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Host Sensitized Lanthanide Photoluminescence from Post-synthetically Modified Semiconductor Nanoparticles Depends on Reactant Identity
摘要： This work investigates the photoluminescence characteristics where cadmium selenide (CdSe) and zinc sulfide (ZnS) nanoparticles are treated post-synthetically by the trivalent lanthanide cations (Ln3+) [Ln = Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb] separately to form either CdSe/Ln or ZnS/Ln nanoparticles. Host sensitized Ln3+ emission was found to be present only in CdSe/Eu, CdSe/Tb, ZnS/Eu, ZnS/Tb and ZnS/Yb nanoparticles. In all the cases tuning of emission of the nanoparticles has been observed, irrespective of the presence or absence of host sensitization. The elemental compositions of CdSe and ZnS nanoparticles upon post-synthetic treatment show a remarkable difference. Incorporation of lanthanides in the nanoparticles is evident with significant alteration in the anionic content, and complete cation exchange of either Cd2+ or Zn2+ by Ln3+ has not been detected; as evaluated from energy dispersive X-ray spectroscopy. Further evaluation on this comes from considering thermodynamic parameters of inter cation interaction. In cases where the host sensitized Ln3+ emission have been observed, luminescence lifetime measurements reveal significant protection of Ln3+ in the nanoparticles. Noticeable difference in photophysical properties for a given Ln3+ has been realized in the two hosts. The photophysical observations have been rationalized using (i) charge trapping mediated host sensitized dopant emission, (ii) autoionization of excited electrons, and (iii) environment induced photoluminescence quenching. The post-synthetic modification discussed in the present work provides an easy and less synthetically demanding room temperature based protocol to avail lanthanide incorporated (doped) semiconductor nanoparticles that can potentially use the unique emission properties of the lanthanide cations.
关键词： Semiconductor Nanoparticles,Host Sensitization,Trivalent Lanthanides,Photoluminescence,Post-synthetic Modification
更新于2025-09-23 15:23:52
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Solvation of quantum dots in 1-alkyl-1-methylpyrrolidinium ionic liquids: toward stably luminescent composites
摘要： CdTe nanoparticles capped with a cationic thiolate ligand were stably dispersed in ionic liquids, 1-alkyl-1-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)amides with an alkyl group of n-propyl, butyl and octyl-chain, and in an ionic plastic crystal, 1-ethyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide. Dispersion behavior of CdTe nanoparticles in these ionic media was evaluated, in which the solvation of nanoparticles by the ionic components was particularly interested. The ionic media showed alkyl-chain length-dependent solvation behavior, which was suggested by the thermal analysis of nanocomposites. The longer alkyl-chains led to the greater decrease in the thermal melting enthalpy of ionic media with the introduction of nanoparticles. The ionic liquid with an octyl-chain, which is considered to form a thicker solvation layer, afforded better emission durability of CdTe nanoparticles compared to the ionic liquid with a shorter alkyl chain.
关键词： ionic liquid,photoluminescence,semiconductor,nanoparticles,solvation
更新于2025-09-23 15:21:01
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Handbook of Nanoparticles || Laser Fabrication of Nanoparticles
摘要： Lasers are widely used for material processing (cutting, drilling, cleaning, ?lm deposition, etc.). A recent application is for nanoparticle fabrication. Pulsed laser ablation is by far the fastest and clean method to fabricate nanoparticles directly from bulk targets. For this purpose, target ablation is performed in vacuum, in gas atmosphere, or in liquids with fast (nanosecond) and ultrafast (picosecond, femtosecond) laser pulses. Mostly metal but also semiconductor and ceramic nanoparticles were fabricated. In the early stage of this technique, the main problem was the large size distribution of the produced nanoparticles. But the possibility to independently handle laser pulse characteristics (wavelength, power density, pulse duration, etc.) and the accurate control and optimization of the ambient parameters is leading to an ef?cient tailoring of the nanoparticle size, due also to helpful theoretical and numerical models. A review is presented of the most important studies and of the obtained results.
