TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The method further involves adding to the dispersing medium when the dispersing medium is at second temperature an initial portion of the other of the first and second precursor species which is less than the total amount of other of the first and second precursor species is used to produce nanoparticles. The method involves monitoring the average size of the grown nanoparticles; and terminating nanoparticle growth when the average nanoparticle size reaches a predetermined value. The method involves forming a precipitate of the nanoparticle material by the addition of a precipitating reagent. In the method, the temperature of the dispersing medium containing the growing nanoparticles is increased at a rate of 0.05 - 1 (preferably 0.2degreesC/minutes). The first temperature is in the range of 15 - 80 (preferably 15 - 60)degreesC. The second temperature is in the range of 90 - 150degreesC or 140 - 300degreesC. Each further portion of the nanoparticle precursor composition is added dropwise to the dispersing medium containing the growing nanoparticles. Each further portion of the nanoparticle precursor composition is added to the dispersing medium containing the growing nanoparticles at a rate of 0.1 ml/minutes - 20 ml/minutes/l of dispersing medium. One further portion of the nanoparticle precursor composition is added to the dispersing medium containing the growing nanoparticles and one further portion (less than or equal to90%) is used to produce the nanoparticles. More than one further portion of the nanoparticle precursor composition is added to the dispersing medium containing the growing nanoparticles and each of further portions (less than or equal to45 preferably less than or equal to10)% is used to produce nanoparticles. The molecular cluster compound is in situ in dispersing medium prior to dispersing the molecular cluster compound and the initial portion of the nanoparticle precursor composition in dispersing medium. The dispersing medium containing the growing nanoparticles is increased at a rate which is other than 50degreesC over a period of 24 hours. The average size of the grown nanoparticles which is monitored by UV-visible emission spectroscopy. The average size of the nanoparticles is grown which is monitored by photoluminescence spectroscopy. The nanoparticle growth is terminated by reducing the temperature of the solution from the second temperature to a third temperature. At least one further portion of other first and second precursor species is added to the dispersing medium containing the growing nanoparticles. The temperature of the dispersing medium containing the growing nanoparticles is increased before, during and/or after the addition of each further portion of other of the first and second precursor species. The temperature of the dispersing medium containing the growing nanoparticles is maintained at second temperature during the addition of each further portion of other of the first and second precursor species. The nanoparticle growth is terminated by reducing the temperature of the solution from the second temperature to a third temperature. The temperature of the dispersing medium containing the growing nanoparticles is increased from the first temperature to the second temperature at 0.05 - 2 (preferably 0.5 - 1.5)degreesC/minutes. Each further portion of at least one of the first and second precursor species is added dropwise to the dispersing medium containing the growing nanoparticles. Preferred Components: The ratio of the number of moles of cluster compound compared to the total number of moles of the first and second precursor species is 0.0001 - 0.1:1 (preferably 0.001 - 0.1:1). The molar ratio of the first precursor species to the second precursor species is 100 - 1:1 (preferably 50 - 1:1). The initial portion of the nanoparticle precursor composition is less than or equal to90 (preferably less than or equal