Solid-state Precursor Research Articles

Mechanical densification synthesis of single-crystalline Ni-rich cathode for high-energy lithium-ion batteries

The intergranular microcracking in polycrystalline Ni-rich cathode particle is led by anisotropic volume change and stress corrosion along grain boundary, accelerating battery performance decay. Herein, we have suggested a simple but advanced solid-state method that ensures both uniform transition metal distribution and single-crystalline morphology for Ni-rich cathode synthesis without sophisticated co-precipitation. Pelletization-assisted mechanical densification (PAMD) process on solid-state precursor mixture enables the dynamic mass transfer through the increased solid-solid contact area which facilitates the grain growth during sintering process, readily forming micro-sized single-crystalline particle. Furthermore, the improved chemical reactivity by a combination of capillary effect and vacancy-assisted diffusion provides homogeneous element distribution within each primary particle. As a result, single-crystalline Ni-rich cathode with PAMD process has eliminated a potential evolution of intergranular cracking, thus achieving superior energy retention capability of 85% over 150 cycles compared to polycrystalline Ni-rich particle even after high-pressure calendering process (corresponding to electrode density of ∼3.6 g cm−3) and high cut-off voltage cycling. This work provides a concrete perspective on developing facile synthetic route of micron-sized single-crystalline Ni-rich cathode materials for high energy density lithium-ion batteries (LIBs).

A one-pot solid-state synthesis of MgO nanoparticles and their catalytic, biological, and electrochemical sensor activities: hexaaquamagnesium(ii) bis(6-oxo-1,6-dihydropyridine-3-carboxylate) as a tool

MgO nanoparticles produced from a solid-state precursor, hexaaquamagnesium(ii) bis(6-oxo-1,6-dihydropyridine-3-carboxylate), showed proficient catalytic activity and enhanced biological and electrochemical sensor activities.

One-step topochemical transformation of MoAlB into metastable Mo2AlB2 using a metal chloride salt reaction.

Reacting MoAlB with ZnCl2 at 550 °C produces metastable Mo2AlB2 through a one-step topochemical transformation. This reaction showcases differences in reactivity between boride-based MAB phases and carbide-based MAX phases, which are solid-state precursors to an important family of 2-D materials.

Milligrams to Kilograms - Scaling Production of Cobalt Free Lithium Excess Cathode Materials through Rotary Calcination

Both Tesla and the Government of the United States have listed the elimination of cobalt and the resilience of the battery cathode supply chain as critical issues in need of advancement 1,2. This investigation answered this call to action through scaling the production of a high-performance cobalt free lithium excess cathode material using rotary calcination. The cathode in this investigation is of the chemical series Li[NixLi(1/3-2x/3)Mn(2/3-x/3)]O2 (where x = 0.25), and to our knowledge this marks the first time an investigation has demonstrated the scaling of this class of materials. In order to achieve the several orders of magnitude increase in production scale the precursor feedstock for rotary calcination required comparison of sol-gel, Pechini, and solid-state precursors routes. Viability of each precursor synthesis route required comparison of synthesis time, synthesis complexity, Thermogravimetric Analysis, Dynamic Scanning Calorimetry, X-Ray Diffraction of intermediate and final materials, as well as Galvanostatic cycling of final cathode materials. Modification and controlled decomposition of sol-gel processing was ultimately used for the scaled production of precursor powders. Once the precursor feedstocks were fed through the rotary kiln we used X-Ray Diffraction, X-Ray Fluorescence, Galvanostatic Testing, and Scanning Electron Microscopy of resultant materials to optimize rotary calcination conditions to find the pareto optimal conditions that allowed for maximized material quality, and output, with minimized energy and time costs. These materials were also compared to our baseline material, which was made in a box furnace in ambient conditions over the course of 24 hours. Synthesis conditions were also modified to allow for the inclusion rapid water quenching of final scaled material to ensure material quality.Sources: F. C. for A. Batteries, National blueprint for lithium batteries 2021–2030, (2021).E. Musk and R. Denholm, UPDATES TO 2020 ANNUAL MEETING OF STOCKHOLDERS AND BATTERY DAY EVENT, (2020).

