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New chemistries are being developed to increase the capacity and power of rechargeable batteries. However, the risk of safety issues increases when high-energy batteries using highly active materials encounter harsh operating conditions. Here we report on the synthesis of a unique ionogel electrolyte for abuse-tolerant lithium batteries. A hierarchically architected silica/polymer scaffold is designed and fabricated through a facile soft chemistry route, which is competent to confine ionic liquids with superior uptake ability (92.4 wt%). The monolithic ionogel exhibits high conductivity and thermal/mechanical stability, featuring high-temperature elastic modulus and dendrite-free lithium cycling. The Li/LiFePO4 pouch cells achieve outstanding cyclability at different temperatures up to 150 °C, and can sustain cutting, crumpling, and even coupled thermal–mechanical abuses. Moreover, the solid-state lithium batteries with LiNi0.60Co0.20Mn0.20O2, LiNi0.80Co0.15Al0.05O2, and Li1.2Mn0.54Ni0.13Co0.13O2 cathodes demonstrate excellent cycle performances at 60 °C. These results indicate that the resilient and high-conductivity ionogel electrolyte is promising to realize high-performance lithium batteries with high energy density and safety.

The achievement of atomic control over the organic-inorganic interface is key to engineering electronic and spintronic properties of molecular devices. We leverage insights from inorganic chemistry to create hard-soft acid-base (HSAB) theory-derived design principles for incorporation of single molecules onto metal electrodes. A single molecule circuit is assembled via a bond between an organic backbone and an under-coordinated metal atom of the electrode surface, typically Au. Here, we study molecular composition factors affecting the junction assembly of coordination complexes containing transition metals atoms on Au electrodes. We employ hetero- and homobimetallic lantern complexes and systematically change the coordination environment to vary the character of the intramolecular bonds relative to the electrode-molecule interaction. We observe that trends in the robustness and chemical selectivity of single molecule junctions formed with a range of linkers correlate with HSAB principles, which have traditionally been used to guide atomic arrangements in the synthesis of coordination complexes. We find that this similarity between the intermolecular electrode-molecule bonding in a molecular circuit and the intramolecular bonds within a coordination complex has implications for the design of metal-containing complexes compatible with electrical measurements on metal electrodes. Our results here show that HSAB principles determine which intramolecular interactions can be compromised by inter molecule-electrode coordination; in particular on Au electrodes, soft-soft metal-ligand bonding is vulnerable to competition from soft-soft Au-linker bonding in the junction. Neutral donor-acceptor intramolecular bonds can be tuned by the Lewis acidity of the transition metal ion, suggesting future synthetic routes toward incorporation of transition metal atoms into molecular junctions for increased functionality of single molecule devices.

Dense and homogeneous BaTi1-xSnxO3 (BTS, x = 0.1, 0.15, 0.2, 0.25, and 0.3) thin films are prepared by sol-gel and spin-coating soft chemistry, which is a simple, repeatable and quality-controlled method. The effects of Sn content on the structure and dielectric properties are systemically studied. The BTS thin film with 0.25 mol% Sn is found to exhibit a moderate dielectric constant of 225–398, a high tunability of 43.3% under a low bias electric field of 8 kV/mm, and a corresponding leakage current density of 6.2×10−8 A/cm2. These improvements are a result of the enhancement in relaxor characteristics, the good crystallization conditions leading to a denser and more uniform structure, as well as the inhibition of oxygen vacancies resulting from the suppression of electronic transition from Ti4+ to Ti3+. The findings reported in this work provide a simple and effective way to prepare excellent tunable thin films that show great potential for the development of electrically tunable components and devices.

