Semiconductor nanocrystals quantum tunability

A modified SILAR system has been used to grow CdSe in CdS/CdSe core shell semiconductor nanocrystals.12 A cadmium precursor solution, with CdO dissolved with oleic acid in octadecane, was injected onto the substrate, and the Se solution (Se powder dissolved with tributylphosphine in octadecane) was similarly injected. The temperature of the reaction solution was 185 °C. A CdS outer layer in the CdS/CdSe/CdS colloidal quantum wells was deposited by alternating injections of cadmium and sulfur both in octadecane solutions at 230-240 °C. These structures showed high PL quantum yields (20-40%), relatively narrow emission bands, and tunable emission colors from about 520 to 650 nm depending on the number of CdSe monolayers. 

Quantum dots are CdSe/ZnS semiconductor nanocrystals which have robust fluorescent properties with size-tunable emission properties. By using hy-droxylated nanocrystals, oligonucleotides may be conjugated. When four different sequences attached to four different size quantum dots are mixed, it was shown that it was possible to separate each type of quantum dot by hybridisation to a complementary sequence on a defined micrometer-size surface. ... 

The broad spectral coverage for luminescence from the ultraviolet (UV) to the NIR offered via the tunability of composition, size and shape in semiconductor nanocrystals, presents an obvious advantage for the use of such materials as tunable optical gain media, and in laser applications. Furthermore, low lasing thresholds are predicted for QDs and quantum wires, compared with two-dimensionally confined quantum wells, form the basis of the present semiconductor diode laser devices which are ubiquitous in information and telecommunication technologies [86, 87]. 

The development of semiconductor nanocrystals, known as quantum dots (QDs), and similar inorganic fluorescent particles has made NIR diagnostic imaging possible for both in vivo and in vitro applications. QDs benefit from minimal biological interaction (due to their inorganic makeup), minimal photobleaching, tunability, and quantum yields over... 

The size of a quantum dot is important for the tunable light emission characteristic. A small quantum dot, such as a colloidal semiconductor nanocrystal, can be as small as 2 to 10 nm [6]. A self-assembled quantum dot is typically between 10 and 50 nm in size [7]. A quantum dot defined by lithographically patterned gate electrodes or by etching on two-dimensional electron gases in semiconductor heterostructures can have lateral dimensions exceeding 100 nm [8]. 

Owing to their unique (tunable-electronic) properties, semiconductor (quantum dots) nanocrystals have generated considerable interest for optical DNA detection [12], Recent activity has demonstrated the utility of quantum dot nanoparticles for enhanced electrical DNA detection [33, 34, 50], Willner et al. reported on a photoelectrochemical transduction of DNA sensing events in connection with DNA cross-linked CdS nanoparticle arrays [50], The electrostatic binding of the Ru(NH3)63+ electron acceptor to the dsDNA... 

Qnantnm dots (QDs) are nearly spherical flnorescent nanocrystals composed of semicondnctor materials that bridge the gap between individual atoms and bulk semiconductor sohds. Owing to the quantum-size effect, they exhibit size-tunable bandgaps and luminescence energies. They can be fabricated in a variety of materials, such as small regions of one material being buried in another material... 

---