WO2009092684A2 - Synthesis of metal oxide nanoparticles - Google Patents

Synthesis of metal oxide nanoparticles Download PDF

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WO2009092684A2
WO2009092684A2 PCT/EP2009/050544 EP2009050544W WO2009092684A2 WO 2009092684 A2 WO2009092684 A2 WO 2009092684A2 EP 2009050544 W EP2009050544 W EP 2009050544W WO 2009092684 A2 WO2009092684 A2 WO 2009092684A2
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metal oxide
nanoparticles
organic phase
phase
water phase
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PCT/EP2009/050544
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French (fr)
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WO2009092684A3 (en
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Taolei Sun
Kangjian Tang
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Westfälische Wilhelms-Universität Münster
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Priority to EP09704125A priority Critical patent/EP2244981A2/en
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Publication of WO2009092684A3 publication Critical patent/WO2009092684A3/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G23/00—Compounds of titanium
    • C01G23/04—Oxides; Hydroxides
    • C01G23/047—Titanium dioxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G23/00—Compounds of titanium
    • C01G23/04—Oxides; Hydroxides
    • C01G23/047—Titanium dioxide
    • C01G23/053—Producing by wet processes, e.g. hydrolysing titanium salts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G25/00—Compounds of zirconium
    • C01G25/02—Oxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area

