Chemiluminescence Intensity Research Articles

Performance enhancement of swirl-assisted distributed combustion with hydrogen-enriched methane

Effect of hydrogen addition to methane fuel on the performance of swirl-assisted distributed combustion was studied at 5.72 MW/m3-atm thermal intensity using different hydrogen-enrichment (at 0, 10, 20, and 40%) to methane fuel and CO2 and N2 as the flowfield diluents. High-speed chemiluminescence imaging performed (without spectral filtering) exhibited a gradual increase of chemiluminescence intensity along with gradually narrowing of the flame shape for both swirl and distributed combustion with increase in hydrogen-enrichment from increased reactivity in flame brush. Fluctuations of pressure (p′) and heat release (q′) were signals showed the existence of a peak in swirl combustion indicating the possibility of thermo-acoustic coupling. This peak mostly diminished in distributed combustion. Investigation of fluctuation with the proper orthogonal decomposition exhibited no prominent structures in distributed combustion. Measurement of lean blowoff equivalence ratios (ϕLBO) at different combustion conditions showed extended ϕLBO in distributed combustion indicating wider operational limits in distributed combustion. The NO emission increased in conventional swirl combustion while it consistently decreased in distributed combustion even at increased H2 enrichment to methane fuel. The exhaust CO2 gradually decreased with increase in H2 enrichment for both swirl and distributed reaction zones at constant thermal intensity. Reduced pollutants emission with hydrogen enrichment was also observed with air preheats in the range of 373–573 K to support distributed combustion for gas turbine conditions.

Mesoporous silica-encapsulated Co-doped ceria nanodots with enhanced peroxidase-like activity enable intensive and long-lasting chemiluminescence for glutathione detection

Chemiluminescence (CL) assay has been considered as a sensitive method for quantitative detection of glutathione (GSH), a significant regulatory metabolite in cells. However, most reported CL assays present flash-type CL emission with limited detection accuracy and repeatability. Herein, an intensive and long-lasting glow-type CL system was proposed based on a novel bimetallic Co-doped ceria mesoporous nanocomposite (Co-ceria@MSN), which was prepared by in-situ growth of sub-3 nm ultrasmall Co-ceria nanodots within the pore channels of mesoporous silica nanospheres (MSN). Attributing to the confinement effect of MSN and the superior peroxidase-like catalytic activity of Co-ceria nanodots, this nanocomposite could function as a nanozyme to catalyze luminol/H2O2 CL reaction, producing a robust and long-lasting CL emission with a long plateau for over 1.2 h at physiological pH. Surprisingly, both the CL intensity and duration time were found to exist a strong dependence on GSH concentration. Accordingly, the proposed glow-type CL platform was further applied for GSH determination with a limit of detection down to 10 nM. This strategy was successfully utilized for quantitative evaluation of cellular GSH levels, indicating its broad prospects in clinical diagnosis.

FOF1-ATP synthase molecular motor biosensor for miRNA detection of colon cancer

AimsTo establish a FOF1-ATP synthase molecular motor biosensor to accurately identify colon cancer miRNAs. Main methodsThe FOF1-ATP synthase molecular motor is extracted by fragmentation–centrifugation and connected to the colon cancer-specific miR-17 capture probe in the manner of the ε subunit-biotin-streptavidin-biotin system. Signal probes are designed for dual-signal characterization to increase detection accuracy. The FOF1-ATPase rotation rate decreases when the signaling and capture probes are combined with the target miRNA, resulting in a decrease in ATP synthesis. miR-17 concentrations are determined by changes in ATP-mediated chemiluminescence intensity and signal probe-mediated OD450nm. Key findingsThe chemiluminescence intensity and OD450nm show a good linear relationship with the miR-17 concentration in the range of 5 to 200 nmol L−1 (R2 = 0.9985, 0.9989). The colon cancer mouse model is established for the blood samples, and miR-17 in serum and RNA extracts is quantitatively determined using the constructed sensor. SignificanceThe results are consistent with colon cancer progression, and the low concentration of miR-17 detecting accuracy is comparable to the PCR assay. In conclusion, the developed method is a direct, rapid, and promising method for miRNA detection of colon cancer.

