Chemical Solution Synthesis Research Articles

Wet-Chemical Synthesis of Elemental 2D Materials.

Wet-chemical synthesis refers to the bottom-up chemical synthesis in solution, which is among the most popular synthetic approaches towards functional two-dimensional (2D) materials. It offers several advantages, including cost-effectiveness, high yields,, precious control over the production process. As an emerging family of 2D materials, elemental 2D materials (Xenes) have shown great potential in various applications such as electronics, catalysts, biochemistry,, sensing technologies due to their exceptional/exotic properties such as large surface area, tunable band gap,, high carrier mobility. In this review, we provide a comprehensive overview of the current state-of-the-art in wet-chemical synthesis of Xenes including tellurene, bismuthene, antimonene, phosphorene,, arsenene. The current solvent compositions, process parameters utilized in wet-chemical synthesis, their effects on the thickness, stability of the resulting Xenes are also presented. Key factors considered involves ligands, precursors, surfactants, reaction time, temperature. Finally, we highlight recent advances, existing challenges in the current application of wet-chemical synthesis for Xenes production, provide perspectives on future improvement.

Facile Ball Milling Preparation of Flame-Retardant Polymer Materials: An Overview

To meet the growing needs of public safety and sustainable development, it is highly desirable to develop flame-retardant polymer materials using a facile and low-cost method. Although conventional solution chemical synthesis has proven to be an efficient way of developing flame retardants, it often requires organic solvents and a complicated separation process. In this review, we summarize the progress made in utilizing simple ball milling (an important type of mechanochemical approach) to fabricate flame retardants and flame-retardant polymer composites. To elaborate, we first present a basic introduction to ball milling, and its crushing, exfoliating, modifying, and reacting actions, as used in the development of high-performance flame retardants. Then, we report the mixing action of ball milling, as used in the preparation of flame-retardant polymer composites, especially in the formation of multifunctional segregated structures. Hopefully, this review will provide a reference for the study of developing flame-retardant polymer materials in a facile and feasible way.

Laser-machined thin copper films on silicon as physical unclonable functions.

Physical unclonable functions (PUFs) are receiving significant attention with the rise of cryptography and the drive towards creating unique structures for security applications and anti-counterfeiting. Specifically, nanoparticle based PUFs can produce a high degree of randomness through their size, shape, spatial distribution, chemistry, and optical properties, rendering them very difficult to replicate. However, nanoparticle PUFs typically rely on complex preparation procedures involving chemical synthesis in solution, therefore requiring dispersion, and embedding within a host medium for application. We propose laser machining of surfaces as a one-step process for the creation of complex nanoparticle based PUFs by machining 600 nm thick copper films on a silicon substrate to yield a complex spatial and chemical distribution of redeposited copper, silicon, and oxide species. The approaches and material system investigated have potential applications in silicon chip authentication.

High Velocity, Low-Voltage Collective In-Plane Switching in (100) BaTiO3 Thin Films.

Ferroelectrics are being increasingly called upon for electronic devices in extreme environments. Device performance and energy efficiency is highly correlated to clock frequency, operational voltage, and resistive loss. To increase performance it is common to engineer ferroelectric domain structure with highly‐correlated electrical and elastic coupling that elicit fast and efficient collective switching. Designing domain structures with advantageous properties is difficult because the mechanisms involved in collective switching are poorly understood and difficult to investigate. Collective switching is a hierarchical process where the nano‐ and mesoscale responses control the macroscopic properties. Using chemical solution synthesis, epitaxially nearly‐relaxed (100) BaTiO3 films are synthesized. Thermal strain induces a strongly‐correlated domain structure with alternating domains of polarization along the [010] and [001] in‐plane axes and 90° domain walls along the [011] or [011¯] directions. Simultaneous capacitance–voltage measurements and band‐excitation piezoresponse force microscopy revealed strong collective switching behavior. Using a deep convolutional autoencoder, hierarchical switching is automatically tracked and the switching pathway is identified. The collective switching velocities are calculated to be ≈500 cm s−1 at 5 V (7 kV cm−1), orders‐of‐magnitude faster than expected. These combinations of properties are promising for high‐speed tunable dielectrics and low‐voltage ferroelectric memories and logic.

