Solution Synthesis Route Research Articles

Interpretable Machine Learning Enabled Inorganic Reaction Classification and Synthesis Condition Prediction

Data-driven synthesis planning with machine learning is a key step in the design and discovery of novel inorganic compounds with desirable properties. Inorganic materials synthesis is often guided by heuristics and chemists’ prior knowledge and experience, built upon experimental trial-and-error that can be both time and resource consuming. Recent developments in natural language processing have enabled large-scale text mining of scientific literature, providing open-source databases of synthesis information on realized compounds, material precursors, and reaction conditions (temperatures, times). We employ supervised classification machine learning (ML) models to distinguish between solid-state, sol–gel, and solution (hydrothermal, precipitation) synthesis routes based on specified reaction target material and/or precursor materials. We demonstrate regression ML models that are able to predict suitable temperatures and times for the crucial inorganic synthesis steps of calcination and sintering given the reaction target and precursor materials. We contrast this regression-based condition modeling with a conditional variational autoencoder neural network that can generate appropriate distributions for the synthesis conditions of interest. We evaluate model interpretability using the Shapley additive explanations approach to gain insight into factors influencing suitability of synthesis route and reaction conditions. We find that the aforementioned models are capable of learning subtle differences in target material composition, precursor compound identities, and choice of synthesis route that are present in the inorganic synthesis space. Moreover, they generalize well to unseen chemical entities, outperform common heuristics in the field, and show promise for predicting appropriate reaction routes and conditions for previously unsynthesized compounds of interest.

Controlled Synthesis of Transition Metal Phosphide Nanoparticles to Establish Composition-Dependent Trends in Electrocatalytic Activity

Transition-metal phosphides (TMPs) are versatile materials with tunable electronic and structural properties that have led to exceptional catalytic performances for important energy applications. Identifying predictive relationships between the catalytic performance and key features such as the composition, morphology, and crystalline structure hinges on the ability to independently tune these variables within a TMP system. Here, we have developed a versatile, low-temperature solution synthesis route to alloyed nickel phosphide (Ni1.6M0.4P, where M = Co, Cu, Mo, Pd, Rh, or Ru) nanoparticles (NPs) that retains the structure of the parent Ni2P NPs, allowing investigation of compositional effects on activity without convoluting factors from differences in morphology and crystalline phase. As a measure of the controlled changes introduced within the isostructural series by the second metal, the binary and alloyed ternary TMP NPs supported on carbon at a nominal 5% weight loading were studied as electrocatalysts for the hydrogen evolution reaction (HER). The resultant activity of the electrocatalyst series spanned a 125 mV range in overpotential, and composition-dependent trends were investigated using density functional theory calculations on flat (0001) and corrugated (101̅0) Ni1.67M0.33P surfaces. Applying the adsorption free energy of atomic H (GH) as a descriptor for HER activity revealed a facet-dependent volcano-shaped correlation between the overpotential and GH, with the activity trend well represented by the corrugated (101̅0) surfaces on which metal–metal bridge sites are available for H adsorption but not the flat (0001) surfaces. The versatility of the rational synthetic methodology allows for the preparation of a wide range of compositionally diverse TMP NPs, enabling the investigation of critical composition–performance relationships for energy applications.

Realization of high thermoelectric performance in solution-synthesized porous Zn and Ga codoped SnSe nanosheets

A high average ZT of 0.8 and a high peak ZT of 1.86 are obtained in porous Zn and Ga codoped SnSe nanosheets fabricated by a solution synthesis route.

전고체전지 상용화를 위한 황화물 고체전해질 기술 개발 동향

본 논문에서는 차세대 전지 중 가장 주목받고 있는 전지 중 하나인 전고체전지의 상용화를 위한 황화물계 고체전해질 기술의 개발 동향을 살펴 보고, 특히 대량 생산이 용이한 액상합성법과 최근 한국전기연구원에서 개발한 공침 제조기술에 대해 소개한다. This paper presents the recent trends in the development of sulfide solid electrolytes for all-solid-state batteries which have been considered as one of the most promising next-generation batteries. In particular, the solution synthesis routes including recently developed co-precipitation method are introduced in view of the mass-production of sulfide solid electrolytes.

