共查询到20条相似文献,搜索用时 15 毫秒
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Dr. Dokyoung Kim Dr. Jinmyoung Joo Dr. Youlin Pan Alice Boarino Yong Woong Jun Prof. Dr. Kyo Han Ahn Dr. Barry Arkles Prof. Dr. Michael J. Sailor 《Angewandte Chemie (International ed. in English)》2016,55(22):6423-6427
Organic trihydridosilanes can be grafted to hydrogen‐terminated porous Si nanostructures with no catalyst. The reaction proceeds efficiently at 80 °C, and it shows little sensitivity to air or water impurities. The modified surfaces are stable to corrosive aqueous solutions and common organic solvents. Octadecylsilane H3Si(CH2)17CH3, and functional silanes H3Si(CH2)11Br, H3Si(CH2)9CH=CH2, and H3Si(CH2)2(CF2)5CF3 are readily grafted. When performed on a mesoporous Si wafer, the perfluoro reagent yields a superhydrophobic surface (contact angle 151°). The bromo‐derivative is converted to azide, amine, or alkyne functional surfaces via standard transformations, and the utility of the method is demonstrated by loading of the antibiotic ciprofloxaxin (35 % by mass). When intrinsically photoluminescent porous Si films or nanoparticles are used, photoluminescence is retained in the grafted products, indicating that the chemistry does not introduce substantial nonradiative surface traps. 相似文献
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Dr. Sergei V. Voitekhovich André Wolf Chris Guhrenz Dr. Alexander S. Lyakhov Dr. Ludmila S. Ivashkevich Marion Adam Prof. Dr. Nikolai Gaponik Prof. Dr. Stefan Kaskel Prof. Dr. Alexander Eychmüller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(41):14746-14752
A facile method for the preparation of the novel capping ligand 5‐(2‐mercaptoethyl)‐1H‐tetrazole for the stabilization of water‐soluble nanocrystals was developed. This effective synthetic procedure is based on the cycloaddition of sodium azide to 3,3′‐dithiobis(propionitrile) followed by the reductive cleavage of a S?S bond with triphenylphosphine. The structure of the synthesized compound was confirmed by single‐crystal X‐ray analysis. A target tetrazole was successfully applied for the direct aqueous synthesis of CdTe and Au nanocrystals. CdTe nanocrystals capped with 5‐(2‐mercaptoethyl)‐1H‐tetrazole were found to reveal high photoluminescence efficiencies (up to 77 %). Nanocrystals capped with this tetrazole ligand are able to build 3D structures in a metal‐ion‐assisted gelation process in aqueous solution. Critical point drying of the as‐formed hydrogels allowed the preparation of the corresponding aerogels, while preserving the mesoporous structure. 相似文献
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Functionalization of Hydride‐Terminated Photoluminescent Silicon Nanocrystals with Organolithium Reagents 下载免费PDF全文
Ignaz M. D. Höhlein Arzu Angı Regina Sinelnikov Prof. Jonathan G. C. Veinot Prof. Bernhard Rieger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):2755-2758
Hydride‐terminated photoluminescent silicon nanocrystals (SiNCs) were functionalized with organolithium compounds. The reaction is proposed to proceed through cleavage of Si?Si bonds and formation of a Si?Li surface species. The method yields colloidally stabilized SiNCs at room temperature with short reaction times. SiNCs with mixed surface functionalities can be prepared in an easy two‐step reaction by this method by quenching of the Si?Li group with electrophiles or by addressing free Si?H groups on the surface with a hydrosilylation reaction. 相似文献
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Diazonium Salts as Grafting Agents and Efficient Radical‐Hydrosilylation Initiators for Freestanding Photoluminescent Silicon Nanocrystals 下载免费PDF全文
Ignaz M. D. Höhlein Julian Kehrle Tobias Helbich Zhenyu Yang Prof. Jonathan G. C. Veinot Prof. Bernhard Rieger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(15):4212-4216
