HK1106275B

HK1106275B - Preparation of nanoparticle materials

Info

Publication number: HK1106275B
Application number: HK08100250.7A
Authority: HK
Inventors: P‧奥布赖恩; N‧皮克特
Original assignee: 纳米技术有限公司
Priority date: 2004-04-30
Filing date: 2005-04-27
Publication date: 2012-04-27

Description

Preparation of nanoparticle materials

There has been substantial interest in the preparation and characterization of compound semiconductors composed of particles, often referred to as quantum dots and/or nanocrystals, with dimensions of about 2-100nm^[1-8]Due to their optical, electronic and chemical properties. These studies have emerged primarily because of their size-tunable electronic, optical, and chemical properties and optical and electronic devices^[9，10]Further miniaturization is required and the optical and electronic devices now extend into a variety of new and emerging applications such as various commercial applications of biomarkers, solar cells, catalysis, bio-imaging, light emitting diodes.

Although some earlier examples appear in the literature^[11]Recently, however, methods have been developed for preparing particles from atoms by atoms from renewable "bottom-up" technologies, i.e. from molecules to clusters to particles using "wet" chemistry^[12，13]. Conversely, the "top-down" technique involves grinding a solid into a finer and finer powder.

The most studied and prepared semiconductor materials so far are chalcogenide II-VI materials, i.e., ZnS, ZnSe, CdS, CdSe, CdTe; most interesting is CdSe due to its tunability over the visible region of the spectrum. Semiconductor nanoparticles as described have academic and commercial interest because their different and unique properties are distinguished from those of the same material but in a macrocrystalline large form. Two fundamental factors, both related to the size of individual nanoparticles, are responsible for their unique properties. The first factor is the large surface to volume ratio; as the particles become smaller, the ratio of the number of surface atoms to the number of atoms in the interior increases. This results in surface properties that play an important role in the overall properties of the material. The second factor is that with semiconductor nanoparticles, the electronic properties of the material change with size, and the band gap gradually becomes larger as the particle size decreases due to quantum confinement effects. This effect is a result of the confinement of "electrons in the box", giving rise to discrete energy levels similar to those observed in atoms and molecules, rather than a continuous band as in the corresponding bulk semiconductor material. Thus, for semiconductor nanoparticles, because of the physical parameters, the "electrons and holes" generated by absorption of electromagnetic radiation, photons with greater energy than the first excitonic transition are closer together than in the corresponding macrocrystalline material, so that coulomb interactions cannot be neglected. This results in a narrow bandwidth emission, depending on the particle size and composition. Thus, quantum dots have higher kinetic energy than the corresponding macrocrystalline material, and thus the energy of the first excitonic transition (band gap) increases with decreasing particle size.

Single-core nanoparticles composed of a single semiconductor material together with an external organic passivation layer tend to have relatively low quantum efficiency due to electron-hole recombination occurring at defects and drag bonds (daggling bonds) located on the surface of the nanoparticles, which results in non-radiative electron-hole recombination. One way to eliminate defects and dragging bonds is to epitaxially grow a second material having a wider band gap and a small lattice mismatch with the core material on the core particle (e.g., another II-VI material) to produce a "core-shell particle". Core-shell particles separate any carriers confined in the core from surface states that otherwise act as non-radiative recombination centers. One example is ZnS grown on the surface of a CdSe core. The shell is typically a material having a wider bandgap than the core material and a small lattice mismatch with the core material so that the interface of the two materials has as little lattice strain as possible. Excessive strain can further lead to defects and nonradiative electron-hole recombination resulting in low quantum efficiency.

However, the growth of more monolayers of shell material than a few layers may have the opposite effect, and thus the lattice mismatch between CdSe and ZnS is sufficiently large that in a core-shell structure only a few monolayers of ZnS may grow before a reduction in quantum yield is observed, showing the formation of defects due to lattice collapse caused by high lattice strain. Another approach is to prepare core-multishell structures in which the "electron-hole" pair is completely confined to a single shell, e.g. quantum dot-quantumA sub-well structure. Here, the core is a wide bandgap material followed by a thin shell of narrower bandgap material and closed with a wider bandgap layer, e.g., CdS/HgS/CdS grown on the surface of the core nanocrystal with Hg instead of Cd to deposit HgS with only 1 monolayer¹⁴. The resulting structure shows clear confinement of photo-excited carriers in the HgS layer.

Coordination to the final inorganic surface atoms in any core, core-shell or core-multishell nanoparticle is incomplete, with highly reactive "dangling bonds" on the surface, which can lead to particle agglomeration. This problem is overcome by passivating (blocking) the "bare" surface atoms with protective organic groups. The encapsulation or passivation of the particles not only prevents the occurrence of particle agglomeration, it also protects the particles from their surrounding chemical environment and provides electronic stability (passivation) to the particles in the case of the core material. The blocking agent is typically in the form of a lewis base compound covalently bound to the surface metal atoms of the outermost inorganic layer of the particle, but more recently, in order to incorporate the particle into a composite, an organic or biological system may take the form of an organic polymer that forms a bundle around the particle with chemical functional groups for further chemical synthesis, or an organic group bound directly to the surface of the particle with chemical functional groups for further chemical synthesis.

A number of synthetic methods have been reported for the preparation of semiconductor nanoparticles, early routes using conventional colloidal aqueous chemistry, and more recent methods involving kinetically controlled precipitation of nanocrystals using organometallic compounds.

Over the past six years, an important issue has been the synthesis of high quality semiconductor nanoparticles in terms of uniform shape, size distribution, and quantum efficiency. This results in a large number of methods that can routinely produce semiconductor nanoparticles with monodispersity < 5% and quantum yield > 50%. Most of these methods are based on the original "nucleation and growth" method described by Murray, Norris and Bawendi¹⁵But using saidOther precursors for those of organic metals. Murray et al originally used a metal-alkyl (R)₂M) M ═ Cd, Zn, Te; r ═ Me, Et and tri-n-octylphosphine sulfide/selenide (TOPS/Se) in an organometallic solution of tri-n-octylphosphine. These precursor solutions were injected into hot tri-n-octylphosphine oxide (TOPO) at a temperature range of 120 ℃ - & 400 ℃, depending on the material to be produced. This results in TOPO coated/encapsulated with semiconductor nanoparticles of II-VI materials. The size of the particles is controlled by the temperature at which the synthesis is carried out, the concentration of the precursors used and the length of time, larger particles being obtained at higher temperatures, higher precursor concentrations and prolonged reaction times. This organometallic route has advantages over other synthetic methods, including near monodispersity < 5% and high particle crystallinity. As mentioned, many variations of this approach have now emerged in the literature, which routinely gives high quality core and core-shell nanoparticles with monodispersity < 5% and quantum yield > 50% (for core-shell particles such as prepared solutions), with many of the approaches showing high dimensions¹⁶And shape¹⁷And (5) controlling.

Recent attention has focused on "greener" which is less exotic and cheaper but not necessarily more environmentally friendly "The precursor is used. Some of these new precursors include oxides, CdO¹⁸(ii) a Carbonate salt MCO₃M is Cd and Zn; acetate salt M (CH)₃CO₂)₂M ═ Cd, Zn and acetylacetonates [ CH ]₃COCH＝C(O^-)CH₃]₂M is Cd and Zn; among others^19，20。

Single source precursors have also proven useful in the synthesis of II-VI semiconductor nanoparticle materials, as well as other semiconductor nanoparticles. Bis (dialkyldithio-/diselenyl-carbamato) cadmium (II)/zinc (II) compounds, M (E)₂CNR₂)₂(M ═ Zn or Cd, E ═ S or Se, and R ═ alkyl), analogous "one-pot" syntheses have been usedProcess involving dissolution in tri-n-octylphosphine (TOP)

(the use of the term "greener" precursor in the synthesis of semiconductor particles generally means that a less expensive, readily available and more easily handled precursor feedstock is taken than the volatile and air and moisture sensitive organometallic compounds originally used, and does not necessarily mean that a "greener precursor" is more environmentally friendly)

The precursor was then rapidly injected into hot tri-n-octylphosphine oxide/tri-n-octylphosphine (TOPO/TOP) above 200 ℃.

For all of the above methods, fast particle nucleation followed by slow particle growth is necessary for a narrow particle size distribution. All of these synthetic methods are based on the synthesis of the peptide by Murray et al¹⁵The original organometallic compound "nucleation and growth" process proposed involves the rapid injection of the precursors into a hot solution of a lewis base coordinating solvent (capping agent) that may also contain one of the precursors. The addition of the cooling solvent subsequently lowers the reaction temperature and aids in particle growth but inhibits further nucleation. The temperature is then maintained for a period of time, wherein the size of the resulting particles depends on the reaction time, temperature and the ratio of the blocking agent to the precursor used. The resulting solution is cooled and then an excess of polar solvent (methanol or ethanol or sometimes acetone) is added to produce a precipitate of the particles for separation by filtration or centrifugation.

Due to their enhanced covalent character, III-V and IV-VI highly crystalline semiconductor nanoparticles are more difficult to prepare and generally require longer annealing times. However, there are many reports at present¹⁵Preparation of II-VI and IV-VI materials GaN by similar degree²¹、GaP²²、GaAs^{22，23，24，25，26}、InP^27，28，29 InAs ^30，27And for PbS³¹And PbSe³²。

Fundamentally, all of these preparations rely on the principle of particle nucleation followed by growth, and, in order to have a monodisperse ensemble of nanoparticles, there must be a suitable separation of nanoparticle nucleation from nanoparticle growth. This is achieved by rapid injection of one or both precursors into a hot coordinating solvent (containing the other precursors if otherwise not present) which causes particle nucleation, however, the sudden addition of a cooling solution at the time of injection subsequently lowers the reaction temperature (the volume of solution added is about 1/3 of the total solution) and inhibits further nucleation to maintain a narrow nanoparticle size distribution. Depending on the precursor used, particle growth as a surface-catalyzed process or via ostwald ripening continues at lower temperatures and nucleation and growth are thereby separated. This method works well for small scale syntheses where one solution can be added quickly to another while maintaining a uniform temperature during the reaction. However, on larger production scales, whereby large volumes of solution need to be injected into each other quickly, temperature differences may occur in the reaction, which subsequently lead to large particle size distributions.

