Chemical sensors for rare earth metal ions

Rare earth elements (REEs) are a group of fifteen elements ranging from lanthanum (Z = 57) to lutetium (Z = 71), also called lanthanides. Two further elements, namely scandium (Z = 21) and yttrium (Z = 39), are often referred to as REEs because they have chemical properties similar to lanthanides and are commonly found in the same mineral assemblages. The modern applications of these elements are countless. They constitute critical components of many technological devices and new functional materials, as well as they are extensively used in medical diagnostic applications and for these reasons, REEs are raising new interests of scientists worldwide. The search for chemical sensors suitable for selective sensing of trivalent REE ions represents an important and hard challenge because of their complicated coordination properties due to not well-defined stereo-chemical requirements and an uncertain coordination number, especially in aqueous solution. This review focuses on some of the main works published in the area of fluorescent and electrochemical probes for the detection of REE ions.