25th anniversary article: metal oxide particles in materials science: addressing all length scales

Hierarchical 3D Flower-like Metal Oxides Micro/Nanostructures: Fabrication, Surface Modification, Their Crucial Role in Environmental Decontamination, Mechanistic Insights, and Future Perspectives

Hierarchical micro/nanostructures are constructed by micro-scaled objects with nanoarchitectures belonging to an interesting class of crystalline materials that has significant applications in diverse fields. Featured with a large surface-to-volume ratio, facile mass transportation, high stability against aggregation, structurally enhanced adsorption, and catalytical performances, three dimenisional (3D) hierarchical metal oxides have been considered as versatile functional materials for waste-water treatment. Due to the ineffectiveness of traditional water purification protocols for reclamation of water, lately, the use of hierarchical metal oxides has emerged as an appealing platform for the remediation of water pollution owing to their fascinating and tailorable physiochemical properties. The present review highlights various approaches to the tunable synthesis of hierarchical structures along with their surface modification strategies to enhance their efficiencies for the removal of different noxious substances. Besides, their applications for the eradication of organic and inorganic contaminants have been discussed comprehensively with their plausible mechanistic pathways. Finally, overlooked aspects in this field as well as the major roadblocks to the implementation of these metal oxide architectures for large-scale treatment of wastewater are provided here. Moreover, the potential ways to tackle these issues are also presented which may be useful for the transformation of current water treatment technologies.

Nanotechnology Advances in the Detection and Treatment of Cancer: An Overview

Over the last few years, progress has been made across the nanomedicine landscape, in particular, the invention of contemporary nanostructures for cancer diagnosis and overcoming complexities in the clinical treatment of cancerous tissues. Thanks to their small diameter and large surface-to-volume proportions, nanomaterials have special physicochemical properties that empower them to bind, absorb and transport high-efficiency substances, such as small molecular drugs, DNA, proteins, RNAs, and probes. They also have excellent durability, high carrier potential, the ability to integrate both hydrophobic and hydrophilic compounds, and compatibility with various transport routes, making them especially appealing over a wide range of oncology fields. This is also due to their configurable scale, structure, and surface properties. This review paper discusses how nanostructures can function as therapeutic vectors to enhance the therapeutic value of molecules; how nanomaterials can be used as medicinal products in gene therapy, photodynamics, and thermal treatment; and finally, the application of nanomaterials in the form of molecular imaging agents to diagnose and map tumor growth.

The Importance of the Macroscopic Geometry in Gas-Phase Photocatalysis

Photocatalysis has the potential to make a major technological contribution to solving pressing environmental and energy problems. There are many strategies for improving photocatalysts, such as tuning the composition to optimize visible light absorption, charge separation, and surface chemistry, ensuring high crystallinity, and controlling particle size and shape to increase overall surface area and exploit the reactivity of individual crystal facets. These processes mainly affect the nanoscale and are therefore summarized as nanostructuring. In comparison, microstructuring is performed on a larger size scale and is mainly concerned with particle assembly and thin film preparation. Interestingly, most structuring efforts stop at this point, and there are very few examples of geometry optimization on a millimeter or even centimeter scale. However, the recent work on nanoparticle-based aerogel monoliths has shown that this size range also offers great potential for improving the photocatalytic performance of materials, especially when the macroscopic geometry of the monolith is matched to the design of the photoreactor. This review article is dedicated to this aspect and addresses some issues and open questions that arise when working with macroscopically large photocatalysts. Guidelines are provided that could help develop novel and efficient photocatalysts with a truly 3D architecture.

