METHOD OF PREPARATION OF ZINC OXIDE NANOPARTICLES, ZINC OXIDE NANOPARTICLES OBTAINED BY THIS METHOD AND THEIR USE

Abstract

The subject matter of the invention is a method of a preparation of zinc oxide nanoparticles, in which the organozinc precursor in an aprotic organic solvent is subjected to an oxidizing agent. A compound of the formula [R.sub.2ZnL.sub.n].sub.m is used as the organozinc precursor, where R is C1-C5 alkyl, straight or branched, benzyl, phenyl, mesityl, cyclohexyl group, L is low-molecular-weight organic compound containing one Lewis base center of formula (I) or of formula (2) or of formula (3), where R.sup.1, R.sup.2 and R.sup.3 are C1-C5 alkyl, straight or branched, phenyl, benzyl, tolyl, mesityl or vinyl group, in which any hydrogen atom may be substituted by fluorine, chlorine, bromine or iodine atom, n is 0, 1 or 2, m is a natural number from 1 to 10. Furthermore, the subject matter of the invention are also zinc oxide nanoparticles obtained by the said method. Moreover, the subject matter of the invention is also the use of the disclosed zinc oxide nanoparticles in sensors or as ETL layers for the construction of solar cells, or as UV filters, or as materials for use in electronics or in catalysis.

##STR00001##

Claims

1. The method of a preparation of zinc oxide nanoparticles, in which an organozinc precursor in an aprotic organic solvent is subjected to an oxidizing agent, characterized in that as the organozinc precursor a compound of the formula [R.sub.2ZnL.sub.n].sub.m is used, in which R is C1-C5 alkyl, straight or branched, benzyl, phenyl, mesityl, cyclohexyl group, L is low-molecular-weight organic compound containing one Lewis base center of Formula 1 or of Formula 2 or of Formula 3, ##STR00004## where R.sup.1, R.sup.2 and R.sup.3 are C1-C5 alkyl, straight or branched, phenyl, benzyl, tolyl, mesityl or vinyl group, in which any hydrogen atom may be substituted by fluorine, chlorine, bromine or iodine atom, n is 0, 1 or 2, m is a natural number from 1 to 10.

2. The method of claim 1, characterized in that a solvent with solvating and/or coordinating properties is used as the solvent.

3. The method. of claim 1, characterized in that dimethyl sulfoxide, dibuthyl sulfoxide, tetrahydrofuran, dichloromethane, dioxane, acetonitrile, chloroform, toluene, benzene, hexane, acetone or a mixture thereof is used as the solvent.

4. The method of claim 1, characterized in that, when a liquid compound is used as L, it has a function of both a L-type ligand and an aprotic solvent for the organozinc precursor.

5. The method of claim 1, characterized in that a solvent with the addition of water is used.

6. The method of claim 5, characterized in that the concentration of water in the solvent does not exceed 0.5% w/w.

7. The method of claim 1, characterized in that oxygen, water, atmospheric air or a mixture of thereof is used as the oxidizing agent.

8. The method of claim 1, characterized in that the reaction is carried out at a temperature range from 0° C. to 100° C.

9. The method of claim 1, characterized by the fact that the reaction is carried out at a molar concentration. of the precursor in an organic solvent from 0.01 mol/L to 0.4 mol/L.

10. The method of claim 1, characterized by the fact that the reaction is carried out from 24 to 336 hours.

11. Zinc oxide nanoparticles obtained by the method according to claim 1.

12. Zinc oxide nanoparticles of claim 11 characterized in that are stabilized by neutral short-chain donor organic ligands, wherein neutral short-chain organic donor ligands are compounds of Formula 1 or of Formula 2 or of Formula 3, ##STR00005## where R.sup.1, R.sup.2 and R.sup.3 are C1-C5 alky straight or branched, phenyl, benzyl, tolyl, mesityl or vinyl group, in which any hydrogen atom may be substituted by fluorine, chlorine, bromine or iodine atom, more preferably neutral short-chain donor organic ligands are sulfoxides, the most preferably dimethyl sulfoxide.

13. Nanoparticles of claim 11, characterized in that the diameter of the zinc oxide nanoparticles is less than equal to 15 nm and is characterized by narrow size distribution.

14. Nanoparticles according to claim 11, characterized that nanoparticles have a wurtzite core structure.

15. Solar cells, UV filters, or materials for use in electronics or in catalysis, comprising the zinc oxide nanoparticles of claim 11.

16. The method of claim 2, characterized in that, when a liquid compound is used as L, it has a function of both a L-type ligand and an aprotic solvent for the organozinc precursor.

17. The method of claim 3, characterized in that, when a liquid compound is used as L, it has a function of both a L-type ligand and an aprotic solvent for the organozinc precursor.

18. The method of claim 1, characterized in that the reaction is carried out at a temperature range from 10° C. to 60° C.