Stable and Bright CsPbX3 Nanocrystals in Metal–Organic Frameworks for White Light-Emitting Diodes

The stability of metal halide perovskite (CsPbX3, X = Cl, Br, and I) nanocrystals (NCs) is crucial for their practical applications. In this paper, perovskite NCs were synthesized in situ in lead-based metal-organic frameworks (Pb-MOFs: [Pb2(1,3,5-HBTC)2(H2O)4]·H2O), and we obtained stable and bright luminescence composites with different colors. Namely, CsPbBr3@Pb-MOF composites were created by the in situ growth of CsPbBr3 crystals (NCs) on Pb-MOF, which had high ion resistance, bright photoluminescence (PL), and excellent stability. The composites still had bright luminescence after 11 months of storage. The PL intensity of green-emitting CsPbBr3@Pb-MOF composites was increased compared with as-prepared CsPbBr3 NCs. Bright and stable blue- and red-emitting CsPbX3@Pb-MOF composites were obtained by adjusting the amount of PbX2 (X = Cl, Br, and I) in the synthesis process. These CsPbX3 NCs were homogeneously distributed in Pb-MOF substrates. The growth of CsPbX3 NCs in Pb-MOFs prevented NC aggregation and decreased surface defects against nonradiative recombination during emitting. Thus, the PL lifetime and stability were improved. Furthermore, white light-emission diodes were prepared using three color CsPbX3@Pb-MOF composites with Commission Internationale de I'Eclairage color coordinates of (0.296, 0.316). This result provided an efficient way to overcome the limitation of chemical solution synthesis and improve the stability of CsPbX3 NCs.

PO4 3- Coordinated Robust Single-Atom Platinum Catalyst for Selective Polyol Oxidation.

Achieving efficient catalytic conversion over a heterogeneous catalyst with excellent resistance against leaching is still a grand challenge for sustainable chemical synthesis in aqueous solution. Herein, we devised a single-atom Pt1 /hydroxyapatite (HAP) catalyst via a simple hydrothermal strategy. Gratifyingly, this robust Pt1 /HAP catalyst exhibits remarkable catalytic selectivity and catalyst stability for the selective oxidation of C2 -C4 polyols to corresponding primary hydroxy acids. It is found that the Pt-(O-P) linkages with strong electron-withdrawing function of PO4 3- (Pt1 -OPO4 3- pair active site) not only realize the activation of the C-H bond, but also destabilize the transition state from adsorbed hydroxy acids toward the C-C cleavage, resulting in the sharply increased selectivity of hydroxy acids. Moreover, the strong PO4 3- -coordination effect provides electrostatic stabilization for single-atom Pt, ensuring the highly efficient catalysis of Pt1 /HAP for over 160 hours with superior leaching resistance.

PO43− Coordinated Robust Single‐Atom Platinum Catalyst for Selective Polyol Oxidation**

AbstractAchieving efficient catalytic conversion over a heterogeneous catalyst with excellent resistance against leaching is still a grand challenge for sustainable chemical synthesis in aqueous solution. Herein, we devised a single‐atom Pt1/hydroxyapatite (HAP) catalyst via a simple hydrothermal strategy. Gratifyingly, this robust Pt1/HAP catalyst exhibits remarkable catalytic selectivity and catalyst stability for the selective oxidation of C2–C4 polyols to corresponding primary hydroxy acids. It is found that the Pt−(O−P) linkages with strong electron‐withdrawing function of PO43− (Pt1−OPO43− pair active site) not only realize the activation of the C−H bond, but also destabilize the transition state from adsorbed hydroxy acids toward the C−C cleavage, resulting in the sharply increased selectivity of hydroxy acids. Moreover, the strong PO43−‐coordination effect provides electrostatic stabilization for single‐atom Pt, ensuring the highly efficient catalysis of Pt1/HAP for over 160 hours with superior leaching resistance.

Piezoelectric properties of PZT by an ethylene glycol-based chemical solution synthesis

We have investigated a water-stable sol–gel method based on ethylene glycol as a solvent and bridging ligand for the synthesis of ferroelectric lead zirconate titanate in bulk and thin film forms. This method offers lower toxicity of the solvent, higher stability toward atmospheric moisture and a simplified synthetic procedure compared to traditional sol–gel methods. However, the piezoelectric properties of products produced using this method have yet to be systematically studied. We have measured the ferroelectric and piezoelectric properties and compared them to existing literature using different synthesis techniques. Ceramic pellets of Nb-doped lead zirconate titanate (PNZT) in the tetragonal phase were produced with high density and good piezoelectric properties, comparable to those reported in the literature and those found in commercial piezoelectric elements. In addition, a nine-layer thin film stack was fabricated by spin coating onto platinized silicon substrates. The films were crack-free and showed a perovskite grain structure with a weak (111) orientation. Piezoelectric measurements of the film showed a piezoelectric coefficient comparable to literature values and good stability toward fatigue.

