Solid-state Mechanochemical Reaction Research Articles

Studies on the mechanochemically induced chromene-annulation of meso-tetrakis(pentafluorophenyl)-2,3-dihydroxychlorin: Non-innocence of the grinding aids

The modification of chlorins to fine-tune their optical properties is important for their application in medical and technical fields. The solution phase, base-induced formation of a chromene-annulated chlorin from the corresponding meso-tetrakis(pentafluorophenyl)-2,3-dihydroxychlorin by intramolecular S[Formula: see text]Ar displacement of an [Formula: see text]-F atom of a meso-aryl group by an adjacent hydroxy group is well-known. Organic transformations performed by grinding the dry reagents together promise to be a much greener and possibly simpler method compared to traditional solution-based reactions. However, the use of such mechanochemical approaches to accomplish porphyrinoid chromophore modifications are virtually unexplored. We report here the translation of the solution-based base-induced formation of a chromene-annulated chlorin to a solid state mechanochemical reaction in a planetary powder mill. The factors determining the success (and failure) of the reaction are delineated. While this report shows that porphyrinoid framework modifications can principally be induced mechanochemically, the mechanochemical reaction is not (yet) competitive with the solution state reaction. The outcome of the reaction is very sensitive to the particular milling conditions, specifically-and importantly as it is unexpected – the grinding aids used. What we previously believed to be inert or merely basic aids affected a significant degradation of the chlorins under the milling conditions, a finding that might generally limit mechanochemical approaches in porphyrinoid chemistry, or at least require careful adjustments.

Mixed-Metal Cu-Zn Thiocyanate Coordination Polymers with Melting Behavior, Glass Transition, and Tunable Electronic Properties.

The solid-state mechanochemical reactions under ambient conditions of CuSCN and Zn(SCN)2 resulted in two novel materials: partially Zn-substituted α-CuSCN and a new phase CuxZny(SCN)x+2y. The reactions take place at the labile S-terminal, and both products show melting and glass transition behaviors. The optical band gap and solid-state ionization potential can be adjusted systematically by adjusting the Cu/Zn ratio. Density functional theory calculations also reveal that the Zn-substituted CuSCN structure features a complementary electronic structure of Cu 3d states at the valence band maximum and Zn 4s states at the conduction band minimum. This work shows a new route to develop semiconductors based on coordination polymers, which are becoming technologically relevant for electronic and optoelectronic applications.

Solid-state mechanochemical technology for deep processing of brown coal: energy efficiency improvement and dust formation control

Energy efficiency – a compromise between reaction depth and expended energy - is an actual question for any technology implementation. Mechanochemical technology for brown coal deep processing has one more compromise - between reaction depth and dust formation. Indeed, the depth of mechanochemical reactions usually correlates with grinding efficiency, but for coal cases dust formation is an unwanted process. Here we consider a solid-state mechanochemical reaction of humic acid oxidation by sodium percarbonate in one laboratory mill at different conditions. The ratio between the grinding bodies load and the payload was varied, the reaction yield and the ground samples characteristics were controlled.

Synthesis of Pb(Zr, Ti)O3 fine ceramic powder at room temperature by dry mechanochemical solid-state reaction evaluated using synchrotron radiation X-ray diffraction

The validity of the mechanochemical solid-state reaction by dry ball milling for synthesizing Pb(Zr, Ti)O3 (PZT) fine ceramic powder at room temperature (RT) was evaluated using synchrotron radiation X-ray diffraction (SXRD). A mixture of PbZrO3 (PZ) and PbTiO3 (PT) powders with a molar ratio of 1:1 was prepared as the starting powder. To confirm the synthesis of PZT, the structural characteristics of the ball-milled samples with different milling times were investigated by analyzing the SXRD data using the Rietveld method. The solid-state reaction was nearly complete in a short milling time of 4 h at RT. After ball milling for approximately 8 h, only a single phase of PZT was detected. The Rietveld refinement for the crystal structure analysis demonstrated that slightly Ti-rich PZT, Pb(Zr0.485(1)Ti0.515(1))O3, with a tetragonal crystal system, is synthesized in the 8 h sample. The tetragonality is sufficiently suppressed to resemble a cubic system even at RT, whereas the phase transition temperature (T C) is significantly high. We quantitatively demonstrate that PZT with a higher T C can be synthesized at RT by dry ball milling, despite the smaller spontaneous lattice distortion.

