Soft Chemical Research Articles

Photocatalytic activity of Fe/Ti-based compounds obtained from ferro-titaniferous mineral sands via a simple soft chemistry route

Fe/Ti-based compounds were synthesized from ferro-titaniferous mineral sands using aqueous oxalic acid under subcritical water (sCW) conditions (135°C/50 bar/4 h) and their photocatalytic activity was evaluated against methylene blue or caffeine under UV-A and visible radiation. The X-ray diffraction and Raman spectroscopy analyses revealed that the as-synthetized compounds were mainly comprised of ferrous oxalate, followed by titanium dioxide. This proved the complete transformation of the mineral precursor within 4 h using oxalic acid/sCW as the reaction medium. The photocatalytic studies showed that methylene blue and caffeine were photodegraded under UV-A and visible radiation by the as-synthesized Fe/Ti-based compounds. Methylene blue removal was up to 92.8 and 97.4% after 6 hours under UV-A or visible irradiation, respectively. Caffeine removal, however, reached 69.3 and 59.6% after 16 h of exposure to UV-A and visible light, respectively. The as-synthesized compounds can be potentially used as a ferrous-based catalyst in heterogeneous photocatalysis for decontamination of water systems from organic pollutants.

Investigation of Hydrogen Incorporations in Bulk Infinite-Layer Nickelates

Infinite-layer (IL) nickelates are an emerging class of superconductors, where the Ni1+ valence state in a square planar NiO2 coordination can only be reached via topotactic reduction of the perovskite phase. However, this topotactic soft chemistry with hydrogenous reagents is still at a stage of rapid development, and there are a number of open issues, especially considering the possibility of hydrogen incorporation. Here, we study the time dependence of the topotactic transformation of LaNiO3 to LaNiO2 for powder samples with x-ray diffraction and gas extraction techniques. While the hydrogen content of the powder increases with time, neutron diffraction shows no negative scattering of hydrogen in the LaNiO2 crystal lattice. The extra hydrogen appears to be confined to grain boundaries or secondary-phase precipitates. The average crystal structure, and possibly also the physical properties, of the primary LaNiO2 phase are, therefore, not noticeably affected by hydrogen residues created by the topotactic transformation.

Biomimetic and Biologically Compliant Soft Architectures via 3D and 4D Assembly Methods: A Perspective.

Recent progress in soft material chemistry and enabling methods of 3D and 4D fabrication-emerging programmable material designs and associated assembly methods for the construction of complex functional structures-is highlighted. The underlying advances in this science allow the creation of soft material architectures with properties and shapes that programmably vary with time. The ability to control composition from the molecular to the macroscale is highlighted-most notably through examples that focus on biomimetic and biologically compliant soft materials. Such advances, when coupled with the ability to program material structure and properties across multiple scales via microfabrication, 3D printing, or other assembly techniques, give rise to responsive (4D) architectures. The challenges and prospects for progress in this emerging field in terms of its capacities for integrating chemistry, form, and function are described in the context of exemplary soft material systems demonstrating important but heretofore difficult-to-realize biomimetic and biologically compliant behaviors.

From waste incineration by-products to functional materials: a “Chimie douce” route to VOCs mineral adsorbents

One of today’s major world challenges is the accumulation and the storage of tens of millions of tons per year of final materials resulting from the incineration of domestic and industrial waste. This raises the question of the recycling of these “raw materials”, while making allowance for environmental, economic, social and public health aspects. Our strategy targets the incorporation of waste incineration by-products in a totally circular economy. We propose an innovative process combining templated sol–gel growth of an inorganic or hybrid silica-based network with a solubilized fraction of bottom ash coming from the combustion of industrial and household wastes. The resulting materials engineered via aerosol processing demonstrate maximum adsorption capacity of model pollutant compounds (1-2 dichlorobenzene) competitive with activated carbons currently used in modern incineration plants. We believe that they have the potential to replace conventional activated carbon commonly used in incineration plants, enabling the first step of the long road of recycling final waste.Graphical abstract

Knowledge of eggplant farmers on the proper use of pesticides in Khartoum State, Sudan

The knowledge of eggplant farmers on the proper use of pesticides was evaluated in Khartoum State. Questionnaire was distributed to farmers in North Nile Farms (NN), East Nile Farms (ENF), and West Nile Farms (WNF) to solicit information. Interviews and questionnaires revealed that there is a limited level of awareness among farmers. The majority (94%) of farmers did not abide by recommended disposal procedures, they only damage and bury the containers inside the farms. The majority of farmers (66%) were not aware of the safety period for any given product. The excessive use of pesticides in eggplant production and reliance only on pesticides as a pest management strategy calls for the implementation of IPM programs integrating the use of environmentally soft chemicals with other non-chemical control methods to manage pests and diseases. Safety periods should be carefully watched to reduce the level of residues in eggplant fruits below the acceptable level and to ensure sustainable and safe production.

