Field of the invention

The present invention relates to new nanoparticles and a process for obtaining them. The present invention further relates to a composition, formulation and use of a semiconducting nanoparticle, an optical medium; and an optical device

Background Art

Extensive research was conducted on CdSe/CdS nanorods and good results at fields of polarization, self-absorption and charge separation were achieved. However, main disadvantage of the reported nanorods is the presence of cadmium. Due to its toxicity the industrial potential of Cd- containing semiconductors, however, is limited, while there is a strong need for developing Cd-free light emitting nanorods.

So far little is known core/shell in a rod structure. For example, US 2013 0115455 A1 (YISSUM) discloses an anisotropic semiconductor

nanoparticle embedded in a rod-like shell.

From the state of the art various processes are known to obtain assemblies from individual quantum dots, these mechanisms strongly depending on their chemical composition.

For example, XU Et Al, JACS 133, p 18062-18065 (2011) suggests a repeated precipitation of colloidal semiconductor quantum dots from a solution for obtaining an increased number of quantum dot dimers and trimers.

A lot of research has been spent in recent years on the so-called“oriented attachment mechanism”, first described by PENN ET AL (Penn, R. L.; Banfield, J. F. Science 1998, 281 ), according to which for example ZnS and ZnSe nanorods can be obtained.

JIA ET AL, NATURE MATERIALS 13, p 301-307 (2014) reports couples of colloidal semiconductor nanorods formed by self-limited assembly, where nanocrystals are formed first and then agglomerate through weak

interactions involving Van der Waals interactions and hydrogen bonds.

According to LV ET AL, NANOSCALE 6, p 2531-2547 (2014), oriented attachment of crystals is driven via collision and reaction of the individual particles.

An investigation of band offsets in colloidal nanorods using scanning tunneling spectroscopy is reported by STEINER ET AL in NANO LETTERS, 8(9), p 2954-2958 (2008).

“Economic and size-tunable synthesis of InP/ZnSe colloidal quantum dots“ CHEM. MATERIALS 27, p 4893-4898 (2015) reports nanocrystals with an InP core and a ZnS or ZnSe shell that emit from 510 to 630 nm. However, so far neither nanosized InP/Zn chalcogenide assemblies are known, nor a process for their manufacture.

Therefore, it has been the object of the present invention to provide nanorods with high emission and an easy process for their manufacture and/ or less toxic.

Patent Literature

1. US 2013 0115455 A Non-Patent Literature

2. XU et al., JACS 133, p 18062-18065 (2011 )

3. PENN et al ., (Penn, R. L.; Banfield, J. F. Science 1998, 281 ) 4. JIA et al„ NATURE MATERIALS 13, p 301 -307 (2014)

5. LV et al„ NANOSCALE 6, p 2531-2547 (2014)

6. STEINER et al„ NANO LETTERS, 8(9), p 2954-2958 (2008)

7. CHEM. MATERIALS 27, p 4893-4898 (2015)

Summary of the invention

A first object of the present invention is directed to a semiconducting nanoparticle comprising at least two of first semiconducting materials, and a second semiconducting material, wherein the first semiconducting materials are embedded in the second semiconducting material, and

the second semiconducting material comprises at least a first element of group 12 elements of the periodic table and a second element of group 16 elements of the periodic table, preferably the first element is Zn, and the second element is S.

A second object of the present invention refers to a process for fabricating the nanoparticle according to any one of claims 1 to 10, encompassing at least the following steps:

(a) mixing at least two of the first semiconductor materials with another compound to get a reaction mixture, preferably said compound is a solvent, (b) forming the second semiconducting material over the first

semiconducting materials by injecting (i) a metal cation precursor and (ii) an anion precursor into the reaction mixture, on condition that during the coating procedure the temperature is increased stepwise to the temperature in the range from 280 to 315 °C, preferably in the range from 290 to 310 °C, more preferably in the range from 295 to 305 °C from 180 to 300 °C, preferably to realize an oriented attachment of the second semiconducting material to said first semiconducting materials, and (c) cooling down the reaction mixture to room temperature to quench shell formation.

In another aspect, the present invention further relates to a semiconducting nanoparticle obtainable or obtained from the process of the invention.

