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.     

A novel chemiluminescent flow injection analysis of trace amounts of rutin by its inhibition of the luminol–hydrogen peroxide reaction catalyzed by tetrasulfonated colbalt phthalocyanine

Based on the inhibition effect of rutin on the luminol–hydrogen peroxide chemiluminescence (CL) system catalyzed by tetrasulfonated colbalt phthalocyanine (CoTSPc), a sensitive flow‐injection CL method has been developed for the determination of rutin. The CL reaction mechanism was carefully investigated by examining CL emission spectra, UV–visible spectra and variation of reaction conditions. It was found that there existed a linear relationship between CL intensity and the concentration of rutin in the range of 8.0 × 10^?9 to 1.0 × 10^?6 mol L^?1, and the detection limit is 3.8 × 10^?9 mol L^?1. This proposed method is sensitive, convenient and simple, and has been applied to the determination of rutin in commercial rutin tablets with satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd.     

Chemiluminescence detection of trace iodide with flow injection analysis of KMnO4‐carbon dots system

Ultra‐weak chemiluminescence (CL) from the reaction of iodide and KMnO₄ was strongly enhanced by carbon nanodots (CNDs) in an acidic medium. The CL intensity was directly proportional to the concentration of iodide in the solution. Therefore, a flow‐injection CL system with high sensitivity, selectivity and reproducibility is proposed for the determination of iodide. The proposed method exhibited advantages over a linear range of 3.0 × 10^?6–1.0 × 10^?4 mol/L and had a detection limit of 3.5 × 10^?7 mol/L. The method was successfully applied to the evaluation of iodide in food samples with recoveries of between 96 and 103%. The relative standard deviations were 2.1 and 4.1% for intra‐ and inter‐assay precision, respectively.     

Perturbation of the tris(2,2′‐bipyridine) ruthenium(II)‐catalyzed Belousov–Zhabotinsky oscillating chemiluminescence reaction by l‐cysteine and its application

Perturbation of the tris(2,2′‐bipyridine)ruthenium(II) [Ru(bpy)₃²⁺]‐catalyzed Belousov–Zhabotinsky (BZ) oscillating chemiluminescence (CL) reaction induced by l ‐cysteine was observed in the closed system. It was found that the CL intensity was decreased in the presence of l ‐cysteine. Meanwhile, oscillation period and oscillating induction period were prolonged. The sufficient reproducible induction period was used as parameter for the analytical application of oscillating CL reaction. Under the optimum conditions, the changes in the oscillating CL induction period were linearly proportional to the concentration of l ‐cysteine in the range from 8.0 × 10^?7 to 5.0 × 10^?5 mol L^?1 (r = 0.997) with a detection limit of 4.3 × 10^?7 mol L^?1. The possible mechanism of l ‐cysteine perturbation on the oscillating CL reaction was also discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

The behaviors of metal ions in the CdTe quantum dots–H2O2 chemiluminescence reaction and its sensing application

The behaviors of 15 kinds of metal ions in the thiol‐capped CdTe quantum dots (QDs)–H₂O₂ chemiluminescence (CL) reaction were investigated in detail. The results showed that Ag⁺, Cu²⁺ and Hg²⁺ could inhibit CdTe QDs and H₂O₂ CL reaction. A novel CL method for the selective determination of Ag⁺, Cu²⁺ and Hg²⁺ was developed, based on their inhibition of the reaction of CdTe QDs and H₂O₂. Under the optimal conditions, good linear relationships were realized between the CL intensity and the logarithm of concentrations of Ag⁺, Cu²⁺ and Hg²⁺. The linear ranges were from 2.0 × 10^?6 to 5.0 × 10^?8 mol L^?1 for Ag⁺, from 5.0 × 10^?6 to 7.0 × 10^?8 mol L^?1 for Cu²⁺ and from 2.0 × 10^?5 to 1.0 × 10^?7 mol L^?1 for Hg²⁺, respectively. The limits of detection (S/N = 3) were 3.0 × 10^?8, 4.0 × 10^?8 and 6.7 × 10^?8 mol L^?1 for Ag⁺, Cu²⁺ and Hg²⁺, respectively. A possible mechanism for the inhibition of CdTe QDs and H₂O₂ CL reaction was also discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Interaction of glucose‐derived carbon quantum dots with silver and gold nanoparticles and its application for the fluorescence detection of 6‐thioguanine

The interaction of glucose‐derived carbon quantum dots (CQDs) with silver (Ag) and gold (Au) nanoparticles (NPs) was explored by fluorescence spectroscopy. Both metal NPs cause an efficient quenching of CQD fluorescence, which is likely due to the energy transfer process between CQDs as donors and metal NPs as acceptors. The Stern–Volmer plots were evaluated and corresponding quenching constants were found to be 1.9 × 10¹⁰ and 2.2 × 10⁸ M^?1 for AgNPs and AuNPs, respectively. The analytical applicability of these systems was demonstrated for turn‐on fluorescence detection of the anti‐cancer drug, 6‐thioguanine. Because the CQD–AgNP system had much higher sensitivity than the CQD–AuNP system, we used it as a selective fluorescence probe in a turn‐on assay of 6‐thioguanine. Under optimum conditions, the calibration graph was linear from 0.03 to 1.0 μM with a detection limit of 0.01 μM. The developed method was applied to the analysis of human plasma samples with satisfactory results.     