19. The method of claim 1, characterized in that the reaction is carried out at a temperature range from 15° C. to 35° C.

Description

[0025] The drawing shows:

[0026] FIG. 1—SE (a-c) and HR TEM (d-f) images of ZnO.L1 NPs as well as (g) size distribution of the obtained nanoparticles (Example 1).

[0027] FIG. 2—Powder X-ray diffraction pattern of ZnO.L1 NPs together with a reference bulk ZnO pattern (Example 1).

[0028] FIG. 3—a) Normalized absorption and emission spectra of ZnO.L1 NPs; b) UV (366 nm) and visible light images of a stable colloidal solution of ZnO.L1 NPs (Example 1).

[0029] FIG. 4—Normalized absorption and emission spectra of ZnO.L2 NPs (Example 3).

[0030] FIG. 5—Powder X-ray diffraction pattern of ZnO.L2 NPs together with a reference bulk ZnO pattern (Example 3).

[0031] FIG. 6—IR spectrum of ZnO.L2 NPs (Example 3).

[0032] FIG. 7—Normalized absorption and emission spectra of ZnO.L3 NPs (Example 4).

[0033] FIG. 8—Powder X-ray diffraction pattern of ZnO.L3 NPs together with a reference bulk ZnO pattern (Example 4).

[0034] FIG. 9—Normalized absorption and emission spectra of ZnO.L4 NPs (Example 5).

[0035] FIG. 10—Powder X-ray diffraction pattern of ZnO.L4 NPs together with a reference bulk ZnO pattern (Example 5).

[0036] FIG. 11—IR spectrum of ZnO.L4 NPs (Example 5).

[0037] FIG. 12—Normalized absorption and emission spectra of ZnO.L5 NPs (Example 6).

[0038] FIG. 13—Powder X-ray diffraction pattern of ZnO.L5 NPs together with a reference bulk ZnO pattern (Example 6).

[0039] FIG. 14—IR spectrum of ZnO.L5 NPs (Example 6).

[0040] FIG. 15—Normalized absorption and emission spectra of ZnO.L6 NPs (Example 7).

[0041] FIG. 16—Powder X-ray diffraction pattern of ZnO.L6 NPs together with a reference bulk ZnO pattern (Example 7).

[0042] FIG. 17—IR spectrum of ZnO.L6 NPs (Example 7).

[0043] FIG. 18—Normalized absorption and emission spectra of ZnO.L7 NPs (Example 9).

[0044] FIG. 19—Powder X-ray diffraction pattern of ZnO.L7 NPs together with a reference bulk ZnO pattern (Example 9).

[0045] FIG. 20—IR spectrum of ZnO.L7 NPs (Example 9).

[0046] FIG. 21—Normalized absorption and emission spectra of ZnO.L8 NPs (Example 10).

[0047] FIG. 22—Powder X-ray diffraction pattern of ZnO.L8 NPs together with a reference bulk ZnO pattern (Example 10).

[0048] FIG. 23—IR spectrum of ZnO.L8 NPs (Example 10).

[0049] FIG. 24—Normalized absorption and emission spectra of ZnO.L9 NPs (Example 11).

[0050] FIG. 25—Powder X-ray diffraction pattern of ZnO.L9 together with a reference bulk ZnO pattern (Example 11).

[0051] FIG. 26—IR spectrum of ZnO.L9 NPs (Example 11).

[0052] FIG. 27—Normalized absorption and emission spectra of ZnO.L10 NPs (Example 12).

[0053] FIG. 28—Powder X-ray diffraction pattern of ZnO.L10 NPs together with a reference bulk ZnO pattern (Example 12).

[0054] FIG. 29—IR spectrum of ZnO.L10 NPs (Example 12).

[0055] FIG. 30—SE (a-b) and HR TEM (c-f) images of ZnO.L11 NPs (Example 14).

[0056] FIG. 31—SE (a-b) and HR TEM (c-f) images of ZnO.L12 NPs (Example 15).

[0057] FIG. 32—IR spectrum of ZnO.L13 NPs (Example 16).

[0058] FIG. 33—Powder X-ray diffraction pattern of ZnO.L13 NPs together with a reference bulk ZnO pattern (Example 16).

[0059] The subject matter of the invention is presented in more detail in the following examples.

