Nanomaterials

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16 pages, 5203 KiB

Open AccessArticle

Hybrid Sol–Gel Matrices Doped with Colorimetric/Fluorimetric Imidazole Derivatives

by Rui P. C. L. Sousa, Rita B. Figueira, Bárbara R. Gomes, Sara Sousa, R. Cristina M. Ferreira, Susana P. G. Costa and M. Manuela M. Raposo

Nanomaterials 2021, 11(12), 3401; https://doi.org/10.3390/nano11123401 - 15 Dec 2021

Cited by 4 | Viewed by 2088

Abstract

Organic–inorganic hybrids (OIH) are materials that can be easily synthesized by the sol–gel method and combine the advantages of organic and inorganic moieties within a single polymeric matrix. Imidazole derivatives are versatile organic compounds that can change their optical properties with the variation [...] Read more.

Organic–inorganic hybrids (OIH) are materials that can be easily synthesized by the sol–gel method and combine the advantages of organic and inorganic moieties within a single polymeric matrix. Imidazole derivatives are versatile organic compounds that can change their optical properties with the variation of pH due to the protonation or deprotonation of the nitrogen atoms. This work reports the preparation of different OIHs doped with different contents of two imidazole compounds (3a,b). The obtained materials were characterized structurally by FTIR, and the dielectric properties were studied by electrochemical impedance spectroscopy. The optical properties were studied by UV-Vis absorption and fluorescence spectroscopies. The FTIR analysis showed that the presence of the imidazole does not change the structural properties of the matrices. The normalized resistance values obtained for the doped matrices ranged between 8.57 and 9.32 Ω cm², all being higher than the undoped matrix. The σ ranged between 9.49 and 10.28 S cm⁻¹, being all higher than the pure OIH samples. Compound 3a showed a maximum absorption peak at 390 nm, which is present in the OIH spectra, proving the presence of the compound. In the case of compound 3b, a maximum absorption wavelength at 412 nm was found, and the compound peak was not clear, which may indicate that an interaction between the compound and the matrix occurred. A synergetic effect between the intrinsic emission of the matrix and the fluorescence of 3a is found on the OIH-doped matrices. Full article

(This article belongs to the Special Issue Luminescent Nanomaterials and Their Applications)

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13 pages, 2317 KiB

Open AccessArticle

The Influence of Aryl Substituents on the Supramolecular Structures and Photoluminescence of Cyclic Trinuclear Pyrazolato Copper(I) Complexes

by Kiyoshi Fujisawa, Mai Saotome, Yoko Ishikawa and David James Young

Nanomaterials 2021, 11(11), 3101; https://doi.org/10.3390/nano11113101 - 17 Nov 2021

Cited by 1 | Viewed by 1411

Abstract

Cyclic trinuclear complexes with group 11 metal(I) ions are fascinating and important to coordination chemistry. One of the ligands known to form these cyclic trinuclear complexes is pyrazolate, which is a bridging ligand that coordinates many transition metal ions in a Npz–M–Npz linear [...] Read more.

Cyclic trinuclear complexes with group 11 metal(I) ions are fascinating and important to coordination chemistry. One of the ligands known to form these cyclic trinuclear complexes is pyrazolate, which is a bridging ligand that coordinates many transition metal ions in a Npz–M–Npz linear mode (Npz = pyrazolyl nitrogen atom). In these group 11 metal(I) ions, copper is the most abundant metal. Therefore, polynuclear copper(I) complexes are very important in this field. The cyclic trinuclear copper(I) complex [Cu(3,5-Ph₂pz)]₃ (3,5-Ph₂pz^– = 3,5-diphenyl-1-pyrazolate anion) was reported in 1988 as a landmark complex, but its photoluminescence properties have hitherto not been described. In this study, we report the photoluminescence and two different polymorphs of [Cu(3,5-Ph₂pz)]₃ and its derivative [Cu(3-Me-5-Phpz)]₃ (3-Me-5-Phpz^– = 3-metyl-5-phenyl-1-pyrazale anion). The substituents in [Cu(3-Me-5-Phpz)]₃ cause smaller distortions in the solid-state structure and a red-shift in photoluminescence due to the presence of intermolecular cuprophilic interactions. Full article