Definitions

  • the present invention is directed to the field of the manufacture of metal oxide nanoparticles.
  • Inorganic semiconductor nanoparticles have attracted great interest in recent decades due to their implementation in a wide variety of applications including photo catalysis, electronic devices, light- emitting devices, solar cells, bioimaging and biosensors.
  • One of the most important factors regarding nanoparticles in these applications is that the size of the nanoparticles must be substantially uniform in order for the nanoparticles to function accordingly.
  • the present invention teaches a method for the manufacture of metal oxide nanoparticles, preferably but is not limited to nanoparticles used in the semiconductor industry.
  • the method comprises providing at least one water phase and at least one organic phase in a chamber of a hydrothermal apparatus.
  • the organic phase is a solution of a metal oxide precursor.
  • the metal oxide precursor is soluble in the organic phase and not the water phase. Once heated to a hydrothermal reaction temperature, hydrolysis and nucleation of the metal oxide precursor occurs at the interface of the organic phase and the water phase resulting in the simultaneous nucleation of the insoluble metal oxide nanoparticles.
  • the method provides a simple yet novel method for the manufacture of metal oxide nanoparticles.
  • the method further allows the controlling of the size of the metal oxide nanoparti- cles by altering the hydrothermal reaction temperature.
  • the present invention produces nanoparticles that have good monodispersity, are highly crystalline, and additionally possess strong photoluminescence and excellent photocatalytic activities.
  • the invention discloses a method for the manufacture of nanoparticles whereby the manipulation of the hydrothermal reaction temperature allows the manufacture of nanoparticles with a size below 10 nm.
  • the method also exhibits other distinct advantages, compared with other methods of manufacture reported previously.
  • the preparation process is simple and cheap, and does not contain any complicated post-treatment procedure.
  • products (without coating) can be collected from the organic phase which effectively avoids grain aggregation induced by the capillary condensation in water environment.
  • the production yield is very high (almost 100 %) and the organic and water phases after reaction can be easily recycled.
  • the present invention can be used for the industrial manufacture of nanoparticles and help to reduce the cost of manufacture.
  • Figure 1 Depicts the manufacture of metal oxide nanoparticles under the separate two-phase hydrothermal reaction conditions.
  • Figure 2 Depicts a flow diagram for the steps to manufacture metal oxide nanoparticles under the separate two-phase hydrothermal reaction conditions.
  • Figure 3 Shows low resolution TEM (a) and corresponding high resolution TEM images (b) of Zr ⁇ 2 nanoparticles prepared at 160 0 C. Further magnified images show the coexistence of the tetragonal (c) and monoclinic Zr ⁇ 2 nanoparticles (d) in the samples.
  • Figure 4 Shows a) Size distribution function of Zr ⁇ 2 nanoparticles that calculated from the SAXS data, b) Relationship between the particle size (max probability of diameter) and the hydrothermal temperature.
  • Figure 5 Shows XRD patterns for Zr ⁇ 2 nanoparticles that prepared at different temperatures, a): 100 0 C; b) 120 0 C; c) 140 0 C; d): 160 0 C; e) 180 0 C; f) 200 0 C.
  • Red lines characteristic peaks for tetragonal phase; Blue lines: characteristic peaks for monoclinic phase.
  • Figure 6 Shows fluorescence spectra of the Zr ⁇ 2 nanoparticles prepared at different temperatures (T), which were dispersed in chloroform, a) Excitation spectra, in which obvious red-shift of the absorption peaks can be observed, b) Emission spectra (excitation wavelength: 285nm). Four main peaks located at 331, 344, 401 and 423 nm in blue-light region can be observed. Inset: blue-light emission of Zr ⁇ 2 nanoparticles dispersed in chloroform (recorded by a CCD camera in dark room, irradiated by a black-light lamp (365 nm), left tube: with Zr ⁇ 2 nanoarticles, right tube: without Zr ⁇ 2 nanoparticles).
  • Figure 7 Shows photocatalytic properties of the Zr ⁇ 2 nanoparticles with different particle sizes, hydrogen output efficiency; specific reaction rate considering the specific surface area of the nanopartlcies.
  • Fugure 8 Shows average sizes of the Ti ⁇ 2 nanoparticles prepared at different temperatures.
  • Figure 9 Shows average particle size and specific surface area (BET) of the Zr ⁇ 2 nanoparticles prepared at different temperatures.
  • the present invention teaches a method for the manufacture of metal oxide nanoparti- cles 10.
  • the invention is not limited to the use of the metal oxide nanoparticles 10 in a specific application, for example in photo catalysis, electronic devices, light- emitting devices, solar cells, bioimaging and biosensors etc.
  • the nanoreactors due to their substantially uniform size, provide an environment for the manufacture of the nanoparticles 10 of substantially uniform sizes.
  • the size of the nanoreactors accordingly determines the size of the nanoparticles and will also consequently confine the further growth of nanoparticles.
  • the process of diffusion at the interface of the droplets of the organic phase 30 by the water phase 20 is a dynamic process.
  • the sizes of the tiny droplets (nanoreactors) and the diffusion at the interface of the organic phase 30 with the water phase 20 depends upon the hydrothermal reaction temperature. Therefore, if a hydrolysable chemical substance is present in the organic phase 30, a size of the nanoparticles can be controlled by altering the hydrothermal reaction temperature.
