A critical review of copper nanoclusters for monitoring of water quality

Abstract

Copper nanoclusters (Cu NCs) with a core size smaller than 2 nm exhibit fascinating physical and chemical properties, bridging between nanoparticles and atomic/molecular structures. In particular, the unique fluorescence (FL) characteristics of Cu NCs have attracted increasingly attention in the past decade. Compared with gold or silver NCs, Cu is a relatively cheap, abundant and readily available element, which makes Cu NCs more attractive to the development of sensors. However, Cu NCs still face serious issues, such as low quantum yield and easy to oxidation. This review discusses the latest developments in Cu NCs, with particular emphasis on their synthesis, optical properties, and applications in monitoring water quality. Pivotal factors that control the stability and FL properties of Cu NCs are emphasized. Examples of Cu NCs for monitoring of pH values and sensing of various analytes such as Hg2+, NO2−, S2−, I−, and 2,4,6-trinitrotoluene are provided to show their sensing mechanisms, advantages, and disadvantages. Possible strategies for overcoming the low quantum yields and small scales of preparation of Cu NCs are suggested. To make Cu NCs more popular for sensing, we suggest that Cu NCs shall be integrated with portable microsystems such as array and microfluidic devices.

Keywords

• Copper nanoclusters
• Water quality monitoring
• Fluorescence
• Chemical sensor