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Melanin, a bio-polymer responsible for visible pigmentation in the human body, works as a protective layer in our skin by absorbing UV radiation and efficiently dissipating it into heat, preventing DNA damage. The primary structure of eumelanin, one of the two main forms of melanin, is presumed to be a co-polymer of 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole- 2-carboxylic acid (DHICA) monomers, with DHI being the major component. The solution phase investigation into the origin of broadband monotonic absorption spectrum of melanin has been unfolded through the polymerization of dopamine and L-DOPA, the molecular precursors of DHI and DHICA, respectively, in an ionic liquid (IL). This study reveals that the evolution of the electronic absorption spectrum of polymerized L-DOPA did not mimic the electronic spectrum of eumelanin, which was attributed to their inability to form stable redox states, as elucidated via structural characterization. Contrary to that, polymerized DA (pDA) mimics the eumelanin absorption spectrum, and the structural characterization of the polymerization process performed with 1H and 13C NMR and DOSY spectroscopy allowed us to identify chromophores responsible for the absorption profile of pDA. Furthermore, identified chromophores were subjected to quantum chemical calculations and their absorption spectra not only supported their presence in the experimental UV-Vis spectra but also allowed us to identify their gradual evolution during polymerisation. The knowledge of chromophores responsible for the optical properties of melanin will undoubtedly result in their increased application in functional materials.

Minimal understanding of the formation mechanism and structure of polydopamine (pDA) and its natural analogues, eumelanin impedes the practical application of these versatile polymers and limits our knowledge of the origin of melanoma.1–8 The lack of conclusive structural evidence stems from the insolubility of these materials, which has spawned significantly diverse suggestions of pDA’s structure in the literature.9,10 We discovered that pDA is soluble in certain ionic liquids. Using these ionic liquids (ILs) as solvents, we present an experimental methodology to solvate pDA, enabling us to identify pDA’s chemical structure. The resolved pDA structure consists of self-assembled supramolecular aggregates that contribute to the increasing complexity of the polymer. The underlying molecular energetics of pDA solvation and a macroscopic picture of the disruption of the aggregates using IL solvents have been investigated, along with studies of the aggregation mechanism in water.

Understanding how insect-derived biomaterials interact with light has led to new advances and interdisciplinary insights in entomology and physics. Leafhoppers are insects that coat themselves with highly ordered biological nanostructures known as brochosomes. Brochosomes are thought to provide a range of protective properties to leafhoppers, such as hydrophobicity and anti-reflectivity, which has inspired the development of synthetic brochosomes that mimic their structures. Despite recent progress, the ultra-high anti-reflective properties of brochosome structures are not fully understood. In this work, we use a combination of experiments and computational modeling to understand the structure-, material-, and polarization-dependent optical properties of brochosomes modeled on the geometries found in three leafhopper species. Our results show that that Fano resonance is responsible for the ultra-high anti-reflectivity of brochosomes. Whereas prior work has focused on computational modeling of idealized pitted particles, our work shows that light-matter interactions with brochosome structures can be tuned by varying the geometry of their cage-like nanoscale features and by changing the arrangement of multi-particle assemblies. Broadly, this work establishes principles for the guided design of new optically active materials inspired by these unique insect nanostructures.

Water swollen polymer networks are attractive for applications ranging from tissue regeneration to water purification. For water purification, charged polymers provide excellent ion separation properties. However, many ion exchange membranes (IEMs) are brittle, necessitating the use of thick support materials that ultimately decrease throughput. To this end, a series of double network hydrogels (DNHs), synthesized with varied composition to decrease water content, are examined as robust membrane materials for water purification. One network contains fixed anionic charges, while the other comprises a copolymer with different ratios of hydrophobic ethyl acrylate (EA) and hydrophilic dimethyl acrylamide (DMA) repeat units. Characterizing water content and mechanical performance in free standing DNH films reveals a ~5× decrease in water content, while increasing ultimate stress and strain by ~3.5× and ~4.5× for 90:5 EA:DMA relative to pure DMA. Salt transport properties relevant to water purification, including permeability, solubility, and diffusivity, are measured and show improved performance upon reducing water content. Overall, the ability to simultaneously reduce water content, increase mechanical integrity, and decrease salt transport rates highlights the potential of DNHs for membrane applications.