  • the metal oxide precursors 40 will be initially soluble in the organic phase 30. Once the metal oxide precursors 40 are hydrolysed to form a metal oxide nanoparticle 10, the metal oxide nanoparticle 10 will neither be soluble in the organic phase 30 or the water phase 20. The metal oxide nanoparticle 10 will crystallise from the mixture of the water phase 20 and the organic phase 30 during manufacture.
  • the method for the preparation of nanoparticles commences as in step 200.
  • the water phase 20 and the organic phase 30 are prepared as in step 210.
  • the organic phase 30 contains a metal oxide precursor 40 dissolved in the organic phase 40 to form a solution.
  • the solution is prepared in the open atmosphere and the ration of the organic phase to the water phase is 1 :1.
  • the water phase 20 and the organic phase 30, which contains the metal oxide precursor 40 are then placed in the sealed hydrothermal chamber 60 of a hydrothermal apparatus as in step
  • the mixture of the water phase 20 and the organic phase 30 is then heated to a hydro- thermal reaction temperature as in step 230.
  • the hydrothermal reaction temperature determines the size of the manufactured nanoparticles 10.
  • hydrolysis 240 of the metal oxide precursor 40 occurs almost instantaneously.
  • the manufactured nanoparticles 10 fall from the solution as in step 250 as ultrafine, crystalline metal oxide nanoparticles 10.
  • the manufactured nanoparticles 10 are then collected and analysed as in step 260.
  • the analysis is carried out by transmission electron microscopy (TEM), small angle X-Ray scattering (SAXS), X-Ray diffraction (XRD).
  • TEM transmission electron microscopy
  • SAXS small angle X-Ray scattering
  • XRD X-Ray diffraction
  • Photoluminescent and photocatalytic activity of the manufactured nanoparticles are measured using a Perkinelmer Is55 luminescence spectrometer and photo- catalytic hydrogen production experiments
  • step 270 Following the analysis 260 of the manufactured nanoparticles 10, the method is complete (step 270).
  • the water phase 20 and the organic phase 30 may then be recycled by distillation.
  • FIG. 1 shows a TEM of the manufactured Zr ⁇ 2 nanoparticle.
  • the manufactured Zr ⁇ 2 nanoparticle shows excellent dispersity and no toluene coating as determined by proton NMR.
  • Figure 3b displays a high resolution TEM depicting well crystallised quantum dots of the manufactured Zr ⁇ 2 nanoparticle and a particle size of approximately 4.4nm is observed.
  • Example 1 The reaction of Example 1 was then carried out at different hydrothermal reaction temperatures and the manufactured nanoparticles 10 were investigated by SAXS.
  • the curves of distribution function ( Figure 4a) show good monodispersity for all samples prepared at different temperatures with the average size of the manufactured nanoparticles 10 increasing monotonously from l.Onm to approximately 6.1nm when the temperature was increased from 110 0 C to 240 0 C ( Figure 4b).
  • the XRD patterns ( Figure 5) show that the samples have very good crystallinity, which increases with the increase of preparation temperature.
  • Photo luminescent and photocatalytic activities of the manufactured Zr ⁇ 2 was measured.
  • the size of the manufactured Zr ⁇ 2 nanoparticle decreases to a value that is comparable to the Bohr exciton radius of the manufactured Zr ⁇ 2 nanoparticles, e.g. 10 nm or less, the manufactured Zr ⁇ 2 nanoparticles will exhibit some unique properties because of the nanosize effect, such as photoluminescent properties.
  • the luminescent properties and the photocatalytic properties were further investigated.
  • the emission spectra ( Figure 6b) show four emission peaks in blue light region for all the samples. As a result, strong blue light emission (inset of Figure 4b) when irradiated by a UV- light lamp (365 nm) can be clearly observed even at daytime.
  • FIG. 7 shows the relationship between the nanoparticle size and the photocatalytic efficiency of the Zr ⁇ 2 nanoparticles (as denoted by the hydrogen output in the photocatalytic hydrogen production experiment). It can be observed that the photocatalytic efficiency increases firstly with the increase of crystal size and reach a maximum value of 1676 ⁇ mol-g '-h "1 at the size of ⁇ 5.5 nm (prepared at 210 0 C) and then decreases dramatically when the size increases further. Because the specific surface area (SSA) is an important factor influencing the photocatalytic efficiency, SSA values were measured from the samples prepared at different temperatures.
  • SSA specific surface area
  • the SSA values increase significantly with the decrease of the reaction temperatures.
  • the specific reaction rate of the photocatalytic reaction after considering the SSA values is also included in Figure 7. It can be observed that 5.5 nm also shows a highest specific reaction rate, which indicates that the crystallinity is another important factor influencing the photocatalytic efficiency of Zr ⁇ 2 nanoparticles.
  • a further investigateion into the photocatalytic activity of the commercial Zr ⁇ 2 (Beijing Chemical Plant, China) and Ti ⁇ 2 (p25, Degussa) powders was performed, which show hydrogen output efficiencies of about 673 and 300 ⁇ mol-g 'h "1 , respectively. It indicates that the manufactured Zr ⁇ 2 nanoparticles have excellent photocatalytic activity that are superior to the commercially available metal oxide nanoaprticles.
  • a water phase 20 and an organic phase 30 of toluene which contains the metal oxide precursor 40 Ti(OC 4 Hg) 4 were placed in the hydrothermal chamber 60 and the hydrothermal reaction temperature varied stepwise from 100 0 C to 200 0 C.
  • the average size of the manufactured nanoparticle 10 shows an increase from ap- proximately 1.0 nm to approximately 22 nm (Figure 8).
  • Figure 8 also shows the dimensions of the particles indicating a spherical morphology of the manufactured nanoparticles 10.

