The present invention addresses the problem of providing phosphine for fumigation, by which clogging of a pipe of a fumigation gas feed device due to impurities is effectively suppressed and which has low spontaneous ignitability. The present invention also addresses the problem of providing a phosphine fumigation method in which clogging of a pipe of a fumigation gas feed device and a possibility of spontaneous ignition are reduced and which is safe. The phosphine for fumigation of the present invention has a P.sub.4 content of 10 mass ppm or less and a water content of 10 mass ppm or less. The fumigation method of the present invention includes fumigating a material to be fumigated, using phosphine having a P.sub.4 content of 10 mass ppm or less and having a water content of 10 mass ppm or less.

A nanocrystal preparation method comprises the following steps: dissolving, in a first selected solvent, a first precursor which is in a gaseous state under normal temperature and normal pressure, to form a first precursor solution; dissolving a second precursor in a second selected solvent to form a second precursor solution, wherein the second precursor is a precursor of a metal element of Group I, Group II, Group III or Group IV; and in an inert gas atmosphere, adding the first precursor solution into a reaction vessel which contains the second precursor solution, wherein the first precursor chemically reacts with the second precursor to generate a nanocrystal. The present invention further discloses a nanocrystal prepared by the above method and an apparatus for preparing and storing a gas-dissolved solution. With the preparation method according to the invention, the amount of the first precursor in a gaseous state can be accurately controlled, the reaction is more uniform and more controllable, and the obtained nanocrystal has uniform volume distribution and a higher luminescent quantum yield.

A nanocrystal preparation method comprises the following steps: dissolving, in a first selected solvent, a first precursor which is in a gaseous state under normal temperature and normal pressure, to form a first precursor solution; dissolving a second precursor in a second selected solvent to form a second precursor solution, wherein the second precursor is a precursor of a metal element of Group I, Group II, Group III or Group IV; and in an inert gas atmosphere, adding the first precursor solution into a reaction vessel which contains the second precursor solution, wherein the first precursor chemically reacts with the second precursor to generate a nanocrystal. The present invention further discloses a nanocrystal prepared by the above method and an apparatus for preparing and storing a gas-dissolved solution. With the preparation method according to the invention, the amount of the first precursor in a gaseous state can be accurately controlled, the reaction is more uniform and more controllable, and the obtained nanocrystal has uniform volume distribution and a higher luminescent quantum yield.

The invention relates to flame retardant compositions comprising heptaphosphorus-derived compounds and to novel heptaphosphorus-derived compounds. These heptaphosphorus-derived compounds are especially useful for the manufacture of flame retardant compositions based on thermoplastic polymers, especially polyolefin homo- and copolymers, polycondensates, such as polyamides, or polyesters and duroplastic polymers, such as the ones based on polyepoxides.

The invention relates to flame retardant compositions comprising heptaphosphorus-derived compounds and to novel heptaphosphorus-derived compounds. These heptaphosphorus-derived compounds are especially useful for the manufacture of flame retardant compositions based on thermoplastic polymers, especially polyolefin homo- and copolymers, polycondensates, such as polyamides, or polyesters and duroplastic polymers, such as the ones based on polyepoxides.

A nanocrystal preparation method comprises the following steps: dissolving, in a first selected solvent, a first precursor which is in a gaseous state under normal temperature and normal pressure, to form a first precursor solution; dissolving a second precursor in a second selected solvent to form a second precursor solution, wherein the second precursor is a precursor of a metal element of Group I, Group II, Group III or Group IV; and in an inert gas atmosphere, adding the first precursor solution into a reaction vessel which contains the second precursor solution, wherein the first precursor chemically reacts with the second precursor to generate a nanocrystal. The present invention further discloses a nanocrystal prepared by the above method and an apparatus for preparing and storing a gas-dissolved solution. With the preparation method according to the invention, the amount of the first precursor in a gaseous state can be accurately controlled, the reaction is more uniform and more controllable, and the obtained nanocrystal has uniform volume distribution and a higher luminescent quantum yield.

A nanocrystal preparation method comprises the following steps: dissolving, in a first selected solvent, a first precursor which is in a gaseous state under normal temperature and normal pressure, to form a first precursor solution; dissolving a second precursor in a second selected solvent to form a second precursor solution, wherein the second precursor is a precursor of a metal element of Group I, Group II, Group III or Group IV; and in an inert gas atmosphere, adding the first precursor solution into a reaction vessel which contains the second precursor solution, wherein the first precursor chemically reacts with the second precursor to generate a nanocrystal. The present invention further discloses a nanocrystal prepared by the above method and an apparatus for preparing and storing a gas-dissolved solution. With the preparation method according to the invention, the amount of the first precursor in a gaseous state can be accurately controlled, the reaction is more uniform and more controllable, and the obtained nanocrystal has uniform volume distribution and a higher luminescent quantum yield.

The invention relates to flame retardant compositions comprising heptaphosphorus-derived compounds and to novel heptaphosphorus-derived compounds.

These heptaphosphorus-derived compounds are especially useful for the manufacture of flame retardant compositions based on thermoplastic polymers, especially polyolefin homo- and copolymers, polycondensates, such as polyamides, or polyesters and duro-plastic polymers, such as the ones based on polyepoxides.