Metallic-phase MoS2 (M-MoS2) is metastable and does not exist in nature. Pure and stable M-MoS2 has not been previously prepared by chemical synthesis, to the best of our knowledge. Here we report a hydrothermal process for synthesizing stable two-dimensional M-MoS2 nanosheets in water. The metal–metal Raman stretching mode at 146 cm−1 in the M-MoS2 structure, as predicted by theoretical calculations, is experimentally observed. The stability of the M-MoS2 is associated with the adsorption of a monolayer of water molecules on both sides of the nanosheets, which reduce restacking and prevent aggregation in water. The obtained M-MoS2 exhibits excellent stability in water and superior activity for the hydrogen evolution reaction, with a current density of 10 mA cm−2 at a low potential of −175 mV and a Tafel slope of 41 mV per decade.

Materials exhibiting a spontaneous electrical polarization that can be switched easily between antiparallel orientations are of potential value for sensors, photonics and energy-efficient memories. In this context, organic ferroelectrics are of particular interest because they promise to be lightweight, inexpensive and easily processed into devices. A recently identified family of organic ferroelectric structures is based on intermolecular charge transfer, where donor and acceptor molecules co-crystallize in an alternating fashion known as a mixed stack: in the crystalline lattice, a collective transfer of electrons from donor to acceptor molecules results in the formation of dipoles that can be realigned by an external field as molecules switch partners in the mixed stack. Although mixed stacks have been investigated extensively, only three systems are known to show ferroelectric switching, all below 71 kelvin. Here we describe supramolecular charge-transfer networks that undergo ferroelectric polarization switching with a ferroelectric Curie temperature above room temperature. These polar and switchable systems utilize a structural synergy between a hydrogen-bonded network and charge-transfer complexation of donor and acceptor molecules in a mixed stack. This supramolecular motif could help guide the development of other functional organic systems that can switch polarization under the influence of electric fields at ambient temperatures.

The design and fabrication of materials that exhibit both semiconducting and magnetic properties for spintronics and quantum computing has proven difficult. Important starting points are high-purity thin films as well as fundamental theoretical understanding of the magnetism. Here we show that small molecules have great potential in this area, due to ease of insertion of localised spins in organic frameworks and both chemical and structural purity. In particular, we demonstrate that archetypal molecular semiconductors, namely the metal phthalocyanines (Pc), can be readily fabricated as thin film quantum antiferromagnets, important precursors to a solid state quantum computer. Their magnetic state can be switched via fabrication steps which modify the film structure, offering practical routes into information processing. Theoretical calculations show that a new mechanism, which is the molecular analogue of the interactions between magnetic ions in metals, is responsible for the magnetic states. Our combination of theory and experiments opens the field of organic thin film magnetic engineering

The viability of dilute magnetic semiconductors in applications is linked to the strength of the magnetic couplings, and room temperature operation is still elusive in standard inorganic systems. Molecular semiconductors are emerging as an alternative due to their long spin-relaxation times and ease of processing, but, with the notable exception of vanadium-tetracyanoethylene, magnetic transition temperatures remain well below the boiling point of liquid nitrogen. Here we show that thin films and powders of the molecular semiconductor cobalt phthalocyanine exhibit strong antiferromagnetic coupling, with an exchange energy reaching 100 K. This interaction is up to two orders of magnitude larger than in related phthalocyanines and can be obtained on flexible plastic substrates, under conditions compatible with routine organic electronic device fabrication. Ab initio calculations show that coupling is achieved via superexchange between the singly occupied a1g () orbitals. By reaching the key milestone of magnetic coupling above 77 K, these results establish quantum spin chains as a potentially useable feature of molecular films.