Abstract

A method for the manufacture of metal oxide nanoparticles via a two phase interface hydrolysis reaction under hydrothermal reaction conditions is disclosed. The manufactured nanoparticles have good monodispersity, high crystallinity, as well as further advantageous properties such as strong photo luminescence and excellent photocatalytic properties. The nanoparticle size can be controlled by the manipulation of the hydrothermal reaction temperature.

Description

Description Titel: Synthesis of Metal Oxide Nanoparticles
CROSS RELATION TO OTHER APPLICATIONS
[0001] This application claims the priority of UK Patent Application 0801123.1 filed on 22 January 2008.
FIELD OF INVENTION
[0002] The present invention is directed to the field of the manufacture of metal oxide nanoparticles.
PRIOR ART
[0003] Methods for the manufacture of metal comprising nanoparticles are known in the literature. For example J. Phys Chem. B 2006 110, 14262-14265, titled "Synthesis Of FeNi3 alloyed na- noaprticles by hydrothermal reduction" by Xun Wang et al, discloses the reduction of Ni(NO3^- 9H2O with hydrazine hydrate in strong alkaline media. Transmission electron microscope images show that the size of the nanoparticles increases with prolongation of the hydrothermal reaction time.
[0004] Furthermore, the paper in Nature 2005, 437. 121-124, titled "a general strategy for nanocrystal synthesis" by Qilong Liao et al, discloses the manufacture of nanocrystals through the reduction of noble metal ions by ethanol at a temperature of 20 to 200 0C under hydrothermal or atmospheric conditions.
[0005] None of the prior art provides an enabling disclosure for the manufacture of metal oxide nanoparticles according to present invention.
BACKGROUND OF THE INVENTION
[0006] Inorganic semiconductor nanoparticles have attracted great interest in recent decades due to their implementation in a wide variety of applications including photo catalysis, electronic devices, light- emitting devices, solar cells, bioimaging and biosensors. One of the most important factors regarding nanoparticles in these applications is that the size of the nanoparticles must be substantially uniform in order for the nanoparticles to function accordingly.
[0007] Although numerous methods for the manufacture of inorganic nanoparticles (also re- ferred to as nanocrystals) have been developed, such as sol techniques, micelles or emulsion methods, sol-gel process, pyrolysis, chemical vapour deposition (CVD) and electrochemical methods, the prior art methods of manufacture suffer from complicated preparation and post-treatment procedures, problems of aggregation, size and poor monodispersity which greatly influence and hinder the desired properties of the nanoparticles and restrict their large-scale production and application in industry.
[0008] Currently simple methods that are suitable for the industrial production of monodis- persed semiconductor nanoparticles with a tuneable size (especially under 10 nm), remain a challenge to the manufacturing industry.
SUMMARY OF INVENTION
[0009] The present invention teaches a method for the manufacture of metal oxide nanoparticles, preferably but is not limited to nanoparticles used in the semiconductor industry.
[0010] The method comprises providing at least one water phase and at least one organic phase in a chamber of a hydrothermal apparatus. The organic phase is a solution of a metal oxide precursor. The metal oxide precursor is soluble in the organic phase and not the water phase. Once heated to a hydrothermal reaction temperature, hydrolysis and nucleation of the metal oxide precursor occurs at the interface of the organic phase and the water phase resulting in the simultaneous nucleation of the insoluble metal oxide nanoparticles.
[0011] The method provides a simple yet novel method for the manufacture of metal oxide nanoparticles. The method further allows the controlling of the size of the metal oxide nanoparti- cles by altering the hydrothermal reaction temperature.
[0012] The present invention produces nanoparticles that have good monodispersity, are highly crystalline, and additionally possess strong photoluminescence and excellent photocatalytic activities. [0013] The invention discloses a method for the manufacture of nanoparticles whereby the manipulation of the hydrothermal reaction temperature allows the manufacture of nanoparticles with a size below 10 nm.
[0014] Furthermore, the method also exhibits other distinct advantages, compared with other methods of manufacture reported previously. First, the preparation process is simple and cheap, and does not contain any complicated post-treatment procedure. Second, products (without coating) can be collected from the organic phase which effectively avoids grain aggregation induced by the capillary condensation in water environment. Third, the production yield is very high (almost 100 %) and the organic and water phases after reaction can be easily recycled.
[0015] The present invention can be used for the industrial manufacture of nanoparticles and help to reduce the cost of manufacture.
DESCRIPTION OF DRAWINGS
Figure 1. Depicts the manufacture of metal oxide nanoparticles under the separate two-phase hydrothermal reaction conditions.
Figure 2. Depicts a flow diagram for the steps to manufacture metal oxide nanoparticles under the separate two-phase hydrothermal reaction conditions.
Figure 3. Shows low resolution TEM (a) and corresponding high resolution TEM images (b) of Zrθ2 nanoparticles prepared at 160 0C. Further magnified images show the coexistence of the tetragonal (c) and monoclinic Zrθ2 nanoparticles (d) in the samples.
