Functional Titanium Dioxide: Photocatalytic, Nano, Antimicrobial & Conductive Grades — Supply Chain Overview

Photocatalytic TiO₂ functions by generating hydroxyl radicals under UV irradiation (λ < 387 nm), oxidising organic pollutants, bacteria, and VOCs on contact. SEMITECH's photocatalytic anatase grade delivers BET surface area ≥ 200 m²/g, anatase phase purity > 99%, and average primary particle size of 10–20 nm. These parameters are not cosmetic — higher BET directly increases active site density, accelerating first-order degradation rate constants. Typical applications include HVAC filter coatings, ceramic tile glazes, exterior architectural glass, and air-purification membranes. From a supply chain perspective, photocatalytic-grade TiO₂ is produced exclusively via the chloride (vapor-phase) route, which confines qualified upstream supply to a handful of Chinese and Japanese producers running TiCl₄ oxidation reactors, creating real scarcity when downstream demand spikes.

• Phase — Anatase > 99%; no rutile contamination — rutile suppresses photocatalytic activity.
• BET — ≥ 200 m²/g; measurable by N₂ adsorption (BET method, ISO 9277).
• Particle size — D50 10–20 nm primary; agglomerate D50 < 200 nm in aqueous dispersion.
• Key markets — Indoor air purification, self-cleaning glass, anti-fouling marine coatings, photovoltaic anti-reflective layers.

Nano-scale TiO₂ blocks UV radiation without visible whitening — the optical transparency threshold sits below roughly 50 nm primary particle size. Nano anatase (D50 ≈ 10–25 nm) absorbs strongly in UVA (315–400 nm) and is the preferred phase for sunscreen formulations requiring transparent film formation. Nano rutile (D50 ≈ 15–30 nm) extends absorption into UVB (280–315 nm) and offers superior photostability, making it the dominant choice for automotive clear coats and plastic UV stabilisation. Both grades are surface-treated — silica or alumina encapsulation prevents photocatalytic activity from degrading the matrix polymer. Upstream, nano TiO₂ is tightly correlated to TiCl₄ availability: any disruption to chlorine supply or TiCl₄ logistics from Shandong or Yunnan cascades directly into nano-grade spot prices within 4–6 weeks.

• Anatase D50 — 10–25 nm; optimal UVA transparency; used in mineral sunscreen SPF formulations.
• Rutile D50 — 15–30 nm; broader UV coverage; surface-treated to eliminate photocatalytic side reactions.
• Surface treatment — SiO₂ or Al₂O₃ encapsulation; loading 3–8 wt%; confirmed by TGA or XRF.
• Price sensitivity — Nano grades track TiCl₄ spot prices; 1Q2026 TiCl₄ was ~¥4,800–5,200/mt ex-Shandong.

Standard TiO₂ requires UV excitation, limiting antimicrobial effectiveness indoors. Silver doping narrows the effective band gap toward visible light (λ < 550 nm) through a plasmonic resonance mechanism: Ag nanoparticles (0.5–2 wt% loading, 3–8 nm) deposited on the TiO₂ surface trap conduction-band electrons, reducing carrier recombination and enabling reactive oxygen species generation under fluorescent or LED illumination. SEMITECH's Ag-TiO₂ achieves JIS Z 2801 antimicrobial activity values > 2 log reduction against E. coli and S. aureus under standard indoor lighting at 1,000 lux. Applications include hospital touch-surface coatings, food-contact packaging, HVAC duct liners, and antimicrobial textile finishes. Silver price volatility is the primary cost variable: Ag-TiO₂ production cost moves roughly ±$0.80/kg for every $1/troy oz change in silver spot — buyers should lock forward contracts when silver trades below the 90-day moving average.

• Ag loading — 0.5–2.0 wt%; confirmed by ICP-OES; higher loading increases cost, not performance linearly.
• Particle size — TiO₂ host D50 ≈ 20 nm; Ag clusters 3–8 nm by TEM.
• Test standard — JIS Z 2801; ISO 22196; log reduction ≥ 2 within 24 h under 1,000 lux visible light.
• Cost driver — Silver metal is 60–70% of variable cost; price hedge is critical above $30/troy oz.

Antimony tin oxide (ATO) — SnO₂ doped with 5–15 mol% Sb₂O₃ — delivers volume resistivity of 10²–10⁴ Ω·cm in a thermally stable, optically transparent package. When co-processed or blended with TiO₂ carriers, the composite enables ESD-safe clear coats for electronics packaging, conductive primers for plastic substrates, and anti-static film coatings. The ATO/TiO₂ route avoids carbon black’s optical opacity and ITO’s indium cost and brittleness. Sheet resistance in thin film is tunable from 10³ to 10⁶ Ω/sq by varying ATO loading (10–40 wt%) and film thickness (0.5–3 µm). Upstream, the critical input is antimony trioxide (Sb₂O₃) — China controls approximately 90% of global antimony mine output, and Sb₂O₃ prices have swung between $6,500–$12,000/mt over the past 24 months, the principal landed-cost volatility for this grade.

• Resistivity — 10²–10⁴ Ω·cm bulk; sheet resistance 10³–10⁶ Ω/sq at 1–3 µm coating thickness.
• ATO composition — SnO₂ + 5–15 mol% Sb₂O₃; phase-pure by XRD; D50 15–40 nm.
• Optical — Transmission > 85% at 550 nm in film at recommended loading — no visual haze.
• Supply risk — Antimony sourced 90% from China; Sb₂O₃ price swings ±30% intra-year — monitor SHFE antimony spot.

The table below maps each grade to its defining physical parameters, primary application, and upstream supply sensitivity. Use this as a first-pass screening filter before requesting SEMITECH technical datasheets or sample qualification lots.