10196-67-5Relevant articles and documents
Shape control of zincblende CdSe nanoplatelets
Bertrand, Guillaume H.V.,Polovitsyn, Anatolii,Christodoulou, Sotirios,Khan, Ali Hossain,Moreels, Iwan
, p. 11975 - 11978 (2016)
The lateral dimensions of CdSe nanoplatelets have a strong and unique influence on their opto-electronic properties, with sizes that can be tuned from the weak to the strong exciton confinement regime. There are state-of-the-art reports on several nanoplatelet syntheses; however, at present only the thickness is well-controlled. We demonstrate here that we can achieve a control over the aspect ratio and overall nanoplate area by carefully adjusting the reagents that induce the in-plane growth. A variation of the fraction of hydrated Cd(OAc)2 in a Cd(OAc)2/Cd(OAc)2·2H2O mixture tailors the nanoplatelet aspect ratio. This occurs independently of the reaction time, which can be used to fine-tune the overall length and width. An interpretation is given by the in situ formation of a small amount of hydroxide anions that alter the surface energy of specific planes.
Transformation Pathway from CdSe Magic-Size Clusters with Absorption Doublets at 373/393 nm to Clusters at 434/460 nm
Cao, Zhaopeng,Jiang, Gang,Li, Yan,Rowell, Nelson,Wang, Shanling,Yu, Kui,Zeng, Jianrong,Zhang, Chunchun,Zhang, Meng,Zhu, Jinming,Zhu, Yongcheng
, p. 20358 - 20365 (2021)
Divergent interpretations have appeared in the literature regarding the structural nature and evolutionary behavior for photoluminescent CdSe nanospecies with sharp doublets in optical absorption. We report a comprehensive description of the transformation pathway from one CdSe nanospecies displaying an absorption doublet at 373/393 nm to another species with a doublet at 433/460 nm. These two nanospecies are zero-dimensional (0D) magic-size clusters (MSCs) with 3D quantum confinement, and are labeled dMSC-393 and dMSC-460, respectively. Synchrotron-based small-angle X-ray scattering (SAXS) returns a radius of gyration of 0.92 nm for dMSC-393 and 1.14 nm for dMSC-460, and indicates that both types are disc shaped with the exponent of the SAXS form factor equal to 2.1. The MSCs develop from their unique counterpart precursor compounds (PCs), which are labeled PC-393 and PC-460, respectively. For the dMSC-393 to dMSC-460 transformation, the proposed PC-enabled pathway is comprised of three key steps, dMSC-393 to PC-393 (Step 1), PC-393 to PC-460 (Step 2 involving monomer addition), and PC-460 to dMSC-460 (Step 3). The present study provides a framework for understanding the PC-based evolution of MSCs and how PCs enable transformations between MSCs.
Core-crown Quantum Nanoplatelets with Favorable Type-II Heterojunctions Boost Charge Separation and Photocatalytic NO Oxidation on TiO2
Ebrahimi, Elnaz,Irfan, Muhammad,Shabani, Farzan,Kocak, Yusuf,Karakurt, Bartu,Erdem, Emre,Demir, Hilmi Volkan,Ozensoy, Emrah
, p. 6329 - 6343 (2020)
Functionalization of TiO2 (P25) with oleic acid-capped CdSe(core)/CdSeTe(crown) quantum-well nanoplatelets (NPL) yielded remarkable activity and selectivity toward nitrate formation in photocatalytic NOx oxidation and storage (PHONOS) under both ultraviolet (UV-A) and visible (VIS) light irradiation. In the NPL/P25 photocatalytic system, photocatalytic active sites responsible for the NO(g) photo-oxidation and NO2 formation reside mostly on titania, while the main function of the NPL is associated with the photocatalytic conversion of the generated NO2 into the adsorbed NO3? species, significantly boosting selectivity toward NOx storage. Photocatalytic improvement in NOx oxidation and storage upon NPL functionalization of titania can also be associated with enhanced electron-hole separation due to a favorable Type-II heterojunction formation and photo-induced electron transfer from the CdSeTe crown to the CdSe core of the quantum well system, where the trapped electrons in the CdSe core can later be transferred to titania. Re-usability of NPL/P25 system was also demonstrated upon prolonged use of the photocatalyst, where NPL/P25 catalyst surpassed P25 benchmark in all tests.
Synthesis of metal selenide colloidal nanocrystals by the hot injection of selenium powder
Flamee, Stijn,Dierick, Ruben,Cirillo, Marco,Van Genechten, Dirk,Aubert, Tangi,Hens, Zeger
, p. 12654 - 12661 (2013)
We describe the synthesis of metal selenide nanocrystals, including CdSe, ZnSe, CuInSe2 and Cu2(Zn,Sn)Se4, by the hot injection of selenium powder dispersed in a carrier solvent. Since this results in a fast and high yield nanocrystal formation, we argue that the approach is well suited for the low cost, large volume production of nanocrystals.