Highly efficient and freely soluble titanium sub-oxide powder as interfacial functional material for versatile photovoltaic cells

Metal suboxides (MOs) are among the most attractive interfacial materials owing to their outstanding functionality and excellent electrical and optical properties. However, the limitations of solution processability and ambient stability of the precursor hinder their widespread application. In this study, we developed a novel methodology for the solidification of sol–gel-derived MO-based organic complexes without affecting the properties of the MO products. By controlling the polarity of a conventional sol–gel derived titanium suboxide solution (STO) with organic functional side groups, we can easily obtain a nearly monodispersed solid-state precursor of STO (PTO) with excellent solubility in alcohols. PTO demonstrates ideal optical and electrical properties as an electron transport layer (ETL) with a significantly enhanced stability due to the elimination of the reactive residue. Owing to the optical, electrical, and excellent film-forming properties of PTO, organic and perovskite solar cells with PTO exhibit drastically improved performances and stability. Thus, a PTO-based ETL was successfully fabricated on various active layers, including those prepared from organic and perovskite materials, demonstrating the universality of PTO.

Synthesis of Platinum-Rare Earth Metal Alloy Catalysts for Proton Exchange Membrane Fuel Cells

Electrocatalysts for low temperature fuel cells are based on noble metals and can be promoted by development of alloys of platinum with e.g. late transition metals such as Ni and Co.[1,2] It has been reported that Pt alloys with rare earth (RE) metals exhibit remarkable activity and high stability towards the oxygen reduction reaction.[3] Due to the very low standard reduction potentials and high oxophilicity of rare earth metals, preparation platinum alloys in form of nanoparticles meets great challenges for chemical routes of co-reduction. A one-step method is recently developed to prepare Pt−RE nanoalloys from a mixture of solid state precursors consisting of metal halides in their hydrate forms, a suitable nitrogen-rich compound and a carbon support.[4,5] The synthesis involves in situ formation of a carbon-nitrogen network, onto which the two metals are atomically dispersed. The coordination with nitrogen sites stabilizes the metals, which, upon thermal decomposition under a mild reducing atmosphere, leads to the formation of Pt-RE nanoalloys. The carbon support is introduced either as carbon blacks or carbon supported platinum powder. The pre-formed, either in or ex situ, platinum nanoparticles, facilitates the reduction of rare earth metals thermodynamically driven by the negative alloying free energy. A series of pure crystal phases such as Pt5RE (e.g. La, Ce, Nd), and Pt3RE (e.g. Y, Gd, Tb) have been synthesized in form of carbon supported nanoparticles with tunable metal loadings and alloy particle sizes. One of the typical catalysts is the Pt5Ce/C in a metal to carbon ratio of 30 wt% and an average alloy particle size of ca. 5.5 nm which exhibits an area specific activity of 3.7 times and a mass activity of 1.9 times higher than those of the Pt/C analogue. Further understanding and improvement of the process are in progress and the updated results will be presented in this talk.[1]. J. K. Norskov et al., Nature Chemistry 1, 37-46 (2009)[2]. X. Q. Huang et al., Science 348, 1230-1234 (2015)[3]. M. Escudero-Escribano et al., Science 352, 73-76 (2016)[4]. Y. Hu et al., J. Am. Chem. Soc. 142, 953–961 (2020)[5]. Y. Hu et al., Chem. Mater. 33, 2, 535–546 (2021)

Dual-electroactive metal–organic framework nanosheets as negative electrode materials for supercapacitors

