Search

Carbon nanorods with a yield of about 90%, which are prepared using the copyrolysis of C6H6 and C5H6 under the cocatalysis of Fe and Mg at 600 degree centigrade are discussed. The synergic effect of C5H6 and C6H6 and cocatalysts Fe and Mg affected the yield of carbon nanorods.

Epitaxial growth stands as a key method for integrating semiconductors into heterostructures, offering a potent avenue to explore the electronic and optoelectronic characteristics of cutting-edge materials, such as transition metal dichalcogenide (TMD) and perovskites. Nevertheless, the layer-by-layer growth atop TMD materials confronts a substantial energy barrier, impeding the adsorption and nucleation of perovskite atoms on the 2D surface. Here, we epitaxially grown an inorganic lead-free perovskite on TMD and formed van der Waals (vdW) heterojunctions. Our work employs a monomolecular membrane-assisted growth strategy that reduces the contact angle and simultaneously diminishing the energy barrier for Cs 3 Sb 2 Br 9 surface nucleation. By controlling the nucleation temperature, we achieved a reduction in the thickness of the Cs 3 Sb 2 Br 9 epitaxial layer from 30 to approximately 4 nm. In the realm of inorganic lead-free perovskite and TMD heterojunctions, we observed long-lived interlayer exciton of 9.9 ns, approximately 36 times longer than the intralayer exciton lifetime, which benefited from the excellent interlayer coupling brought by direct epitaxial growth. Our research introduces a monomolecular membrane-assisted growth strategy that expands the diversity of materials attainable through vdW epitaxial growth, potentially contributing to future applications in optoelectronics involving heterojunctions.

Electron beam lithography uses an accelerated electron beam to fabricate patterning on an electron-beam-sensitive resist but requires complex dry etching or lift-off processes to transfer the pattern to the substrate or film on the substrate. In this study, etching-free electron beam lithography is developed to directly write a pattern of various materials in all-water processes, achieving the desired semiconductor nanopatterns on a silicon wafer. Introduced sugars are copolymerized with metal ions-coordinated polyethylenimine under the action of electron beams. The all-water process and thermal treatment result in nanomaterials with satisfactory electronic properties, indicating that diverse on-chip semiconductors (e.g., metal oxides, sulfides, and nitrides) can be directly printed on-chip by an aqueous solution system. As a demonstration, zinc oxide patterns can be achieved with a line width of 18 nm and a mobility of 3.94 cm 2 V -1 s -1 . This etching-free electron beam lithography strategy provides an efficient alternative for micro/nanofabrication and chip manufacturing.

Molybdenum ditelluride (MoTe 2 ) has attracted ever-growing attention in recent years due to its novel characteristics in spintronics and phase-engineering, and an efficient and convenient method to achieve large-area high-quality film is an essential step toward electronic applications. However, the growth of large-area monolayer MoTe 2 is challenging. Here, for the first time, we achieve the growth of a centimeter-sized monoclinic MoTe 2 monolayer and manifest the mechanism of immobilized precursor particle driven growth. Microscopic characterizations reveal an obvious trend of immobilized precursor particles being consumed by the monolayer and continuing to provide a source for the growth of the monolayer. Time-of-flight secondary ion mass spectrometry verifies the attachment of hydroxide ions on the surface of the MoTe 2 monolayer, thereby realizing the inhibition of crystal growth along the [001] zone axis and the continuous growth of the MoTe 2 monolayer. The first-principles DFT calculations prove the mechanism of immobilized precursor particles and the absorption of hydroxide ions on the MoTe 2 monolayer. The as-grown MoTe 2 monolayer exhibits a surface roughness of 0.19 nm and average conductivity of 1.5 × 10 -5 S/m, which prove the smoothness and uniformity of the MoTe 2 monolayer. Temperature-dependent electrical measurements together with the transfer characteristic curves further demonstrate the typical semimetallic properties of monoclinic MoTe 2 . Our research elaborates the microscopic process of immobilized precursor particles to grow large-area MoTe 2 monolayer and provides a new thinking about the growth of many other two-dimensional materials.