Soft chemistry synthesis and laser powder bed fusion processing of Fe–Ni alloy based powders: A route for the manufacturing of porous multiphase Fe–Ni alloy parts

Fe–Ni alloy based powders of different stoichiometry and purity were synthesized by thermal decomposition of a co-precipitated oxalic precursor. By modifying the oxygen partial pressure of the gaseous flow, a nearly pure Fe64Ni36 Invar powder and a composite Fe50Ni50-Fe3O4 powder were prepared. The composite particles present an original microstructure consisting of an intimate mixture of Fe50Ni50 and Fe3O4 submicronic grains. The behavior of the composite powder was studied in laser powder bed fusion (LPBF) process. Reduction of iron oxide and specific microstructural changes were revealed. Subsequent conventional heat post-treatment allowed to remove the remaining iron oxides and to form porous multiphase Fe–Ni alloy 3D parts. Repeatable heterogeneities of microstructure and composition, at a periodicity corresponding to the thickness of the powder bed used in the LPBF process, constitute the hallmark of the laser treatment carried out on the composite powder.

Soft Chemistry Synthesis and Characterization of CoFe1.8RE0.2O4 (RE3+ = Tb3+, Er3+) Ferrite

Nanosized CoFe1.8RE0.2O4 (RE3+ = Tb3+, Er3+) ferrites were obtained through wet ferritization method. These ferrites were characterized by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM/HR-TEM), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy and magnetic measurements. The XRD results revealed that the average crystallite size is 5.77 nm for CoFe1.8Tb0.2O4 and 6.42 nm for CoFe1.8Er0.2O4. Distribution of metal cations in the spinel structure estimated from X-ray diffraction data showed that the Tb3+ and Er3+ ions occupy the octahedral sites. TEM images indicated the presence of polyhedral particles with average size 5.91 nm for CoFe1.8Tb0.2O4 and 6.80 nm for CoFe1.8Er0.2O4. Room temperature Mössbauer spectra exhibit typical nanoscaled cobalt ferrite spectra in good agreement with XRD and TEM data. The saturation magnetization value (Ms) is 60 emu/g for CoFe1.8Tb0.2O4 and 80 emu/g for CoFe1.8Er0.2O4. CoFe1.8RE0.2O4 nanoparticles showed similar antimicrobial efficacy against the five tested microbial strains, both in planktonic and biofilm state. The results highlight the promising potential of these types of nanoparticles for the development of novel anti-biofilm agents and materials.

Synthesis of highly calibrated CsPbBr3 nanocrystal perovskites by soft chemistry.

A new synthetic method for preparing highly calibrated CsPbBr3 nanocrystal perovskites is described and analyzed using high-resolution scanning transmission electron microscopy. This new method based on soft chemistry leads to the large-scale production of nanocrystals. Such monodisperse nanocrystals allow for the deposition of homogeneous films, which provides new opportunities for the next generation of optoelectronic devices.

Evaporation-driven liquid flow in sessile droplets.

The evaporation of a sessile droplet spontaneously induces an internal capillary liquid flow. The surface-tension driven minimisation of surface area and/or surface-tension differences at the liquid-gas interface caused by evaporation-induced temperature or chemical gradients set the liquid into motion. This flow drags along suspended material and is one of the keys to control the material deposition in the stain that is left behind by a drying droplet. Applications of this principle range from the control of stain formation in the printing and coating industry, to the analysis of DNA, to forensic and medical research on blood stains, and to the use of evaporation-driven self-assembly for nanotechnology. Therefore, the evaporation of sessile droplets attracts an enormous interest from not only the fluid dynamics, but also the soft matter, chemistry, biology, engineering, nanotechnology and mathematics communities. As a consequence of this broad interest, knowledge on evaporation-driven flows in drying droplets has remained scattered among the different fields, leading to various misconceptions and misinterpretations. In this review we aim to unify these views, and reflect on the current understanding of evaporation-driven liquid flows in sessile droplets in the light of the most recent experimental and theoretical advances. In addition, we outline open questions and indicate promising directions for future research.

