Patent Application: US-94505304-A

Abstract:
a method for synthesis of high quality colloidal nanoparticles using comprises a high heating rate process . irradiation of single mode , high power , microwave is a particularly well suited technique to realize high quality semiconductor nanoparticles . the use of microwave radiation effectively automates the synthesis , and more importantly , permits the use of a continuous flow microwave reactor for commercial preparation of the high quality colloidal nanoparticles .

Description:
in the following description of the preferred embodiment , reference is made to the accompanying drawings which form a part hereof , and in which is shown by way of illustration a specific embodiment in which the invention may be practiced . it is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention . in the present invention , nanoparticles are synthesized by heating the reaction system from room temperature to elevated temperatures . the reaction system herein is a closed system that consists of materials that are necessary for the synthetic reaction . each of these materials will hereafter be called a constituent element . in the most primitive reaction system , the sole constituent element is the precursor . however , in general , the constituent elements are solvent and precursor . the solvent can be a mixture of plural solvents , and also the precursor can be a mixture of plural precursors . these elements can either be dispersed homogeneously or inhomogeneously . the constituent elements of the reaction system are mixed at or near room temperature and heated for nanoparticle synthesis . here , near room temperature is below 100 ° c . in the present invention , the temperature of the reaction system is typically monitored by devices such as thermometer , pyrometer , or thermocouples . the reaction described in the present invention comprise one or more of each of the ( 1 ) heating at a high heating rate , ( 2 ) stabilization at elevated temperature , and ( 3 ) cooling at a high cooling rate . as a specific feature in one of the preferred embodiments , heating of the reaction system is performed by microwave irradiation . [ 20 - 23 ] the heating of the reaction system can either be achieved by sole use of microwave or with the aid of other heat sources such as oil - bath , mantle - heater , or burners . the frequency of the microwave is typically 2 . 45 ghz but not limited . use of focused microwave is preferred over unfocused , and single - mode is preferred over multimode for efficient heating . ramping the temperature of the reaction system up is done solely by microwave irradiation or microwave irradiation with the use of additional heat sources , during which the heating rate can be controlled by the input power of the microwave by a continuous or pulsed power supply . the average heating rate during each process of the synthesis is defined as : ( temperature at the end of heating (° c . )− temperature at the beginning of heating (° c . ))/( duration of heating ( min )) the synthetic scheme described in the present invention comprises one or more stages of high heating rate . here , high heating rate refers to a rate of 30 ° c ./ min or higher , more preferably 32 ° c ./ min or higher , most favorably 34 ° c ./ min or higher . when the average heating rate is below 30 ° c ./ min , synthesis may result in nanoparticulate materials with unfavorable properties such as lower dispersibility or wider size distribution . during the stage where the temperature is stable at elevated temperature , heating by microwave irradiation with or without other heat sources is performed together with cooling by using means as flow of air or water , ice , oil or cryogenic gas , to balance the input / output of heat to / from the system to hold the temperature constant . when the heat capacitance of the reaction system is large enough such that the change in the temperature can be ignored , temperature stabilization may be achieved by merely leaving the system free of any heat input / output . here , stable temperature refers to processes in which the temperature change is 5 ° c ./ min or less . cool - down of the reaction system can be achieved by removing heat from the system by standard means such as air , water , ice , oil or cryogenic gas . microwave irradiation with or without other heat sources can be used to control this cool - down process . the average cooling rate of each cool - down process is defined as : ( temperature at the beginning of cooling (° c . )− temperature at the end of cooling (° c . ))/( duration of cooling ( min )) the synthetic scheme described in the present invention comprises one or more stages of high cooling rate . here , high cooling rate refers to a rate of 80 ° c ./ min or higher , more preferably 85 ° c ./ min or higher , most favorably 90 ° c ./ min or higher . when the average cooling rate is below 80 ° c ./ min , synthesis may result in nanoparticulate materials with unfavorable properties such as lower dispersibility or wider size distribution . hereinafter , this high rate cooling process may be referred to as quenching . hence , the simplest embodiment of the present invention for synthesizing nanoparticles comprise of three stages that are high - rate heating , temperature stabilization , and high - rate cooling . in order to control the heating and cooling rates of the reaction system , additives can be intentionally introduced to the system as a constituent element . in general , there is no limitation to the nature of such additives , and can be either organic or inorganic materials . the additives can either be dispersed homogeneously or inhomogeneously in the reaction system . moreover , the additives can be present in the reaction system from the beginning of the process or can be introduced during the course of the reaction . examples of such additives are : graphite , silicon carbide , glycols , ionic liquids , tetrabutylammonium bromide and