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The Glass Transition Temperature of Heterogeneous Biopolymer Systems

Pereira Espíndola, S. (author), Norder, B. (author), Koper, G.J.M. (author), Picken, S.J. (author)

Biopolymers are abundant, renewable, and biodegradable resources. However, bio-based materials often require toughening additives, like (co)polymers or small plasticizing molecules. Plasticization is monitored via the glass transition temperature versus diluent content. To describe this, several thermodynamic models exist; nevertheless, most...

journal article 2023

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Competition and Interhalogen Formation during Parallel Electrocatalytic Oxidation of Bromide and Chloride on Pt

Vos, Johannes G. (author), Venugopal, A. (author), Smith, W.A. (author), Koper, Marc T.M. (author)

Hydrogen production from seawater electrolysis is highly promising for the capture and storage of intermittent renewable energy, but is hindered by the possibility of unwanted reactions at the anode. The oxidation reactions of chloride and (to a lesser extent) bromide, which can occur in parallel to the evolution of oxygen, lead to...

journal article 2020

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The Effect of Magnetic Field on Catalytic Properties in Core-Shell Type Particles

Westsson, E.E. (author), Picken, S.J. (author), Koper, G.J.M. (author)

Magnetic field effects can provide a handle on steering chemical reactions and manipulating yields. The presence of a magnetic field can influence the energy levels of the active species by interacting with their spin states. Here we demonstrate the effect of a magnetic field on the electrocatalytic processes taking place on platinum-based...

journal article 2020

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Competition and selectivity during parallel evolution of bromine, chlorine and oxygen on IrO_x electrodes

Vos, Johannes G. (author), Venugopal, A. (author), Smith, W.A. (author), Koper, Marc T.M. (author)

During hydrogen production for (renewable) energy storage, direct seawater electrolysis offers several notable advantages over freshwater electrolysis. Unfortunately, it is also hindered by possible oxidation reactions of chloride and (to a lesser extent) bromide, which can occur in parallel to the evolution of oxygen and form harmful by...

journal article 2020

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The effect of lattice strain on catalytic activity

Westsson, E.E. (author), Picken, S.J. (author), Koper, G.J.M. (author)

We report on the effect of lattice strain in three different types of core-shell electrocatalyst particles on their catalytic activity towards the oxygen reduction reaction. We decouple the changes in catalytic activity with respect to a geometrical and an energetic contribution, both of electronic origin.

journal article 2019

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Cathodic Corrosion of a Bulk Wire to Nonaggregated Functional Nanocrystals and Nanoalloys

Feng, J. (author), Chen, Dong (author), Sediq, Ahmad S. (author), Romeijn, Stefan (author), Tichelaar, F.D. (author), Jiskoot, Wim (author), Yang, J. (author), Koper, M.T.M. (author)

A key enabling step in leveraging the properties of nanoparticles (NPs) is to explore new, simple, controllable, and scalable nanotechnologies for their syntheses. Among "wet" methods, cathodic corrosion has been used to synthesize catalytic aggregates with some control over their size and preferential faceting. Here, we report on a...

journal article 2018

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Effects of Substrate and Polymer Encapsulation on CO₂ Electroreduction by Immobilized Indium(III) Protoporphyrin

Birdja, Yuvraj Y. (author), Vos, Rafaël E. (author), Wezendonk, T.A. (author), Jiang, Lin (author), Kapteijn, F. (author), Koper, M.T.M. (author)

Heterogenization of molecular catalysts for CO₂ electroreduction has attracted significant research activity, due to the combined advantages of homogeneous and heterogeneous catalysts. In this work, we demonstrate the strong influence of the nature of the substrate on the selectivity and reactivity of electrocatalytic CO<sub>2</sub...

journal article 2018

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MnO_x/IrO_x as Selective Oxygen Evolution Electrocatalyst in Acidic Chloride Solution

Vos, J.G. (author), Wezendonk, T.A. (author), Jeremiasse, Adriaan W. (author), Koper, Marc T.M. (author)

The oxygen evolution reaction (OER) and chlorine evolution reaction (CER) are electrochemical processes with high relevance to water splitting for (solar) energy conversion and industrial production of commodity chemicals, respectively. Carrying out the two reactions separately is challenging, since the catalytic intermediates are linked by...

journal article 2018

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Gas Phase Sensing of Alcohols by Metal Organic Framework-Polymer Composite Materials

Sachdeva, S. (author), Koper, S.J.H. (author), Sabetghadam, A. (author), Soccol, Dimitri (author), Gravesteijn, Dirk J. (author), Kapteijn, F. (author), Sudhölter, Ernst J. R. (author), Gascon, Jorge (author), de Smet, L.C.P.M. (author)

Affinity layers play a crucial role in chemical sensors for the selective and sensitive detection of analytes. Here, we report the use of composite affinity layers containing Metal Organic Frameworks (MOFs) in a polymeric matrix for sensing purposes. Nanoparticles of NH₂-MIL-53(Al) were dispersed in a Matrimid polymer matrix with...

journal article 2017

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Intermediate stages of electrochemical oxidation of single-crystalline platinum revealed by in situ Raman spectroscopy

Huang, Yi Fan (author), Kooyman, P.J. (author), Koper, M.T.M. (author)

