WO2018197532A1

WO2018197532A1 - A semiconducting light emitting nanoparticle

Info

Publication number: WO2018197532A1
Application number: PCT/EP2018/060535
Authority: WO
Inventors: Artyom SEMYONOV; Ehud SHAVIV
Original assignee: Merck Patent Gmbh
Priority date: 2017-04-28
Filing date: 2018-04-25
Publication date: 2018-11-01
Also published as: TW201906983A

Abstract

The present invention refers to the area of semiconductors and relate to new nanoparticles, a process for obtaining them and further applications of the new semiconductors.

Description

A SEMICONDUCTING LIGHT EMITTING NANOPARTICLE

FIELD OF INVENTION

[0001] The present invention refers to the area of semiconductors and relate to new nanoparticles, a process for obtaining them and further applications of the new semiconductors.

STATE OF THE ART

[0002] Quantum Dots (QD) are semiconducting particles with diameters in the nanometre range (about 2 to 20 nm), which are so small that the optical and electronic properties of the crystals change. A special feature of the Quantum Dots is that they change their colour with the particle diameter. In order to produce, for example, blue QDs, no other materials are required as for red QDs - they only have to be produced with different particle sizes. Thus, blue QDs are in the range of about 2 nm, green at about 2.5 to 2 nm and red/orange at about 5 to 6 nm. In addition to typical applications such as displays, QDs are now also used in many other areas, such as solar cells or processors.

[0003] Quantum Dots can fluoresce and convert photons to other wavelengths as well as emit light. However, their outstanding

characteristics are undoubtedly the ability to improve the background lighting in displays. LCD TVs use a white background light and then filter the blue, green and red light to display colours. Blue LEDs with a phosphor layer are usually used for this so-called "backlight". However, it is disadvantageous that the phosphor layer cannot completely convert blue light into white light. However, white LEDs do not represent an alternative that these emit mainly blue light, which means that the primary colours are not evenly distributed. In this way, luminous intensity is lost, and colour reproduction sometimes leaves something to be desired.

[0004] With the help of Quantum Dots, this problem can be solved since they are capable of converting blue light exactly to the desired wavelength depending on their size. By means of more or fewer Dots of a colour, the colour ratio can also be controlled so that the colour-generating LC layer has to correct less. In this way, the luminous intensity is increased and the number of reproducible colours multiplied up to a value of about 1 billion. The strongest technological advantage of QD backlight over phosphor based "white LED" backlight is the narrow FWHM (< 50 nm) which enables wide colour gamut, e. G. increasing the amount of displayed colours. Some phosphor films can give EQE as high as > 90 %, comparable to EQE of QD films.

[0005] The most important semiconducting materials, which are also suitable for the production of Quantum Dots, include cadmium compounds, especially CdS and CdSe. However, the disadvantage is that cadmium is highly toxic, which in particular attempts to solve the end products at a later time. A promising alternative would be InP, but here the quantum yield is not satisfactory.

[0006] In this context reference is made to WO 2015 016533 A1

(SAMSUNG) directed to a process for preparing magnesium selenide nanoparticles encompassing the step of reacting a first precursor including a magnesium compound and a second precursor including a selenium compound in the presence of an attaching group source in an organic solvent to form nanoparticles of MgSe or an alloy thereof, with the proviso that neither the attaching group nor the organic solvent comprise an oxygen functional group.

[0007] Another paper issued by KWAK ET AL titled "Tuning the energy bandgap of CdSe nanoparticles via Mg doping" [(NANOTECHNOLOGY 18, p1 -4 (2007)] describes the preparation of a CdSe nanoparticle composition into which magnesium ions are incorporated.

[0008] Another paper issued by KIM ET AL titled "Highly-color-saturated Quantum Dot light-emitting devices using cadmium-free Quantum Dots" [https://www.researchgate.net/ publication/259542463), uploaded 17.02.2015] traches Cd-free Quantum Dots consisting of InP nanoparticles capped with ZnSe/ZnS multi-shells. The Dots do not carry additional metals on its outer-shell. [0009] Further on in their paper titled "One-pot synthesis of highly luminescent InP/ZnS nanoparticles with precursor injection" [J. Am. Chem. Soc. 130(35), p11588-11589 (2008)] LI ET AL describes a process for obtaining specific core-shell nanoparticles, particularly of InP/ZnS type, where all precursors are mixed and then heated up instead of the so-called "hot-injection method" where the core materials are heated and the shell components are added later.

