Versatile and low‐cost manufacturing processes/materials are essential for the development of paper electronics. Here, a direct‐write laser patterning process is developed to make conductive ...molybdenum carbide–graphene (MCG) composites directly on paper substrates. The hierarchically porous MCG structures are converted from fibrous paper soaked with the gelatin‐mediated inks containing molybdenum ions. The resulting Mo3C2 and graphene composites are mechanically stable and electrochemically active for various potential applications, such as electrochemical ion detectors and gas sensors, energy harvesters, and supercapacitors. Experimentally, the electrical conductivity of the composite is resilient to mechanical deformation with less than 5% degradation after 750 cycles of 180° repeated folding tests. As such, the direct laser conversion of MCGs on papers can be applicable for paper‐based electronics, including the 3D origami folding structures.
A direct‐write laser‐patterning process to induce molybdenum carbide–graphene composites on paper substrates is developed by using inks of molybdenum ions and gelatin media with potential applications in 3D foldable energy generators, electrochemical sensors, and supercapacitors.
Low‐dimensional (0/1/2 dimension) transition metal carbides (TMCs) possess intriguing electrical, mechanical, and electrochemical properties, and they serve as convenient supports for transition ...metal catalysts. Large‐area single‐crystalline 2D TMC sheets are generally prepared by exfoliating MXene sheets from MAX phases. Here, a versatile bottom‐up method is reported for preparing ultrathin TMC sheets (≈10 nm in thickness and >100 μm in lateral size) with metal nanoparticle decoration. A gelatin hydrogel is employed as a scaffold to coordinate metal ions (Mo5+, W6+, Co2+), resulting in ultrathin‐film morphologies of diverse TMC sheets. Carbonization of the scaffold at 600 °C presents a facile route to the corresponding MoCx, WCx, CoCx, and to metal‐rich hybrids (Mo2−xWxC and W/Mo2C–Co). Among these materials, the Mo2C–Co hybrid provides excellent hydrogen evolution reaction (HER) efficiency (Tafel slope of 39 mV dec−1 and 48 mVj = 10 mA cm‐2 in overpotential in 0.5 m H2SO4). Such performance makes Mo2C–Co a viable noble‐metal‐free catalyst for the HER, and is competitive with the standard platinum on carbon support. This template‐assisted, self‐assembling, scalable, and low‐cost manufacturing process presents a new tactic to construct low‐dimensional TMCs with applications in various clean‐energy‐related fields.
Transition metal ions (Mo, Co, W) self‐organize within a gelatin template into a lamellar‐nanostructured soft material (metallohydrogel). Subsequent carbonization at moderate temperatures in a reducing atmosphere (600 °C) yields ultrathin (≈10 nm) and large (≈100 μm) 2D transition metal carbide sheets with high conductivity and rich active sites, which are ideal for the hydrogen evolution reaction (HER).
An ultraviolet detector is demonstrated through a whole‐wafer, thin diamond film transfer process to realize the heterojunction between graphene and microcrystalline diamond (MCD). Conventional ...direct transfer processes fail to deposit graphene onto the top surface of the MCD film. However, it is found that the 2 µm thick MCD diamond film can be easily peeled off from the growth silicon substrate to expose its smooth backside for the graphene transfer process for high‐quality graphene/MCD heterojunctions. A vertical graphene/MCD/metal structure is constructed as the photodiode device using graphene as the transparent top electrode for solar‐blind ultraviolet sensing with high responsivity and gain factor. As such, this material system and device architecture could serve as the platform for next‐generation optoelectronic systems.
A solar‐blind ultraviolet (UV) detector is accomplished through a whole‐wafer, thin diamond film transfer process. By utilizing the smooth backside of the microcrystalline diamond (MCD) film, the UV detector based on high‐quality graphene/MCD heterojunctions is realized for the first time. Based on the graphene/MCD/metal structure, a photodiode device is achieved for solar‐blind ultraviolet sensing with high responsivity and gain factor.
While electrochemical supercapacitors often show high power density and long operation lifetimes, they are plagued by limited energy density. Pseudocapacitive materials, in contrast, operate by fast ...surface redox reactions and are shown to enhance energy storage of supercapacitors. Furthermore, several reported systems exhibit high capacitance but restricted electrochemical voltage windows, usually no more than 1 V in aqueous electrolytes. Here, it is demonstrated that vertically aligned carbon nanotubes (VACNTs) with uniformly coated, pseudocapacitive titanium disulfide (TiS2) composite electrodes can extend the stable working range to over 3 V to achieve a high capacitance of 195 F g−1 in an Li‐rich electrolyte. A symmetric cell demonstrates an energy density of 60.9 Wh kg−1—the highest among symmetric pseudocapacitors using metal oxides, conducting polymers, 2D transition metal carbides (MXene), and other transition metal dichalcogenides. Nanostructures prepared by an atomic layer deposition/sulfurization process facilitate ion transportation and surface reactions to result in a high power density of 1250 W kg−1 with stable operation over 10 000 cycles. A flexible solid‐state supercapacitor prepared by transferring the TiS2–VACNT composite film onto Kapton tape is demonstrated to power a 2.2 V light emitting diode (LED) for 1 min.
