A new selectophore for gadolinium selective sensor

Chemical Sensors using Single-Molecule Electrical Measurements

Driven by the digitization and informatization of contemporary society, electrical sensors are developing toward minimal structure, intelligent function, and high detection resolution. Single-molecule electrical measurement techniques have been proven to be capable of label-free molecular recognition and detection, which opens a new strategy for the design of efficient single-molecule detection sensors. In this review, we outline the main advances and potentials of single-molecule electronics for qualitative identification and recognition assays at the single-molecule level. Strategies for single-molecule electro-sensing and its main applications are reviewed, mainly in the detection of ions, small molecules, oligomers, genetic materials, and proteins. This review summarizes the remaining challenges in the current development of single-molecule electrical sensing and presents some potential perspectives for this field.

An Electrolyte-Gated Graphene Field-Effect Transistor for Detection of Gadolinium(III) in Aqueous Media

In this work, an electrolyte-gated graphene field-effect transistor is developed for Gd³⁺ ion detection in water. The source and drain electrodes of the transistor are fabricated by photolithography on polyimide, while the graphene channel is obtained by inkjet-printing a graphene oxide ink subsequently electro-reduced to give reduced graphene oxide. The Gd³⁺-selective ligand DOTA is functionalized by an alkyne linker to be grafted by click chemistry on a gold electrode without losing its affinity for Gd³⁺. The synthesis route is fully described, and the ligand, the linker and the functionalized surface are characterized by electrochemical analysis and spectroscopy. The as functionalized electrode is used as gate in the graphene transistor so to modulate the source-drain current as a function of its potential, which is itself modulated by the concentration of Gd³⁺captured on the gate surface. The obtained sensor is able to quantify Gd³⁺ even in a sample containing several other potentially interfering ions such as Ni²⁺, Ca²⁺, Na⁺ and In³⁺. The quantification range is from 1 pM to 10 mM, with a sensitivity of 20 mV dec^-1 expected for a trivalent ion. This paves the way for Gd³⁺ quantification in hospital or industrial wastewater.

A selective fluorescent probe for gadoliniumIII in water based on a PdII-preorganized chromone-receptor

The synthesis, solution studies, photochemical properties and the X-ray structure of a chromone based fluorescent Pd^II complex are reported. The ligand contains two chromone units linked as side arms to an ethylenediamine moiety; in the Pd^II complex the metal ion preorganizes the two hydroxychromone units forming a rigid structure with a negatively charged pocket formed by four oxygen atoms that is able to interact with hard metal cations, such as ions, giving rise to stable bimetallic complexes. Upon interaction with La^III and Gd^III, in particular, the emission intensity at 423 nm increases by a factor of 2 and 8, respectively, while the other rare earth ions quench the fluorescence. Spectrofluorimetric studies on real matrices showed the possibility to use this system as a selective fluorescence probe to detect and trace the presence of Gadolinium in environmental water acting as an OFF-ON chemosensor, with a LOD of 0.4 ppm and a LOQ of 1.2 ppm.

Rapid Detection of Gadolinium-Based Contrast Agents in Urine with a Chelated Europium Luminescent Probe

Gadolinium-based contrast agents are widely used in magnetic resonance imaging procedures to enhance image contrast. Despite their ubiquitous use in clinical settings, gadolinium is not an innocuous element, as suggested by several disorders associated with its use. Therefore, novel analytical technologies capable of tracking contrast agent excretion through urine are necessary for optimizing patient safety after imaging procedures. Here, we describe an assay to detect and quantify contrast agents in urine based on the luminescence quenching of a metal chelate probe, Eu³⁺-3,4,3-LI(1,2-HOPO), which only requires 10 min incubation before measurement. Gadolinium-based contrast agents prevent the formation of the Eu³⁺-3,4,3-LI(1,2-HOPO) complex, subsequently decreasing the luminescence of the assay solution. Three commercial contrast agents, Magnevist, Multihance, and Omniscan, were used to demonstrate the analytical concept in synthetic human urine, and subsequent quantification of mouse urine samples. To the best of our knowledge, this is the first assay capable of detecting and quantifying gadolinium-based contrast agents in urine without sample preparation or digestion.