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We have developed a simple and convenient route to prepare fluorescent carbon dots with dual emission peaks respectively at 470 and 570 nm. The prepared dual-emission carbon dots can be used for ratiometric detection of Fe3+ ions in the range from 0 to 50 μmol·L-1 with 0.8 μmol·L-1 detection limit based on the fluorescence quenching at 570 nm. The quenched fluorescence induced by Fe3+ ions could be recovered by pyrophosphate. We further used the carbon dots-Fe3+ ions-pyrophosphate mixed system for ratiometric detection of acid phosphatase in the range from 0.08 to 6.75 μg·mL-1 with 0.01 μg·mL-1 detection limit. Image 1 • The carbon dots were directly prepared by carbonizing gallic acid and o-phenylenediamine in aqueous solutions. • The carbon dots exhibited dual emission peaks at 470 nm and 570 nm with excitation of 360 nm. • An obvious fluorescence quenching around 570 nm was observed with the addition of Fe3+ in acidic environments. • The GN-CDs can be used as a ratiometric probe for detection of Fe3+ ions and acid phosphatase. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we have developed a simple and rapid method for the detection of Pb2+ based on the DNA sequence capped CdS quantum dots (QDs). We utilized the designed guanine (G)-rich DNA sequence (PS2.M) as a coating reagent to synthesize the DNA-capped CdS QDs. The designed G-rich DNA sequence PS2.M can bind with hemin to form G-quadruplex/hemin complex with K+, accompanied by the fluorescence quenching of CdS QDs via the photoinduced electron transfer. Pb2+ can induce conformational changes in the G-quadruplex/hemin complex to release the hemin molecules, so the quenched fluorescence of CdS QDs could be recovered. Therefore, the new fluorescent analysis system could be applied for the detection of Pb2+ based on the label-free DNA sequence capped CdS QDs. [Copyright &y& Elsevier]

[Display omitted] • The dual emission polymer carbon nanoparticles PDA-OPD were synthesized. • The PDA-OPD exhibited dual emission peaks at 460 nm and 540 nm upon single excitation wavelength. • The PDA-OPD can be used for detection of pH value in the range from 3.0 to 7.4. • The PDA-OPD can be used for detection of bilibrubin in the alkaline environment. Herein, we prepared a novel fluorescent polymer carbon nanoparticles by polymerizing dopamine (DA) and o-phenylenediamine (OPD) through oxidation of hydrogen peroxide. In a neutral environment, the synthesized fluorescent polymer carbon nanoparticles (PDA-OPD) exhibited two emission peaks at 460 nm and 540 nm with 400 nm excitation wavelength. In an acidic environment, the fluorescence emission peaks of PDA-OPD at 540 nm showed an obvious fluorescence quenching, and there existed a good linear relationship between the fluorescence ratio F 540 /F 460 and environment pH value. In an alkaline environment, the fluorescence emission peak at 460 nm showed obvious fluorescence quenching after the addition of bilirubin, while a novel fluorescence emission peak at 560 nm emerged gradually. The PDA-OPD could be also used to detect bilirubin in the range of 0–400 μmol·L−1. [ABSTRACT FROM AUTHOR]

Highlights: [•] The water-soluble CuInS2 QDs was functionalized with dopamine molecules. [•] The fluorescence of the dopamine functionalized CuInS2 QDs was sensitive to pH value changes. [•] Urea would release OH− to change the pH value with urase as the catalyst. [•] The dopamine functionalized CuInS2 QDs could be utilized as a fluorescence probe for urea. [ABSTRACT FROM AUTHOR]

Abstract: A novel sensing strategy for specific recognition of hemoglobin has been designed. In the presence of trypsin, hemoglobin was cleaved to release heme which could effectively bind to a FITC-labeled guanine (G)-rich oligonucleotide sequence to form the G-quadruplex/hemin complex. This binding process would lead to fluorescence quenching of FITC via photoinduced electron transfer. Therefore, a fluorescence assay for the determination of hemoglobin could be established. Under the optimized conditions, there was a linear relationship between the fluorescence intensity of probe DNA and the hemoglobin concentration in the range of 5–200nmol/L, with the limit of detection (LOD) as low as 2nmol/L. [Copyright &y& Elsevier]

