Carbon Dot Emission Enhancement in Covalent Complexes with Plasmonic Metal Nanoparticles

Fine-dispersed YGdAG:Ce nanopowders with various degrees of isomorphic substitution of yttrium by gadolinium were synthesized. The structure and luminescent properties were studied by X-ray diffraction, attenuated total reflection Fourier-transform infrared spectroscopy, luminescence spectroscopy and scanning electron microscopy. The possibility of synthesis of YGdAG:Ce nanopowders with a degree of gadolinium substitution up to 60% and nanocrystals with average sizes of 25–30 nm were shown. The red-shift of the cerium luminescence band with an increase in Gd content was studied. The CIE diagram for emission of YGdAG:Ce synthesized by the polymer–salt method shows that the degree 30–40% substitution of Y by Gd is optimal for the fabrication of a white light source based on LED with an emission wavelength of 470 nm.

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“…where A 1,2 and τ 1,2 are the amplitude and luminescence lifetime of each component in biexponential function, respectively [52].…”

Section: Methodsmentioning

confidence: 99%

YAG:Ce Nanophosphors Synthesized by the Polymer–Salt Method for White LEDs with Isomorphic Substitution of Yttrium by Gadolinium

et al. 2023

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Gadolinium-doped carbon dots with long-wavelength emission for dual-modal imaging

Efimova,

Badrieva,

Brui

et al. 2024

J. Opt. Technol.

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Subject of study. This study is focused on luminescent carbon dots derived from o-phenylenediamine and gadolinium chloride or nitrate hexahydrate. Aim of study. The study aims to fabricate long-wavelength photoluminescent gadolinium-doped carbon dots that could function as contrast agents for magnetic resonance imaging. Additionally, the study investigates the impact of the precursor type used on the chemical composition and optical transitions of the resulting nanoparticles. Method. Carbon dots were synthesized using a one-step solvothermal method, and their composition and optical properties were analyzed using spectroscopy methods. Magnetic resonance imaging was conducted using a clinical magnetic resonance imaging scanner with a field strength of 1.5 T. Main results. In this study, two types of carbon dots were synthesized from o-phenylenediamine and gadolinium chloride or nitrate hexahydrate using the solvothermal method. Metal doping, at a concentration sufficient for further investigations, is achieved only when gadolinium chloride is used. Additionally, the presence of gadolinium chloride during the synthesis leads to the formation of luminescent centers within the carbon dots with emission at 600–720 nm and a photoluminescence quantum yield of 6.3%. In contrast, gadolinium nitrate increases the nitrogen content within the o-phenylenediamine-based carbon dots while inhibiting metal doping. The luminescent band with an emission maximum at 550 nm and a photoluminescence quantum yield of 7.4% originates from the o-phenylenediamine derivatives formed within such carbon dots. The study results also show that the gadolinium-doped carbon dots alter the relaxation times during magnetic resonance scanning, and the calculated relaxivity (r1 and r2) values are 6.4 and 38.6L⋅mmol−1⋅s−1, respectively. Thus, the synthesized carbon dots function as positive contrast agents during magnetic resonance scanning. Practical significance. Carbon dots with long-wavelength emission are promising nanoprobes for luminescence imaging. With gadolinium doping, these nanoparticles can also be used as contrast agents during magnetic resonance imaging. Consequently, carbon dots based on o-phenylenediamine and gadolinium chloride hexahydrate can be further utilized as dual-mode nanoprobes for bioimaging.

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Study on the chiroptical properties of carbon dots based on citric acid and formamide with the addition of various chiral molecules

Stepanidenko,

Vedernikova,

Mitroshin

et al. 2024

J. Opt. Technol.

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Subject of study. The study focuses on luminescent carbon nanoparticles, specifically carbon dots, based on citric acid, formamide, and various chiral molecules. Aim of study. The aim is to assess the influence of chiral molecules used in the synthesis of carbon dots on optical transitions in the long-wavelength spectral region and to investigate the mechanism underlying the circular dichroism signal of these nanoparticles. Method. Carbon dot samples were synthesized using two methods: (i) a one-step solvothermal synthesis of carbon dots from citric acid, formamide, and various chiral molecules and (ii) a two-step method involving the solvothermal synthesis of achiral carbon dots from citric acid and formamide, followed by surface treatment with L-cysteine. Absorption and luminescence spectroscopy methods were employed to study the chemical structure and optical properties of the carbon dots. The chiroptical properties of the obtained samples were analyzed using circular dichroism spectroscopy. Main results. The addition of various chiral molecules to a mixture of precursors during one-step synthesis enabled the fabrication of carbon dots with different chemical compositions, including variations in surface groups and types of emission centers in the spectral region of 350–700 nm. The use of L-phenylglycine and L-tryptophan in the one-step synthesis was shown to lead to the formation of nanoparticles with optical transitions in both short- and long-wavelength regions of the spectrum. The addition of L-glutathione during the one-step synthesis resulted in the formation of carbon dots with short-wavelength emission, while the addition of L-cysteine did not alter the emission characteristics of achiral carbon dots based on citric acid and formamide. The optical properties of the chiral carbon dots obtained using the two-step synthesis method with L-cysteine remained unchanged compared with those of the achiral carbon dots synthesized from citric acid and formamide. The circular dichroism spectra of all the samples showed a signal at ∼250nm, which was attributed to the derivatives of the chiral precursors attached to the surface of the nanoparticles, irrespective of the preparation method. Practical significance. Chiral carbon dots hold promise in biomedicine as sensors, luminescent biomarkers, and other applications due to their biocompatibility and non-toxicity. The results obtained in this work will serve as a foundation for the further fabrication and investigation of chiral carbon nanoparticles with long-wavelength luminescence.

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Carbon Dot Emission Enhancement in Covalent Complexes with Plasmonic Metal Nanoparticles

Cited by 3 publications

References 46 publications

YAG:Ce Nanophosphors Synthesized by the Polymer–Salt Method for White LEDs with Isomorphic Substitution of Yttrium by Gadolinium

YAG:Ce Nanophosphors Synthesized by the Polymer–Salt Method for White LEDs with Isomorphic Substitution of Yttrium by Gadolinium

Gadolinium-doped carbon dots with long-wavelength emission for dual-modal imaging

Study on the chiroptical properties of carbon dots based on citric acid and formamide with the addition of various chiral molecules

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