The construction of aqueous Zn-ion hybrid capacitors (ZICs) reconciling high energy/power density is practically meaningful yet remains a grand challenge. Herein, a high-capacitance and long-life ZIC is demonstrated by 3D printing of a Ti 3 C 2 MXene cathode, affording optimized carrier transport, facile electrolyte penetration, and ample porosity. The 3D-printable additive-free MXene ink with desirable rheological property is derived by a fast gelation process employing a trace amount of divalent cations, which overcomes the tedious post-treatments required for additive removal. The thus-fabricated 3D-printed (3DP) MXene cathode results in a dual-ion storage mechanism to synergize pseudocapacitive behavior of H + and electrical double-layer capacitive behavior of Zn 2+ , which is systematically probed by a wide suite of in situ / ex situ electroanalytic characterizations. The 3DP MXene cathode accordingly exhibits a favorable areal capacitance of 1006.4 mF cm -2 at 0.38 mA cm -2 and excellent rate capability (184.4 F g -1 at 10 A g -1 ), outperforming the state-of-the-art ZICs. More impressively, ZIC full cells comprising a 3DP MXene cathode and a 3DP Zn anode deliver a competitive energy/power density of 0.10 mWh cm -2 /5.90 mW cm -2 as well as an ultralong lifespan (86.5% capacity retention over 6000 cycles at 10 mA cm -2 ).

Controllable nucleation sites play a key role in the selective growth of heterostructures. Here, we are the first to report a one-pot strategy to realize the confined and selective growth of large MoS 2 /WS 2 lateral and vertical heterostructures. A hydroxide-assisted process is introduced to control the nucleation sites, thereby realizing the optional formation of lateral and vertical heterostructures. Time-of-flight secondary ion mass spectrometry verifies the critical role of hydroxide groups toward the controllable growth of these heterostructures. The size of the as-grown MoS 2 /WS 2 lateral heterostructures can be as large as 1 mm, which is the largest lateral size reported thus far. The obtained MoS 2 /WS 2 heterostructures have a high carrier mobility of ∼58 cm 2 V -1 s -1 , and the maximum on/off current ratio is >10 8 . This approach provides not only a pathway for the selective growth of large MoS 2 /WS 2 lateral and vertical heterostructures but also a fundamental understanding of surface chemistry for controlling the selective growth of transition-metal dichalcogenide heterostructures.

3D printing technology has stimulated a burgeoning interest to fabricate customized architectures in a facile and scalable manner targeting wide ranged energy storage applications. Nevertheless, 3D-printed hybrid capacitor devices synergizing favorable energy/power density have not yet been explored thus far. Herein, we demonstrate a 3D-printed sodium-ion hybrid capacitor (SIC) based on nitrogen-doped MXene ( N -Ti 3 C 2 T x ) anode and activated carbon cathode. N-Ti 3 C 2 T x affording a well-defined porous structure and uniform nitrogen doping can be obtained via a sacrificial template method. Thus-formulated ink can be directly printed to form electrode architecture without the request of a conventional current collector. The 3D-printed SICs, with a large areal mass loading up to 15.2 mg cm -2 , can harvest an areal energy/power density of 1.18 mWh cm -2 /40.15 mW cm -2 , outperforming the state-of-the-art 3D-printed energy storage devices. Furthermore, our SIC also achieves a gravimetric energy/power density of 101.6 Wh kg -1 /3269 W kg -1 . This work demonstrates that the 3D printing technology is versatile enough to construct emerging energy storage systems reconciling high energy and power density.

Based on first-principles density functional theory calculations, we investigated a modified routine using hydroxyl adsorption that recently demonstrated the controlled growth of MoS 2 monolayers. The new growth approach impedes the deposition of a second MoS 2 layer; however, the hydroxyl adsorption and its effects have been mostly unexplored. Through this study, we first explored the adsorption behaviors of the hydroxyl radical (OH) on monolayer MoS 2 and briefly discussed its effects on the stability and electronic structure. Monolayer MoS 2 repels charged OH - , whereas the adsorption of the neutral OH radical is energetically favorable; the corresponding adsorption energies are 0.09 eV and -1.35 eV, respectively. The diffusion barrier of the OH radical on MoS 2 is 0.52 eV, indicating that the molecule can quickly diffuse. Next, the study demonstrated that for multiple OH adsorptions, a concerted reaction including OH dissociation and H 2 O formation is more energetically favorable than the adsorption of two OH molecules by 2.50 eV, which in turn results in a mixed adsorption configuration of O and OH. In addition, we revealed that the OH adsorption creates a mid-gap state and facilitates the reconstruction of the MoS 2 edge., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

p-Type compounds Cu 2 BaSnS 4 (CBTS) are extremely attractive materials for photocathode applications because of their suitable conduction and valence bands, earth-abundant sources, and environmental friendly nature. Herein, an inexpensive and reproducible aqueous solution approach has been developed to synthesize CBTS films with single-crystalline grains as large as micron scale. Because of the large crystalline grains, the as-grown CBTS films show excellent carrier mobility (1.29 cm 2 /V·s). Greater than 4 mA·cm -2 photocurrent density has been obtained in a neutral solution for bare Mo/CBTS film photocathodes under 100 mW·cm -2 illumination at 0 V versus reversible hydrogen electrode.

