Simple Solution Method Research Articles

Uniform lithium deposition enabled by a carbon nanotubes framework modified with nanosized ZIF-8 particles for dendrite-free lithium metal anode

Lithium (Li) metal is considered as an exciting anode candidate for next-generation high-performance Li metal batteries because of its high theoretical capacity and lowest redox potential. Unfortunately, unavoidable challenges consisting of dendritic behavior and volume change obstruct its widely commercial application. Here, a three-dimensional (3D) oxidized carbon nanotubes framework modified with lithiophilic nano-ZIF-8 particles (CNTs@ZIF-8) has been fabricated by a simple solution method as the collector for uniform Li deposition. The polar groups from oxidized CNTs and ZIF-8 nanoparticles provide adhesion sites for Li nucleation. Meanwhile, the nano-ZIF-8 particles with large specific surface area enhance electrolyte absorption, attracting electrolyte to the CNTs surface. The composite structure with nanoscale surface modification can guide homogeneous Li plating and restrain Li dendrites growth. As a consequence, the symmetrical cell of CNTs@ZIF-8/Cu–Li reveals a stable cycle time (over 1500 h) with a hysteresis voltage (9 mV) at 1 mA cm−2. The full cell assembled by LiFePO4 (LFP) cathode and CNTs@ZIF-8/Cu–Li anode achieves outstanding rate and cycle performance which is superior to the CNTs/Cu–Li‖LFP, demonstrating that the CNTs@ZIF-8 is prospective for practical applications.

Self-driven near infrared photoelectric detector based on C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub>/Au Schottky junction

Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>, as one of new two-dimensional materials MXene, has abundant surface functional groups (—OH, —F, and —O, etc.) and can exhibit semiconductor properties through further surface functionalization. In addition, it has excellent absorption capabilities for both infrared and visible light. Currently, there is limited research on applying the semiconductor properties of Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> to infrared photodetectors. In this study, a self-driven near-infrared photodetector based on a C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub>/Au Schottky junction is developed. The modified C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub> two-dimensional semiconductor is prepared by a simple solution method, in which the phosphonic acid group reacts with the hydroxyl group on the Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> surface. The C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub>/Au photodetector is constructed by using a drop-coating method at room temperature. The observation of an S-shaped curve in the <i>I</i>-<i>V</i> characteristics indicates the formation of a Schottky junction between C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub> nanosheets and the Au electrode. The device exhibits good detection performance in the near-infrared band (808–1342 nm), with a maximum responsivity of 0.28 A/W, a detectivity of 4.3×10<sup>7</sup> Jones and an external quantum efficiency (EQE) of 32.75% under 1064 nm infrared light illumination. The <i>I</i><sub>on</sub>/<i>I</i><sub>off</sub> ratio is 10.4, which is about 7.3 times higher than that under 1342 nm light. The response time and the recovery time of the device are 0.9 s and 0.5 s, respectively. After 10 cycles of <i>I</i>-<i>t</i>, the photocurrent does not show any significant decay, indicating excellent repeatability and cycle stability of the device. Owing to the built-in electric field formed by the Schottky junction, photo-generated electrons and holes can quickly separate and produce photocurrent in the external circuit without the need for external voltage driving. In addition, the C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub> film obtained by drop-casting on Au is composed of several layers of nanosheets that are randomly stacked, which can effectively relax the plasma momentum limitation, promote the generation of hot electrons, and contribute to the photocurrent. As the C<sub>14</sub>H<sub>31</sub>O<sub>3</sub>P-Ti<sub>3</sub>C<sub>2</sub>/Au Schottky junction photodetector possesses self-driven characteristics and simple fabrication process, it exhibits great potential applications in detecting weak light signals, such as in the fields of astronomy and biomedical science. The successful fabrication of this photodetector provides a new approach for designing and developing MXene-based near-infrared detectors, thus promoting further advancements in this field.

Influence of Sn doping on the optoelectronic properties of ZnO nanoparticles.