Abstract: In this paper, a novel near-infrared fluorescence probe for the determination of 2,4,6-trinitrophenol (TNP) was developed based on bovine serum albumin (BSA) coated CuInS2 quantum dot (QD). Water-soluble CuInS2 QDs were directly synthesized in aqueous solution with mercaptopropionic acid (MPA) as stablizers, and it was coated by BSA via an amide link interacting with carboxyl of the MPA-capped CuInS2 QDs. The obtained BSA coated CuInS2 QDs (BSA-CuInS2 QDs) can bind TNP in water via the acid–base pairing interaction between electron-rich amino groups of BSA and electron-deficient nitroaromatic rings, and leading the fluorescence quenching of BSA-CuInS2 QDs. The quenched fluorescence intensity of BSA-CuInS2 QDs was proportional to the concentration of TNP in the concentration ranges from 50nmol/L to 3.0μmol/L. The detection limit (LOD) for TNP was 28nmol/L. The developed fluorescence probe showed a excellent resistant to interference of metal ions such as K+, Na+, Zn2+, Cu2+, Hg2+, and Pb2+. The developed biosensor was applied to the determination of TNP in spiked water samples with satisfactory results. [Copyright &y& Elsevier]

Abstract: Water-soluble CuInS2 ternary quantum dots (QDs) capped by mercaptopropionic acid were directly synthesized in aqueous solution. Consequently, the CuInS2 QDs were covalently linked to 3-aminophenyl boronic acid molecules to form the 3-aminophenyl boronic acid-functionalized CuInS2 QDs (F-CuInS2 QDs). The F-CuInS2 QDs had a fairly symmetric fluorescence emission centered at 736nm that was in the near-infrared region (NIR). The F-CuInS2 QDs containing boronic acid functional groups were reactive toward vicinal diols to form five- or six-member cyclic esters in an alkaline aqueous solution. The reaction would cause the fluorescence quenching, which could be used as a fluorescence probe for the determination of dopamine (DA). This assay could also probe other vicinal diols such as catechol, pyrogallol, and gallate, based on the fluorescence quenching of the F-CuInS2 QDs, and this assay was nearly unaffected by other phenol compounds such as phenol, resorcinol, and hydroquinone without the vicinal diol structures. The developed F-CuInS2 QDs were applied to the detection of DA in human serum samples with satisfactory results. Therefore, this experment provided a simple and sensitve NIR fluorescence probe for the detection of DA, catechol, pyrogallol, and gallate. [Copyright &y& Elsevier]

Abstract: In this paper, a sensitive and simple method for the determination of melamine (MA) was developed based on the fluorescence changes of the water-soluble CuInS2 quantum dots (QDs). The water-soluble CuInS2 QDs capped by mercaptopropionic acid (MPA) was directly synthesized by hydrothermal method based on our previous report. The fluorescence emission of CuInS2 QDs was quenched by the oxidation of the surface of the QDs with H2O2, and the quenched fluorescence of CuInS2 QDs could be recovered upon the addition of small amounts of MA, which might be due to the surface passivation of the CuInS2 QDs by MA. The other amino acids such as glycine and lysine had no effect on the quenched fluorescence of CuInS2 QDs. Under optimum conditions, there was a good linear relationship between the fluorescence intensity of CuInS2 QDs and the concentration range of MA from 1.0×10−8 to 1.0×10−5 mol/L with a detection limit as low as 5nM. The proposed method was successfully applied to detect trace MA in raw milk with satisfactory results. Compared with previous reports, the proposed method manifested several advantages such as high sensitivity, short analysis time, low cost and ease of operation. [Copyright &y& Elsevier]