Self-powered broadband photodetector based on a solution-processed p-NiO/n-CdS:Al heterojunction

Solution-processed photodetectors have emerged as the next generation of sensing technology owing to their ease of integration with electron devices and of tuning photodetector performance. Currently, novel self-powered photodetectors without an external power source, for use in sensing, imaging and communication, are in high demand. Herein, we successfully developed a self-powered photodetector based on a novel solution-processed p-NiO/n-CdS:Al heterojunction, which shows an excellent current rectification characteristic ratio of up to three orders in the dark and distinctive photovoltaic behavior under light illumination. The complete solution synthesis route followed the development of CdS:Al thin films on ITO substrates by chemical bath deposition and NiO thin films by the sol-gel route. Optical absorption data revealed that NiO is more active in the UV region and CdS:Al has a majority of absorption in the visible region; so, upon light illumination, the effective separation of photogenerated carriers produces fast photodetection in the UV–visible region. The photoresponsivity values of the fabricated device were calculated to be 55 mA W−1 and 30 mA W−1 for UV and visible illumination, respectively. Also, the device has a fast rise and decay photoresponse speed at zero bias voltage, due to the self-driven photovoltaic effect which makes this heterojunction a self-powered device. This complete solution and new method of fabrication make it possible to combine different materials and flexible substrates, enhancing its potential applications in photodetectors, optoelectronic devices and sensors.

A Comparative Study on the Thermoelectric Properties of Bismuth Chalcogenide Alloys Synthesized through Mechanochemical Alloying and Microwave-Assisted Solution Synthesis Routes

The way a material is synthesized and processed has an immense effect on its microstructure, which in turn has a big impact on its transport properties. Here we compare the thermoelectric (TE) properties of n- and p-type Bi2-xSbxTe3 (x: 0 and 1.5) materials synthesized through two different routes, specifically mechanochemical alloying (MA) -as a solid-state synthesis route, and microwave-assisted (MW) polyol synthesis -as a solution synthesis route. Reaction time is significantly reduced in the MW synthesis, leading to a significantly lower energy consumption (i.e. higher energy efficiency) per batch as compared to the MA route. The resultant materials are compared for their crystallinity, phase purity, morphology, and microstructure. Spark plasma sintering was used to prepare pellets and the resultant consolidates were evaluated for their transport properties. TE properties and microstructure of the specimens were investigated in relation to processing conditions and composition. MA samples formed fused structures (from 200 nm to several micrometers in size) composed of smaller particles. MW synthesized materials exhibit hexagonal platelet morphology, high crystallinity and phase purity. They also show lower thermal conductivity, leading to a higher resultant TE figure-of-merit -ZT. TE properties of Bi2-xSbxTe3 samples were studied on sintered cylindrical pellet samples, where the highest ZT values achieved were 1.04 (@ 440 K) for MW-Bi2Te3 and 0.76 (@ 523 K) for MW-Bi0.5Sb1.5Te3 samples, while MA-Bi2Te3 and MA-Bi0.5Sb1.5Te3 samples showed maximum ZT values of 0.74 (@ 460 K) and 0.27 (@ 300 K), respectively as n- and p-type TE materials. The observed trend is much higher ZT values for MW samples, ascribed to their higher degree of texturing and nanostructured grains reducing the thermal conductivity, thus achieving a better overall performance, verifying the prospect to enhance ZT using MW-assisted solution synthesis approach.

Visible light responsive CsPbBr3/TiO2 photocatalyst with long-term stability in aqueous solution

In this work, CsPbBr3/TiO2 nanocomposite photocatalyst exhibiting high visible light photocatalytic activity has been fabricated via a facile solution synthesis route at low temperature. CsPbBr3 quantum dots (QDs) were prepared by using supersaturated recrystallization method, and the surface was coated with amorphous TiO2 to enhance its stability. The CsPbBr3/TiO2 photocatalyst had excellent light absorption performance in a broad wavelength range and strong adsorption capacity for the organic pollutant. The formation of heterojunction between CsPbBr3 and TiO2 promoted the charge separation and thus improved the photocatalytic activity. In addition, photocatalytic degradation tests showed that the as-prepared nanocomposite exhibited high visible-light-induced photocatalytic activity under the simulated sunlight irradiation. And the obtained composite had long-term stability in water system and potential practical application value in the field of environmental governance.

Composition Tuning of Nanostructured Binary Copper Selenides through Rapid Chemical Synthesis and their Thermoelectric Property Evaluation.