Example 1

The Preparation of ZnO NPs as a Result of a Direct Exposition of a Solution of Et.SUB.2.Zn in Dimethyl Sulfoxide (DMSO) to Atmospheric Air

[0060] 1 mL of 2M Et.sub.2Zn (a solution in hexane) was added dropwise at room temperature to 20 mL of dimethyl sulfoxide placed in a 50 mL round-bottom flask equipped with a magnetic stirring bar. The reaction mixture was subjected to controlled exposure to atmospheric air for 24 48 hrs at ambient temperature. After this time, a suspension exhibiting an intense yellow fluorescence under UV excitation was obtained. The precipitate was separated by centrifugation (15 min, 12500 rpm) and a stable colloidal solution was obtained. ZnO nanoparticles can also be purified by a precipitation method from the post-reaction mixture with acetone, and further by washing the resulting precipitate 3 times with small portions of acetone. The nanocrystalline ZnO obtained as a result of controlled transformation (hereinafter referred to as ZnO.L1 NPs) was characterized by a wide range of analytical techniques such as: high resolution scanning transmission electron microscopy (STEM), powder X-ray diffraction (PXRD), dynamic light scattering (DLS), infrared spectroscopy (FTIR), UV-Vis spectrophotometry and spectrofluorometry (PL).

[0061] STEM images of the resulting ZnO nanoparticles that were taken in the immersion mode, which records the signal of secondary electrons (SE) and allows the morphological study of the nanoparticles as well as in a mode that allows the characterization of both the structure and the chemical composition at the atomic scale (HR TEM) along with the size distribution of the inorganic ZnO.L1 NPs core are shown in FIG. 1. These micrographs show a nanocrystalline ZnO aggregates composed of single quasi-spherical nanocrystallites of a size of several nanometers (2-7 nm), which indicates a narrow size distribution of the resulting ZnO.L1 NPs. DLS analysis has shown that the average size of ZnO.L1 NPs aggregates present in the DMSO solution is about 103 nm, and the relatively low polydispersity index (PdI=0.28) indicates a high similarity, almost uniform shape and a narrow size distribution of the hydrodynamic diameter of the obtained nanostructures. Aside from size, very important features of NPs are their chemical composition and crystalline structure of the core. PXRD analysis (FIG. 2) confirmed nanocrystalline (i.e. NPs diameter<15 nm), wurtzite-type structure of ZnO.L1 NPs. FTIR analysis allowed the determination of the coordination mode a L-type ligand, here DMSO, to the surface of ZnO NPs. The presence of a strong band at 1017 cm.sup.-1 is characteristic for the bending vibrations of the S═O bond and indicates the coordination of DMSO to the surface of the inorganic ZnO core via an oxygen atom. Additionally, the band at 3404 cm.sup.−1 is characteristic for stretching vibrations of O—H bond. The position of the hydroxyl group band in Zn(OH).sub.2 is very similar, i.e. 3384 cm.sup.−1. Thus, on the surface of the inorganic core there are not only coordinated DMSO molecules, but also Zn—OH moieties being the result of the reaction between dialkylzinc compound and water present in the air. Based on the position and the shape of the band of OH group, it can be concluded that there are hydrogen bonds between the Zn—OH group and DMSO molecule in the system. ZnO.L1 NPs exhibit the photoluminescent properties both in the solid state and in the solution (FIG. 3). The absorption and the emission spectra of the colloidal solution of ZnO.L1 NPs in DMSO are shown in FIG. 3a. In the region of 290 - 370 nm, a wide absorption band with the maximum located at 330 nm is visible. By contrast, a relatively wide emission band (with a half width (FWHM) of about 135 nm) is in the green light area (λ.sub.em=531 nm) (FIG. 3a). The colloidal solution of ZnO.L1 NPs in DMSO is stable over time and no changes are observed (e.g. appearance of sediment at the bottom of the vessel) even after 9 months of storage.

Example 2

The Preparation of ZnO NPs as a Result of a Direct Exposition of a Solution of Me.SUB.2.Zn in DMSO to Atmospheric Air

[0062] 1 mL of 2M Me.sub.2Zn (a solution in hexane) was added dropwise at room temperature to 20 mL of dimethyl sulfoxide placed in a 50 mL round-bottom flask equipped with a magnetic stirring bar. Then, the reaction mixture was subjected to a controlled exposure to atmospheric air for 7 days at ambient temperature. The as-prepared ZnO nanoparticles exhibit a similar physicochemical properties to those observed for ZnO.L1 NPs.

Example 3

The Preparation of ZnO NPs as a Result of a Direct Exposition of a Solution of iPr.SUB.2.Zn in DMSO to Atmospheric Air

[0063] 1 mL of 1M iPr.sub.2Zn (a solution in toluene) was added dropwise to 20 mL of dimethyl sulfoxide placed in a 50 mL round-bottom flask equipped with a magnetic stirring bar. Then, the reaction mixture was subjected to a controlled exposure to atmospheric air for 5 days at ambient temperature. ZnO.L2 nanoparticles exhibit the photoluminescent properties both in the solution and in the solid state. The absorption and emission spectra of ZnO.L2 NPs dispersed in DMSO are shown in FIG. 4. The obtained system is characterized by a well-defined absorption band with the maximum at 345 nm as well as by a relatively wide emission band with the maximum at 531 nm (FIG. 4). Based on PXRD analysis (FIG. 5) nanocrystalline, wurtzite-type structure of ZnO.L2 NPs was confirmed. The presence of passivating, coordinated to the surface of ZnO core DMSO moieties was confirmed via FTIR measurement (FIG. 6).

