A smartphone-assisted fluorescent sensing platform for ochratoxin A using Mn-doped CsPbBr3 perovskite quantum dots embedded in the mesoporous silica as a ratiometric probe.

Food sources are susceptible to contamination with ochratoxin A (OTA), which is a serious threat to human health. Thus, the construction of novel, simple sensing platforms for OTA monitoring is of utmost need. Manganese-doped lead halide perovskite quantum dots encapsulated with mesoporous SiO2 (Mn-CsPbBr3 QDs@SiO2) were prepared here and used as a ratiometric fluorescent probe for OTA. Mn-CsPbBr3 QDs, synthesized at room temperature, exhibit dual emission with maximum wavelengths of 440 and 570 nm and, when embedded in the SiO2 layer, produce a stable and robust photoluminescence signal. By adding OTA to the probe, emission at 440 nm increases while emission at 570 nm decreases, so a ratiometric response is obtained. Experimental variables affecting the probe signal were studied and optimized and the mechanism of sensing was discussed. This ratiometric sensor demonstrated excellent selectivity and low detection limit (4.1 ng/ml) as well as a wide linear range from 5.0 to 250 ng/ml for OTA. A simple portable smartphone-based device was also constructed and applied for the fluorescence assay. With different OTA concentrations, the multicolor transition from pink to blue under a UV lamp led to simple visual and smartphone-assisted sensing of OTA by using a color analyzing application. Satisfactory recoveries in black tea, coffee, moldy fig and flour samples confirmed the reliability of the assay. The accuracy of the probe was proved by comparison of the results with high-performance liquid chromatography (HPLC).

Detection of Coronavirus Disease 2019 (COVID-19) by TaqMan Real-Time PCR in Iran.

Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is known as a positivesense single-strand RNA virus and leads to Coronavirus disease 2019 (COVID-19). Coronaviruses significantly impact the human respiratory tract. Coronavirus disease is potentially fatal and transmissible in the world. In this study we evaluated the presence or absence of SARS-CoV-2 in 220 patients with un-explained pneumonia by TaqMan real-time PCR assay regarding open reading frame (ORF1ab) and nucleocapsid (N) protein genes. Materials and methods: Totally, 224 patients entered the study. Upper and lower respiratory tract secretion samples were obtained during 2020 from patients. Samples contained nose and throat swabs with viral transport medium. RNA was isolated from clinical samples with the GenePure Plus fully automatic Nucleic Acid Purification System, NPA-32+ (Hangzhou Bioer Technology Co. Ltd, Hangzhou, China). Outcomes: 72.32% of cases were positive for COVID-19. All positive cases had the most common symptoms of illness regarding fatigue, dry cough, dyspnea, headache, abdominal pain, nausa, vomiting and myalgia. Fever was observed in 50% of positive cases. Chest computed tomography (CT) scan of all tested patients indicated two-sided chest involvement. Conclusion:Detection of COVID-19 by TaqMan real-time PCR seems to be a powerful method for the screening and detection of novel corona virus infection.

Nitrogen and copper-doped saffron-based carbon dots: Synthesis, characterization, and cytotoxic effects on human colorectal cancer cells.

AIM: Doped carbon dots (CDs) have attracted tremendous attention in cancer therapy. We aimed to synthesize copper, nitrogen-doped carbon dots (Cu, N-CDs) from saffron and investigated their effects on HCT-116 and HT-29 colorectal cancer (CRC) cells. MAIN METHODS: CDs were synthesized by hydrothermal method and characterized by transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, and fluorescence spectroscopy. HCT-116 and HT-29 cells were incubated with saffron, N-CDs, and Cu, N-CDs for 24 and 48 h for cell viability. Cellular uptake and intracellular reactive oxygen species (ROS) were evaluated by immunofluorescence microscopy. Oil Red O staining was used to monitor lipid accumulation. Apoptosis was evaluated using acridine orange/propidium iodide (AO/PI) staining and quantitative real-time polymerase chain reaction (Q-PCR) assay. The expression of miRNA-182 and miRNA-21 was measured by Q-PCR, while the generation of nitric oxide (NO) and lysyl oxidase (LOX) activity was calculated by colorimetric methods. KEY FINDINGS: CDs were successfully prepared and characterized. Cell viability decreased in the treated cells dose- and time-dependently. HCT-116 and HT-29 cells uptook Cu, N-CDs with a high level of ROS generation. The Oil Red O staining showed lipid accumulation. Concomitant with an up-regulation of apoptotic genes (p < 0.05), AO/PI staining showed increased apoptosis in the treated cells. In comparison to control cells, NO generation, and miRNA-182 and miRNA-21 expression significantly changed in the Cu, N-CDs treated cells (p < 0.05). SIGNIFICANCE: The results indicated that Cu, N-CDs could inhibit CRC cells through the induction of ROS generation and apoptosis.