to10)% of the total amount of the nanoparticle precursor composition. The dispersing medium is a Lewis base coordination compound selected from a phosphine, phosphine oxide and amine. The inorganic salt is selected from an oxide and nitrate. The oxide is selected from strontium oxide, zinc oxide, cadmium oxide, indium oxide, gallium oxide, tin oxide, lead oxide, phosphorus oxide, arsenide oxide, antimony oxide, bismuth oxide sulfur dioxide, selenium oxide, tellurium oxide, stannous oxide, lead oxide and lead dioxide. The nitrate is selected from magnesium nitrate, calcium nitrate, strontium nitrate, barium nitrate, cadmium nitrate, zinc nitrate, mercury nitrate, aluminum nitrate, indium nitrate, gallium nitrate, tin nitrate, lead nitrate, bismuth nitrate, tin nitrate. The molecular cluster compound comprises third and fourth ions which are incorporated into the growing nanoparticles. The third ion is selected from group 12 of the periodic table and the fourth ion is selected from group 16 of the periodic table. The molecular cluster compound comprises molecules selected from (((PPh3)Hg)4(SPh)6), (Ph4P)2((SEt)5(Br)(HgBr)4), (Ph4P)2(Hg4(SEt)5Br), (Hg4Te12)(N(CH2CH2Et)4)4, (Et3NH)4(Cd10Se4(SPh)16), (RM1E1-tertbutyl)5, (X)4 ((E1)4(M1)10(SR1)16), (Cd32S14(SPh)36)L1, (Hg10Se4(SePh)(PPh2-(n-propyl))4), (Hg32Se14(SePh)36), (Cd10Se4(SePh)12(PPr3)4), (Cd32Se14(SePh)36(PPh3)4), ((M1)4(SPh)12)+((X1)2)-, (Zn(SEt)Et)10, (MeM1E1-isopropyl), (R2CdSR3)5, (Cd10(E1)4(E1Ph)12(P(R4)3)4), (Cd8Se(SePh)12Cl4)2-, ((M2)4Te12)4-, (Ph12(M3)18Cd10(PEt3)3). The third ion is selected from group 12 of the periodic table and the fourth ion is selected from group 15 of the periodic table. The molecular cluster compound comprises molecules selected from (R5CdNR6)4, (R7CdNR7)5, ((R8Zn)6(PR9)4), ((M4)4Cl4(PPh2)4(P-(n-propyl)3)2), (Li(thf)4)2((Ph2P)10Cd4), (Zn4(PPh2)4Cl4(PRaRb)2), (Zn4(P-(tertbutyl)2)4Cl4). The third ion is selected from group 13 of the periodic table and the fourth ion is selected from group 15 of the periodic table. The molecular cluster compound comprises molecules selected from (EtGaNEt)6, (MeGaN(4-C6H4F))6, (MeGaNiBu)6, (R10AlNR11)4, ((Si(isopropyl)3)3AsAlH)6, (isopropylNAlH)4, (R12AlNR13)6, (CH3Ga-NCH2CH(CH3)2)6, (MeGaN(tertbutyl))6, (R14GaNR15)4, (EtGaNEt)6, (R16GaPR17)4, (R18NInR19)4, (R20InPR21)4 or (R22InPR23)6. The third ion is selected from group 13 of the periodic table and the fourth ion is selected from group 16 of the periodic table. The molecular cluster compound comprises molecules selected from ((tertbutyl)GaSe)4, (tertbutyl-GaS)7, (R24InSe)4, (R25InS)4, (R26GaS)4, (SAlR27)4, (SAlNMe3)5, (TeAlR28)4, ((C(SiMe3)3)GaS)4, (tertbutyl-GaS)6, (R29GaSe)4 or Cd4In16S33.(H2O)20(C10H28N4)2.5. The third ion is selected from group 14 of the periodic table and the fourth ion is selected from group 16 of the periodic table. The molecular cluster compound comprises molecules selected from (S6(SnR30)4) or (Se6(SnR31)4). The third ion is selected from the transition metal group of the periodic table and the fourth ion is selected the d-block of the periodic table. The molecular cluster compound comprises molecules selected from (Cu12Se6(PR32)8), (Cu18Te6(tertbutyl)6(PPh2Et)7), (Cu19Te6(tertbutyl)7(PEt3)S), (Cu27Te15(P(isopropyl)2Pr2Me)12), (Ni34Se22(PPh3)10), (Ag30(TePh)12Te9(PEt3)12), (Ag3Ose8(Se(tertbutyl))14(P(n-propyl)3)8), (Co4(mu3-Se)4(PPh3)4), (Co6(mu3-Se)8(PPh3)6), (W3Se4(dmpe)3Br3)+, Ru4Bi2(CO)12, Fe4P2(CO)12 or Fe4N2(CO)12. The first ion is selected from the group consisting of group 2 of the periodic table, group 12 of the periodic table, group 13 of the periodic table and group 14 of the periodic table. The second ion is selected from the group consisting of group 14 of the periodic table, group 15 of the periodic table and group 16 of the periodic table. The second precursor species is separate to the first precursor species in the nanoparticle precursor composition. The first precursor species is selected from the group