Luminescent Hydrogel Based on Silver Nanocluster/Malic Acid and Its Composite Film for Highly Sensitive Detection of Fe3+

Xiangkai Liu,Ning Feng,Xia Xin,Wenjuan Wang,Zhi Wang,Chunhui Li,Na Zhang

doi:10.3390/gels7040192

Xiangkai Liu, Ning Feng + Show 5 more

Open Access

https://doi.org/10.3390/gels7040192

Copy DOI

Abstract

Metal nanoclusters (NCs) with excellent photoluminescence properties are an emerging functional material that have rich physical and chemical properties and broad application prospects. However, it is a challenging problem to construct such materials into complex ordered aggregates and cause aggregation-induced emission (AIE). In this article, we use the supramolecular self-assembly strategy to regulate a water-soluble, atomically precise Ag NCs (NH4)9[Ag9(C7H4SO2)9] (Ag9-NCs, [Ag9(mba)9], H2mba = 2-mercaptobenzoic acid) and L-malic acid (L–MA) to form a phosphorescent hydrogel with stable and bright luminescence, which is ascribed to AIE phenomenon. In this process, the AIE of Ag9-NCs could be attributed to the non-covalent interactions between L–MA and Ag9-NCs, which restrict the intramolecular vibration and rotation of ligands on the periphery of Ag9-NCs, thus inhibiting the ligand-related, non-radiative excited state relaxation and promoting radiation energy transfer. In addition, the fluorescent Ag9-NCs/L–MA xerogel was introduced into polymethylmethacrylate (PMMA) to form an excellently fluorescent film for sensing of Fe3+. Ag9-NCs/L–MA/PMMA film exhibits an excellent ability to recognize Fe3+ ion with high selectivity and a low detection limit of 0.3 μM. This research enriches self-assembly system for enhancing the AIE of metal NCs, and the prepared hybrid films will become good candidates for optical materials.

Highlights

Metal nanoclusters (NCs), such as gold, silver, and copper NCs, represent a class of multifunctional materials with attractive optoelectronic and photoluminescence properties [1,2,3,4,5]
In order to regulate the aggregation behavior and aggregation-induced emission (AIE) of Ag9-NCs, though the non-covalent interaction force dominated by hydrogen bonds, L-malic acid (L–MA) with hydroxyl and carboxyl functional groups is selected as a hydrogen bond donors, and Ag9-NCs, with carboxylate on the periphery, act as hydrogen bond acceptors
This is attributed to the fact that when cAg9-NCs = 8 mM and cL–MA = 0.3 M, Ag9-NCs and L–MA self-assemble to form highly ordered aggregates, and L–MA sufficiently limits the ligands of Ag9-NCs, while when cL–MA is too high or too low, the uniformity of the formed aggregates is poor, and the self-assembly strategy cannot be effectively implemented, which leads to the weakening of fluorescence intensity

Summary

Introduction

Metal nanoclusters (NCs), such as gold, silver, and copper NCs, represent a class of multifunctional materials with attractive optoelectronic and photoluminescence properties [1,2,3,4,5]. It consists of a metal core, composed of several to hundreds of metal atoms and a peripheral organic ligand, forming a unique core-shell structure [6,7,8,9,10].

Results and Discussion

Conclusions

Characterization