Luminescence Spectroscopy Studies Research Articles

Synthesis and functionalization of red-emissive carbon dots towards sensing of copper(II) and ATP in aqueous media

Red-emissive carbon dots, RCDs, were prepared in a bottom-up approach, from citric acid and urea, through a single solvothermal step, which were posteriorly surface-functionalized with di-(2-picolyl)amine (DPA) groups. The functionalized RCDs, henceforth named CD1, were analyzed through high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), dynamic light-scattering (DLS) and infrared spectroscopy (FTIR), and were found to be spherical, with diameter of circa 4 nm. UV-Vis and luminescence spectroscopic studies showed that CD1 display an absorption maximum at 550 nm, with emission maxima at around 640 nm. Fluorescence measurements indicated that Cu(II) induces the strongest changes in the emission of CD1 among eleven investigated metal ions, with a full quenching effect being observed. Further addition of an anionic species, adenosine 5-triphosphate (ATP), resulted in a recovery of the luminescence, which suggests that ATP is capable of sequestering metal ions from the surface of CD1. These results highlight the potential of simple and easy-to-make carbon nanomaterials as sensors for ions in aqueous media.

On the potential of Transparent Rare-Earth-Free ZnAl2O4 Ceramics targeted at the UV-C to UV-B emission

Materials capable of emitting in the ultraviolet UV-C to UV-B spectral range have received considerable attention due to their potential applications in biophotonics, plant lighting, optical cleaning, sterilization, and disinfection. However, progress in the development of phosphors that emit in this short-wavelength range has been relatively sluggish. Most UV-C phosphors developed to date are based on hosts doped with the rare-earth cation Pr3+ due to its bright UV luminescence originating from the 4f15d1 → 4f2 interconfigurational transitions. In this study, we explore how the UV emission can be tailored to different wavelength ranges by developing rare-earth-free materials. Specifically, we demonstrate that UV-C to UV-B emission can be achieved in transparent ZnAl2O4 – based ceramics. For the first time, such transparent ceramics have been successfully produced with the help of reactive spark plasma sintering with SiO2 or LiF additives, which modified the process of grain growth resulting in an increase in the average grain size from 250 nm to 4 µm. Moreover, these additives also improved the optical transmission properties, with in-line transmission measurements at a wavelength of 550 nm reaching values of 50 % and nearly 65 % in the infrared region. Depending on the addition of SiO2 and LiF, the excitation by photons with energy exceeding 6.2 eV has generated the deep UV emission peaks in the range from 230 to 300 nm. Based on the analysis of the results of luminescence spectroscopy and EPR studies, the observed UV-C emission is suggested to originate from the excitons localised near oxygen vacancies. The number of vacancies is the highest in undoped ZnAl2O4 ceramics, whereas adding SiO2 and LiF suppresses their number and modifies their local environment due to changes in charge compensation, which in turn allows tuning the spectral position of the UV-C band. The quantum yield of the UV-C emission reached 5 % for undoped ZnAl2O4 ceramics. The sintered ZnAl2O4 transparent ceramic shows a versatile solution for next-generation rare-earth-free deep-UV devices.

Dependence of oxygen impurity concentration in AlN on the surface roughness during growth

In the cathode luminescence spectroscopic study of AlN thin films grown on c-plane sapphire, we found that the luminescence of 3–4 eV is correlated with O impurities, and it is first enhanced and then weakened with the increase in the temperature. The results of an SIMS test show that the concentration of O impurities in the samples is weakly correlated with the growth conditions but strongly correlated with the surface roughness of the samples at the time of growth. The rougher surface exposes more crystalline plane to the growth environment and different crystalline planes have different absorption capacities for O impurities, leading to an inhomogeneous distribution of O impurities in AlN. This inhomogeneous distribution results in a specific variation in the luminescence intensity of O impurities with temperature.