V2O5 nanocrystals: Chemical solution synthesis, hydrogen thermal treatment and enhanced rate capability as cathode materials for lithium-ion batteries

Vanadium pentoxide (V2O5) is regarded as a promising cathode material for high-performance lithium-ion batteries (LIBs). In this study, V2O5 nanocrystals with an elongated plate-like morphology are prepared via a chemical solution approach that involves the hydrolyzation of vanadyl sulfate in alkaline solution. Oxygen vacancies are intentionally created by thermal treating the V2O5 samples under hydrogen-containing gases at different temperatures. Although the annealing process does not change the shape, morphology and crystalline structure of V2O5 nanocrystals, it does bring about a small amount of oxygen vacancies, as evidently from the results of XRD patterns and Raman spectra. The presence of oxygen vacancies has positive effects on the electrochemical properties. A higher initial discharge capacity, and excellent rate capability and cycling stability are observed on the oxygen vacancy-containing V2O5 samples. Especially, the sample annealed at 350 °C is found to have an initial capacity of 284 mAh g−1and the capacity still maintains at about 153 mAh g−1 even at 10 C. The combination of nanoscale dimension and oxygen vacancies in V2O5 nanocrystals presents a simple way to improve their rate capability and cycling stability for potential high-performance LIB applications.

The chemistry of Amino Acid and Peptides via Solution-Phase-Peptide Synthesis

In this review, we have presented the different chemical structures of proteinogenic amino acids. Also, we performed a precise reference scan of the proton balance of amino acids. It is worth noting that, the two most important parts in this review are the principles of chemical peptide synthesis in solution and the protection of the amino acid side group, so we focused the reference survey on them, and we reached many old and new references in these two important parts in the field of peptide synthesis. On the other hand, we also performed an important reference survey of peptide-coupling methodologies. Finally, in this review we presented an important part, the use of peptide coupling reagents, in this part; we focused on the most important and most popular methods used in peptide chemistry reactions.

Comparative Solution Synthesis of Mn Doped (Na,K)NbO3 Thin Films.

(K0.5 Na0.5 )NbO3 (KNN) is a promising lead-free alternative for ferroelectric thin films such as Pb(Zr,Ti)O3 . One main drawback is its high leakage current density at high electric fields, which has been previously linked to alkali non-stoichiometry. This paper compares three acetate-based chemical solution synthesis and deposition methods for 0.5 mol % Mn-doped KNN film fabrication, using lower crystallization temperature processes in comparison to the sintering temperatures necessary for fabrication of KNN ceramics. This paper shows the crucial role of the A site homogenization step during solution synthesis in preserving alkali chemical homogeneity of Mn doped KNN films. Chemically homogeneous films show a uniform grain size of 80 nm and a leakage current density under 2.8×10-8 A cm-2 up to electric fields as high as 600 kV cm-1 , which is the highest breakdown strength reported for KNN thin films. Solution synthesis involving two-step pyrolysis resulted in films with dense, columnar microstructures, which are interesting for orientation control and enhancement of piezoelectric properties. This study reports detailed solution synthesis and deposition processes with good dielectric, ferroelectric and breakdown field properties. An optimized fabrication method that should couple low leakage current density with dense and oriented microstructures is proposed.

On-Surface Intramolecular Reactions.

In the past decade, on-surface chemistry has provided fascinating concepts for the construction of covalently bonded molecular nanostructures and the exploration of new synthetic pathways that may be different from chemical synthesis in solution. Although the intermolecular reaction of precursor molecules may lead to the formation of the desired low-dimensional molecular architectures, it remains challenging to realize defect-free syntheses over large areas. Recently, intramolecular on-surface reactions have attracted increasing attention because they offer promising ways to synthesize functional organic molecules, especially those with extended conjugated π-systems. In this Perspective, we summarize the recent achievements in the field of on-surface intramolecular reactions and discuss future prospects.

Selective Phase Control of Dopant-Free Potassium Sodium Niobate Perovskites in Solution.