Exploring high-efficiency and robust multifunctional negative electrode materials are vital to develop high-performance asymmetric supercapacitors (ASCs). As one class of important functional materials, metal–organic frameworks (MOFs) have been widely applied in adsorption/separation, optoelectronics, sensing, catalysis, and energy storage fields, but they are rarely served as negative electrodes for construction of ASCs. Herein, the novel electrochromic MOFs-based hierarchical nanosheets (called EV-HNSs) that self-assembled from negative electroactive organic viologen ligands and europium ions, are successfully synthesized through a solid-state precursor and surfactant dual-template-directed approach, and employed as negative electrode of supercapacitors. The obtained EV-HNSs show high areal capacity (186.25 mF cm−2 at 1 mA cm−2), excellent cycling stability, and good rate capability under the voltage from −0.9 to −0.1 V (vs. Ag/AgCl), superior to their bulk counterparts. Especially, during the charge and discharge process, such EV-HNSs display a smart potential-correlated electrochromic feature. The color of EV-HNSs electrode turns from colorless to bright purple when the voltage gets negative, and then it can go back reversibly. Their distinct dual-electroactive composition, molecular stacking mode, and hierarchical porous nanosheet assembly structures endow the specific energy storage performance of EV-HNSs. Next, by choosing the electrodeposited MnO2 as positive electrode, the EV-HNSs//MnO2 ASCs are further fabricated, which manifest satisfactory operating voltage (1.55 V) and high areal energy density (9.4 μWh cm−2 at 775 μW cm−2), outperforming most of reported ASCs devices. This work may shed light on developing hierarchical MOFs-nanosheets-based multifunctional negative electrodes, and promote their applications in smart energy storage devices or other clean energy options.

Nanoarchitectonics of Glass Coatings for Near-Infrared Shielding: From Solid-State Cluster-Based Niobium Chlorides to the Shaping of Nanocomposite Films.

The high potential of [{Nb6Cli12}La6] cluster-based building blocks as near-infrared radiation blockers for energy saving applications is exposed in the present paper (i = inner edge-bridging ligand, a = apical ligand of the Nb6; L = H2O and/or Cl). To do so, a combined experimental and theoretical investigation of edge-bridged [{Nb6Cli12}Cla6-x(H2O)x]m+/0/n- cluster unit series (x = 0, 4, 6; m = 2, 3, 4; n = 2, 3, 4) has been carried out. By using the K4[{Nb6Cli12}Cla6] starting solid-state precursor, we explored the behavior of the [{Nb6Cli12}Cla6]4- cluster unit during the different steps of its integration as a building block into a polyvinylpyrrolidone (PVP) matrix to form a glass coating composite denoted {Nb6Cli12}m+@PVP (m = 2 or 3). The optical, vibrational and redox properties [{Nb6Cli12}Cla6-x(H2O)x]m+/0/n- building blocks have been interpreted with the support of electronic structure calculations and simulation of properties. The chemical modifications and oxidation properties have been identified and studied thanks to various techniques in solution. Combining Raman and ultraviolet-visible spectroscopies, electrochemistry, and quantum chemical simulations, we bring new knowledge to the understanding of the evolution of the properties of the [{Nb6Cli12}Cla6-x(H2O)x]m+/0/n- cluster units as a function of the number of valence electron per cluster (VEC) and the nature of terminal ligands (x = 0, n = 4; x = 4, charge = 0; x = 6, m = 4). The fine understanding of the physical properties and vibrational fingerprints depending on the VEC and chemical modifications in solution are mandatory to master the processing of cluster-based building blocks for the controlled design and shaping of glass coating nanocomposites. On the basis of this acquired knowledge, [{Nb6Cli12}Cla6-x(H2O)x]m+/0/n- building blocks were embedded in a PVP matrix. The resulting {Nb6Cli12}2+@PVP nanocomposite film shows excellent ultraviolet (UV, 280-380 nm) and near-infrared (NIR, 780-1080 nm) blocking ability (>90%) and a highly visible light transmittance thanks to the controlled integration of the {Nb6Cli12}2+ cluster core. The figures of merit (FOM) value of Tvis/Tsol (Tvis = visible transmittance and Tsol = solar transmittance) as well as the haze, clarity, and the NIR shielding values (SNIR) were measured. After optimization of the integration process, a {Nb6Cli12}2+@PVP nanocomposite on glass substrate has been obtained with a high FOM equal to 1.29. This high value places the transparent green olive {Nb6Cli12}2+@PVP nanocomposites at the top system in the benchmark in the field of glass coating composites for energy-saving applications.