International audience; In this article, we report a facile precursor pyrolysis by sol-gel method to prepare spinel-type Cobalt-substituted zinc aluminate nanoparticles (Zn1–xCoxAl2O4, 0≤x≤1). The relationship between the degree of crystallinity and the optical properties under the effect of the calcination temperature was investigated. The synthesized powders were characterized by means of X-ray diffraction (XRD), Thermogravimetry and Differential thermal analysis (TG–DTA), field emission scanning electron microscopy (FE-SEM), Brunauer–Emmett–Teller analysis (BET), UV–Vis absorption spectroscopy analysis and colorimetric analysis (CIELab). A single-phase Zn1–xCoxAl2O4 (0≤x≤1) spinel was formed at an annealing temperature of 700°C. Structural refinement via the Rietveld method shows that an annealing temperature in excess of 700°C leads to a decrease in the amorphous phase rate. At 800 °C, the enrichment in 50% of cobalt leads to blue powders with a degree of crystallinity of approximately 92% and a quasi-spherical morphology of nanometric size less than 100 nm.

The in-situ high-content carbon-containing calcium aluminate cement (HCCAC) with the carbon content of 20.1 wt.% was prepared by the soft chemistry method with citric acid, calcium carbonate, and alumina as raw materials. The cement product was characterized by X-ray diffractometry, scanning electron microscopy, and Raman spectroscopy. In HCCAC, plate-like and fibrous carbon formed by the pyrolysis of organic acids were uniformly embedded between the calcium aluminate grains. Moreover, the carbon floating ratio of HCCAC in water was lower than that of the mechanical mixing powder of calcium aluminate cement (CAC) and carbon black, which indicated that the water dispersion of carbon was improved. Besides, the slag corrosion resistance properties of Al2O3-SiC-C castables bonded with HCCAC and CAC respectively were compared, and the results showed that the corrosion resistance depth of the HCCAC bonded castables was 45% lower than that of the CAC bonded castables. Therefore, HCCCA can be used as a novel binder of carbon-containing refractory castables.

Nanocrystalline bismuth orthoferrite (BiFeO3) was prepared by soft chemistry. The hydroxide coprecipitation method was shown to influence the formation of nanocrystalline bismuth orthoferrite. Synthetic conditions were determined to prepare nanocrystalline BiFeO3 free of other phases of the Bi2O3–Fe2O3 system with a narrow crystallite-size distribution and the smallest crystallite size of about 6–7 nm.

In this paper, we investigate the improvement of varistor devices with a ZnO-based material. In this goal, pure and 1% Bi-doped ZnO nano-powders have been synthesized at different sintering temperatures by a soft chemistry method: the sol–gel route. The used temperatures were carefully chosen to obtain the desired phases: (α-Bi2O3, β-Bi2O3, and δ-Bi2O3). Characterizations were made by XRD and TEM to determine the structural properties and particle sizes of Bi phases. XRD spectra confirmed the wurtzite structure and the presence of many transition phases for each sintering temperatures with an average grain size varying from 42 nm to 76 nm. TEM and SEM images of the samples allowed us to study the location of different phases, their morphologies, and the size of particles, and they show a mixture of nano-objects of different sizes and shapes. The electrical characteristics J(E) were measured to correlate these results with the varistor effect which indicate a good nonohmic behavior for all samples; the threshold voltage VB ranges between 242 and 701 V/cm and the coefficient of nonlinearity between 10.26 and 14.5. The total absence of phase transitions between the grains of the triple point in the ZnO–Bi2O3-based varistor is presented. Moreover, we show that the majority of phase transitions are located at the boundary of grains and forms a Shottky barrier which is suitable to improve the protective effect of surge arresters for hugely suppressing over-voltages in power and network systems.

