Determination of the Wurtzite and Zincblende Fractions in II–VI Semiconductor Nanowires

Harder, Philip; Nielsen, A.D.; Sassnau, Ann-Katrin; Bonatz, Dennis; Perbandt, Markus; Kipp, Tobias; Mews, Alf

doi:10.1021/acs.chemmater.0c04689

Cited by 8 publications

(10 citation statements)

References 28 publications

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“…The XRD pattern of the CdSe QDs exhibited characteristic diffraction peaks located at ∼26°(111), ∼43°(220), and ∼50°( 311) 2θ values, which were consistent with the zinc blende crystal lattice (ICDD/PDF no. 41528) 57 (Figure 4a). However, the diffraction peaks of the CdSe lattice were significantly attenuated in the diffractograms of QDs (I), QDs (II), and QDs (III), and new peaks appeared toward larger 2θ angles, consistent with the diffraction pattern of the zinc blende crystal lattice of ZnS (ICDD/PDF no.…”

Section: Acs Applied Nano Materialsmentioning

confidence: 99%

Singlet Molecular Oxygen Generation via Unexpected Emission Color-Tunable CdSe/ZnS Nanocrystals for Applications in Photodynamic Therapy

Khan

Uchiyama

et al. 2023

ACS Appl. Nano Mater.

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It is highly desirable in biomedical sciences to utilize the multifunctional nanoparticles of similar size with tunable emission. Since the optoelectronic properties of quantum dots (QDs) originate from size-dependent quantum confinement effects, we developed an alternate approach to synthesize color-tunable CdSe/ZnS QDs based on interfacial ion exchange (predominantly exchange of Se2– by S2– anions), using 1-dodecanethiol and oleylamine solvent systems as a sensitive parameter. The wide-range color-tunability (490–570 nm) was achieved unexpectedly as a result of interfacial alloying without inducing a significant change in the size (from 4.45 to 4.81 nm) of QDs. The local atomic structure order, chemical composition, and nature of alloying in QDs were unraveled by XAFS data analysis. Owing to the molecular-like sensitization behavior, the QDs were evaluated for singlet molecular oxygen (1O2) efficiency. They were further studied in RAW 264.7 macrophages for biocompatibility, bioimaging, and delivering pathways for use in future photodynamic therapy (PDT). The QDs demonstrated efficient singlet molecular oxygen (1O2) quantum yields (ΦQDs) of 14, 12, and 18% for QDs (I), QDs (II), and QDs (III), respectively. The QD-treated cells presented high cell viability above 85% and induced no cell activation. Fluorescence and transmission electron microscopy (TEM) images of cells manifested a considerable amount of QDs in the vicinity of the cell membrane and intracellular regions. The pathway-specific inhibition measurements revealed that the QDs were internalized by cells via energy-dependent endocytosis, predominantly macropinocytosis and other receptor-mediated endocytic pathways, and accumulated them presumably in endosome/lysosomes. This study will open new possibilities for engineering interfacial alloying-based tunable emission QDs and pathway-specific delivery of QD-based theranostics into a site of interest for simultaneous bioimaging and PDT.

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Section: Acs Applied Nano Materialsmentioning

confidence: 99%

Singlet Molecular Oxygen Generation via Unexpected Emission Color-Tunable CdSe/ZnS Nanocrystals for Applications in Photodynamic Therapy

Khan

Uchiyama

et al. 2023

ACS Appl. Nano Mater.

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“…The PL scans in Figure (c,d) further highlight a feature of the PL of CdSe QWs which was in the focus of investigations in the past. , Observing localized PL enhancement at the illuminated spots shows that CdSe QWs exhibit bound excitonic emission. The fixation of excitons along the length of the QWs might result from the formation of excitonic complexes, which are locally bound to alternating zincblende and wurtzite segments or dopants. , …”

Section: Resultsmentioning

confidence: 99%

“…The Bi NPs ( d = 7.4 ± 1.3 nm) used in the synthesis were prepared according to a synthesis published in ref . A detailed description of the synthesis can be found in ref . The precursor cadmium di- n -octylphosphinate Cd(DOPT) 2 was synthesized as described in ref .…”

