US 2003/0032192 A1 · Synthesis of nanoparticles

Abstract

The present invention relates to methods for the preparation of inorganic nanoparticles capable of fluorescence, wherein the nanoparticles consist of a host material that comprises at least one dopant. The synthesis of the invention in organic solvents allows to gain a considerably higher yield compared to the prior art synthesis in water. All kinds of objects can advantageously be marked and reliably authenticated by using an automated method on the basis of a characteristic emission. Further, the size distribution of the prepared nanoparticles is narrower which renders a subsequent size-selected separation process superfluous.

Claims58

Dependent claims

A method for synthesizing metal salt nanoparticles, comprising a crystal lattice or host lattice of which the cation is capable of being produced from a cation source and of which the anion is capable of being produced from a class of substances that serves as an anion source, in which method the host material can include compounds particularly from the group consisting of phosphates, halophosphates, arsenates, sulphates, borates, aluminates, gallates, silicates, germanates, oxides, vanadates, niobates, tantalates, wolframates, molybdates, alkalihalogenates, other halides, nitrides, sulphides, selenides, sulphoselenides, as well as oxysulphides, the method being characterized by the following steps:

a) preparation of a synthesis mixture, at least from
aa) an organic solvent which comprises at least one component controlling the crystal growth of the nanoparticles, in particular a component comprising a phosphororganic compound, or a monoalkylamine, particularly dodecylamine, or a dialkylamine, particularly bis(ethylhexyl)amine,
bb) a cation starting material which serves as cation source and which is soluble or at least dispersible in the synthesis mixture, particularly a metal salt starting compound, preferred a metal chloride or an alkoxide, or a metal acetate, and
cc) an anion starting material that serves as anion source, which is soluble or at least dispersible in the synthesis mixture and which is selected from said class of substances, said class of substances comprising:
aaa) free acids of the salts of the particular metal salt nanoparticles which are to be prepared, or
bbb) salts that are soluble or at least dispersible in the synthesis mixture, in particular salts with an organic cation, or metal salts, the latter preferably being alkali metal salts, or
ccc) organic compounds which release the anion beyond an increased synthesis minimum temperature, and a suitable, anion-donating substance is selected from the class of substances depending on a respective selection of the salt of the nanoparticles to be prepared, and
b) keeping the mixture at a predetermined synthesis minimum temperature during a synthesis period appropriate for said temperature.

5 more elements

The method according to the preceding claim, wherein at least one of the following substances is comprised of the solvent as the phosphororganic compound for the growth controlling component:

a) esters of phosphinic acid, ((R1—)(R2—)(R3—O—)P═O),
b) diesters of phosphonic acid, ((R1—)(R2O—)(R3—O—)P═O),
c) triesters of phosphoric acid (trialkyl phosphates), ((R1—O—)(R2—O—)(R3—O—)P═O),
d) trialkyl phosphines, ((R1—)(R2—)(R3—)P), particularly trioctylphosphine (TOP),
e) trialkyl phosphine oxides, ((R1—)(R2—)(R3—)P═O), particularly trioctylphosphine oxide (TOPO),
wherein R1, R2, R3 are branched or unbranched alkane chains comprising at least one carbon atom, or phenyl, tolyl, xylyl, or benzyl groups, or
f) a phosphoric amide, preferred tris-(dimethylamino)-phosphine, or
g) a phosphoric amide oxide, preferred tris-(dimethylamino)-phosphine oxide.

5 more elements

The method according to the preceding claim, wherein a triallyl phosphate or a trialkyl phosphine is used as a controlling component for the preparation of nanoparticles, and wherein per mol metal ions less than 10 mol, preferred 0.9 to 5 mol, and more preferred 0.95 to 2 mol of the controlling component is used.

The method according to one of the preceding claims, wherein at least one further component with preferably metal-chelating properties is added to the synthesis mixture, preferably in order to displace any water of crystallization present in the metal salt starting compounds, in particular

a) an ether compound, preferred dipentyl ether, dihexyl ether, diheptyl ether, dioctyl ether, dibenzyl ether, diisoamyl ether, ethylene glycol dibutyl ether, diethylene glycol dibutyl ether, or diphenyl ether, or/and
b) an alkane compound that boils above the synthesis minimum temperature, preferred dodecane or hexadecane, or/and
c) an amine compound, preferred dihexylamine, bis(2-ethylhexyl)amine, trioctylamine, tris(2-ethylhexyl)amine.

The method according to clam 3, wherein mixtures of the phosphororganic compounds are used.

The method according to one of the preceding claims, wherein at least one of the group consisting of chlorides, bromides, iodides, alkoxides, metal acetates, or acetylacetonate is used as a starting material for the cation source.

The method according to the preceding claim further comprising the step of removing the preferably lower alcohol by distillation from the synthesis mixture during the synthesis

The method according to one of the preceding claims further comprising the step of:

Removing of one or more of the solvent components by distillation from the synthesis mixture, preferred under vacuum, preferred after the end of the synthesis period.

The method according to one of the preceding claims further comprising the step of:

Purifying the nanoparticles by washing with an alcohol, preferred with ethanol, or by diafiltration to get rid of attached by-products.

The method according to one of the preceding claims further comprising the step of:

Neutralizing the synthesis mixture using a base that is soluble in the synthesis mixture, preferred trihexylamine, triheptylamine, trioctylamine, tris(2-ethylhexyl)amine.

The method according to one of the preceding claims, wherein a hydrated metal salt is used as starting material.

The method according to one of the preceding claims which is used for synthesizing nanoparticles capable of fluorescence.

The method according to one of the preceding claims, wherein several different cation sources are used, particularly metal salt starting compounds, of which at least one metal is used as doping agent for the nanoparticles to be produced.

The method according to one of the preceding claims, wherein a phosphate ester, in particular a trialkyl phosphate, and preferred tributyl phosphate, is used as growth controlling component of the solvent for the preparation of LaPO4 nanoparticles.

The method according to one of the preceding claims, wherein one ore more elements selected from a group comprising elements of the main groups 1a, 2a, or Al, Cr, Tl, Mn, Ag, Cu, As, Nb, Ni, Ti, In, Sb, Ga, Si, Pb, Bi, Zn, Co, and/or elements of the lanthanides are used for the doping.

A substance, comprising nanoparticles, comprising a crystal lattice or, in case of a doping, a host lattice, wherein

the host lattice comprises compounds of the type XY, wherein X is a cation of one or more elements of the main groups 1a, 2a, 3a, 4a, the subgroups 2b, 3b, 4b, 5b, 6b, 7b, or of the lanthanides of the periodical system, and wherein Y is either a polyatomic anion of one or more of the elements of the main groups 3a, 4a, 5a, of the subgroups 3b, 4b, 5b, 6b, 7b, and/or 8b as well as of elements of the main groups 6a, and/or 7, or a monoatomic anion of the main groups 5a, 6a, or 7a of the periodical system, and wherein
one ore more elements selected from a group comprising elements of the main groups 1a, 2a, or Al, Cr, Tl, Mn, Ag, Cu, As, Nb, Ni, Ti, In, Sb, Ga, Si, Pb, Bi, Zn, Co, and/or elements of the lanthanides are contained as a doping.

Dependencies are inferred from the claim text.

Synthesis of nanoparticles

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Synthesis of nanoparticles

Life of this patent

Abstract

Claims58