Metal Atom Clusters as Building Blocks for Multifunctional Proton-Conducting Materials: Theoretical and Experimental Characterization

Abstract

The search for new multifunctional materials displaying proton-conducting properties is of paramount necessity for the development of electrochromic devices and supercapacitors as well as for energy conversion and storage. In the present study, proton conductivity is reported for the first time in three molybdenum cluster-based materials: (H)[MoBrS(OH)]-12HO and (H)[MoX(OH)]-12HO (X = Cl, Br). We show that the self-assembling of the luminescent [MoL(OH)] cluster units leads to both luminescence and proton conductivity (σ = 1.4 × 10 S·cm in (H)[MoCl(OH)]-12HO under wet conditions) in the three materials. The latter property results from the strong hydrogen-bond network that develops between the clusters and the water molecules and is magnified by the presence of protons that are statistically shared by apical hydroxyl groups between adjacent clusters. Their role in the proton conduction is highlighted at the molecular scale by ab initio molecular dynamics simulations that demonstrate that concerted proton transfers through the hydrogen-bond network are possible. Furthermore, thermogravimetric analysis also shows the ability of the compounds to accommodate more or less water molecules, which highlights that vehicular (or diffusion) transport probably occurs within the materials. An infrared fingerprint of the mobile protons is finally proposed based on both theoretical and experimental proofs. The present study relies on a synergic computational/experimental approach that can be extended to other proton-conducting materials. It thus paves the way to the design and understanding of new multifunctional proton-conducting materials displaying original and exciting properties.

Zn–Al Layered Double Hydroxide Film Functionalized by a Luminescent Octahedral Molybdenum Cluster: Ultraviolet–Visible Photoconductivity Response

“…Its photoelectrical property stabilization is valid for the development of an optical sensing device. Many reasonable hypotheses have discussed the origin of the redox, photophysical, and photochemical properties of the Mo 6 cluster based on the molecular structure, chemical compositions, and their intrinsic interactions. ,,, Moreover, the proton-conducting properties of the (H) 2 [Mo 6 X 8 (OH) 6 ]·12H 2 O (X = Cl, Br) have been clarified through the hydrogen-bond network that develops between apical hydroxyl groups and the adsorbed water molecules . Kuttipillai et al also suggested that the counter cations can play an important role in charge injection, transport, recombination, and exciton formation in the electrically pumped devices fabricated from the core cluster .…”

PLGA nanoparticles embedding molybdenum cluster salts: Influence of chemical composition on physico-chemical properties, encapsulation efficiencies, colloidal stabilities and in vitro release

“…For blank PLGA nanoparticles, colloidal stability was conserved during the 3 months study whatever the temperature (Supplementary material 1). Figure 3 shows (Daigre et al, 2018;Kirakci et al, 2016Kirakci et al, , 2019Svezhentseva et al, 2017). Encapsulating the cluster in a matrix such as SiO 2 nanoparticles (Aubert et al, 2013), polystyrene microparticles (Efremova et al, 2014) or nanoassemblies with betacyclodextrins (Kirakci et al, 2014) was shown to be a solution to circumvent the tendency to easily hydrolyse in water.…”

Enhanced Photocatalytic Activity and Stability in Hydrogen Evolution of Mo6 Iodide Clusters Supported on Graphene Oxide

“…As molybdenum (and tungsten) is sufficiently cheap and abundant, their compounds constitute viable alternatives to costly noble metal-based luminophores, not to mention the environmentally hazardous lead-based hybrid perovskites and cadmium containing quantum dots [ 6 , 7 , 8 ]. Octahedral halide-bridged cluster compounds of Mo(II) and W(II), of the general type [M 6 X i 8 L a 6 ] (M = Mo, W; X i = Cl, Br, I (bridging or “inner”); L a = organic/inorganic ligand (terminal or “apical”, see Figure 1 ) show remarkable photoluminescence properties and emit red light in high quantum yields, which makes them particularly attractive in the design of functional hybrid nanomaterials [ 9 ] with potential applications in optoelectronic [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ], lighting [ 19 ], hydrogen storage [ 20 ], biomedicine [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ], catalysis [ 30 , 31 ], and photocatalysis [ 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ].…”