Solution-phase Synthesis Research Articles

In-Plane Anisotropic Faceting of Ultralarge and Thin Single-Crystalline Colloidal SnS Nanosheets.

The colloidal synthesis of large, thin two-dimensional (2D) nanosheets is fascinating but challenging, since the growth along the lateral and vertical dimensions needs to be controlled independently. In-plane anisotropy in 2D nanosheets is attracting more attention as well. We present a new synthesis for large colloidal single-crystalline SnS nanosheets with the thicknesses down to 7 nm and lateral sizes up to 8 μm. The synthesis uses trioctylphosphine-S (TOP-S) as sulfur source and oleic acid (with or without trioctylphosphine, TOP) as ligands. Upon adjusting the capping ligand amount, the growth direction can be switched between anisotropic directions (armchair and zigzag) and isotropic directions ("ladder" directions), leading to an edge-morphology anisotropy. This is the first report on solution-phase synthesis of large thin tin(II) sulfide (SnS) nanosheets (NSs) with tunable edge faceting. Furthermore, electronic transport measurements show strong dependency on the crystallographic directions confirming structural anisotropy.

Direct solution-phase synthesis of 1T\u2019 WSe2 nanosheets

Crystal phase control in layered transition metal dichalcogenides is central for exploiting their different electronic properties. Access to metastable crystal phases is limited as their direct synthesis is challenging, restricting the spectrum of reachable materials. Here, we demonstrate the solution phase synthesis of the metastable distorted octahedrally coordinated structure (1T’ phase) of WSe2 nanosheets. We design a kinetically-controlled regime of colloidal synthesis to enable the formation of the metastable phase. 1T’ WSe2 branched few-layered nanosheets are produced in high yield and in a reproducible and controlled manner. The 1T’ phase is fully convertible into the semiconducting 2H phase upon thermal annealing at 400 °C. The 1T’ WSe2 nanosheets demonstrate a metallic nature exhibited by an enhanced electrocatalytic activity for hydrogen evolution reaction as compared to the 2H WSe2 nanosheets and comparable to other 1T’ phases. This synthesis design can potentially be extended to different materials providing direct access of metastable phases.

Shape-selective isolation of Au nanoplates from complex colloidal media by depletion flocculation

Au nanoplates represent an emerging class of plasmonic nanostructures of anisotropy that are promising great performance as a probe in biosensing and a building block for nanodevices. In spite of the rapid development of solution-phase synthesis, it has remained an open challenge for colloidal chemists to prepare Au nanoplates in high yield established for their Ag counterparts. This limitation largely compromises the practical use of Au nanoplates in plasmonic applications. Here we report a simple yet versatile approach for efficient purification of Au nanoplates in diverse colloidal mixtures based upon micelle-induced depletion flocculation. By means of calculation on free energy change upon depletion flocculation, we are able to pre-determine the flocculation conditions of different nanoparticles, allowing for predictable nanoparticle precipitation that depends on size and shape. We further demonstrate that the present approach is capable of isolating Au nanoplates of varied sizes in low yield (<10%) in various complex media, including a polyvinylpyrrolidone (PVP)-based colloid solution and a quadruple nanoparticle mixture. This post-synthesis purification method that doesn’t rely on professional background suggests wide applicability in extraction of frontier nanostructures at low abundance yet in high demand.

Crystalline Facet-Directed Generation Engineering of Ultrathin Platinum Nanodendrites.

In this work, we successfully prepare two-dimensional ultrathin single-crystalline platinum nanodendrites (PtNDs) with precisely controlled generation (size) through a surfactant-directed solution-phase synthesis. The amphiphilic surfactant of C22H45-N+(CH3)2CH2COOH (Br-) acts as the structure-directing template and facet-capping agent simultaneously to kinetically engineer in-the-plane epitaxial growth of Pt nanocrystals along selectively exposed {111} facets into ultrathin PtNDs. A novel formation mechanism defined as crystalline facet-directed step-by-step in-the-plane epitaxial growth, similar to the synthesis of organic dendrimers, is proposed on the basis of the nanostructure and crystalline evolution of PtNDs. The generation growth process is readily extended to precisely engineer the generation of PtNDs (from 0 to 25) and can also be utilized to grow other noble metal NDs (e.g., PdNDs and AuNDs) and core-shell Pt-Pd NDs. Because of the structural advantages, ultrathin PtNDs exhibit enhanced electrocatalytic performance toward hydrogen evolution reaction.

