Coordination-Driven Hierarchical Assembly of Hybrid Nanostructures Based on 2D Materials

2D materials have received tremendous scientific and engineering interests due to their remarkable properties and broad-ranging applications such as energy storage and conversion, catalysis, biomedicine, electronics, and so forth. To further enhance their performance and endow them with new functions, 2D materials are proposed to hybridize with other nanostructured building blocks, resulting in hybrid nanostructures with various morphologies and structures. The properties and functions of these hybrid nanostructures depend strongly on the interfacial interactions between 2D materials and other building blocks. Covalent and coordination bonds are two strong interactions that hold high potential in constructing these robust hybrid nanostructures based on 2D materials. However, most 2D materials are chemically inert, posing problems for the covalent assembly with other building blocks. There are usually coordination atoms in most of 2D materials and their derivatives, thus coordination interaction as a strong interfacial interaction has attracted much attention. In this review, recent progress on the coordination-driven hierarchical assembly based on 2D materials is summarized, focusing on the synthesis approaches, various architectures, and structure-property relationship. Furthermore, insights into the present challenges and future research directions are also presented.

Preparation and Characterization of WS₂@SiO₂ and WS₂@PANI Core-Shell Nanocomposites

Two tungsten disulfide (WS₂)-based core-shell nanocomposites were fabricated using readily available reagents and simple procedures. The surface was pre-treated with a surfactant couple in a layer-by-layer approach, enabling good dispersion of the WS₂ nanostructures in aqueous media and providing a template for the polymerization of a silica (SiO₂) shell. After a Stöber-like reaction, a conformal silica coating was achieved. Inspired by the resulting nanocomposite, a second one was prepared by reacting the surfactant-modified WS₂ nanostructures with aniline and an oxidizing agent in an aqueous medium. Here too, a conformal coating of polyaniline (PANI) was obtained, giving a WS₂@PANI nanocomposite. Both nanocomposites were analyzed by electron microscopy, energy dispersive X-ray spectroscopy (EDS) and FTIR, verifying the core-shell structure and the character of shells. The silica shell was amorphous and mesoporous and the surface area of the composite increases with shell thickness. Polyaniline shells slightly differ in their morphologies dependent on the acid used in the polymerization process and are amorphous like the silica shell. Electron paramagnetic resonance (EPR) spectroscopy of the WS₂@PANI nanocomposite showed variation between bulk PANI and the PANI shell. These two nanocomposites have great potential to expand the use of transition metals dichalcogenides (TMDCs) for new applications in different fields.

Nanocomposites based on tubular and onion nanostructures of molybdenum and tungsten disulfides: inorganic design, functional properties and applications

The review concerns the development and the state-of-the-art in studies on the surface modification methods aimed at fabricating promising nanocomposites based on multilayer inorganic tubular and onion (fullerene-like) MoS2 and WS2 nanostructures. The synthetic details and structural features of these materials are considered. Considerable attention is paid to targeted functionalization of molybdenum and tungsten disulfide nanostructures and to fundamental principles that underlie their ability to chemical interactions. The functional properties and applications of the obtained materials are described.

The bibliography includes 183 references.

Tubular Hybrids: A Nanoparticle-Molecular Network

We report here a new methodology for the formation of freestanding nanotubes composed of individual gold nanoparticles (NPs) cross-linked by coordination complexes or porphyrin molecules using WS₂ nanotubes (INT-WS₂) as a template. Our method consists of three steps: (i) coverage of these robust inorganic materials with monodispersed and dense monolayers of gold NPs, (ii) formation of a molecular AuNP network by exposing these decorated tubes to solutions containing a ruthenium polypyridyl complex or meso-tetra(4-pyridyl)porphyrin, and (iii) removal of the INT-WS₂ template with a hydrogen peroxide solution. Nanoindentation of the template-free AuNP tubes with atomic force microscopy indicates a radial elastic modulus of 4 GPa. The template-free molecular AuNP tubes are characterized using scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, and micro-Raman spectroscopy. The methodology provides a convenient and scalable strategy for the realization of molecular AuNP tubes with a defined length and diameter, depending on the dimensions of the template.