Perovskite quantum dots as a chemiluminescence platform for highly sensitive assay of cefazolin.

This paper reports on a chemiluminescence (CL) probe consist of CsPbBr3 quantum dots (QDs) in organic phase together with Fe(II) and K2S2O8 in aqueous medium for the highly selective and sensitive determination of the antibiotic, cefazolin (CFZ). The CsPbBr3perovskite QDs prepared by the ligand assisted reprecipitation method, exhibit a narrow fluorescence at 533 nm under 460 nm excitation with a high quantum yield (42 %). The Fe(II) - S2O82- as an ultra-weak CL system is converted to a rather strong CL sensing platform in the presence of organic-phase CsPbBr3 QDs. It was observed that CFZ exerts an enhancement effect on the CL signal of the designed probe in the linear range of 25 - 300 nM, with a low limit of detection (9.6 nM). The introduced sensor has broad application prospects in biosensing, food detection, and other fields with recovery ranging from 94 to 106 %.

Sonochemically synthesized mesoporous cobalt oxide nanoparticles for luminol-enhanced chemiluminescence sensing.

In recent years, mesoporous cobalt oxides have attracted more attention due to their exceptional physical and chemical properties and their important applications in various fields. The synthesis of cobalt oxides of various sizes, morphologies, and porosity is still a challenging process. In this report, mesoporous Co3O4NPs with different porosity were synthesized through facile, one-step, and cost-effective routes, without using any complicated materials or instruments, via the sonochemical process. X-ray powder diffraction (XRD), BET, and transmission electron microscopy (TEM) were used to characterize the as-synthesized NPs. XRD technique was used to determine the crystal structure and phase of the NPs, BET to describe the porous nature of the NPs, and TEM to investigate the structure and morphology of the NPs. Next, the effect of as-synthesized Co3O4NPs as a catalyst for the luminol-H2O2chemiluminescence system was studied. Co3O4NPs were chosen since they have nanoscale size, high specific surface area, and mesoporous nature. Therefore, these NPs can form more active sites and thus show unique catalytic activity than common ionic catalysts such as Co2+, Fe3+, Cu2+used in the luminol-H2O2CL system. Finally, this system was used to detect and measure H2O2and glucose under optimal conditions. A good linear relationship was observed between the chemiluminescence intensity of the designed system and the concentration of H2O2and glucose. A linear range like 0.25-10 pM for H2O2and 1-30 nM for glucose was obtained. The excellent LOD of the proposed method for measuring H2O2was about 0.07 pM, and for measuring glucose was about 0.14 nM.

Sulfur quantum dots as a novel platform to design a sensitive chemiluminescence probe and its application for Pb2+ detection.

The monitoring of Pb as a hazardous heavy metal element for the environment and human health is of high importance. In this study, a simple and sensitive chemiluminescence (CL) probe based on sulfur quantum dots (SQDs) was designed for the determination of Pb2+ . To the best of our knowledge, this is the first report on the analytical application of the CL method based on SQDs. For this purpose, SQDs were synthesized using a simple hydrothermal method and characterized using transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. Then, the direct CL of SQDs elicited by common oxidants was investigated. The highest CL intensity was observed for the SQDs-KMnO4 reaction, and its CL mechanism was studied. We indicated that the CL intensity of introduced system can be diminished as a result of the interaction between Pb2+ and SQDs, and exploited this fact for designing a CL-based probe for the determination of Pb2+ . The CL intensity of the SQDs-KMnO4 reaction was linearly quenched using Pb2+ in the range 50-2000 nM with a limit of detection of 16 nM (S/N = 3). The probe was used for the determination of Pb2+ in different water samples and the recovery results (95.2-102.8%) indicated the good analytical performance of the developed method.

Microwave-assisted facile synthesis of N, P co-doped fluorescent carbon dot probe for the determination of nifedipine.

