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1. The Dopamine Assisted Synthesis of MoO3/Carbon Electrodes With Enhanced Capacitance in Aqueous Electrolyte

   https://doi.org/10.3389/fchem.2022.873462  

   Norouzi, Nazgol ; Omo-Lamai, Darrell ; Alimohammadi, Farbod ; Averianov, Timofey ; Kuang, Jason ; Yan, Shan ; Wang, Lei ; Stavitski, Eli ; Leshchev, Denis ; Takeuchi, Kenneth J. ; et al ( April 2022 , Frontiers in Chemistry)

   A capacitance increase phenomenon is observed for MoO 3 electrodes synthesized via a sol-gel process in the presence of dopamine hydrochloride (Dopa HCl) as compared to α-MoO 3 electrodes in 5M ZnCl 2 aqueous electrolyte. The synthesis approach is based on a hydrogen peroxide-initiated sol-gel reaction to which the Dopa HCl is added. The powder precursor (Dopa) x MoO y , is isolated from the metastable gel using freeze-drying. Hydrothermal treatment (HT) of the precursor results in the formation of MoO 3 accompanied by carbonization of the organic molecules; designated as HT-MoO 3 /C. HT of the precipitate formed in the absence of dopamine in the reaction produced α-MoO 3 , which was used as a reference material in this study (α-MoO 3 -ref). Scanning electron microscopy (SEM) images show a nanobelt morphology for both HT-MoO 3 /C and α-MoO 3 -ref powders, but with distinct differences in the shape of the nanobelts. The presence of carbonaceous content in the structure of HT-MoO 3 /C is confirmed by FTIR and Raman spectroscopy measurements. X-ray diffraction (XRD) and Rietveld refinement analysis demonstrate the presence of α-MoO 3 and h-MoO 3 phases in the structure of HT-MoO 3 /C. The increased specificmore »capacitance delivered by the HT-MoO 3 /C electrode as compared to the α-MoO 3 -ref electrode in 5M ZnCl 2 electrolyte in a −0.25–0.70 V vs. Ag/AgCl potential window triggered a more detailed study in an expanded potential window. In the 5M ZnCl 2 electrolyte at a scan rate of 2 mV s −1 , the HT-MoO 3 /C electrode shows a second cycle capacitance of 347.6 F g −1 . The higher electrochemical performance of the HT-MoO 3 /C electrode can be attributed to the presence of carbon in its structure, which can facilitate electron transport. Our study provides a new route for further development of metal oxides for energy storage applications.« less
2. EXPRESS: Vibrational Spectroscopic Monitoring of the Gelation Transition in Nafion Ionomer Dispersions

   https://doi.org/10.1177/0003702820949129  

   Liang, Ying ; Kitt, Jay ; Minteer, Shelley D. ; Harris, Joel ; Korzeniewski, Carol ( July 2020 , Applied Spectroscopy)

   Infrared and Raman spectroscopy techniques were applied to investigate the drying and aggregation behavior of Nafion ionomer particles dispersed in aqueous solution. Gravimetric measurements aided the identification of gel-phase development within a series of time-resolved spectra that tracked transformations of a dispersion sample during solvent evaporation. A spectral band characteristic of ionomer sidechain end group vibration provided a quantitative probe of the dispersion-to-gel change. For sets of attenuated total reflection Fourier transform infrared (ATR-FTIR) spectra, adherence to Beer’s law was attributed to the relatively constant refractive index in the frequency region of hydrated -SO3 - group vibrations as fluorocarbon-rich ionomer regions aggregate in forming the structural framework of membranes and thin films. Although vibrational bands associated with ionomer backbone CF2 stretching vibrations were affected by distortion characteristic of wavelength-dependent refractive index change within a sample, the onset of band distortion signaled gel formation and coincided with ionomer mass % values just below the critical gelation point for Nafion aqueous dispersions. Similar temporal behavior was observed in confocal Raman microscopy experiments that monitored the formation of a thin ionomer film from an individual dispersion droplet. For the ATR FTIR spectroscopy and confocal Raman microscopy techniques, intensity in the water H-O-H bendingmore »vibrational band dropped sharply at the ionomer critical gelation point and displayed a time dependence consistent with changes in water content derived from gravimetric measurements. The reported studies lay groundwork for examining the impact of dispersing solvents and above-ambient temperatures on fluorinated ionomer transformations that influence structural properties of dispersion-cast membranes and thin films.« less
3. In situ quasi-elastic neutron scattering study on the water dynamics and reaction mechanisms in alkali-activated slags

   https://doi.org/10.1039/c9cp00889f  

   Gong, Kai ; Cheng, Yongqiang ; Daemen, Luke L. ; White, Claire E. ( May 2019 , Physical Chemistry Chemical Physics)

