Photoinduced electron transfer at the interface of semiconductor and organic donor-acceptor layer

This work investigates the electron transfer process (ET) at the interface between organic donor-acceptor dyads and semiconductor layers. The main goal was to identify possible combinations of organic dyads and semiconductors to be used in molecular heterojunction organic solar cells. The chosen donor acceptor pairs were porphyrin-fullerene (PC60) and perylene diimide-fullerene (PDIC60) whereas the studied semiconductors were zinc oxide (ZnO) and titanium dioxide (TiO2), with alumina (Al2O3) being the insulator and reference layer. Free-based porphyrin (CPTPP) was initially used to study the formation of monolayers. Spectroscopic studies were carried out to characterize the organic compounds both in solution and as monolayers on different surfaces. The organic monolayer absorption was studied by means of Langmuir-Blodgett (LB) deposition on flat glass substrates and on glass substrates covered by a thin spin-coated ZnO layer. Subsequent self-assembled monolayers (SAM) were prepared by dipping method on the same ZnO layer and their quality was compared to that of the LB ones. Photo-voltage measurements were carried out, by means of time-resolved Maxwell displacement charge (TRMDC) method, to study the vectorial electron transfer process in the organic layer and between the organic and semiconductor layers. Three different sets of samples were appositely prepared for these measures. An Al2O3 layer was deposited via atomic-layer-deposition (ALD) on ITO supports and served as insulating and reference layer with no electron transfer activity. Additional layers of either ZnO or TiO2 were deposited via ALD on top of the Al2O3 layer to yield two other sets of samples. SAM monolayers of the organic dyads were then deposited on each set and then covered with insulating LB ODA layers. The preparation of PDIC60 containing samples was satisfactory only on ZnO substrate whereas the one of PC60 on all substrates. Spectroscopic measurements were carried out to characterize the samples and confirm the presence of each molecular layer. TRMDC measures revealed the formation of a charge separated state in the active layer and the following charge recombination process in each sample. In particular the effect of the additional semiconductor layers was characterized. ZnO serves as efficient secondary electron acceptor as concluded from ten folds increase of the photo-voltage response of the PC60 SAM on ZnO as compared to that on Al2O3. For SAMs on TiO2 the response was somewhat lower in intensity as compared to Al2O3 samples. For both semiconductors long-lived charge separated states were observed, further confirming the oxide role as secondary electron acceptors. Despite of the observed sample degradation, these structures were considered as promising for organic photovoltaic applications

Flexible Photonic Cellulose Nanocrystal Films.

The fabrication of self-assembled cellulose nanocrystal (CNC) films of tunable photonic and mechanical properties using a facile, green approach is demonstrated. The combination of tunable flexibility and iridescence can dramatically expand CNC coating and film barrier capabilities for paints and coating applications, sustainable consumer packaging products, as well as effective templates for photonic and optoelectronic materials and structures.CelluForce Inc., Biotechnology and Biological Sciences Research Council (David Phillips fellowship (Grant ID: BB/K014617/1, 76933), European Research Council (Grant ID: ERC-2014-STG H2020 639088), Engineering and Physical Sciences Research Council (Grant ID: 1525292

Hierarchical Photonic Pigments via the Confined Self-Assembly of Bottlebrush Block Copolymers

Hierarchical, structurally colored materials offer a wide variety of visual effects that cannot be achieved with standard pigments or dyes. However, their fabrication requires simultaneous control over multiple length-scales. Here we introduce a robust strategy for the fabrication of hierarchical photonic pigments via the confined self-assembly of bottlebrush block copolymers within emulsified microdroplets. The bottlebrush block copolymer self-assembles into highly ordered concentric lamellae, giving rise to a near perfect photonic multi-layer in the solid-state, with reflectivity up to 100%. The reflected color can be readily tuned across the whole visible spectrum by either altering the molecular weight or by blending the bottlebrush block copolymers. Furthermore, the developed photonic pigments are responsive, with a selective and reversible color change observed upon swelling in different solvents. Our system is particularly suited for the scalable production of photonic pigments, arising from their rapid self-assembly mechanism and size-independent color.European Research Council [ERC-2014-STG H2020 639088] BBSRC [David Phillips Fellowship BB/K014617/1] EPSRC [1525292; EP/N016920/1; EP/R511675/1] National Natural Science Foundation of China [Grant 51873098] Winton Programme for the Physics of Sustainability

The role of Attachment Insecurity in the emergency of anxiety symptoms in children and adolescent with migraine: an empirical study