Microbe-focused glycan array screening platform

Interactions between glycans and glycan binding proteins are essential for numerous processes in all kingdoms of life. Glycan microarrays are an excellent tool to examine protein-glycan interactions. Here, we present a microbe-focused glycan microarray platform based on oligosaccharides obtained by chemical synthesis. Glycans were generated by combining different carbohydrate synthesis approaches including automated glycan assembly, solution-phase synthesis, and chemoenzymatic methods. The current library of more than 300 glycans is as diverse as the mammalian glycan array from the Consortium for Functional Glycomics and, due to its microbial focus, highly complementary. This glycan platform is essential for the characterization of various classes of glycan binding proteins. Applications of this glycan array platform are highlighted by the characterization of innate immune receptors and bacterial virulence factors as well as the analysis of human humoral immunity to pathogenic glycans.

Cu induced low temperature ordering of fct-FePtCu nanoparticles prepared by solution phase synthesis

Cu doping can occupy the Fe sites in the FePt lattice, contract c axis and increase atom diffusivity, favoring atoms rearrangement and phase transformation from fcc to fct at lower temperature.

Novel defect-fluorite pyrochlore sodium niobate nanoparticles: solution-phase synthesis and radiation tolerance analysis.

Materials possessing a defect-fluorite pyrochlore structure can have a range of useful properties that are sought after, which include their radiation tolerance, nuclear waste immobilization, and phase stability at elevated temperatures. In this study, we demonstrate for the first time the synthesis and a detailed analysis of defect-fluorite pyrochlore sodium niobate (NaNbO3) nanoparticles. This analysis included an investigation into their stability to elevated temperatures and neutron irradiation. A surfactant-assisted solvothermal method is used to prepare nanoparticles of NaNbO3. This solution-phase approach results in the formation of crystalline nanoparticles of a defect-fluorite pyrochlore NaNbO3 at relatively low temperatures. The products had an average diameter of ∼74 ± 11 nm. The nanoparticles adopted a defect-fluorite pyrochlore phase and matched the cubic Fm3[combining macron]m space group. This pyrochlore form of NaNbO3 was found to be stable up to 500 °C. The nanoparticles transformed into the orthorhombic and rhombohedral perovskite phases of NaNbO3 along with the introduction of a pseudo-hexagonal Nb2O5 at higher temperatures. These defect-fluorite pyrochlore nanoparticles of NaNbO3 also exhibited a resistance to radiation induced amorphization. The dimensions, phase, and crystallinity of the defect-fluorite pyrochlore nanoparticles after exposure to a flux of neutrons were comparable to those of the as-synthesized product. The thermal stability and radiation tolerance of these pyrochlore nanoparticles could be useful in the design of thermally resilient materials, high temperature catalysts, and durable materials for the handling and storage of radioactive waste.

Direct comparison of solution and solid phase synthesis of sequence-defined macromolecules

Sequence-defined macromolecules of high molecular weight are synthesised by the combination of click chemistry with multicomponent reactions. The synthesis is performed on solid phase as well as in solution to directly compare the two approaches.

Preparation, Characterization and Properties of Newly Synthesized SnO2-Polycarbazole Nanocomposite via Room Temperature Solution Phase Synthesis Process

Abstract The introduction of inorganic metal oxide nanoparticles in a polymer matrix is found to significantly modulate its optical, electrical and electrochemical properties. Here, we report the one-pot synthesis of SnO2-polycarbazole (PCz) nano composite via solution phase technique (in situ chemical oxidative polymerization route) for the first time. The morphological and compositional analyses of these organic-inorganic hybrid nano composites were done by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), the Fourier transform infrared (FTIR) spectroscopy and ultraviolet-visible (UV–visible) spectroscopy. The successful loading of SnO2 nanoparticles by PCz was apparent from FESEM micrographs. UV-Visible spectroscopy revealed that optical property of the pristine PCz was significantly revamped after incorporation of SnO2 nanoparticles. The Synergetic interactions between polycarbazole and tin oxide nanoparticles were apparent from the FTIR and XRD spectra. Thermal stability of the material estimated by Thermo gravimetric (TGA) analysis; which shows thermal strength is significantly increased after incorporation of SnO2 nanoparticles in the PCz matrix. The I-V curve shows good ohmic contact of the material with tin electrode and electrical conductivity of the material is significantly altered with varying the loading percentage of SnO2 nano particles in PCz matrix.