cholesterols . furthermore , for synthesizing the same or different nanoparticles , in addition to the precursors that exist in the reaction system , one may further introduce the same or different precursors during the course of reaction . as described above , the reaction system comprises one or more constituent elements . the main constituent element is the element with the largest molar equivalent . in the present invention , the dielectric constant of the main constituent element is 20 or less , preferably 18 or less , more preferably 16 or less , and most preferably 14 or less . if the dielectric constant is over 20 , it may result in loss of stability of the precursors in the system due to the exceedingly high polarity of the main constituent element . additives can be introduced into the system before or during the course of reaction as long as their amounts are less than the main constituent element in molar equivalent . the nanoparticles synthesized by the method described in the present invention comprise mainly inorganic materials , and their diameters are on the order of nanometers ( nm ). the main crystal may be single crystal , polycrystal , alloys with or without phase separation due to stoichiometric variations , or core - shell structures that will be described later . the average diameter of such crystals are 0 . 5 ˜ 100 nm , preferably 1 ˜ 20 nm in order to warrant dispersibility , more preferably 2 ˜ 12 nm , most preferably 2 ˜ 10 nm . such diameters can be determined through characterization by transmission electron microscopy ( tem ). when the micrographs cannot be obtained with sufficient contrast to make such determination of the diameter , for instance when the constituent atoms are those of low atomic numbers , techniques such as matrix assisted laser desorption ionization spectroscopy , atomic force microscopy ( afm ), or for colloidal solutions , dynamic light scattering or neutron scattering can often be used instead . while there is no limitation in the size distribution of the above mentioned nanoparticles , in general , the standard deviation is ± 20 %, preferably ± 15 %, more preferably ± 10 %, and most preferably ± 5 %. when the size distribution exceeds the above , the nanoparticles will often not exhibit their desired physical and chemical properties to their best performance . methods that are typically used to characterize the crystallinity of the nanoparticles are dark field transmission electron microscopy which is used to look for glide plane defects and / or twinning . powder x - ray diffraction , which reveals the approximate diameters and shapes of the crystallites through peak intensities and scherrer broadening of the reflection peaks . finally , z - contrast transmission electron microscopy is used to image the dopant ion in nanoparticle alloys . when the nanoparticles synthesized by the method described in the present invention are semiconductor , there is no limitation in their composition , but typical examples are single substances of group 14 elements , such as c , si , ge , or sn , single substances of group 15 elements , such as p ( black phosphorus ), single substances of group 16 elements , such as se or te , compounds of group 14 elements , such as sic , compounds of group 14 and group 16 elements , such as ges , gese , gete , sns , snse , snte , pbs , pbse , or pbte , and their ternary and quaternary alloys , such as ge x sn 1 - x s y se 1 - y ( x = 0 ˜ 1 , y = 0 ˜ 1 ), compounds of group 13 and group 15 elements , such as aln , alp , alas , alsb , gan , gap , gaas , gasb , inn , inp , inas , or insb , and their ternary and quaternary alloys , such as ga x in 1 - x p y as 1 - y ( x = 0 ˜ 1 , y = 0 ˜ 1 ), compounds of group 13 and group 16 elements or their alloys , such as gas , gase , gate , ins , inse , inte , tls , tlse , tlte , and their ternary and quaternary alloys , such as ga x in 1 - x s y se 1 - y ( x = 0 ˜ 1 , y = 0 ˜ 1 ), compounds of group 13 and group 17 elements , such as tlcl , tibr , tli , compounds of group 12 and group 16 elements , such as zns , znse , znte , cds , cdse , cdte , hgs , hgse , hgte , and their ternary and quaternary alloys , such as zn x cd 1 - x s y se 1 - y ( x = 0 ˜ 1 , y = 0 ˜ 1 ), compounds of group 15 and group 16 elements , such as as 2 s 3 , as 4 s 4 , as 2 se 3 , as 2 te 3 , sb 2 s 3 , sb 2 se 3 , sb 2 te 3 , bi 2 s 3 , bi 2 se 3 , bi 2 te 3 , and their ternary and quaternary alloys , compounds of group 11 and group 16 elements , such as cuo , cu 2 o , ag 2 s and cuse , compounds of group 11 and group 17 elements , such as cucl , agbr and aucl , ccompounds of group 10 and group 16 elements , such as nis 2 , pds and ptse , compounds of group 9 and group 16 elements , such as cose , rhs and irse , compounds of group 8 and group 16 elements , such as feo , fes , fese and rus , compounds of group 7 and group 16 elements , such as mno , mns , mnse and res , compounds of group 6 and group 16 elements , such as cr 2 s 3 , cr 2 se 3 and mos 2 , compounds of group 5 and group 16 elements , such as vs , vse , and nbs , compounds of group 4 and group 16 elements , such as tio 2 , tis 2 , and zrs 2 , compounds of group 2 and group 16 elements , such as beo , mgs , and case , and chalcogen spinnels , barium titanates ( batio 3 ). the crystals that form the main body of the nanoparticles of the present invention can be the so - called core - shell structure in which the crystals comprise inner - core and outer - shell for modification of their physical and chemical properties . such shells are preferably metal , semiconductor , or insulator . as for semiconductor , examples of preferred materials are compounds of group 13 and group 15 elements , such as me ( where m = b , al , ga , in and e = n , p , as , sb ) and compounds of group 12 and group 16 elements , such as ma ( where m = zn , cd , hg and a = o , s , se , te ) and compounds of group 2 and group 16 elements , such as ta ( where t = be , mg , ca sr , ba and a = o , s , se , te ). examples of more preferred materials for the shells are iii - v compound semiconductors , such as bn , bas , or gan , ii - vi compound semiconductors , such as zno , zns , znse , cds , compounds of group 12 and group 16 elements , such as mgs , or mgse . in the compositions described above in sections 5 and 6 , minute amounts of additives can be intentionally doped for modification of the physical and chemical properties of the nanoparticles . examples of such doping materials are al , mn , cu , zn , ag , cl , ce , eu , th , er , or tm . the nanoparticles synthesized by the method described in the present invention can have organic compounds attached to their surface . the attachment of organic compounds to the surface is defined as the state in which the organic compound is chemically bonded to the surface . while there is no limitation in the form of bonding between the organic compound and the nanoparticle surface , examples are coordination bond , covalent bond , relatively strong bonds such as ionic bond , or through relatively weak interaction such as van der waals force , hydrogen bond , hydrophobic - hydrophobic interaction , or entanglement of molecular chains . the organic compounds can be a single species or a mixture of two or more . in general , in order to attach to the nanoparticle surface , organic compounds consist of the following coordinating functional groups that form bonds to the nanoparticle surface . typically , coordinating functional groups that comprise group 15 or group 16 elements constitute the above mentioned organic compounds . examples of such functional groups are , primary amines , secondary amines , tertiary amines , radicals containing nitrogen multiple bonds , such as nitryl , or isocyanate , nitrogen containing radicals such as nitric aromatics , such as pyridine or triazine , functional groups containing group 15 element such as phosphorus containing radicals , such as primary phosphine , secondary phosphine , tertiary phosphine , primary phosphine oxide , secondary phosphine oxide , tertiary phosphine oxide , primary phosphine selenide , secondary phosphine selenide , tertiary phosphine selenide , or phosphonic acid , oxygen containing radicals , such as hydroxyl , ether , or carboxyl , sulfur containing radicals , such as thiol , methylsulfide , ethylsulfide , phenylsulfide , methyldisulphide , phenyldisulfide , thioacid , dithioacid , xanthogenic acid , xanthete , isothiocyanate , thiocarbamate , sulfonic , sulfoxide , or thiophene rings , functional groups containing group 16 element such as selenium containing radicals , such as — seh , — sech 3 , — sec 6 h 5 , or tellurium containing radicals , such as — teh , — tech 3 , — tec 6 h 5 . among these examples , functional groups containing nitrogen such as pyridine rings , functional groups containing group 15 elements such as phosphorus , such as primary amine , tertiary phosphine , tertiary phosphine oxide , tertiary phosphine selenide , or phosphonic acid , functional groups containing oxygen , such as hydroxyl , ether , or carboxyl , or functional groups containing group 16 elements such as sulfur , such as thiol or methylsulfide , are used preferably . more precisely , trialkylphosphines , trialkylphosphine oxides , alkane sulfonic acids , alkane phosphonic acids , alkyl amines , dialkylsulfoxides , dialkylether , and alkylcarboxyl acids are such examples . while the detailed coordination chemistry of these organic compounds on the nanoparticle surface is not totally understood , in the present invention , as long as the nanoparticle surface is covered with these organic compounds , the functional groups may either retain their original structure or be modified . in the present invention , the amount of organic compounds present at the surface depends on the kind of nanoparticles and their surface area , such as their size , after proper separation , among the total weight of the nanoparticles and the organic compounds , is typically 1 to 90 % of the weight , and for chemical stability and in order to disperse them into organic matrices such as solvents or resin binders that are practically important preferably . 5 ˜ 80 %, more preferably , 10 ˜ 70 %, and most preferably 15 ˜ 60 %. the above mentioned organic composition can be determined , for example , by the various elemental analyses or thermogravimetric analysis ( tga ). furthermore , information regarding the chemical species and environment can be obtained by infrared ( ir ) spectroscopy or nuclear magnetic resonance ( nmr ). when the nanoparticles synthesize by the method described in the present invention are semiconductor , cationic materials that can be chosen from elements in group 2 ˜ 15 and anionic materials that can be chosen from elements in group 15 ˜ 17 can be used as precursors . when more than one material is used , they may be mixed prior to the synthetic reaction or may be separately introduced into the reaction system . examples of the precursors for semiconductors that contain cationic elements are , dialkylated compounds of group 2 elements , such as diethyl magnesium , or di - n - butyl magnesium ; alkyl halides of group 2 elements , such as methyl magnesium chloride , methyl magnesium bromide , methyl magnesium iodide , ethynyl magnesium chloride ; dihalides , such as magnesium iodide ; halides of group 4 elements , such as titanium ( iv ) tetrachloride , titanium ( iv ) tetrabromide , or titanium ( iv ) tetraiodide ; halides of group 5 elements , such as vanadium ( ii ) dichloride , vanadium ( iv ) tetrachloride , vanadium ( ii ) dibromide , vanadium ( iv ) tetrabromide , vanadium ( ii ) diiodide , vanadium ( iv ) tetraiodide , tantalum ( v ) pentachloride , tantalum ( v ) pentabromide , and tantalum ( v ) pentaiodide ; halides of group 6 elements , such as chromium ( iii ) tribromide , chromium ( iii ) triiodide , molybdenum ( iv ) tetrachloride , molybdenum ( iv ) tetrabromide , molybdenum ( iv ) tetraiodide , tungsten ( iv ) tetrachloride , tungsten ( iv ) tetrabromide , and tungsten ( iv ) tetraiodide ; halides of group 7 elements , such as manganese ( ii ) dichloride , manganese ( ii ) dibromide , and manganese ( iii ) diiodide ; halides of group 8 elements , such as iron ( ii ) dichloride , iron ( iii ) trichloride , iron ( ii ) dibromide , iron ( iii ) tribromide , iron ( ii ) diiodide , and iron ( iii ) triiodide ; halides of group 9 elements , such as cobalt ( ii ) dichloride , cobalt ( ii ) dibromide , and cobalt ( ii ) diiodide ; halides of group 10 elements , such as nickel ( ii ) dichloride , nickel ( ii ) dibromide , and nickel ( ii ) diiodide ; halides of group 11 elements , such as copper ( i ) iodide ; dialkylated compounds of group 12 elements , such as dimethyl zinc , diethyl zinc , di - n - propyl zinc , diisopropyl zinc , di - n - butyl zinc , diisobutyl zinc , di - n - hexyl zinc , dicyclohexyl zinc , dimethyl cadmium , diethyl cadmium , dimethyl mercury ( ii ), diethyl mercury ( ii ), and dibenzyl mercury ( ii ); alkyl halides of group 12 elements , such as methyl zinc chloride , methyl zinc chloride , methyl zinc iodide , ethyl zinc iodide , methyl cadmium chloride , and methyl mercury ( ii ) chloride ; dihalides of group 12 elements , such as zinc chloride , zinc bromide , zinc iodide , cadmium chloride , cadmium bromide , cadmium iodide , mercury ( ii ) chloride , zinc chloride iodide , cadmium chloride iodide , mercury ( ii ) chloride iodide , zinc bromide iodide , cadmium bromide iodide , and mercury ( ii ) bromide iodide ; carboxylic acid salt of group 12 elements , such as zinc acetate , cadmium acetate , and 2 - ethyl hexanoic acid cadmium ; oxides of group 12 elements , such as cadmium oxide and zinc oxide ; trialkylated compounds of group 13 elements , such as trimethyl boron , tri - n - propyl boron , triisopropyl boron , trimethyl aluminum , trimethyl aluminum , triethyl aluminum , tri - n - butyl aluminum , tri - n - hexyl aluminum , trioctyl aluminum , tri - n - butyl gallium ( iii ), trimethyl indium ( iii ), triethyl indium ( iii ), and tri - n - butyl indium ( iii ); dialkyl monohalides of group 13 elements , such as dimethyl aluminum chloride , diethyl aluminum chloride , di - n - butyl aluminum chloride , di - ethyl aluminum bromide , di - ethyl aluminum iodide , di - n - butyl gallium ( iii ) chloride , or di - n - butyl indium ( iii ) chloride ; monoalkyl dihalides of group 13 elements , such as methyl aluminum dichloride , ethyl aluminum dichloride , ethyl aluminum dibromide , ethyl aluminum diiodide , n - butyl aluminum dichloride , n - butyl gallium ( iii ) dichloride , and n - butyl indium ( iii ) dichloride ; tri - halides of group 13 elements , such as boron trichloride , boron tribromide , boron triiodide , aluminum trichloride , aluminum tribromide , aluminum triiodide , gallium ( iii ) trichloride , gallium ( iii ) tribromide , gallium ( iii ) triiodide , indium ( iii ) trichloride , indium ( iii ) tribromide , indium ( iii ) triiodide , gallium ( iii ) dichloride bromide , gallium ( iii ) dichloride iodide , gallium ( iii ) chloride diiodide , and indium ( iii ) dichloride iodide ; carboxylic acid salt of group 13 elements , such as indium ( iii ) acetate and gallium ( iii ) acetate ; halides of group 14 elements , such as germanium ( iv ) tetrachloride , germanium ( iv ) tetrabromide , germanium ( iv ) tetraiodide , tin ( ii ) dichloride , tin ( iv ) tetrachloride , tin ( ii ) dibromide , tin ( iv ) tetrabromide , tin ( ii ) diiodide , tin ( iv ) tetraiodide , tin ( iv ) dichloride diiodide , tin ( iv ) tetraiodide , lead ( ii ) dichloride , lead ( ii ) dibromide , and lead ( ii ) diiodide ; hydrates of group 14 elements , such as diphenyl silane ; trialkyls of group 15 elements , such as trimethyl antimony ( iii ), triethyl antimony ( iii ), tri - n - butyl antimony ( iii ), trimethyl bismuth ( iii ), triethyl bismuth ( iii ), and tri - n - butyl bismuth ( iii ); monoalkyl halides of group 15 elements , such as methyl antimony ( iii ) dichloride , methyl antimony ( iii ) dibromide , methyl antimony ( iii ) diiodide , ethyl antimony ( iii ) diiodide , methyl bismuth ( iii ) dichloride , and ethyl bismuth ( iii ) diiodide ; trihalides of group 15 elements , such as arsenic ( iii ) trichloride , arsenic ( iii ) tribromide , arsenic ( iii ) triiodide , antimony ( iii ) trichloride , antimony ( iii ) tribromide , antimony ( iii ) triiodide , bismuth ( iii ) trichloride , bismuth ( iii ) tribromide , and bismuth ( iii ) triiodide ; etc . for synthesis of nanoparticles of group 14 elemental semiconductors such as si , ge , or sn , halides of group 14 elements , such as germanium ( iv ) tetrachloride , germanium ( iv ) tetrabromide , germanium ( iv ) tetraibdide , tin ( ii ) dichloride , tin ( iv ) tetrachloride , tin ( ii ) dibromide , tin ( iv ) tetrabromide , tin ( ii ) diiodide , tin ( iv ) diiodide , tin ( iv ) dichloride diiodide , tin ( iv ) tetraiodide , lead ( ii ) dichloride , lead ( ii ) dibromide , and lead ( ii ) diiodide ; or hydrides and / or alkylated compounds of group 14 elements , such as diphenyl silane , can be used as precursors . examples of anionic compounds that can be used as precursors for semiconductors are , elements of groups 15 ˜ 17 , such as n , p , as , sb , bi , o , s , se , te , f , cl , br , and i ; hydrides of group 15 elements , such as ammonia , phosphine ( ph 3 ), arsine ( ash 3 ), and stibine ( sbh 3 ); silylated compounds of elements of group 15 of the periodic table , such as tris ( trimethylsilyl ) amine , tris ( trimethylsilyl ) phosphine , and tris ( trimethylsilyl ) arsine ; hydrides of group 16 elements , such as hydrogen sulfide , hydrogen selenide , and hydrogen telluride ; silylated compounds of group 16 elements , such as bis ( trimethylsilyl ) sulfide and bis ( trimethylsilyl ) selenide , alkaline metal salts of group 16 elements , such as sodium sulfide and sodium selenide ; trialkylphosphine chalcogenides , such as tributylphosphine sulfide , trihexylphosphine