[0010] According to a paper submitted by PARK ET AL titled "Surface stabilized InP/GaP/ZnS Quantum Dots with Mg ions for WLED application" [(J NANOSCIENCE AND NANOTECHNOLOGY VOL 16(5), p5312-5315, (2016)] Quantum Dots based on InP, GaP and ZnS were prepared which include amounts of magnesium cations to improve stability. Looking at the experimental section, the magnesium compound is added along with ZnS forming the outer shell of the crystals. Thus the magnesium is not bound to the outer shell, but incorporated therein. Applicant has found out that any incorporation of magnesium ions into the structure of conventional semiconducting materials does not solve the problem of insufficient QY.

[0011] Therefore, it has been the object of the present invention to provide new semiconducting light emitting nanoparticles, preferably but not mandatory free of cadmium, showing improved quantum yields.

[0012]

DESCRIPTION OF THE DRAWINGS

Fig.1 : shows a XPS data of the sample from example 1 .

Fig.2: shows a XPS data of the sample from example 2 with the

magnesium oleate ligand.

Fig.3: shows a XPS data of the sample from example 3. [0013]

LIST OF REFERENCE SIGNS IN FIGURE 1

301 . Selenium peak (general)

302. Selenium peak (general) 303. Surfade selenium peak

304. Surface selenium peak

[0014]

LIST OF REFERENCE SIGNS IN FIGURE 2

401 . Selenium peak (general)

402. Selenium peak (general)

403. Surfade selenium peak

404. Surface selenium peak

405. Magnesium peak

[0015]

LIST OF REFERENCE SIGNS IN FIGURE 3

501 . Selenium peak (general)

502. Selenium peak (general)

503. Magnesium peak

DESCRIPTION OF THE INVENTION

[0016] A first object of the present invention is directed to a

semiconducting light emitting nanopartide comprising or consisting of a core, optionally one or more shell layers and an attaching group coated onto the core or the outermost surface of the shell layers, wherein the attaching group is a magnesium salt.

[0017] Although the term "nanopartide" is clear for every skilled person working in the technological are to which the present invention belongs, it should be expressed that nanopartide has the meaning of an average particle diameter in the range of about 2 nm to about 50 nm, preferably about 3 to about 20 and more preferably about 4 to about 15 nm depending on the desired colour of the nanopartide.

[0018] According to the present invention, the term "nanopartide" includes quantum dots, quantum rods. [0019] Surprisingly, it has been observed that light-induced deposition of magnesium salts leads to a significant increase of up to 30 % in quantum yields and overcomes the drawbacks of the prior art.

[0020] Without wishing to be bound by theory, it is believed that the particularly magnesium carboxylates placed onto core or core-shell nanoparticles passivate the traps on the surface of the particles, and thus leads to a significant increase of up to 30 % in quantum yields.

[0021] A second object of the present invention refers to a semiconducting light emitting nanopartide comprising or consisting of a core, optionally one or more shell layers and an attaching group coated onto the core or the outermost surface of the shell layers,

obtainable or obtained by the following steps:

(a) providing at least one salt of at least one metal [A¹] and/or [A²] optionally dissolved in a suitable solvent;

(b) adding at least one source of at least one non-metal [B¹] and/or [B²] to obtain an intermediate compound [A¹B¹]/[A²B²];

(c) coating said intermediate compound [A¹B¹]/[A²B²] from step (b), optionally in the presence of a solvent, by bringing it into contact with a source of a magnesium salt, and

(d) subjecting said coated intermediate of step (c) to illumination with light with a peak light wavelength of about 300 to about 600 nm to form the nanopartide.

[0022] SEMICONDUCTING NANOPARTICLE

[0023] Suitable semiconducting nanoparticles forming the core or the core/shell body of the nanopartide according to the present invention may represent single compounds or mixtures of two, three or even more of them.