consisting of an organometallic compound, an inorganic salt, and a coordination compound. The coordination compound is a carbonate selected from M5CO3, ((MgCO3)4Mg(OH)2) or M4CO3. The coordination compound is selected from cadmium acetate, M6(CH3CO2)2, M7(CH3CO2)3, M8(CH3COCH=C(O-)CH3)2, M7(CH3COCH=C(O-)CH3)3, M9C2O4, M10(OH)2 or M11(C17H35COO)2. The coordination compound is a carbonate selected from M12CO3 or M13(CO3)2. The coordination compound is selected from M14(CH3CO2)2, M15(CH3CO2)2, M15(CH3CO2)4, (CH3COCH=C(O-)CH3)3M16, (CH3COCH=C(O-)CH3)2M14, (CH3COCH=C(O-)CH3)2M15, thiourea or H2NC(=Se)NH2. The first precursor species is obtained by dissolving an elemental source selected from magnesium, calcium, strontium, barium, zinc, cadmium, mercury, boron, aluminum, gallium, indium, antimony and lead in a suitable solvent. The second precursor species is selected from the group consisting of an organo compound, a hydrido compound, an inorganic salt and a coordination compound. The second precursor species is obtained by dissolving an elemental source selected from tin, germanium, nitrogen, phosphorus, arsenide, antimony, bismuth, sulfur, selenium, tellurium and lead in a suitable solvent. The first and second precursor species are part of a single chemical entity in the nanoparticle precursor composition. The nanoparticles have cores comprises a core compound containing fifth and sixth ions. The fifth ion is selected from group 2 of the periodic table and the sixth ion is selected from group 16 of the periodic table. The core compound is selected from magnesium sulfide, magnesium selenide, magnesium telluride, calcium sulfide, calcium selenide, calcium telluride, strontium sulfide, strontium selenide, strontium telluride, barium sulfide, barium selenide and barium telluride. The fifth ion is selected from group 12 of the periodic table and the sixth ion is selected from group 16 of the periodic table. The core compound is selected from the zinc sulfide, zinc selenide, zinc telluride, cadmium sulfide, cadmium selenide, cadmium telluride, mercury sulfide and mercury telluride. The fifth ion is selected from group 12 of the periodic table and the sixth ion is selected from group 15 of the periodic table. The core compound is selected from the group consisting of zinc phosphide, zinc arsenide, cadmium phosphide, cadmium arsenide, cadmium nitride and zinc nitride. The fifth ion is selected from group 13 of the periodic table and the sixth ion is selected from group 15 of the periodic table. The core compound is selected from the group consisting of boron phosphide, aluminum phosphide, aluminum arsenide, aluminum antimonide, gallium nitride, gallium phosphide, gallium arsenide, gallium antimonide, indium nitride, indium phosphide, indium arsenide, indium antimonide, aluminum nitride and boron nitride. The fifth ion is selected from group 13 of the periodic table and the sixth ion is selected from group 14 of the periodic table. The core compound is selected from the group consisting of boron carbide, aluminum carbide, and gallium carbide. The firth ion is selected from group 13 of the periodic table and the sixth ion is selected from group 16 of the periodic table. The core compound is selected from aluminum sulfide, aluminum selenide, aluminum telluride, gallium sulfide, germanium telluride, indium sulfide, indium selenide, gallium telluride, indium telluride. The fifth ion is selected from group 14 of the periodic table and the sixth ion is selected from group 16 of the periodic table. The core compound is selected from the group consisting of lead sulfide, lead selenide, lead telluride, antimony telluride, tin sulfide, tin selenide and tin telluride. The fifth ion is selected from the transition metal group of the periodic table and the sixth ion is selected from the d-block of the periodic table. The core compound is selected from nickel sulfide, chromium sulfide and copper indium sulfide. The nanoparticle