A novel encoding system and methods for determining the location and/or identity of a particular item or component of interest is provided. In particular, the present invention utilizes a "barcode" comprising one or more sizes of semiconductor nanocrystals (quantum dots) having characteristic spectral emissions, to either "track" the location of a particular item of interest or to identify a particular item of interest. The semiconductor nanocrystals used in the inventive "barcoding" scheme can be tuned to a desired wavelength to produce a characteristic spectral emission in narrow spectral widths, and with a symmetric, nearly Gaussian line shape, by changing the composition and size of the quantum dot. Additionally, the intensity of the emission at a particular characteristic wavelength can also be varied, thus enabling the use of binary or higher order encoding schemes. The information encoded by the quantum dot can be spectroscopically decoded, thus providing the location and/or identity of the particular item or component of interest. In particular, a single primary light source can be used to decode the inventive barcode. In particularly preferred embodiments, the present system and method is used in applications to security systems, to the tracking of consumer items such as jewelry, vehicles, or paper. In other particularly preferred embodiments, the present system and method is used in applications for biochemistry to track the location of biomolecules such as DNA sequences, combinatorial chemistry, and genomics for encoding and probe identifiers.
This application is a continuation (and claims the benefit of priority under 35 USC 120) of U.S. patent application Ser. No. 09/160,458, filed Sep. 24, 1998 now U.S. Pat. No. 6,617,583, which claims priority to U.S. Patent Application Serial No. 60/101,046, filed on Sep. 18, 1998, each of which is incorporated by reference.
This application is related to the following applications which were filed in even day herewith and which are incorporated in their entirety by reference: application U.S. Ser. No. 09/160,454, entitled "Biological Applications of Quantum Dots," filed Sep. 24, 1998, and provisional U.S. Appln. No. 60/100,947, entitled "Detection of Compounds and Interactions," filed Sep. 18, 1998. Additionally, this application is also related to the following application, which was filed on Sep. 18, 1998, and which is incorporated in its entirety by reference: application entitled "Water Soluble Luminescent Nanocrystals," filed Sep. 18, 1998, now U.S. Pat. No. 6,251,303 B1.
In a method of coding and retrieving information by using the unique emission properties of the semiconductor nanocrystals (quantum dots) for the identification of valuable documents, articles and objects, a carrier medium is prepared containing quantum dots selected to give the carrier medium defined fluorescent emission characteristics encoding predetermined information. The carrier medium is then applied to the object, preferably in the form of an ink.
A method for preparing water-stable semiconductor nanocrystal complexes that can be stably coupled to tertiary molecules using a self-assembled coating of diblock polymers. The diblock polymers have hydrophilic ends containing hydrophilic functional groups and hydrophobic ends containing hydrophobic functional groups. The diblock polymers are assembled around a semiconductor nanocrystal having a lyophilic surface outer layer. The diblock polymers are further crosslinked via bridging molecules that link adjacent diblock polymers through the hydrophilic functional groups of the hydrophilic ends of the diblock polymers to form a semiconductor nanocrystal complex. The functional groups present on the outer surface of the amphiphilic diblock polymer may serve as attachment sites for coupling tertiary molecules to the semiconductor nanocrystal complex.
A method of detecting target biological molecules in a target sample is provided. The method includes using spectral, temporal, and polarization characteristics of emitted light from water-stable semiconductor nanocrystal complexes to detect the presence of target biological molecules in a target sample.
This invention provides PEG-modified semiconductor nanoparticles of which fluorescence intensity is effectively inhibited from lowering, which are capable of forming a stable dispersion in water, and which are capable of bonding easily with biomolecules having specific recognition, as well as methods for conveniently preparing such nanoparticles, and a material for biological diagnosis. The water-soluble PEG-modified semiconductor nanoparticles of the present invention includes a structure having PEG of a number average molecular weight of 300 to 20000 having a thiol group at one end, bonded via cadmium to II VI semiconductor nanocrystals of a core-shell structure having a ZnX (wherein X stands for O, S, Se, or Te) shell.
One embodiment relates to an electron beam apparatus for automated imaging of a substrate surface. An electron source is configured to emit electrons, and a gun lens is configured to focus the electrons emitted by the electron source so as to form an electron beam. A condenser lens system is configured to receive the electron beam and to reduce its numerical aperture to an ultra-low numerical aperture. An objective lens is configured to focus the ultra-low numerical aperture beam onto the substrate surface. Other embodiments are also disclosed.