Determination of Anthraquinone-Tagged Amines Using High-Performance Liquid Chromatography with Online UV Irradiation and Luminol Chemiluminescence Detection

Quinones are frequently used as derivatization reagents in HPLC analysis to improve detection sensitivity. In the present study, a simple, sensitive, and selective chemiluminescence (CL) derivatization strategy for biogenic amines, prior to their HPLC-CL analysis, was developed. The novel CL derivatization strategy was established based on using anthraquinone-2-carbonyl chloride as derivatizing agent for amines and then using the unique property of the quinones' moiety to generate reactive oxygen species (ROS) in response to UV irradiation. Typical amines such as tryptamine and phenethylamine were derivatized with anthraquinone-2-carbonyl chloride and then injected into an HPLC system equipped with an online photoreactor. The anthraquinone-tagged amines are separated and then UV-irradiated when they pass through a photoreactor to generate ROS from the quinone moiety of the derivative. Tryptamine and phenethylamine can be determined by measuring the chemiluminescence intensity produced by the reaction of the generated ROS with luminol. The chemiluminescence disappears when the photoreactor is turned off, suggesting that ROS are no longer generated from the quinone moiety in the absence of UV irradiation. This result indicates that the generation of ROS could be controlled by turning the photoreactor on and off. Under the optimized conditions, the limits of detection for tryptamine and phenethylamine were 124 and 84 nM, respectively. The developed method is successfully applied to determine the concentrations of tryptamine and phenethylamine in wine samples.

Strong enhancement of the chemiluminescence of cerium (IV)-Na2S system by mono-dispersed N-CDs generated in situ

In this study, nitrogen-doped carbon dots (N-CDs) was observed to strongly amplify the chemiluminescence (CL) intensity of Ce (IV)-Na2S system with an enhancement factor around 55. Possible mechanism was explored and discussed on account of results of free radical scavenger experiments, CL spectra and X-ray photoelectron spectroscopy (XPS), etc. During the CL process, mono-dispersed N-CDs generated in situ catalyzed the production of more 1O2 on its surface and the CL enhancement mainly attributed to the chemiluminescence resonance energy transfer (CRET) between (1O2)2*/Ce (III)* and N-CDs. The new CL system was then developed as a convenient and sensitive platform for H2S detection. The linear range was 20–200 nM and the limit of detection (LOD) was 0.32 nM. The applications in different water samples were proved to have good recovery rate (tap water: 100.46%-109.22%; pool water: 99.91%-102.87%) with satisfactory results.

Strong chemiluminescence intensities of bis-acridinium esters under neutral and alkaline conditions

Four novel bis-acridinium esters were synthesized using common methods, and their chemiluminescence properties were investigated at pH 7−10. In the chemiluminescence of bis-acridinium esters, the introduction of fluorine at the 2-position of the phenyl ring and methyl groups at the 2,7-positions of the acridine ring changed greatly the chemiluminescence intensities. Pentane-1,5-diyl bis(2-fluoro-4-(2,7,10-trimethylacridinium-9-carbonyloxy)benzoate) bis(trifluoromethanesulfonate) showed strong chemiluminescence and long-lasting chemiluminescence under both neutral and alkaline conditions. Pentane-1,5-diyl bis(2-fluoro-4-(10-methylacridinium-9-carbonyloxy)benzoate) bis(trifluoromethanesulfonate) was applied for highly sensitive chemiluminescence determination of hydrogen peroxide and catalase activity. The linear calibration ranges of hydrogen peroxide and catalase activity were 5–1000 μM (R = 0.999) and 0.05−1 U/mL (R = 0.998), respectively.

Investigation of a low emission peripheral vortex reverse flow (PVRF) combustor fuelled by LPG and ethylene