[0024] In a first preferred embodiment of the present invention said core is formed from one, two or more compounds according to formula (I)

[A¹B¹] (I) in which

[A¹] stands for a metal selected from the group consisting of zinc,

cadmium, indium or their mixtures; preferably, Zn(ll), Cd(ll), In(lll) or their mixtures.

[B¹] stands for a non-metal selected form the group consisting of

sulphur, selenium, phosphor or their mixtures.

[0025] More preferably [A¹B¹] stands for one, two or more compounds selected from the group consisting of CdS, CdSe, CdSeS, CdZnS, ZnS, ZnSe, ZnSeS, and InP.

[0026] In another preferred embodiment of the present invention said shell or said shells are formed from one, two or more compounds according to formula (II)

[A²B²] (II)

in which

[A²] stands for a metal selected from the group consisting of zinc,

cadmium or their mixtures;

[B²] stands for a non-metal selected form the group consisting of

sulphur, selenium, or their mixtures.

[0027] Preferably [A²B²] stands for one, two or more compounds selected from the group consisting of CdS, CdSe, CdSeS, CdZnS, ZnS, ZnSe, ZnTe, ZnTeSeS and ZnSeS.

[0028] Overall preferred are materials comprising a core [A¹B¹] and at least one shell [A²B²], said core/shell structure [A¹B¹]/[A²B²] being selected from the group consisting of CdSeS/CdZnS, CdSeS,CdS/ZnS,

CdSeS/CdS,ZnS CdSe/ZnS, InP/ZnS, InP/ZnSe, lnP/ZnSe,ZnS,

lnP(Zn)/ZnSe, lnP(Zn)/ZnSe,ZnS, ZnSe/CdS, ZnSe/ZnS,

lnP(Zn)/ZnSe,ZnS,ZnTe, or their mixtures.

[0029] Although a broad range of magnesium salts are suitable for acting as a ligand, the preferred magnesium salt is a magnesium carboxylate, more preferably a magnesium salt of an organic acid having 2 to about 22 carbon atoms and particularly 6 to 18 carbon atoms. [0030] In another preferred embodiment of the present invention the materials are free of cadmium.

[0031] MANUFACTURING PROCESS

Another object of the present invention is directed to a process for manufacturing a semiconducting light emitting nanoparticle comprising or consisting of a core, optionally one or more shell layers and an attaching group coated onto the core or the outermost surface of the shell layers, obtainable or obtained by the following steps:

(d) subjecting said coated intermediate of step (c) to illumination with light with a peak light wavelength of about 300 to about 600 nm to form the nanoparticle.

[0032] Therefore, the present invention includes two alternative

embodiments for the materials: the first is a structure consisting of a [A¹B¹] as a single core on which the attaching group is deposited and the second is a structure consisting of a core [A¹B¹] and at least one shell [A²B²], preferably two or more shells [A²B²]² ... [AB]^X. In case the materials consist of a core and at least one shell, core material [A¹B¹] and [A²B²] are different, for example InP as the core and ZnSe forming a shell. In case there are more shells, the materials may be still different, such as for example lnP/ZnS,ZnSe, however it also possible that core and for example the outer shell are identical, e.g. ZnS/ZnSe,ZnS.

[0033] As far as the nature of the compounds showing an [AB] structure and the preferred single or multiple structures are concerned reference is made to the explanations infra which apply also with regard to the process. [0034] Therefore, a preferred embodiment of the present invention is a process wherein step (a) and/or step (b) encompasses providing salts of two different metals [A¹] or [A²] and/or adding sources of two different non- metals [B¹] or [B¹] respectively. In case all raw materials are added at the same time a core consisting of all these compounds is formed. However, it is particularly preferred forming the core first and subsequently adding those components designated to form a shell around said core. This can be done stepwise to build up complex particles with a core and two or more shells.

[0035] For example, suitable salts of metal [A1 ] or [A²] encompass halides, particularly chlorides or iodides, or carboxylates, such as for example acetates or oleates. Suitable sources of non-metals [B¹] or [B¹] comprise for example esters or amides of phosphoric acid. The molar ratio of these components [A] and [B] can differ in wide ranges, however it is preferred to apply molar ratios in the range of about 2:1 to 1 :2, and particularly about 1 :1 . Reaction usually takes place in the presence of a solvent, for example a high-boiling amine like oleyl amine. Once the components to form the core are brought into contact they were kept under reflux at a temperature of about 150 to about 200 °C. Subsequently the remaining components designated to form the shell are introduced an temperature increased stepwise up to 350 °C, preferably 200 to 320 °C. The complete reaction requires up to 5 hours.

