Intense Emission Band Research Articles

Structural and spectroscopic investigation of a novel orange-red Ca9Bi(PO4)7:Sm3+ nano-scaled phosphor

A series of Sm3+ activated Ca9Bi(PO4)7 novel tunable orange-red-emitting nanophosphors with an intense emission band at 600 nm were synthesized using the solution combustion method. The crystal structure, phase purity, structural parameters, optical band gap values, photoluminescence (PL) behavior, energy transfer, quantum efficiencies, lifetime values, and CIE chromaticity index of Ca9Bi(1-x)Smx(PO4)7 white powdered samples were consistently analyzed. Rietveld refinement of Ca9Bi0.88(PO4)7:012Sm3+ sample resulted into a trigonal crystal structure of sample having space group R3c(161) with refinement converged to Rp = 7.62%, Rwp = 12.01%, and ꭓ2 = 2.08. Meanwhile, the average crystallite size for Ca9Bi0.88Sm0.12(PO4)7 system was found out to be nearly 60 nm which was also supported by TEM images. The energy band-gap (Eg) value of Ca9Bi0.88Sm0.12(PO4)7 was estimated to be 4.07 eV and the critical distance between Sm3+ ions was calculated to be 21.09 Å. The optimum concentration of dopant Sm3+ ions in Ca9Bi(PO4)7 sample was ascertained to be 12 mol% and as per Dexter's theory and Huang study, the mechanism behind energy transfer between Sm3+ ions was concluded as dipole-dipole interactions. Under excitation at 403 nm, these nanophosphors exhibited three bands in the PL emission spectrum peaking at 562 nm, 600 nm, and 646 nm corresponding to 4G5/2 → 6HJ transitions (J = 5/2, 7/2, and 9/2, respectively). A decrease in lifetime values from 1.95 ms to 1.39 ms was observed with increased Sm3+ ions concentration. Upon employing Auzel's fitting function, radiative lifetime; non-radiative rates, and quantum efficiencies for as-synthesized nanophosphors were measured. The CIE color coordinate of Ca9Bi0.88(PO4)7:0.12Sm3+ was found to be (0.435, 0.354) and the corresponding quantum efficiency was estimated at 70.6%. The results obtained from our current study indicate that Ca9Bi(PO4)7 doped with Sm3+ ions can have applicability as a promising orange-red-emitting nanophosphor for near-UV energized WLEDs.

Synthesis, crystal structure and photoluminescence properties of novel far-red-emitting SrLaZnSbO6:Mn4+ double-perovskite phosphors for plant cultivation LEDs

In this work, we demonstrated novel Mn4+-activated double-perovskite SrLaZnSbO6 (SLZS) far-red-emitting phosphors for plant cultivation LED lighting. These SLZS:Mn4+ far-red-emitting phosphors doped with various Mn4+ concentrations were successfully prepared by using a traditional high-temperature solid-state reaction route. The phase purity, crystal structure, photoluminescence properties, decay lifetimes, CIE chromaticity coordinates and temperature-dependent spectra of as-prepared samples were systematically studied. The SLZS:Mn4+ phosphors showed an intense far-red emission band in the 650−800 nm spectral region with a maximum at 706 nm under 364 nm excitation, which was due to the 2Eg→4A2g transition of Mn4+ ions. The optimal doping concentration of Mn4+ ions in SLZS:Mn4+ phosphors was found to be 0.5 mol%. And the CIE chromaticity coordinates of SLZS:0.5 %Mn4+ phosphors were calculated to be (0.7276, 0.2724), which were located in the far-red region. The emission spectrum of SLZS:Mn4+ phosphors could match well with the absorption band of phytochrome PFR. All of these results demonstrate that SLZS:Mn4+ phosphors have a huge potential application in indoor plant cultivation.

Synthesis, Structure, and Optical Properties of Sodium Complex Based on 3-Hydroxyquinoline-4-carboxylic Acid

A novel sodium complex [Na2(L)2(Phen)2(H2O)2]·2(H2O) (L = 3-hydroxyquinoline-4-carboxylic acid anion; Phen = 1,10-phenanthroline) is synthesized by solvothermal approach and is structurally determined by single-crystal X-ray diffraction. The title complex crystallizes in the orthorhombic system of the Pbcn space group. The strong π⋯π stacking and hydrogen bonding interactions produce three-dimensional (3D) chains. A series of properties of the title complex were tested by solid-state photoluminescence, CIE analysis and solid-state diffuse reflectance. The results show that the title complex is a blue light emitter, CIE (x = 0.1542, y = 0.0211) and has an energy bandwidth of 1.607 eV. A novel sodium complex is synthesized via solvothermal approach, which is characteristic of an isolated structure. At the same time, it displays a narrow and intense photoluminescence emission band in the blue region and has an energy bandwidth of 1.607 eV.