From the preparation of a cluster of molecules of a single origin, Cooney and co-workers used the cluster [ S ]₄Cd₁₀(SPh)₁₆][Me₃NH]₄By oxidizing surface-blocked SPh with iodine^-Ligand to produce CdS nano-particles. This route takes the fragmentation of most clusters into ions that are retained S₄Cd₁₀(SPh)₁₆]^4-The clusters are consumed and subsequently grown into CdS nanoparticles.³⁴

Strouse³⁵And partners use a similar synthetic route, but thermal decomposition (thermosol) is used instead of chemical reagents to cause particle growth. Furthermore, a single-source precursor [ M ]₁₀Se₄(SPh)₁₆][X]₄X＝Li⁺Or (CH)₃)₃NH⁺Thermal decomposition of M ═ Cd or Zn thus produces fragmentation of some clusters, followed by removal of others from the free M and Se ions or simply by growth of aggregated clusters to form larger clusters, followed bySmall nanoparticles, which then continue to grow into larger particles.

According to the present invention there is provided a method of producing nanoparticles, the method comprising effecting conversion of a nanoparticle precursor composition to the material of said nanoparticles, said precursor composition comprising a first precursor species containing a first ion to be incorporated into the growing nanoparticles and a separate second precursor species containing a second ion to be incorporated into the growing nanoparticles, wherein said conversion is effected in the presence of a molecular cluster compound under conditions permitting seeding and growth of the nanoparticles.

The present invention relates to a method of producing nanoparticles in any suitable form and allows the rapid production of a monodisperse population of such particles, and thus of high purity. It is contemplated that the present invention is suitable for producing nanoparticles of any particular size, shape or chemical composition. The nanoparticles may have a size falling within the range of 2-100 nm. A sub-class of nanoparticles of particular interest relates to compound semiconductor particles, also known as quantum dots or nanocrystals.

An important feature of the present invention is that the conversion of the precursor composition (comprising separate first and second precursor species) to the nanoparticles is carried out in the presence of a molecular cluster compound (which is different from the first or second precursor species). Without wishing to be bound by any particular theory, one possible mechanism by which nanoparticle growth occurs is that each of the same cluster molecules acts as a seed or nucleation site that can cause nanoparticle growth. In this way, nanoparticle nucleation does not necessarily lead to nanoparticle growth, since suitable nucleation sites are already provided in the system by the molecular clusters. The cluster molecules serve as templates to guide nanoparticle growth. "molecular clusters" are terms that are widely understood in the relevant art, but for clarity should be understood herein as relating to clusters of 3 or more metal or non-metal atoms and their associated ligands of sufficiently well defined chemical structure that all cluster molecules have the same relative molecular weight. Such that the molecular cluster is such that one H₂O molecule with another H₂The O molecules are identical to each other in the same manner. The use of molecular cluster compounds provides an ensemble of nanoparticles that are substantially monodisperse. By providing nucleation sites that are more fully defined than those employed in the foregoing work, nanoparticles formed using the method of the present invention have a significantly more fully defined final structure than those obtained using the foregoing method. An additional significant advantage of the process of the present invention is that it can be more easily scaled up for industrial applications than current processes. Methods for producing suitable molecular clusters are known in the art, examples of which are found in the Cambridge crystal Data center (www.ccdc.ca.ac.uk).

The conversion of the precursor composition to nanoparticles is carried out under conditions to ensure that there is direct reaction and growth between the precursor composition and the clusters; or some clusters grow at the expense of others until a certain size is reached, at which size there is direct growth between the nanoparticle and the precursor composition, due to ostwald ripening. Such conditions ensure that the monodispersity of the clusters is maintained throughout the nanoparticle growth, which in turn ensures that a monodispersity population of nanoparticles is obtained.

Any suitable molar ratio of the molecular cluster compound to the first and second nanoparticle precursors may be used, depending on the structure, size and composition of the nanoparticles formed, and also on the identity and concentration of other reactants, such as one or more nanoparticle precursors, capping agents, size directing compounds and solvents. It has been found that a particularly useful ratio of the number of moles of cluster compound to the total number of moles of the first and second precursor species is preferably in the range of from 0.0001 to 0.1 (number of moles of cluster compound) to 1 (total number of moles of first and second precursor species), more preferably from 0.001 to 0.1: 1, still more preferably from 0.001 to 0.060: 1. A more preferred ratio of the number of moles of cluster compound to the total number of moles of first and second precursor species is in the range of 0.002-0.030: 1, and more preferably 0.003-0.020: 1. In particular, it is preferred that the number of moles of cluster compound is in the range of 0.0035 to 0.0045: 1 relative to the total number of moles of the first and second precursor substances.

It is contemplated that any suitable molar ratio of the first precursor species to the second precursor species may be used. For example, the molar ratio of the first precursor species to the second precursor species may be in the range of 100-1 (first precursor species) to 1 (second precursor species), more preferably 50-1: 1. A more preferred range of the molar ratio of the first precursor species compared to the second precursor species is in the range of 40-5: 1, more preferably 30-10: 1. In certain applications, it is preferred to use approximately equimolar amounts of the first and second precursor materials in the process of the invention. The molar ratio of the first precursor species to the second precursor species is preferably in the range of 0.1-1.2: 1, more preferably 0.9-1.1: 1, and most preferably 1: 1. In other applications, about twice the number of moles of one precursor species compared to another may be suitably used. Thus, the molar ratio of the first precursor species to the second precursor species may be in the range of 0.4-0.6: 1, more preferably the molar ratio of the first precursor species to the second precursor species is 0.5: 1. It will be appreciated that the above precursor molar ratios may be reversed such that they relate to the molar ratio of the second precursor species compared to the first precursor species. Thus, the molar ratio of the second precursor species to the first precursor species may be in the range of 100-1 (second precursor species) to 1 (first precursor species), more preferably 50-1: 1, 40-5: 1, or 30-10: 1. Further, the molar ratio of the second precursor species to the first precursor species may be in the range of 0.1-1.2: 1, 0.9-1.1: 1, 0.4-0.6: 1, or may be 0.5: 1.

The methods of the present invention involve the conversion of a nanoparticle precursor composition to the desired nanoparticles. Suitable precursor compositions comprise two or more separate precursor species, each of which contains at least one ion to be included in the growing nanoparticles. The total amount of precursor required to form the final desired yield of nanoparticles may be added before the nanoparticles begin to grow, or alternatively, the precursor composition may be added at a stage during the reaction.

The conversion of the precursor composition to the nanoparticle material may be carried out in any suitable solvent. In the process of the invention, it is important to ensure that: when the cluster and precursor composition are introduced into the solvent, the temperature of the solvent is sufficiently high to ensure satisfactory dissolution and mixing of the cluster and precursor composition. Once the cluster and precursor composition are sufficiently well dissolved in the solvent, the temperature of the solution so formed is raised to a sufficiently high temperature or temperature range to cause nanoparticle growth. The temperature of the solution can then be maintained at this temperature or range for as long as necessary to form nanoparticles with suitable properties.

Many suitable solvents are available. The particular solvent used will generally depend, at least in part, on the nature of the species being reacted, i.e., the precursor composition and/or the cluster, and/or the type of nanoparticles being formed. Typical solvents include lewis base type coordinating solvents such as phosphines (e.g., TOP), phosphine oxides (e.g., TOPO), or amines (e.g., HDA), or non-coordinating organic solvents such as alkanes and alkenes. If a non-coordinating solvent is used, it will generally be used in the presence of an additional coordinating agent that acts as a capping agent for the following reasons.

If the formed nanoparticles tend to function as quantum dots, it is important to ensure that any dangling bonds on the nanoparticle surface are blocked to minimize non-radiative electron-hole recombination and to suppress particle agglomeration which can reduce quantum efficiency. A large number of different coordinating solvents are known which may also act as blocking or passivating agents, for example TOP, TOPO or HDA. If a solvent is selected that does not act as a capping reagent, any suitable capping reagent may be added to the reaction mixture during nanoparticle growth. Such capping agents are typically lewis bases, but many other agents are available, such as oleic acid and organic polymers that form a protective sheath around the nanoparticles.

Yet another approach to avoid the involvement of non-radiative electron-hole recombination is to grow one or more shells around the nanoparticle core to form a "core-shell" nanoparticle. Such shells are known in the art and typically comprise a different material than the core material. The shell material is typically selected to have a wider bandgap than the core material, but to have as little lattice mismatch as possible with the core to minimize the lattice strain at the core-shell interface, which can reduce quantum efficiency due to non-radiative electron-hole recombination.

The development of nanoparticle growth can be monitored by any conventional method, such as Photoluminescence (PL) or ultraviolet-visible (UV-vis) spectroscopy. Once the nanoparticles have been produced to have the desired properties, such as when the nanoparticle peak is observed on the PL/UV-vis emission spectrum at the desired wavelength, further growth is inhibited by changing the reaction conditions, such as lowering the temperature of the solution below the temperature necessary to ensure nanoparticle growth. At this stage, the nanoparticles may be immediately isolated from solution by any conventional means, such as precipitation, or allowed to anneal at a suitable temperature for any desired amount of time, such as 10 minutes to 72 hours, to "size-concentrate" via ostwald ripening prior to isolation. After initial isolation, the nanoparticle material is then subjected to one or more washing cycles to provide a high purity final product.