[0036] Once reaction is completed the intermediate semiconducting material [AB] - either consisting of a single core or showing a core-shell(s) structure - is purified by washing and centrifugation using polar and unpolar solvents.

[0037] Subsequently the nanoparticles are dissolved or at least dispersed in an organic solvent (e.g. toluene) and treated with a solution of a magnesium metal salt respectively. Suitable The salts may be selected from the group consisting of carboxylates, halogens, acetylacetonates, phosphates, phosphonates, sulfates, sulfonates, thiocarbamates, dithiocarbamates, thiolates, dithiolates, alkoxylates and their mixtures. Saturated or unsaturated carboxylates comprising 2 to 22 and preferably 12 to 18 carbon atoms in its acyl moiety are highly preferred. The most preferred carboxylates are oleates, such as magnesium oleate, but also acetates, acrylates or stearates work very well.

[0038] The divalent metals or their salts are deposited on the surface of the intermediate compound [A¹B¹] or [A¹ B¹]/[A²B²] in an amount of from about 2 to about 98 wt.-%, more preferably from about 3 to about 50 wt.-% and even more preferably from about 5 to about 25 wt.-%, which may depend on the molar mass of the attaching group. For example, a preferred amount for metal carboxylates derived from carboxylic acids with 1 to 1 1 carbon atoms in their acyl residue is about 3 to about 15 wt.-%. For similar ligands where the carboxylate contains more than 12 carbon atoms the preferred minimum amount is 25 wt.-%, more preferably from about 30 to about 50 wt.-%.

[0039] It has been found by the applicant that for example simple impregnation, spray coating or the like does not lead to a material that solves the problem underlying the present invention.

[0040] In a preferred embodiment of the present invention, a light source for light irradiation in step (d) is selected from one or more of artificial light sources, preferably selected from a light emitting diode, an organic light emitting diode, a cold cathode fluorescent lamp, or a laser device.

Preferred peak light wavelengths range from about 300 to about 600 nm and particularly from about 365 about 470 nm. In another preferred embodiment light intensities range from about 0.025 to about 1 Wcnrr², more preferably from about 0.05 to about 0.5 Wcnrr²

INDUSTRIAL APPLICATION

[0041] COMPOSITION

[0042] Another object of the present invention refers to a composition comprising at least one semiconducting light emitting nanoparticle as explained above in the section of "semiconducting nanoparticles" and "manufacturing process" and at least one additional transparent matrix material.

[0043] According to the present invention, a wide variety of publically known transparent matrix materials suitable for optical devices can be used preferably. According to the present invention, the term "transparent" means at least around 60 % of incident light transmit at the thickness used in an optical medium and at a wavelength or a range of wavelength used during operation of an optical medium. Preferably, it is over 70 %, more preferably, over 75%, the most preferably, it is over 80 %.

[0044] In some embodiments of the present invention, the transparent matrix material can be a transparent polymer.

[0045] According to the present invention the term "polymer" means a material having a repeating unit and having the weight average molecular weight (Mw) 1000 g/mol, or more.

[0046] The molecular weight M_w is determined by means of GPC (= gel permeation chromatography) against an internal polystyrene standard.

[0047] In some embodiments of the present invention, the glass transition temperature (Tg) of the transparent polymer is 70°C or more and 250°C or less.

[0048] Tg is measured based on changes in the heat capacity observed in Differental scanning colorimetry like described in

http://pslc.ws/macrog/dsc.htm; Rickey J Seyler, Assignment of the Glass Transition, ASTM publication code number (PCN) 04-012490-50.

[0049] For examples, as the transparent polymer for the transparent matrix material, poly(meth)acrylates, epoxides, polyurethanes, polysiloxanes, can be used preferably.

[0050] In a preferred embodiment of the present invention, the weight average molecular weight (Mw) of the polymer as the transparent matrix material is in the range from 1 ,000 to 300,000 g/mol, more preferably it is from 10,000 to 250,000 g/mol.