In another aspect, the present invention further relates to a composition comprising at least one semiconducting nanoparticle of the present invention, and at least one additional material, preferably the additional material is selected from the group consisting of organic light emitting materials, inorganic light emitting materials, charge transporting materials, scattering particles, host materials, nanosized plasmonic particles, photo initiators, and matrix materials.

In another aspect, the present invention further relates to a formulation comprising at least one semiconducting nanoparticle of the present invention, or a composition, and at least one solvent, preferably the solvent is selected from one or more members of the group consisting of aromatic, halogenated and aliphatic hydrocarbon solvents, more preferably selected from one or more members of the group consisting of toluene, xylene, ethers, tetrahydrofuran, chloroform, dichloromethane and heptane, purified water, ester acetates, alcohols, sulfoxides, formamides, nitrides, ketones.

In another aspect, the present invention further relates to an optical medium comprising at least one semiconducting nanoparticle of the present invention, or a composition, or the formulation. In another aspect, the present invention further relates to optical device comprising at least one optical medium of the present invention. Description of drawings

Figure 1 shows absorption and PL spectra of red emitting InP/ZnS nanorods.

Figure 2 shows a TEM image of InP/ZnS red nanorods of working example 1 .

Figure 3 (a), (b) show TEM images of cleaned InP/ZnS red emitting nanorods of working example 1 (a) low magnification, (b) high

magnification.

Detailed description of the invention

The semiconducting nanoparticle comprises at least two of first

semiconducting materials, and a second semiconducting material as a shell, wherein the first semiconducting materials are embedded in the second semiconducting material, and

the second semiconducting material comprises at least a first element of group 12 elements of the periodic table and a second element of group 16 elements of the periodic table.

In some embodiments of the present invention, said nanoparticle comprises 2 to 10 first semiconducting materials, more preferably from 2 to 7 first semiconducting materials, even more preferably from 2 to 4 first

semiconducting materials.

In a preferred embodiment of the present invention, the nanoparticle is a semiconducting light emitting nanoparticle.

In a preferred embodiment of the present invention, said first

semiconducting materials are 2 to 10 first semiconducting materials, more preferably from 2 to 7 first semiconducting materials, even more preferably from 2 to 4 first semiconducting materials.

According to the present invention, the term“semiconductor” means a material which has electrical conductivity to a degree between that of a conductor (such as copper) and that of an insulator (such as glass) at room temperature.

In a preferred embodiment of the present invention, the semiconducting light emitting nanoparticle of the present invention is a quantum sized material.

According to the present invention, the term“quantum sized” means the size of the semiconducting material itself without ligands or another surface modification, which can show the quantum confinement effect, like described in, for example, ISBN:978-3-662-44822-9.

Generally, it is said that the quantum sized materials can emit tunable, sharp and vivid colored light due to“quantum confinement” effect.

In a preferred embodiment of the present invention, the length of the nanoparticle is in the range from 5 to 20 nm and/or the width of the nanoparticle is in the range from 3 to 8 nm. The length and the width of the nanoparticle are calculated based on 100 semiconducting nanoparticles in a TEM image created by a Tecnai G2 Spirit Twin T-12 Transmission Electron Microscope.

In a preferred embodiment of the present invention, the nanoparticle has an elongated shape, preferably it is a rod shaped, curved rod shaped and/or non-spherical shaped. In a preferred embodiment of the present invention, the first semiconducting materials are connected by the second semiconducting material.

- First semiconducting material

According to the present invention, preferably said first semiconducting nanosized material comprises at least a 1 ^st element selected from the group consisting of group 13 elements of the periodic table and group 12 elements of the periodic table, and a 2 ^nd element selected from the group consisting of group 15 elements of the periodic table and group 16 elements of the periodic table, preferably said 1 ^st element is selected from group 13 elements of the periodic table and said 2 ^nd element is selected from group 15 elements, more preferably said 1 ^st element is In or Ga and said 2 ^nd element is P or As, more preferably said 1 ^st element is In and said 2 ^nd element is P.

