Soft Chemical Method Research Articles

A simple and soft chemical deaggregation method producing single-digit detonation nanodiamonds.

Detonation nanodiamonds (DNDs) are a class of very small and spherical diamond nanocrystals. They are used in polymer reinforcement materials or as drug delivery systems in the field of nanomedicine. Synthesized by detonation, only the final deaggregation step down to the single-digit nanometer size (<10 nm) unfolds their full potential. Existing deaggregation methods mainly rely on mechanical forces, such as high-power sonication or bead milling. These techniques entail drawbacks such as contamination of the sample and the need for a specialized apparatus. In this paper, we report a purely chemical deaggregation method by simply combining oxidation in air followed by a boiling acid treatment, to produce highly stable single-digit DNDs in a suspension. The resulting DNDs are surface functionalized with carboxyl groups, the final boiling acid treatment removes primary metal contaminants such as magnesium, iron or copper and the nanoparticles remain dispersed over a wide pH range. Our method can be easily carried out in a standard chemistry laboratory with commonly available laboratory apparatus. This is a key step for many DND-based applications, ranging from materials science to biological or medical applications.

Bottom-up synthesis of 2D layered high-entropy transition metal hydroxides.

Low-dimensional high-entropy materials, such as nanoparticles and two-dimensional (2D) layers, have great potential for catalysis and energy applications. However, it is still challenging to synthesize 2D layered high-entropy materials through a bottom-up soft chemistry method, due to the difficulty of mixing and assembling multiple elements in 2D layers. Here, we report a simple polyol process for the synthesis of a series of 2D layered high-entropy transition metal (Co, Cr, Fe, Mn, Ni, and Zn) hydroxides (HEHs), involving the hydrolysis and inorganic polymerization of metal-containing species in ethylene glycol media. The as-synthesized HEHs demonstrate 2D layered structures with interlayer distances ranging from 0.860 to 0.987 nm and homogeneous elemental distribution of designed equimolar stoichiometry in the layers. These 2D HEHs exhibit a low overpotential of 275 mV at 10 mA cm−2 in a 0.1 M KOH electrolyte for the oxygen evolution reaction. Superparamagnetic spinel-type high-entropy nanoparticles can also be obtained by annealing these HEHs. Our polyol approach creates opportunities for synthesizing low-dimensional high-entropy materials with promising properties and applications.

Soft Chemical Synthesis of Nickel-Zinc-Cobalt-Ferrite Nanoparticles and their Structural, Morphological and Magnetic Study at Room Temperature

The cobalt substituted Nickel-Zinc ferrites with the composition Ni0.95-xZn0.05CoxFe2O4, for x= 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 were synthesized by the soft chemical route method and were found to have cubic system of ferrimagnetic spinel using XRD. The grain sizes decreases significantly with the cobalt content (x) and are 1.62-1.36nm for x = 0.01 to 0.06 which are small enough to produce appropriate high density recording media. The particle size is found to be in the range 29-22 nm with the help of SEM. Their magnetic properties determined with VSM show the dependency on the exchange interaction due to the cobalt substitution between the metal ions of tetra and octahe.

Synthesis and Characterization of Undoped and Mn‐Doped Copper Oxide Nanoparticles

AbstractCopper oxide (CuO) is a p‐type metal‐oxide semiconductor with a bandgap of 1.2 eV and a minimal bandgap. Solar cells, superconductors, and sensors are among the applications for which it is used. To dope transition metals, researchers use a low‐cost soft chemical process (Mn). The aim of this research is to identify CuO nanopowders using a low‐cost soft chemical method to dope transition metals (Mn). The nanopowders' structural, morphological, functional, and optical properties are investigated. X‐ray diffraction (XRD) analysis findings point to the synthesis of high purity single monoclinic phase CuO nanoparticles. The crystallite size (30 nm) and lattice parameters of Mn‐doped CuO samples are reduced. These results suggest that Mn‐doped CuO nanoparticles may be a promising candidate for optoelectronic devices and photocatalytic organic compound degradation.

Highly Active Co3O4-Based Catalysts for Total Oxidation of Light C1-C3 Alkanes Prepared by a Simple Soft Chemistry Method: Effect of the Heat-Treatment Temperature and Mixture of Alkanes.

