Montmorillonite-based ceramic membranes as novel lithium-ion battery separators

Novel montmorillonite-based ceramic membrane (CM) has been prepared with poly(vinylidene fluoride-co-hexafluoropropene) (PVdF-HFP) copolymer as binder. Physical properties such as surface morphology, porosity, liquid electrolyte uptake and thermal stability were analysed. The ceramic membrane was activated by soaking it in a non-aqueous liquid electrolyte (1.0 M LiPF₆ solution in 1/1 v/v ethylene carbonate/diethyl carbonate mixture) for 10 min. The compatibility of the membrane with lithium metal anode as a function of storage time was analysed by assembling a Li/CM/Li symmetric cell. Finally, a lab-scale cell composed of Li/CM/LiFePO₄ is assembled and its cycling performance analysed at different C-rates. Although the ceramic membrane is not flexible, it shows high thermal stability and stable interfacial properties when in contact with the lithium metal anode. A stable cycling behaviour is demonstrated even at 1C-rate with limited fade in capacity.     

The kinetics and mechanism of reaction between ethylenediaminetetraacetomanganate(III) and cyanide ion

Summary The title reaction has been followed spectrophotometrically at 325 nm (_max of [Mn(CN)₆]^3–) under pseudo-first order conditions with cyanide in a large excess at pH=10.0, I=0.1M (NaClO₄) and 25°C. The reaction follows first-order kinetics in [MnEDTA(OH)]^2– and exhibits variable-order dependence in [CN^–] one at high cyanide concentration, and two at low cyanide concentration. The product of above reaction has been identified as [Mn(CN)₆]^3–.The kinetics of the reverse reaction,i.e., the reaction of [Mn(CN)₆]^3- with EDTA^4– have also been followed spectrophotometrically. This reactions is first-order with respect to both [Mn(CN) ₆ ^3– ] and [EDTA^4–] and exhibits an inverse first-order dependence on [CN^–]. A six-step mechanism has been proposed in which the penultimate step is rate-determining. The activation parameters have been obtained and support the postulated mechanism.     

Adsorption and photocatalytic degradation of methylene blue using high surface area titanate nanotubes (TNT) synthesized via hydrothermal method

Removal of methylene blue (MB) via adsorption and photocatalysis using titanate nanotubes (TNTs) with different surface areas were investigated and compared to commercial titanium dioxide (TiO₂) P25 Degussa nanoparticles. The TNTs with surface area ranging from 20 m²/g to 200 m²/g were synthesized via hydrothermal method with different reaction times. TEM imaging confirmed the tubular structure of TNT while XRD spectra indicated all TNTs exhibited anatase crystallinity. Batch adsorption rate showed linearity with surface properties of TNTs, where materials with higher surface area showed higher adsorption rate. The highest MB adsorption (70%) was achieved by TNT24 in 60 min whereas commercial TiO₂ exhibited the lowest adsorption of only 10% after 240 min. Adsorption isotherm studies indicated that adsorption using TNT is better fitted into Langmuir adsorption isotherm than Freundlich isotherm model. Furthermore, TNT24 was able to perform up to 90% removal of MB within 120 min, demonstrating performance that is 2-fold better compared to commercial TiO₂. The high surface area and surface Bronsted acidity are the main reasons for the improvement in MB removal performance exhibited by TNT24. The improvement in surface acidity enhanced the adsorption properties of all the nanotubes prepared in this study.     

A regioselective multicomponent protocol for the synthesis of novel bioactive 4-hydroxyquinolin-2(1H)-one grafted monospiropyrrolidine and thiapyrrolizidine hybrids

An expedient route toward the synthesis of 4-hydroxyquinolone grafted spiropyrrolidines or pyrrolizidines has been accomplished through 1,3-dipolar cycloaddition reaction of various azomethine ylides derived from isatin or acenaphthalene and sarcosine with 4-hydroxyquinolone derivatives as dipolarophile. The regio and stereo chemical outcome of the cycloaddition reaction is ascertained by X-ray crystallographic studies and spectroscopic techniques of the cycloadducts. Furthermore, cytotoxicity evaluation of selected compounds showed significant inhibition of cell proliferation against cervical as well as colon cancer cell lines.     

Zinc(II) mediated imine-enamine tautomerization

Reduction of imine-anthracenone compounds selectively produces secondary alcohols leaving the external imine group unreacted. Addition of the Zn(II) ion induces a metal-mediated imine-enamine tautomerization reaction that is selective for Zn(II), a new fluorescence detection method not previously observed for this important cation.     

