Schiff Base-Modified Nanomaterials for Ion Detection: A Review

Ion detection is crucial for environmental quality, human health, and industry development. Schiff bases and their complexes are widely applied as the probes for ion detection in chemistry, environment, and biology fields. There are many kinds of interesting Schiff bases and their coordination complexes that have been designed and synthesized based on the facile synthesis. Recently, Schiff base chemistry has intercrossed with nanomaterials toward wide applications. Nanomaterials are characterized by their sizes in the range of several nanometers to several hundreds of nanometers and then with large specific surface area. They have unusual properties such as mechanical property, optical property, and catalytic property, which are usually not active for their bulk materials. The development of new nanomaterials has dramatically increased in the past two decades, especially the hybridization of inorganic nanomaterials with organic functional species. Schiff base is a very famous class of organic molecules with diversity structures and properties. The remarkable point is that they are synthesized facilely. In this review, the principles and methods of Schiff base preparation have been scanned briefly. Then nanomaterials functionalized by Schiff base to achieve efficient, rapid, and sensitive recognition of ions were elaborated. The types of nanomaterials are included the metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) constructed by Schiff base ligands with nanosized pores and surface modification of nanoparticles (NPs) with Schiff bases, which can not only retain the advantages of the original nanomaterials but also improve the ability of ion-specific recognition. The development of colorimetric, fluorescence, and electrochemical sensors based on Schiff base nanomaterials for ion detection in recent years was carefully summarized as well. It should be mentioned that the types of ions in this review are mainly metal ions. Finally, the challenges in the future in this field have been proposed.