Growth and Assembly of Crystalline Tungsten Oxide Nanostructures Assisted by Bioligation

One-step construction of hexagonal WO3 nano-shuttles with enhanced lithium storage performance

In this work, WO3 nanorod-based aggregates and WO3 nano-shuttles were constructed by a facile hydrothermal route. The structure, morphology, element composition and valence state of the formed WO3 samples were characterized using different testing instruments. As the active anode for lithium-ion batteries, the WO3 nano-shuttle electrode can deliver a reversible specific capacity of 614.7 mA h g-1 after 300 cycles at a current density of 500 mA g-1. The excellent electrochemical properties indicate that WO3 nano-shuttles are a prospective anode candidate for high performance lithium-ion batteries.

Single-Atom Cu Stabilized on Ultrathin WO2.72 Nanowire for Highly Selective and Ultrasensitive ppb-Level Toluene Detection

Various catalysts are developed to improve the performance of metal oxide semiconductor gas sensors, but achieving high selectivity and response intensity in chemiresistive gas sensors (CGSs) remains a significant challenge. In this study, an in situ-annealing approach to synthesize Cu catalytic sites on ultrathin WO2.72 nanowires for detecting toluene at ultralow concentrations (Ra /Rg = 1.9 at 10 ppb) with high selectivity is developed. Experimental and molecular dynamic studies reveal that the Cu single atoms (SAs) act as active sites, promoting the oxidation of toluene and increasing the affinity of Cu single-atom catalysts (SACs)-containing sensing materials for toluene while weakening the association with carbon dioxide or water vapor. Density functional theory studies show that the selective binding of toluene to Cu SAs is due to the favorable binding sites provided by Cu SAs for toluene molecules over other gaseous species, which aids the adsorption of toluene on WO2.72 nanowires. This study demonstrates the successful atomic-level interface regulation engineering of WO2.72 nanowire-supported Cu SAs, providing a potential strategy for the development of highly active and durable CGSs.

Study on the photocatalytic properties differences between the 1-D and 3-D W18O49 particles†

The morphology of W₁₈O₄₉ catalysts has a significant effect on their photocatalytic performance. Herein, we successfully prepared two commonly used W₁₈O₄₉ photocatalysts just by changing the reaction temperature in the hydrothermal system, namely 1-D W₁₈O₄₉ nanowires (1-D W₁₈O₄₉) and 3-D urchin-like W₁₈O₄₉ particles (3-D W₁₈O₄₉), and evaluated the difference of their photocatalytic performances by taking the degradation of methylene blue (MB) as an example. Remarkably, 3-D W₁₈O₄₉ exhibited an impressive photocatalytic degradation performance towards MB with photocatalytic reaction rates of 0.00932 min⁻¹, which was about 3 times higher than that of 1-D W₁₈O₄₉. The comprehensive characterization and control experiments could further reveal that the hierarchical structure of 3-D W₁₈O₄₉ brought higher BET surface areas, stronger light harvesting, faster separation of photogenerated charges and so on, which was the main reason for its better photocatalytic performance. ESR results confirmed that the main active substances were superoxide radicals (˙O₂⁻) and hydroxyl radicals (˙OH). This work aims to explore the intrinsic relationship between the morphology and photocatalytic properties of W₁₈O₄₉ catalysts, so as to provide a theoretical basis in the morphology selection of W₁₈O₄₉ or its composite materials in the field of photocatalysis.

Comprehensive characterization and control experiments were used to deeply explore the intrinsic relationship between the morphology and photocatalytic properties of W₁₈O₄₉ catalysts.

Highly selective and sensitive fluorescence detection of tetracyclines based on novel tungsten oxide quantum dots

Tetracyclines (TCs) residues in animal products have attracted extensive concern due to their potential toxic to human health. Accordingly, it is urgent to develop an efficient method to determine TCs for providing consumers with risk pre-warning. Herein, a novel tungsten oxide quantum dots (W_xO_y QDs) fluorescence probe for tetracycline (TET) detection was constructed through ethanol-thermal method, which exhibited intense blue fluorescence under 365 nm UV light. Interestingly, blue-emitting W_xO_y QDs could be quenched obviously after the addition of TET, which may be attributed to the synergism of inner filter effect (IFE), fluorescence resonance energy transfer (FRET) and photo-induced electron transfer (PET). Thereby, the fluorescence method was established for TET detection based on W_xO_y QDs. Additionally, the presented method was demonstrated by monitoring TET in milk and milk powder with satisfactory recoveries. More importantly, this work offered good demonstration for the detection of food hazard factors.