Nanotechnology-based approaches applied to nutraceuticals

Nutraceuticals and food industries are opening to a tremendously upcoming technology in the field of "Nano science". A new prospect has been defined by nanotechnology by conferring modified properties of nanomaterials and its application in the development of nanoformulations, nutritional supplements and food industry. Nanomaterials reveal exclusive properties because of their small size and high surface/volume ratio; thus, they have a complete application in nutraceuticals and food sector. In the existent review article, we obligate to present a comprehensive outline of the application of nanomaterials in development of advanced nano-based nutraceuticals with enhanced bioavailability, solubility, improved encapsulation efficiency, increased stability, sustained and targeted drug delivery, protection against degradation and microbial contamination and with improved pharmacological activity. It also highlights the importance of nanomaterials as nanosensors/nano-bio sensors for encapsulating peptides, antibodies, enzymes, etc. and in the food packaging industry and its future application. Thus, the review aims to focus on the benefits and new dimensions provided by nanomaterials and nanotechnology in health sectors by improving treatment strategies and quality of life.

Regulating the surface state of ZnIn2S4 by gamma-ray irradiation for enhanced photocatalytic hydrogen evolution

Surface state of ZnIn2S4 is regulated with γ-ray radiation, achieving over 10 times enhanced photocatalytic H2-evolution performance, which provides reasonable inspiration to regulate the surface vacancies of photocatalysts for enhanced activity.

Fabrication and application of macroscopic nanowire aerogels

Assembly of nanowires into three-dimensional macroscopic aerogels not only bridges a gap between nanowires and macroscopic bulk materials but also combines the benefits of two worlds: unique structural features of aerogels and unique physical and chemical properties of nanowires, which has triggered significant progress in the design and fabrication of nanowire-based aerogels for a diverse range of practical applications. This article reviews the methods developed for processing nanowires into three-dimensional monolithic aerogels and the applications of the resultant nanowire aerogels in many emerging fields. Detailed discussions are given on gelation mechanisms involved in every preparation method and the pros and cons of the different methods. Furthermore, we systematically scrutinize the application of nanowire-based aerogels in the fields of thermal management, energy storage and conversion, catalysis, adsorbents, sensors, and solar steam generation. The unique benefits offered by nanowire-based aerogels in every application field are clarified. We also discuss how to improve the performance of nanowire-based aerogels in those fields by engineering the compositions and structures of the aerogels. Finally, we provide our perspectives on future development of nanowire-based aerogels.

Catalytic hairpin assembly indirectly covalent on Fe3O4@C nanoparticles with signal amplification for intracellular detection of miRNA

Fluorescence resonance energy transfer, a promising method for in situ imaging of miRNA in living cells, has intrinsic limitation on sensitivity and selectivity. Herein, a fluorescent amplification strategy based on catalyzed hairpin assembly indirectly covalent on Fe₃O₄@C nanoparticles via short single-stranded DNA was investigated for cellular miRNA detection in living cells, integrating non-enzyme target-active releasing for amplifying the signal output, highly quenching efficiency of Fe₃O₄@C nanoparticles with low background, ssDNA assisted fluorescent group-fueled chain releasing from Fe₃O₄@C nanoparticles with enhanced fluorescence response. The designed platform exhibits highly sensitive in a wide linear concentration range of 0.450 pM-190 pM and is highly specific for miRNA-20a detection with the ability of discriminating one mistake base. Additionally, the CHA-Fe₃O₄@C was successfully applied in imaging visualization of miRNA-20a in the living cell. The strategy provides a promising bioassay approach for clinical research.

There's no place like real-space: elucidating size-dependent atomic structure of nanomaterials using pair distribution function analysis

The development of new functional materials builds on an understanding of the intricate relationship between material structure and properties, and structural characterization is a crucial part of materials chemistry. However, elucidating the atomic structure of nanomaterials remains a challenge using conventional diffraction techniques due to the lack of long-range atomic order. Over the past decade, Pair Distribution Function (PDF) analysis of X-ray or neutron total scattering data has become a mature and well-established method capable of giving insight into the atomic structure in nanomaterials. Here, we review the use of PDF analysis and modelling in characterization of a range of different nanomaterials that exhibit unique atomic structure compared to the corresponding bulk materials. A brief introduction to PDF analysis and modelling is given, followed by examples of how essential structural information can be extracted from PDFs using both model-free and advanced modelling methods. We put an emphasis on how the intuitive nature of the PDF can be used for understanding important structural motifs, and on the diversity of applications of PDF analysis to nanostructure problems.