One-pot synthesis of sub-10nm LiNbO3 nanocrystals exhibiting a tunable optical second harmonic response.

Nanophotonics, dealing with the properties of light interacting with nanometer scale materials and structures, has emerged as a sought after platform for sensing and imaging applications, and is impacting fields that include advanced information technology, signal processing circuits, and cryptography. Lithium niobate (LiNbO3) is a unique photonic material, often referred to as the “silicon of photonics” due to its excellent optical properties. In this article, we introduce a solution-phase method to prepare single-crystalline LiNbO3 nanoparticles with average diameters of 7 nm. This one-pot approach forms well-dispersed LiNbO3 nanocrystals without additional organic additives (e.g., surfactants) to control growth and aggregation of the nanoparticles. Formation of these LiNbO3 nanocrystals proceeds through a non-aqueous sol–gel reaction, in which lithium hydroxide and niobium hydroxide species were generated in situ. The reaction proceeded through both a condensation and crystallization of these reactants to form the solid nanoparticles. These nanocrystals of LiNbO3 were active for optical second harmonic generation (SHG) with a tunable response from 400 to 500 nm. These nanoparticles could enable further development of non-linear optical techniques such as SHG microscopy for bioimaging, which requires the dimensions of nanoparticles to be well below 100 nm.

Instantaneous, room-temperature, open-air atmosphere, solution-phase synthesis of perovskite quantum dots through halide exchange employing non-metal based inexpensive HCl/HI: ensemble and single particle spectroscopy.

Herein, the instantaneous synthesis of highly crystalline, uniform-sized (ca. 11.3 ± 0.1 nm), blue-to-green to yellow to red-emitting all-inorganic perovskite quantum dots (CsPbBr3 and mixed halide PQDs) was achieved at room temperature under an open-air atmosphere (no glove box) through halide exchange in the solution phase employing easily available, inexpensive non-metal-based halide sources such as HCl and HI. No complicated pre-treatment of the halide source was required. Moreover, these PQDs were stable for a few weeks under an open-air atmosphere. The PL emission spectra are quite narrow, and the PLQYs are quite high (80% for even Br/I mixed PQDs). At the single particle level, the 〈ON fraction〉 has been noted to vary from 75% to 85% for different PQDs, the mON values are close to 1.0, and the mOFF values are >1.5. The latter indicates that long ON durations are more probable. The increase in the ON event truncation time (from 2.7 to 4.0 s) and the concomitant decrease in the OFF event truncation time (from 6.6 to 4.3 s) could be correlated with the increase in the PLQY (from 0.55 to 0.75). In addition, an interesting memory effect could be observed in both the ON and the OFF event durations.

Solution-phase synthesis of CsPbI3 nanowire clusters via polymer-induced anisotropic growth and self-assembly.

A facile solution-phase synthesis of black γ-phase CsPbI3 nanowire clusters was developed using poly(methyl methacrylate) (PMMA) as surfactant. PMMA was found to efficiently retard the crystal growth, thereby inducing anisotropic growth for formation of the nanowire structure, while the intermolecular hydrogen bonds of PMMA act as a driving force for self-assembly of the nanowires.

Solution-phase synthesis of two-dimensional silica nanosheets using soft templates and their applications in CO2 capture.