Section: Methodsmentioning

confidence: 99%

“…The fixation of excitons along the length of the QWs might result from the formation of excitonic complexes, which are locally bound to alternating zincblende and wurtzite segments or dopants. 38,43 In the past, investigations about photoinduced PL enhancement of CdSe NPs have shown that Se sites at the surface play a key role in the process, as PL enhancement was only observed for Se-rich CdSe particle surfaces. 44 In fact, our sample exhibits a slightly increased Se content (Se:Cd = 1.1− 1.3), as determined by EDX spectroscopy and ICP-MS (see Figure S3 and Table S1 in the Supporting Information).…”

Section: Synthesismentioning

confidence: 99%

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Reversible and Irreversible Effects of Oxygen on the Optical Properties of CdSe Quantum Wires

et al. 2022

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We investigated the effects of oxygen on the optical properties of wet-chemically synthesized colloidal CdSe quantum wires using confocal spectroscopy. By comparing the photoluminescence characteristics of CdSe quantum wires in oxygen and in inert gas atmospheres, we observed both irreversible photoluminescence enhancement and quenching processes in oxygen as well as reversible changes in the emission spectra and Raman spectra when changing the gas atmosphere during continuous excitation. We attribute the irreversible photoluminescence enhancement to reduction of Auger recombination by formation of oxides on the surface, which eventually leads to photoluminescence quenching. The reversible atmosphere-dependent changes in the emission intensity and wavelengths, accompanied by changes in the Raman spectra, are attributed to electron scavenging by oxygen. This was demonstrated as the presence of excess negative charge carriers led to radiative emission of higher excited states and reduced Raman frequencies when illuminating in inert gas atmospheres. Thereby, this work provides insight into the possible photoinduced effects of oxygen on the optical properties of semiconducting nanoparticles and thus contributes to a more detailed understanding of photobrightening mechanisms.

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“…Polytypes, occurring in different structural modifications, are a special case of polymorphs, which share identical close-packed planes but differ only in the stacking sequence in the third dimension normal to these planes. Polytypes commonly exist in group II–VI, III–V, and IV-IV compound semiconductors, − whose structures generally display cubic zinc-blende (ZB) and hexagonal wurtzite (WZ) forms. As one of the typical II–VI semiconductors, cadmium selenide (CdSe) has attracted extensive interest over the past 20 years, owing to its robust synthetic method − and its ability to tune the optical behavior across the entire visible spectrum.…”

Section: Introductionmentioning

confidence: 99%

Shape Evolution and Control of Wurtzite CdSe Nanocrystals through a Facile One-Pot Strategy

Zhang

Cao

et al. 2021

J. Phys. Chem. C

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The synthesis of one-dimensional (1D) CdSe nanocrystals (NCs) with hexagonal wurtzite (WZ) structures such as nanorods has been well developed over the past years. However, the shape modulation of WZ-CdSe with two-dimensional (2D)/three-dimensional (3D) morphologies remains challenging because of its intrinsic hexagonal unit and the involved ligands selectively binding to specific crystal facets. Here, we present a facile and general one-pot approach for the shape control of WZ-CdSe NCs without using pre-existing seeds. Interestingly, the low supersaturation in a drip injection mode enabled the control and formation of various shapes including the nanorods, long nanowires, and hexagonal platelets, compared to the traditional one-time injection. Such shape evolutions could be conveniently tuned by the parameters such as the temperature, growth time, and injection rates. The underlying growth mechanisms for the morphological evolution and control were discussed in the context of kinetic/thermodynamic factors. Our studies provide a fundamental understanding of shape modulations in polytypic compound NCs, offering great opportunities to tune the shape–size–property relationship for optoelectronic applications.

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Determination of the Wurtzite and Zincblende Fractions in II–VI Semiconductor Nanowires

Cited by 8 publications

References 28 publications

Singlet Molecular Oxygen Generation via Unexpected Emission Color-Tunable CdSe/ZnS Nanocrystals for Applications in Photodynamic Therapy

Singlet Molecular Oxygen Generation via Unexpected Emission Color-Tunable CdSe/ZnS Nanocrystals for Applications in Photodynamic Therapy

Reversible and Irreversible Effects of Oxygen on the Optical Properties of CdSe Quantum Wires

Shape Evolution and Control of Wurtzite CdSe Nanocrystals through a Facile One-Pot Strategy

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