The hydrogen evolution reaction in an alkaline environment using a non‐precious catalyst with much greater efficiency represents a critical challenge in research. Here, a robust and highly active system for hydrogen evolution reaction in alkaline solution is reported by developing MoS2 nanosheet arrays vertically aligned on graphene‐mediated 3D Ni networks. The catalytic activity of the 3D MoS2 nanostructures is found to increase by 2 orders of magnitude as compared to the Ni networks without MoS2. The MoS2 nanosheets vertically grow on the surface of graphene by employing tetrakis(diethylaminodithiocarbomato)molybdate(IV) as the molybdenum and sulfur source in a chemical vapor deposition process. The few‐layer MoS2 nanosheets on 3D graphene/nickel structure can maximize the exposure of their edge sites at the atomic scale and present a superior catalysis activity for hydrogen production. In addition, the backbone structure facilitates as an excellent electrode for charge transport. This precious‐metal‐free and highly efficient active system enables prospective opportunities for using alkaline solution in industrial applications.

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The development of molecular nanostructures plays a major role in emerging organic electronic applications, as it leads to improved performance and is compatible with our increasing need for miniaturisation. In particular, nanowires have been obtained from solution or vapour phase and have displayed high conductivity 1, 2 or large interfacial areas in solar cells. 3 In all cases however, the crystal structure remains as in films or bulk, and the exploitation of wires requires extensive post-growth manipulation as their orientations are random. Here we report copper phthalocyanine (CuPc) nanowires with diameters of 10-100 nm, high directionality and unprecedented aspect ratios. We demonstrate that they adopt a new crystal phase, designated η-CuPc, where the molecules stack along the long axis. The resulting high electronic overlap along the centimetre length stacks achieved in our wires mediates antiferromagnetic couplings and broadens the optical absorption spectrum. The ability to fabricate ultralong, flexible metal phthalocyanine nanowires opens new possibilities for applications of these simple molecules.Keywords: nanowire, phthalocyanine, organic vapour phase deposition, polymorph, molecular magnetism, molecular optoelectronics.Organic vapour phase deposition (OVPD) has been very successful at generating a wide range of film morphologies with a number of functional molecular materials, including smooth amorphous films, 4 textured islands, 5 and, more recently, nanowires . 6 The latter have been investigated for a variety of applications including sensors, 7 field effect transistors 1-2, 8 and photovoltaic cells. 3 So far, with the exception of 2 some very short nanobrushes, 9 only wires randomly oriented on a substrate have been produced. Their implementation on a device therefore requires micromanipulation, which is severely limiting for future applications where texture and length are desirable.Metal phthalocyanines (MPcs) are planar aromatic macrocyles which crystallise as a range of at least fifteen distinct polymorphs. 10,11 Typically, thin films exist as either α or β-phases, which have also been observed in relatively thick ( > 100 nm in diameter) wires. 6 The optoelectronic 12 and magnetic 13 properties of Pc materials are strongly dependent on their structure, and the creation of a new polymorph can have important consequences both for devices and in industry where α, β and ε-CuPc forms are routinely used as pigments.Through the optimisation of growth parameters in the OVPD we have obtained CuPc nanowires with diameters of 10-100 nm for lengths up to 1.4 cm. They adopt a new structure, with novel electronic absorption and magnetic properties. Their high directionality could significantly facilitate parallel integration into devices, and leads to confined antiferromagnetically coupled spin chains along the long wire axis. Figure 1.a shows a photograph of the CuPc branches after a growth time of typically 120 minutes. Those branches nucleate in a region of the sample tube which is ~ 10 cm outside the...

We study exchange couplings in the organic magnets copper͑II͒ phthalocyanine ͓Cu͑II͒Pc͔ and manganese͑II͒ phthalocyanine ͓Mn͑II͒Pc͔ by a combination of Green's function perturbation theory and ab initio density-functional theory ͑DFT͒. Based on the indirect exchange model, our perturbation-theory calculation of Cu͑II͒Pc qualitatively agrees with the experimental observations. DFT calculations performed on Cu͑II͒Pc dimer show a very good quantitative agreement with exchange couplings that our theoretical group extracts by using a global fitting for the magnetization measurements to a spin-1 2 Bonner-Fisher model. These two methods give us remarkably consistent trends for the exchange couplings in Cu͑II͒Pc when changing the stacking angles. The situation is more complex for Mn͑II͒Pc owing to the competition between superexchange and indirect exchange.