Peripheral Vortex Reverse Flow (PVRF) combustor is characterized by a strong peripheral recirculation zone resulting in stable combustion and low pollutant emissions. In this study, a PVRF combustor is investigated in the premixed and non-premixed modes with LPG and ethylene fuels at a maximum heat load of 6.25 kW and thermal intensity of 25 MW/m3-atm, relevant to gas turbine combustors. The fuel is injected co-axially, with respect to the air jet, using two different fuel injection diameters of 1 mm, and 2 mm. For both the fuels, the fuel injection velocity is higher as compared to the air injection velocity for fuel injection diameter of 1 mm, while it is lower for fuel injection diameter of 2 mm. CH* chemiluminescence images are acquired, and CO and NOx emissions are measured. Reynolds Averaged Navier Stokes (RANS) simulations are carried out at an equivalence ratio of 0.8 using the Eddy Dissipation Concept (EDC) model with a H2/CO/C1–C4 mechanism comprising of 50 species and 373 reactions. Delayed ignition and downstream shifting of the reaction zone facilitating higher product gas entrainment prior to reactions is observed in the non-premixed mode as compared to the premixed mode. NOx emissions were found to be lower in the non-premixed mode as compared to the premixed mode for both the fuels. This is possibly due to suppression of NO formation in the reaction zone via. prompt route which is also supported by lower CH* chemiluminescence intensity in the non-premixed mode. With LPG, the case with larger fuel injection diameter showed further delayed mixing as compared to the case with smaller fuel injection diameter, and resulted in even lower NOx emissions. For all the cases, CO emissions were of similar levels in the non-premixed and premixed modes suggesting that lower NOx emissions in the non-premixed mode is not at the expense of increase in CO emissions. Overall, the investigation shows that lower NOx emissions can be achieved in the non-premixed mode as compared to the premixed mode if more product gas entrainment is facilitated prior to the reactions by delayed mixing between fuel and oxidizer.

Photosystem II as a chemiluminescence-induced photosensitizer for photoelectrochemical biofuel cell-type biosensing system

Herein, photosystem II (PSII), extracted from spinach, is used for the first time as an efficient and green sensitizer for a photobioanode in a photoelectrochemical glucose biofuel cell (PBFC) setup. The concept is based on the formation of hemin-catalyzed luminol chemiluminescence (CL) after the enzymatic oxidation of glucose and the simultaneous production of hydrogen peroxide by glucose oxidase. The photosynthetic enzyme PSII, combined with an osmium polymer serving as mediator and photosensitizer, is immobilized and wired on microporous carbonaceous material (MC) for the chemiluminescence-induced oxidation of water to O2 at the photobioanode (GCE|MC|Os polymer|PSII). Also, bilirubin oxidase immobilized on multiwalled carbon nanotubes (MWCNTs) coated electrode (GCE|MWCNT|BOx) serves as a biocathode. The photoelectrochemical biofuel cell (PBFC) is applied to a biosensor model system to validate the appropriateness of such a bioanode operating in a self-powered mode. Os redox polymer attached to MCs provides abundant PSII immobilization and a reliable electron transfer pathway. The well-matching energy levels of photosensitive entities reduce recombination phenomena while MC enhances the charge collection. Substantial photocatalytic water oxidation was observed under CL due to the well-matched CL emission and PSII absorption. The electrode is rationally designed to gain the maximum luminol CL power for the photobioanode. The open circuit potential of PBFC linearly increased with the CL power intensity and, in turn, glucose concentrations in the range of 0–6 mmol L−1. The PBFC yielded an OCP of 0.531 V in 30 mmolL−1 glucose. The study may open a new horizon to the green and pioneering PEC biosensing realm.

Optical and Thermodynamic Investigations of a Methane- and Hydrogen-Blend-Fueled Large-Bore Engine Using a Fisheye Optical System

The following paper presents thermodynamic and optical investigations of hydrogen-enriched methane combustion, showing the potential of a hydrogen admixture as a means to decarbonize stationary power generation. The optical investigations are carried out through a fisheye optical system directly mounted into the combustion chamber, replacing one exhaust valve. All of the tests were carried out with constant fuel energy producing 16 bar indicated mean effective pressure. The engine under investigation is a port-fueled 4.8 L single-cylinder large-bore research engine. The test series compared the differences between a conventional spark plug and an unscavenged pre-chamber spark plug as an ignition system. The fuel blends under investigation are 5 and 10%V hydrogen mixed with methane and pure natural gas acting as a reference fuel. The thermodynamic results show a beneficial influence of the hydrogen admixture on both ignition systems and for all variations concerning the lean running limit, combustion stability and indicated efficiency, with the most significant influence being visible for the tests using conventional spark plugs. With the unscavenged pre-chamber spark plug and the combustion of the 10%V hydrogen admixture, an increase in the indicated efficiency of 0.8% compared to NG is achievable. The natural chemiluminescence intensity traces were observed to be predominantly influenced by the air–fuel equivalence ratio. This results in a 20% higher intensity for the unscavenged pre-chamber spark plug for the combustion of 10%V hydrogen compared to the conventional spark plug. This is also visible in the evaluations of the flame color derived from the dewarped combustion image series. The investigation of the torch flames also shows a difference in the air–fuel equivalence ratio but not between the different fuels. The results encourage the development of hydrogen-based fuels and the potential to store surplus sustainable energy in the form of hydrogen in existing gas grids.