[0051] SOLVENT FORMULATION [0052] Another object of the present invention covers a formulation comprising the composition as explained above in the section of ^"

Composition^" and at least one solvent. These kinds of formulations are of interest in case the nanoparticle is designated for coating on a specific surface.

[0053] Suitable solvents can be selected from the group consisting of purified water; ethylene glycol monoalkyl ethers, such as, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, and ethylene glycol monobutyl ether; diethylene glycol dialkyl ethers, such as, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, and diethylene glycol dibutyl ether; ethylene glycol alkyl ether acetates, such as, methyl cellosolve acetate and ethyl cellosolve acetate; propylene glycol alkyl ether acetates, such as, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, and propylene glycol monopropyl ether acetate;; ketones, such as, methyl ethyl ketone, acetone, methyl amyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols, such as, ethanol, propanol, butanol, hexanol, cyclo hexanol, ethylene glycol, and glycerin; esters, such as, ethyl 3-ethoxypropionate, methyl 3- methoxypropionate and ethyl lactate; and cyclic asters, such as, γ-butyro- lactone; chlorinated hydrocarbons, such as chloroform, dichloromethane, chlorobenzene, dichlorobenzene.

[0054] Also preferred are solvents selected from one or more members of the group consisting of aromatic, halogenated and aliphatic hydrocarbons solvents, more preferably selected from one or more members of the group consisting of toluene, xylene, ethers, tetrahydrofuran, chloroform, dichloromethane and heptane.

[0055] Those solvents are used singly or in combination of two or more, and the amount thereof depends on the coating method and the thickness of the coating.

[0056] More preferably, propylene glycol alkyl ether acetates, such as, propylene glycol monomethyl ether acetate (hereafter "PGMEA"), propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, purified water or alcohols can be used.

[0057] Even more preferably, purified water can be used.

[0058] The amount of the solvent in the formulation can be freely controlled according to further treatments. For example, if the formulation is designated to be spray-coated, it can contain the solvent in an amount of 90 wt. % or more. Further, if a slit-coating method, which is often adopted in coating a large substrate, is to be carried out, the content of the solvent is normally 60 wt. % or more, preferably 70 wt. % or more.

[0059] DEVICES

[0060] The present invention is also directed to the use of the

semiconducting light emitting nanoparticle of the present invention in an electronic device, optical device or in a biomedical device as for example In some embodiments of the present invention, the optical device can be a liquid crystal display, Organic Light Emitting Diode (OLED), backlight unit for display, Light Emitting Diode (LED), Micro Electro Mechanical Systems (here in after "MEMS"), electro wetting display, or an electrophoretic display, a lighting device, and / or a solar cell.

[0061] The present invention also covers an optical medium comprising the semiconducting light emitting nanoparticle, the composition or the formulation each of them as explained above.

[0062] Finally, the present invention also refers to an optical device comprising said optical medium as explained above.

EXAMPLES

[0063] EXAMPLES 1

Synthesis of InP/ZnSe

[0064] 1 12 mg of lnl₃, and 150mg ZnC are dissolved in 2.5 mL

oleylamine. At 180 °C 0.22mL of hexaethylphosphorous triamide (DEA)3P) is added to the solution and is kept at this temperature for 20 min. After 20 min, 0.55 ml_ of anion shell precursor (2M TOP:Se) are added slowly.

Subsequently, the solution is heated stepwise, followed by successive injections of cation (2.4ml_ of 0.4 M Zn(oleate) in ODE) and anion (0.38ml_ of 2M TOP:Se) shell precursor at temperatures between 200 °C and 320 °C.

[0065] EXAMPLE 2

Mg-carboxylate photo-deposition and characterization method

[0066] 1 ml of the sample from Example 1 is purified from access ligands using toluene and ethanol as solvent and anti-solvent and centrifugation. 80 mg of the precipitant are dissolved in 1 ml of anhydrous hexane. In order to analyse organic ligands percentage in the solid content of the sample after purification TGA (model TGA2, Metier Toledo) is applied: TG analysis showed 13.4 wt.% of organic content (4.6 wt% of octadecene, 3.65 wt% of trioctylphosphine and 3.9 wt% of Zn-oleate). The purified and dried material is dissolved in 7 ml of toluene, then 2 ml of isopropyl alcohol is added; final concentration is 8.44 mg/ml. 1 .5ml of solution is taken as reference measurements before magnesium addition (for QY, TGA, XPS and ICP-AES).

