Compact In Situ Electrochemical NMR with Wireless and Anti-interference Strategy in Multiscenario Applications.

The integration of electrochemistry with nuclear magnetic resonance (NMR) spectroscopy recently offers a powerful approach to understanding oxidative metabolism, detecting reactive intermediates, and predicting biological activities. This combination is particularly effective as electrochemical methods provide excellent mimics of metabolic processes, while NMR spectroscopy offers precise chemical analysis. NMR is already widely utilized in the quality control of pharmaceuticals, foods, and additives and in metabolomic studies. However, the introduction of additional and external connections into the magnet has posed challenges, leading to signal deterioration and limitations in routine measurements. Herein, we report an anti-interference compact in situ electrochemical NMR system (AICISENS). Through a wireless strategy, the compact design allows for the independent and stable operation of electrochemical NMR components with effective interference isolation. Thus, it opens an avenue toward easy integration into in situ platforms, applicable not only to laboratory settings but also to fieldwork. The operability, reliability, and versatility were validated with a series of biomimetic assessments, including measurements of microbial electrochemical systems, functional foods, and simulated drug metabolisms. The robust performance of AICISENS demonstrates its high potential as a powerful analytical tool across diverse applications.

In Situ Real-Time Quantitative Determination in Electrochemical Nuclear Magnetic Resonance Spectroscopy.

For the purpose of acquiring highly sensitive and differential spectra in in situ electrochemical nuclear magnetic resonance (EC-NMR) spectroscopy, uniform distributions of amplitudes and phases of radio frequency (RF) fields in the sample are needed for consistent flip angles of all nuclei under scrutiny. However, intrinsic electromagnetic incompatibility exists between such requirements with electric properties of the conductive material in an electrolytic cell, including metallic electrodes and ionic electrolytes. This proposed work presents the adverse repercussions of gradually varying electrolyte conductivity, which is strongly associated with the change of ion concentrations in a real-time electrochemical reaction, on spatial distributions of RF field amplitude and phase in the detective zone of an NMR probe coil. To compensate for such a non-linear trend of the spatial dependent distribution, we eliminate different excitation effects of the RF field on the build-in external standard and the electrolyte both situated in nearly the same detection area, as well as promote the greater accuracy of quantitative determination of reactant concentrations. The reliability and effectiveness of the improved in situ EC-qNMR (quantitative NMR) method are confirmed by the real-time monitoring of the electrochemical advanced oxidation process for phenol, in which instant concentrations of reactants and products are detected simultaneously to verify the degradation reaction scheme of phenol.

Versatile, Robust, and Facile Approach for in Situ Monitoring Electrocatalytic Processes through Liquid Electrochemical NMR Spectroscopy.

With the strength of liquid nuclear magnetic resonance (NMR) to noninvasively and specifically realize the structural elucidation and quantitative analysis of small organic molecules, in principle, liquid in situ electrochemical-NMR (EC-NMR) possesses great advantages for detecting dissolved species during the electrochemical process. However, the intrinsic incompatibilities between the coupling techniques as well as the sophisticated setups modification still limit the applications toward a wide range. To overcome these bottlenecks, herein we propose an easy-to-construct design with good compatibility and presenting improved electrochemical and NMR performances. As proof of concept, model experiments of alcohol electrooxidation were performed to confirm the capacity of this device for liquid in situ EC-NMR study. The temporal evolution of both the product and the current distributions can be reliably recorded to aid mechanistic and kinetic understanding of electrocatalysis. The depiction of the selective electrooxidation reveals the surface structure-catalytic functionality. This work demonstrates the universality and effectivity of the proposed platform to develop the liquid in situ EC-NMR technique as a useful tool for the dynamic analysis of electrochemical processes at a molecular level.

In Situ Monitoring Potential-Dependent Electrochemical Process by Liquid NMR Spectroelectrochemical Determination: A Proof-of-Concept Study.

We report the design and the performance of a two-chamber thin-layer electrochemical device for in situ potential-dependent liquid NMR measurement. Liquid NMR spectra, simultaneously recorded with cyclic voltammetry (CV), have been obtained to reveal molecular changes with potentials scanning. As a proof of concept, redox properties of 1,4-benzoquinone based systems have been investigated, and a π dimerization has been identified by combining both in situ and ex situ NMR analyses. This work provides a new approach for spectroelectrochemistry, which will contribute to developing electrochemical NMR (EC-NMR) as an important tool for the analysis of electrochemical process at a molecular level.

[Coupling liquid phase electrochemistry with nuclear magnetic resonance spectroscopy and its applications].

The combination of liquid nuclear magnetic resonance spectroscopy (NMR) and electrochemistry (EC) is a new technique with promising prospect which provides novel, exciting, and crucial insights into the processes near or on the electrode surface at a molecular or atomic level. The development of in situ EC-NMR spectroscopy with flow or static electrolysis was summarized, the structures of the electrolysis cell and the characteristics of the NMR spectra were analyzed, and the feature of the in situ EC-NMR spectroscopy in practice was described in detail. The electrolysis electrode located at radio-frequency detection area of the NMR spectrometer reduced homogeneity of the magnetic field. Furthermore, the electrolysis current results in broadened spectral lines and loss of resolution. The working electrode consisting of a thin metal film and the electrolysis current parallel to the static magnetic field can overcome such shortcomings. Besides, several high-resolution methods in inhomogeneous fields were discussed and compared, such as intramolecular multiple quantum coherences, nutation echos, intermolecular nuclear Overhauser effects, and intermolecular multiple quantum coherences.