Synthesis of mono- and few-layered n-type WSe2 from solid state inorganic precursors.

Tuning the charge transport properties of two-dimensional transition metal dichalcogenides (TMDs) is pivotal to their future device integration in post-silicon technologies. To date, co-doping of TMDs during growth still proves to be challenging, and the synthesis of doped WSe2, an otherwise ambipolar material, has been mainly limited to p-doping. Here, we demonstrate the synthesis of high-quality n-type monolayered WSe2 flakes using a solid-state precursor for Se, zinc selenide. n-Type transport has been reported with prime electron mobilities of up to 10 cm2 V-1 s-1. We also demonstrate the tuneability of doping to p-type transport with hole mobilities of 50 cm2 V-1 s-1 after annealing in air. n-Doping has been attributed to the presence of Zn adatoms on the WSe2 flakes as revealed by X-ray photoelectron spectroscopy (XPS), spatially resolved time of flight secondary ion mass spectroscopy (SIMS) and angular dark-field scanning transmission electron microscopy (AD-STEM) characterization of WSe2 flakes. Monolayer WSe2 flakes exhibit a sharp photoluminescence (PL) peak at room temperature and highly uniform emission across the entire flake area, indicating a high degree of crystallinity of the material. This work provides new insight into the synthesis of TMDs with charge carrier control, to pave the way towards post-silicon electronics.

Insight into the effect of OH modification on the piezo-photocatalytic hydrogen production activity of SrTiO3

Surface modification by hydrophilic functional group have a tremendous influence on the catalytic activity of photocatalyst, however, there are few reports on improving piezoelectric catalytic performance through surface functionalization. Herein, OH-modified SrTiO3 was successfully obtained via a novel low-temperature solid-state precursor method and employed as a catalyst for photocatalytic, piezocatalytic and piezo-photocatalytic hydrogen production. Thanks to the super hydrophilic that is facilitating the contact of catalyst and water molecular and the more oxygen vacancies that can promote electron-hole separation, the photocatalytic, piezocatalytic and piezo-photocatalytic hydrogen generation of OH-modified SrTiO3 (OH-STO) is about two times higher than pristine SrTiO3 (STO). It is worth mentioning that the optimal piezo-photocatalytic hydrogen evolution rate of OH-STO (701.2 µmol h−1 g−1) is 5.3 times higher than the photocatalytic hydrogen evolution process of STO. This study presents a low-energy approach to the rational design of functional group modification nanomaterials that possess excellent piezo-photocatalytic performance.

Decoration of Ru/RuO2 hybrid nanoparticles on MoO2 plane as bifunctional electrocatalyst for overall water splitting

Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are the two branches of artificial overall water splitting (OWS), in which the reaction efficiency usually depends on different specific catalysts. Although effective bifunctional electrocatalyst for OWS (HER and OER) are highly desired, designing and constructing such suitable materials is full of challenges to overcome several difficulties, involving slow kinetics, differences in catalytic mechanisms, large overpotential values, and low round-trip efficiencies. In this work, we reported a new bifunctional electrocatalyst Ru/RuO2-MoO2 catalyst (RRMC) via a redox solid phase reaction (RSPR) strategy to achieve the high electrocatalytic activity of OWS. Briefly, due to the restricted transport behavior of atoms in solid state precursor, the designed redox reaction occurred between the adjacent part of RuO2 and MoS2, forming Ru/RuO2 hybrid NPs and MoO2 plane. Therefore, the newly formed Ru/RuO2 hybrid NPs and MoO2 plane were tightly combined and used as an electrocatalyst for OWS. Benefiting from the exposed active sites and optimized electronic structure, the RRMC sample annealed at 500 °C (RRMC-500) exhibited low overpotential for HER (18 mV) and for OER (260 mV) at 10 mA cm−2 under alkaline conditions. Especially, a low cell voltage of 1.54 V was required at 10 mA cm−2 under alkaline condition.

