The thermal degradation of silicones
is exploited and engineered to make superhydrophobic coatings that are scalable, healable, and ecofriendly for various outdoor applications. The coatings can be ...generated and regenerated at the rate of 1 m2 min−1 using premixed flames, adhere to a variety of substrates, and tolerate foot traffic (>1000 steps) after moderate wear and healing.
The recent years have seen an explosive interest in one‐dimensional nanostructures1, as testified by the number of citations this field has accrued; as customary, its blossoming was enabled by ...chemical breakthroughs that allowed the reproducible and affordable synthesis of such structures.2, 3 The limitations of those syntheses was in the diameter of the nanowires that it could produce (hardly < 10 nm), and in the use of expensive and low‐yield techniques, such as chemical vapor deposition (CVD).
This paper attempts to summarize the very recent chemical breakthroughs that have allowed the production of ultrathin nanowires, often in solution, and often in gram‐scale quantities. By no means is this a comprehensive coverage of the field, which can in part be found in other excellent reviews1, 2, 4–6 but a selection of those contributions that we feel would most help put this emerging field in perspective. We will review the various synthetic strategies, their pros and cons, and we will give our best guesses as to the future directions of the field and what we can expect from it.
Ultrathin nanowires, especially in colloidal form, represent a new material platform in the study of materials' behaviour, at the border between nanostructures and polymers. We here discuss some of the recent breakthroughs in the field and the synthetic methodologies they have introduced, their pros and cons, and some future directions of the field.
Root phenotypes are increasingly explored as predictors of crop performance but are still challenging to characterize. Media that mimic field conditions (e.g., soil, sand) are opaque to most forms of ...radiation, while transparent media do not provide field-relevant growing conditions and phenotypes. We describe here a “transparent soil” formed by the spherification of hydrogels of biopolymers. It is specifically designed to support root growth in the presence of air, water, and nutrients, and allows the time-resolved phenotyping of roots in vivo by both photography and microscopy. The roots developed by soybean plants in this medium are significantly more similar to those developed in real soil than those developed in hydroponic conditions and do not show signs of hypoxia. Lastly, we show that the granular nature and tunable properties of these hydrogel beads can be leveraged to investigate the response of roots to gradients in water availability and soil stiffness.
Increasing the sustainability of nanocrystals is crucial to their application and the protection of the environment. Sulfur precursors for their synthesis are commonly obtained through multiple steps ...from H
S, only to be converted back to H
S during the synthesis of the nanocrystals. This convoluted process requires energy, reduces yields, increases waste and auxiliaries, and complicates recycling. Using H
S directly could drastically improve sustainability, but is prevented by toxicity and handling. We here show that H
S is stabilized by reaction with oleylamine (the most common and versatile ligand in nanoparticle synthesis) to form an ionic liquid precursor that addresses all major principles of green chemistry: it is made in one exothermic step, it leaves the reaction yielding a safer product and allowing the separate recycling of the precursors, and it produces high quality nanocrystals with high yields (sulfur yield > 70%) and concentrations (90 g L
) in ambient conditions.
This review discusses the recent reports on one-dimensional(1D) nanostructures with unusual flexibility.We discuss the importance that flexibility could have in future applications of nanowires and ...other nanostructures,and detail the two main approaches that have been followed to this day to synthesize highly flexible 1D nanostructures.One approach is based on making crystals in which one or two dimensions of the structure are comparable in size with the unit cell.Such thinness has been shown to provide unusual flexibility.The other approach conjoins hard nanostructures with flexible joints.
