Chemical Solution Process Research Articles

Design of 2D mesoporous Zn/Co-based metal-organic frameworks as a flexible electrode for energy storage and conversion

Electrode materials with a large internal surface area, tunable pore size, efficient transport of electrons and high ion-accessibility are highly desired in the development of advanced flexible supercapacitors. Recently, transition metal sulfides with rationally designed nanostructures have attracted considerable attention as electrode materials for supercapacitors. In this study, we report the synthesis of Zn0.76Co0.24S/NiCo2S4 nanosheets grown on carbon cloth using a two-dimensional bimetallic Zn/Co zeolitic imidazolate framework (named as Zn/Co-ZIF-L) as a precursor through a simple and cost-effective chemical solution process. The ZIF-derived Zn0.76Co0.24S/NiCo2S4 electrode nanosheets deliver an ultrahigh specific capacitance of 2674 F g−1 at 1 A g−1, a superior ratio performance and cycle stability. Furthermore, the as-fabricated Zn0.76Co0.24S/NiCo2S4//AC all-solid-state asymmetric supercapacitor (ASC) achieves a maximum energy density of 48.1 Wh kg−1 as well as a power density of 837 W kg−1, and a superior cycling performance of 91% retention after 5000 cycles. The detailed electrochemical kinetic analysis demonstrates that the total capacitance of Zn0.76Co0.24S/NiCo2S4 is derived from its capacitive-effective charge storage mechanism. This ZIF-derived strategy provides a reasonable and simple way to synthesize transition metal sulfides as potential active materials for next-generation flexible supercapacitors.

Deposition of uniform carbon film on silicon substrate by chemical solution process

AbstractUniform carbon film was grown on silicon substrate treated by low energy electron at temperature of 60° in the methanol solution. The treatment was carried out to modify the silicon surface by electron irradiation of 50 eV using electron‐beam‐excited plasma. From the results of Raman and X‐ray diffraction spectra, it was confirmed that the film is crystalline carbon containing small amounts of diamond component. The ID/IG ratio and work function of carbon film increased with increasing treatment time of the silicon substrate. The increases of ID/IG ratio and work function suggest that the carbon film had greater concentration of diamond component. On the other hand, the surface roughness and work function of the silicon substrate increased due to an increase of treatment time. The variations of physical and electronic properties are attributed to carbon deposition during the growth process.

Hybrid discrete‐continuum solvation methods

AbstractHybrid discrete‐continuum approaches for solvation have been widely applied for diverse problems in chemistry suck as pKa calculation in aqueous and nonaqueous solvents, activation free energy barriers for ionic processes in solution, and surface reactions. A special version of this approach, the cluster‐continuum quasichemical model, has also been used for establishing a single‐ion solvation free energy scale in different solvents compatible with the tetraphenylarsonium tetraphenylborate assumption. The use of discrete‐continuum solvation methods can lead to meaningful improvement with respect to pure continuum solvation models for modeling diverse chemical process in solution. In the case of pKa calculations, there are cases where the root mean squared error is as large as 7 pKa units with pure continuum solvation model and becomes around 1 pKa unit with the hybrid approach. For complex reactions in solution, errors as large as 10 kcal/mol for activation free energies with the pure continuum approach can be substantially reduced with the inclusion of explicit solvent molecules. A discussion of the theory of hybrid discrete‐continuum methods is also presented and further development is expected in the coming years.This article is categorized under:Structure and Mechanism > Reaction Mechanisms and CatalysisSoftware > Quantum ChemistryMolecular and Statistical Mechanics > Free Energy Methods

Modeling of carbon nanotube ISFETs with high‐κ gate dielectrics for biosensing applications

AbstractAn electrochemical model for two fabricated CNT‐ISFETs has been developed by considering all chemical and physical parameters of the device and then simulated in MATLAB environment. Model has been developed by studying on some aspects of carbon nanotube‐based ion sensitive field effect transistor (CNT‐ISFET) with two high‐κ dielectric materials (HfO2 and ZrO2) fabricated by chemical solution process at low temperature. DC experiments have been performed on pH of the solution to determine the dependence of surface potential, threshold voltage, and drain current. Sensitivities of the devices have also been determined experimentally and found to be 57.5 and 60 mV/pH compared with theoretical values of 56.6 and 58.6 mV/pH for HfO2 and ZrO2 CNT‐ISFETs, respectively in the pH range of 5 to 9. Time domain experiments have been performed to determine the memory effects of the devices. Experiments showed drift rate of 0.52 and 0.683 mV/h at pH 7 for HfO2 and ZrO2 as gate oxides, respectively. The hysteresis widths are found to be 5.88 and 5.26 mV in a pH loop of 7 → 9 → 7 → 5 → 7 for loop time of 60 minutes, respectively, for HfO2 and ZrO2 dielectrics. The simulated results of the developed model are compared with experimentally obtained data and found to be in good agreement.

