The essence of nanoscience is observing, measuring, and understanding the variations of properties and reactivities as a function of size and shape. Structural variations that respond to size change or surface area change may include expansion and contraction of bonds, changes in bond angles, and variations in population and distribution of vacancies and other defects such as steps, kinks, edges, and corners. In the smallest nanoparticles, this results in a redistribution of electronic structure that affects reaction characteristics with the outside world. Measurement of these aspects remains a great challenge and priority for future mineralogists, the authors note.
The size at which properties and reactivities change can be measured and depends upon the mineral, whether it is a metal, semiconductor, or insulator, and on the property being measured, whether optical, mechanical, or electrical.
Chemical interactions also change. For example, seven nanometer hematite -- a common iron oxide mineral -- catalyzes the oxidation of manganese ions (Mn2+) one to two orders of magnitude faster than does a 37-nanometer hematite crystal, resulting in the rapid formation of the manganese oxide minerals that are important heavy metal sorbants in water and soils.
Thermodynamic considerations in the nano-range are just as critical to predicting whether a biogeochemical reaction will occur. In the smallest particles, surface energies can dominate and dictate which structure of a mineral will be stable. Solubilitys of nanophases are also different than their larger counterpart
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