Synthesis, characterization, and anticancer activity of some mononuclear ruthenium(II) compounds

Mononuclear Ru-based compounds cis-RuII(dppm)2Cl2 (1) and trans-RuII(dppe)2Cl2 (4) were synthesized by treatment of RuIICl2(DMSO)4 with dppm or dppe, respectively (dppm = bis(diphenylphosphino) methane, dppe = 1,2-bis(diphenylphosphino) ethane, DMSO = dimethyl sulfoxide). Mononuclear Ru-based compounds trans-RuII(dppm)2Cl2 (2) and cis-RuII(dppe)2Cl2 (3) were obtained by reaction of RuIICl2(PPh3)3 with dppm or dppe, separately. These two pair of cis–trans isomers, cis/trans-RuII(dppm)2Cl2 and cis/trans-RuII(dppe)2Cl2, were characterized by electronic absorption spectra, infrared, elemental analysis, 1H NMR, 13C NMR, 31P NMR, and single-crystal X-ray diffraction analysis. Both the crystal structure data and electronic absorption spectra indicate that the cis-isomer is a more thermodynamically stable structure and has lower energy than the trans-isomer. The luminescence spectroscopic study and relative cell viability of 1–4 on HeLa cancer cells has been investigated.

The effect of the CH3NH3PbClxI3-x perovskite layer thickness and grain size on its electrophysical and optical properties

Lead halide perovskite CH3NH3PbClxI3-x thin films are widely used as photoactive layers in perovskite solar cells. CH3NH3PbClxI3-x is a low band gap semiconductor with a broad absorption spectrum and a high conductivity showing excellent compatibility with exciting hole and electron selective layers in terms of electronic energy alignment, which provide efficient charge generation, separation and transport in perovskite solar cells. In this paper, CH3NH3PbClxI3-x layers were deposited on the TiO2 surface by one step spin-coating technique from a methylammonium iodide (MAI) and lead chloride (PbCl2) solution. To prepare the perovskite solution, PbCl2 (Sigma-Aldrich) 230 mg of PbCl2 and 394 mg of MAI were dissolved in 1 ml of N, N-Dimethylformamide (Sigma-Aldrich) solvent. As expected, the elevation of the spin-coating rate resulted in CH3NH3PbClxI3-x thickness reduction, which should lead to a decrease in the R3 resistance in CH3NH3PbClxI3-x. However, the impedance spectroscopy revealed that with thickness reduction from 955 nm to 753 nm, the R3 resistance of CH3NH3PbClxI3-x declines from about 2590 Ώ to 2258 Ώ reaching the minimum value at 505 nm. The further decrease in CH3NH3PbClxI3-x thickness increased CH3NH3PbClxI3-x film resistance. The study of CH3NH3PbClxI3-x absorbance and luminescence spectra showed that the change in CH3NH3PbClxI3-x defect density occurred, which explains the decrease in CH3NH3PbClxI3-x resistance. According to the absorbance and luminescence spectroscopy study, the CH3NH3PbClxI3-x thickness reduction led to a decrease in the density of interstitial CH3NH3PbClxI3-x+ defects. CH3NH3PbClxI3-x+ species form deep levels trapping free electrons and as a result, increasing CH3NH3PbClxI3-x resistance. The PSCs based on a 505 nm thick CH3NH3PbClxI3-x layer showed the highest performance with the improved short current density and fill factor. The champion device had a power conversion efficiency of 9.92 %.

Molecular layer deposition to grow a luminescent metalorganic monolayer on inorganic substrate: Breaking monopoly of solution routes to self-assembled monolayer

A gas-phase route such as molecular layer deposition has been applied for the first time to create a monolayer of metalorganic Eu(III) molecules on NiO oxide layer. The surface of the as-deposited NiO layer is activated using H2O/O2 vapors, and then functionalized by anchoring molecules of the Eu complex working at different temperatures to favor the chemisorption process. The effects of the activation process and of the MLD temperature on the chemisorption of the Eu complex were evaluated through in-depth X-ray photoelectron and luminescence spectroscopy studies. These analyses allowed to define the stoichiometry of the Eu moiety chemisorbed on the surface and the optimization of an impressive strategy to the synthesis of hybrid metalorganic/inorganic systems. The hybrid system's luminescence properties have proved the monolayer's energy conversion phenomena and produced further information about the local environment around the Eu(III) anchored as a complex on the NiO surface.

