US Patent 7264527 - Q-dot light source using primary and secondary light

http://www.freepatentsonline.com/7264527.html

This patent seems to present some fairly basic claims to a method of formed quantum dot light sources in a host matrix. In has a fairly early priority date (Apr. 1 1998) and provides an alternative to epitaxal growth of the quantum dots on a semiconductor layer. Claim 1 reads:

1. A method of producing a light-emitting device, comprising steps of: (a) providing a population of quantum dots (QDs) and a host matrix, wherein each QD of the population comprises a core of an independently selected size and composition, the population comprises a selected size distribution of QDs, and the QDs have a surface adapted to allow the QDs to be dispersed in the host matrix; (b) dispersing the QDs in the host matrix; and (c) providing a light source in optical communication with the host matrix with QDs dispersed therein, wherein the light source emits primary light and when used to illuminate the QDs dispersed in the host matrix causes the QDs to photoluminesce secondary light, and wherein the matrix is disposed to allow both the primary light emitted by the light source and the secondary light emitted by the QDs to pass therethrough, thereby causing the light-emitting device to emit light comprising a mixture of primary and secondary light.

US Patent 7253452 - Blue light semiconductor nanocrystal

http://www.freepatentsonline.com/7253452.html

This patent from M.I.T. teaches fabrication methods for improved light emissive nanocrystals of blue wavelengths. Claim 1 reads:

1. A semiconductor nanocrystal comprising: a core including a first semiconductor material; and an overcoating on the core, the overcoating including a second semiconductor material, wherein the nanocrystal is substantially free of deep-trap emission sites, and the nanocrystal when excited emits blue light.

US Patent 7227177 - Room temperature quantum confinement in nanocrystal

http://www.freepatentsonline.com/7227177.html

Doping of nanostructured materials is important if they are ever to be used to form diode, transistor, or various other electronic structures based on semiconductor physics. This patent is from a company called Arch Development (which appears to be some type of venture capital fund based on Google searching) and presents some seemingly very broad claims to semiconductor nanocrystals (aka quantum dots) used in photovoltaics. Apparently, based on the specification, the inventors teach using electrons instead of n-type dopant atoms (P, As, Sb)to dope quantum dots and allege that quantum dots of the prior art only include electrons in a trapped state rather than in a "quantum confined state at room temperature" as claimed. Claim 1 reads:

1. A photovoltaic device, comprising: a semiconductor nanocrystal for the photovoltaic device, wherein said nanocrystal is doped with an electron, such that the electron is in a quantum confined state at room temperature and in the absence of an applied electric potential.

US Patent 7227173 - LED with quantum dot/quantum well coupling

http://www.freepatentsonline.com/7227173.html

Quantum wells are thin films that create a two-dimensional barrier structure that confine electrons and are useful in a variety of applications including lasers and photodetectors. Quantum dots are structures which further confine electrons into zero dimensions. While quantum well based optoelectronic devices are fairly well established, there is a desire to use quantum dots to improve efficiency. However, it is difficult to achieve the necessary uniformity of size and sufficient distribution density to use quantum dot layers effectively. This patent proposes using adjacent quantum wells to create a bridge to facilitate the electron transfer between quantum dots. Claim 2 is representative.

2. A semiconductor device, comprising: a plurality of semiconductor layers; means for coupling signals to and/or from semiconductor layers of said semiconductor device; and a layer of doped quantum dots, comprised of III-V semiconductor material, disposed in at least one of said semiconductor layers as a source of carriers that communicate in either direction between said doped quantum dots and another layer.

US Patent 7226953 - Alkoxysilane-terminated nanocrystal sol-gel composites

http://www.freepatentsonline.com/7226953.html

One of the key difficulties in applying semiconductor nanocrystals in materials is coupling nanocrystals to a composite matrix. This patent teaches mixing colloidal nanocrystals with a sol-gel precursor to facilitate the forming of composites. Claim 1 reads:

1. A solid composite comprising the reaction product of (i) colloidal nanocrystals including at least a portion of alkoxysilane-terminated groups thereon and (ii) a sol-gel precursor material.

US Patent 7213923 - Fluorescent nanoparticles in transparent substrate

http://www.freepatentsonline.com/7213923.html

Fluorescence is generally defined as the emission of electromagnetic radiation, generally visible light, stimulated in a substance by the absorption of incident radiation and persisting only as long as the stimulating radiation is continued. The use of quantum dots to achieve fluorescence has been known for decades and may have existed since medieval times when artisans made stained glass windows. Nevertheless this patent presents a broad claim to transparent substrates with fluorescent nanoparticles (which may include atoms, molecules, or any other particles less than 500 nm in diameter). Claims 1, 37, and 38 reads:

1. An apparatus comprising light emitting material integrated into a substantially transparent substrate, wherein: the light emitting material is configured to emit visible light in response to absorption of excitation light; the wavelength of the visible light varies according to the wavelength of the excitation light; the light emitting material comprises a plurality of light emitting particles; and each of the plurality of light emitting particles has a diameter less than about 500 nanometers.

37. The apparatus of claim 1, wherein each of the plurality of light emitting particles is an individual molecule.

38. The apparatus of claim 1, wherein each of the plurality of light emitting particles is an individual atom.

While these claims would seem to place the holder of this patent (a company called Superimaging) as the owner of all fluorescent materials (especially in light of claims 37 and 38 since everything is fundamentally made of atoms or molecules and the physics of fluorescence happens on the molecular or atomic level) there is plenty of prior art missed (or not understood) by the Examiner to invalidate this patent. See for example US 7,094,361
http://www.freepatentsonline.com/7094361.html.

US Patent 7189455 - Carbon nanotube/nanocrystal heterostructure

http://www.freepatentsonline.com/7189455.pdf

In order to create useful electronic structures from nanotubes they need to be connected to other electrical elements. This patent from the State University of New York teaches how to manufacture a nanotube/nanocrystal mixture wherein the nanotubes are linked to the nanocrystals via oxygen mediated covalent bonding so as to create a nanostructure more easily integrated in electronic systems. Claim 1 reads:

1. A fused heterostructure comprising a carbon nanotube and at least one nanocrystal, wherein the nanocrystal is directly attached by a covalent linkage to at least one oxygen moiety on the nanotube, and wherein there is no intermediary linker between the nanotube and the nanocrystal.

US Patent 7181266 - Lymphatic imaging using nanoparticles

http://www.freepatentsonline.com/7181266.pdf

This patent from M.I.T. seems to lay claim to a fundamental usage of quantum dots in imaging the lymphatic system. Claim 1 reads:

1. A method of imaging a lymphatic system of an animal comprising: introducing at an injection site a composition subcutaneously in the animal, the composition including a particle including a semiconductor nanocrystal; exciting the particle with an excitation light source; and detecting emission from the particle.

US Patent 7175778 - Clumping resistant quantum dots

http://www.freepatentsonline.com/7175778.pdf

The company Nanocrystal Technology has developed a way to take advantage of single dopant atom inside of a nanocrystal to produce high efficiency optical devices. This patent teaches the inclusion of a clumping resistant coating material to avoid agglomeration of the nanocrystals. Claim 1 reads:

1. A particle of material comprising a plurality of host atoms in a nanoparticle of a size of less than 10 nm with a single atom of a dopant confined within, and an anti-agglomeration coating surrounding the nanoparticle, the anti-agglomeration coating surrounding the nanoparticle being selected from the group consisting of alkoxysilane, octylphosphine oxide, carboxylic acid, stearic acid, mercepto acetic acid, polyphosphates, polyethylene glycols and oleic acids.