Semiconducting quantum dots, whose particle sizes are in the nanometer range, have very unusual properties. The quantum dots have band gaps that depend in a complicated fashion upon a number of factors, described in the article. Processing-structure-properties-performance relationships are reviewed for compound semiconducting quantum dots. Various methods for synthesizing these quantum dots are discussed, as well as their resulting properties. Quantum states and confinement of their excitons may shift their optical absorption and emission energies. Such effects are important for tuning their luminescence stimulated by photons (photoluminescence) or electric field (electroluminescence). In this article, decoupling of quantum effects on excitation and emission are described, along with the use of quantum dots as sensitizers in phosphors. In addition, we reviewed the multimodal applications of quantum dots, including in electroluminescence device, solar cell and biological imaging.

https://www.mdpi.com/1996-1944/3/4/2260/pdf

Quantum Dots and Their Multimodal Applications: A Review

Spintronics refers commonly to phenomena in which the spin of electrons in a solid state environment plays the determining role In a more narrow sense spintronics is an emerging research field of electronics: spintronics devices are based on a spin control of electronics, or on an electrical and optical control of spin or magnetism This review presents selected themes of semiconductor spintronics, introducing important concepts in spin transport, spin injection, Silsbee-Johnson spin-charge coupling, and spindependent tunneling, as well as spin relaxation and spin dynamics The most fundamental spin-dependent nteraction in nonmagnetic semiconductors is spin-orbit coupling Depending on the crystal symmetries of the material, as well as on the structural properties of semiconductor based heterostructures, the spin-orbit coupling takes on different functional forms, giving a nice playground of effective spin-orbit Hamiltonians The effective Hamiltonians for the most relevant classes of materials and heterostructures are derived here from realistic electronic band structure descriptions Most semiconductor device systems are still theoretical concepts, waiting for experimental demonstrations A review of selected proposed, and a few demonstrated devices is presented, with detailed description of two important classes: magnetic resonant tunnel structures and bipolar magnetic diodes and transistors In most cases the presentation is of tutorial style, introducing the essential theoretical formalism at an accessible level, with case-study-like illustrations of actual experimental results, as well as with brief reviews of relevant recent achievements in the field

/pdf/semiconductor-spintronics-1ed0d0goer.pdf

Semiconductor Spintronics

Biomimetic multifunctional surfaces inspired from animals.

The preparation and characterization of multifunctional ZnO1−xNx (x ≤ 0.15) via a simple solution combustion method is reported. ZnO1−xNx exhibits visible light absorption, thermal stability, nanometer-/micrometer-sized triangular particles, and catalytic properties. X-ray diffraction studies of ZnO1−xNx demonstrate that the lattice oxygen in ZnO is replaced by nitrogen without any major change in the wurtzite structure; however, charge compensation occurs, because of interstitial Zn atoms, as well as oxygen vacancies. Microscopic studies reveal the dominance of nanometer- and micrometer-sized triangles of ZnO1−xNx. UV−visible and Raman spectra indicate a midgap state, derived from N 2p states, and direct Zn−N interaction, respectively. Secondary ion mass spectrometry studies show the presence of N and ZnN species in the bulk and support the direct Zn−N interaction. Electron paramagnetic resonance (EPR) studies indicate the presence of a small amount of defects. Photocatalytic decomposition of rhodamine B...

Combustion Synthesis of Triangular and Multifunctional ZnO1−xNx (x ≤ 0.15) Materials

This work explores the sensitization of luminescent lanthanide Tb3+ and Eu3+ cations by electronic structure of zinc sulfide (ZnS) semiconductor nanoparticles. Excitation spectra collected while monitoring the lanthanide emission bands reveal that the ZnS nanoparticles act as an antenna for the sensitization of Tb3+ and Eu3+. The mechanism of lanthanide ion luminescence sensitization is rationalized in terms of an energy and charge transfer between trap sites and is based on a semiempirical model, proposed by Dorenbos and co-workers (Dorenbos, P. J. Phys.: Condens Matter 2003, 15, 8417-8434; J. Lumin. 2004, 108, 301-305; J. Lumin. 2005, 111, 89-104. Dorenbos, P.; van der Kolk, E. Appl. Phys. Lett. 2006, 89, 061122-1-061122-3; Opt. Mater. 2008, 30, 1052-1057. Dorenbos, P. J. Alloys Compd. 2009, 488, 568-573; references 1-6.) to describe the energy level scheme. This model implies that the mechanisms of luminescence sensitization of Tb3+ and Eu3+ in ZnS nanoparticles are different; namely, Tb3+ acts as a hole trap, whereas Eu3+ acts as an electron trap. Further testing of this model is made by extending the studies from ZnS nanoparticles to other II-VI semiconductor materials; namely, CdSe, CdS, and ZnSe.