Due to remarkable electronic property, optical transparency, and mechanical flexibility, monolayer molybdenum disulfide (MoS 2 ) has been demonstrated to be promising for electronic and optoelectronic devices. To date, the growth of high-quality and large-scale monolayer MoS 2 has been one of the main challenges for practical applications. Here we present a MoS 2 -OH bilayer-mediated method that can fabricate inch-sized monolayer MoS 2 on arbitrary substrates. This approach relies on a layer of hydroxide groups (-OH) that are preferentially attached to the (001) surface of MoS 2 to form a MoS 2 -OH bilayer structure for growth of large-area monolayer MoS 2 during the growth process. Specifically, the hydroxide layer impedes vertical growth of MoS 2 layers along the [001] zone axis, promoting the monolayer growth of MoS 2 , constrains growth of the MoS 2 monolayer only in the lateral direction into larger area, and effectively reduces sulfur vacancies and defects according to density functional theory calculations. Finally, the hydroxide groups advantageously prevent the MoS 2 from interface oxidation in air, rendering high-quality MoS 2 monolayers with carrier mobility up to ∼30 cm 2 V -1 s -1 . Using this approach, inch-sized uniform monolayer MoS 2 has been fabricated on the sapphire and mica and high-quality monolayer MoS 2 of single-crystalline domains exceeding 200 μm has been grown on various substrates including amorphous SiO 2 and quartz and crystalline Si, SiC, Si 3 N 4 , and graphene This method provides a new opportunity for the monolayer growth of other two-dimensional transition metal dichalcogenides such as WS 2 and MoSe 2 .

4,7-Diphenyl-1,10-phenanthroline (Bphen) is an efficient electron transport and hole blocking material in organic photoelectric devices. Here, we report cesium carbonate (Cs 2 CO 3 ) doped Bphen as cathode interfacial layer in CH 3 NH 3 PbI 3-x Cl x based planar perovskite solar cells (PSCs). Investigation finds that introducing Cs 2 CO 3 suppresses the crystallization of Bphen and benefits a smooth interface contact between the perovskite and electrode, resulting in the decrease in carrier recombination and the perovskite degradation. In addition, the matching energy level of Bphen film in the PSCs effectively blocks the holes diffusion to cathode. The resultant power conversion efficiency (PCE) achieves as high as 17.03% in comparison with 12.67% of reference device without doping. Besides, experiments also demonstrate the stability of PSCs have large improvement because the suppressed crystallization of Bphen by doping Cs 2 CO 3 as a superior barrier layer blocks the Ag atom and surrounding moisture access to the vulnerable perovskite layer.

The underlayer plays an important role for organic-inorganic hybrid perovskite formation and charge transport in perovskite solar cells (PSCs). Here, we employ a classical organic small molecule, 5,6,11,12-tetraphenyltetracene (rubrene), as the underlayer of perovskite films to achieve 15.83% of power conversion efficiency with remarkable moisture tolerance exposed to the atmosphere. Experiments demonstrate rubrene hydrophobic underlayer not only drives the crystalline grain growth of high quality perovskite, but also contributes to the moisture tolerance of PSCs. Moreover, the matching energy level of the desirable underlayer is conductive to extracting holes and blocking electrons at anode in PSCs. This introduction of organic small molecule into PSCs provides alternative materials for interface optimization, as well as platform for flexible and wearable solar cells.