(Invited) Silicon Nanosheets as Candidates for Silicon-Based Optoelectronics

Colloidal Group IV nanomaterials (Si, Ge, Sn and their alloys) are of great interest due to their potential to offer broadly tunable optical properties. By manipulating composition, size, or surface chemistry Group IV nanomaterials have potential to serve as nontoxic, earth abundant phosphors or semiconductors that can be used for optoelectronic applications that span the ultraviolet to the mid-infrared spectral ranges. The synthesis of colloidal Group IV nanostructures is challenging due to the highly covalent character of Si and Ge, and typically require temperatures in excess of 400°C to form crystalline particles. We have recently reported new synthetic methods for Si and Ge nanomaterials derived from precursors synthesized in the solid-state, including suboxides and Zintl phases. In each of these cases, colloidal nanostructures can be accessed by selectively removing unwanted components from the solid-state precursor, liberating nanostructures that are terminated with atomic or molecular species such as hydrogen atoms or methyl groups. We also characterize the structural properties of the Group IV nanostructures that we synthesized using a combination of infrared spectroscopy, solid-state NMR, and pair distribution function analysis to confirm the structure and order. In the case of Si and Ge, single-atom thick nanosheets were synthesized, their stability and decomposition at elevated temperatures were characterized. The optical properties of Group IV nanomaterials have sparked debate over the past few decades. We found that Si nanosheets exhibit fast (nanosecond) photoluminescence lifetime, which is several orders of magnitude greater than Si nanocrystals, and offer potential explanations for the observed difference. Finally we show that Si and Ge nanocrystals and nanosheets can be used for sensing applications, including infrared photodetectors and ionophore-based sensing schemes.

Evolution of cellulose acetate to monolayer graphene

Converting biomass waste into high-value products presents a challenging task in the environmental field. Growth of graphene from solid-state precursors is cost-effective and is becoming a hot research topic. However, the underlying mechanisms are as yet unclear. In this work, we report a novel method for directly growing adlayer-free large area graphene from cellulose acetate, the main component of cigarette filter waste. The evolution of cellulose acetate to reduced graphene oxide and finally to graphene is shown in this work for the first time. The effect of various growth parameters, hydrogen concentration and Cu grain boundaries on the size and qualities of the monolayer graphene domains is clarified. Finally, the mechanism for the growth of graphene from a solid-state precursor is proposed. The field-effect-transistor fabricated from transferred monolayer graphene demonstrated high electron and hole mobilities ∼1500 cm2/(V·s). This work presents a new opportunity for converting biomass waste into high-value graphene products.

Influence of Strontium on the Structural and Dielectric Properties of Hydrothermally Processed PbTiO3 Ceramic

Perovskite ceramic materials of the composition Pb1-xSrxTiO3 (PSxT) were prepared by hydrothermal process at a relatively low temperature. The solution of KOH favours the solubility of the precursors in solid state. Pressure and temperature are critical factors for the formation of pure perovskite PSxT phase. The reaction mixture in stoichiometric amount is put in an autoclave and treated at 180 ºC for 24 h. The powder obtained after grinding is treated at 400 ºC for 4 h. X-ray diffraction shows that the compounds crystallize in a pure phase of perovskite type. SEM morphology indicates a homogeneous microstructure of the grains with the presence of pores. The impedance spectroscopy study in the frequency range (1 KHz − 2 MHz) confirms the insertion of stronium into the lead titanate matrix and highlights the strontium effect on the transition temperature (Tc) and the value of dielectric permittivity (εr).

