An efficient synthesis of (±)-β-herbertenol by a 1,3-cyclopentadione annelation strategy

A simple and efficient synthesis of sesquiterpene (±)-β-herebertenol is described. The formation of cyclopentadione onto the aromatic moiety is the key feature of this protocol.     

Applicability of the Mayo–Lewis equation to high conversion copolymerization of styrene and methylmethacrylate

In contradiction to reports from this and other laboratories, this study reports that the integrated Mayo–Lewis equation, or Meyer–Lowery equation, adequately describes the high-conversion free radical copolymerization of styrene and methylmethacrylate. The copolymerization was monitored by following the changes in the feed composition using NMR, as well as determination of the resulting copolymer compositions by NMR and UV. “Error in all Variables” statistical techniques were used to produce estimates of the reactivity ratios. The reactivity ratios estimated were, from feed composition, NMR, r₁ (styrene) = 0.472, r₂ = 0.454, from copolymer composition, UV, r₁ = 0.497, r₂ = 0.464, and NMR, r₁ = 0.432, r₂ = 0.422.     

Simple approach to access tricyclic spiro dihydrofurans in a one-pot reaction

A simple and efficient one-pot protocol is accomplished to access tricyclic spiro dihydrofurans (4) by the reaction of β-enamino ketones (1) and dimedone (2) in ethanol followed by sequential addition of N-chlorosuccinimide at ambient temperature for the first time. The selectivity in desired product formation in good yields is the advantage of this protocol.     

Selective oxidation of metallic single-walled carbon nanotubes

In this work we present a simple and non-invasive approach to the preparation of semi-conducting single-walled carbon nanotubes (SWCNTs) through selective destruction of the metallic counterparts present in the starting material. Most separation techniques require chemical treatment, the application of ultrasound, or the addition of auxiliary molecules, which lead to the introduction of defects and impurities. In this contribution, laser ablation SWCNTs were selectively oxidised via long-term heating leading to the enrichment of semi-conductive nanotubes. Spectroscopic analysis demonstrates that the selective character of oxidation occurs only in the optimal temperature range, determined by thermo-gravimetric analysis. By tuning the process parameters, one can obtain a sample exhibiting different purity (up to 95 % of semi-conducting nanotubes) and separation efficiency. The samples’ quality and yield of separation were determined by UV-VIS-NIR spectroscopy, Raman spectroscopy, and TG analysis. The approach presented is readily scaleable.     

Comparison of different soft chemical routes synthesis of nanocrystalline LiMn2O4 and their influence on its physicochemical properties

A comparative study of nanocrystalline spinel LiMn₂O₄ powders prepared by two different soft chemical routes such as solution and sol-gel methods using lithium and manganese acetates are the precursors under different calcination temperatures. The dependence of the physicochemical properties of the spinel LiMn₂O₄ powder has been extensively investigated by using thermal analysis (TGA/DTA), FTIR, X-ray diffraction studies, SEM, specific surface area (BET) and electrical conductivity measurements. The results show that pure LiMn₂O₄ can be prepared from acetate precursors as starting materials at a low temperature of 600°C from solution route and 500°C from sol-gel method. The charge-discharge characteristics and the cycling behavior of Li/1M LiBF₄-EC/DEC electrolyte / LiMn₂O₄cells revealed that LiMn₂O₄ calcined at higher temperatures showed a high initial capacity, while the LiMn₂O₄calcined at lower temperatures exhibited a good cycling behavior.     

A novel catalyst-free synthesis of vertically aligned silicon nanowire-carbon nanotube heterojunction arrays for high performance electron field emitters

A novel, catalyst-free strategy for the direct synthesis of vertically aligned silicon nanowire-carbon nanotube (SiNW-CNT) heterojunction arrays is presented. Such a heterojunction with the junction area in the nanoscale displays enhanced field emission characteristics at low turn-on field, with a nearly three times increase in the field enhancement factor.     

Application of an electrodynamic balance to the study of particle-fluid interactions

An electrodynamic balance was used to study the aerodynamics and mass transfer characteristics of spherical and nonspherical particles up to 200 m in size. The balance uses an electric field established by a DC potential to a pair of end electrodes and an AC potential to the central electrode to suspend single changed particles. The suspended particle is then subjected to a steady and/or oscillating air jet. Results from this study indicate that the drag coefficient of irregular-shaped particles was greater than that for spheres, and was unaffected by rotation. Measured mass transfer rates for irregular-shaped naphthalene particles were consistently higher than values predicted for equivalent spheres. These results suggest a strong influence of mass transfer on particle shape and particle Reynolds number.List of symbols A project area - d diameter - d _e area equivalent diameter - F _D drag force - F _E electrostatic force - g gravitational constant - K _B, K _B balance constants - k ₁, k ₂ calibration constants - m mass - P pixel count - q charge - Re Reynolds number - U jet velocity - V _DC balance DC voltage - V _DC,O balance DC voltage without air flow - particle density - _a density of air - v viscosity of air     

Complex IIR filter design through balance model reduction of FIRprototypes

The author extend the use of the balance model truncation and Hankel-norm optimal approximation to permit close approximation of complex FIR prototypes by IIR filters     

Diazotrifluoropropionamido-containing prenylcysteines: syntheses and applications for studying isoprenoid-protein interactions

Photoaffinity-labeled prenylcysteines (1 and 2) incorporating a diazotrifluoropropionamide-based photophore have been prepared. Photolyses of 2 in the presence of RhoGDI, a protein that interacts with prenylated proteins, and prenylcysteine-containing competitors demonstrate the effectiveness of this photoaffinity-labeled analogue as a tool for studying isoprenoid binding sites.     

Fluorinated Covalent Organic Framework as a Positive Tribo-Material for High-Performance Triboelectric Nanogenerators

Along with the increasingly wide application of intelligent electronics, triboelectric nanogenerator (TENG), as a promising sustainable micro-power source has attracted considerable attention recently. However, most of the reported research focuses on negative triboelectric materials, while research on alternative positive tribo-layers is still limited. In this study, a new highly fluorinated covalent organic framework (COF) Tp-TFAB is successfully synthesized and utilized as positive triboelectric materials for high-performance TENGs. Unusually, compared with the non-fluorinated Tp-TAPB COF, both the pristine Tp-TFAB COF and corresponding hybrid films with polyvinyl alcohol (PVA) based TENGs demonstrate much higher triboelectric performance. Especially, a PVC-PVA/FTC TENG composed of polyvinyl chloride (PVC) and hybrid PVA/Tp-TFAB (PVA/FTC) films reveal much superior triboelectric performance with a short-circuit current density of 26.34 mA m⁻², a transferred charge density of 148.5 µC m⁻², and a maximum peak power density of 8.24 W m⁻², nearly six times higher than that of the PVC-PVA TENG. Detailed investigations revealed that the fluorinated Tp-TFAB COF has enhanced electron donating ability, which significantly boosts the triboelectric output of TENGs. This study provides an effective strategy of chemically designing and synthesizing new alternative triboelectric materials, which will pave the way to significantly enhance the triboelectric performance of TENGs.