Mechanochemically oxidized chitosan-based adsorbents with outstanding Penicillin G adsorption capacity

Despite mild oxidation is a facile and efficacious method to enhance chitosan properties, like adsorption capacity of pollutants, currently developed solvent-based approaches can be hardly scaled up in an economic way because of complicated multi-step process and high solvent separation cost. In this study, a novel, solvent-free, simple, fast, and effective oxidation method was successfully applied to prepare oxidized chitosan by direct mechanochemical solid-state reaction with an oxidant in a high energy ball mill. Reaction products were employed to remove penicillin G from aqueous solutions by adsorption process. Chitosan ball milled for 1 h with 20%w/w potassium persulfate showed the highest adsorption capacity (2165 mg g−1), followed by the polysaccharide co-milled for 2 h with 30%w/w sodium percarbonate (1847 mg g−1) and with 50%w/w calcium peroxide for 2 h (1157 mg g−1). Such performance was likely owed to higher density of oxygen-containing functional groups, shorter polysaccharidic chain, and greater particle surface amorphization, compared to pristine chitosan. The spent adsorbents were successfully regenerated using NaOH solution for five consecutive times before penicillin G uptake loss was observed. The proposed mechanochemical method could serve as an economic and rapid method to synthesize at large-scale efficacious adsorbents to remove organic pollutants from wastewater.

Synthesis and photoluminescence properties of the Eu(III)-containing silica nanoparticles via a mechanochemical solid-state reaction between SiO2 and EuCl3·6H2O

In this study, Eu3+-containing amorphous silica nanoparticles and Eu compounds were successfully synthesized via a mechanochemical solid-state reaction between silica nanoparticles and EuCl3·6H2O. This reaction was induced by a grinding process, and the states of Eu3+ in the silica/europium composites were investigated. The silica/europium composites exhibited orange–red color luminescence owing to the 5D0–7F0, 5D0–7F1, and 5D0–7F2 transitions, which indicated the presence of Eu3+ in the silica framework and the newly formed Eu compounds such as EuOCl and Eu(OH)2Cl. The mechanochemical reaction because of the grinding process effectively induced an interaction between the silica surface and europium chloride; subsequently, Eu(OH)2Cl was formed in the silica/europium composites. Additionally, the Eu(OH)2Cl in the silica/europium composite exhibited a higher thermal stability than that of simple Eu(OH)2Cl, indicating that the mechanochemical reaction mediated the formation of Eu(OH)2Cl and new chemical bonding between the newly formed Eu(OH)2Cl and the silica surface, providing improved thermal stability to Eu(OH)2Cl. Thus, we successfully prepared silica nanoparticles containing not only Eu(III) in the silica framework but also Eu compounds that exhibit unique chemical bonding during a mechanochemical reaction.

Metal-doped bioceramic nanopowders with tunable structural properties aimed at enhancing bone density: Rapid synthesis and modeling

Metal doped bioceramic nanopowders were prepared by solid-state mechanochemical reactions. Also, genetic programming (GP) and gene expression programming (GEP) models were developed to predict the structural features of the mechanosynthesized nanopowders aimed at developing an innovative solution to enhance bone mineral density. The substitution of Ca2+ with different ions in the apatite structure was confirmed from chemical analysis and structural assessment, where irregular changes in the lattice parameters and unit cell volume were observed due to the replacement of the Ca2+ bivalent cation with monovalent, bivalent or trivalent ions as well as the carbonate ions effects on the apatite lattice. It was found that the crystallite size and micro-strain of the substituted bioceramics were between ~11 and 98 nm and ~0.31–2.49%, respectively. From the functional group analysis, the intensity of the hydroxyl groups decreased as the dopant content increased. The electron microscopy images showed that both undoped and low-doped samples consist of spheroidal particles in the nano regime, whereas the high-doped specimens exhibited a high propensity to agglomerate. The results of cytotoxicity assays corroborated that appropriate ionic substitution can prevent the toxic effects of Li on Mus musculus fibroblast cells, and thus by increasing dopant concentration up to z = 0.25, cell viability of around 90% was observed. The results obtained from the modeling demonstrated that both GP and GEP methods are reliable in predicting the structural properties of the synthetic metal-doped bioceramic nanopowders.

An efficient mechanochemical synthesis of alpha-aluminum hydride: Synergistic effect of TiF3 on the crystallization rate and selective formation of alpha-aluminum hydride polymorph.

