Colourimetric and fluorimetric metal ion chemosensor based on a benzimidazole functionalised Schiff base

Stöber method to amorphous metal-organic frameworks and coordination polymers

The Stöber method is a widely-used sol-gel route for synthesizing amorphous SiO2 colloids and conformal coatings. However, the material systems compatible with this method are still limited. Herein, we have extended the approach to metal-organic frameworks (MOFs) and coordination polymers (CPs) by mimicking the Stöber method. We introduce a general synthesis route to amorphous MOFs or CPs by making use of a base-vapor diffusion method, which allows to precisely control the growth kinetics. Twenty-four different amorphous CPs colloids were successfully synthesized by selecting 12 metal ions and 17 organic ligands. Moreover, by introducing functional nanoparticles (NPs), a conformal amorphous MOFs coating with controllable thickness can be grown on NPs to form core-shell colloids. The versatility of this amorphous coating technology was demonstrated by synthesizing over 100 core-shell composites from 20 amorphous CPs shells and over 30 different NPs. Besides, various multifunctional nanostructures, such as conformal yolk-amorphous MOF shell, core@metal oxides, and core@carbon, can be obtained through one-step transformation of the core@amorphous MOFs. This work significantly enriches the Stöber method and introduces a platform, enabling the systematic design of colloids exhibiting different level of functionality and complexity.

Schiff Bases: A Versatile Fluorescence Probe in Sensing Cations

Metal cations such as Zn²⁺, Al³⁺, Hg²⁺, Cd²⁺, Sn²⁺, Fe²⁺, Fe³⁺ and Cu²⁺ play important roles in biology, medicine, and the environment. However, when these are not maintained in proper concentration, they can be lethal to life. Therefore, selective sensing of metal cations is of great importance in understanding various metabolic processes, disease diagnosis, checking the purity of environmental samples, and detecting toxic analytes. Schiff base probes have been largely used in designing fluorescent sensors for sensing metal ions because of their easy processing, availability, fast response time, and low detection limit. Herein, an in-depth report on metal ions recognition by some Schiff base fluorescent sensors, their sensing mechanism, their practical applicability in cell imaging, building logic gates, and analysis of real-life samples has been presented. The metal ions having biological, industrial, and environmental significance are targeted. The compiled information is expected to prove beneficial in designing and synthesis of the related Schiff base fluorescent sensors.

Study on the interactions between melamine-cored Schiff bases with cucurbit[n]urils of different sizes and its application in detecting silver ions

Three different complexes, TMeQ[6]-TBT, Q[7]-TBT, and Q[8]-TBT are constructed by three different cucurbiturils and synthesized by guest melamine-cored Schiff bases (TBT) through outer-surface interaction and host-guest interactions. TBT forms a TMeQ[6]-TBT complex with TMeQ[6] through outer-surface interaction, while Q[7]-TBT and Q[8]-TBT form complexes with Q[7,8] through host-guest interactions. Among them, Q[7]-TBT is selected as a UV detector for the detection of silver ions (Ag+). This work makes full use of the characteristics of each cucurbituril and melamine-cored Schiff base to construct a series of complexes and these are applied to metal detection.