Nanomaterials Chemistry
Nanomaterials chemistry studies the synthesis, structure, and size-dependent properties of materials with at least one dimension in the nanometre range, where quantum confinement and very high surface-to-volume ratio give behaviour distinct from the bulk.
Definition
Nanomaterials chemistry is the study of how the size, shape, and surface chemistry of nanoscale materials are controlled by synthesis and how they give rise to properties — optical, electronic, and catalytic — that differ from those of the corresponding bulk solid.
Scope
This area covers the chemical principles of matter at the nanoscale: zero-dimensional quantum dots and nanocrystals whose optical properties depend on size; two-dimensional sheets such as graphene and transition-metal dichalcogenides; the colloidal and solution-phase synthesis of nanoparticles and their assembly into ordered superstructures; and the soft-chemical, sol-gel, and template routes used to build nanostructured solids. Throughout it links size and shape to electronic, optical, and catalytic function.
Sub-topics
Core questions
- Why do material properties change when a solid is reduced to nanometre dimensions?
- How are nanocrystals, nanosheets, and nanoparticles synthesised with controlled size and shape?
- How does the dominance of surface atoms alter chemistry at the nanoscale?
- How can nanoscale building blocks be assembled into functional architectures?
Key concepts
- Quantum confinement
- Surface-to-volume ratio
- Colloidal nanocrystal synthesis
- Shape and facet control
- Self-assembly of nanostructures
- Surface ligands and capping agents
Key theories
- Quantum confinement in nanocrystals
- When a semiconductor crystal becomes comparable in size to the exciton, the electronic levels become discrete and the effective band gap widens as size decreases, so optical absorption and emission can be tuned simply by changing particle size.
- Shape and surface control of nanocrystals
- The properties of nanocrystals depend not only on size but on shape and exposed crystal facets, which are controlled kinetically during colloidal synthesis through surfactants and growth conditions, and which govern catalytic and plasmonic behaviour.
Clinical relevance
Nanomaterials chemistry underlies a wide range of technologies: size-tunable quantum dots are used in displays and bio-imaging, high-surface-area nanoparticles serve as catalysts and electrodes, and two-dimensional materials are explored for electronics, sensors, and membranes.
History
The recognition in the 1980s and 1990s that semiconductor nanocrystals show size-dependent optical properties, codified in Alivisatos's 1996 review, established quantum confinement as a chemically controllable phenomenon. Advances in colloidal synthesis then enabled precise control of size and shape, and the 2004 isolation of graphene opened the chemistry of two-dimensional materials, broadening the field into the discipline of nanochemistry.
Key figures
- A. Paul Alivisatos
- Mostafa El-Sayed
- Geoffrey Ozin
Related topics
Seminal works
- alivisatos1996
- elsayed2005
- ozin2009
Frequently asked questions
- Why does a nanoparticle behave differently from the same material in bulk?
- Two effects dominate at the nanoscale: a large fraction of the atoms sit at the surface, changing reactivity and energetics, and for small enough semiconductors the electrons are quantum-confined, which discretises the energy levels and shifts optical and electronic properties relative to the bulk.
- How can the colour of quantum dots be tuned?
- Because of quantum confinement, the effective band gap of a semiconductor nanocrystal increases as its size decreases. Making smaller dots shifts absorption and emission to higher energy (bluer), so colour can be selected simply by controlling particle size during synthesis.