10 GHz ultra-stable short optical pulse generation via phase-modulation enhanced dual-loop optoelectronic oscillator

We report on a high rate, ultra-low timing jitter, short optical pulse generator based on cascaded amplitude and phase modulation in an optoelectronic oscillator. The radio-frequency supermodes are shown to be greatly suppressed with the dual-loop architecture, and a highly coherent and flat optical frequency comb is generated. Optical pulses of 12.8 ps duration are obtained with 27.5 fs integrated timing jitter from 100 Hz to 10 MHz.     

Utilization of phosphinoamide ligands in homobimetallic fe and mn complexes: the effect of disparate coordination environments on metal-metal interactions and magnetic and redox properties

A series of homobimetallic phosphinoamide-bridged diiron and dimanganese complexes in which the two metals maintain different coordination environments have been synthesized. Systematic variation of the steric and electronic properties of the phosphinoamide phosphorus and nitrogen substituents leads to structurally different complexes. Reaction of [(i)PrNKPPh(2)] (1) with MCl(2) (M = Mn, Fe) affords the phosphinoamide-bridged bimetallic complexes [Mn((i)PrNPPh(2))(3)Mn((i)PrNPPh(2))] (3) and [Fe((i)PrNPPh(2))(3)Fe((i)PrNPPh(2))] (4). Complexes 3 and 4 are iso-structural, with one metal center preferentially binding to the three amide ligands in a trigonal planar arrangement while the second metal center is ligated by three phosphine donors. A fourth phosphinoamide ligand caps the tetrahedral coordination sphere of the phosphine-ligated metal center. M?ssbauer spectroscopy of complex 4 suggests that the metals in these complexes are best described as Fe(II) centers. In contrast, treatment of MnCl(2) or FeI(2) with [MesNKP(i)Pr(2)] (2) leads to the formation of the halide-bridged species [(THF)Mn(μ-Cl)(MesNP(i)Pr(2))(2)Mn(MesNP(i)Pr(2))] (5) and [(THF)Fe(μ-I)(MesNP(i)Pr(2))(2)FeI (7), respectively. Utilization of FeCl(2) in place of FeI(2), however, leads exclusively to the C(3)-symmetric complex [Fe(MesNP(i)Pr(2))(3)FeCl] (6), structurally similar to 4 but with a halide bound to the phosphine-ligated Fe center. The M?ssbauer spectrum of 6 is also consistent with high spin Fe(II) centers. Thus, in the case of the [(i)PrNPPh(2)](-) and [MesNP(i)Pr(2)](-) ligands, zwitterionic complexes with the two metals in disparate coordination environments are preferentially formed. In the case of the more electron-rich ligand [(i)PrNP(i)Pr(2)](-), complexes with a 2:1 mixed donor ligand arrangement, in which one of the ligand arms has reversed orientation relative to the previous examples, are formed exclusively when [(i)PrNLiP(i)Pr(2)] (generated in situ) is treated with MCl(2) (M = Mn, Fe): (THF)(3)LiCl[Mn(N(i)PrP(i)Pr(2))(2)(P(i)Pr(2)N(i)Pr)MnCl] (8) and [Fe(N(i)PrP(i)Pr(2))(2)(P(i)Pr(2)N(i)Pr)FeCl] (9). Bimetallic complexes 3-9 have been structurally characterized using X-ray crystallography, revealing Fe-Fe interatomic distances indicative of metal-metal bonding in complexes 6 and 9 (and perhaps 4, to a lesser extent). All of the complexes appear to adopt high spin electron configurations, and magnetic measurements indicate significant antiferromagnetic interactions in Mn(2) complexes 5 and 8 and no discernible magnetic superexchange in Fe(2) complex 4. The redox behavior of complexes 3-9 has also been investigated using cyclic voltammetry, and theoretical investigations (DFT) were performed to gain insight into the metal-metal interactions in these unique asymmetric complexes.     

Wafer-scale thin encapsulated two-dimensional nanochannels and its application toward visualization of single molecules

We present a new and simple approach to fabricate wafer-scale, thin encapsulated, two-dimensional nanochannels by using conventional surface-micromachining technology and thin-film evaporation. The key steps to the realization of two-dimensional nanochannels are a fine etching of a sacrificial layer to create underetching spaces at the nanometer regime, and an accurate thin-film evaporation for encapsulation. Well-defined cross-sectional, encapsulated nanochannel arrays with dimensions as small as 20 nm in both width and height have been realized at the wafer-scale. The fabricated nanochannels with a channel length of 10mm have been used as a suitable fluidic platform for confining a solution containing nanomolar concentrations of Alexa fluorescent molecules. Initial results toward visualization of single Alexa molecules in the confined solution are reported.