General Microwave Route to Single-Crystal Porous Transition Metal Nitrides for Highly Sensitive and Stable Raman Scattering Substrates

The synthesis of metallic transition metal nitrides (TMNs) has traditionally been performed under harsh conditions, which makes it difficult to prepare TMNs with high surface area and porosity due to the grain sintering. Herein, we report a general and rapid (30 s) microwave synthesis method for preparing TMNs with high specific surface area (122.6-141.7 m² g^-1) and porosity (0.29-0.34 cm³ g^-1). Novel single-crystal porous WN, Mo₂N, and V₂N are first prepared by this method, which exhibits strong surface plasmon resonance, photothermal conversion, and surface-enhanced Raman scattering effects. Different from the conventional low-temperature microwave absorbing media such as water and polymers, as new concept absorbing media, hydrated metal oxides and metallic metal oxides are found to have a remarkable high-temperature microwave heating effect and play key roles in the formation of TMNs. The current research results provide a new-concept microwave method for preparing high lattice energy compounds with high specific surface.

Gram-scale selective synthesis of WO3-x nanorods and (NH4)xWO3 ammonium tungsten bronzes with tunable plasmonic properties

Localized surface plasmon resonance properties in unconventional materials like metal oxides or chalcogenide semiconductors have been studied for use in signal detection and analysis in biomedicine and photocatalysis. We devised a selective synthesis of the tungsten oxides WO_3-x and (NH₄)_xWO₃ with tunable plasmonic properties. We selectively synthesized WO_3-x nanorods with different aspect ratios and hexagonal tungsten bronzes (NH₄)_xWO₃ as truncated nanocubes starting from ammonium metatungstate (NH₄)₆H₂W₁₂O₄₀·xH₂O. Both particles form from the same nuclei at temperatures >200 °C; monomer concentration and surfactant ratio are essential variables for phase selection. (NH₄)_xWO₃ was the preferred reaction product only for fast heating rates (25 K min^-1), slow stirring speeds (∼150 rpm) and high precursor concentrations. A proton nuclear magnetic resonance (¹H-NMR) spectroscopic study of the reaction mechanism revealed that oleyl oleamide, formed from oleic acid and oleylamine upon heating, is a key factor for the selective formation of WO_3-x nanorods. Since oleic acid and oleylamine are standard surfactants for the wet chemical synthesis of many metal and oxide nanoparticles, the finding that oleyl oleamide acts as a chemically active reagent above 250 °C may have implications for many nanoparticle syntheses. Oriented attachment of polyoxotungstate anions is proposed as a model to rationalize phase selectivity. Magic angle spinning (MAS) ¹H-NMR and powder X-ray diffraction (PXRD) studies of the bronze after annealing under (non)inert conditions revealed an oxidative phase transition. WO_3-x and (NH₄)_xWO₃ show a strong plasmon absorption for near infra-red light between 800 and 3300 nm. The maxima of the plasmon bands shift systematically with the nanocrystal aspect ratio.

Sol-gel synthesis of 2-dimensional TiO2: self-assembly of Ti-oxoalkoxy-acetate complexes by carboxylate ligand directed condensation

2-Dimensional (2D) metal oxides have many potential industrial applications including heterogeneous catalysis, water splitting, renewable energy conversion, supercapacitor applications, biomaterials, gas separation and gas storage. Herein we report a simple and scalable method for the preparation of 2D TiO₂ nanostructures by reaction of titanium isopropoxide with acetic acid at 333 K in isopropanol, followed by calcination at 673 K to remove the organic ligands. Both the products and reaction intermediates have been studied using electron microscopy, X-ray diffraction, N₂ physisorption, nuclear magnetic resonance, thermogravimetric analysis, and X-ray photoelectron, Raman, and infrared spectroscopy. The anisotropic condensation of the planar Ti₆O₄(OⁱPr)₈(OAc)₈ complex is believed to be responsible for the formation of the 2D structure, where OⁱPr and OAc represent isopropoxide and acetate ligands, respectively. This research demonstrates that the metal complexes are promising building blocks for desired architectures, and the self-assembly of an acetate bidentate ligand is a versatile tool for manipulating the shape of final products.