It is also contemplated that a shape directing compound, such as a phosphonic acid derivative, may be added to the reaction mixture to cause the growth particles to adopt a particular shape, such as a sphere, rod, disk, tetrapod, or star shape, which may be used in particular applications.

The present invention comprises primarily a method of producing nanoparticle materials, but is not limited to compound semiconductor nanoparticles from the use of molecular clusters, whereby the clusters are defined as the same molecular entity as compared to the entirety of featureless small nanoparticles that inherently lack molecular clusters. The present invention consists of using molecular clusters as templates to seed the growth of nanoparticles, thereby using other molecular sources "molecular feedstocks" to promote particle growth. These molecular starting materials are a combination of individual precursors each containing one or more elements/ions that are desired for the nanoparticle to be grown.

Type of system to be manufactured

The present invention relates to the preparation of a multitude of nanoparticle materials and comprises compound semiconductor particles, in other words quantum dots or nanocrystals in the size range of 2-100nm, and comprises a core material comprising: -

IIA-VIB (2-16) materials, consisting of a first element from group 2 of the periodic table of elements and a second element from group 16 of the periodic table of elements, and also ternary and quaternary materials and doping materials. Nanoparticle materials include, but are not limited to: -MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe.

IIB-VIB (12-16) materials, consisting of a first element from group 2 of the periodic Table of the elements and a second element from group 16 of the periodic Table of the elements, and also ternary and quaternary materials and doped materials. Nanoparticle materials include, but are not limited to: -ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe.

II-V materials, consisting of a first element from group 12 of the periodic Table of the elements and a second element from group 15 of the periodic Table of the elements, and also ternary and quaternary materials and doped materials. Nanoparticle materials include, but are not limited to: -Zn₃P₂、Zn₃As₂、Cd₃P₂、Cd₃As₂、Cd₃N₂、Zn₃N₂。

III-V materials, consisting of a first element from group 13 of the periodic table and a second element from group 15 of the periodic table, and also ternary and quaternary materials and doped materials. Nanoparticle materials include, but are not limited to: -BP, AlP, AlAs, AlSb; GaN, GaP, GaAs, GaSb; InN, InP, InAs, InSb, AlN, BN.

III-IV material fromA first element from group 13 of the periodic table and a second element from group 16 of the periodic table, and also ternary and quaternary materials and doped materials. Nanoparticle materials include, but are not limited to: -B₄C、Al₄C₃、Ga₄C。

III-VI materials, consisting of a first element from group 13 of the periodic table and a second element from group 16 of the periodic table, and also include ternary and quaternary materials. Nanoparticle materials include, but are not limited to: -Al₂S₃、Al₂Se₃、Al₂Te₃、Ga₂S₃、Ga₂Se₃、GeTe；In₂S₃、In₂Se₃、Ga₂Te₃、In₂Te₃、InTe。

IV-VI materials, consisting of a first element from group 14 of the periodic table and a second element from group 16 of the periodic table, and also ternary and quaternary materials and doped materials. Nanoparticle materials include, but are not limited to: PbS, PbSe, PbTe, Sb₂Te₃、SnS、SnSe、SnTe。

Nanoparticle materials consisting of a first element from any group of the transition metals of the periodic table and a second element from any group of the d-block elements of the periodic table and also ternary and quaternary materials and doped materials. Nanoparticle materials include, but are not limited to: NiS, CrS, CuInS₂。

For the purposes of the specification and claims, the term doped nanoparticles refers to nanoparticles as described above and to dopants comprising one or more main group or rare earth elements, most typically transition metals or rare earth elements, such as but not limited to manganese-containing zinc sulphide, e.g. doped Mn⁺ZnS nanoparticles of (1).

Ternary phase

For the purposes of the specification and claims, the term ternary phase refers to the nanoparticles described above but to a ternary phase material. The three components are generally compositions of elements from the groups mentioned above, examples being (Zn)_xCd_x-1S)_mL_nNanocrystals (where L is a capping agent).

Quaternary phase

For purposes of the specification and claims, the term quaternary phase refers to the nanoparticles described above but to a four-component material. The four components are generally compositions of elements from the groups mentioned above, with examples being (Zn)_xCd_x-1S_ySe_y-1)_mL_nNanocrystals (where L is a capping agent). Thermal solvolysis (Solvothermal)

For the purposes of the specification and claims, the term thermosol refers to heating the reaction solution in order to induce and sustain particle growth and also takes the meaning of thermosollysis (solvothermal), thermolysis (thermolysis), thermosollysis (thermolsolvol), solution-pyrolysis (solution-pyrolysis), thermosol (lyothermalyl).

Core-shell and core/multishell particles

In most cases, the material used for any shell or subsequent shells grown onto the core particle will be of a similar lattice type to the core material, i.e. a material having a close lattice match to the core material so that it can grow epitaxially onto the core, but is not necessarily limited to this compatible material. The material used on any shell or many subsequent shells grown onto the core that is present in most cases will have a wider bandgap than the core material, but is not necessarily limited to this compatible material. The material of any shell or subsequent shells grown onto the core may comprise a material comprising: -

IIA-VIB (2-16) materials, consisting of a first element from group 2 of the periodic table of elements and a second element from group 16 of the periodic table of elements, and also ternary and quaternary materials and doping materials. Nanoparticle materials include, but are not limited to: -MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe.

III-IV materials, consisting of a first element from group 13 of the periodic table and a second element from group 16 of the periodic table, and also ternary and quaternary materials and doped materials. Nanoparticle materials include, but are not limited to: -B₄C、Al₄C₃、Ga₄C。

III-VI materials, consisting of a first element from group 13 of the periodic table and a second element from group 16 of the periodic table, and also include ternary and quaternary materials. Nanoparticle materials include, but are not limited to: -Al₂S₃、Al₂Se₃、Al₂Te₃、Ga₂S₃、Ga₂Se₃；In₂S₃、In₂Se₃、Ga₂Te₃、In₂Te₃。

Nanoparticle materials, consisting of a first element from any group of the transition metals of the periodic table and a second element from any group of the d-block elements of the periodic table, and also ternary and quaternary materials and doped materials. Nanoparticle materials include, but are not limited to: NiS, CrS, CuInS₂。

Outermost particle layer

Sealing agent

The outermost layer of organic material or sheath material (capping agent) is to inhibit particle aggregation and to protect the nanoparticle from the surrounding chemical environment, and provides a means of chemical bonding with other inorganic, organic or biological materials. The capping agent may be a solvent in which nanoparticle preparation is carried out and consists of a lewis base compound whereby there is a lone pair of electrons capable of donor-type coordination to the nanoparticle surface and may include, but is not limited to, the following types of mono-or poly-dentate ligands: phosphines (trioctylphosphine, triphenylphosphine, tert-butylphosphine), phosphine oxides (trioctylphosphine oxide), alkylamines (hexadecylamine, octylamine), arylamines, pyridines and thiophenes.

The outermost layer (capping reagent) may consist of coordinating ligands with functional groups that can be used to chemically bond with other inorganic, organic or biological materials, such as, but not limited to: -a mercapto-functional amine or mercapto-carboxylic acid.

The outermost layer (capping agent) may consist of coordinating ligands, polymerizable ligands having functional groups that are polymerizable and may be used to form polymers around the particles, such as but not limited to styrene-functionalized amine, phosphine, or phosphine oxide ligands.

Nanoparticle shape

The nanoparticle shape is not limited to spherical and may consist of, but is not limited to, rods, spheres, discs, tetrapyramids or stars. The shape of the nanoparticles is controlled by the addition of compounds that will preferentially bind to specific lattice planes of the growing particles and subsequently inhibit or slow particle growth in a specific direction. Examples of compounds that may be added, but are not limited to, include: phosphonic acids (n-tetradecylphosphonic acid, hexylphosphonic acid, 1-decanesulfonic acid, 12-hydroxydodecanoic acid, n-octadecylphosphonic acid).

Description of the preparation procedure

The invention is intended to obtain pure, monodisperse, nanocrystalline particles which are stable in terms of particle aggregation and the surrounding chemical environment by means of an organic layer, in (ME)_nL_yM and E in the particles are two different elements and L is the coordinating organic layer/capping agent, e.g. II-VI semiconductors (ZnS) consisting of a ZnS core surrounded by a trioctylphosphine oxide ligand (TOPO)_n(TOPO)_yNanoparticles.

The first step in the preparation of nanoparticles of semiconductor material is the use of molecular clusters as templates to seed the growth of the nanoparticles from other elemental source precursors. This is achieved by mixing a small amount of clusters used as templates with a high boiling solvent that can also act as a blocking agent, which is a lewis base coordination compound such as, but not limited to, a phosphine, phosphine oxide or amine such as TOP, TOPO or HDA; or an inert solvent such as an alkane (octadecene) plus a blocking compound such as oleic acid. In addition to this, a source for M and a source for E (for ME particles) are added to the reaction mixture. The M and E precursors are in the form of two separate precursors, one containing M and the other containing E.

In addition to this, other reagents having the ability to control the shape of the nanoparticle growth may or may not be added to the reaction. These additives are in the form of compounds that are capable of preferentially binding to a particular surface (lattice plane) of the growing nanoparticle and thereby inhibiting or slowing growth in a particular direction of the particle. Other elemental source precursors may or may not be added to the reaction to produce ternary, quaternary or doped particles.