Example 4

The Preparation of ZnO NPs as a Result of Direct Exposition of a Solution of Et.SUB.2.Zn in Dibuthyl Sulfoxide to Atmospheric Air

[0064] 1 mL of 2M Et.sub.2Zn (a solution in hexane) was added dropwise at room temperature to 20 mL of dibuthyl sulfoxide placed in a 50 mL round-bottom flask equipped with a magnetic stirring bar. Then, the reaction mixture was subjected to a controlled exposure to atmospheric air for 5 days at ambient temperature. The obtained ZnO.L3 NPs exhibit the photoluminescent properties both in the solution and in the solid state. The absorption and emission spectra of ZnO.L.sub.3 NPs are shown in FIG. 7. The obtained system is characterized by a well-defined absorption band with the maximum at 343 nm. A relatively wide emission band with a maximum at 515 nm is responsible for the green fluorescence of ZnO.L3 NPs (FIG. 7). Based on the PXRD analysis (FIG. 8) nanocrystalline, wurtzite-type structure of ZnO L3 NPs was confirmed.

Example 5

The Preparation of ZnO NPs Stabilized by DMSO Ligand

[0065] 156 mg (2 mmol) (CH.sub.3).sub.2SO in 10 mL of THF was placed in a Schlenk vessel equipped with a magnetic stirring bar. It was cooled in an isopropanol bath to −78° C. Then, in an inert gas atmosphere, 1 mL of 2M (2 mmol) Et.sub.2Zn (a solution in hexane) was added dropwise via a syringe. The reaction was initially carried out at reduced temperature and then gradually warmed to room temperature and left at this temperature for 24 hours. Then, the reaction mixture was subjected to control exposure to atmospheric air for 5 days at ambient temperature. Nanoparticles ZnO.L4 NPs exhibit the luminescent properties both in the solution and in the solid state. The absorption and emission spectra of ZnO.L3 NPs dispersion are shown in FIG. 9. Based on PXRD analysis (FIG. 10) nanocrystalline, wurtzite-type structure of ZnO.L4 NPs was confirmed. Similarly as it is in the case of Zn0.1, 1 and ZnO.L2 NPs, FTIR analysis confirmed the presence of an organic layer composed of DMSO molecules on the surface of the nanocrystalline ZnO (FIG. 11).

Example 6

The Preparation of ZnO NPs Stabilized by DMSO Ligand using iPr2Zn as an Organometallic Precursor

[0066] 78 mg (1 mmol) (CH.sub.3).sub.2SO in 10 mL of THF was placed in a Schlenk vessel equipped with a magnetic stirring bar. Then, in an inert gas atmosphere, 1 mL of 1M (2 mmol) iPr.sub.2Zn (a solution in toluene) was added dropwise via a syringe. The reaction was carried out at room temperature and stirred for 24 hours. After this time, the reaction mixture was subjected to a controlled exposure to atmospheric air for 5 days at ambient temperature. Nanoparticles ZnO.L5 NPs exhibit the luminescent properties both in the solution and in the solid state. The absorption and emission spectra of ZnO.L5 NPs dispersion are shown in FIG. 12. Based on PXRD analysis (FIG. 13) nanocrystalline, wurtzite-type structure of ZnO.L5 NPs was confirmed. The lack of additional reflections on the powder X-ray diffraction pattern indicates a high degree of sample purity. Similarly as it is in the case of ZnO.L1 and ZnO.L3 NPs, FTIR analysis confirmed the presence of an organic layer composed of DMSO molecules on the surface of the nanocrystalline ZnO (FIG. 14).

Example 7

[0067] The Preparation of ZnO NPs Stabilized by (CH.sub.3(CH.sub.2).sub.3).sub.2SO) ligand.

[0068] 324 mg (1 mmol) (CH.sub.3(CH.sub.2).sub.3).sub.2SO in 10 mL of THF was placed in a Schlenk vessel equipped with a magnetic stirring bar. It was cooled in an isopropanol bath to −78° C. Then, in an inert gas atmosphere, 0.5 mL of 2M (1 mmol) Et.sub.2Zn (a solution in hexane) was added dropwise via a syringe. The reaction was initially carried out at reduced temperature and then gradually warmed to room temperature and left at this temperature for 24 hours. Then, the reaction mixture was subjected to a controlled exposure to atmospheric air for 5 days at ambient temperature. Nanoparticles ZnOL6 NPs exhibit the luminescent properties both in the solution and in the solid state. The absorption and emission spectra of ZnO. L6 NPs dispersion are shown in FIG. 15. Based on PXRD analysis (FIG. 16) nanocrystalline, wurtzite-type structure of ZnOL6 NPs was confirmed whereas MIR analysis confirmed the presence of an organic layer composed of dibuthyl sulfoxide molecules on the surface of the nanocrystalline ZnO (FIG. 17). Changes in both intensity and shifts of the bands characteristic for (CH.sub.3(CH.sub.2).sub.3)2SO in IR spectrum indicate the coordination of sulfoxide ligands to the surface of ZnO NPs.

