(12) Patent Application Publication (10) Pub. No.: US 2006/0061017 A1 Strouse Et Al
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US 2006006 1017A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2006/0061017 A1 Strouse et al. (43) Pub. Date: Mar. 23, 2006 (54) METHOD FOR SYNTHESIS OF COLLOIDAL (22) Filed: Sep. 20, 2004 NANOPARTICLES Publication Classification (75) Inventors: Geoffrey Fielding Strouse, Tallahassee, FL (US); Jeffrey A. Gerbec, Goleta, (51) Int. Cl. CA (US); Donny Magana, Madera, CA B29C 67/00 (2006.01) (US) (52) U.S. Cl. .............................................................. 264/489 Correspondence Address: (57) ABSTRACT GATES & COOPER LLP HOWARD HUGHES CENTER A method for Synthesis of high quality colloidal nanopar 6701 CENTER DRIVE WEST, SUITE 1050 ticles using comprises a high heating rate proceSS. Irradia LOS ANGELES, CA 90045 (US) tion of Single mode, high power, microwave is a particularly well Suited technique to realize high quality Semiconductor (73) Assignee: The Regents of the University of Cali nanoparticles. The use of microwave radiation effectively fornia automates the Synthesis, and more importantly, permits the use of a continuous flow microwave reactor for commercial (21) Appl. No.: 10/945,053 preparation of the high quality colloidal nanoparticles. Patent Application Publication Mar. 23, 2006 Sheet 1 of 6 US 2006/0061017 A1 U O a O S. - 4.5mm CC Se - - - 5.5nm CC Se s D s N 500 600 Wavelength (nm) FIG. 1 Patent Application Publication Mar. 23, 2006 Sheet 2 of 6 US 2006/0061017 A1 18 2O 1 O O O. 8 9. 2. O O 6 B 2 O o f 0. 4. O 2 7. O. 5 rus 0. O O O 400 500 600 700 Wavelength (nm) FIG. 2 Patent Application Publication Mar. 23, 2006 Sheet 3 of 6 US 2006/0061017 A1 d . he O ot a. CN 400 450 500 550 600 650 700 600 700 800 Wavelength (nm) Wavelength (nm) FIG. 3A FIG. 3B Patent Application Publication Mar. 23, 2006 Sheet 4 of 6 US 2006/0061017 A1 30 32 9. al O s s S O d S. Ci o 34 400 500 600 700 800 Wavelength (nm) FIG. 4 Patent Application Publication Mar. 23, 2006 Sheet 5 of 6 US 2006/0061017 A1 PREPAIRE 38 CONSTITUENT ELEMENTS HIGH-RATE 40 HEATING 42 TEMPERATURE STABILIZATION HIGH-RATE 44 COOLING FIG. 5 Patent Application Publication Mar. 23, 2006 Sheet 6 of 6 US 2006/0061017 A1 S. US 2006/0061017 A1 Mar. 23, 2006 METHOD FOR SYNTHESIS OF COLLODAL SUMMARY OF THE INVENTION NANOPARTICLES 0009. To overcome the limitation in the prior art BACKGROUND OF THE INVENTION described above, and to overcome other limitations that will become apparent upon reading and understanding the 0001) 1. Field of the Invention present specification, the present invention describes meth 0002 The invention is related to chemical synthesis of ods of chemical Synthesis of nanoparticles, Such as quantum nanoparticles, and more particularly, to the large-scale, Safe, dots, comprising a high temperature ramp process, warrant convenient, reproducible, energy-conserving Synthesis of ing large-scale, Safe, convenient, reproducible, and energy highly-dispersive inorganic nanoparticles with narrow size efficient production. distribution. 0010. In the present invention, inorganic nanoparticles 0003 2. Description of the Related Art are Synthesized by a Scheme that comprises heating of the 0004 (Note: This application references a number of reaction System. It has been found that the above mentioned different publications as indicated throughout the Specifica limitation can be overcome by including a heating process tion by one or more reference numbers within brackets, e.g., with high ramping rate. Hence, the critical issues that X). A list of these different publications ordered according distinguish the present invention are: to these reference numbers can be found below in the section 0011 (1) a method for synthesizing nanoparticles that entitled “References.” Each of these publications is incor comprises a high temperature ramping rate during heating, porated by reference herein.) 0012 (2) the above mentioned method wherein micro 0005 Over the past decade, numerous advances have wave irradiation is used for the heating process, been made in the Synthetic procedures for formation and isolation of high quality inorganic nanoparticles. These 0013 (3) the above mentioned method wherein the materials are finding applications in a wide range of disci dielectric constant of the main constituent element, which is plines, including optoelectronic devices, biological tagging, the element that dominates the largest amount of molar ratio optical Switching, Solid-State lighting, and Solar cell appli among the entire reactant, is 20 or lower, and cations. 1-11 0014 (4) high crystallinity of the nanoparticles that is 0006. One of the major hurdles for industrialization of often achieved by employing the results of the present these materials has been the development of a reproducible, invention. high quantity Synthetic methodology that is adaptable to high throughput automation for preparation of quantities of BRIEF DESCRIPTION OF THE DRAWINGS >100's of grams of single size (<5% RMS) crystalline 0015 Referring now to the drawings in which like ref quantum dots of various composition to be isolated. 