Zinc Oxide (ZnO) nanoparticles (NPs) obtained a lot of attention from researchers and industries because of their superior properties as an optoelectronic material. Doping, especially tin (Sn), can further fine-tune their optoelectronic properties. In this manuscript, we have reported the optoelectronic properties of Sn-doped ZnO NPs, which were synthesized by a simple chemical solution method. A wide range of dopant (Sn) concentrations were used in the ratios of 0, 1, 3, 5, 7, and 10 weight percent. The effects of dopant (Sn) concentration on the structural, morphological, elemental composition, and optical properties of ZnO NPs were investigated by using an X-ray diffractometer (XRD), Field Emission Scanning Electron Microscope (FESEM), X-ray photoelectron spectrometer (XPS) and UV-Vis-NIR respectively. XRD analysis revealed the shifting of diffraction patterns towards a higher angle along with decreasing intensity. The calculated crystallite size using the XRD varied from 40.12 nm to 28.15 nm with an increasing doping percentage. Sn doping notably influences the size of ZnO NPs, along with crystal quality, strain, and dislocation density. The X-ray photoelectron spectroscopy (XPS) study showed the presence of zinc (Zn), oxygen (O), and tin (Sn) with their preferred oxidation states in the synthesized NPs. UV-Visible spectroscopy (UV-Vis) showed that the bandgap changed from 3.55 to 3.85 eV with the increasing concentration of Sn. FE-SEM revealed that the structures and surfaces were irregular and not homogeneous. The above findings for ZnO nanostructures show their potential application in optoelectronic devices.

Molecular layer-by-layer re-stacking of MoS2–In2Se3 by electrostatic means: assembly of a new layered photocatalyst

Selective assembly of monolayered MoS2 (A) and In2Se3 (B) in solution gives a controllable atomic AB-type layer stacking. A new class of photocatalysts can be tailor-made with high activity using this simple but inexpensive bottom-up solution method.

An extended Bueckner–Rice theory for arbitrary geometric perturbations of cracks

The aim of this paper is to define a new, simple and efficient method of solution of elasticity problems for 3D bodies containing cracks slightly perturbed out of their original plane or surface. This method extends that proposed by Rice (1985, 1989), from a re-formulation of Bueckner (1987)’s 3D weight function theory, for the treatment of coplanar crack perturbations. First, a general formula is derived for the variation of total energy of a cracked elastic body, resulting from some small but otherwise arbitrary geometric perturbation of the embedded crack(s). This formula, which involves integrals over both the front and the surface of the crack, is derived from an expression of deLorenzi (1982) and Destuynder et al. (1983) in the form of a volumic integral, originally limited to purely tangential crack perturbations but duly extended here to arbitrary perturbations having both tangential and normal components. It is then used to derive a general expression of the variation of displacement arising from a general perturbation of the crack(s), anywhere in the cracked body. The reasoning here basically follows the same lines as in the works of Rice (1985, 1989), but for the presence of an additional normal component of the crack perturbation. The possible use of the formalism developed to treat problems of out-of-plane, or out-of-surface perturbations of cracks is finally briefly evoked; the straightforwardness of the new method proposed is hoped to permit future applications to non-coplanar crack problems too complex to be accessible by more conventional methods.

Flow boiling heat transfer enhancement via micro-pin-fins/ZnO nanorods hierarchical surface

In this study, ZnO nanorods were synthesized on micro-pin-fins by a simple and inexpensive aqueous solution method for flow boiling heat transfer enhancement. The morphology, chemical composition and wickability of the micro/nano hierarchical surface (PF+NR) were characterized. The heat transfer performance of PF+NR was investigated under various flow velocities together with a micro-pin-finned surface (PF), a ZnO nanorod-coated surface (NR) and a smooth surface (S). The results indicated that the boiling performance is improved significantly by the hierarchical surface and demonstrated a synergism between the microstructure and the nanostructure. The maximum boiling heat transfer coefficient of PF+NR is increased by 63%, 76%, and 158% compared with PF, NR and S, respectively. The critical heat flux is also increased by 31%, 33%, and 74%, respectively. The onset of nucleate boiling temperature of PF+NR is decreased compared with that of the other surfaces. The comprehensive improvement of boiling heat transfer performance is attributed to the cooperation of structures in different scales: the nanorods provide abundant nucleation sites, and the micro-pin-fins improve the liquid replenishment capacity and suppress the lateral coalescence of large bubbles at high heat fluxes.

