Synthesis and characterization of the TiO2(B) phase

TiO2(B) or “bronze” is a TiO2 polymorph which is difficult to synthesise in a pure form and does not commonly exist in minerals. TiO2(B) potentially plays an important role in applications both as a photocatalytic component alongside anatase for degradation reactions and as an anode material in lithium ion batteries due to its distinctive crystal structure which exhibits large channels and voids. In this research, TiO2(B) has been successfully synthesised by both a hydrothermal route and a Low Pressure Chemical Vapour Deposition (LPCVD) process. Samples were characterised using powder-XRD, Raman spectroscopy, TEM, SEM and UV-Vis spectroscopy. Phase formation mechanisms for both the hydrothermal route and LPCVD process have been proposed. Initially, in order to investigate the TiO2(B) phase formation mechanism via a sodium titanate phase transformation, hydrothermal synthesis was employed to produce TiO2(B) nanorods including an investigation of the products at each stage of the reaction. The results were used to propose an integrated reaction mechanism which corresponds well with literature. This involved the structural transformation of a sodium titanate intermediate phase which is of interest in relation to the other TiO2(B) fabrication methods where Na+ ions are present in the system such as CVD on glass substrates. As a result, the synthesis of mixed phase TiO2(B) and anatase thin films on a soda lime glass substrate has been achieved, for the first time, by LPCVD synthesis. Titanium isopropoxide (TTIP) and N2 gas were used as the precursor and carrier gas respectively. The optimal LPCVD condition for preparing a mixed phase of TiO2 containing TiO2(B) was 550oC (actual temperature) with a 1 mL/s N2 flow rate. A possible thin-film formation mechanism during the LPCVD process has been proposed. Subsequently a pre-treatment method involving spraying a Na+-containing solution, such as sodium ethoxide, onto a number of different substrates including silicon wafer, fused quartz, highly ordered pyrolytic graphite (HOPG) and pressed graphite flake (grafoil) was applied in conjunction with the LPCVD method in order to promote the TiO2(B) phase in the thin film products formed on any substrate. Finally, the effects of different alkali metal ions (Li+, Na+ and K+ from alkali metal hydroxide solutions) during the pre-treatment step were investigated in relation to the phase formation in the thin films produced during the LPCVD process. Only Na+ ions were found to encourage the phase formation of TiO2(B), K+ ions produced only a minority of the TiO2(B) phase, whereas Li+ ions did not produce TiO2(B). Phase formation mechanisms have been proposed based on alkali metal migration from the pre-treatment layer into the deposited nascent titania film and the formation of intermediate titanate phases

Tris(ethyl­enediamine)cobalt(II) sulfate

The structure of the title compound, [CoII(C2H8N2)3]SO4, the cobalt example of [M(C2H8N2)3]SO4, is reported. The Co and S atoms are located at the 2d and 2c Wyckoff sites (point symmetry 32), respectively. The Co atom is coordinated by six N atoms of three chelating ethyl­enediamine mol­ecules generated from half of the ethyl­enediamine mol­ecule in the asymmetric unit. The O atoms of the sulfate anion are disordered mostly over two crystallographic sites. The third disorder site of O (site symmetry 3) has a site occupancy approaching zero. The H atoms of the ethyl­enediamine mol­ecules inter­act with the sulfate anions via inter­molecular N—H⋯O hydrogen-bonding inter­actions

Base-Directed Formation of Isostructural Lanthanide–Sulfate–Glutarate Coordination Polymers with Photoluminescence

A series of five isostructural 3D lanthanide-based coordination polymers [LnIII2(H2O)6(glu)(SO4)2]n [Ln = Pr(1), Nd(2), Sm(3), Eu(4), and Gd(5)] was effortlessly obtained within a few minutes via the microwave-heating method. The employment of auxiliary bases, that is, sodium hydroxide, 4,4′-bipyridine, and 1,4-diazabicyclo[2.2.2]octane, led to the formation of the title complex, whereas base-free synthesis yielded a three-dimensional inorganic coordination polymer, [Ln2(H2O)4(SO4)3]n·nH2O, Ln = Nd (2a). The robustness of the synthetic method was illustrated as both microwave-heating and conventional hydrothermal techniques also enabled the formation of a high-crystalline phase-pure complex 1–5. In the structure of 1–5, glutarato (glu2–) and sulfato ligands link dinuclear Ln(III) building units into three-dimensional frames. The glu2– ligands act as tethering linkers, expanding the structure into a neutral 3D coordination network. Hydrogen bonds were found to be the predominant intermolecular interactions in the crystal structures. Photoluminescence of the complex 1–5 was studied

Base-Directed Formation of Isostructural Lanthanide–Sulfate–Glutarate Coordination Polymers with Photoluminescence

A series of five isostructural 3D lanthanide-based coordination polymers [LnIII2(H2O)6(glu)(SO4)2]n [Ln = Pr(1), Nd(2), Sm(3), Eu(4), and Gd(5)] was effortlessly obtained within a few minutes via the microwave-heating method. The employment of auxiliary bases, that is, sodium hydroxide, 4,4′-bipyridine, and 1,4-diazabicyclo[2.2.2]octane, led to the formation of the title complex, whereas base-free synthesis yielded a three-dimensional inorganic coordination polymer, [Ln2(H2O)4(SO4)3]n·nH2O, Ln = Nd (2a). The robustness of the synthetic method was illustrated as both microwave-heating and conventional hydrothermal techniques also enabled the formation of a high-crystalline phase-pure complex 1–5. In the structure of 1–5, glutarato (glu2–) and sulfato ligands link dinuclear Ln(III) building units into three-dimensional frames. The glu2– ligands act as tethering linkers, expanding the structure into a neutral 3D coordination network. Hydrogen bonds were found to be the predominant intermolecular interactions in the crystal structures. Photoluminescence of the complex 1–5 was studied