Removing organics from hybrid nanostructures is a crucial step in many bottom-up materials fabrication approaches. It is usually assumed that calcination is an effective solution to this problem, ...especially for thin films. This assumption has led to its application in thousands of papers. We here show that this general assumption is incorrect by using a relevant and highly controlled model system consisting of thin films of ligand-capped ZrO
nanocrystals. After calcination at 800 °C for 12 h, while Raman spectroscopy fails to detect the ligands after calcination, elastic backscattering spectrometry characterization demonstrates that ~18% of the original carbon atoms are still present in the film. By comparison plasma processing successfully removes the ligands. Our growth kinetic analysis shows that the calcined materials have significantly different interfacial properties than the plasma-processed counterparts. Calcination is not a reliable strategy for the production of single-phase all-inorganic materials from colloidal nanoparticles.
We hereby show that root systems adapt to a spatially discontinuous pattern of water availability even when the gradients of water potential across them are vanishingly small. A paper microfluidic ...approach allowed us to expose the entire root system of
plants to a square array of water sources, separated by dry areas. Gradients in the concentration of water vapor across the root system were as small as 10
⋅mM⋅m
(∼4 orders of magnitude smaller than in conventional hydrotropism assays). Despite such minuscule gradients (which greatly limit the possible influence of the well-understood gradient-driven hydrotropic response), our results show that 1) individual roots as well as the root system as a whole adapt to the pattern of water availability to maximize access to water, and that 2) this adaptation increases as water sources become more rare. These results suggest that either plant roots are more sensitive to water gradients than humanmade water sensors by 3-5 orders of magnitude, or they might have developed, like other organisms, mechanisms for water foraging that allow them to find water in the absence of an external gradient in water potential.
Using shape for self-assembly Cademartiri, Ludovico; Bishop, Kyle J. M.; Snyder, Phillip W. ...
Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences,
06/2012, Volume:
370, Issue:
1969
Journal Article
Peer reviewed
Open access
A 1980 poem by Alan Mackay outlines his aspiration 'to see what all have seen but think what none have thought': a daunting task, which he accomplished not once, but several times. A 'truly ...myriadminded, manysided man-a veritable triacontahedron' in the words of his colleagues and friends, Alan Mackay pursued a lifelong interest in the problems of morphogenesis and form, a comprehension of which necessitated him crisscrossing the borders of the inanimate and animate world of soft and hard materials, through the integration of concepts and methods of chemistry, physics, mathematics and biology. In other words, he realized in his time a genuinely interdisciplinary approach to complex problems that still to this day remains beyond much of the academic community. Being invited to contribute a paper on the theme 'beyond crystals', we naturally wondered how Alan Mackay would think about the world of nanoscale self-assembly where so much depends on shape and form.
After being the standard plant propagation protocol for decades, cultures of Arabidopsis thaliana sealed with Parafilm remain common today out of practicality, habit, or necessity (as in co-cultures ...with microorganisms). Regardless of concerns over the aeration of these cultures, no investigation has explored the CO2 transport inside these cultures and its effect on the plants. Thereby, it was impossible to assess whether Parafilm-seals used today or in thousands of older papers in the literature constitute a treatment, and whether this treatment could potentially affect the study of other treatments.For the first time we report the CO2 concentrations in Parafilm-sealed cultures of A. thaliana with a 1 minute temporal resolution, and the transcriptome comparison with aerated cultures. The data show significant CO2 deprivation to the plants, a drastic suppression of photosynthesis, respiration, starch accumulation, chlorophyll biosynthesis, and an increased accumulation of reactive oxygen species. Most importantly, CO2 deprivation occurs as soon as the cotyledons emerge. Gene expression analysis indicates a significant alteration of 35% of the pathways when compared to aerated cultures, especially in stress response and secondary metabolism processes. On the other hand, the observed increase in the production of glucosinolates and flavonoids suggests intriguing possibilities for CO2 deprivation as an organic biofortification treatment in high-value crops.
Crack‐free, ligand‐free, phase‐pure nanostructured solids, using colloidal nanocrystals as precursors, are fabricated by a scalable and facile approach. Films produced by this approach have ...conductivities comparable to those of bulk crystals over more than 1 cm (1.370 S cm−1 for PbS films).