The reactivity of diazonium salts towards freestanding, photoluminescent silicon nanocrystals (SiNCs) is reported. It was found that SiNCs can be functionalized with aryl groups by direct reductive grafting of the diazonium salts. Furthermore, diazonium salts are efficient radical initiators for SiNC hydrosilylation. For this purpose, novel electron‐deficient diazonium salts, highly soluble in nonpolar solvents were synthesized. The SiNCs were functionalized with a variety of alkenes and alkynes at room temperature with short reaction times. 相似文献
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Mojtaba Mirhosseini Moghaddam Dr. Mostafa Baghbanzadeh Dr. Amin Sadeghpour Prof. Dr. Otto Glatter Prof. Dr. C. Oliver Kappe 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(35):11629-11636
In recent years, continuous‐flow/microreactor processing for the preparation of colloidal nanocrystals has received considerable attention. The intrinsic advantages of microfluidic reactors have opened new opportunities for the size‐controlled synthesis of nanocrystals either in the laboratory or on a large scale. Herein, an experimentally simple protocol for the size‐tunable continuous‐flow synthesis of rather monodisperse CdSe quantum dots (QDs) is presented. CdSe QDs are manufactured by using cadmium oleate as cadmium source, selenium dioxide as selenium precursor, and 1‐octadecene as solvent. Exploiting selenium dioxide as selenium source and 1‐octadecene as solvent allows execution of the complete process in open air without any requirement for air‐free manipulations using a glove box or Schlenk line. Continuous‐flow processing is performed with a stainless steel coil of 1.0 mm inner diameter pumping the combined precursor solution through the reactor by applying a standard HPLC pump. The effect of different reaction parameters, such as temperature, residence time, and flow rate, on the properties of the resulting CdSe QDs was investigated. A temperature increase from 240 to 260 °C or an extension of the residence time from 2 to 20 min affords larger nanocrystals (range 3–6 nm) whereas the size distribution does not change significantly. Longer reaction times and higher temperatures result in QDs with lower quantum yields (range 11–28 %). The quality of the synthesized CdSe QDs was confirmed by UV/Vis and photoluminescence spectroscopy, small‐angle X‐ray scattering, and high‐resolution transmission electron microscopy. Finally, the potential of this protocol for large‐scale manufacturing was evaluated and by operating the continuous‐flow process for 87 min it was possible to produce 167 mg of CdSe QDs (with a mean diameter of 4 nm) with a quantum yield of 28 %. 相似文献
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The Influence of Surface Modification on the Photoluminescence of CdTe Quantum Dots: Realization of Bio‐Imaging via Cost‐Effective Polymer 下载免费PDF全文
To impart biocompatibility, stability, and specificity to quantum dots (QDs)—and to reduce their toxicity—it is essential to carry out surface modification. However, most surface‐modification processes are costly, complicated, and time‐consuming. In addition, the modified QDs often have a large size, which leads to easy aggregation in biological environments, making it difficult to excrete them from in vivo systems. To solve these problems, three kinds of conventional polymers, namely, polyvinyl alcohol (PVA, neutral), sodium polystyrene sulfonate (PSS, negative charged), and poly(diallyl dimethyl ammonium chloride) (PDDA, positive charged) were selected to modify the surface of QDs at low cost via a simple process in which the size of the QDs was kept small after modification. The effect of polymer modification on the photoluminescence (PL) properties of the QDs was systematically investigated. High quantum yields (QYs) of 65 % were reached, which is important for the realization of bio‐imaging. Then, the cytotoxicity of CdTe QD–polymer composites was systematically investigated via MTT assay using the Cal27 and HeLa cell lines, especially for high concentrations of QD–polymer composites in vitro. The experimental results showed that the cytotoxicity decreased in the order CdTe‐PDDA>CdTe>CdTe‐PSS>CdTe‐PVA, indicating that PSS and PVA can reduce the toxicity of the QDs. An obvious cytotoxicity of CdTe‐PVA and CdTe‐PSS was present until 120 h for the Cal27 cell line and until 168 h for the HeLa cell line. At last, the Cal27 cell line was selected to realize bio‐imaging using CdTe‐PSS and CdTe‐PVA composites with different emission colors under one excitation wavelength. 相似文献
