Effect of size and shell: Enhanced optical and surface properties of CdS, ZnS and CdS/ZnS quantum dots

Kumar, Hitanshu; Barman, P. B.; Singh, Ragini Raj

doi:10.1016/j.physe.2014.11.018

Cited by 28 publications

(10 citation statements)

References 61 publications

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“…Both optical properties, absorption and emission, were significantly affected by the composition of the Zn x Cd 1 − x S alloys but with distinct energies from the predicted linear behavior of Vegard’s law. In general, similar to Vegard’s law [ 39 ], other models are used for calculating the correlation of optical properties with the size and composition of semiconductor nanocrystals, such as effective mass approximation (EMA) [ 41 ], semi-empirical tight-binding model (TBM) [ 42 ], and chemical bond model (CBM) [ 43 – 45 ]. Nonetheless, they usually overestimate the bandgap energies under the quantum confinement of the exciton mainly because of simplified assumptions such as by considering a spherical volume of the nanocrystallite, minimizing the complexity and reducing the parameters involved [ 42 , 44 ].…”

Section: Resultsmentioning

confidence: 99%

“…In general, similar to Vegard’s law [ 39 ], other models are used for calculating the correlation of optical properties with the size and composition of semiconductor nanocrystals, such as effective mass approximation (EMA) [ 41 ], semi-empirical tight-binding model (TBM) [ 42 ], and chemical bond model (CBM) [ 43 – 45 ]. Nonetheless, they usually overestimate the bandgap energies under the quantum confinement of the exciton mainly because of simplified assumptions such as by considering a spherical volume of the nanocrystallite, minimizing the complexity and reducing the parameters involved [ 42 , 44 ]. Although not accurate and valid for all ternary and quaternary alloyed QDs, the chemical bond model (CBM) [ 43 – 45 ], which is not a linear function, is suggested as more adequate for correlating the effect of quantum dependence of optical properties (bandgap energy) with the concentration of alloyed QDs such as Zn x Cd 1 − x S (dashed line).…”

Section: Resultsmentioning

confidence: 99%

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Composition-Tunable Optical Properties of Zn x Cd(1 − x)S Quantum Dot–Carboxymethylcellulose Conjugates: Towards One-Pot Green Synthesis of Multifunctional Nanoplatforms for Biomedical and Environmental Applications

Mansur

Caires

et al. 2017

Nanoscale Res Lett

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Quantum dots (QDs) are colloidal semiconductor nanocrystals with unique properties that can be engineered by controlling the nanoparticle size and chemical composition by doping and alloying strategies. However, due to their potential toxicity, augmenting their biocompatibility is yet a challenge for expanding to several biomedical and environmentally friendly applications. Thus, the main goal of this study was to develop composition-tunable and biocompatible ZnxCd1 − xS QDs using carboxymethylcellulose polysaccharide as direct capping ligand via green colloidal aqueous route at neutral pH and at room temperature for potential biomedical and environmental applications. The ternary alloyed QDs were extensively characterized using UV–vis spectroscopy, photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), X-ray diffraction (XRD), electron energy loss spectroscopy (EELS), and X-ray photoelectrons spectroscopy (XPS). The results indicated that ZnxCd(1 − x)S QDs were surface stabilized by carboxymethylcellulose biopolymer with spherical morphology for all composition of alloys and narrow sizes distributions ranging from 4 to 5 nm. The XRD results indicated that monophasic ternary alloyed ZnxCd1 − xS nanocrystals were produced with homogenous composition of the core as evidenced by EELS and XPS analyses. In addition, the absorption and emission optical properties of ZnxCd1 − xS QDs were red shifted with increasing the amount of Cd2+ in the alloyed nanocrystals, which have also increased the quantum yield compared to pure CdS and ZnS nanoparticles. These properties of alloyed nanomaterials were interpreted based on empirical model of Vegard’s law and chemical bond model (CBM). As a proof of concept, these alloyed-QD conjugates were tested for biomedical and environmental applications. The results demonstrated that they were non-toxic and effective fluorophores for bioimaging live HEK293T cells (human embryonic kidney cells) using confocal laser scanning fluorescence microscopy. Moreover, these conjugates presented photocatalytic activity for photodegradation of methylene blue used as model organic industrial pollutant in water. Hence, composition-tunable optical properties of ternary ZnxCd1 − xS (x = 0–1) fluorescent alloyed QDs was achieved using a facile eco-friendly aqueous processing route, which can offer promising alternatives for developing innovative nanomaterials for applications in nanomedicine and environmental science and technology.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Composition-Tunable Optical Properties of Zn x Cd(1 − x)S Quantum Dot–Carboxymethylcellulose Conjugates: Towards One-Pot Green Synthesis of Multifunctional Nanoplatforms for Biomedical and Environmental Applications

Mansur

Caires

et al. 2017

Nanoscale Res Lett

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“…In addition, ZnS nanocrystals also have high specific surface area and quantum size effect and quantum tunneling effect [9][10][11], leading to the zinc sulfide doped matrix material exhibiting high quantum efficiency in photoluminescence and electroluminescence, and are often used as an important matrix material multicolor fluorescent powder. Therefore, in order to obtain the intrinsic dilute magnetic semiconductors, transition metal doped ZnS has been widely studied by different methods.…”

Section: Introductionmentioning

confidence: 99%

Optical and Magnetic Properties of Ni Doped ZnS Diluted Magnetic Semiconductors Synthesized by Hydrothermal Method

