Method for preparing zinc oxide, titanium dioxide nanocrystal water suspension and its applications in UV protection and filtering
Problem or Unmet Need
The active ingredients in common sunscreens are organic, typically benzonphenones or octinaoxate. More powerful SPFs required to effectively block UVA/UVB rays need the use of inorganic oxides, (zinc oxide and titanium dioxide). Among other advantages to the enhanced SPF of the oxides are their longevity (stability) and absorbing/reflecting power relative to organics, but integration with base mixtures suitable for dermatological/topological applications can prove difficult. The oxides are not well disposed to homogenous mixing with the other ingredients often due to the oxide powders used, which consist of particles in micron range with broad size distribution (0.1-10μm). Such powders are often purchased from vendors and used by research scientists at cosmetic R&D facilities. These scientists do not have a great deal of control over the materials and use them as-synthesized.
This invention is related to improvements in control over crystal growth of zinc oxide and titanium dioxide at the nanometer scale. It allows for a simple and scalable production of stable ZnO and TiO2 nanocrystals colloidal water suspension with particle sizes less than 10nm. The ZnO or TiO2 nanocrystals have larger surface area, exhibit excellent UV adsorption, and therefore filter more UV sources compared with those with larger particle sizes.
Details of the Invention
The invention reports the preparation of colloidal water suspension of zinc oxide (ZnO) and titanium dioxide (TiO2) nanocrystals with sizes less than 10nm and its applications in UV protection and filtering. The nano-crystal synthesis involves a solvothermal treatment of a metal salt source such as zinc acetate or titanium oxide acetylacetonate with an alcohol solvent such as ethanol, isopropanol, benzyl alcohol, and oleyl alcohol at mild crystallization temperatures (90-180 °C) for hours. The process is simple and easy for large-scale production. The nanocrystals are aggregate free and can be easily transferred to water by ultrasonication to form a stable colloidal suspension without ay aid of surfactants or additives. The nano-crystal surface can be coated with variety of surfactants, polymers or phospholipids to improve the biocompatibility of the nanocrystal.
With the particle sizes smaller than 10nm and particles suspended in water, ZnO, or TiO2, nanocrystals have larger surface area, exhibit excellent UV adsorption, and therefore filter more UV sources compared with those with larger particle sizes, which is more ideal for applications in UV protection for cosmetics, sunglass coatings, and other high-performance coatings. The colloidal water suspension is environmentally benign and bio-compatible, and it is also eliminates the health and environmental concerns associated with ZnO or TiO2 nanopowders. In addition, ZO nanocrystals can also be used as antibacterial agent and additives, and TiO2 nanocrystals can also be used in catalysis and additives applications.
Zinc oxide has found use in a wide range of medical and cosmetic applications. The ability to absorb ultraviolet light makes zinc oxide an active ingredient of choice in suntan lotions. Zinc oxide is well known for its ability to neutralize acid and for its mild bactericidal properties, making it an ideal component in body cream/antiseptic healing cream to help reduce soreness and redness.
It is also used in medical tapes and plasters, some toothpaste formulations and in dental cements.
And, last but not least, zinc oxide is incorporated in dietary supplements and vitamin tablets as source of the essential micronutrient zinc for the human body.
Other Applications
Zinc Oxide plays an important role in a wide range of applications. In 2004, world usage of zinc oxide was estimated at over 1000000 tones. Zinc oxide plays an important role in a very wide range of applications varying from tires to ceramics, from pharmaceuticals to agriculture, and from paints to chemicals.
Zinc oxide is recognized as an essential micronutrient to both plants and animals. In crop farming, zinc oxide is added to fertilizers to compensate for deficiency in zinc or for poor bio-availability resulting from the composition of the soil. Zinc oxide is used in compound animal feeds and mineral premixes as a source for the essential element zinc.
The biggest use of zinc oxide is in glass and ceramics, where the main role is as a fluxing agent in the preparation of frits and enamels for ceramic wall and floor tiles, or of enamels for sanitary and tableware ceramic objects. Zinc oxide is currently used in the fabrication of artistic glass, table and cooking ware, crystalline glass, etc.
Zinc oxide is used both for the production of zinc dithiophosphates and certain specialized lubricants and grease formulations. The main role of zinc oxide in automotive engine oils is to help in reducing the oxidation, corrosion and wear on the engine.
Zinc oxide is an essential part of most rubber products, both for its chemical activity during vulcanization and for its effect on the physical properties of the finished rubber product.
There have been reports of other methods for preparing ZnO nanocrystals in the past. However, the invented method differs from those techniques in several aspects.
• In this invention, the synthesis is based on the alcoholysis of a metal salt with an alcohol solvent such as ethanol without the presence of any metal hydroxide, thus reducing the impurity from alkali and the possibility of aggregation.
• The nanocrystals are easy to collect and the whole process is environmentally benign.
• The invention affords a simple and scalable synthesis of aggregate free ZnO and TiO2 nanocrystals with sizes less than 10nm, which ca be easily dispersed in water to form a stable colloidal suspension.
• The colloidal water suspension is environmentally benign and bio-compatible. Furthermore, it eliminates the health and environment concerns associated with zinc oxide or titanium dioxide nanopowders.
• The ZnO or TiO2 nanocrystals prepared by the invention have larger surface area, exhibit excellent UV adsorptions; and can filter more UV sources compared with those with larger particle sizes, which is ideal for applications in UV protection for cosmetics, sunglass coatings, and other high-performance coatings.
ADDITIONAL INFORMATION
File Number:
M06-091
Detailed Description:
Lead Inventor: Stephen O’Brien, Ph.D.
Patent Status: Patent Pending
Licensing Status: Available for Licensing and Sponsored Research Support
Further Information: Science and Technology Ventures, Columbia University Paul van der Wilt, Ph.D., Tel: (212) 854-4177; Email: pv2001@columbia.edu
Other information:
Opportunity
STV is actively seeking licensing partner(s) who will develop and market the proposed technology for “Method for preparing zinc oxide, titanium dioxide nanocrystal water suspension and its applications in UV protection and filtering” for academic research as well as industrial manufacturing.
| Patent Information: | A non-provisional patent application has been filed. |
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