Solution-phase Technique Research Articles

Towards the Synthesis of a Heterocyclic Analogue of Natural Cyclooligopeptide with Improved Bio-properties.

The present investigation is targeted towards the synthesis of a novel analogue of a natural peptide of marine origin. Marine sponges are enriched with bioactive secondary metabolites, especially circu-lar peptides. Heterocycles are established organic compounds with potential biological value. Tak-ing into consideration the bio-properties of heterocycles and marine sponge-derived natural pep-tides, an effort was made for the synthesis of a heterocyclic analogue of a natural cyclopeptide. A heterocyclic analogue of a sponge-derived proline-containing cyclic peptide, rolloam-ide A, was synthesized by interaction of Boc-protected L-histidinyl-L-prolyl-L-valine and L-prolyl-L-leucyl-L-prolyl-L-isoleucine methyl ester and compared with synthetic rolloamide A with bioac-tivity against bacteria, fungi, and earthworms. The synthesis of cycloheptapeptide was accomplished employing the liquid phase method. The larger peptide segment was prepared by interaction of Boc-protected L-prolyl-L-leu-cine with L-prolyl-L-isoleucine methyl ester. Similarly, the tripeptide unit was synthesized from Boc-protected L-histidinyl-L-proline with L-valine ester. The linear heptapeptide segment (7) was cyclized by utilizing pentafluorophenyl (pfp) ester, and the structure was elucidated by elemental and spectral (IR, 1H/13C NMR, MS) analysis. The peptide was also screened for diverse bioactivities such as antibacterial, antifungal, and potential against earthworms and cytotoxicity. The novel cyclooligopeptide was synthesized with 84% yield by making use of car-bodiimides. The synthesized cyclopeptide exhibited significant cytotoxicity against two cell lines. In addition, promising antifungal and antihelmintic properties were observed for newly synthesized heterocyclic peptide derivative (8) against dermatophytes and three earthworm species at 6 μg/mL and 2 mg/mL, respectively. Solution-phase technique employing carbodiimide chemistry was established to be promising for synthesizing the cycloheptapeptide derivative (8), and C5H5N was proved to be a better base for heptapeptide circling when compared to N-methylmorpholine and triethylamine.

In-situ solution phase synthesis of LiFePO4@VSe2 composite as highly active cathode for Li-ion batteries

Surface engineering of transition metal oxide cathode materials for Li-ion batteries is highly important to achieve high-capacity retention, high-rate capability, and long-life term. In this study, VSe2 nanosheets are prepared and used as a surface sensitizer to enhance the electrochemical properties of LiFePO4 (LFP) cathode material. The LiFePO4 @VSe2 (LFP@VSe2) composite is formed by anchoring 1D-LFP particles with the as-prepared 2D-VSe2 nanosheets by using an in-situ solution phase technique. When the LFP@VSe2 composites are used as cathode materials for Li-ion batteries, the Li surface-controlled storage behavior of the batteries is reasonably enhanced. The performance is attributed to the improvement in the inherent Li-ion conductivity of LFP particles, thereby inhibiting surface diffusion drawbacks and decreasing charge transfer resistance. The exterior VSe2 attached to the LFP serves as a second electrically conducting layer to increase conductivity into the entire electrode. Thus, these conditions enhance the electron transfer kinetics and surface stability of the LFP cathode. LFP@VSe2 composite cathode exhibits an ultrastable specific capacity of 166.5 mAh g−1 after 100 cycles @ 0.1 C and can retain a specific capacity of 146.7 and 46.5 mAh g−1 after 700 and 2000 cycles respectively at a current rate of 0.3 C and 10 C.

Mass production of self-passivated perovskite microlaser particles by solution-phase processing for gas sensors

Developing mass-productive and high-performance microlaser particles (MLPs) by cost-effective approaches is highly promising for MLP-based optoelectronic applications, which remains a daunting challenge. Herein, we develop a novel solution-phase technique to realize the halide perovskite-based MLPs in a scalable manner. By regulating the dynamic process of crystallization in a two-step spin-coating procedure, the large-scale CsPbBr3 microcrystals are acquired. Importantly, the solution-processed CsPbBr3 microcrystals exhibit much stronger emission than the ones prepared by the chemical vapor deposition method, which is attributed to the low carrier trap density by the formation of a self-passivated and bromine-rich surface. These CsPbBr3 microcrystals with inverted pyramid morphology are demonstrated to support the whispering-gallery mode lasing, featuring low pump threshold and high Q-factor. Moreover, the technologically important single-mode lasing is achieved from the sub-5 μm-sized MLPs, thanks to the superior optical property. Eventually, the laser-emission-based gas sensor is demonstrated. These results represent a significant step toward scalable MLPs and related applications.