First, the compounds of the reaction mixture are mixed at the molecular level at a temperature sufficiently low that particle growth does not occur. The reaction mixture is then heated at a steady rate until particle growth is induced on the surface of the molecular cluster template. If desired, further amounts of the M and E precursors may be added to the reaction mixture at a suitable temperature after particle growth has been induced, in order to inhibit mutual consumption of the particles by the Ostwald ripening process. More precursor may be added in a batch addition whereby the solid precursor or the solution containing the precursor is added over a period of time or by continuous dropwise addition. Because of the complete separation of particle nucleation and growth, the present invention shows a high degree of control over particle size, which is controlled by the reaction temperature and the concentration of the precursor present. Once the desired particle size is obtained, either by an on-line optical probe or a UV and/or PL spectrum determined from a portion of the reaction solution from the reaction solution, the temperature may or may not be lowered by about 30-40 ℃, and the mixture is subjected to a "size-concentration" for a period of 10 minutes to 72 hours.

The formed nanoparticles may be further subjected to successive treatments to form core-shell or core-multishell particles. Either before or after nanoparticle isolation, core-shell particle preparation is performed, whereby the nanoparticles are isolated from the reaction and redissolved in new (clean) capping reagent, as this results in better quantum yield. The source for N and the source for the Y precursor are added to the reaction mixture and the core-shell particles of ME/NY core-shell material can be formed either as two separate precursors, one containing N and the other containing Y, or as a single source precursor containing both N and Y in a single molecule.

The process can be repeated with the appropriate elemental precursors until the desired core-multishell material is formed. The nanoparticle size and size distribution in the population of particles is determined by the growth time, temperature and reactant concentration in the solution, with higher temperatures producing larger nanoparticles.

Cluster type for vaccination

The present invention involves the use of molecular clusters, where the clusters used are the same molecular entities as compared to the nanoparticles, which inherently lack the featureless nature of the molecular clusters in the collection. The clusters act as "embryo-type" templates for nanoparticle growth, whereby other molecular source precursors provide ions for the growth process and thus the clusters subsequently grow into particles. The molecular clusters to be used may consist of: -

The presence or absence of other elements plus organic moieties in the two elements essential for the interior of the nanoparticle to be grown;

one element, with or without the addition of an organic moiety to the other element, necessary for the interior of the nanoparticle to be grown;

neither the elements essential for the interior of the nanoparticle to be grown, nor the presence or absence of other elements plus organic moieties;

the requirement of the clusters used is to cause particle growth either via consumption of other clusters or reaction with the precursors present. In this way, the clusters can be used as templates for particle growth.

Examples of clusters used include, but are not limited to: -

IIB-VIB：-[{(PPh₃)Hg}₄(SPh)₆]：(Ph₄P)₂[(SEt)₅(Br)(HgBr)₄]：(Ph₄P)₂[Hg₄(SEt)₅Br]：[Hg₄Te₁₂][N(CH₂CH₂Et)₄]₄

IIB-VIB：-[Et₃NH]₄[Cd₁₀Se₄(SPh)₁₆]；[RME^tBu]₅ M＝Zn，Cd，Hg；E＝S，Se，Te；R＝Me，Et，Ph：[X]₄[E₄M₁₀(SR)₁₆]E＝S，Se，Te，M＝Zn，Cd，Hg；X＝Me₃NH⁺，Li⁺Et₃NH⁺：[Cd₃₂S₁₄(SPh)₃₆]L：[Hg₁₀Se₄(SePh)(PPh₂ ⁿPr)₄]；[Hg₃₂Se₁₄(SePh)₃₆]；[Cd₁₀Se₄(SePh)₁₂(PPr₃)₄]；[Cd₃₂Se₁₄(SePh)₃₆(PPh₃)₄]；[M₄(SPh)₁₂]⁺[X]₂ ^-M＝Zn，Cd，Hg；X＝Me₄N⁺，Li⁺：[Zn(SEt)Et]₁₀：[MeMEiPr]M＝Zn，Cd，Hg；E＝S，Se，Te：[RCdSR’]₅ R＝O(ClO₃)，R’＝PPh₃，ⁱPr：[Cd₁₀E₄(E’Ph)₁₂(PR₃)₄]E，E’＝Te，Se，S：[Cd₈Se(SePh)₁₂Cl₄]^2-：[M4Te₁₂]^4-M＝Cd，Hg：[Ph₁₂M₁₈Cd₁₀(PEt₃)₃]M＝Te，Se：II-V：-[RCdNR’]₄ R＝Cl，Br，I，PEt₃Or C ═ CSME₃；R’＝PEt₃，I：[RCdNR’]₅R ═ alkyl or aryl and R ═ alkyl or aryl: [ { RZn }₆{PR’}₄]R ═ I or PEt₂Ph，R’＝

SiMe₃：[M₄Cl₄(PPh₂)₄(PⁿPr₃)₂] M＝Zn，Cd：[Li(thf)₄]₂[(Ph₂P)₁₀Cd₄]：

[Zn₄(PPh₂)₄Cl₄(PRR₂’)₂]PRR’₂＝PMeⁿPr₂，PⁿBu₃，PEt₂Ph：[Zn₄(P^tBu₂)₄Cl₄]

III-V[EtGaNEt]₆；[MeGaN(4-C₆H₄F)]₆；(MeGaNiBu)₆；[RAlNR’]₄ R＝Me，CH₂PRⁱ，

Ph；R’＝Prⁱ，CH₂Prⁱ，C₆H₂Me₃；[(SiPrⁱ ₃)₃AsAlH]₆；[ⁱPrNAlH]₄；[RAlNR’]₆ R＝Me，

Et，Cl，CH₂Ph，CH₂Prⁱ，Ph；R’＝Me H，Br，C＝CPh，Prⁱ，(CH₂)₂Me，(CH₂)2NMe₂，

SiPh₃：[CH₃Ga-NCH₂CH(CH₃)₂]₆：[MeGaNⁱBu]₆：[RGaNR’]₄ R＝Ph，Me；R’＝Ph，

C₆F₅，SiMe₃，^tBu：[EtGaNEt]₆：[RGaPR’]₄ R＝ⁱPr，C₆H₂Me₃；R’＝^tBu：C₆H₂Me₃：

[RNInR’]₄ R＝Cl，Br，I，Me；R’＝^tBu，C₆F₅，C₆H₄F：[RInPR’]₄ R＝ⁱPr，C₆H₂Me₃，Et；

R’＝SiPh₃，C₆H₂Me₃，SiⁱPr₃：[RInPR’]₆ R＝Et，R’＝SiMe₂(CMe₂ ⁱPr)

III-VI[(^tBu)GaSe]₄；[^tBuGaS]₇；[RInSe]₄ R＝^tBu，CMe₂Et，Si(^tBu)₃，C((SiMe₃)₃)₃；

[RInS]₄ R＝^tBu，CMe₂Et；[RGaS]₄ R＝^tBu， CMe₂Et，CEt₃：[SAlR’]₄ R＝C(SMe₃)₃，

CEtMe₂：[SAlNMe₃]₅：[TeAIR]4 R＝Cp^*，CEtMe₂：[(C(SiMe₃)₃)GaS]₄：[^tBuGaS]₆：

[RGaSe]₄ R＝^tBu，CMe₂Et，CEt₃，C(SiMe₃)₃，Cp^*，Bu：

Cd₄In₁₆S₃₃.(H₂O)₂₀(C₁₀H₂₈N₄)_2.5：

IV-VI[S₆{SnR}₄]R＝C(SiMe₃)₃，Me，Ph；[Se₆{SnR}₄]R＝C₆F₅，C₆H₂Me₃，p-Tol，

C(SiMe₃)₃

Materials composed of a first element from any group of the transition metals of the periodic table and a second element from any group of the d-block elements include, but are not limited to: - [ Cu₁₂Se₆(PR₃)₈]R＝Et₂Ph，

ⁿPr₃，Cy₃；[Cu₁₈Te₆(^tBu)₆(PPh₂Et)₇]；[Cu₁₉Te₆(^tBu)₇(PEt₃)₈]；

[Cu₂₇Te₁₅(PⁱPr₂Me)₁₂]；[Ni₃₄Se₂₂(PPh₃)₁₀]；[Ag₃₀(TePh)₁₂Te₉(PEt₃)₁₂]；

[Ag₃₀Se₈(Se^tBu)₁₄(PnPr₃)₈]；[Co₄(μ₃-Se)₄(PPh₃)₄]；[Co₆(μ₃-Se)₈(PPh₃)₆]；

[W₃Se₄(dmpe)₃Br₃]⁺；Ru₄Bi₂(CO)₁₂；Fe₄P₂(CO)₁₂；Fe₄N₂(CO)₁₂

M source

For Element (ME)_nL_mCompound semiconductor nanoparticles of composition, a source of element M is further added to the reaction and may be composed of any M-containing species capable of providing a source of M ions for growth of the particles. The precursor may be, but is not limited to, composed of an organometallic compound, an inorganic salt, a coordination compound, or the element.

