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US-12624283-B2 - Blue to UV up-converter comprising lanthanide ions such as Pr3+ activated and optionally Gd3+ co-activated silicates and its application for surface disinfection purposes

US12624283B2US 12624283 B2US12624283 B2US 12624283B2US-12624283-B2

Abstract

A silicate-based lanthanide ion doped material converts electromagnetic radiation energy of a longer wavelength of below 530 nm to electromagnetic radiation energy of shorter wavelengths in the range of 220 to 425 nm. The silicate-based material is a crystalline silicate material doped with lanthanide ions selected from praseodymium, gadolinium, erbium, and neodymium. For co-doping, at least two of the lanthanide ions are used. The silicate-based material is obtainable from a blend comprising salts and an organic solvent, followed by specific calcination processes and tribological impacts to adjust particle size and to increase the crystallinity of the particles. The silicate-based material can be used to inactivate microorganisms or cells covering a surface containing the silicate-based material under exposure of electromagnetic radiation energy of a longer wavelength of below 500 nm.

Inventors

  • Stefan Fischer
  • David Böhnisch
  • Thomas Jüstel
  • Simone SCHULTE
  • Markus Hallack

Assignees

  • EVONIK OPERATIONS GMBH

Dates

Publication Date
20260512
Application Date
20201005
Priority Date
20191014

Claims (10)