Pt2+-Exchanged ZIF-8 nanocube as a solid-state precursor for L10-PtZn intermetallic nanoparticles embedded in a hollow carbon nanocage.

Nanoparticles with an atomically ordered alloy phase have received enormous attention for application as catalysts in fuel cells because of their unique electronic properties resulting from unusually strong d-orbital interactions between two metal components. However, the synthesis of intermetallic nanoparticles requires a high reaction temperature, thus necessitating the protection of nanoparticles with inorganic layers to prevent aggregation of nanoparticles during synthesis. The protective layer needs to be removed later for application as a catalyst, which is a cumbersome process. Herein, a novel synthetic strategy is reported for the preparation of L10-PtZn intermetallic nanoparticles by utilizing Pt2+-exchanged ZIF-8 nanocubes as a solid-state precursor. The Pt2+-exchanged ZIF-8 phase plays a dual role as a metal ion source for L10-PtZn nanoparticles and as a carbonaceous matrix that restrains the aggregation of nanoparticles during thermal treatment. The L10-PtZn nanoparticles embedded in a hollow carbon nanocage obtained from one-step annealing of Pt2+-exchanged ZIF-8 showed better electrocatalytic activity and durability toward methanol oxidation under acidic electrolyte conditions than those obtained from commercial Pt/C catalysts.

Synthesis and Characterization of Ethyl Formate Precursor for Activated Release Application.

Ethyl formate (EF) is a generally recognized-as-safe flavoring agent commonly used in the food industry. It is a naturally occurring volatile with insecticidal and antimicrobial properties, promising as an alternate fumigant to methyl bromide which is undesirable due to its ozone depletion in the stratosphere and toxic properties. However, EF is highly volatile, flammable, and susceptible to hydrolytic degradation. These properties present considerable end-use challenges. In this study, a precursor of EF was synthesized via the condensation reaction of adipic acid dihydrazide and triethyl orthoformate to form diethyl N,N'-adipoyldiformohydrazonate, as confirmed by Fourier transformed infrared and solid-state nuclear magnetic resonance spectroscopies. Differential scanning calorimetry analysis showed that the precursor had a melting point of 174 °C. The physical properties of the precursor were studied using scanning electron microscopy and dynamic light scattering analysis, which showed that the precursor was made up of agglomerated particulates with irregular shapes and sizes. The resulting precursor was nonvolatile and remained stable under dry conditions but could be hydrolyzed readily to trigger the release of EF. The release behaviors of EF from the precursor was evaluated by citric acid-catalyzed hydrolysis, showing that 0.38 ± 0.008 mg EF/mg precursor was released after 2 h at 25 °C, representing about 98% of the theoretical loading. Both EF release rate and its total release amount decreased significantly (p < 0.05) with decreasing temperature and relative humidity. The conversion of the highly volatile EF into a solid-state precursor, in conjunction with the activated release strategy, can be useful for controlled release of EF for fumigation and other applications in destroying insect pests and inhibiting the proliferation of spoilage microorganisms.

Synthesis of the high dielectric permittivity perovskite (Na1/3Ca1/3 Bi1/3Cu3Ti4O12) by different routes

A high dielectric permittivity perovskite (Na1/3Ca1/3 Bi1/3Cu3Ti4O12) or NCBCTO was successfully synthesized by three different routes: solid state (SSS), solution combustion (SCS) and polymeric precursor (PPS). Wide angle x-rays (WAXD) and scanning electron microscopy (SEM) were used as control characterization techniques. A pure NCBCTO phase was obtained straightforward by the SSS method; by the SCS synthesis, however, only after a calcination at 800 °C was the resultant powder converted into the pure NCBCTO. The PPS samples maintained the same initial level of impurities (probably CuO), even after the calcination step. Further sintering of all the samples at 1000 and 1080 °C and characterization of their microstructures by SEM, their density and porosity by immersion tests and dielectric permittivity by impedance spectroscopy were done. Grain size increase and porosity decrease with the increase of the sintering temperature were observed. The samples produced by the PPS method, calcined at 800 °C and sintered at 1080 °C displayed the highest dielectric permittivity (above 20 000), but also the highest dielectric loss (tan δ = 0.35) at 1 kHz. However, the highest ε’/tan δ ratio (160 400 at 1 kHz, with ε’ = 9500 and tan δ = 0.059) was observed in samples produced by the SCS route, calcined at 800 °C and sintered at 1080 °C; these samples had also the smallest and sharpest grain size of all the samples. Thus, this last material was considered the best perovskite to be used as a high k ceramic in dielectric nanocomposites.

