FIELD OF THE DISCLOSURE

The present disclosure relates to systems, methods, and devices for producing quantum particles (e.g., quantum dots). More particularly, the present disclosure relates to systems, methods, and devices for producing quantum particles having a uniform size by vaporization of droplets formed from a melt of solid materials (i.e., a melt made from heating solid material(s) to a temperature above its melting temperature).

BACKGROUND OF THE DISCLOSURE

Quantum dots (QDs) are of interest in a number of fields, including electronics, photovoltaics, computing, imaging, catalysis, and medicine. Quantum dots are a form of semiconductor nanoparticles having a small size on the order of about 1 to about 100 nm, or from about 1 to about 10 nm, and which may have optical, electronic, or magnetic properties which vary from those of bulk materials. In particular, many of these properties may vary with the size of the individual dots. That is, one or more material properties can be altered or changed by merely a change in size of the dot through the angstrom and nanometer scales. For example, in general conductivity of metals typically goes down as temperature goes up. The rate of change of conductivity with temperature may be altered by size changes in the nanometer scale. As a result, tight control over size is an important factor in the manufacture of quantum dots. These properties may vary with the size of the particles either in a linear or continuous proportion with size changes, or in a quantized fashion, that is the value associated with a given property may change in a step-wise manner at particular sizes of the particle, but will be relatively constant in-between those steps.

Other factors that can affect the quality or commercial manufacture of quantum dots include purity and stoichiometry. For example, the lack of control over purity, such as by the presence of contaminants may interfere with the formation of the desired crystalline structure or result in broadening of the electronic and optical characteristics of the particles.

Stoichiometry of quantum dots is an important consideration. The particular stoichiometry may control the ability of particles to form at all, as well as characteristics (electrical, optical, magnetic, etc.) of the quantum dot. Some quantum dots may have two or more components which are each present in substantially comparable concentrations, e.g. 1:1, 2:1, 3:1, 4:1, 5:1, 10:1. Other quantum dots may have one or more dopants which are present in much smaller quantities, such as 100:1, 500:1, 1000:1. Quantum dots may also have both one or more stoichiometric components and one or more dopants.

Precise control of particle size may also critical to many applications. The electrical and optical characteristics of any given particle may depend on its size, whether in a quantized or proportional relationship. In addition to the size of individual particles, the distribution of size within a population of the same quantum dot may also been important. In many applications, a narrow size distribution will be desired so that characteristics that correspond to size will also be relatively narrow, e.g., narrow absorbance and emission bands. Size effects may be proportional within certain size domains and may be quantized within certain other size domains.

Existing synthetic methods for forming quantum dots may largely be grouped as physical and chemical methods. Physical methods include inert gas condensation, arc discharge, ion sputtering, laser ablation, and pyrolysis. Chemical methods may be grouped under various categories, such as by solvent used (aqueous or organic) or conditions of the reaction (e.g., solvothermal reactions carried out above the normal boiling point of the solvent by applying high pressure, or arrested precipitation reactions at high pH).

Conventional synthetic methods are plagued with multiple problems. For example, chemical methods may utilize hazardous or expensive solvent precursors. In addition, disposal of waste solvents can be expensive. Further, efficient conversion of precursor material plagues both synthetic method routes. That is, typically a large amount of waste is generated in processing the precursor materials in comparison to the amount of quantum dots manufactured.

Another measure of efficiency relates to control over particle size. Where particle size is widely distributed, it may be necessary to separate the desired product particles and discard particles outside the appropriate tolerance. This results in a further reduction is efficiency.

SUMMARY OF THE TECHNOLOGY

The current technology relates to a novel means for manufacturing quantum particles (e.g., quantum dots), through the use of a droplet maker-plasma chamber system. The system can achieve one or more of high purity, a narrow size distribution, and/or desirable electronic and optical characteristics in the product quantum dots. Furthermore, the system can operate at lower cost, more rapidly, and/or with greater environmental sensitivity, as compared to existing methods.

In an embodiment, the present disclosure relates to a system for the manufacture of quantum dots from a solid precursor material (i.e., from a molten melt made from heating solid material at or above its melting temperature). The system includes a molten material droplet maker capable of providing substantially uniformly sized droplets of a molten material while maintaining the droplets in a molten state, the molten material being formed from the solid precursor material; a plasma chamber in communication with the droplet maker and disposed to receive a flow of molten droplets from the droplet maker; at least one inlet for introducing a gas or vapor into the plasma chamber; an energy source (e.g., a microwave energy source) for forming the plasma, the energy source in communication with the plasma chamber and disposed to apply energy to the gas or vapor in the plasma chamber to form the plasma at a location within the plasma chamber to permit the flow of molten droplets to be vaporized to form a quantum particle precursor material; and a quenching chamber in communication with the plasma chamber and disposed to receive the quantum particle precursor material, the quenching chamber adapted to quench the quantum particle precursor material to inhibit growth and to form the quantum particles.

