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1. Structure and Luminescence Studies of Salts of the Helical Dication, [Au ₂ (μ-bis(diphenylphosphine)ethane) ₂ ] ²⁺ and Comparison with Salts of [Au ₂ (μ-bis(diphenylphosphine)propane) ₂ ] ²⁺

   https://doi.org/10.1021/acs.inorgchem.3c01961  

   Costa, Sarah; Walters, Daniel T; McNamara, Lauren E; Olmstead, Marilyn M; Fettinger, James C; Balch, Alan L (October 2023, Inorganic Chemistry)

   Six salts ([Au2(μ-dppe)2](BF4)2·CHCl3, [Au2(μ- dppe)2](BF4)2·1,2-Cl2C2H4, [Au2(μ-dppe)2](PF6)2·CHCl3, [Au2(μ-dppe)2](PF6)2, [Au2(μ-dppe)2](SbF6)2, and [Au2(μ- dppe)2](OTf)2·2CHCl3), (dppe is bis(diphenylphosphine)ethane) containing the dication, [Au2(μ-dppe)2]2+, have been prepared and structurally characterized by single-crystal X-ray crystallography. Unlike the three-coordinate dppe-bridged dimers, Au2X2(μ-dppe)2 (X = Br, I), which show considerable variation in the distance between the gold(I) ions over the range 3.0995(10) to 3.8479(3) Å in various solvates, the structure of the helical dication, [Au2(μ- dppe)2], in the new salts is remarkably consistent with the Au···Au separation falling in the narrow range 2.8787(9) to 2.9593(5) Å. In the solid state, the six crystals display a green luminescence both at room temperature and at 77 K, which has been assigned as phosphorescence. However, solutions of the dication are not luminescent. Salts containing the analogous dication [Au2(μ-dppp)2](PF6)2 (dppp is bis(diphenylphosphine)propane) have been prepared to determine whether the longer bridging ligand might also twist into a helical shape. These salts include [Au2(μ- dppp)2](OTf)2 (OTf is triflate) and three crystalline forms of [Au2(μ-dppp)2](PF6)2: the solvate [Au2(μ-dppp)2](PF6)2·(CHCl3) and two polymorphs of the unsolvated salt. None of these crystals are luminescent, but all contain a similar dication, [Au2(μ- dppp)2]2+, that contains two nearly parallel, linear P−Au−P groups and a long separation between the gold ions that varies from 5.3409(4) to 5.6613(6)Å. 

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2. Self-assembled HfO ₂ -Au nanocomposites with ultra-fine vertically aligned Au nanopillars

   https://doi.org/10.1039/D2NR03104C  

   Zhang, Yizhi; Zhang, Di; Liu, Juncheng; Lu, Ping; Deitz, Julia; Shen, Jianan; He, Zihao; Zhang, Xinghang; Wang, Haiyan (August 2022, Nanoscale)

   Oxide-metal-based hybrid materials have gained great research interest in recent years owing to their potential for multifunctionality, property coupling, and tunability. Specifically, oxide-metal hybrid materials in a vertically aligned nanocomposite (VAN) form could produce pronounced anisotropic physical properties, e.g. , hyperbolic optical properties. Herein, self-assembled HfO 2 -Au nanocomposites with ultra-fine vertically aligned Au nanopillars (as fine as 3 nm in diameter) embedded in a HfO 2 matrix were fabricated using a one-step self-assembly process. The film crystallinity and pillar uniformity can be obviously improved by adding an ultra-thin TiN-Au buffer layer during the growth. The HfO 2 -Au hybrid VAN films show an obvious plasmonic resonance at 480 nm, which is much lower than the typical plasmonic resonance wavelength of Au nanostructures, and is attributed to the well-aligned ultra-fine Au nanopillars. Coupled with the broad hyperbolic dispersion ranging from 1050 nm to 1800 nm in wavelength, and unique dielectric HfO 2 , this nanoscale hybrid plasmonic metamaterial presents strong potential for the design of future integrated optical and electronic switching devices. 

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3. TiN‐Au/HfO ₂ ‐Au Multilayer Thin Films with Tunable Hyperbolic Optical Response

   https://doi.org/10.1002/smtd.202400087  

   Zhang, Yizhi; Shen, Jianan; Tsai, Benson Kunhung; Sheng, Xuanyu; Hu, Zedong; Zhang, Xinghang; Wang, Haiyan (March 2024, Small Methods)

   Abstract Hyperbolic metamaterials (HMM) possess significant anisotropic physical properties and tunability and thus find many applications in integrated photonic devices. HMMs consisting of metal and dielectric phases in either multilayer or vertically aligned nanocomposites (VAN) form are demonstrated with different hyperbolic properties. Herein, self‐assembled HfO₂‐Au/TiN‐Au multilayer thin films, combining both the multilayer and VAN designs, are demonstrated. Specifically, Au nanopillars embedded in HfO₂and TiN layers forming the alternative layers of HfO₂‐Au VAN and TiN‐Au VAN. The HfO₂and TiN layer thickness is carefully controlled by varying laser pulses during pulsed laser deposition (PLD). Interestingly, tunable anisotropic physical properties can be achieved by adjusting the bi‐layer thickness and the number of the bi‐layers. Type II optical hyperbolic dispersion can be obtained from high layer thickness structure (e.g., 20 nm), while it can be transformed into Type I optical hyperbolic dispersion by reducing the thickness to a proper value (e.g., 4 nm). This new nanoscale hybrid metamaterial structure with the three‐phase VAN design shows great potential for tailorable optical components in future integrated devices. 

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4. Au-MoS ₂ Hybrids as Hydrogen Evolution Electrocatalysts

   https://doi.org/10.1021/acsaem.9b01147  

   Bar-Ziv, Ronen; Ranjan, Priyadarshi; Lavie, Anna; Jain, Akash; Garai, Somenath; Bar Hen, Avraham; Popovitz-Biro, Ronit; Tenne, Reshef; Arenal, Raul; Ramasubramaniam, Ashwin; et al (August 2019, ACS Applied Energy Materials)
5. Au@MoS ₂ @WS ₂ Core–Shell Architectures: Combining Vapor Phase and Solution-Based Approaches

   https://doi.org/10.1021/acs.jpcc.9b11365  

   DiStefano, Jennifer G.; Murthy, Akshay A.; Lescott, Chamille J.; dos Reis, Roberto; Li, Yuan; Dravid, Vinayak P. (January 2020, The Journal of Physical Chemistry C)