Part C. Nanoparticles as Chemical Selective Sensors 1. Colloidal gold solution +

Question

Part C. Nanoparticles as Chemical Selective Sensors 1. Colloidal gold solution + 1 M NaCl solution: Appearance of the solution after adding the 1 M NaCI: 2. Colloidal gold solution +1 M sucrose solution: Appearance of the solution after adding the 1 M sucrose: 3. Colloidal gold solution + substance write identity of substance here Appearance of the solution after adding substance 4. Colloidal gold solution + substance, Appearance of the solution after adding substance write identiry of substance here Evaluate the results you obtained when adding the salt, sugar and other substances to the colloidal gold. Did the Au nanoparticles change in size? If so, did they get larger or smaller, and why? 1. Adding NaCl: 2. Adding sugar: 3. Adding substance write identitry of substance here 4. Adding substance write identity of substance here

Explanation / Answer

Colloidal gold particle solution

1. Addition of NaCl : the size becomes larger.

Color changes to deep blue

This is because the previously negatively charged gold particles (before addition NaCl) in the colloidal solution is now charge shielded (by addition of NaCl), which allows them to come closer and forms large aggreagates. thereby increasing the size of particles.

2. adding sucrose : Particles becomes smaller

color changes to pink

This is because the large sucrose molecules now does not allow the individial particles to forms agregates by comming together, thereby smaller particles are seen.

3. Substance : NaCl turns solution to blue.

4. Substance : Sucrose (or polymer as PEG) turns solution to pink

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