Redox Active Metal/Metal Oxide Composites For Antimicrobial Applications

Abstract

The invention relates to a method of preparing a metal oxide/metal composite, comprising depositing a metal oxide from a dispersion in a liquid on a metal surface; or depositing a metal oxide in the presence of a metal from a dispersion in a liquid on a substrate; or depositing a metal oxide from a metal salt solution on a metal substrate. The metal oxide/metal composites obtained by the process show synergistic antimicrobial activity due to release of high concentrations of redox active species (ROS) at the metal oxide/metal heterojunction. The invention also relates to use of the metal oxide/metal composite as an antimicrobial coating.

Claims

1.-33. (canceled)

34. A method of preparing an antimicrobial metal oxide/metal composite material comprising: a) preparing a depositing medium comprising a metal oxide or a metal salt in a liquid; and b1) depositing the metal oxide from a dispersion in the liquid on a metal surface; or b2) depositing the metal oxide in the presence of a metal from a dispersion in the liquid on a substrate; or b3) depositing a metal oxide from a metal salt solution on a metal substrate; and c) separating the depositing medium from the formed composite material.

35. The method according to claim 34, wherein the, metal oxide is selected from zinc oxide, iron (III) oxide, iron (II) oxide, cobalt (Ill) oxide, cobalt (II) oxide, nickel (III) oxide, nickel (II) oxide, copper (II) oxide or copper (I) oxide, manganese (II) oxide, titanium oxide, chromium (III) oxide, chromium (II) oxide, vanadium (V) oxide, aluminum (III) oxide, germanium dioxide, or tin dioxide, or mixtures thereof or wherein the metal is selected from zinc, aluminum, iron, cobalt, nickel, copper, manganese, chromium, vanadium, germanium, or tin; or mixtures and/or alloys thereof.

36. The method according to claim 34, wherein in operation b1) the dispersion of the metal oxide in the liquid is casted on the surface of a metal and in operation c) the solvent is removed to deposit the metal oxide.

37. The method according to claim 34, wherein in operation b2) the dispersion of the metal oxide is deposited together with a metal powder, which preferably has a particle size of 0.1 to 100 m and in operation c) the liquid is removed to deposit the metal oxide and the metal.

38. The method according to claim 34, wherein operations b1) or b2) and c) are repeated at least once.

39. The method according to claim 34, wherein the metal oxide is dispersed in the solvent by ultrasonic in operation a).

40. The method according to claim 34, wherein the liquid comprises an alcohol, or wherein the alcohol comprises an aliphatic alcohol selected from primary aliphatic alcohol or secondary aliphatic alcohol, or wherein the primary aliphatic alcohol comprises ethanol.

41. The method according to claim 34, wherein in operation b3) the metal oxide is deposited by high temperature growth reaction from a metal salt solution on a metal substrate and wherein the high temperature growth synthesis operation is carried out at a temperature of between about 50 C. and 300 C.

42. The method according to claim 41, wherein the metal substrate is a particle of a size of about 0.01 to 100 m.

43. The method according to claim 41, wherein the metal oxide is zinc oxide which is deposited from a zinc salt solution.

44. The method according to claim 34, wherein in operation b3) the metal oxide is deposited by high temperature growth reaction from a metal salt solution on the metal particle in a layer form or wherein the layer form deposition is carried out over a time period in the range of 5 minutes to 1 hour.

45. The method according to claim 34, wherein in operation b3) the metal oxide is deposited by precipitation of the metal oxide from a metal salt solution on the metal particle by reaction with a base or wherein the base is NaOH or KOH or wherein the metal oxide is zinc oxide or wherein the metal salt solution is a Zn(NO.sub.3).sub.2 solution.

46. The method according to claim 34, wherein in operation b3) the metal oxide is deposited by precipitation of the metal oxide from a metal salt solution on the metal particle in a pillar form.

47. The method according to claim 46, wherein the pillar form precipitation is carried out over a time period in the range of 1 to 5 hours, preferably in the range of 1 to 4 hours, more preferably in the range of 1 to 3 hours.