Transition-metal oxide nanostructured materials are potentially attractive alternatives as anodes for Li ion batteries and as photocatalysts. Combining the structural and thermal stability of titanium oxides with the relatively high oxidation potential and charge capacity of molybdenum(VI) oxides was the motivation for a search for approaches to mixed oxides of these two metals. Challenges in traditional synthetic methods for such materials made development of a soft chemistry single-source precursor pathway our priority. A series of bimetallic Ti-Mo alkoxides were produced by reactions of homometallic species in a 1:1 ratio. Thermal solution reduction with subsequent reoxidation by dry air offered in minor yields Ti2Mo2O4(OMe)6(OiPr)6 (1) by the interaction of Ti(OiPr)4 with MoO(OMe)4 and Ti6Mo6O22(OiPr)16(iPrOH)2 (2) by the reaction of Ti(OiPr)4 with MoO(OiPr)4. An attempt to improve the yield of 2 by microhydrolysis, using the addition of stoichiometric amounts of water, resulted in the formation with high yield of a different complex, Mo7Ti7+xO31+x(OiPr)8+2x (3). Controlled thermal decomposition of 1–3 in air resulted in their transformation into the phase TiMoO5 (4) with an orthorhombic structure in space group Pnma, as determined by a Rietveld refinement. The electrochemical characteristics of 4 and its chemical transformation on Li insertion were investigated, showing its potential as a promising anode material for Li ion batteries for the first time. A lower charge capacity and lower stability were observed for its application as an anode for a Na ion battery., Controlled decomposition of a structurally characterized Ti-Mo oxo-alkoxide precursor offered an approach to the new ternary oxide TiMoO5, showing promising characteristics as an anode material for Li ion batteries.

Carbon nano-onions (CNOs), as one of the allotropes of carbon, have attracted great attention because of their excellent performance in many fields, especially in capacitors. Developing soft-chemistry synthesis methods is critically of importance, while the forming mechanism in this area is not clear. In this paper, we present a critical review of CNOs regarding the structure, especially interlayer spacing, and synthesis processes, elaborating the recent progress on soft-chemistry methods. Hansen solubility parameter theory is applied to predict and regulate the solubility of CNOs. This article would be inspirational and give new insights into understanding the formation and properties of CNOs.

Spinel oxides with the general formula Mn1.7Cu1.3-xFexO4 (x= 0, 0.1, 0.3, 0.5) were prepared and evaluated in this work for their properties at high temperatures. The effect of partially substituting Cu by Fe has not been studied so far for this group of materials and is thus evaluated in this work. Mn1.7Cu1.3-xFexO4 powders were synthesised by a soft chemistry process and studied in terms of crystallographic phase analysis, electrical conductivity, thermal expansion, and sinterability behaviour. The results show that the Fe content has a significant influence on the phase composition and the resulting properties. Characterisation of the dilatometry and conductivity coupled with XRD phase analysis across a wide temperature range allowed the relations between the materials properties and compositions to be observed. The results indicate that Mn1.7Cu0.8Fe0.5O4 is a promising material for use as a protective coating for interconnects in intermediate temperature Solid Oxide Fuel Cells.

Titanomagnetite is widely distributed in nature, and has potentials in environmental remediation. Nanometric titanomagnetite particles were usually prepared via soft chemistry routes in aqueous solutions. Herein a novel soft chemistry route carried out in a deep eutectic solvent (DES) comprising choline chloride and urea in a molar ratio of 1:2 was successfully developed to make titanomagnetite nanoparticles (Fe2.5Ti0.5O4-DES, ~30 nm). The chemical composition analyzed by different methods revealed that Fe2.5Ti0.5O4-DES nanoparticles possess the Ti-rich core and Fe-rich shell. The Fe2.5Ti0.5O4-DES nanoparticles exhibited enhanced activities in catalytic decomposition of H2O2 and oxidative degradation of organic contaminants at circumneutral pH values and room temperature, which was mainly attributed to the increased content of ferrous (Fe2+) ions upon substitution of Ti4+ for ferric (Fe3+) ions in spinel structure of magnetite.