Combustion and emission characteristics of NH3/CH4/air in a model swirl combustor: Comparison between premixed and non-premixed modes

Ammonia (NH3) is a promising hydrogen carrier and can be used as carbon-free alternative fuel. However, NH3 combustion faces critical challenges, such as narrower flammability range and high NOx emission, which limits its applications. To extend the knowledge on NH3 combustion characteristics, intensive previous studies have been carried out, but most of them were concerned on premixed swirl flames. This work aims to experimentally provide a thorough comparison between premixed and non-premixed NH3/CH4/air swirl flames in terms of their flame structure, chemiluminescence spectrum, and pollutant emission characteristics at various NH3 volumetric blending ratios (XNH3) and global equivalence ratios (φ). The results show that, at a fixed φ of 0.85, the premixed combustion features a closely attached flame profile at any XNH3 of interest, while the non-premixed combustion exbibits a lifted flame appearance for all XNH3 conditions, hence a higher flammability limit of XNH3 is attained by the premixed combustion mode. At a fixed XNH3 of 50%, the non-premixed combustion tends to move the whole flammability range towards the rich direction slightly. Considering the monotonic relationship between chemiluminescence intensity of different excited radicals and operating parameters, OH∗/CH∗ intensity ratio is suggested to be used for sensing the change of XNH3 in both premixed and non-premixed combustion modes, while NH∗/CH∗ intensity ratio is recommended for sensing the change of φ. Comparing to premixed combustion, the non-premixed combustion produces a lower NO emission in the whole ranges of considered XNH3 and φ. Moreover, the NO emission profiles suggest the necessity of employing rich-lean technology for achieving acceptably low NO emission for both premixed and non-premixed combustion modes, while the latter shows a possibility to be operated in relatively leaner condition in the first stage.

Enhanced Luminol Chemiluminescence with Oxidase-like Properties of FeOOH Nanorods for the Sensitive Detection of Uric Acid.

FeOOH nanorods, as one-dimensional nanomaterials, have been widely used in many fields due to their stable properties, low cost, and easy synthesis, but their application in the field of chemiluminescence (CL) is rarely reported. In this work, FeOOH nanorods were synthesized by a simple and environmentally friendly one-pot hydrothermal method and used for the first time as a catalyst for generating strong CL with luminol without additional oxidant. Remarkably, luminol-FeOOH exhibits about 250 times stronger CL than the luminol-H2O2 system. Its CL intensity was significantly quenched by uric acid. We established a simple, rapid, sensitive, and selective CL method for the detection of uric acid with a linear range of 20-1000 nM and a detection limit of 6.3 nM (S/N = 3). In addition, we successfully applied this method to the detection of uric acid in human serum, and the standard recoveries were 95.6-106.4%.

Rare earth complexes chemiluminescence catalyzed by gold nanoparticles for fast sensing of Tb3+ and Eu3+

Developing multiplex sensing technique is of great significance for fast sample analysis. However, the broad emissions of most chemiluminescence (CL) luminophores make the multiplex CL analysis be difficult. In this work, a simple and sensitive CL analytical method has been developed for the simultaneous determination of Tb3+ and Eu3+ thanking to their narrow band emission. The technique was based on a mixed CL system of periodate (IO4−)-hydrogen peroxide (H2O2)-rare earth complexes, in which the reactive oxygen species (ROSs) especially singlet oxygen (1O2) can transfer its energy to the complex of Tb3+/Eu3+-ethylenediaminetetraacetic acid disodium salt (EDTA) and then produce the characteristic emissions of Tb3+ and Eu3+ without cross-interference. The further experiment found that the CL emissions of Tb3+ and Eu3+ could be catalyzed by the gold nanoparticles (AuNPs) via enhancing the yield of 1O2. The CL intensities of Tb3+ (at 490 nm) and Eu3+ (at 620 nm) increased linearly with concentration of Tb3+ and Eu3+. After the optimization of the CL sensing conditions, the limits of detection (LOD) were 5.0 × 10−9 mol/L and 8.0 × 10−7 mol/L for Tb3+ and Eu3+, respectively. Finally, the method has been applied for measuring the contents of Tb3+ and Eu3+ in leaching solution of mine sample and Tb3+/Eu3+-contained nanomaterials with satisfactory results. The present system provides a new CL technique for multiplex sensing with simplicity and high sensitivity.