High-Performance Dual-Gate Carbon Nanotube Ion-Sensitive Field Effect Transistor With High-$\kappa$ Top Gate and Low-$\kappa$ Bottom Gate Dielectrics

We have reported the fabrication and characterization of dual-gate (high- $\kappa $ as top gate and low- $\kappa $ as bottom gate dielectrics) carbon nanotube (CNT) ion-sensitive field effect transistor (DG-CNTISFET) for detection of pH of electrolyte. To improve the sensing performance beyond the Nernstian sensitivity limit of 59 mV/pH at room temperature (25° C), HfO2 ( $\kappa \sim 25$ ) has been used as a top gate dielectric and ZnO ( $\kappa \sim 1.5$ ) as a bottom gate dielectric. The device has been fabricated by chemical solution process (using AUTOLAB Potentiostat/Galvanostat PGSTAT128N system) and characterized in electrolyte solutions of range 5–9 pH. In this range of pH, the device has shown a good linearity and an improved sensitivity of 943 mV/pH at room temperature. The device showed the drift rate of 13.5 mV/pH at pH 7 and the hysteresis width of 15.8 mV in a pH loop of ${7\to 9\to 7\to 5\to 7.}$ These suppressed non-ideal effects of the device along with the high sensitivity are suitable for nanobiosensing applications.

Highly Conducting p-Type Transparent LnCuOS (Ln = La and Nd) and p–n Junction by Using Ink

The development of high performance p-type transparent conducting oxides (TCOs) remains as the greatest challenge to the achievement of advanced future optoelectronics including transparent electronics. In this work, we proposed and succeeded in designing a novel chemical solution method to prepare highly conducting p-type oxychalcogenides LnCuOS (Ln = La and Nd). Not only is our proposed chemical solution process much more economically efficient, versatile, and safer than all the currently available methods, but also the synthesized NdCuOS demonstrates the record high intrinsic p-type conductivity of 11.4 S cm–1 for oxychalcogenides. The large improvement in the electrical conductivity is attributed to our synthesis process, leading to high Cu vacancies. The good phase stability of our highly Cu-deficient film was also proven by our computational calculation. At the same time, thin films of LnCuOS were also prepared via spin-coating methods for the first time. As the nanoparticles were used for spin-coating, the fabricated thin films are rather dense and smooth. Moreover, the strong photoluminescence (PL) peaks also indicate its great potential to be used in many future optoelectronics. The great performance demonstrated by the fabricated p–n junctions indicates the good opportunity to be integrated in devices like transparent electronics.

Deposition of Uniform Carbon Film on Silicon Substrate by Chemical Solution Process

Deposition of Uniform Carbon Film on Silicon Substrate by Chemical Solution Process

Electric field induced manipulation of resistive and magnetization switching in Pt/NiFe1.95Cr0.05O4/Pt memory devices

In this letter, both resistive and magnetization switching were realized in Pt/NiFe1.95Cr0.05O4 (Cr-NFO)/Pt devices by the manipulation applied electric field process, where a Cr-NFO switching layer was prepared by a facile chemical solution process method. The Cr-NFO based devices exhibited stable unipolar switching behavior, uniform operating voltages, good endurance (>103 cycles), large ON/OFF memory window (>102), and excellent retention characteristic time (>105 s at 25 °C). Meanwhile, the saturation magnetization of Cr-NFO based devices showed reversible switching in different resistance states. The significant change between the high magnetization state and the low magnetization state could reach as high as ∼50% during resistive switching operation. The ON-OFF switching can be achieved at room temperature in resistive and magnetization switching. The proposed physical mechanism of resistive and magnetized switching of Cr-NFO based devices was related to the formation and rupture of conduction filaments consisting of oxygen vacancies and cations, which was based on the conversion of Fe (Fe3+ → Fe2+) and Cr (Cr3+ → Cr4+) valence change, redox reaction, and Joule heating effects. The coexistence of resistive and magnetization switching in ferrite thin film based devices has potential application in nonvolatile memory and magneto-electric coupling devices.

