Continuous flow reactor for the synthesis of nanoparticles

Abstract

A continuous flow reactor for the efficient synthesis of nanoparticles with a high degree of crystallinity, uniform particle size, and homogenous stoichiometry throughout the crystal is described. Disclosed embodiments include a flow reactor with an energy source for rapid nucleation of the procurors following precursors to form nucleates followed by a separate heating source for growing the nucleates. Segmented flow may be provided to facilitate mixing and uniform energy absorption of the precursors, and post production quality testing in communication with a control system allow automatic real-time adjustment of the production parameters. The nucleation energy source can be monomodal, multimodal, or multivariable frequency microwave energy and tuned to allow different precursors to nucleate at substantially the same time thereby resulting in a substantially homogenous nanoparticle. A shell application system may also be provided to allow one or more shell layers to be formed onto each nanoparticle.

Description

PRIORITY CLAIM

Where a COV <15% within a single run demonstrates uniform particle size, and a COV <15% from batch-to-batch demonstrates reproducibility.

Degree of Crystallinity and Homogeneous Stoichiometry: The degree of crystallinity or the purity of the crystalline phase (as shown in FIG. 11A and FIG. 11B) can be determined by TEM using diffraction scattering patterns and performing a fourier transform analysis to determine the crystalline structure of the material. Another technique that may be used to determine this is XRD, where the resultant diffraction pattern can be matched to a library of known crystal structures and verified as to being inhomogeneous (multiple contributions from different crystals) or homogeneous (one contributing pattern diffraction matching the desired crystal structure). Lack of a diffraction pattern in either XRD and/or TEM is indicative of an amorphous material, indicating poor or non-existent crystal structure.

Homogeneous Stoichiometry and Uniform Particle Size: This information is obtained using either absorbance spectrophotometry or photoluminescent emission. The absorption and photoluminescence characteristics of a nanoparticle are determined by the FWHM (full width half max, where the width of the absorbance or photoluminescence peak is determined at half the height of the peak of interest) obtained through the spectrum. An increase in the FWHM means that one of multiple effects could be taking place, such as: large particle size distribution (COV >15%), insufficient degree of crystallinity resulting in trap states that have different energies than a highly crystalline nanoparticle, and inhomogeneity of the material—giving rise to multiple excitations or emissions from the various regions within the nanoparticle or batch of nanoparticles. A nanoparticle having a high degree of crystallinity, a homogeneous stoichiometry, and being monodisperse will give rise to absorption and/or photoluminescence peaks of: <50 nm FWHM from 400 nm-700 nm, <150 nm FWHM from 700 nm-2000 nm, <300 nm FWHM from 2000 nm-10000 nm.

In the case of metallic nanoparticles, instead of a first exciton excitation and emission, a surface resonance plasmon can be observed. Using the same arguments presented above, a metallic nanoparticle having a high degree of crystallinity will have <50 nm FWHM when excited at the surface plasmon resonance frequency when excited between 400 nm and 700, and <150 nm FWHM when excited in the near-infrared range (700 nm-2000 nm) when exciting at the surface plasmon resonance frequency.

The frequency or frequencies which the microwave operates can also be selected to excite a particular material in the process without exciting other materials such as binders or the like. Microwave frequencies ranging from between 300 MHz (1.24 μeV) to 300 GHz (1.24 meV), which are sufficiently low enough in energy that they do not chemically change the substances by ionization. These energies affect the rotational and bi-rotational energies of molecules when absorbed by such species. These absorbances are unique to each type of bending transition, rotation transition and bi-rotational transition; hence, energies may be selected that interact specifically with each transition. This property allows the ability to select the desired microwave frequency to interact with a specific reactant in a flow cell reactor, which allows several capabilities.

For example, this allows temperature limitations associated with the boiling point of solids to be overcome. By selectively activating only the precursors associated with the synthesis of nanoparticles, the solvent selection can be increased significantly to allow for the solubility of precursors that would not normally be used. Additionally, temperatures of the precursors can effectively be much greater than the solvent, thereby allowing for reactions that are not allowed through traditional heating of the solvent.