In a preferred embodiment of the present invention, as a first

semiconducting material, for example, CdS, CdSe, CdTe, ZnS, ZnSe, ZnSeS, ZnTe, ZnO, GaAs, GaP, GaSb, HgS, HgSe, HgSe, HgTe, InAs,

InP, InPS, InPZnS, InPZn, InPZnSe, InCdP, InPCdS, InPCdSe, InGaP, InGaPZn, InSb, AIAs, AIP, AlSb, CU2S, Cu2Se, CulnS2, CulnSe2,

Cu2(ZnSn)S ₄ , Cu2(lnGa)S ₄ , T1O2 alloys and a combination of any of these can be used.

In a preferred embodiment of the present invention, Cd atom is not included in the core. More preferably, Cd atom is not included in the shell also.

More preferably, the first semiconducting material comprises at least In, and P atoms. Even more preferably, the first semiconducting material is selected from one or more members of the group consisting of InP, lnP:Zn, ln _x Gai _-x P, and ln _x Gai _-x P:Zn, lnP:S, lnP:Se, lnP:Te, or any other combination between InP and S, Se, Te, Zn, Ga.

- Second semiconducting material

In some embodiments of the present invention, the second semiconducting material as a shell is represented by following chemical formula (I),

ZnS ₍ i-x-y ₎ (Se)y(Te)x (I) wherein 0£x<1 , 0£y<1 , and 0£x+y<1 , preferably 0<x<1 , 0<y<1 , and

0<x+y<1 , even more preferably the chemical formula (I) is ZnS.

- Elemental Analysis

According to the present invention, the following elemental analysis is used.

The semiconducting light emitting nanoparticle is dissolved in toluene and the obtained solution is diluted. One droplet of the diluted solution is dripped on a Cu/C TEM grid with ultrathin amorphous carbon layer. The grid is dried in vacuum at 80°C for 1.5 hours to remove the residues of the solvent as well as possible organic residues.

EDS measurements are carried out in STEM mode using high resolution

TEM - Tecnai F20 G2 machine operating at 200kV equipped with EDAX

Energy Dispersive X-Ray Spectrometer. TIA software is used for spectra acquisition and calculations and no standards are used.

The term“organic” means any material containing carbon atoms or any compound that containing carbon atoms ionically bound to other atoms such as carbon monoxide, carbon dioxide, carbonates, cyanides, cyanates, carbides, and thiocyanates. In some embodiments of the invention, the nanoparticle shows a peak absorption wavelength in the range from 420 to 630 nm, preferably the nanoparticle shows the peak maximum absorption wavelength in the range from 420 to 630 nm.

In specific embodiments of the present invention, the nanoparticle preferably has a relative quantum yield in the range of 10 % or more, more preferably in the range of 20 or more, even more preferably in the range of 50 to 90 %, and even more preferably in the range of 60 to 90 % measured by calculating the ratio of the emission counts of the QD and the dye coumarin 153 (CAS 53518-18-6) and multiplying by the QY of the dye (54.4%) measured at 25°C.

The relative quantum yield is preferably calculated using absorbance and emission spectrum (excited at 350 nm), obtained using Shimadzu UV-1800 and Jasco FP-8300 spectrophotometer, using the following formula, with coumarin 153 dye in ethanol was used as a reference, with a quantum yield of 55%.

wherein the symbols have the following meaning

QY = Quantum Yield of the sample

QYref = Quantum Yield of the reference/standard

n = the refractive index of the sample solvent (especially ethanol) n _ref = the refractive index of the reference/standard

I = the integral of the sample emission intensity as measured on the

Jasco. Calculated as Jl dv with I intensity, v =wavelength.

A = is the percentage absorbance of the sample. The percentage of the sampling light that the sample absorbs. I _ref = the integral of the reference emission intensity as measured on the Jasco. Calculated as Jl dv with I intensity, v =wavelength. A _ref is the percentage absorbance of the reference. The percentage of the sampling light that the reference absorbs.

The absorbance and emission spectrum is achieved at a temperature of about 25°C.

In some embodiments of the present invention, the semiconducting light emitting nanoparticle can further comprise one or more additional shell layers onto the second shell layer as a multishell.