cores comprise a dopant selected from the group consisting of a main group element, and a rare earth element. Each nanoparticle comprises at least one shell grown onto the nanoparticle core. Each shell has a similar lattice type to the nanoparticle core. Each shell has a wider band-gap than the nanoparticle core. Each shell comprises a shell compound comprised of seventh and eighth ions. The seventh ion is selected from group 2 of the periodic table and the eighth ion is selected from group 16 of the periodic table. The shell compound is selected from magnesium sulfide, magnesium selenide, magnesium telluride, calcium sulfide, calcium selenide, calcium telluride, strontium sulfide, strontium selenide and strontium telluride. The seventh ion is selected from group 12 of the periodic table and the eighth ion is selected from group 16 of the periodic table. The shell compound is selected from zinc sulfide, zinc selenide, zinc telluride, cadmium sulfide, cadmium selenide, cadmium telluride, mercury sulfide, mercury selenide and mercury telluride. The seventh ion is selected from group 12 of the periodic table and the eighth ion is selected from group 15 of the periodic table. The shell compound is selected from zinc phosphide, zinc arsenide, cadmium phosphide, cadmium arsenide, cadmium nitride and zinc nitride. The seventh ion is selected from group 13 of the periodic table and the eighth ion is selected from group 15 of the periodic table. The shell compound is selected from boron phosphide, aluminum phosphide, aluminum arsenide, aluminum antimonide, gallium nitride, gallium phosphide, gallium arsenide, gallium antimonide, indium nitride, indium phosphide, indium arsenide, indium antimonide, aluminum nitride and boron nitride. The seventh ion is selected from group 13 of the periodic table and the eighth ion is selected from group 14 of the periodic table. Each shell compound is selected from boron carbide, aluminum carbide and gallium carbide. The seventh ion is selected from group 13 of the periodic table and the eighth ion is selected from group 16 of the periodic table. The shell compound is selected from aluminum sulfide, aluminum selenide, aluminum telluride, gallium telluride, gallium selenide, indium sulfide, indium selenide, gallium telluride and indium telluride. The seventh ion is selected from group 14 of the periodic table and the eighth ion is selected from group 16 of the periodic table. The shell compound is selected from lead sulfide, lead selenide, lead telluride, antimony telluride, tin sulfide, tin selenide and tin selenide. The seventh ion is selected from the transition metal group of the periodic table and the eighth ion is selected from the d-block of the periodic table. The shell compound is selected from the nickel sulfide, chromium sulfide and copper indium sulfide.M1= Zn, Cd or Hg;E1=S, Se or Te;R=Me or Et;X=Me3NH+, Li+ or Et3NH+;R1= Me, Et or Ph;L1=coordinating ligand;X1=Me4N+ or Li+;R2=O(ClO3);R3=PPh3 or isopropyl;R4=coordinating ligand;M2=Cd or Hg;M3 = Te or Se;R5=Cl, Br, I, PEt3 or C=CSMe3;R6=PEt3 or I;R7=alkyl or aryl;R8=I or PEt2Ph;R9=SiMe3;M4=Zn or Cd;PRaRb= PMe-(n-propyl)2, P-(n-butyl)3 or PEt2Ph;R10=Me, CH2-isopropyl or Ph;R11=isopropyl, CH2-isopropyl, C6H2Me3, R12=Me, Et, Cl, CH2Ph, CH2-isopropyl or Ph;R13=Me, H, Br, C=CPh, isopropyl, (CH2)2Me, (CH2)2NMe2 or SiPh3;R14= Ph or Me;R15=Ph, C6F5, SiMe3 or tertbutyl;R16=isopropyl or C6H2Me3;R17=tertbutyl or C6H2Me3;R18= Cl, Br3, I or Me;R19=tertbutyl, C6H5 or C6H4F5;R20=isopropyl, C6H2Me3 or Et;R21=SiPh3, C6H2Me3, Si(isopropyl)3;R22=Et;R23=SiMe2(CMe2-isopropyl);R24=tertbutyl, CMe2Et, Si(tertbutyl)3 or C((SiMe3)3)3;R25=tertbutyl or CMe2Et;R26=tertbutyl, CMe2Et or CEt3;R27=C(Sme3)3 or CEtMe2;R28=Cp or CEtMe2;R29=tertbutyl, CMe2Et, CEt3, C(SiMe3)3, Cp or Bu;R30=C(SiMe3)3, Me or Ph;R31=C6F5, C6H2Me3, p-Tol or C(SiMe3)3;R32=Et2Ph, (n-propyl)3 or Cy3;M5=Ca, Sr, Ba or Pb;M6= Mg, Ca, Sr, Ba, Zn or Hg;M7=B, Al, Ga or In;M8= Mg, Ca, Sr, Ba, Zn, Cd or Hg;M9=Sr, Ca, Ba or SnC2O4 or Cd(OH)2;M10=Mg, Ca, Sr, Ba, Zn or Hg;M11=Mg, Ca, Sr, Ba, Zn, Cd or Hg;M12=P or (BiO)2CO3;M13=monovalent metal ion;M14=S, Se or Te;M15=Sn or Pb;M16=Bi.