Provided is a method for producing a semiconductor nanoparticle including preparing a mixture containing a Ag salt, a salt containing at least one of In and Ga, and an organic solvent; raising the temperature of the mixture to a raised temperature in a range of from 120 C. to 300 C.; and adding a supply source of S to the mixture at the raised temperature in such a manner that a ratio of a number of S atoms to a number of Ag atoms in the mixture increases at a rate of not more than 10/min.

A quantum dot includes: a core including at least one first positive ion precursor and at least one negative ion precursor; a shell including at least one second positive ion precursor and at least one negative ion precursor and wrapping the core; and a ligand formed on a surface of the shell, wherein the first positive ion precursor is an n-period element and the second positive ion precursor is an (n-1)-period element, where n is an integer of 3 to 6.

A novel near-IR emitting cationic silver chalcogenide quantum dot with a mixed coating wherein the coating comprises of at least 2 different types of materials and is capable of luminescence at the desired near IR bandwidth at wavelengths of 800-850 nm. The quantum dot is fabricated via an advantageous single-step, homogeneous, aqueous method at a low temperature resulting a near IR emitting semiconductor quantum dot with high Quantum Yield, high transfection with low toxicity. The quantum dots may be used in medical imaging, tumor detection, drug delivery and labeling as well as in quantum dot sensitized solar cells.

Provided is a quantum dot including a quaternary core including a first-first Group I element, a first-second Group III element, and a first-third Group VI element and not including Se, and a ternary shell surrounding at least a portion of the quaternary core.

A quantum dot includes a core containing a first semiconductor nanocrystal, a first shell around (e.g., surrounding) the core and containing a second semiconductor nanocrystal different from the first semiconductor nanocrystal, and a second shell around (e.g., surrounding) the first shell and containing a third semiconductor nanocrystal different from the first semiconductor nanocrystal and the second semiconductor nanocrystal, wherein the core has a band gap of about 1.5 eV to about 3.3 eV, a band gap of the second shell is greater than a band gap of the core and is about 3.54 eV or less, and a band gap of the first shell is greater than a band gap of the core and smaller than a band gap of the second shell.

The present invention relates to a semiconductor nanoparticle composed of a compound containing Ag, Au, S and a metal M as essential constitutional elements. In the present invention, the metal M is at least any of Al, Ga, In, Tl, Zn, Cd, Hg and Cu, and the compound has a total content of Ag, Au, S and the metal M of 95 mass % or more. In addition, a ratio (x/(x+y)) of the number of atoms of Ag to a sum of the number of atoms of Ag, x, and the number of atoms of Au, y, in the AgAuS-based multicomponent compound is preferably 0.50 or more and 0.88 or less. The semiconductor nanoparticle of the present invention has appropriate emission and extinction characteristics and is biocompatible.

A method for producing a quantum dot that includes synthesizing a quantum dot represented by AgInE.sub.2 (E is at least one of tellurium, selenium, and sulfur) from a silver raw material, an indium raw material, and a chalcogenide raw material (chalcogenide is at least one of tellurium, selenium, and sulfur).

The present invention relates to a semiconductor nanoparticle composed of a compound containing Ag, Au, S and a metal M as essential constitutional elements. In the present invention, the metal M is at least any of Al, Ga, In, Tl, Zn, Cd, Hg and Cu, and the compound has a total content of Ag, Au, S and the metal M of 95 mass % or more. In addition, a ratio (x/(x+y)) of the number of atoms of Ag to a sum of the number of atoms of Ag, x, and the number of atoms of Au, y, in the AgAuS-based multicomponent compound is preferably 0.50 or more and 0.88 or less. The semiconductor nanoparticle of the present invention has appropriate emission and extinction characteristics and is biocompatible.

Provided is a method of producing semiconductor nanoparticles exhibiting band-edge emission with a short emission peak wavelength. The method of producing semiconductor nanoparticles comprises: obtaining a first mixture that contains a Ag salt, an In salt, a compound containing Ga and S, and an organic solvent; and performing a heat treatment of the first mixture at a temperature in a range of 125 C. or higher and 300 C. or lower to obtain first semiconductor nanoparticles.

A quantum dot being a nanocrystal represented by AgInTe.sub.2 contains silver, indium, and tellurium, the quantum dot being a near-infrared absorbing particle