Microplasmas for Advanced Materials and Devices

Microplasmas are low-temperature plasmas that feature microscale dimensions and a unique high-energy-density and a nonequilibrium reactive environment, which makes them promising for the fabrication of advanced nanomaterials and devices for diverse applications. Here, recent microplasma applications are examined, spanning from high-throughput, printing-technology-compatible synthesis of nanocrystalline particles of common materials types, to water purification and optoelectronic devices. Microplasmas combined with gaseous and/or liquid media at low temperatures and atmospheric pressure open new ways to form advanced functional materials and devices. Specific examples include gas-phase, substrate-free, plasma-liquid, and surface-supported synthesis of metallic, semiconducting, metal oxide, and carbon-based nanomaterials. Representative applications of microplasmas of particular importance to materials science and technology include light sources for multipurpose, efficient VUV/UV light sources for photochemical materials processing and spectroscopic materials analysis, surface disinfection, water purification, active electromagnetic devices based on artificial microplasma optical materials, and other devices and systems including the plasma transistor. The current limitations and future opportunities for microplasma applications in materials related fields are highlighted.

Indoor Air Pollution, Related Human Diseases, and Recent Trends in the Control and Improvement of Indoor Air Quality

Indoor air pollution (IAP) is a serious threat to human health, causing millions of deaths each year. A plethora of pollutants can result in IAP; therefore, it is very important to identify their main sources and concentrations and to devise strategies for the control and enhancement of indoor air quality (IAQ). Herein, we provide a critical review and evaluation of the major sources of major pollutant emissions, their health effects, and issues related to IAP-based illnesses, including sick building syndrome (SBS) and building-related illness (BRI). In addition, the strategies and approaches for control and reduction of pollutant concentrations are pointed out, and the recent trends in efforts to resolve and improve IAQ, with their respective advantages and potentials, are summarized. It is predicted that the development of novel materials for sensors, IAQ-monitoring systems, and smart homes is a promising strategy for control and enhancement of IAQ in the future.

Macroscopic macroporous titanosilicate constructed of a micro-mesoporous ultrathin nanofilm

MNCMM-TiSis have been successfully prepared by a templating approach and show excellent catalytic performance in the epoxidation of bulky alkenes.

Impurity Segregation and Nanoparticle Reorganization of Indium Doped MgO Cubes

Metal oxide nanocomposites are non-equilibrium solids and promising precursors for functional materials. Annealing of such materials can provide control over impurity segregation and, depending on the level of consolidation, represents a versatile approach to engineer free surfaces, particle-particle interfaces and grain boundaries. Starting with indium-magnesium-oxide nanoparticle powders obtained via injection of an indium organic precursor into the magnesium combustion flame and subsequent particle quenching in argon, we investigated the stability of the trivalent In3+ ions in the host lattice of MgO nanoparticles by determining grain growth, morphology evolution and impurity segregation. The latter process is initiated by vacuum annealing at 873 K and can be tracked at 1173 K on a time scale of minutes. In the first instance the surface segregated indium wets the nanoparticle interfaces. After prolonged annealing indium evaporates and leaves the powder via the gas phase. Resulting MgO nanocubes are devoid of residual indium, regain their high morphological definition and show spectroscopic fingerprints (UV Diffuse Reflectance and Photoluminescence emission) that are characteristic of electronically unperturbed MgO cube corner and edge features. The results of this combined XRD, TEM, and spectroscopy study reveal the parameter window within which control over indium segregation is used to introduce a semiconducting metal oxide component into the intergranular region between insulating MgO nanograins.

Surface and interface design for heterogeneous catalysis

Recent progresses in catalytic nanocrystals with uniform and well-defined structures, in situ characterization techniques, and theoretical calculations are facilitating the innovation of efficient catalysts via surface and interface designs, including crystal phase design, morphology/facet design, and size design, followed by controlled synthesis.