The International Year of The Periodic Table of Chemical Elements revealed that the Table remains both a deeply fundamental paradigm for various branches of chemistry and a universal practical tool for predictable design of new materials. Silver is a notable “nanoelement” particularly known by its plasmonic properties. A key advantage of this metal is an easily achievable morphological variety of nanostructured materials. This element represents a research branch of precise engineering of shapes and sizes of nanoparticle ensembles and smart hierarchic nanostructures. In the review, unique features of silver are discussed with respect to the development of novel analytical methods for forthcoming applications of surface-enhanced Raman spectroscopy (SERS) in ecology, biology and medicine.

Neodymium oxide (Nd2O3) powder with closed packed hexagonal (cph) crystal structure was synthesized from the elemental neodymium (Nd) using soft chemistry route. The hydrated neodymium nitrate was produced by reacting metallic Nd with nitric acid. At 546 °C, the hydrated neodymium nitrate was thermally transformed to body centered cubic (bcc) Nd2O3 in four-stage thermodynamic reactions. The bcc-Nd2O3 was subsequently transformed to cph-Nd2O3 at 1037 °C. A crystallite size of ~ 50 nm was attainable in the process. It was observed that the degree of crystallinity of the powder was increased with longer exposure time (> 30 min) at 1037 °C. In DSC/TGA studies, five endothermic peaks were observed at different temperatures. During XRD evaluations, it was elaborated that each peak corresponded to certain phase transformation, i.e., Nd (OH)2·NO3 monoclinic (at 160 °C), Nd(OH)3 cph (at 315 °C), Nd2O fcc (at 500 °C), Nd2O3 bcc (at 590 °C), and Nd2O3 cph (at 1050 °C). The FTIR evaluation further validated the findings. The grain size and cph structure of the final product were also verified by TEM study.

This study is focused on the development of a nanostructured coating by soft chemistry in order to obtain antibacterial and self-cleaning properties. The strategy adopted was to implement an energy-efficient aqueous chemical method for environmental reasons: the adopted protocol involves the formation of nanometric zinc oxide rods using a liquid route at temperatures below 100 ° C. First, we studied the relationship between the substrate preparation method and the durability of the final deposited coating (initial surface condition, part geometry, etc.). In order to improve the resistance of growth-initiating germs, a silica gel has been developed, optimized and previously deposited on the substrate as a chemical bonding base. The choice of zinc oxide as nanostructuring crystallites then provides a photo-catalytic characteristic which activates the degradation of various organic substances (dirt, bacteria). This property has also been verified by firstly studying the mortality of model bacteria and secondly by monitoring the discoloration of a dye, methylene blue, to simulate soiling. Tests with common bacterial strains like E. coli have been performed and have shown less proliferation on a treated surface compared to a bare surface. A population of bacteria 3 to 4 times less important on the surface was noted. There is also 3 times more mortality in washing water. This shows the difficulty of bacteria to attach on the surface as well as a mortality effect induced by the coating. Vapor deposition of a long carbon chain molecule increases the superhydrophobic property of the surface, thereby preventing soil deposition and reducing the use of cleaning products, without reducing the desired properties. The mechanical durability of the coating has also been studied in order to verify the maintenance of the self-cleaning properties in use. A tailored tribological test has been developed to simulate the friction of a finger on the surface. Despite the observed wear of the needles, the coating retains its hydrophobic character and its ability to degrade. It has also been observed that the superhydrophobic layer degrades in priority for the benefit of the integrity of the nano-needles.; Cette étude est focalisée sur l’élaboration d’un revêtement nanostructuré par procédé chimie douce afin d’obtenir des propriétés antibactériennes et autonettoyantes. La stratégie adoptée a été de mettre en place une méthode chimique en voie aqueuse peu énergivore pour des raisons environnementales : le protocole adopté met en jeu la formation d’oxyde de zinc nanométrique par voie liquide à des températures inférieures à 100°C. En premier lieu, nous nous sommes attachés à étudier la relation entre la méthode de préparation du substrat et la durabilité du revêtement final déposé (état de surface initial, géométrie de la pièce…). Afin d’améliorer la tenue des germes initiateurs de croissance, un gel de silice a été mis au point, optimisé et préalablement déposé sur le substrat comme base d’accroche chimique. Le choix de l’oxyde de zinc en tant que cristallites nano-structurants apporte ensuite un caractère photo-catalytique qui active la dégradation de diverses substances organiques (salissures, bactéries). Cette propriété a par ailleurs été vérifiée via d’une part l’étude de la mortalité de bactéries modèles et d’autre part le suivi de décoloration d’un colorant, le bleu de méthylène, permettant de simuler une salissure. Les tests avec des souches bactériennes communes comme E. coli ont été réalisés et ont montré une prolifération plus réduite sur une surface traitée comparé à une surface nue. Une population de bactéries 3 à 4 fois moins importante sur la surface a été relevée. Il y a également 3 fois plus de mortalité dans les eaux de lavage. Ceci montre une difficulté d’accroche des bactéries ainsi qu’un effet de mortalité induit par le revêtement. Un dépôt en phase vapeur d’une molécule à longue chaîne carbonée permet d’accroître la propriété superhydrophobe de la surface, empêchant ainsi un dépôt de salissure et réduisant l’utilisation de produits de nettoyage, sans pour autant amoindrir les propriétés recherchées. La durabilité mécanique du revêtement a également été étudiée afin de vérifier le maintien des propriétés autonettoyantes à l’usage. Un test tribologique sur-mesure a été élaboré pour permettre de simuler le frottement d’un doigt sur la surface. Malgré l’usure constatée des aiguilles, le revêtement conserve son caractère hydrophobe et sa capacité de dégradation. Il a également été observé que la couche superhydrophobe se dégradait en priorité au profit de l’intégrité des nano-aiguilles.