Example 8

The Preparation of ZnO NPs Stabilized by (CH.SUB.3.(CH.SUB.2.).SUB.3.).SUB.2.SO Ligand using tBu.SUB.2.Zn as an Organometallic Precursor

[0069] 324 mg (1 mmol) (CH.sub.3(CH.sub.2).sub.3).sub.2SO in 10 mL of THF was placed in a Schlenk vessel equipped with a magnetic stirring bar. It was cooled in an isopropanol bath to −78° C. Then, in an inert gas atmosphere, 1 mL of 1M (1 mmol) tBu.sub.2Zn (a solution in toluene) was added dropwise via a syringe. The reaction was initially carried out at reduced temperature and then gradually warmed to room temperature and left at this temperature for 24 hours. Then, the reaction mixture was subjected to a controlled exposure to atmospheric air for 8 days at ambient temperature. The as-prepared ZnO nanoparticles exhibit a similar physicochemical properties to those observed for ZnO.L6 NPs.

Example 9

The Preparation of ZnO NPs Stabilized by Diphenylsulfoxide Ligand

[0070] 404 mg (2 mmol) (C.sub.6H.sub.5).sub.2S in 10 mL of THF was placed in a Schlenk vessel equipped with a magnetic stirring bar. It was cooled in an isopropanol bath to −78° C. Then, in an inert gas atmosphere, 1 mL of 2M (2 mmol) Et2Zn (a solution in hexane) was added dropwise via a syringe. The reaction was initially carried out at reduced temperature and then gradually warmed to room temperature and left at this temperature for 24 hours. Then, the reaction mixture was subjected to a controlled exposure to atmospheric air for 5 days at ambient temperature. ZnO.L7 NPs were obtained as a powder that exhibit yellow fluorescence under UV excitation. The absorption and emission spectra of ZnO.L7 NPs dispersion are shown in FIG. 18. After decantation, ZnO nanoparticles were characterized by PXRD (FIG. 19). The powder X-ray diffraction pattern analysis confirmed the crystalline wurtzite structure of ZnO.L7 NPs. The additional reflections indicate the presence of the ligand phase in the sample, what was also confirmed by FTIR analysis (FIG. 20).

Example 10

The Preparation of ZnO NPs Stabilized by CH.SUB.3.SOC.SUB.6.H.SUB.5 .Ligand

[0071] 280 mg (2 mmol) CH.sub.3SOC.sub.6H.sub.5 in 10 mL of THF was placed in a Schlenk vessel equipped with a magnetic stirring bar. It was cooled in an isopropanol bath to −78° C. Then, in an inert gas atmosphere, 1 mL of 2M (2 mmol) Et.sub.2Zn (a solution in hexane) was added dropwise via a syringe. The reaction was initially carried out at reduced temperature and then gradually warmed to room temperature and left at this temperature for 24 hours. Then, the reaction mixture was subjected to a controlled exposure to atmospheric air for 5 days at ambient temperature. ZnO.L8 nanoparticles were obtained as a powder, which exhibits a yellow fluorescence with a maximum of emission located at 525 nm. The absorption and emission spectra of ZnO.L8 NPs dispersion are shown in FIG. 21. PXRD analysis (FIG. 22) confirmed nanocrystalline, wurtzite-type structure of ZnO.L8 NPs while the presence of the NPs organic stabilizing layer was confirmed based on FTIR analysis (FIG. 23).

Example 11

The Preparation of ZnO NPs Stabilized by C.SUB.6.H.SUB.5.SOCH═CH.SUB.2 .Ligand

[0072] 304 mg (2 mmol) C6H5SOCH=CH2 in 10 mL of THF was placed in a Schlenk vessel equipped with a magnetic stirring bar. It was cooled in an isopropanol bath to -78° C. Then, in an inert gas atmosphere, 1 mL of 2M (2 mmol) Et2Zn (a solution in hexane) was added dropwise via a syringe. The reaction was initially carried out at reduced temperature and then gradually warmed to room temperature and left at this temperature for 24 hours. Then, the reaction mixture was subjected to a controlled exposure to atmospheric air for 5 days at ambient temperature. ZnO L9 nanoparticles have luminescent properties. The absorption and emission spectra of ZnOL9 NPs dispersion are shown in FIG. 24. PXRD analysis indicates the nanocrystalline nature of the sample (FIG. 25), while FTIR analysis confirmed the presence of an organic layer consisting of sulfoxide molecules on the surface of the nanocrystalline ZnO (FIG. 26).