A second object of the present invention refers to a process for fabricating the nanoparticle, encompassing at least the following steps:

(a) mixing at least two of the first semiconductor materials with another compound to get a reaction mixture, preferably said compound is a solvent,

(b) forming the second semiconducting material over the first

semiconducting materials by injecting (i) a metal cation precursor and (ii) an anion precursor into the reaction mixture, on condition that during the coating procedure the temperature is increased stepwise to the temperature in the range from 280 to 315 °C, preferably in the range from 290 to 310 °C, more preferably in the range from 295 to 305 °C from 180 to 300 °C, preferably to realize an oriented attachment of the second semiconducting material to said first semiconducting materials, and

(c) cooling down the reaction mixture to room temperature to quench shell formation. ln an embodiment of the present invention, the preparation of the shell is preferably achieved by a reaction mixture comprising a solvent and the solvent comprises at least one alkene, preferably an alkene having 6 to 36 carbon atoms, more preferably 8 to 30 carbon atoms, even more preferably 12 to 24 carbon atoms, most preferably 16 to 20 carbon atoms. More preferably, the alkene is a 1 -alkene, such as 1-decene, 1 -dodecene, 1 - Tetradecene, 1 -hexadecene, 1 -octadecene, 1-eicosene. 1 -docosene. The alkene may be linear or branched.

In a further embodiment of the present invention, the preparation of the shell is preferably achieved by a reaction mixture comprising a solvent and the solvent comprises at least one phosphorus compound, such as phosphine compounds, preferably alkyl phosphine compounds having 3 to 108 carbon atoms, phosphine oxide compounds, preferably alkyl phosphine oxide having 3 to 108 carbon atoms and/or phosphonate compounds, more preferably an alkyl phosphonate compounds having 1 to 36 carbon atoms, preferably 6 to 30 carbon atoms, even more preferably 10 to 24 carbon atoms, most preferably 12 or 20 carbon atoms in the alkyl group.

Preferably, Trioctylphosphine (TOP) is used as a solvent for the preparation of a shell.

Regarding the preparation step of the shell, alkenes are preferred in view of the other solvents mentioned above. In a further preferred embodiment, the solvent for the preparation of the shell comprises a mixture of an alkene and a phosphorus compound.

Preferably, the step (b) is conducted at a temperature 150 °C or more, preferably in the range of 150 to 400 °C, more preferably from 200 to 350°C, even more preferably in the range from 250 to 320 °C. furthermore, preferably from 280 to 320 °C. According to the present invention, as a cation precursor for formation of the second semiconducting nanosized material as a shell layer, one or more of known cation precursors for shell layer synthesis comprising group 12 element of the periodic table or 13 elements of the periodic table can be used preferably.

For example, as a first and a second cation shell precursor, one or more members of the group consisting of Zn-oleate, Zn-carboxylate, Zn-acetate, Zn-myristate, Zn-stearate, Zn-undecylenate, Zn-acetate-alkyl amine complexes, Zn-phosphonate, ZnCh, Znh, ZnBr2, Zn-palmitate, Cd-oleate,

Cd-carboxylate, Cd-acetate, Cd-myristate, Cd-stearate and Cd- undecylenate, Cd-phosphonate, CdCh, Ga-oleate, Ga-carboxylate, Ga- acetate, Ga-myristate, Ga-stearate, Ga-undecylenate, Ga-acetylacetonate can be used, More preferably, one or more members of the group consisting of Zn-oleate, Zn-carboxylate, Zn-acetate, Zn-myristate, Zn- stearate, Zn-undecylenate and Zn-acetate-oleylamine complexes are used to coat said shell layer(s) onto the first semiconducting material.

In some embodiments, the metal halides and the cation precursor can be mixed, or, the metal halide can be used as a single cation precursor instead of the cation precursor which is mentioned in the column of cation precursors for formation of the second semiconducting material, if necessary. Thus, in some embodiments of the present invention, the metal cation precursor in step (b) is selected from one or more members of the group consisting of Zn-oleate, Zn-carboxylate, Zn-acetate, Zn-myristate, Zn- stearate, Zn-undecylenate, Zn-acetate-alkyl amine complexes, Zn- phosphonate, ZnC , Znh, ZnBr2, Zn-palmitate, preferably it is selected from one or more members of the group consisting of Zn-oleate, Zn-carboxylate, Zn-acetate, Zn-myristate, Zn-stearate, Zn-undecylenate and Zn-acetate- oleylamine complexes. - Anion precursors for formation of the second semiconducting material According to the present invention, as an anion precursor for formation of the second semiconducting material (shell layer coating), known anion precursor for shell layer synthesis comprising a group 16 element of the periodic table can be used preferably.