The tube 40 carrying the precursors 32, 34 through the energy source 50 can be configured with a cooling system, such as tubes that encircle the tube and carry cooling liquid. This allows the precursors within the tube to be heated, by microwaves or the like, to high enough energy levels to promote nucleation without overheating the tube itself and compromising its structural limits.

Also, nanoparticles may be formed that are not feasible using traditional colloidal nanoparticle synthetic techniques. For example, the energy required for the formation of GaN nanoparticles is great enough to surpass the boiling point of any solvent that is available for synthetic techniques. Accordingly, the formation of these nanoparticles is only done through high energy intensive and expensive deposition systems such as Atomic Layer Deposition (“ALD”). This is done because only the precursors needed for the formation of the GaN nanoparticles are heated in the microwave initiated reaction of the present invention.

Moreover, in cases where one or more reaction pathways are possible, the selective application of microwave frequencies allows for the activation of a desirable reaction pathway. For example, if a given reaction is thermodynamically dominated, the use of selective microwave activating allows for the formation of the kinetic product. The ability to selectively target which species the reaction is going to absorb the microwave energy extends the ability of the continuous flow cell reactor to deliver products that would not normally be delivered at a cost that the microwave continuous flow cell reactor is capable of delivering.

Another example of a possible benefit with selective frequency microwaving involves the use of a polyol process to synthesize nanoparticles of metallic salts. In this process, the metallic (Ni, Co, Ag, and mixtures thereof) salts (acetate, chloride, fluoride, nitrate) are dissolved at 1.0-3.0 mmol ethylene glycol or polypropylene glycol (or similar polyol). At 2.45 GHz, the solvent absorbs the microwave irradiation very strongly, heating the solvent to the point where it then acts as the reducing agent for the metallic precursor, allowing for the formation of metallic nanoparticles. These types of reactions can be shown symbolically as noted below:
Ni(O₂CCH₃)₂+propylene glycol→Ni(0) nanoparticles
AgNO₃+ethylene glycol→Ag(0) nanoparticles

Another example is the microwave absorption of precursors for the synthesis of PbS nanoparticles. The synthesis of PbS may be done in the following manner. 1.5 mmol of lead oleate is dissolved in 1-octadecene with the addition of 3.0 mmol-12.0 mmol of oleic acid. 1.4 mmol of bis(trimethylsilyl)sulfide (TMS₂S) which was previously dissolved in the 1-octadecene. The microwave frequency of 2.45 GHz is chosen because both the oleic acid and the 1-octadecene have very low absorption cross-sections at this frequency. On the other hand, both the TMS₂S and the lead oleate have a relatively large absorption cross-section at this frequency, allowing the absorption by these materials and the selective activation. This exemplar reaction can be shown symbolically as noted below.
Pb(oleate)₂+TMS₂S→PbS(oleate) nanoparticles

Zone 3—Growth

This is the growth zone. At this point, the nucleates undergo one of two processes: (1) combination with other nucleates to form nanoparticles/quantum dots of the correct core size, or (2) combination with unreacted precursors to form an epitaxial growth system allowing for the formation of the nanoparticles/quantum dots at a very controlled pace. The material is allowed to remain in the growth zone for a period necessary for them to grow to the specific desired core size, after which, the material is moved through Zone 4.

In general, in the growth phase, the nucleates are preferably heated in a heat source 60 over a longer period of time, such as greater than 100 seconds, at a lower energy level than what they faced during nucleation. This allows thermodynamic growth and Ostwald Ripening. This heating may be done using several different systems, including, but not limited to, sand baths, convection ovens, forced air heating, induction ovens, oil baths and column heaters. Preferably, this heat source 60 is spaced apart from the energy source 50 used in nucleation and is custom-tailored to provide optimal growth of the nucleates. The length of the flow path tube 40 extending through the heat source, diameter of the tube, temperature of the heat source, uniform distribution of heat within the tube, and nucleate flow rate though the heat source are selected to optimize growth of the nucleates during this phase (as shown in FIGS. 4A-C and 5A-B) thereby providing uniform morphology and size among the nanoparticles produced.