Synthesizing 1D and 2D metal oxide nanostructures: using metal acetate complexes as building blocks

1D and 2D metal oxide nanostructures are important for potential applications in alternative energy, batteries, supercapacitors, catalysts, biomaterials, and electronic nanodevices. Many current approaches for making the desired nanomaterials require multiple steps, which are often exotic and complex for production on a commercial scale. In contrast, the sol-gel reactions between metal alkoxides and organic acids have emerged as a simple protocol for producing metal oxides and inorganic/organic hybrid materials with a controllable 1D or 2D architecture. Our knowledge of this process continues to evolve through the fundamental goal of designing a desired nanostructure from the corresponding molecular building blocks. Our research was driven by the discovery of various morphologies by fine-tuning the synthesis parameters, such as the reaction temperature and molar ratio of the reactants, as well as switching solvents. These discoveries lead to several quesions: What are the building blocks of the 1D and 2D nanostructures and how does the self-assembly occur? What are the reaction kinetics and the mechanisms of nanostructure formation? What role does the solvent play in the assembly process? What are the effects of reaction temperature and pressure? How can we manipulate the nanostructure-for example, the parallel growth of 1D semiconductors-from a substrate surface? And lastly, what are the industrial applications of macroporous aerogels and xerogels? This minireview will highlight documented research accounts to answer these questions.

Facile Preparation of WO3-x Dots with Remarkably Low Toxicity and Uncompromised Activity as Co-reactants for Clinical Diagnosis by Electrochemiluminescence

The exceptional nature of WO_3-x dots has inspired widespread interest, but it is still a significant challenge to synthesize high-quality WO_3-x dots without using unstable reactants, expensive equipment, and complex synthetic processes. Herein, the synthesis of ligand-free WO_3-x dots is reported that are highly dispersible and rich in oxygen vacancies by a simple but straightforward exfoliation of bulk WS₂ and a mild follow-up chemical conversion. Surprisingly, the WO_3-x dots emerged as co-reactants for the electrochemiluminescence (ECL) of Ru(bpy)₃ ²⁺ with a comparable ECL efficiency to the well-known Ru(bpy)₃ ²⁺ /tripropylamine (TPrA) system. Moreover, compared to TPrA, whose toxicity remains a critical issue of concern, the WO_3-x dots were ca. 300-fold less toxic. The potency of WO_3-x dots was further explored in the detection of circulating tumor cells (CTCs) with the most competitive limit of detection so far.

Facile synthesis of fluorescent tungsten oxide quantum dots for telomerase detection based on the inner filter effect

The traditional detection of telomerase activity is mainly based on the polymerase chain reaction (PCR), which has the disadvantages of being time-consuming and susceptible to interferences; thus, here, we propose a facile method for the fabrication of fluorescent tungsten oxide quantum dots (WO_x QDs) and employ them for telomerase activity sensing. It is found that the fluorescence of WO_x QDs can be significantly quenched by hemin based on the inner filter effect (IFE). However, in the presence of telomerase, the primer-DNA can be extended to generate repeating units of TTAGGG to form G-quadruplex and thus, hemin can be encapsulated to reduce its absorbance, resulting in decreased IFE and efficient fluorescence recovery of WO_x QDs. Based on the fluorescence changes of IFE between hemin and WO_x QDs, the telomerase activity within the range of 50-30 000 HeLa cells can be detected and the lowest detection amount can reach 17 cells. The method exhibits good versatility that can also be applied to telomerase detection in A549 and L929 cells. In addition, because of the good biocompatibility of the sensor, it can be used for the real-time monitoring of telomerase activity in living cells, thus showing great potential in tumor diagnosis and inhibitor drug screening.

Improved Surface-Enhanced Raman Spectroscopy Sensitivity on Metallic Tungsten Oxide by the Synergistic Effect of Surface Plasmon Resonance Coupling and Charge Transfer

Increasing the sensitivity of non-noble metal surface-enhanced Raman spectroscopy (SERS) is an urgent issue that needs to be solved at present. Herein, metallic W₁₈O₄₉ nanowires with a strong localized surface plasmon resonance (LSPR) effect are prepared. Interestingly, the LSPR peaks of these nanowires would undergo a strong blue shift from near-infrared (NIR) to visible light regions as the aggregation degree of the nanowires increases. By narrowing the gap between the LSPR absorption peak and the Raman excitation wavelength (532 nm), the oriented W₁₈O₄₉ bundles with a LSPR peak centered at 561 nm have greatly improved SERS sensitivity compared with that of the dispersed nanowires with a LSPR peak centered at 1025 nm. Enhancement mechanism investigation shows that the high sensitivity can be attributed to the synergistic effect of LSPR coupling among the oriented ultrathin nanowires and oxygen vacancy (V_o)-assisted charge transfer.