Electroanalytical characterization of F-doped MoS2 cathode material for rechargeable magnesium battery

Fluorine (F)-doped MoS2 was prepared by F-doping into layered MoS2 via chemical solution process with fluoroboric acid. X-ray photoelectron spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction were applied to conform the effect of F on the structure. The electrochemical performance was investigated by using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge studies. The F-doped MoS2 as cathode material for rechargeable Mg battery exhibited a good discharge capacity of 55[Formula: see text]mAhg[Formula: see text], with a good rate capability and good cycling stability when compared to pristine B-MoS2. The effective performance of F-doped MoS2 are attributed to the unique structure and synergetic effect between layered MoS2.

A noniterative mean-field QM/MM-type approach with a linear response approximation toward an efficient free-energy evaluation.

Mean-field treatment of solvent provides an efficient technique to investigate chemical processes in solution in quantum mechanics/molecular mechanics (QM/MM) framework. In the algorithm, an iterative calculation is required to obtain the self-consistency between QM and MM regions, which is a time-consuming step. In the present study, we have proposed a noniterative approach by introducing a linear response approximation (LRA) into the solvation term in the one-electron part of Fock matrix in a hybrid approach between molecular-orbital calculations and a three-dimensional (3D) integral equation theory for molecular liquids (multicenter molecular Ornstein-Zernike self-consistent field [MC-MOZ-SCF]; Kido et al., J. Chem. Phys. 2015, 143, 014103). To save the computational time, we have also developed a fast method to generate electrostatic potential map near solute and the solvation term in Fock matrix, using Fourier transformation (FT) and real spherical harmonics expansion (RSHE). To numerically validate the LRA and FT-RSHE method, we applied the present approach to water, carbonic acid, and their ionic species in aqueous solution. Molecular properties of the solutes were evaluated by the present approach with four different types of initial wave functions and compared with those by the original (MC-MOZ-SCF). We found that an initial wave function considering solvation effects is needed to appropriately reproduce the properties by MC-MOZ-SCF. Furthermore, a benchmark test for 32 solute molecules was performed to evaluate the accuracy of the present approach for solvation free energy (SFE) and measure the speedup ratio for MC-MOZ-SCF. The error of SFE for MC-MOZ-SCF does not correlate with the SFE but increases in proportion to the electronic reorganization energy. Similar to water and carbonic acid, an initial wave function with solvation effects is also important to make the error small. From the averaged speed up ratio, the present approach is 13.5 times faster than MC-MOZ-SCF. © 2019 Wiley Periodicals, Inc.

A new approach to growth of chemically depositable different ZnS nanostructures

Different ZnS nanostructures synthesized by a chemical solution process were deposited on the glass substrate by dip coating technique. The effect of the sol-pH variation on the surface morphology, crystalline quality, optical band gap, and photoluminescence of the ZnS nanosphere, nanorod and mixed hexagonal cubic and rectangular-like nano-grains were investigated. It was found that the triethanolamine/ethanolamine played a key role to get desired nanostructure quality with different surface morphology. All nanostructures, derived in acidic and basic medium showed mixed cubic and hexagonal crystalline structure with preferred orientation along (111) plane of predominant cubic phase without oxidation. Nanospherical grains, sharply increased in size observed in acidic medium, whereas nanorods and mixed hexagonal, cubic and rectangular-like grains, slightly increased and then decreased in size, observed in basic medium with increased pH. The increased/decreased in average crystallite size was confirmed by reduced/enhanced dislocation density and micro strain. Comparatively, the band gap (Eg) of the nano-grains, reduced by pH derived in acidic medium was higher than those derived in basic medium. Comparatively, the higher surface defects related emission was observed in nanostructures derived in acidic medium than those derived in basic medium, whereas a higher green emission was observed in nanostructures fabricated at basic medium compared with the nanostructures synthesized in acidic medium. The results showed better crystalline quality in nano-grains derived at acidic medium than those derived at basic medium, whereas better optical quality in nanostructures derived at basic medium compared with the nanostructures derived at acidic medium. The observed characteristics are highly attractive for solar cells and optoelectronic applications.

Damage evolution model of sandstone under coupled chemical solution and freeze-thaw process

