As discussed in Chapter 1, unique features of nanomaterials such as size-dependent optical and magnetic properties, and high surface-to-volume ratio make them particularly interesting for applications in electronics and biomedicine. Biomedical applications are a powerful driver of the development of bionano hybrids, and novel preparation strategies have already enabled manufacturing of high-quality nanomaterials such as carbon nanotubes at scales that can satisfy market demands. Although the size of nanomaterials brings numerous advantages, working with them can be challenging. Due to their high surface energy, nanoparticles can form random aggregates, or non-selectively bind various molecular species, which impacts their physiochemical properties. This can be prevented by the functionalisation of nanomaterials’ surface with known molecules in a controllable way. Surface modification not only improves the stability of nanomaterials, but enables introduction of various functional groups that can change their properties and make them more adaptable to a broad range of applications.

Bionanotechnology has the potential not only to improve existing medical processes but also to introduce entirely new tools and materials. Advances have already been made, in particular, in design of probes and biosensors for advanced diagnostics, targeted drug nanocarriers and environment-responsive materials for tissue engineering. We need to keep in mind that at the core of all of these applications is the fundamental question of the nature of the interaction of nanomaterials and nanostructured surfaces with biological systems. The exploration of these interactions is strongly embedded within the field of nanomedicine, but it is also a part of nanotoxicology, a field that studies the environmental impact of new materials. Some strategies, findings and policy actions concerning the regulation of use of nanomaterials will be covered in the last chapter.

Deformation of some sort often accompanies metamorphism and, when it does, it is possible to learn more about the metamorphic processes by also considering the accompanying deformation. Detailed analysis of the deformation of metamorphic rocks is beyond the scope of this book, but further reading is suggested at the end of the chapter. Here, we will look at how rocks can deform during metamorphism in general terms, and then focus on three aspects of the relationships between metamorphism and deformation.

Despite the relative youth of the term nanotechnology, as far as we know nanomaterials have been around for centuries. Hundreds of years ago, dispersions of gold and silver nanoparticles were used by master glassblowers to produce coloured decorative glass for church windows (Figure 2.1a) or luxury glassware such as the Lycurgus Cup from fourth century CE Rome (Figure 2.1b). In the late nineteenth and early twentieth centuries, industrialists used carbon black to reinforce rubber and thus improve its strength, tensile properties and tear. We know now that carbon black is made of carbon particles that can vary in size, and some of them are nanosized spheres. But practical uses of early nanotechnology were not constrained only to Europe. A corrosion resistant azure pigment known as Mayan blue, first produced in 800 CE, was discovered in the pre-Columbian Mayan city of Chichen Itza (Figure 2.1c). It is a complex material made of nanoporous clay used to stablise the blue indigo dye. Damascus steel swords made in the Middle East between 300 CE and 1700 CE were known for their impressive strength and exceptionally sharp cutting edge, and studies have shown that the steel contains nanotubes and nanowire structures (Reibold, 2008). Swords were produced in a process of forging and forming that employs coal, iron powder, high temperatures and high pressures applied during hammering, a protocol that is in many ways similar to how the nanotubes are made today (see Section 2.4.2).

Much of the material in this book so far has skirted around the problem of how quickly metamorphic rocks form and how long metamorphism lasts. Regional metamorphism can be thought of as taking place in a metamorphic cycle, involving burial, heating, exhumation and cooling. The question of ‘how long’ a metamorphic cycle takes from start to finish may be determined either directly or indirectly. Indirect methods involve calculations of how long it takes for rocks to heat up, cool down, or be buried or exhumed. Based on the thermal properties of rocks, indirect approaches have been used for many years to calculate the rates of heating and cooling associated with igneous intrusions.

Metamorphic rocks derived from carbonate-rich sediments, such as limestones and marls, also reflect the temperatures and pressures of metamorphism like metapelites and metabasites, but there is an additional factor that influences their mineralogy. Carbonate minerals release carbon dioxide during metamorphism and the mineral assemblages that form are influenced by the balance between water and carbon dioxide in the metamorphic fluid. In this chapter we will investigate the way in which minerals and fluids interact as limestones undergo metamorphism.

In the previous chapters, the emphasis has been on the attainment of chemical equilibrium in metamorphism, because it is only by identifying assemblages of minerals that have co-existed together in equilibrium that the pressures and temperatures of their formation can be determined. Equilibrium studies alone tell us only about the P–T conditions prevailing when a particular assemblage formed, they cannot tell us anything about the rock’s history before or after the assemblage grew.

Historical periods are almost always introduced in hindsight, with some agenda. This is doubly true for ‘Middle Ages,’ a term we employed in previous chapters to designate the period after the fall of the Roman Empire. The millennium this term designates was far from being just ‘in the middle,’ and the people living through it experienced as many changes and upheavals as in any other era.