Structure protects function - An enabler for the functionalization of component surfaces by biohybrid coatings

The biological transformation is a growing part of current research in manufacturing and enables new possibilities in the development of innovative products. Modular functional assemblies based on biological building blocks potentially enable efficient and economical functionalization of component surfaces. Surface functionalization covers a range of industries and applications with high economic and technological potential and societal relevance. In dentistry, inflammation of the gums near the implant (periimplant infection) is one of the most common complications after implant implantation. The infections are mainly due to bacterial contamination or bacterial colonization at the implant. Biohybrid coatings based on modular functional assemblies represent an innovative solution for surface functionalization to prevent these periimplant infections. However, in addition to the advantages of modular functional assemblies, there are various challenges for the establishment of functional assemblies in series production. These pose new requirements for the manufacturing technology. The aim of interdisciplinary collaboration between biotechnology, soft matter nanotechnology, polymer chemistry, and production engineering is to provide implant surfaces (using titanium dental implants as an example) with an innovative biohybrid coating in combination with microstructuring. The coating prevents the bacterial colonization of the implant while the microstructure increases the robustness and longevity of the coating. The challenges in manufacturing these micro-structures of surfaces, the generation of biohybrid coatings as well as an outlook on the innovative use of functionalized surfaces are described in this paper.

Bottom-up synthesis of 2D layered high-entropy transition metal hydroxides.

Low-dimensional high-entropy materials, such as nanoparticles and two-dimensional (2D) layers, have great potential for catalysis and energy applications. However, it is still challenging to synthesize 2D layered high-entropy materials through a bottom-up soft chemistry method, due to the difficulty of mixing and assembling multiple elements in 2D layers. Here, we report a simple polyol process for the synthesis of a series of 2D layered high-entropy transition metal (Co, Cr, Fe, Mn, Ni, and Zn) hydroxides (HEHs), involving the hydrolysis and inorganic polymerization of metal-containing species in ethylene glycol media. The as-synthesized HEHs demonstrate 2D layered structures with interlayer distances ranging from 0.860 to 0.987 nm and homogeneous elemental distribution of designed equimolar stoichiometry in the layers. These 2D HEHs exhibit a low overpotential of 275 mV at 10 mA cm−2 in a 0.1 M KOH electrolyte for the oxygen evolution reaction. Superparamagnetic spinel-type high-entropy nanoparticles can also be obtained by annealing these HEHs. Our polyol approach creates opportunities for synthesizing low-dimensional high-entropy materials with promising properties and applications.

Hard-soft chemistry guides the adaptable charge transport in lysine-doped heptapeptide junctions.

Counterions always coexist with charged peptides in charge transport processes, which are excellent candidate components for tunable molecular electronic devices. Here, we introduced hard-soft acid base theory to analyze the counterion-modulated peptide charge transport. We demonstrate that the peptide charge transport is improved by enhanced peptide-counterion interactions.

Low-temperature synthesis and characterization of lead-free BaTi0.89Sn0.11O3 piezoelectric powders

Barium stannate titanate (BaTi0.89Sn0.11O3, BTS11) is one of the reported lead-free materials that exhibit high dielectric and piezoelectric properties near ambient temperature. In this work, BTS11 powders were elaborated via a soft chemistry method at very low temperatures using two synthesized approaches combining sol-gel and hydrothermal processes. In the first approach, the effect of the barium precursor on the purity and the crystallinity of the BTS11 powders were studied. In contrast, in the second approach, the influence of the hydrothermal temperature on the BTS11 proprieties was analyzed. As a result, pure and uniform fine powders were obtained at 180 °C. The appropriate mass fraction of BTS11, which leads to high suspension stability in water, is below 3%. These eco-friendly and pure piezoelectric powders can be used without further heat-treatment in several applications such as lead-free piezoelectric decontamination of organic pollutants and photocatalyst, hydrogen generation and as fillers in flexible nanocomposites nano-generators for energy harvesting and energy storage.