Heterostructures of polyaniline and Ce–ZnO nanomaterial coated flexible PET thin films for LPG gas sensing at standard environment

The n-type Ce doped ZnO (Ce–ZnO) and p-type polyaniline (PANI) heterojunction were successfully synthesized via simple chemical solution method for sensing liquefied petroleum gas (LPG) at standard environment. The morphology and structures of as-prepared Ce–ZnO & PANI nanoparticles were analyzed by numerous kinds of techniques. Ce–ZnO & PANI nanoparticles were mixed with n-methylpyrrolidone (NMP) which is coated over the gold coated PET electrode by doctor blade method and dried overnight at 60 °C to form p-n junction. The as-formed p-n junction is to be driven with the help of 1.5 V potential at ambient temperature. X-ray photoelectron spectroscopy results of Ce–ZnO nanoparticles confirmed the existence of Ce4+ and the improved amount of both chemisorbed oxygen and oxygen vacancy after the formation of Ce–ZnO heterojunction. The maximum response of 80% was realized for hollow Ce–ZnO/PANI sensor at 100 ppm. The proposed material is a novel candidate to detect the LPG even at low (30) ppm and this study reveals the possibility of developing a potentially inexpensive hollow Ce–ZnO/PANI sensor for sensing LPG efficiently.

Controllable preparation and photocatalytic performance of hollow hierarchical porous TiO2/Ag composite microspheres

Mesoporous titania-based composites have attracted much attention in the world due to their large specific surface area, high material transport efficiency, and photocatalytic efficiency. The hollow and hierarchical porous structure is rarely involved in a binary photocatalytic material. In the present work, a novel type of hollow hierarchical porous TiO2/Ag composite microsphere with tunable microstructure was successfully prepared by simple solution methods, including sol-gel method, template method and impregnation method. Hollow hierarchical porous TiO2 microspheres were prepared by a sol-gel process with P123 as a hierarchical pore structure guide agent and template method with polystyrene microspheres as a hollow hard template. Further, hollow hierarchical porous TiO2/Ag composite microspheres were obtained by modifying Ag in the hollow hierarchical porous TiO2 microspheres by the impregnation method. The different hollow hierarchical porous TiO2/Ag composite microspheres are obtained by changing the molar ratio R of Ti/Ag. The optimal addition amount of Ti and Ag in sample HHPA6 (10:0.5) is the molar ratio of 10:0.5, and the experimental value of XPS is the molar ratio of 10:0. 91. Compared with the hollow hierarchical porous TiO2 microspheres, the excitation wavelength of composite microspheres is shifted to the visible light direction by 24 nm, and their response range and their light utilization rate were improved. When the molar ratio R of Ti/Ag is 10:0.5, hollow hierarchical porous TiO2/Ag composite microspheres have a specific surface area of 177 m2/g, the pore volume of 0.37 cm3/g, and the primary and secondary pore size of 4.04 nm and 7.74 nm, respectively. It shows the highest photocatalytic activity in the ultraviolet band of 365 nm and 395 nm, and the degradation rate of methyl orange solution is 96.84% and 98.65%, respectively. Their excellent photocatalytic performance is attributed to their special structure combining hierarchical pores and hollow structures as well as the synergistic effect of Ag and TiO2.