Bandgap engineering of kesterite Cu 2 Zn(Sn, Ge)(S, Se) 4 with well-controlled stoichiometric composition plays a critical role in sustainable inorganic photovoltaics. Herein, a cost-effective and reproducible aqueous solution-based polymer-assisted deposition approach is developed to grow p-type Cu 2 Zn(Sn, Ge)(S, Se) 4 thin films with tunable bandgap. The bandgap of Cu 2 Zn(Sn, Ge)(S, Se) 4 thin films can be tuned within the range 1.05-1.95 eV using the aqueous polymer-assisted deposition by accurately controlling the elemental compositions. One of the as-grown Cu 2 Zn(Sn, Ge)(S, Se) 4 thin films exhibits a hall coefficient of +137 cm 3 /C. The resistivity, concentration and carrier mobility of the Cu 2 ZnSn(S, Se) 4 thin film are 3.17 ohm·cm, 4.5 × 10 16 cm -3 , and 43 cm 2 /(V·S) at room temperature, respectively. Moreover, the Cu 2 ZnSn(S, Se) 4 thin film when used as an active layer in a solar cell leads to a power conversion efficiency of 3.55%. The facile growth of Cu 2 Zn(Sn, Ge)(S, Se) 4 thin films in an aqueous system, instead of organic solvents, provides great promise as an environmental-friendly platform to fabricate a variety of single/multi metal chalcogenides for the thin film industry and solution-processed photovoltaic devices.

In this letter, we report a facile self-foaming strategy to synthesize Ni 3 C nanoparticles embedded in a porous carbon network (Ni 3 C@PCN) by rationally incorporating a nickel salt precursor into the carbon source. As a novel hydrogen evolution reaction (HER) catalyst, the Ni 3 C@PCN shows superior catalytic activity with an onset potential of -65 mV, an overpotential of 262 mV to achieve 50 mA cm -2 current density, a Tafel slope of 63.4 mV/dec, and durability over 12 h in acidic media. The excellent performance of the novel 3D composite material along with its low-cost merits is suggestive of great potential for scalable electrocatalytic H 2 production.

Neutral green-emitting four-coordinate Cu(I) complexes with general formula POPCu(NN), where POP = bis[2-(diphenylphosphino)phenyl]ether and NN = substituted 2-pyridine-1,2,4-triazole ligands, were synthesized. The crystal structures of (POPCuMeCN)(+)(PF6)(-) (1), POPCuPhPtp (2a, PhPtp = 2-(5-phenyl-2H-[1,2,4]triazol-3-yl)-pyridine), and POPCu(3,5-2FPhPtp) (2d, 3,5-2FPhPtp = 2-(5-(3,5-difluorophenyl)-2H-1,2,4-triazol-3-yl)pyridine) were determined by single-crystal X-ray diffraction analysis. The electronic and photophysical properties of the complexes were examined by UV-vis, steady-state, and time-resolved spectroscopy. At room temperature, weak emission was observed in solution, while in the solid state, all complexes exhibit intense green emission with quantum yield up to 0.54. The electronic and photophysical properties were further supported by calculation performed at the (time-dependent) density functional theory level. One of the complexes was also tested as dopant in electroluminescent devices.

Sub-8 nm titanium oxynitride (TiON) nanoparticles were uniformly formed on the surface of carbon nanotubes (CNTs) by annealing amorphous TiO2 (a-TiO2) conformally coated CNTs (CNTs/a-TiO2) at 600 °C in ammonia gas. The novel CNTs/TiON nanocomposite was systematically characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy imaging (HRTEM), scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDX), and X-ray photoelectron spectroscopy (XPS). The results show that Ti, O, and N are homogeneously distributed in TiON nanoparticles. The specific capacitance of CNTs/TiON exhibits 187 F g(-1) at a current density of 0.5 A g(-1), which is much higher than that of CNTs (33.4 F g(-1)) and CNTs/TiO2 (83.4 F g(-1)) obtained by annealing CNTs/a-TiO2 at 450 °C in nitrogen gas. CNTs/TiON also exhibits enhanced cycle durability, which enables it to be considered as a promising candidate for supercapacitors.

In this study, we report the growth of molybdenum oxide (MoOx) film by polymer-assisted deposition (PAD), an environmentally friendly strategy in an aqueous system. The MoOx film has good crystal quality and is dense and smooth. The transparency of the film is >95% in the wavelength range of 300-900 nm. The device based on P3HT:PCBM absorber material was fabricated. The solar cell with PAD-MoOx as an anode interfacial layer exhibits great performance, even better than that of a solar cell with, Pedot: PSS or evaporated MoOx as an anode interfacial layer. More importantly, the solar cells based on the growth of MoOx have a longer term stability than that of solar cells based on, Pedot: PSS. These results demonstrate the aqueous PAD technology provides an alternative strategy not only for the thin films' growth of applied materials but also for the solution processing for the low-cost fabrication of future materials to be applied in the field of solar cells.

