Titanium dioxide (TiO2), also known as titania, is a high-refractive-index metal oxide with strong ultraviolet absorption and useful photocatalytic, surface, and optical properties. By controlling particle size, morphology, crystal phase, surface chemistry, and formulation, titania nanoparticles can be engineered for applications including optical coatings, photocatalysis, photovoltaics, advanced pigments, nanotoxicology, and materials research.
nanoComposix has developed a broad range of titania structures, including nanorods, nanowires, spherical particles, surface-functionalized particles, and TiO2 shells around other nanoparticle cores. Selected titania samples are available for purchase, while custom development supports additional particle designs and formulations.
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Properties of Titanium Dioxide Nanoparticles
Titania nanoparticle behavior depends on particle dimensions, crystal phase, morphology, surface chemistry, and surrounding environment. These variables influence optical scattering, UV absorption, photocatalytic activity, dispersion behavior, and interactions with other materials.
High Refractive Index & Optical Scattering
Anatase TiO2 has a high refractive index of approximately 2.5 and a bandgap of approximately 3.2 eV. The large refractive-index contrast between titania and many surrounding materials enables strong optical scattering, particularly as particle dimensions increase.
This high refractive index also gives TiO2 its characteristic opacity and white appearance in bulk pigment applications. At smaller particle sizes and in well-dispersed formulations, titania can produce different scattering and opalescent optical effects that are useful in coatings, composites, and cosmetic research.
For spherical particles, the Mie Theory Calculator can be used to explore how TiO2 particle size and surrounding refractive index affect calculated absorption and scattering.
UV Absorption & Photocatalytic Activity
Titanium dioxide strongly absorbs ultraviolet light because photons with sufficient energy can promote electrons across the semiconductor bandgap. In crystalline TiO2, the resulting charge carriers can participate in surface reactions, which forms the basis of many photocatalytic applications.
Anatase titania is widely investigated for photocatalysis, including solar-driven chemical transformations and water-splitting systems that incorporate appropriate co-catalysts. Particle morphology, exposed crystal facets, surface chemistry, and interactions with co-catalytic materials can all influence photocatalytic behavior.
Surface & Chemical Properties
The TiO2 surface can interact with organic ligands, silanes, polymers, biomolecules, and other materials, providing multiple routes for modifying particle compatibility and functionality. Surface modification can be used to alter dispersion behavior, introduce reactive functionality, or integrate titania into different matrices.
Titania and silica also differ in surface chemistry and aqueous behavior. TiO2 can provide greater stability than silica under some conditions where silica dissolution becomes problematic, although stability depends on crystal phase, pH, temperature, and formulation.
Titania surfaces also have affinity for phosphate-containing species, a property that has been used in applications involving adsorption and enrichment of phosphorylated biomolecules.
Titania Nanoparticle Architectures
Titanium dioxide can be synthesized in a variety of dimensions, morphologies, crystal phases, and surface states. The examples below illustrate titania structures that nanoComposix has developed for research and custom programs.
Titania Nanorods
Titania nanorods developed by nanoComposix are one-dimensional crystalline anatase particles with narrow length and diameter distributions, high refractive index, and strong UV absorption.
One example nanorod formulation has an average length of approximately 55 nm and diameter of approximately 15 nm. The particles are surface-functionalized with stearic acid, provided at 1 mg/mL TiO2 in n-butanol, and can disperse in a range of organic solvents.
The combination of anisotropic morphology and controlled crystal structure makes titania nanorods useful for studying morphology-dependent optical behavior, carrier transport, photocatalysis, and facet-dependent surface interactions.
Titania Nanowires
Titania nanowires represent a high-aspect-ratio one-dimensional TiO2 architecture. One example material has an average length of approximately 600 nm and an average diameter of approximately 20 nm and is dispersible in water and polar, aqueous-compatible solvents.
Nanowire dimensions and crystalline phase can be adjusted through synthesis conditions, providing a route to investigate how aspect ratio and crystal structure affect optical, surface, and photocatalytic properties.
Spherical Titanium Dioxide
nanoComposix has developed spherical titania particles across a range of sizes, solutions, and crystalline phases. Amorphous titania provides high refractive index and can be formulated in water and alcohols, while crystalline phases such as anatase and rutile provide different refractive-index and photocatalytic properties.
Particle size and crystallinity can therefore be selected independently as important design variables when developing materials for optical scattering, coatings, catalysis, or other applications.
Titania Coatings on Nanoparticles
Titanium dioxide can also be deposited as a shell around other nanoparticle cores. Shell crystallinity can be modified through processing such as calcination, providing additional control over refractive index, surface properties, and photocatalytic behavior.
Because titania has a substantially higher refractive index than silica, a TiO2 shell around a plasmonic nanoparticle can produce a larger change in the local dielectric environment. This can shift the extinction spectrum of the underlying metal core and provides another route for engineering nanoparticle optical response.
These core-shell structures can combine the optical properties of a metal nanoparticle with the surface chemistry, refractive index, or photocatalytic properties of titania.
Surface-Functionalized Titania Nanoparticles
Titania particle surfaces can be modified with organic ligands using both adsorptive and covalent approaches. Depending on the particle and application, surface modification can introduce polymers, small molecules, or functional silanes that alter charge, dispersion stability, solvent compatibility, or downstream reactivity.
Silane chemistry can also be adapted to the TiO2 surface. For example, hydrophobic alkyl silanes can be used to increase compatibility with less-polar organic environments and matrices.
Applications of Titanium Dioxide Nanoparticles
Optical Coatings, Pigments & Scattering
The high refractive index of TiO2 makes titania useful where strong optical scattering, refractive-index modification, opacity, or controlled appearance is required. Particle size and morphology determine how strongly particles interact with visible light, while surface chemistry affects their compatibility with coatings, polymers, and other matrices.
These properties support research involving high-refractive-index optical coatings, advanced pigments, and cosmetic or topical formulations. For broader application guidance, see Nanomaterials for Optical Engineering and Particle Development for Dermatology & Aesthetics.
Photocatalysis & Photovoltaics
Titanium dioxide is widely used in photocatalysis because its UV absorption and semiconductor properties allow photoexcited charge carriers to participate in chemical reactions at the particle surface. Crystal phase, exposed facets, particle morphology, surface area, and co-catalysts can all influence these processes.
Titania also plays an important role in energy research. TiO2 is used in dye-sensitized solar-cell architectures and has been investigated in other photovoltaic systems where particle morphology and crystal structure can affect carrier transport, interfacial behavior, and device performance.
Reference Materials & Nanotoxicology Research
Precisely engineered TiO2 particles with controlled size, morphology, crystal phase, and surface chemistry can help researchers isolate the effect of individual nanoparticle properties in comparative studies. Well-characterized materials are particularly useful when particle dimensions, aggregation state, or surface chemistry need to be controlled across an experimental series.
Explore Reference Material Nanoparticles and Nanotoxicology: Particle Selection for additional guidance.
Custom Titania Nanoparticle Development
nanoComposix develops TiO2 nanoparticles with varying particle sizes, morphologies, crystal phases, surface chemistries, concentrations, and dispersion media. Custom projects can also evaluate titania coatings on other nanoparticle cores and more complex particle architectures.
Development can be tailored around an application-specific requirement such as optical response, photocatalytic behavior, particle geometry, surface functionality, solvent compatibility, or integration into another material.
For broader development pathways, see Custom Nanoparticle Development.
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