Band 89, Heft 12

This work studied the growth of calcium carbonate single crystals on top of the monolayer of Fe 3 O 4 @SiO 2 nanoparticles (NPs) with added external magnetic field. It showed that the occlusion process of the NPs into calcium carbonate single crystals varies as the force balance on the NPs shifts. Under no or weak magnetic field, the NPs are relatively mobile, the separation force from the substrate on NPs due to the growing calcium carbonate crystals is larger than the attraction force to the substrate by the magnetic field. The complete occlusion of the NPs into the single crystals is therefore observed. As the magnetic field strength increases, the balance shifts toward the attraction force. The mobility of NPs decreases and partial occlusion of the NPs into the single crystals is gradually observed. The findings in this study offer further insight into the occlusion process experienced by the NPs and also potential approach in engineering the force balance for the design and generation of composite materials that occlude foreign materials into their matrix.

Vegetal and animal reigns offer many examples of surfaces with surprising and interesting wetting properties. As example, springtails present superoleophobic properties allowing to live in soil and Lotus leaves show self-cleaning ability even under rainfalls. Indeed, it is known that self-cleaning properties can help to remove dust and particles during rainfalls and as a consequence to clean the surface. The bioinspiration of these surface properties is of a real interest for industrial applications in the nanotechnology field such as photovoltaic systems or anti corrosive material. Here, we use a strategy based on electropolymerization to obtain these properties. The Staudinger-Vilarrasa reaction is used to prepare innovative 3,4-ethylenedioxypyrrole (EDOP) monomers with fluorinated chains. Using C 6 F 13 or C 8 F 17 chains, the polymer surfaces formed after electrodeposition show superhydrophobic and superoleophobic features. Here we study the surface wettability depending on the surface energy (based on the perfluorinated chain length), the surface roughness and morphology.

In the ground state, the p-methoxyphenyl-substituted pyranoflavylium cation I , prepared by the reaction of the 5,7-dihydroxy-4-methylflavylium cation with p-methoxybenzaldehyde, is a weak acid (pK a =3.7±0.1). In its lowest excited singlet state, I is a moderate photoacid (pK a *=0.67) in 30% methanol-water acidified with trifluoroacetic acid (TFA). In comparison to anthocyanins and 7-hydroxyflavylium cations, the photoacidity of I is much less pronounced and the rate of proton loss from the excited acid form of I much slower (by a factor of up to 100). In 50% ethanol:0.10 mol dm −3 HClO 4 , the excited state of the acid form of I undergoes fast (12 ps) initial relaxation (potentially in the direction of an intramolecular charge transfer state), followed by much slower (340 ps) adiabatic deprotonation to form the excited base. The excited base in turn exhibits a moderately fast relaxation (70 ps), consistent with solvent hydrogen-bond reorganization times, followed by slower but efficient decay (1240 ps) back to the ground state. As in uncomplexed anthocyanins and 7-hydroxyflavylium cations, the photophysical behavior of I points to excited state proton transfer as the dominant excited state deactivation pathway of pyranoanthocyanins, consistent with relatively good photostability of natural pyranoanthocyanins.

Silks are well known natural fibers used for textile applications and have got for the first time available upon sericulture of silkworms ( Bombyx mori ) several thousand years ago in China. In contrast to silkworm silk, spider silks offer better mechanical properties such as higher tensile strength and much better toughness, but natural spider silk is less accessible due to the cannibalistic behavior of spiders prohibiting large scale farming, and therefore has not been employed in textile industry yet. In this study, a biotechnologically produced spider silk protein was introduced as a new material for textile applications in form of foam coating material. The spider silk foam coating was developed to increase the abrasion behavior of natural and polymeric furniture textiles. Modern textiles are high-tech materials and optimized concerning yarn design and fabric weave to fit a wide range of applications. Often hydrofluorocarbons based coatings are used to enhance textile performances. Upon coating with sustainable spider silk, yarn fraying was significantly reduced lowering the tendency to form knots and loops. Further, the textile abrasion resistance, analyzed by pilling tests, was improved significantly (17–200%) for all tested types of fabrics, in particular long term strain pilling was minimized.

Molecular-level control of charge transfer (CT) is essential for both, organic electronics and solar-energy conversion, as well as for a wide range of biological processes. This article provides an overview of the utility of local electric fields originating from molecular dipoles for directing CT processes. Systems with ordered dipoles, i.e. molecular electrets, are the centerpiece of the discussion. The conceptual evolution from biomimicry to biomimesis, and then to biological inspiration, paves the roads leading from testing the understanding of how natural living systems function to implementing these lessons into optimal paradigms for specific applications. This progression of the evolving structure-function relationships allows for the development of bioinspired electrets composed of non-native aromatic amino acids. A set of such non-native residues that are electron-rich can be viewed as a synthetic proteome for hole-transfer electrets. Detailed considerations of the electronic structure of an individual residue prove of key importance for designating the points for optimal injection of holes (i.e. extraction of electrons) in electret oligomers. This multifaceted bioinspired approach for the design of CT molecular systems provides unexplored paradigms for electronic and energy science and engineering.