α-AlH3 is one of the most promising hydrogen storage materials due to its high gravimetric hydrogen capacity and low dehydriding temperature. In present work, a convenient and cost-efficient solid-state mechanochemical reaction is proposed to obtain α-AlH3 nano-composite. With the addition of TiF3, α-AlH3 nano-composite was formed in a short period by milling of LiH and AlCl3. Based on XRD and NMR results, the average grain size of the α-AlH3 in the nano-composite was 45 nm. The reaction pathway as well as the synergistic effect of TiF3 on the solid state reaction between LiH and AlCl3 were confirmed. In the α-AlH3/LiCl nano-composite, TiF3 reduced the temperature of dehydriding reaction and improved dehydrogenation rate of α-AlH3. Within the temperature range between 80 and 160 °C, dehydrogenation of the as-milled α-AlH3 nano-composite showed fast kinetics. At 160 °C, a maximum hydrogen desorption of 9.92 wt% was obtained within 750 s, very close to the theoretical hydrogen capacity of α-AlH3.

Mechanochemical synthesis of binary phosphorus telluride: Short range structure and thermal properties

A binary phosphorus telluride sample (20 at% Te) was synthesized by mechanochemical solid state reaction from elemental powders. The X-ray diffraction pattern and neutron total structure factor show no detectable Bragg peaks, indicating that the sample is amorphous with respect to X-ray and neutron diffraction. The neutron and X-ray total pair distribution functions show correlation peak arising from PTe heteropolar bonds in addition to those arising from PP and TeTe bonds. The TeTe bond length is slightly shorter than that in the crystal structure of trigonal tellurium, suggesting a different environment from a polymeric chain structure. The thermal analysis results show that the binary phosphorus telluride is thermally unstable, that is, it decomposes above 200 °C into trigonal tellurium crystals and gaseous phosphorus, where phosphors begins to gasify at a lower temperature than the sublimation temperature of red phosphors.

One-Step, Solventless, and Scalable Mechanosynthesis of WO3·2H2O Ultrathin Narrow Nanosheets with Superior UV–Vis-Light-Driven Photocatalytic Activity

Environmentally benign, high-yield, cost-efficient, and facile fabrication of ultrathin two-dimensional (2D) nanomaterials has been a bottleneck restricting their massive and extensive applications. In this work, a one-step, solvent-free, and easily scalable approach for the preparation of WO3·2H2O ultrathin narrow nanosheets has been proposed for the first time, which is based on solid-state mechanochemical reaction between sodium tungstate dihydrate (Na2WO4·2H2O) and oxalate dihydrate (H2C2O4·2H2O) at ambient temperature. The resulting WO3·2H2O presents uniform rectangular nanosheets with a typical length of 50–80 nm, a width of about 10 nm, and a thickness of 5.67 nm. Phase evolution in the synthetic process of WO3·2H2O ultrathin narrow nanosheets was investigated by X-ray diffractometry. Their formation mechanism was also rationalized on the basis of in situ precipitation and preferential growth of ionized WO42– on the surface of mechanically exfoliated oxalate nanosheets. The WO3·2H2O ultrathin narro...

Eu3+-Doped Wide Band Gap Zn2SnO4 Semiconductor Nanoparticles: Structure and Luminescence

Nanocrystalline Zn2SnO4 powders doped with Eu3+ ions were synthesized via a mechanochemical solid-state reaction method followed by postannealing in air at 1200 °C. X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and Raman and photoluminescence (PL) spectroscopies provide convincing evidence for the incorporation of Eu3+ ions into the host matrix on noncentrosymmetric sites of the cubic inverse spinel lattice. Microstructural analysis shows that the crystalline grain size decreases with the addition of Eu3+. Formation of a nanocrystalline Eu2Sn2O7 secondary phase is also observed. Luminescence spectra of Eu3+-doped samples show several emissions, including narrow-band magnetic dipole emission at 595 nm and electric dipole emission at 615 nm of the Eu3+ ions. Excitation spectra and lifetime measurements suggest that Eu3+ ions are incorporated at only one symmetry site. According to the crystal field theory, it is assumed that Eu3+ ions participate at octahedral sites of Zn2+ or Sn4+ under a weak cr...

Ambient solid-state mechano-chemical reactions between functionalized carbon nanotubes.