A soft chemistry approach was applied to synthesize de(sodiated) transition-metal hydroxy molybdates under hydrothermal conditions. Different NaM2(H3O2)(MoO4)2 and M2MoO4(OH)2 compositions (M = Ni, Zn) were prepared at mild temperatures (110–250 °C) for times ranging from 10 min to 24 h. Sodiated compounds were obtained after a microwave-assisted hydrothermal process at 150 °C (10–120 min) for zinc-based materials. Besides, conventional heating destabilized the sodiated NaZn2(H3O2)(MoO4)2 phase at 110 °C, thus increasing the amount of Zn2MoO4(OH)2 at temperatures up to 250 °C. NaNi2(H3O2)(MoO4)2 phases were noted only for 10 min under microwave irradiation, while longer times promoted a chemical reaction towards a new desodiated phase. This novel Ni2MoO4(OH)2 phase was also obtained by conventional hydrothermal processing (110–250 °C, 24 h). Slow precipitation rates yielded a hydrated nickel molybdate (triclinic, P) after coprecipitation followed or not by microwave irradiation. Raman spectroscopy analysis results showed a good agreement with experimental results and group-theory calculations for both sodiated and desodiated materials. A temperature-induced polymorphic transformation was observed from NiMoO4·xH2O (triclinic, P) to α-NiMoO4 (monoclinic, C2/m). For all the obtained polymorphs, the relevant Raman modes were depicted, allowing us to determine their spectroscopic fingerprints. The results constitute an important basis on the understanding of the synthesis of (de)sodiated transition-metal hydroxy molybdates under hydrothermal conditions.

Designing a solid state crystal architecture at nanoscale, using a soft chemistry approach, is the key step toward their scalable synthesis for sustainable application in electrochemical charge sto...