In the present work, a simple soft chemistry method was employed to prepare cobalt mixed oxide (Co3O4) materials, which have shown remarkably high activity in the heterogeneously catalyzed total oxidation of low reactive VOCs such as the light alkanes propane, ethane, and methane. The optimal heat-treatment temperature of the catalysts was shown to depend on the reactivity of the alkane studied. The catalytic activity of the Co3O4 catalysts was found to be as high as that of the most effective catalysts based on noble metals. The physicochemical properties, from either the bulk (using XRD, TPR, TPD-O2, and TEM) or the surface (using XPS), of the catalysts were investigated to correlate the properties with the catalytic performance in the total oxidation of VOCs. The presence of S1 low-coordinated oxygen species at the near surface of the Co3O4-based catalysts appeared to be linked with the higher reducibility of the catalysts and, consequently, with the higher catalytic activity, not only per mass of catalyst but also per surface area (enhanced areal rate). The co-presence of propane and methane in the feed at low reaction temperatures did not negatively affect the propane reactivity. However, the co-presence of propane and methane in the feed at higher reaction temperatures negatively affected the methane reactivity.

Tuning of Photoluminescence and Antibacterial Properties of ZnO Nanoparticles through Sr Doping for Biomedical Applications

Sr-doped ZnO nanoparticles have been synthesized using a soft chemical method. The doping ratio of Sr is varied in the range of 0 at.%, 3 at.%, and 5 at.% to 7 at.%. X-ray diffractograms revealed that the samples had hexagonal (wurtzite) structure without a trace of any mixed phase. The average crystallite size of the nanoparticles (NPs) ranged from 39 to 46 nm. The average crystallite size was increased for the initial doping (3 at.%) of Sr ions, and further increase in the doping ratio reduced the particle size due to some distortion produced in the lattice. The surface morphology of the samples and structure of the NPs were investigated using FESEM (Field Emission Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy) pictures, respectively. EDX (energy-dispersive X-ray) spectroscopy confirmed the presence of strontium (Sr) in the host lattice. Photoluminescence and X-ray diffraction confirmed that the dopant ions replace some of the lattice zinc ions and that Sr2+ and Sr3+ ions coexist in the ZnO lattice. The Sr-doped ZnO exhibited violet and blue luminescence spectra at 408 nm and 492 nm, respectively. ZnO : Sr nanoparticles showed increased antibacterial activity against one gram-positive as well as one gram-negative bacteria.

Synthesis Method and Electrochemical Properties of H2Ti12O25 from Cubic Li2TiO3 for Lithium-Ion Batteries

A novel synthesis route of H2Ti12O25 was developed by a soft chemical method using cubic Li2TiO3 as a precursor compound. Cubic Li2TiO3 prepared by the hydrothermal method and having spherical primary particles, with diameters ranging from 30–50 nm, was converted to H2TiO3 by a Li+/H+ ion-exchange reaction using an HCl solution after annealing. H2Ti12O25, spherical in shape with diameters ranging from 20–40 nm, was prepared by heating the H2TiO3 under vacuum. The discharge capacity of the H2Ti12O25 was found to be approximately 280 mAh g−1, which is higher than that previously reported for H2Ti12O25 prepared from Na2Ti3O7. The retention rate of the sample was about 96% and the crystal structure of the sample was maintained after 100 cycles.

Effect of Al, Ga, and In Doping on the Optical, Structural, and Electric Properties of ZnO Thin Films

ZnO thin films with oxygen vacancies and doped with Al, Ga, and In (Zn1-xMxO1−y (x = 0.03)) have been successfully deposited on soda-lime glass substrates using a simple soft chemical method. The crystalline structure shows a single hexagonal phase of wurtzite with preferred crystal growth along the 002 plane. The surface morphology, characterized by SEM, revealed that the grain shape varies depending on the dopant agent used. Optical measurements displayed an increase in the bandgap values for doped films from 3.29 for ZnO to 3.35, 3.32, and 3.36 for Al, Ga, and In doped films, respectively, and an average transmittance superior to 90% in some cases (in the range between 400 and 800 nm). The electrical response of the films was evaluated with a four-point probe being 229.69, 385.71, and 146.94 Ω/sq for aluminium, gallium, and indium doped films, respectively.