48. An antimicrobial composite material comprising a metal oxide/metal composite and wherein at least one metal component and one metal oxide component with heterojunction are obtained according to a method of preparing an antimicrobial metal oxide/metal composite material comprising: a) preparing a depositing medium comprising a metal oxide or a metal salt in a liquid; and b1) depositing the metal oxide from a dispersion in the liquid on a metal surface; or b2) depositing the metal oxide in the presence of a metal from a dispersion in the liquid on a substrate; or b3) depositing a metal oxide from a metal salt solution on a metal substrate; and c) separating the depositing medium from the formed composite material.

49. A material according to claim 48, wherein the metal oxide/metal composite is an iron (III) oxide/zinc, zinc oxide/zinc, zinc oxide/aluminum or zinc oxide/iron composite.

50. An antimicrobial composite material in layered structure or particle form comprising a metal oxide/metal composite wherein the metal oxide is selected from zinc oxide, iron (III) oxide or iron (II) oxide and the metal is selected from zinc or iron; and comprising at least one metal component and one metal oxide component with heterojunction.

51. The material according to claim 48, wherein the material can release ROS concentrations of at least about 1 mol/cm.sup.2 of its surface within 5 minutes.

52. The material according to claim 48, wherein the material is in alloy, doping, core-shell or layered structure, coating or co-crystallization form or a mixture of the components.

53. The material according to claim 48, in particle form comprising a metal core and a metal oxide shell structure and wherein the core particle size is about 0.01 to 100 m, preferably between about 0.05 to 50 m, more preferably between about 0.1 to 10 m or wherein the metal oxide particle shell is in layer form, nano needle or pillar form.

Description

DESCRIPTION OF DRAWINGS

[0085] The accompanying drawings illustrate a disclosed embodiment or reaction scheme and serve to explain the principles of the disclosed embodiments. It is to be understood, however, that the drawings are designed for purposes of illustration of examples only, and not as a limitation of the invention.

[0086] FIG. 1 shows (A) the surface of the sub-micrometer particles after deposition of the oxide; (B) an XRD pattern of the ZnO powder of the example; (C) the surface of ZnO powder coated onto a glass substrate.

[0087] FIG. 2 shows the results of the antibacterial activity (against E. coli) measurement of ZnO particle coated on different substrates.

[0088] FIG. 3 shows (A) Zn.sup.2+ ion concentration in the TSB solution, and (B) the ROS concentration in the testing solution with ZnO coated surfaces.

[0089] FIG. 4 shows (A) an image of untreated Zn powder, and (B) an image of Zn powder treated in KOH/Zn(NO.sub.3).sub.2 solution at room temperature, (C) an image of Zn powder treated with [Zn(NH.sub.3).sub.4].sup.2+ solution at 95 C. for 15 min, and (D) the XRD pattern of Zn powders before and after treatment (* are XRD peaks of ZnO).

[0090] FIG. 5 shows the results of the antibacterial properties (against E. coli) of ZnO/Zn core-shell particles as measured.

[0091] FIG. 6 shows an SEM image of Fe.sub.2O.sub.3 particles (A) and the results of antibacterial properties (against E. coli) of Fe.sub.2O.sub.3/Zn composite as measured.

INDUSTRIAL APPLICABILITY

[0092] The metal oxide/metal composite materials obtained by the method according to the first aspect of the invention exert anti-microbial activity. The activity is based in release of redox active species in high concentration. In this way they can be the basis for new environmentally friendly inorganic antimicrobial materials which are very stable and have long-term activity. The new materials are not size dependent and they are active in the size ranging from nanoscale to macroscale. The new materials could be used as additives in many consumer care, healthcare and cosmetic products. They can also be applied as surface coatings to create long term self-disinfecting surfaces including both hard surfaces and fabrics or textiles. The inorganic antimicrobial materials are clean and safe, stable and scalable in production and have a broad range of applications. They are susceptible to mass production by the inventive method. A scale up for water disinfection applications while avoiding the need for chemical treatment may be developed. The materials can also be recycled after use.

[0093] The new materials may replace common antimicrobial materials in the applications mentioned above.

[0094] It will be apparent that various other modifications and adaptations of the invention are available to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.