Referring to FIGS. 4A-4C, the flow tube 40 may be arranged in a serpentine arrangement within a rack 41 that is receivable within the heat source 60. A plurality of racks may be stacked on top of each other as shown in FIG. 4C thereby allowing effective heat distribution to the flow tubes 40 while optimizing space within the heat source 60. An alternative possible arrangement is shown in FIGS. 5A & 5B where individual flow tubes are coiled to define a heat transfer coil 43 with a plurality of heat transfer coils received within the heat source 60

Zone 4—Quenching

The flow path continues past zone 3 to zone 4, where the reaction is immediately terminated through a temperature reduction using a quenching system 86 such as a quenching bath or the like. After quenching the growth of the nanoparticle 70, the segmentation is removed through a degassing step 150 (FIG. 7) to allow for introduction of more material for shell growth and for ease of in-line analysis to be performed.

If needed, increasing the pressure in the flow path 22 can increase the boiling point of a solvent used in the process, thereby allowing the system to operate at higher temperatures and energy levels. One possible way to increase the pressure in the flow path involves inserting a restrictive flow valve into the flow path downstream of the quenching stage. The flow through the valve can be adjusted so as to increase the pressure in the tube upstream of the valve, thereby increasing the pressure in the tube through zones 2 and 3, where the precursor and nucleates are activated and grown.

Preferably and as best shown in FIG. 7, the reactively inert gas 42 is also separated from the nanoparticles 70. The flow path 22 extends into a chamber 160 where the nucleates drop downward and exit from below while the gas escapes and is collected from a vent 162 above. Alternatively, the reactively inert gas can be separated at a future point downstream in the flow path as needed.

Real-Time Quality Testing and System Optimization

As shown in FIG. 1, a testing system 72 can be provided following nanoparticle production that tests the quality of the nanoparticles produced. For example, Dynamic Light Scattering (“DLS”) can be used to test the properties of the particles produced. Other possible in-line testing systems include spectrophotometry including UV, VIS and IR spectra, fluorometry, and measurement of refractive index.

The testing structure can be in communication with a control system 80 that monitors the results from the testing system 72 and can modulate, preferably in real-time, components in zones 1-4 as needed to optimize the quality of the nanoparticles produced. For example, the flow of the individual precursors, the time and temperature-heating-excitation energy applied through zone 2 and 3 and the amount of reactively inert gas segmented into the flow path in zone 1 can be adjusted by the control system as needed to optimize detected quality of the nanoparticles produced.

Depending on how many shells are introduced onto the surface of the core material (which is produced in Zones 1-4), Zones 1, 3 and 4 can be repeated using a different set of materials (precursors/components) to form core/shell, core/shell/shell and core/shell/shell/shell type structures.

Shell Fabrication System

A post-production shell application system 100 may be provided following the production of the nanoparticles as shown in FIG. 1. As shown in FIG. 2, the shell fabrication system may include structures for supplying one or more additional precursors (here precursors 170, 172, 174, and 176 are shown) and a supplemental heat source 61 for heating downstream therefrom. A continuous flow loop 180 may be provided where any combination of the precursors can be applied to any given shell layer and passed through the heat source 61, thereby allowing multiple shell layers to be formed on each nanoparticle. A second quality testing system 72′ may be provided following each shell layer application. With this testing system 72′ and the components of the shell fabrication system in operable communication with the control system 80, the control system 80 can provide real-time modulation of the shell fabrication systems as needed to optimize quality of the shell layer on each nanoparticle produced.

The purpose for the shell architecture surrounding the core nanoparticle material is two-fold. First, by matching the lattice parameters closely of the core material, a first shell can be added which increases the quantum yield of the resultant nanoparticle upon exposure to light. This is done by passivating the nanoparticle core surface and eliminating dangling bonds which contribute to non-radiative recombination events. Also, by lattice matching the materials of the nanoparticle core and the first shell, strain effects are reduced, which also causes an increase in the quantum yield of the resultant nanoparticle.