A Nonmetal Plasmonic Z-Scheme Photocatalyst with UV- to NIR-Driven Photocatalytic Protons Reduction

Ultrabroad-spectrum absorption and highly efficient generation of available charge carriers are two essential requirements for promising semiconductor-based photocatalysts, towards achieving the ultimate goal of solar-to-fuel conversion. Here, a fascinating nonmetal plasmonic Z-scheme photocatalyst with the W₁₈ O₄₉ /g-C₃ N₄ heterostructure is reported, which can effectively harvest photon energies spanning from the UV to the nearinfrared region and simultaneously possesses improved charge-carrier dynamics to boost the generation of long-lived active electrons for the photocatalytic reduction of protons into H₂ . By combining with theoretical simulations, a unique synergistic photocatalysis effect between the semiconductive Z-scheme charge-carrier separation and metal-like localized-surface-plasmon-resonance-induced "hot electrons" injection process is demonstrated within this binary heterostructure.

Growth of TiO2 microspheres with a radially oriented configuration

Hierarchical microspheres constructed from radially oriented TiO₂ nanorods have been fabricated. The obtained three-dimensional mesoporous TiO₂ microspheres have a high accessible surface area (66 m² g⁻¹), large pore volume (0.15 cm³ g⁻¹), and well single-crystallized rutile nanorod walls.

Colloidal metal oxide nanocrystals as charge transporting layers for solution-processed light-emitting diodes and solar cells

This review bridges the chemistry of colloidal oxide nanocrystals and their application as charge transporting interlayers in solution-processed optoelectronics.

Large-scale synthesis of ultrathin tungsten oxide nanowire networks: an efficient catalyst for aerobic oxidation of toluene to benzaldehyde under visible light

As a very important chemical raw material, the selective formation of benzaldehyde from toluene at preparative or industrial levels requires the use of highly corrosive chlorine and high reaction temperatures, which severely corrodes equipment, pollutes the environment, and consumes a lot of energy. Herein, we report a robust and highly active catalyst for the benzaldehyde evolution reaction that is constructed by the surfactant-free growth of oxygen vacancy-rich W18O49 ultrathin nanowire networks. Under atmospheric pressure and visible-light irradiation, the new catalyst can selectively (92% selectivity) catalyze the aerobic oxidation of toluene to benzaldehyde with yields of above 95%.

Ultrasmall Biocompatible WO3- x Nanodots for Multi-Modality Imaging and Combined Therapy of Cancers

Ultrasmall biocompatible WO3 - x nanodots with an outstanding X-ray radiation sensitization effect are prepared, and demonstrated to be applicable for multi-modality tumor imaging through computed tomography and photoacoustic imaging (PAI), and effective cancer treatment combining both photothermal therapy and radiation therapy.

Absorption and electrochromic modulation of near-infrared light: realized by tungsten suboxide

In the present study, needle-like tungsten suboxide W18O49 nanocrystals were fabricated as the optical active substance to realize the aim of optical control of near-infrared light. The W18O49 nanocrystals were selected in this regard due to their unique optical performance. As revealed by the powder absorption result, the needle-like W18O49 nanocrystals show strong and wide photoabsorption in the entire near infrared region of 780-2500 nm, from which thin films with the W18O49 nanocrystal coating thus benefits and can strongly shield off almost all near infrared irradiation, whereas transmitting the majority of visible light. To make it more tunable, the W18O49 nanocrystals were finally assembled onto an ITO glass via the layer-by-layer strategy for later electrochromic investigation. The nanostructured architectures of the W18O49 nanocrystal electrochromic films exhibit high contrast, faster switching response, higher coloration efficiencies (150 cm(2) C(-1) at 650 nm and 255 cm(2) C(-1) at 1300 nm), better long-term redox switching stability (reversibility of 98% after 500 cycles) and wide electrochromic spectrum coverage of both the visible and infrared regions.

Self-supported tungsten/tungsten dioxide nanowires array as an efficient electrocatalyst in the hydrogen evolution reaction

A tungsten/tungsten dioxide nanowires array was constructed on a carbon paper through the thermal annealing of tungsten trioxide, and was proven to be an efficient hydrogen evolution cathode with strong durability in acidic solutions.

Fabrication and multifunctional properties of ultrasmall water-soluble tungsten oxide quantum dots

Novel ultrasmall water-soluble tungsten oxide quantum dots with multifunctional properties have been successfully developed by a facile and green method.

