Colourimetric and fluorescent probes for the optical detection of palladium ions

In recent years, the development of optical probes to analyse trace palladium ions (Pd²⁺) has attracted great attention because of the residual palladium released by catalytic converters or from various Pd-catalysed reactions. These residual palladium ions may cause potential health hazards. This review provides a brief introduction to the new methods used to determine trace amounts of Pd²⁺, which then mainly focuses on the different reporting systems and unique mechanisms of the colourimetric and fluorescent probes used to detect Pd²⁺, including Pd²⁺ complex formation or Pd-catalysed reactions.