DNA‐based chemiluminescent nanoprobes for highly sensitive and selective detection of mercury(II) ion

A simple and sensitive DNA‐stablized gold nanoparticle (AuNP)‐based chemiluminescent (CL) probe for detecting mercury ion (Hg²⁺) in aqueous solution has been developed. The CL strategy relies upon the catalytic activity of unmodified AuNPs on the luminol–H₂O₂ CL reaction, and the interaction of unmodified AuNPs with DNA. The unmodified AuNPs can effectively differentiate unstructured and folded DNA. The DNA desorbs from AuNPs in the presence of Hg²⁺, leading to the increase in CL signal. By rationally varying the number of thymine in single‐strand oligonucleotides, the detection range could be tuned. Employing single‐strand oligonucleotides with 14 thymine in the detecting system, a sensitive linear range for Hg²⁺ ions from 5.0 × 10^–10 to 1.0 × 10^–7 mol/L and a detection limit of 2.1 × 10^–10 mol/L are obtained. Changing the number of thymine to 10 and 6, it leads to a narrow detection range but a high sensitivity. Besides, DNA‐based CL nanoprobes exhibit a remarkable selectivity for Hg²⁺ ions over a variety of competing metal ions. Copyright © 2012 John Wiley & Sons, Ltd.     

Employment of 4‐(1,2,4‐triazol‐1‐yl)phenol as a signal enhancer of the chemiluminescent luminol–H2O2–horseradish peroxidase reaction for detection of hepatitis C virus in real samples

Highly sensitive detection of hepatitis C virus (HCV) in serum is a key method for diagnosing and classifying the extent of HCV infection. In this study, a p‐phenol derivative, 4‐(1,2,4‐triazol‐1‐yl)phenol (4‐TRP), was employed as an efficient enhancer of the luminol–hydrogen peroxide (H₂O₂)–horseradish peroxidase (HRP) chemiluminescence (CL) system for detection of HCV. Compared with a traditional enhancer, 4‐TRP strongly enhanced CL intensity with the effect of prolonging and stabilizing light emission. The developed CL system was applied to detecting HCV core antigen (HCV‐cAg) using a sandwich structure inside microwells. Our experimental results showed that there was good linear relationship between CL intensity and HCV‐cAg concentration in the 0.6–3.6 pg/mL range (R = 0.99). The intra‐ and inter‐assay coefficients of variation were 4.5–5.8% and 5.0–7.3%, respectively. In addition, sensitive determination of HCV‐cAg in serum samples using the luminol–H₂O₂–HRP–4‐TRP CL system was also feasible in clinical settings. Copyright © 2015 John Wiley & Sons, Ltd.     

Evaluation of lophine derivatives as L‐012 (luminol analog)‐dependent chemiluminescence enhancers for measuring horseradish peroxidase and H2O2

8‐Amino‐5‐chloro‐7‐phenylpyrido[3,4‐d]pyridazine‐1,4(2H,3H)dione (L‐012) was recently synthesized as a new chemiluminescence (CL) probe; the light intensity and the sensitivity of L‐012 are higher than those of other CL probes such as luminol. Previously, our group developed four lophine‐based CL enhancers of the horseradish peroxidase (HRP)‐catalyzed CL oxidation of luminol, namely 2‐(4‐hydroxyphenyl)‐4,5‐diphenylimidazole (HDI), 2‐(4‐hydroxyphenyl)‐4,5‐di(2‐pyridyl)imidazole (HPI), 4‐(4,5‐diphenyl‐1H‐imidazol‐2‐yl)phenylboronic acid (DPA), and 4‐[4,5‐di(2‐pyridyl)‐1H‐imidazol‐2‐yl]phenylboronic acid (DPPA), and showed that DPPA was suitable for the photographic detection of HRP. In this study, we replaced luminol with L‐012 and evaluated these as L‐012‐dependent CL enhancers. In addition, to detect HRP and/or H₂O₂ with higher sensitivity, each detection condition for the L‐012–HRP–H₂O₂ enhanced CL was optimized. All the derivatives enhanced the L‐012‐dependent CL as well as luminol CL; HPI generated the highest enhanced luminescence. Under optimized conditions for HRP detection, the detection limit of HRP was 0.08 fmol. By contrast, the detection limit of HRP with the enhanced L‐012‐dependent CL using 4‐iodophenol, which is a common enhancer of luminol CL, was 1.1 fmol. With regard to H₂O₂ detection, the detection limits for enhanced CL with HPI and 4‐iodophenol were 0.29 and 1.5 pmol, respectively. Therefore, it is demonstrated that HPI is the most superior L‐012‐dependent CL enhancer. Copyright © 2013 John Wiley & Sons, Ltd. Copyright © 2013 John Wiley & Sons, Ltd.     