12-13 erence numbers represent corresponding parts throughout: 0007. The general synthetic approach for preparation of colloidal Semiconductor nanoparticles employs a bulky 0016 FIG. 1 is a graph that illustrates the absorption and reaction flask under continuous Ar flow with a heating photoluminescence for 4.5 nm and 5.5 nm CdSe; mantle operating in excess of 240 C. The reaction is 0017 FIG. 2 is a graph that illustrates the absorption and initiated by rapid injection of the precursors, which are the photoluminescence for 4.6 mm CdSe; Source materials for the nanoparticles, at high temperatures and growth is controlled by the addition of a strongly 0018 FIGS. 3A and 3B are graphs that illustrate the coordinating ligand to control kinetics. And to a more absorption and photoluminescence of InGaP nanocrystals limited extent, domestic microwave ovens have been used to synthesized with hexadecene (HDE) and octadecene as the Synthesize nanoparticles. 14-19 The high temperature non-coordinating Solvents, method imposes a limiting factor for industrial Scalability and rapid nanomaterial discovery for Several reasons: (1) 0019 FIG. 4 is a graph that illustrates the absorption and random batch-to-batch irregularities Such as temperature photoluminescence of InGaP showing the dependence of ramping rates and thermal instability; (2) time and cost crystallinity on power; required for preparation for each individual reaction; and (3) 0020 FIG. 5 is a flowchart that illustrates the processing low product yield for device applications. StepS used in the preferred embodiment of the present 0008 While recent advances in the field have developed invention; and better reactants, including inorganic Single Source precur 0021 FIG. 6 is an illustration of the processing steps Sors, metal Salts, and oxides, better passivants, Such as used in the preferred embodiment of the present invention. amines and non-coordinating Solvents, and better reaction technologies, Such as thermal flow reactors, the reactions are DETAILED DESCRIPTION OF THE still limited by reproducibility. Coupled to this problem is INVENTION the lack of control over reaction times, which require continuous monitoring. In the case of III-V compound 0022. In the following description of the preferred Semiconductors, the Synthetic pathways have rates of growth embodiment, reference is made to the accompanying draw on the order of days, while in the case of II-VI's, size control ings which form a part hereof, and in which is shown by way is very difficult and depends on the ability to rapidly cool the of illustration a specific embodiment in which the invention reaction. In these cases, the reaction depends on heating rate, may be practiced. It is to be understood that other embodi heat uniformity over the reaction vessel, Stirring and rapid ments may be utilized and Structural changes may be made and uniform cool-down. without departing from the Scope of the present invention. US 2006/0061017 A1 Mar. 23, 2006 0023 1. The Reaction System free of any heat input/output. Here, Stable temperature refers to processes in which the temperature change is 5 C./min or 0024. In the present invention, nanoparticles are synthe leSS. sized by heating the reaction System from room temperature to elevated temperatures. The reaction System herein is a 0031 Cool-down of the reaction system can be achieved closed System that consists of materials that are necessary by removing heat from the System by Standard means Such for the synthetic reaction. Each of these materials will as air, water, ice, oil or cryogenic gas. Microwave irradiation hereafter be called a constituent element. In the most primi with or without other heat Sources can be used to control this tive reaction System, the Sole constituent element is the cool-down process. The average cooling rate of each cool precursor. However, in general, the constituent elements are down process is defined as: Solvent and precursor. The Solvent can be a mixture of plural (Temperature at the beginning of cooling ( C.)-Tem Solvents, and also the precursor can be a mixture of plural perature at the end of cooling( C.))/(Duration of precursors. These elements can either be dispersed homo cooling (min)) geneously or inhomogeneously. 0032. The synthetic scheme described in the present invention comprises one or more Stages of high cooling rate. 0.025 The constituent elements of the reaction system are Here, high cooling rate refers to a rate of 80 C./min or mixed at or near room temperature and heated for nanopar higher, more preferably 85 C/min or higher, most favor ticle synthesis. Here, near room temperature is below 100 ably 90° C./min or higher. When the average cooling rate is C. below 80 C./min, synthesis may result in nanoparticulate 0.026 2.