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1. Light angle dependence of photothermal properties in oxide and porphyrin thin films for energy-efficient window applications

   https://doi.org/https://doi.org/10.1557/mrc.2020.39  

   1. Lyu M, Lin J ( June 2020 , MRS communications)

   null (Ed.)

   The photothermal experiments on the incident light angle dependence are carried out using simulated solar light on thin films of both iron oxides (Fe3O4 and Fe3O4@Cu2-xS) and porphyrin compounds (chlorophyll and chlorophyllin). Fe3O4 and Fe3O4@Cu2-xS are synthesized using various solution methods that produce mono-dispersed nanoparticles on the order of 10 nm. Chlorophyll is extracted from fresh spinach and chlorophyllin sodium copper is a commercial product. These photothermal (PT) materials are dispersed in polymethyl methacrylate (PMMA) solutions and deposited on glass substrates via spin coating that result in clear and transparent thin films. The iron-oxide based thin films show distinctive absorption spectra; Fe3O4 exhibits a strong peak near UV and gradually decreases into the visible and NIR regions; the absorption of Fe3O4@Cu2-xS is similar in the UV region but shows a broad absorption in the NIR region. Both chlorophyll and chlorophyllin are characterized with absorption peaks near UV and NIR showing a “U”-shaped spectrum, ideally required for efficient solar harvest and high transparency in energy-efficient single-pane window applications. Upon coating of the transparent PT films on the window inner surfaces, solar irradiation induces the photothermal effect, consequently raising the film temperature. In this fashion, the thermal loss through the window can be significantly lowered by reducing the temperature difference between the window inner surface and the room interior, based on a new concept of so-called “optical thermal insulation” (OTI) without any intervention medium, such as air/argon, as required in the glazing technologies. Single-panes are therefore possible to replace double- or triple panes. As OTI is inevitably affected by seasonal and daily sunlight changes, an incident light angle dependence of the photothermal effect is crucial in both thin film and window designs. It is found that the heating curves reach their maxima at small angles of incidence while the photothermal effect is considerably reduced at large angles. This angle dependence is well explained by light reflection by the thin film surface, however, deviated from what is predicted by the Fresnel’s law, attributable to non-ideal surfaces of the substrates. The angle dependence data provides an important reference for OTI that window exposure to sun is greater at winter solstice while that is considerably reduced in the summer. This conclusion indicates much enhanced solar harvesting and heat conversion via optically insulated windows in the winter season, resulting in much lower U-factors. 

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2. A Kinetic Study on H 2 Reduction of Fe 3 O 4 for Long-Duration Energy-Storage-Compatible Solid Oxide Iron Air Batteries

   https://doi.org/10.1149/1945-7111/acfbbc  

   Morey, Chaitali ; Tang, Qiming ; Sun, Shichen ; Huang, Kevin ( October 2023 , Journal of The Electrochemical Society)

   Long duration energy storage (LDES) is economically attractive to accelerate widespread renewable energy deployment. But none of the existing energy storage technologies can meet LDES cost requirements. The newly emerged solid oxide iron air battery (SOIAB) with energy-dense solid Fe as an energy storage material is a competitive LDES-suitable technology compared to conventional counterparts. However, the performance of SOIAB is critically limited by the kinetics of Fe₃O₄reduction (equivalent to charging process) and the understanding of this kinetic bottleneck is significantly lacking in the literature. Here, we report a systematic kinetic study of Fe₃O₄-to-Fe reduction in H₂/H₂O environment, particularly the effect of catalyst (iridium) and supporting oxides (ZrO₂and BaZr_0.4Ce_0.4Y_0.1Yb_0.1O₃). With in situ created Fe₃O₄, the degree of reduction is measured by the change of H₂O and H₂concentrations in the effluent using a mass spectrometer, from which the kinetic rate constant is extracted as a function of inlet H₂concentration and temperature. We find that kinetics can be nicely described by Johson-Mehl-Avrami (JMA) model. We also discuss the stepwise reduction mechanisms and activation energy for the reduction process.

    

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3. Activation and deactivation of the commercial‐type CuO–Cr 2 O 3 –Fe 2 O 3 high temperature shift catalyst

   https://doi.org/10.1002/aic.16846  

   Zhu, Minghui ; Tian, Pengfei ; Chen, Jiacheng ; Ford, Michael E. ; Xu, Jing ; Wachs, Israel E. ; Han, Yi‐Fan ( November 2019 , AIChE Journal)