Self-assembled growing ultrathin Ag@NiO core-shell nanowires for stable freestanding transparent conductive colorless polyimide nanomembranes

Among the alternatives to indium tin oxide, silver nanowire (Ag NW) networks have received widespread attention for their superior optoelectronic properties. However, the rapid degradation of Ag under ambient conditions essentially limits its practical application. In this paper, we innovatively propose the synthesis of ultrathin Ag@NiO core-shell nanowires by a simple and low-cost solution method to enhance the thermal, electrical and chemical stability of NWs. The Ni2+ and Ag atoms undergo a redox reaction in the presence of water, and a reasonable mechanism of NiO formation is proposed. The Ag@NiO NW networks show low sheet resistance of 12.1 Ω/sq. and high transmittance of 84.8%. The encapsulation of the NiO shell can significantly improve their resistance to heat (85 °C) and humidity (85%) for 96 h, and NaCl solution for 200 min, while their resistance remains similar to the original values. The stable free-standing transparent conductive nanomembrane (FTCNM), consisting of an Ag@NiO NW nanowire network embedded in an ultrathin colorless polyimide, is fabricated by all-solution-process, which is perfectly conformal with human skin. We also present a skin-attachable capacitive nanomembrane sensor based on the FTCNM, the sensor shows remarkable pressure-sensing capability.

Analysis and characterization of tin-doped ZnO nanostructures

In this paper, undoped and tin-doped ZnO nanostructures were grown onto non-conductive substrates by a simple solution method. Structural, morphological, optical and electrical properties of the structures were investigated with respect to tin concentration. From XRD studies, all the ZnO nanostructures were found as hexagonal wurtzite type structures growing preponderantly oriented with c-axis nor- mal to the substrate. An increase in tin content resulted in a decrease in grain size, whereas the dislocation density in- creases. SEM observations indicated that all the structures were textured throughout the substrates without any cracks or pores. The influence of incorporation of tin on surface morphology of the samples was clearly seen. Average diameter of the nanostructures decreased with increasing tin content. Absorption spectra of the structures revealed that the band gap of the films increases with increasing tin concentration. It is found that the tin-doped samples have higher average transmittance than the undoped one. The 1 % tin-doped sample exhibited ∼80 % average transparency, which was the best transparency among the doped samples. Electrical measurements showed that resistivity of the structures increased with increasing dopant concentration. This increasing was attributed due to a decrease in carrier con- centration caused by carrier traps at the grain boundaries.

Achieving Ultrahigh Efficiency Vacancy-Ordered Double Perovskite Microcrystals via Ionic Liquids.

Lead-free perovskites have gained much interest for photovoltaic and optoelectronic applications. But instability and low quantum efficiency significantly limit their prospects for future applications. Here, a general route is reported to synthesize highly stable lead-free perovskites on a large scale with remarkably enhanced quantum efficiency. Two typical vacancy-ordered double perovskites (Cs2 ZrCl6 and Cs2 SnCl6 ) and their corresponding Bi3+ or Sb3+ doped samples are synthesized in ionic liquids (ILs) solutions via a simple solution method. These prepared perovskite samples all exhibit high-quality crystalline structures and their photoluminescence quantum yields (PLQYs) all show an increase close to 200% compared to the samples prepared in the hydrochloric acid system. The PLQY of Sb-doped Cs2 ZrCl6 with excellent thermal stability can reach up to 90.2%, which is the highest value reported for this system (Cs2 ZrCl6 :Sb). Density functional theory calculations reveal that the corresponding interaction between the ILsand the samples can effectively improve the crystal quality and reduce energy loss. The potential applications of the prepared samples for high-performance white light-emitting diodes and optical anti-counterfeiting are also demonstrated. The findings provide a straightforward way to obtain ultrahigh quantum efficiency vacancy-ordered double perovskites with good thermal stability and excellent optoelectronic properties.

Ni3+-enriched nickel-based electrocatalysts for superior electrocatalytic water oxidation

A good understanding of the strategy to improve the reconstruction process and catalytic mechanism of non-noble transition metal electrocatalysts in the oxygen evolution reaction (OER) is crucial to achieving high-efficiency and energy-saving hydrogen production because it is considered the rate-determining step in water splitting. In this work, Fe-doped NiO nanosheet arrays are prepared on carbon cloth (Fe/NiO/CC) by a simple solution method and subsequent sonication. The Fe dopants facilitate energy-efficient and rapid surface reconstruction, activate more Ni3+ species, and generate more oxygen vacancies to enable fast and efficient OER. As a result, an overpotential of merely 288 mV is required for a current density of 100 mA cm−2 by the Fe/NiO/CC electrocatalyst and a small Tafel slope of 72.6 mV dec−1 is observed in the alkaline electrolyte. Based on density-functional theory calculation, the difference in the bonding and charge redistribution in NiO caused by Fe dopants modulates the electronic structure and coordination unequally, consequently increasing the number of active sites and enhancing the intrinsic catalytic activity as well. The results provide a deeper understanding of how heteroatom doping modulates the intrinsic activity of active atoms in transition metal-based electrocatalysts and reveal the role in reconstruction in electrocatalytic OER.

