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To date, nanostructures of 3d-group transition metal (i.e., Fe, Co, Ni, etc.) derivatives show the highest electrocatalytic performance among non-noble-metal electrocatalysts for water splitting in acidic electrolyte. However, the poor electrochemical conductivity (~10-4 S/cm) of nanostructures restricts practical application for overall electrocatalytic activity. Herein, continuously networked nanostructures of phase-tuned nickel sulfide foams for efficient water splitting electrocatalysts in both acidic and alkaline electrolytes are reported. Because continuously networked nanostructures of nickel sulfide foams possess an integral structure, they exhibit high electrochemical conductivity (~1 S/cm), which eases adsorption/desorption of H+ and OH- ions for efficient overall water splitting. By tuning the stoichiometry of sulfur, four different phases of continuously networked nanostructures of nickel sulfides (aNiS, BNiS, Ni3S2, and Ni7S6) foams are formed by facile phase transformation of nickel. Among them, the Ni7S6 foam (Ni7S6-F) possesses superior electrocatalytic activity with extremely low overpotential of 70 mV (for hydrogen evolution reaction) and 1.37 V (for oxygen evolution reaction) at 10 mA/cm² in acidic and alkaline medium, respectively, which is close to noble-metal- based electrocatalysts. As a result, this work demonstrates a facile synthesis route to optimize nickel sulfide electrocatalysts through phase-tuning and continuous networking for overall water splitting and would be applicable on other nanostructured electrocatalysts to improve their electrocatalytic activity for practical applications in future energy devices. [ABSTRACT FROM AUTHOR]

Myelination is one of the fundamental processes in vertebrates. A major challenge is to quantitatively image myelin distribution in the central nervous system. For this reason, we designed and synthesized a series of fluorinated radioligands that can be radiolabeled as radiotracers for positron emission tomography (PET) imaging of myelin. These newly developed radioligands readily penetrate the blood-brain barrier and selectively bind to myelin membranes in the white matter region. Structure-activity relationship studies of such ligands suggested that optimal permeability could be achieved with calculated lipophilicty in the range of 3-4. After radiolabeling with fluorine-18, the brain uptake and retention of each radioligand were determined by microPET/CT imaging studies. These pharmacokinetic studies led us to identify a lead compound ([18F]FMeDAS, 32) with promising in vivo binding properties, which was subsequently validated by ex vivo autoradiography. [ABSTRACT FROM AUTHOR]

Myelin is the protective sheath that surrounds nerves in vertebrates to protect axons, which thereby facilitates impulse conduction. Damage to myelin is associated with many neurodegenerative diseases such as multiple sclerosis and also includes spinal cord injury (SCI). The small size of the spinal cord poses formidable challenges to in vivo monitoring of myelination, which we investigated via conducting a structure-activity relationship study to determine the optimum positron-emitting agent to use for imaging myelin using positron emission tomography (PET). From these studies, [ 18 F]PENDAS was identified as the lead agent to use in conjunction with PET imaging to delineate the integrity of spinal cord myelin. A subsequent in vivo PET imaging study of [ 18 F]PENDAS in rats with SCI showed promising pharmacokinetic results that justify further development of imaging markers for diagnosing myelin-related diseases. Additionally, [ 18 F]PENDAS could be valuable in determining the efficacy of therapies that are currently under development.

Two-dimensional (2D) transitional metal oxides (TMOs) are an attractive class of materials due to the combined advantages of high active surface area, enhanced electrochemical properties, and stability. Among the 2D TMOs, 2D tungsten oxide (WO 3 ) nanosheets possess great potential in electrochemical applications, particularly in electrochromic (EC) devices. However, feasible production of 2D WO 3 nanosheets is challenging due to the innate 3D crystallographic structure of WO 3 . Here we report a novel solution-phase synthesis of 2D WO 3 nanosheets through simple oxidation from 2D tungsten disulfide (WS 2 ) nanosheets exfoliated from bulk WS 2 powder. The complete conversion from WS 2 into WO 3 was confirmed through crystallographic and elemental analyses, followed by validation of the 2D WO 3 nanosheets applied in the EC device. The EC device showed color modulation of 62.57% at 700 nm wavelength, which is 3.43 times higher than the value of the conventional device using bulk WO 3 powder, while also showing enhancement of ∼46.62% and ∼62.71% in switching response-time (coloration and bleaching). The mechanism of enhancement was rationalized through comparative analysis based on the thickness of the WO 3 components. In the future, 2D WO 3 nanosheets could also be used for other promising applications such as sensors, catalysis, thermoelectric, and energy conversion.

Myelin pathology is present in many neurological conditions such as multiple sclerosis (MS) and traumatic spinal cord injury (SCI). To facilitate development of novel therapies aimed at myelin repair, we set out to develop imaging agents that permit direct quantification of myelination in vivo. In this work, we designed and synthesized a series of fluorescent fluorinated myelin imaging agents that can be used for in vivo positron emission tomography (PET) imaging combined with subsequent post-mortem fluorescent cryoimaging. Structure-activity relationship (SAR) studies of the newly developed myelin imaging agents led us to identify a lead compound (TAFDAS, 21) that readily enters the brain and spinal cord and selectively binds to myelin. By conducting sequential PET and 3D cryoimaging in an SCI rat model, we demonstrated for the first time that PET and cryoimaging can be combined as a novel technique to image the spinal cord with high sensitivity and spatial resolution.