Synthesis of gold nanoparticles

There was another week of Ampli Science, in which we focused more on the Chemical Synthesis of nanoparticles.

Experiment 1: chemical synthesis of nanoparticles

The goal of this experiment was to synthesize nanoparticles (to create) through a chemical reacion

First of all, let’s take a look of what a nanoparticle is. A nanoparticle is a piece of matter that is generally between 1-100 nanometers in diameter. They are used in a range of optical, biomedical, and catalytic applications due to their unique size and shape dependent optical properties.

In this experiment we will be creating gold nanoparticles (AuNPs). AuNPs are formed by combining a gold salt (AuCl) with a Goods Buffer (HEPES), which acts as a reducing agent for the gold salt. Nanoparticles can be formed with a range of colors depending on the ratio of HEPES:gold in the synthesis reaction. The higher the ratio, the larger the particles which reflect light in such a way that the larger particles appear more red/pink. The smaller the ratio, the smaller the particles which shift in the blue/green range. The ratio you will be using in this experiment is ~5:1 of HEPES:Gold which should result in a deep purple color. 

The different colors that nanoparticles can acquire depending on the ratio of HEPES:gold

The first step was to assemble the set up: on the left port we put a piece of glass fiber paper impregnated with HEPES; on the middle bridge, we also put a piece of glass fiber paper, but this time impregnated with a gold salt (AuCl); finally, on the right port we used a normal glass fiber paper as an absorbent pad.

The set up

For the chemical reaction to happen, we applied some drops (one at a time) of a saline solution on the left port. This liquid mixed with the HERPES, and consequently, when the it flowed through the different pieces, it reacted with gold. As time went by, I observed that the middle paper started to turn purple. To better see this change of color, I used a color sensor that came with the Ampli Kit and measured the RGB values every 20 seconds.

In the end the normal glass fiber paper ended up being a purple color, indicating the presence of synthesied nanoparticles.

The results
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