Successive ionic layer adsorption and reaction processed CuSCN for efficient inverted perovskite solar cells

Copper thiocyanate (CuSCN) is a promising inorganic hole transport material for perovskite solar cells (PSCs) due to its wide-bandgap, low cost, high carrier mobility and good transmittance. However, there are limited reports about CuSCN application in PSCs mainly due to its inferior solubility. Here, we prepared high-quality CuSCN films through a simple solution method named successive ionic layer adsorption and reaction (SILAR). Using SILAR method, high-quality CuSCN films could be obtained on ITO (indium tin oxide) substrate with good morphology and photoelectric properties. As a result, efficient inverted PSCs were fabricated with SILAR-prepared CuSCN and the efficiency can be increased from 11.10 % to 18.71 %.

Enhanced sunlight-absorption of Fe2O3 covered by PANI for the photodegradation of organic pollutants and antimicrobial inactivation

• Fabrication of core–shell S-scheme heterojunction Fe 2 O 3 -PANI nanocomposite via simple solution method. • Booted photodegradation of diverse organic pollutants under sunlight. • The enhanced antimicrobial characteristics against various bacterial strains. • The improved charge carrier’s kinetics via S-scheme with PANI. • A promising material against bacterial disinfection and an excellent stable photocatalyst. The current study focused on preparing S-scheme heterojunction Fe 2 O 3 -PANI nanocomposite and pristine Fe 2 O 3 using surfactant-assisted sol–gel and polymerization routes. The structural conformation was assessed through XRD diffractograms that confirmed the Fe 2 O 3 phase in both samples. FTIR data traces the metal–oxygen and carbon-related bonds. PL results showed that the recombination rate is retarded in nanocomposite. TEM images confirmed the covering of PANI over Fe 2 O 3 . EDX mapping showed that Fe, C, N, and O were present in the grown nanocomposite. XPS study revealed the binding energies of constituent atoms. The optical energy bandgap 2.8 and 2.7 eV for Fe 2 O 3 and Fe 2 O 3 -PANI was observed through UV–Vis analysis. The photocatalytic test against methyl blue (MB), eosin yellow (EY), and methyl red (MR) dyes were executed for 50 min under direct sunlight. The Fe 2 O 3 -PANI showed 99.8, 98.5, and 99.6% degradation efficiency against MB, EY, and MR dyes, respectively, which was higher than Fe 2 O 3 . The recyclability assessment confirmed the reusability upto four cycles. The antimicrobial property against E. coli, P-aeruginosa, K-pneumoniae, S. aureus, and P. vulgaris bacterial strains revealed a higher response for Fe 2 O 3 -PANI with the zone of inhibition 30, 31, 31, 30, and 30 nm, respectively. The enhanced performance of Fe 2 O 3 -PANI is being credited to S-scheme heterostructure supported with PANI, which can hinder the recombination process and support electron/hole separation. The results indicated that the as-grown nanocomposite could be a promising candidate against bacterial disinfection and an excellent stable photocatalyst.

Planar Polymer Optical Waveguide with Metal‐Organic Framework Coating for Carbon Dioxide Sensing

AbstractAn easily fabricated gas sensor based on planar polymer optical waveguides with an integrated zeolite imidazole framework‐8 (ZIF‐8) thin film is presented for carbon dioxide detection and sensing. The planar optical waveguides are made of polymethylmethacrylate and fabricated by hot embossing, which makes it flexible and cost‐efficient. Thin ZIF‐8 films are uniformly grown on the waveguides surface through a simple solution method, which is crucial for the envisioned production of metal organic framework‐based sensing devices on a large scale. Experimental results show that the produced optical elements exhibit a sensitivity of ≈2.5 μW/5 vol% toward carbon dioxide (CO2) with very rapid response time (≈6 s) and excellent reversibility of adsorption and desorption of the gas molecules. The demonstrated planar polymer sensing devices provide the potential to develop flexible on‐chip gas sensors in an inexpensive and reproducible way.

