In touch: the outcome of contact electrification between dielectrics depends not only on the transfer of charge but also on the transfer of material. Although only minute quantities of materials are being exchanged during contact, they can reverse the polarity of dielectrics. The reported results corroborate the mosaic model and suggest that the observations are because of the mechanical softness/hardness of the materials.

The pursuit to achieve miniaturization has tantalized researchers across the fields of chemistry, physics, biology, materials science and engineering for over half a century because of its many alluring potential applications. As alternatives to traditional "top-down" manufacturing, "bottom-up" approaches, originating from the (supra)molecular level, have enabled researchers to develop switches which can be manipulated on surfaces at nanoscale dimensions with deft precision using simple external triggers. Once on surfaces, these organic switches have been shown to modulate both the physical and chemical surface properties. In this Progress Report, we shed light on recent advances made in our laboratories towards integrated systems using all-organic switches on a variety of substrates. Design concepts are revealed, as well as the overall impact of all-organic switches on the properties of their substrates, while emphasizing the considerable promise and formidable challenges these advanced composite materials pose when it comes to conferring function on them.

procedures, elemental analysis, tables of DFT results, and notes on cell design and construction (PDF).

Following previous experimental work examining a layered oxyfluoride as cathode material for Mg-ion batteries [Incorvati et al., Chem. Mater. 2016, 28, 17], we study the role of fluorination on the structural and electronic properties of molybdenum trioxide and its impact on Mg intercalation and diffusion using firstprinciples methods. Although bulk α-MoO 3 is a 2D layered compound, we find that it provides 3D channels for Mg diffusion. When F atoms are incorporated into the α-MoO 3 lattice, they replace the O atoms sitting at a specific crystallographic site that is linked by two nearest Mo atoms within a single Mo−O layer. As a consequence of F substitution, the local Mo-anion bonds are distorted, which leads to closure of the electronic band gap. From the analysis of zone center phonon vibrational frequencies, it is found that the local Mo-anion bonding strength is weakened by replacing O 2− with F − , which ultimately facilitates Mg diffusion through the F-substituted lattice. For example, it is shown that upon fluorination the activation barriers for Mg diffusion along selected pathways can be lowered by as much as 0.6 eV, estimated from our nudged elastic band simulations at 0K. Our results imply that direct anion doping can be a viable approach toward improving ion diffusivity in Mg-ion battery cathodes.

In touch: The outcome of contact electrification between dielectrics depends not only on the transfer of charge but also on the transfer of material (see picture). Although only minute quantities of materials are being exchanged during contact, they can reverse the polarity of dielectrics. The reported results corroborate the mosaic model and suggest that the observations are because of the mechanical softness/hardness of the materials.

The effects of cation doping on cathode performance has been extensively studied; however, the field of anion doping has historically received much less attention. Fluoride doping can greatly increase the initial diffusivity of the layered MoO3 system. The first discharge cycle of the layered α-MoO3 and MoO2.8F0.2 phases were investigated and compared using the galvanostatic intermittent titration technique (GITT) in a lithium ion cell. The analysis revealed that a slight reduction of the oxide by fluoride doping to form a fluorobronze (MoO2.8F0.2) eliminated a slow electrochemical process observed in α-MoO3. Galvanostatic cycling studies show that while α-MoO3 has a higher initial capacity, it exhibits a first cycle Coulombic efficiency of only 86% with rapid capacity fade which has been associated with lithium trapping within the MoO3 layer. In contrast, the Li+ intercalation process in the fluorobronze was found to have a 94% Coulombic efficiency on the first cycle. By the third cycle Coulombic efficiencies greater than 99% were observed for five cycles. A thorough investigation of the synthesis of MoO2.8F0.2 is also presented. Under mild hydrothermal conditions, the fluorination of α-MoO3 to form MoO2.8F0.2 is topotactic, while a competing reaction in solution forms MoO2.4F0.6 (ReO3 structure). Methods to prevent the solution phase reaction from occurring are discussed.

Alessandro Volta (portrait by N. Cianfanelli) was the first modern scientist who aimed to rank dielectric materials. No such rankings have proven accurate because of the effects of material transfer, as described by B. A. Grzybowski and co‐workers in their Communication on In the picture, the upper half of the circle illustrates a typical ranking of contact charging (red=positive polarity, blue=negative polarity). The lower half shows atomic force microscopy images of contact‐charged surfaces.

The widespread adoption of multivalent batteries is hampered by the lack of stable, reliable, high voltage cathodes that can reversibly intercalate divalent cations. In lithium-based systems, molybdenum trioxide has been studied for several years as a high capacity cathode material. Although its voltage is lower than other systems, e.g. V2O5, it has advantages including crystallographic stability on cycling. A key issue that is believed to limit its performance is that, as a d0 metal oxide, it has limited electronic conductivity at top of charge.1 In this poster we will be discussing the role of fluoride incorporation into the layered charged cathode MoO3 and its effect on the materials physical properties. Utilizing synthetic methodologies developed in our lab we have studied the fluoride solubility in the host material as a way to induce electronic conductivity across the whole range of use. We have shown that the maximum fluoride incorporation in the material yields a stoichiometry of MoO2.8F0.2. Incorporation above this value results in isolation of the perovskite phase MoO2.6F0.4. We have evaluated the material using multiple intercalating cations and compared it to the undoped parent material. While the electrochemical activity of the material using a lithium-based electrolyte is similar, remarkable differences have been observed when Mg is used as the cation. While the undoped material has little or no activity, the fluorinated materials shows excellent cycleability and structural reversibility.2 References: (1) Spahr, M. E.; Novák, P.; Haas, O.; Nesper, R., Electrochemical insertion of lithium, sodium, and magnesium in molybdenum(VI) oxide. J. Power Sources 1995, 54, 346-351. (2) Incorvati, J. T.; Wan, L. F.; Key, B.; Zhou, D.; Liao, C.; Fuoco, L.; Holland, M.; Wang, H.; Prendergast, D.; Poeppelmeier, K. R.; Vaughey, J. T., Reversible Magnesium Intercalation into a Layered Oxyfluoride Cathode. Chemistry of Materials 2016, 28, 17-20. Figure 1