Following the graphene isolation, strong interest in two dimensional (2D) materials has been driven by their outstanding properties. Their typical intrinsic structure, including strong in-plane covalent bonding and weak out-of-plane Van der Waals interaction, makes them highly promising in diverse areas such as electronics, catalysis, and environment. Growth of 2D materials requires a synthesis approach able to control the deposition onto a support at the atomic scale. Thanks to their simplicity, versatility and ability to control thickness at the angstrom level, Atomic Layer Deposition (ALD) and its variant Atomic Layer Etching (ALET) appear as ones of the most suited techniques to synthesize 2D materials. The development of ALD technique for fabricating 2D materials in the last ten years justifies reviewing its most recent groundbreaking discoveries and progresses. Particular attention will be paid to stable 2D materials especially graphene, h-BN, Mo and W dichalcogenides and few monolayered metal oxides. Specificities and outputs of ALD for 2D material as well as emerging directions and remaining technical challenges will be highlighted. layers. This kind of materials exhibits interesting properties related to their size restriction: electronic confinement, modifying both optical and electronic properties, and high surface to volume ratio that affects the mechanical and chemical properties. 4,5 Therefore, 2D materials are highly attractive due to their potential in cutting edge domains such as micro-, and opto-electronics 4,6 as well as renewable energy, 4,7-9 catalysis, 10,11 gas sensing 12,13 and environment. 4,7,14,15 They are also exciting because of their possibility to be stacked into VdW heterostructures combining and/or tuning their chemical and physical properties. 6,[16][17][18] However, since 2D materials are atomically thin, a suitable manufacturing process capable of controlling their fabrication in terms of structure, composition, thickness, defects, purity and crystallinity without degradation of their original properties is necessary. Two approaches can be considered: the top-down and bottom-up synthetic routes. 19 Historically, top-down approach has first been developed using mechanical and chemical exfoliation techniques, 1,2,20,21 the first example being the well-known graphene exfoliation using scotch tape.Later on, etching processes have been adapted. Recently, Atomic Layer Etching (ALET), 22 the top down variant of Atomic Layer Deposition (ALD), has been introduced for fabricating 2D materials. On the other hand, bottom-up techniques have largely been developed using conventional thin film deposition. These techniques include sputtering, evaporation and Chemical Vapor Deposition (CVD). 3,23,24 However, they are mainly based on either high temperature processes, substrate restrictive deposition or low thickness control. 21,25,26 Amongst all the fabrication processes, ALD appears to be one of the most suited techniques to synthesize 2D materials, because of its simplicity, versatility and c...

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3D hierarchical pompon-like Co3O4 porous spheres were produced by a simple hydrothermal method. The 3D structure is composed of many nanowires which gathered as a ring in the centre and fanned out via a special self-assembly fashion, resulting in good lithium ion battery performance.

Developing lithium ion batteries (LIBs) with fast charging/discharging capability and high capacity is a significant issue for future technical requirements. Transition-metal oxide (TMO) materials are widely studied as the next-generation LIB anode to satisfy this requirement due to their specific capacity, nearly three times than that of conventional graphite anode, and low cost. Meanwhile, they also suffer from slow lithium diffusion and limited electrochemical and structural stability, especially at high charging/discharging rate. The structure design of TMO is an effective strategy to obtain desirable LIB performance. Herein, inspired by natural fibrous roots consisting of functional and supporting units that can enhance substances and energy exchange efficiently, fibrous-root-like Zn(x)Co(3-x)O4@Zn(1-y)Co(y)O binary TMO nanoarrays are designed and synthesized on Cu substrates through a facile one-pot, successive-deposition process for use as an integrated LIB anode. In a multilevel array ordered by orientation, ultrafine Zn(x)Co(3-x)O4 nanowire functional units and stable Zn(1-y)Co(y)O nanorod supporting units synergize, resulting in superior rate performance. At a high current density of 500 mAg(-1), they could maintain a discharge capacity as high as 804 mAh g(-1) after 100 cycles, working much higher than unary cobalt-based and zinc-based nanoarrays. This binary synergistic nanoarray system identifies an optimized electrode design strategy for advanced battery materials.

Due to their high potential in energy and environment domains, synthetic approach allowing fabrication of high quality boron nitride (BN) structures in a controlled manner is of great interest. Herein, a two-step ammonia-free atomic layer deposition approach of BN, based on polymer derived ceramics chemistry is reported for the first time. Using trichloroborazine and hexamethyldisilazane as precursors, conformal pre-ceramic polymer layer is grown at low temperature, 80 °C, and then converted into dense hexagonal BN (h-BN). The present approach allows conformal and homogeneous deposition of h-BN films on various substrates with a thickness control at the atomic scale. It proves to be successful for fabricating various tuned BN nanostructures and composites that showed to be efficient in water purification. In particular, the obtained nanostructures demonstrate high hydrophobicity and they are investigated as water filter for organic/water separation. Good separation efficiency is demonstrated that highlights the high potential of such atomic layer deposition (ALD) structures in water treatment.

ALD BN nanotube mats are successfully applied as reusable absorptive sponges and filters for oil/organic solvents.

The effect of the sensitive area of the two-port resonator configuration on the mass sensitivity of a Rayleigh surface acoustic wave (R-SAW) sensor was investigated theoretically, and verified in experiments. A theoretical model utilizing a 3-dimensional finite element method (FEM) approach was established to extract the coupling-of-modes (COM) parameters in the absence and presence of mass loading covering the electrode structures. The COM model was used to simulate the frequency response of an R-SAW resonator by a P-matrix cascading technique. Cascading the P-matrixes of unloaded areas with mass loaded areas, the sensitivity for different sensitive areas was obtained by analyzing the frequency shift. The performance of the sensitivity analysis was confirmed by the measured responses from the silicon dioxide (SiO2) deposited on different sensitive areas of R-SAW resonators. It is shown that the mass sensitivity varies strongly for different sensitive areas, and the optimal sensitive area lies towards the center of the device.

Design, fabrication and experiments of a miniature particulate matter (PM) 2.5 sensor based on the surface acoustic wave (SAW) technology were proposed. The sensor contains a virtual impactor (VI) for particle separation, a thermophoretic precipitator (TP) for PM 2.5 capture and a SAW sensor chip for PM 2.5 mass detection. The separation performance of the VI was evaluated by using the finite element method (FEM) model and the PM 2.5 deposition characteristic in the TP was obtained by analyzing the thermophoretic theory. Employing the coupling-of-modes (COM) model, a low loss and high-quality SAW resonator was designed. By virtue of the micro electro mechanical system (MEMS) technology and semiconductor technology, the SAW based PM 2.5 sensor detecting probe was fabricated. Then, combining a dual-port SAW oscillator and an air sampler, the experimental platform was set up. Exposing the PM 2.5 sensor to the polystyrene latex (PSL) particles in a chamber, the sensor performance was evaluated. The results show that by detecting the PSL particles with a certain diameter of 2 µm, the response of the SAW based PM 2.5 sensor is linear, and in accordance with the response of the light scattering based PM 2.5 monitor. The developed SAW based PM 2.5 sensor has great potential for the application of airborne particle detection.