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Grafting Poly(3‐hexylthiophene) from Silicon Nanocrystal Surfaces: Synthesis and Properties of a Functional Hybrid Material with Direct Interfacial Contact 下载免费PDF全文
Muhammad Amirul Islam Dr. Tapas K. Purkait Dr. Md Hosnay Mobarok Dr. Ignaz M. D. Hoehlein Regina Sinelnikov Dr. Muhammad Iqbal Dr. Doron Azulay Prof. Isaac Balberg Prof. Oded Millo Prof. Dr. Bernhard Rieger Prof. Dr. Jonathan G. C. Veinot 《Angewandte Chemie (International ed. in English)》2016,55(26):7393-7397
Hybrid functional materials (HFMs) comprised of semiconductor nanoparticles and conjugated polymers offer the potential of synergetic photophysical properties. We have developed HFMs based upon silicon nanocrystals (SiNCs) and the conductive polymer poly(3‐hexylthiophene) (SiNC@P3HT) by applying surface‐initiated Kumada catalyst transfer polycondensation (SI‐KCTP). One unique characteristic of the developed SiNC@P3HT is the formation of a direct covalent bonding between SiNCs and P3HT. The presented method for obtaining direct interfacial attachment, which is not accessible using other methods, may allow for the development of materials with efficient electronic communication at the donor–acceptor interfaces. Systematic characterization provides evidence of a core–shell structure, enhanced interfacial electron and/or energy transfer between the P3HT and SiNC components, as well as formation of a type‐II heterostructure. 相似文献
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Hui Du Luying Ma Dr. Xin Wang Yifei Li Maopeng Xu Dr. Xiaoyong Liang Dr. Desui Chen Prof. Yizheng Jin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(44):11298-11302
Solution-processed NiOx thin films have been applied as hole-injection layers (HILs) in quantum-dot light-emitting diodes (QLEDs). The commonly used NiOx HILs are prepared by the precursor-based route, which requires high annealing temperatures of over 275 °C to in situ convert the precursors into oxide films. Such high processing temperatures of NiOx HILs hinder their applications in flexible devices. Herein, we report a low-temperature approach based on Cu-modified NiOx (NiOx-Cu) nanocrystals to prepare HILs. A simple post-synthetic surface-modification step, which anchors the copper agents onto the surfaces of oxide nanocrystals, is developed to improve the electrical conductivity of the low-temperature-processed (135 °C) oxide-nanocrystal thin films. In consequence, QLEDs based on the NiOx-Cu HILs exhibit an external quantum efficiency of 17.5 % and a T95 operational lifetime of ∼2,800 h at an initial brightness of 1,000 cd m−2, meeting the commercialization requirements for display applications. The results shed light on the potential of using NiOx-Cu HILs for realizing high-performance flexible QLEDs. 相似文献
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Nicoleta Joo Séverine Renaudineau Guillaume Delapierre Dr. Gérard Bidan Dr. Lise‐Marie Chamoreau René Thouvenot Dr. Pierre Gouzerh Prof. Dr. Anna Proust Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(17):5043-5051
Organosilyl/‐germyl polyoxotungstate hybrids [PW9O34(tBuSiO)3Ge(CH2)2CO2H]3? ( 1 a ), [PW9O34(tBuSiO)3Ge(CH2)2CONHCH2C?CH]3? ( 2 a ), [PW11O39Ge(CH2)2CO2H]4? ( 3 a ), and [PW11O39Ge(CH2)2CONHCH2C≡CH]4? ( 4 a ) have been prepared as tetrabutylammonium salts and characterized in solution by multinuclear NMR spectroscopy. The crystal structure of (NBu4)3 1 a? H2O has been determined and the electrochemical behavior of 1 a and 2 a has been investigated by cyclic voltammetry. Covalent grafting of 2 a onto an n‐type silicon wafer has been achieved and the electrochemical behavior of the grafted clusters has been investigated. This represents the first example of covalent grafting of Keggin‐type clusters onto a Si surface and a step towards the realization of POM‐based multilevel memory devices. 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(41):12471-12475