A simple approach for sensing and accurate prediction of multiple organic vapors by sensors based on CuO nanowires

• CuO nanowires have been synthesized using a facile solution phase method. • The room-temperature operability of CuO sensors were developed for methanol, acetone and acetonitrile and might aid in reducing the power requirements of the sensors. • A simple algorithm was developed in this research that could predict the vapors fairly accurately. • The prediction accuracy of the algorithm was improved when high-temperature data was included with room temperature data. • This work includes integration and application of knowledge of different domains to aid in prototype and product development. Development of sensors that can sense volatile organic compounds (VOCs) efficiently is imperative for different real-life applications. This paper reports synthesis of CuO nanowires using a facile solution-phase technique. The samples were found to have monoclinic polycrystalline structure when characterized using an X-ray diffractometer (XRD). The morphology was confirmed to be nanowires with diameter of approximately 10 nm when studied using field emission scanning electron microscope (FESEM), and the bandgap of the CuO nanowires was found to be 1.9 eV when characterized using UV–vis spectroscopy. The CuO nanowires based sensors were tested for five different concentrations (500–7000 ppm) of methanol, acetone, and acetonitrile at room temperature (25 °C) and four different concentrations (500–5000 ppm) of the three vapors at 200 °C. At room temperature, the response of the sensor ranged between 4.3 % and 29.9 %, 0.83 % and 14.7 %, and 1 % and 7 % for 500–7000 ppm methanol, acetonitrile, and acetone respectively. The response of the sensor was observed to be ranging between 13 % and 70 %, 150 % and 700 %, and 610 % and 2300 % for 500–5000 ppm of methanol, acetonitrile, and acetone respectively when tested at 200 °C. A novel and simple algorithm was developed that considered the initial 60 s responses of CuO nanowires exhibited for methanol, acetone, and acetonitrile at room temperature and at 200 °C and could predict the vapors along with their concentrations accurately.

Controlled synthesis of two-dimensional (2-D) ultra-thin bismuth selenide (Bi2Se3) nanosheets by bottom-up solution-phase chemistry and its electrical transport properties for thermoelectric application

Bismuth Selenide and associated compounds inheriting stacked layered structure represent a unique class of materials where bulks are insulating with conducting surfaces, best known as thermoelectric materials. The bottom-up solution-based approach is a convenient alternative producing ultrathin high quality two-dimensional Bi2Se3 nanosheets. The present investigation deals with glycol mediated synthesis of highly crystalline ultrathin Bi2Se3 nanosheets. The as-synthesized Bi2Se3 nanosheets exhibit a rhombohedral crystal structure with a substantial surface-to-volume ratio that can possess several potential applications. Besides, the ultrathin Bi2Se3 nanosheets produced herein, found to be n-type with robust spatial confinement of charge carriers advantageous for thermoelectric applications, delivering a high-power factor of 1.55 μW/cmK2 at 150 °C. The method demonstrates the generic feature of the solution phase technique for the synthesis of highly crystalline nanosheets allowing mass production of identical ultra-thin nanosheets that can be easily integrated into devices for several promising applications, including spintronics, energy storage, and topological quantum computation.

Study on Aging and Recover of Poly (Lactic) Acid Composite Films with Graphene and Carbon Nanotubes Produced by Solution Blending and Extrusion

The aging, annealing, and reprocessing of the biodegradable poly (lactic) acid (PLA) based composite films incorporating graphene and carbon nanotubes were investigated in this work. Various monofiller and bifiller nanocomposite films with 6 wt.% filler content were produced by a solution-phase technique followed by extrusion. The freshly produced films were compared with the aged films after 18 months of shelf life in a room environment. The effects of aging, annealing, and melt reprocessing on the crystalline structure, the thermal stability, the hardness, and Young’s modulus were analyzed by differential scanning calorimetry (DSC), TGA, and nanoindentation methods. The fresh and the aged samples were found to have semi-crystalline materials with 3%–7% crystallinity, while the crystallinity was significantly enhanced to 34%–38% by annealing at 80 °C and subsequent slow cooling. A good dispersion was observed in the bifiller films with filler ratios of 4.5:1.5 and 1.5:4.5 [graphene nanoplatelets (GNP) to carbon nanotubes (CNT)], which affected the crystallization processes. The reprocessing at 200 °C followed by fast cooling resulted in amorphous films, which significantly reduced the hardness and Young’s modulus. The nanoindentation properties were dependent on the dispersion of nanofillers at the surfaces. The efficiency of annealing and reprocessing for the recovery and the reuse of aged nanocomposite films is discussed herein. The paper underlines that properties of the nanocomposites under investigation were influenced not only by the composition, the chemical nature of the added filler, and the processing condition, but also by the aging processes, which in turn depended on the type of nanopartcles added to PLA and the compositions. The paper provides valuable information for selection of material and processing conditions.