Example 12

The Preparation of ZnO NPs Stabilized by Triphenylphosphine

[0073] 524 mg (2 mmol) P(C.sub.6H.sub.5).sub.3 in 10 mL of THF was placed in a Schlenk vessel equipped with a magnetic stirring bar. It was cooled in an isopropanol bath to −78° C. Then, in an inert gas atmosphere, 1 mL of 2M (2 mmol) Et.sub.2Zn (a solution in hexane) was added dropwise via a syringe. The reaction was initially carried out at reduced temperature and then gradually warmed to room temperature and left at this temperature for 24 hours. Then, the reaction mixture was subjected to a controlled exposure to atmospheric air for 4 days at ambient temperature. ZnO.L10 nanoparticles have luminescent properties (FIG. 27). Based on PXRD analysis (FIG. 28) nanocrystalline, wurtzite-type structure of ZnO.L10 NPs was confirmed, while FTIR analysis confirmed the presence of an organic layer consisting of triphenylphosphine molecules on the surface of the nanocrystalline ZnO (FIG. 29).

Example 13

The Preparation of ZnO NPs Stabilized by Triphenylphosphine using Me.SUB.2.Zn as an Organometallic Precursor

[0074] 648 mg (2 mmol) (CH.sub.3(CH.sub.2).sub.3).sub.2SO in 10 mL of THF was placed in a Schlenk vessel equipped with a magnetic stirring bar. It was cooled in an isopropanol bath to −78° C. Then, in an inert gas atmosphere, 1 mL of 2M (2 mmol) Me.sub.2Zn (a solution in hexane) was added dropwise via a syringe. The reaction was initially carried out at reduced temperature and then gradually warmed to room temperature and left at this temperature for 24 hours. Then, the reaction mixture was subjected to a controlled exposure to atmospheric air for 9 days at ambient temperature. The as-prepared ZnO nanoparticles exhibit a similar physicochemical properties to those observed for ZnO.L10 NPs.

Example 14

The Preparation of ZnO NPs as a Result of a Direct Exposition of a Solution of Et.SUB.2.Zn in THF to Atmospheric Air

[0075] 1 mL of 2M Et.sub.2Zn (a solution in hexane) was added dropwise at room temperature to 20 mL of THF placed in a 50 mL round-bottom flask equipped with a magnetic stirring bar. The reaction mixture was subjected to a controlled exposure to atmospheric air for 2 days at ambient temperature. ZnO.L11 nanoparticles exhibit fluorescence both in the solution and in the solid state. Microscopic measurements showed the presence of ZnO NPs of the pseudo-spherical shape and of a size in the range of 1-7 nm as well as characterized by a relatively narrow size distribution (FIG. 30).

Example 15

The Preparation of ZnO NPs as a Result of a Direct Exposition of a Solution of Et.SUB.2.Zn in Acetone to Atmospheric Air

[0076] 1 mL of 2M Et.sub.2Zn (a solution in hexane) was added dropwise at room temperature to 20 mL of acetone placed in a 50 mL round-bottom flask equipped with a magnetic stirring bar. The as-prepared reaction mixture was subjected to a controlled exposure to air for 3 days at ambient temperature, and then the obtained luminescent ZnO.L12 NPs was characterized. Microscopic measurements showed the presence of nanocrystalline ZnO with a core diameter in the range of 2-10 nm (FIG. 31).

Example 16

The Preparation of ZnO NPs Stabilized by (CH.SUB.3.C.SUB.6.H.SUB.4.).SUB.2.S Ligand

[0077] 460.6 mg (2 mmol) (CH.sub.3C.sub.6H.sub.4).sub.2SO in 10 mL of THF was placed in a Schlenk vessel equipped with a magnetic stirring bar. It was cooled in an isopropanol bath to −78° C. Then, in an inert gas atmosphere, 1 mL of 2M (2 mmol) Et.sub.2Zn (a solution in hexane) was added dropwise via a syringe. The reaction was initially carried out at reduced temperature and then gradually warmed to room temperature and left at this temperature for 24 hours. Then, the reaction mixture was subjected to a controlled exposure to atmospheric air for 5 days at ambient temperature. ZnO.L13 nanoparticles exhibit luminescent properties. FTIR analysis confirmed the presence of organic layer consisting of sulfoxide molecules on the surface of the nanocrystalline ZnO (FIG. 32). Based on PXRD analysis (FIG. 33) nanocrystalline, wurtzite-type structure of ZnO.L13 NPs was confirmed. The lack of additional reflections on the diffraction pattern indicates a high degree of sample purity.

