Quantum dots are fluorescent nanoparticles of semiconducting material. The colour of light that they emit varies with the size of the dot, shifting toward the blue end of the spectrum, as they get smaller. Main current and future applications for quantum dots are LED lighting, electronic displays, bio imaging and solar power. Other applications include security and anti-counterfeiting, “functional decoration” and printing.
Prices for quantum dots range from US$3,000 to $10,000 per gram. The market has mainly catered to specialized applications, with a small number of companies selling dots directly to researchers, using the particles to develop their own products or licensing their technologies to partners. Nanoco has a partnership with a major Japanese LED manufacturer to produce LEDs for the general lighting and LCD backlight market. Nanoco is currently charging $5000 per gram for its materials, but expects this to decrease to $500 per gram in the near future as it plans a 400kg per year production facility. Quantum Materials Corp. is also planning to scale-up production considerably. Samsung has produced a full-colour quantum dot panel as a potential replacement for LCD and OLED. When compared to LCD, quantum dots use fifth of the power. In comparison to OLEDs, quantum dots are brighter, will eventually have a longer lifespan, and cost half as much to make. LG is currently working with QD Vision to produce quantum dot displays. In April 2013, Nanosys announced it’s plans to incrase production to over 1,000KG of quantum dots per year.
Displays
As well as enabling novel approaches to display designs, nanomaterials are also incorporated into display components, such as transparent electrodes, thin film transistors and coatings, sensors, transparent conductors, and infrared and visible photodetectors. Prototypes and products have already been developed.
Quantum dots are being produced as replacements for phosphor pixels. The colour emitted by a quantum dot can be controlled by changing its size (e.g. 6nm quantum dots are red). These quantum dots are arranged in alternating colour blocks, which are excited by electrons. LEDs and displays utilizing quantum dots can be made ultra-thin, on flexible substrates and thus produced at a much lower cost. QD emissions are also usually much narrower and more symmetric (clearer colour) than typical emissions from dyes or fluorophors, so displays and LEDs can produce much clearer colours.
Quantum dots “warm up” the colour of the light while increasing its quality (colour rendering index),delivering a superior blend of color quality and efficiency. Quantum dot technology can potentially replace the organic luminescent materials to provide superior colour quality, efficiency, and lifetime.
Nanosys, Inc. (www.nanosysinc.com) has developed QDEF™ and QuantumRail™ , which are composed of Nanosys’ proprietary, high efficiency quantum dot phosphors. They find application in LED displays. Nanosys Quantum Dot Enhancement Film, or QDEF, is an optical film component for LED driven LCD displays. The company has an agreement with 3M for product development. Nanosys also sells its products to LG and Samsung.
Figure 1: Schematic of QLED display (Source: Nanosys)
QD Vision’s (www.qdvision.com) Quantum Light™ product platform exploits the unique light-emitting properties of semiconductor nanocrystals for application in LED-based products, with enhanced colour quality, high power efficiency, manufacturing versatility, and design flexibility.
Solar Power
Nanomaterials are a key component of third generation solar devices, providing the material requirements to significantly, rather than incrementally, improve photovoltaic cell performance beyond that of present devices. There are a significant number of companies utilizing quantum dots in photovoltaics including:
• NN-Labs (www.nn-labs.com) have developed high-quality cadmium telluride (CdTe) nanocrystals for photovoltaic applications.
• Solterra Renewable Technologies (www.solterrasolarcells.com) focuses on the use of tetrapod quantum dots to produce solar cells.
• Cyrium Technologies, Inc. (www.cyriumtechnologies.com) is developing a proprietary photovoltaic solar cell technology using QDEC® (Quantum Dot Enhanced Cell). The QDEC product family offers efficiency levels of ~40% at >500-1000 suns and a minimum efficiency offering of 38% on a standard 10x10mm cell.
Figure 2: Cyrium Technologies Quantum Dots
Lighting
Luminescent and non-luminescent nanomaterials are used today in a variety of lighting applications. Thin layers of densely packed nano alumina between glass and phosphor in fluorescent lamps serve to increase the efficiency, to improve the maintenance and to reduce the mercury consumption of the lamps.
NNCrystal US Corp. (www.nncrystal.com) is the owner of two patented and trademarked technology platforms for solid-state lighting applications-Qshift Lucid and Qshift Coral. NNCrystal has established several application platforms such as LED luminescence based on remote phosphor excitation, medical and pharmaceutical bio-detection, solar energy conversion and others. The company has the ability to manufacture optical devices with intelligent high colour rendering.
Evident Technologies (www.evidenttech.com) produces quantum dots for various markets including life sciences, solid-state lighting, energy, security, telecommunications and emergent nanotechnology markets.
Medical
Medical uses for quantum dots include image-guided surgery, light-activated therapies and sensitive diagnostic tests. The use of quantum dots for biological imaging provides researchers and clinicians new and versatile approaches to a range of biomedical challenges. The structural properties of quantum dots are also being utilized for drug delivery. QDs have been applied to cells and small animals as drug carriers, serving as an outstanding discovery tool for drug screening and validation, and as prototype materials for drug carrier engineering.
French company Attonuclei (www.attonuclei.com) offers flexible custom manufacturing services to produce high quality “functionalized custom quantum dots”.
DiagNano’s (http://nanohc.com/) platform technology is based on a “non-stick” surface coating that allows quantum dots and other metal nanoparticles to be used for biological applications, including in vitro diagnostics, without nonspecific binding and agglomeration. DiagNano can develop optically active quantum dots capable of imaging at the molecular level. Nanohistochemistry, or NanoHC™, uses multiple colors of fluorescent nanoparticles to accurately and simultaneously measure multiple biomarkers in a single sample, taking the guess work out of sample analysis and providing oncologists with the best information to make a diagnosis and choose a therapy.