  1. 1 . A silicate-based material, comprising: a crystalline silicate material doped with at least one lanthanide ion selected from the group consisting of praseodymium, gadolinium, and wherein the crystalline silicate material converts electromagnetic radiation energy of at least one longer wavelength in a range of 380-550 nm electromagnetic radiation energy of at least one shorter wavelength in a range of 220 to 425 nm, wherein the at least one longer wavelength has a longer wavelength than the at least one shorter wavelength; wherein the crystalline silicate material is selected from the general formula I A 1-x-y-z B* y B 2 SiO 4 :Ln 1 x ,Ln 2 z . I wherein x=0.0001-0.05, z=0 or z=0.0001 to 0.3, and y=x+z, wherein A is selected from the group consisting of Mg, Ca, Sr and Ba, wherein B is selected from the group consisting of Li, Na, K, Rb and Cs, wherein B* is selected from the group consisting of Li, Na and K, wherein B equal to B* or B being not equal to B*, Ln 1 is praseodymium (Pr), and Ln 2 is gadolinium (Gd).
  2. 2 . The silicate-based material according to claim 1 , wherein the crystalline silicate material is not a hydrate of a silicate.
  3. 3 . The silicate-based material according to claim 1 , wherein a crystallinity of the silicate-based material is greater than 70%.
  4. 4 . The silicate-based material according to claim 1 , wherein the crystalline silicate material comprises: a crystalline pure phase, or a silica-based material comprising at least one crystal phase that encompasses at least 90 weight-% of the silica-based material.
  5. 5 . The silicate-based material according to claim 1 , wherein the crystalline silicate material is a solid solution of a crystalline silicate or of crystalline silicate doped with lanthanide ions comprising at least one alkali ion and at least one earth alkali ion.
  6. 6 . A process for the production of a silicate-based material, the process comprising: combining the following components i), ii), and iii), i) and/or lanthanide oxide, wherein a lanthanide ion in the at least one lanthanide salt and/or lanthanide oxide is selected from the group consisting of praseodymium, gadolinium, erbium, and neodymium, ii) a silicate, and iii) at least one earth alkali salt and at least one alkali salt selected from the group consisting of a lithium salt, a lithium compound, a sodium salt, and a potassium salt, wherein the combining comprises: a) blending i), ii), and iii) by milling, and obtaining a mixture, or b) blending i), ii), and iii) in an organic polar or non-polar solvent that is not a protic solvent, and obtaining a mixture, wherein the obtained mixture of b) is calcinated at 600° C. to 1000° C. to remove organic components, and to obtain a calcinated mixture, performing a calcination of the mixture of a) or the calcinated mixture of b) in a calcination at a temperature below a melting temperature of the silicate-based material, wherein at least partial crystallization occurs, and performing a further calcination under a reducing atmosphere, wherein the lanthanide ion is reduced to an Ln 3+ ion, and obtaining the silicate-based material, wherein the obtained silicate-based material is milled, and wherein the obtained silicate-based material is subjected to tribological impacts at 100 to 500 rotations/min for 1 to 6 hours, using corundum as milling material.
  7. 7 . A composition, foil or film, comprising the silicate-based material according to claim 1 for self-disinfection purposes or for reduction of microorganisms.
  8. 8 . A method, comprising: adding the silicate-based material according to claim 1 into a coating composition or a material to provide a coating or surface that is able to inactivate microorganisms covering the coating or surface under exposure of electromagnetic radiation energy of a longer wavelength in a range of 500 nm and below.
  9. 9 . The silicate-based material according to claim 1 , wherein an emission maximum of the electromagnetic radiation energy of the shorter wavelengths has an intensity of at least 1⋅10 3 counts/(mm 2 *s).
  10. 10 . The silicate-based material according to claim 1 , wherein in formula I, B and B* are not equal.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is the National Stage entry under § 371 of International Application No. PCT/EP2020/077798, filed on Oct. 5, 2020, and which claims the benefit of priority to European Application No. 19202910.6, filed on Oct. 14, 2019. The content of each of these applications is hereby incorporated by reference in its entirety. BACKGROUND OF THE INVENTION Field of the Invention A silicate-based lanthanide ion doped material for converting electromagnetic radiation energy of a longer wavelength of below 530 nm to electromagnetic radiation energy of shorter wavelengths in the range of 220 to 425 nm, wherein the silicate-based material is a crystalline silicate material doped with lanthanide ions selected from praseodymium, gadolinium, erbium, neodymium and for co-doping at least two of them. Further the silicate-based material is obtainable, in a particular, from a blend comprising salts and an organic solvent followed by specific calcination processes and tribological impacts to adjust particle sizes and increase the crystallinity of the particles. The silicate-based material can be used to inactivate microorganisms or cells under exposure of electromagnetic radiation energy of a longer wavelength of below 500 nm. DESCRIPTION OF RELATED ART Since the invention of efficiently blue or UV-A emitting (In,Ga)N semiconductor materials (365-500 nm), inorganic solid state light sources have outperformed other lighting technologies such as incandescent and discharge lamps and thus indoor and, in the meantime also outdoor lighting is dominated by phosphor converted light emitting diodes (pcLEDs) utilizing the inorganic semiconductor material (In,Ga)N as the primary radiation source. It is expected that this situation will settle for the next decades and that light sources relying on blue emitting (In,Ga)N LEDs as primary radiation source will penetrate into and dominate all kind of lighting application areas, e.g. indoor, outdoor, advertisement, architecture, decoration, special, and street lighting. Therefore, indoor illumination will rely on semiconductor light sources, with an emission band between 400 and 480 nm, which will partly be converted by inorganic phosphors into other colours to obtain white light. However, depending on the colour temperature aimed at about 5 to 10% of the overall power distribution will remain in the blue spectral range, which in turn means that this radiation can enforce the excitation of an illuminated up-converter to obtain UV radiation at the point of illumination. Recently, this opportunity caused dedicated R&D projects in aiming at the identification of efficient blue to UV-C up-conversion materials, such as Y2SiO5:Pr,Gd,Li and some other. The main problem of materials discovered and published so far is their rather low up-conversion efficiency, which is just above the detection level or signal to noise ratio. Further, US 2013/0052079 discloses a composition comprising phosphors capable of converting an initial electromagnetic energy (A) to an electromagnetic energy (B) in order to deactivate or kill microorganism. However, the method as described therein does not lead to a phosphor with up-conversion property. What is really wanted is an up-converting material, which enables the significant reduction of infectious microorganisms within a period typical for daylight illumination, i.e. within a few hours, so that a daily reduction of microorganisms can be effectively achieved. Moreover, the material must be non-hazardous to the environment and should show an operational lifetime of at least 10000 hours. Finally, the material must be cost-effective and recyclable to achieve a wide penetration into such surface coatings. Further, the efficiency of the up-conversion material must therefore be much better than of the known materials as only the remaining 5 to 10% of the overall power distribution in the LED remain in the blue spectral range and shall be used to enforce the excitation of an illuminated up-converter to obtain UV radiation at the point of illumination. SUMAMRY OF THE INVENTION Subject of the current invention is therefore to furnish a blue/green to UV radiation up-converting inorganic material with an increased efficiency as well as a process for the production of that material. The subject is solved by the disclosed novel blue/green to UV radiation up-converting inorganic silicate-based materials, the process to produce them and their application in coatings, surfaces of matrix materials, thin film, composite layers. Particularly preferred embodiments are disclosed in the description. One preferred embodiment of the invention concerns Pr3+ activated and Gd3+ co-doped silicates, according to the idealised general formula A1-x-y-zB*yB2SiO4:Prx and optional Gdz, in particular A1-x-y-zB*yB2SiO4:Prx and optional Gdz, with A=Mg, Ca, Sr, Ba; and B=Li, Na, K, Rb, Cs, preferred are Li, Na, K, particular preferred Li; and B*=Li, Na, K, Rb,