Two-step synthesis of self-assembled 3D graphene/shuttle-shaped zinc oxide (ZnO) nanocomposites for high-performance microwave absorption

A unique three-dimensional (3D) structure nanocomposites composed of 3D graphene and shuttle-shaped ZnO nanoparticles (3DGZ) were fabricated via a novel and facile two-step synthetic method in a solution phase technique. The microwave absorption properties of 3DGZ nanocomposites with different ZnO proportions were investigated. Morphology analysis showed that the shuttle-shaped ZnO nanoparticles were uniformly scattered on and embedded into 3D graphene without any aggregation, which is favorable to enhance the interfacial polarization. The sample 3DGZ-2 displayed the most outstanding microwave absorption performance. A minimum reflection loss of −48.05 dB was obtained at 11.71 GHz with a thickness of 1.82 mm, and the RL exceeding −10 dB were acquired in the frequency range covering from 12.98 to 17.06 GHz at a given thickness of 1.5 mm. Considering the outstanding performance of 3DGZ nanocomposites, we believe it has great potential to be used as a highly effective, lightweight, excellent heat stable and tunable microwave absorber.

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.

Rationally designed ultrathin Ni-Al layered double hydroxide and graphene heterostructure for high-performance asymmetric supercapacitor

A novel 3 dimensional (3D) heterostructure that is composed of exfoliated Ni-Al layered double hydroxide nanosheet and reduced graphene oxide (Ni-Al LDH/rGO) is synthesized by adopting a simple and feasible solution-phase technique. The unique hierarchical heterostructure has a stable layered structure, more active sites and fast electron transport channels, which play an important role for improving the cycle stability and rate capacity performance. The prepared Ni-Al LDH/rGO electrode exhibits excellent performance with a capacitance of 629.8 C g−1 at 1 A g−1, and a high specific capacitance of 471.6 C g−1 even at a high current density of 20 A g−1. The asymmetric supercapacitor (ASC) fabricated by using the Ni-Al LDH/rGO as the positive electrode and using active carbon (AC) as the negative electrode, which exhibits a high energy density of 58.6 Wh kg−1 at the power density of 359 W kg−1 and remains good cycle stability. The superior electrochemical properties are due to the 3D heterostructure, where the large specific surface area of rGO nanosheets serve as a conductive 2D backbone successfully offset structure limitation by the potential synergistic effect. The exfoliated ultrathin Ni-Al LDH nanosheets with only a few atomic layers in this architecture are expected to provide large reactive active sites for fast charge transfer. Therefore, the unique 3D heterostructure is favorable for stabilizing crystal structure and enhancing capability and cycling stability for pseudocapacitors during the charge−discharge process.

Following a Folding Transition with Capillary Electrophoresis and Ion Mobility Spectrometry.

Ion mobility spectrometry (IMS) is increasingly used to describe solution-phase phenomena and has recently been used to establish the presence of multiple intermediates during the folding of a model polypeptide, polyproline. These observations, however, are made on gas-phase structures. Capillary electrophoresis (CE) is a complementary solution-phase technique, also based on the separation of charged species as a function of size and charge. Here, both ion mobility and capillary electrophoresis are used to follow the folding transition of a 13-mer polyproline peptide from the all-cis polyproline I (PPI) conformation to the all-trans polyproline II (PPII) conformation upon immersion in aqueous solvent. Synchronous folding processes are observed using both techniques. Eight conformers are observed using ion mobility. Although only five peaks are observed using capillary electrophoresis, these peaks can be modeled as sums of the observed IMS conformers; this is strong evidence that ion mobility is sampling solution-phase structures. CE measurements provide the first direct evidence that multiple folding intermediates are present in solution.

Metal nanoparticle assisted growth of assembled zinc oxide nanostructure by low temperature solution phase technique

Herein we report metal nanoparticle directed growth of assembled zinc oxide nanostructures by a facile solution phase route. Si substrates with silver nanoparticles are subjected to low temperature hydrothermal growth. Coulombic attraction resulted in migration of Zn growth species onto Ag nanoparticle surface. SEM analysis revealed preferential nucleation and growth of zinc oxide nanostructures on Ag nanoparticles. Longer reaction period lead to formation of mulberry like assembled ZnO nanostructures. XRD analysis confirmed growth of zinc oxide nanostructures. The formed ZnO nanostructures exhibit well defined band edge PL peak corresponding to excitonic recombination.