In an embodiment, of the above system for the manufacture of quantum dots from a solid precursor material requires that the substantially uniformly sized droplets of molten material each has a droplet diameter that is within 50% (e.g., 25%, 10%, 5%) of a predetermined droplet size. In another embodiment, the present disclosure relates to a system for the manufacture of quantum dots from a solid precursor material (e.g., molten melt of the solid material) where the energy source includes a microwave energy source. In an embodiment, the present disclosure relates to a system for the manufacture of quantum dots from a solid precursor material where the microwave energy source has a radiation frequency from about 900 MHz to about 5900 MHz. In an embodiment, the present disclosure relates to a system for the manufacture of quantum dots from a solid precursor material where the droplet maker includes a heating element disposed to maintain the molten material formed from the solid precursor material in the molten state. In an embodiment, the present disclosure relates to a system for the manufacture of quantum dots from a solid precursor material includes a piezo electric actuator, a flexible plate, and at least one capillary for delivery molten material. In an embodiment, the present disclosure relates to a system for the manufacture of quantum dots from a solid precursor material including a low-pressure pump in communication with the quenching chamber and disposed to produce low pressure within the quenching chamber. In an embodiment, the present disclosure relates to a system for the manufacture of quantum dots from a solid precursor material where the quenching chamber comprises one or more exterior walls and a cooling fluid source, at least one exterior wall comprising a plurality of holes, the plurality of holes disposed to receive a flow of cooling fluid from the cooling fluid source.

In an embodiment, the present disclosure relates to a method for the manufacture of quantum particles (e.g., quantum dots) from a solid precursor material. The method includes melting the solid precursor material to create a molten precursor material; forming droplets of the molten precursor material; vaporing the droplets within a plasma to form a plasma treated vapor; and quenching the plasma treated vapor to form quantum particles.

In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material including introducing a second vapor including a functionalizing material. The second vapor can be added prior to the quenching step, during the quenching step, or after the quenching step. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material including introducing a second vapor prior to the quenching step, the second vapor including an allowing material to form a mixture with the plasma treated vapor. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material where the second vapor including silane for forming silicon based alloys. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material including generating the plasma, which includes generating microwave radiation, guiding microwave radiation to the plasma chamber using a waveguide, introducing an entrainment gas into the plasma chamber, and igniting the plasma. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material including mixing the molten precursor material prior to forming droplets. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material where the quenching step occurs partially in a plasma chamber and partially in a quenching chamber. In another embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material where the vaporizing step occurs in a plasma chamber and the quenching step occurs in a quenching chamber, and a pressure gradient is established and such that the quenching chamber is maintained at a lower pressure than the plasma chamber. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material including maintaining the plasma chamber between about 700 to 1100 Torr and maintaining the quenching chamber between about 1 to 100 Torr. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material where the step of forming droplets comprises agitating the molten precursor material with a piezoelectric actuator and forming the molten precursor material through at least one capillary. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material where the quenching step is achieved by causing supersaturation, nucleation and controlled growth (e.g., limited growth) to form the quantum particles/dots. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material where the quenching step includes establishing low pressure in the quenching chamber, the low pressure being sufficient to achieve rapid expansion and condensation of the vapor. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material where at least 50% of the precursor material consumed in the method is converted into quantum dots. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material where the quenching step comprises creating a controlled gaseous environment in which the plasma treated vapor passes through. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material where the controlled gaseous environment includes one or more elemental gases. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material where the controlled gaseous environment includes one or more molecular gases. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material where the quenching step includes flowing a cooling fluid proximate the plasma treated vapor. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material including a functionalizing step, which includes providing a functionalizing gas or vapor within the quenching chamber where the functionalizing gas or vapor contains a function group precursor. In an embodiment, the present disclosure relates to a method for the manufacture of quantum dots from a solid precursor material, wherein the solid precursor material is a material selected from the group consisting of: tin, selenium, aluminum, gallium, indium, cadmium, zinc, lead, bismuth, europium, arsenic, iodine, thallium, silver, strontium, lithium, barium, and alloys of the same. In some embodiments, the solid precursor material is any element or alloy with a melting temperature lower than about 1000 C. In general these solid precursor materials can be used to form a semiconductive material. In one embodiment, the method of the present disclosure further includes a filtering or collection step.

In an embodiment, the present disclosure relates to a method of manufacturing a quantum dot having a core at least partially surrounded by a shell. The method includes: melting a core precursor material to create a molten core precursor material; forming core precursor material droplets from the molten core precursor material; vaporizing the core precursor material droplets within plasma; forming quantum dot cores from the vaporized core precursor material droplets; melting a shell precursor material to create a molten shell precursor material; forming shell precursor material droplets of the molten shell precursor material; vaporizing shell precursor material droplets within plasma; and forming quantum dot shells on the quantum dot cores.