Graphite/nickel nanoparticle composites prepared by soft chemical methods

The aim of this work is to obtain and characterize a composite material using an environmentally friendly matrix and green processes. To this end, different composites of as-received commercial graphite flakes (G) and nickel nanoparticles (Ni NPs) have been prepared by a one-step soft synthesis and by mechanical mixing. The properties of the composites have been compared by means of X-ray diffraction analysis, electron microscopy, Raman spectroscopy, and magnetometry. The microwave absorption behavior of the composites has also been assessed in the 0.1–3 GHz frequency range, to explore potential applications. The composites prepared by chemical synthesis followed by heat-treatment display improved crystallinity and magnetization. Small amounts of Ni NPs in the chemically synthesized composite not only enhance the microwave absorption properties of graphite, reaching values above 10 dB at 2.5 GHz, but also extend the use of graphite as a microwave absorber to low frequencies.

Ternary ACd4P3 (A = Na, K) Nanostructures via a Hydride Solution-Phase Route.

Complex pnictides such as I-II4-V3 compounds (I = alkali metal; II = divalent transition metal; V = pnictide element) display rich structural chemistry and interesting optoelectronic properties, but can be challenging to synthesize using traditional high-temperature solid-state synthesis. Soft chemistry methods can offer control over particle size, morphology, and properties. However, the synthesis of multinary pnictides from solution remains underdeveloped. Here, we report the colloidal hot-injection synthesis of ACd4P3 (A = Na, K) nanostructures from their alkali metal hydrides (AH). Control studies indicate that NaCd4P3 forms from monometallic Cd0 seeds and not from binary Cd3P2 nanocrystals. IR and ssNMR spectroscopy reveal tri-n-octylphosphine oxide (TOPO) and related ligands are coordinated to the ternary surface. Computational studies show that competing phases with space group symmetries R3̅m and Cm differ by only 30 meV/formula unit, indicating that synthetic access to either of these polymorphs is possible. Our synthesis unlocks a new family of nanoscale multinary pnictide materials that could find use in optoelectronic and energy conversion devices.

Synthesis and physical properties of perovskite Sm1−x Sr x NiO3 (x = 0, 0.2) and infinite-layer Sm0.8Sr0.2NiO2 nickelates

Recently, superconductivity at about 9–15 K was discovered in Nd1−x Sr x NiO2 (Nd-112, x ≈ 0.125–0.25) infinite-layer thin films, which has stimulated enormous interests in related rare-earth nickelates. Usually, the first step to synthesize this 112 phase is to fabricate the RNiO3 (R-113, R: rare-earth element) phase, however, it was reported that the 113 phase is very difficult to be synthesized successfully due to the formation of unusual Ni3+ oxidation state. And the difficulty of preparation is enhanced as the ionic radius of rare-earth element decreases. In this work, we report the synthesis and investigation on multiple physical properties of polycrystalline perovskites Sm1−x Sr x NiO3 (x = 0, 0.2) in which the ionic radius of Sm3+ is smaller than that of Pr3+ and Nd3+ in related superconducting thin films. The structural and compositional analyses conducted by x-ray diffraction and energy dispersive x-ray spectrum reveal that the samples mainly contain the perovskite phase of Sm1−x Sr x NiO3 with small amount of NiO impurities. Magnetization and resistivity measurements indicate that the parent phase SmNiO3 undergoes a paramagnetic–antiferromagnetic transition at about 224 K on a global insulating background. In contrast, the Sr-doped sample Sm0.8Sr0.2NiO3 shows a metallic behavior from 300 K down to about 12 K, while below 12 K the resistivity exhibits a slight logarithmic increase. Meanwhile, from the magnetization curves, we can see that a possible spin-glass state occurs below 12 K in Sm0.8Sr0.2NiO3. Using a soft chemical reduction method, we also obtain the infinite-layer phase Sm0.8Sr0.2NiO2 with square NiO2 planes. The compound shows an insulating behavior which can be described by the three-dimensional variable-range-hopping model. And superconductivity is still absent in the polycrystalline Sm0.8Sr0.2NiO2.

High-temperature oxidation behaviour of refurbished (Ni,Pt)Al coating on Ni-based superalloy at 1100 °C

A single-phase (Ni,Pt)Al coating was removed by soft chemical stripping method successfully after preceding oxidation at 1100 °C for 300 h, and a fresh one was refurbished subsequently. Oxidation behaviour of the refurbished (Ni,Pt)Al coating was studied in comparison with the virgin one at 1100 °C. The results show that the refurbished coating exhibited superior isothermal and cyclic oxidation resistance than the virgin one in terms of oxidation rate and surface rumpling. The effects of surface roughness and residual elements in the refurbished coating on oxidation rate, surface rumpling and interdiffusion behaviour were discussed.