[0067] Magnesium-oleate (from Sigma-Aldrich) is dried at 120 °C for 10 minutes to remove water.

[0068] The remaining volume (7.5 ml) of InP/ZnSe solution is added to 1 ml of Mg-oleate solution (29.8 mg of Mg-oleate were re-dissolved in 1 ml of toluene, heated to 70C to improve solubility). Subsequently the Mg-oleate organic content of the solid (inorganic and organic contents taken together) in the solution increased up to 50 wt.-% (according TG analysis). The mixed solution is stirred for 1 hour under inert conditions. Part of the sample is subjected to blue light illumination for 24 hours in the setup described Example 3. The quantum yield (QY) of the sample with and without illumination is measured using Hamamatsu absolute quantum yield spectrometer (model: Quantaurus C1 1347). The zinc, selenium and magnesium content of the sample before and after illumination is determined by digesting the sample with "aqua regia" and performing ICP- AES measurement (model: Perkin Elmer Optima 3000). The surface structure of the sample before and after Mg-oleate adsorption is examined using X-ray Photoelectron Spectroscopy (Kratos, model: Ultra Axis)

[0069] EXAMPLE 3

Illumination process

[0070] Lighting setup built with Philips Fortimo 30001m 34W 4000K LED downlight module (with its phosphor disc removed). A 1 .9 mm thick

Perspex pane is placed on top of this. The distance between the LEDs and the Perspex is 31 .2 mm. The 20 ml sealed sample vials are placed on the Perspex inside a plastic cylinder, diameter 68 mm, height 100 mm. The cylinder is then closed with a cardboard top.

[0071] Photo-enhancement system with sealed sample vials inside the cylinder. To reduce temperature, the vials can be placed inside chemical beaker with water. The peak wavelength of the illumination was 455nm. The irradiance at 450 nm is measured by an Ophir Nova II and PD300-UV photodetector and found to be 300 mW/cm².

[0072] The results are shown in the following Tables 1 , 2 and 3.

[0073] Table 1

Quantum yield for Magnesium-oleate treated samples

Samples QY (%)

InP/ZnSe prior to magnesium oleate addition 32

Coating by 50% w/w Mg-oleate, illuminated for 24 hours 53

[0074] Table 2

Samples QY (%)

Coating by 50% w/w Mg-oleate, non-illuminated 15

Coating by 50% w/w Mg-oleate, illuminated for 24 hours 53 [0075] Table 3

ICP-AES results

[0076] Proof of magnesium deposition:

[0077] Magnesium is detected in samples after addition of Mg-oleate. The Mg:Zn ratio increased after illumination, probably due to adsorption of additional Mg-oleate. Zn:Se ratio do not change significantly upon magnesium addition. This implies that the magnesium is probably adsorbed onto the ZnSe shell and does not replace the Zinc cations on the surface.

[0078] The results shown in Table 3 are also depicted in Figures 1 to 3:

[0079] Figure 1 : XPS data - Sample without magnesium ligand

[0080] Figure 2: Same sample after adding the magnesium ligand

No. Reference Peak Position Area [a.u] Area-%

[eV]

401 Selenium 3d 5/2 (ZnSe) 54.4 1240.2 48.57

402 Selenium 5d 3/2 (ZnSe) 55.26 826.0 32.35 403 Selenium 3d 5/2 (surface) 55.8776 238.0 9.32

404 Selenium 3d 3/2 (surface) 56.7376 158.5 6.21

405 Magnesium 2p 51 .0762 90.6 3.55

[0081] Figure 3: Same sample after adding the magnesium ligand and illumination

No. Reference Peak Position Area [a.u] Area-%

[eV]

501 Selenium 3d 5/2 (ZnSe) 54.4 1010.6 54.29

503 Selenium 5d 3/2 (ZnSe) 55.26 673.1 36.16

503 Magnesium 2p 50.9571 177.9 9.55

[0082] XPS data show adsorption of Mg-oleate onto QDs surface. Coating of selenium is evident by disappearance of selenium surface peaks and appearance of a magnesium peak. The sample with Mg-oleate but without illumination still contains small signals from selenium atoms on the surface. However, looking at the illuminated sample the selenium signals have disappeared which means that they are coated by magnesium. It seems that in particular magnesium is suitable acting as a Z-type ligand, passivating the surface traps and thus increasing QY.

