II-VI Semiconductor Nanocrystals and Hybrid Polymer-Nanocrystal Systems

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanoelectronics, Nanosensors and Devices".

Deadline for manuscript submissions: closed (31 October 2020) | Viewed by 24231

Special Issue Editor

Special Issue Information

Dear Colleagues,

II-VI semiconductor nanocrystals and hybrids polymer–nanocrystal systems have been subject of intense interdisciplinary research activity in the last few years.

This research includes the development of synthesis protocols for obtaining nanocrystals with high control of chemical composition, shape, size and optical and electronic properties, the investigation of the electronic properties by a wide range of advanced spectroscopic techniques and the demonstration and optimization of a wide range of devices, such as light emitting diodes, solar cells, optically-pumped lasers, and sensors. Moreover the combination of nanocrystals with organic polymers allows the development of novel functional materials combining the best properties of the components and thus with performances improved with respect to the ones of the individual components.

This Special Issue of Nanomaterials aims to describe the state-of-the-art and the recent advances of the synthesis methods of II-VI nanocrystals, of the photophysics investigation of their electronic properties and of their possible applications in photonic and optoelectronic devices.

Research articles, review articles, as well as short communications, are invited.

Dr. Marco Anni
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Colloidal synthesis
  • Ultrafast Spectroscopy
  • Single emitter Spectroscopy
  • Optically pumped Lasers
  • Light Emitting Diodes
  • Solar cells
  • Biomarkers
  • semiconductor nanocrystals
  • hybrids polymer–nanocrystal
  • nanodevices

Published Papers (8 papers)

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Editorial

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3 pages, 172 KiB  
Editorial
Special Issue “II-VI Semiconductor Nanocrystals and Hybrid Polymer–Nanocrystal Systems”
Nanomaterials 2021, 11(2), 467; https://doi.org/10.3390/nano11020467 - 12 Feb 2021
Viewed by 1381
Abstract
The continuous need to improve the performance of photonic, electronic and optoelectronic devices has stimulated research toward the development of innovative semiconducting materials which display better properties with respect to standard bulk semiconductors [...] Full article