Electrospinning is a versatile technique to produce micron or nano sized fibers using synthetic or bio polymers. The unique structural characteristic of the electrospun mats (ESM) which mimics extracellular matrix (ECM) found influential in regenerative tissue engineering application. ESM with different morphologies or ESM functionalizing with specific growth factors creates a favorable microenvironment for the stem cell attachment, proliferation and differentiation. Fiber size, alignment and mechanical properties affect also the cell adhesion and gene expression. Hence, the effect of ESM physical properties on stem cell differentiation for neural, bone, cartilage, ocular and heart tissue regeneration will be reviewed and summarized. Electrospun fibers having high surface area to volume ratio present several advantages for drug/biomolecule delivery. Indeed, controlling the release of drugs/biomolecules is essential for sustained delivery application. Various possibilities to control the release of hydrophilic or hydrophobic drug from the ESM and different electrospinning methods such as emulsion electrospinning and coaxial electrospinning for drug/biomolecule loading are summarized in this review.

Unnatural peptide self-assembly offers the means to design hierarchical nanostructures of controlled geometries, chemical function and physical properties. N-acyl β 3 peptides, where all residues are unnatural amino acids, are able to form helical fibrous structures by a head-to-tail assembly of helical monomers, extending the helix via a three point supramolecular hydrogen bonding motif. These helical nanorods were shown to be stable under a wide range of physical conditions, offering a self-assembled analogue of polymeric fibres. Hitherto the self-assembly has only been demonstrated between identical monomers; however the self-assembly motif is sequence-independent, offering the possibility of hetero-assembly of different peptide monomers. Here we present a proof of principle study of head-to-tail co-assembly of two different helical unnatural peptides Ac-β 3 [WELWEL] and Ac-β 3 [LIA], where the letters denote the β 3 analogues of natural amino acids. By atomic force microscopy imaging it was demonstrated that the homo-assembly and co-assembly of these peptides yield characteristically different structures. Synchrotron small angle X-ray scattering experiments have confirmed the presence of the fibres in the solution and the averaged diameters from modelled data correlate well to the results of AFM imaging. Hence, there is evidence of co-assembly of the fibrous superstructures; given that different monomers may be used to introduce variations into chemical and physical properties, the results demonstrate a self-assembled analogue of a statistical co-polymer that can be used in designing complex functional nanomaterials.

The development of active, cheap, efficient and visible-light-driven water splitting catalysts is currently the center of intense research efforts. Amongst the most promising avenues, the design of titania and plasmonic nanoparticle hybrids is particularly appealing. Titania has been known for long to be an active photocatalyst, able to perform water splitting under light irradiation. However, this activity is limited to the ultraviolet spectrum and suffers from too rapid charge carrier recombination. The addition of plasmonic nanostructures enables to push absorption properties to the visible region and prevent unwanted charge recombination. In this review, we explain the principles behind the activity of such nanohybrids towards visible light water splitting and detail the recent research developments relying on plasmonic metals, namely Au, Ag and Cu.

In this study thin films based on a blend of collagen, chitosan and hyaluronic acids were prepared and their surface and mechanical properties were studied. The structure of the films was studied using FTIR spectroscopy, contact angle measurement and AFM images. Swelling and mechanical analyses were also performed. The hair protection possibility of collagen/chitosan/hyaluronic was studied using SEM microscopy and the mechanical testing of hair coated by the blends. It was found that the addition of hyaluronic acid to a collagen/chitosan blend improves the mechanical resistance of biopolymeric films. Samples with the addition of hyaluronic acid were more stable in aqueous conditions and provided higher roughness of surface.

Today, there is an increasing concern about protection of ecological systems. Petro-based synthetic polymers are not biodegradable and cause environmental pollution. These polymers that are stuck in nature, affect wildlife adversely. Also, in future petrochemical materials will drain away and demand for eco-friendly plastics which can substitute synthetic plastics will increase. Biopolymers are products which can be degraded by enzymatic activities of various microorganisms, and the degradation products are nontoxic. They are attractive alternatives to non-degradable materials in short-term applications such as packaging. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a member of polyhydroxyalkanoate (PHA) family which is biodegradable and produced by microorganism. It has good gas barrier properties that make it convenient to use in different applications. The present paper gives an overview on PHAs and their composites, their main properties, with a specific focus on potential applications of PHBV in packaging.

This IUPAC Technical Report describes and compares the currently applied methods for the calibration and standardization of multi-dimensional fluorescence (MDF) spectroscopy data as well as recommendations on the correct use of chemometric methods for MDF data analysis. The paper starts with a brief description of the measurement principles for the most important MDF techniques and a short introduction to the most important applications. Recommendations are provided for instrument calibration, sample preparation and handling, and data collection, as well as the proper use of chemometric data analysis methods.