This first shell may also have the added benefit of providing a barrier against environmental degradation effects, such as photo-bleaching and/or oxidation of the core material, which will result in either a blue-shifting of emitted light, or provide multiple trap sites for reduction of effective and desirable electronic properties. However, in the event that this is not provided by the first shell, a second and/or third shell may be provided that will enhance the operational lifetime of nanoparticle materials when used in applications. These second and third shells do not necessarily have to be lattice matched to enhance optical properties unless they interact with the wave function associated with the nanoparticle in the excited state. The primary purpose of the second and third shell are to provide increased operational lifetime by providing protection to the nanoparticle core/shell from environmental effects, which include, but are not limited to: oxidation, photobleaching and temperature extremes.

The first shell integrity can be verified by measuring the quantum yield of the nanoparticle after the first shell has been placed onto the core of the nanoparticle. Poor coverage by the first shell, or poor lattice matching by the first shell will result in low quantum yields (<50%), whereas good coverage by the first shell and good lattice matching between the first shell and the core material will result in large quantum yields (>50%).

The lifetime of the materials can be evaluated by exposure to light, preferably between 250 nm and 700 nm, and measuring the photoluminescent response as a function of time. Increased operational lifetime and enhancement of the stability of these nanoparticles by inclusion of a second and, perhaps, a third shell, will show less than 5% photodegration of a 10 wt % material in solvent exposed to a minimum of 5 mW light source over the period of two weeks upon continuous exposure in standard atmospheric conditions.

System Redundancy and Redirectable Flow Paths

As shown in FIG. 8, a plurality of reductant elements of the production line, such as two energy sources 50 and two heat sources 60 may be provided with redundant sets of the individual precursors 32, 24 and nanoparticle flow 22 paths interconnectable with valves 300 or the like to allow redirection of the flow path 22 through alternative components should one component before inoperable.

Conservation of Excess Microwave Energy

As shown schematically in FIG. 10, in cases where the energy source 50 in zone 2 is a microwave oven, excess microwave energy may be directed to assist with warming the growth area heating source 60 in zone 3. For example, a series of mirrors or the like can be directed to a heat sink such as rubber or the like that collects the excess microwaves and coverts them to heat.

The microwave energy entering the growth chamber can be controlled through an insertable and movable baffle 310 which can attenuate the amount of microwave energy entering the growth area heating source. The temperature of the growth area heating source can be monitored by the control system 72 which modulates the baffle position as needed to maintain a desired temperature in the growth chamber.

Exemplar precursor combinations that have may work particularly well in this flow cell reactor include first precursors selected from those found in “Group A” below with the second precursor is selected from “Group B” or “Group C” below using conventional periodic table nomenclature.

Group A—Precursors

H₂X

• • Where X=O, S, Se, Te

R₃P=X

• • Where R=—H, —(CH₂)_n—CH₃, —C₆H₅, —C₆H₄—R′
    • n=3-18
    • R′=—(CH₂)_m—CH₃, —CH(CH₃)₂, —C(CH₃)₃
    • m=0-17
    • X=Se, Te

R₃N=X

• • Where R=—H, —(CH₂)_n—CH₃, —Si(CH₃)₃
    • n=0-4
    • X=S, Se, Te

((CH₃)₃Si)₂X

• • Where X=S, Se, Te

(((CH₃)₃Si)₂N)₂X

• • Where X=S, Se, Te

H—X—(CH₂)_n—CH₃

• • Where X=O, S, Se, Te
    • n=1-18, preferably n=4-12, more preferably n=8-10

HO—CH₂—(CH(OH))_n—CH₃

• • n=1-50, preferably n=1-25, more preferably n=1-5

HO—CH₂—(CH(OH))_n—CH₂—OH

• • n=1-50, preferably n=1-25, more preferably n=1-5

H₂NNH₂

NaBH₄

NaCNBH₃

and mixtures thereof

including anionic precursors and/or reducing agents

Group B—Precursors

M(ligand)_y

• • When y=1, M=Tl, Ag, Cu
  • When y=2, M=Zn, Cd, Hg, Cu, Pb, Ni
  • When y=3, M=Al, Ga, B, In, Bi, Fe
  • Ligand=—(O₂C—(CH₂)_n—CH₃), —(O₂C—(CH₂)_m—
    • CH=CH—(CH₂)_o—CH3), —S—(CH₂)_n—CH₃, —PR₃, —OPR₃
    • n=2-24, preferably n=8-20, more preferably n=12-16
    • m and o=1-15, preferably n and o=12-16, more preferably n and o=7-9
    • R=—(CH₂)_pCH₃, —C₆H₅, —C₆H₄—R′
      • p=0-18
      • R′=—(CH₂)_p—CH₃, —CH(CH₃)₂, —C(CH₃)₃

Or mixtures thereof.