Highly luminescent S,N co‐doped carbon quantum dots‐sensitized chemiluminescence on luminol–H2O2 system for the determination of ranitidine

S,N co‐doped carbon quantum dots (N,S‐CQDs) with super high quantum yield (79%) were prepared by the hydrothermal method and characterized by transmission electron microscopy, photoluminescence, UV–Vis spectroscopy and Fourier transformed infrared spectroscopy. N,S‐CQDs can enhance the chemiluminescence intensity of a luminol–H₂O₂ system. The possible mechanism of the luminol–H₂O₂–(N,S‐CQDs) was illustrated by using chemiluminescence, photoluminescence and ultraviolet analysis. Ranitidine can quench the chemiluminescence intensity of a luminol–H₂O₂–N,S‐CQDs system. So, a novel flow‐injection chemiluminescence method was designed to determine ranitidine within a linear range of 0.5–50 μg ml^?1 and a detection limit of 0.12 μg ml^?1. The method shows promising application prospects.     

Studies of visible oscillating chemiluminescence in luminol–H2O2–KSCN–CuSO4 system using (2‐hydroxyethyl) trimethylammonium hydroxide

Visible oscillating chemiluminescence (CL) of luminol–H₂O₂–KSCN–CuSO₄ was studied using the organic base (2‐hydroxyethyl)trimethylammonium hydroxide. The effect of concentrations of luminol, H₂O₂, KSCN, CuSO₄ and the base were investigated in a batch reactor. This report shows how the concentration of components involved in the oscillating CL system influenced the oscillation period, light amplitude and total time of light emission. The oscillating CL with different bases was also investigated. Results indicated that using 2‐HETMAOH causes regular oscillating CL with nearly the same oscillating period. Copyright © 2008 John Wiley & Sons, Ltd.     

The determination of glutamine with flow‐injection chemiluminescence detection and mechanism study

The main purpose of this study was to develop an inexpensive, simple, rapid and sensitive chemiluminescence (CL) method for the determination of glutamine (Gln) using a flow‐injection (FI) system. Gln was found to strongly inhibit the CL signal of the luminol–H₂O₂–CuSO₄ system in Na₂B₄O₇ solution. A new FI‐CL method was developed for the determination of Gln. Parameters affecting the reproducibility and CL detection were optimized systematically. Under the optimized conditions, the corresponding linear regression equation was established over the range of 5.0 × 10^?7 to 2.5 × 10^?6 mol/L with the detection limit of 1.8 × 10^?8 mol/L. The relative standard deviation was found to be 1.8% for 11 replicate determinations of 1.5 × 10^?6 mol/L Gln. The proposed method has been satisfactorily applied for the determination of Gln in real samples (Marzulene‐s granules) with recoveries in the range of 98.7–108.6%. The minimum sampling rate was about 100 samples/h. The possible mechanism of this inhibitory CL was studied by fluorescence spectrophotometer and UV–vis spectrophotometer. Copyright © 2009 John Wiley & Sons, Ltd.     

Copper nanocluster‐enhanced luminol chemiluminescence for high‐selectivity sensing of tryptophan and phenylalanine

A remarkable method for the highly sensitive detection of phenylalanine and tryptophan based on a chemiluminescence (CL) assay was reported. It was found that fluorescent copper nanoclusters capped with cysteine (Cys‐CuNCs) strongly enhance the weak CL signal resulting from the reaction between luminol and H₂O₂. Of the amino acids tested, phenylalanine and tryptophan could enhance the above CL system sensitively. Under optimum conditions, this method was satisfactorily described by a linear calibration curve over a range of 1.0 × 10^?6 to 2.7 × 10^?5 M for phenylalanine and 1.0 × 10^?7 to 3.0 × 10^?5 M for tryptophan, respectively. The effect of various parameters such as Cys‐CuNC concentration, H₂O₂ concentration and pH on the intensity of the CL system were also studied. The main experimental advantage of the proposed method was its selectivity for two amino acids compared with others. To evaluate the applicability of the method to the analysis of a real biological sample it was used to determine tryptophan and phenylalanine in human serum and remarkable results were obtained.     