Fast response 4f15d1→4f2 emission and host-to-impurity energy transfer in Pr3+ doped Na3LuSi3O9 double salt silicate

Understanding of host-to-impurity energy transfer process is crucial for the development of efficient and fast response scintillator materials. In this work, Pr3+ doped Na3LuSi3O9 (NLS) double salt silicate has been successfully synthesized using a high temperature solid-state reaction method and further comprehensively characterized by means of XRD measurements, crystal structure refinement, luminescence spectroscopic and time-domain study upon VUV-UV and X-ray synchrotron excitation, and thermally stimulated luminescence (TSL) study. Based on these results a model of host to Pr3+ 4f15d1 and 4f2 has been proposed. It has been demonstrated that NLS:Pr3+ has a good potential for fast response scintillator applications due to the presence of an efficient energy transfer from host electronic excitations to Pr3+ 4f15d1 states. The Pr3+ 4f15d1→4f2 emission reveals a good thermal stability and is characterized by a lifetime of about 16 ns. Upon pulse X-ray excitation the main fast decay component is accompanied by slower one with lifetime of about 64 ns that is ascribed to the presence of shallow traps which retrap carriers and cause appearance of delayed recombination. Parameters for the corresponding traps have been calculated based on the TSL glow curve analysis.

The complexation of lanthanides by glycolamide extractants: Evidences from electronic spectroscopy and DFT calculations

The extraction of trivalent metal ions (Nd and Eu) in N,N,N’,N’-tetraoctyldiglycolamide (TODGA) was compared with N,N-di-octyl-2-hydroxyacetamide (DOHyA), a monoglycolamide derivative of TODGA. The studies based on UV–visible spectroscopy showed the differences in Nd(III) ion complexation for the extractants in both polar and non-polar diluents. n-Dodecane modified with 5 vol% 1-octanol was employed as diluent for extraction studies with TODGA, while DOHyA was studied with no modifiers in n-Dodecane. Time resolved luminescence spectroscopy studies of the Eu(III) extracted organic phases showed strong complexation of metal ion with both the extractants. The co-extraction of water in DOHyA solvent phase during Eu(III) extraction from nitric acid medium was found to be more as compared to TODGA. The better solubilization of water in DOHyA solvent was substantiated by DFT analysis of the optimized electronic structures of Eu-DMHyA (dimethyl hydroxyacetamide) and Eu-TMDGA (tetramethyldiglycolamide) complexes.

A Novel Method for the Synthesis of MOF-199 for Sensing and Photocatalytic Applications.

Multifunctional Cu (II)-based Metal Organic Framework (MOF) [Cu3(BTC)2] has been synthesized by a facile electrochemical method. Crystallographic and morphological characterizations of synthesized MOF have been done using Powder X-ray Diffractometer and Scanning Electron Microscope (SEM), respectively, whereas Fourier Transform Infrared Spectroscopy (FT-IR), Energy Dispersive X-ray Spectroscopy (EDS), UV-Vis Absorption Spectroscopy and Energy Resolved Luminescence Spectroscopic studies have been used for the detailed qualitative, quantitative as well as optical analyses. Sharp PXRD peaks indicate the formation of highly crystalline MOF with face centered cubic (fcc) structure. Flakes (average length = 0.71µm and width = 0.10µm) and rods (average aspect ratio = ((0.1:8.3) µm) like morphologies have been observed in SEM micrographs. The presence of C, O and Cu has been confirmed by EDS analysis. Photocatalytic activity potential of the synthesized MOF has been tested using methylene blue dye (MB) as a test contaminant in aqueous media under sunlight irradiation. Selective and sensitive fluorescent sensing of different Nitroaromatic compounds (NACs) like 4-Nitroaniline (4-NA), 2-Nitroaniline (2-NA), 3-Nitroaniline (3-NA), 4-Nitrotoulene (4-NT), 2,4-Dinitrotoulene (2,4-DNT), 1,3-Dinitrobenzene (1,3-DNB), 2,6- Dinitrotoulene (2,6-DNT) has been done by exploring the photoluminescent behaviour of chemically stable Cu3(BTC)2. Synthesized MOF is extremely sensitive towards 4-NA, which is having PL quenching efficiency of 82.61% with highest quenching rate till reported. Indeed, a large quenching coefficient KSV = 34.02 × 10-7M-1 and correlation coefficient R2 = 0.9962 in KSV plot have been elucidated with limit of detection (LOD) = 0.7544ppb. The possible ways of luminescence quenching are successfully explained by the combination of Photoinduced Electron Transfer (PET) and Resonance Energy Transfer (RET) mechanisms. Additionally, the Density Functional Theory (DFT) calculations have been employed to support the experimental results. Cu3(BTC)2 fully demonstrates the power of a multi component MOF, which provides a feasible pathway for the design of novel material towards fast responding luminescence sensing and photocatalytic degradation of pollutants.