Helicos BioSciences Corporation’s (www.helicosbio.com) True Single Molecule Sequencing (tSMS) technology enables rapid analysis of large quantities of genetic material by directly sequencing single molecules of deoxyribonucleic acid (DNA) or single DNA copies of ribonucleic acid (RNA) (cDNA) and its approach of direct sequencing of RNA. The company uses quantum dots as biomarkers.
Invitrogen Corporation (www.invitrogen.com) produces Qdot® nanocrystals mainly for life sciences applications. Qdot® nanocrystals are fluorophores—substances that absorb photons of light, then re-emit photons at a different wavelength. However, they exhibit some important differences as compared to traditional fluorophores such as organic fluorescent dyes and naturally fluorescent proteins, ends there.
Figure 3: Schematic of the overall structure of a Qdot® nanocrystal conjugate. (Source: Invitrogen).
NanoAxis produces (www.nanoaxisllc.com) axicad quantum for pharma and diagnostics applications. AxiCad brand quantum dots come in wavelengths ranging from 530 nm to 740 nm. Nanoaxis is developing new therapies and diagnostics for detection, measurement and treatment of medical conditions and diseases including chronic pain, depression, Alzheimer’s, cancer, diabetes and influenza. They have an agreement with Quantum Materials Corp. to develop technologies for Cancer diagnostic kits and theranostic applications including Alzheimer’s, Type 1 and Type 2 Diabetes, Breast Cancer and Major Depression. Quantum Materials Corp. is one of the largest mass producers of quantum dots.
Other companies developing quantum dots for biomedical applications include Affymetrix, Inc., Amnis Corporation, Applera Corporation, Biocrystal Ltd., Genoptix, Inc., Illumina, Inc., LI-COR Incorporated, and Luminex Corporation.
Product security and anti-counterfeiting
The worldwide counterfeit goods trade, excluding counterfeit money, is believed to be on the order of $1 trillion annually. The U.N. estimates counterfeit drug sales alone were over $300 billion in 2008, while the World Customs Organization believes that other counterfeit goods sold for more than $600 billion. According to U.S. Immigration and Customs Enforcement, these losses cost American industry and trade between $200 billion and $250 billion each year and equate to 750,000 American jobs lost.
Nanotechnology-enabled applications are leading to new non-reproducible technological features that will lead to preventing illegal copying of intellectual property and products. Quantum dots are being employed in holograms, laser surface authentication, physically unclonable functionality, magnetic fingerprints and nanobarcodes and taggants.
Advantages of utilizing quantum dots in anti-counterfeiting include:
• Difficulty in counterfeiting specific uniform nanomaterials as these materials cannot be produced by standard equipment
• Functionalisation of nanomaterials requires a high standard of training
• The special multifunctional surface, magnetic, fluorescent, and infrared properties of nanomaterials and patterns created thereof can create unique profiles.
Quantum dots have different fluorescence based on size and chemical composition which can be exploited as an identification tool. They offer difficulty in reproducing due to infinite combinations, covert security feature, non-toxicity and multi-functionality. These nanoscaled tags can be applied in inks, adhesives, laminates, paper, packaging, textiles, glass etc. The quantum dots may be read with an optical reader, which may be combined with readers using other technologies.
Evident Technologies (www.evidenttech.com) produces formulated quantum dot inks and paints for security and anti-counterfeiting applications that can be applied to any surface, including paper, plastic and metal.
Nanosys (www.nanosysinc.com) are collaborating with Life Technologies to develop quantum dots for anti-counterfeiting.
Other Producers
• Ocean NanoTech
The company’s product line includes quantum dots, core shell quantum dots in organic solvents, nanocrystals for LEDs and solar cells, water soluble biocompatible nanocrystals, reaction buffers for conjugating nanocrystals to biomolecules, conjugation kits, and services to meet our customer needs. http://oceannanotech.com
• American Elements
Manufacturer and supplier specializing in producing quantum dots from several semiconductor materials, including Cadmium Telluride (CdTe), Cadmium Selenide/Zinc Sulfide (CdSe/ZnS), Lead Selenide (PbSe) and Zinc Cadmium Selenide/Zinc Sulfide (ZnCdSe/ZnS) nanoparticles with well-defined peak emission frequencies between approximately 470 to 730 nm wavelengths. www.americanelements.com
• Bayer MaterialScience AG
The company produces BayDots for the enhancement of drug delivery. Other applications include opto-electronics, photovoltaics, security labeling and functional polymer composites. www.bayertechnology.com/en/products.html
• Nanoco Technologies Ltd
Nanoco manufactures large quantities of quantum dots. The company’s molecular seeding process for the bespoke manufacture of these quantum dots on a commercial scale is protected by worldwide patents. Nanoco Technologies is presently able to supply production quantities of quantum dots which do not use a regulated heavy metal. Nanoco is supplying electronics manufacturers in Japan, the USA, Korea and Taiwan with quantum dots for electronic displays. www.nanocotechnologies.com
• Nanosquare, Inc.
The company is a spin-out from Seoul National University. The company is a manufacturer of quantum dots, which they can mass produce. www.nanosquare.co.kr
• Crystalplex
The company produces the following range of quantum dots: Carboxyl Quantum Dots; Amine Quantum Dots; Hydroxyl Quantum Dots; Alkyl Quantum Dots. www.crystalplex.com
• QD Light
The company is a Russia-based producer of quantum dots. Their current capacity is 20kg per year. http://nanotech-dubna.com
