Niclas Solin

White Light with Phosphorescent Protein Fibrils in OLEDs

Red and yellow phosphorescent insulin amyloid fibrils are used as guest-emitting species within a blue-emitting polyfluorene matrix in light-emitting diodes. The integration of the phosphorescent Ir-complex into the amyloid structures strongly improves the triplet exciton confinement and allows the fabrication of white-emitting device with a very low loading of phosphorescent complex. The overall performances of the devices are improved in comparison with the corresponding bare Ir-complexes. This approach opens a way to explore novel device architectures and to understand the exciton/charge transfer dynamics in phosphorescent light emitting diodes.

High performance PEDOT/lignin biopolymer composites for electrochemical supercapacitors

Developing sustainable organic electrode materials for energy storage applications is an urgent task. We present a promising candidate based on the use of lignin, the second most abundant biopolymer in nature. This polymer is combined with a conducting polymer, where lignin as a polyanion can behave both as a dopant and surfactant. The synthesis of PEDOT/Lig biocomposites by both oxidative chemical and electrochemical polymerization of EDOT in the presence of lignin sulfonate is presented. The characterization of PEDOT/Lig was performed by UV-Vis-NIR spectroscopy, FTIR infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, cyclic voltammetry and galvanostatic charge–discharge. PEDOT doped with lignin doubles the specific capacitance (170.4 F g−1) compared to reference PEDOT electrodes (80.4 F g−1). The enhanced energy storage performance is a consequence of the additional pseudocapacitance generated by the quinone moieties in lignin, which give rise to faradaic reactions. Furthermore PEDOT/Lig is a highly stable biocomposite, retaining about 83% of its electroactivity after 1000 charge/discharge cycles. These results illustrate that the redox doping strategy is a facile and straightforward approach to improve the electroactive performance of PEDOT.

Hybrid bioinorganic insulin amyloid fibrils

Herein we report a method to functionalize in vitro grown insulin amyloid fibrils with various inorganic materials. The counterion of the positively charged amyloid fibril is exchanged with anions from various salts; subsequent addition of appropriate cations results in functionalization of the amyloid fibril. We demonstrate the formation of apatite and platinum complex structures ordered by the amyloid template.

Preparation of Phosphorescent Amyloid-Like Protein Fibrils

The capability to prepare functional materials, designed at the molecular level in order to tune their physical and chemical properties lies at the heart of material science. A promising approach to achieve this goal is to use the self-assembly of smaller building blocks. However, synthesis of such building blocks is often challenging, and it is therefore attractive to envisage a system in which one separates the information for assembly from that for function into physically different parts of the self-assembling species. Such a separation would allow for rapid changes in material function, with the functional element simply acting as cargo with its spatial arrangement dictated by the self-assembling element. Herein, we report a method in which insulin is used as the self-assembly directing agent by forming amyloid-like structures, and the phosphorescent iridium complexes factris[2-phenylpyridinato-C,N]iridium ACHTUNGTRENNUNG(III) ([Ir ACHTUNGTRENNUNG(ppy)3], 1) and fac-tris[1-phenylisoquinoline-C,N]iridium ACHTUNGTRENNUNG(III) ([Ir ACHTUNGTRENNUNG(piq)3], 2) are used as functionalizing agents. The preparation of the amyloid-like structures is extremely facile as the two materials are mixed simply by grinding them together in the solid state, followed by heating of the resulting hybrid material in aqueous acid. When exposed to destabilizing conditions many proteins aggregate into well-ordered fibrillar assemblies, known as amyloid fibrils. An example is the preparation of amyloid fibrils from insulin in vitro, which can be achieved by heating insulin in aqueous acid. The fibrils typically have a diameter in the range of 10 nm and lengths in the micrometer range; this geometry makes them useful as a template for material organization. Nevertheless, for most applications in the materials science field it is essential to functionalize amyloid fibrils with guest molecules with the desired properties. The approaches used so far have been to use chemically modified peptide sequences with the guest attached covalently to the peptide prior to fibril formation, or to functionalize the fibrils after or during their formation, either by metallization or by decoration of the fibril with guest molecules that form supramolecular complexes. All of these approaches are limited by the range of applicable materials that can be used. For instance, many molecules that are desirable to use for fibril functionalization are hydrophobic, and are therefore insoluble in the aqueous reaction media used for fibrillation. A further complication is that the guest molecule might perturb the fibrillation process, leading to the formation of amorphous aggregates or even inhibiting the aggregation processes. We decided to investigate the incorporation of hydrophobic iridium complexes 1 and 2 into insulin amyloid fibrils.

