Semiconductor nanoparticles of cadmium chalcogenides are known to exhibit pronounced thickness-dependent E0 series of exciton transitions at the Γ point of the Brillouin zone (BZ). In this work, we report an experimental evidence for high-energy series of exciton transitions, which originates from BZ points different from the Γ point, in the family of cadmium chalcogenide quasi-2D nanoplatelets (NPLs). Intensive UV absorption bands demonstrating a pronounced size effect are observed for CdTe, CdSe, and CdS NPLs in addition to the E0 exciton bands in the visible region. These new bands are attributed to transitions analogous to the E1, E1 + ∆1, and E2 series observed in bulk crystals. First-principles DFT calculations of the electronic structure and absorption spectra support this explanation and show that the main contribution to these optical transitions comes from X and M points of the 2D BZ, which originate from L and X points of the 3D BZ. At the same time, the E0 series of transitions at the Γ point is well described by the multiband effective-mass model. The observation of the UV exciton bands reveals tunable optical properties of cadmium chalcogenide NPLs in UV spectral region, which may be interesting for practical applications.

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The mechanism of SAPO-34 deactivation in the course of the MTO conversion has been studied in a slurry reactor in polydimethylsiloxane medium.

Colloidal semiconductor nanoparticles have a great potential for designing high-quality white-light-emitting diodes (WLEDs). However, the nanoparticles suffer from the reabsorption effect due to the characteristic small Stokes-shifts, which limits the power conversion efficiency of the light sources. In order to resolve this problem, absorption and emission spectra of the nanoparticles should be separated. Here, we report on gradient alloy CdSe 1−x S x nanoplatelets (NPLs), which allow for suppression of the reabsorption. Thanks to the gradient composition, the S-rich domains of CdSe 1−x S x NPLs behave as an efficient antenna, adsorbing light and funneling the generated carriers into the Se-rich domains, where they recombine. The gradient structure of CdSe 1−x S x NPLs allows one to control the overlap of the emission and absorption spectra simply by varying their composition. By controlling the composition of CdSe 1−x S x NPLs, their photometric parameters, including chromaticity color coordinates, color rendering index (CRI), and correlated color temperature (CCT), can be tuned. Due to the wide trap-assisted emissions associated with unsaturated S/Se surface atoms, CdSe 1−x S x NPLs demonstrate exceptionally high CRI values ranging from 87 up to 94 at CCT values in the range of 2509−6448 K, making them promising for high-quality white-light generation. Finally, WLEDs based on as-obtained gradient alloy CdSe 1−x S x NPLs are fabricated that show high luminous efficiencies (LE) reaching values up to 250 lm/W and CRI values as high as 91, demonstrating their potential for commercial applications.

Nanocrystalline ZnO, ZnO(Ga), and ZnO(Ga, In) samples with different indium contents were prepared by wet-chemical method and characterized in detail by ICP-MS and XRD methods. Gas sensing properties toward NO 2 were studied at 150-450 • C by DC conductance measurements. The optimal temperature for gas sensing experiments was determined. The dependence of the ZnO(Ga, In) sensor signal to NO 2 at 250 • C correlates with the change of conductivity of the samples. The introduction of indium into the system leads to an increase in the values of the sensor signal in the temperature range T < 250 • C. The investigation of the local sample conductivity by scanning spreading resistance microscopy demonstrates that, at high indium content, the sensor properties are determined by the In-Ga-Zn-O layer that forms on the ZnO surface.

The optical( UV/Vis absorbance, fluorescence in the solid state and in solution) and semiconducting properties of an umber of di-and trigermanes as well as relateds ilicon-andt

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