Materials chemistry

Synthesis and characterization of nanomaterials

Understand how nucleation, growth, surface chemistry, and measurement methods govern nanomaterial size, shape, composition, and function.

1 Lower secondary 2 Upper secondary 3 Undergraduate 4 Advanced 5 Research

IntuitionMake, then measure

Nanoparticle properties are not specified by composition alone. Diameter, shape, surface ligands, aggregation, and defects can alter colour, catalytic activity, and toxicity, so synthesis and trustworthy characterization must be designed together.

Explore how a burst of nucleation followed by controlled growth changes the particle-size distribution; a narrow distribution requires separating these time scales.

SchoolCore concepts and methods

Definition: Nucleation and growth

Nucleation creates stable clusters from supersaturated precursors; growth adds material to existing nuclei. Separating the two processes often narrows the particle-size distribution, while continued nucleation broadens it.

Bottom-up routes include solution reduction, sol–gel chemistry, hydrothermal synthesis, and vapor deposition. Top-down routes such as milling or lithography break down or pattern larger materials. Each route trades throughput, purity, cost, and control differently.

What common measurements tell you
Method	Primary information and caveat
TEM	Local projected size/shape; sampling and drying bias
DLS	Hydrodynamic size in dispersion; strongly weights large scatterers
XRD	Crystalline phases and coherent-domain size, not necessarily particle size

Example: Reading a broadened diffraction peak

Solution

With K≈0.9, D=Kλ/(β cosθ)≈0.9×0.154/(0.020 cos20°)=7.4 nm. This is a coherent diffraction-domain estimate; strain and instrumental broadening must be treated, and a particle may contain multiple domains.

UndergraduateKinetics, interfaces, and distributions

\Delta G(r)=4\pi r^2\gamma-\frac{4\pi r^3}{3}\Delta g_v,\\qquad r^*=\frac{2\gamma}{\Delta g_v}

Classical nucleation theory balances the positive surface cost against the bulk free-energy gain. It is a useful organizing model, but assumes idealized spherical nuclei and bulk-like interfacial properties; heterogeneous nucleation and nanoscale chemistry can violate those assumptions.

AdvancedCharacterization is an inverse problem

A spectrum or micrograph is an indirect signal convolved with instrument response, sample preparation, and model assumptions. Combine orthogonal probes (for example microscopy, scattering, spectroscopy, and elemental analysis), report distributions and uncertainty, and avoid treating one technique as a complete description.

ResearchResearch frontier

References

Synthesis of Monodisperse Spherical Nanocrystals · J. Park, J. Joo, S. G. Kwon, Y. Jang, T. Hyeon, 2007
Mechanisms of Nucleation and Growth of Nanoparticles in Solution · N. T. K. Thanh, N. Maclean, S. Mahiddine, 2014
The Scherrer Formula for X-Ray Particle Size Determination · A. L. Patterson, 1939