sulfide , trioctylphosphine sulfide , tributylphosine selenide , trihexylphosphine selenide , and trioctylphosphine selenide , hydrides of group 17 elements , such as hydrogen fluoride , hydrogen chloride , hydrogen bromide , and hydrogen iodide ; and silylated compounds of group 17 elements , such as trimethylsilyl chloride , trimethylsilyl bromide , and trimethylsilyl iodide ; etc . among these , from the stand points of reactivity , stability , and handling , the preferred materials are , elemental materials in groups 15 ˜ 17 , such as phosphorus , arsenic , antimony , bismuth , sulfur , selenium , tellurium , and iodine ; silylated compounds of group 15 elements , such as tris ( trimethylsilyl ) phospine and tri ( trimethylsilyl ) arsine ; hydrides of group 16 elements , such as hydrogen sulfide , hydrogen selenide and hydrogen telluride ; silylated compounds of group 16 elements , such as bis ( trimethylsilyl ) sulfide and bis ( trimethylsilyl ) selenide ; alkaline metal salts of group 16 elements , such as sodium sulfide and sodium selenide ; trialkylphosphine chalcogenides such as , tributylphosphine sulfide , trihexylphosphine sulfide , trioctylphosphine sulfide , tributylphosphine selenide , trihexylphosphine selenide , and trioctylphosphine selenide ; silylated compounds of group 17 elements , such as trimethylsilyl chloride , trimethylsilyl bromide , and trimethysilyl iodide ; etc . among the above , more preferably used materials are , elemental materials in groups 15 and 16 , such as phosphorus , arsenic , antimony , sulfur , and selenium ; silylated compounds of group 15 elements , such as tris ( trimethylsilyl ) phospine and tri ( trimethylsilyl ) arsine ; silylated compounds of group 16 elements , such as bis ( trimethylsilyl ) sulfide and bis ( trimethylsilyl ) selenide ; alkaline metal salts of group 16 elements , such as sodium sulfide and sodium selenide ; trialkylphosphine chalcogenides such as , tributylphosphine sulfide , trioctylphosphine sulfide , tributylphosphine selenide , and trioctylphosphine selenide ; etc . examples of precursors for metal nanoparticles for group 4 through 13 including au , ag , fe , ni , co , pt , pd , cu , hg , in , nipt , fept , feco are : gold : auric acid , chlorocarbonyl gold ( i , and gold ( i ) chloride ; silver : silver ( i ) acetate , silver ( i ) nitrate , silver ( i ) chloride , silver ( i ) bromide , silver ( i ) iodide , and silver sulfate ; iron ( either as ii or iii oxidation state ): iron chloride , iron bromide , iron iodide , iron ( 0 ) carbonyl , iron acetate , iron acetyl acetonate , iron hexapyridine , iron hexamine , iron sterate , iron palmitate , iron sulfonate , iron nitrate , iron dithiocarbamate , iron dodecylsulfate , and iron tetrafluroborate ; nickel : nickel ( ii ) nitrate , nickel ( ii ) chloride , nickel ( ii ) bromide , nickel ( ii ) iodide , nickel ( ii ) carbonyl , nickel ( ii ) acetate , nickel ( ii ) acetyl acetonate , nickel ( ii ) hexapyridine , nickel ( ii ) hexamine , nickel ( ii ) sterate , nickel ( ii ) palmitate , nickel ( ii ) sulfonate , nickel ( ii ) nitrate , nickel ( ii ) dithiocarbamate , nickel ( ii ) dodecylsulfate , and nickel ( ii ) tetrafluroborate ; cobalt : cobalt ( ii ) nitrate , cobalt ( ii ) chloride , cobalt ( ii ) bromide , cobalt ( ii ) iodide , cobalt ( ii ) carbonyl , cobalt ( ii ) acetate , cobalt ( ii ) acetyl acetonate , cobalt ( ii ) acetyl acetonate cobalt ( ii ) hexapyridine , cobalt ( ii ) hexamine , cobalt ( ii ) sterate , cobalt ( iii ) palmitate , cobalt ( ii ) sulfonate , cobalt ( ii ) nitrate , cobalt ( ii ) dithiocarbamate , cobalt ( ii ) dodecylsulfate , and cobalt ( ii ) tetrafluroborate ; platinum : platinum ( ii ) nitrate , platinum ( ii ) chloride , platinum ( ii ) bromide , platinum ( ii ) iodide , platinum carbonyl , platinum ( ii ) acetate , platinum ( ii ) acetyl acetonate , platinum ( ii ) hexapyridine , platinum ( ii ) hexamine , platinum ( ii ) sterate , platinum ( ii ) palmitate , platinum ( ii ) sulfonate , platinum ( ii ) nitrate , platinum ( ii ) dithiocarbamate , platinum ( ii ) dodecylsulfate , and platinum ( ii ) tetrafluroborate ; palladium : palladium ( ii ) nitrate , palladium ( ii ) chloride , palladium ( ii ) bromide , palladium ( ii ) iodide , palladium carbonyl , palladium ( ii ) acetate , palladium ( ii ) acetyl acetonate , palladium ( ii ) hexapyridine , palladium ( ii ) hexamine , palladium ( ii ) sterate , palladium ( ii ) palmitate , palladium ( ii ) sulfonate , palladium ( ii ) nitrate , palladium ( ii ) dithiocarbamate , palladium ( ii ) dodecylsulfate , and palladium ( ii ) tetrafluroborate ; copper ( i or ii oxidation state ): copper nitrate , copper chloride , copper bromide , copper iodide , copper carbonyl , copper acetate , copper acetyl acetonate , copper hexapyridine , copper hexamine , copper sterate , copper palmitate , copper sulfonate , copper nitrate , copper dithiocarbamate , copper dodecylsulfate , and copper tetrafluroborate ; mercury :, dimethyl mercury ( 0 ), diphenyl mercury ( 0 ), mercury ( ii ) acetate , mercury ( ii ) bromide , mercury ( ii ) chloride , mercury ( ii ) iodide , and mercury ( ii ) nitrate ; indium : trimethyl indium ( iii ), indium ( iii ) dichloride , indium ( iii ) trichloride , indium ( ii ) tribromide , and indium ( iii ) triiodide . the solvent effect for nanoparticle formation under dielectric heating is twofold : ( 1 ) it provides the matrix for which the reactants form products ; and ( 2 ) they have the ability to absorb microwaves to intrinsically heat the reaction matrix . the matrix effect can be noncoordinating or coordinating in nature . noncoordinating implies that the solvent does not form bonds to the precursor molecules or intermediate complexes during nanoparticle formation ( it usually does not have functional groups ). coordinating implies the solvent forms bonds to the precursor molecules and intermediates during nanoparticle formation . noncoordinating solvents used for nanoparticle formation