A new peroxyoxalate chemiluminescence of bis (2, 4-dinitrophenyl) oxalate (DNPO) using pyronin Y as the fluorophore and its application to the flow-based determination of cysteamine

Peroxyoxalate chemiluminescence (POCL) systems have received great attention due to their high quantum yield and the ability to emit a wide-range colors by the utilizing different fluorophores. In this research, Pyronin Y (PY) was first introduced as the fluorophore for a POCL system. Our results indicated that the reaction of (2, 4-dinitroophenyl) oxalate (DNPO) with hydrogen peroxide (H2O2) catalyzed by sodium salicylate (SS) could transfer energy to Pyronin Y via the formation of the dioxetanedione intermediate and emit orange-red light. The relationships between chemiluminescence (CL) intensity and the concentrations of DNPO, fluorophore, H2O2, and the catalyst were investigated. Moreover, the analytical utilization of the new CL system was evaluated by detecting a drug, cysteamine, in pharmaceuticals. A linear working range for cysteamine concentrations from 3 × 10 −8 to 7.5 × 10 −6 molL−1 (r > 0.9907, n = 5) and a detection limit of 7.8 × 10−9 molL−1 were obtained, respectively. The relative standard deviation for five repetitive determinations was less than 3.8 %, with estimated recoveries of 100.1 % and 103.4 %. This method shows high sensitivity for the assay of cysteamine.

Digital Twin for Experimental Data Fusion Applied to a Semi-Industrial Furnace Fed with H2-Rich Fuel Mixtures

The objective of this work is to build a Digital Twin of a semi-industrial furnace using Gaussian Process Regression coupled with dimensionality reduction via Proper Orthogonal Decomposition. The Digital Twin is capable of integrating different sources of information, such as temperature, chemiluminescence intensity and species concentration at the outlet. The parameters selected to build the design space are the equivalence ratio and the benzene concentration in the fuel stream. The fuel consists of a H2/CH4/CO blend, doped with a progressive addition of C6H6. It is an H2-rich fuel mixture, representing a surrogate of a more complex Coke Oven Gas industrial mixture. The experimental measurements include the flame temperature distribution, measured on a 6×8 grid using an air-cooled suction pyrometer, spatially resolved chemiluminescence measurements of OH* and CH*, and the species concentration (i.e., NO, NO2, CO, H2O, CO2, O2) measured in the exhaust gases. The GPR-based Digital Twin approach has already been successfully applied on numerical datasets coming from CFD simulations. In this work, we demonstrate that the same approach can be applied on heterogeneous datasets, obtained from experimental measurements.

Clustered Regularly Interspaced Short Palindromic Repeats-Associated Proteins13a combined with magnetic beads, chemiluminescence and reverse transcription-recombinase aided amplification for detection of avian influenza a (H7N9) virus.

