Numerical differentiation methods for the logarithmic derivative technique used in dielectric spectroscopy

In dielectric relaxation spectroscopy the conduction contribution often hampers the evaluation of dielectric spectra, especially in the low-frequency regime. In order to overcome this the logarithmic derivative technique could be used, where the calculation of the logarithmic derivative of the real part of the complex permittivity function is needed. Since broadband dielectric measurement provides discrete permittivity function, numerical differentiation has to be used. Applicability of the Savitzky-Golay convolution method in the derivative analysis is examined, and a detailed investigation of the influential parameters (frequency, spectrum resolution, peak shape) is presented on synthetic dielectric data

Methanol oxidation catalyst by atomic layer deposition

Direct liquid fuel cells (DMFCs) are very appealing alternatives for fighting climate change, particularly in the field of personal mobility solutions. However, DMFCs also have some serious competitive disadvantages, like the high cost of the noble metal catalysts, the difficulties of the catalyst application, and the poisoning of the catalyst due to carbon monoxide formation. Here we demonstrate that depositing platinum on TiO2 by atomic layer deposition (ALD) is an easy, reproducible method for the synthesis of TiO2-supported platinum catalyst for methanol oxidation with excelent anti CO poisoning properties

Oxygen reduction activity of cobalt-nitride on nitrogen-doped graphene

Fuel cells technology can offer suitable alternatives to replace one of the most important environmental issues of our days, i.e., fossil fuels. In the last decades, non-precious metal catalysts came in the view such as transition metal-oxides, -nitrides, or even metal free catalysts like N-graphene. Such systems are expected to replace high cost oxygen reduction reaction (ORR) catalysts used nowadays [1]. We hereby demonstrate a simple method for the simultaneous synthesis of cobalt-nitride nanoparticles on nitrogen-doped graphene support. The reported non-precious metal catalyst showed high electrocatalytic activity in ORR, and thus it is a promising alternative cathode-side catalyst in polymer electrolyte membrane (PEM) fuel cells. The catalyst was synthesized from lyophilized graphene-oxide and cobalt(II)-acetate in NH3 flow at high temperature, and the effect of cobalt-nitride amount on catalyst properties was further examined. To this end, transmission electron microscopy (TEM) and X-ray diffractometry (XRD) were employed to monitor the morphological and structural changes in the graphene sheets and the supported cobalt-nitride particles. The electrochemical properties of the catalyst were investigated in a three-electrode cell in oxygen saturated 0.1 M potassiumhydroxide solution at different rotation rates with a rotating disk electrode (RDE) setup. The optimal amount of cobalt-nitride and nitrogen-doped graphene was determined, producing a promising non-precious metal catalyst for oxygen reduction reaction

Quality by Design-Driven Zeta Potential Optimisation Study of Liposomes with Charge Imparting Membrane Additives

Liposomal formulations, as versatile nanocarrier systems suitable for targeted delivery, have a highly focused role in the therapy development of unmet clinical needs and diagnostic imaging techniques. Formulating nanomedicine with suitable zeta potential is an essential but challenging task. Formulations with a minimum ±30 mV zeta potential are considered stable. The charge of the phospholipid bilayer can be adjusted with membrane additives. The present Quality by Design-derived study aimed to optimise liposomal formulations prepared via the thin-film hydration technique by applying stearylamine (SA) or dicetyl phosphate (DCP) as charge imparting agents. This 32 fractional factorial design-based study determined phosphatidylcholine, cholesterol, and SA/DCP molar ratios for liposomes with characteristics meeting the formulation requirements. The polynomials describing the effects on the zeta potential were calculated. The optimal molar ratios of the lipids were given as 12.0:5.0:5.0 for the SA-PBS pH 5.6 (optimised sample containing stearylamine) and 8.5:4.5:6.5 for the DCP-PBS pH 5.6 (optimised sample containing dicetyl phosphate) particles hydrated with phosphate-buffered saline pH 5.6. The SA-PBS pH 5.6 liposomes had a vesicle size of 108 ± 15 nm, 0.20 ± 0.04 polydispersity index, and +30.1 ± 1.2 mV zeta potential, while these values were given as 88 ± 14 nm, 0.21 ± 0.02, and −36.7 ± 3.3 mV for the DCP-PBS pH 5.6 vesicles. The prepared liposomes acquired the requirements of the zeta potential for stable formulations

Platinum nanoparticles on nitrogen-doped graphene for oxygen reduction reaction

Excess use of non-renewable energy resources is a serious environmental problem nowadays. Fuel cells can be a promising alternative as they provide rather clean energy and they can be used for various purposes in many sizes. Our work focuses on the oxygen reduction reaction (ORR) in polymer electrolyte membrane (PEM) fuel cells. Generally, platinum nanoparticles are used on carbon black support which is an expensive and easily degradable catalyst. Nitrogen-doped graphene support can be an alternative solution with various advantages, which improve the ORR efficiency of the dispersed platinum. Our aim was to achive a one step method to synthesize Pt/Nitrogen-doped graphene composite with reduced platinum content. A mixture of platinum (II)-acetylacetonate and graphene oxide was thermally treated at three different temperatures. The resulting material was examined by several characterization techniques: thermogravimerty (TGA) was used to determine the platinum content of the samples, transmission electron microscopy (TEM) was applied to examine the graphene sheets and platinum particles, and X-ray photoelectron spectra (XPS) were taken to determine the physical states of the graphitic materials and the oxidation state of Pt. Linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were performed in a threeelectrode cell in oxygen saturated 0.1 M HClO4 solution by a rotating disk electrode (RDE) at different rotation rates to see the electrochemical behaviour of the samples, compared to a conventional Pt/CB catalyst. The results revealed the successful synthesis of the desired catalyst with promising electrochemical performances

Nature inspired solid–liquid phase amphibious adhesive

Here we report a new class of bio-inspired solid–liquid adhesive, obtained by simple mechanical dispersion of PVDF (polyvinylidene fluoride) (solid spheres) into PDMS (polydimethylsiloxane) (liquid). The adhesive behavior arises from strong solid–liquid interactions. This is a chemical reaction free adhesive (no curing time) that can be repeatedly used and is capable of instantaneously joining a large number of diverse materials (metals, ceramic, and polymer) in air and underwater. The current work is a significant advance in the development of amphibious multifunctional adhesives and presents potential applications in a range of sealing applications, including medical ones

Binder-Free Construction of a Methanol Tolerant Pt/TiO2/Carbon Paper Anode by Atomic Layer Deposition

Direct liquid fuel cells are very appealing alternatives for fighting climate change, particularly in the field of personal mobility solutions. This is especially true for direct methanol fuel cells (DMFCs) that use and burn safe fuels that are readily available from sustainable sources using well-established C1 chemistry. However, DMFCs also have some serious competitive disadvantages, like the high cost of the noble metal catalysts, the difficulties of the catalyst application, and the poisoning of the catalyst due to carbon monoxide formation. Here we demonstrate that depositing platinum on TiO2 by atomic layer deposition (ALD) is an easy, reproducible method for the synthesis of TiO2-supported platinum catalyst for methanol oxidation with superior anti-poisoning properties