Efficient Piezoelectric Energy Harvesting from a Discrete Hybrid Bismuth Bromide Ferroelectric Templated by Phosphonium Cation

Bismuth containing hybrid molecular ferroelectrics are receiving tremendous attention in recent years owing to their stable and non-toxic composition. However, these perovskite-like structures are primarily limited to ammonium cations. Herein, we report a new phosphonium based discrete perovskite-like hybrid ferroelectric with a formula [Me(Ph)₃P]₃[Bi₂Br₉] ( MTPBB ) and its mechanical energy harvesting capability. The Polarization-Electric field (P-E) measurements resulted in a well-defined ferroelectric hysteresis loop with a remnant polarization value of 2.1 μC cm⁻². Piezoresponse force microscopy experiments enabled visualization of the ferroelectric domain structure and evaluation of the piezoelectric strain coefficient (d₃₃) for an MTPBB single crystal and thin film sample. Furthermore, flexible devices incorporating MTPBB in polydimethylsiloxane (PDMS) matrix at various concentrations were fabricated and explored for their mechanical energy harvesting properties. The champion device with 20 wt % of MTPBB in PDMS rendered a maximum peak-to-peak open-circuit voltage of 22.9 V and a maximum power density of 7 μW cm⁻² at an optimal load of 4 MΩ. Moreover, the potential of MTPBB -based devices in low power electronics was demonstrated by storing the harvested energy in various electrolytic capacitors.     

An Efficient Straightforward Synthesis of (-)-Bulgecinine

(-)-Bulgecinine 1, a component of the antibiotic bulgecins, was efficiently synthesized from (S)-pyroglutaminol2.     

Particle tracking velocimetry with an ant colony optimization algorithm

A new concept algorithm based on the ant colony optimization is developed for the use in 2-D and 3-D particle tracking velocimetry (PTV). In the particle matching process of PTV, the ant colony optimization is usually aimed at minimization of the sum of the distances between the first-frame and second-frame particles. But this type of minimization often goes unsuccessfully in the regions where the particles are located very close to each other. In order to avoid this flaw, a new type of minimization is attempted using a physical property corresponding to the flow consistency or the quasi-rigidity of particle distribution patterns. Specifically, the ant colony optimization is now aimed at minimization of the sum of the relaxation of neighbor particles. In the present study, the new algorithm is applied to sets of 2-D and 3-D synthetic particle images as well as the experimental images with successful results.     

Trace analysis of rare earth elements and other impurities in high purity scandium by inductively coupled plasma mass spectrometry after liquid-liquid extraction of the matrix

Bis(2-ethyl hexyl)-orthophosphoric acid in toluene has been used to extract scandium selectively from an aqueous phase containing nearly thirty elements at various concentrations. The trace elements (Li, Mg, Al, Mn, Co, Ni, Cu, Zn, Ga, Sr, Y, Cd, In, Sb, Ba, REE, Hf, Pt, Tl, Pb, Bi and u) have been determined quantitatively in the aqueous phase using inductively coupled plasma mass spectrometry (ICP-MS). The recoveries have been quantitative for most of the analytes studied and ICP-MS has been found suitable for the determination of trace quantities of these elements in the aqueous extract. The procedure has been applied to the quantitative ultra-trace analysis of rare earth elements (REE) and other trace impurities in high purity scandium metal (4N) using ICP-MS and ID-ICP-MS techniques.Presented in part at the 2nd Regensburger Symposium Massenspektrometrische Verfahren der Elementspurenanalyse, 6.-8.10.93, Regensburg, Germany     

Pyroglutamic acid: a unique chiral synthon

1. Download : Download full-size image

     

Structure-Activity Relations for Imidazo-pyridine-Type Inhibitors of β-D-Glucosidases

The triazole 7 and the known gluco- and manno-configurated imidazoles 10 and 11 have been prepared by annulation of the azole ring to the aldonothiolactam 14 in a Hg(OAc)₂-promoted reaction with either hydrazine-carbaldehyde or aminoacetaldehyde dimethyl acetal. Depending upon the reaction conditions, the synthesis of the imidazoles yielded mostly the gluco-imidazole 19 or a mixture of the gluco/manno epimers 19/20 . In contrast to the triazole 4, the isomeric triazole 7 proved a good inhibitor of retaining β-glucosidases from sweet almonds and from Caldocellum saccharolyticum. This observation and the qualitative correlation between basicity and inhibitory power of the tetrahydropyridoazoles provide further evidence for the hypothesis of the ‘lateral protonation’ of glycosides by (some) retaining β-glucosidases.     

Evaluation of kinetic parameters for oxidation of thioacids by benzimidazolium dichromate: A mechanistic study

In a non-aqueous medium, oxidation kinetics of thioglycolic, thiolactic and thiomalic acids by benzimidazolium dichromate have been studied. In the temperature range of 20°C–50°C, oxidation kinetics were examined by spectrophotometry. In terms of oxidant, the reaction is dependent on the unitary order. In the case of thioacids, we find the Michaelis-Menten type kinetics. Hydrogen-ions act as catalyst in this process. The reaction rate slows down as the Mn²⁺ ion concentration increases. The reaction does not cause acrylonitrile to polymerize. The formation of a thioester into the pre-equilibrium followed by its progressive degradation was postulated as a mechanism.     

Preparation,Spectroscopic and Structural Investigations of Spiro Derivatives of Hexachlorocyclotriphosphazatriene

Abstract

Mono-(N₃P₃Cl₄Y₂), bis-(N₃P₃Cl₂Y₄) and tris-spiro derivatives (N₃P₃Y₆) have been prepared with ethylene, 1, 3-propylene and 1,4-butylene glycols (Y₂ = glycol residue). The ¹H NMR spectra of mono- and tris-derivatives are relatively simple; those of the bis- very complex due to the intrinsic asymmetry of the methylene protons. This effect is made use of in studying the replacement pattern of N₃P₃Cl₄ [O (CH₂)₃O] with primary and secondary amines. Homonuclear ¹H decoupling simplifies the spectra and allows an unambiguous distinction to be made between the different isomeric possibilities of the bis amino derivatives N₃P₃Cl₂R₂ [O(CH₂)₃O] where R = amino residue. Primary amines give geminal, secondary amines nongeminal trans-derivatives. The trans-structure of the bis-pyrrolidino derivative has been confirmed by X-ray crystallography.     

Particle Tracking Velocimetry using the genetic algorithm

A new concept genetic algorithm (GA) has been implemented and tested for the use in the 2-D and 3-D Particle Tracking Velocimetry (PTV). The algorithm is applicable to particle images with larger (greater than 2000) number of particles without losing the excellent accuracy in the particle matching results. This is mainly due to a new fitness function as well as unique genetic operations devised especially for the purpose of particle matching problem. The new fitness function is based on the relaxation of movement of a group of particles and is particularly suited for an increased density of particle images. The unique genetic operations give rise to the concentration of more fit genes in the forward part of the gene strings where the crossover and mutation processes are suppressed. The new algorithm also profits from the new genetic encoding scheme which can deal with the loss-of-pair particles (i.e., those particles which exist in one frame but do not have their matching pair in the other frame), a typical problem in the real image particle tracking velocimetry. In the present study, the new method is tested with 2-D and 3-D synthetic as well as real particle images with a large number of particles.     

Synthesis of styryl-linked fused dihydropyridines by catalyst-free multicomponent reactions

Molecular Diversity - Herein, we report a rapid catalyst-free three-component reaction of 2-hydroxy-1,4-naphthoquinone, cinnamaldehydes and 3-aminopyrazoles in ethanol medium under reflux...