Metal nanoclusters: New fluorescent probes for sensors and bioimaging

We report a facile green approach for in situ growth of silver nanoparticles (AgNPs) on the surface of graphene quantum dots (GQDs). GQDs serve as both reducing agent and stabilizer, and no additional reducing agent and stabilizer is necessary. The GQDs/AgNPs hybrid exhibits a superior absorbance fading response toward the reduction of H2O2. A simple colorimetric procedure is thus proposed for ultrasensitive detection of H2O2 without additional chromogenic agent. It provides a record detection limit of 33 nM for the detection of H2O2 by the AgNPs-based sensing system. This colorimetric sensing system is further extended to the detection of glucose in combination with the specific catalytic effect of glucose oxidase for the oxidation of glucose and formation of H2O2, giving rise to a detection limit of 170 nM. The favorable performances of the GQDs/AgNPs hybrid are due to the peroxidase-like activity of GQDs.

In Situ Growth of Silver Nanoparticles on Graphene Quantum Dots for Ultrasensitive Colorimetric Detection of H2O2 and Glucose

Metal nanoclusters (NCs) are emerging as a new class of functional nanomaterials in the area of biological sensing, labelling, imaging and therapy due to their unique physical and chemical properties, such as ultrasmall size, HOMO–LUMO transition, strong luminescence together with good photostability and biocompatibility. A recent surge of interest in this field is the surface functionalization of these metal NCs through which one can tailor their physicochemical properties, such as stability in solution, and strong luminescence, as well as their biodistribution and toxicity in biological systems, which in turn can empower these functionalized NCs with desirable targeting, imaging, and therapeutic ability for biomedical applications. In this review, we first introduce the functionalization strategies for the metal NCs developed in the past few years, followed by highlighting some biomedical applications of these functionalized metal NCs. We then discuss the difference of in vitro and in vivo fate as well as toxicity between various functionalized metal NCs. Finally, we present a short discussion on the current challenges and provide an outlook of the future developments of these functional metal NCs.

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Functionalization of metal nanoclusters for biomedical applications

A fluorescent biosensor based on carbon dots-labeled oligodeoxyribonucleotide and graphene oxide for mercury (II) detection

We report a graphene oxide (GO)-based fluorescent sensor for Hg2+ detection in aqueous solutions by using hybridization chain reactions (HCRs). GO is used as an adsorption material for capturing single-stranded DNA and an efficient fluorescence quencher for reducing the background signal. In the detection strategy, two hairpin probes and a helper DNA are employed. Without Hg2+, they are adsorbed by the GO and the fluorescence of one of the hairpin probes is quenched. In the presence of Hg2+, the HCRs between the two hairpin probes are initiated by Hg2+ with the aid of the helper DNA through T-Hg2+-T coordination chemistry. The double-stranded DNA products of the HCRs are released by the GO and the fluorescence is recovered. The detection limit of the sensing method is 0.3 nM, which is sufficiently sensitive for practical applications. The sensing system also exhibits high selectivity against other divalent metal ions, and the application of the sensor for drinking water shows that the proposed method work...

Graphene Oxide-Based Amplified Fluorescent Biosensor for Hg2+ Detection through Hybridization Chain Reactions

A facile, sensitive, and rapid spectrophotometric method for copper(II) ion detection in aqueous media using polyethyleneimine

Polyethyleneimine-capped silver nanoclusters as a fluorescence probe for sensitive detection of hydrogen peroxide and glucose

Fluorescent detection of hydrogen peroxide and glucose with polyethyleneimine-templated Cu nanoclusters

Coupling T base with Hg2+ to form stable T–Hg2+–T complexes represents a new direction in detection of Hg2+ Here a graphene oxide (GO)-based fluorescence Hg2+ analysis using DNA duplexes of poly(dT) that allows rapid, sensitive, and selective detection is first reported The Hg2+-induced T15–(Hg2+)n–T15 duplexes make T15 unable to hybridize with its complementary A15 labelled with 6′-carboxyfluorescein (FAM-A15), which has low fluorescence in the presence of GO On the contrary, when T15 hybridizes with FAM-A15 to form double-stranded DNA because of the absence of Hg2+, the fluorescence largely remains in the presence of GO A linear range from 10 nM to 20 μM (R2 = 09963) and a detection limit of 05 nM for Hg2+ were obtained under optimal experimental conditions Other metal ions, such as Al3+, Ag+, Ca2+, Ba2+, Mg2+, Zn2+, Mn2+, Co2+, Pb2+, Ni2+, Cu2+, Cd2+, Cr3+, Fe2+, and Fe3+, had no significant effect on Hg2+ detection Moreover, the sensing system was used for the determination of Hg2+ in river water samples with satisfactory results

Highly sensitive, selective, and rapid fluorescence Hg2+ sensor based on DNA duplexes of poly(dT) and graphene oxide.

A novel sensing system has been designed for the detection of sodium dodecyl sulfate (SDS) based on the recovered fluorescence signal of eosin Y and polyethyleneimine (PEI) complex. The eosin Y reacted with PEI to form a complex by virtue of hydrophobic interaction as well as the electrostatic interaction, which resulted in a strong fluorescence quenching of the eosin Y. Subsequently, with the addition of SDS to the eosin Y/PEI system, a strong surface interaction and electrostatic interactions between PEI and SDS resulted in the formation of the PEI/SDS complex and the dissociation of the eosin Y/PEI complex, which led to the significant fluorescence recovery. Herein, we have demonstrated that this facile methodology can offer a rapid, reliable, and selective detection of SDS with a detection limit as low as 0.02 μg mL–1 and a linear range from 0.4 to 6 μg mL–1. Furthermore, the method has been successfully applied to the detection of SDS in real samples with satisfied recovery and accuracy. Overall, the...

Ting Wen

Papers

A facile, sensitive, and rapid spectrophotometric method for copper(II) ion detection in aqueous media using polyethyleneimine

Polyethyleneimine-capped silver nanoclusters as a fluorescence probe for sensitive detection of hydrogen peroxide and glucose

Fluorescent detection of hydrogen peroxide and glucose with polyethyleneimine-templated Cu nanoclusters

Highly sensitive, selective, and rapid fluorescence Hg2+ sensor based on DNA duplexes of poly(dT) and graphene oxide.

A turn-on fluorescent sensor for sensitive and selective detection of sodium dodecyl sulfate based on the eosin Y/polyethyleneimine system.