A mechanophysical phase transition provides a dramatic example of colour polymorphism: the tribochromism of a substituted tri(methylene)tetrahydrofuran-2-one

BACKGROUND: Derivatives of fulgides have been shown to have interesting photochromic properties. We have synthesised a number of such derivatives and have found, in some cases, that crystals can be made to change colour on crushing, a phenomenon we have termed "tribochromism". We have studied a number of derivatives by X-ray crystallography, to see if the colour is linked to molecular structure or crystal packing, or both, and our structural results have been supported by calculation of molecular and lattice energies. RESULTS: A number of 5-dicyanomethylene-4-diphenylmethylene-3-disubstitutedmethylene-tetrahydrofuran-2-one compounds have been prepared and structurally characterised. The compounds are obtained as yellow or dark red crystals, or, in one case, both. In two cases where yellow crystals were obtained, we found that crushing the crystals gave a deep red powder. Structure determinations, including those of the one compound which gave both coloured forms, depending on crystallisation conditions, showed that the yellow crystals contained molecules in which the structure comprised a folded conformation at the diphenylmethylene site, whilst the red crystals contained molecules in a twisted conformation at this site. Lattice energy and molecular conformation energies were calculated for all molecules, and showed that the conformational energy of the molecule in structure IIIa (yellow) is marginally higher, and the conformation thus less stable, than that of the molecule in structure IIIb (red). However, the van der Waals energy for crystal structure IIIa, is slightly stronger than that of structure IIIb - which may be viewed as a hint of a metastable packing preference for IIIa, overcome by the contribution of a more stabilising Coulomb energy to the overall more favourable lattice energy of structure IIIb. CONCLUSIONS: Our studies have shown that the crystal colour is correlated with one of two molecular conformations which are different in energy, but that the less stable conformation can be stabilised by its host crystal lattice. Graphical abstractGraphical representation of the structural and colour change in the tribochromic compound (III)

Increasing efficiency of perovskite solar cells using low concentrating photovoltaic systems

This is the final version. Available from Royal Society of Chemistry via the DOI in this record. Perovskite solar cell (PSC) technology is the flag bearer for the future of photovoltaics allowing unlimited possibilities for its application. This technology is currently limited by issues related to its scale-up, stability and the composition of the materials used in its preparation. Using small sized solar cells with higher efficiency under solar concentration is gaining traction as a methodology for scaling up this technology and broadening its applications. However, this has only been reported in devices with size <1 mm2 neglecting the series resistance of the device. Here, we report the performance of a 9 mm2 PSC at varying solar concentration levels and correlate it with the series resistance of the solar cell. The n–i–p structured device using a triple cation perovskite absorber with a mesoporous titanium oxide/SnO2 layer as the electron transporting layer and Spiro-OMeTAD as the hole transporting material achieved a peak efficiency of 21.6% under 1.78 Suns as compared to the 21% obtained under 1 Sun (1000W m−2) and AM1.5G. We further boosted the power output up to 15.88 mW under 10.7 Suns compared to the 1.88 mW obtained under 1 Sun; however this results in an actual efficiency drop of the PSC owing to the device series resistance. Further, we investigated the impact of the increasing solar cell temperature at higher concentration levels and identified the influence of series resistance on the performance of the PSC. Our work identifies the potential of concentrating photovoltaics and highlights the challenges and makes recommendations for future development.EPSRCEuropean Union's Horizon 202

Certified high-efficiency "large-area" perovskite solar cells module for Fresnel lens-based concentrated photovoltaic

This is the author accepted manuscript. The final version is available on open access from Cell Press via the DOI in this recordData availability: All data generated or analysed during this study are included in the Supplementary Information article and its data source. Source data are provided in this paper. All data reported in this paper will be shared by the lead contact upon request.The future of energy generation is well in tune with the critical needs of the global economy, leading to more green innovations and emissions-abatement technologies. Introducing concentrated photovoltaic (CPV) is one of the most promising technologies owing to its high photo-conversion efficiency (PCE). While most researchers use silicon and cadmium telluride for CPV, we investigate the potential in nascent technologies, such as perovskite solar cell (PSC). This work constitutes a preliminary investigation into a ‘large-area’ PSC module under a Fresnel lens (FL) with a ‘refractive optical concentrator-silicon-on-glass’ base to minimise the PV performance and scalability trade-off concerning the PSCs. The FL-PSC system measured the solar current-voltage characteristics in variable lens-to-cell distances and illuminations. A systematic study of the PSC module temperature was monitored using the COMSOL transient heat transfer mechanism. The FL-based technique for ‘large-area’ PSC architecture is an unfolded technology that further facilitates the potential for commercialisation.Engineering and Physical Sciences Research Council (EPSRC)Valais Energy Demonstrators FundEuropean Union Horizon 2020Deputyship for Research & Innovation, Ministry of Education, Saudi Arabi

Search for Gravitational Waves from Primordial Black Hole Binary Coalescences in the Galactic Halo

We use data from the second science run of the LIGO gravitational-wave detectors to search for the gravitational waves from primordial black hole (PBH) binary coalescence with component masses in the range 0.2--$1.0 M_\odot$. The analysis requires a signal to be found in the data from both LIGO observatories, according to a set of coincidence criteria. No inspiral signals were found. Assuming a spherical halo with core radius 5 kpc extending to 50 kpc containing non-spinning black holes with masses in the range 0.2--$1.0 M_\odot$, we place an observational upper limit on the rate of PBH coalescence of 63 per year per Milky Way halo (MWH) with 90% confidence.Comment: 7 pages, 4 figures, to be submitted to Phys. Rev.

