1,721,171 research outputs found
Photonic crystals: Sustainable sensors from silk
No full textSunghwan Kim and co-workers demonstrated the controlled fabrication of a silk inverse opal (SIO), a type of photonic crystal, from fibroin, a silk-derived protein that meets all the criteria for sustainability. The extracted fibroin solution is poured over a self-assembled colloidal crystal of close-packed poly(methyl methacrylate) (PMMA) spheres and left to dry. The PMMA is then dissolved, leaving an inverse lattice of fibroin. The periodic variation of the refractive index between the lattice and the voids imparts structural color to the crystal. Kim and co-researchers control the color of the SIOs, both by varying the size of the PMMA spheres and by filling the voids with acetone. They then irradiate their samples with white light, and observe that the color of their crystals changes according to the specified optogeometric parameters
Molecular self-assembly on graphene
No full textThe formation of ordered arrays of molecules via self-assembly is a rapid, scalable route towards the realization of nanoscale architectures with tailored properties. In recent years, graphene has emerged as an appealing substrate for molecular self-assembly in two dimensions. Here, the first five years of progress in supramolecular organization on graphene are reviewed. The self-assembly process can vary depending on the type of graphene employed: epitaxial graphene, grown in situ on a metal surface, and non-epitaxial graphene, transferred onto an arbitrary substrate, can have different effects on the final structure. On epitaxial graphene, the process is sensitive to the interaction between the graphene and the substrate on which it is grown. In the case of graphene that strongly interacts with its substrate, such as graphene/Ru(0001), the inhomogeneous adsorption landscape of the graphene moiré superlattice provides a unique opportunity for guiding molecular organization, since molecules experience spatially constrained diffusion and adsorption. On weaker-interacting epitaxial graphene films, and on non-epitaxial graphene transferred onto a host substrate, self-assembly leads to films similar to those obtained on graphite surfaces. The efficacy of a graphene layer for facilitating planar adsorption of aromatic molecules has been repeatedly demonstrated, indicating that it can be used to direct molecular adsorption, and therefore carrier transport, in a certain orientation, and suggesting that the use of transferred graphene may allow for predictible molecular self-assembly on a wide range of surfaces. Understanding the behavior of monolayer and sub-monolayer films of molecules on graphene is critical to controlling the growth of these films, and exploiting them for doping, bandgap engineering, and for yet unforeseen applications. Here, the recent progress towards understanding molecular self-assembly on graphene is reviewed. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Probing functional self-assembled molecular architectures with solution/solid scanning tunnelling microscopy
No full textOver the past two decades, solution/solid STM has made clear contributions to our fundamental understanding of the thermodynamic and kinetic processes that occur in molecular self-assembly at surfaces. As the field matures, we provide an overview of how solution/solid STM is emerging as a tool to elucidate and guide the use of self-assembled molecular systems in practical applications, focusing on small molecule device engineering, molecular recognition and sensing and electronic modification of 2D materials
Tailoring the Heterostructure of Colloidal Quantum Dots for Ratiometric Optical Nanothermometry
No full textColloidal quantum dots (QDs) are a fascinating class of semiconducting nanocrystals, thanks to their optical properties tunable through size and composition, and simple synthesis methods. Recently, colloidal double-emission QDs have been successfully applied as competitive optical temperature sensors, since they exhibit structure-tunable double emission, temperature-dependent photoluminescence, high quantum yield, and excellent photostability. Until now, QDs have been used as nanothermometers for in vivo biological thermal imaging, and thermal mapping in complex environments at the sub-microscale to nanoscale range. In this Review, recent progress for QD-based nanothermometers is highlighted and perspectives for future work are described
Ultrasensitive, Biocompatible, Self-Calibrating, Multiparametric Temperature Sensors
No full textCore-shell quantum dots serve as self-calibrating, ultrasensitive, multiparametric, near-infrared, and biocompatible temperature sensors. They allow temperature measurement with nanometer accuracy in the range 150-373 K, the broadest ever recorded for a nanothermometer, with sensitivities among the highest ever reported, which makes them essentially unique in the panorama of biocompatible nanothermometers with potential for in vivo biological thermal imaging and/or thermoablative therapy
Antibacterial Coatings: Challenges, Perspectives, and Opportunities
No full textAntibacterial coatings are rapidly emerging as a primary component of the global mitigation strategy of bacterial pathogens. Thanks to recent concurrent advances in materials science and biotechnology methodologies, and a growing understanding of environmental microbiology, an extensive variety of options are now available to design surfaces with antibacterial properties. However, progress towards a more widespread use in clinical settings crucially depends on addressing the key outstanding issues. We review release-based antibacterial coatings and focus on the challenges and opportunities presented by the latest generation of these materials. In particular, we highlight recent approaches aimed at controlling the release of antibacterial agents, imparting multi-functionality, and enhancing long-term stability. Coatings releasing antibacterial agents have shown great potential to reduce nosocomial infections.The development of controlled release strategies is necessary to optimize therapeutic effects. Next-generation coatings should be multifunctional and integrate multiple antibacterial effects.Standardized assessment of both stability and antibacterial properties still need to be addressed, especially for long-term applications
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