12 research outputs found
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
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