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The solvent is selected from tri-p-octylphosphine, tri-n-octylphosphine oxide and hexadecylamine. The solvent is a non-coordinating solvent. The solvent is an organic solvent. The organic solvent is selected from the group consisting of an alkane, and an alkene. The alkene is octadecene. The precipitating reagent is selected from the ethanol and acetone. The organometallic compound is selected from M17(R32)2, Mg(tertbutyl)2, M18R32, Me2Zn, Et2Zn, Me2Cd, Et2Cd, M19(R32)3, Al(R33)3, Ga(R33)3 or In(R33)3. The single chemical entity is selected from an organometallic compound, an inorganic salt and a coordination compound. The single chemical entity incorporates ions from group 12 and group 16 of the periodic table. The single chemical entity is a bis(dialkyldithio-carbamato)M(II) complex or related Se and Te compounds of the formula M4((E2)2CN(R32)2)2. The single chemical entity is selected from cadmium sulfide, Cd(SSiMe3)2, Cd(SCNHNH2)2Cl2, Cd(SOCR)2.py and CdSe(Cd(SePh)2)2. The single chemical entity incorporates ions from group 13 and group 15 of the periodic table. The single chemical entity is selected from ((Me)2GaN(H)-tertbutyl)2, (H2GaNH2)3, (Ph2GaP(SiMe3)3Ga(Ph)2Cl)(Et2GaP(SiMe3)2)2, (Et2GaPEt2)3, ((tertbutyl)GaPH2)3, (Me2GaP(isopropyl)2)3, (tertbutyl-GaPAr)2, ((tertbutyl)2GaP(H)C5H9)2, Ga(As-(tertbutyl)2)S, (Et2GaAs(SiMe3)2)2, ((tertbutyl)2GaAs(SiMe3)2)2, (Et2GaSb(SiMe3)2)2, ((Me3SiCH2)2InP(SiMe3)2)2, ((R')2InP(SiMe3)2)2, (Me2InP(tertbutyl)2)2, (Me2InSb4(tertbutyl)2)3, (Et2InSb(SiMe3)2)3, (Me2InNEt2)2, (Et2AlAs(tertbutyl)2)2, ((tertbutyl)2AlSb(SiMe3)2)2, ((n-butyl)2GaAs(tertbutyl)2)2, (Me2Ga2As(tertbutyl)2)2 or (Et2GaAs(tertbutyl)2)2. The single chemical entity incorporates ions from group 12 and group 15 of the periodic table. The single chemical entity is selected from (MeCdP-(tertbutyl)2)3, Cd(P(SiPh3)2)2, Zn3P2 or Zn(P(SiPh3)2)2. The single chemical entity incorporates ions from group 14 and group 16 of the periodic table. The single chemical entity is selected from the group consisting of a lead (II) dithiocarbamate and a lead (II) selenocarbamate. The organo or hydrido compound is selected from N(R34)3, P(R34)3, As(R34)3, Sb(R34)3, NH(R34)2, PH(R34)2, AsH(R34)2, SbH(R34)2, NH2R34, PH2R34, AsH2R34, SbH2(R34)3, PH3, AsH3, M20(NMe)3, Me2NNH2, Et-N3, H2NNH2, Me3SiN3, M14R34, HMR34, S=C(NH2)2, Se=C(NH2)2, Sn(CH4)4, Sn(C4H9) or Sn(CH3)2(OOCH3)2.M17=Mg;R32=alkyl or aryl;M18=Zn, Cd or Te;M19=Ga, In, Al or B;R33= Me, Et or isopropyl;R'=not defined;E2=S, Se, O, Te;M20=P, Sb or As;R34=Me, Et, tertbutyl, isobutyl, isopropyl or Ph. EXAMPLE - To a stirred acetonitrile solution (100 ml) of (HNEt3)2(Cd4(SPh)10) (80 g) was added selenium powder (3.57 g), the resulting slurry was left to stirrer for 12 hours to produce a white precipitate. Followed by, acetonitrile (750 ml) was added and the solution warmed to 75degreesC to give a clear pale yellow solution which was allowed to cool to 50degreesC. After work-up, (HNEt3)4(Cd10Se4(SPh)16) was obtained. Hexadecylamine (HDA) (200 g) was placed in a three-neck round- bottomed flask and dried and degassed by heating to 120degreesC under a dynamic vacuum for greater than 1 hour. The solution was cooled to 60degreesC, the reaction flask was filled with nitrogen and (HNEt3)4(Zn10S4(SPh)16) (0.6 g), Et2Zn (4 ml) in trioctylphosphine, and elemental sulphur (4 ml) in octylamine were loaded into the flask. The temperature was increased to 120degreesC and allowed to stir for 2 hours. Simultaneously, Et2Zn (8 ml) and S-octylamine (8 ml) were added dropwise at a rate of -0.05 ml/minutes. The reaction was stopped by cooling to 60degreesC followed by dry ethanol or acetone was added. After work-up, zinc sulfide nanoparticle (0.9 g) was obtained.