A novel chemiluminescent flow‐injection analysis of transferrin by its reduction of the luminol—hydrogen peroxide reaction catalysed by meso‐tetra‐(3‐methoxyl‐4‐hydroxyl) phenyl manganese porphyrin

Based on the inhibition effect of transferrin (Tf) on the reaction of the luminol–hydrogen peroxide (H₂O₂) chemiluminescence (CL) system, catalysed by meso‐tetra‐(3‐methoxyl‐4‐hydroxyl) phenyl manganese porphyrin (MnP) as a mimetic enzyme of peroxides, a sensitive flow‐injection CL method has been developed for the determination of Tf in an alkaline medium. The CL reaction was carefully investigated by examining the variations of reaction conditions. Under optimum conditions, the linear range for the determination of transferrin was 0.04–20.0 μg/mL and the detection limit was 1.62 ng/mL. This proposed method was sensitive, convenient and simple, and has been successfully applied to the determination of transferrin in a serum sample. Copyright © 2011 John Wiley & Sons, Ltd.     

Study on the reaction mechanism and the static injection chemiluminescence method for detection of acetaminophen

Acetaminophen, also called paracetamol, is found in Tylenol, Excedrin and other products as over–the‐counter medicines. In this study, acetaminophen as a luminol signal enhancer was used in the chemiluminescence (CL) substrate solution of horseradish peroxidase (HRP) for the first time. The use of acetaminophen in the luminol–HRP–H₂O₂ system affected not only the intensity of the obtained signal, but also its kinetics. It was shown that acetaminophen was to be a potent enhancer of the luminol–HRP–H₂O₂ system. A putative enhancement mechanism for the luminol–H₂O₂–HRP–acetaminophen system is presented. The resonance of the nucleophilic amide group and the benzene ring of acetaminophen structure have a great effect on O‐H bond dissociation energy of the phenol group and therefore on phenoxyl radical stabilization. These radicals act as mediators between HRP and luminol in an electron transfer reaction that generates luminol radicals and subsequently light emission, in which the intensity of CL is enhanced in the presence of acetaminophen. In addition, a simple method was developed to detect acetaminophen by static injection CL based on the enhanced CL system of luminol–H₂O₂–HRP by acetaminophen. Experimental conditions, such as pH and concentrations of substrates, have been examined and optimized. The proposed method exhibited good performance, the linear range was from 0.30 to 7.5 mM, the relative standard deviation was 1.86% (n = 10), limit of detection was 0.16 mM and recovery was 99 ± 4%. Copyright © 2013 John Wiley & Sons, Ltd.     

A chelate complex‐enhanced luminol system for selective determination of Co(II), Fe(II) and Cr(III)

A determination method for Co(II), Fe(II) and Cr(III) ions by luminol‐H₂O₂ system using chelating reagents is presented. A metal ion‐chelating ligand complex with a Co(II) ion and a chelating reagent like ethylenediaminetetraacetic acid (EDTA) produced highly enhanced chemiluminescence (CL) intensity as well as longer lifetime in the luminol‐H₂O₂ system compared to metals that exist as free ions. Whereas free Cu(II) and Pb(II) ions had a strong catalytic effect on the luminol‐H₂O₂ system, significantly, the complexes of Cu(II) and Pb(II) with chelating reagents lost their catalytic activity due to the chelating reagents acting as masking agents. Based on the observed phenomenon, it was possible to determine Co(II), Fe(II) and Cr(III) ions with enhanced sensitivity and selectivity using the chelating reagents of the luminol‐H₂O₂ system. The effects of ligand, H₂O₂ concentration, pH, buffer solution and concentrations of chelating reagents on CL intensity of the luminol‐H₂O₂ system were investigated and optimized for the determination of Co(II), Fe(II) and Cr(III) ions. Under optimized conditions, the calibration curve of metal ions was linear over the range of 2.0 × 10^‐8 to 2.0 × 10^‐5 M for Co(II), 1.0 × 10^‐7 to 2.0 × 10^‐5 M for Fe (II) and 2.0 × 10^‐7 to 1.0 × 10^‐4 M for Cr(III). Limits of detection (3σ/s) were 1.2 × 10^‐8, 4.0 × 10^‐8 and 1.2 × 10^‐7 M for Co(II), Fe(II) and Cr(III), respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Long‐term chemiluminescence signal is produced in the course of luminol oxidation catalyzed by enhancer‐independent peroxidase purified from Jatropha curcas leaves

