Optimization of high-yield biological synthesis of single-crystalline gold nanoplates

In this work, single-crystalline gold nanoplates were obtained by reducing aqueous chloroauric acid solution with the extract of Sargassum sp. (brown seaweed) at room temperature. The gold nanoplates so obtained were characterized by UV-vis spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy. The formation of gold nanoplates was found to depend on a number of environmental factors, such as the time taken to age the seaweed extract, pH of the reaction medium, reaction temperature, reaction time, and initial reactant concentrations. The size of the gold nanoplates could be controlled to between 200 and 800 nm by manipulating the initial reactant concentrations. The yield of the flat gold nanocrystals relative to the total number of nanoparticles formed was as high as approximately 80-90%.     

Rapid, large-scale synthesis and electrochemical behavior of faceted single-crystalline selenium nanotubes

This article describes a rapid, solution-phase approach to the large-scale synthesis of faceted single-crystalline Se nanotubes, in the presence of cetyltrimethylammonium bromide. The products were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, laser Raman spectrography, differential scanning calorimetry analysis, and thermogravimetric analysis. The growth mechanism of the Se nanotubes was investigated by a series of experiments, and the rationality of the faceted morphology model for the Se nanotubes was demonstrated from the energetics and geometry. Furthermore, the electrochemical behavior of the Se nanotubes was studied by voltammetric techniques.     

Metastable gamma-MnS hierarchical architectures: synthesis, characterization, and growth mechanism

Preparation of shape-controlled metastable gamma-MnS semiconductor nanocrystals has been achieved on a large scale through a simple solvothermal method in the presence of PVP. The key strategy is the use of sulfur powder as sulfur source in ethylene glycol (EG) solvent that also acted as a weak reducing agent. Reaction parameters such as reaction time and temperature are found to be important in controlling various hierarchical architectures, such as homogeneous semi-hollow core-shell, hollow nanospheres, and nanowires. Transmission electron microscopy observations indicate that these hierarchical architectures are formed mainly via Ostwald ripening. The optical absorption measurements reveal that these novel architectures exhibit remarkable shift of absorption peak during the course of structural compaction and grain growth.     

PbTe nanostructures: Microwave-assisted synthesis by using lead Schiff-base precursor,characterization and formation mechanism

Pure cubic phase lead telluride (PbTe) nanostructures have been produced by using a Schiff-base complex as a precursor in the presence of microwave irradiation. The Schiff base used as ligand was derived from salicylaldehyde and ethylenediamine. The Schiff-base complex was marked as [Pb(salen)]. In addition, the effect of the irradiation time and the type of reducing agent on the morphology and purity of the final products was investigated. The as-synthesized PbTe nanostructures were characterized extensively by techniques like X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The microwave formation mechanism of the PbTe nanostructures was studied by XRD patterns of the products. Although it was found that both ionic and atomic mechanisms could take place for the preparation of PbTe, the main steps were according to the atomic reaction process, which could occur between elemental Pb and Te.     

Selective synthesis of single-crystalline selenium nanobelts and nanowires in micellar solutions of nonionic surfactants

Single-crystalline nanobelts and nanowires of trigonal selenium (t-Se) have been selectively synthesized in micellar solutions of nonionic surfactants. In particular, t-Se nanobelts about 30 nm in thickness were obtained in micellar solutions of poly(oxyethylene(20)) octadecyl ether (C18EO20), whereas t-Se nanowires were obtained in micellar solutions of poly(oxyethylene(10)) dodecyl ether (C12EO10). The obtained t-Se nanobelts exhibit a low-energy absorption peak that is considerably red shifted from that for t-Se nanowires, which has been presumably attributed to the lower degree of crystal perfection for the t-Se nanobelts with rectangular cross sections.     

Practical,high-yield synthesis of thiol-terminated diacetylenes for formation of conductive monolayers

Self-assembled monolayers of thiol terminated conjugated diacetylenes can be cross-linked using ultraviolet light to form highly conjugated polydiacetylenic conductive monolayers [1]; however, the reported syntheses of the diacetylene monomers present numerous problems that prevent the wide spread application of these in functional materials. We report a redesigned four-step synthesis that proceeds in 75–80% overall yields and allows gram scale production of an array of thiol terminated conjugated diacetylenes, thereby allowing examination and application of these low-dimensional conductive materials.     

Imprinted polymer particles for selenium uptake: synthesis, characterization and analytical applications

This work reports the preparation of molecularly imprinted polymer (MIP) particles for selective extraction and determination of selenium ions from aqueous media. Polymerization was achieved in a glass tube containing SeO₂, o-phenylenediamine, 2-vinylpyridine (VP), ethyleneglycoldimethacrylate (EDMA), 2,2′-azobisisobutyronitrile (AIBN). The polymer block obtained was ground and sieved (55-75 μm) and the Se-o-phenylenediamine complex was removed from polymer particles by leaching with 2 M of HCl, which leaves a cavity in the polymer particles. The polymer particles both prior to and after leaching have been characterized by IR and thermogravimetric (TG) studies. The effect of different parameters, such as pH, extraction time, type and least amount of eluent for elution of complex from polymer were evaluated. Extraction efficiencies >99% were obtained by elution of the polymers with 15 mL of methanol-acetonitrile mixture (1:2, v/v). The limit of detection of the proposed method followed by hydride generation atomic absorption spectroscopy (HG-AAS) was found to be 3.3 μg L⁻¹ and a dynamic linear range (DLR) of 10-200 μg L⁻¹ was obtained. The relative standard deviations (R.S.D.s) at 30.0 μg L⁻¹ of Se were below than 8.1%. The influence of various cationic interferences on percent recovery of complex was studied. The method was applied to the recovery and determination of selenium in different real samples.     

