O 4 magnetic nanoparticles and naked CoFe 2O 4 magnetic nanoparticles on the luminol–hydrogen peroxide CL system was investigated. It was found that inclusion complexes between β−CD and CoFe 2O 4 magnetic nanoparticles could greatly enhance the CL of the luminol–hydrogen peroxide system. Investigation on the kinetic curves and the chemiluminescence spectra of the luminol–hydrogen peroxide system demonstrates that addition of CoFe 2O 4 MNPs or inclusion complexes between β−CD and CoFe 2O 4 MNPs does not produce a new luminophor of the chemiluminescent reaction. The luminophor for the CL system was still the excited-state 3-aminophthalate anions (3-APA*). The enhanced CL signals were thus ascribed to the possible catalysis from CoFe 2O 4 MNPs or inclusion complexes between β−CD and CoFe 2O 4 nanoparticles. The feasibility of employing the proposed system for hydrogen peroxide sensing was also investigated. Experimental results showed that the CL emission intensity was linear with hydrogen peroxide concentration in the range of 1.0 × 10 −7 to 4.0 × 10 −6 mol L −1 with a detection limit of 2.0 × 10 −8 mol L −1 under optimized conditions. The proposed method has been used to determine hydrogen peroxide in water samples successfully.

Effects of thermal ageing on mechanical and thermal behaviors of linear low density polyethylene pipe

The mechanical and thermal behaviors of linear low density polyethylene (LLDPE) pipe with variation in thermal exposure time were studied. The prolongation of thermal exposure time leads to a progressive increase, until 6000 h, in tensile strength and a slight increase in hardness, while a proportional decrease in elongation at break. These results can be explained by the increase of crystallinity, followed by the increase of crosslinking density and the decrease in chain mobility due to thermal oxidation as the exposure time increases. The additional ageing to the antioxidant-depleted LLDPE pipe induces the formation of T2 endotherm, which leads to a negative effect in mechanical properties. Long-term hydrostatic pressure test result implies the existence of transition point from ductile to brittle fracture in terms of the thermal exposure time. Chemiluminescence (CL) and oxidation induction time (OIT) tests are employed to monitor the thermo-oxidative degradation of LLDPE pipe. The CL emission intensity increases with increasing with thermal exposure time. Furthermore, the OIT result suggests that after 6000 h of the thermal ageing, the depletion of antioxidant originally added in LLDPE pipe occurs. Fourier transform-infrared spectroscopy results show the increase of carbonyl (–C O) and hydroxyl (O–H) function groups on the surface of thermally exposed LLDPE pipe. This result suggests that the hydrocarbon groups locally undergo the oxidation on the LLDPE surface due to thermal degradation.

Chemiluminescence determination of gossypol at trace levels using flow injection as sample introduction techniques

A simple and sensitive flow injection method with chemiluminescence (CL) detection is developed for the determination of gossypol at trace levels. The method is based on the reaction of luminol with ferricyanid in a sodium hydroxide medium sensitized by gossypol. Under the optimum conditions, the CL intensity is proportional to the concentration of gossypol over the range of 1.11 × 10−17 − 2.78 × 10−16 M in an acidic solution and 8.00 × 10−11 − 7.39 × 10−8 M in a neutral solution with correlation coefficients of 0.9983 and 0.9905, respectively. The detection limit is 1.48 × 10−18 M (3σ). The proposed method has been applied to the determination of gossypol in cottonseeds and pharmaceutical preparations with satisfactory results. The CL mechanism is discussed by examining the CL emission spectrum and the effect of various free radical scavengers on the CL emission intensity.