Evolution of magnetism by rolling up hexagonal boron nitride nanosheets tailored with superparamagnetic nanoparticles

Controlling tunable properties by rolling up two dimensional nanomaterials is an exciting avenue for tailoring the electronic and magnetic properties of materials at the nanoscale. We demonstrate the tailoring of a magnetic nanocomposite through hybridization with magnetic nanomaterials using hexagonal boron nitride (h-BN) templates as an effective way to evolve magnetism for the first time. Boron nitride nanosheets exhibited their typical diamagnetism, but rolled-up boron nitride sheets (called nanoscrolls) clearly have para-magnetism in the case of magnetic susceptibility. Additionally, the Fe₃O₄ NP sample shows a maximum ZFC curve at about 103 K, which indicates well dispersed superparamagnetic nanoparticles. The ZFC curve for the h-BN-Fe₃O₄ NP scrolls exhibited an apparent rounded maximum blocking temperature at 192 K compared to the Fe₃O₄ NPs, leading to a dramatic increase in T_B. These magnetic nanoscroll derivatives are remarkable materials and should be suitable for high-performance composites and nano-, medical- and electromechanical-devices.

Evolution of a high local strain in rolling up MoS2 sheets decorated with Ag and Au nanoparticles for surface-enhanced Raman scattering

We report that a high local strain was obtained for multilayer MoS₂ nanoscrolls decorated with noble nanoparticles (Ag and Au NPs) using a rolling process beyond breaking or slipping of MoS₂. The local strain was estimated through the bending strain in the nanoscrolls and the extent of coverage of Ag and Au NPs decorated on MoS₂, exhibiting magnified surface-enhanced Raman scattering. TEM images showed that the MoS₂-Ag and MoS₂-Au nanoscrolls have a tube-like morphology decorated with NPs on the inner and outer sides of the MoS₂ nanoscrolls. In the Raman spectra, we confirmed the red shift and broadness of the FWHM for nanoscrolls in the eigenvectors of the [Formula: see text] and [Formula: see text] modes. From the Grüneisen parameter γ and the shear deformation potential β, we obtained peak shifts of ∼4.9 cm^-1/% at [Formula: see text] and ∼1.1 cm^-1/% strain at [Formula: see text] for free-standing MoS₂. According to the obtained relationship of the Raman shift and the induced uniaxial tensile strain, the [Formula: see text] and [Formula: see text] peaks shifted upwards to around -12.8 cm^-1 and -2.9 cm^-1, respectively, and can be converted to an induced uniaxial tensile strain of about 2.6% for MoS₂-Ag nanoscrolls.

Highly efficient hydrogen evolution reaction by strain and phase engineering in composites of Pt and MoS2 nano-scrolls

Our strategy begins with MoS₂ sheets decorated with Pt NPs and their scrolls (called MoS₂@Pt scrolls) with intrinsic bending strain (2.4%) to provide the phase transition from the 2H to the 1T phase (28%). MoS₂@Pt scrolls have the amount of Pt NPs (8.3 wt%) and high catalytic activity (39 mV per decade).

Modifying candle soot with FeP nanoparticles into high-performance and cost-effective catalysts for the electrocatalytic hydrogen evolution reaction

Developing inexpensive and highly efficient non-precious-metal electrocatalysts has been proposed as a promising alternative to platinum-based catalysts for the hydrogen evolution reaction (HER). Herein, we report novel FeP NPs supported on inexpensive and available candle soot (FeP-CS) derived from Fe3O4-CS hybrid precursors obtained after a phosphidation reaction. As HER electrocatalysts, the FeP-CS hybrids exhibit high electrocatalytic ability for HER with a Tafel slope of 58 mV dec(-1), a low onset overpotential of 38 mV, a large exchange current density of 2.2 × 10(-1) mA cm(-2) and an overpotential of 112 mV to obtain a current of 10 mA cm(-2). The present work shows significant advance in designing and developing non-precious-metal electrocatalysts for hydrogen evolution reaction.