As one of the perovskite families, potassium sodium niobates (K1-xNax)NbO3 (KNN) have been gaining tremendous attention due to their various functional properties which can be largely determined by their crystallographic phase and composition. However, a selective evolution of different phases for KNN with controlled composition can be difficult to achieve, especially in solution chemical synthesis because of its strong tendency to stabilize into orthorhombic phase at conventional synthetic temperature. We herein developed a facile solution approach to control the phase and composition of dopant-free KNN particles selectively through the modification of reaction parameters. A conventional hydrothermal synthesis method yielded orthorhombic KNN particles, while the monoclinic phase, which has never been observed in a bulk counterpart, was kinetically generated by the compositional modification of an intermediate phase under a high-intensity ultrasound irradiation. Cubic KNN particles were stabilized when ethylene glycol was used as a co-solvent together with deionized water through bonding between ethylene glycol molecules and the surface of the KNN. Composite-structured piezoelectric harvesters were fabricated using each phase of KNN particles and the β-phase poly(vinylidene fluoride-co-trifluoroethylene) polymer. Maximum output power was found for the harvester containing orthorhombic KNN particles. This facile synthetic methodology could pave a new pathway for fabricating numerous phase-controlled materials.

Design and Synthesis of New Protease‐Triggered CO‐Releasing Peptide–Metal‐Complex Conjugates

Aiming at the development of novel protease‐triggered CO‐releasing molecules (PT‐CORMs) we designed a series of oxycyclohexadiene‐Fe(CO)3 complexes, which are connected through a self‐immolative linker with a plasmin‐specifying peptide unit. The challenging synthesis of these compounds was elaborated employing a combination of solid‐phase peptide synthesis and solution chemical synthesis. Late‐stage attachment of the organometallic unit and Pd‐catalyzed cleavage of an alloc‐protected lysine side chain afforded the target compounds in good yields and high purity.

Phosphate Ion-Modified RuO₂/Ti₃C₂ Composite as a High-Performance Supercapacitor Material.

Pseudocapitor materials, usually metal oxides, are used as active materials in an electrode to achieve high energy density. However, these kinds of materials often suffer from poor conductivity and high cost. Herein, a phosphate ion-modified RuO2/Ti3C2 composite is prepared via a chemical solution synthesis followed by an annealing process. In this composite material, Ti3C2 layers are introduced to improve the conductivity and the binary material is doped with phosphate ions into to increase the number of active reaction sites. As a result, the phosphate ion-modified RuO2/Ti3C2 delivers a high specific capacitance of 612.72 F g−1 at a current density of 2 A g−1 in H2SO4 electrolyte. What is more, the capacitance of the phosphate ion-modified RuO2/Ti3C2 can retain 97.95% (600.14 F g−1) of the original value even after 10,000 cycles at a current density of 2 A g−1.

Interface-Assisted Synthesis of 2D Materials: Trend and Challenges.

The discovery of graphene one decade ago has triggered enormous interest in developing two-dimensional materials (2DMs)-that is 2D allotropes of various elements or compounds (consisting of two or more covalently bonded elements) or molecular frameworks with periodic structures. At present, various synthesis strategies have been exploited to produce 2DMs, such as top-down exfoliation and bottom-up chemical vapor deposition and solution synthesis methods. In this review article, we will highlight the interfacial roles toward the controlled synthesis of inorganic and organic 2DMs with varied structural features. We will summarize the state-of-the-art progress on interfacial synthesis strategies and address their advancements in the structural, morphological, and crystalline control by the direction of the arrangement of the molecules or precursors at a confined 2D space. First, we will provide an overview of the interfaces and introduce their advantages and uniqueness for the synthesis of 2DMs, followed by a brief classification of inorganic and organic 2DMs achieved by interfacial synthesis. Next, the currently developed interfacial synthesis strategies combined with representative inorganic and organic 2DMs are summarized, including the description of method details, the corresponding structural features, and the insights into the advantages and limitations of the synthesis methods, along with some recommendable characterization methods for understanding the interfacial assembly of the precursors and crystal growth of 2DMs. After that, we will discuss several classes of emerging organic 2DMs with particular emphasis on the structural control by the interfacial synthesis strategies. Note that, inorganic 2DMs will not be categorized separately due to the fact that a number of review articles have covered the synthesis, structure, processing, and applications. Finally, the challenges and perspectives are provided regarding the future development of interface-assisted synthesis of 2DMs with diverse structural and functional control.