Base-Directed Formation of Isostructural Lanthanide–Sulfate–Glutarate Coordination Polymers with Photoluminescence

A series of five isostructural 3D lanthanide-based coordination polymers [LnIII2(H2O)6(glu)(SO4)2]n [Ln = Pr(1), Nd(2), Sm(3), Eu(4), and Gd(5)] was effortlessly obtained within a few minutes via the microwave-heating method. The employment of auxiliary bases, that is, sodium hydroxide, 4,4′-bipyridine, and 1,4-diazabicyclo[2.2.2]octane, led to the formation of the title complex, whereas base-free synthesis yielded a three-dimensional inorganic coordination polymer, [Ln2(H2O)4(SO4)3]n·nH2O, Ln = Nd (2a). The robustness of the synthetic method was illustrated as both microwave-heating and conventional hydrothermal techniques also enabled the formation of a high-crystalline phase-pure complex 1–5. In the structure of 1–5, glutarato (glu2–) and sulfato ligands link dinuclear Ln(III) building units into three-dimensional frames. The glu2– ligands act as tethering linkers, expanding the structure into a neutral 3D coordination network. Hydrogen bonds were found to be the predominant intermolecular interactions in the crystal structures. Photoluminescence of the complex 1–5 was studied

Development of Bronze Phase Titanium Dioxide Nanorods for Use as Fast-Charging Anode Materials in Lithium-Ion Batteries

Bronze phase titanium dioxide (TiO2(B)) nanorods were successfully prepared via a hydrothermal method together with an ion exchange process and calcination by using anatase titanium dioxide precursors in the alkali hydrothermal system. TiO2 precursors promoted the elongation of nanorod morphology. The different hydrothermal temperatures and reaction times demonstrated that the synthesis parameters had a significant influence on phase formation and physical morphologies during the fabrication process. The effects of the synthesis conditions on the tailoring of the crystal morphology were discussed. The growth direction of the TiO2(B) nanorods was investigated by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The as-synthesized TiO2(B) nanorods obtained after calcination were used as anode materials and tested the efficiency of Li-ion batteries. This research will study the effects of particle morphologies and crystallinity of TiO2(B) derived from a modified hydrothermal method on the capacity and charging rate of the Li-ion battery. The TiO2(B) nanorods, which were synthesized by using a hydrothermal temperature of 220 °C for 12 h, presented excellent electrochemical performance with the highest Li storage capacity (348.8 mAh/g for 100 cycles at a current density of 100 mA/g) and excellent high-rate cycling capability (a specific capacity of 207.3 mAh/g for 1000 cycles at a rate of 5000 mA/g)

Ligand-Substitution-Induced Single-Crystal to Single-Crystal Transformations in a Redox-Versatile Cu(II) MOF toward Smartphone-Based Colorimetric Detection of Iodide

Fabrication of a new three-dimensional Cu(II) metal–organic framework, {[Cu4(4,4′-bipy)3(OH)2(mal)3]·4H2O}n (1a; 4,4′-bipy = 4,4′-bipyridine, H2mal = malonic acid; P21/m), that undergoes an unprecedented redox-versatile ligand-substitution-induced single-crystal to single-crystal transformation, for smartphone-based detection of iodide was studied. The Cu-MOF 1a has been effortlessly synthesized by the microwave-heating technique. Phase formation of the Cu-MOF 1a depended on counter-anions. The transformations can be triggered by halides to corresponding coordination polymers through both non-redox and redox-associated pathways. The changes in the local structure and oxidation state of copper during the transformation were studied by ex situ and in situ synchrotron X-ray absorption spectroscopies. The selectivity of the halide-triggered transformation was investigated. A study on smartphone-based colorimetric detection of iodide was found to be linearly proportional to the iodide concentration in the range 10–1500 mg/L with a limit of detection of 5 mg/L and good precision relative standard deviation of 1.9% (n = 11), possibly to construct the iodide test kit

Synergistic Induction of Solvent and Ligand-Substitution in Single-Crystal to Single-Crystal Transformations toward a MOF with Photocatalytic Dye Degradation

External-stimuli responsiveness as found in natural organisms and smart materials is attractive for functional materials scientists who attempt to design and imitate fascinating behavior into their materials. Herein, we report a couple of new solvent-responsive isostructural two-dimensional cationic metal–organic frameworks (MOFs) of Mn(II) (1a) and Zn(II) (2a) that undergo unprecedented single-crystal to single-crystal (SCSC) transformation toward the corresponding isostructural three-dimensional MOFs of Mn(II) (1b) and Zn(II) (2b). The 2D MOFs 1a and 2a have been effortlessly and rapidly synthesized via the microwave-heating technique. The SCSC transformations are synergistically induced by solvent and ligand-substitution reactions and able to be triggered by water, methanol, ethanol, and n-propanol. Time-dependent SCSC transformations were studied by in situ X-ray diffraction. Investigations on photodegradation of methyl orange showed that Zn-MOF 2b has higher efficiency than Mn-MOF 1b under UV–C irradiation at 300 min, 94.27%, and 21.91%, respectively. The influence of charge on the dye molecules, heterogeneity of the catalysis, and •OH radical-scavenging test was studied. First-principles computations suggest that the high photocatalytic activity of 2b may be attributed to its suitable band-edge position for redox reactions