The Research Development of Quantum Dots in Electrochemical Energy Storage

Quantum dots, which are made from semiconductor materials, possess tunable physical dimensions and outstanding optoelectronic characteristics, and they have aroused widespread interest in recent years. In addition to applications in biomolecular analysis, sensors, organic photovoltaic devices, fluorescence, solar cells, photochemical reagents, light-emitting diodes, and catalysis, quantum dots have attracted mounting attention in the field of electrochemical energy storage owing to their size confinement and anisotropic geometry. In this review, a comprehensive summary is given and the research progress of the study of quantum dots for batteries and electrochemical capacitors in recent years, including their synthesis methods, micro/nanostructural features, and electrochemical performance, is appraised.

Radio-luminescence spectral features and fast emission in hafnium dioxide nanocrystals

In this work, we investigate the optical properties of hafnium dioxide nanocrystals, upon X-ray irradiation, looking for spectral evolution following thermal treatments in air up to 1000 °C that modify the crystal size as well as their point defect concentrations. Radio-luminescence measurements from 10 K up to room temperature reveal a rich and evolving picture of the optical features. A complete spectral analysis of the broad luminescence spectra reveals the presence of several emission components in the visible and UV regions. The lower energy components peaking at 2.1, 2.5, and 2.9 eV are characterized by a thermal quenching energy of 0.08 eV, while the corresponding value for the UV bands at 4.1 and 4.7 eV is close to 0.23 eV. We tentatively assign the components ranging from 2 to 3 eV to the presence of optically active defects of an intrinsic nature, together with the occurrence of titanium impurities; conversely, the bands at higher energies are likely to be of an excitonic nature. The comparison with previous photo-luminescence studies allows evidencing characteristic differences between the features of luminescence emissions caused by intra-centre excitation and those occurring under ionizing irradiation. Finally, scintillation measurements in the visible range reveal the existence of a fast decay in the nanosecond time scale for the smallest hafnia nanocrystals. This study offers a clear description of HfO2 luminescence characteristics upon excitation by X-rays and can lead to a better comprehension of the structure-property relationship at the nanoscale in metal oxides.

Nature-Inspired 2D-Mosaic 3D-Gradient Mesoporous Framework: Bimetal Oxide Dual-Composite Strategy toward Ultrastable and High-Capacity Lithium Storage

In allusion to traditional transition-metal oxide (TMO) anodes for lithium-ion batteries, which face severe volume variation and poor conductivity, herein a bimetal oxide dual-composite strategy based on two-dimensional (2D)-mosaic three-dimensional (3D)-gradient design is proposed. Inspired by natural mosaic dominance phenomena, Zn_1-xCo_xO/ZnCo₂O₄ 2D-mosaic-hybrid mesoporous ultrathin nanosheets serve as building blocks to assemble into a 3D Zn-Co hierarchical framework. Moreover, a series of derivative frameworks with high evolution are controllably synthesized, based on which a facile one-pot synthesis process can be developed. From a component-composite perspective, both Zn_1-xCo_xO and ZnCo₂O₄ provide superior conductivity due to bimetal doping effect, which is verified by density functional theory calculations. From a structure-composite perspective, 2D-mosaic-hybrid mode gives rise to ladder-type buffering and electrochemical synergistic effect, thus realizing mutual stabilization and activation between the mosaic pair, especially for Zn_1-xCo_xO with higher capacity yet higher expansion. Moreover, the inside-out Zn-Co concentration gradient in 3D framework and rich oxygen vacancies further greatly enhance Li storage capability and stability. As a result, a high reversible capacity (1010 mA h g^-1) and areal capacity (1.48 mA h cm^-2) are attained, while ultrastable cyclability is obtained during high-rate and long-term cycles, rending great potential of our 2D-mosaic 3D-gradient design together with facile synthesis.

Neglected nano-effects of nanoparticles in the interpretation of their toxicity

Considering the traditional mass, concentration, or surface area of nanoparticles can affect the conclusions drawn from cell viability tests about the toxicity of nanoparticles.