Two-dimensional V2O5 and manganese-doped V2O5 sheet network were synthesized by a one-step polymer-assisted chemical solution method and characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal-gravimetric analysis, and galvanostatic discharge-charge analysis. The V2O5 particles were covered with thin carbon layers, which remained after decomposition of the polymer, forming a network-like sheet structure. This V2O5 network exhibits a high capacity of about 300 and 600 mA·h/g at a current density of 100 mA/g when it was used as a cathode and anode, respectively. After doping with 5% molar ratio of manganese, the capacity of the cathode increases from 99 to 165 mA·h/g at a current density of 1 A/g (∼3 C). This unique network structure provides an interconnected transportation pathway for lithium ions. Improvement of electrochemical performance after doping manganese could be attributed to the enhancement of electronic conductivity.

Carbide films exhibit many unique properties. The development of a versatile and simple technique for the deposition of carbide films will enable a wide range of technological applications. Here we report a cost-effective chemical solution deposition or polymer-assisted deposition method for growing epitaxial carbide (including TiC, VC, and TaC) films. These epitaxial carbide films exhibit structural and physical properties similar to the films grown by vapor deposition methods.

Directly spinning carbon nanotube (CNT) fibers from vertically aligned CNT arrays is a promising way for the application of CNTs in the field of high-performance materials. However, most of the reported CNT arrays are not spinnable. In this work, by controlling catalyst pretreatment conditions, we demonstrate that the degree of spinnability of CNTs is closely related to the morphology of CNT arrays. Shortest catalyst pretreatment time led to CNT arrays with the best spinnability, while prolonged pretreatment resulted in coarsening of catalyst particles and nonspinnable CNTs. By controlling the coalescence of catalyst particles, we further demonstrate the growth of undulating CNT arrays with uniform and tunable waviness. The CNT arrays can be tuned from well-aligned, spinnable forests to uniformly wavy, foam-like films. To the best of our knowledge, this is the first systematical study on the correlation between catalyst pretreatment, CNT morphology, and CNT spinnability.

This paper reports well-aligned arrays of CuO nanoplatelets synthesized through a hydrothermal route without template's assistance. The surface of well-aligned arrays of CuO nanoplatelets looks like a wall. These nanoplatelets, possessing four clear edges, are 50-80 nm in thickness, 150-250 nm in width, and 0.8-1.5 microm in length. Electron microscopic detection shows that the nanoplatelet grows along the [010] direction. The Ostwald ripening mechanism has been used to describe the growth of CuO nanoplatelets. In addition, the optic and electrochemical properties of as-obtained products have been discussed. And the arrays of CuO nanoplatelets exhibit the blue shift in UV-visible spectra, a slow capacity fading rate, and a relatively high Coulombic efficiency in charge-discharge process.

Fe3O4 novel fractal nanocrystals have been synthesized by a surfactant-assisted solvothermal process for the first time. X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Mössbauer spectroscopy (MS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been used to investigate the novel fractal nanocrystals. The lengths of the fractals are about 2-3 microm, and the trunks and branches of Fe3O4 fractals have almost the same diameters of ca. 30-50 nm. The roles of surfactant PEG-20000 and N2H4 have been discussed in detail. One key fact has been found that the ferrocene concentration has a vital effect on the morphologies of the products. The side-branching process and the oscillation of the concentration have been proposed to illustrate the formation mechanisms of the fractal nanocrystals. In addition, magnetic properties of Fe3O4 fractal nanocrystals have also been detected by a vibrating sample magnetometer, showing relatively high saturation magnetization (Ms) of ca. 78.75 emu/g.

Flowerlike cupped-end ZnO microrod bundles have been hydrothermally synthesized from precursor ZnCl2(N2H4)2 in sheet shape at 140 degrees C for 12 h; under the same conditions using the same precursor in rod shape, uniform ZnO nanorods were obtained. XRD pattern indicated the sample is ZnO with hexagonal cell contants a = 3.251 A and c = 5.206 A. FE-SEM and TEM show the formation process of the ZnO sample. HRTEM revealed that the flowerlike cupped-end ZnO microrod bundles grow along the [101] axis. The UV emission peak at approximately 396 nm and the blue band emission peak at approximately 469 nm were observed by PL spectra. A possible formation mechanism was proposed.