How Can Materials Chemists Contribute to Food Supply Security in the Age of AI and Robotics?

Global factors are compromising the security of the food supply. Many of us in our community might be unsure about how to help with our seemingly inapplicable expertise. In this piece, I describe how materials chemistry and materials chemists will be essential in addressing this problem, but not only in the way we might think.

Colloidal TiO nanocrystals with engineered defectivity and optical properties.

Partially reduced forms of titanium dioxide (sometimes called "black" titania) have attracted widespread interest as promising photocatalysts of oxidation due to their absorption in the visible region. The main approaches to produce it rely on postprocessing at high temperatures (up to 800 °C) and high pressures (up to 40 bar) or on highly reactive precursors (, TiH), and yield powders with poorly controlled sizes, shapes, defect concentrations and distributions. We describe an approach for the one-step synthesis of TiO colloidal nanocrystals at atmospheric pressure and temperatures as low as 280 °C.

Plasma-based post-processing of colloidal nanocrystals for applications in heterogeneous catalysis.

This review summarizes the work on the use of plasmas to post-process nanostructures, in particular colloidal nanocrystals, as promising candidates for applications of heterogeneous catalysis. Using plasma to clean or modify the surface of nanostructures is a more precisely controlled method compared to other conventional methods, which is preferable when strict requirements for nanostructure morphology or chemical composition are necessary. The ability of plasma post-processing to create mesoporous materials with high surface areas and controlled microstructure, surfaces, and interfaces has transformational potential in catalysis and other applications that leverage surface/interface processes.

Evidence for root adaptation to a spatially discontinuous water availability in the absence of external water potential gradients.

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).

Growth of Colloidal Nanocrystals by Liquid-Like Coalescence*.

We here describe, model, and predict the growth kinetics of amine-capped PbS colloidal nanoparticles in the absence of supersaturation. The particles grow by coalescence rather than by Ostwald ripening. A comparison of different models indicates that the effective activation energy of coalescence (67.

Suppressing Evaporative Loss in Slippery Liquid-Infused Porous Surfaces (SLIPS) with Self-Suspended Perfluorinated Nanoparticles.

This article describes an approach to resolving the issue of evaporative loss from slippery liquid-infused porous surfaces (SLIPS). Hydrophobic and oleophobic fluids with significantly reduced evaporative loss rates at temperatures of up to 90 °C were obtained by the one-step mixing of commercially available perfluorinated lubricants with colloidal nanoparticles to form self-suspended nanoparticle fluids (i.e.

Self-Limiting Processes in the Flame-Based Fabrication of Superhydrophobic Surfaces from Silicones.

Outdoor applications of superhydrophobic coatings require synthetic approaches that allow their simple, fast, scalable, and environmentally benign deployment on large, heterogeneous surfaces and their rapid regeneration . We recently showed that the thermal degradation of silicones by flames fulfills these characteristics by spontaneously structuring silicone surfaces into a hierarchical, textured structure that provides wear-resistant, healable superhydrophobicity. This paper elucidates how flame processing-a simple, rapid, and out-of-equilibrium process-can be so counterintuitively reliable and robust in producing such a complex structure.

Hydrogel-based transparent soils for root phenotyping in vivo.

Root phenotypes are increasingly explored as predictors of crop performance but are still challenging to characterize. Media that mimic field conditions (e.g.

Stress response to CO2 deprivation by Arabidopsis thaliana in plant cultures.

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.

On the kinetics of the removal of ligands from films of colloidal nanocrystals by plasmas.

This paper describes the kinetic limitations of etching ligands from colloidal nanocrystal assemblies (CNAs) by plasma processing. We measured the etching kinetics of ligands from a CNA model system (spherical ZrO nanocrystals, 2.5-3.

Sustainable scalable synthesis of sulfide nanocrystals at low cost with an ionic liquid sulfur precursor.

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 HS, only to be converted back to HS during the synthesis of the nanocrystals. This convoluted process requires energy, reduces yields, increases waste and auxiliaries, and complicates recycling.

Large-Scale Synthesis of Colloidal Si Nanocrystals and Their Helium Plasma Processing into Spin-On, Carbon-Free Nanocrystalline Si Films.

