Classifications

• • 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
• • 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
• • 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
  • 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.

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• 2008
  • 2008-01-22 GB GB0801123A patent/GB2457134A/en not_active Withdrawn
• 2009
  • 2009-01-19 WO PCT/EP2009/050544 patent/WO2009092684A2/en not_active Ceased
  • 2009-01-19 EP EP09704125A patent/EP2244981A2/de not_active Withdrawn

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