Tuning Properties of Iron Oxide Nanoparticles in Aqueous Synthesis without Ligands to Improve MRI Relaxivity and SAR

Aqueous synthesis without ligands of iron oxide nanoparticles (IONPs) with exceptional properties still remains an open issue, because of the challenge to control simultaneously numerous properties of the IONPs in these rigorous settings. To solve this, it is necessary to correlate the synthesis process with their properties, but this correlation is until now not well understood. Here, we study and correlate the structure, crystallinity, morphology, as well as magnetic, relaxometric and heating properties of IONPs obtained for different durations of the hydrothermal treatment that correspond to the different growth stages of IONPs upon initial co-precipitation in aqueous environment without ligands. We find that their properties were different for IONPs with comparable diameters. Specifically, by controlling the growth of IONPs from primary to secondary particles firstly by colloidal and then also by magnetic interactions, we control their crystallinity from monocrystalline to polycrystalline IONPs, respectively. Surface energy minimization in the aqueous environment along with low temperature treatment is used to favor nearly defect-free IONPs featuring superior properties, such as high saturation magnetization, magnetic volume, surface crystallinity, the transversal magnetic resonance imaging (MRI) relaxivity (up to r₂ = 1189 mM⁻¹·s⁻¹ and r₂/r₁ = 195) and specific absorption rate, SAR (up to 1225.1 W·g_Fe⁻¹).

The Structural Fate of Individual Multicomponent Metal-Oxide Nanoparticles in Polymer Nanoreactors

Multicomponent nanoparticles can be synthesized with either homogeneous or phase-segregated architectures depending on the synthesis conditions and elements incorporated. To understand the parameters that determine their structural fate, multicomponent metal-oxide nanoparticles consisting of combinations of Co, Ni, and Cu were synthesized by using scanning probe block copolymer lithography and characterized using correlated electron microscopy. These studies revealed that the miscibility, ratio of the metallic components, and the synthesis temperature determine the crystal structure and architecture of the nanoparticles. A Co-Ni-O system forms a rock salt structure largely owing to the miscibility of CoO and NiO, while Cu-Ni-O, which has large miscibility gaps, forms either homogeneous oxides, heterojunctions, or alloys depending on the annealing temperature and composition. Moreover, a higher-ordered structure, Co-Ni-Cu-O, was found to follow the behavior of lower ordered systems.

Ligand-Stabilized ZnO Quantum Dots: Molecular Dynamics and Experimental Study

Different aminoalcohol ligands, monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) were employed to passivate the surface of ZnO quantum dots (ZnO QDs). High-resolution transmission electron microscopy (HRTEM) imaging revealed that the higher branched aminoalcohols produced smaller sized ZnO QDs. The average size for ZnO/MEA, ZnO/DEA, and ZnO/TEA were found to be 3.2, 2.9, and 2.4 nm. TEA ligands were effective in producing stable, monodisperse ZnO QDs compared with DEA and MEA ligands. Molecular dynamics and semi-empirical calculations suggested that TEA and DEA ligands interact strongly with the partial charge of ZnO dangling bonds and have a large molar volume to hinder the diffusion of precursors through the ligands to the surface of ZnO resulting in a smaller particle size as compared with MEA ligands. As the size of ZnO QDs decreases from ZnO/MEA to ZnO/TEA, the absorption edge and emission peak maximum blue-shifts to a shorter wavelength due to the quantum size effect. The bandgap of ZnO/MEA, ZnO/DEA, and ZnO/TEA was determined to be 3.97, 4.07, and 4.23 eV, and the emission peak was found to be 472, 464, and 458 nm when excited using a 325 nm excitation wavelength, respectively.

Nanostructures prepared via laser ablation of tin in water

Ablation of Sn in water with millisecond and nanosecond pulsed lasers produces different core@shell nanostructures.

Synthesis of aerogels: from molecular routes to 3-dimensional nanoparticle assembly

Colloidal nanocrystals are extensively used as building blocks in nanoscience, and amazing results have been achieved in assembling them into ordered, close-packed structures. But in spite of great efforts, the size of these structures is typically restricted to a few micrometers, and it is very hard to extend them into the macroscopic world. In comparison, aerogels are macroscopic materials, highly porous, disordered, ultralight and with immense surface areas. With these distinctive characteristics, they are entirely contrary to common nanoparticle assemblies such as superlattices or nanocrystal solids, and therefore cover a different range of applications. While aerogels are traditionally synthesized by molecular routes based on aqueous sol-gel chemistry, in the last few years the gelation of nanoparticle dispersions became a viable alternative to improve the crystallinity and to widen the structural, morphological and compositional complexity of aerogels. In this Review, the different approaches to inorganic non-siliceous and non-carbon aerogels are addressed. We start our discussion with wet chemical routes involving molecular precursors, followed by processing methods using nanoparticles as building blocks. A unique feature of many of these routes is the fact that a macroscopic, often monolithic body is produced by pure self-assembly of nanosized colloids without the need for any templates.