Rectangular Coordination Polymer Nanoplates: Large-Scale, Rapid Synthesis and Their Application as a Fluorescent Sensing Platform for DNA Detection

In this paper, we report on the large-scale, rapid synthesis of uniform rectangular coordination polymer nanoplates (RCPNs) assembled from Cu(II) and 4,4′-bipyridine for the first time. We further demonstrate that such RCPNs can be used as a very effective fluorescent sensing platform for multiple DNA detection with a detection limit as low as 30 pM and a high selectivity down to single-base mismatch. The DNA detection is accomplished by the following two steps: (1) RCPN binds dye-labeled single-stranded DNA (ssDNA) probe, which brings dye and RCPN into close proximity, leading to fluorescence quenching; (2) Specific hybridization of the probe with its target generates a double-stranded DNA (dsDNA) which detaches from RCPN, leading to fluorescence recovery. It suggests that this sensing system can well discriminate complementary and mismatched DNA sequences. The exact mechanism of fluorescence quenching involved is elucidated experimentally and its use in a human blood serum system is also demonstrated successfully

JOURNAL OF MOLECULAR STRUCTURE

In this work, an organic nonlinear optical material (E)-1-(4-bromophenyl)-3-(4-(dimethylamino)phenyl)prop-2-en-1-one (C17H16NOBr) was synthesized by reacting 4-bromoacetophenone and N,N-dimethyl benzaldehyde in ethanol in the presence of sodium hydroxide. FT-IR and FT-Raman spectra were recorded in the region 4000-500 cm(-1) and 4000-50 cm(-1), respectively. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method (B3LYP) with 6-311++G(d,p) basis set. The vibrational frequencies were calculated and compared with the experimental frequencies, which yield good agreement between observed and calculated frequencies. The infrared and Raman spectra were also predicted from the calculated intensities. H-1 NMR spectrum was recorded in CDC13 and H-1 NMR chemical shifts of the molecule were calculated using the gauge independent atomic orbital (GIAO) method. UV-visible spectrum of the compound was recorded in water in the range of 200-800 nm and the electronic properties were calculated by time-dependent density functional theory (TD-DFT) approach. Besides, Mulliken atomic charges, molecular electrostatic potential (MEP) were performed. Nonlinear optical features and thermodynamic properties were also outlined theoretically. The geometric parameters, energies, harmonic vibrational frequencies, chemical shifts and absorption wavelengths were compared with the available experimental data of the molecule. Comprehensive theoretical and experimental structural studies on the molecule were carried out by FT-IR, FT-Raman, NMR and UV spectrometry. (C) 2015 Elsevier B.V. All rights reserved

Greater cardiomyocyte density on aligned compared with random carbon nanofibers in&nbsp;polymer composites

Abdullah M Asiri,1 Hadi M Marwani,1 Sher Bahadar Khan,1 Thomas J Webster1,2 1Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi&nbsp;Arabia; 2Department of Chemical Engineering,&nbsp;Northeastern University, Boston, MA, USA Abstract: Carbon nanofibers (CNFs) randomly embedded in poly(lactic-co-glycolic-acid) (PLGA) composites have recently been shown to promote cardiomyocyte growth when compared with conventional PLGA without CNFs. It was shown then that PLGA:CNF composites were conductive and that conductivity increased as greater amounts of CNFs were added to pure PLGA. Moreover, tensile tests showed that addition of CNFs increased the tensile strength of the PLGA composite to mimic that of natural heart tissue. Most importantly, throughout all cytocompatibility experiments, cardiomyocytes were viable and expressed important biomarkers that were greatest on 50:50 wt% CNF:PLGA composites. The increased selective adsorption of fibronectin and vitronectin (critical proteins that mediate cardiomyocyte function) onto such composites proved to be the mechanism of action. However, the natural myocardium is anisotropic in terms of mechanical and electrical properties, which was not emulated in these prior PLGA:CNF composites. Thus, the aim of this in vitro study was to create and characterize CNFs aligned in PLGA composites (at 50:50 wt%, including their mechanical and electrical properties and cardiomyocyte density), comparing such results with randomly oriented CNFs in PLGA. Specifically, CNFs were added to soluble biodegradable PLGA (50:50 PGA:PLA weight ratio) and aligned by applying a voltage and then allowing the polymer to cure. CNF surface micron patterns (20 &micro;m wide) on PLGA were then fabricated through a mold method to further mimic myocardium anisotropy. The results demonstrated anisotropic mechanical and electrical properties and significantly improved cardiomyocyte density for up to 5 days on CNFs aligned in PLGA compared with being randomly oriented in PLGA. These results indicate that CNFs aligned in PLGA should be further explored for improving cardiomyocyte density, which is necessary in numerous cardiovascular applications. Keywords: cardiomyocytes, poly(lactic-co-glycolic acid), carbon nanofibers, aligned, nanotechnology, anisotrop