Carbon nanotubes can be chemically modified by attaching various functionalities to their surfaces, although harsh chemical treatments can lead to their break-up into graphene nanostructures. On the other hand, direct coupling between functionalities bound on individual nanotubes could lead to, as yet unexplored, spontaneous chemical reactions. Here we report an ambient mechano-chemical reaction between two varieties of nanotubes, carrying predominantly carboxyl and hydroxyl functionalities, respectively, facilitated by simple mechanical grinding of the reactants. The purely solid-state reaction between the chemically differentiated nanotube species produces condensation products and unzipping of nanotubes due to local energy release, as confirmed by spectroscopic measurements, thermal analysis and molecular dynamic simulations.

Structural conversion of cubane-type thallium complex to hexagon silver complex by solid-state mechanochemical reaction

Solid-state structural transformation of TlI supramolecular polymer comprised from cubane-type thallium complex of [Tl4(μ3-4-BN)4] (1) (4-HBN=4-hydroxy benzonitrile) to AgI coordination polymer with three nuclear units of [Ag3(μ3-4-BN)2(μ4-4-BN)] (2) has been studied upon mechanochemical reaction of compound 1 with AgNO3.

Mechanochemical Neutralization of Hypericin in Hypericum perforatum Studied by Spectroluminescence

The speciation of hypericin in plant raw material was determined. The solid-state mechanochemical reaction of hypericin in plant raw material with alkaline reagents was studied in order to produce a very soluble salt species.

Solution and Mechanochemical Syntheses of Two Novel Cocrystals: Ligand Length Modulated Interpenetration of Hydrogen-Bonded 2D 63-hcb Networks Based on a Robust Trimeric Heterosynthon

Cocrystallization of a versatile organic tecton, 3,3′,5,5′-tetramethyl-4,4′-bipyrazole (tmbpz), with aliphatic dicarboxylic acid suberic acid (H2sub) and sebacic acid (H2seb) generates two supramolecular solids [(tmbpz)2·(H2sub)] (1) and [(tmbpz)2·(H2seb)] (2). In the present case, both cocrystals could be obtained from either solution evaporation or mechanochemical solid-state reaction. Single-crystal structural analyses reveal that the 1 and 2 are 4-fold and 5-fold 2D → 2D parallel interpenetrated 63-hcb networks, respectively. The substantial dissimilarities in the degree of interpenetration are modulated by the different lengths of dicarboxylic acids. The thermal stabilities and photoluminescence behaviors of them were also discussed.

ChemInform Abstract: A Review on Mechanochemical Syntheses of Functional Materials

AbstractReview: 35 refs.

Mechanochemical synthesis of an yttrium based metal–organic framework

For the first time a metal hydride has been used for the preparation of a metal-organic framework. MIL-78 has been synthesized by the solid-state mechanochemical reaction between yttrium hydride and trimesic acid. The process does not involve solvents and does not generate liquid by-products, thus proving the viability of the solid-state approach to the synthesis of MOFs.

Mechanochemical Preparation of 8-Hydroxyquinoline/Hydroxyapatite Hybrid Nanocrystals and Their Photofunctional Interfaces

Hybrid nanocrystals of 8-hydroxyquinoline (8Hq) molecules and hydroxyapatite nanocrystals (HAp) were successfully prepared by a mechanochemical solid-state reaction. The hybrid nanocrystals exhibit a significant thermal stability and efficient photoluminescence peak at 500 nm, which were attributed to metal–ligand charge transfer at the interface between the oxygen atoms of 8Hq and the calcium ions of HAp, and the interfacial photofunctions were mechanochemically controlled. The interfacial bonding structures were also supported by a DV-Xα molecular orbital calculation.

Efficient incorporation of monomeric anthracene into nanoporous silica/surfactant nanocomposite spheres using a mechanochemical solid state reaction

The incorporation of anthracene (Ant) into nanoporous silica/surfactant nanocomposite spheres was successfully achieved using a mechanochemical solid state reaction. The Ant molecules were incorporated into the nanopores while preserving the silica nanostructures, indicating the effective hydrophobic interactions with the alkyl chains of the surfactant. The blue photoluminescence intensity due to the monomer state was enhanced by increasing the mechanochemical milling force, suggesting this is an efficient preparation method for a luminescent medium by monomeric assembly of the Ant molecules.

Annealing Effect of Ce-Doped CaGa2S4Synthesized by Mechanochemical Solid-State Reaction

Annealing Effect of Ce-Doped CaGa₂S₄Synthesized by Mechanochemical Solid-State Reaction