Research

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17 pages, 8008 KiB  
Article
Photoinduced Enhancement of Photoluminescence of Colloidal II-VI Nanocrystals in Polymer Matrices
Nanomaterials 2020, 10(12), 2565; https://doi.org/10.3390/nano10122565 - 21 Dec 2020
Cited by 6 | Viewed by 2301
Abstract
The environment strongly affects both the fundamental physical properties of semiconductor nanocrystals (NCs) and their functionality. Embedding NCs in polymer matrices is an efficient way to create a desirable NC environment needed for tailoring the NC properties and protecting NCs from adverse environmental [...] Read more.
The environment strongly affects both the fundamental physical properties of semiconductor nanocrystals (NCs) and their functionality. Embedding NCs in polymer matrices is an efficient way to create a desirable NC environment needed for tailoring the NC properties and protecting NCs from adverse environmental factors. Luminescent NCs in optically transparent polymers have been investigated due to their perspective applications in photonics and bio-imaging. Here, we report on the manifestations of photo-induced enhancement of photoluminescence (PL) of aqueous colloidal NCs embedded in water-soluble polymers. Based on the comparison of results obtained on bare and core/shell NCs, NCs of different compounds (CdSe, CdTe, ZnO) as well as different embedding polymers, we conclude on the most probable mechanism of the photoenhancement for these sorts of systems. Contrary to photoenhancement observed earlier as a result of surface photocorrosion, we do not observe any change in peak position and width of the excitonic PL. Therefore, we suggest that the saturation of trap states by accumulated photo-excited charges plays a key role in the observed enhancement of the radiative recombination. This suggestion is supported by the unique temperature dependence of the trap PL band as well as by power-dependent PL measurement. Full article
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8 pages, 2496 KiB  
Article
Influence of Size and Shape Anisotropy on Optical Properties of CdSe Quantum Dots
Nanomaterials 2020, 10(8), 1589; https://doi.org/10.3390/nano10081589 - 12 Aug 2020
Cited by 24 | Viewed by 3878
Abstract
We used low-temperature reactions to synthesize different-sized CdSe quantum dots (QDs) capped with fatty-acid and phosphine ligands. From the correlation of high-resolution transmission electron microscopy and X-ray diffraction (XRD) analyses of the synthesized QDs, we observed size-dependent shape anisotropy. In addition, the recorded [...] Read more.
We used low-temperature reactions to synthesize different-sized CdSe quantum dots (QDs) capped with fatty-acid and phosphine ligands. From the correlation of high-resolution transmission electron microscopy and X-ray diffraction (XRD) analyses of the synthesized QDs, we observed size-dependent shape anisotropy. In addition, the recorded XRD patterns revealed mixed crystal facets with zinc blende and wurtzite structures in small-sized QDs. Furthermore, from differential absorption (DA) spectra, we extracted the electronic transition energies for different-sized QDs, which were found to be similar to the calculated values of the quantum size levels associated with band mixing of CdSe QDs with a moderate bandgap. We found that the excitonic absorption peaks are increasingly “hidden” with decreasing QD size because of the crystal structure and crystalline quality. The results show good agreement with the obtained diffraction patterns and the estimation errors obtained from the DA spectra. Full article
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13 pages, 2425 KiB  
Article
Atomic Sulfur Passivation Improves the Photoelectrochemical Performance of ZnSe Nanorods
Nanomaterials 2020, 10(6), 1081; https://doi.org/10.3390/nano10061081 - 31 May 2020
Cited by 5 | Viewed by 3400
Abstract
We introduced atomic sulfur passivation to tune the surface sites of heavy metal-free ZnSe nanorods, with a Zn2+-rich termination surface, which are initially capped with organic ligands and under-coordinated with Se. The S2− ions from a sodium sulfide solution were [...] Read more.
We introduced atomic sulfur passivation to tune the surface sites of heavy metal-free ZnSe nanorods, with a Zn2+-rich termination surface, which are initially capped with organic ligands and under-coordinated with Se. The S2− ions from a sodium sulfide solution were used to partially substitute a 3-mercaptopropionic acid ligand, and to combine with under-coordinated Zn termination atoms to form a ZnS monolayer on the ZnSe surface. This treatment removed the surface traps from the ZnSe nanorods, and passivated defects formed during the previous ligand exchange process, without sacrificing the efficient hole transfer. As a result, without using any co-catalysts, the atomic sulfur passivation increased the photocurrent density of TiO2/ZnSe photoanodes from 273 to 325 μA/cm2. Notably, without using any sacrificial agents, the photocurrent density for sulfur-passivated TiO2/ZnSe nanorod-based photoanodes remained at almost 100% of its initial value after 300 s of continuous operation, while for the post-deposited ZnS passivation layer, or those based on ZnSe/ZnS core–shell nanorods, it declined by 28% and 25%, respectively. This work highlights the advantages of the proper passivation of II-VI semiconductor nanocrystals as an efficient approach to tackle the efficient charge transfer and stability of photoelectrochemical cells based thereon. Full article
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19 pages, 3995 KiB  
Article
Expanded Electroluminescence in High Load CdS Nanocrystals PVK-Based LEDs
Nanomaterials 2019, 9(9), 1212; https://doi.org/10.3390/nano9091212 - 28 Aug 2019
Cited by 17 | Viewed by 3226
Abstract
Immiscibility between dimethyl sulfoxide (DMSO) and polar solvents used for poly(N-vinylcarbazole) (PVK) solutions, leads to failed light-emitting diodes when colloidal cadmium sulfide (CdS) nanoparticles capped with thiophenol are incorporated to their active layer. To prevent this, a heat treatment is applied [...] Read more.
Immiscibility between dimethyl sulfoxide (DMSO) and polar solvents used for poly(N-vinylcarbazole) (PVK) solutions, leads to failed light-emitting diodes when colloidal cadmium sulfide (CdS) nanoparticles capped with thiophenol are incorporated to their active layer. To prevent this, a heat treatment is applied to the CdS nanoparticles in order to evaporate DMSO solvent. After evaporation most of the nanoparticles increased their size, and some of them show hexagonal crystalline structure instead of the original cubic zinc-blende observed in colloidal pre-treated nanoparticles. Nevertheless, enhanced electronic properties are measured in light-emitting devices when DMSO-free nanoparticles are embedded in the poly(N-vinylcarbazole) active layer. Light emission from these hybrid devices comprises the whole visible range of wavelengths as searched for white LEDs. Moreover, electroluminescence from both types of CdS nanoparticles (smaller cubic and bigger hexagonal) has been discriminated and interpreted through Gaussian deconvolution. Full article
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16 pages, 5274 KiB  
Article
Diameter- and Length-controlled Synthesis of Ultrathin ZnS Nanowires and Their Size-Dependent UV Absorption Properties, Photocatalytical Activities and Band-Edge Energy Levels
Nanomaterials 2019, 9(2), 220; https://doi.org/10.3390/nano9020220 - 07 Feb 2019
Cited by 12 | Viewed by 3185 | Correction
Abstract
Benefiting from their ultra-small diameters and highly structural anisotropies, ultrathin semiconductor nanowires (USNWs) are well-known for their fascinating physical/chemical properties, as well as their promising applications in various fields. However, until now, it remains a challenge to synthesize high-quality USNWs with well-controlled diameters [...] Read more.
Benefiting from their ultra-small diameters and highly structural anisotropies, ultrathin semiconductor nanowires (USNWs) are well-known for their fascinating physical/chemical properties, as well as their promising applications in various fields. However, until now, it remains a challenge to synthesize high-quality USNWs with well-controlled diameters and lengths, let alone the exploration of their size-dependent properties and applications. To solve such a challenge, we report herein a ligand-induced low-temperature precursor thermolysis route for the controlled preparation of ultrathin ZnS nanowires, which is based on the oriented assembly of the in-situ formed ZnS clusters/tiny particles. Optimized synthetic conditions allowed the synthesis of ZnS nanowires with a diameter down to 1.0 nm and a length approaching 330 nm. The as-prepared ultrathin ZnS nanowires were then intensively examined by morphological, spectroscopic and electrochemical analytical means to explore their size-dependent optical absorption properties, photocatalytic activities and band-edge energy levels, as well as their underlying growth mechanism. Notably, these USNWs, especially for the thinnest nanowires, were identified to possess an excellent performance in both the selective absorption of ultraviolet (UV) light and photocatalytic degradation of dyes, thus enabling them to serve as longpass ultraviolet filters and high-efficiency photocatalysts, respectively. For the ultrathin ZnS nanowires with a diameter of 1.0 nm, it was also interesting to observe that their exciton absorption peak positions were kept almost unchanged during the continuous extension of their lengths, which has not been reported previously. Full article
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Review