Background: It is widely recognised that there are associations between headache, psychiatric comorbidity and attachment insecurity in both adults and children. The aims of this study were: 1) to compare perceived attachment security and anxiety in children and adolescents with migraine without aura and a healthy control group; 2) to test whether the child’s perceived security of attachment to the mother and the father mediated the association between migraine and anxiety. Methods: One hundred children and adolescents with Migraine without Aura were compared with a control group of 100 children without headache. The Security Scale (measures perceived security of attachments) and the Self-Administered Psychiatric Scales for Children and Adolescents, a measure of anxiety symptoms, were administered to all participants. Results: The clinical group had lower attachment security than the control group and higher scores on all anxiety scales. Anxiety was negatively correlated with attachment. Children’s attachment to their mother mediated the increase in global anxiety in the clinical group. Insecure paternal attachment was associated with greater insecurity in maternal attachment, suggesting that there is a complex pathway from migraine to anxiety symptoms mediated by perceived insecurity of paternal attachment and hence also by perceived insecurity of maternal attachment. Conclusion: These results suggest that insecure parental attachment may exacerbate anxiety in children and adolescents with migraine and point to the importance of multimodal interventions, perhaps taking account of family relationships, for children and adolescents with migraine

Research data supporting Co-assembly of Cellulose Nanocrystals and Silk Fibroin into Photonic Cholesteric Films

The dataset is compressed into “.zip” files grouped in folders corresponding to the figures in which they were reported. All spectra were exported in format that are accessible with free software, and sometimes in additional format that require a license (Matlab, Origin, MS Excel).EPSRC (1525292), MSCA Individual fellowship (BINGO 743543), the Office of Naval research, USA (N000141812258), National Science Foundation, USA (award CMMI-1752172)

Research data supporting Effect of thermal treatments on chiral nematic cellulose nanocrystal films

the dataset content is described in the associated pdf summary

Somatic muscolature of Tardigrada: phylogenetic signal and metameric patterns

Although studies describing molecular-based phylogenies within tardigrades are now frequently being published, this is not the case for studies combining molecular and morphological characters. Tardigrade phylogeny is still based, from a morphological point of view, almost exclusively on chitinous structures and little attention has been given to detecting and using novel morphological data. Consequently, we analysed the musculature of seven tardigrade species belonging to the main phyletic lines by confocal laser scanning microscopy and compared these morphological results with new molecular analyses (18S+28S rRNA genes). Finally, we analysed all the data with a total evidence approach. A consilience in the phylogenetic relationships among orders and superfamilies of tardigrades was obtained among the evolutionary trees obtained from morphological, molecular and total evidence approaches. Comparative analysis on the musculature allowed the identification of serial homologies and repeated metameric patterns along the longitudinal animal body axis. A phenomenon of mosaic evolution was detected in musculature anatomy, as dorsal musculature was found to be highly modified with respect to the other body muscle groups, probably related to the evolution of dorsal cuticular plates. An understanding of tardigrade musculature anatomy will give fundamental information to understand the evolution of segmental pattern within Panarthropoda

The angular optical response of cellulose nanocrystal films explained by the distortion of the arrested suspension upon drying.

Cellulose nanocrystals (CNCs) are bio-sourced chiral nanorods that can form stable colloidal suspensions able to spontaneously assemble above a critical concentration into a cholesteric liquid crystal, with a cholesteric pitch usually in the micron range. When these suspensions are dried on a substrate, solid films with a pitch of the order of few hundreds of nanometers can be produced, leading to intense reflection in the visible range. However, the resulting cholesteric nanostructure is usually not homogeneous within a sample and comports important variations of the cholesteric domain orientation and pitch, which affect the photonic properties. In this work, we first propose a model accounting for the formation of the photonic structure from the vertical compression of the cholesteric suspension upon solvent evaporation, starting at the onset of the kinetic arrest of the drying suspension and ending when solvent evaporation is complete. From that assumption, various structural features of the films can be derived, such as the variation of the cholesteric pitch with the domain tilt, the orientation distribution density of the final cholesteric domains and the distortion of the helix from the unperturbed cholesteric case. The angular-resolved optical response of such films is then derived, including the iridescence and the generation of higher order reflection bands, and a simulation of the angular optical response is provided, including its tailoring under external magnetic fields. Second, we conducted an experimental investigation of CNC films covering a structural and optical analysis of the films. The macroscopic appearance of the films is discussed and complemented with angular-resolved optical spectroscopy, optical and electron microscopy, and our quantitative analysis shows an excellent agreement with the proposed model. This allows us to access the precise composition and the pitch of the suspension when it transited into a kinetically arrested phase directly from the optical analysis of the film. This work highlights the key role that the anisotropic compression of the kinetically arrested state plays in the formation of CNC films and is relevant to the broader case of structure formation in cast dispersions and colloidal self-assembly upon solvent evaporation.This work was supported by a BBSRC David Phillips fellowship [BB/K014617/1], the EPSRC grants [1525292], [EP/R511675/1], [EP/N016920/1] and [EP/K503757/1], The Isaac Newton Trust Cambridge [1423(g) 76933] and the European Research Council grants [ERC-2014-STG H2020 639088] and [ERC-PoC-2017 790518]

Research Data supporting "Angular optical response of cellulose nanocrystal films explained by the distortion of the arrested suspension upon drying"

The data are organized and grouped in dedicated .zip files for each Figure they contribute to. All figures (1-21) are present in high resolution in each sub-folder. Software for file extensions: .tif, .png (image format), .m and .fig (MATLAB), text files (.txt). For further details, see the file "Open data summary"