Isoenzyme c of horseradish peroxidase (HRP‐C) is widely used in enzyme immunoassay combined with chemiluminescence (CL) detection. For this application, HRP‐C activity measurement is usually based on luminol oxidation in the presence of hydrogen peroxide (H₂O₂). However, this catalysis reaction was enhancer dependent. In this study, we demonstrated that Jatropha curcas peroxidase (JcGP1) showed high efficiency in catalyzing luminol oxidation in the presence of H₂O₂. Compared with HRP‐C, the JcGP1‐induced reaction was enhancer independent, which made the enzyme‐linked immunosorbent assay (ELISA) simpler. In addition, the JcGP1 catalyzed reaction showed a long‐term stable CL signal. We optimized the conditions for JcGP1 catalysis and determined the favorable conditions as follows: 50 mM Tris buffer (pH 8.2) containing 10 mM H₂O₂, 14 mM luminol and 0.75 M NaCl. The optimum catalysis temperature was 30°C. The detection limit of JcGP1 under optimum condition was 0.2 pM. Long‐term stable CL signal combined with enhancer‐independent property indicated that JcGP1 might be a valuable candidate peroxidase for clinical diagnosis and enzyme immunoassay with CL detection. Copyright © 2014 John Wiley & Sons, Ltd.     

1,10‐Phenanthroline–H2O2–KSCN–CuSO4–NaOH oscillating chemiluminescence system

In this paper, oscillating chemiluminescence (CL), 1,10‐phenanthroline H₂O₂–KSCN–CuSO₄–NaOH system, was studied in a batch reactor. The system described is a novel, slowly damped oscillating CL system, generated by coupling the well‐known Epstein–Orban, H₂O₂–KSCN–CuSO₄–NaOH chemical oscillator reaction with the CL reaction involving the oxidation of 1,10‐phenanthroline by hydrogen peroxide, catalyzed by copper(II) in alkaline medium. In this system, the CL reaction acts as a detector or indicator system of the far‐from‐equilibrium dynamic system. Narrow and slightly asymmetric light pulses of 1.2 s half‐width are emitted at 440 nm with an emitted light time of 200–1000 s, induction period of 3.5–357 s and oscillation period of 28–304 s depending on the reagent concentrations. In this report the effect of the concentration variation of components involved in the oscillating CL system on the induction period, the oscillation period and amplitude was investigated and the parameters were plotted with respect to reagent concentrations. Copper concentration showed a significant effect on the oscillation period. The possible mechanism for the oscillating CL reaction was also discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Luminol–silver nitrate chemiluminescence enhancement induced by cobalt ferrite nanoparticles

CoFe₂O₄ nanoparticles (NPs) could stimulate the weak chemiluminescence (CL) system of luminol and AgNO₃, resulting in a strong CL emission. The UV–visible spectra, X‐ray photoelectron spectra and TEM images of the investigated system revealed that AgNO₃ was reduced by luminol to Ag in the presence of CoFe₂O₄ NPs and the formed Ag covered the surface of CoFe₂O₄ NPs, resulting in CoFe₂O₄–Ag core–shell nanoparticles. Investigation of the CL reaction kinetics demonstrated that the reaction among luminol, AgNO₃ and CoFe₂O₄ NPs was fast at the beginning and slowed down later. The CL spectra of the luminol ? AgNO₃ ? CoFe₂O₄ NPs system indicated that the luminophor was still an electronically excited 3‐aminophthalate anion. A CL mechanism has been postulated. When the CoFe₂O₄ NPs were injected into the mixture of luminol and AgNO₃, they catalyzed the reduction of AgNO₃ by luminol to produce luminol radicals and Ag, which immediately covered the CoFe₂O₄ NPs to form CoFe₂O₄–Ag core–shell nanoparticles, and the luminol radicals reacted with the dissolved oxygen, leading to a strong CL emission. With the continuous deposition of Ag on the surface of CoFe₂O₄ NPs, the catalytic activity of the core–shell nanoparticles was inhibited and a decrease in CL intensity was observed and also a slow growth of shell on the nanoparticles. Copyright © 2011 John Wiley & Sons, Ltd.     