For example, as a first and a second anion precursor for formation of the second semiconducting material can be selected from one or more members of the group consisting of Se anion: Se, Se-trioctylphopshine, Se- tributylphosphine, Se-oleylamine complex, Selenourea, Se-octadecene complex, Se-octadecene suspension, S anion and thiols such as

octanethiol, dodecanthiol, ter-doedecanthiol,: S, S-trioctylphopshine, S- tributylphosphine, S-oleylamine complex, Selenourea, S-octadecene complex, and S-octadecene suspension, Te anion: Te, Te- trioctylphopshine, Te- tributylphosphine, Te-oleylamine complex,

Telenourea, Te-octadecene complex, and Te-octadecene suspension.

In some embodiments of the present invention, at least said first anion precursor and a second anion precursor are added simultaneously in the process of formation of the second semiconducting material, preferably said first anion precursor is selected from the group consisting of Se anion: Se, Se-trioctylphopshine, Se- tributylphosphine, Se-oleylamine complex, Selenourea, Se-octadecene complex, and Se-octadecene suspension, and the second anion shell precursor is selected from the group consisting of S anion: S, S-trioctylphopshine, S- tributylphosphine, S-oleylamine complex, Selenourea, S-octadecene complex, and S-octadecene suspension, Te anion: Te, Te-trioctylphopshine, Te- tributylphosphine, Te-oleylamine complex, Telenourea, Te-octadecene complex, and Te-octadecene suspension. ln some embodiments of the present invention, at least said first anion precursor and a second anion precursor are added sequentially in step of the formation of the second semiconducting material, preferably said first anion precursor is selected from the group consisting of Se anion: Se, Se- trioctylphopshine, Se- tributylphosphine, Se-oleylamine complex,

Selenourea, Se-octadecene complex, and Se-octadecene suspension, and the second anion precursor is selected from the group consisting of S anion: S, S-trioctylphopshine, S- tributylphosphine, S-oleylamine complex, Selenourea, S-octadecene complex, and S-octadecene suspension, Te anion: Te, Te-trioctylphopshine, Te- tributylphosphine, Te-oleylamine complex, Telenourea, Te-octadecene complex, and Te-octadecene suspension.

In a preferred embodiment of the present invention, the anion precursor is a sulfur precursor, a selenium precursor or a mixture of the sulfur and the selenium precursor. Preferably it is selected from one or more members of the group consisting of S-TOP, S-oleylamine, thiourea, S-octyldecylamine, S-hexadecylamine, Se-TOP, Se-oleylamine, Se-octadecylamine, and S- hexadecylamine, more preferably it is a sulfur precursor.

By changing the reaction temperature in step of the formation of the second semiconducting material, and total amount of precursors used in the step, the volume ratio between the first semiconducting nanosized material and the shell is more preferably controlled.

In a preferred embodiment of the present invention, said first

semiconducting material is selected from the group consisting of InP, lnP:Zn, ln _x Gai _-x P, and ln _x Gai _-x P:Zn.

Preferably, the preparation of the InP is achieved by a reaction mixture comprising a phosphorus precursor being selected from the group consisting of organic phosphine compounds, preferably alkyl silyl phosphine compounds having 1 to 3 silicon atoms preferably alkyl silyl phosphine compounds having 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms, even more preferably 1 to 4 carbon atoms, most preferably 1 or 2 carbon atoms in the alkyl groups or aryl silyl phosphine compounds, preferably aryl silyl phosphine compounds having 1 -3 silicon atoms preferably aryl silyl phosphine compounds having 6 to 30 carbon atoms, preferably 6 to 18 carbon atoms, even more preferably 6 to 12 carbon atoms, most preferably 6 or 10 carbon atoms in the aryl groups. In addition to a phosphorus precursor, the preparation of the InP is preferably achieved by a reaction mixture comprising an indium precursor preferably being selected from the group consisting of indium carboxylates, more preferably indium carboxylates having 2 to 30 carbon atoms, preferably 4 to 24 carbon atoms, even more preferably 8 to 20 carbon atoms, most preferably 10 to 16 carbon atoms.