Sm3+ driven enhancement in photocatalytic degradation of hazardous dyes and photoluminescence properties of hexagonal-ZnO nanocolumns

Samarium doped ZnO (Sm-ZnO) nanocolumns were grown by wet chemical method and the doping effect of Sm3+ on visible light photocatalytic (PC) and photoluminescence (PL) properties of ZnO was investigated. Methylene blue (MB) and methyl orange (MO) were considered for the degradation study as a step initiated towards the remediation of industrial wastewater. Subsequent characterization studies by x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) enumerate that the hexagonal-wurtzite structured Sm-ZnO is highly crystalline in nature and possesses hexagonal column like nano-architectures. Although, a charge imbalance exists between the ions, the substitutional effects of Sm3+ at Zn2+ sites have been observed from the XRD spectra and discussed by suitable mechanisms. FTIR measurement gives the information on the evolution of peaks related to metal-oxygen bond in Sm-ZnO which may be linked with Sm ions. PC measurement shows that the degradation efficiency of 95% can be achieved by Sm-ZnO photocatalysts in degrading MB and 91% for MO. Sm doping induces high charge separation efficiency and generation of OH ions in ZnO leading to such improvisation in degradation efficiency. The prepared Sm-ZnO nanocatalysts possess high degree of photostability and reusability even after fourth cycle of photodegradation. PL spectra show the suppression of the sharp and intense excitonic emission band of ZnO in Sm-ZnO due to low rated direct recombination of carriers. Incorporation of Sm3+ ends up with intrinsic defect mediated enhancement in the visible emissions especially in the blue, yellow and red region of light spectrum.

MoS2@ZnO Nanoheterostructures Prepared by Electrospark Erosion for Photocatalytic Applications.

MoS2@ZnO nanoheterostructures were synthesized by electrospark erosion of zinc granules in a hydrogen peroxide solution and simultaneous addition of MoS2 nanostructured powder into the reaction zone. The morphology, size of the crystallites, as well as elemental and phase composition of the prepared structures, were examined using transmission electron microscopy and X-ray diffraction analysis. It was found that the synthesized products represent heterostructures containing MoS2 nanoparticles formed on ZnO nanoparticles. Raman spectroscopy and photoluminescence analysis were also used for characterization of the prepared heterostructures. The obtained MoS2@ZnO nanostructures revealed an intense broad emission band ranging from 425 to 625 nm for samples with different fractions of MoS2. Photocatalytic measurements showed that the maximal hydrogen evolution rate of the prepared nanoheterostructures was about 906.6 μmol·g−1·h−1. The potential of their application in photocatalytic water splitting was also estimated.

Short review on recent progress in Mn4+ -activated oxide phosphors for indoor plant light-emitting diodes.

In the modern era, growing number of indoor plants for various purposes, such as vegetation, flowering, and decorations, has increased over the traditional follow-up trends for plantation. However, the indoor plantation requires different parameters for their growth; among these, light plays a significant role. In order to control the growth of plants using light-emitting diodes, Mn-doped oxide phosphors have emerged as promising candidates due to their broad and intense emission bands in the red and far-red spectral range. In this review article, recent progress on Mn-doped oxides for indoor plant growth has been reviewed. This review article is mainly divided into three parts. In the first part, different reaction conditions for the synthesis of Mn-doped oxide phosphors are compared. In the second part, the luminescent and other photometric parameters of these are discussed. The influence of different co-dopants on the luminescent characteristics has been elucidated in detail. The third part discusses the properties of light-emitting diodes fabricated using these phosphors for plant growth. The present review article elucidates the synthesis parameters, luminescent properties, and light-emitting diodes fabricated using Mn-doped oxide materials for plant growth applications.

Broadband photoluminescence in a ceramic (Mg2SnO4\u2013SnO2):Cr3+ system

This study reports the synthesis and photoluminescence spectroscopic studies of Cr3+-doped Mg2SnO4–SnO2 ceramics. The crystal structure was analyzed by X-ray powder diffraction, and photoluminescence was investigated at room temperature. The diffractogram confirmed the presence of Mg2SnO4 and SnO2 phases. Photoluminescence spectroscopy identified broad and intense emission bands assigned to the Cr3+ cation occupation in octahedral Mg2SnO4 sites and an orange band assigned to SnO2 emission. All spectra were analyzed and interpreted according to crystal field theory and Tanabe–Sugano theory for the d3 electronic configuration. The broad and intense emission band covering the visible/near-infrared region suggests that this system may be a promising material for use as an active medium in a broadband light source at room temperature.