A simple and fast microwave synthesis method was applied for the preparation of several carbon dots (CDs) from various combinations of urea, phosphoric acid, and B-alanine as nitrogen, phosphorus, and carbon precursors. The maximum quantum yield (44%) was obtained for nitrogen and phosphorus co-doped carbon dots (N, P-CDs) prepared from urea, B-alanine, and phosphoric acid. Furthermore, N, P-CDs were exploited to synthesize a simple and sensitive fluorometric probe to determine nifedipine (NFD). We determined that the analytical response of the designed sensor could be affected by the kind of dopant and synthesis precursors. It is worth mentioning that the fluorescence intensity of N, P-CDs was weakened by NFD, and no fluorescence quenching was observed for other prepared CDs. The NFD-developed sensor demonstrated a linear response range of 3.3 × 10-8-3.2 × 10-5 mol/L, with the detection limit of 1.0 × 10-8 mol/L. The sensor was successfully applied to measure NFD in human biological fluids.

A turn off-on fluorometric and paper-based colorimetric dual-mode sensor for isoniazid detection.

In the present study, cobalt oxyhydroxide (CoOOH) nanosheets were applied for establishing a dual fluorometric and smartphone-paper-based colorimetric method to detect isoniazid. CoOOH nanosheets quenched the fluorescence emission of sulfur and nitrogen co-doped carbon dots (S,N-CDs) due to inner filter effect (IFE). The quenched fluorescence intensity of S,N-CDs restored in the presence of isoniazid due to destroying CoOOH nanosheets by this drug. Moreover, with adding isoniazid the solution color of CoOOH nanosheets altered from brownish yellow to pale yellow. We exploited these facts to design a turn off-on fluorometric and paper-based colorimetric sensor for isoniazid measurement at the range 0.5-5 and 5-100 µM with detection limits of 0.28 µM and 4.0 µM, respectively. The introduced dual sensor was used for pharmaceutical, environmental and biological analysis of isoniazid with satisfactory results. The paper-based colorimetric sensor can be applied for isoniazid portable monitoring using a smartphone as a detector or even the naked eye.

Plasmon-enhanced fluorimetric and colorimetric dual sensor based on fluorescein/Ag nanoprisms for sensitive determination of mancozeb.

A plasmon-enhanced fluorimetric and colorimetric dual sensor was designed to detect mancozeb based on fluorescein (as a fluorimetric reporter) and AgNPRs (as a fluorescence enhancer and colorimetric reporter). The sensing mechanism was based on the shape transformation of AgNPRs due to etching and anti-etching effect of S2O32- and mancozeb. We observed that AgNPRs enhanced the fluorescence intensity of fluorescein around 4-fold. By adding S2O32-, the AgNPR florescence enhancement effect decreased, also SPR peak of AgNPRs blue-shifted and the solution color altered from blue to purple. The fluorescein fluorescence intensity and AgNPR's SPR peak position restored in the presence of mancozeb due to its protecting effect on AgNPRs. The restored fluorescence intensity and the SPR wavelength shift were proportional to the mancozeb concentration at the range of 0.005-0.1 and 0.005-0.075 mg/L, respectively. The developed sensor was successfully applied to measure mancozeb in fruit juice samples.

A sensitive homogeneous enzyme assay for euchromatic histone-lysine-N-methyltransferase 2 (G9a) based on terbium-to-quantum dot time-resolved FRET.

Introduction: Histone modifying enzymes include several classes of enzymes that are responsible for various post-translational modifications of histones such as methylation and acetylation. They are important epigenetic factors, which may involve several diseases and so their assay, as well as screening of their inhibitors, are of great importance. Herein, a bioassay based on terbium-to-quantum dot (Tb-to-QD) time-resolved Förster resonance energy transfer (TR-FRET) was developed for monitoring the activity of G9a, the euchromatic histone-lysine N-methyltransferase 2. Overexpression of G9a has been reported in some cancers such as ovarian carcinoma, lung cancer, multiple myeloma and brain cancer. Thus, inhibition of this enzyme is important for therapeutic purposes. Methods: In this assay, a biotinylated peptide was used as a G9a substrate in conjugation with streptavidin-coated ZnS/CdSe QD as FRET acceptor, and an anti-mark antibody labeled with Tb as a donor. Time-resolved fluorescence was used for measuring FRET ratios. Results: We examined three QDs, with emission wavelengths of 605, 655 and 705 nm, as FRET acceptors and investigated FRET efficiency between the Tb complex and each of them. Since the maximum FRET efficiency was obtained for Tb to QD705 (more than 50%), this pair was exploited for designing the enzyme assay. We showed that the method has excellent sensitivity and selectivity for the determination of G9a at concentrations as low as 20 pM. Furthermore, the designed assay was applied for screening of an enzyme inhibitor, S-(5'-Adenosyl)-L-homocysteine (SAH). Conclusion: It was shown that Tb-to-QD FRET is an outstanding platform for developing a homogenous assay for the G9a enzyme and its inhibitors. The obtained results confirmed that this assay was quite sensitive and could be used in the field of inhibitor screening.