Figure 4. Shows a) Size distribution function of Zrθ2 nanoparticles that calculated from the SAXS data, b) Relationship between the particle size (max probability of diameter) and the hydrothermal temperature.
Figure 5. Shows XRD patterns for Zrθ2 nanoparticles that prepared at different temperatures, a): 100 0C; b) 120 0C; c) 140 0C; d): 160 0C; e) 180 0C; f) 200 0C. Red lines: characteristic peaks for tetragonal phase; Blue lines: characteristic peaks for monoclinic phase.
Figure 6. Shows fluorescence spectra of the Zrθ2 nanoparticles prepared at different temperatures (T), which were dispersed in chloroform, a) Excitation spectra, in which obvious red-shift of the absorption peaks can be observed, b) Emission spectra (excitation wavelength: 285nm). Four main peaks located at 331, 344, 401 and 423 nm in blue-light region can be observed. Inset: blue-light emission of Zrθ2 nanoparticles dispersed in chloroform (recorded by a CCD camera in dark room, irradiated by a black-light lamp (365 nm), left tube: with Zrθ2 nanoarticles, right tube: without Zrθ2 nanoparticles).
Figure 7. Shows photocatalytic properties of the Zrθ2 nanoparticles with different particle sizes, hydrogen output efficiency; specific reaction rate considering the specific surface area of the nanopartlcies.
Fugure 8. Shows average sizes of the Tiθ2 nanoparticles prepared at different temperatures.
Figure 9. Shows average particle size and specific surface area (BET) of the Zrθ2 nanoparticles prepared at different temperatures.
DETAILED DESCRIPTION OF THE INVENTION
[0016] The present invention teaches a method for the manufacture of metal oxide nanoparti- cles 10. The invention is not limited to the use of the metal oxide nanoparticles 10 in a specific application, for example in photo catalysis, electronic devices, light- emitting devices, solar cells, bioimaging and biosensors etc.
[0017] Under hydrothermal reaction temperatures an almost 1 :1 ratio mixture of a water phase 20 and an organic phase 30 (which are immiscible at room temperature and pressure) will exhibit different characteristics. These different characteristics are due to the pressure increase that occurs when the temperature of the mixture of the water phase and the organic phase exceeds both the boiling point of the water phase 20 and the boiling point of the organic phase 30. The mixture of the water phase and the organic phase exhibit a non-liquid and non-gaseous state and, conse- quently, the mixture of the organic phase 30 and water phase 20 exists as tiny droplets. These tiny droplets diffuse with each other to form an interface. The tiny droplets of the organic phase 30 and water phase 20 exist with substantially uniform sizes and can therefore be envisaged as a "nanore- actor". [0018] The nanoreactors, due to their substantially uniform size, provide an environment for the manufacture of the nanoparticles 10 of substantially uniform sizes. The size of the nanoreactors accordingly determines the size of the nanoparticles and will also consequently confine the further growth of nanoparticles.
[0019] Under these circumstances where the mixture of the organic phase 30 and the water phase 20 are subjected to hydrothermal reaction temperatures and where the organic phase 30 contains a chemical substance that comprises hydrolysable groups, hydrolysis of the hydrolysable groups will occur at the interface of the water phase 20 and the organic phase 30. This hydrolysis results in a hydrolysed chemical substance with a substantially uniform particle size.
[0020] The process of diffusion at the interface of the droplets of the organic phase 30 by the water phase 20 is a dynamic process. The sizes of the tiny droplets (nanoreactors) and the diffusion at the interface of the organic phase 30 with the water phase 20 depends upon the hydrothermal reaction temperature. Therefore, if a hydrolysable chemical substance is present in the organic phase 30, a size of the nanoparticles can be controlled by altering the hydrothermal reaction temperature.
[0021] Where the chemical substances to be hydrolysed are metal oxide precursors 40, the metal oxide precursors 40 will be initially soluble in the organic phase 30. Once the metal oxide precursors 40 are hydrolysed to form a metal oxide nanoparticle 10, the metal oxide nanoparticle 10 will neither be soluble in the organic phase 30 or the water phase 20. The metal oxide nanoparticle 10 will crystallise from the mixture of the water phase 20 and the organic phase 30 during manufacture.
[0022] The hydrolysis reactions are carried out in a Teflon lined hydrothermal chamber 60 as shown in Fig 1.
[0023] In one aspect of the present invention shown in Fig. 2, the method for the preparation of nanoparticles commences as in step 200. The water phase 20 and the organic phase 30 are prepared as in step 210. The organic phase 30 contains a metal oxide precursor 40 dissolved in the organic phase 40 to form a solution. The solution is prepared in the open atmosphere and the ration of the organic phase to the water phase is 1 :1. [0024] The water phase 20 and the organic phase 30, which contains the metal oxide precursor 40 are then placed in the sealed hydrothermal chamber 60 of a hydrothermal apparatus as in step
220.
[0025] The mixture of the water phase 20 and the organic phase 30 is then heated to a hydro- thermal reaction temperature as in step 230. As discussed above, the hydrothermal reaction temperature determines the size of the manufactured nanoparticles 10.
[0026] Once the hydrothermal reaction temperature has been reached, hydrolysis 240 of the metal oxide precursor 40 occurs almost instantaneously.
[0027] Upon hydrolysis 240 of the metal oxide precursor 40, the manufactured nanoparticles 10 fall from the solution as in step 250 as ultrafine, crystalline metal oxide nanoparticles 10.
