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Layered molybdenum disulphide (MoS2) crystals in combination with graphene create the opportunity for the development of heterostructures with tailored surface and structural properties for energy storage applications. Herein, 2D heterostructures are developed by growing MoS2 on epitaxial and self-standing nanoporous graphene (NPG) using chemical vapor deposition (CVD). The effect of substrate as well as different CVD growth parameters such as temperature, amount of sulfur and MoO3 precursors, and argon flow on the growth of MoS2 is systematically investigated. Interestingly, various structures of MoS2 such as monolayer triangular islands, spirals, standing sheets, and irregular stacked multilayered MoS2 are successfully developed. The growth mechanism is proposed using different advanced characterization techniques. The formation of a continuous wetting layer with grain boundaries over the surface prior to formation of any other structures is detected. As a proof of principle, MoS2/NPG is employed for the first time as anode material in potassium ion battery. The electrode delivers a specific capacity of 389 mAh g−1 with over 98% stability after 200 cycles. The porous structures clearly facilitate the ion transport which is beneficial for the ion battery. These encouraging results open new opportunities to develop hierarchical heterostructures of 2D-materials for next-generation energy storage technologies.

The expected widespread use of wearable and other low-power healthcare devices has triggered great interest in piezoelectric materials as a promising energy harvester. However, traditional piezoelectric materials suffer from poor interfacial energy transfer when used in self-charging power cells. Herein, piezoelectric supercapacitors (PSCs) are engineered using MXene-incorporated polymeric piezo separator and MXene (Ti3C2Tx) multilayered sheets as electrodes. The MXene-blended polymer film showed considerable improvement with maximum output voltage of 28 V and current of 1.71 µA. The electromechanical properties studied by piezoelectric force microscopy suggest that the integration of MXene in polyvinylidene fluoride (PVDF) matrix induces the degree of dipole moment alignment, thereby improving the piezoelectric properties of PVDF. At the device level, the PSC featured the capacitance of 61 mF cm–2, the energy density of 24.9 mJ cm−2, the maximum power density of 1.3 mW cm−3, and the excellent long-term cycling stability. A way is paved toward green, integrated energy harvesting and storing technology for next-generation self-powered implantable and wearable electronics.

The synthesis of highly crystalline mesoporous materials is key to realizing high-performance chemical and biological sensors and optoelectronics. However, minimizing surface oxidation and enhancing the domain size without affecting the porous nanoarchitecture are daunting challenges. Herein, we report a hybrid technique that combines bottom-up electrochemical growth with top-down plasma treatment to produce mesoporous semiconductors with large crystalline domain sizes and excellent surface passivation. By passivating unsaturated bonds without incorporating any chemical or physical layers, these films show better stability and enhancement in the optoelectronic properties of mesoporous copper telluride (CuTe) with different pore diameters. These results provide exciting opportunities for the development of long-term, stable, and high-performance mesoporous semiconductor materials for future technologies.

Organic-inorganic hybrid perovskite solar cells (PSCs) have the issue of interdiffusion at the interfaces that causes undesirable phenomena affecting device efficiency and stability. In this paper, we have investigated MoOx thin films as interlayer between the hole transport material and gold electrode and develop a model using the SCAPS solar cell simulator as a function of the interlayer film thickness to enhance device efficiency and stability. First, different thicknesses (2, 5, 10, 50, and 100 nm) of MoOx films were deposited on glass substrate by electron beam evaporation (e-beam) and their physical, chemical, optical, and electronic properties for PSC were examined. In this research, uniform, homogeneous and pinhole free MoOx films with high transmittance (> 80%), very low surface roughness, and resistivity were obtained from the 5 and 10 nm thick samples. In addition, the 10 nm film has shown the lowest photoluminescence emission. Using SCAPS solar cell simulation software and including MoOx thin films as passivation layer, the performance of the PSCs for a Pb-based and Pb-free perovskite absorber were modelled. Results showed that the 10 nm MoOx film is found to provide the best benefit to the device performance with enhanced power conversion efficiency (PCE) of 16.9% and 12.4% for the lead-based MAPb(I1-xBrx)3 and lead-free (MASnI3) perovskite solar cells, respectively.

Geometrical structuring of monolithic metal-organic frameworks (MOFs) components is required for their practical implementation in many areas, including electronic devices, gas storage/separation, catalysis, energy storage as well as bio-medical applications. Despite progress in structuring MOFs, an approach for the precise patterning of MOF functional geometries in the millimeter- to micro-meter depth is lacking. Here, a facile and flexible concept for the microfabrication of complex MOF patterns on large surfaces is reported. The method relies on the engineering of easily-writable sheets of precursor metal oxide nanoparticles. The gas-phase conversion of these patterned ceramic nanoparticle sheets results in monolithic MOF objects with arbitrarily shaped geometries and thicknesses of up to hundreds of micrometers. The writing of complex patterns of zeolitic imidazolate framework-8 (ZIF-8) is demonstrated by a variety of approaches including ion beam, laser, and hand writing. Nanometer-scale patterns are achieved by focused ion beam (FIB). Artless handwritings are obtained by using a pen in a similar fashion to writing on a paper. The pure ZIF-8 composition of the resulting patterns is confirmed by a series of physical and chemical characterization. This facile MOF precursor-writing approach provides novel opportunities for the design of MOF-based devices with applications ranging from micro-fluidics to renewable energy systems.