A dual colorimetric and fluorometric sensor based on N, P-CDs and shape transformation of AgNPrs for the determination of 6-mercaptopurine.

In this study, we designed a dual colorimetric and fluorometric sensor by using nitrogen and phosphor doped carbon dots (N, P-CDs) and Ag nanoprisms (AgNPrs) to detect 6-mercaptopurine (6-MP). For this purpose, we applied the AgNPrs/I- mixture to establish a shape transformation based colorimetric method for the detection of 6-MP. The assay mechanism of colorimetric method was based on etching and protecting effect of I- and 6-MP on the AgNPrs. In the presence of I-, as an etching agent, the solution color altered from blue to purple and the position of AgNPrs' local surface plasmon resonance (LSPR) peak shifted to the blue wavelengths. This phenomenon was assigned to the morphological change of AgNPrs. In the presence of 6-MP, AgNPrs were protected from etching by I-, so the LSPR peak position and solution color of AgNPrs remained unchangeable. Furthermore, the fluorescence intensity of N, P-CDs decreased with adding AgNPrs/I- due to the spectral overlap between etched AgNPrs and N, P-CDs. The CDs' quenched fluorescence was restored in the presence of 6-MP, as a result of the protecting effect of 6-MP on the AgNPrs. These facts have been applied to develop a dual sensor for the determination of 6-MP at the range of 10-500 nM and 30-500 nM by colorimetric and fluorometric detection methods. The detection limits were obtained 10 and 4 nM for fluorometric and colorimetric methods, respectively. The developed sensor was utilized for dual signal analysis of 6-MP in human serum samples with satisfactory results.

Doped-carbon dots: Recent advances in their biosensing, bioimaging and therapy applications.

As a fascinating class of fluorescent carbon dots (CDs), doped-CDs are now sparked intense research interest, particularly in the diverse fields of biomedical applications due to their unique advantages, including low toxicity, physicochemical, photostability, excellent biocompatibility, and so on. In this review, we have summarized the most recent developments in the literature regarding the employment of doped-CDs for pharmaceutical and medical applications, which are published over approximately the past five years. Accordingly, we discuss the toxicity and optical properties of these nanomaterials. Beyond the presentation of successful examples of the application of these multifunctional nanoparticles in photothermal therapy, photodynamic therapy, and antibacterial activity, we further highlight their application in the cellular labeling, dual imaging, and in vitro and in vivo bioimaging by use of fluorescent-, photoacoustic-, magnetic-, and computed tomography (CT)-imaging. The potency of doped-CDs was also described in the biosensing of ions, small molecules, and drugs in biological samples or inside the cells. Finally, the advantages, disadvantages, and common limitations of doped-CD technologies are reviewed, along with the future prospects in biomedical research. Therefore, this review provides a concise insight into the current developments and challenges in the field of doped-CDs, especially for biological and biomedical researchers.

A sensitive turn-off-on fluorometric sensor based on S,N co-doped carbon dots for environmental analysis of Hg(II) ion.

A simple and sensitive fluorescence turn-off-on sensor was established by means of S,N co-doped carbon dots (S,N-CDs) and Ag nanoparticles (AgNPs) for the determination of Hg2+ . For this purpose, blue emissive S,N-CDs were hydrothermally synthesized and characterized using transmission electron microscopy, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy. We observed that the fluorescence intensity of the as-prepared S,N-CDs was impressively quenched by AgNPs. The quenching mechanism was studied and attributed to nanosurface energy transfer and the inner filter effect between S,N-CDs and AgNPs. Furthermore, by adding Hg2+ , the fluorescence intensity of S,N-CDs/AgNPs was restored as a result of aggregation of AgNPs in the presence of Hg2+ . Based on these facts, S,N-CDs and AgNPs were exploited to design a sensitive turn-off-on sensor for analysis of Hg2+ . The recovered fluorescence signal was proportional to the concentration of Hg2+ in the range 1.5-2000 nM with a detection limit of 0.51 nM. The established sensor was used with satisfactory results for measurement of Hg2+ in environmental water samples.

Angiotensin-converting enzyme as a new immunologic target for the new SARS-CoV-2.

