Flexible electronics is the research field with interdisciplinary crossing and integration. It shows the promising advantages of novel device configurations, low-cost and low-power consumption due to their flexible and soft characteristics. Atomic layered two-dimensional (2D) materials especially transition metal dichalcogenides, have triggered great interest in ultra-thin 2D flexible electronic devices and optoelectronic devices because of their direct and tunable bandgaps, excellent electrical, optical, mechanical, and thermal properties. This review aims to provide the recent progress in 2D TMDs and their applications in flexible electronics. The fundamental electrical properties and mechanical properties of materials, flexible device configurations, and their performance in transistors, sensors, and photodetectors are thoroughly discussed. At last, some perspectives are given on the open challenges and prospects for 2D TMDs flexible electronic devices and new device opportunities.

Two-dimensional (2D) ferromagnets with out-of-plane (OOP) magnetic anisotropy are potential candidates for realizing the next-generation memory devices with ultra-low power consumption and high storage density. However, a scalable approach to synthesize 2D magnets with OOP anisotropy directly on the complimentary metal-oxide semiconductor (CMOS) compatible substrates has not yet been mainly explored, which hinders the practical application of 2D magnets. This work demonstrates a cascaded space confined chemical vapor deposition (CS-CVD) technique to synthesize 2D Fe_xGeTe₂ ferromagnets. The weight fraction of iron (Fe) in the precursor controls the phase purity of the as-grown Fe_xGeTe₂. As a result, high-quality Fe₃GeTe₂ and Fe₅GeTe₂ flakes have been grown selectively using the CS-CVD technique. Curie temperature (T_C) of the as-grown Fe_xGeTe₂ can be up to ~ 280 K, nearly room temperature. The thickness and temperature-dependent magnetic studies on the Fe₅GeTe₂ reveal a 2D Ising to 3D XY behavior. Also, Terahertz spectroscopy experiments on Fe₅GeTe₂ display the highest conductivity among other Fe_xGeTe₂ 2D magnets. The results of this work indicate a scalable pathway for the direct growth and integration of 2D ternary magnets on CMOS-based substrates to develop spintronic memory devices.

The catalysis of Au thin film could be improved by fabrication of array structures in large area. In this work, nanoimprint lithography has been developed to fabricate flexible Au micro-array (MA) electrodes with ~ 100% coverage. Advanced electron microscopy characterisations have directly visualised the atomic-scale three-dimensional (3D) nanostructures with a maximum depth of 6 atomic layers. In-situ observation unveils the crystal growth in the form of twinning. High double layer capacitance brings about large number of active sites on the Au thin film and has a logarithmic relationship with mesh grade. Electrochemistry testing shows that the Au MAs perform much better ethanol oxidation reaction than the planar sample; MAs with higher mesh grade have a greater active site utilisation ratio (ASUR), which is important to build electrochemical double layer for efficient charge transfer. Further improvement on ASUR is expected for greater electrocatalytic performance and potential application in direct ethanol fuel cell.

Layered MoTe₂ has shown great promises for optoelectronics and energy-storage applications due to its exceptional optical and electrochemical properties. To date, considerable efforts have been devoted to fabricating layered MoTe₂ with lateral orientation by means of mechanical/chemical exfoliation and chemical vapor deposition (CVD) methods. As compared to its horizontal counterparts, vertically aligned MoTe₂ with higher density of active edge sites is expected to possess unique optoelectronic and electrochemical properties, while which has not been reported yet. In this work, we report a versatile and scalable CVD growth of vertically aligned MoTe₂ with length of up to ~ 7.5 µm on Mo foil. Remarkably, the dominant phase of the vertically aligned MoTe₂ can be tuned from 2H to 1T’ by increasing the growth temperature from 630 to 780 °C. Owing to the weak interaction between the as-grown MoTe₂ and Mo foil, the as-grown MoTe₂ can be easily detached from the Mo foil. This in turn enabled economic reuse of the Mo foil for multiple growth. Moreover, the vertical growth of the MoTe₂ is proposed to be caused by the internal strain generated during tellurization of Mo foil. Furthermore, the as-grown MoTe₂ can also be directly dispersed in solvent to produce high-quality MoTe₂ nanosheets. The versatility of this growth strategy was further demonstrated by fabricating other vertically aligned transition metal chalcogenides (TMDs) such as TaTe₂ and MoSe₂. Hence, this work paves the path towards achieving unique TMDs structures to enable high-performance optoelectronic and electrochemical devices.

A topologically mediated synthesis of porous boron nitride aerogel has been experimentally and theoretically investigated for carbon dioxide (CO₂) uptake. Replacement of the carbon atoms in a precursor aerogel of graphene oxide and carbon nanotubes was achieved using an elemental substitution reaction, to obtain a boron and nitrogen framework. The newly prepared BN aerogel possessed a specific surface area of 716.56 m²/g and exhibited an unprecedented twentyfold increase in CO₂ uptake over N₂, adsorbing 100 cc/g at 273 K and 80 cc/g in ambient conditions, as verified by adsorption isotherms via the multipoint Brunauer-Emmett-Teller (BET) method. Density functional theory calculations were performed to give hints on the mechanism of such high selectivity of CO₂ over N₂ adsorption in BN aerogel, which may be due to the interaction between the intrinsic polar nature of B-N bonds and the high quadrupole moment of CO₂ over N₂.