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25 pages, 5158 KiB  
Review
Polymer-II-VI Nanocrystals Blends: Basic Physics and Device Applications to Lasers and LEDs
Nanomaterials 2019, 9(7), 1036; https://doi.org/10.3390/nano9071036 - 19 Jul 2019
Cited by 27 | Viewed by 4627
Abstract
Hybrid thin films that combine organic conjugated molecules and semiconductors nanocrystals (NCs) have been deeply investigated in the previous years, due to their capability to provide an extremely broad tuning of their electronic and optical properties. In this paper we review the main [...] Read more.
Hybrid thin films that combine organic conjugated molecules and semiconductors nanocrystals (NCs) have been deeply investigated in the previous years, due to their capability to provide an extremely broad tuning of their electronic and optical properties. In this paper we review the main aspects of the basic physics of the organic–inorganic interaction and the actual state of the art of lasers and light emitting diodes based on hybrid active materials. Full article
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Other

2 pages, 1327 KiB  
Correction
Correction: Xing, G. et al. Diameter- and Length-Controlled Synthesis of Ultrathin ZnS Nanowires and Their Size-Dependent UV Absorption Properties, Photocatalytical Activities and Band-Edge Energy Levels. Nanomaterials 2019, 9, 220
Nanomaterials 2020, 10(6), 1029; https://doi.org/10.3390/nano10061029 - 28 May 2020
Viewed by 1345
Abstract
The authors wish to make the following corrections to this article [...] Full article
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