SummaryBackground Children's exposure to unhealthy food marketing is a contributor to poor diets and weight gain. Television food advertising, in particular, has been the focus of research and policy discussions. Objectives We aimed to quantify the specific impact of television advertising, as distinct from television viewing generally, on children's usual diet. Methods Four hundred seventeen Australian children aged 10–16 participated in an online survey, which assessed television viewing habits and consumption of 12 frequently advertised unhealthy foods/drinks. Consumption of these foods/drinks was dichotomized (less weekly, weekly or more) and summed (1 point for each item consumed weekly or more) to give cumulative consumption scores. Results After adjusting for age and socioeconomic status, there was strong evidence of an increase in unhealthy food score (P

Around the world, drought inflicts an increasingly unpredictable, frequent and devastating toll on human activities, ranging from, for example, struggling to secure access to sufficient clean water to simply survive, leading to political unrest and instability, increasing the cost of agriculture and manufacturing operations, and damaging the environment, both directly and indirectly. Climate change exacerbates stress on both water supply and demand. Water and energy are inexorably linked, with enormous volumes of water required to generate energy in many cases and large energy inputs required to purify water. In the U.S., thermoelectric power plants account for 41% of total water withdrawals, with nearly all the water requiring some form of purification before use. Horizontal drilling and hydraulic fracturing unleashed a sea of valuable hydrocarbons in the U.S., revitalizing the chemical industry, weakening dependence on foreign energy sources, and reducing oil and gas prices worldwide. However, oil and gas production comes at a substantial price in terms of the amount of water required and the amount of flowback or produced water generated. In many cases, for every barrel of oil produced, 5 or more barrels of water are also produced. This water is contaminated and requires substantial cleanup (i.e., energy input) for any form of beneficial use. An additional indicator of the importance of water is its significance for economic activity. It’s estimated that every million USD of economic activity requires 22,000 m3 of water per year; the faster our economies run, the more clean water we need. However, the world is not at a loss for water. We have more water than we could ever use. But, 96.5% of it is in the oceans, too contaminated with salt for many anthropogenic uses. Of the 2.5% that is freshwater, nearly 70% of it is locked in glaciers and icecaps, leaving precious little water that is both fresh and available, often not in locations where it is most needed. Membrane science is alleviating water shortages, weakening the linkage between energy and water, and arresting the environmental damage occurring due to agricultural runoff (e.g., uncontrolled algal blooms), conventional and unconventional oil and gas production, and energy generation based on fossil fuels. A “moonshot for water” has been proposed in the U.S. to reduce the cost of desalination to be comparable to that of conventional drinking water costs. Disruptive, membrane-based technologies will lead the way in bringing about this revolution. Membrane-based seawater desalination is already the least energy intensive way to desalinate seawater, and membranes are increasingly used for wastewater treatment and reuse. Basic and applied science discoveries are paving the way for next generation membranes that will be highly selective, fouling resistant, low energy and highly resilient. Rational control of pore size and pore size distribution in membrane filters is critical to such developments. Discovering and developing the underpinning science to predict ion and water transport across membranes designed to separate ions from water is already providing profound insight regarding molecular strategies to tailor next generation membranes. This presentation will frame the water/energy nexus challenges and opportunities and provide a glimpse of potential paths forward to supply the world with low energy, abundant access to clean water.

The enhancement of gas diffusivity observed after addition of fumed silica nano-particles to glassy polymers can be described and modeled by considering the additional fractional free volume (FFV) created by filler insertion, which can be evaluated from gas solubility data in the composite matrix by means of the NELF model. In this work, a detailed characterization of the solubility of n-C4 and n-C5 vapors, as well as of their diffusivity in matrices of AF 2400 filled with variable amounts of fumed silica has been performed at 25°C. On the bases of n-C4 solubility in the mixed matrix the FFV variation due to filler loading can be estimated and then used to predict the solubility of n-C5 that is found in good agreement with experimental data. Finally, an empirical correlation can be drawn between the FFV value obtained from solubility data and the infinite dilution diffusivity of the penetrants, as well as with the concentration dependence of the penetrant diffusivity.