Preparation of amyloid-like fibrils containing magnetic iron oxide nanoparticles: effect of protein aggregation on proton relaxivity.

A method to prepare amyloid-like fibrils functionalized with magnetic nanoparticles has been developed. The amyloid-like fibrils are prepared in a two step procedure, where insulin and magnetic nanoparticles are mixed simply by grinding in the solid state, resulting in a water soluble hybrid material. When the hybrid material is heated in aqueous acid, the insulin/nanoparticle hybrid material self assembles to form amyloid-like fibrils incorporating the magnetic nanoparticles. This results in magnetically labeled amyloid-like fibrils which has been characterized by Transmission Electron Microscopy (TEM) and electron tomography. The influence of the aggregation process on proton relaxivity is investigated. The prepared materials have potential uses in a range of bio-imaging applications.

Morphology of organic electronic materials imaged via electron tomography

Organic electronic materials and nanostructures have been studied with the use of electron tomography. Nanostructured materials including contrast enhancing features have been studied and double tilt data collection has been employed to improve reconstructions. Tomography reconstructions of active layers of organic solar cells, where various preparation techniques have been used, have been analysed and compared to device behaviour. Small changes in preparation procedures may lead to large differences in morphology and device performance, and the results also indicate a complex relation between these.

Highly Stable Conjugated Polyelectrolytes for Water-Based Hybrid Mode Electrochemical Transistors

Hydrophobic, self-doped conjugated polyelectrolytes (CPEs) are introduced as highly stable active materials for organic electrochemical transistors (OECTs). The hydrophobicity of CPEs renders films very stable in aqueous solutions. The devices operate at gate voltages around zero and show no signs of degradation when operated for 104 cycles under ambient conditions. These properties make the produced OECTs ideal devices for applications in bioelectronics.

Electronic polymers in lipid membranes

Electrical interfaces between biological cells and man-made electrical devices exist in many forms, but it remains a challenge to bridge the different mechanical and chemical environments of electronic conductors (metals, semiconductors) and biosystems. Here we demonstrate soft electrical interfaces, by integrating the metallic polymer PEDOT-S into lipid membranes. By preparing complexes between alkyl-ammonium salts and PEDOT-S we were able to integrate PEDOT-S into both liposomes and in lipid bilayers on solid surfaces. This is a step towards efficient electronic conduction within lipid membranes. We also demonstrate that the PEDOT-S@alkyl-ammonium:lipid hybrid structures created in this work affect ion channels in the membrane of Xenopus oocytes, which shows the possibility to access and control cell membrane structures with conductive polyelectrolytes.

Development and application of methodology for rapid screening of potential amyloid probes.

Herein, we demonstrate that it is possible to rapidly screen hydrophobic fluorescent aromatic molecules with regards to their properties as amyloid probes. By grinding the hydrophobic molecule with the amyloidogenic protein insulin, we obtained a water-soluble composite material. When this material is dissolved and exposed to conditions promoting amyloid formation, the protein aggregates into amyloid fibrils incorporating the hydrophobic molecule. As a result, changes in the fluorescence spectra of the hydrophobic molecule can be correlated to the formation of amyloid fibrils, and the suitability of the hydrophobic molecular skeleton as an amyloid probe can thus be assessed. As a result, we discovered two new amyloid probes, of which one is the well-known laser dye DCM. The grinding method can also be used for rapid preparation of novel composite materials between dyes and proteins, which can be used in materials science applications such as organic electronics and photonics.

Protein nanowires with conductive properties

Herein we report on the investigation of self-assembled protein nanofibrils functionalized with metallic organic compounds. We have characterized the electronic behaviour of individual nanowires using conductive atomic force microscopy. In order to follow the self assembly process we have incorporated fluorescent molecules into the protein and used the energy transfer between the internalized dye and the metallic coating to probe the binding of the polyelectrolyte to the fibril.