Trace analysis of N‐acetyl‐L‐cysteine using luminol–H2O2 chemiluminescence system catalyzed by silver nanoparticles

N‐Acetyl‐L‐cysteine (NAC) can inhibit the luminol–H₂O₂, reaction, which is catalyzed by silver nanoparticles. Based on this phenomenon a new method was developed for NAC determination. Under optimum conditions, a linear relationship between chemiluminescence intensity and NAC concentration was found in the range 0.034–0.98 µg/mL. The detection limit was 0.010 µg/mL (S/N =3), and the relative standard deviation (RSD) was <5% for 0.480 µg/mL NAC (n =5). This simple, sensitive and inexpensive method has been applied to measure the concentration of NAC in pharmaceutical tablets. Copyright © 2014 John Wiley & Sons, Ltd.     

Pyrophosphate as substrate for alkaline phosphatase activity: A convenient flow‐injection chemiluminescence assay

A sensitive and convenient flow‐injection chemiluminescence (FI‐CL) turn‐on assay for alkaline phosphatase (ALP) activity without any label and synthesis is developed. Cu²⁺ can catalyze the luminol–H₂O₂ CL reaction. Pyrophosphate (PPi) can chelate Cu²⁺ and therefore the Cu²⁺‐mediated luminol‐H₂O₂ CL reaction is inhibited. The addition of ALP can catalyze the hydrolysis of PPi into phosphate ions, Cu²⁺ is released and the chemiluminescence recovers. A detection limit of 1 mU/mL ALP is obtained.     

Turn‐off–on chemiluminescence determination of cyanide

A flow injection chemiluminescence (FI–CL) method was developed for the determination of cyanide (CN⁻) based on the recovered CL signal by Cu²⁺ inhibiting a glutathione (GSH)‐capped CdTe quantum dot (QD) and hydrogen peroxide system. In an alkaline medium, strong CL signals were observed from the reaction of CdTe QDs and H₂O₂, and addition of Cu²⁺ could cause significant CL inhibition of the CdTe QDs–H₂O₂ system. In the presence of CN⁻, Cu²⁺ can be removed from the surface of CdTe QDs via the formation of particularly stable [Cu(CN)_n]^(n‐1)– species, and the CL signal of the CdTe QDs–H₂O₂ system was efficiently recovered. Thus, the CL signals of CdTe QDs–H₂O₂ system were turned off and turned on by the addition of Cu²⁺ and CN⁻, respectively. Further, the results showed that among the tested ions, only CN⁻ could recover the CL signal, which suggested that the CdTe QDs–H₂O₂–Cu²⁺ CL system had highly selectivity for CN⁻. Under optimum conditions, the CL intensity and the concentration of CN⁻ show a good linear relationship in the range 0.0–650.0 ng/mL (R² = 0.9996). The limit of detection for CN⁻ was 6.0 ng/mL (3σ). This method has been applied to detect CN⁻ in river water and industrial wastewater with satisfactory results. Copyright © 2014 John Wiley & Sons, Ltd.     