(This article belongs to the Special Issue Luminescent Nanomaterials and Their Applications)

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22 pages, 9696 KiB

Open AccessArticle

Fluorescence Based Comparative Sensing Behavior of the Nano-Composites of SiO₂ and TiO₂ towards Toxic Hg²⁺ Ions

by Ekta and Divya Utreja

Nanomaterials 2021, 11(11), 3082; https://doi.org/10.3390/nano11113082 - 15 Nov 2021

Cited by 2 | Viewed by 1652

Abstract

We have synthesized sulfonamide based nano-composites of SiO₂ and TiO₂ for selective and sensitive determination of toxic metal ion Hg²⁺ in aqueous medium. Nano-composites (11) and (12) were morphologically characterized with FT-IR, solid state NMR, UV-vis, FE SEM, TEM, EDX, [...] Read more.

We have synthesized sulfonamide based nano-composites of SiO₂ and TiO₂ for selective and sensitive determination of toxic metal ion Hg²⁺ in aqueous medium. Nano-composites (11) and (12) were morphologically characterized with FT-IR, solid state NMR, UV-vis, FE SEM, TEM, EDX, BET, pXRD and elemental analysis. The comparative sensing behavior, pH effect and sensor concentrations were carried out with fluorescence signaling on spectrofluorometer and nano-composites (11) and (12), both were evaluated as “turn-on” fluorescence detector for the toxic Hg²⁺ ions. The LODs were calculated to be 41.2 and 18.8 nM, respectively of nano-composites (11) and (12). The detection limit of TiO₂ based nano-composites was found comparatively lower than the SiO₂ based nano-composites. Full article

(This article belongs to the Special Issue Luminescent Nanomaterials and Their Applications)

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9 pages, 1854 KiB

Open AccessArticle

Precise Control of Green to Blue Emission of Halide Perovskite Nanocrystals Using Terbium Chloride as Chlorine Source

by Wenqiang Deng, Ting Fan, Jiantao Lü, Jingling Li, Tingting Deng and Mingqi Liu

Nanomaterials 2021, 11(9), 2390; https://doi.org/10.3390/nano11092390 - 14 Sep 2021

Viewed by 1642

Abstract

CsPbCl_xBr_3-x nanocrystals were prepared by ligand-assisted deposition at room temperature, and their wavelength was accurately adjusted by doping TbCl₃. The synthesized nanocrystals were monoclinic and the morphology was almost unchanged after doping. The fluorescence emission of CsPbCl_x [...] Read more.

CsPbCl_xBr_3-x nanocrystals were prepared by ligand-assisted deposition at room temperature, and their wavelength was accurately adjusted by doping TbCl₃. The synthesized nanocrystals were monoclinic and the morphology was almost unchanged after doping. The fluorescence emission of CsPbCl_xBr_3-x nanocrystals was easily controlled from green to blue by adjusting the amount of TbCl₃, which realizes the continuous and accurate spectral regulation in the range of green to blue. This method provides a new scheme for fast anion exchange of all-inorganic perovskite nanocrystals in an open environment at room temperature. Full article

(This article belongs to the Special Issue Luminescent Nanomaterials and Their Applications)

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13 pages, 20942 KiB

Open AccessArticle

On the Role of Cs₄PbBr₆ Phase in the Luminescence Performance of Bright CsPbBr₃ Nanocrystals

by Kateřina Děcká, Adéla Suchá, Jan Král, Ivo Jakubec, Martin Nikl, Vítězslav Jarý, Vladimir Babin, Eva Mihóková and Václav Čuba

Nanomaterials 2021, 11(8), 1935; https://doi.org/10.3390/nano11081935 - 27 Jul 2021

Cited by 8 | Viewed by 3006

Abstract

CsPbBr₃ nanocrystals have been identified as a highly promising material for various optoelectronic applications. However, they tend to coexist with Cs₄PbBr₆ phase when the reaction conditions are not controlled carefully. It is therefore imperative to understand how the presence [...] Read more.

