Ostwald Ripening: A Synthetic Approach for Hollow Nanomaterials
TL;DR: In this article, the application of a well-known physical phenomenon of crystal growth (Ostwald ripening) in the fabrication of hollow nanomaterials is introduced. But this work is limited to the case of orthogonal materials.
Abstract: Fabrication of nanomaterials with hollow interiors is an important research area in nanoresearch, owing to their potential applications in photonic devices, drug delivery, material encapsulation, ionic intercalation, surface functionalization, nanocatalysts, membrane nanoreactors, and many other technologies. The common preparative methods for this new class of materials can be broadly divided into hard and soft template-assisted syntheses. In recent years, furthermore, the interest in template-free techniques for these materials has also increased, as the new processes involved in these techniques are relatively simple and less demanding, compared to the template-assisted processes. In this short review, we will introduce the application of a well-known physical phenomenon of crystal growth – Ostwald ripening – in the fabrication of hollow nanomaterials. It has been demonstrated that formation of the interior spaces of nanostructures depends on the aggregative states of the primary crystallites during the synthesis. With this new development, many inorganic nanomaterials with interior spaces can now be fabricated in solution media together with the materials synthesis. Different types of Ostwald ripening observed in this synthetic approach have been reviewed. In particular, various geometric structures and configurations prepared with these methods have been discussed. The prepared hollow materials also allow further compositional and structural modifications under the similar process conditions. Future directions in this research area are also discussed.
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TL;DR: Hollow micro-/nanostructures are of great interest in many current and emerging areas of technology as discussed by the authors, and a comprehensive overview of synthetic strategies for hollow structures is presented.
Abstract: Hollow micro-/nanostructures are of great interest in many current and emerging areas of technology. Perhaps the best-known example of the former is the use of fly-ash hollow particles generated from coal power plants as partial replacement for Portland cement, to produce concrete with enhanced strength and durability. This review is devoted to the progress made in the last decade in synthesis and applications of hollow micro-/nanostructures. We present a comprehensive overview of synthetic strategies for hollow structures. These strategies are broadly categorized into four themes, which include well-established approaches, such as conventional hard-templating and soft-templating methods, as well as newly emerging methods based on sacrificial templating and template-free synthesis. Success in each has inspired multiple variations that continue to drive the rapid evolution of the field. The Review therefore focuses on the fundamentals of each process, pointing out advantages and disadvantages where appropriate. Strategies for generating more complex hollow structures, such as rattle-type and nonspherical hollow structures, are also discussed. Applications of hollow structures in lithium batteries, catalysis and sensing, and biomedical applications are reviewed.
2,767 citations
TL;DR: The recent research activities in the synthesis of metal oxide hollow nanostructures with controlled shape, size, composition, and structural complexity, as well as their applications in LIBs are summarized.
Abstract: Metal oxide hollow structures have received great attention because of their many promising applications in a wide range of fields. As electrode materials for lithium-ion batteries (LIBs), metal oxide hollow structures provide high specific capacity, superior rate capability, and improved cycling performance. In this Research News, we summarize the recent research activities in the synthesis of metal oxide hollow nanostructures with controlled shape, size,composition, and structural complexity, as well as their applications in LIBs. By focusing on hollow structures of some binary metal oxides (such as SnO 2 ,TiO 2 , Fe 2 O 3 , Co 3 O 4 ) and complex metal oxides, we seek to provide some rational understanding on the effect of nanostructure engineering on the electrochemical performance of the active materials. It is thus anticipated that this article will shed some light on the development of advanced electrode materials for next-generation LIBs.
1,391 citations
TL;DR: The unique properties and niche applications of the hollow structures in diverse fields, including micro-/nanocontainers and reactors, optical properties and applications, magnetic properties, energy storage, catalysis, biomedical applications, environmental remediation, and sensors are discussed.
Abstract: In this Review, we aim to provide an updated summary of the research related to hollow micro- and nanostructures, covering both their synthesis and their applications. After a brief introduction to the definition and classification of the hollow micro-/nanostructures, we discuss various synthetic strategies that can be grouped into three major categories, including hard templating, soft templating, and self-templating synthesis. For both hard and soft templating strategies, we focus on how different types of templates are generated and then used for creating hollow structures. At the end of each section, the structural and morphological control over the product is discussed. For the self-templating strategy, we survey a number of unconventional synthetic methods, such as surface-protected etching, Ostwald ripening, the Kirkendall effect, and galvanic replacement. We then discuss the unique properties and niche applications of the hollow structures in diverse fields, including micro-/nanocontainers and rea...
1,135 citations
TL;DR: In this article, the authors show that complex multi-shelled micro-nano-materials show significant material advantages in many applications over conventional simple hollow structures, and discuss the possible application of these novel materials for power generation and storage.
Abstract: Hollow micro-/nano-structured materials are now playing an important role in cutting edge innovations for energy conversion and storage technologies such as solar cells, fuel cells, lithium ion batteries and super capacitors. These materials show great promise in addressing growing environmental concerns for cleaner power sources at a time of increasing global demand for energy. In this perspective, we show that complex multi-shelled micro-/nano-materials show significant material advantages in many applications over conventional simple hollow structures. We also summarize the vast array of synthetic strategies used to create multi-shelled hollow structures, and discuss the possible application of these novel materials for power generation and storage. Finally, the emergent challenges and future developments of multi-shelled hollow structures are further discussed.
1,039 citations
TL;DR: A comprehensive review of recent synthetic methods along with associated synthesis mechanisms, characterization, fundamental properties, and promising applications of Cupric oxide (CuO) nanostructures is presented in this article.
1,030 citations