Supplying fresh drinking water to the world population is a persistent global challenge. Therefore, effective and efficient desalination processes are becoming increasingly important. Oceans account for most of the water on Earth and the presence of salts and other contaminants in seawater prevents them from being used as a source of drinking water. Owing to this challenge, non-thermal plasma can be utilized in order to enhance the existing desalination processes via membrane or material modification while it can also be used as a direct tool for seawater desalination leading to significant process improvements. A direct non-thermal plasma-based desalination process is a new emerging area of research and recent efforts have shown its promise with many unexplored mechanisms, providing benefits that conventional desalination processes cannot offer. Here we critically review the use of plasma technologies in water desalination including membrane modification by plasma for pressure, thermal, photothermal processes and direct plasma-based desalination process. We also address the use of plasmas in water purification. Finally, the existing challenges and future prospects are outlined.

We report enhanced amperometric sensing response of electrospun tungsten oxide (WO3-x) nanofibers towards acetone with low concentrations (1.2-12.5 ppm) at 350 °C. Scanning and transmission electron microscopy (SEM and TEM) revealed the nanocrystalline nature of tungsten oxide nanofibers with a diameter in the range of 200-350 nm. X-ray diffraction (XRD) analysis showed a monoclinic crystal structure with oxygen vacancies, which are confirmed by X-ray photoelectron spectroscopy (XPS) providing an evaluation of the O : W ratio of 2.60. The excellent conductivity of tungsten oxide due to oxygen vacancies makes it a promising material for acetone sensing. Acetone sensing has been tested at various bias potentials (3-9 V), evidencing a variation of sensing response with voltage. The amperometric response has a three fold increase with an increase of the bias potential from 3 V to 9 V. The sensor shows a repeatability of ≥ 99% with an ability to detect low concentrations of acetone down to 10 ppb (calculated detection limit). The sensor also shows fast response kinetics and excellent selectivity when humidity and carbon dioxide were tested as cross-interference gas species.

The potential of transition metal dichalcogenides such as MoS2 for energy storage has been significantly limited so far by the lack of conductivity and structural stability. Employing highly conductive, graphitic materials in combination with transition metal dichalcogenides can address this gap. Here, we explore the use of a layered electrode structure for solid-state supercapacitors, made of MoS2 and epitaxial graphene (EG) on cubic silicon carbide for on-silicon energy storage. We show that the energy storage of the solid-state supercapacitors can be significantly increased by creating layered MoS2/graphene electrodes, yielding a substantial improvement as compared to electrodes using either EG or MoS2 alone. We conclude that the conductivity of EG and the growth morphology of MoS2 on graphene play an enabling role in the successful use of transition metal dichalcogenides for on-chip energy storage.

Polyoxometalates (POMs) represent a class of nanomaterials, which hold enormous promise for a range of energy-related applications. Their promise is owing to their "special"structure that gives POMs a truly unique ability to control redox reactions in energy conversion and storage. One such amazing capability is their large number of redox active sites that arises from the complex three-dimensional cluster of metal-oxide ions linked together by oxygen atoms. Here, a critical review on how POMs emerged from being molecular clusters for fundamental studies, to next-generation materials for energy applications is provided. We highlight how exploiting the versatility and activity of these molecules can lead to improved performance in energy devices such as supercapacitors and batteries, and in energy catalyst applications. The potential of POMs across numerous fields is systematically outlined by investigating structure-property-performance relationships and the determinant factors for energy systems. Finally, the challenges and opportunities for this class of materials with respect to addressing our pressing energy-related concerns are identified. This journal is

Advance of photonics media is restrained by the lack of structuring techniques for the 3D fabrication of active materials with long-range periodicity. A methodology is reported for the engineering of tunable resonant photonic media with thickness exceeding the plasmonic near-field enhancement region by more than two orders of magnitude. The media architecture consists of a stochastically ordered distribution of plasmonic nanocrystals in a fractal scaffold of high-index semiconductors. This plasmonic-semiconductor fractal media supports the propagation of surface plasmons with drastically enhanced intensity over multiple length scales, overcoming the 2D limitations of established metasurface technologies. The fractal media are used for the fabrication of plasmonic optical gas sensors, achieving a limit of detection of 0.01 vol% at room temperature and sensitivity up to 1.9 nm vol%−1, demonstrating almost a fivefold increase with respect to an optimized planar geometry. Beneficially to their implementation, the self-assembly mechanism of this fractal architecture allows fabrication of micrometer-thick media over surfaces of several square centimeters in a few seconds. The designable optical features and intrinsic scalability of these photonic fractal metamaterials provide ample opportunities for applications, bridging across transformation optics, sensing, and light harvesting.