Group C—Precursors

M(ligand)_y

• • When y=1, M=Na, K, Rb, Cs, Ag, Cu
  • When y=2, M=Mg, Ca, Sr, Ba, Pd, Pt, Cu, Ni
  • When y=3, M=La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Au
  • When y=4, M=Ti, Zr, Hf, Pt, Pd
  • ligand=—O₂C—CH₃, —Cl, —F, —NO₃

or mixtures thereof.

The invention is disclosed above and in the accompanying figures with reference to a variety of configurations. The purpose served by the disclosure, however, is to provide an example of the various features and concepts related to the invention, not to limit the scope of the invention. One skilled in the relevant art will recognize that numerous variations and modifications may be made to the configurations described above without departing from the scope of the present invention, as defined by the appended claims.

Claims

1. A method for producing uniformly sized quantum dot nanoparticles comprising:

blending at least a first precursor and at least a second precursor together to form a liquid precursor mixture;

conducting the liquid precursor mixture along a continuous flow path comprising one or more tubes through which the liquid precursor mixture flows, wherein at least one of the one or more tubes comprises an inner diameter of ¼ inch to ½ inch;

introducing gas into the continuous flow path fluidically so as to form partitions of the gas in the continuous flow path;

after introducing the gas into the continuous flow path, activating the liquid precursor mixture with one or more of multimodal and multivariable frequency microwave energy from a microwave energy source along the continuous flow path for a first duration at a first energy level thereby allowing uniform nucleation of quantum dot nucleates in the mixture of precursors;

heating the liquid precursor mixture with a heating source along the continuous flow path for a second duration at a controlled temperature, thereby promoting uniform thermodynamic growth around previously formed the quantum dot nucleates previously formed to form desired core sized nanoparticles core quantum dot nanoparticles, wherein the core quantum dot nanoparticles fluoresce with a full width half max (FWHM) of less than 50 nm at wavelengths from 400 nm-700 nm; and

quenching the growth of the quantum dot nanoparticles after heating.

2. The method of claim 1, wherein the microwave energy is multimodal.

3. The method of claim 1, wherein the microwave energy is multivariable in frequency.

4. The method of claim 1, further comprising introducing gas into the continuous flow path fluidically upstream of the microwave energy source, so as to form partitions of wherein the gas in the is introduced into multiple lines, which separate adjacent segments of the liquid precursor mixture of the continuous flow path.

5. The method of claim 4, wherein the gas includes one or more of nitrogen and argon.

6. The method of claim 1, wherein the first duration is less than or equal to 60 seconds.

7. The method of claim 1, wherein the first duration is less than or equal to 10 seconds.

8. The method of claim 1, wherein the first duration is less than or equal to 3 seconds.

9. The method of claim 1, wherein the first duration is less than or equal to 2 seconds.

10. The method of claim 1, further comprising monitoring a quality of the quantum dot nanoparticles via one or more sensors; and adjusting the first duration, first energy level, second duration, and temperature, via one or more actuators, in response to the detected quality of the quantum dot nanoparticles.

11. The method of claim 1, wherein a mixture of two or more precursors from Groups B or C herein, having different microwave absorption cross sections, nucleate with a precursor from Group A herein, at substantially equal rates upon flowing through the microwave energy source,

wherein Group A includes H₂X where X=O, S, Se, Te; R₃PX where R=H, (CH₂)_nCH₃, C₆H₅, C₆H₄R′, n=3-18, R′=(CH₂)_mCH₃, CH(CH₃)₂, C(CH₃)₃, m=0-17, X=Se, Te; R₃NX where R=H, (CH₂)_nCH₃, Si(CH₃)₃, n=0-4, X=S, Se, Te; ((CH₃)₃Si)₂X where X=S, Se, Te; HX(CH₂)_nCH₃ where X=O, S, Se, Te, n=1-18; HO(CH₂)(CH(OH))_n(CH₃) where n=1-50; HO(CH₂)(CH(OH))_n(CH₂OH) where n=1-50; H₂NNH₂; NaBH₄, NaCNBH₃; and mixtures thereof including anionic precursors and/or reducing agents,