The solution-phase synthesis of silica nanosheets with tunable thickness and textural properties is still a challenge. We have developed a robust protocol to synthesize silica nanosheets using lamellar micelles as soft templates in a water-cyclohexane solvent mixture. The synthesized silica nanosheets (∼3.7 nm) possess significantly improved textural properties, with as high as 1420 m2 g-1 surface area and 3.47 cm3 g-1 pore volume. When functionalized with tetraethylenepentamine (TEPA) molecules using a physisorption method, the silica nanosheets showed a CO2 working capture capacity of 3.8 mmol g-1 at 75 °C with fast capture kinetics and good sorbent stability.

Solid phase synthesis and self-assembly of higher-order siRNAs and their bioconjugates.

New methods for the synthesis of higher-order siRNA motifs and their bioconjugates have recently gained widespread attention in the development of new and improved gene therapeutics. Our efforts aim to produce new chemical tools and protocols for the generation of modified siRNAs that screen for important oncogene targets as well as silence their activity for effective gene therapy in cancer models. More specifically, we have developed an efficient solution-phase synthesis for the production of a ribouridine branchpoint synthon that can be effectively incorporated by solid phase synthesis within higher-order RNA structures, including those adopting V-, and Y- and >-< shape RNA templates. Self-assembly of complementary RNA to the template strands produced higher-order siRNA nanostructures that were characterized by a combination of PAGE, DLS, and TEM techniques. In an effort to extend the repertoire of functionally diverse siRNAs, we have also developed solid phase bioconjugation strategies for incorporating bio-active probes such as fatty acid appendages and fluorescent reporters. Taken together, these methods highlight the ability to generate higher-order siRNAs and their bioconjugates for exploring the influence of modified siRNA structure on anti-cancer activity.

Catalyst-Assisted Solution-Liquid-Solid Synthesis of CdS/CuInSe2 and CuInTe2/CuInSe2 Nanorod Heterostructures.

Axial nanowire heterostructures composed of cadmium sulfide (CdS)/copper indium diselenide (CuInSe2) and copper indium telluride (CuInTe2)/copper indium diselenide (CuInSe2) were synthesized by a solution-liquid-solid (SLS) method with the catalyzer of bismuth nanocrystals. Electron microscopy and diffraction studies show CuInTe2 and CuInSe2 segments growing along the [112] direction with a clear epitaxial interface between them. In CdS/CuInSe2 nanorod heterostructures, CuInSe2 and CdS segments grow along the [112] and [111] direction, respectively, with an obvious epitaxial interface between them. Energy-dispersive X-ray spectrometry demonstrates the alloy-free composition modulation in two nanorod heterostructures. In CuInTe2/CuInSe2 nanorod heterostructures, Te and Se are localized in CuInTe2 and CuInSe2 segments, respectively. Cu/In/Se and Cd/S are localized in the CuInSe2 and CdS sections of the CdS/CuInSe2 nanorod heterostructures. This research confirms that the SLS mechanism provides a general alternate technique to prepare multicomponent axial 1D heterostructures that have been difficult to generate by using either catalyst-free solution-phase synthesis or vapor-liquid-solid growth.

Wavelength-Tunable Band-Edge Photoluminescence of Nonstoichiometric Ag-In-S Nanoparticles via Ga3+ Doping.

The nonstoichiometry of I-III-VI semiconductor nanoparticles, especially the ratio of group I to group III elements, has been utilized to control their physicochemical properties. We report the solution-phase synthesis of nonstoichiometric Ag-In-S and Ag-In-Ga-S nanoparticles and results of the investigation of their photoluminescence (PL) properties in relation to their chemical compositions. While stoichiometric AgInS2 nanoparticles simply exhibited only a broad PL band originating from defect sites in the particles, a narrow band edge PL peak newly appeared with a decrease in the Ag fraction in the nonstoichiometric Ag-In-S nanoparticles. The relative PL intensity of this band edge emission with respect to the defect-site emission was optimal at a Ag/(Ag + In) value of ca. 0.4. The peak wavelength of the band edge emission was tunable from 610 to 500 nm by increased doping with Ga3+ into Ag-In-S nanoparticles due to an increase of the energy gap. Furthermore, surface coating of Ga3+-doped Ag-In-S nanoparticles, that is, Ag-In-Ga-S nanoparticles, with a GaS x shell drastically and selectively suppressed the broad defect-site PL peak and, at the same time, led to an increase in the PL quantum yield (QY) of the band edge emission peak. The optimal PL QY was 28% for Ag-In-Ga-S@GaS x core-shell particles, with green band-edge emission at 530 nm and a full width at half-maximum of 181 meV (41 nm). The observed wavelength tunability of the band-edge PL peak will facilitate possible use of these toxic-element-free I-III-VI-based nanoparticles in a wide area of applications.