Chemiluminescence from luminol solution after illumination of a 355 nm pulse laser

Chemiluminescence (CL) on the time scale of microseconds to milliseconds from luminol solution after illumination of a 355 nm pulse laser is reported. It was found that the CL is the emission from 3‐aminophthalate ion (AP*). In CL decay after the pulse laser illumination, a peak was observed from about 200 to 30 µs depending on the laser power and the luminol concentration. It seemed that there was a fast and slow decay process; their kinetics were greatly dependent on the laser power and the luminol concentration. Dissolved oxygen was involved in the CL and played the same role on the whole time scale of microseconds to milliseconds. Involvement of reactive oxygen species such as H₂O₂, ¹O₂, O₂^?? and OH in the CL was examined by adding their scavengers. Experimental results suggested that the possibility of involvement of H₂O₂ and ¹O₂ in the CL was low. The CL in time periods less than 50 µs might be related to ?OH. The ^?O₂^??‐induced CL increased with time after 50 µs and became dominant on the time scale of milliseconds. The CL was considered to be caused by both the photoionization and type I reaction mechanisms. Copyright © 2009 John Wiley & Sons, Ltd.     

Highly sensitive and selective electrochemiluminescence determination of cholesterol utilizing a functional electrode with a core–shell nanostructure

A highly sensitive and selective method for the determination of cholesterol is required to evaluate trace amounts of cholesterol in test samples. In this work, selected gold nanoparticles (AuNPs) and 5‐amino‐2‐mercapto‐1,3,4‐thiadiazole (AMT) were used and a thin film of three‐dimensional gold–AMT core–shell nanoparticles (p‐AMT–AuNPs) was prepared using an electrochemical method. Cholesterol oxidase was then bonded to the film surface to give a functional electrode. Based on catalysis by the electrode functionalized for cholesterol and a luminol–H₂O₂ electrochemiluminescence (ECL) system, a highly sensitive and selective ECL method was developed for the determination of cholesterol. Under optimized conditions, ECL intensity showed a good linear relationship with cholesterol over the concentration range 0.05–11.0 µg/ml, with a correlation coefficient of 0.999 and a limit of detection of 0.02 µg/ml. The proposed method was used to determine cholesterol in dairy products with a relative standard deviation of < 1.8% and recovery rates of 98.1–104%. Copyright © 2015 John Wiley & Sons, Ltd.     

Sulfur and nitrogen co‐doped graphene quantum dot‐assisted chemiluminescence for sensitive detection of tryptophan and mercury (II)

A simple one‐step thermal treatment to prepare strong fluorescent sulfur and nitrogen co‐doped graphene quantum dots (SN‐GQD) using citric acid and l ‐cysteine as precursors was developed. The ultra‐weak chemiluminescence (CL) from the reaction of hydrogen peroxide (H₂O₂) and periodate (IO₄^?) was significantly enhanced by SN‐GQD in acidic medium. The enhanced CL was induced by excited‐state SN‐GQD (SN‐GQD*), which was produced from the transfer energy of (O₂)₂* and ¹O₂ to SN‐GQD and recombination of oxidant‐injected holes and electrons in SN‐GQD. In the presence of tryptophan (Trp), the CL intensity of the SN‐GQD–H₂O₂–KIO₄ system was greatly diminished. This finding was used to design a novel method for determination of Trp in the linear range 0.6–20.0 μM, with a limit of detection (LOD) of 58.0 nM. Furthermore, Hg²⁺ was detectable in the range 0.1–9.0 μM with a LOD of 64.0 nM, based on its marked enhancement of the SN‐GQD–H₂O₂–KIO₄ CL system. The proposed method was successfully applied to detect Trp in milk and human plasma samples and Hg²⁺ in drinking water samples, with recoveries in the range 95.7–107.0%.     

Flow‐injection chemiluminescence of the luminol–potassium periodate system enhanced by TGA–capped CdTe quantum dots for the determination of theophylline

The chemiluminescence (CL) behaviour of the luminol–potassium periodate system enhanced by CdTe quantum dots capped with thioglycolic acid (TGA–CdTe QDs) was studied using kinetic experiments, CL spectra, UV–vis absorption spectra and fluorescence spectra. The production of oxygen‐containing reactant intermediates (O₂^?? and OH^?) in the present CL system was verified by CL. The possible CL mechanism was discussed in detail. Furthermore, theophylline (THP) was determined based on its enhancement of the CL intensity of the CdTe QDs–luminol–potassium periodate system coupled with a flow‐injection technique. Under these optimized conditions, the linear range was found to be from 1.0 × 10^?8 to 1.0 × 10^?5 g/mL with a detection limit of 2.8 × 10^?9 g/mL (3σ). The recoveries for the determination of THP in tablets were from 98.2 to 99.6%.