Pursuing the Crystallization of Mono- and Polymetallic Nanosized Crystalline Inorganic Compounds by Low-Temperature Wet-Chemistry and Colloidal Routes (original) (raw)

Low‐Temperature Solution Crystallization of Nanostructured Oxides and Thin Films

Chemistry – A European Journal, 2020

As an introduction to this themed issue, a critically selected overview of recent progress on the topic of solution methods for the low‐temperature crystallization of nanoscale oxide materials is presented. It is focused on the low‐temperature solution processing of oxide nanostructures and thin films. Benefits derived from these methods span from minimizing the environmental impact to reducing the fabrication costs. In addition, this topic is regarded as a key objective in the area because it offers a unique opportunity for the use of these materials in areas like flexible electronics, energy conversion and storage, environmental sciences, catalysis, or biomedicine.

A conceptual change in crystallisation mechanisms of oxide materials from solutions in closed systems

Scientific Reports

Atomic and molecular level interactions in solutions dictate the structural and functional attributes of crystals. These features clearly dictate the properties of materials and their applicability in technologies. However, the microscopic phenomena of particle formation—nucleation and growth—in real systems are still not fully understood. Specifically, crystallisation occurring in closed systems are largely unproven. Combining coherent experimental data, we here demonstrate a fundamental nucleation-growth mechanism that occurs in a model zinc oxide system when particles are formed under continuous, rapid heating under closed reaction conditions. Defying all previous reports, we show that the nucleation commences only when the heating is terminated. A prenucleation clusters pathway is observed for nucleation, followed by crystallite assembly-growth. We show that the nucleation-growth processes result from temporal and dynamic activity of constituent ions and gaseous molecules in sol...

Nanostructured Colloidal Crystals from Forced Hydrolysis Methods

Langmuir, 2009

In this work, an original route for ZnO nanostructured spherical colloids and their assembly into colloidal crystals are presented. The temporal evolution of crystal size and shape was followed by X-ray diffraction and the colloids size distribution by scanning electron microscopy. These spherical colloids showed a change in their size dispersion with aging time. Early stage suspensions, with a narrow size distribution, were settled to the bottom and dried with a slow evaporation rate to obtain colloidal crystals. This original route provides a new material for future applications in opalline photonic crystals, with a dielectric constant higher than that of classical materials (silica and latex). Moreover, this route means an improvement of previously reported data from the literature since it involves a one-pot strategy and room-temperature colloid assembly.

Anatase-TiO2 Nanomaterials: Morphological/Size Dependence of the Crystallization and Phase Behavior Phenomena

The Journal of Physical Chemistry C, 2007

Nanoparticulated TiO 2 materials with anatase structure were synthesized by using a microemulsion method. Three different syntheses with varying surfactant-to-water molar ratio (ω) were used to obtain amorphous solid precipitates at room temperature. The structural characteristics of these solid precursors were studied by using X-ray absorption structure (X-ray absorption near-edge structure and extended X-ray absorption fine structure) and Raman spectroscopies, which showed that all lack 3D (tridimensional) order but contain a different degree of 2D-confined connectivity. While heating such solid precursors under dry air, marked differences appeared in the phase behavior; the onset temperature for anatase crystallization increases ca. 150°C while the ω parameter decreases and only one of the samples shows the anatase-to-rutile transformation below 900°C. In all cases, the crystallization of the anatase structure does not follow a traditional nucleation and growth mechanism and its analysis using the Avrami formalism gives conclusive evidence of a surface nucleation-dominated process. This appears as a distinctive feature of anatase-TiO 2 nanomaterials, far from the corresponding behavior of microsized or bulk materials. After nucleation, the grain growth of anatase nanoparticles was found to follow the kinetic equation D 2-D 0 2) k 0 exp(-E a /RT), where the activation energy is a function of several structural properties of the solid materials mainly related to the hydration characteristics of the surface layer. A combined in situ X-ray diffraction/Raman/infrared study aimed to unveil the physical basis of the phase behavior and to interpret key variables allowing control of the crystallization mechanism and morphological properties, particularly primary particle size, in the nanometer regime.

Review on Inorganic Nano crystals unique benchmark of Nanotechnology

2014

Most generally, "Nanocrystal" is used to mean a crystalline nanoparticle. Some sources define a nanocrystal as any singlecrystalline nanomaterial with at least one dimension ≤ 100 nm., while others define it more generally to be a nanoparticle with any kind of crystalline structure including e.g. multiply twinned configurations. A general material object with all dimensions less than 1 micrometre, i.e., 1000 nanometers, should be referred to as a nanoparticle, not a nanocrystal. In case it is single-crystalline or polycrystalline, it may be referred to as a nanocrystal. Crystalline nanoparticles are of interest because of many reasons. Silicon nanocrystals can provide efficient light emission even while bulk Si does not and be used as for memory components. Nanocrystals embedded in solids can exhibit much more complex melting behaviour than conventional solids [ and can form the basis of a special class of solids. They can also provide single-domain crystalline systems tha...