Complexes of In(III) with 8-hydroxyquinoline-5-sulfonate in solution: structural studies and the effect of cationic surfactants on the photophysical behaviour.

Following previous studies on the complexation in aqueous solutions of 8-hydroxyquinoline-5-sulfonate (8-HQS) with the trivalent metal ions, Al(III) and Ga(III) and various other metal ions, using multinuclear NMR, DFT calculations, UV-vis absorption and luminescence techniques, we have extended our studies on 8-HQS complexation to the trivalent metal ion In(III). The study combines the high sensitivity of luminescence techniques and the selectivity of multinuclear NMR spectroscopy with the structural details accessible through DFT calculations, and aims to obtain a complete understanding of the complexation between the In3+ metal ion and 8-HQS, and how this influences the luminescence behaviour. A full speciation study has been performed and, as has been reported for the complexes of 8-hydroxyquinoline (8-HQ), the dominant complexes of 8-HQS with In(III) show marked differences in the complexation behaviour when compared with the equivalent complexes with the other group 13 cations Al(III) and Ga(III). While all three complexes have a 1 : 3 (metal : ligand) stoichiometry, those with Al(III) and Ga(III) show a mer-geometry of the ligands around the metal centre, whereas the fac-geometry is observed for the complexes with In(III). On binding to metal ions, 8-HQS shows a marked increase in the intensity of the fluorescence emission band compared to that of the virtually non-luminescent free ligand. However, the increase for In(III) is less pronounced than with Al(III) or Ga(III). These observations have important implications for the application of the complexes in sensing, light emitting devices (e.g. OLEDs), or as electron transport layers in photovoltaics for solar energy conversion. Furthermore, surfactant complexation is known to improve the fluorescence intensity in metal complexes with 8-HQS, by inhibiting the ligand exchange, as we have reported for complexes of HQS with Al(III) and Ga(III). Accordingly, in view of the development of applications in either sensing or optoelectronics, our interest also includes the study of HQS complexes of In(III) in the presence of cationic surfactants, in comparison with previous results with Al(III) and Ga(III).

Excitons Bound to Defect States in Two-Dimensional (2D) MoS2

In this work, the effect of atomic defects created by gallium ion irradiation on the optical properties of single-layer molybdenum disulfide is studied by means of micro-photoluminescence measurements. The induced defects give rise to an additional emission band located at about 170 meV below the free exciton. The micro-photoluminescence intensity of this defect-related emission band is found to be proportional to the defect density. The large spectral width suggests the presence of binding sites with different binding energies available for excitons that remain optically active up to 230 K.

Изменение оптических свойств оксида титана при кристаллизации

Crystallization of amorphous titanium oxide films synthesized by magnetron sputtering was carried out at temperatures of 700, 800, and 900 oC in an oxygen atmosphere. The refractive index of the films increases during crystallization with a time constant that depends on temperature, which made it possible to determine the activation energy of the crystallization process on the order of 0.6 eV. The growth kinetics model for the titanium oxide nanocrystals, which is used in this work, showed that the indicated activation energy corresponds to the diffusion energy of oxygen vacancies. This process is decisive for the growth of titanium oxide nanocrystals upon annealing in an oxygen atmosphere. The study of photoluminescence has shown that crystallization leads to a change in the ratio of intensities of different emission bands. The bands that are associated with the oxygen vacancy are extinguished. A decrease in the concentration of these vacancies in films leads to an increase in their resistance and stabilization of the films in time.

Effect of annealing temperature on the electrical and photoluminascence properties of tin oxide thin films prepared by sol-gel spin coating technique

Tin oxide thin films were sucessfully synthesized by sol–gel spin coating technique using SnCl2·2H2O and Ethanol as precurser. The prepared films were post annealed at different temperatures such as 300, 400, 500, 600 and 700 °C. The room temperature electrical conductivities of the as prepared and post annealed tin oxide thin films at different temperatures were ranging from 0.0820 × 103 Ω−1 m−1–0.5766 × 103 Ω−1 m−1. The Figure of merit values were calculated and are ranging from 4.3336 × 10−6 Ω−1 –25.0907 × 10−6 Ω−1. PL study shows that an intense and broad blue asymmetric emission band centered at 389 nm.