Carbon monoxide-assisted synthesis of single-crystalline Pd tetrapod nanocrystals through hydride formation

Carbon monoxide can adsorb specifically on Pd(111) to induce the formation of unique Pd nanostructures. In the copresence of CO and H(2), single-crystalline Pd tetrapod nanocrystals have now been successfully prepared. The Pd tetrapods are enclosed by (111) surfaces and are yielded through hydride formation. Density functional theory calculations revealed that the formation of PdH(x) in the presence of H(2) reduces the binding energy of CO on Pd and thus helps to decrease the CO coverage during the synthesis, which is essential to the formation of the PdH(x) tetrapod nanocrystals. In addition to tetrapod nanocrystals, tetrahedral nanocrystals were also produced in the copresence of CO and H(2) when the reaction temperature was ramped to further lower the CO coverage. Upon aging in air, the as-prepared PdH(x) nanocrystals exhibited a shape-dependent hydrogen releasing behavior. The conversion rate of PdH(x) tetrapod nanocrystals into metallic Pd was faster than that of tetrahedral nanocrystals.     

Copolymer nanosphere encapsulated CdS quantum dots prepared by RAFT copolymerization: synthesis,characterization and mechanism of formation

Cadmium sulfide (CdS) quantum dots (QDs) encapsulated in block copolymer spheres were synthesized by an aqueous emulsion polymerization process. First, stable dispersions of CdS QDs in water were prepared using a polymer dispersant, either poly(acrylic acid) or a random copolymer having an average of ten acrylic acid and five butyl acrylate units. These polymer dispersants were prepared by reversible addition-fragmentation chain transfer polymerization. Then, the CdS QDs dispersed in water were encapsulated in a polystyrene shell using an emulsion polymerization process. Spectroscopic and microscopic techniques were used to characterize the resulting nanocomposites. Optical properties of QDs in polymer microspheres were investigated by UV-vis and fluorescence spectroscopic studies. Particle sizes of all CdS QD samples were calculated from absorption edges using Henglein's empirical curve. Transmission electron microscopy was used to determine the size and morphology of CdS QD samples. These observations were used to elucidate the mechanism of formation of the resulting well-defined polymer-encapsulated CdS nanoparticles.     

One-dimensional BiPO4 nanorods and two-dimensional BiOCl lamellae: fast low-temperature sonochemical synthesis,characterization, and growth mechanism

Regular BiPO4 nanorods, for the first time, and BiOCl lamellae have been successfully synthesized via a facile sonochemical method in a surfactant/ligand-free system under ambient air. The as-prepared products are characterized by XRD, TEM, SAED, FE-SEM, HRTEM, and Raman spectroscopy. The effects of pH and ultrasound irradiation on the phase and morphology of the products are studied and the sonochemical formation mechanisms of 1D and 2D structures are discussed. TEM data from samples made after different reaction times suggest an ultrasound-induced nucleation and an oriented-attachment growth mechanism.     

Hydrothermal synthesis of TiO2 nanorods: formation chemistry,growth mechanism,and tailoring of surface properties for photocatalytic activities

Titanium dioxide (TiO₂) is one of the best semiconductor photocatalysts with optical band gap of 3.2 eV. The optical band gap and photocatalytic properties could be further tuned by tailoring shape, size, composition, and morphology of the nanostructures. Hydrothermal synthesis methods have been applied to produce well-controlled nanostructured TiO₂ materials with different morphologies and improved optoelectronic properties. Among various morphologies, one-dimensional (1D) TiO₂ nanostructures are of great importance in the field of energy, environmental, and biomedical because of the directional transmission properties resulting from their 1D geometry. Particularly, TiO₂ nanorods (NRs) have gained special attention because of their densely packed structure, quantum confinement effect, high aspect ratio, and large specific surface area that could specially improve the directional charge transmission efficiency. This results in the effective photogenerated charge separation and light absorption, which are really important for potential applications of TiO₂-based materials for photocatalytic and other important applications. In this review, hydrothermal syntheses of TiO₂ NRs including the formation chemistry and the growth mechanism of NRs under different chemical environments and effects of various synthesis parameters (pH, reaction temperature, reaction time, precursors, solvents etc.) on morphology and optoelectronic properties have been discussed. Recent developments in the hydrothermal synthesis of TiO₂ NRs and tailoring of their surface properties through various modification strategies such as defect creation, doping, sensitization, surface coating, and heterojunction formation with various functional nanomaterials (plasmonic, oxide, quantum dots, graphene-based nanomaterials, etc.) have been reported to improve the photocatalytic activities. Furthermore, applications of TiO₂ NRs/tailored TiO₂ NRs as superior photocatalysts in degradation of organic pollutants and bacterial disinfection have been discussed with emphasis on mechanisms of action and recent advances in the fields.     