Unique transport behaviour of Am(III)/Eu(III) ions across a supported liquid membrane containing a TREN-based diglycolamide dendrimer ligand

Abstract Appropriately functionalized dendrimers are exotic ligands and are expected to give rise to better extraction/transport results than the corresponding monofunctional ones. Diglycolamide- (DGA) based dendrimers and their transport studies are rarely reported. Transport of Am(III) and Eu(III) was studied across a PTFE- (polytetrafluoroethylene) based flat sheet supported liquid membrane containing a tris(2-aminoethyl)amine (TREN) dendrimer ligand containing six DGA pendent arms (termed as TREN-G1-DGA) in 5% isodecanol modified n-dodecane. The transport results were compared with those of the monofunctional ligand TODGA (N,N,N′,N′-tetra-n-octyl diglycolamide). In case of a 5.75 × 10−4 M TREN-G1-DGA solution, Am(III) transport was slower than that of Eu(III) under identical conditions. In case of TREN-G1-DGA the role of acid on the metal ion transport was less important than that while using TODGA as a carrier. However, a nitric acid medium is much more suitable for metal ion transport than a mixture containing sodium nitrate as the major component. Insight into the extraction and transport of the Eu(III) complexes was obtained from luminescence spectroscopic studies.

1,1′-Binaphthol annulated perylene diimides: Aggregation-induced emission enhancement and chirality inversion

Aggregation-induced emission enhancement and aggregation-induced chirality inversion are two individual phenomena for the enantiomerically pure organic dyes in the aggregates. Herein we reported for the first time that these two interesting phenomena could be observed simultaneously in the aggregated states of enantiomerically pure S/R-1,1′-binaphthol annulated perylene diimides, in which two perylene diimides moieties were bridged by S/R-1,1′-binaphthol (BINOL) at the bay positions. Owing to the rotatable C2 axes between two naphthol annulated perylene diimides moieties, both of them display intrinsic behaviors of aggregation-induced emission enhancements. At the same time, due to the steric hindrances in the imide and methoxy positions, the neighboring two π-systems of these two unique polycyclic aromatic imides in poor solvents are preferable to adopt a cross-stacking mode and thus form helical X-aggregates of opposite chirality (M/P) with chirality inversion characteristics in their circular dichroism and circularly polarized luminescence spectroscopic studies.

Synthesis, Structural and Physicochemical Characterization of a Titanium(IV) Compound with the Hydroxamate Ligand N,2-Dihydroxybenzamide.