wherein Group B includes ML_y where M=Tl, Ag, Cu when y=1, M=Zn, Cd, Hg, Cu, Pb, Ni when y=2, M=Al, Ga, B, In, Bi, Fe when y=3, L=O₂ C(CH₂)_nCH₃, O₂C(CH₂)_mCHCH(CH₂)OCH₃) O₂C(CH₂)_mCH═CH(CH₂)_oCH₃, S(CH₂)_nCH₃, PR₃, OPR₃, n=2-24, m and o=1-15, R=(CH₂)_pCH₃, C₆H₅, C₆H₄R′, p=0-18, R′=(CH₂)_pCH₃, CH(CH₃)₂, C(CH₃)₃; and mixtures thereof, and

wherein Group C includes: ML_y where M=Na, K, Rb, Cs, Ag, Cu when y=1, M=Mg, Ca, Sr, Ba, Pd, Pt, Cu, Ni when y=2, M=La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Au when y=3, M=Ti, Zr, Hf, Pt, Pd when y=4, L=O₂CCH₃, Cl, F, NO₃; and mixtures thereof.

12. The method of claim 1, wherein nucleation of the first and second precursors over the first duration results in a substantially homogeneous quantum dot nanoparticle.

13. The method of claim 1, further comprising:

using a continuous-flow process to expose the quantum dot nanoparticles to a mixture of at least a third precursor from Group A herein and a fourth precursor from Group B or Group C herein; and

heating the exposed quantum dot nanoparticles in a heat source to form a first shell around the quantum dot nanoparticle,

wherein Group A includes: H₂X where X=O, S, Se, Te; R₃PX where R=H, (CH₂)_nCH₃, C₆H₅, C₆H₄R′, n=3-18, R′=(CH₂)_mCH₃, CH(CH₃)₂, C(CH₃)₃, m=0-17, X=Se, Te; R₃NX where R=H, (CH₂)_nCH₃, Si(CH₃)₃, n=0-4, X=S, Se, Te; ((CH₃)₃Si)₂X where X=S, Se, Te; HX(CH₂)_nCH₃ where X=O, S, Se, Te, n=1-18; HO(CH₂)(CH(OH))_n(CH₃) where n=1-50; HO(CH₂)(CH(OH))_n(CH₂OH) where n=1-50; H₂NNH₂; NaBH₄, NaCNBH₃; and mixtures thereof including anionic precursors and/or reducing agents,

wherein Group B includes: ML_y where M=Tl, Ag, Cu when y=1, M=Zn, Cd, Hg, Cu, Pb, Ni when y=2, M=Al, Ga, B, In, Bi, Fe when y=3, L=O₂C(CH)_nCH₃, O₂C(CH₂)_mCHCH(CH₂)OCH₃) O₂C(CH₂)_mCH═CH(CH₂)_oCH₃, S(CH₂)_nCH₃, PR₃, OPR₃, n=2-24, m and o=1-15, R=(CH₂)_nCH₃, C₆H₅, C₆H₄R′, p=0-18, R′=(CH₂)_pCH₃, CH(CH₃)₂, C(CH₃)₃; and mixtures thereof, and

wherein Group C includes: ML_y where M=Na, K, Rb, Cs, Ag, Cu when y=1, M=Mg, Ca, Sr, Ba, Pd, Pt, Cu, Ni when y=2, M=La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Au when y=3, M=Ti, Zr, Hf, Pt, Pd when y=4, L=O₂CCH₃, Cl, F, NO₃; and mixtures thereof.

14. The method of claim 13, further comprising:

using a continuous-flow process to expose the quantum dot nanoparticles to a mixture of a fifth precursor and a sixth precursor; and

heating the exposed quantum dot nanoparticle to form a second shell around the first shell.

