@article{sen_volya_muhammed_lazenby_2025, title={Fabrication and Characterization of a Tunable Microelectrode Array Probe for Simultaneous Multiplexed Electrochemical Detection}, DOI={10.1021/acs.analchem.4c05175}, abstractNote={Individually addressable microelectrode arrays (MEAs) enable the simultaneous and independent measurement of multiple analytes and benefit from a small size scale, which enables highly localized electrochemical detection. In this work, we describe a new methodology to fabricate low-cost and tunable MEA probes in which the number, spatial arrangement, and spacing of the electrodes and electrode material can be changed and controlled. This was achieved using a 3D printed support assembly to position wires of the electrode material into designated positions and a mold to seal the electrodes in place using epoxy resin. After curing of the epoxy, mechanical polishing exposed the surface of closely spaced disk microelectrodes embedded in the insulating material, which formed the MEA. The individual electrodes of the array were characterized using electrochemical methods and optical and electron microscopy to evaluate the surface quality and the integrity of the seal with the insulating epoxy. To validate the fabrication method and to demonstrate the controlled electrode spacing, we used a dual-disk electrode device, while four-, five-, and seven-electrode probes were used to demonstrate some of the different numbers and geometric arrangements of electrodes that are possible. While the developed probes have numerous potential applications, including as probes or substrates in scanning electrochemical microscopy, we fabricated electrochemical aptamer-based sensors on the individual electrodes, for the simultaneous detection of adenosine triphosphate and dopamine in phosphate-buffered saline solution, with and without 10% fetal bovine serum.}, journal={Analytical Chemistry}, author={Sen, Debashis and Volya, Nicholas and Muhammed, Yusuf and Lazenby, Robert A.}, year={2025}, month={Apr} }
 @article{nelson_schmidt_adelabu_nantogma_dilday_volya_mandzhieva_kiselev_abdurraheem_maissin_et al._2025, title={RASER for Increased Spectral Resolution in Carbon-13 NMR}, volume={3}, DOI={10.1021/acs.analchem.4c05527}, abstractNote={Precision in nuclear magnetic resonance (NMR) spectroscopy and resolution in magnetic resonance imaging (MRI) are thought to be fundamentally limited by the transverse relaxation time. With the recent advent of radiofrequency amplification by stimulated emission of radiation (RASER), it is becoming apparent that RASERs can break these fundamental limitations and provide significant improvements in the resolution of NMR spectra and the resolution in MRI images. In this article, we show that carbon-13 RASERs can be controlled by changes to the magnetic field homogeneity and the spin coupling network. As illustrative examples of tools commonly employed in high-resolution NMR spectroscopy, we employ the control of magnetic field homogeneity with simple changes to the sample geometry and the spin-coupling network with proton decoupling pulses. These changes control the distance of the NMR system from the RASER threshold. Finally, we demonstrate that the <sup>13</sup>C-RASER spectra can be obtained reflecting the usual, thermal NMR spectra without significant distortions except with at least 10-fold narrower spectral-resonance line widths, thereby significantly increasing our precision in determining NMR parameters such as the <i>J</i>-coupling in the spin system. In contrast to <sup>1</sup>H RASERs, we discuss how <sup>13</sup>C-RASER systems retain the spin information (<i>J</i>-couplings and chemical shifts) with high fidelity.}, journal={Analytical Chemistry}, author={Nelson, Christopher and Schmidt, Andreas B. and Adelabu, Isaiah and Nantogma, Shiraz and Dilday, Seth and Volya, Nicholas and Mandzhieva, Iuliia and Kiselev, Valerij G. and Abdurraheem, Abubakar and Maissin, Henri and et al.}, year={2025}, month={Mar} }