Quantum dots & Nanoparticles
Introduction of our Quantum dots and Nanoparticles
When one of the dimensions of a semiconductor nanocrystal is comparable with, or smaller than, the bulk exciton, its electronic band structure becomes strongly dependent on the size of the nanocrystal due to quantum mechanical effects. In these tiny particles, called quantum dots or nanoparticles, the allowed energy states become discrete, as opposed to the continuum of energy levels found in the corresponding bulk crystal. These quantum effects in semiconductor nanocrystals naturally result in precise optical and optoelectronic properties that depend on the dimensions of the quantum dots. With perfect control of size, shape, facet, and surface ligands, colloidal quantum dots have outstanding optical and optoelectronic properties that are unachievable using other optical/optoelectronic materials.
Until recently, monodispersed colloidal quantum dots have been impossible to synthesize on a commercial scale. Over the past 40 years, synthetic chemistry of colloidal quantum dots has succeeded in controlling size and shape on the nanometer scale, but control on the atomic scale is limited to very small, specifically arranged clusters, known as magic size clusters.
NN labs is the leading firm in providing colloidal nanoparticles and quantum dots to scientists and engineers. A description of the different types of nanocrystals that we provide can be found below.
Colloidal quantum dots. Colloidal quantum dots (CQDs, QDs, or QD) are nanometer-sized fragments of semiconductor single crystals (semiconductor nanocrystals), which are synthesized, processed, and sold in solution. To achieve their outstanding optical and optoelectronic properties, quantum dots must be single crystalline, however, they are often classified into a large category of nanomaterials, i.e., nanoparticles. Visit our catalog page to buy quantum dots with the optimal properties for your application.
Tailor-designed quantum dots for specific applications. Humans evolved with sunlight as the main energy source, and optical/optoelectronic materials play a central role in society today. One can see endless products based on these materials in modern technology, yet there is great room for further development in many and various industrial sectors. Colloidal quantum dots are the premier choice of commercially available optical and optoelectronic materials. As a leading provider of quantum dots and quantum nanocrystals, NN labs provides a wide range of quantum dots for sale that can be specifically tailored to your application.
Quantum-dot displays have been commercialized on a large scale. Modern displays are all based on three primary color emitters. As long as each primary color is color-pure (defined as the peak width of emission) and accurate, a display can provide any color visible to human eyes. Presently, colloidal quantum dots—typically cadmium selenide nanocrystals epitaxially grown with wide bandgap shells, such as CdSe/ZnS core/shell quantum dots—are the only primary-color emitters that can provide satisfactory color purity and color accuracy without lasers. After ~10 years of research, CdSe-based core/shell quantum dots containing a limited amount of cadmium have been developed to satisfy stringent environmental regulations, including the European RoHS standards. To further protect the environment, NNCrystal developed Cadmium-free quantum dots, especially indium phosphide (InP) quantum dots with cadmium-free shells (such as InP/ZnS core/shell quantum dots), as another member in the family of high-efficiency quantum dots. The color purity of InP quantum dots is significantly better than alternative Cadmium-free commercial primary-color emitters, including organic dyes in OLEDs and inorganic phosphors found in LCD displays.
Quantum-dot solid-state lighting is a rapidly growing field. Experimental results suggest that lighting devices with quantum-dot emitting materials can be highly efficient yet with an ideal color rendering index (CRI). Though both display and lighting are based on photoluminescence and electroluminescence of quantum dots, the latter requires a different type of quantum dots. Instead of three primary-color emitters with high color purity, quantum-dot for general-purpose lighting need to offer a continuous spectrum covering the entire visible range.
Quantum-dot solar cells convert light into energy as opposed to converting energy into light for displays and lighting. The tunability of the quantum dots allows increased efficiency of solar power by harvesting different parts of the solar spectrum. Conventional solar cells based on single-crystalline silicon (Si) and cadmium telluride (CdTe) thin films are rapidly becoming viable alternative energy sources, but the fabrication cost and environmental impact are problematic. Quantum-dot solar cells can readily solve these issues through their solution-based processing techniques. To absorb solar radiation efficiently, quantum dots in solar cells possess a narrower optical bandgap than that of the visible light emitters. CdSe-based quantum dots are unsuitable in this regard. NN labs provides lead sulfide (PbS) and lead selenide (PbSe) quantum dots, which have been widely explored as alternative nanomaterials for solar cell development. Lead-free quantum dots for solar cells are mostly I-III-VI ones, such as copper indium sulfide (CuInS2) nanoparticles.
Quantum-dot bio-medical labeling was introduced more than 20 years ago. Their narrow emission peak and broad absorption spectrum imply readily accessible multiplexity for bio-medical detection. Different from all other major applications discussed above, bio-medical labeling requires water-soluble quantum dots. In addition, the high-efficiency quantum dots for bio-medical labeling needs to be bio-functionalized and stable in aqueous media, including various buffer solutions and biological tissues.
Other types of colloidal nanoparticles. Magnetic nanoparticles and noble metal nanoparticles are also of interest for scientists in various fields. Iron oxide magnetic nanoparticles, more precisely Fe3O4 nanocrystals, are the most common magnetic nanoparticles. Iron oxide nanoparticles are primarily used in bio-medical applications and can be made as water-soluble magnetic nanoparticles. Silver (Ag) nanoparticles and gold (Au) nanoparticles are studied as model systems of noble metal nanoparticles for their outstanding stability and biocompatibility, especially water-soluble Au nanocrystals.
NN-Labs is the leading firm in the field of colloidal nanoparticles. NN-Labs was founded in 2000 as one of the early developers and suppliers in the category. In 2002, NN-Labs launched CdSe and CdS quantum dots for sale with the dominating intellectual property in the field. After building a strong patent portfolio for other types of colloidal nanoparticles, NN-Labs further expanded its product lines to include iron oxide magnetic nanocrystals and gold nanoparticles for sale. In the past 20 years, NN-Labs has been the leading supplier that scientists and engineers trust when they buy quantum dots and other nanoparticles.