Nanoparticle Synthesis Laboratory Notebook: Using Aloe Vera Extract (Green Synthesis)

JUNE 14

Experiment: Gold Nanoparticle Synthesis using Aloe Vera Extract Optimization Trial #1

A) Make Aloe Vera Plant Extract

1. Wash aloe vera leaves with tap water

2. Use a scalpel or scissors to finely cut the aloe vera leaves into small bits or thin slices (increase exposed surface)

3. Take a 250mL beaker and wrap with aluminum foil on its exterior - the aloe vera plant extract is LIGHT SENSITIVE, therefore minimize the amount of light exposure of the solution

4. Weigh out ~30g of the finely cut aloe vera and place into a 250mL beaker

5. Measure out 100mL of ddH2O into a graduated cylinder

6. Pour the ddH2O into the 250mL beaker containing the bits of aloe vera

7. Boil the aloe vera in ddH2O solution for ~10min

8. Place a Whatman paper 2 filter properly atop a plastic/glass funnel and position the filter over the opening of a clean 250mL beaker wrapped with aluminum foil on its exterior

9. Pour the boiled aloe vera mixture into the funnel so that the remaining solid chunks of aloe vera are removed from the liquid plant extract which is collected in the beaker

10. The top of the beaker containing the plant extract is sealed with parafilm and an overlying layer of aluminum foil to prevent light exposure of the solution - the aloe vera extract is LIGHT SENSITIVE

The aloe vera extract solution can be stored at 4C degree in the fridge

*Perform in a BIOSAFETY CABINET or FUME HOOD if using the stir plate

 

B) Make Nanoparticles using the Aloe Vera Extract

1. In a clean 100mL beaker wrapped with aluminum foil to prevent light exposure, add a chosen volume of aloe vera plant extract using a pipet:

- Varying volumes ranging between 0.5mL - 4mL of aloe vera plant extract can be used to synthesize gold nanoparticles

-The greater the volume of aloe vera extract used (eg. 1mL) the smaller the gold nanotriangles that will be generated

-To synthesize nanoparticles to target size (less than 100nm), use 4mL of aloe vera extract

 

2. Prepare a 10^-3 M chloroauric acid (HAuCl4) aqueous solution: Using a 10mL graduated cylinder, measure 6mL of ddH2O

3. Pour the ddH2O into a 25-40mL beaker

4. Weigh out 0.00204g (2.0387mg) of chloroauric acid solid

CAUTION: oxidizes quickly - do not expose to air for longer than required. Do NOT use metal scoopula - use plastic/Teflon scoopula to transfer the solid. LIGHT SENSITIVE - use for short duration under light conditions

5. RAPIDLY add the measured chloroauric acid into the ddH2O in the 25-40mL beaker

6. Parafilm the top of the beaker to seal it

7. Add a stir bar and place the beaker on a stir plate to dissolve the chloroauric acid

8. Using a 10mL graduated cylinder, measure ~4mL of ddH2O and add it to the chloroauric acid solution in the beaker to make up the volume to 10mL - continue stirring throughout

9. Remove the beaker with solution from the stir plate and leave it covered with Parafilm in the dark or covered in aluminum foil (minimize light exposure of solution) in the biosafety cabinet for 30hr (reduction of gold occurs during this period)

9. At ~5hr in, the solution should appear dark brown/purple in color - indicator of nanoparticle synthesis (may test for color formation using UV spectrophotometer)

10. The nanoparticle solution can be stored between 4C - 20C degrees. At temperature lying outside the range of 4-20C degrees, the nanoparticles aggregate and become unstable. Store AWAY from direct sunlight. Do NOT freeze

 

JUNE 15

Observation: Gold Nanoparticle Synthesis using Aloe Vera Extract Optimization Trial #1

A)Results: In the glass tube containing the aloe vera extract and HAuCl4, a colour change was observed from clear to dark purple, indicating the successfully synthesis of nanoparticles.

UV-vis-IR: The results on the absorbance profile shows a high absorbance peak at 550 nm, indicating the presence of gold nanoparticles.

Figure I: Absorbance profile of aloe vera

 

 

 

JUNE 20

Experiment: Gold Nanoparticle Synthesis using Aloe Vera Extract Optimization Trial #2

Prepared AuNP using Aloe Vera method introducing the variables indicated on Table 1

A 20 mL stock 1mM HAuCl4 solution was prepared by weighing out 7.7 mg of solid HAuCl4 and dissolved in 20 mL of ddH2O (all of the HAuCl4 solution was used within 10 minutes of making it as this solution is not stable)

 

 

Solution was left overnight in the biosafety cabinet.

Results: UV-vis-IR reading of the Aloe Vera samples were taken. the optimal percentage of aloe vera extract is between 40 and 60% (more testing needed) since the highest peak between 500 - 600 nm is observed with these trials (gold NP have their highest absorption within this range). 20% Aloe Vera showed a strong peak within that same range indicating the formation of nanotriangles, but it also has a peak at around 900 nm. This indicates that the production of NPs was not homogenous and that there's multiple shapes within the solution.

JUNE 21

Observation: Gold Nanoparticle Synthesis using Aloe Vera Extract Optimization Trial #2

 

TEM Images of gold nanotriangles synthesized using aloe vera extract:

We had initially expected Aloe Vera Gold nanoparticles to be triangular in shape and to be around 100 nm in size. Upon inspection, we found that the nanoparticles were a variety of sizes from 10 to 100 nm and were not exclusively triangular. We also found that there was a film around the nanoparticles, which we learned was potentially organics from our extracts. We didn’t find this to be troublesome since it would lead to a variety of shapes on the surfaces of the cells.

An Energy-dispersive X-ray spectrogram (EDS) was obtained for our aloe vera samples to confirm that they were indeed gold. Below is the spectogram; high peaks for copper and carbon are a result of the grid used in the microscope. The peaks containing gold (Au) are a confirmation that the nanoparticles are made of gold.