Sensitive and selective determination of aloin with highly stable histidine-capped silver nanoclusters based on the inner filter effect

Aloin is a natural medicine, which possesses the functions of enhancing immune function, anti-tumour, detoxification, anti-bacterial, anti-stomach damage, liver protection and skin protection. Excessive use will cause side effects. Thus, sensitive aloin determination is very necessary in daily life. As far as we know, there are rare reports about aloin sensing through fluorescent methods. In this work, a simple method for the synthesis of fluorescence silver nanoclusters (Ag NCs) was demonstrated by using histidine (His) as the templating agent and ascorbic acid as the reducer. The as-prepared silver nanoclusters (Ag NCs@His) possessed excellent water solubility and dispersion. Detailed research illustrated that the FL intensities of Ag NCs@His were linearly quenched in the presence of aloin (varying from 0.5 to 200 µM). The corresponding detection limit reached 0.052 µM. The static quenching and inner filter effect were the main fluorescence quenching mechanisms. This fluorescent sensor has been successfully employed for the detection of aloin in natural samples.