usually consist of long chain , high boiling alkanes and alkenes such as hexadecane , octadecane , eicosane , 1 - hexadecene , 1 - octadecene and 1 - eicosene . typical coordinating solvents consist of long chain ( backbone of 6 to 20 carbons ) alkyl amines ( primary , secondary and tertiary ), carboxylic acids , sulfonic acids phosphonic acids , phosphines and phosphine oxides . the ability for a solvent to absorb microwaves is highly dependant on its dipole moment . the dipole moment is defined as the product of the distance between two charges and the magnitude of the charge ; hence , when a coordinating solvent is used as the solvent , it has a higher propencity of heating the bulk solution faster than a noncoordinating solvent that has a lower dipole moment by definition . when comparing the heating rates of trioctylphosphineoxide ( 760 ° c ./ min ) to 1 - aminohexadecane ( 30 ° c ./ min ), trioctylphosphineoxide converts electric energy to heat more efficiently . comparing these to the heating rate of tetradecene ( 12 ° c ./ min ) shows that the choice of solvents has a substantial influence on the rate at which the heat is transferred to the bulk solution . one way to slow down the rate of heating for a solvent that absorbs microwave strongly , like trioctylphosphineoxide , is to reduce the incident microwave power . this will allow the ramp rate to be tailored to suite a particular nanoparticle formation . technical grade solvent dielectric heating rates for nanoparticle synthesis will depend on several factors : the dielectric constant , the volume of solvent , and its boiling point . for nonpolar solvents such as c 6 - c 20 straight chain alkanes , the heating rates are slow for 5 ml of solvent at 300 w of incident power . for example , super - heated noncoordinating technical grade octane plateaus at 147 ° c . after 15 minutes of heating at 300 w with 10 atm of pressure . however , in the presence of cd and se monomers ( 57 mm ), super - heating octane can reach nanoparicle formation temperatures as high as 250 ° c . in 6 minutes with 15 atm of pressure with 300 w of incident microwave power . the lower boiling point alkanes will have a lower plateau temperature in terms of the maximum sustained temperature at high pressure . the higher boiling alkanes can achieve higher temperatures in a shorter period of time when compared to alkanes . when 5 ml of technical grade tetradecene is dielectrically heated at 300 w , it can reach 250 ° c . in 13 min . coordinating solvents typically heat faster at lower pressure due to their higher boiling points and functional groups . for example , 5 ml of technical grade hexadecylamine can be dielectrically heated at 300 w to 280 ° c . in 11 minutes with 1 atm of pressure . in the same manner , trioctylphosphine oxide can be dielectrically heated to 280 ° c . in 15 seconds with 1 atm of pressure . as provided hereunder , embodiments of the present invention will be illustrated in more detail by ways of examples , although the present invention is not limited to these examples provided that the outcome is within the gist of the present invention . with regard to the material reagents , commercially available reagents were used without purification unless otherwise stated . a . discover system , cem corporation , nc , u . s . a . b . milestone ethos system ( continuous and pulsed power supply ), milestone corporation , monroe , conn ., u . s . a . ( 2 ) uv / v is absorption spectroscopy : cary 50bio win uv spectrometer . ( 3 ) photoluminescence spectroscopy : cary eclipse fluorescence spectrometer . ( 4 ) x - ray diffractometry : scintag x2 powder diffractometer . ( 5 ) transmission electron microscopy : jeol 2010 transmission electron microscope the duration of nanoparticle reactions have been optimized to 15 minutes at a maximum temperature of 280 ° c . it is shown that under the influence of microwave radiation , the crystallinity becomes dependant on the power of the radiation in concert with the temperature of the reaction . the microwave reactor allows the precursors to be prepared at or near room temperature ( rt ) and loaded into a reaction vessel prior to its introduction into an rt chamber of the microwave reactor . the reaction vessel is then heated to temperatures between 200 ° c . and 300 ° c . with active cooling . the microwave reactor operates at 2 . 45 ghz and can be adapted to a continuous flow or autosampler system . incorporation of integrated absorption and fluorescent detectors allow the reaction stream to be continuously monitored for applications where high throughput , high volume preparation of colloidal semiconductor nanoparticles is desired . in a typical small scale synthesis ( 5 ml or less ), the reactants are mixed in a high - pressure reaction vessel and placed in the rt chamber of the microwave reactor . the reaction is controlled by a predetermined program that controls and monitors reaction time , temperature , pressure , and microwave power ( wattage ) in real time . these reaction parameters control material size , purity , crystallinity , and dispersity . the synthetic protocol allows reproducible production of materials . the isolation and storage of the materials can be done directly inside the high - pressure reaction vessel , thereby eliminating the step of material transfer that potentially exposes the materials to contaminants such as oxygen and water . the teflon liner in the chamber of the microwave reactor was re - designed from typical commercial specifications in order to tolerate high temperatures for extended periods of time . the reaction vessel comprises a 5 ml vial with a high - pressure aluminum crimp top with teflon septa . all glassware was dried prior to use . all reagents were manipulated by standard airless techniques . in a typical large scale reaction ( 5 ml or greater ), the reactants are placed in a standard round bottom flask ( kirmax , pyrex or chemglass ) and placed in a rt chamber and irradiated with continuous or pulsed power with dual magnetrons until the desired temperature is reached . preparation of cdse from a single source precursor li 4 [ cd 10 se 4 ( sph ) 16 ] it has been shown by cumberland et al . in [ 7 ] that a novel single source precursor based upon li 4 [ cd 10 se 4 ( sph ) 16 ] in the presence of mild coordinating alkyl amine solvent can yield cdse quantum dots in the size range of 2 - 9 nm with a reaction time of 720 minutes on average . using this single source precursor in the presence of hexadecylamine ( hda ) microwave irradiation yields nanoparticles in a fraction of the time . 