Claims

1 . A semiconducting light emitting nanopartide comprising or consisting of a core, optionally one or more shell layers and an attaching group coated onto the core or the outermost surface of the shell layers, wherein the attaching group is a magnesium salt.

2. The nanopartide of Claim 1 , wherein said core is formed from one, two or more compounds according to formula (I)

[A¹B¹] (I) in which

[A¹] stands for a metal selected from the group consisting of zinc,

cadmium, indium or their mixtures;

[B¹] stands for a non-metal selected form the group consisting of

sulphur, selenium, phosphor or their mixtures.

3. The nanopartide of Clam 2, wherein [A¹B¹] stands for one, two or more compounds selected from the group consisting of CdS, CdSe, CdSeS, CdZnS, ZnS, ZnSe, ZnSeS, and InP.

4. The nanopartide of Claim 1 , wherein said shell or said shells are formed from one, two or more compounds according to formula (II)

[A²B²] (II) in which

[A²] stands for a metal selected from the group consisting of zinc,

cadmium or their mixtures;

[B²] stands for a non-metal selected form the group consisting of

sulphur, selenium, or their mixtures.

5. The nanopartide of Claim 4, wherein [A²B²] stands for one, two or more compounds selected from the group consisting of CdS, CdSe, CdSeS, CdZnS, ZnS, ZnSe and ZnSeS, ZnSeSTe.

6. The nanopartide of Claim 1 , comprising a core [A¹B¹] and at least one shell [A²B²], said core/shell structure [A¹B¹]/[A²B²] being selected from the group consisting of CdSeS/CdZnS, CdSeS,CdS/ZnS,

CdSeS/CdS,ZnS CdSe/ZnS, InP/ZnS, InP/ZnSe, lnP/ZnSe,ZnS, lnP(Zn)/ZnSe, lnP(Zn)/ZnSe,ZnS, lnP(Zn)/ZnSe,ZnS,ZnTe, ZnSe/CdS, ZnSe/ZnS or their mixtures.

7. A semiconducting light emitting nanopartide comprising or consisting of a core, optionally one or more shell layers and coated onto the core or the outermost surface of the shell layers, obtainable or obtained by the following steps:

8. A process for manufacturing a semiconducting light emitting nanopartide comprising or consisting of a core, optionally one or more shell layers and an attaching group coated onto the core or the outermost surface of the shell layers, wherein the process comprising or consisting of the following steps: (a) providing at least one salt of at least one metal [A¹] and/or [A²] optionally dissolved in a suitable solvent;

(b) adding at least one source of at least one non-metal [B¹] and/or [B²] to obtain an intermediate compound [A¹B¹] or [A¹B¹]/[A²B²];

9. The process of Claim 8, wherein the magnesium salt is deposited on the surface of the intermediate compound [A¹B¹] or [A¹B¹]/[A²B²] in an amount of from about 2 to about 98 wt.-%.

10. The process of Claim 8, wherein illumination is carried out using light with a peak light wavelength of about 365 to about 470 nm and/or intensities of about 0.025 to about 1 Wcm^"2.

1 1 . A composition comprising at least one semiconducting light emitting

nanopartide of Claim 1 or 7 and at least one additional transparent matrix material.

12. A formulation comprising the semiconducting light emitting nanopartide of Claim 1 or 7, or the composition of Claim 1 1 and at least one solvent.

13. The use of the semiconducting light emitting nanopartide of Claim 1 or 7, or the formulation of Claim 12 in an electronic device, optical device or in a biomedical device.

14. An optical medium comprising the semiconducting light emitting

nanopartide of Claim 1 or 7 or the composition of Claim 1 1 or the formulation of Claim 12.

15. An optical device comprising said optical medium according to Claim 14.