Reduced energy consumption and environmentally friendly, abundant constituents are gaining more attention for the synthesis of energy materials. A rapid, highly scalable, and process-temperature-sensitive solution synthesis route is demonstrated for the fabrication of thermoelectric (TE) Cu2−xSe. The process relies on readily available precursors and microwave-assisted thermolysis, which is sensitive to reaction conditions; yielding Cu1.8Se at 200 °C and Cu2Se at 250 °C within 6–8 min reaction time. Transmission electron microscopy (TEM) revealed crystalline nature of as-made particles with irregular truncated morphology, which exhibit a high phase purity as identified by X-ray powder diffraction (XRPD) analysis. Temperature-dependent transport properties were characterized via electrical conductivity, Seebeck coefficient, and thermal diffusivity measurements. Subsequent to spark plasma sintering, pure Cu1.8Se exhibited highly compacted and oriented grains that were similar in size in comparison to Cu2Se, which led to its high electrical and low thermal conductivity, reaching a very high power-factor (24 µW/K−2cm−1). Density-of-states (DOS) calculations confirm the observed trends in electronic properties of the material, where Cu-deficient phase exhibits metallic character. The TE figure of merit (ZT) was estimated for the materials, demonstrating an unprecedentedly high ZT at 875 K of 2.1 for Cu1.8Se sample, followed by 1.9 for Cu2Se. Synthetic and processing methods presented in this work enable large-scale production of TE materials and components for niche applications.

Facile Solution Synthesis, Processing and Characterization of n- and p-Type Binary and Ternary Bi–Sb Tellurides

The solution synthesis route as a scalable bottom-up synthetic method possesses significant advantages for synthesizing nanostructured bulk thermoelectric (TE) materials with improved performance. Tuning the composition of the materials directly in the solution, without needing any further processing, is important for adjusting the dominant carrier type. Here, we report a very rapid (2 min) and high yield (>8 g/batch) synthetic method using microwave-assisted heating, for the controlled growth of Bi2–xSbxTe3 (x: 0–2) nanoplatelets. Resultant materials exhibit a high crystallinity and phase purity, as characterized by XRD, and platelet morphology, as revealed by SEM. Surface chemistry of as-made materials showed a mixture of metallic and oxide phases, as evidenced by XPS. Zeta-potential analysis exhibited a systematic change of isoelectric point as a function of the material composition. As-made materials were directly sintered into pellets by using spark plasma sintering process. TE performance of Bi2−xSbxTe3 pellets were studied, where the highest ZT values of 1.04 (at 440 K) for Bi2Te3 and 1.37 (at 523 K) for Sb2Te3 were obtained, as n- and p-type TE materials. The presented microwave-assisted synthesis method is energy effective, a truly scalable and reproducible method, paving the way for large scale production and implementation of towards large-area TE applications.

Effect of particle size and morphology on the performance of BiFeO3–PDMS piezoelectric generators

The effect of the size and morphology of piezoelectric BiFeO3 particles on the performance of BiFeO3–PDMS composite generators is revealed.

Magnetic and tunable dielectric properties of DyCrO3 thin films

DyCrO3 (DCO) belongs to the family of rare-earth chromites, some members of which exhibit magnetoelectric multiferroic properties. This work characterizes the dielectric tunability in DCO, which is typically, for conventional ferroelectrics, found to maximize near the ferroelectric to paraelectric transition. Two films of DCO were fabricated via a hybrid solution synthesis route on different substrates: one on single crystalline (001) LaAlO3 (LAO) and the other on (001) LAO coated with a conducting LaNiO3 (LNO) layer. The synthesis method resulted in films with both out-of-plane and in-plane texture in the DCO. The lattice mismatch strain between film and substrate caused a slight increase in the Neel temperature of the DCO film on LAO. Transmission electron microscopy images of the DCO film on the LNO/LAO revealed the epitaxial relationship between these phases. The temperature dependence of the relative permittivity showed diffused transition and a frequency dispersion similar to what is observed in typical relaxor ferroelectrics. Isothermal dielectric constant versus dc electric field measurements showed an electric field tunable relative permittivity (i.e., tunability). This tunability reached a broad plateau near the Neel temperature. Such maxima in dielectric tunability are typically observed near a ferroelectric–paraelectric transition, and its proximity to the magnetic ordering temperature in DCO indicates magnetically driven ferroelectricity in this material.

Aqueous Solution-Processed Multifunctional SnO2 Aggregates for Highly Efficient Dye-Sensitized Solar Cells

A room temperature based environmentally friendly aqueous solution synthesis route was developed to fabricate highly dispersed small SnO2 nanoparticles (3–5 nm) without the application of any pressurized reaction vessel or organic solvents. The subsequent treatments, that is, dialyzing and freezing, allow for the acquision of dual-function nanostructures with sheet-like feature and large aspect ratio except for the ordinary irregular aggregates. Dye-sensitized solar cells (DSCs) constructed with the resultant multifunctional SnO2 showed an outstanding photovoltaic conversion efficiency (PCE) of 6.92% and an unexpected JSC of 19.5 mA cm–2 at an optimized thickness of 14.1 μm. The excellent performance can be ascribed to the effective coordination of the favorable features (i.e., strong light scattering, large dye loading capability, and fast electron transport) via rational film thickness control as indicated by diffused reflectance spectra, UV–vis absorption spectra, and electrochemical impedance spectros...