Protonated oxides, H2[Sr2Nb2MO9.5] (M = Al, Ga) and H2[Sr2Nb2ZrO10] related to the Ruddlesden–Popper family of layered perovskite oxides, have been successfully synthesized at room temperature starting from Aurivillius phases Bi2Sr2Nb2MO11.5 (M = Al, Ga) and Bi2Sr2Nb2ZrO12 by the extraction of bismuth oxide sheets using acids. Synthesis of crystalline protonated oxides was also found to be possible under microwave treatment within a short time duration of 5 min. The protonated oxides have been found to undergo facile ion-exchange reactions with an aqueous solution of NaOH or KOH resulting in novel oxides A2Sr2Nb2MO9.5 (A = Na, K; M = Al, Ga) and A2Sr2Nb2ZrO10 (A = Na, K), which could not be synthesized by conventional high temperature solid state synthetic methods. Powder X-ray diffraction patterns confirmed the topochemical nature of the reactions by reflecting changes only in the c-dimensions. Rietveld refinements carried out in the case of K+ ion-exchanged products confirmed their structural similarity...

Mesoporous alumina and γ-Al2O3–NaAlO2 composites with different morphology were produced by soft chemistry methods using polyethylenimine (PEI), pluronic P123 (P123), and polymer–colloid complex (PCC) derived from them as templates in solution. Sodium aluminate was applied as an additive for production of the mesoporous γ-Al2O3–NaAlO2 composite. The obtained samples were characterized by scanning and transmission electron microscopy, atomic force microscopy, Fourier transform IR spectrometry, X-ray diffraction analysis, and low-temperature N2 adsorption–desorption analysis. The effect of sodium aluminate introduction on the morphological features of the obtained samples was investigated. Mesostructured aluminum oxide obtained using individual templates such as P123 and PEI possesses cylindrical pores, whereas applying PCC resulted in the formation slit-shaped pores. The produced mesoporous aluminum oxide and γ-Al2O3–NaAlO2 composite had a narrow pore size distribution and large surface area. This approach was demonstrated to allow for the control of pore sizes and shapes.

Benzoate anions were immobilized into layered zinc hydroxide nitrate (ZHN) via a soft chemistry method. The hybrid material was characterized by powder X-ray diffraction (PXRD), thermogravimetry (TG/DTA), differential scanning calorimetry (DSC) analysis, Fourier-transform infrared (FT-IR) spectroscopy, and impedance spectroscopy. The expansion of the interlayer space at 20.0 A confirmed the incorporation of the benzoate forming bilayers into the layered structure. The interaction of the organic molecules occurs through the coordination of the carboxylate group to the Zn+2 atoms in the tetrahedral sites of the layered structure. The conductivity, e′, and e″ values of the hybrid materials were reduced five orders of magnitude in comparison with those of the inorganic ZHN host matrix at low frequencies. The results suggest that the solvation process between hydroxyl groups of the layers and adsorbed water molecules contributes in the electric response, whereas an induced dipole interaction describes the dielectric behavior of the hybrid material. The description of the electrical and dielectric properties can open new potentialities of this hybrid material for their possible application in electrochemical devices.

Silver nanoparticles (AgNPs) were synthesizd by a light-assisted liquid phase reduction method with sodium hypophosphite as a reducing agent. DTAB was used to perform as the surfactant. AgNPs were characterized with powder X-ray diffraction (XRD) and scanning electron microscope (SEM). The result showed that the nanoparticles are spherical and cube. The effect of temperature on the morphology and properties of silver nanoparticles was investigated. The ultraviolet-visible (UV-vis) absorption and the fluorescent properties of the as-prepared AgNPs were explored.

Bismuth doped ZnO nanopowders with doping concentrations between 0 and 7 %mol were successfully synthesized with a soft chemistry method: the sol-gel route. This method allows obtaining powders with a good quality in a nanometric size range. The well-defined optimal conditions for the synthesized powders are given. The hydrated zinc acetate dissolved in ethylene glycol is used as a precursor for the zinc oxide (ZnO), with different small amount of Bi concentrations (1%, 3%, 5% and 7%). After calcination at 500 °C, the powders are consolidated into pellets and sintered using a conventional furnace and then characterized by: X-ray diffraction, SEM, TEM, and J(E) electrical measurements. Finally, the obtained material has been used to prepare varistors. The XRD patterns indicate that pure and Bi doped ZnO are solid solutions with average grain sizes varying between 65 nm and 48 nm. The β-Bi2O3 liquid phase of tetragonal structures appears as a secondary phase for a 5% mol concentration of Bi. High-resolution TEM images of Bi doped ZnO particles indicate that during the sintering of Bi-doped ZnO, the growth of particles leads to a change in the microstructure of ZnO giving semi-transparent cylindrical nanotubes. J(E) results indicate that the content of Bi increases the nonlinearity coefficient α and the breakdown fields VB of the binary Zn %Bi-O varistors. The 7% doped Bi-ZnO varistor gives the best electrical characteristics for varistors.