Recent advances in single-crystalline two-dimensional polymers: Synthesis,characterization and challenges

Two-dimensional polymers (2DPs) are emerging crystalline 2D organic material comprising free-standing, single-atom/monomer-thick, planar, and covalent networks with long-ranging structural order. Benefiting from their intrinsic porosity, crystallinity, and electrical properties, 2DPs have displayed great potential for separation, energy conversion and electronic fields. In this mini review, we aim to provide the recent progress in crystalline 2DPs films form synthesis strategies to characterization methods, as well as the future trends. We first present the synthesis strategy of single-crystalline 2DPs films including crystal engineering approaches and surface science. Also, we summarize the characterization methods of 2DPs films and highlight the advantages and limitations of different methods focusing on chemical bonding, morphology, and crystal structure. Finally, we will present the current challenges and trends regarding the future developments of crystallinity, monomer design, synthesis strategy and characterization.     

An innovative rhein-matrine cocrystal: Synthesis,characterization, formation mechanism and pharmacokinetic study

Rhein (Rhe), an anthraquinone derivative, exhibits excellent anti-inflammatory effects and other pharmacological activities, but its clinical application remains limited due to poor solubility. The present work aims at the improvement of solubility and oral bioavailability of Rhe through cocrystal formation. For this purpose, Rhe and matrine (Mat) were selected as pharmaceutical ingredient (API) and cocrystal former (CCF), respectively, and the Rhe-Mat cocrystal was synthesized and characterized by single crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC). The formation mechanism of Rhe-Mat cocrystal was elucidated by molecular surface electrostatic potential (MSEP). It is worth mentioning that the 50-fold increment of dissolution in vitro was observed in pure water in the form of Rhe-Mat cocrystal. Furthermore, the in vivo studies revealed that Rhe-Mat cocrystal indicated the faster absorption rate and the higher peak blood concentration than the pure Rhe. Hence, it can be concluded that current study successfully improved the solubility and oral bioavailability of Rhe.     

Exceptionally mild, high-yield synthesis of alpha-fluoro acrylates

Novel achiral and chiral alkyl alpha-(1,3-benzothiazol-2-ylsulfonyl)-alpha-fluoroacetates can be readily synthesized by metalation-fluorination of (1,3-benzothiazol-2-ylsulfonyl)acetates. DBU-mediated condensations of these fluorinated synthons with aldehydes proceed in a facile manner at 0 degrees C or at room temperature giving high yields of alpha-fluoro acrylates. Ketones are unreactive under these conditions. The presence of fluorine renders the synthon substantially more reactive compared to the unfluorinated analogue. Reactivity of alpha-(1,3-benzothiazol-2-ylsulfonyl)-alpha-fluoroacetate and the Horner-Wadsworth-Emmons reagent (EtO)2P(O)CHFCOOEt has also been compared.     

Extending the series: synthesis and characterization of a dicationic N-heterocyclic selenium carbene analogue

The room-temperature reaction between the Dipp2DAB ligand, SnCl2, and SeCl4 results in the quantitative formation of a dicationic N-heterocyclic "carbenoid". This represents the first example of a chalcogenium dication that mimics the ubiquitous Arduengo-type carbenes; however, the electronic structure is significantly different.     

Large-Scale, solution-phase growth of single-crystalline SnO2 nanorods

Small-diameter (<5 nm), single-crystalline SnO2 nanorods were synthesized in solution with a mean length of 17 +/- 4 nm (mean aspect ratio of 4:1) with the [001] direction along the major axis. Two characteristic peaks at 576 and 356 cm-1 in the Raman spectrum further confirmed the small crystal size. The SnO2 nanorods exhibit a red emission at 580 nm.     

Fe3O4 nanostructures: synthesis, growth mechanism, properties and applications

Recent progress in research on Fe(3)O(4) nanocrystals has attracted much attention both for investigating fundamental nanomagnetism and their potential applications in nanocatalysis, biosensing, magnetic resonance imaging (MRI) contrast agents and drug delivery. In this feature article, we provide an overview of synthetic strategies and growth mechanisms of various Fe(3)O(4) nanostructures, discuss the uniqueness of associated properties, and illustrate their potential applications.     

Fabrication and characterization of single-crystalline ZnTe nanowire arrays

Semiconductor ZnTe nanowire arrays have been synthesized by the pulsed electrochemical deposition from aqueous solutions into porous anodic alumina membranes. X-ray diffraction analyses show that the as-synthesized nanowires have a highly preferential orientation. Scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy indicate that high-filling, ordered, and single-crystalline nanowire arrays have been obtained. The optical absorption spectra of the nanowire arrays show that the optical absorption band edge of the ZnTe nanowire array exhibits a blue shift compared with that of bulk ZnTe. The growth mechanism and the electrochemical deposition process are discussed together with the chemical compositions analysis.