Nanoporous Solids: How Do They Form? An In Situ Approach

Chemistry of Materials, 2014

Understanding the crystallization mechanisms of nanoporous solids remains one of the most challenging issues in materials science. This Short Review focuses on the use of in situ nuclear magnetic resonance (NMR) spectroscopy under hydrothermal conditions to investigate the structure, dynamics, and stability/reactivity of the soluble species present in the synthesis medium during the crystallization. We describe how the formal SBU (secondary building units) concept for solid construction can experimentally be investigated, checked, and validated on some representative purely inorganic porous phosphates as well as hybrid metal organic framework (MOF) materials. We also discuss the specific role of reactive species identified in solution to lead to intermediate or more elaborate structures such as the PNBU (prenucleation building units) or the MBU (neutral molecular building units), respectively. In certain cases, the proposed models could not to be generalized depending on the reaction conditions, the chemistry of the metallic cation, and the stability/solubility of the target phase. We also point out that experimental and theoretical approaches for identification and enumeration of existing and new SBU are essential for the discovery and/or structure determination of new materials.

Room temperature synthesis of crystalline metal oxides

Journal of materials Science, 1997

Crystalline titanium dioxide powders have been synthesized as either rutile or anatase from aqueous solutions at low temperatures (T≤ 100C) and atmospheric pressure. First, a sol is prepared by the hydrolysis of a titanium alkoxide in an acidic solution. The ...

Design of metal oxide nanoparticles: Control of size, shape, crystalline structure and functionalization by aqueous chemistry

Comptes Rendus Chimie, 2010

The aim of this paper is to show that a very simple but well controlled chemistry in an aqueous medium allows one to efficiently control the main characteristics of oxide nanoparticles. Examples concerning titania, alumina, iron and manganese oxides are discussed to illustrate various effects on the control of size, shape and structure of nanoparticles. Some examples of functionalization of these particles are also illustrated. Experimental data, procedures and detailed references can be found in the cited literature. To cite this article: J.-P. Jolivet et al., C. R. Chimie 13 (2010). # 2009 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Solid-state synthesis of embedded single-crystal metal oxide and phosphate nanoparticles and in situ crystallization

Journal of Colloid and Interface Science, 2011

A new solid state organometallic route to embedded nanoparticle-containing inorganic materials is shown, through pyrolysis of metal-containing derivatives of cyclotriphosphazenes. Pyrolysis in air and at 800°C of new molecular precursors gives individual single-crystal nanoparticles of SiP 2 O 7 , TiO 2 , P 4 O 7, WP 2 O 7 and SiO 2 , depending on the precursor used. High resolution transmission electron microscopy investigations reveal, in most cases, perfect single crystals of metal oxides and the first nanostructures of negative thermal expansion metal phosphates with diameters in the range 2-6 nm for all products. While all nanoparticles are new by this method, WP 2 O 7 and SiP 2 O 7 nanoparticles are reported for the first time. In situ recrystallization formation of nanocrystals of SiP 2 O 7 was also observed due to electron beam induced reactions during measurements of the nanoparticulate pyrolytic products SiO 2 and P 4 O 7 . The possible mechanism for the formation of the nanoparticles at much lower temperatures than their bulk counterparts in both cases is discussed. Degrees of stabilization from the formation of P 4 O 7 affects the nanocrystalline products: nanoparticles are observed for WP 2 O 7 , with coalescing crystallization occurring for the amorphous host in which SiP 2 O 7 crystals form as a solid within a solid. The approach allows the simple formation of multimetallic, monometallic, metal-oxide and metal phosphate nanocrystals embedded in an amorphous dielectric. The method and can be extended to nearly any metal capable of successful coordination as an organometallic to allow embedded nanoparticle layers and features to be deposited or written on surfaces for application as high mobility pyrophosphate lithium-ion cathode materials, catalysis and nanocrystal embedded dielectric layers.

Ion irradiation effects in nonmetals: formation of nanocrystals and novel microstructures

Materials Research Innovations, 2000

Ion implantation is a versatile and powerful technique for producing nanocrystal precipitates embedded in the near-surface region of materials. Radiation effects that occur during the implantation process can lead to complex microstructures and particle size distributions, and in the present work, we focus on the application of these effects to produce novel microstructural properties for insulating or semiconducting nanocrystals formed in optical host materials. Nanocrystal precipitates can be produced in two ways: by irradiation of pure (i.e., non-implanted) crystalline or amorphous materials, or by ion implantation followed by either thermal annealing or subsequent additional irradiation. Different methods for the formation of novel structural relationships between embedded nanocrystals and their hosts have been developed, and the results presented here demonstrate the general flexibility of ion implantation and irradiation techniques for producing unique near-surface nanocomposite microstructures in irradiated host materials.