50 g of hda was degassed under vacuum at 110 ° c . 80 mg of li 4 [ cd 10 se 4 ( sph ) 16 ] was placed in the reaction vessel and sealed with a high pressure crimp cap followed by the addition of 4 ml of molten , degassed hda ( at approximately 70 ° c .). the reaction vessel was placed in the chamber of the microwave reactor and irradiated with 300 watts of power until it reached 230 ° c ., at which time the power was decreased to 230 watts . this power and temperature was held constant for 60 minutes . at 60 minutes , the power was turned off and the latent heat of the reaction vessel was quickly removed by passing compressed air across it . this produced monodisperse 4 . 5 nm to 5 . 5 nm cdse nanoparticles . smaller sizes can be isolated under these experimental parameters simply by quenching the reaction at shorter time intervals . increasing the microwave power to 250 watts for 60 minutes at 230 ° c . can yield sizes larger than 4 . 5 nm , e . g ., 5 . 5 nm , as shown in fig1 , wherein traces 10 and 12 represent the absorption and photoluminescence , respectively , of 4 . 5 nm cdse synthesized at 230 ° c . and 230w , while traces 14 and 16 represent the absorption and photoluminescence , respectively , of 5 . 5 nm cdse grown at 230 ° c . and 250w . stock solutions of cd and se were prepared separately . the cation solution was prepared by dissolving 435 mg of cadmium nitrate tetrahydrate in 9 . 6 ml of trioctylphosphine ( top ). this solution was heated to 100 ° c . under vacuum for 30 minutes . the reaction mixture was purged with ar three times and then cooled to room temperature for later use . the anion solution was prepard by mixing 182 mg of 200 mesh se powder in 2 . 8 ml top the coordinating solvent , trioctyphosphine oxide ( topo ), was degassed under vacuum at 110 ° c . three times and back filled with ar over a two hour period . the cd ( 0 . 5 ml ) and se ( 0 . 6 ml ) were mixed in a teflon sealed reaction vial , and diluted with 3 . 9 ml molten topo ( approximately 65 ° c .) to make a 5 ml solution . the reaction vessel was placed in the chamber of the microwave reactor at room temperature . 300 watts were applied for several seconds , at which time the temperature spiked from 40 ° c . to 230 ° c . in 15 seconds . the power was reduced to 40 watts to stabilize the temperature at 250 ° c . for 8 minutes . at 8 minutes , the power was turned off and the reaction was quenched . this resulted in a 4 . 6 nm cdse nanoparticle , approximated by the excitonic peak position , as shown in fig2 , wherein traces 18 and 20 represent the absorption and photoluminescence , respectively , of cdse grown from cadmium nitrate and trioctylphosphineselenide . note that nanoparticle diameter can be tuned by reaction temperature . the preparation of the stock precursor solutions was done according to literature methods , such as those in [ 9 ]. a solution of indium acetate and hexadecanoic acid was prepared in hexadecene . the mole ratio of in to hexadecanoic acid was adjusted to a 1 to 3 . the salts were dissolved at 100 ° c . to make a 15 . 6 mm solution in in . the solution was degassed at this temperature for 1 hour and purged with ar three times . a stock solution of tris ( trimethylsilyl ) phosphine at 86 . 1 mm was prepared in dry hexadecene . the in and p precursors were mixed at 50 ° c . in a 10 ml sealed reaction vessel in a 2 : 1 ratio to make a total volume of 5 ml precursor solution . the reaction vessel was irradiated with 300 watts of power until the solution reached a temperature of 280 ° c . the power was reduced to maintain 280 watts . this temperature and power was maintained for 15 minutes , at which time the reaction was rapidly quenched . preparation of ingap from in ( oac ), ga ( acac ), and p ( sime 3 ) 3 the stock solution was prepared by a modification of literature methods [ 9 ]. indium iii acetate ( 0 . 700 mmol ), gallium iii 2 , 4 - pentanedionate ( 0 . 070 mmol ) and hexadecanoic acid ( 2 . 30 mmol ) were mixed with 50 ml either octadecene or hexadecene . the mixture was heated to 160 ° c . until the solution turned clear . the temperature of the stock solution was reduced to 110 ° c . under vacuum and purged with ar three times . for 4 . 8 nm quantum dots , the cation stock solution was prepared with octadecene and mixed with tris ( trimethylsilyl ) phosphine in the reaction vessel via syringe at 50 ° c . with a cation : anion mole ratio of 2 : 1 . 5 ml of the stock solution was placed in a 10 ml sealed reactor vial ( cem ). the 2 . 3 nm quantum dots were prepared in the same fashion , but the stock solution was prepared in hexadecene . reactor temperature and pressures were monitored continuously to ensure safety , with pressures not exceeding 1 . 7 atm during the course of the reaction . the power level of the ramp was 300 watts . the hold temperature was 280 ° c . for 15 min ., with a constant power level of 280 watts during the reaction . to ensure controlled dispersity , the reaction vessel was rapidly cooled , via a quenching oswald ripening process , from 280 ° c . to 95 ° c . over a period of 2 min using compressed air . depending on the concentration of precursors , the ramp rate to achieve the hold temperature ranged from 4 - 6 minutes with the more dilute samples taking longer , due to the heating arising from direct dielectric heating of the precursors , rather then the thermal heating of the solvent . size control for these materials was achieved by controlling the concentration of the constituent elements in the reactant . main constituent of the reactant : octadecene ( dielectric constant estimated to be 2 . 