Highly Active Co3O4-Based Catalysts for Total Oxidation of Light C1-C3 Alkanes Prepared by a Simple Soft Chemistry Method: Effect of the Heat-Treatment Temperature and Mixture of Alkanes.

In the present work, a simple soft chemistry method was employed to prepare cobalt mixed oxide (Co3O4) materials, which have shown remarkably high activity in the heterogeneously catalyzed total oxidation of low reactive VOCs such as the light alkanes propane, ethane, and methane. The optimal heat-treatment temperature of the catalysts was shown to depend on the reactivity of the alkane studied. The catalytic activity of the Co3O4 catalysts was found to be as high as that of the most effective catalysts based on noble metals. The physicochemical properties, from either the bulk (using XRD, TPR, TPD-O2, and TEM) or the surface (using XPS), of the catalysts were investigated to correlate the properties with the catalytic performance in the total oxidation of VOCs. The presence of S1 low-coordinated oxygen species at the near surface of the Co3O4-based catalysts appeared to be linked with the higher reducibility of the catalysts and, consequently, with the higher catalytic activity, not only per mass of catalyst but also per surface area (enhanced areal rate). The co-presence of propane and methane in the feed at low reaction temperatures did not negatively affect the propane reactivity. However, the co-presence of propane and methane in the feed at higher reaction temperatures negatively affected the methane reactivity.

Vanadium oxides obtained by chimie douce reactions: The influences of transition metal species on crystal structures and electrochemical behaviors in zinc–ion batteries

Rechargeable aqueous zinc–ion batteries (RAZIBs) have received increasing attention due to cost−effectiveness and inherent safety. A wide variety of advanced cathode materials have been revealed with promising performance in RAZIBs. However, these materials usually require sophisticated procedures at high temperatures, which greatly limit further practical application. Herein, a chimie douce approach is adopted to prepare vanadium oxides from V2O5 suspension with the addition of various transition metal cations (Mn2+, Zn2+, Ag+, and Fe3+) by simple liquid−solid mixing under ambient conditions. For the cases of Mn2+ and Zn2+, the dissolution−recrystallization process takes place leading to layered Mn0.31V3O7·1.40H2O (MnVO) and Zn0.32V3O7·1.52H2O (ZnVO). The use of Ag+ forms tunneled Ag0.33V2O5 (AgVO), and the present of Fe3+ stays mainly unreacted V2O5. The underlying reaction chemistries are proposed, for which the pH values of precursor solutions are found to be a key factor. Among the prepared materials, layered vanadium oxides exhibit promising battery performance. Particularly, MnVO delivers 340 and 217 mAh g−1 at 1 and 8 A g−1, respectively. A specific capacity of 164 mAh g−1 can be retained after 500 cycles at 1 A g−1. By contrast, AgVO and FeVO demonstrate inferior performance with retaining only 89 and 20 mAh g−1 after 500 cycles.

Chemical Preintercalation of H2V3O8‐reduced Graphene Oxide Composites for Improved Na‐ and Li‐ion Battery Cathodes

AbstractDue to a growing demand for sustainable electrical energy storage alternatives to Li‐ion batteries (LIBs), Na‐ion batteries (SIBs) are of great interest because of the abundance of Na+. By modifying layered H2V3O8 by preintercalation and composite formation, improved electrochemical properties were obtained in LIBs. In analogy, a scalable soft chemistry synthesis is developed, to chemically presodiate H2V3O8 for the first time, in addition to a composite formation reaction with reduced graphene oxide (rGO). Crystal structure and morphology of all compounds are determined and their electrochemical properties as cathode are evaluated with respect to both Na+ and Li+ intercalation. The combination of preintercalation and composite formation leads to excellent initial capacities of 96 mAh ⋅ g−1 for SIBs and 371 mAh ⋅ g−1 for LIBs (58 % and 48 % higher than unmodified H2V3O8) at a practical current density of 100 mA ⋅ g−1, demonstrating that H2V3O8 is a promising cathode material for SIBs and LIBs.

