Self-Cleaning Glass with TiO2 Coatings

ISEF Category: Materials Science

Subcategory: Ceramic and Glasses  ·  Difficulty: Intermediate  ·  Setup: School Lab  ·  Time: 1 to 2 Months

The Hook

Some glass can clean itself when light hits it. That sounds like magic, but it comes from a surface reaction you can measure. If you can track how fast a blue dye fades, you can test whether a TiO2 coating really works. That gives you a real materials science project with a visible result.

What Is It?

Photocatalytic self-cleaning glass uses a coating that speeds up chemical breakdown when light shines on it. TiO2, or titanium dioxide, acts like a light-activated helper. Sunlight gives the coating enough energy to trigger reactions that can damage dye molecules and other organic grime.

Think of the coating like a tiny outdoor work crew on the glass surface. The light turns the crew on, and the dye slowly disappears. Methylene blue works well as a test dye because it has a strong color, so you can track how much remains by measuring how dark the solution looks over time.

Your project asks a simple question with useful data behind it. Does a TiO2-coated slide fade methylene blue faster than an uncoated slide, and how does the rate change with coating thickness, light exposure, or surface prep?

Why This Is a Good Topic

This project is testable because you can measure color change over time and compare treated and untreated glass. It connects to a real problem, keeping windows, solar panels, and building surfaces cleaner with less scrubbing and fewer chemicals. You can learn coating control, light-driven chemistry, and basic kinetics without needing a university lab.

Research Questions

• How does TiO2 coating thickness affect the rate of methylene blue degradation under sunlight?
• What is the effect of surface cleaning before coating on photocatalytic performance?
• Does adding a binder or changing the dip-coating method change how evenly the TiO2 film covers the glass?
• To what extent does direct sunlight versus shaded daylight change the degradation rate?
• Which glass surface treatment gives the largest drop in absorbance over time?
• How does repeated reuse of the same coated slide affect its photocatalytic activity?

Basic Materials

• Microscope slides or plain glass coupons with similar size and thickness.
• Food-grade TiO2 powder.
• Distilled water.
• Small beakers or clear cups.
• Digital scale with at least 0.01 g precision.
• Dropper pipettes or disposable transfer pipettes.
• Clean stirring rods or plastic stirrers.
• Timer or stopwatch.
• UV-blocking safety glasses.
• Nitrile gloves.
• Smartphone camera with manual exposure control.
• White background or light box for consistent photos.
• Metric ruler or caliper.
• Methylene blue solution prepared by a school lab or teacher.

Advanced Materials

• Spin coater or controlled dip-coating setup.
• Analytical balance.
• UV-Vis spectrophotometer.
• Quartz or borosilicate cuvettes.
• Surface profilometer or ellipsometer.
• SEM access for coating morphology.
• XRD access for TiO2 phase confirmation.
• Contact angle goniometer.
• LED UVA lamp with known irradiance.
• Solar simulator or calibrated outdoor light meter.
• ImageJ software for image-based intensity analysis.
• Lab oven or hot plate for drying, if your protocol allows it.

Software & Tools

• ImageJ: Measures color intensity changes in photos and helps you turn images into data.
• Python: Organizes time series data, fits kinetic models, and plots degradation curves.
• Google Sheets: Tracks sample labels, light conditions, and absorbance or color data.
• GeoGebra: Fits simple trend lines and exponential decay models if you want a lighter analysis workflow.
• NIH ImageJ macro recorder: Automates repeated image measurements across many samples.

Experiment Steps

1. Define the one coating variable you will change first, such as TiO2 loading, surface prep, or dip-coating count.
2. Plan a control group with uncoated glass so you can separate true photocatalysis from normal dye fading.
3. Decide how you will measure color loss, either with a spectrophotometer or with standardized photos and image analysis.
4. Build a calibration plan so your signal can be converted into concentration or relative absorbance values.
5. Map out how you will keep light exposure, sample size, and starting dye color as constant as possible.
6. Choose the kinetic model you will test, such as linear, first-order, or comparative rate analysis.

Common Pitfalls

• Using inconsistent sunlight between trials, which makes one run look faster even when the coating did not change.
• Letting the TiO2 settle before each dip, which gives uneven films and weakens comparisons.
• Comparing photos taken under different room lighting, which changes the apparent color even when the dye level stays the same.
• Skipping an uncoated glass control, which makes it hard to prove the coating caused the effect.
• Mixing up surface roughness, coating thickness, and light angle, which hides the real reason one sample performs better.

What Makes This Competitive

A stronger project does more than show that the blue color gets lighter. You can compare several coating designs, quantify the surface quality, and test whether the rate follows a real kinetic model. Strong entries also control light dose carefully, use repeated trials, and back up the photos with calibrated data. That turns a simple demo into a real materials study.

Project Variations

• Test how TiO2-coated glass performs under UVA LED light instead of sunlight.
• Compare methylene blue with another dye, such as food coloring or rhodamine B, to see whether molecular structure changes the decay rate.
• Change the glass pretreatment, such as washing, sanding, or plasma cleaning, and measure how surface condition affects coating performance.

Learn More

• PubChem: Look up methylene blue properties, structure, and safety details by searching PubChem for the compound name.
• NOAA Solar Calculator: Find sunlight timing and angle for your location when planning outdoor exposure tests.
• NASA Earth Observatory: Read about how sunlight and surface reflectivity affect materials in outdoor settings, then search the site for related articles.
• Photocatalysis: Fundamentals and Perspectives in peer-reviewed journals: Search for review articles on photocatalysis through PubMed or Google Scholar through your school library.
• MIT OpenCourseWare: Search for materials science and surface chemistry lectures that explain thin films, reaction rates, and optical measurement.