1 ˜ 2 . 2 ) when hexadecene was used as the non - coordinating solvent , approximately 2 . 3 nm ingap was grown . when octadecene was used as the non - coordinating solvent , 4 . 8 nm nanoparticles were grown . the size is determined by scherrer broadening of the powder x - ray diffraction peaks , as shown in fig3 a and 3b . fig3 a illustrates the absorption and fig3 b illustrates the photoluminescence of ingap nanoparticles synthesized at 280 ° c . for 15 minutes at 280 watts . traces 22 and 26 represent ingap synthesized with hexadecene ( hde ) as the non - coordinating solvent , and traces 24 and 28 represent ingap synthesized with octadecene as the non - coordinating solvent . an important feature of the specific microwave effect on iii - v ternary compound crystal growth is that the crystallinity ( optical properties of the final product ) is dependant on the microwave power . if the reaction time and temperature are held constant while the power is reduced , low energy defect emission begins to form , as shown in fig4 . fig4 illustrates the absorption and photoluminescence of ingap showing the dependence of crystallinity on power , wherein trace 30 represents the absorption for ingap and trace 32 represents the photoluminescence for ingap that were synthesized with a constant power of 230 watts , while trace 34 represents the absorption for ingap and trace 36 represents the photoluminescence for ingap that were synthesized at a constant power of 270 watts . the defect emission can be attributed to surface vacancies or glide plane defects . it is clear that not only high temperature is important for high quality material , but high power is needed as well . the structural characterization of the material exhibits the zinc blende structure of bulk inp . fig5 is a flowchart that illustrates the processing steps for synthesizing nanoparticles used in the preferred embodiment of the present invention . these steps are typically performed using a single reaction vessel , continuous flow reactor or stopped flow reactor . block 38 represents the step of preparing one or more constituent elements at or near room temperature , wherein the room temperature is below 100 ° c . preferably , a dielectric constant of a main one of the constituent elements is 20 or higher . block 40 represents the step of heating the prepared constituent elements to an elevated temperature using high - rate heating , in order to create a reaction mixture . preferably , the heating step is performed using microwave irradiation , and the high heating rate comprises a rate of 30 ° c ./ min or higher . block 42 represents the step of stabilizing the reaction mixture at the elevated temperature . preferably , the elevated temperature is greater than 240 ° c . block 44 represents the step of cooling the stabilized reaction mixture to a reduced temperature using high - rate cooling . preferably , the high cooling rate comprises a rate of 125 ° c ./ min or higher . fig6 is an illustration of the processing steps for synthesizing nanoparticles used in the preferred embodiment of the present invention . as noted above , the reactor 46 typically comprises a single reaction vessel , continuous flow reactor or stopped flow reactor . the reactant 48 includes the consituent elements , such as one or more precursors 50 and 52 that contain elements that turn into nanoparticles , passivants 54 , and / or solvents 56 . arrow 58 represents the heating / cooling process that creates the nanoparticles 60 . r . l . wells , s . r . aubuchon , s . s . kher , m . s . lube , p . s . white , chemistry of materials 1995 , 7 , 793 . o . i . micic , c . j . curtis , k . m . jones , j . r . sprague , a . j . nozik , journal of physical chemistry 1994 , 98 , 4966 . o . i . micic , j . r . sprague , c . j . curtis , k . m . jones , j . l . machol , a . j . nozik , h . giessen , b . fluegel , g . mohs , n . peyghambarian , journal of physical chemistry 1995 , 99 , 7754 . a . a . guzelian , j . e . b . katari , a . v . kadavanich , u . banin , k . hamad , e . juban , a . p . alivisatos , r . h . wolters , c . c . arnold , j . r . heath , journal of physical chemistry 1996 , 100 , 7212 . o . i . micic , s . p . ahrenkiel , a . j . nozik , applied physics letters 2001 , 78 , 4022 . z . a . peng , x . g . peng , journal of the american chemical society 2001 , 123 , 183 . s . l . cumberland , k . m . hanif , a . javier , g . a . khitrov , g . f . strouse , s . m . woessner , c . s . yun , chemistry of materials 2002 , 14 , 1576 . d . v . talapin , a . l . rogach , i . mekis , s . haubold , a . kornowski , m . haase , h . weller , colloids and surfaces a - 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applied science and manufacturing 1999 , 30 , 1055 . d . a . jones , t . p . lelyveld , s . d . mavrofidis , s . w . kingman , n . j . miles , resources conservation and recycling 2002 , 34 , 75 . d . r . lide , ed ., crc handbook of chemistry and physics , 76th ed ., crc 1995 pp . 6 - 159 . bogovikov , u . y ., et al ., zh . obchei himii 1969 , 40 , pp . 1957 - 1962 . this concludes the description of the preferred embodiment of the present invention . in summary , the present invention has shown that colloidal nanoparticles can be rapidly synthesized under high power microwave radiation to provide industrial scalability with no sacrifice to structural integrity or optical quality . the foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description . it is not intended to be exhaustive or to limit the invention to the precise form disclosed . many modifications and variations are possible in light of the above teaching . it is intended that the scope of the invention be limited not by this detailed description , but rather by the claims appended hereto .