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.

Hollow Micro-/Nanostructures: Synthesis and Applications**

Metal sulfide hollow nanostructures (MSHNs) have received intensive attention as electrode materials for electrical energy storage (EES) systems due to their unique structural features and rich chemistry. Here, we summarize recent research progress in the rational design and synthesis of various metal sulfide hollow micro-/nanostructures with controlled shape, composition and structural complexity, and their applications to lithium ion batteries (LIBs) and hybrid supercapacitors (HSCs). The current understanding of hollow structure control, including single-shelled, yolk-shelled, multi-shelled MSHNs, and their hybrid micro-/nanostructures with carbon (amorphous carbon nanocoating, graphene and hollow carbon), is focused on. The importance of proper structural and compositional control on the enhanced electrochemical properties of MSHNs is emphasized. A relationship between structural and compositional engineering with improved electrochemical activity of MSHNs is sought, in order to shed some light on future electrode design trends for next-generation EES technologies.

Metal Sulfide Hollow Nanostructures for Electrochemical Energy Storage

Arrays of CuS ultrafine nanoneedles supported on a carbon nanotube (CNT) backbone (CNT@CuS) are fabricated by an efficient template-engaged chemical conversion route. First, the silica coated CNTs (CNT@SiO2) are introduced as the substrate for the growth of copper silicate (CuSilicate) nanoneedles to form CNT@SiO2@CuSilicate core–shell one-dimensional (1D) structures. In the second step, the CuSilicate nanoneedles are completely transformed into CuS nanoneedles via a hydrothermal treatment with Na2S. Simultaneously the intermediate silica layer is removed during the hydrothermal process, thus resulting in hierarchical CNT@CuS complex nanostructures. In virtue of the unique architecture and intrinsic properties, the as-prepared CNT@CuS hierarchical structures exhibit high capacitance and excellent cycling stability.

Arrays of ultrafine CuS nanoneedles supported on a CNT backbone for application in supercapacitors

Blue solution of copper(II) acetylacetonate complex, [Cu(acac)2] in dichloromethane (DCM) and an aqueous alkaline solution of thioacetamide (TAA) constitute a biphasic system. The system in a screw cap test tube under a modified hydrothermal (MHT) reaction condition produces a greenish black solid at the liquid−liquid interface. It has been characterized that the solid mass is an assembly of hexagonal copper sulfide (CuS) nanoplates representing a hierarchical structure. The as-synthesized CuS nanoplates are well characterized by several physical techniques. An ethanolic dispersion of CuS presents a high band gap energy (2.2 eV) which assists visible light photocatalytic mineralization of different dye molecules. Thus a cleanup measure of dye contaminated water body even under indoor light comes true.

Evolution of Hierarchical Hexagonal Stacked Plates of CuS from Liquid−Liquid Interface and its Photocatalytic Application for Oxidative Degradation of Different Dyes under Indoor Lighting

Well‐Defined Non‐spherical Copper Sulfide Mesocages with Single‐Crystalline Shells by Shape‐Controlled Cu2O Crystal Templating

A novel single-step approach have been applied to fabricate CuS micrometer-sized hollow spheres; the procedure is based on a template interface reaction between CuCl and sulfur liquid droplets in ethylene glycol solvent.

Single-step synthesis of copper sulfide hollow spheres by a template interface reaction route

A novel nonaqueous route was applied to synthesize CuS macroporous material by the reaction between CuCl2·2H2O and S via the reducing action of ethylene glycol solvent. The CuS macroporous material...

A Nonaqueous Route to Prepare Novel CuS Macroporous Material

Co9S8 hexagonal aggregations were synthesized in hydrazine hydrate (N2H4·H2O) solvent at 150 °C for 12 h using cobalt(II) sulfate hydrate (CoSO4·7H2O) and sodium sulfite (Na2SO3) as starting materi...

Yiya Peng

Papers

Single-step synthesis of copper sulfide hollow spheres by a template interface reaction route

A Nonaqueous Route to Prepare Novel CuS Macroporous Material

In Situ Deposition of Co9S8 Nanocrystallite on Its Single-Crystal Flakes at Low Temperatures

Molecular assembly of CuBrSe3 in ethylene glycol solvent