Applications of Markov chain approximation methods to optimal control problems in economics

In this paper we explore some benefits of using the finite-state Markov chain approximation (MCA) method of Kushner and Dupuis (2001) to solve continuous-time optimal control problems in economics. We first show that the implicit finite-difference scheme of Achdou et al. (2022) amounts to a limiting form of the MCA method for a certain choice of approximating chains and policy function iteration for the resulting system of equations. We then illustrate that relative to the implicit finite-difference approach, using variations of modified policy function iteration to solve income fluctuation problems both with and without discrete choices can lead to an increase in the speed of convergence of more than an order of magnitude. Finally, we provide several consistent chain constructions for stationary portfolio problems with correlated state variables, and illustrate the flexibility of the MCA approach by using it to construct and compare two simple solution methods for a general equilibrium model with financial frictions.

Structural, Optical, and Photoluminescence Studies of Ti-Doped ZnO Nanopowders by a Simple Solution Method

Structural, Optical, and Photoluminescence Studies of Ti-Doped ZnO Nanopowders by a Simple Solution Method

Newly designed ignition circuit to improve the ignition reliability of Hall thruster

This study proposes a newly designed ignition circuit that does not change the ignition starting parameters of a Hall thruster, reduces the critical ignition voltage, and improves ignition reliability. The complexity and weight of the Hall thruster power supply system are reduced by multiplexing the ignition and discharge power supplies. Under the condition that the design parameters are satisfied, that is, R3+REC2 is much larger than RCC1, the residual energy in the circuit after the cathode breakdown can be fed into the thruster discharge channel to improve the ignition energy supply. The experimental results show that when the anode voltage is 98 V, only nine of the 100 ignition tests are successful using the traditional ignition circuit, whereas the number of successes using the newly designed ignition circuit is as high as 99, which provides a simple solution method for improving the ignition reliability.

Solution-Processed Organic Photodetectors with Renewable Materials.

An organic photodetector prepared by a simple solution method based on renewable citrus pectin with an optimized concentration of aluminum nitrate (AlC05) is introduced herein. The effects of different concentrations of aluminum nitrate on the morphology and optical properties were investigated through various characterization methods. An AlC concentration of 0.5 mg/mL was found to provide the highest on/off ratio and acceptable rise and decay times. Also, the optimized device (Al/AlC0.5/ITO) exhibited good stability and repeatability at a 0.1 V bias under 440 nm visible light. Based on these results, citrus pectin materials were successfully used to fabricate an organic photodetector with a simple and cost-efficient fabrication process, while taking into account environmental commitments.

Three-dimensional hedgehog-like ZnO/SnO2 hierarchical heterostructure for high performance self-powered ultraviolet photodetector

A novel hedgehog-like ZnO/SnO2 hierarchical heterostructures composing of one-dimensional ZnO nanorods (NRs) and three-dimensional SnO2 octahedron nano-blocks (ONBs) have been successfully prepared on ITO substrate through a simple solution method. The results show that ZnO NRs are uniformly and densely distributed perpendicular to the surface of the SnO2 ONB. The as-prepared ZnO NRs/SnO2 ONB (Z/S) hierarchical heterostructure is applied to assemble ultraviolet photodetector (UVPD). Under UV light illumination, it can obviously find that the Z/S UVPD can work at zero bias voltage and exhibits a remarkable stability and repeatability. In addition, the Z/S UVPD displays excellent characteristics over that based on SnO2 ONBs, in particular a relatively high photoresponsivity, a strong photocurrent density of 0.94 mA cm−2, together with a high on/off ratio of 5362. Moreover, the possible mechanisms for growth and UV detection on the hedgehog-like Z/S hierarchical heterostructure have been discussed.