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.     

A novel method for sensing of methimazole using gold nanoparticle‐catalyzed chemiluminescent reaction

Based on the inhibition effect of methimazole (MMI) on the reaction of luminol–H₂O₂ catalyzed by gold nanoparticles, a novel chemiluminescence (CL) method was developed for the determination of MMI. Under the optimum conditions, the relative CL intensity was linearly related to MMI concentration in the range from 5.0 × 10^?8 to 5.0 × 10^?5 mol L^?1. The detection limit was 1.6 × 10^?8 mol L^?1 (S/N = 3), and the RSD for 6.0 × 10^?6 mol L^?1 MMI was 4.83 (n = 11). This method has high sensitivity, wide linear range, inexpensive instrumentation and has been applied to detect MMI in pharmaceutical tablets and pig serum samples. Furthermore, a possible reaction mechanism is discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

New luminol chemiluminescence reaction using diperiodatoargentate as oxidate for the determination of amikacin sulfate

A new chemiluminescence (CL) reaction between luminol and diperiodatoargentate {K₂ [Ag (H₂IO₆) (OH) ₂]} was observed in alkaline medium. The CL intensity could be greatly enhanced by amikacin sulfate. Therefore a new CL method for the determination of amikacin sulfate was built by combining with flow injection technology. A possible mechanism of the CL reaction was proposed via the investigation of the CL kinetic characteristics, the CL spectrum and the UV absorption spectra of some related substance. The concentration range of linear response was 5.1 × 10^?8 to 5.1 × 10^?6 mol L^?1 with a detection limit of 1.9 × 10^?8 mol L^?1 (3σ). The proposed method had good reproducibility with a relative standard deviation of 2.8% (n = 7) for 5.1 × 10^?7 mol L^?1 of amikacin sulfate. It was successfully applied to determine amikacin sulfate in serum. Copyright © 2009 John Wiley & Sons, Ltd.     

Multiway analysis applied to time‐resolved chemiluminescence for simultaneous determination of paracetamol and codeine in pharmaceuticals

This method is based on the enhancing effect of codeine (COD) and paracetamol (PAR) on the chemiluminescence (CL) reaction of Ru(phen)₃²⁺ with Ce(IV). In the batch mode, COD gives a relatively sharp peak with the highest CL intensity at 4.0 s, whereas the maximum CL intensity of the PAR appears at ~60 s after injection of Ce(IV) solution. Whole CL time profiles allowed use of the time‐resolved CL data in combination with multiway calibration techniques, as multiway partial least squares (N‐PLS), for the quantitative determination of both COD and PAR in binary mixtures. In this work, we found that the impact of Ce(IV) concentration on the CL intensity was different for COD and PAR. Therefore, a Ce(IV) concentration mode was added to the time and sample modes to obtain 3D data. The percent relative standard deviation (%RSD) values for 10 determinations of 1.0 × 10^?5 mol/L of COD and 1.0 × 10^?4 mol/L of PAR were 6.1% and 8.7%, respectively. The limit of detection (LOD) values (S/N = 3) were 0.9 × 10^?8 mol/L and 1.0 × 10^?6 mol/L for COD and PAR, respectively. The proposed method was successfully applied to the determination of PAR and COD in commercial pharmaceutical formulations. Acceptable recoveries (90–110%) were obtained for the quantification of these drugs in the real samples. Copyright © 2016 John Wiley & Sons, Ltd.     

DPPH·–luminol chemiluminescence system and its application in the determination of scutellarin in pharmaceutical injections and rat plasma with flow injection analysis

In this article, a DPPH·–luminol chemiluminescence (CL) system was reported and the CL mechanism was discussed according to the CL kinetic properties after sequence injecting DPPH· into the DPPH·–luminol reaction mixture. It was observed that scutellarin could inhibit the CL response of the DPPH·–luminol system. Based on this observation, a simple and rapid flow injection CL method was developed for the determination of scutellarin using the inhibition effect in alkaline medium. The optimized chemical conditions for the CL reaction were 5 × 10^?6 mol/L DPPH · and 1.0 × 10^?4 mol/L luminol in 0.01 mol/L NaOH. Under optimized conditions, the CL intensity was inversely proportional to the concentration of scutellarin over the ranges 5–2000 and 40–3200 ng/ml in pharmaceutical injection and rat plasma, respectively. The limits of detection (S/N  = 3) were 5 and 40 ng/ml in preparations and rat plasma, respectively. Furthermore, the precision, recovery and stability of the validated method were acceptable for the determination of scutellarin in both pharmaceutical injections and rat plasma. The presented method was successfully applied in the determination of scutellarin in pharmaceutical injections and real rat plasma samples.     