15. The method of claim 13, further comprising: using a continuous-flow process to expose the quantum dot nanoparticles to a mixture of a fifth precursor to from Group A herein and a sixth precursor from Group B or Group C herein; and

heating the exposed quantum dot nanoparticle to form a second shell around the first shell,

wherein Group A includes: H₂X where X=O, S, Se, Te; R₃PX where R=H, (CH₂)_nCH₃, C₆H₅, C₆H₄R′, n=3-18, R′=(CH₂)_mCH₃, CH(CH₃)₂, C(CH₃)₃, m=0-17, X=Se, Te; R₃NX where R=H, (CH₂)_nCH₃, Si(CH₃)₃, n=0-4, X=S, Se, Te; ((CH₃)₃Si)₂X where X=S, Se, Te; HX(CH₂)_nCH₃ where X=O, S, Se, Te, n=1-18; HO(CH₂)(CH(OH))_n(CH₃) where n=1-50; HO(CH₂)(CH(OH))_n(CH₂OH) where n=1-50; H₂NNH₂; NaBH₄, NaCNBH₃; and mixtures thereof including anionic precursors and/or reducing agents,

wherein Group B includes: ML_y where M=Tl, Ag, Cu when y=1, M=Zn, Cd, Hg, Cu, Pb, Ni when y=2, M=Al, Ga, B, In, Bi, Fe when y=3, L=O₂C(CH₂)_nCH₃, O₂C(CH₂)_mCHCH(CH₂)OCH₃) O₂C(CH₂)_mCH═CH(CH₂)_oCH₃, S(CH₂)CH₃, PR₃, OPR₃, n=2-24, m and o=1-15, R=(CH₂)_pCH₃, C₆H₅, C₆H₄R′, p=0-18, R′=(CH₂)_pCH₃, CH(CH₃)₂, C(CH₃)₃; and mixtures thereof, and

wherein Group C includes: ML_y where M=Na, K, Rb, Cs, Ag, Cu when y=1, M=Mg, Ca, Sr, Ba, Pd, Pt, Cu, Ni when y=2, M=La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Au when y=3, M=Ti, Zr, Hf, Pt, Pd when y=4, L=O₂CCH₃, Cl, F, NO₃; and mixtures thereof.

16. The method of claim 15, further comprising:

using a continuous-flow process to expose the quantum dot nanoparticles to a mixture of a seventh precursor from Group A herein and a an eighth precursor from Group B or Group C herein; and

heating the exposed quantum dot nanoparticle to form a third shell around the second shell.

17. The method of claim 4, further including the step of separating the gas from the quantum dot nanoparticles following the step of quenching the growth of the quantum dot nanoparticle.

18. The method of claim 1, wherein the continuous flow path comprises multiple lines, and wherein one or more of the multiple lines comprises an inner diameter between 1/16 of an inch and 1 inch.

19. The method of claim 18, wherein one or more of the multiple lines has an inner diameter between ¼ and ½ inch.

20. The nanoparticle method of claim 1, wherein the microwave energy operates at frequencies that cause the first and second precursors to nucleate at substantially the same time thereby producing substantially homogenous quantum dot nanoparticles.

21. A method for producing uniformly sized quantum dot nanoparticles comprising:

blending together a first and second precursor to form a liquid precursor mixture;

conducting the liquid precursor mixture along multiple lines of a continuous flow path comprising one or more tubes through which the liquid precursor mixture flows, wherein at least one tube of the one or more tubes comprises an inner diameter of ¼ inch to ½ inch;

introducing gas into the continuous flow path fluidically upstream of the microwave energy source, so as to form partitions of the gas in the multiple lines, which separate adjacent segments of the liquid precursor mixture;

activating the liquid precursor mixture with multimodal and/or multivariable frequency microwave energy from a microwave energy source in the continuous flow path, the microwave energy source configured to uniformly irradiate the multiple lines and thereby uniformly nucleate the liquid precursor mixture, for a first duration at a first energy level, to form quantum dot nucleates;

heating the activated liquid precursor mixture with a heating source in the continuous flow path for a second duration at a controlled temperature, thereby promoting uniform thermodynamic growth around previously formed the quantum dot nucleates previously formed to form desired core sized nanoparticles core quantum dot nanoparticles, wherein the core quantum dot nanoparticles fluoresce with a full width half max (FWHM) of less than 50 nm at wavelengths from 400 nm-700 nm; and

quenching the growth of the quantum dot nanoparticles after heating.

