Oxo- and hydroxo-based composite inorganic ligands for quantum dots

1. A particulate luminescent material comprising quantum dots with a capping agent coordinating to the quantum dots, wherein the capping agent comprises a zincate ion (Zn(OH) 4 2− ), and the particulate luminescent material comprises particles having an inorganic matrix hosting the quantum dots with inorganic capping agents.

2. The luminescent material according to claim 1 , wherein when also organic capping agents are coordinating to the quantum dots, the amount of organic capping agents is less than 5 wt. % relative to the total weight of quantum dots.

3. The luminescent material according to claim 1 , wherein the quantum dots have an outer layer comprising an inorganic compound, and wherein one or more of the following applies (i) the inorganic matrix and an outer layer of the quantum dots have an element in common, (ii) the capping agent and the inorganic matrix have an element in common, and (iii) an outer layer of the quantum dots and the capping agent have an element in common.

4. The luminescent material according to claim 1 , wherein the quantum dots are dispersed within the particles, wherein the particles have a number averaged particle size in the range of 0.5-40 μm, and wherein the luminescent material comprises in the range of 0.01-5 wt. % quantum dots relative to the total weight of the luminescent material.

5. The luminescent material according to claim 1 , obtainable by a method comprising: (i) providing luminescent quantum dots with an organic capping agent and providing in an exchange process said luminescent quantum dots with an inorganic capping agent in a first liquid, wherein the inorganic capping agent comprises M x O y (OH) z n , wherein M is selected from the group consisting of B, Al, P, S, V, Zn, Ga, Ge, As, Se, Nb, Mo, Cd, In, Sn, Sb, Te, Ta and W, wherein x≥1, y+z≥1, and wherein n indicates a positive or negative charge of the capping agent.

6. A wavelength converter element comprising a host material with a particulate luminescent material embedded therein, the particulate luminescent material comprising quantum dots with a capping agent coordinating to the quantum dots, the capping agent comprising a zincate ion (Zn(OH) 4 2− ), wherein the particulate luminescent material comprises particles having an inorganic matrix hosting the quantum dots with inorganic capping agents.

7. A lighting device comprising a light source and a particulate luminescent material, wherein

the light source is configured to illuminate the particulate luminescent material, and wherein

the particulate luminescent material comprises quantum dots with a capping agent coordinating to the quantum dots, the capping agent comprising a zincate ion (Zn(OH) 4 2− ), wherein the particulate luminescent material comprises particles having an inorganic matrix hosting the quantum dots with inorganic capping agents.

8. A method for the production of a luminescent material based on quantum dots, the method comprising:

(i) providing luminescent quantum dots with an organic capping agent and providing in an exchange process said luminescent quantum dots with the inorganic capping agent in a first liquid, wherein the capping agent comprises M x O y (OH) z n , wherein M is selected from the group consisting of B, Al, P, S, V, Zn, Ga, Ge, As, Se, Nb, Mo, Cd, In, Sn, Sb, Te, Ta and W, wherein x≥1, y+z≥1, and wherein n indicates a positive or negative charge of the capping agent, wherein the exchange process comprises a phase transfer process;

(ii) precipitating in a co-precipitation process an inorganic salt comprising precipitated material from the first liquid, the precipitated material comprising said quantum dots hosted by the co-precipitated inorganic salt; and

(iii) separating in a separation process the precipitated material from the first liquid.

9. The method according to claim 8 , wherein the luminescent quantum dots have an outer layer, wherein in the co-precipitation process two or more salts (M 1 -A 1 ; M 2 -A 2 ) are applied, wherein at least one of the salts and the outer layer have an element in common, and wherein the inorganic capping agent and one or more of the salts have an element in common.

10. The method according to claim 8 , wherein the inorganic capping agents comprise one or more of an aluminate ion (Al(OH) 4 − ), a stannate ion (SnO 3 − , SnO 3 2− , and SnO 4 4− ), a vanadate ion (VO 3 − ,VO 4 3− ), a molybdate ion (MoO 4 2− ), a tungstate ion (WO 4 2 ), a phosphate ion (PO 4 3− ), and a zincate ion (Zn(OH) 4 2− ).