Controlled release of organic&ndash;inorganic nanohybrid:cefadroxil intercalated Zn&ndash;Al-layered double hydroxide

Sher Bahadar Khan,1,2 Khalid A Alamry,2 Nedaa A Alyahyawi,3 Abdullah M Asiri1,2 1Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, Jeddah, Saudi Arabia; 2Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia; 3Chemistry Department, Faculty of Science, University of Jeddah, Jeddah, Saudi Arabia Background: The intercalation of an antibiotic drug, cefadroxil (CD), into the inter-gallery of Zn, Al nitrate-layered double hydroxide (LDH) was accomplished using a co-precipitation method. This formed a nanostructured organic&ndash;inorganic hybrid material that can be exploited for the preparation of a controlled release formulation. Materials and methods: The drug&ndash;LDH nanohybrid was characterized by using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) thermogravimetric (TG) analysis, X-ray powder diffraction (XRD) and UV&ndash;visible (UV&ndash;vis) absorption spectroscopy, which confirmed the intercalation process. Release tests of nanohybrid in the presence or absence of NaCl or polyacrylamide (PAM) were performed in vitro in gastric (pH 1.2), lysosomal (pH 4.0), intestinal (pH 6.8) and blood (pH 7.4) simulated fluid using UV&ndash;vis spectroscopy. Results: At pH 1.2, LDH was dissolved and intercalated antibiotic released from ZnAl-CD in a molecular form, which led to a significant increase in the antibiotic&rsquo;s solubility. Results showed that the release of drug from nanohybrid at pH 4.0, 6.8 and 7.4 was a sustained process. Conclusion: This material might reduce side effects by the release of the drug in a controlled manner. However, it was found that the presence of Cl or PAM species in the release media has a negative impact on the release behavior. The weathering mechanism is responsible for the release of CD from the nanocomposite at pH 1.2, while the mechanism of anion exchange may be responsible for the release behavior at pH 4.0, 6.8 and 7.4. A number of kinetic models were chosen to gain more insights into the mechanisms of drug release. At pH 1.2, the zero-order model most satisfactorily explained the release kinetics of CD, while the release data of CD at pH 4.0, 6.8 and 7.4 were governed by Bhaskar kinetics. Keywords: drug delivery system, ZnAl-CD LDH nanohybrid, hydrotalcite, antibiotic, drug release, kinetic

Understanding greater cardiomyocyte functions on aligned compared to random carbon nanofibers in PLGA

Abdullah M Asiri,1 Hadi M Marwani,1 Sher Bahadar Khan,1 Thomas J Webster1,2 1Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia; 2Department of Chemical Engineering, Northeastern University, Boston, MA, USA Abstract: Previous studies have demonstrated greater cardiomyocyte density on carbon nanofibers (CNFs) aligned (compared to randomly oriented) in poly(lactic-co-glycolic acid) (PLGA) composites. Although such studies demonstrated a closer mimicking of anisotropic electrical and mechanical properties for such aligned (compared to randomly oriented) CNFs in PLGA composites, the objective of the present in vitro study was to elucidate a deeper mechanistic understanding of how cardiomyocyte densities recognize such materials to respond more favorably. Results showed lower wettability (greater hydrophobicity) of CNFs embedded in PLGA compared to pure PLGA, thus providing evidence of selectively lower wettability in aligned CNF regions. Furthermore, the results correlated these changes in hydrophobicity with increased adsorption of fibronectin, laminin, and vitronectin (all proteins known to increase cardiomyocyte adhesion and functions) on CNFs in PLGA compared to pure PLGA, thus providing evidence of selective initial protein adsorption cues on such CNF regions to promote cardiomyocyte adhesion and growth. Lastly, results of the present in vitro study further confirmed increased cardiomyocyte functions by demonstrating greater expression of important cardiomyocyte biomarkers (such as Troponin-T, Connexin-43, and &alpha;-sarcomeric actin) when CNFs were aligned compared to randomly oriented in PLGA. In summary, this study provided evidence that cardiomyocyte functions are improved on CNFs aligned in PLGA compared to randomly oriented in PLGA since CNFs are more hydrophobic than PLGA and attract the adsorption of key proteins (fibronectin, laminin, and vironectin) that are known to promote cardiomyocyte adhesion and expression of important cardiomyocyte functions. Thus, future studies should use this knowledge to further design improved CNF:PLGA composites for numerous cardiovascular applications. Keywords: cardiomyocytes, poly(lactic-co-glycolic acid), carbon nanofibers, aligned, nanotechnology, anisotropy, mechanism, vitronectin, fibronectin, lamini