The indium carboxylate is preferably selected from the group consisting of indium myristate, indium laurate, indium palmitate, indium stearate and indium oleate. Preferably, the phosphorous precursor comprises

tris(trimethylsilyl)phosphine and similar materials having an aryl, and/or alkyl group instead of the methyl unit, such as tris(triphenyl silyl)phosphine, tris(triethylsilyl)phosphine, tris(diphenylmethylsilyl)phosphine,

tris(phenyldimethylsilyl)phosphine, tris(triphenylsilyl)phosphine,

tris(triethylsilyl)phosphine, tris(diethylmethylsilyl)phosphine,

tris(ethyldimethylsilyl)phosphine.

In a preferred embodiment of the present invention, the temperature of the reaction mixture in step (b) is increased stepwise at the temperature in the range from 160 to 200°C, preferably from 170 to 190°C.

In a preferred embodiment of the present invention, the quenching step (c) includes a lowering of the temperature of a reaction mixture by at least 130 °C, preferably at least 150°C within a period of time less than 2 seconds, preferably less than 1 second by adding a solvent, removing a heat source and/or applying air blow. These data can be measured with any

conventional method and is based on the average temperature decrease.

According to the present invention the optional ligand compound include phosphines and phosphine oxides such as Trioctylphosphine oxide

(TOPO), Trioctylphosphine (TOP), and Tributylphosphine (TBP);

phosphonic acids such as Dodecylphosphonic acid (DDPA), Tetradecyl phosphonic acid (TDPA), Octadecylphosphonic acid (ODPA), and

Hexylphosphonic acid (HPA); amines such as Oleylamine, Dedecyl amine (DDA), Tetradecyl amine (TDA), Hexadecyl amine (HDA), and Octadecyl amine (ODA), Oleylamine (OLA), alkenes, such as 1 -Octadecene (ODE), thiols such as hexadecane thiol and hexane thiol; mercapto carboxylic acids such as mercapto propionic acid and mercaptoundecanoicacid;

carboxylic acids such as oleic acid, stearic acid, myristic acid; acetic acid and a combination of any of these. Polyethylenimine (PEI) also can be used preferably. The ligands mentioned above, especially the acids, can be used in acidic form and/or as a salt. The person skilled in the art will be aware that the ligand will bind to the core in an appropriate manner, e.g. the acids may get deprotonated. In view of the ligands mentioned above, carboxylate ligands such as stearate and oleate and phosphine ligands, such as Trioctylphosphine oxide (TOPO), Trioctylphosphine (TOP), and Tributylphosphine (TBP) are preferred. The used solvent at step (b) is not specifically restricted. Preferably, the solvent is selected from amines, aldehydes, alcohols, ketones, ethers, esters, amides, sulfur compounds, nitro compounds, phosphorus compounds, hydrocarbons, halogenated hydro-carbons (e.g. chlorinated hydrocarbons), aromatic or heteroaromatic hydrocarbons, halogenated aromatic or heteroaromatic hydrocarbons and/or (cyclic) siloxanes, preferably cyclic hydrocarbons, terpenes, epoxides, ketones, ethers and esters. Preferably a non-coordinating solvent is used.

The used ligands and solvents have the same meaning as described above and will not be repeated. In another aspect, the present invention further relates to a semiconducting nanoparticle obtained or obtainable from the process of the invention, preferably it is a semiconducting light emitting nanoparticle obtained or obtainable from the process. In another aspect, the present invention further relates to a composition comprising at least one semiconducting nanoparticle of the present invention, and at least one additional material, preferably the additional material is selected from the group consisting of organic light emitting materials, inorganic light emitting materials, charge transporting materials, scattering particles, host materials, nanosized plasmonic particles, photo initiators, and matrix materials. Preferably, the composition comprises at least one semiconducting light emitting nanoparticle. More preferably, the composition comprises a plurality of the semiconducting light emitting nanoparticles.

