Type-II Colloidal Quantum Wells: CdSe/CdTe Core/Crown Heteronanoplatelets

Solution-processed quantum wells, also known as colloidal nanoplatelets (NPLs), are emerging as promising materials for colloidal optoelectronics. In this work, we report the synthesis and characterization of CdSe/CdTe core/crown NPLs exhibiting a Type-II electronic structure and Type-II specific optical properties. Here, based on a core-seeded approach, the CdSe/CdTe core/crown NPLs were synthesized with well-controlled CdTe crown coatings. Uniform and epitaxial growth of CdTe crown region was verified by using structural characterization techniques including transmission electron microscopy (TEM) with quantitative EDX analysis and X-ray diffraction (XRD). Also the optical properties were systematically studied in these Type-II NPLs that reveal strongly red-shifted photoluminescence (up to similar to 150 nm) along with 2 orders of magnitude longer fluorescence lifetimes (up to 190 ns) compared to the Type-I NPLs owing to spatially indirect excitons at the Type-II interface between the CdSe core and the CdTe crown regions. Photoluminescence excitation spectroscopy confirms that this strongly red-shifted emission actually arises from the CdSe/CdTe NPLs. In addition, temperature-dependent time-resolved fluorescence spectroscopy was performed to reveal the temperature-dependent fluorescence decay kinetics of the Type-II NPLs exhibiting interesting behavior. Also, water-soluble Type-II NPLs were achieved via ligand exchange of the CdSe/CdTe core/crown NPLs by using 3-mercaptopropionic acid (MPA), which allows for enhanced charge extraction efficiency owing to their shorter chain length and enables high quality film formation by layer-by-layer (LBL) assembly. With all of these appealing properties, the CdSe/CdTe core/crown heterostructures having Type-II electronic structure presented here are highly promising for light-harvesting applications

Cobalt and ruthenium complexes with pyrimidine based schiff base: Synthesis, characterization, anticancer activities and electrochemotherapy efficiency

BULDURUN, Kenan/0000-0002-2462-7006; Turan, Nevin/0000-0001-6740-6812WOS:000609168500009In this study, a new Schiff base ligand and its two M(II) complexes [CoCl center dot L(H2O)(2)]center dot 2H(2)O, [RuCl(p-cymene)L] were synthesized. The structural features were confirmed from their micro analytical, IR, UV-Vis., (HC)-H-1-C-13 NMR, TGA, X-ray diffraction analysis, mass spectral data and magnetic susceptibility measurements. The Co(II) and Ru(II) complexes displayed an octahedral geometry. In vitro anticancer activities of the Schiff base, Co(II) and Ru(II) complexes were evaluated on the human colon cancer cell line (Caco-2) and biocompatibility characteristics were determined in the L-929 (normal fibroblast cells) cell line by using the MIT assay. Furthermore, we examined the effectiveness of electrochemotherapy (ECT) on cytotoxic activities of these compounds in Caco-2 cancer cell line. According to the findings of the study, Co(II) and Ru(II) complexes showed considerable anticancer properties in the Caco-2 colon cancer cells; however, the ligand did not show significant anticancer activity. It was determined that the combined application of electroporation (EP)+complexes were much more effective than the application of complexes alone in the treatment of Caco-2 colon cancer cells. In a conclusion, the Co(II) and Ru(II) complexes, which showed significant anticancer activity in Caco-2 colon cancer cells, increased cytotoxicity levels by 2.07 and 2.12, respectively in their combined applications with EP. These complexes can be developed as chemotherapeutic agents for colon cancer treatment and can yield promising results when used in ECT. (C) 2020 Elsevier B.V. All rights reserved.Scientific Research Project Fund of Mus Alparslan University [BAP-18-MMF-4901-02]This work is supported by the Scientific Research Project Fund of Mus Alparslan University under the project number BAP-18-MMF-4901-02

Synthesis, characterization, antiproliferative of pyrimidine based ligand and its Ni(II) and Pd(II) complexes and effectiveness of electroporation