Recent Advances of Mesoscale-Structured Cathode Materials for High Energy Density Lithium-Ion Batteries

To meet the demands for Li-ion batteries in consumer electronics and renewable technologies, Ni-high and Li-rich layered oxides are attracting significant research interests for their extraordinarily high reversible capacities and being environmentally benign. However, both Ni-high and Li-rich layered oxides undergo serious cation mixing, superficial structural instability, and undesirable voltage decay, thus resulting in unsatisfactory electrochemical performance, which may trade off their benefits. Herein, this spotlight article focuses on recent advances in the rational design, preparation, and modification of mesoscale materials to overcome the shortcomings of Ni-high and Li-rich layered oxides, including soft chemical method, sequential precipitation method, poly(vinylpyrrolidone) (PVP: PVP-K30 [(C6H9NO)n] (molecular mass: 44000–54000)) bridging coating method, etching-induced coating method, and near-equilibrium deposition method, etc. This work will provide a scientific basis in material design and synthetic strategies toward high-performance mesoscale-structured Ni-high and Li-rich layered oxides and lay an experimental foundation for their future applications.

Vermiwash-derived enzyme-activated ZnO nanomaterial towards two cascading applications: enhanced photocatalysis and effective irrigation

This study focuses on the preparation of enzyme-activated zinc oxide nanomaterial using vermiwash via a simple soft chemical method. This vermiwash––an aqueous extract obtained from vermin reactor––is produced using earthworm, Eudrilus eugeniae, cow dung and leaf litter. The prepared nanoproduct was used to decompose toxic dye molecules through photocatalysis. The enzymes present in the vermiwash (like amylase, phosphatase, urease and protease) are found to be inherited by the prepared nanoproduct as well as the photocatalytically treated water. The quantitative study of enzymes shows that the quantity of enzymes present in the nanoproduct as well as in the photocatalytically treated water increases as the proportion of vermiwash used in the starting solution increases. This increase in the quantity of enzymes causes an increase in the photocatalytic efficiency of the nanoproduct. The photocatalytically treated water which consists of enzymes can be used as a potential candidate for effective irrigation. Thus, the vermiwash-activated ZnO nanopowder prepared in this study shows a two linear cascading applications. The results of the studies on enzymes, photocatalysis, XRD, SEM and FTIR are appropriately correlated with one another to address the enhancement in the photocatalytic activity of the prepared nanomaterials and the underlying mechanism.

Synthesis of in-situ high-content carbon-containing calcium aluminate cement and its effect on the properties of Al2O3-SiC-C castables

ABSTRACT The in-situ high-content carbon-containing calcium aluminate cement (HCCAC) with the carbon content of 20.1 wt.% was prepared by the soft chemistry method with citric acid, calcium carbonate, and alumina as raw materials. The cement product was characterized by X-ray diffractometry, scanning electron microscopy, and Raman spectroscopy. In HCCAC, plate-like and fibrous carbon formed by the pyrolysis of organic acids were uniformly embedded between the calcium aluminate grains. Moreover, the carbon floating ratio of HCCAC in water was lower than that of the mechanical mixing powder of calcium aluminate cement (CAC) and carbon black, which indicated that the water dispersion of carbon was improved. Besides, the slag corrosion resistance properties of Al2O3-SiC-C castables bonded with HCCAC and CAC respectively were compared, and the results showed that the corrosion resistance depth of the HCCAC bonded castables was 45% lower than that of the CAC bonded castables. Therefore, HCCCA can be used as a novel binder of carbon-containing refractory castables.

Soft-chemistry synthesis, solubility and interlayer spacing of carbon nano-onions.

Carbon nano-onions (CNOs), as one of the allotropes of carbon, have attracted great attention because of their excellent performance in many fields, especially in capacitors. Developing soft-chemistry synthesis methods is critically of importance, while the forming mechanism in this area is not clear. In this paper, we present a critical review of CNOs regarding the structure, especially interlayer spacing, and synthesis processes, elaborating the recent progress on soft-chemistry methods. Hansen solubility parameter theory is applied to predict and regulate the solubility of CNOs. This article would be inspirational and give new insights into understanding the formation and properties of CNOs.