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

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

Flow‐injection chemiluminescence method for the determination of naphazoline hydrochloride and oxymetazoline hydrochloride

A sensitive and simple flow‐injection chemiluminescence (FI‐CL) method, which was based on the CL intensity generated from the redoxreaction of potassium permanganate (KMnO₄)–formaldehyde in vitriol (H₂SO₄) medium, has been developed, validated and applied for the determination of naphazoline hydrochloride and oxymetazoline hydrochloride. Besides oxidants and sensitizers, the effect of the concentration of H₂SO₄, KMnO₄ and formaldehyde was investigated. Under the optimum conditions, the linear range was 1.0 × 10^?2–7.0 mg/L for naphazoline hydrochloride and 5.0 × 10^?2–10.0 mg/L for oxymetazoline hydrochloride. During seven repeated inter‐day and intra‐day precision tests of 0.1, 1.0 and 10.0 mg/L samples, the relative standard deviations all corresponded to reference values. The detection limit was 8.69 × 10^?3 mg/L for naphazoline hydrochloride and 3.47 × 10^?2 mg/L for oxymetazoline hydrochloride (signal‐to‐noise ratio ≤3). This method has been successfully implemented for the determination of naphazoline hydrochloride and oxymetazoline hydrochloride in pharmaceuticals. Copyright © 2009 John Wiley & Sons, Ltd.     

Determination of trace amounts of dopamine by flow‐injection analysis coupled with luminol–Ag(III) complex chemiluminescence detection

A novel flow injection analysis‐direct chemiluminescence (FI‐CL) method has been developed for determination of trace amounts of dopamine (DA) based on the enhancing effect of DA on the CL reaction of luminol with an Ag(III) complex in alkaline solution. Under optimum conditions, CL intensities are proportional to the concentration of DA in the range of 1.0 × 10^?10 to 4.0 × 10^?8 mol L^?1. The detection limit is 3.0 × 10^?11 mol L^?1 for DA (3s), with a relative standard deviation (n = 13) of 2.3% for 1.0 × 10^?8 mol L^?1 DA. This method has also been applied for the determination of DA in commercial pharmaceutical injection samples. On the basis of the CL spectra and the results of the free‐radical trapping experiment of this work, a reaction mechanism for this CL reaction is proposed and discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation and application of solvent‐modulated self‐doped N–S multicolour fluorescence carbon quantum dots

In this paper, two types of carbon quantum dot (CQDs) were prepared using biocompatible l ‐methionine as the carbon source and urea as the nitrogen source and a one‐step hydrothermal treatment. By changing the reaction solvents (deionized (DI) water and dimethylformamide (DMF)), the maximum emission of the resulting CQDs shifted from blue to red light. Specifically, the emission wavelength of the CQDs moved from 433 nm to 625 nm following embedding of a new functional group (–CONH–) on the surface of the CQDs. Photoluminescence quantum yields of the CQDs with blue and red emission reached 64% and 61%, respectively. The R‐CQDs were used to detect metal ions and a linear relationship was demonstrated between ln(F/F₀) and Fe³⁺ concentration in the range 0–0.5 mmol/L with a detection limit of 0.067 μM. Therefore these R‐CQDs have great potential as fluorescent probes for Fe³⁺ detection. We expect that the excellent water‐soluble, biocompatible and optical properties of the CQDs developed in this work mean that they will be widely used to detect biological cells.     

Chemiluminescence determination of naproxen based on europium(III)‐sensitized KIO4–H2O2 reaction

A simple and sensitive chemiluminescence (CL) method combined with flow injection technique was developed for the determination of naproxen. It was based upon the weak CL signal arising from the reaction of KIO₄ with H₂O₂ being significantly increased by naproxen in the presence of europium(III) ion. The experimental conditions that affected the CL signal were carefully optimized and the CL reaction mechanism was briefly discussed. Under the optimum conditions, the increment of CL intensity was proportional to the concentration of naproxen ranging from 5.0 × 10^?8 to 5.0 × 10^?6 g/mL. The detection limit was 1 × 10^?8 g/mL naproxen and the relative standard deviation for 5.0 × 10^?7 g/mL naproxen solution was 2.1% (n = 11). The proposed method was applied to the determination of naproxen in tablets and in spiked human urine samples with satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd.     

