Fluorescent sensing of $^{99}$Tc pertechnetate in water

Abstract

The selective binding of $^{99}$Tc pertechnetate ($^{99}$TcO$_4$−) in water is a big challenge. Recently, our group reported on the p-xylyl aza-cryptand, as the first molecular receptor for $^{99}$TcO$_4$− in aqueous solution. Here, we show that the introduction of a fluorescent unit in the azacryptand's framework leads to a new molecular system, able to selectively recognize and sense the pertechnetate anion at μM concentration. In water at pH 2, where the cage is in the hexaprotonated form, pertechnetate recognition is signalled by the quenching of the receptor's emission. Noticeably, environmentally ubiquitous anions, such as chloride, nitrate and sulfate do not interfere in the sensing, as they have no effect on our chemo-sensor's fluorescence. These unprecedented results are promising for the development of simple and smart devices for the recovery of $^{99}$TcO$_4$− from contaminated aqueous solutions.