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Colloidal solids are solid particles suspended in solution. They are usually negatively charged, attracting a compact primary layer of positively charged ions, which attract more counterions to form an electrical double layer. Electrostatic repulsion between the charged double layers prevents the particles from colliding, stabilizing the colloids. These solids are often undesirable because they can contain toxins that are difficult to remove. Coagulation is a technique that helps aggregate and...

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Related Experiment Video

Updated: Jun 22, 2026

Gold Nanostar Synthesis with a Silver Seed Mediated Growth Method

Gold Nanostar Synthesis with a Silver Seed Mediated Growth Method

Published on: January 15, 2012

Gold colloids with unconventional angled shapes.

Ana Sanchez-Iglesias¹, Marek Grzelczak, Benito Rodríguez-González

¹Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.

Langmuir : the ACS Journal of Surfaces and Colloids

|June 19, 2009

Summary

Researchers created porous gold nanoparticles with unique angled shapes using tellurium templates and galvanic replacement. These novel nanostructures significantly enhance Raman scattering signals for adsorbed molecules.

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A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

A Simple Method for the Size Controlled Synthesis of Stable Oligomeric Clusters of Gold Nanoparticles under Ambient Conditions

Published on: February 5, 2016

Area of Science:

Materials Science
Nanotechnology
Chemistry

Background:

Gold nanoparticles are crucial in various applications, including catalysis and sensing.
Controlling nanoparticle morphology is key to optimizing their properties.
Galvanic replacement is a common method for synthesizing metal nanostructures.

Purpose of the Study:

To synthesize porous gold nanoparticles with unusual, angled shapes.
To investigate the mechanism of nanoparticle formation via galvanic replacement.
To evaluate the SERS enhancement capabilities of the synthesized nanostructures.

Main Methods:

Synthesis of porous gold nanoparticles using tellurium sacrificial templates.
Employing gradual galvanic replacement for controlled transformation.
Utilizing high-resolution electron microscopy to study intermediate stages and final products.

Main Results:

Successfully formed porous gold nanoparticles with unique, angled morphologies (e.g., nanocheckmarks).
Elucidated the galvanic replacement mechanism involving initial gold island growth and subsequent engulfment.
Demonstrated significantly enhanced Raman scattering signals due to high porosity and unique shapes.

Conclusions:

Porous gold nanoparticles with unusual shapes can be fabricated via a template-assisted galvanic replacement process.
The study provides insights into the mechanism of nanoparticle formation and transformation.
The synthesized nanostructures show great potential for surface-enhanced Raman spectroscopy (SERS) applications.