# Green synthesis of silver and gold nanoparticles

> Leaves are boiled in water and the filtered extract is added to silver nitrate or chloroauric acid. Phytochemicals in the extract, such as polyphenols and flavonoids, reduce Ag⁺ and Au³⁺ to metal atoms that nucleate into nanoparticles, and the same molecules cap the particles. The colloid changes colour as the particles form: yellow-brown for silver, ruby red to purple for gold.

- Page: https://www.labcanvas.com/templates/nanomaterial-synthesis/green-synthesis-silver-gold-nanoparticles
- Open in the LabCanvas editor (LabCanvas account): https://www.labcanvas.com/editor.html?template=green-synthesis-ag-au
- Updated: 2026-10-14
- Category: Nanomaterial synthesis
- Method: Green synthesis, bottom-up
- Starting materials: Plant leaves (e.g. neem) and aqueous AgNO₃ or HAuCl₄
- Product: Silver or gold nanoparticles capped by phytochemicals, as a colloid in water
- Typical size: Polydisperse nanoparticles; with neem broth many gold particles are flat plates (Shankar et al.)
- Key result: Crystalline metal cores; size and shape vary with the plant, extract amount, pH and temperature
- Scalability: High: water, cheap plant material, no toxic reducing agents
- Figure: 1920 × 1080 px, 78 editable layers (14 generated objects with settings)

## Steps

1. **Leaf extract**: Wash and cut the leaves, boil them in water, cool and filter: the broth carries polyphenols, flavonoids and terpenoids
2. **Reduction**: Add the extract to aqueous AgNO₃ or HAuCl₄: the phytochemicals reduce Ag⁺ / Au³⁺ to metal atoms, which nucleate and grow
3. **Colour change**: The solution turns yellow-brown (Ag) or ruby red to purple (Au) as the plasmon band appears
4. **Capping**: Extract molecules adsorb on the particles and keep them apart; centrifuge and wash to collect them

## Strengths

- No hazardous reductants or organic solvents
- One step: the extract both reduces and caps
- Fast with plant broths (faster than with microorganisms)
- Biocompatible capping layer

## Limitations

- Extract composition varies with plant, season and preparation
- Broader size and shape distributions than citrate or seed-mediated routes
- The capping layer is poorly defined

## Uses

- Antimicrobial coatings and materials (Ag)
- Catalysis
- Sensing and SERS
- Biomedical research

## References

1. Shankar et al., “Rapid synthesis of Au, Ag, and bimetallic Au core–Ag shell nanoparticles using Neem (Azadirachta indica) leaf broth”, J. Colloid Interface Sci. 2004. https://doi.org/10.1016/j.jcis.2004.03.003 (primary)
2. Iravani, “Green synthesis of metal nanoparticles using plants”, Green Chem. 2011. https://doi.org/10.1039/C1GC15386B (review)
3. Ahmed et al., “A review on plants extract mediated synthesis of silver nanoparticles for antimicrobial applications: a green expertise”, J. Adv. Res. 2016. https://doi.org/10.1016/j.jare.2015.02.007 (review)

Credit: Redrawn and simplified after Shankar et al., J. Colloid Interface Sci. 2004 (doi:10.1016/j.jcis.2004.03.003); reviews: Iravani, Green Chem. 2011 (doi:10.1039/C1GC15386B) and Ahmed et al., J. Adv. Res. 2016 (doi:10.1016/j.jare.2015.02.007).

## Questions

**What does the “Green synthesis of silver and gold nanoparticles” template show?** Leaves are boiled in water and the filtered extract is added to silver nitrate or chloroauric acid. Phytochemicals in the extract, such as polyphenols and flavonoids, reduce Ag⁺ and Au³⁺ to metal atoms that nucleate into nanoparticles, and the same molecules cap the particles. The colloid changes colour as the particles form: yellow-brown for silver, ruby red to purple for gold.

**What are the steps shown in “Green synthesis of silver and gold nanoparticles”?** 1. Leaf extract: Wash and cut the leaves, boil them in water, cool and filter: the broth carries polyphenols, flavonoids and terpenoids. 2. Reduction: Add the extract to aqueous AgNO₃ or HAuCl₄: the phytochemicals reduce Ag⁺ / Au³⁺ to metal atoms, which nucleate and grow. 3. Colour change: The solution turns yellow-brown (Ag) or ruby red to purple (Au) as the plasmon band appears. 4. Capping: Extract molecules adsorb on the particles and keep them apart; centrifuge and wash to collect them.

**What are the starting materials and the product?** Starting materials: Plant leaves (e.g. neem) and aqueous AgNO₃ or HAuCl₄. Product: Silver or gold nanoparticles capped by phytochemicals, as a colloid in water.

**Which papers is “Green synthesis of silver and gold nanoparticles” based on?** Shankar et al., “Rapid synthesis of Au, Ag, and bimetallic Au core–Ag shell nanoparticles using Neem (Azadirachta indica) leaf broth”, J. Colloid Interface Sci. 2004 (doi:10.1016/j.jcis.2004.03.003); Iravani, “Green synthesis of metal nanoparticles using plants”, Green Chem. 2011 (doi:10.1039/C1GC15386B); Ahmed et al., “A review on plants extract mediated synthesis of silver nanoparticles for antimicrobial applications: a green expertise”, J. Adv. Res. 2016 (doi:10.1016/j.jare.2015.02.007).

**Can I edit the “Green synthesis of silver and gold nanoparticles” template?** Yes. Open it in the LabCanvas editor: all 78 layers are editable, including 14 generated objects (structures, plots, equipment) with their own settings. Change the text, colours and layout, then export PNG, TIFF, SVG or PDF.

**Do I need an account to use this template?** Not to view it here. To open and edit it, sign in to LabCanvas or create a free account (the free plan keeps one design of each kind). Downloading the figure is part of LabCanvas Pro (US$19 a month or US$199 a year).