Porous TiO2 Assembled from Monodispersed Nanoparticles

Porous TiO2 were assembled by evaporating or refluxing TiO2 colloid, which was obtained by dispersing the TiO2 nanoparticles with a crystallite size (d XRD) of 3.2 nm into water or ethanol without any additives. Porous transparent bulk TiO2 was obtained by evaporating the TiO2-C2H5OH colloid at room temperature for 2 weeks, while porous TiO2 nanospheres were assembled by refluxing the TiO2-H2O colloid at 80 °C for 36 h. Both of the porous TiO2 architectures were pore-size-adjustable depending on the further treating temperature. Porous TiO2 nanospheres exhibited enhanced photocatalysis activity compared to the nanoparticles.

From 1D to 3D - macroscopic nanowire aerogel monoliths

Here we present a strategy to assemble one-dimensional nanostructures into a three-dimensional architecture with macroscopic size. With the assistance of centrifugation, we successfully gel ultrathin W18O49 nanowires with diameters of 1 to 2 nm and aspect ratios larger than 100 into 3D networks, which are transformed into monolithic aerogels by supercritical drying.

Three-dimensional splitting microfluidics

Microfluidic systems with splitting structures are excellent for increasing emulsion production. However, traditional two-dimensional (2D) lithographic systems require complex modification of the microchannel surfaces and achieve only 2D splitting of the droplets. Herein, we present new glass capillary microfluidic devices that perform three-dimensional (3D) splitting of droplets. These devices are simply constructed using different structural glass capillaries as the collection microchannels of the droplet microfluidic systems. We demonstrate that the devices are able to produce a 3D split of both single emulsions and double emulsions into two and three portions, respectively. These emulsions, after the splitting process, still have high monodispersity. We believe that this new technique for 3D splitting could be widely used, not only in the field of microfluidics but also in chemical/biological applications (e.g., drug delivery, micro-dispersion, etc.).

Three-Dimensional Assembly of Yttrium Oxide Nanosheets into Luminescent Aerogel Monoliths with Outstanding Adsorption Properties

The preparation of macroscopic materials from two-dimensional nanostructures represents a great challenge. Restacking and random aggregation to dense structures during processing prevents the preservation of the two-dimensional morphology of the nanobuilding blocks in the final body. Here we present a facile solution route to ultrathin, crystalline Y2O3 nanosheets, which can be assembled into a 3D network by a simple centrifugation-induced gelation method. The wet gels are converted into aerogel monoliths of macroscopic dimensions via supercritical drying. The as-prepared, fully crystalline Y2O3 aerogels show high surface areas of up to 445 m(2)/g and a very low density of 0.15 g/cm(3), which is only 3% of the bulk density of Y2O3. By doping and co-doping the Y2O3 nanosheets with Eu(3+) and Tb(3+), we successfully fabricated luminescent aerogel monoliths with tunable color emissions from red to green under UV excitation. Moreover, the as-prepared gels and aerogels exhibit excellent adsorption capacities for organic dyes in water without losing their structural integrity. For methyl blue we measured an unmatched adsorption capacity of 8080 mg/g. Finally, the deposition of gold nanoparticles on the nanosheets gave access to Y2O3-Au nanocomposite aerogels, proving that this approach may be used for the synthesis of catalytically active materials. The broad range of properties including low density, high porosity, and large surface area in combination with tunable photoluminescence makes these Y2O3 aerogels a truly multifunctional material with potential applications in optoelectronics, wastewater treatment, and catalysis.