LITERATURE

[0078] [1] Morkoc, H.; Özgür, U. Zinc Oxide: Fundamentals, Materials and Device Technology, Willey-VCH, Weinheitn, 2009. [0079] [2] Spanhel, L.; Anderson, M. A., Semiconductor Clusters in the Sol-Gel Process: Quantized Aggregation, Gelation, and Crystal Growth in Concentrated ZnO Colloids. J. Am. Chem. Soc. 1991, 113, 2826-2833. [0080] [3] Meulenkamp, E. A., Synthesis and Growth of ZnO Nanoparticles. J. Phys. Chem. B 1998, 102, 5566-5572. [0081] [4] a) Monge, M.; Kahn, M. L.; Maisonnat, A.; Chaudret, B., Room-Temperature Organometallic Synthesis of Soluble and Crystalline ZnO Nanoparticles of Controlled Size and Shape. Angew. Chem. Int. Ed. 2003, 42, 5321-5324; b) Kahn, M. L.; Monge, M.; Maisonnat, A.; Chaudret, B. French Patent CNRS, Fr03-042825, 2004; c) Patent US 2006/0245998, 2006. [0082] [5] Orchard K. L.; Shaffer M. S. P.; Williams C. K., Organometallic Route to Surface-Modified ZnO Nanoparticles Suitable for In Situ Nanocomposite Synthesis: Bound Carboxylate Stoichiometry Controls Particle Size or Surface Coverage. Chem. Mater. 2012, 24, 2443-2448. [0083] [6] a) Lewiński, J.; Bojarski, E.; Bury, W.; Kościelski, M., P-383356, 2007; b) Lewiński, J.; Bury, W.; Kościelski, M.; Bojarski, E., P-383357, 2007; c) Lewiński, J.; Suwala, K.; Kubisiak, M., P-385938, 2008; d) Lewiński, J.; Suwala, K., P-386289, 2008; e) Lewiński, J.; Sokolowski, K.; Leszczyński, M.; Zelga K., P-393834, 2011; f) Krupiński, P.; Komowicz, A.; Lewiński, J., P-402624, 2013. [0084] [7] a) Paczesny, J.; Wolska-Pietkiewicz, M.; Binkiewicz, I.; Wróbel, Z.; Wadowska, M.; Matula, K.; Dziçcielewski, I.; Pociecha, D.; Smalc-Koziorowska, J.; Lewiński, J.; Holyst, R., Towards Organized Hybrid Nanomaterials at the air/water Interface Based on Liquid Crystal-ZnO Nanocrystals. Chem. Eur. J. 2015, 21, 16941-16947; b) Paczesny, J.; Wolska-Pietkiewicz, M.; Binkiewicz, I.; Wadowska, M.; Wróbel, Z.; Matula, K.; Nogala, W.; Lewiński, J.; Holyst, R., Photoactive Langmuir-Blodgett, Freely Suspended and Free Standing Films of Carboxylate Ligand-Coated ZnO Nanocrystals. ACS Appl. Mater. Interfaces, 2016, 8, 13532-13541; c) Grala, A.; Wolska-Pietkiewicz, M.; Danowski, W.; Wróbel, Z.; Grzonka, J.; Lewiński, J., ‘Clickable’ ZnO nanocrystals: the superiority of a novel organometallic approach over the inorganic sol-gel procedure. Chem. Commun. 2016, 52, 7340-7343; d) Wolska-Pietkiewicz, M.; Grala, A.; Justyniak, I.; Hryciuk, D.; Jçdrzejewska, M.; Grzonka, J.; Kurzydlowski, K. J., Lewiński, J., From well-defined alkylzinc phosphinates to quantum-sized ZnO nanocrystals. Chem. Eur. J. 2017, 49, 11856-11865; e) Chwojnowska, E.; Wolska-Pietkiewicz, M.; Grzonka, J.; Lewiński J., An Organometallic Route to Chiroptically Active ZnO Nanocrystals. Nanoscale, 2017, 9, 14782-14786; f) Wolska-Pietkiewicz, M.; Tokarska, K.; Grala, A.; Wojewódzka, A.; Chwojnowska, E.; Grzonka, J.; Cywiński, P.; Kruczala, K.; Sojka, Z.; Chudy, M.; Lewiński, J., ‘Safe-by-design’ ligand coated-ZnO nanocrystals engineered by an organometallic approach: unique physicochemical properties and low toxicity toward lung cells. Chem. Eur. J. 2018, 24, 4033-4042. [0085] [8] Chang, J.; Waclawik, E. R., Colloidal Semiconductor Nanocrystals: Controlled Synthesis and Surface Chemistry in Organic Media. RSC Adv. 2014, 4, 23505-23527. [0086] [9] Sookhakian, M.; Amin, Y. M.; Basirun, W. J.; Tajabadi, M. T.; Kamarulzaman, N., Synthesis, Structural, and Optical Properties of Type-II ZnO—ZnS Core-Shell Nanostructure. JOL 2014, 145, 244-252. [0087] [10] Tang, X.; Choo, E. S. G.; Li, L.; Ding, J.; Xue, J., Synthesis of ZnO Nanoparticles with Tunable Emission Colors and Their Cell Labeling Applications. Chem. Mater. 2010, 22, 3383-3388.