Well-dispersed small-sized MnOx nanoparticles and porous carbon composites for effective methylene blue degradation

We report here the fabrication of MnOx nanoparticles and porous carbon composite via a solution synthesis route followed by carbonization. Poly (acrylic acid) stabilized ultra-small MnO2 nanoparticles (around 1.0 nm) are first produced and then in situ incorporated into the RF resin matrix. The as-prepared composites are carbonized at 500 °C in N2 atmosphere, during which the MnO2 are reduced to Mn3O4 and MnO (denoted as MnOx), which are more active in heterogeneous Fenton catalysis. Thanks to the small sized Mn source we used, under the optimized synthesis condition, the average size of the MnOx particles is only 2.9 nm. Moreover, the MnOx particles are homogeneously dispersed in the carbon matrix and the BET surface area of the composite is as large as 227.7 m3 g−1, which shows superior catalytic performance toward methylene blue degradation.

White LED based on CsPbBr3 nanocrystal phosphors via a facile two-step solution synthesis route

All-inorganic CsPbBr3 perovskite nanocrystals with mean size of ∼300 nm were synthesized via a facile two-step solution synthesis route. High-resolution transmission electron microscopy and X-ray diffraction characterizations confirm the as-prepared CsPbBr3 nanoparticles are single-crystals with good crystallinity, although a CsPb2Br5 impure phase also exists in the final product. Power-/temperature-dependent and time-resolved photoluminescence measurements reveal the notable and stable excitonic emission feature of these CsPbBr3 nanocrystals. As a proof-of-concept demonstration, a LED with p-GaN/n-ZnO heterojunction as blue-violet excitation chip and CsPbBr3 nanocrystals as green phosphors, was fabricated and a white electroluminescence was achieved from this perovskite nanocrystals decorated LED.

Fully solution-induced high performance indium oxide thin film transistors with ZrO x high-k gate dielectrics.

Solution based deposition has been recently considered as a viable option for low-cost flexible electronics. In this context, research efforts have been increasingly focused on the development of suitable solution-processed materials for oxide based transistors. In this work, we report a fully solution synthesis route, using 2-methoxyethanol as solvent, for the preparation of In2O3 thin films and ZrOx gate dielectrics, as well as the fabrication of In2O3-based TFTs. To verify the possible applications of ZrOx thin films as the gate dielectric in complementary metal oxide semiconductor (CMOS) electronics, fully solution-induced In2O3 TFTs based on ZrO2 dielectrics have been integrated and investigated. The devices, with an optimized annealing temperature of 300 °C, have demonstrated high electrical performance and operational stability at a low voltage of 2 V, including a high μsat of 4.42 cm2 V−1 s−1, low threshold voltage of 0.31 V, threshold voltage shift of 0.15 V under positive bias stress for 7200 s, and large Ion/Ioff of 7.5 × 107, respectively. The as-fabricated In2O3/ZrOx TFTs enable fully solution-derived oxide TFTs for potential application in portable and low-power consumption electronics.

Silver and molybdenum disulfide nanoparticles synthesized in situ in dimethylformamide as dielectric for micro-electro discharge machining

The research focuses on the applicability of silver (Ag) and molybdenum disulfide (MOS2) nanoparticle synthesized in situ in dimethylformamide solution as dielectric material for micro-electro discharge machining. Ag nanoparticles (~120 nm size) and MOS2 nanoparticles (~20 nm size) were synthesized in dimethylformamide solution using a combination of nanoparticle solution synthesis routes. A setup for micro-electro discharge machining was developed in-house with an arrangement to generate spark at varying voltages. The setup was integrated with a precise linear height gauge to measure the spark gap during the experiments where Ag and MOS2 nanoparticles in dimethylformamide solution served as dielectric. The debris was collected and was characterized for each of the experiments. The feature size of the crater generated during the micro-electro discharge machining was also studied. The experiments were repeated with silver and MOS2 nanoparticle powder mixed with dimethylformamide as dielectric. It was observed that in situ prepared nanoparticles in dimethylformamide offered much better machining performance in terms of process stability, crater size and material removal rates. On use of in situ synthesized nanoparticle dielectric, the material removal rate increased by nearly two to three times whereas the spark gap increased by about two times.