In this work, we developed a simple route to synthesize green fluorescence carbon nanoparticles (FCPs) at room temperature with dopamine and p-phenylenediamine as raw materials. The FCPs exhibited a salient fluorescence emission peak at 525 nm and well stability in the intricate surroundings. Only Cu2+ ions could significantly inhibited the fluorescence of FCPs and could be successfully detected in the concentration scope of 0–200 µmol·L−1 based on the fluorescence quenching of FCPs. The Cu2+ ion-quenched fluorescence of FCPs system can be further recovered by the addition of dipicolinic acid (DPA) and could be utilized for DPA detection within the dynamic scope of 10–150 µmol·L−1. [ABSTRACT FROM AUTHOR]

In this paper, bovine serum albumin served as the initial materials for preparing a kind of cyan-emitting fluorescent protein nanoparticles (BSA NPs). The BSA NPs were further adopted as a template to synthesize protein nanoparticles-stabilized silver nanoclusters (BSA NPs@Ag NCs) that offered two well-separated fluorescence emission peaks respectively at 470 nm and 670 nm. Dopamine could specifically induce the fluorescence enhancement at 470 nm and the fluorescence quenching at 670 nm of BSA NPs@Ag NCs. Moreover, cupric ions could cause the fluorescence quenching at 670 nm of BSA NPs@Ag NCs just with a negligible impact on the fluorescence intensity at 470 nm. The BSA NPs@Ag NCs can serve as a ratiometric probe for detection of dopamine and cupric ions. [ABSTRACT FROM AUTHOR]

Determination of iodide ions has attracted considerable interest due to the importance and urgency. In the current work, we have developed a novel fluorescent and colorimetric platform for simple and selective detection of iodide ions based on the DNA-templated gold/silver nanoclusters (DNA-Au/Ag NCs). The detection system is based on the unique interaction between iodide ions and DNA-Au/Ag NCs, which shows an obvious fluorescence quenching with the addition of iodide ions and a good linear range from 0 to 10 μmol/L for iodide ions. In the mean time, the detection system also exhibits an obvious color change from colorless transparent to purple red with the addition of iodide ions. Furthermore, the proposed system has been successfully applied for determination of iodide ions in real water samples. [ABSTRACT FROM AUTHOR]

• A novel and simple approach for the preparation of GSH@CDs-Cu NCs were prepared. • The GSH@CDs-Cu NCs exhibited dual emission peaks at 450 nm and 750 nm under single excitation wavelength. • The dual emissions fluorescence of GSH@CDs-Cu NCs were highly sensitive to pH changes in the range from 6.2–7.0. • Cr 2 O 7 2- and Cd2+ ions can be ratiometric and visual detected based on GSH@CDs-Cu NCs. The pollution of heavy metal increases greatly accompanying by the development of industries. So, it is very important to build up a quick and reliable technique for detection of heavy metal ions. In this work, we developed a simple and convenient method for ratiometric and visual detection of Cr 2 O 7 2- ions and Cd2+ ions. We utilized glutathione as raw material to prepare cyan-emitting carbon dots (GSH@CDs). The GSH@CDs were further used as the template to prepare carbon dots-stabilized copper nanoclusters (GSH@CDs-Cu NCs) that displayed two well-separated emission peaks respectively at 450 nm and 750 nm. The GSH@CDs-Cu NCs can be applied for the ratiometric and visual detection of Cr 2 O 7 2- and Cd2+ ions based on the fluorescence quenching or enhancement of GSH@CDs-Cu NCs at 750 nm. A linear range of 2–40 μmol L-1 with a detection limit of 0.9 μmol L-1 for Cr 2 O 7 2- ions, and a linear range of 0–20 μmol L-1 with a detection limit of 0.6 μmol L-1 for Cd2+ ions were achieved based on this method. The fluorescent test strips for Cr 2 O 7 2- ions were successfully prepared based on GSH@CDs-Cu NCs. Moreover, the GSH@CDs-Cu NCs were successfully applied to determine Cr 2 O 7 2- and Cd2+ ions in real samples with promising results. [ABSTRACT FROM AUTHOR]