[0088] [11] a) Xiong, H.-M.; Xu, Y.; Ren, Q.-G.; Xia, Y.-Y., Stable Aqueous ZnO@polymer Core-Shell Nanoparticles with Tunable Photoluminescence and Their Application in Cell Imaging. J. Am. Chem. Soc. 2008, 130, 7522-7523; b) Xiong, H.-M., ZnO Nanoparticles Applied to Bioimaging and Drug Delivery. Adv. Mater. 2013, 25, 5329-5335. [0089] [12] a) Guo, L.; Yang, S. H.; Yang, C. L.; Yu, P.; Wang, J. N.; Ge, W. K.; Wong, G. K. L., Synthesis and Characterization of Poly(vinylpyrrolidone)-Modified Zinc Oxide Nanoparticles. Chem. Mater. 2000, 12, 2268-2274; b) Xiong, H. M.; Wang, Z. D.; Liu, D. P.; Chen, J. S.; Wang, Y. G.; Xia, Y. Y., Bonding Polyether onto ZnO Nanoparticles: an Effective Method for Preparing Polymer Nanocomposites with Tunable Luminescence and Stable Conductivity. Adv. Funct. Mater. 2005, 15, 1751-1756; c) Xiong, H. M.; Wang, Z. D.; Xia, Y. Y., Polymerization Initiated by Inherent Free Radicals on Nanoparticle Surfaces: a Simple Method of Obtaining Ultrastable (ZnO)Polymer Core-Shell Nanoparticles with Strong Blue Fluorescence. Adv. Mater. 2006, 18, 748-751; (d) Xiong, H.-M.; Xie, D.-P.; Guan, X.-Y.; Tan, Y.-J.; Xia, Y.-Y., Water-Stable Blue-Emitting ZnO@polymer Core-Shell Microspheres. J. Mater. Chem. 2007, 17, 2490-2496. [0090] [13] a) Li, F.; Li, Q.; Chen, Y., Observations of Energy Transfer and Anisotropic Behavior in ZnO Nanoparticles Surface-Modified by Liquid-Crystalline Ligands. JOL 2012, 132, 2114-2121; b) Neaime, C.; Prevot, M.; Amela-Cortes, M.; Circu, V.; Grasset, F.; Folliot, H.; Molard, Y., Voltage-Driven Photoluminescence Modulation of Liquid-Crystalline Hybridized ZnO Nanoparticles. Chem. Eur. J. 2014, 20, 13770-13776. [0091] [14] a) Fu, Y.-S.; Du, X.-W.; Kulinich, S. A.; Qiu, J.-S.; Qin, W.-J.; Li, R.; Sun, J.; Liu, J., Stable Aqueous Dispersion of ZnO Quantum Dots with Strong Blue Emission via Simple Solution Route. J. Am. Chem. Soc. 2007, 129, 16029-16033; (b) Rubio-Garcia, J.; Dazzazi, A.; Coppel, Y.; Mascalchi, P.; Salome, L.; Bouhaouss, A.; Kahn, M. L.; Gauffre, F., Transfer of Hydrophobic ZnO Nanocrystals to Water: an Investigation of the Transfer Mechanism and Luminescent Properties. J. Mater. Chem. 2012, 22, 14538-14545. [0092] [15] a) Fu, Y.-S.; Du, X.-W.; Kulinich, S. A.; Qiu, J.-S.; Qin, W.-J.; Li, R.; Sun, J.; Liu, J., Stable Aqueous Dispersion of ZnO Quantum Dots with Strong Blue Emission via Simple Solution Route. J. Am. Chem. Soc. 2007, 129, 16029-16033; b) Rubio-Garcia, J.; Dazzazi, A.; Coppel, Y.; -Mascalchi, P.; Salome, L.; Bouhaouss, A.; Kahn, M. L.; Gauffre, F., Transfer of Hydrophobic ZnO Nanocrystals to Water: an Investigation of the Transfer Mechanism and Luminescent Properties. J. Mater. Chem. 2012, 22, 14538-14545. [0093] [16] Chang, J.; Waclawik, E. R., Experimental and Theoretical Investigation of Ligand Effects on the Synthesis of ZnO Nanoparticles. J. Nanopart. Res. 2012, 14:1012. [0094] [17] Shim, M.; Guyot-Sionnest, P., Organic-Capped ZnO Nanocrystals: Synthesis and n-Type Character. J. Am. Chem. Soc. 2001, 123, 11651-11654. [0095] [18] Valdez, C. N.; Schimpf, A. M.; Gamelin, D. R.; Mayer, J. M., Low Capping Group Surface Density on Zinc Oxide Nanocrystals. ACS Nano 2014, 8, 9463-9470.