Semiconductor nanoparticles electronic structure

The electron hyperfine interaction thus has important effects on both NMR relaxation and frequency shifts, and can provide valuable information on the incorporation of magnetic ions into semiconductor lattices and the resulting electronic structure as characterized by transferred hyperfine constants. Examples in Sect. 4 will show how the possible incorporation of magnetic ions into semiconductor nanoparticles can be studied by NMR. 

There are two very broad, general conclusions resulting from the above review. The first is that MoS2-type nanoparticles are very different than other types of semiconductor nanoparticles. Nanoparticles of several different types of semiconductors, such as CdSe, CdS, and InP, have been extensively studied. Experimental and theoretical studies have elucidated much of their spectroscopy, photophysics, and dynamics. The results reviewed above are, in many places, in sharp contrast with those obtained on other types of quantum dots. This does not come as a surprise. The properties of the bulk semiconductor are reflected in those of the nanoparticle, and properties of layered semiconductors are vastly different from those of semiconductors having three-dimensional crystal structures. Although the electronic and spectroscopic properties of nanoparticles are strongly influenced by quantum confinement effects, the differences in the semiconductors cause there to be few generalizations about semiconductor quantum dots that can be made. 

The formula (11) in view of relations for /ie and /ih describes above-mentioned basic features of size effects in semiconductor crystal. It is important that as against metals, semiconductors show appreciable quantum dimensional effects at the sizes of particles from 3 to lOnm (depending on electronic structure of the semiconductor and sizes of AE0) [20]. Such nanoparticles are usually formed at synthesis of nanocomposite films. 

Although aggregation of metallic nanoparticles perturbs their electronic structure and especially the plasmon resonance frequency, the semiconductor quantum dots are much more resistant to such effects. 

HENGLEIN, A., Nanoclusters of Semiconductors and Metals. Colloidal Nanoparticles of Semiconductors and Metals. Electronic structure and Processes , Ber. Bunsenges. Phys. Chem. 1997, 101, 1562-1572. 

We have previously presented results of calculations showing that polymer nanoparticles with excess electrons exhibit discrete electronic structure and chemical potential in close analog with semi-conductor quantum dots. The dynamics of the formation of polymer nanoparticles can be simulated by the use of molecular dynamics and the morphology of these particles may be predicted. The production method that is used for the creation of these polymer particles can also be used to mix polymer components into a nanoparticle when otherwise they are immiscible in the bulk Quantum drops, unlike the semiconductor quantum dots, can be generated on demand and obtained in the gas phase. In the gas phase, these new polymer nanoparticles have the capacity to be used for catalytic purposes which may involve the deUveiy of electrons with chosen chemical potential. Finally, quantum drops have unusual properties in magnetic and electric fields, which make them suitable for use in applications ranging from catalysis to quantum computation. 

Semiconductor nanoparticles exhibit size-dependent unique optical and electronic properties that are different from their bulk counterpart due to quantum confinement. Bulk semiconductor crystal is considered as one large molecule, and electronic excitation of semiconductor crystals generates an electron-hole pair. The size of the delocalization area of this electron-hole pair is generally many times larger than the lattice constant. Decrease in the size of a semiconductor crystal down to a size comparable with the delocalization area of the electron-hole pair or to that of the Bohr excitonic radius of those materials modifies the electronic structure of the nanocrystals. When the particle radius decreases below the Bohr excitonic radius, there is widening in the energy band gap, which results in a blue shift in the excitonic absorption band of a semiconductor crystal. For example, in CdS semiconductor material, the blue shift of the excitonic absorption band is observed to begin at a crystal size of 5-6 nm [138-141]. 

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