Jun 17, 2026
Green Synthesis of Titanium Dioxide Nanoparticles (TiO2 NPs) Using Pomegranate Peel Aqueous Extract
- Mohammadreza Ashayeri1
- 1Tarbiat Modares University
Protocol Citation: Mohammadreza Ashayeri 2026. Green Synthesis of Titanium Dioxide Nanoparticles (TiO2 NPs) Using Pomegranate Peel Aqueous Extract. protocols.io https://dx.doi.org/10.17504/protocols.io.36wgq253kgk5/v1
License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: June 16, 2026
Last Modified: June 17, 2026
Protocol Integer ID: 319266
Keywords: Titanium dioxide nanoparticles, Green synthesis, Punica granatum, Biogenic nanoparticles, green synthesis of titanium dioxide nanoparticle, titanium dioxide nanoparticle, using pomegranate peel aqueous extract, pomegranate peel aqueous extract this protocol, using titanium, tio2 np, phytochemical coating, nanoparticle formation, green synthesis, aqueous pomegranate, peel extract
Abstract
This protocol describes the green synthesis of titanium dioxide nanoparticles (TiO2 NPs) using titanium tetraisopropoxide (TTIP) as the precursor and aqueous pomegranate (Punica granatum) peel extract as a natural capping and growth-controlling medium. The method is designed to be simple, low-cost, and environmentally friendly, while avoiding high-temperature calcination in order to preserve the phytochemical coating formed during synthesis. In the source material, the extract is prepared at 60 °C for 60 min, nanoparticle formation is carried out at 70 °C under continuous stirring, and the final product is dried mildly at 80 °C for 1 h.
Materials
Reagents:
- Fresh pomegranate (Punica granatum) peels
- Deionized water
- Titanium tetraisopropoxide (TTIP), ≥97%
- Ethanol, analytical grade
- Optional: sterile distilled water for final resuspension
Equipment:
- Analytical balance
- Hot plate with magnetic stirring and temperature control
- Magnetic stir bars
- Beakers and Erlenmeyer flasks
- Filtration setup
- Centrifuge capable of 10,000 rpm
- Drying oven set to 80 °C
- Thermometer or temperature probe
- Ultrasonicator, optional
Troubleshooting
Problem
Problem 1: No visible change in suspension
Solution
Possible causes:
- degraded extract
- TTIP added too quickly
- insufficient stirring
- incorrect temperature
Solution:
- prepare a fresh extract
- add TTIP more slowly
- verify temperature at 70 °C
- maintain continuous stirring at 500 rpm
Problem
Problem 2: Large aggregates or broad size distribution
Solution
Possible causes:
- rapid precursor addition
- insufficient extract concentration
- contamination
- overheating
Solution:
- extend the dropwise addition time
- use fresh extract
- ensure clean glassware and deionized water
- keep the reaction strictly at 70 °C
Problem
Problem 3: Poor pellet recovery
Solution
Possible causes:
- highly stable colloid
- insufficient centrifugation force
Solution:
- confirm centrifugation at 10,000 rpm
- extend centrifugation time slightly if needed
- let the sample stand briefly before spinning
Problem
Problem 4: Product aggregates after drying
Solution
Possible causes:
- overheating
- insufficient washing
- residual salts
Solution:
- dry only at 80 °C
- wash thoroughly
- avoid calcination or any higher-temperature treatment
Safety warnings
Critical Notes:
- Do not exceed the mild extraction temperature. The source files specifically describe shade drying and 60 °C extraction to preserve heat-sensitive phytochemicals that contribute to surface stabilization.
Safety Notes:
- Handle TTIP in a fume hood with gloves, lab coat, and eye protection.
- Avoid inhalation of peel powder during grinding.
- Use caution with heated solutions and hot glassware.
- Dispose of titanium-containing waste according to institutional chemical waste guidelines.
- Follow standard nanoparticle-handling procedures during downstream processing.
Before start
- Clean and dry all glassware.
- Prepare the pomegranate peel extract fresh on the day of synthesis, or store it briefly at 4 °C.
- Keep TTIP tightly sealed and protected from moisture.
- Preheat the hot plate and confirm the temperature settings before starting.
Preparation of pomegranate peel aqueous extract
Collect fresh pomegranate peels and wash them thoroughly with distilled water.
Dry the peels in the shade at room temperature for 72 h.
Grind the dried peels into a fine powder.
Add 10 g of peel powder to 100 mL of deionized water.
Heat the suspension at 60 °C for 60 min under magnetic stirring.
Filter first through cheesecloth or muslin, then through Whatman No. 1 filter paper.
Use the clear extract immediately for nanoparticle synthesis.
Synthesis of TiO2 nanoparticles
Transfer 50 mL of the filtered pomegranate peel extract into an Erlenmeyer flask.
Place the flask on a magnetic stirrer and heat to 70 °C.
Set stirring to 500 rpm.
Add 5 mL TTIP dropwise over 5–10 min while maintaining continuous stirring.
Continue the reaction at 70 °C for 4 h.
Observe the development of a milky colloidal suspension, which indicates nanoparticle formation.
Allow the reaction mixture to cool to room temperature.
Purification
Centrifuge the reaction mixture at 10,000 rpm for 20 min.
Discard the supernatant carefully.
Wash the pellet with deionized water.
Repeat the centrifugation and washing step three times.
Perform an additional wash with ethanol if needed to remove residual organic impurities.
Do not perform calcination. The source files identify elimination of the calcination step as a key feature because it preserves the organic coating and helps maintain colloidal stability.
Dry the purified pellet in an oven at 80 °C for 1 h.
Store the dried nanoparticles in a clean, dry vial.
Timing
Peel washing and shade drying: 72 h
Peel powder preparation: 15–30 min
Aqueous extraction: 60 min
Filtration: 10–20 min
Nanoparticle synthesis: 4 h
Centrifugation and washing: 60–90 min
Final drying: 1 h
Characterization
Use transmission electron microscopy (TEM) to confirm particle shape, size range, and presence of a thin organic coating around the nanoparticle surface.
Use dynamic light scattering (DLS) to determine hydrodynamic diameter, size distribution, and polydispersity index.
Use zeta potential analysis to assess: surface charge and colloidal stability.
Expected Results
Successful completion of this protocol should result in the formation of a stable milky colloidal suspension of titanium-based nanoparticles and a fine nanoparticle powder after purification and drying.
The synthesized nanoparticles are expected to exhibit predominantly spherical morphology by TEM.
Particle sizes of approximately 20–80 nm by TEM.
Hydrodynamic diameters of approximately 80–90 nm by DLS.
Positive zeta potential values indicative of good colloidal stability (approximately +31 mV in the source study).
A phytochemical surface coating derived from pomegranate peel extract, contributing to nanoparticle stabilization.
Minor variations in particle size and surface charge may occur between synthesis batches; therefore, characterization by TEM, DLS, and zeta potential analysis is recommended for each preparation.