CsPbBr₃ nanocrystals have been identified as a highly promising material for various optoelectronic applications. However, they tend to coexist with Cs₄PbBr₆ phase when the reaction conditions are not controlled carefully. It is therefore imperative to understand how the presence of this phase affects the luminescence performance of CsPbBr₃ nanocrystals_. We synthesized a mixed CsPbBr₃-Cs₄PbBr₆ sample, and compared its photo- and radioluminescence properties, including timing characteristics, to the performance of pure CsPbBr₃ nanocrystals. The possibility of energy transfer between the two phases was also explored. We demonstrated that the presence of Cs₄PbBr₆ causes significant drop in radioluminescence intensity of CsPbBr₃ nanocrystals, which can limit possible future applications of Cs₄PbBr₆-CsPbBr₃ mixtures or composites as scintillation detectors. Full article

(This article belongs to the Special Issue Luminescent Nanomaterials and Their Applications)

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17 pages, 30041 KiB

Open AccessEditor’s ChoiceArticle

Characterization of Plasmonic Scattering, Luminescent Down-Shifting, and Metal-Enhanced Fluorescence and Applications on Silicon Solar Cells

by Wen-Jeng Ho, Jheng-Jie Liu and Jhih-Ciang Chen

Nanomaterials 2021, 11(4), 1013; https://doi.org/10.3390/nano11041013 - 15 Apr 2021

Cited by 4 | Viewed by 1989

Abstract

This paper studied characterized the plasmonic effects of silver nanoparticles (Ag-NPs), the luminescent down-shifting of Eu-doped phosphor particles, and the metal-enhanced fluorescence (MEF) achieved by combining the two processes to enhance the conversion efficiency of silicon solar cells. We obtained measurements of photoluminescence [...] Read more.

This paper studied characterized the plasmonic effects of silver nanoparticles (Ag-NPs), the luminescent down-shifting of Eu-doped phosphor particles, and the metal-enhanced fluorescence (MEF) achieved by combining the two processes to enhance the conversion efficiency of silicon solar cells. We obtained measurements of photoluminescence (PL) and external quantum efficiency (EQE) at room temperature to determine whether the fluorescence emissions intensity of Eu-doped phosphor was enhanced or quenched by excitation induced via surface plasmon resonance (SPR). Overall, fluorescence intensity was enhanced when the fluorescence emission band was strongly coupled to the SPR band of Ag-NPs and the two particles were separated by a suitable distance. We observed a 1.125× increase in PL fluorescence intensity at a wavelength of 514 nm and a 7.05% improvement in EQE (from 57.96% to 62.05%) attributable to MEF effects. The combined effects led to a 26.02% increase in conversion efficiency (from 10.23% to 12.89%) in the cell with spacer/NPs/SOG-phosphors and a 22.09% increase (from 10.23% to 12.48%) in the cell with spacer/SOG-phosphors, compared to the bare solar cell. This corresponds to an impressive 0.85% increase in absolute efficiency (from 12.04% to 12.89%), compared to the cell with only spacer/SOG. Full article

(This article belongs to the Special Issue Luminescent Nanomaterials and Their Applications)

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9 pages, 3688 KiB

Open AccessArticle

O-Band Emitting InAs Quantum Dots Grown by MOCVD on a 300 mm Ge-Buffered Si (001) Substrate

by Oumaima Abouzaid, Hussein Mehdi, Mickael Martin, Jérémy Moeyaert, Bassem Salem, Sylvain David, Abdelkader Souifi, Nicolas Chauvin, Jean-Michel Hartmann, Bouraoui Ilahi, Denis Morris, Ali Ahaitouf, Abdelaziz Ahaitouf and Thierry Baron