The siderophore organic ligand N,2-dihydroxybenzamide (H2dihybe) incorporates the hydroxamate group, in addition to the phenoxy group in the ortho-position and reveals a very rich coordination chemistry with potential applications in medicine, materials, and physical sciences. The reaction of H2dihybe with TiCl4 in methyl alcohol and KOH yielded the tetranuclear titanium oxo-cluster (TOC) [TiIV4(μ-O)2(HOCH3)4(μ-Hdihybe)4(Hdihybe)4]Cl4∙10H2O∙12CH3OH (1). The titanium compound was characterized by single-crystal X-ray structure analysis, ESI-MS, 13C, and 1H NMR spectroscopy, solid-state and solution UV–Vis, IR vibrational, and luminescence spectroscopies and molecular orbital calculations. The inorganic core Ti4(μ-O)2 of 1 constitutes a rare structural motif for discrete TiIV4 oxo-clusters. High-resolution ESI-MS studies of 1 in methyl alcohol revealed the presence of isotopic distribution patterns which can be attributed to the tetranuclear clusters containing the inorganic core {Ti4(μ-O)2}. Solid-state IR spectroscopy of 1 showed the presence of an intense band at ~800 cm−1 which is absent in the spectrum of the H2dihybe and was attributed to the high-energy ν(Ti2–μ-O) stretching mode. The ν(C=O) in 1 is red-shifted by ~10 cm−1, while the ν(N-O) is blue-shifted by ~20 cm−1 in comparison to H2dihybe. Density Functional Theory (DFT) calculations reveal that in the experimental and theoretically predicted IR absorbance spectra of the ligand and Ti-complex, the main bands observed in the experimental spectra are also present in the calculated spectra supporting the proposed structural model. 1H and 13C NMR solution (CD3OD) studies of 1 reveal that it retains its integrity in CD3OD. The observed NMR changes upon addition of base to a CD3OD solution of 1, are due to an acid–base equilibrium and not a change in the TiIV coordination environment while the decrease in the complex’s lability is due to the improved electron-donating properties which arise from the ligand deprotonation. Luminescence spectroscopic studies of 1 in solution reveal a dual narrow luminescence at different excitation wavelengths. The TOC 1 exhibits a band-gap of 1.98 eV which renders it a promising candidate for photocatalytic investigations.

Investigations of the photochemical charge-transfer reduction of uranyl UO22+(VI) to uranyl UO2+(V) by benzene-1,4-diol (1,4-C6H4(OH)2) and oxalate (C2O42−) by UV–Vis, electron paramagnetic resonance, and luminescence spectroscopies

The aqueous mixtures of UO22+(VI) (as the nitrate salt) with benzene-1,4-diol (hydroquinone, HQ) 1,4-C6H4(OH)2 and those with oxalate C2O42− (as the sodium salt) exhibited broad absorptions at 350–400 nm in their UV–Vis spectra. The intensities of the absorptions for both the UO22+(VI)–HQ and UO22+(VI)–C2O42− mixtures, represented by the absorbance at 375 nm, were shown to be directly proportional to the molar concentrations of HQ and C2O42−, respectively. For each mixture, the absorbance was also found to be directly proportional to the molar concentration of UO22+(VI). The broad absorptions are characteristic of the charge-transfer (CT) bands from the electron-donor–acceptor (EDA) complexes formed between UO22+(VI) and HQ and between UO22+(VI) and C2O42−. Upon photolysis of the UO22+(VI)–HQ and UO22+(VI)–C2O42− mixtures, UO22+(VI) was found by electron paramagnetic resonance (EPR) to be reduced to UO2+(V) (g = 2.08) by HQ and C2O42−, respectively (CT reductions), and the hydroquinone radical 1,4-HOC6H4O. (HQ.) (g = 2.00) was identified simultaneously by EPR spectroscopy. Both HQ and C2O42− at the very low molar ratios of [HQ]/[UO22+] < 1/100 and [C2O42−]/[UO22+] < 1/100 were shown to quench the UO22+ luminescence (emission) for more than 60%. The quenching constants of HQ and C2O42− were determined to be 10,800 M−1 and 4,300 M−1, respectively, using the Stern-Volmer relationship. The results indicated a CT quenching mechanism, namely that the interactions of HQ and C2O42− with the excited *UO22+(VI) lead to transfer of a single electron from the quencher to *UO22+(VI) to reduce it to UO2+(V). This converts the light energy to chemical energy to quench the UO22+(VI) luminescence. Possible photochemical processes associated to the UO22+(VI)–HQ and UO22+(VI)–C2O42− redox reactions have been proposed on the basis of the UV–Vis, EPR, and luminescence spectroscopic studies.

