Gold Nanorods as Visual Sensing Platform for Chiral Recognition with Naked Eyes

Yanwei Wang,Baoxin Li,Xiaojuan Zhou,Yan Jin,Chunli Xu

doi:10.1038/s41598-018-23674-y

Abstract

Chirality plays a key role in modern science and technology. Here, we report a simple and effective sensing platform for visual chiral recognition of enantiomers. In this sensing platform, gold nanorods (AuNRs) prepared through a common synthesis route are used as colorimetric probes for visual recognition of glutamine (Gln) enantiomers. D-Gln could rapidly induce the aggregation of AuNRs, thereby resulting in appreciable blue-to-gray color change of AuNRs solution; however, L-Gln could not induce color change of AuNRs. This distinct color change can be easily distinguished by the naked eyes; as a result, a visual method of chiral recognition was suggested. The method was applied to determine the enantiometric excess of D-Gln through the whole range of −100% ~ 100%. The chiral assay can be performed with a simple UV-vis spectrometer or the naked eyes. Notably, the AuNRs do not need any chiral labeling or modification, and the chiral recognition is based on the inherent chirality of AuNRs. This chiral assay method is simple, sensitive, cheap and easy to operate. This study is the first example using AuNRs for direct visual recognition of enantiomers, and will open new opportunity to construct more chiral recognition methods for some important compounds.

Highlights

Chirality is an intriguing natural phenomenon, and is one of the basic characteristics of life system[1,2,3]
In most of the reported AuNPs/AgNPs-based chiral recognition systems, the chirality of metal nanoparticles originated from the chiral ligands
The results showed that D-Gln rapidly induced the aggregation of AuNRs, and ΔA620 of the system reached a maximum after 9 min incubation time

Summary

Introduction

Chirality is an intriguing natural phenomenon, and is one of the basic characteristics of life system[1,2,3]. In AuNPs/ AgNPs-based colorimetric assay, target can induce the obvious color changes of AuNPs or AgNPs solution, which is easy to be detected even by naked eyes. Glutamine (Gln), an essential and important amino acid[42], was chosen as model chiral molecule to evaluate the colorimetric discrimination enantiomers of AuNRs. Without any pre-treatment and prior derivatization, L- and D-Gln, respectively, was directly added into AuNRs solution. The color change of AuNRs solution was used to recognize the chirality of Gln with the naked eyes. In this method, AuNRs don’t need any modifying with chiral compounds, and the inherent chirality of AuNRs is utilized. This study will help people to understand the chirality of nanostructures[43]

Methods

Results

Discussion

Conclusion