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and Clustered Regularly Interspaced Short Palindromic Repeats-Associated Proteins (CRISPR-Cas) have promising prospects in the field of nucleic acid molecular diagnostics. However, Clustered Regularly Interspaced Short Palindromic Repeats-based fluorescence detection technology is mainly hindered by proteins with conjugated double bonds and autofluorescence, resulting in high fluorescence background, low sensitivity and incompatible reaction systems, which are not conducive to automatic clinical testing. Chemiluminescence (CL) detection technology has been applied mainly owing to its greatly high sensitivity, as well as low background and rapid response. Therefore, we developed a rapid, ultrasensitive and economical detection system based on Clustered Regularly Interspaced Short Palindromic Repeats-Clustered Regularly Interspaced Short Palindromic Repeats-Associated Proteins 13a combined with magnetic beads (MBs) and chemiluminescence (CL) (Cas13a-MB-CL) to detect Influenza A (H7N9), an acute respiratory tract infectious disease. The carboxyl functionalized magnetic beads (MBs-COOH) were covalently coupled with aminated RNA probe while the other end of the RNA probe was modified with biotin. Alkaline phosphatase labeled streptavidin (SA-ALP) binds with biotin to form magnetic beads composites. In presence of target RNA, the collateral cleavage activity of Cas13a was activated to degrade the RNA probes on MBs and released Alkaline phosphatase from the composites. The composites were then magnetically separated followed by addition of ALP substrate Disodium 2-chloro-5-{4-methoxyspiro [1,2-dioxetane-3,2'-(5'-chloro) tricyclo (3.3.1.13,7) decan]-4-yl}-1-phenyl phosphate (CDP-star), to generate the chemiluminescence signal. The activity of Associated Proteins 13a and presence of target RNA was quantified by measuring the chemiluminescence intensity. The proposed method accomplished the detection of H7N9 within 30min at 25°C. When combined with Reverse Transcription- Recombinase Aides Amplification (RT-RAA), the low detection limit limit of detection was as low as 19.7fM (3S/N). Our proposed MB-Associated Proteins 13a-chemiluminescence was further evaluated to test H7N9 clinical samples, showing superior sensitivity and specificity.

LACTOFERRIN – A ROLE IN THE PROTECTIVE FUNCTIONS IN ADOLESCENTS WITH LATENT TUBERCULOSIS INFECTION

When evaluating the role of lactoferrin to improve the effectiveness of preventive treatment of latent tuberculosis infection in adolescents, it was found that the prescriptions of Lactoferrin imun + Colostrum contributed to a significantly more pronounced decrease in the frequency of hyperergic reactions in test with tuberculosis recombinant allergen (from 51.3% to 12.5% in the main group, from 50.7 % to 33.3% in the comparison group, p < 0.05), a decrease in the average size of the papule (from 17.6 mm to 8.2 mm in the main group and from 17.1 to 14.5 mm in the comparison group, p < 0.05). In patients of the main group, the restoration of free radical oxidation and antioxidant protection indicators to the level of healthy donors was established, while in the comparison group, the intensity of blood plasma chemiluminescence and the activity of myeloperoxidase in neutrophils remained elevated, while the activity of catalase and superoxidedismutase remained reduced. The level of lactoferrin during treatment in the main group increased to normal values (740 ng/ml, 95%CI 702.2-777.8), and in the control group remained reduced (440 ng/ml, 95%CI 411.5-478.5), p < 0.05. At the same time, the continuing level of positive reactions to tuberculosis recombinant allergen (Diaskintest®) against the background of normalization of the lactoferrin level indicates the high diagnostic capabilities of Diaskintest® to detect LTBI in adolescents

Spin Trapping Analysis of Radical Intermediates on the Thermo-Oxidative Degradation of Polypropylene.

The purpose of this study is to investigate the thermo-oxidative degradation behavior of polypropylene (PP) by comparing three types of pristine PP granules (consisting of homopolymer, random copolymer, and block copolymer) with their corresponding oxidized analogues. These analogues were intensely oxidized under oxygen at 90 °C for 1000 h by using the electron spin resonance (ESR) spin trapping method that can detect short-lived radical intermediates during the degradation. The degrees of oxidation could be evaluated by chemiluminescence (CL) intensity, which was related to the concentration of hydroperoxide groups generated in the PP chain. In the pristine PP samples, a small amount of hydroperoxides were found to be formed unintentionally, and their homolysis produces alkoxy radicals, RO•, which then undergo β-scission to yield chain-end aldehydes or chain-end ketones. These oxidation products continue to take part in homolysis to produce their respective carbonyl and carbon radicals. On the other hand, in the oxidized PP granules, because of their much higher hydroperoxide concentration, the two-stage cage reaction and the bimolecular decomposition of hydroperoxides are energetically favorable. Carbonyl compounds are formed in both reactions, which are then homolyzed to form the carbonyl radical species, •C(O)-. PP homopolymer produced the largest amount of carbonyl radical spin adduct; thus, it was found that the homopolymer is most sensitive to oxygen attack, and the presence of ethylene units in copolymers enhances the oxidation resistance of PP copolymers.

