Analytical Chemistry and Nanotechnology

Experiment: Synthesis of Silver Nanoparticles Using a Chemical Reduction Method

Significance:

Nanotechnology deals with the manipulation of matter at the atomic and molecular scale. Nanoparticles, with sizes ranging from 1 to 100 nanometers, exhibit unique properties that differ from their bulk counterparts. This experiment demonstrates the synthesis of silver nanoparticles using a simple chemical reduction method, providing insights into nanomaterial synthesis and their potential applications.

Procedure:

Materials:

• Silver nitrate (AgNO3) solution (0.1 M)
• Sodium borohydride (NaBH4) solution (0.1 M)
• Sodium citrate solution (1%)
• Distilled water
• Glassware (beakers, stirring rod, cuvettes)
• UV-Vis spectrophotometer

Steps:

1. Preparation of Silver Nitrate Solution: Dissolve 0.85 g of silver nitrate (AgNO3) in 100 mL of distilled water to obtain a 0.1 M solution.
2. Preparation of Sodium Borohydride Solution: Dissolve 0.38 g of sodium borohydride (NaBH4) in 100 mL of distilled water to obtain a 0.1 M solution. (Caution: Handle sodium borohydride with care as it is a reducing agent and can be harmful if ingested or inhaled.)
3. Preparation of Sodium Citrate Solution: Dissolve 1 g of sodium citrate in 100 mL of distilled water to obtain a 1% solution.
4. Synthesis of Silver Nanoparticles: In a clean beaker, mix 50 mL of AgNO3 solution, 5 mL of sodium citrate solution, and 10 mL of distilled water. Stir the mixture gently for 5 minutes.
5. Reduction of Silver Ions: Add 1 mL of NaBH4 solution dropwise to the mixture while stirring continuously. Observe the color change from colorless to yellowish-brown, indicating the formation of silver nanoparticles.
6. Purification of Nanoparticles: Centrifuge the solution at 10,000 rpm for 10 minutes to separate the nanoparticles from the excess reactants and impurities. Discard the supernatant and redisperse the nanoparticles in distilled water.
7. Characterization of Nanoparticles: Using a UV-Vis spectrophotometer, obtain the absorption spectrum of the nanoparticle solution in the range of 300-800 nm. The spectrum should exhibit a characteristic surface plasmon resonance (SPR) peak, indicating the presence of silver nanoparticles.

Key Procedures and Observations:

• Color Change: The initial colorless mixture turns yellowish-brown upon addition of NaBH4, indicating the reduction of silver ions (Ag+) to silver nanoparticles (Ag0).
• Surface Plasmon Resonance (SPR) Peak: The UV-Vis spectrum shows a prominent SPR peak around 420-450 nm, confirming the formation of silver nanoparticles. The exact peak position depends on the size and shape of the nanoparticles.

Significance and Applications:

• Nanomaterial Synthesis: This experiment demonstrates a simple and widely used method for synthesizing silver nanoparticles.
• Optical Properties: Silver nanoparticles exhibit unique optical properties, including strong light scattering and absorption, which make them useful in various applications such as sensing, imaging, and photocatalysis.
• Antimicrobial Activity: Silver nanoparticles have been extensively studied for their antimicrobial properties, making them potential candidates for use in healthcare and consumer products.
• Catalytic Properties: Silver nanoparticles find applications in catalysis, where they can enhance the efficiency and selectivity of chemical reactions.

Note:

This experiment should be conducted under the supervision of a qualified instructor and with appropriate safety precautions, including the use of personal protective equipment (PPE) and proper waste disposal practices.