关键词： laser ablation in liquids,ps-laser ablation,oxide nanoparticles,fs-laser ablation,metal nanoparticles,semiconductor nanoparticles,ns-laser ablation
更新于2025-09-23 15:19:57
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Spectroscopy and Dynamics of Single Molecules || Quantum dots in single molecule spectroscopy
摘要： In the early-to-mid 1990s, fluorescence from single organic dye molecules, single fluorescent proteins (FPs) and single direct-bandgap semiconductor nanoparticles (also called quantum dots, QDs) were separately observed. There are other luminescent nanomaterial species which have also sometimes been observed (and utilized) at the single particle level, such as small metal clusters, organic polymers/nanomaterials, and lanthanide/actinide ion-doped upconverting nanocrystals, some of which have also been called quantum dots (albeit somewhat inconsistently) in the literature. However, in this book chapter, the primary focus will be on direct-bandgap semiconductor nanoparticles and so we will use the term quantum dots to refer to this specific class of fluorescent nanoparticle. The key criterion for such single molecule/nanoparticle observations (beyond the equipment perspective) is the “brightness” of the fluorophore – the product of extinction coefficient (ε) and the photoluminescence quantum yield (PL QY). It is possible to overcome a low extinction coefficient by increasing the excitation power. However, the background also increases with excitation power so, at some point, the background fluorescent signal may dominate over the signal from the single molecule or particle. Organic dye molecules and fluorescent proteins usually combine a moderate extinction coefficient at their peak absorbance wavelength (λmax) with a moderate-to-high PL QY (with some common dye molecules reaching unity PL QY). QDs exhibit a higher extinction coefficient at or above their band gap energy than organic dyes and FPs do at their λmax (approx. 3–10 fold higher). In the 1990s, PL QYs of QDs were usually below 50%, but nowadays can approach unity, meaning that QDs are often significantly brighter than organic dyes and FPs under similar experimental conditions. This fact, combined with their much higher photostability, narrower emission spectra and broad excitation bands have led to QDs becoming somewhat of a competitor to organic dyes and FPs for certain applications. Of course, the advantages of QDs come with some disadvantages that still render organic dyes and FPs superior for other applications. In particular, the size of QDs, while they can be made to a size comparable to FPs, are larger than organic dyes. Moreover, QDs are rarely monovalent/monofunctional, meaning that conjugates of 1:1 label: target are much more difficult to achieve with QDs than with organic dyes or FPs. Finally, the most common QD compositions contain heavy elements (usually Cd, although some may contain Hg and Pb), and much more care must be taken in their handling and disposal. This latter disadvantage was first mitigated by “shelling” the QD with a lower toxicity material (usually ZnS) and, more recently, by replacing the toxic elements with less toxic ones, such as In, Cu and/or Ag.
关键词： quantum dots,single molecule spectroscopy,semiconductor nanoparticles,photoluminescence,fluorescence
更新于2025-09-19 17:13:59
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Nanotechnology in Water and Wastewater Treatment || Application of Semiconductor Nanoparticles for Removal of Organic Pollutants or Dyes From Wastewater
摘要： Increasing demand and shortage of pure water sources due to the rapid development of industrialization, population growth and long-term droughts have become an issue world-wide. Industrial growth produces a great variety of organic products and frequently these substances are complex to degrade. Industrial wastewater contains various chemicals especially synthetic dyes. Example, Textile industry generate large amount of wastewater derived to different processes of color impregnation in textile fibers, which has a great amount of detergents, dyes, microfiber (cellulose, wool, and synthetic fibers), and inorganic salts. This residual water, with great load pollutants, generates the contaminations of natural waters bodies. Now a day, more than 50% of dyes used in the textile industry are monoazo, diazo, and triazo dyes, considering their chemical stability (recalcitrant) and negative influence on the ecological systems, the regulations of the removal color in the factory effluent is a current issue of discussion all over the world. The presence of even very low concentrations of dyes in effluent is highly visible and degradation products of these textile dyes are often carcinogenic. These effluent wastewaters have been recognized to have high color, high BOD and COD load, as well as high dissolve organic matter (DOM) concentration. Dyes are aromatic compounds which can absorb light in the visible wavelengths range (400–700 nm). The dye molecule is a combination of a chromophore which is a part of the molecule that can absorb light, that is, the color-absorbing coordination group and a conjugated system, and a structure with alternating double and single bonds. Chromophores are containing C=C and C=O (carbonyl), and azo group -N=N- or nitro group (-NO2). A complex mixture containing various organic materials, including carbohydrates or polysaccharides, amino acids or peptides or proteins, lipids, humic substances, and anthropogenic organic pollutants is known as Dissolved organic matter (DOM). It plays critical roles both in drinking water (DWTPs) and wastewater treatment plants (WWTPs) in determining the treatment performance and the distributed water quality and it is found in everywhere. The presence of DOM not only affects the current discharge standards, but also presents significant challenges in wastewater restoration.
关键词： Wastewater,ZnO,Dyes,Fe2O3,Photocatalysis,Semiconductor Nanoparticles,Organic Pollutants,TiO2
更新于2025-09-10 09:29:36
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The effect of manganese doping on structural, optical, and photocatalytic activity of zinc oxide nanoparticles
摘要： In this work, polyethylene glycol-6000 (PEG-6000) capped ZnO nanoparticles (NPs) were synthesized by doping with varying levels of Mn (0, 1, 2, 3, and 4 wt.%; 0% implies no doping). The crystalline sizes of the hexagonal wurtzite-structured nanoparticles, when measured with (4%) and without Mn doping (0%), were 30 and 28 nm, respectively. The Mn doping led to a shift of the ZnO optical band gap from 3.36 to 3.51 eV. The Mn2+ ions from the doping agent caused tail states in the absorbance spectrum of ZnO NPs, allowing them to be used as effectual UV photocatalysts for the degradation of organic contaminants (e.g., methyl orange (MO), methylene blue (MB), and congo red (CR)). This effect was optimized when doped with 4% Mn. When comparing 0 and 4% Mn doping, the degradation efficiency of the three contaminants was approximately 87/93.5 (MO), 85/88 (MB), and 86/93 (CR)%, respectively. Accordingly, Mn doping on ZnO NPs was found to significantly enhance their photo-degradation efficiency.
关键词： Mn-ZnO,photocatalytic degradation,organic contaminants,UV irradiation,semiconductor nanoparticles
更新于2025-09-10 09:29:36