Construction of Hierarchical α-MnO2 Nanowires@Ultrathin δ-MnO2 Nanosheets Core-Shell Nanostructure with Excellent Cycling Stability for High-Power Asymmetric Supercapacitor Electrodes.

Poor electrical conductivity and mechanical instability are two major obstacles to realizing high performance of MnO2 as pseudocapacitor material. The construction of unique hierarchical core-shell nanostructures, therefore, plays an important role in the efficient enhancement of the rate capacity and the stability of this material. We herein report the fabrication of a hierarchical α-MnO2 nanowires@ultrathin δ-MnO2 nanosheets core-shell nanostructure by adopting a facile and practical solution-phase technique. The novel hierarchical nanostructures are composed of ultrathin δ-MnO2 nanosheets with a few atomic layers growing well on the surface of the ultralong α-MnO2 nanowires. The first specific capacitance of hierarchical core-shell nanostructure reached 153.8 F g(-1) at the discharge current density of as high as 20 A g(-1), and the cycling stability is retained at 98.1% after 10,000 charge-discharge cycles, higher than those in the literature. The excellent rate capacity and stability of the hierarchical core-shell nanostructures can be attributed to the structural features of the two MnO2 crystals, in which a 1D α-MnO2 nanowire core provides a stable structural backbone and the ultrathin 2D δ-MnO2 nanosheet shell creates more reactive active sites. The synergistic effects of different dimensions also contribute to the superior rate capability.

GaN nanostructures-poly(vinyl alcohol) composite based hydrostatic pressure sensor device

The wide band-gap semiconductor material gallium nitride was synthesized using a one step microwave-assisted solution phase technique. The synthesized GaN nanocrystals showed an intense ultraviolet-blue emission typical of GaN materials. Hydrostatic pressure sensors were fabricated using a GaN/polyvinyl alcohol (PVA) composite film deposited onto an interdigitated electrode and studied by measuring the change in alternating current conductance of the devices at varied applied pressures. Three different GaN concentrations of 29, 50 and 67% were used. A very high sensitivity in the range 100–200 kPa was observed for these devices. The composite devices demonstrated both response and recovery times of less than 16 s.

Efficient and Large Scale Synthesis of Graphene from Coal and Its Film Electrical Properties Studies

Coal, which is abundant and has an incompact structure, is a good candidate to replace graphite as the raw material for the production of graphene. Here, a new solution phase technique for the preparation of graphene from coal has been developed. The precursor: graphene oxide got from coal was examined by atomic force microscopy, dynamic light scattering and X-ray diffraction, the results showed the GO was a small and single layer sheet. The graphene was examined by X-ray photoelectron spectroscopy, and Raman spectroscopy. Furthermore, graphene films have been prepared using direct solution process and the electrical conductivity and Hall effect have been studied. The results showed the conductivity of the films could reach as high as 2.5 x 10(5) Sm(-1) and exhibited an n-type behavior.

Novel rGO/α-Fe2O3 composite hydrogel: synthesis, characterization and high performance of electromagnetic wave absorption

A novel 3D composite hydrogel composed of reduced graphene oxide nanosheets and α-Fe2O3 nanoparticles (rGO/α-Fe2O3) was synthesized via a two-step process in a solution phase technique. The experimental results show the composite has an interconnected 3D porous network with micrometer pores, and the α-Fe2O3 nanoparticles with the size of about 50–100 nm are uniformly dispersed onto the thin graphene nanosheets. The rGO/α-Fe2O3 composite hydrogel exhibits excellent microwave absorbability. Compared to a pristine reduced graphene oxide (rGO) hydrogel, the reported composite hydrogel has both wider and stronger wave absorption achieved in the frequency range of 1–18 GHz. The composite with a coating layer thickness of 5.0 mm exhibits a maximum absorption of −33.5 dB at 7.12 GHz and in particular, the product with a coating layer thickness of only 3.0 mm shows a bandwidth of 6.4 GHz (from a frequency of 10.8–17.2 GHz) corresponding to reflection loss at −10 dB. The excellent microwave absorption properties are ascribed to the improved impedance matching. Our findings pave a way to design and prepare lightweight and high performance electromagnetic wave absorption materials based on 3D graphene and other nanomaterials.