Ligand-free and size-controlled synthesis of oxygen vacancy-rich WO3−x quantum dots for efficient room-temperature formaldehyde gas sensing

The present work provides an effective synthetic route for oxygen vacancy-rich WO_3−x QDs. More importantly, the WO_3−x QDs displayed high formaldehyde sensitivity with a detection limit of 1.5 ppm at room temperature.

Bi-template assisted synthesis of mesoporous manganese oxide nanostructures: Tuning properties for efficient CO oxidation

Bi-template assisted synthesis of mesoporous manganese oxide catalysts with tuned morphology, crystal structure, and textural properties for use in efficient catalysis of CO oxidation.

Tungsten Oxides for Photocatalysis, Electrochemistry, and Phototherapy

The conversion, storage, and utilization of renewable energy have all become more important than ever before as a response to ever-growing energy and environment concerns. The performance of energy-related technologies strongly relies on the structure and property of the material used. The earth-abundant family of tungsten oxides (WOx ≤3 ) receives considerable attention in photocatalysis, electrochemistry, and phototherapy due to their highly tunable structures and unique physicochemical properties. Great breakthroughs have been made in enhancing the optical absorption, charge separation, redox capability, and electrical conductivity of WOx ≤3 through control of the composition, crystal structure, morphology, and construction of composite structures with other materials, which significantly promotes the efficiency of processes and devices based on this material. Herein, the properties and synthesis of WOx ≤3 family are reviewed, and then their energy-related applications are highlighted, including solar-light-driven water splitting, CO2 reduction, and pollutant removal, electrochromism, supercapacitors, lithium batteries, solar and fuel cells, non-volatile memory devices, gas sensors, and cancer therapy, from the aspect of function-oriented structure design and control.

Twin Polymerization--a New Principle for Hybrid Material Synthesis

Twin polymerization is a novel modular approach for the synthesis of hybrid materials. Using this strategy two distinct polymers of either inorganic or organic nature are produced from a single source monomer in a mechanistically coupled process. Twin polymerization is an elegant way for producing nanostructured organic-inorganic hybrid materials of composition and morphology on demand. The main objective of this Review is the explanation of the principle of various twin polymerization processes and their appropriate terminologies. Different types of twin polymerization are classified with respect to the underlying processes as described in individual examples, demonstrating its potential in material synthesis. Prospects of the synthetic methodology of twin polymerization are demonstrated for different molecular structures of twin monomers and the resulting hybrid materials. A comparison with other scenarios for the synthesis of two different polymers within one procedure is included.

Aerosol-assisted chemical vapor deposition of tungsten oxide films and nanorods from oxo tungsten(VI) fluoroalkoxide precursors

Aerosol-assisted chemical vapor deposition (AACVD) of WOx was demonstrated using the oxo tungsten(VI) fluoroalkoxide single-source precursors, WO[OCCH3(CF3)2]4 and WO[OC(CH3)2CF3]4. Substoichiometric amorphous tungsten oxide thin films were grown on indium tin oxide (ITO) substrates in nitrogen at low deposition temperature (100-250 °C). At growth temperatures above 300 °C, the W18O49 monoclinic crystalline phase was observed. The surface morphology and roughness, visible light transmittance, electrical conductivity, and work function of the tungsten oxide materials are reported. The solvent and carrier gas minimally affected surface morphology and composition at low deposition temperature; however, material crystallinity varied with solvent choice at higher temperatures. The work function of the tungsten oxide thin films grown between 150 and 250 °C was determined to be in the range 5.0 to 5.7 eV, according to ultraviolet photoelectron spectroscopy (UPS).

Combustion synthesis and excellent photocatalytic degradation properties of W18O49

One-dimensional W₁₈O₄₉ nanoneedles were fabricated by solution combustion synthesis and exhibited an excellent visible light-driven photocatalytic performance.

Reaction time effect of straw-like MoO3 prepared with a facile, additive-free hydrothermal process

This paper presents the synthesis of straw-like MoO₃ prepared with a facile, additive-free hydrothermal process. It is worth mentioning that the median state of the product exhibits the most optimal photochromic properties.

Micro-wheels composed of self-assembled tungsten oxide nanorods for highly sensitive detection of low level toxic chlorine gas

Gas nanosensor based on micro-wheels composed of self-assembled tungsten oxide nanorods exhibited excellent sensing performance to ppb level Cl₂.

Ultrathin tungsten oxide nanowires: oleylamine assisted nonhydrolytic growth, oxygen vacancies and good photocatalytic properties

Ultrathin tungsten oxide nanowires with the diameter of around 1.1 nm have been fabricated through controlling the amount of oleylamine in a ​nonhydrolytic process.

