Sodium hexametaphosphate modulated fluorescence responsive biosensor based on self-assembly / disassembly mode of reduced-graphene quantum dots / chitosan system for alkaline phosphatase.

Herein, a sodium hexametaphosphate ((NaPO)) modulated fluorescence responsive probe based on the integration of reduced graphene quantum dots (rGQDs) and chitosan (CS) via self-assembly/disassembly for label-free alkaline phosphatase assay was constructed. The cationic-charged CS can couple with anionic rGQDs and quench their fluorescence intensity through electrostatic attraction and structure transformation. This self-assembly system above could be decomposed when (NaPO) present, because (NaPO) could competes with rGQDs for the binding sites on the CS, leading to the disassembly of the rGQDs/CS system, as well as to the system exhibiting a turn-on fluorescence signal.

Graphene quantum dots as selective fluorescence sensor for the detection of ascorbic acid and acid phosphatase via Cr(vi)/Cr(iii)-modulated redox reaction.

A facile and rapid fluorescence assay based on a redox reaction for successively detecting ascorbic acid and acid phosphatase was developed via Cr(vi)-modulated graphene quantum dots (GQDs). Graphene quantum dots with yellow-green emission were first synthesized via a one-pot hydrothermal method. Based on the electrostatic adsorption of Cr on GQDs and the strong chelation between Cr and the -COOH and -OH groups on the surface of GQDs, the fluorescence of GQDs could be greatly quenched by Cr ions.

Multi-positively charged dendrimeric nanoparticles induced fluorescence quenching of graphene quantum dots for heparin and chondroitin sulfate detection.

A label-free fluorescence assay for rapid and sensitive detection of heparin (Hep) or chondroitin sulfate (CS) was developed by guanidine-terminated poly (amidoanime) (PAMAM-Gu(+)) dendrimers induced aggregation of graphene quantum dots (GQDs). The fluorescence of GQDs was obviously quenched after mixing with PAMAM-Gu(+). However, the addition of highly negatively charged Hep or CS into the fluorescence sensing system resulted in the fluorescence recovery.

Dopamine functionalized-CdTe quantum dots as fluorescence probes for l-histidine detection in biological fluids.

In this paper, we developed dopamine functionalized-CdTe quantum dots as fluorescence probes for the determination of l-histidine. Firstly, CdTe was covalently linked to dopamine to form a kind of fluorescence sensor with pyrocatechol structure on the surface. The photoluminescence intensity of CdTe-dopamine (QDs-DA) could be quenched by Ni(2+) due to the strong coordination interaction between the pyrocatechol structure of QDs-DA and Ni(2+).

A label-free fluorescence detection strategy for lysozyme assay using CuInS₂ quantum dots.

We have developed a simple and efficient fluorescence detection system for lysozyme utilizing I-III-VI type Cu-In-S ternary quantum dots (CuInS2 QDs) as the probe. Water-soluble near-infrared CuInS2 QDs capped with 3-mercaptopropionic acid were directly synthesized by using a hydrothermal method. Poly(dimethyl diallyl ammonium chloride), as a cationic polyelectrolyte, could bind to 3-mercaptopropionic acid-capped CuInS2 QDs via electrostatic interactions that would lead to fluorescence quenching of CuInS2 QDs.

Bovine serum albumin coated CuInS2 quantum dots as a near-infrared fluorescence probe for 2,4,6-trinitrophenol detection.

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.

Tyrosine-functionalized CuInS2 quantum dots as a fluorescence probe for the determination of biothiols, histidine and threonine.

A novel, rapid and highly sensitive fluorescence turn-on assay for the detection of biothiols (glutathione, and L-cysteine), histidine and threonine was developed. Water-soluble CuInS2 ternary quantum dots (QDs) capped by mercaptopropionic acid (MPA) were directly synthesized in aqueous solution, and then functionalized using tyrosine molecules to form tyrosine-functionalized CuInS2 QDs (T-CuInS2 QDs). The fluorescence of T-CuInS2 QDs would decrease in the presence of Cu(2+) due to the coordination effect of phenolic hydroxyls of the tyrosine molecules.

3-Aminophenyl boronic acid-functionalized CuInS2 quantum dots as a near-infrared fluorescence probe for the determination of dopamine.

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).

Determination of catecholamine in human serum by a fluorescent quenching method based on a water-soluble fluorescent conjugated polymer-enzyme hybrid system.

In this paper, a sensitive water-soluble fluorescent conjugated polymer biosensor for catecholamine (dopamine DA, adrenaline AD and norepinephrine NE) was developed. In the presence of horse radish peroxidase (HRP) and H(2)O(2), catecholamine could be oxidized and the oxidation product of catecholamine could quench the photoluminescence (PL) intensity of poly(2,5-bis(3-sulfonatopropoxy)-1,4-phenylethynylenealt-1,4-poly(phenylene ethynylene)) (PPESO(3)). The quenching PL intensity of PPESO(3) (I(0)/I) was proportional to the concentration of DA, AD and NE in the concentration ranges of 5.