The coronavirus disease 2019 (COVID-19) pandemic has affected the daily lives of millions of people worldwide and had caused significant mortality; hence, the assessment of therapeutic options is of great interest. The leading cause of death among COVID-19 patients is acute respiratory distress syndrome caused by hyperinflammation secondary to cytokine release syndrome (CRS). Cytokines, such as tumor necrosis factor-α, interleukin-6, interferon-γ and interleukin-10, are the main mediators of CRS. Based on recent evidence, the angiotensin-converting enzyme (ACE) II is known to be the target of the COVID-19 spike protein, which enables the virus to penetrate human cells. ACE II also possesses an anti-inflammatory role in many pathologies such as cardiovascular disease, hypertension, diabetes mellitus and other conditions, which are the main risk factors of poor prognosis in COVID-19 infection. Changes in tissue ACE II levels are associated with many diseases and hyperinflammatory states, and it is assumed that elevated levels of ACE II could aggravate the course of COVID-19 infection. Therefore, the use of renin-angiotensin-aldosterone system inhibitors (RASis) in COVID-19 patients could be hypothetically considered, though sufficient evidence is not presented by the scientific community. In this work, based on the most recent pieces of evidence, the roles of RAS and RASi in immunologic interactions are addressed. Furthermore, the molecular and immunologic aspects of RASi and their potential significance in COVID-19 are discussed.

Inhibition of CD73 using folate targeted nanoparticles carrying anti-CD73 siRNA potentiates anticancer efficacy of Dinaciclib.

Conventional therapeutic methods against cancer, including chemotherapy, radiotherapy, surgery, and combination therapy, have exhibited different toxicity levels due to their unspecific mechanism of action. To overcome the challenges facing conventional cancer therapies, newly developed methods are being investigated. Significant levels of specificity, remarkable accumulation at the tumor site, limited side effects, and minimal off-target effects enable the newly synthesized nanoparticles (NPs) to become the preferred drug delivery method in anticancer therapeutic approaches. According to the literature, CD73 has a pivotal role in cancer progression and resistance to chemotherapy and radiotherapy. Therefore, CD73 has attracted considerable attention among scientists to target this molecule. Accordingly, FDA approved CDK inhibitors such as Dinaciclib that blocks CDK1, 2, 5, and 9, and exhibits significant anticancer activity. So in this study, we intended to simultaneously suppress CD73 and CDKs in cancer cells by using the folic acid (FA)-conjugated chitosan-lactate (CL) NPs loaded with anti-CD73 siRNA and Dinaciclib to control tumor progression and metastasis. The results showed that NPs could effectively transfect cancer cells in a FA receptor-dependent manner leading to suppression of proliferation, survival, migration, and metastatic potential. Moreover, the treatment of tumor-bearing mice with this combination strategy robustly inhibited tumor growth and enhanced survival time in mice. These findings imply the high potential of FA-CL NPs loaded with anti-CD73 siRNA and Dinaciclib for use in cancer treatment shortly.

Terbium-to-quantum dot Förster resonance energy transfer for homogeneous and sensitive detection of histone methyltransferase activity.

The development of rapid, simple, and versatile biosensors for monitoring the activity of histone modifying enzymes (HMEs) is needed for the improvement of diagnostic assays, screening of HME inhibitors, and a better understanding of HME kinetics in different environments. Nanoparticles can play an important role in this regard by improving or complementing currently available enzyme detection technologies. Here, we present the development and application of a homogeneous methyltransferase (SET7/9) assay based on time-gated Förster resonance energy transfer (TG-FRET) between terbium complexes (Tb) and luminescent semiconductor quantum dots (QDs). Specific binding of a Tb-antibody conjugate to a SET7/9-methylated Lys4 on a histone H3(1-21) peptide substrate attached to the QD surface resulted in efficient FRET and provided the mechanism for monitoring the SET7/9 activity. Two common peptide-QD attachment strategies (biotin-streptavidin and polyhistidine-mediated self-assembly), two different QD colors (625 and 705 nm), and enzyme sensing with post- or pre-assembled QD-peptide conjugates demonstrated the broad applicability of this assay design. Limits of detection in the low picomolar concentration range, high selectivity tested against non-specific antibodies, enzymes, and co-factors, determination of the inhibition constants of the SET7/9 inhibitors SAH and (R)-PFI-2, and analysis of the co-factor (SAM) concentration-dependent enzyme kinetics of SET7/9 which followed the Michaelis-Menten model highlighted the excellent performance of this TG-FRET HME activity assay.

