Nanotech: Photocatalysis, Self‑Cleaning Surfaces, Medical Uses

In 1857 Michael Faraday demonstrated ruby‑gold particles in a Royal Institution lecture, an early glimpse of nanoscopic materials. The Lycurgus Cup, a Roman glass vessel that changes colour with light, illustrates how ancient artisans already exploited nanoscale effects without modern terminology.

Defining the Nanoscale

One nanometre equals 10⁻⁹ metre, roughly the distance a fingernail grows in one second. A line of one‑million such particles would span the length of a typical full stop. Comparing sizes, a 2 nm gold nanoparticle is far smaller than a virus yet large enough to interact with visible light.

Institutional Collaboration

UCL celebrates its 200th anniversary, boasting 33 Nobel laureates, 12 000 staff and 50 000 students. The Royal Institution, with a legacy of public science communication, shares joint professorships that link academic discovery to industrial translation. Partnerships with firms such as Pilkington (NSG) and Endomagnetics exemplify this synergy.

Functional Materials & Applications

Titanium Dioxide and Photocatalysis

Titanium dioxide (TiO₂) acts as a light‑activated catalyst that breaks down organic dirt and renders surfaces hydrophilic. Transparent coatings as thin as 25 nm can be deposited on glass during the float‑glass process using atmospheric‑pressure chemical vapour deposition (APCVD). Forming heterojunctions—such as anatase/rutile or tungsten‑oxide/TiO₂—improves electron‑hole separation and boosts photocatalytic efficiency.

Superhydrophobic Surfaces

Superhydrophobicity combines a low‑energy surface chemistry with nanoscale roughness. Water contact angles above 150° cause droplets to roll like marbles, picking up contaminants as they travel. Rugged formulations now survive physical abrasion, extending the “lotus effect” to real‑world windows and vehicle exteriors.

Energy‑Related Technologies

Zinc‑ion batteries benefit from nanostructured electrodes that suppress dendrite growth, while gas‑sensing platforms such as Aqual record nine million air‑quality measurements daily across 128 countries. Radiative‑cooling coatings emit mid‑infrared radiation through the atmospheric window, providing a passive way to keep buildings, buses or cars cooler in summer.

Healthcare & Medical Technology

Gold nanoparticles around 2 nm, when coupled with photosensitising dyes, generate lethal reactive species under light, killing MRSA, E. coli and other pathogens. Laser‑diffuser fibers deliver this treatment to the anterior nares and periodontal pockets. Photo‑acoustic imaging uses nanoparticle‑coated fiber tips to convert pulsed light into ultrasound, delivering high‑resolution images for diagnostics. Magnetic nanoparticles commercialised by Endomagnetics enable sensitive cancer detection, already serving over half a million patients.

Mechanisms Behind the Technologies

Photocatalysis relies on light‑induced electron‑hole pairs that oxidise organic contaminants or destroy bacterial cells. Heterojunctions improve the separation of these charge carriers, preventing recombination and raising reaction rates. Surface‑enhanced Raman scattering (SERS) exploits the oscillating electron clouds of gold nanoparticles to amplify molecular signals, while photo‑induced enhanced Raman scattering (PEERS) merges photocatalysis with SERS for even greater detection sensitivity. Radiative cooling is achieved by engineering materials that preferentially emit thermal radiation within the 8–13 µm atmospheric window, allowing heat to escape directly to space.

Hard Facts & Numbers

• 1 nm = 1 × 10⁻⁹ m.
• Pilkington Active glass sells roughly 200 million units per year.
• Float‑glass furnaces operate at about 1 300 °C.
• Aqual logs 9 million measurements per day.
• One in sixteen hospital patients acquires an infection.