Abstract

Fluorescent nanomaterials, such as quantum dots, have developed rapidly in recent years and have been significantly developed. Herein, we demonstrate a facile, one-pot, and in-situ synthesis strategy to obtain fluorescent silver nanoclusters (AgNCs) coated with eight-armed poly (ethylene glycol) polymers (8PEG-AgNCs) via a direct gel-mediated process. During the synthesis, ammonium (NH3) served as the crosslinker for the gel formation via a amine-type Michael addition reaction. This hydrogel can be used as a template to synthesize AgNCs using its volume-limiting effect. The in-situ generation of AgNCs takes place inside the nanocages of the formed gels, which guarantees the homogenous distribution of AgNCs in the gel matrix, as well as the efficient coating of PEG on the nanoclusters. After the degradation of gels, the released 8PEG-AgNCs nanohybrids showed strong blue fluorescence and exhibited long-term stability in aqueous solution for nearly one year. Results showed that the fabricated sensor revealed excellent fluorescent sensitivity for the selective detection of Cu2+ with a detection limit of 50 nM and a wide linear detection range of 5–100 μM. It is proposed that the greater cross-linking density leads to smaller gel pores and allows the synthesis of AgNCs with fluorescent properties. These results indicate that this novel hydrogel with certain biodegradation has the potential to be applied as a fluorescent sensor for catalytic synthesis, fluorescence tracing in cells, and fluorescence detection fields. Meanwhile, the novel design principle has a certain versatility to accelerate the development and application of other kinds of metal nanoclusters and quantum dots.

Highlights

  • In the past few decades, fluorescent metal nanoclusters, consisting of several to a few hundred atoms, have been widely utilized in the fields of biosensing, bioimaging, as well as diagnostics [1,2,3,4,5,6], due to their facile synthesis, strong photoluminescence and high photostability [7,8]

  • This section begins with the properties of the modified 8PEG hydrogels cross-linked with ammonia

  • The basic gelation properties and gelation principles of polyethylene glycol (PEG) hydrogels were initiated to determine the function of eight-armed PEG hydrogels in the process of template synthesis of AgNCs nanomaterials

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Summary

Introduction

In the past few decades, fluorescent metal nanoclusters (usually less than 2 nm in diameter), consisting of several to a few hundred atoms, have been widely utilized in the fields of biosensing, bioimaging, as well as diagnostics [1,2,3,4,5,6], due to their facile synthesis, strong photoluminescence and high photostability [7,8]. AgNCs in aqueous solution are highly susceptible to oxidization, and undergo aggregation to form plasmonic particles at ambient temperatures [12,13,14]. Various additives, such as thiolates [15], dendrimers [16], polymers [17], and some biomolecules, including peptides [18], proteins [19], and DNA [20], have been employed to synthesize and stabilize AgNCs. The use of polyethylene glycol (PEG) long chains [21] or branched chains such as star polymers [22] as templates.

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