Examples of II-VI, III-V, III-VI, or IV-V for the first element include, but are not limited to:

organometallic compounds such as, but not limited to, MR₂Wherein M ═ Mg, R ═ alkyl or aryl (Mg)^tBu₂)；MR₂Wherein M is Zn, Cd, Te; r ═ alkyl or aryl (Me)₂Zn，Et₂Zn Me₂Cd，Et₂Cd)；MR₃Wherein M ═ Ga, In, Al, B; r ═ alkyl or aryl [ AlR ]₃，GaR₃，InR₃(R＝Me，Et，ⁱPr)]。

Coordination compounds such as carbonates but not limited to MCO₃M ═ Ca, Sr, Ba, [ magnesium carbonate hydroxide [ (MgCO)₃)₄·Mg(OH)₂]；M(CO₃)₂ M＝Zn，Cd，；MCO₃M ═ Pb: acetate salt: m (CH)₃CO₂)₂M＝Mg，Ca，Sr，Ba；Zn，Cd，Hg；M(CH₃CO₂)₃M ═ B, Al, Ga, In: beta-diketonates or derivatives thereof, e.g. acetylacetonate (2, 4-pentanedionate) M [ CH₃COCH＝C(O^-)CH₃]₂ M＝Mg，Ca，Sr，Ba，Zn，Cd，Hg；M[CH₃COCH＝C(O^-)CH₃]₃M ═ B, Al, Ga, In. Oxalate SrC₂O₄，CaC₂O₄，BaC₂O₄，SnC₂O₄. Hydroxide M (OH)₂M ═ Mg, Ca, S r, Ba, Zn, Cd, Hg, e.g. Cd (OH)₂. Stearate M (C)₁₇H₃₅COO)₂ M＝Mg，Ca，Sr，Ba，Zn，Cd，Hg。

Inorganic salts such as, but not limited to, oxides SrO, ZnO, CdO, In₂O₃、Ga₂O₃、SnO₂、PbO₂(ii) a Nitrate salt Mg (NO)₃)₂、Ca(NO₃)₂、Sr(NO₃)₂、Ba(NO₃)₂、Cd(NO₃)₂、Zn(NO₃)₂、Hg(NO₃)₂、Al(NO₃)₃、In(NO₃)₃、Ga(NO₃)₃、Sn(NO₃)₄、Pb(NO₃)₂

Elements Mg, Ca, Sr, Ba, Zn, Cd, Hg, B, Al, Ga, In, Sn, Pb.

E source

For Element (ME)_nL_mCompound semiconductor nanoparticles of composition, a source of element E is further added to the reaction and may be composed of any E-containing species capable of providing a source of E ions for growing particles. The precursor may be composed of, but is not limited to, organometallic compounds, inorganic salts, coordination compounds, or elemental sources. Examples for II-VI, III-V, III-VI or IV-V semiconductors are second elements including, but not limited to: -

Organometallic compounds such as, but not limited to NR₃、PR₃、AsR₃、SbR₃(R＝Me，Et，^tBu，ⁱBu，PrⁱPh, etc.); NHR₂、PHR₂、AsHR₂、SbHR₂(R＝Me，Et，^tBu，ⁱBu，PrⁱPh, etc.); NH (NH)₂R、PH₂R、AsH₂R、SbH₂R₃(R＝Me，Et，^tBu，ⁱBu，PrⁱPh, etc.); PH value₃、AsH₃；M(NMe)₃M ═ P, Sb, As; dimethylhydrazine (Me)₂NNH₂) (ii) a Ethyl azide (Et-NNN); hydrazine (H)₂NNH₂)；Me₃SiN₃。

MR₂(M＝S，Se Te；R＝Me，Et，^tBu，ⁱBu, etc.); HMR (M ═ S, Se Te; R ═ Me, Et,^tBu，ⁱBu，ⁱpr, Ph, etc.); thiourea S ═ C (NH)₂)₂；Se＝C(NH₂)₂。

Sn(CH₄)₄、Sn(C₄H₉)、Sn(CH₃)₂(OOCH₃)₂。

Coordination compounds such as, but not limited to, carbonate, MCO₃M ═ P, bismuth subcarbonate (BiO)₂CO₃；M(CO₃)₂(ii) a Acetate salt M (CH)₃CO₂)₂ M＝S，Se，Te：M(CH₃CO₂)₂M ═ Sn, Pb, or M (CH)₃CO₂)₄M ═ Sn, Pb: beta-diketonates or derivatives thereof, e.g. acetylacetonate (2, 4-pentanedionate) [ CH₃COCH＝C(O^-)CH₃]₃M M＝Bi；[CH₃COCH＝C(O^-)CH₃]₂M M＝S，Se，Te：[CH₃COCH＝C(O^-)CH₃]₂M M ═ Sn, Pb: thiourea, selenourea (H)₂NC(＝Se)NH₂。

Inorganic salts such as, but not limited to, oxides P₂O₃、As₂O₃、Sb₂O₃、Sb₂O₄、Sb₂O₅、Bi₂O₃、SO₂、SeO₂、TeO₂、Sn₂O、PbO、PbO₂(ii) a Nitrate salt Bi (NO)₃)₃、Sn(NO₃)₄、Pb(NO₃)₂

Elements: sn, Ge, N, P, As, Sb, Bi, S, Se, Te, Sn, Pb.

The invention is illustrated by the following non-limiting examples and figures, in which

FIG. 1) is a view of a) core particles composed of a CdSe core and HDA as organic capping agent, b) core-shell particles composed of a CdSe core, a ZnS shell and HDA as organic capping agent, c) core-multi-shell organic capping particles composed of a CdSe core, a HgS shell followed by a ZnS shell and HDA capping agent;

fig. 2) molecular clusters used as inoculants: a) zn₁₀(SEt)₁₀Et₁₀；b)[RGaS]₄；c)[Bu^tGaS]₇；d)[RInSe]₄(ii) a And e) [ X ]]₄[M₁₀Se₄(SPh)₁₆]X is cation, M is Zn, Cd, Te;

FIG. 3) formation of cadmium selenide quantum dots using [ M ]₁₀Se₄(SPh)₁₆][X]₄ X＝Li⁺Or (CH)₃)₃NH⁺、Et₃NH⁺As molecular seeds and cadmium acetate and tri-n-octyl phosphine selenide as cadmium and selenium source precursors, and hexadecylamine as a capping reagent;

FIG. 4) formation of gallium sulfide quantum dots using [ alpha ], [ beta ], [ alpha^tBuGaS]₇As molecular seeds and gallium (II) acetylacetonate and tri-n-octylphosphine sulfide as gallium and sulfur source precursors, and hexadecylamine as a capping agent;

fig. 5) formation of indium selenide quantum dots using indium acetylacetonate (I1) and tri-n-octylphosphine sulfide as indium and selenium source precursors as molecular seeds and hexadecylamine and tri-n-octylphosphine oxide as capping agents;

FIG. 6) formation of Zinc sulfide Quantum dots with Zn₁₀(SEt)₁₀Et₁₀As molecular seeds and zinc acetate and tri-n-octylphosphine sulfide as zinc and sulfur source precursors, and hexadecylamine as a capping agent;

FIG. 7) the development of PL spectra of CdSe nanoparticles as the nanoparticles become larger during growth. From [ Et in HDA according to example 1₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPSe/Cd(CH₃CO₂)₂Preparing;

FIG. 8) the development of PL spectra of CdSe nanoparticles as the nanoparticles become larger during growth. From [ Et in HDA according to example 2₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPSe/Cd(CH₃CO₂)₂Preparing;

FIG. 9) the development of PL spectra of CdSe nanoparticles as the nanoparticles become larger during growth. From [ Et in HDA according to example 3₃NH]₄[Cd₁₀Se₄(SPh)₁₆]Preparation of/TOP/Se/CdO;

FIG. 10) the development of PL spectra of CdSe nanoparticles as the nanoparticles become larger during growth. From [ Et in HDA according to example 4₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPSe/Cd(OH)₂Preparing;

FIG. 11) the development of PL spectra of CdSe nanoparticles as the nanoparticles become larger during growth. From [ Et in HDA according to example 5₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPSe/Me₂Preparing Cd;

FIG. 12) PL Spectrum emission of CdSe nanoparticles as the nanoparticles become larger during growthAnd (5) unfolding. From [ Et in HDA according to example 7₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPSe/(C₁₇H₃₅COO)₂Preparing Cd;

FIG. 13) the development of PL spectra of CdSe nanoparticles as the nanoparticles become larger during growth. From [ Et in HDA according to example 8₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPSe/CdCO₃Preparing;

FIG. 14) the development of PL spectra of CdTe nanoparticles as the nanoparticles become larger during growth. According to example 9 from HDA as in TOP/Cd (CH)₃CO₂)₂Of the intermediate slurry [ Et₃NH]₄[Cd₁₀Se₄(SPh)₁₆]And preparing/Te.

Examples

All syntheses and manipulations were carried out under a dry, oxygen-free argon or nitrogen atmosphere using standard Schlenk or glove box techniques. All solvents (Na/K-benzophenone for THF, Et)₂O, toluene, hexane and pentane) are distilled from a suitable desiccant prior to use. HDA, octylamine, TOP, Cd (CH)₃CO₂)₂Selenium powder, CdO, CdCO₃(Adrich) was obtained commercially and used without further purification.

UV-vis absorption spectra were measured on a He λ ios β Thermospectronic. Photoluminescence (PL) spectra were measured at an excitation wavelength of 380nm using a Fluorolog-3(FL3-22) spectrometer (photospectrometer). Using a monochromatic Cu-K on a Bruker AXS D8 diffractometer_αThe radiation was subjected to powder X-ray diffraction (PXRD) measurements.

For all methods, the entire sealant solution was dried and degassed under dynamic vacuum (dynamic vacuum) for at least 1 hour prior to use by heating the mixture to 120 ℃. The reaction mixture is then cooled to a temperature suitable for that particular reaction before any seeding agent or growth precursor is added to the solution.