A potential high color purity and thermally stable red-emitting phosphor based on Tb3+ and Eu3+ co-doped sodium yttrium borate: Synthesis and luminescence spectroscopic characterization

A series of Tb3+ and Eu3+ single- and co-doped Na3Y(BO3)2 (NYB) was prepared by the solid-state reaction method and characterized their structural, thermal and photoluminescence properties while focusing on the development of efficient narrow-band red-emitting phosphors for near-UV chip-based phosphor-converted white LED (pc-WLED). Luminescence spectroscopic and decay kinetics studies of NYB:Tb3+, Eu3+ sample series demonstrated an occurrence of energy transfer from Tb3+ to Eu3+ with its efficiency dependent on Eu3+ concentration and temperature. The highest quantum yield of 83.5% was observed for NYB:5.0%Tb3+, 40%Eu3+ composition with excellent thermal stability. The phosphor was finally tested for the use as a red phosphor component in pc-WLED, which demonstrated a high color rendering index of 84.7. The phosphor is a good modelling composition for the development of wider family of narrow-band red-emitting phosphors based on Tb3+/Eu3+ co-doped inorganic oxides for application in pc-WLED.

Substituent Effect on the Selective Separation and Complexation of Trivalent Americium and Lanthanides by N,O-Hybrid 2,9-Diamide-1,10-phenanthroline Ligands in Ionic Liquid.

The extraction and complexation of trivalent americium (Am) and lanthanides (Ln) by four 2,9-diamide-1,10-phenanthroline (DAPhen) ligands with different alkyl substituent groups on the diamide moiety in an ionic liquid (IL), C4mimNTf2, were studied through a combination of batch extraction, spectroscopic, and calorimetric approaches. All four DAPhen ligands can achieve selective separation of Am(III) from Eu(III), but the detailed extractability and the extraction kinetics are affected significantly by the length of the alkyl substituent groups. UV-vis absorption spectrophotometric titrations indicate that Ln(III) coordinates with all four ligands in a 1:2 mode in the ionic liquid and the binding strength decreases with the increase of the alkyl chain length. The complexation of the DAPhen ligands with Ln(III) in the ionic liquid is driven by highly positive entropies and opposed by endothermic enthalpies. A luminescence spectroscopy study suggests that each DAPhen ligand coordinates in a tetradentate form with Eu(III). This work further unravels the unique extraction and coordination behavior in an ionic liquid system and offers additional guidelines to design more efficient DAPhen ligands for Ln(III)/An(III) separation.

Synthesis, structure and photoluminescent properties of Eu:Gd2O3 nanophosphor synthesized by cw CO2 laser vaporization

Europium doped Gd2O3 sphere-like nanoparticles with dm = 9.3 ± 3.5 nm were synthesized by cw CO2 laser vaporization technique in a flowing mixture of argon and oxygen. According to XRD data, the Eu:Gd2O3 nanoparticles crystallize in the monoclinic symmetry class (C2/m space group). High-resolution luminescence spectroscopy study showed that the ultra-narrow 5D0 → 7F0 transition of Eu3+ demonstrates only two peaks corresponding to two inequivalent Cs positions of Eu3+ ion in monoclinic Gd2O3 lattice that is explained by the peculiarities of local environment of Eu3+ ion at these sites. The hypersensitive transition 5D0 → 7F2 dominates in the spectrum and is expanded to the red part of the spectrum in comparison with cubic Eu:Gd2O3 due to intense transitions terminating at higher-lying components of the crystal-field-split 7F2 state. In the luminescence spectrum, an additional weak band with the maximum at 407 nm corresponding to the electronic transitions 4f65 d1(7FJ) → 4f7(8S7/2) of Eu2+ was detected. The obtained values of chromaticity coordinates and absolute quantum yield are (0.644; 0.325) and ca. 1%, respectively. The phase transformations have been investigated using differential scanning calorimetry and thermogravimetry (50–1400 °C). After annealing in air at 700 °C, the monoclinic symmetry class of the Eu:Gd2O3 nanoparticles is preserved and the particle size increases to dm= 17.8 ± 6.1 nm. After annealing, the chromaticity coordinates (0.659; 0.334) and absolute quantum yield (ca. 4%) can be obtained using red phosphor based on monoclinic Gd2O3:Eu3+. The lifetime of the excited 5D0 state of Eu3+ in the annealed nanoparticles is longer than that in the as-synthesized nanoparticles, due to the suppression of nonradiative decay after annealing.

Synthesis and luminescence spectroscopy study of a novel orange-red colour emissions phosphor based on Tb3+ ion-doped Na2 ZnP2 O7.