Lead‐based perovskite nanocrystals (NCs) have outstanding optical properties and cheap synthesis conferring them a tremendous potential in the field of optoelectronic devices. However, two critical problems are still unresolved and hindering their commercial applications: one is the fact of being lead‐based and the other is the poor stability. Lead‐free all‐inorganic perovskite Cs3Bi2X9 (X=Cl, Br, I) NCs are synthesized with emission wavelength ranging from 400 to 560 nm synthesized by a facile room temperature reaction. The ligand‐free Cs3Bi2Br9 NCs exhibit blue emission with photoluminescence quantum efficiency (PLQE) about 0.2 %. The PLQE can be increased to 4.5 % when extra surfactant (oleic acid) is added during the synthesis processes. This improvement stems from passivation of the fast trapping process (2–20 ps). Notably, the trap states can also be passivated under humid conditions, and the NCs exhibited high stability towards air exposure exceeding 30 days. 相似文献
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Ziqian He Juan He Caicai Zhang Shin‐Tson Wu Yajie Dong 《Chemical record (New York, N.Y.)》2020,20(7):672-681
Metal halide perovskite nanocrystals are emerging as novel optoelectronic materials. Owing to their excellent optical and electronic properties such as tunable band gap, narrow‐band emission and high charge mobility, they are quite promising in various fields including liquid‐crystal display backlighting, solid‐state lighting and other energy conversion applications. However, the intrinsic low formation energy makes them vulnerable to external stimulus, e. g. water, oxygen, heat, etc. Among many methods, swelling‐deswelling microencapsulation emerges as one of the most promising strategies to improve their stability. Herein, recent developments and future research directions in swelling‐deswelling microencapsulation‐enabled ultrastable perovskite?polymer composites are summarized. We believe this strategy has great potential to deliver successful perovskite‐based commercial products for many photonics applications. 相似文献
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Tuning Optical Properties and Photocatalytic Activities of Carbon‐based “Quantum Dots” Through their Surface Groups 下载免费PDF全文
Shengliang Hu 《Chemical record (New York, N.Y.)》2016,16(1):219-230
We report recent progress in tuning optical properties and photocatalytic activities of carbon‐based quantum dots (carbon‐based QDs) through their surface groups. It is increasingly clear that the properties of carbon‐based QDs are more dependent on their surface groups than on their size. The present challenge remains as to how to control the type, number, and conformation of the heterogeneous groups on the surface of carbon‐based QDs when considering their target applications. By reviewing the related achievements, this personal account aims to help us understand the roles different surface groups play in tuning the properties of carbon‐based QDs. A number of significant accomplishments have demonstrated that surface groups possess strong power in engineering electronic structure and controlling photogenerated charge behaviors of carbon‐based QDs. However, effective strategies for modifying carbon‐based QDs with diverse heterogeneous groups are still needed. 相似文献
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Rinki Bhadra Vidya Nand Singh Bodh Raj Mehta Pranayee Datta 《Journal of Dispersion Science and Technology》2013,34(9):1202-1207
ZnO nanocrystals are synthesized using the quenching method. The properties of the grown nanocrystals are studied using ultraviolet-vis spectroscopy, x-ray diffraction, photoluminescence, electron diffraction, energy dispersive x-ray spectroscopy, and high resolution transmission electron microscopy. Current-voltage characteristics of the prepared samples are studied for investigating the possible application of the samples as switch and memristor. 相似文献