Preparation of clusters

[HNEt₃]₂[Cd₄(SPh)₁₀]Preparation of

Cd (NO) which had been previously dissolved in methanol (60mL)₃)₂·4H₂O (21.00g, 68.00mmoL) was added dropwise to a stirred solution of benzenethiol (20.00g, 182mmoL) and triethylamine (18.50g, 182mmoL) in methanol (60 ml). The solution was then stirred while warm until the precipitate was completely dissolved leaving a clear solution. It was then left to stand at 5 ℃ for 24 hours, during which time [ HNEt formed₃]₂[Cd₄(SPh)₁₀]Large and colorless crystals. FW is 1745.85. C₇₂H₈₂N₂S₁₀Cd₄C49.53, H4.70, N1.61, S18.37, Cd 25.75%; found C-49.73, H-4.88, N-1.59, S-17.92%

[HNEt₃]₄[Cd₁₀Se₄(SPh)₁₆]Preparation of

This is achieved by analogy with the general principles of Dance et al³⁶The described process proceeds.

3.57g 45.21mmol selenium powder was added to the stirred [ HNEt₃]₂[Cd₄(SPh)₁₀](80.00g, 45.58mmol) in acetonitrile (100ml) and the resulting slurry was kept stirring for 12 hours, which yielded a white precipitate. An additional 750ml of acetonitrile was added and the solution was warmed to 75 ℃ to give a clear pale yellow solution which was cooled to 5 ℃ to give large colorless crystals. The crystals were washed in hexane and recrystallized from hot acetonitrile. 22.50g of [ HNEt ] were obtained₃]₄[Cd₁₀Se₄(SPh)₁₆]。FW＝3595.19，C₁₂₀H₁₄₄N₄Se₄S₁₆Cd₁₀C is 40.08, H is 4.00, N is 1.56, S is 14.27, Se is 8.78, Cd is 31.26%; found value of C40.04, H4.03, N1.48,S＝14.22，Cd＝31.20％。

example 1

From [ Et in HDA₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPSe/Cd(CH₃CO₂)₂Preparation of CdSe nanoparticles

HDA (300g) was placed in a three-neck flask and dried/degassed by heating to 120 ℃ under dynamic vacuum for 1 hour. The solution was then cooled to 70 ℃. To this solution, 1.0g of [ Et ] was added₃NH]₄[Cd₁₀Se₄(SPh)₁₆](0.311mmol), TOPSe (20ml, 40.00mmol) [ prepared by dissolving selenium powder in TOP beforehand]And Cd (CH)₃CO₂)₂(10.66g 40.00mmol) and the temperature of the reaction mixture was gradually raised from 70 ℃ to 180 ℃ over a period of 8 hours. The progressive formation/growth of the nanoparticles was monitored with their emission wavelength by sampling from the reaction mixture and determining their UV-vis and PL spectra. When the emission spectrum reached 572nm, the reaction was terminated by cooling the reaction to 60 ℃ followed by the addition of 200ml of dry "warm" ethanol, which resulted in the precipitation of the nanoparticles. The resulting CdSe were dried and then redissolved in toluene, filtered through celite, and then reprecipitated from warm ethanol to remove any excess HDA and Cd (CH)₃CO₂)₂. This produced 9.26g of HDA-blocked CdSe nanoparticles.

Example 2

From [ Et in HDA₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPSe/Cd(CH₃CO₂)₂Preparation of CdSe sodium

Rice grains

HDA (250g) and octylamine (20g) were placed in a three-necked flask and dried/degassed by heating to 120 ℃ under dynamic vacuum for 1 hour. The solution was then cooled to 70 ℃. To this solution, 1.0g of [ Et ] was added₃NH]₄[Cd₁₀Se₄(SPh)₁₆](0.311mmol), TOPSe (1M, 4ml, 4.00mmol) [ prepared by dissolving selenium powder in TOP]And Cd (CH) dissolved in TOP₃CO₂)₂(0.5M, 4ml, 2.00mmol) and the temperature of the reaction mixture was gradually increased from 70 ℃ to 150 ℃ over a period of 1 hour. A further 17ml (17.00mmol) of TOPSe and 27ml of 0.5M Cd (CH) dissolved in TOP (13.50mmol)₃CO₂)₂Added dropwise while gradually increasing the temperature to 200 ℃ over a period of 24 h. The progressive formation/growth of the nanoparticles was monitored with their emission wavelength by sampling from the reaction mixture and determining their UV-vis and PL spectra. When the emission spectrum reached the desired size of 630nm, the reaction was terminated by cooling the reaction to 60 ℃ followed by the addition of 200ml of dry "warm" ethanol, which resulted in the precipitation of nanoparticles. The resulting CdSe was dried and then redissolved in toluene, filtered through celite, and then reprecipitated from warm ethanol to remove any excess HDA. This produced 4.56g of HDA-blocked CdSe nanoparticles.

Example 3

From [ Et in HDA₃NH]₄[Cd₁₀Se₄(SPh)₁₆]Preparation of CdSe nanoparticles from/TOP/Se/CdO

HDA (150g) and tert-decylphosphonic acid (0.75g) were placed in a three-necked flask and dried/degassed by heating to 120 ℃ under dynamic vacuum for 1 hour. The solution was then cooled to 80 ℃. To this solution, 0.5g of [ Et ] was added₃NH]₄[Cd₁₀Se₄(SPh)₁₆](0.156mmol), 20ml of TOP, 0.6g of selenium powder (7.599mmol) and 0.8g of CdO (6.231mmol), the reaction mixture was stirred to give a pale yellow turbid mixture. The temperature of the reaction mixture was gradually increased from 80 ℃ to 250 ℃ over a period of 24 hours. The progressive formation/growth of the nanoparticles is followed by their emission wavelength by sampling from the reaction mixture and determining their UV-vis and PL spectra. When the emission spectrum reached the desired size (593nm), the reaction was stopped by cooling the reaction to 60 ℃ followed by the addition of 200ml ofThe "warm" ethanol was dried, which resulted in precipitation of the nanoparticles. The resulting CdSe was dried and then redissolved in toluene, filtered through celite, and then reprecipitated from warm ethanol to remove any excess HDA. This produced 1.55g of HDA-blocked CdSe nanoparticles.

Example 4

From [ Et in HDA₃NH]₄[Cd₁₀Se₄(SPh)₁₆]Preparation of CdSe nanoparticles from/TOPSe/CdO

HDA (400g) was placed in a three-neck flask and dried/degassed by heating to 120 ℃ under dynamic vacuum for 1 hour. The solution was then cooled to 70 ℃. To this solution, 1.00g of [ Et ] was added₃NH]₄[Cd₁₀Se₄(SPh)₁₆](0.278mmol), 20.0ml of TOPSe (2M solution) and 5.85g of Cd (OH)₂(40.00mmol) and the reaction mixture was stirred to give a pale yellow turbid mixture. The temperature of the reaction mixture was gradually increased from 70 ℃ to 240 ℃ over a period of 24 hours. The progressive formation/growth of the nanoparticles was followed by their emission wavelength by sampling from the reaction mixture and determining their UV-vis and PL spectra. When the emission spectrum reached the desired size (609nm), the reaction was terminated by cooling the reaction to 60 ℃ followed by the addition of 200ml of dry "warm" ethanol, which resulted in the precipitation of the nanoparticles. The resulting CdSe was dried and then redissolved in toluene, filtered through celite, and then reprecipitated from warm ethanol to remove any excess HDA. This produced 10.18g of HDA-blocked CdSe nanoparticles.

Example 5

From [ Et in HDA₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPSe/Me₂Preparation of CdSe nanoparticles with Cd

HDA (100g) was placed in a three-neck flask and dried/degassed by heating to 120 ℃ under dynamic vacuum for 1 hour. The solution was then cooled to 70 ℃. To this solution, 0.13g of [ Et ] was added₃NH]₄[Cd₁₀Se₄(SPh)16](0.036mmol), 2.5ml of TOPSe (2M solution) and 0.71g of Me₂Cd [ which had been pre-dissolved in TOP) (0.358ml, 5.00mmol), the reaction mixture was stirred. The temperature of the reaction mixture was gradually increased from 80 ℃ to 260 ℃ over a period of 24 hours. The progressive formation/growth of the nanoparticles was followed by their emission wavelength by sampling from the reaction mixture and determining their UV-vis and PL spectra. When the emission spectrum reached the desired size (587nm), the reaction was terminated by cooling the reaction to 60 ℃ followed by the addition of 100ml of dry "warm" ethanol, which resulted in the precipitation of nanoparticles. The resulting CdSe was dried and then redissolved in toluene, filtered through celite, and then reprecipitated from warm ethanol to remove any excess HDA. This produced 1.52g of HDA-blocked CdSe nanoparticles.

Example 6

HDA (100g) was placed in a three-neck flask and dried/degassed by heating to 120 ℃ under dynamic vacuum for 1 hour. The solution was then cooled to 70 ℃. To this solution, 0.13g of [ Et ] was added₃NH]₄[Cd₁₀Se₄(SPh)₁₆](0.036 mmol). The temperature was then increased to 100 ℃ and maintained at this temperature, while 2.5ml of TOPSe (2M solution) and 0.71g of Me were added dropwise over a period of 4 hours₂Cd [ which had been previously dissolved in TOP) (0.358ml, 5.00 mmol). The progressive formation/growth of the nanoparticles was followed by their emission wavelength by sampling from the reaction mixture and determining their UV-vis and PL spectra. When the emission spectrum reaches the desired size (500nm), the reaction is terminated by cooling the reaction to 60 ℃ followed by the addition of 100ml of dry "warm" ethanol, which produces the precipitation of the nanoparticles. The resulting CdSe was dried and then redissolved in toluene, filtered through celite, and then reprecipitated from warm ethanol to remove any excess HDA. This results in1.26g of HDA-blocked CdSe nanoparticles were used.