Evaluation of Na2TiO3 formation for producing crystalline BaTiO3 nanoparticles by liquid–solid–solution process at low temperature

Crystalline barium titanate (BaTiO3) nanoparticles were synthesized by refluxing in an air atmosphere at a low temperature using sodium hydroxide. The reaction mechanism of BaTiO3 nanoparticle formation by this new liquid–solid–solution (LSS) synthesis route with refluxing in an air atmosphere at a low temperature of 80 °C was demonstrated to be a facile fabrication process for BaTiO3 nanoparticles with a high crystalline quality and minimized agglomeration rate. BaTiO3 nanoparticles were formed via sodium titanate (Na2TiO3), and the size of the BaTiO3 nanoparticles decreased with increasing sodium hydroxide concentration. The formation of a Na2TiO3 intermediate phase was confirmed by energy dispersive X-ray spectroscopy and X-ray diffraction analysis. The capping ligands of BaTiO3 suggest that hydroxyl and oleic acid are present. The dielectric constant of the crystalline BaTiO3 nanoparticles was higher than 150.

Comparative characterisations of structural and optical properties of zinc oxide modified by carbon nanotubes and graphene

In the present work, we report on the fabrications of ZnO/carbon nanotubes (CNTs) and ZnO/graphene composites based on a simple solution synthesis route. The effects of CNTs and graphene on the structure and optical properties of ZnO were investigated by X-ray diffraction (XRD), Raman scattering, optical absorption and photoluminescence measurements. The XRD patterns indicated that both CNTs and graphene could enhance the diffraction intensity of ZnO and the diffraction peaks shifted toward lower 2θ angles. The optical band gap of ZnO/CNTs and ZnO/graphene composites was narrower compared with that of undoped ZnO. Raman scattering spectra showed that the scattering intensities of both the oxygen atom and Zn sublattice-related phonon modes were reduced with the CNTs or graphene doping. The photoluminescence intensities of ZnO samples modified by both CNTs and graphene layers were significantly decreased compared with that of undoped ZnO owing to the interfacial charge-transfer between ZnO and CNTs (graphene).

Improved Low Temperature Solution Synthesis of Silicon Nanoparticles for Lithium-Ion Batteries

Silicon nanoparticles have extraordinary electrochemical performance for lithium-ion batteries. This paper gives an improved low temperature solution synthesis route of Si NPs. Reduced by magnesium and then passivated by four kinds of amines/amides respectively, stable yellow Si NPs ranging from 5-50 nm were prepared. When passivated by N-methyl-2-pyrrolidone, grape-like aggregation of 5-20 nm particles were generated. FTIR, XRD, SEM and Electrochemical Characterization were performed to confirm the product. The Si NPs passivated by NMP achieve good electrochemical performance with a first discharge capacity of 1154 mAhg-1at a current density of 200 mAg-1and good capacity retention of 95.3% after 5 cycles.

A novel non-vacuum process for the preparation of CuIn(Se,S)2 thin-film solar cells from air-stable, eco-friendly, metal salts based solution ink

A facile solution-based non-vacuum process for deposition of CuIn(Se,S)2 (CISeS) absorber layers is presented in this work, which indicates a promising way for the low-cost applications in thin-film solar cells. Firstly, low-boiling-point solvents Monobutylamine C4H11N and Carbon disulfide CS2 are selected as the complexing and thickening agents and added into the Cu/In metal salts based solution. Thus the air-stable, eco-friendly solution ink is successfully synthesized through a simple solution synthesis route. The detailed chemical reaction mechanism and the influence of the composition of precursor solution have been discussed intensively as well. After sequential spin-coating, hot-treatment and selenization process, the high-quality CISeS films are obtained and then characterized by XRD, Raman, SEM, EDS, Metallographic microscope, Hall Effect measurement and UV–vis–NIR spectroscopy, respectively. It is found that the compact CISeS films with chalcopyrite α-phase possess a double-layer structure, and also incorporate with a little ordered vacancy compounds (OVCs) and Cu2−xSe impurities. The typical near stoichiometric CISeS films without Carbon residuals have superior photoelectric properties with carrier concentration of 3.46 × 1016 N cm−3 and band gap of 1.15 eV. Finally, the original first-made PV devices provide a power conversion efficiency (PCE) of 4.25%, which can be further improved by increasing the thickness of CISeS films and/or optimizing the selenization and sulfuration technologies.