A chemiluminescence reaction consisting of manganese(IV), sodium sulfite, and sulfur- and nitrogen-doped carbon quantum dots, and its application for the determination of oxytetracycline.

Sulfur- and nitrogen-doped carbon quantum dots (S,N-CQDs) were prepared by a solid-phase hydrothermal method from cysteine and citric acid and characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and FTIR spectroscopy. These QDs were exploited as enhancers to amplify the chemiluminescence (CL) of manganese(IV)-sodium sulfite reaction. S,N-CQDs exceptionally enhanced the CL intensity of this system, around 900-fold. This effect was attributed to the energy transfer from SO2*, produced by reaction of Mn(IV) with SO32-, to S,N-CQDs. The maximum wavelength of CL emission was 480 nm, which confirmed that the final emitting species was S,N-CQDs. After optimization of reaction conditions, the analytical applicability of S,N-CQD-Mn(IV)-SO32- CL system was studied. In the presence of oxytetracycline, the CL intensity was significantly diminished. A linear relationship was observed between CL signal and the logarithm of oxytetracycline concentration in the range of 0.075-3.0 µM with a detection limit of 25 nM. This CL assay for oxytetracycline was used for analysis of spiked milk and water samples. Graphical abstractSchematic representation of the amplified chemiluminescence (CL) reaction consisting of sulfur- and nitrogen-doped carbon quantum dots (S,N-CQDs) Mn(IV) and Na2SO3. Sub-micromolar levels of oxytetracycline can be determined by using this system.

A sensitive colorimetric probe for detection of 6-thioguanine based on its protective effect on the silver nanoprisms.

In this work a non-aggregated colorimetric probe for detection of chemotherapeutic drug, 6-thioguanine (6-TG), is introduced. It is based on the protective effect of 6-TG on silver nanoprisms (AgNPRs) against the iodide-induced etching reaction. Iodide ions can attack the corners of AgNPRs and etch them, leading to the morphological transition from nanoprisms to nanodiscs. As a consequence, the solution color changes from blue to pink. However, in the presence of 6-TG, due to its protective effect on the corners of AgNPRs, I- ions cannot etch the prisms and the blue color of solution remains unchanged. Using this effect, selective sensor was designed for detection of 6-TG in the range of 2.5-500 µg L-1, with a detection limit of 0.95 µg L-1. Since with varying the concentration of 6-TG in this range, the color variation from pink to blue can be easily observed, the designed sensing scheme can be used as a colorimetric probe. The method was used for analysis of human plasma samples.

An amplified chemiluminescence system based on Si-doped carbon dots for detection of catecholamines.

We report on a chemiluminescence (CL) system based on simultaneous enhancing effect of Si-doped carbon dots (Si-CDs) and cetyltrimethylammonium bromide (CTAB) on HCO3--H2O2 reaction. The possible CL mechanism is investigated and discussed. Excited-state Si-CDs was found to be the final emitting species, which are probably produced via electron and hole injection by oxy-radicals. The effect of several other heteroatom-doped CDs and undoped CDs was also investigated and compared with Si-CDs. Furthermore, it was found that catecholamines such as dopamine, adrenaline and noradrenaline remarkably diminish the CL intensity of Si-CD-HCO3--H2O2-CTAB system. By taking advantage of this fact, a sensitive probe was designed for determination of dopamine, adrenaline and noradrenaline with a limit of detection of 0.07, 0.60 and 0.01 µM, respectively. The method was applied to the determination of catecholamines in human plasma samples.

A novel chemiluminescence sensor for the determination of indomethacin based on sulfur and nitrogen co-doped carbon quantum dot-KMnO4 reaction.

We report on a simple and sensitive sulfur and nitrogen co-doped carbon quantum dot (S,N-CQD)-based chemiluminescence (CL) sensor for the determination of indomethacin. S,N-CQDs were prepared by a hydrothermal method and characterized by fluorescence spectra, Fourier transform infrared spectroscopy and transmission electron microscopy. To obtain the best CL system for determination of indomethacin, the reaction of S,N-CQDs with some common oxidants was studied. Among the tested systems, the S,N-CQD-KMnO4 reaction showed the highest sensitivity for the detection of indomethacin. Under optimum conditions, the calibration plot was linear over a concentration range of 0.1-1.5 mg L-1 , with a limit of detection (3σ) of 65 µg L-1 . The method was applied to the determination of indomethacin in environmental and biological samples with satisfactory results.