Revealing the Surface Structure of CdSe Nanocrystals by Dynamic Nuclear Polarization-Enhanced 77Se and 113Cd Solid-State NMR Spectroscopy
Adamson, Marquix A. S.,Blome-Fernández, Rafael,Chen, Yunhua,Dorn, Rick W.,Flintgruber, Anne H.,Hanrahan, Michael P.,Medina-Gonzalez, Alan M.,Rossini, Aaron J.,Vela, Javier,Wei, Lin
, p. 8747 - 8760 (2021)
Dynamic nuclear polarization (DNP) solid-state NMR (SSNMR) spectroscopy was used to obtain detailed surface structures of zinc blende CdSe nanocrystals (NCs) with plate or spheroidal morphologies which are capped by carboxylic acid ligands. 1D 113Cd and 77Se cross-polarization magic angle spinning (CPMAS) NMR spectra revealed distinct signals from Cd and Se atoms on the surface of the NCs, and those residing in bulk-like environments, below the surface. 113Cd cross-polarization magic-angle-turning (CP-MAT) experiments identified CdSe3O, CdSe2O2, and CdSeO3 Cd coordination environments on the surface of the NCs, where the oxygen atoms are presumably from coordinated carboxylate ligands. The sensitivity gain from DNP enabled natural isotopic abundance 2D homonuclear 113Cd-113Cd and 77Se-77Se and heteronuclear 113Cd-77Se scalar correlation solid-state NMR experiments which revealed the connectivity of the Cd and Se atoms. Importantly, 77Se{113Cd} scalar heteronuclear multiple quantum coherence (J-HMQC) experiments were used to selectively measure one-bond 77Se-113Cd scalar coupling constants (1J(77Se, 113Cd)). With knowledge of 1J(77Se, 113Cd), heteronuclear 77Se{113Cd} spin echo (J-resolved) NMR experiments were used to determine the number of Cd atoms bonded to Se atoms and vice versa. The J-resolved experiments directly confirmed that major Cd and Se surface species have CdSe2O2 and SeCd4 stoichiometries, respectively. Considering the crystal structure of zinc blende CdSe and the similarity of the solid-state NMR data for the platelets and spheroids, we conclude that the surface of the spheroidal CdSe NCs is primarily composed of {100} facets. The methods outlined here will generally be applicable to obtain detailed surface structures of various main group semiconductor nanoparticles.
Insights into the structural complexity of colloidal cdse nanocrystal surfaces: Correlating the efficiency of nonradiative excited-state processes to specific defects
Saniepay, Mersedeh,Mi, Chenjia,Liu, Zhihui,Abel, E. Paige,Beaulac, Rémi
, p. 1725 - 1736 (2018)
II-VI colloidal semiconductor nanocrystals (NCs), such as CdSe NCs, are often plagued by efficient nonradiative recombination processes that severely limit their use in energy-conversion schemes. While these processes are now well-known to occur at the surface, a full understanding of the exact nature of surface defects and of their role in deactivating the excited states of NCs has yet to be established, which is partly due to challenges associated with the direct probing of the complex and dynamic surface of colloidal NCs. Here, we report a detailed study of the surface of cadmium-rich zinc-blende CdSe NCs. The surfaces of these cadmium-rich species are characterized by the presence of cadmium carboxylate complexes (CdX2) that act as Lewis acid (Z-type) ligands that passivate undercoordinated selenide surface species. The systematic displacement of CdX2 from the surface by N,N,N′,N′-tetramethylethylene-1,2-diamine (TMEDA) has been studied using a combination of 1H NMR and photoluminescence spectroscopies. We demonstrate the existence of two independent surface sites that differ strikingly in the binding affinity for CdX2 and that are under dynamic equilibrium with each other. A model involving coupled dual equilibria allows a full characterization of the thermodynamics of surface binding (free energy, as well as enthalpic and entropic terms), showing that entropic contributions are responsible for the difference between the two surface sites. Importantly, we demonstrate that cadmium vacancies only lead to important photoluminescence quenching when created on one of the two sites, allowing a complete picture of the surface composition to be drawn where each site is assigned to specific NC facet locale, with CdX2 binding affinity and nonradiative recombination efficiencies that differ by up to two orders of magnitude.
Identifying reactive organo-selenium precursors in the synthesis of CdSe nanoplatelets
Riedinger, Andreas,Mule, Aniket S.,Knüsel, Philippe N.,Ott, Florian D.,Rossinelli, Aurelio A.,Norris, David J.
, p. 11789 - 11792 (2018)
In the synthesis of CdSe nanoplatelets, the selenium-to-selenide reduction pathway is unknown. We study solvent-free growth of CdSe nanoplatelets and identify bis(acyl) selenides as key reactive intermediates. Based on our findings, we prepare a series of bis(acyl) selenides that provide useful precursors with tailored reactivity for liquid-phase syntheses of nanoplatelets.
