We found a method that utilises a process of producing photocatalytic nanoparticles in situ by flame spray pyrolysis (FSP) and depositing the nanoparticles on the substrate via aerosol deposition to produce a photocatalytic nanoparticle film on the substrate, followed by immersing the photocatalytic nanoparticle film with a polymer solution, or a liquid polymer precursor material, to form a composite layer.
The method used results in a composite layer comprising a percolating network of photocatalytic nanoparticles in a polymer matrix, wherein the composite layer has enhanced durability and maintains activity after several cycles of irradiation, which is an improvement over currently known coatings.
Method of Production
A method for the production of a composite layer in which photocatalytic nanoparticles are embedded in a polymer matrix, wherein the method comprises the steps of:
a. providing a substrate;
b. producing photocatalytic nanoparticles in situ by flame spray pyrolysis and depositing the nanoparticles on a surface of the substrate via aerosol deposition to produce a photocatalytic nanoparticle film on the surface of the substrate; and
c. immersing the photocatalytic nanoparticle film with a polymer solution, or a liquid polymer precursor material, to form the composite layer,
wherein, the photocatalytic nanoparticle film has a thickness of from about 200 to about 1200nm.
The result is the production of a composite layer comprising a percolating network of photocatalytic nanoparticles in a polymer matrix.
In particular the nanoparticles are photocatalytically active in the visible light spectrum range, and the nanoparticles have a broad absorption band starting at about 400 nm (visible-light range) and extending into the near-infrared region of the spectrum. Such nanoparticles that can achieve this absorption/activation range include silver-titanium nanoparticles, which material is commonly referred to as “black titania”. By the term “silver-titanium nanoparticles” we refer to TiO2 nanoparticles which have been doped with silver (Ag) atoms, thus arriving at visible-light-active Ag/TiOx nanoparticles, with TiOx often being given the term “suboxide”, and shifts the peak absorption of the nanoparticles from the UV into the visible-light activation range.
The use of the composite layer has been studied as an antimicrobial coating, to provide antimicrobial properties towards gram-positive and gram-negative bacteria.
The method of treatment and prevention comprised a step of irradiating the coated surface of the catheter with visible light to thus produce ROS from the photocatalytic nanoparticles, which impart an anti-bacterial effect. The power of the light used was about 5 to about 75 mW cm-2. Irradiation took place for from about 15 to about 90 minutes.