   This work elucidates the structural evolution of a commercial‐type iron oxide‐based high temperature water–gas shift (HT‐WGS) catalyst during activation and deactivation stages. The findings highlight the importance of Cu–FeO_xinterfaces. Based on the new insights, future improvement of commercial iron‐based catalysts should focus on stabilization of the active Cu–FeO_xinterface. Much effort has been devoted to understanding the structure, mechanism, and promotion of the commercial‐type CuO–Cr₂O₃–Fe₂O₃catalyst for the high temperature water–gas shift (HT‐WGS) reaction. However, structural evolution of the catalyst during the activation and deactivation stages was rarely reported. Herein, catalyst characterization, temperature‐programmed studies, and kinetic analysis were conducted on iron oxide‐based HT‐WGS catalysts. Addition of Cu was found to accelerate both the bulk (Fe₂O₃ → Fe₃O₄) and surface (active FeO_x–Cu interface) transformations during the catalyst activation stage. During catalyst deactivation, Cu accelerated both sintering of the Fe₃O₄bulk phase and unfavorable encapsulation of the metallic Cu particles with a substantial FeO_xoverlayer. The loss of the initial active Cu–FeO_xinterfacial sites reversed the promotional effect of Cu.

    

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4. Synthesis and SERS application of gold and iron oxide functionalized bacterial cellulose nanocrystals (Au@Fe 3 O 4 @BCNCs)

   https://doi.org/10.1039/d0an00711k  

   Kang, Seju ; Rahman, Asifur ; Boeding, Ethan ; Vikesland, Peter J. ( June 2020 , The Analyst)

   Bacterial cellulose nanocrystals (BCNCs) are biocompatible cellulose nanomaterials that can host guest nanoparticles to form hybrid nanocomposites with a wide range of applications. Herein, we report the synthesis of a hybrid nanocomposite that consists of plasmonic gold nanoparticles (AuNPs) and superparamagnetic iron oxide (Fe 3 O 4 ) nanoparticles supported on BCNCs. As a proof of concept, the hybrid nanocomposites were employed to isolate and detect malachite green isothiocyanate (MGITC) via magnetic separation and surface-enhanced Raman scattering (SERS). Different initial gold precursor (Au 3+ ) concentrations altered the size and morphology of the AuNPs formed on the nanocomposites. The use of 5 and 10 mM Au 3+ led to a heterogenous mix of spherical and nanoplate AuNPs with increased SERS enhancements, as compared to the more uniform AuNPs formed using 1 mM Au 3+ . Rapid and sensitive detection of MGITC at concentrations as low as 10 −10 M was achieved. The SERS intensity of the normalized Raman peak at 1175 cm −1 exhibited a log-linear relationship for MGITC concentrations between 2 × 10 −10 and 2 × 10 −5 M for Au@Fe 3 O 4 @BCNCs. These results suggest the potential of these hybrid nanocomposites for application in a broad range of analyte detection strategies. 

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5. Rationally Engineered Vertically Aligned β ‐Ga 2− x W x O 3 Nanocomposites for Self‐Biased Solar‐Blind Ultraviolet Photodetectors with Ultrafast Response

   https://doi.org/10.1002/admt.202300014  

   Das, Debabrata ; Sanchez, Francelia ; Barton, Dallin J. ; Tan, Susheng ; Shutthanandan, Vaithiyalingam ; Devaraj, Arun ; Ramana, Chintalapalle V. ( May 2023 , Advanced Materials Technologies)

   With the astonishing advancement of present technology and increasing energy consumption, there is an ever‐increasing demand for energy‐efficient multifunctional sensors or transducers based on low‐cost, eco‐friendly material systems. In this context, self‐assembled vertically alignedβ‐Ga_2−xW_xO₃nanocomposite (GWO‐VAN) architecture‐assisted self‐biased solar‐blind UV photodetection on a silicon platform, which is the heart of traditional electronics is presented. Utilizing precisely controlled growth parameters, the formation of W‐enriched verticalβ‐Ga_2−xW_xO₃nanocolumns embedded into the W‐deficientβ‐Ga_2−xW_xO₃matrix is reached. Detailed structural and morphological analyses evidently confirm the presence ofβ‐Ga_2−xW_xO₃nanocomposite with a high structural and chemical quality. Furthermore, absorption and photoluminescence spectroscopy explains photo‐absorption dynamics and the recombination through possible donor–acceptor energy states. The proposed GWO‐VAN framework facilitates evenly dispersed nanoregions with asymmetric donor energy state distribution and thus forms build‐in potential at the verticalβ‐Ga_2−xW_xO₃interfaces. As a result, the overall heterostructure evinces photovoltaic nature under the UV irradiation. A responsivity of ≈30 A/W is observed with an ultrafast response time (≈350 µs) under transient triggering conditions. Corresponding detectivity and external quantum efficiency are 7.9 × 10¹²Jones and 1.4 × 10⁴%, respectively. It is believed that, while this is the first report exploiting GWO‐VAN architecture to manifest self‐biased solar‐blind UV photodetection, the implication of the approach is enormous in designing electronics for extreme environment functionality and has immense potential to demonstrate drastic improvement in low‐cost UV photodetector technology.

    

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