Facile synthesis of the magnetic metal–organic framework Fe3O4/Cu3(BTC)2 for efficient dye removal

Dyeing wastewaters present high hazards for the environment and human health. Advanced dye removal may be achieved by magnetic metal–organic frameworks (MMOFs) due to their high adsorption and catalyst efficiencies. However, the existing synthesis strategies of frameworks are often cumbersome and time-consuming in the presence of toxic solvents. Hence, a simple and environmentally-friendly synthetic method is desired. Here, a kind of MMOF, Fe3O4/Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate), was synthesized via a novel aqueous solution-phase synthesis. The product Fe3O4/Cu3(BTC)2 has a high specific surface area of 755.15 m2 g−1, and excellent magnetic performance of 31.2 emu g−1. The Fe3O4/Cu3(BTC)2 can effectively remove methylene blue from wastewater in the presence of H2O2. After having been finished the dye removal, it was easily separated and recycled several times by use of the magnetic technology.

Peptide Synthesis Utilizing Micro-flow Technology.

Peptide drugs have garnered much attention in recent years. However, conventional peptide synthesis requires an excess amount of expensive reagents of low atom economy, and the large amount of waste produced by these reagents complicates the purification of desired peptides. Solid-phase approaches simplify the purification of these peptides, but these require expensive solid-phase, excess amounts of reagents, substrates, and solvents. This makes it important to develop high-yielding, cost-effective, and less wasteful synthetic approaches. Micro-flow technology (reaction space ≤1 mm) has produced many advantages over conventional batch synthesis. The advantages include precise control of short reaction time and temperature, high levels of light penetration efficiency, lowered risks of handling dangerous compounds, and ready scale-up with high reproducibility. Micro-flow peptide syntheses using these advantages have been reported in recent years. This review summarizes the solid-phase and solution-phase syntheses of α- and β-peptides and of cyclic peptides using micro-flow technology.

Single-Crystal Electrochemistry Reveals Why Metal Nanowires Grow

Shape-control is used to tune the properties of metal nanostructures in applications ranging from catalysts to touch screens, but the origins of anisotropic growth of metal nanocrystals in solution are unknown. We show single-crystal electrochemistry can test hypotheses for why nanostructures form and predict conditions for anisotropic growth by quantifying the degree to which different species cause facet-selective metal deposition. Electrochemical measurements show disruption of alkylamine monolayers by chloride ions causes facet-selective Cu deposition. An intermediate range of chloride concentrations maximizes facet-selective Cu deposition on single crystals and produces the highest aspect ratio nanowires in a solution-phase synthesis. DFT calculations similarly show an intermediate monolayer coverage of chloride displaces the alkylamine capping agent from the ends but not the sides of a nanowire, facilitating anisotropic growth.

Investigation for the cyclization efficiency of linear tetrapeptides: Synthesis of tentoxin B and dihydrotentoxin

Investigation of the cyclization efficiency of N-methyl linear tetrapeptides using a molecular modeling study and chemical synthesis is described. The linear peptide with two N-methyl groups, MeAla-Leu-MePhe-Gly, forms γ-turn like conformation with the amine at N-terminus and the carbonyl at C-terminus in closer proximity to give the desired cyclic tetrapeptide, dihydrotentoxin. In addition, synthesis of tentoxin B by the combination of Fmoc solid-phase peptide synthesis and cyclization in solution phase has been reported. An unusual amino acid, an L-N-methyl-β-hydroxyphenylalanine derivative, which was assembled on solid support, was prepared from ethyl cinnamate. Cyclic tetrapeptide formation and cleavage of benzyl ether were optimized with DIPCI/HOBt/DIPEA and Et3SiH/Pd(OH)2, respectively.