[0028] The manufactured nanoparticles 10 are then collected and analysed as in step 260. The analysis is carried out by transmission electron microscopy (TEM), small angle X-Ray scattering (SAXS), X-Ray diffraction (XRD). Photoluminescent and photocatalytic activity of the manufactured nanoparticles are measured using a Perkinelmer Is55 luminescence spectrometer and photo- catalytic hydrogen production experiments
[0029] Following the analysis 260 of the manufactured nanoparticles 10, the method is complete (step 270). The water phase 20 and the organic phase 30 may then be recycled by distillation.
Examples
[0030] The examples demonstrate the various aspects of the invention but are not intended to limit the invention when taken in conjunctions with the claims and the detailed description.
Example 1 Preparation of Zrθ2 nanoparticles
[0031] A water phase 20 and an organic phase 30 of toluene which contains the metal oxide precursor 40 Zr(OC4Hg)4 were placed in the hydrothermal chamber 60 and the hydrothermal reaction temperature set to 160 0C. The manufactured Zrθ2 nanoparticles 10 were prepared in 99.9 % yield. [0032] Figure 3a shows a TEM of the manufactured Zrθ2 nanoparticle. The manufactured Zrθ2 nanoparticle shows excellent dispersity and no toluene coating as determined by proton NMR. Figure 3b displays a high resolution TEM depicting well crystallised quantum dots of the manufactured Zrθ2 nanoparticle and a particle size of approximately 4.4nm is observed.
[0033] The reaction of Example 1 was then carried out at different hydrothermal reaction temperatures and the manufactured nanoparticles 10 were investigated by SAXS. The curves of distribution function (Figure 4a) show good monodispersity for all samples prepared at different temperatures with the average size of the manufactured nanoparticles 10 increasing monotonously from l.Onm to approximately 6.1nm when the temperature was increased from 110 0C to 240 0C (Figure 4b). The XRD patterns (Figure 5) show that the samples have very good crystallinity, which increases with the increase of preparation temperature.
[0034] Photo luminescent and photocatalytic activities of the manufactured Zrθ2 was measured. When the size of the manufactured Zrθ2 nanoparticle decreases to a value that is comparable to the Bohr exciton radius of the manufactured Zrθ2 nanoparticles, e.g. 10 nm or less, the manufactured Zrθ2 nanoparticles will exhibit some unique properties because of the nanosize effect, such as photoluminescent properties. In order to verify the performance of the manufactured Zrθ2 nanoparticles 10, the luminescent properties and the photocatalytic properties were further investigated. As shown in the excitation spectra (Figure 6a), the absorption peaks for the Zrθ2 nanoparticles exhibit obvious red-shift from ~ 278.0 - 284.0 nm to ~ 288.5 nm when the size of the nanoparticles increases from - 1.0 nm (prepared at T = 110 0C) to ~ 6.1 nm (T = 240 0C), indicating a distinct quantum size effect. The emission spectra (Figure 6b) show four emission peaks in blue light region for all the samples. As a result, strong blue light emission (inset of Figure 4b) when irradiated by a UV- light lamp (365 nm) can be clearly observed even at daytime. These features are related to the near band-edge transitions and a mid-gap trap state that results from incomplete surface passivation such as surface defects and oxygen vacancies, and the change of the corresponding band gap with the decrease of the nanocrystal size.
[0035] The manufactured Zrθ2 nanoparticles also show excellent and size-dependent photocatalytic activity. Figure 7 shows the relationship between the nanoparticle size and the photocatalytic efficiency of the Zrθ2 nanoparticles (as denoted by the hydrogen output in the photocatalytic hydrogen production experiment). It can be observed that the photocatalytic efficiency increases firstly with the increase of crystal size and reach a maximum value of 1676 μmol-g '-h"1 at the size of ~ 5.5 nm (prepared at 2100C) and then decreases dramatically when the size increases further. Because the specific surface area (SSA) is an important factor influencing the photocatalytic efficiency, SSA values were measured from the samples prepared at different temperatures. As shown in Figure 9, the SSA values increase significantly with the decrease of the reaction temperatures. The specific reaction rate of the photocatalytic reaction after considering the SSA values is also included in Figure 7. It can be observed that 5.5 nm also shows a highest specific reaction rate, which indicates that the crystallinity is another important factor influencing the photocatalytic efficiency of Zrθ2 nanoparticles. In order to make a comparison, a further investigateion into the photocatalytic activity of the commercial Zrθ2 (Beijing Chemical Plant, China) and Tiθ2 (p25, Degussa) powders was performed, which show hydrogen output efficiencies of about 673 and 300 μmol-g 'h"1, respectively. It indicates that the manufactured Zrθ2 nanoparticles have excellent photocatalytic activity that are superior to the commercially available metal oxide nanoaprticles.
Example 2 Preparation of Tiθ2 nanoparticles
[0036] A water phase 20 and an organic phase 30 of toluene which contains the metal oxide precursor 40 Ti(OC4Hg)4 were placed in the hydrothermal chamber 60 and the hydrothermal reaction temperature varied stepwise from 100 0C to 200 0C.
[0037] The average size of the manufactured nanoparticle 10, shows an increase from ap- proximately 1.0 nm to approximately 22 nm (Figure 8). Figure 8 also shows the dimensions of the particles indicating a spherical morphology of the manufactured nanoparticles 10.