Understanding the atomistic details of how platinum surfaces are oxidized under electrochemical conditions is of importance for many electrochemical devices such as fuel cells and electrolysers. Here we use in situ shell-isolated nanoparticle-enhanced Raman spectroscopy to identify the intermediate stages of the electrochemical oxidation of...

journal article 2016

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Iridium-based double perovskites for efficient water oxidation in acid media

Diaz-Morales, Oscar (author), Raaijman, Stefan (author), Kortlever, Ruud (author), Kooyman, P.J. (author), Wezendonk, T.A. (author), Gascon, Jorge (author), Fu, W. (author), Koper, M.T.M. (author)

The development of active, cost-effective and stable oxygen-evolving catalysts is one of the major challenges for solar-to-fuel conversion towards sustainable energy generation. Iridium oxide exhibits the best available compromise between catalytic activity and stability in acid media, but it is prohibitively expensive for large-scale...

journal article 2016

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Composition dependent properties of graphene (oxide)-alginate biopolymer nanocomposites

Vilcinskas, K. (author), Jansen, K.M.B. (author), Mulder, F.M. (author), Picken, S.J. (author), Koper, G.J.M. (author)

We report on the thermal, electrical, and mechanical properties of alginate biopolymer nanocomposites prepared by solution casting with various amounts of graphene oxide (GO) or reduced GO (rGO). Our data shows that the thermal stability of alginate nanocomposites can be improved by the introduction of cross-linking through divalent metal...

journal article 2016

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Electrocatalytic Activity and Durability of Pt-Decorated Non-Covalently Functionalized Graphitic Structures

Negro, E. (author), Stassi, A. (author), Baglio, V. (author), Arico, A.S. (author), Koper, G.J.M. (author)

Carbon graphitic structures that differ in morphology, graphiticity and specific surface area were used as support for platinum for Oxygen Reduction Reaction (ORR) in low temperature fuel cells. Graphitic supports were first non-covalently functionalized with pyrene carboxylic acid (PCA) and, subsequently, platinum nanoparticles were nucleated...

journal article 2015

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Bicontinuous microemulsions for high yield, wet synthesis of ultrafine nanoparticles: A general approach

Latsuzbaia, R. (author), Negro, E. (author), Koper, G.J.M. (author)

The design of a synthesis strategy for metal nanoparticles by templating dense microemulsions is proposed. Particle size is controlled by surfactant size rather than by microemulsion composition. The strategy was demonstrated with various systems with different surfactant: cationic, anionic and non-ionic and of different sizes. Formulations were...

journal article 2015

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How to Determine the Core-Shell Nature in Bimetallic Catalyst Particles?

Westsson, E.E. (author), Koper, G.J.M. (author)

Nanometer-sized materials have significantly different chemical and physical properties compared to bulk material. However, these properties do not only depend on the elemental composition but also on the structure, shape, size and arrangement. Hence, it is not only of great importance to develop synthesis routes that enable control over the...

journal article 2014

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Experimental and molecular dynamics characterization of dense microemulsion systems: Morphology, conductivity and SAXS

Negro, E. (author), Latsuzbaia, R. (author), De Vries, A.H. (author), Koper, G.J.M. (author)

Microemulsions are exciting systems that are promising as tuneable self-assembling templating reaction vessels at the nanoscale. Determination of the nano-structure of microemulsions is, however, not trivial, and there are fundamental questions regarding their design. We were able to reproduce experimental data for an important microemulsion...

journal article 2014

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High yield, controlled synthesis of graphitic networks from dense micro emulsions

Negro, E. (author), Dieci, M. (author), Sordi, D. (author), Kowlgi, K. (author), Makkee, M. (author), Koper, G.J.M. (author)

We report on the production of Carbon Nano Networks (CNNs) from dense microemulsions in which catalyst nanoparticles have been synthesized. CNNs are 3D carbon networks, consisting of branches and junctions, and are mesoporous, graphitic, and conductive being suitable as electrode materials.

journal article 2014

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Optimal ionic strength for nonionically initiated polymerization

Dobrowolska, M.E. (author), Koper, G.J.M. (author)

Surfactant-free emulsion polymerization involving a nonionic, and hence uncharged initiator presents a new approach towards environmentally friendly procedures to synthesize latex particles. Under optimal solvent conditions, notably pH and ionic strength, the latex particles are stabilized by the natural development of ionic charge at the...

journal article 2013

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Slow growth of the Rayleigh-Plateau instability in aqueous two phase systems

Geschiere, S.D. (author), Ziemecka, I. (author), Van Steijn, V. (author), Koper, G.J.M. (author), Van Esch, J.H. (author), Kreutzer, M.T. (author)

This paper studies the Rayleigh-Plateau instability for co-flowing immiscible aqueous polymer solutions in a microfluidic channel. Careful vibration-free experiments with controlled actuation of the flow allowed direct measurement of the growth rate of this instability. Experiments for the well-known aqueous two phase system (ATPS, or aqueous...

journal article 2012

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Proton binding by linear, branched, and hyperbranched polyelectrolytes

Koper, G.J.M. (author), Borkovec, M. (author)

This article reviews our understanding of ionization processes of weak polyelectrolytes. The emphasis is put on a general introduction to site binding models, which are able to account for many experimental features of linear and branched polyelectrolytes, including dendrimers. These models are fully compatible with the classical description of...

journal article 2010