/pdf/lanthanide-sensitization-in-ii-vi-semiconductor-materials-a-3d251dtngv.pdf

Lanthanide Sensitization in II−VI Semiconductor Materials: A Case Study with Terbium(III) and Europium(III) in Zinc Sulfide Nanoparticles

Two-dimensional materials with unique physical and chemical properties have recently attracted widespread attention in the field of solar thermal conversion. However, affected by the Fresnel effect, traditional two-dimensional materials such as MXenes, graphene, transition metal disulfide often have relatively significant light reflection losses at the solid-liquid or gas interface. So how to improve the light absorption of the two-dimensional material performance has become a new challenge in photothermal conversion. Here, we use an improved thermal-injection method to uniformly grow Tricopper(I) Bismuth Sulfide (Cu3BiS3, CBS) on the surface of Ti3C2 nanosheets in a nonaqueous polar solvent environment. A three-dimensional nanoflower-nanosheet structure CBS-Ti3C2 for photothermal conversion has been constructed successfully. Owing to the excellent photothermal performance of Cu3BiS3 in the near-infrared region, the good thermal conductivity of Ti3C2, and the unique porous structure of the composite material, the composite achieves broadband absorption of light (more than 90% in the visible light region, more than 80% in the near-infrared region), which optical model and finite element simulation have theoretically verified. The composite material has obtained higher solar-to-heat conversion performance than similar material systems, and the steady-state temperature can reach 62.3 °C under 1 sun incident light intensity. CBS-Ti3C2 is expected to become a light-absorbing layer material for solar vapor generation devices due to its excellent light-to-heat conversion performance and good material flexibility. It still guarantees a reasonably high steam generation rate (1.32 kg·m-2·h-1) even with a thinner material thickness (0.48 mg·cm-2) and a comprehensive conversion efficiency higher than 90%. Besides, CBS-Ti3C2 also exhibits the characteristics of resisting surface salt accumulation, which is conducive to maintaining the long-lasting photothermal seawater evaporation process. The material's electronic structure and the charge transfer process of the heterojunction interface have been studied with the first-principles calculation. The high light absorption performance and good thermal conductivity of the composite material are theoretically explained and supported.

Cu3BiS3/MXenes with Excellent Solar-Thermal Conversion for Continuous and Efficient Seawater Desalination.

Influence of annealing temperature on the photoluminescence properties of ZnO quantum dots

NiS2 Nanocubes Coated Ti3C2 Nanosheets with Enhanced Light-to-Heat Conversion for Fast and Efficient Solar Seawater Steam Generation

SiO2 and ZnO inverse structure replicas have been synthesized using butterfly wings as templates. The laser diffraction performance of the SiO2 inverse structure replica was investigated and it was found that the zero-order light spot split into a matrix pattern when the distance between the screen and the sample was increased. This unique diffraction phenomenon is closely related to the structure of the SiO2 inverse structure replica. On the other hand, by analyzing the photoluminescence spectrum of the ZnO replica, optical anisotropy in the ultraviolet band was demonstrated for this material. Open image in new window

Optical properties of SiO2 and ZnO nanostructured replicas of butterfly wing scales

Cu 2+ -doped ZnS quantum dots were synthesized by a chemical precipitation method in water/ethanol solution. The quantum dots obtained were characterized by X-ray diffraction, transmission electron microscopy and spectroscopy techniques including X-ray photoelectron spectroscopy. The [S 2- ]/ [Zn 2+ ] ratios have an effect on the photoluminescence of both aqueous solutions and powders of Cu 2+ -doped ZnS quantum dots. For aqueous samples, a green luminescence centre is observed in the spectrum of sample 1 with [S 2- ]/[Zn 2 +] = 1:2 and a blue one for sample 2 with [S 2- ]/[Zn 2+ ] = 1:1. For powders, only the green emission is the main luminescence centre, and the integrated intensity in the blue emission region of sample 1 is stronger than that of sample 2. Compared with the spectrum of CuS powders, the X-ray-induced Auger electron spectrum of Cu L 3 M 45 M 45 in ZnS quantum dots shows a unique spectral characteristic. The 3d level of the Cu 2+ ion is split into two different energy levels at 334.0 and 347.2 eV, respectively.

Photoluminescence and XPS investigations of Cu2+-doped ZnS quantum dots capped with polyvinylpyrrolidone

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