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1. A study of TiO ₂ nanocrystal growth and environmental remediation capability of TiO ₂ /CNC nanocomposites

   https://doi.org/10.1039/c9ra08861j  

   Zhan, Chengbo; Li, Yanxiang; Sharma, Priyanka R.; He, Hongrui; Sharma, Sunil K.; Wang, Ruifu; Hsiao, Benjamin S. (December 2019, RSC Advances)

   Nanocellulose, which can be derived from any cellulosic biomass, has emerged as an appealing nanoscale scaffold to develop inorganic–organic nanocomposites for a wide range of applications. In this study, titanium dioxide (TiO 2 ) nanocrystals were synthesized in the cellulose nanocrystal (CNC) scaffold using a simple approach, i.e. , hydrolysis of a titanium oxysulfate precursor in a CNC suspension at low temperature. The resulting TiO 2 nanoparticles exhibited a narrow size range between 3 and 5 nm, uniformly distributed on and strongly adhered to the CNC surface. The structure of the resulting nanocomposite was evaluated by transmission electron microscopy (TEM) and X-ray diffraction (XRD) methods. The growth mechanism of TiO 2 nanocrystals in the CNC scaffold was also investigated by solution small-angle X-ray scattering (SAXS), where the results suggested the mineralization process could be described by the Lifshitz–Slyozov–Wagner theory for Ostwald ripening. The demonstrated TiO 2 /CNC nanocomposite system exhibited excellent performance in dye degradation and antibacterial activity, suitable for a wide range of environmental remediation applications. 

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2. Isostructural metal-insulator transition in VO ₂

   https://doi.org/10.1126/science.aam9189  

   Lee, D.; Chung, B.; Shi, Y.; Kim, G.-Y.; Campbell, N.; Xue, F.; Song, K.; Choi, S.-Y.; Podkaminer, J. P.; Kim, T. H.; et al (November 2018, Science)

   The metal-insulator transition in correlated materials is usually coupled to a symmetry-lowering structural phase transition. This coupling not only complicates the understanding of the basic mechanism of this phenomenon but also limits the speed and endurance of prospective electronic devices. We demonstrate an isostructural, purely electronically driven metal-insulator transition in epitaxial heterostructures of an archetypal correlated material, vanadium dioxide. A combination of thin-film synthesis, structural and electrical characterizations, and theoretical modeling reveals that an interface interaction suppresses the electronic correlations without changing the crystal structure in this otherwise correlated insulator. This interaction stabilizes a nonequilibrium metallic phase and leads to an isostructural metal-insulator transition. This discovery will provide insights into phase transitions of correlated materials and may aid the design of device functionalities. 

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3. Sodium Transition Metal Vanadates from Hydrothermal Brines: Synthesis and Characterization of NaMn ₄ (VO ₄ ) ₃ , Na ₂ Mn ₃ (VO ₄ ) ₃ , and Na ₂ Co ₃ (VO ₄ ) ₂ (OH) ₂

   https://doi.org/10.1002/ejic.202000518  

   Smith Pellizzeri, Tiffany M.; Morrison, Gregory; McMillen, Colin D.; zur Loye, Hans‐Conrad; Kolis, Joseph W. (September 2020, European Journal of Inorganic Chemistry)

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4. A Reconfigurable Remotely Epitaxial VO ₂ Electrical Heterostructure

   https://doi.org/10.1021/acs.nanolett.9b02696  

   Guo, Yuwei; Sun, Xin; Jiang, Jie; Wang, Baiwei; Chen, Xinchun; Yin, Xuan; Qi, Wei; Gao, Lei; Zhang, Lifu; Lu, Zonghuan; et al (December 2019, Nano Letters)
5. Spatially Distributed Ramp Reversal Memory in VO ₂

   https://doi.org/10.1002/aelm.202300085  

   Basak, Sayan; Sun, Yuxin; Banguero, Melissa Alzate; Salev, Pavel; Schuller, Ivan K; Aigouy, Lionel; Carlson, Erica W; Zimmers, Alexandre (July 2023, Advanced Electronic Materials)

   Abstract Ramp‐reversal memory has recently been discovered in several insulator‐to‐metal transition materials where a non‐volatile resistance change can be set by repeatedly driving the material partway through the transition. This study uses optical microscopy to track the location and internal structure of accumulated memory as a thin film of VO₂is temperature cycled through multiple training subloops. These measurements reveal that the gain of insulator phase fraction between consecutive subloops occurs primarily through front propagation at the insulator‐metal boundaries. By analyzing transition temperature maps, it is found, surprisingly, that the memory is also stored deep inside both insulating and metallic clusters throughout the entire sample, making the metal‐insulator coexistence landscape more rugged. This non‐volatile memory is reset after heating the sample to higher temperatures, as expected. Diffusion of point defects is proposed to account for the observed memory writing and subsequent erasing over the entire sample surface. By spatially mapping the location and character of non‐volatile memory encoding in VO₂, this study results enable the targeting of specific local regions in the film where the full insulator‐to‐metal resistivity change can be harnessed in order to maximize the working range of memory elements for conventional and neuromorphic computing applications. 

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