22. The method of claim 21, wherein first duration is less than or equal to 10 seconds.

23. The method of claim 21, wherein the first duration is less than or equal to 3 seconds.

24. The method of claim 21, wherein the first duration is less than or equal to 2 seconds.

25. The method of claim 21, wherein the microwave energy is multimodal.

26. The method of claim 21, the microwave energy is of multivariable frequency.

27. The method of claim 21, wherein the gas includes one or more of nitrogen and argon.

28. The method of claim 21, further comprising monitoring a quality of the quantum dot nanoparticles via one or more sensors; and adjusting the first duration, first energy level, second duration, and temperature, via one or more actuators, in response to the detected quality of the quantum dot nanoparticles.

29. The method of claim 21, wherein a mixture of two or more precursors from Groups B or C herein, having different microwave absorption cross sections, nucleate with a precursor from Group A herein, at substantially equal rates upon flowing through the first energy source,

wherein Group A includes: H₂X where X=O, S, Se, Te; R₃PX where R=H, (CH₂)_nCH₃, C₆H₅, C₆H₄R′, n=3-18, R′=(CH₂)_mCH₃, CH(CH₃)₂, C(CH₃)₃, m=0-17, X=Se, Te; R₃NX where R=H, (CH₂)_nCH₃, Si(CH₃)₃, n=0-4, X=S, Se, Te; ((CH₃)₃Si)₂X where X=S, Se, Te; HX(CH₂)_nCH₃ where X=O, S, Se, Te, n=1-18; HO(CH₂)(CH(OH))_n(CH₃) where n=1-50; HO(CH₂)(CH(OH))_n(CH₂OH) where n=1-50; H₂NNH₂; NaBH₄, NaCNBH₃; and mixtures thereof including anionic precursors and/or reducing agents,

wherein Group B includes: ML_y where M=Tl, Ag, Cu when y=1, M=Zn, Cd, Hg, Cu, Pb, Ni when y=2, M=Al, Ga, B, In, Bi, Fe when y=3, L=O₂C(CH₂)_nCH₃, O₂C(CH₂)_mCHCH(CH₂)OCH₃)OCH₃) O₂C(CH₂)_mCH═CH(CH₂)_oCH₃, S(CH₂)_nCH₃, PR₃, OPR₃, n=2-24, m and o=1-15, R=(CH₂)_pCH₃, C₆H₅, C₆H₄R′, p=0-18, R′=(CH₂)_pCH₃, CH(CH₃)₂, C(CH₃)₃; and mixtures thereof, and

wherein Group C includes: ML_y where M=Na, K, Rb, Cs, Ag, Cu when y=1, M=Mg, Ca, Sr, Ba, Pd, Pt, Cu, Ni when y=2, M=La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Au when y=3, M=Ti, Zr, Hf, Pt, Pd when y=4, L=O₂CCH₃, Cl, F, NO₃; and mixtures thereof.

30. The method of claim 29, wherein the nucleation of the first and second precursors over the first duration results in substantially homogeneous quantum dot nanoparticles.

31. The method of claim 1 wherein the first and second precursors are blended prior to conduction along the continuous flow path.

32. The method of claim 1 wherein the first and second precursors are blended during conduction along the continuous flow path.

33. The method of claim 4, wherein the continuous flow path comprises at least one line having an inner diameter between 1/16 of an inch and 1 inch two or more lines of the multiple lines have an inner diameter of ¼ inch to ½ inch.

34. The method of claim 33, wherein the at least one line has an inner diameter between ¼ and ½ inch.

35. The method of claim 1, wherein the continuous flow path comprises multiple flow cell tubes that pass through a same microwave reactor cavity.

36. The method of claim 1, wherein the multivariable frequency microwave energy is tuned to a first frequency for the first precursor and is tuned to a second frequency for the second precursor.