(Invited) Chimie Douce for Variety of Layered Materials

This talk is dedicated to Prof. Claude Delmas and three of his magnificent study fields, namely, those on “Chimie Douce” (soft chemistry) [1], LiNiO2 [2] and Ni(OH)2 derivatives [3].Though LiNiO2 has been extensively studied as a powerful substitute for LiCoO2, its use as the source of Chimie Douce has been limited. This study shows possibilities to use LiNiO2 for obtaining metastable phases that are hardly obtained by high-temperature calcination. The NiO2 templet for Chimie Douce was obtained by the disproportionation reaction of LiNiO2 using proton as the catalyst [4,5]. Alkaline ion insertion to the NiO2 templet was employed using OH- as the reductant [6,7]. Low temperature heating is also effective for obtaining new polymorphs.The NiO2 templet has the nickel oxidation state of 3.8±0.1 and has the CdCl2 structure (O3) unless the Cdl2 structure (O1) is formed by using strong acids [8]. The Pourbaix diagram suggests that the NiO2 templet is stable only in the low pH regions and can be reduced in other regions. Treating NiO2 with LiOH leads to the formation of Li0.5NiO2 that is essentially the same as that obtained by electrochemical reactions. On the other hand, NaOH and KOH treatments typically produce M0.3NiO2•0.5H2O (P3), which corresponds to highly crystalline γ-NiOOH. The significant increase of the interlayer distance (Fig. 1) is caused by the water uptake on the Na+/K+ insertion. It is noteworthy that strongly solvated Li+ is inserted with desolvation while weakly solvated Na+/K+ are inserted as solvated.The P3 phases as rechargeable electrodes were inactive in non-aqueous lithium cells due to water decomposition on discharging, but were active in aqueous KOH electrolytes. Operando XRD analysis indicated that the cycle performance was better than that of the hydrated nickel hydroxide obtained by the conventional co-precipitation method, though the strong XRD peaks of the P3 phase weakened during discharging [9]. The longer interlayer distance of the discharged product suggests further water uptake on discharging. The use of Ni4+/ Ni3+/ Ni2+ redox couples is attractive for high energy aqueous rechargeable cells.In addition, we propose new proton insertion chemistry as a part of Chimie Douce application [10], which will be detailed in the presentation.

Structural and Compositional Characteristics of Ball-Milled Lepidocrocite Alkali Titanate and the Correlation to Its Surface Acidic-Basic Properties.

The studies on mechanical treatments of layered alkali metal oxides are limited despite their diverse compositions/structures and potential for property tuning. In this work, we vibratory mill Cs0.7Zn0.35Ti1.65O4, K0.8Zn0.4Ti1.6O4, and Cs2Ti6O13 for up to 4 h, during which the lepidocrocite-type structure and the plate-like morphology are well preserved. X-ray diffraction (XRD) indicates a tiny (≤0.6 Å) interlayer expansion accompanied by the enhancement of the preferred orientation along the stacking direction. Chemical analyses across multiple length scales suggest Cs deintercalation, elemental redistributions, and bulk-to-surface (or crystal edge) Cs migration. This ball-milling-induced Cs-rich moiety partially blocks the surface acid sites, although the solids still show a dominating acidic character. The ball-milled samples Cs0.7-pZn0.35-qTi1.65O4-δ contain vacancies between the sheets (p) and at the sheets (q and δ). It is deduced from Sanderson's electronegativity equalization principle and experimentally verified by X-ray photoelectron spectroscopy (XPS) that ball milling increases (decreases) the partial charge at the surface acidic Ti4+/Zn2+ (basic O2-) sites. These nonporous solids (≤20 m2·g-1) contain water sorbed on the external surface as high as 1.1 mol·mol-1, which is comparable to that in a water-intercalated sample. Our work expands the current understanding of the reactivity vs robustness in layered alkali titanates under physically demanding conditions, complementing knowledge gathered via the soft chemistry approach.

Synthesis of [formula omitted]-FeSe by 2-propanol solvothermal method

Using elemental iron and selenium as well as NH4Cl and 2-propanol as starting materials, a low temperature (473 K) method of solvothermal synthesis of β–FeSe superconducting at Tc≃8K has been successfully applied. This method may result in new possibilities for soft chemistry approaches to the synthesis and modification of iron-based superconductors.

Tiny yet tough: Maximizing the toughness of fiber-reinforced soft composites in the absence of a fiber-fracture mechanism

Tiny yet tough: Maximizing the toughness of fiber-reinforced soft composites in the absence of a fiber-fracture mechanism