Claims

Claims
1. A method for the manufacture of metal oxide nanoparticles (10) comprising: providing at least one water phase (20); providing at least one organic phase (30), wherein the at least one organic phase (30) contains a metal oxide precursor (40); placing the at least one water phase (20) and the at least one organic phase (30) in a same chamber (60) providing heat to reach a hydrothermal temperature, thus hydrolysing the metal oxide pre- cursor (40) to form the metal oxide nanoparticles (10).
2. The method according to claim 1, wherein the formation of the metal oxide nanoparticles (10) is at a two phase interface reached by heating the at least one water phase (20) and at least one organic phase (30 to the hydrothermal temperature.
3. The method according to any of the above claims, wherein the at least one water phase (20) and the at least one organic phase (30) are placed in a hydrothermal chamber (60).
4. The method according to any of the above claims wherein a ratio of organic phase (30) and water phase (20) is substantially a 1 :1 ratio.
5. The method according to any of the above claims, wherein the organic phase is selected from a group comprising of toluene, chloroform, isooctane and ethyl acetate.
6. A method according to any of the above claims, wherein the metal oxide precursor (50) is selected from a group comprising a metal alkyl-oxides and metal alkyls.
7. A method according to any of the above claims, wherein a metal in the metal oxide precursor is selected from group two metal of the transition elements of the periodic table.
8. A method according to any of the above claims, wherein the hydrothermal temperature is selected to control the size of the metal oxide nanoparticles (10).
PCT/EP2009/050544 2008-01-22 2009-01-19 Synthesis of metal oxide nanoparticles WO2009092684A2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP09704125A EP2244981A2 (en) 2008-01-22 2009-01-19 Synthesis of metal oxide nanoparticles

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0801123.1 2008-01-22
GB0801123A GB2457134A (en) 2008-01-22 2008-01-22 Synthesis of Metal Oxide Nanoparticles

Publications (2)

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