Example 7

From [ Et in HDA₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPSe/(C₁₇H₃₅COO)₂Preparation of CdSe nanoparticles with Cd

HDA (200g) was placed in a three-neck flask and dried/degassed by heating to 120 ℃ under dynamic vacuum for 1 hour. The solution was then cooled to 80 ℃. To this solution, 0.5g of [ Et ] was added₃NH]₄[Cd₁₀Se₄(SPh)₁₆](0.139mmol), 20ml of TOPSe (2M solution) and 2.568g of CdO (20mmol) solution which had been dissolved beforehand in stearic acid (steric acid) (23.00g), the reaction mixture was stirred to give a pale yellow clear solution. The temperature of the reaction mixture was gradually increased from 70 ℃ to 220 ℃ over a period of 24 hours. The progressive formation/growth of the nanoparticles was followed by their emission wavelength by sampling from the reaction mixture and determining their UV-vis and PL spectra. When the emission spectrum reaches the desired size (590nm), the reaction is terminated by cooling the reaction to 60 ℃ followed by the addition of 400ml of dry "warm" ethanol, which produces the precipitation of the nanoparticles. The resulting CdSe was dried and then redissolved in toluene, filtered through celite, and then reprecipitated from warm ethanol to remove any excess HDA. This produced 4.27g of HDA-blocked CdSe nanoparticles.

Example 8

From [ Et in HDA₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPSe/CdCO₃Preparation of CdSe nanoparticles

HDA (50g) was placed in a three-neck flask and dried/degassed by heating to 120 ℃ under dynamic vacuum for 1 hour. The solution was then cooled to 75 ℃. To this solution, 0.5g of [ Et ] was added₃NH]₄[Cd₁₀Se₄(SPh)₁₆](0.156mmol), TOPSe (1.0M, 5ml, 5.00mmol) [ selenium powder dissolvedPrepared beforehand by dissolving in TOP]And CdCO dissolved in TOP₃(0.5M, 5ml, 2.5mmol) and the temperature of the reaction mixture was gradually raised from 70 ℃ to 200 ℃ over a period of 48 hours. The progressive formation/growth of the nanoparticles was monitored with their emission wavelength by sampling from the reaction mixture and determining their UV-vis and PL spectra. When the emission spectrum reached the desired size (587nm), the reaction was terminated by cooling the reaction to 60 ℃ followed by the addition of 200ml of dry "warm" ethanol, which resulted in the precipitation of nanoparticles. The resulting CdSe was dried and then redissolved in toluene, filtered through celite, and then reprecipitated from warm ethanol to remove any excess HDA. This produced 0.95g of HDA-blocked CdSe nanoparticles.

Example 9

From [ Et in HDA₃NH]₄[Cd₁₀Se₄(SPh)₁₆]/TOPTe/Cd(CH₃CO₂)₂Preparation of CdTe nanoparticles

HDA (200g) was placed in a three-neck flask and dried/degassed by heating to 120 ℃ under dynamic vacuum for 1 hour. The solution was then cooled to 70 ℃. To this solution, 1.0g of [ Et ] was added₃NH]₄[Cd₁₀Se₄(SPh)₁₆](0.311mmol), tellurium (2.55g, 20.00mmol) and Cd (CH)₃CO₂)₂(4.33g, 20.00mmol) of TOP brown slurry (20 ml). The temperature of the reaction mixture was gradually increased from 70 ℃ to 160 ℃ over a period of 8 hours. The progressive formation/growth of the nanoparticles was monitored with their emission wavelength by sampling from the reaction mixture and determining their UV-vis and PL spectra. When the emission spectrum reached the desired size (624nm), the reaction was terminated by cooling the reaction to 60 ℃ followed by the addition of 200ml of dry "warm" ethanol, which resulted in the precipitation of the nanoparticles. The resulting CdTe was dried and then redissolved in toluene, filtered through celite, and then reprecipitated from warm ethanol to remove any excess HDA. This produced 6.92g of HDA blocked CdTe nanoparticles.

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Claims

1. A method of producing nanoparticles, the method comprising effecting conversion of a nanoparticle precursor composition to the nanoparticle material, the precursor composition comprises a first precursor species comprising a first ion to be incorporated into the growing nanoparticles and a separate second precursor species comprising a second ion to be incorporated into the growing nanoparticles, wherein the conversion is carried out in the presence of a molecular cluster compound under conditions permitting seeding and growth of the nanoparticles, wherein the molecular cluster compound and nanoparticle precursor composition are dissolved in a solvent at a first temperature to form a solution, the temperature of the solution is then increased to a second temperature sufficient to cause seeding and growth of nanoparticles on the molecular clusters of the compound, the first temperature is a temperature in the range of 50 ℃ to 100 ℃ and the second temperature is a temperature in the range of 120 ℃ to 280 ℃.

2. A method according to claim 1, wherein the ratio of the number of moles of cluster compound to the total number of moles of said first and second precursor species is in the range 0.0001-0.1: 1.

3. A method according to claim 1, wherein the ratio of the number of moles of cluster compound to the total number of moles of said first and second precursor species is in the range 0.001-0.1: 1.

4. A method according to claim 1, wherein the molar ratio of the first precursor species to the second precursor species is in the range of 100-1: 1.

5. A method according to claim 1, wherein the molar ratio of the first precursor species to the second precursor species is in the range 50-1: 1.

6. A method according to claim 2, wherein the molar ratio of the first precursor species to the second precursor species is in the range of 100-1: 1.

7. A method according to claim 2, wherein the molar ratio of the first precursor species to the second precursor species is in the range 50-1: 1.

8. A method according to claim 3, wherein the molar ratio of the first precursor species to the second precursor species is in the range of 100-1: 1.

9. A method according to claim 3, wherein the molar ratio of the first precursor species to the second precursor species is in the range 50-1: 1.

10. The method according to claim 1, wherein the solvent is a lewis base coordination compound selected from the group consisting of a phosphine, a phosphine oxide, and an amine.

11. The method according to claim 1, wherein the solvent is a non-coordinating solvent.

12. A method according to any one of claims 1 to 11, wherein the first temperature is in the range of from 70 ℃ to 80 ℃.

13. The method according to any one of claims 1 to 11, wherein the first temperature is about 75 ℃.

14. A method according to any one of claims 1 to 11, wherein the second temperature is in the range 150 ℃ to 250 ℃.

15. The method according to any one of claims 1 to 11, wherein the second temperature is about 200 ℃.

16. A method according to any one of claims 1 to 11, wherein the temperature of the solution is increased from the first temperature to the second temperature over a time period of up to 48 hours.

17. A method according to any one of claims 1 to 11, wherein the temperature of the solution is increased from the first temperature to the second temperature over a time period of up to 24 hours.

18. A method according to any one of claims 1 to 11, wherein the temperature of the solution is increased from the first temperature to the second temperature over a time period of 1 hour to 24 hours.

19. A method according to any one of claims 1 to 11, wherein the temperature of the solution is increased from the first temperature to the second temperature over a time period of 1 hour to 8 hours.

20. A method according to any one of claims 1 to 11, wherein the method comprises monitoring the average size of the nanoparticles grown; and terminating nanoparticle growth when the average nanoparticle size reaches a predetermined value.

21. A method in accordance with claim 20, wherein nanoparticle growth is terminated by lowering the temperature of the solution from the second temperature to a third temperature.

22. The method according to claim 21, wherein the third temperature is in the range of 50 ℃ to 70 ℃.

23. The method of claim 21, wherein the third temperature is about 60 ℃.

24. A method according to any one of claims 1 to 11, wherein the method comprises forming a precipitate of the nanoparticle material by addition of a precipitating agent.

25. A method according to any one of claims 1 to 11, wherein the first precursor species is selected from the group consisting of organometallic compounds, inorganic salts and coordination compounds.

26. The method according to claim 25, wherein the inorganic salt is selected from the group consisting of an oxide, a nitrate, and a carbonate.

27. The method according to claim 1, wherein the first precursor substance is obtained by dissolving an element source selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Cd, Hg, B, Al, Ga, In, Sn, and Pb In a suitable solvent.

28. The method of claim 1, wherein the second precursor species is selected from the group consisting of organometallic compounds, inorganic salts, and coordination compounds.

29. The method according to claim 28, wherein the inorganic salt is selected from the group consisting of an oxide, a nitrate, and a carbonate.

30. The method according to claim 1, wherein the second precursor substance is obtained by dissolving an element source selected from the group consisting of Sn, Ge, N, P, As, Sb, Bi, S, Se, Te, Sn, and Pb in a suitable solvent.

31. A method in accordance with claim 1, wherein said molecular cluster compound comprises third and fourth ions to be incorporated into the growing nanoparticles.

32. The method of claim 31, wherein the third ion is selected from group 12 of the periodic table and the fourth ion is selected from group 16 of the periodic table.

33. The method of claim 32, wherein the molecular cluster compound comprises molecules selected from the group consisting of: [ { (PPh)₃)Hg}₄(SPh)₆]，(Ph₄P)₂[(SEt)₅(Br)(HgBr)₄]，(Ph₄P)₂[Hg₄(SEt)₅Br]，[Hg₄Te₁₂][N(CH₂CH₂Et)₄]₄，[Et₃NH]₄[Cd₁₀Se₄(SPh)₁₆]，[RME^tBU]₅Wherein M ═ Zn, Cd or Hg, E ═ S, Se or Te, and R ═ Me or Et, [ X ]]₄[E₄M₁₀(SR)₁₆]Where M is Zn, Cd or Hg, E is S, Se or Te, and X is Me₃NH⁺、Li⁺Or Et₃NH⁺And R ═ Me, Et or Ph, [ Cd ]₃₂S₁₄(SPh)₃₆]L, wherein L ═ is a coordinating ligand, [ Hg ═₁₀Se₄(SePh)(PPh₂ ⁿPr)₄]，[Hg₃₂Se₁₄(SePh)₃₆]，[Cd₁₀Se₄(SePh)₁₂(PPr₃)₄]，[Cd₃₂Se₁₄(SePh)₃₆(PPh₃)₄]，[M₄(SPh)₁₂]⁺[X]₂ ^-Where M ═ Zn, Cd or Hg, and X ═ Me₄N⁺、Li⁺，[Zn(SEt)Et]₁₀，[MeMEⁱPr]Wherein M ═ Zn, Cd, or Hg and E ═ S, Se or Te, [ RCdSR']₅Wherein R ═ O (ClO)₃)、R’＝PPh₃OrⁱPr，[Cd₁₀E₄(E’Ph)₁₂(PR₃)₄]Where E ═ Te, Se or S, E ═ Te, Se or S and R ═ is the coordinating ligand, [ Cd ═ Te, [ Se ] or S₈Se(SePh)₁₂C₁₄]^2-，[M₄Te₁₂]^4-Where M ═ Cd or Hg, and [ Ph₁₂M₁₈Cd₁₀(PEt₃)₃]Where M ═ Te or Se.