Here, we report the synthesis and study of new orange-red (OR) colour-emitting phosphors Na2 ZnP2 O7 :xTb3+ (x = 1, 1.25, 1.5, and 1.75 mol%) using a conventional solid-state reaction. The sample crystallographic structures and their room temperature photoluminescence properties were measured using X-ray powder diffraction, excitation and emission spectra, as well as emission decay curves. X-ray diffraction analysis showed an isostructural tetragonal structure for all the doped materials with no impurities. Several colour emissions corresponding to 5 D4 →7 F6 (blue), 5 D4 →7 F5 (green), 5 D4 →7 F4 (orange) and 5 D4 →7 F3,2,0 (red) intraconfigurational transitions were observed and investigated. These colours were dominated by the OR colours. 5 D4 energy level lifetime was independent of Tb3+ concentration. Various radiative and luminescence parameters, such as experimental branching ratio, radiative decay rate, and luminescence quantum efficiencies, were calculated and discussed. Chromaticity diagram calculations illustrated an orange emission for all the studied materials.

Role of diluent in the unusual extraction of Am3+ and Eu3+ ions with benzene-centered tripodal diglycolamides: local structure studies using luminescence spectroscopy and XAS

Two benzene-centered tripodal DGA ligands (LI and LII) were used for the extraction of Am3+/Eu3+ from HNO3 medium into n-dodecane modified with various amounts of isodecanol. Luminescence spectroscopy and EXAFS studies were carried out for structural information.

Polarization-Induced Quantum-Mechanical Charge Transfer in Perovskite–Graphene Nanocomposites with Superior Electro-optic Switching Modulation

Understanding the concept of light–matter interaction in organic–inorganic nanostructures such as graphene and metal-halide perovskites has been explored to realize photonic and optoelectronic devices. The strong light–matter interaction and impressive performance achieved by tuning the optical/electrical properties have enabled them as potential candidates for optoelectronic applications. In this perspective, we report the synthesis of metal-halide perovskite nanocomposites by incorporation of graphene sheets into the perovskite framework, which exhibits a significant enhancement in electro-optic (E-O) switching modulation. The carrier dynamics in the nanocomposite is investigated using time-resolved luminescence and broadband dielectric spectroscopy studies to get insights into the carrier relaxation and transfer mechanisms. The presence of graphene in the perovskite nanocomposites induced dielectric polarization with a strong electrical conduction and a nonlinear dielectric behavior with negative permittivity at the percolation threshold concentration because of the large resonance derived from the plasmonic oscillations of delocalized charges. A custom-designed optical fiber integrated with nanocomposites is scrutinized to explore the light modulation and E-O sensitivity under an applied electrical field. The E-O interference that leads to phase modulation of light by change in the refractive index of the graphene–CsPbBr3 nanocomposites resulted in a higher E-O sensitivity of 18 nm/V than those of CsPbBr3 nanostructures.

Highly Efficient N-Pivot Tripodal Diglycolamide Ligands for Trivalent f-Cations: Synthesis, Extraction, Spectroscopy, and Density Functional Theory Studies.

A series of four N-pivot tripodal diglycolamide (DGA) ligands, where three DGA moieties are attached to the central N atom via spacers of different lengths and with varying alkyl substituents on the amidic nitrogen of DGA (LI-LIV), were studied for their extraction and complexation ability toward trivalent lanthanide/actinide ions, including solvent extraction, complexation using spectrophotometric titrations, and luminescence spectroscopic studies. Introduction of a methyl group on the amidic nitrogen atom gives rise to a 400 fold increase of the Eu distribution ( D) value [LIII (NMe) vs LII (NH)] at 1 M HNO3. Enlargement of the spacer length between the pivotal N atom and the DGA moieties with one carbon atom results in a 14 times higher DEu value [LI (C3) vs LII (C2)]. Slope analyses showed that Eu3+ was extracted as a bis-solvated species with all four ligands. The compositions of the Eu3+/L complexes were further confirmed by spectroscopic measurements, its formation constants following the order: LIII > LIV > LI > LII. Luminescence spectroscopy and electrospray ionization mass spectrometry revealed that all four ligands form [Eu(L)2(NO3)3] complexes. Density functional theory and thermodynamic parameters corroborated the existence of [Eu(L)2(NO3)3] complexes.