Nanomaterials 2020, 10(12), 2450; https://doi.org/10.3390/nano10122450 - 07 Dec 2020

Cited by 6 | Viewed by 2169

Abstract

The epitaxy of III-V semiconductors on silicon substrates remains challenging because of lattice parameter and material polarity differences. In this work, we report on the Metal Organic Chemical Vapor Deposition (MOCVD) and characterization of InAs/GaAs Quantum Dots (QDs) epitaxially grown on quasi-nominal 300 [...] Read more.

The epitaxy of III-V semiconductors on silicon substrates remains challenging because of lattice parameter and material polarity differences. In this work, we report on the Metal Organic Chemical Vapor Deposition (MOCVD) and characterization of InAs/GaAs Quantum Dots (QDs) epitaxially grown on quasi-nominal 300 mm Ge/Si(001) and GaAs(001) substrates. QD properties were studied by Atomic Force Microscopy (AFM) and Photoluminescence (PL) spectroscopy. A wafer level µPL mapping of the entire 300 mm Ge/Si substrate shows the homogeneity of the three-stacked InAs QDs emitting at 1.30 ± 0.04 µm at room temperature. The correlation between PL spectroscopy and numerical modeling revealed, in accordance with transmission electron microscopy images, that buried QDs had a truncated pyramidal shape with base sides and heights around 29 and 4 nm, respectively. InAs QDs on Ge/Si substrate had the same shape as QDs on GaAs substrates, with a slightly increased size and reduced luminescence intensity. Our results suggest that 1.3 μm emitting InAs QDs quantum dots can be successfully grown on CMOS compatible Ge/Si substrates. Full article

(This article belongs to the Special Issue Luminescent Nanomaterials and Their Applications)

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11 pages, 2752 KiB

Open AccessArticle

Femtosecond Pulse Ablation Assisted Mg-ZnO Nanoparticles for UV-Only Emission

by Anubhab Sahoo, Muralidhar Miryala, Tejendra Dixit, Alicja Klimkowicz, Bellarmine Francis, Masato Murakami, Mamidanna Sri Ramachandra Rao and Sivarama Krishnan

Nanomaterials 2020, 10(7), 1326; https://doi.org/10.3390/nano10071326 - 06 Jul 2020

Cited by 6 | Viewed by 2321

Abstract

The need for improved UV emitting luminescent materials underscored by applications in optical communications, sterilization and medical technologies is often addressed by wide bandgap semiconducting oxides. Among these, the Mg-doped ZnO system is of particular interest as it offers the opportunity to tune [...] Read more.

The need for improved UV emitting luminescent materials underscored by applications in optical communications, sterilization and medical technologies is often addressed by wide bandgap semiconducting oxides. Among these, the Mg-doped ZnO system is of particular interest as it offers the opportunity to tune the UV emission by engineering its bandgap via doping control. However, both the doped system and its pristine congener, ZnO, suffer from being highly prone to parasitic defect level emissions, compromising their efficiency as light emitters in the ultraviolet region. Here, employing the process of femtosecond pulsed laser ablation in a liquid (fs-PLAL), we demonstrate the systematic control of enhanced UV-only emission in Mg-doped ZnO nanoparticles using both photoluminescence and cathodoluminescence spectroscopies. The ratio of luminescence intensities corresponding to near band edge emission to defect level emission was found to be six-times higher in Mg-doped ZnO nanoparticles as compared to pristine ZnO. Insights from UV-visible absorption and Raman analysis also reaffirm this defect suppression. This work provides a simple and effective single-step methodology to achieve UV-emission and mitigation of defect emissions in the Mg-doped ZnO system. This is a significant step forward in its deployment for UV emitting optoelectronic devices. Full article

(This article belongs to the Special Issue Luminescent Nanomaterials and Their Applications)

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