Polymer-assisted chemical solution synthesis of La0.8Sr0.2MnO3-based perovskite with A-site deficiency and cobalt-doping for bifunctional oxygen catalyst in alkaline media

The polymer-assisted chemical solution (PACS) method was used for the synthesis of La0.8Sr0.2MnO3 (LSM)-based perovskite catalyst network with nanoparticle size of 30–80 nm to enhance oxygen evolution reaction (OER) activity and maintain highly active oxygen reduction reaction (ORR). Samples investigated include the A-site cation deficient (La0.8Sr0.2)0.95MnO3-δ (ALSM) and the A-site cation deficient with the B-site cobalt-doped (La0.8Sr0.2)1-xMn1-xCoxO3-δ (x = 0.05 and 0.1 for LSMC5 and LSMC10, respectively). X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) aided in physical characterizations. Electrochemical properties were tested in 0.1 M KOH solution by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Our results indicate as compared to LSM, the lattice-shrunk ALSM with high oxygen vacancy displays enhanced OER performance, but its inferior ORR activity could be caused by reduced crystallinity. LSMC5 and LSMC10 show lowest total overpotential (0.93 and 0.91 V vs. Ag/AgCl (3.5 M)) with slightly less efficient ORR, despite their superior specific kinetic current density. Oxygen vacancy induces Fermi level upshift and reduced resistivity, while Co-doping increases orbital hybridization and enhances charge transfer. Understanding how the A-site non-stoichiometry and the B-site doping influence the BO covalence is the key to the rational design of perovskite bifunctional oxygen catalysts.

A simple chemical solution synthesis of nanowire-assembled hierarchical CuO microspheres with enhanced photochemical properties

Hierarchical micro/nanostructures manifest attractive prospects for photocatalytic application. Nevertheless, large-scale hierarchical micro/nanostructures for industrial application with facile, low-cost and eco-friendly routes remain difficult. Herein, nanowire-assembled hierarchical CuO microspheres (HCMAW) are synthesized for the first time by CO32- ions induced synthesis route. The time-dependent SEM images reveal that the growth mechanism for HCMAW is the well-known Ostwald ripening with self-assembly. The specific surface area of the HCMAW is 7.265 m2 g-1, which is higher than that of hierarchical CuO microspheres assembled with nanosheets (HCMAS) (4.952 m2 g-1) prepared by direct self-assembly scheme without the introduction of CO32- ions. Meanwhile, the HCMAW possess strong light absorption around a broadband wavelength from 300 nm to 800 nm. As a result, the photodegradation activity test demonstrates that the HCMAW shows the degradation efficiency of 98.8% for rhodamine B (RhB) under white light irradiation for 30 min in the presence of H2O2 higher than those of HCMAS (66.3%) and commercial CuO (48.3%) under the same condition, which is one of the highest reported till date related to CuO nanomaterials for the degradation of RhB. The novel HCMAW synthesized by the ion-induced protocol is worth being generalized to more assembled hierarchical micro/nanostructures for versatile applications.

Chemical solution synthesis and ferromagnetic resonance of epitaxial thin films of yttrium iron garnet

Cubic Yttrium Iron Garnet (YIG) is a technologically important material due to its excellent magneto-optical properties, high electrical resistivity, and a very narrow ferromagnetic resonance, which makes it particularly suitable for applications in filters and resonators at microwave frequencies. These properties depend on the precise stoichiometry and distribution of Fe${}^{3+}$ ions among the octahedral/tetrahedral sites of a complex structure, which required the use of high-vacuum deposition methods for the fabrication of high-quality YIG thin films. In this paper the authors report the synthesis of nanometer-thick epitaxial films of YIG by a simple water-based chemical method. The films show a long spin relaxation time, comparable to that obtained from high-vacuum physical deposition methods. These results demonstrate that chemical methods can compete to develop nanometer-thick YIG films with the quality required for spintronic devices and other high-frequency applications.

Hexagonal plate-shaped CuSe nanocrystals by polylol solution chemical synthesis

ABSTRACT(0001)-oriented hexagonal klockmannite CuSe nanoplates were successfully synthesized by polylol solution chemical method, in which triethylene glycol (TEG), triethylenetetramine (TETA) and polyvinylpyrrolidone (PVP) were used as the reaction solvent, reducing agent and capping agent, respectively. The influence of synthesis temperature, TETA adding amounts and refluxing time was mainly investigated.