Low-cost visible-light photodetector based on Ag/CdSe Schottky diode fabricated using soft chemical solution method

Low-cost visible-light photodetector based on Ag/CdSe Schottky diode fabricated using soft chemical solution method

Low Temperature Synthesis of Halide Phosphors Using Novel Water-Assisted Solid-State Reaction Method

In recent years, nano-phosphor materials have attracted much attention due to their significant potential for high-performance micro-LED displays and solid state lighting devices. In addition, nano-phosphors are considered to be promising candidates for spectral-converters to enhance the energy-conversion efficiency of silicon solar cells. Synthesis of nano-phosphors can be categorized in two ways namely, chemical and physical methods. Various methods such as the sol-gel, hydro-thermal, or the polymerized complex methods are usually used to synthesize nano-phosphor materials. However, these methods require expensive and special experimental equipment, raw materials, or solvents.In this study, we synthesized nano-sized halide phosphors using a novel water-assisted solid-state reaction (WASSR) method. This novel soft chemical synthesis method is very simple and can synthesize nano-particle materials just by storing or mixing raw materials added a small amount (typically 10wt%) of water in a reactor at low temperature below 500 K. Typical particle sizes (under 100 nm) of the samples prepared by the WASSR method were smaller than that (2 - 10 micrometer size) of the sample prepared by the conventional solid-state reaction method.For example, a stoichiometric mixture of CsCl, CaCl2 and EuCl3 hydrate was mixed for the WASSR synthesis of CsCaCl3:Eu2+ phosphor. Then, a small amount (2 wt%) of water was added to the mixture and mixed using mortar for 1 min to synthesize a single phase of CsCaCl3:Eu3+. For the reduction of Eu3+ ion, 6 wt % of hydrazine monohydrate was added to the CsCaCl3:Eu3+ and heated in the closed reactor for 12 h at 493 K. The XRD pattern of the products are in good agreement with that of single phase CsCaCl3. The SEM image and the photoluminescence spectra of CsCaCl3:Eu2+ is shown in Figure. CsCa0.09Eu0.01Cl3 shows strong blue emission under the excitation of UV light. Our proposed low cost and low-temperature synthesis technique are promising for an industrial application for phosphor materials synthesis processing.AcknowledgmentThis research was financially supported by the Ministry of Trade, Industry and Energy(MOTIE) and Korea Institute for Advancement of Technology(KIAT) through the International Cooperative R&D program (P0006844_Development of color conversion nanocrystal luminescence materials for next generation display).

Study on preparation and recovery of cobalt hydroxide and cobalt carbonate

In this paper, the potential-pH diagrams of Co-Cl-H2O/Co-C-Cl-H2O systems under the temperature of 25°C were drawn through the basic potential-pH principle with a number of thermodynamic data, and the predominant area of Co(OH)2/CoCO3 in the Co-Cl-H2O/Co-C-Cl-H2O systems which existed stably in the agueous solution were obtained. According to the potential-pH diagram of Co-Cl-H2O/Co-C-Cl-H2O systems as well as numerous published reports in the literature, the potential processes and theoretical feasibility for synthesizing Co(OH)2/CoCO3 using soft-chemical method in agueous solution and recovering valuable metals from the waste lithium-ion batteries by hydrometallurgical method were discussed. The potential-pH diagram of Co-Cl-H2O/Co-C-Cl-H2O systems provided the theoretical foundation for synthesizing Co(OH)2/CoCO3 using electrochemical method in agueous solution and recovering valuable metals by hydrometallurgical method. Hence, high-purity, high-crystallinity submicron Co(OH)2/CoCO3 powder is electro-synthesized through one-step simple deposition procedure. Simultaneously,the influencing factors of dynamics also be discussed. Based on the Stern model, we briefly described the electric double layer model near the electrode in this experiment.

Intercalation-type MoP and WP nanodots with abundant phase interface embedded in carbon microflower for enhanced Li storage and reaction kinetics

High discharging capacity materials with an intercalation-type mechanism are the promising anodes to replace the conventional graphite. In this work, WP and MoP nanodots encapsulated in flower-like carbon framework are prepared by a simple soft chemical method followed by phosphorization. The intercalation-type lithiation mechanisms of WP and MoP are proved by the ex situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electron conductivity and the electrode pulverization of WP@MoP are improved by carbon microflowers. The abundant phase interface facilitates the transfer and storage of Li+, revealed by the galvanostatic intermittent titration technique (GITT) and the density functional theory (DFT). These advantages result in its high discharging capacity (636 mAh g−1 at 0.1 A g−1) and ultralong cycling life (81.5% capacity retention after 1700 cycles at 1 A g−1). The outstanding performances of electrode at high mass loading and full cell further reflect its potential value in practice.