Low-cost fabrication of Li2TiO3 tritium breeding ceramic pebbles via low-temperature solid-state precursor method

Abstract Lithium metatitanate (Li2TiO3) ceramic pebbles were fabricated from the powder synthesised via low-temperature solid-state precursor method. Solid H2TiO3 and LiOH·H2O react chemically during ball milling process to form a nano-sized precursor powder. Pure β-Li2TiO3 powder can be obtained by calcining the precursor powder at 500 °C, which is half the temperature of conventional solid-state method. The synthesis process is simple and low-cost, which would be more available to achieve batch production among all feasible techniques. The low-temperature calcination will effectively avoid hard particle aggregates and poor sinterability caused by high-temperature heat treatment, which is conducive to prepare ceramics with good properties. The results show that the powder exhibits high sinterability with small particle size of 19 nm. The Li2TiO3 ceramic pebbles sintered at 800 °C have small grain size (470 nm), high relative density (83%) and good crush load (45 N), which has great potential as tritium breeding materials for fusion reactors.

Facile one-pot template synthesis of isotypic Co(II), Ni(II) and Cu(II) complexes of a Schiff base derived from glyoxylic acid and ethyl carbazate

Glyoxylic acid and ethyl carbazate condense in situ in the reaction medium and react with metal nitrates of Co, Ni or Cu to yield isostructural metal complexes with the general formula [M(gly-ec)2(H2O)2] (M = Co2+ (1), Ni2+ (2) and Cu2+ (3); Hgly-ec = ethoxycarbonyl-hydrazono-acetic acid). These products are elucidated through various physicochemical techniques including powder and single-crystal X-ray diffraction. X-ray crystallography of complexes 1 and 3 reveals that two anionic Schiff base ligands are coordinated to the metal ion via (N, O) bidentate chelation and situated trans to each other in equatorial positions and are nearly coplanar with the metal atom. The two coordinated water molecules occupy the trans axial positions, with a slightly distorted octahedral geometry. The thermal behavior of complexes 1–3 is studied in air and nitrogen atmosphere from 30 to 800 °C. In both mediums, all of the complexes show endothermic followed by exothermic decomposition to yield metal oxides as the end products at low temperature. Hence, these isotypic complexes may be used as solid-state precursors for the preparation of respective metal oxides due to their low temperatures of decomposition.

Rapid-Heating-Triggered in Situ Solid-State Transformation of Amorphous TiO2 Nanotubes into Well-Defined Anatase Nanocrystals

Fabrication of nanocrystals from their disordered solid-state precursors represents a new synthetic strategy. Compared to the widely used chemical vapor deposition and wet-chemistry based methods employing gas and liquid phased precursors, the solid-state transformation of disordered solid precursors to highly ordered crystals is a great challenge due to the severely restricted mass transport and inadequate structural directing mechanism. Herein, we report a rapid-heating-triggered in situ solid-state crystal growth method capable of transforming amorphous TiO2 nanotubes into anatase nanocrystals with well-defined facets and uniform sizes within a minute. The results obtained from in situ transmission electron microscopy and three-dimensional phase-field simulation indicate that the basic building blocks are formed through mechanical rupture of an amorphous TiO2 nanotube precursor, followed by an enhanced diffusion and concomitant oriented attachment onto TiO2 crystal nuclei mediated by the fluorine speci...