Lu(OH)CO3:Ln3+/LuBO3:Ln3+ (Ln = Eu, Tb) nanospheres have been synthesized by the soft chemistry route. This synthesis process does not require the addition of any organic solvents and surfactant. The whole process consists of homogeneous precipitation and hydrothermal process. First, uniform spherical Lu(OH)CO3:Ln3+ (Ln = Eu, Tb) nanoparticles with the sizes of 70 nm were obtained by the classic urea-based homogeneous precipitation. Then, with the above Lu(OH)CO3:Ln3+ (Ln = Eu, Tb) nanosphere as the precursor, the composites of Lu(OH)CO3:Ln3+/LuBO3:Ln3+ (Ln = Eu, Tb) nanospheres formed by the simple hydrothermal process. The phases, morphologies, as well as the luminescence properties of as-prepared samples were characterized by means of X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and photoluminescence. Under a short wavelength excitation, the down-conversion Eu3+ and Tb3+-doped LuBO3 samples were investigated and explained.

International audience; The novel Mo12 cluster sulfides Rb2.65Mo12S14 have been synthesized by direct solid-state reaction at a temperature of about 1500 °C in a welded Mo tubing. The crystal structure of Rb2.65Mo12S14 (space group P-31c: a = 9.2828(6) Å, c = 16.446(5) Å) was solved from X-ray single-crystal data. It is isomorphous with the K1+xMo12S14 compounds in which x ranges from 0 to 1.6. Consequently, the Mo-S network presents interconnected Mo12S14 cluster units delimiting large tunnels that are randomly occupied by a part of the Rb+ ions, the other ones being localized in large voids between two consecutive Mo12S14 units along the [001] direction. By topochemical redox reactions at around 90 °C, we could remove a part of the Rb+ ions from the channels and thus, form the oxidized phase Rb1.08Mo12S14. Electrical resistivity measurements performed on single crystals of Rb2.65Mo12S14 and Rb1.08Mo12S14 shows that the oxidized form is a semimetal while the reduced form is a metal and becomes superconducting below 4.07 K. The evolution of Mo-Mo bond lengths within the trioctahedral Mo12 cluster with respect to the cationic charge x is discussed and, compared with that found in the potassium series.

Designing and synthesising new metastable compounds is a major challenge of today’s material science. While exploration of metastable oxides has seen decades-long advancement thanks to the topochemical deintercalation of oxygen as recently spotlighted with the discovery of nickelate superconductor, such unique synthetic pathway has not yet been found for chalcogenide compounds. Here we combine an original soft chemistry approach, structure prediction calculations and advanced electron microscopy techniques to demonstrate the topochemical deintercalation/reintercalation of sulfur in a layered oxychalcogenide leading to the design of novel metastable phases. We demonstrate that La2O2S2 may react with monovalent metals to produce sulfur-deintercalated metastable phases La2O2S1.5 and oA-La2O2S whose lamellar structures were predicted thanks to an evolutionary structure-prediction algorithm. This study paves the way to unexplored topochemistry of mobile chalcogen anions. Great progress has been made in topochemistry of mobile oxygen anions, but metastable compounds have not yet been achieved by deintercalation of sulfur anions. Here, the authors prepare metastable oxychalcogenide phases by taking advantage of redox-reactive sulfur dimers embedded in a layered oxysulfide.