Editorial

3 pages, 172 KiB

Open AccessEditorial

Special Issue “II-VI Semiconductor Nanocrystals and Hybrid Polymer–Nanocrystal Systems”

by Marco Anni

Nanomaterials 2021, 11(2), 467; https://doi.org/10.3390/nano11020467 - 12 Feb 2021

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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

(This article belongs to the Special Issue II-VI Semiconductor Nanocrystals and Hybrid Polymer-Nanocrystal Systems)

Research

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17 pages, 8008 KiB

Open AccessArticle

Photoinduced Enhancement of Photoluminescence of Colloidal II-VI Nanocrystals in Polymer Matrices

by Volodymyr Dzhagan, Oleksandr Stroyuk, Oleksandra Raievska, Oksana Isaieva, Olga Kapush, Oleksandr Selyshchev, Volodymyr Yukhymchuk, Mykhailo Valakh and Dietrich R. T. Zahn

Nanomaterials 2020, 10(12), 2565; https://doi.org/10.3390/nano10122565 - 21 Dec 2020

Cited by 6 | Viewed by 2429

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

(This article belongs to the Special Issue II-VI Semiconductor Nanocrystals and Hybrid Polymer-Nanocrystal Systems)

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8 pages, 2496 KiB

Open AccessArticle

Influence of Size and Shape Anisotropy on Optical Properties of CdSe Quantum Dots

by Sung Hun Kim, Minh Tan Man, Joong Wook Lee, Kyoung-Duck Park and Hong Seok Lee

Nanomaterials 2020, 10(8), 1589; https://doi.org/10.3390/nano10081589 - 12 Aug 2020

Cited by 25 | Viewed by 4056

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

(This article belongs to the Special Issue II-VI Semiconductor Nanocrystals and Hybrid Polymer-Nanocrystal Systems)

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13 pages, 2425 KiB

Open AccessArticle

Atomic Sulfur Passivation Improves the Photoelectrochemical Performance of ZnSe Nanorods

by Fei Huang, Jiajia Ning, Wei Xiong, Ting Shen, Yanling Zhao, Jianjun Tian, Ruiqin Zhang and Andrey L. Rogach

Nanomaterials 2020, 10(6), 1081; https://doi.org/10.3390/nano10061081 - 31 May 2020

Cited by 6 | Viewed by 3508

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

(This article belongs to the Special Issue II-VI Semiconductor Nanocrystals and Hybrid Polymer-Nanocrystal Systems)

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19 pages, 3995 KiB

Open AccessArticle

Expanded Electroluminescence in High Load CdS Nanocrystals PVK-Based LEDs

by Fernando Rodríguez-Mas, Juan Carlos Ferrer, José Luis Alonso and Susana Fernández de Ávila

Nanomaterials 2019, 9(9), 1212; https://doi.org/10.3390/nano9091212 - 28 Aug 2019

Cited by 17 | Viewed by 3335

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

(This article belongs to the Special Issue II-VI Semiconductor Nanocrystals and Hybrid Polymer-Nanocrystal Systems)

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16 pages, 5274 KiB

Open AccessArticle

Diameter- and Length-controlled Synthesis of Ultrathin ZnS Nanowires and Their Size-Dependent UV Absorption Properties, Photocatalytical Activities and Band-Edge Energy Levels

by Guanjie Xing, Xiaoli Liu, Simeng Hao, Xiaohong Li, Louzhen Fan and Yunchao Li

Nanomaterials 2019, 9(2), 220; https://doi.org/10.3390/nano9020220 - 07 Feb 2019

Cited by 12 | Viewed by 3278 | 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

(This article belongs to the Special Issue II-VI Semiconductor Nanocrystals and Hybrid Polymer-Nanocrystal Systems)

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Review

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25 pages, 5158 KiB

Open AccessFeature PaperReview

Polymer-II-VI Nanocrystals Blends: Basic Physics and Device Applications to Lasers and LEDs

by Marco Anni

Nanomaterials 2019, 9(7), 1036; https://doi.org/10.3390/nano9071036 - 19 Jul 2019

Cited by 27 | Viewed by 4717

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

(This article belongs to the Special Issue II-VI Semiconductor Nanocrystals and Hybrid Polymer-Nanocrystal Systems)

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Other

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2 pages, 1327 KiB

Open AccessCorrection

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

by Guanjie Xing, Xiaoli Liu, Simeng Hao, Xiaohong Li, Louzhen Fan and Yunchao Li

Nanomaterials 2020, 10(6), 1029; https://doi.org/10.3390/nano10061029 - 28 May 2020

Viewed by 1384

Abstract

The authors wish to make the following corrections to this article [...] Full article

(This article belongs to the Special Issue II-VI Semiconductor Nanocrystals and Hybrid Polymer-Nanocrystal Systems)

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