Brussels, 23 Jul 2003
Mention the word 'nanotechnology' and images of serious high-tech innovation come to mind, not Renaissance potters firing their richly glazed ceramics. New evidence looks set to change this.
A team of Italian researchers from the University of Perugia have stumbled across a rather unexpected finding while studying 15th century Umbrian ceramics: that the materials used to glaze the ancient pottery consisted of copper and silver nanoparticles.
The discovery, documented in the June issue of the Journal of Applied Physics, provides historical evidence that Renaissance craftsmen had mastered a primitive form of nanotechnology. Coloured glazes in pottery samples found in the Umbrian town of Deruta took advantage of the reflective properties of minute metal grains, resulting in a rich red and gold lustre. The sophistication of these decorations, according to the scientists, is shown by the richness of the colourants used by the 15th century artisans, which produced striking metallic glazes. Some of the pots resemble gold, while others take on a shifting iridescent hue when viewed from different angles.
The study was carried out using non-destructive techniques, such as Rutherford backscattering spectrometry, ultraviolet and visible spectroscopy, x-ray fluorescence, and extended x-ray absorption fine structure, so-called 'EXAFS'.
Alchemy of the highest order
During the Renaissance period – the early 14th to late 16th century – these glazed effects would have been more than decorative. Converting minute metal particles into something resembling gold demonstrated enormous skill, bordering on alchemy.
Reporting the findings, Nature describes glazes as "… basically thin films of coloured glass. Metal salts give colour to a glassy matrix produced by fusing sand alkalis such as soda in the heat of a kiln." At its peak in the late 15th century, delicately painted Deruta pottery was highly sought after across Europe.
In earlier research, Italian researchers demonstrated that the red and gold lustre is produced by tiny particles of copper and silver between 5 and 100 billionth of a metre in width, thus conforming with the definition of a nanoparticle, which would have to be magnified over 10 million times before the naked eye could appreciate its detail.
Because of their minuscule size, light bounces off the particles' surface at different wavelengths, creating the iridescent metallic effects. Silver nanoparticles determine the gold colour, while the red colour is determined by copper nanoparticles, according to the study.
Modern-day nanotechnologists have the benefit of up to 700 years of scientific development. Today, nanotechnology refers to technologies in which matter is manipulated on the atomic and molecular scale to create novel materials and processes in, for example, electronics, biotechnology and materials science.
Under the European Union's current Framework Programme for research (FP6), around €1.3 billion has been set aside for 'Nanotechnologies and nanosciences, knowledge-based multifunctional materials and new production processes and devices'. This is, arguably, fair recognition for a technology that is apparently not as new as once thought.