Development of chemiluminescence method for determination of 10‐hydroxycamptothecin based on luminol–[Ag(HIO6)2]5− reaction in alkaline solution

A novel chemiluminescence (CL) method was developed for the determination of 10‐hydroxycamptothecin(HCPT) based on the CL reaction between [Ag(HIO₆)₂]^5? and luminol in alkaline solution. CL emission of Ag(III) complex–luminol in alkaline medium was very different from that in acidic medium. A possible mechanism of enhanced CL emission was suggested. The enhanced effect of HCPT on CL emission of the [Ag(HIO₆)₂]^5?–luminol system was found. The enhanced degree of CL emission was proportional to HCPT concentration. The effect of the reaction conditions on CL emission was examined. Under optimal conditions, the limit of detection was 6.5 × 10^?9 g mL^?1. The proposed method was applied for the determination of HCPT in real samples with the recoveries of 93.2–109% with the RSD of 1.7–3.3%. Copyright © 2010 John Wiley & Sons, Ltd.     

Simple chemiluminescence determination of ketotifen using tris(1,10 phenanthroline)ruthenium(II)‐ Ce(IV) system

A new method using chemiluminescence (CL) detection has been developed for the simple determination of ketotifen fumarate (KF). The method is based on the catalytic effect of KF in the CL reaction of tris(1,10 phenanthroline)ruthenium(II), Ru(phen)₃²⁺, with Ce(IV) in sulfuric acid medium. The CL response was detected using a lab‐made chemiluminometer. Effects of chemical variables were investigated and under optimum conditions, the CL intensity was proportional to the concentration of the drug over the range 0.34‐34.00 µg mL^?1 KF. The limit of detection (S/N=3) was 0.09 µg mL^?1. Effects of common ingredients were investigated and the method was applied successfully for determining KF in pharmaceutical formulations and human plasma. The percent of relative standard deviation (n=11) at level of 3.4 µg mL^?1 of KF was 4.6% and the minimum sampling rate was 70 samples per hour. The possible CL mechanism is proposed based on the kinetic characteristic of the CL reaction, CL spectrum, UV‐Vis and phosphorescence spectra. Copyright © 2015 John Wiley & Sons, Ltd.     

Highly Passivated n‐Type Colloidal Quantum Dots for Solution‐Processed Thermoelectric Generators with Large Output Voltage

Colloidal quantum dots (CQDs) are attractive materials for thermoelectric applications due to their simple and low‐cost processing; advantageously, they also offer low thermal conductivity and high Seebeck coefficient. To date, the majority of CQD thermoelectric films reported upon have been p‐type, while only a few reports are available on n‐type films. High‐performing n‐ and p‐type films are essential for thermoelectric generators (TEGs) with large output voltage and power. Here, high‐thermoelectric‐performance n‐type CQD films are reported and showcased in high‐performance all‐CQD TEGs. By engineering the electronic coupling in the films, a thorough removal of insulating ligands is achieved and this is combined with excellent surface trap passivation. This enables a high thermoelectric power factor of 24 µW m^?1 K^?2, superior to previously reported n‐type lead chalcogenide CQD films operating near room temperature (<1 µW m^?1 K^?2). As a result, an all‐CQD film TEG with a large output voltage of 0.25 V and a power density of 0.63 W m^?2 at ?T = 50 K is demonstrated, which represents an over fourfold enhancement to previously reported p‐type only CQD TEGs.     

Highly luminescent nitrogen‐doped carbon dots for simultaneous determination of chlortetracycline and sulfasalazine

Here, we have presented a green and facile strategy to fabricate nitrogen‐doped carbon dots (N‐CDs) and their applications for determination of chlortetracycline (CTC) and sulfasalazine (SSZ). The fluorescent N‐CDs, prepared by one‐step hydrothermal reaction of citric acid and l ‐arginine, manifested numerous excellent features containing strong blue fluorescence, good water‐solubility, narrow size distribution, and a high fluorescence quantum yield (QY) of 38.8%. Based on the fluorescence quenching effects, the as‐synthesized N‐CDs as a fluorescent nanosensor exhibited superior analytical performances for quantifying CTC and SSZ. The linear range for CTC was calculated to be from 0.85 to 20.38 μg ml^?1 with a low detection limit of 0.078 μg ml^?1. Meanwhile, the linear range for SSZ was estimated to be from 0.34 to 6.76 μg ml^?1 with a low detection limit of 0.032 μg ml^?1. Therefore, the N‐CDs hold admirable application potential for constructing a fluorescent sensor for pharmaceutical analysis.