Wei

Zhao

et al. 2017

Journal of Nanomaterials

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Diluted magnetic semiconductors Zn 1− Ni S with different consistency ratio ( = 0, 0.01, 0.03, 0.05, and 0.07) were successfully synthesized by hydrothermal method using ethylenediamine as a modifier. The influence of Ni doping concentration on the microstructure, morphology, and optical and magnetic properties of undoped and Ni doped ZnS nanocrystals was characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray energy dispersive spectrometry (XEDS), ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FT-IR), photoluminescence spectra (PL), and the vibrating sample magnetometer (VSM), respectively. The experiment results show the substitution of Ni 2+ on Zn 2+ sites without changing the hexagonal wurtzite structure of ZnS and generate single-phase Zn 1− Ni S with good crystallization. The lattice constant causes distortion and decreases with the increase of Ni 2+ doped concentration. The appearance of the samples is one-dimensional well-dispersed nanorods. UV-vis spectra reveal the band gap of all Zn 1− Ni S samples greater than that of bulk ZnS (3.67 eV), and blue shift phenomenon occurs. The photoluminescence spectra of undoped and doped samples possess the broad blue emission band in the range of 400-650 nm; the PL intensities of Zn 1− Ni S nanorods increase with the increase of Ni content comparing to pure ZnS and reach maximum for = 0.03. Magnetic measurements indicated that the undoped ZnS samples are superparamagnetic, whereas the doped samples exhibit ferromagnetism.

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“…In particular, passivating of the surface of nanoparticles by epitaxial growth of a shell of a semiconductor material with a wider band gap, for example in CdS/ZnS core/shell QDs, is resulting in an increase in PL intensity. [ 10 , 11 , 12 , 13 , 14 ]…”

Section: Introductionmentioning

confidence: 99%

“…Surface defects can lead to a significant broadening of photoluminescence (PL) emission and favor non‐radiative recombination mechanisms. In particular, passivating of the surface of nanoparticles by epitaxial growth of a shell of a semiconductor material with a wider band gap, for example in CdS/ZnS core/shell QDs, is resulting in an increase in PL intensity [10–14] …”

Section: Introductionmentioning

confidence: 99%

Continuous Flow Synthesis of Cd_1‐xZn_xS and CdS/ZnS Core/Shell Semiconductor Nanoparticles by MicroJet Reactor Technology

Hiemer

Stöwe

2022

ChemistryOpen

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From aqueous precursor solutions of metal salts and sodium sulfide using MicroJet Reactor (MJR) technology Cd 1‐x Zn x S and CdS/ZnS core/shell semiconductor nanoparticles were synthesized. The MJR approach represents an automated, continuous, flexible and scalable route for nanoparticle synthesis, providing a tight control over process parameters and thus simple size, shape and composition control. Since particle sizes below the excitonic Bohr radius were obtained by MJR, the nanoparticulate materials exhibit quantum confinement effects. By varying the precursor ratio the band gap of Cd 1‐x Zn x S Quantum Dots (QDs) could be targeted from 3.1 to 3.6 eV. CdS/ZnS core/shell QDs were prepared by enclosing CdS particles from MJR with ZnS produced by thermal decomposition of a Zn‐MPA complex. Adjustment of the shell thickness increased the photoluminescence intensity by 43 %. Synthesis of ternary sulfides in the form of core/shell particles broadens the spectrum of materials accessible by MJR and demonstrates the extraordinary flexibility of the technology.

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Effect of size and shell: Enhanced optical and surface properties of CdS, ZnS and CdS/ZnS quantum dots

Cited by 28 publications

References 61 publications

Composition-Tunable Optical Properties of Zn x Cd(1 − x)S Quantum Dot–Carboxymethylcellulose Conjugates: Towards One-Pot Green Synthesis of Multifunctional Nanoplatforms for Biomedical and Environmental Applications

Composition-Tunable Optical Properties of Zn x Cd(1 − x)S Quantum Dot–Carboxymethylcellulose Conjugates: Towards One-Pot Green Synthesis of Multifunctional Nanoplatforms for Biomedical and Environmental Applications

Optical and Magnetic Properties of Ni Doped ZnS Diluted Magnetic Semiconductors Synthesized by Hydrothermal Method

Continuous Flow Synthesis of Cd_1‐xZn_xS and CdS/ZnS Core/Shell Semiconductor Nanoparticles by MicroJet Reactor Technology

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Effect of size and shell: Enhanced optical and surface properties of CdS, ZnS and CdS/ZnS quantum dots

Cited by 28 publications

References 61 publications

Composition-Tunable Optical Properties of Zn x Cd(1 − x)S Quantum Dot–Carboxymethylcellulose Conjugates: Towards One-Pot Green Synthesis of Multifunctional Nanoplatforms for Biomedical and Environmental Applications

Composition-Tunable Optical Properties of Zn x Cd(1 − x)S Quantum Dot–Carboxymethylcellulose Conjugates: Towards One-Pot Green Synthesis of Multifunctional Nanoplatforms for Biomedical and Environmental Applications

Optical and Magnetic Properties of Ni Doped ZnS Diluted Magnetic Semiconductors Synthesized by Hydrothermal Method

Continuous Flow Synthesis of Cd1‐xZnxS and CdS/ZnS Core/Shell Semiconductor Nanoparticles by MicroJet Reactor Technology

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Continuous Flow Synthesis of Cd_1‐xZn_xS and CdS/ZnS Core/Shell Semiconductor Nanoparticles by MicroJet Reactor Technology