This paper describes a simple approach to the large-scale synthesis of colloidal Si nanocrystals and their processing into spin-on carbon-free nanocrystalline Si films. The synthesized silicon nanoparticles are capped with decene, dispersed in hexane, and deposited on silicon substrates. The deposited films are exposed to nonoxidizing room-temperature He plasma to remove the organic ligands without adversely affecting the silicon nanoparticles to form crack-free thin films.

From Petri Dishes to Model Ecosystems.

Model ecosystems could provide significant insight into the evolution and behavior of real ecosystems. We discuss the advantages and limitations of common approaches like mesocosms. In this context, we highlight recent breakthroughs that allow for the creation of networks of organisms with independently controlled environments and rates of chemical exchange.

HOMEs for plants and microbes - a phenotyping approach with quantitative control of signaling between organisms and their individual environments.

We describe a simple, scalable, modular, and frugal approach to create model ecosystems as millifluidic networks of interconnected habitats (hosting microbes or plants), which offers (i) quantitative and dynamic control over the exchange of chemicals between habitats, and (ii) independent control over their environment. Oscillatory laminar flows produce regions of vortex mixing around obstacles. When these overlap, rapid mass transport by dispersion occurs, which is quantitatively describable as diffusion, but is directional and tunable in rate over 3 orders of magnitude.

Calcination does not remove all carbon from colloidal nanocrystal assemblies.

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.

Simplicity as a Route to Impact in Materials Research.

Materials scientists and engineers desire to have an impact. In this Progress Report we postulate a close correlation between impact - whether academic, technological, or scientific - and simple solutions, here defined as solutions that are inexpensive, reliable, predictable, highly performing, "stackable" (i.e.

Building Materials from Colloidal Nanocrystal Arrays: Evolution of Structure, Composition, and Mechanical Properties upon the Removal of Ligands by O Plasma.

The mechanical properties of colloidal nanocrystal superlattices can be tailored through exposure to low-pressure plasma. The elastic modulus and hardness of the ligand-free 3.7 nm ZrO superlattice are found to be similar to bulk yttria-stabilized tetragonal polycrystals of the same relative density but without any doping.

Building Materials from Colloidal Nanocrystal Arrays: Preventing Crack Formation during Ligand Removal by Controlling Structure and Solvation.

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 for PbS films).

Plant Growth Environments with Programmable Relative Humidity and Homogeneous Nutrient Availability.

We describe the design, characterization, and use of "programmable", sterile growth environments for individual (or small sets of) plants. The specific relative humidities and nutrient availability experienced by the plant is established (RH between 15% and 95%; nutrient concentration as desired) during the setup of the growth environment, which takes about 5 minutes and <1$ in disposable cost. These systems maintain these environmental parameters constant for at least 14 days with minimal intervention (one minute every two days).

Thermal Processing of Silicones for Green, Scalable, and Healable Superhydrophobic Coatings.

The thermal degradation of silicones is exploited and engineered to make super-hydrophobic coatings that are scalable, healable, and ecofriendly for various outdoor applications. The coatings can be generated and regenerated at the rate of 1 m(2) min(-1) using premixed flames, adhere to a variety of substrates, and tolerate foot traffic (>1000 steps) after moderate wear and healing.

LEGO® bricks as building blocks for centimeter-scale biological environments: the case of plants.

LEGO bricks are commercially available interlocking pieces of plastic that are conventionally used as toys. We describe their use to build engineered environments for cm-scale biological systems, in particular plant roots. Specifically, we take advantage of the unique modularity of these building blocks to create inexpensive, transparent, reconfigurable, and highly scalable environments for plant growth in which structural obstacles and chemical gradients can be precisely engineered to mimic soil.

A simple and versatile 2-dimensional platform to study plant germination and growth under controlled humidity.

We describe a simple, inexpensive, but remarkably versatile and controlled growth environment for the observation of plant germination and seedling root growth on a flat, horizontal surface over periods of weeks. The setup provides to each plant a controlled humidity (between 56% and 91% RH), and contact with both nutrients and atmosphere. The flat and horizontal geometry of the surface supporting the roots eliminates the gravitropic bias on their development and facilitates the imaging of the entire root system.

Nanowires and nanostructures that grow like polymer molecules.

Unique properties (e.g., rubber elasticity, viscoelasticity, folding, reptation) determine the utility of polymer molecules and derive from their morphology (i.