TiS2 is coated coaxially onto vertically aligned carbon nanotubes (VACNTs) via an atomic layer deposition sulfurization process, providing an exceptionally high capacitance of 195 F g‐1 and working voltage window up to 3 V in a Li+ ion rich (21 m) electrolyte. The energy density of a supercapacitor based on TiS2–VACNT electrodes is enhanced to 60.9 Wh kg‐1, which outperforms many other pseudocapacitors.
Ultrathin transition metal carbides with high capacity, high surface area, and high conductivity are a promising family of materials for applications from energy storage to catalysis. However, ...large-scale, cost-effective, and precursor-free methods to prepare ultrathin carbides are lacking. Here, we demonstrate a direct pattern method to manufacture ultrathin carbides (MoC
, WC
, and CoC
) on versatile substrates using a CO
laser. The laser-sculptured polycrystalline carbides (macroporous, ~10-20 nm wall thickness, ~10 nm crystallinity) show high energy storage capability, hierarchical porous structure, and higher thermal resilience than MXenes and other laser-ablated carbon materials. A flexible supercapacitor made of MoC
demonstrates a wide temperature range (-50 to 300 °C). Furthermore, the sculptured microstructures endow the carbide network with enhanced visible light absorption, providing high solar energy harvesting efficiency (~72 %) for steam generation. The laser-based, scalable, resilient, and low-cost manufacturing process presents an approach for construction of carbides and their subsequent applications.
Wafer-scale, conformal, two-dimensional (2D) TiO2-Ga2O3n-p heterostructures with a thickness of less than 10 nm were fabricated on the Si/SiO2 substrates by the atomic layer deposition (ALD) ...technique for the first time with subsequent post-deposition annealing at a temperature of 250 °C. The best deposition parameters were established. The structure and morphology of 2D TiO2-Ga2O3n-p heterostructures were characterized by the scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), etc. 2D TiO2-Ga2O3n-p heterostructures demonstrated efficient photocatalytic activity towards methyl orange (MO) degradation at the UV light (λ = 254 nm) irradiation. The improvement of TiO2-Ga2O3n-p heterostructure capabilities is due to the development of the defects on Ga2O3-TiO2 interface, which were able to trap electrons faster.Graphical Abstract
Please be advised that the name of one of the coauthors in the original article 1 has been incorrectly spelled:
‘Ranish M. Ramachandran’
should be
‘Ranjith K. Ramachandran’
.
The strong stray light has huge interference on the detection of weak and small optical signals, and is difficult to suppress. In this paper, a miniaturized baffle with angled vanes was proposed and ...a rapid optimization model of strong light elimination was built, which has better suppression of the stray lights than the conventional vanes and can optimize the positions of the vanes efficiently and accurately. Furthermore, the light energy distribution model was built based on the light projection at a specific angle, and the light propagation models of the vanes and sidewalls were built based on the Lambert scattering, both of which act as the bias of a calculation method of stray light. Moreover, the Monte-Carlo method was employed to realize the Point Source Transmittance (PST) simulation, and the simulation result indicated that it was consistent with the calculation result based on our models, and the PST could be improved by 2-3 times at the small incident angles for the baffle designed by the new method. Meanwhile, the simulation result was verified by laboratory tests, and the new model with derived analytical expressions which can reduce the simulation time significantly.
The star tracker is widely used in attitude control systems of spacecraft for attitude measurement. The attitude update rate of a star tracker is important to guarantee the attitude control ...performance. In this paper, we propose a novel approach to improve the attitude update rate of a star tracker. The electronic Rolling Shutter (RS) imaging mode of the complementary metal-oxide semiconductor (CMOS) image sensor in the star tracker is applied to acquire star images in which the star spots are exposed with row-to-row time offsets, thereby reflecting the rotation of star tracker at different times. The attitude estimation method with a single star spot is developed to realize the multiple attitude updates by a star image, so as to reach a high update rate. The simulation and experiment are performed to verify the proposed approaches. The test results demonstrate that the proposed approach is effective and the attitude update rate of a star tracker is increased significantly.
Submarine communication and geologic examination in deep earth are challenging because high-frequency electromagnetic (EM) waves with short wavelength can be blocked by soil and seawater, as a ...result, the low-frequency (LF) waves are preferred in these applications. However, the conventional LF transmitter facility requires size on the scale of the wavelength (here, >1 km), making portable transmitters extremely challenging. To greatly decrease the size of the conventional LF communication system, this article introduces a novel LF transmitter based on electret, which applies mechanical motion to accelerate the charges on the polymer electret and realize the high-efficiency generation of EM fields. Moreover, a magnetic field analytical model is established to analyze the influence of structure parameters, shapes, rotation frequency, and stacking mode on the EM signals' generation and propagation, in terms of not only distance but also orientation. Finally, an electret-based mechanically actuated transmitter prototype is built to verify the correctness and feasibility of the design.
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