Chemiluminescent Nanogels as Intensive and Stable Signal Probes for Fast Immunoassay of SARS-CoV-2 Nucleocapsid Protein.

It is highly desired to exploit good nanomaterials as nanocarriers for immobilizing chemiluminescence (CL) reagents, catalysts and antibodies to develop signal probes with intensive and stable CL properties for immunoassays. In this work, N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and Co2+ bifunctionalized polymethylacrylic acid nanogels (PMAANGs-ABEI/Co2+) were synthesized via a facile strategy by utilizing carboxyl group-rich PMAANGs as nanocarriers to immobilize ABEI and Co2+. The obtained PMAANGs-ABEI/Co2+ showed extraordinary CL performance. The CL intensity is 2 orders of magnitude higher than that of previously reported ABEI and Cu2+-cysteine complex bifunctionalized gold nanoparticles with high CL efficiency. This was attributed to the excellent catalytic ability of Co2+ and polymethylacrylic acid nanogels, as well as the improved CL catalytic efficiency from a decreased spatial distance between ABEI and the catalyst. The as-prepared nanogels also possess abundant surface reaction sites and good CL stability. On this basis, a sandwich immunoassay for the nucleocapsid protein of SARS-CoV-2 (N protein) was developed by using magnetic bead connected primary antibody as a capture probe and PMAANGs-ABEI/Co2+ connected secondary antibody as a signal probe. The linear range of the proposed method for N protein detection was 3.16-316 ng/mL, and its detection limit was 2.19 ng/mL (S/N = 3). Moreover, the developed immunoassay was performed with a short incubation time of 5 min, which greatly reduced the detection time for N protein. By using corresponding antibodies, the developed strategy might be applied to detect other biomarkers.

The nature of sawtooth wave and its distinction from continuous rotating detonation wave

To pinpoint the nature of the sawtooth wave, extensive experiments of methane-air continuous rotating detonation (CRD) are conducted in a hollow chamber around the boundary of the operating range. The time occupancy ratio and the increasing ratio of pressure rise (Δti/ΔTi and ΔPi/Δti) derived from high-frequency pressure data, and the integral of chemiluminescence intensity (ICI) based on self-luminescence images are proposed as quantitative parameters to distinguish the detonation wave and the sawtooth wave. The results show that the sawtooth wave is a critical unstable mode between conventional isobaric combustion and CRD, propagating with high Δti/ΔTi and low ΔPi/Δti. Meanwhile, the reaction zone of sawtooth wave is verified to be stabilized in the center of combustor through the self-luminescence observation. Especially, the multiple transition processes from the sawtooth wave to the CRD wave are accurately captured, and simultaneously represented as the change from single-peak waveform to double-peak waveform on ICI, the rise of ΔPi/Δti, and the reduction of Δti/ΔTi. The significant distinction of the sawtooth wave and the CRD wave in the coupling characteristics is confirmed through Short-Time Fourier Transform processes on ICI and high-frequency pressure. For the CRD wave, the propagation frequency of the reaction zone matches that of the pressure wave, whereas not for the sawtooth wave. It is ascertained that the reaction zone is decoupled with the pressure wave for the sawtooth wave, and the nature of the sawtooth wave is deflagration combined with a weak pressure wave.

Experimental Study on OH*, CH*, and CO2* Chemiluminescence Diagnosis of CH4/O2 Diffusion Flame with CO2-Diluted Fuel.

OH* and CH* chemiluminescence in hydrocarbon flames are often applied to characterize flame structure, equivalence ratio, strain rate, heat release rate, etc. In this study, chemiluminescence images of OH*, CH*, and CO2* in the CH4/O2 diffusion flame were obtained using a CCD camera imaging system. The effect of CO2 dilution on the flame structure, strain rate, and other flame characteristics of CH4/O2 diffusion flame was discussed. The results show that CO2 dilution greatly affects flame morphology and chemiluminescence intensity. There are quantitative functions between the chemiluminescence peak intensity of OH* and CH* and the CO2 dilution level. The CO2* average intensity in the flame zone is better suited to characterize the dilution level than the CO2* peak intensity. Moreover, the strain rate of CO2-diluted laminar flame is defined. It is found that there is a linear relationship between the thickness of the OH* reaction zone and the square root of the strain rate.