A comprehensive review on synthesis methods for transition-metal oxide nanostructures

Recent developments of transition-metal oxide nanostructures with designed shape and dimensionality, including various synthesis methods and applications, are presented.

Magnetic mesocrystal-assisted magnetoresistance in manganite

Mesocrystal, a new class of crystals as compared to conventional and well-known single crystals and polycrystalline systems, has captured significant attention in the past decade. Recent studies have been focused on the advance of synthesis mechanisms as well as the potential on device applications. In order to create further opportunities upon functional mesocrystals, we fabricated a self-assembled nanocomposite composed of magnetic CoFe2O4 mesocrystal in Sr-doped manganites. This combination exhibits intriguing structural and magnetic tunabilities. Furthermore, the antiferromagnetic coupling of the mesocrystal and matrix has induced an additional magnetic perturbation to spin-polarized electrons, resulting in a significantly enhanced magnetoresistance in the nanocomposite. Our work demonstrates a new thought toward the enhancement of intrinsic functionalities assisted by mesocrystals and advanced design of novel mesocrystal-embedded nanocomposites.

Controlled synthesis of organic nanophotonic materials with specific structures and compositions

Organic nanomaterials have drawn great interest for their potential applications in high-speed miniaturized photonic integration due to their high photoluminescence quantum efficiency, structural processability, ultrafast photoresponse, and excellent property engineering. Based on the rational design on morphological and componential levels, a series of organic nanomaterials have been controllably synthesized in recent years, and their excitonic/photonic behaviors has been fine-tuned to steer the light flow for specific optical applications. This review presents a comprehensive summary of recent breakthroughs in the controlled synthesis of organic nanomaterials with specific structures and compositions, whose tunable photonic properties would provide a novel platform for multifunctional applications. First, we give a general overview of the tailored construction of novel nanostructures with various photonic properties. Then, we summarize the design and controllable synthesis of composite materials for the modulation of their functionalities. Subsequently, special emphasis is put on the fabrication of complex nanostructures towards wide applications in isolated photonic devices. We conclude with our personal viewpoints on the development directions in the novel design and controllable construction of organic nanomaterials for future applications in highly integrated photonic devices and chips.

Solvothermal, chloroalkoxide-based synthesis of monoclinic WO(3) quantum dots and gas-sensing enhancement by surface oxygen vacancies

We report for the first time the synthesis of monoclinic WO3 quantum dots. A solvothermal processing at 250 °C in oleic acid of W chloroalkoxide solutions was employed. It was shown that the bulk monoclinic crystallographic phase is the stable one even for the nanosized regime (mean size 4 nm). The nanocrystals were characterized by X-ray diffraction, High resolution transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis, Fourier transform infrared and Raman spectroscopy. It was concluded that they were constituted by a core of monoclinic WO3, surface covered by unstable W(V) species, slowly oxidized upon standing in room conditions. The WO3 nanocrystals could be easily processed to prepare gas-sensing devices, without any phase transition up to at least 500 °C. The devices displayed remarkable response to both oxidizing (nitrogen dioxide) and reducing (ethanol) gases in concentrations ranging from 1 to 5 ppm and from 100 to 500 ppm, at low operating temperatures of 100 and 200 °C, respectively. The analysis of the electrical data showed that the nanocrystals were characterized by reduced surfaces, which enhanced both nitrogen dioxide adsorption and oxygen ionosorption, the latter resulting in enhanced ethanol decomposition kinetics.

A comprehensive study of the crystallization mechanism involved in the nonaqueous formation of tungstite

We present a detailed study on the nonaqueous synthesis of tungstite nanostructures with the focus on crystallization processes and the evolution of particle morphology. Time-dependent transmission electron microscopy (TEM) revealed a complex, particle-based crystallization mechanism involving first the formation of spherical and single-crystalline primary particles of 2-8 nm, which are cross-linked to large and unordered agglomerates, followed by their organization into rod-like structures of 40 × 200-400 nm. These rods undergo an internal ordering process, during which crystallographically oriented stacks of platelets develop. In situ small angle X-ray scattering (SAXS) experiments confirm this pathway of particle formation. The scattering intensity is dominated by the fast formation of rod-like particles, which cause an inter-platelet peak in the SAXS pattern with ongoing internal ordering. With continuous reaction time, the platelet stacks start to fall apart forming shorter assemblies of just a few platelets or even single platelets.