In chemistry, hydrophobicity is the chemical property of a molecule that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water.
The Mpemba effect is the name given to the observation that a liquid that is initially hot can freeze faster than the same liquid which begins cold, under otherwise similar conditions. There is disagreement about its theoretical basis and the parameters required to produce the effect.
Freezing-point depression is a drop in the maximum temperature at which a substance freezes, caused when a smaller amount of another, non-volatile substance is added. Examples include adding salt into water, alcohol in water, ethylene or propylene glycol in water, adding copper to molten silver, or the mixing of two solids such as impurities into a finely powdered drug.
A nanomotor is a molecular or nanoscale device capable of converting energy into movement. It can typically generate forces on the order of piconewtons.
James Mitchell Tour is an American chemist and nanotechnologist. He is a Professor of Chemistry, Professor of Materials Science and Nanoengineering at Rice University in Houston, Texas.
In thermodynamics, nucleation is the first step in the formation of either a new thermodynamic phase or structure via self-assembly or self-organization within a substance or mixture. Nucleation is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears. For example, if a volume of water is cooled significantly below 0 °C, it will tend to freeze into ice, but volumes of water cooled only a few degrees below 0 °C often stay completely free of ice for long periods (supercooling). At these conditions, nucleation of ice is either slow or does not occur at all. However, at lower temperatures nucleation is fast, and ice crystals appear after little or no delay.
In chemistry and materials science, ultrahydrophobic surfaces are highly hydrophobic, i.e., extremely difficult to wet. The contact angles of a water droplet on an ultrahydrophobic material exceed 150°. This is also referred to as the lotus effect, after the superhydrophobic leaves of the lotus plant. A droplet striking these kinds of surfaces can fully rebound like an elastic ball. Interactions of bouncing drops can be further reduced using special superhydrophobic surfaces that promote symmetry breaking, pancake bouncing or waterbowl bouncing.
Nanofibers are fibers with diameters in the nanometer range. Nanofibers can be generated from different polymers and hence have different physical properties and application potentials. Examples of natural polymers include collagen, cellulose, silk fibroin, keratin, gelatin and polysaccharides such as chitosan and alginate. Examples of synthetic polymers include poly(lactic acid) (PLA), polycaprolactone (PCL), polyurethane (PU), poly(lactic-co-glycolic acid) (PLGA), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and poly(ethylene-co-vinylacetate) (PEVA). Polymer chains are connected via covalent bonds. The diameters of nanofibers depend on the type of polymer used and the method of production. All polymer nanofibers are unique for their large surface area-to-volume ratio, high porosity, appreciable mechanical strength, and flexibility in functionalization compared to their microfiber counterparts.
Menachem Elimelech is the Nancy and Clint Carlson Professor at Rice University, with joint appointments in the Department of Civil & Environmental Engineering and the Department of Chemical & Biomolecular Engineering. Prior to his appointment at Rice University, he was the Sterling Professor of Chemical and Environmental Engineering at Yale University. Elimelech moved from the University of California, Los Angeles (UCLA) to Yale University in 1998 and founded Yale's Environmental Engineering program.
See also artificial metalloenzyme.
Microplastics are fragments of any type of plastic less than 5 mm (0.20 in) in length, according to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Chemicals Agency. US EPA researchers define microplastics, or MPs, as plastic particles ranging in size from 5 millimeters (mm), which is about the size of a pencil eraser, to 1 nanometer (nm). For comparison, a strand of human hair is about 80,000 nanometers wide.
Freeze-casting, also frequently referred to as ice-templating, freeze casting, or freeze alignment, is a technique that exploits the highly anisotropic solidification behavior of a solvent in a well-dispersed solution or slurry to controllably template directionally porous ceramics, polymers, metals and their hybrids. By subjecting an aqueous solution or slurry to a directional temperature gradient, ice crystals will nucleate on one side and grow along the temperature gradient. The ice crystals will redistribute the dissolved substance and the suspended particles as they grow within the solution or slurry, effectively templating the ingredients that are distributed in the solution or slurry.
Graphene quantum dots (GQDs) are graphene nanoparticles with a size less than 100 nm. Due to their exceptional properties such as low toxicity, stable photoluminescence, chemical stability and pronounced quantum confinement effect, GQDs are considered as a novel material for biological, opto-electronics, energy and environmental applications.
Aerogels are a class of synthetic porous ultralight material derived from a gel, in which the liquid component for the gel has been replaced with a gas, without significant collapse of the gel structure. The result is a solid with extremely low density and extremely low thermal conductivity. Aerogels can be made from a variety of chemical compounds. Silica aerogels feel like fragile styrofoam to the touch, while some polymer-based aerogels feel like rigid foams.
The borate fluorides or fluoroborates are compounds containing borate or complex borate ions along with fluoride ions that form salts with cations such as metals. They are in the broader category of mixed anion compounds. They are not to be confused with tetrafluoroborates (BF4) or the fluorooxoborates which have fluorine bonded to boron.
The iodate fluorides are chemical compounds which contain both iodate and fluoride anions (IO3− and F−). In these compounds fluorine is not bound to iodine as it is in fluoroiodates.
Sulfidogermanates or thiogermanates are chemical compounds containing anions with sulfur atoms bound to germanium. They are in the class of chalcogenidotetrelates. Related compounds include thiosilicates, thiostannates, selenidogermanates, telluridogermanates and selenidostannates.
Passive daytime radiative cooling (PDRC) is the use of unpowered, reflective/thermally-emissive surfaces to lower the temperature of a building or other object.
Freeze-fracture is a natural occurrence leading to processes like erosion of the earths crust or simply deterioration of food via freeze-thaw cycles. To investigate the process further freeze-fracture is artificially induced to view in detail the properties of materials. Fracture during freezing is often the result of crystallizing water which results in expansion. Crystallization is also a factor leading to chemical changes of a substance due to changes in the crystal surroundings called eutectic formation.
Xiao Cheng Zeng is a scientist in physical chemistry and materials science. He currently serves as the Head of Department of Materials Science & Engineering and a Chair Professor of Materials Chemistry and Chemical Engineering at City University of Hong Kong. He is also an Emeritus Chancellor's University Professor at University of Nebraska–Lincoln (USA). He is a fellow of the American Association for the Advancement of Science, a fellow of the American Physical Society, a fellow of US Materials Research Society, a fellow of Royal Society of Chemistry, and a foreign fellow of the European Academy of Sciences. He had also held a John Simon Guggenheim fellowship.