In the rock engineering of cold region eroded by chemical solution such as groundwater and acid rain, the pore development law, damage degree and failure characteristics of rock are closely related to the coupling effect of chemical solution and freeze-thaw. The freeze-thaw cycles of sandstones in different chemical solutions are experimented. The pore variation law and damage evolution mechanism of sandstones immersed in different chemical solutions are studied by means of nuclear magnetic resonance (NMR). The sandstone samples are placed in acidic solution, alkaline solution, neutral salt solution and aqueous solution for freeze-thaw cycling test. The composition, porosity change and T2 curve change of the samples are analyzed. The results show that the porosity of sandstone samples increases with the increase of the number of freeze-thaw cycles under the coupling of chemical solutions and freeze-thaw cycle. After 40 freeze-thaw cycles, the change rate of porosity is from large to small: neutral NaCl solution, H2SO4 solution, NaOH solution, aqueous solution. The pore sizes of all the samples affected by the coupling of chemical solution and freeze-thaw are mainly concentrated in two sizes, and the larger pore size is dominant. In neutral NaCl solution, chemical corrosion and freeze-thaw effect promote each other and play a superposition effect. In H2SO4 and NaOH solution, the superposition effect of chemical corrosion and freeze-thaw effect is inhibited to a certain extent. At the same time, according to the variation law of sample porosity in different chemical solutions, the quantitative expression of damage variable of the sample is obtained, and the damage evolution model of sandstone is derived.

Room-temperature synthesis of Bi/BiOBr composites for the catalytic degradation of ciprofloxacin using indoor fluorescent light illumination

This paper reports an efficient process for the room-temperature production of Bi/BiOBr composites. For this purpose, BiOBr was prepared via a solid state synthesis, while metallic bismuth nanoparticles were loaded onto the surface of BiOBr via a chemical reduction process in NaBH4 aqueous solution. Subsequently, both pristine BiOBr and Bi/BiOBr composites were characterized, and their photocatalytic efficiency was evaluated by degrading aqueous ciprofloxacin (CIP) solution (100 mL, 20 ppm), placed at approximately 2.5 m away from a 25 W indoor fluorescent light source. During the photocatalytic degradation process, Bi/BiOBr-20 showed a superior performance as its degradation efficiency reached 94.8% within 60 min, while 85.8% of the total organic carbon (TOC) has been removed after 120 min. Such enhanced performance has been attributed to the efficient separation of the photogenerated charge carriers and strong light absorption by Bi/BiOBr-20 composite photocatalyst. Results from active species studies were used in proposing a possible mechanism for the photodegradation process. The reusability study revealed negligible loss in the performance of Bi/BiOBr-20 composite photocatalyst over the five cycles investigated. Such facile room-temperature production process presented herein, could be useful in the design and large scale production of other bismuth-based photocatalysts.

An effective performance of F-Doped hexagonal boron nitride nanosheets as cathode material in magnesium battery

Abstract A facile method was developed to prepare fluorinated hexagonal boron nitride nanosheets (F-h-BNNSs) through F-doping into the nanosheets of boron nitride via chemical solution process with fluoroboric acid. Prepared F-h-BNNSs were analyzed by using different analytical instruments such as X-ray photoelectron spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and Xray diffraction. The electrochemical analysis was conducted by using cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge. It was observed that the effective performance of F-doped BN nanosheets as cathode material for magnesium batteries, which exhibit a reversible capacity of 50 mAh.g-1 and good capacity retention over the first 80 cycles. The effective performance of F-doped BN nanosheets are attributed to the unique structure and synergetic effects between layered BN.

Ozonesonde Quality Assurance: The JOSIE-SHADOZ (2017) Experience.

The ozonesonde is a small balloon-borne instrument that is attached to a standard radiosonde to measure profiles of ozone from the surface to 35 km with ~100-m vertical resolution. Ozonesonde data constitute a mainstay of satellite calibration and are used for climatologies and analysis of trends, especially in the lower stratosphere where satellites are most uncertain. The electrochemical-concentration cell (ECC) ozonesonde has been deployed at ~100 stations worldwide since the 1960s, with changes over time in manufacture and procedures, including details of the cell chemical solution and data processing. As a consequence, there are biases among different stations and discontinuities in profile time-series from individual site records. For 22 years the Jülich [Germany] Ozone Sonde Intercomparison Experiment (JOSIE) has periodically tested ozonesondes in a simulation chamber designated the World Calibration Centre for Ozonesondes (WCCOS) by WMO. In October-November 2017 a JOSIE campaign evaluated the sondes and procedures used in SHADOZ (Southern Hemisphere Additional Ozonesondes), a 14-station sonde network operating in the tropics and subtropics. A distinctive feature of the 2017 JOSIE was that the tests were conducted by operators from eight SHADOZ stations. Experimental protocols for the SHADOZ sonde configurations, which represent most of those in use today, are described, along with preliminary results. SHADOZ stations that follow WMO-recommended protocols record total ozone within 3% of the JOSIE reference instrument. These results and prior JOSIEs demonstrate that regular testing is essential to maintain best practices in ozonesonde operations and to ensure high-quality data for the satellite and ozone assessment communities.