34. The method of claim 31, wherein the third ion is selected from group 12 of the periodic table and the fourth ion is selected from group 15 of the periodic table.

35. The method according to claim 34, wherein said molecular cluster compound comprises molecules selected from the group consisting of: [ RCdNR']₄Wherein R ═ Cl, Br, I, PEt₃Or C ═ CSME₃And R' ═ PEt₃Or l, [ RCdNR']₅Wherein R ═ alkyl or aryl and R ═ alkyl or aryl, [ { RZn }₆{PR’}₄]Wherein R ═ I or PEt₂Ph and R' ═ SiMe₃，[M₄Cl₄(PPh₂)₄(PⁿPr₃)₂]Where M is Zn or Cd, [ Li (thf)₄]₂[(Ph₂P)₁₀Cd₄]，[Zn₄(PPh₂)₄Cl₄(PRR₂’)₂]Wherein PRR'₂＝PMeⁿPr₂、PⁿBu₃Or PEt₂Ph, and [ Zn ]₄(P^tBu₂)₄Cl₄]。

36. The method of claim 31, wherein the third ion is selected from group 13 of the periodic table and the fourth ion is selected from group 15 of the periodic table.

37. The method of claim 36, wherein the molecular cluster compound comprises molecules selected from the group consisting of: [ EtGaNEt]₆，[MeGaN(4-C₆H₄F)]₆，(MeGaNiBu)₆，[RAlNR’]₄Where R is Me, CH₂PrⁱOr Ph and R' ═ Prⁱ、CH₂Prⁱ、C₆H₂Me₃，[(SiPrⁱ ₃)₃AsAlH]₆，[ⁱPrNAlH]₄，[RAlNR’]₆Wherein R is Me, Et, Cl, CH₂Ph、CH₂PrⁱOr Ph and R' ═ Me, H, Br, C ═ CPh, Prⁱ、(CH₂)₂Me、(CH₂)₂NMe₂Or SiPh₃，[CH₃Ga-NCH₂CH(CH₃)₂]₆，[MeGaNⁱBu]₆，[RGaNR’]₄Wherein R ═ Ph or Me and R' ═ Ph, C₆F₅、SiMe₃Or^tBu，[EtGaNEt]₆，[RGaPR’]₄Wherein R ═ⁱPr or C₆H₂Me₃And R ═^tBu or C₆H₂Me₃，[RNInR’]₄Wherein R ═ Cl, Br, I or Me and R' ═^tBu、C₆F₅Or C₆H₄F，[RInPR’]₄Wherein R ═ⁱPr、C₆H₂Me₃Or Et and R' ═ SiPh₃、C₆H₂Me₃、SiⁱPr₃And [ RInPR']₆Wherein R ═ Et and R' ═ SiMe₂(CMe₂ ⁱPr)。

38. The method of claim 31, wherein the third ion is selected from group 13 of the periodic table and the fourth ion is selected from group 16 of the periodic table.

39. The method according to claim 38, wherein said molecular cluster compound comprises molecules selected from the group consisting of: [(^tBu)GaSe]₄，[^tBuGaS]₇，[RInSe]₄Wherein R ═^tBu、CMe₂Et、Si(^tBu)₃Or C ((SiMe)₃)₃)₃，[RInS]₄Wherein R ═^tBu or CMe₂Et，[RGaS]₄Wherein R ═^tBu、CMe₂Et or CEt₃，[SAlR]₄Wherein R ═ C (SMe)₃)₃Or CEtMe₂，[SAlNMe₃]₅，[TeAlR]₄Wherein R ═ Cp or CEtMe₂，[(C(SiMe₃)₃)GaS]₄，[^tBuGaS]₆，[RGaSe]₄Wherein R ═^tBu、CMe₂Et、CEt₃、C(SiMe₃)₃Cp or Bu, Cd₄In₁₆S₃₃·(H₂O)₂₀(C₁₀H₂₈N₄)_2.5。

40. The method of claim 31, wherein the third ion is selected from group 14 of the periodic table and the fourth ion is selected from group 16 of the periodic table.

41. The method according to claim 40, wherein said molecular cluster compound comprises molecules selected from the group consisting of: [ S ]₆{SnR}₄]Wherein R ═ C (SiMe)₃)₃Me or Ph, [ Se ]₆{SnR}₄]Wherein R ═ C₆F₅、C₆H₂Me₃p-Tol or C (SiMe)₃)₃。

42. The method of claim 31, wherein the third ion is selected from the transition metal group of the periodic table and the fourth ion is selected from the d-block of the periodic table.

43. The method according to claim 42, wherein said molecular cluster compound comprises molecules selected from the group consisting of: [ Cu ]₁₂Se₆(PR)₈]Wherein R is Et₂Ph、ⁿPr₃Or Cy₃，[Cu₁₈Te₆(^tBu)₆(PPh₂Et)₇]，[Cu₁₉Te₆(^tBu)₇(PEt₃)₈]，[Cu₂₇Te₁₅(PⁱPr₂Me)₁₂]，[Ni₃₄Se₂₂(PPh₃)₁₀]，[Ag₃₀(TePh)₁₂Te₉(PEt₃)₁₂]，[Ag₃₀Se₈(Se^tBu)₁₄(PⁿPr₃)₈]，[Co₄(μ₃-Se)₄(PPh₃)₄]，[Co₆(μ₃-Se)₈(PPh₃)₆]，[W₃Se₄(dmpe)₃Br₃]⁺，Ru₄Bi₂(CO)₁₂，Fe₄P₂(CO)₁₂And Fe₄N₂(CO)₁₂。

44. A method in accordance with claim 1, wherein the nanoparticles have a core comprising a core compound comprising fifth and sixth ions.

45. A method in accordance with claim 44, wherein the fifth ion is selected from group 2 of the periodic Table of the elements and the sixth ion is selected from group 16 of the periodic Table of the elements, wherein the fifth ion is selected from group 12 of the periodic Table of the elements and the sixth ion is selected from group 15 of the periodic Table of the elements, wherein the fifth ion is selected from group 13 of the periodic Table of the elements and the sixth ion is selected from group 14 of the periodic Table of the elements, wherein the fifth ion is selected from group 13 of the periodic Table of the elements and the sixth ion is selected from group 16 of the periodic Table of the elements, wherein the fifth ion is selected from group 14 of the periodic Table of the elements and the sixth ion is selected from group 16 of the periodic Table of the elements, or wherein the fifth ion is selected from the transition metal group of the periodic table and the sixth ion is selected from the d-block of the periodic table.

46. A method in accordance with claim 44, wherein the nanoparticle core comprises a dopant selected from the group consisting of main group elements and rare earth elements.

47. A method in accordance with claim 44, wherein each nanoparticle comprises at least one shell grown over a core of the nanoparticle.

48. A method in accordance with claim 47, wherein the or each shell has a similar lattice type to the nanoparticle core.

49. A method in accordance with claim 47 or 48, wherein the or each shell has a wider band gap than the nanoparticle core.

50. A method according to claim 47 or 48, wherein the or each shell comprises a shell compound containing seventh and eighth ions.

51. The method of claim 50, wherein the seventh ion is selected from group 2 of the periodic Table of the elements and the eighth ion is selected from group 16 of the periodic Table of the elements, wherein the seventh ion is selected from group 12 of the periodic Table of the elements and the eighth ion is selected from group 15 of the periodic Table of the elements, wherein the seventh ion is selected from group 13 of the periodic Table of the elements and the eighth ion is selected from group 16 of the periodic Table of the elements, wherein the seventh ion is selected from group 14 of the periodic Table of the elements and the eighth ion is selected from group 16 of the periodic Table of the elements, or wherein the seventh ion is selected from the transition metal group of the periodic table and the eighth ion is selected from the d-block of the periodic table.

52. A method according to claim 50, wherein the or each shell comprises a dopant.

53. The method of claim 50, wherein the shell compound is a ternary phase entity.

54. The method of claim 50, wherein the shell compound is a quaternary phase entity.

55. The method according to claim 1, wherein the nanoparticles are ternary phase nanoparticles.

56. The method of claim 1, wherein the nanoparticles are quaternary phase nanoparticles.

57. A method in accordance with claim 1, wherein said nanoparticles comprise an outermost layer comprising a capping agent.

58. A method in accordance with claim 57, wherein the capping reagent is a solvent in which the nanoparticles are grown.

59. The method according to claim 57 or 58, wherein the blocking agent is a Lewis base.

60. A method in accordance with claim 1, wherein said method further comprises the addition of a shape-directing compound that will preferentially bind to a particular crystal lattice plane of each growing nanoparticle to inhibit or slow nanoparticle growth in a particular direction.