Mantarci, Asim/0000-0001-8369-3559; ALKIS, Mehmet Esref/0000-0002-3321-2873; Turan, Nevin/0000-0001-6740-6812; KELESTEMUR, UNZILE/0000-0003-4531-6378; BULDURUN, Kenan/0000-0002-2462-7006In the study, a new Schiff base (ligand) was obtained using 4-aminopyrimidine-2(1H)-one, the starting material, and 2,3,4-trimethoxy benzaldehyde. Ni(II) and Pd(II) complexes were obtained from the reaction of the ligand and NiCl2 center dot 6H(2)O, PdCl2(CH3CN)(2) (1:1 ratio). These compounds were characterized using the elemental and mass analysis, H-1, C-13-NMR, FT-IR, UV-Vis, magnetic susceptibility, thermal analysis, and the X-ray diffraction analyses. The antiproliferative activities of the synthesized ligand, Ni(II) and Pd(II) complexes were identified on the HepG2 (human liver cancer cells) cell line and their biocompatibility was tested on the L-929 (fibroblast cells) cell line by the MTT analysis method. Furthermore, the effects of electroporation (EP) on the cytotoxic activities of synthesized compounds were investigated in HepG2 cancer cells. According to the MTT findings of the study, the ligand did not exhibit an antiproliferative activity while its Ni(II) and Pd(II) complexes exhibited an antiproliferative activity. Moreover, it was observed that the antiproliferative activity of the Pd(II) complex was stronger than that of the Ni(II) complex. The combined application of EP + compounds is much more effective than the usage of the compounds alone in the treatment of HepG2 cancer cells. The EP increased the cytotoxicity of the Ni(II) and Pd(II) complexes by 1.66, and 2.54 times, respectively. It was concluded that Ni(II) and Pd(II) complexes may contribute as potential anti-cancer agents for the treatment of hepatocellular carcinoma and yield promising results in the case of being used in ECT. Communicated by Ramaswamy H. SarmaScientific Research Project Fund of Mu Alparslan University [BAP-18-MMF-4901-02]This work is supported by the Scientific Research Project Fund of Mu Alparslan University under the project number BAP-18-MMF-4901-02

Amplified Spontaneous Emission and Lasing in Colloidal Nanoplatelets

Colloidal nanoplatelets (NPLs) have recently emerged as favorable light-emitting materials, which also show great potential as optical gain media due to their remarkable optical properties. In this work, we systematically investigate the optical gain performance of CdSe core and CdSe/CdS core/crown NPLs having different CdS crown size with one- and two-photon absorption pumping. The core/crown NPLs exhibit enhanced gain performance as compared to the core-only NPLs due to increased absorption cross section and the efficient interexciton funneling, which is from the CdS crown to the CdSe core. One- and two-photon absorption pumped amplified spontaneous emission thresholds are found as low as 41 μJ/cm² and 4.48 mJ/cm², respectively. These thresholds surpass the best reported optical gain performance of the state-of-the-art colloidal nanocrystals (<i>i.e.</i>, quantum dots, nanorods, <i>etc.</i>) emitting in the same spectral range as the NPLs. Moreover, gain coefficient of the NPLs is measured as high as 650 cm^–1, which is 4-fold larger than the best reported gain coefficient of the colloidal quantum dots. Finally, we demonstrate a two-photon absorption pumped vertical cavity surface emitting laser of the NPLs with a lasing threshold as low as 2.49 mJ/cm². These excellent results are attributed to the superior properties of the NPLs as optical gain media

Colloidal CdSe Quantum Wells with Graded Shell Composition for Low-Threshold Amplified Spontaneous Emission and Highly Efficient Electroluminescence

ISSN:1936-0851ISSN:1936-086

Temperature-Dependent Emission Kinetics of Colloidal Semiconductor Nanoplatelets Strongly Modified by Stacking

We systematically studied temperature-dependent emission kinetics in solid films of solution-processed CdSe nanoplatelets (NPLs) that are either intentionally stacked or nonstacked. We observed that the steady-state photoluminescence (PL) intensity of nonstacked NPLs considerably increases with decreasing temperature, whereas there is only a slight increase in stacked NPLs. Furthermore, PL decay time of the stacked NPL ensemble is comparatively much shorter than that of the nonstacked NPLs, and this result is consistent at all temperatures. To account for these observations, we developed a probabilistic model that describes excitonic processes in a stack using Markov chains, and we found excellent agreement between the model and experimental results. These findings develop the insight that the competition between the radiative channels and energy transfer-assisted hole trapping leads to weakly temperature-dependent PL intensity in the case of the stacked NPL ensembles as compared to the nonstacked NPLs lacking strong energy transfer. This study shows that it is essential to account for the effect of NPL stacking to understand their resulting PL emission properties