Role of Thermal Energy Sources in Chemical Solution Process to Synthesize V2O5 Nanostructures

Role of Thermal Energy Sources in Chemical Solution Process to Synthesize V₂O₅ Nanostructures

Statistical efficiency of methods for computing free energy of hydration.

The hydration free energy (HFE) is a critical property for predicting and understanding chemical and biological processes in aqueous solution. There are a number of computational methods to derive HFE, generally classified into the equilibrium or non-equilibrium methods, based on the type of calculations used. In the present study, we compute the hydration free energies of 34 small, neutral, organic molecules with experimental HFE between +2 and -16 kcal/mol. The one-sided non-equilibrium methods Jarzynski Forward (JF) and Backward (JB), the two-sided non-equilibrium methods Jarzynski mean based on the average of JF and JB, Crooks Gaussian Intersection (CGI), and the Bennett Acceptance Ratio (BAR) are compared to the estimates from the two-sided equilibrium method Multistate Bennett Acceptance Ratio (MBAR), which is considered as the reference method for HFE calculations, and experimental data from the literature. Our results show that the estimated hydration free energies from all the methods are consistent with MBAR results, and all methods provide a mean absolute error of ∼0.8 kcal/mol and root mean square error of ∼1 kcal for the 34 organic molecules studied. In addition, the results show that one-sided methods JF and JB result in systematic deviations that cannot be corrected entirely. The statistical efficiency ε of the different methods can be expressed as the one over the simulation time times the average variance in the HFE. From such an analysis, we conclude that ε(MBAR) > ε(BAR) ≈ ε(CGI) > ε(JX), where JX is any of the Jarzynski methods. In other words, the non-equilibrium methods tested here for the prediction of HFE have lower computational efficiency than the MBAR method.

Isotope Effects in Water: Differences of Structure, Dynamics, Spectrum, and Proton Transport between Heavy and Light Water from ReaxFF Reactive Force Field Simulations.

Investigating properties of both heavy and light water at the atomistic level is essential to understanding chemical and biological processes in aqueous solution. However, appropriately describing their difference on the nanoscale is still challenging. Employing ReaxFF reactive molecular dynamics simulations, we systematically study the structure, dynamics, and spectra of heavy and light water. With the water force field potential we developed, the different features between heavy and light water can be simulated appropriately by the classical treatment on large size and time scale. Here, we also report the structural difference between D3O+ and H3O+ in bulk heavy/light water. In addition, the diffusion constants of heavy and light water are successfully reproduced, and the Grotthuss hopping mechanism of proton transport in liquid water is properly described as well. It allows us to study a complex system in heavy/light aqueous environments, such as proton transport, chemical reaction, and tracing the reaction mechanism with an isotope substitute.

Cost‐effective chemical solution synthesis of bismuth telluride nanostructure for thermoelectric applications

In this work, the bismuth telluride (Bi 2 Te 3 ) nanostructure for thermoelectric applications was successfully synthesised by a new cost-effective chemical solution process. Firstly, the metal solutions of bismuth (III) nitrate pentahydrate and tellurium dioxide were mixed together at room temperature with adjusting the hydrodynamic atmosphere and introduced the sodium hydroxide. After that, different characterisation parameters, such as X-ray diffraction, atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive X-ray, and transverse electron microscopy (TEM) were obtained. Then, the average crystalline size of the Bi 2 Te 3 nanostructure was found 23 nm. According to these obtained results, the materials consist of every specimen in nano range dimension in AFM studies. The elemental of Bi and Te were arranged with their quite stoichiometric atomic ratio observed by SEM. Ultimately, the TEM micrographs showed that the powders exhibited an aggregate phenomenon, and the primary crystalline size was about low dimension.

Toward a Biocompatible and Degradable Battery Using a Mg-Zn-Zr Alloy with β-Tricalcium Phosphate Nanocoating as Anode

A biocompatible β-tricalcium phosphate (β-TCP) nanorod coating on Mg-3 wt.%Zn-0.8 wt.%Zr alloy (MZZ) was fabricated by a chemical solution process. The microstructure and corrosion resistance of β-TCP coating on MZZ were studied using scanning electron microscopy, x-ray diffraction, and potentiodynamic polarization. β-TCP-MZZ was used as the anode for Mg battery with simulated body fluid directly acting as the electrolyte. The experimental results indicate that the β-TCP nanorod coating formed on the surface of MZZ alloy protects the matrix and improves the corrosion resistance of MZZ alloy. The Mg battery showed a voltage of 1.05 V for up to 75 days and continued to discharge for 90 days until 0.7 V at 100 μA/cm2. This indicates potential practical importance of biodegradable batteries.