Fabrication of rutile TiO2 nanorod arrays on a copper substrate for high-performance lithium-ion batteries

TiO₂ nanorods array has been prepared directly on flexible copper substrate via in situ synthesis, presenting enormous potentials in LIBs.

Comprehensive Screen of Metal Oxide Nanoparticles for DNA Adsorption, Fluorescence Quenching, and Anion Discrimination

Although DNA has been quite successful in metal cation detection, anion detectioin remains challenging because of the charge repulsion. Metal oxides represent a very important class of materials, and different oxides might interact with anions differently. In this work, a comprehensive screen of common metal oxide nanoparticles (MONPs) was carried out for their ability to adsorb DNA, quench fluorescence, and release adsorbed DNA in the presence of target anions. A total of 19 MONPs were studied, including Al2O3, CeO2, CoO, Co3O4, Cr2O3, Fe2O3, Fe3O4, In2O3, ITO, Mn2O3, NiO, SiO2, SnO2, a-TiO2 (anatase), r-TiO2 (rutile), WO3, Y2O3, ZnO, ZrO2. These MONPs have different DNA adsorption affinity. Some adsorb DNA without quenching the fluorescence, while others strongly quench adsorbed fluorophores. They also display different affinity toward anions probed by DNA desorption. Finally, CeO2, Fe3O4, and ZnO were used to form a sensor array to discriminate phosphate, arsenate, and arsenite from the rest using linear discriminant analysis. This study not only provides a solution for anion discrimination using DNA as a signaling molecule but also provides insights into the interface of metal oxides and DNA.

Oxygen bubble-templated hierarchical porous ε-MnO2 as a superior catalyst for rechargeable Li-O2 batteries

Nickel foam-supported ε-MnO2 is synthesized through an oxygen-bubble template-assisted electrodeposition route and is applied as a new cathode catalyst for Li-O2 batteries. Owing to the 3D macro/micro/nano (multiscale) porous architecture, the prepared electrode exhibits low overpotential, high rate capability, and superior cycling durability.

TiO2 embedded in carbon submicron-tablets: synthesis from a metal–organic framework precursor and application as a superior anode in lithium-ion batteries

A unique “blueberry muffin” structure provides the ideal anode characteristics of fast rechargeable LIBs, showing excellent long-term cycling stability.

When protein-based biomineralization meets hydrothermal synthesis: the nanostructures of the as-prepared materials are independent of the protein types

Proteins were proved to be type-independent templates for the biomineralization of iron ions into hematite mesocrystals with tunable structures and morphologies under hydrothermal conditions.

Hydrophobic monolayered nanoflakes of tungsten oxide: coupled exfoliation and fracture in a nonpolar organic medium

Coupled exfoliation and fracture induced formation of hydrophobic monolayered nanoflakes of tungsten oxide in a nonpolar organic medium.

Rationale for the crystallization of titania polymorphs in solution

We use in situ X-ray absorption and diffraction studies to directly monitor the crystallization of different titania polymorphs in one and the same solution. We find that, despite the commonly accepted polymorphic-crossover from anatase to rutile triggered by the critical size of nanoparticles, in the solution their respective nucleation and growth are independent processes. Moreover, we find that 5.9 nm rutile nanoparticles are formed prior to the formation of 8.4 nm anatase nanoparticles. Our results suggest that the origins of this crystallization mechanism lie in the formation of an intermediate non-crystalline phase and in time-dependent changes in the chemical environment.

Anisotropically structured magnetic aerogel monoliths

Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.

Growth modes of nanoparticle superlattice thin films

We report on the fabrication and characterization of iron oxide nanoparticle thin film superlattices. The formation into different film morphologies is controlled by tuning the particle plus solvent-to-substrate interaction. It turns out that the wetting vs dewetting properties of the solvent before the self-assembly process during solvent evaporation plays a major role in determining the resulting film morphology. In addition to layerwise growth three-dimensional mesocrystalline growth is also evidenced. The understanding of the mechanisms ruling nanoparticle self-assembly represents an important step towards the fabrication of novel materials with tailored optical, magnetic or electrical transport properties.