   In this study, in situ quasi-elastic neutron scattering (QENS) has been employed to probe the water dynamics and reaction mechanisms occurring during the formation of NaOH- and Na 2 SiO 3 -activated slags, an important class of low-CO 2 cements, in conjunction with isothermal conduction calorimetry (ICC), Fourier transform infrared spectroscopy (FTIR) analysis and N 2 sorption measurements. We show that the single ICC reaction peak in the NaOH-activated slag is accompanied with a transformation of free water to bound water (from QENS analysis), which directly signals formation of a sodium-containing aluminum-substituted calcium–silicate–hydrate (C–(N)–A–S–H) gel, as confirmed by FTIR. In contrast, the Na 2 SiO 3 -activated slag sample exhibits two distinct reaction peaks in the ICC data, where the first reaction peak is associated with conversion of constrained water to bound and free water, and the second peak is accompanied by conversion of free water to bound and constrained water (from QENS analysis). The second conversion is attributed to formation of the main reaction product ( i.e. , C–(N)–A–S–H gel) as confirmed by FTIR and N 2 sorption data. Analysis of the QENS, FTIR and N 2 sorption data together with thermodynamic information from the literature explicitly shows thatmore »the first reaction peak is associated with the formation of an initial gel (similar to C–(N)–A–S–H gel) that is governed by the Na + ions and silicate species in Na 2 SiO 3 solution and the dissolved Ca/Al species from slag. Hence, this study exemplifies the power of in situ QENS, when combined with laboratory-based characterization techniques, in elucidating the water dynamics and associated chemical mechanisms occurring in complex materials, and has provided important mechanistic insight on the early-age reactions occurring during formation of two alkali-activated slags.« less
4. Abstract P332: Microfluidic Model Of Late-stage Calcific Aortic Valve Disease Develops Calcium Phosphate Mineralizations

   https://doi.org/10.1161/res.129.suppl_1.P332  

   Mendoza, Melissa ; Chen, Mei-Hsiu ; Murray, Bruce ; Huang, Peter ; Mahler, Gretchen ( September 2021 , Circulation Research)

   Introduction: Calcific aortic valve disease (CAVD) is an active pathological process leading to severe valve calcification. Late-stage CAVD is characterized by increased leaflet stiffness, disorganized collagen bundles and the deposition of glycosaminoglycans, such as chondroitin sulfate (CS), in the fibrosa layer. However, many details of the cellular pathological cascade remain unknown. Animal models such as mice, rabbits, and pigs are used in understanding human CAVD, but mice do not have similar anatomy, rabbits cannot spontaneously develop atherosclerotic lesions, and pigs require long, expensive and complex studies. Here we utilize microfluidic devices of the aortic valve fibrosa to model late-stage CAVD. Hypothesis: We assessed the hypothesis that microfluidic calcification will increase with increased shear rates and CS content. Methods: Valve-on-a-chip devices contained a hydrogel of 1.5 mg/mL collagen I-only healthy controls or 1.5 mg/mL collagen I with 1 mg/mL or 20 mg/mL CS. Porcine aortic valve interstitial cells (PAVIC) were embedded within and endothelial cells (PAVEC) were seeded onto the matrix. Steady shear stress at 1 dyne/cm 2 and 20 dyne/cm 2 were applied using a peristaltic pump for 14 days. Alizarin Red S (ARS), an assay to assess calcium deposition, was used to quantify calcific nodule formation. Scanning electron microscopymore »with energy dispersive x-ray (SEM/EDX) was used to further analyze sample mineralization. Results: Co-cultures in the presence of increasing shear stress and CS exhibit increased calcific nodule formation compared to static controls, both qualitatively and quantitatively (n≥3). SEM revealed the microstructure of calcified nodules and EDX confirmed calcium phosphate mineralization with physiologically-relevant calcium to phosphorous ratios (Ca/P= 0.88 - 1.4). Conclusions: These results show that in vitro calcification is driven by shear stress in the presence of PAVEC and CS. As seen in ex vivo studies of human calcification, these microfluidic-derived nodules are similarly composed of a range of naturally-occurring calcium phosphates. Given that CAVD has no targeted therapy, the creation of a physiologically relevant model of the aortic valve can provide a test bed for novel therapeutic interventions.« less
5. Self-healing Capacity of Strain-Hardening Fiber Reinforced Geopolymer Composites

   Ohno, M. ( April 2020 , fib Symposium on Concrete Structures for Resilient Societies)

   This study reports on the self-healing capability of a strain-hardening fiber reinforced geopolymer composite, named Engineered Geopolymer Composite (EGC). EGC specimens were first uniaxially loaded to a tensile strain of 1%. The cracked specimens were then subjected to three different conditioning regimes: air curing, water curing, and no curing (i.e. reloading right after the preloading). Stiffness reduction was measured for each series by comparing the initial stiffness of intact specimens and the residual stiffness of the cracked specimens. In the water-cured specimens, white precipitates were observed in microcracks formed by preloading. Experimental results of the series showed significant stiffness recovery for low stress levels in the range of 0.5 – 1.0 MPa. Self-healing products observed by using a scanning electron microscope were mostly angular, stone-like substance. An analysis of energy dispersive spectroscopy showed that the healing products were relatively rich in silicon (Si) and aluminium (Al) and had lower concentration of calcium (Ca), compared to the geopolymer matrix phase. This implies that main product of EGC self-healing is unlikely to be either calcite (CaCO3) or salt deposits such as Na2CO3, but rather a formation of some aluminosilicate compounds. This study provides a baseline for further investigations into the development ofmore »geopolymer composites with robust self-healing.« less