Bi- and trilayer graphene solutions

Bilayer and trilayer graphene with controlled stacking is emerging as one of the most promising candidates for post-silicon nanoelectronics. However, it is not yet possible to produce large quantities of bilayer or trilayer graphene with controlled stacking, as is required for many applications. Here, we demonstrate a solution-phase technique for the production of large-area, bilayer or trilayer graphene from graphite, with controlled stacking. The ionic compounds iodine chloride (ICl) or iodine bromide (IBr) intercalate the graphite starting material at every second or third layer, creating second- or third-stage controlled graphite intercolation compounds, respectively. The resulting solution dispersions are specifically enriched with bilayer or trilayer graphene, respectively. Because the process requires only mild sonication, it produces graphene flakes with areas as large as 50 µm(2). Moreover, the electronic properties of the flakes are superior to those achieved with other solution-based methods; for example, unannealed samples have resistivities as low as ∼1 kΩ and hole mobilities as high as ∼400 cm(2) V(-1) s(-1). The solution-based process is expected to allow high-throughput production, functionalization, and the transfer of samples to arbitrary substrates.

Toward the Synthesis and Biological Screening of a Cyclotetrapeptide from Marine Bacteria

The first synthesis of a naturally occurring tetrapeptide cyclo-(isoleucyl-prolyl-leucyl- alanyl) has been achieved using a solution-phase technique via coupling of dipeptide segments Boc-l-Pro-l-Leu-OH and l-Ala-l-Ile-OMe. Deprotection of the linear tetrapeptide unit and its subsequent cyclization gave a cyclopeptide, identical in all aspects to the naturally occurring compound. Bioactivity results indicated the antifungal and antihelmintic potential of the synthesized peptide against pathogenic dermatophytes and earthworms.

Total Synthesis and Antimicrobial Activity of a Natural Cycloheptapeptide of Marine Origin

The present study deals with the first total synthesis of the proline-rich cyclopolypeptide stylisin 2 via a solution phase technique by coupling of the Boc-l-Pro-l-Ile-l-Pro-OH tripeptide unit with the l-Phe-l-Pro-l-Pro-l-Tyr-OMe tetrapeptide unit, followed by cyclization of the resulting linear heptapeptide fragment. The chemical structure of the finally synthesized peptide was elucidated by FTIR, 1H/13C-NMR and FAB MS spectral data, as well as elemental analyses. The newly synthesized peptide was subjected to antimicrobial screening against eight pathogenic microbes and found to exhibit potent antimicrobial activity against Pseudomonas aeruginosa, Klebsiella pneumoniae and Candida albicans, in addition to moderate antidermatophyte activity against pathogenic Trichophyton mentagrophytes and Microsporum audouinii when compared to standard drugs—gatifloxacin and griseofulvin.

Solution Synthesis of a New Thermoelectric Zn1+xSb Nanophase and Its Structure Determination Using Automated Electron Diffraction Tomography

Engineering materials with specific physical properties have recently focused on the effect of nanoscopic inhomogeneities at the 10 nm scale. Such features are expected to scatter medium- and long-wavelength phonons thereby lowering the thermal conductivity of the system. Low thermal conductivity is a prerequisite for effective thermoelectric materials, and the challenge is to limit the transport of heat by phonons, without simultaneously decreasing charge transport. A solution-phase technique was devised for synthesis of thermoelectric "Zn(4)Sb(3)" nanocrystals as a precursor for phase segregation into ZnSb and a new Zn-Sb intermetallic phase, Zn(1+delta)Sb, in a peritectoid reaction. Our approach uses activated metal nanoparticles as precursors for the synthesis of this intermetallic compound. The small particle size of the reactants ensures minimum diffusion paths, low activation barriers, and low reaction temperatures, thereby eliminating solid-solid diffusion as the rate-limiting step in conventional bulk-scale solid-state synthesis. Both phases were identified and structurally characterized by automated electron diffraction tomography combined with precession electron diffraction. An ab initio structure solution based on electron diffraction data revealed two different phases. The new pseudo-hexagonal phase, Zn(1+delta)Sb, was identified and classified within the structural diversity of the Zn-Sb phase diagram.

A simple solution route to assemble three-dimensional (3D) carbon nanotube networks

Three-dimensional (3D) carbon nanotube networks (CNNW) have been successfully constructed by a simple solution route for the first time. The as-obtained networks consist of the ordered alignment of nanotubes cross-linked with a joint-angle of approximately 90°. Also, the joint points in the networks are very stable and the hollowing joints are conducted with the neighbored carbon nanotubes. These network characteristics would receive much attention to the applications such as electrical conductivity and even mass transport. Further work found that the as-obtained CNNW and CNNW/silver composites can both be applied as NH3 gas sensors. The solution-phase technique for the construction of CNNWs made the assembling networks possible without introducing physical and complicated methodologies, providing an alternative way for the next generation carbon nanotube assembly.