In another aspect, the present invention further relates to a formulation comprising at least one semiconducting nanoparticle, or a composition, and at least one solvent, preferably the solvent is selected from one or more members of the group consisting of aromatic, halogenated and aliphatic hydrocarbon solvents, more preferably selected from one or more members of the group consisting of toluene, xylene, ethers, tetrahydrofuran, chloroform, dichloromethane and heptane, purified water, ester acetates, alcohols, sulfoxides, formamides, nitrides, ketones.

Preferably, the formulation comprises at least one semiconducting light emitting nanoparticle of the present invention. More preferably, the formulation comprises a plurality of the semiconducting light emitting nanoparticles.

In another aspect, the present invention further relates to use of the semiconducting nanoparticle, or a composition, or the formulation, in an electronic device, optical device or in a biomedical device. Preferably said semiconducting nanoparticle is a semiconducting light emitting nanoparticle of the invention.

In another aspect, the present invention further relates to an optical medium comprising at least one semiconducting nanoparticle of the present invention, or a composition, or the formulation.

Preferably, the optical medium comprises at least one semiconducting light emitting nanoparticle. More preferably, the optical medium comprises a plurality of the semiconducting light emitting nanoparticles.

In some embodiments of the present invention, the optical medium can be an optical sheet, for example, a color filter, color conversion film, remote phosphor tape, or another film or filter. According to the present invention, the term ^" sheet ^” includes film and / or layer like structured mediums. ln some embodiments of the present invention, the optical medium comprises at least an anode and a cathode, and at least one organic layer comprising at least one light emitting nanoparticle of the present invention, or the composition, preferably said one organic layer is a light emission layer, more preferably the medium further comprises one or more layers selected from the group consisting of hole injection layers, hole transporting layers, electron blocking layers, hole blocking layers, electron blocking layers, and electron injection layers.

In some embodiments of the present invention, the organic layer of the optical medium comprises at least one light emitting nanoparticle of the present invention and a host material, preferably the host material is an organic host material.

In another aspect, the present invention further relates to optical device comprising at least one optical medium of the present invention.

In some embodiments of the present invention, the optical device can be a liquid crystal display device (LCD), Organic Light Emitting Diode (OLED), backlight unit for an optical display, Light Emitting Diode device (LED),

Micro Electro Mechanical Systems (here in after“MEMS”), electro wetting display, or an electrophoretic display, a lighting device, and / or a solar cell.

Each feature disclosed in the present invention can, unless this is explicitly excluded, be replaced by alternative features which serve the same, an equivalent or a similar purpose. Thus, each feature disclosed in the present invention is, unless stated otherwise, to be regarded as an example of a generic series or as an equivalent or similar feature.

All features of the present invention can be combined with one another in any way, unless certain features and/or steps are mutually exclusive. This applies to preferred features of the present invention. Equally, features of non-essential combinations can be used separately (and not in

combination).

The teaching on technical action disclosed in the present invention can be abstracted and combined with other examples.

The invention is explained in greater detail below with reference to working examples, but without being restricted thereby.

Working Examples

Working Example 1 : Manufacture of red emitting nanorods based on InP/ZnS

0.3 g InCb and 0.9 g ZnCh are placed in a 50 ml 3-neck flask and it is suspended in 15 ml oleylamine. The mixture is degassed at 120 °C and then heated to 180 °C over a period of 60 minutes. Subsequently 1.35 ml P(DEA)3 is injected and the mixture is kept under stirring at 180 °C for another 20 minutes to form the InP core of the nanostructure. Subsequently the shell forming compounds are added according to the following protocol:

Absorption spectra (left) and PL spectra (right) are measured for the red emitting InP/ZnS nanorods obtained according to the procedure described above. The quantum yield (QY) of the material was 60 % as depicted in

Figure 1. The material is subjected to TEM and rods having a length of 10 to 15 nm and a width of 3 to 8 nm are observed as shown in Figure 2. Also, small portions of single dots and dimers to tetramers are found.

The material is subjected to standard cleaning procedure by adding 1 ml toluene and 0.7 ml ethanol to 0.1 ml of the crude material. Subsequently a fraction is obtained containing rods and almost no other shapes; the yield after the cleaning process is 65 %. A TEM image of the cleaned fraction is provided in Figure 3 (left: low magnification, right: high magnification).