TiO2 Photocatalyst Colloid Stabilization at Neutral pH
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Solution Overview
Problem
Existing nanocrystalline TiO2 photocatalysts are limited by their requirement for an acidic environment, restricting their applications, particularly in maintaining physiological conditions for materials like contact lenses and medical catheters.
Innovation Solution
A method to produce a stable nanocrystalline photocatalyst in the form of a transparent colloidal solution by chemisorbing disodium salt of 4,5-dihydroxy-1,3-benzenedisulfonic acid or rutin on TiO2 nanoparticles, followed by dialysis to achieve stability at neutral pH, allowing the photocatalyst to be active under visible light irradiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nanocrystalline TiO2 photocatalysts are used, then photocatalytic activity is achieved, but stability is limited to acidic environments only
Solution Approach 1:
The patent uses organic ligands (ascorbic acid, catechol, or their derivatives) as intermediary substances that chemically bind to the TiO2 nanoparticle surfaces. These ligands act as mediators that stabilize the colloidal suspension at neutral pH by preventing aggregation, while allowing the TiO2 to maintain its photocatalytic activity. This resolves the contradiction by enabling the photocatalyst to function reliably in neutral environments without sacrificing its photocatalytic properties.
Solution Approach 2:
The patent changes the chemical parameters of the TiO2 surface by introducing organic ligands with specific functional groups (carboxyl, hydroxyl, or sulfonic acid groups). This parameter change modifies the surface charge and chemical properties of the nanoparticles, enabling them to remain stable in neutral pH environments. The ligands alter the surface chemistry without compromising the core photocatalytic functionality of TiO2.
2Use of energy by moving object
If TiO2 surface is modified with organic compounds to broaden absorption spectrum, then visible light activity is improved, but system complexity increases
Solution Approach 1:
The patent employs simple, inexpensive organic molecules (ascorbic acid, catechol, or their derivatives) that can be easily synthesized or obtained. These small organic compounds form stable surface complexes with TiO2 through chemisorption, providing visible light absorption enhancement without requiring complex modification procedures. The simplicity of these organic ligands reduces the overall system complexity while achieving the desired optical properties.
3Stability of the object's composition
If colloidal solution is prepared in acidic environment, then nanoparticle dispersion is achieved, but application range is restricted
Solution Approach 1:
The patent performs preliminary surface modification of TiO2 nanoparticles with organic ligands in acidic conditions, where the ligands chemically bind to the nanoparticle surfaces. This preliminary action creates a stable surface complex that can then withstand neutralization to pH 7 without aggregation. The preliminary ligand attachment prepares the nanoparticles for subsequent use in neutral environments, expanding their application range while maintaining colloidal stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resulting photocatalyst exhibits strong photocatalytic and photosterilizing properties, maintaining stability and effectiveness in neutral aqueous environments, enabling its use in various applications including sterilization of medical and cosmetic materials.
Implementation Method 1
a colloidal aqueous solution of TiO2 is supplemented with an organic compound which undergoes chemisorption on the surface of TiO2
Implementation Method 2
nanocrystalline photocatalyst active upon visible light irradiation
Implementation Method 3
exhibiting strong photocatalytic and photosterilising properties
Implementation Method 4
dialysis is performed on the resulting sol being brought to pH = 7 against an aqueous solution
Data Source
Figure 1a~1b
Figure 1c~2
Figure 3a~3g
AI summary
The present invention relates to a nanocrystalline photocatalyst active upon visible light irradiation, with a high degree of dispersion, stable in the form of a transparent colloidal solution in an aqueous environment, containing nanocrystals of titanium dioxide (TiO2) surface-modified via direct chemisorption of organic compounds. The present invention in turn relates to a method of producing the material as well as its use as a photosteriliser, photobacteriocide, photomycocide, and/or photocatalyst, in particular for the sterilisation of glass surfaces, transparent plastics and transparent materials, in particular contact lenses, medical catheters, glass and plastic conduits as well as other surfaces, whose sterilisation is desirable and/or required.