Crystal bowls coloured by nanoparticles? Colour crystal bowls - the stuff of dreams! There are actually different ways to dye a quartz vessel. But did you know that technology now enables the use of nanoparticles?
What are the advantages?
Each dyeing method, whether surface treatment or in the mass, offers a spectrum of different colours. The result varies according to the method, with effects such as sheen, transparency or darker, glazed or frosted colours. Each method has its advantages and drawbacks.
The major advantage of nanoparticle-dyed crystal bowls is the guarantee of a colour that will never change with usage or time. In addition, we obtain a spectral result akin to 3D and the palette of shades is limitless!
Let’s learn more:
What does nano mean?
In the world of the nano, we are on a scale of a billionth of a metre!
As you can imagine, the nanometre (nm) is used to express dimensions on an atomic scale. From a dimensional point of view, nanoparticles are situated between what is known as macroscopic matter and the atomic or molecular scale. Their size is thus much smaller than a human cell.
The nanometre is also used to express electromagnetic wavelength, and in particular the visible spectrum, which is situated between 400 and 800nm.
What is a nanoparticle?
A nanoparticle (ISO TS/27687 standard) is a nano-object of which the three dimensions are on a nanometric scale, i.e. a particle with a nominal diameter less than 100nm.
To obtain nanoparticle-dyed crystal bowls, we need to use baths which contain these tiny colour particles. They also need to adhere homogeneously! There is, therefore, a whole art to this high technology!
How are the crystal bowls dyed?
These bowls are initially clear and transparent. The nanoparticles add colour during a soaking process, thanks to transition metal ions, in this case, silver (Ag). The aim is to trigger a rapid aggregation, in order to obtain a distinct colouring. This is a method of ion exchange, based on the substitution of a quartz ion by a silver ion.
Dyeing by silver ion exchange requires a great deal of expertise in the field of nanomaterials. It consists in introducing silver ions to the quartz matrix, which will then be aggregated to form metal nanoparticles contained in this quartz.
This is complex and hybrid technology, as it draws on conventional physics as well as quantum theories. It also draws on crystal field theory, which describes the electronic structure of transition metal compounds.
A little background:
We tend to think of nanotechnology as a modern science. This is not exactly true when it comes to dyeing materials.
Historically, obtaining bright colours by dispersing metal compounds in glass has been empirically known to man for centuries; dyeing glass in the mass by adding metal powders was used in ancient times to produce art works, followed by stained glass in the Middle Ages.
This technique was used for example for the stained-glass windows in Chartres Cathedral (a Gothic-style cathedral built in the early 13th century). It consisted in adding gold, silver or copper to the glass paste, or in dyeing conventional soda-lime glass. Soda-lime glass is used today for colour glass bottles, perfume bottles, stained windows, etc., and is achieved by ion exchange with silver metal. In the past, we obtained colours thanks to metals, but they were incorporated in the mass:
- Ruby red is obtained with copper or gold particles
- Yellow is obtained with silver
It all lies in the play of the light
Today, we ‘play around’ on an infinitely tiny scale, at the core of material bases. The richness of colour in the CAMAIEUX crystal bowls by CristalvibraSons® is due to:
- The introduction of metal ions (transition metals)
- The degree of oxidation of metals
How does it work? To explain the phenomenon, let’s say that when metal ions receive light, they absorb a part of the energy transported by the light photons, which provokes an excitation of the electrons on their surface layers. These electrons evolve from their fundamental state of energy towards a higher level of energy. Depending on the differences between the energy levels, the ion absorbs a certain frequency of the received light, then re-emits the complementary colour. So, for every possible energy difference, a different colour can be produced!
The unalterable nature of the colours is due to their manufacture! Once the silver has been added to the matrix of the crystal bowl, the bowl undergoes treatment in a bath of aqua regia (a mixture of concentrated hydrochloric acid and concentrated nitric acid) to dissolve what we call the noble metals. The metal then spreads homogeneously throughout the mixture during the subsequent heating phase. This heating enables the silver atoms to move slightly in the quartz.
When they meet each other, they bind together: this is the crystalline growth step, which gradually leads to the formation of aggregates containing several hundreds or thousands of metal atoms!
How do we obtain such accurate colour ‘mixes’?
In fact, the size of the metal aggregates will determine the colour. Let’s examine their structures and optical properties in detail.
What we have here is not an atomic absorption of light (absorption by metal atoms or metal ions), but a very particular optical absorption by whole aggregates. This is based on two concurrent phenomena:
- This is a metal, even on an infinitely small scale, so it absorbs light by inter-strips (between the valence and the conduction strip). This usually occurs at relatively distant wavelengths, towards the ultraviolet (between 10 and 400 nm).
- The aggregates are tiny, so the number of surface atoms is high in comparison to the number of inner atoms. Consequently, the surface atoms form a sort of gas with their free electrons, capable of resonating with all magnetic rays, in this case, light, and of producing what we call ‘plasmon resonance’.
What is a plasmon?
A plasmon is an oscillation of quantified plasma. We also speak about a quantum of plasma oscillation. It is a quasiparticle which arises from the quantification of plasma oscillations, (just like photons and phonons are quantifications of light and mechanical vibrations respectively).
Put simply, the electrons start to vibrate together, which allows them to absorb the light of a particular wavelength. This wavelength, associated with the inter-strip absorption, results in the colours available in the CAMAIEUX collection by CristalvibraSons®.
If the light is not decomposed, it is monochromatic: it corresponds to a radiation. If the light is decomposed, it is polychromatic. The Camaïeux® collection offers both single-colour and multi-colour bowls.
These magnificent colours are obtained thanks to the collaboration of chemists and physicists. This alliance, which has allowed us to understand and control the structure of materials on a nanometric scale, has already revolutionised the glass industry, for example.
Today, this progress has reached rock quartz crucibles and has transformed their production into an industry combining high technology and art craftsmanship.
An innovative and inspiring technology, at the service of man’s creativity.