Analysis of Dielectric Spectra

Schönhals, Andreas; Kremer, Friedrich

doi:10.1007/978-3-642-56120-7_3

Cited by 207 publications

(266 citation statements)

References 60 publications

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“…5b) at low frequencies. Low frequency relaxation processes can be associated with pseudo-DC conduction and the MaxwellWagner effect, which is associated with the trapping of charges either at internal boundaries within materials or at the external electrodes that contact the sample [46]. Here, nanoparticle/matrix interfaces are of considerable importance in this respect and previous studies of nanocomposites have demonstrated that interfacial accumulation of water molecules can be a major contributing factor to the observed low frequency dielectric response [7,45,47].…”

Section: B Nanocomposite Dielectric Responsementioning

confidence: 99%

The Effects of Water on the Dielectric Properties of Aluminum-Based Nanocomposites

Hosier¹,

Praeger²,

Vaughan

et al. 2017

IEEE Trans. Nanotechnology

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Abstract-A series of polyethylene nanocomposites was prepared utilizing aluminum nitride or alumina nano-powders with comparable morphologies. These were subsequently subjected to different conditioning regimes, namely prolonged storage in vacuum, the ambient laboratory environment or in water. The effect of filler loading and conditioning (i.e. water content) on their morphological and dielectric properties was then examined. Measurements indicated that, in the case of aluminum nitride nanocomposites, none of the conditioning regimes led to significant absorption of water and, as such, neither the dielectric properties nor the DC conductivity varied. Conversely, the alumina nanocomposites were prone to the absorption of an appreciable mass of water, which resulted in them displaying a broad dielectric relaxation, which shifted to higher frequencies, and a higher DC electrical conductivity. We ascribe these different effects to the interfacial surface chemistry present in each system and, in particular, the propensity for hydrogen bonding with water molecules diffusing through the host matrix. Technologically, the use of nanocomposites based upon systems such as aluminum nitride, in place of the commonly used metal oxides (alumina, silica, etc.), eliminates variations in dielectric properties due to absorption of environmental water without resorting to the adoption of techniques such as surface functionalization or calcination in an attempt to render nanoparticle surface chemistry hydrophobic.

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Section: B Nanocomposite Dielectric Responsementioning

confidence: 99%

The Effects of Water on the Dielectric Properties of Aluminum-Based Nanocomposites

Hosier¹,

Praeger²,

Vaughan

et al. 2017

IEEE Trans. Nanotechnology

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“…(1) fits NMS's β-relaxation. 25 Next, the fitting parameters were used to calculate the τ α and τ β by means of the equation: …”

Section: Molecular Dynamics Of Pure Nimesulide Above and Below The Glmentioning

confidence: 99%

Molecular Dynamics and Physical Stability of Amorphous Nimesulide Drug and Its Binary Drug–Polymer Systems

et al. 2016

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In this paper we study the effectiveness of three well known polymers: inulin, Soluplus and PVP in stabilizing amorphous form of nimesulide (NMS) drug. The recrystallization tendency of pure drug as well as measured drug-polymer systems were examined at isothermal conditions by using broadband dielectric spectroscopy (BDS), and at non-isothermal conditions by differential scanning calorimetry (DSC). Our investigation has shown that the crystallization half-life time of pure NMS at 328 K is equal to 33 minutes. We found that this time can be prolonged to 40 years after adding to NMS 20% of PVP polymer.This polymer proved to be the best NMS's stabilizer, while the worst stabilization effect was found after adding the inulin to NMS. Additionally, our DSC, BDS and FTIR studies indicate that for suppression of NMS's re-crystallization in NMS-PVP system, the two mechanisms are responsible: the polymeric steric hindrances as well as the antiplastization effect excerted by the excipient.

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“…We have previously described 27,36 that the double layer capacitance of the supported membrane system shows a certain degree of frequency dispersion due to a Maxwell-Wager effect. 37,38 In this study we are primarily concerned with the Faradaic reactions and thus the following approach has been adopted. EIS data were measured in the absence and presence of the inhibitor cyanide.…”

Section: Resultsmentioning

confidence: 99%

Impedance Spectroscopy of Bacterial Membranes: Coenzyme-Q Diffusion in a Finite Diffusion Layer

et al. 2008

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The inner membrane of Escherichia coli, over-expressing an ubiquinol oxidase, cytochrome bo 3 (cbo 3 ), was tethered in a planar configuration to a gold electrode. Electron transfer to cbo 3 was achieved via native ubiquinol-8 or added ubiquinol-10 and impedance spectroscopy was used to characterise the diffusion properties of the ubiquinol/ubiquinone in the tethered membrane system. Spectra were obtained at varying DC potentials covering the potential window in which the voltammetric catalytic wave of cbo 3 is visible. These spectra were compared to those obtained after addition of a potent inhibitor of cbo 3 , cyanide, and the difference in impedance was analysed using a derived equivalent circuit, which is similar to that of Open Finite-Length Diffusion (OFLD) or the finite Warburg circuit, but with the boundary conditions modified to account for the fact that ubiquinol reoxidation is limited by enzyme activity. Analysis of the impedance spectra of the tethered membrane system gave kinetic parameters that are consistent with values obtained using cyclic voltammetry. Importantly, the diffusion rate of ubiquinone (10 −13 -10 −12 cm 2 /s) was found to be orders of magnitude lower than accepted values for lateral diffusion (10 −8 -10 −7 cm 2 /s). It is hypothesised that this result represent perpendicular diffusion of quinone across the membrane, corresponding to a 'flip' time between 0.05 and 1 s.

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Analysis of Dielectric Spectra

Cited by 207 publications

References 60 publications

The Effects of Water on the Dielectric Properties of Aluminum-Based Nanocomposites

The Effects of Water on the Dielectric Properties of Aluminum-Based Nanocomposites

Molecular Dynamics and Physical Stability of Amorphous Nimesulide Drug and Its Binary Drug–Polymer Systems

Impedance Spectroscopy of Bacterial Membranes: Coenzyme-Q Diffusion in a Finite Diffusion Layer

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