Complexes with Furyl-Substituted 3-Hydroxychromone: Synthesis, Characterization and Fluorescence Studies

2-(2-Furyl)-3-hydroxychromone (HL) reacts with MII ions in the formation of quadratic [Cu(L)2] (3), octahedral [M(L)2(OH2)2] (M = Co (1), Ni (2), Zn (4), Mn (5)) and seesaw [M(L)2] (M = Sn (6), Pb (7)) complexes. Recrystallization of complexes 1-3 in presence of pyridine lead to [M(L)2(py)2] (1a-3a) adducts. All compounds were characterized by Fourier transform infrared spectroscopy (FTIR). Complexes 1-7 were analyzed by UV-Vis and diffuse reflectance spectroscopies. The estimated band gap energies range from 2.90-3.15 eV. The crystal structure of complexes 6 and 7 revealed the influence of the stereochemically active lone pair due to their electronic configuration ns2. An intense fluorescence emission band centered at approximately 600 nm (λexc centered at 340 nm) has been observed for complex 6 in the solid state. In N,N‑dimethylformamide (DMF) solution, complex 6 showed two emission bands (468 and 538 nm) when excited from 300 to 380 nm, and only one emission band (468 nm) when excited from 385 to 420 nm.

A New Piano-Stool Ruthenium(II) P-Cymene-Based Complex: Crystallographic, Hirshfeld Surface, DFT, and Luminescent Studies

A new complex (Ru(η6-p-cymene)(5-ASA)Cl2) (1) where 5-ASA is 5-aminosalicylic acid has been prepared by reacting the ruthenium arene precursors ((η6-arene)Ru(μ-Cl)Cl)2, with the 5-ASA ligands in a 1:1 ratio. Full characterization of complex 1 was accomplished by elemental analysis, IR, and TGA following the structure obtained from a single-crystal X-ray pattern. The structural analysis revealed that complex 1 shows a “piano-stool” geometry with Ru-C (2.160(5)- 2.208(5)Å), Ru-N (2.159(4) Å) distances, which is similar to equivalents sister complex. Density functional theory (DFT) was used to calculate the significant molecular orbital energy levels, binding energies, bond angles, bond lengths, and spectral data (FTIR, NMR, and UV–VIS) of complex 1, consistent with the experimental results. The IR and UV–VIS spectra of complex 1 were computed using all of the methods and choose the most appropriate way to discuss. Hirshfeld surface analysis was also executed to understand the role of weak interactions such as H⋯H, C⋯H, C-H⋯π, and vdW interactions, which play a significant role in the crystal environment’s stability. Moreover, the luminescence results at room temperature show that complex 1 gives a more intense emission band positioned at 465 nm upon excitation at 330 nm makes it a suitable candidate for the building of photoluminescent material.

Visible and Near-Infrared emission properties of Yb3+/Pr3+ co-doped lanthanum aluminum silicate glass

Yb3+/Pr3+ co-doped lanthanum aluminum silicate glasses (Yb3+/Pr3+-SAL glass) are prepared by high temperature melting process. The optical properties of Yb3+/Pr3+ co-doped lanthanum aluminum silicate glasses are studied. The result shows that Yb3+/Pr3+ co-doped lanthanum aluminum silicate glasses have intense absorption range from 440 to 500nm. In addition, the intense emission band centered at 620nm and 607nm are observed with the excitation of 488nm in different doping concentration. These results demonstrate that Yb3+/Pr3+ co-doped lanthanum aluminum silicate glasses can be used as a potential material for visible laser and near-infrared broadband fiber amplifiers.

Spectroscopic and electrochemical properties of thiophene-phenylene based Shiff-bases with alkoxy side groups, towards photovoltaic applications

The influence of presence and elongation of alkoxy side chains in the π-conjugated Schiff-bases has been considered on the basis of UV–Vis absorption and photoluminescence spectra of model compounds and polymers solutions in chloroform and binary solvents of different polarity. The results of these investigations have been supported by electrochemical data. It has been demonstrated that introduction of electron donating methoxy side groups decreases the energy gap, however the elongation of alkyl chains only slightly affects the electronic structure of model compounds. In the case of polymers, such octyloxy side chains improves the solubility, enabling formation of longer polymer chains, with the enhanced effective π-conjugation length and narrower energy gap, however the intensity of emission band clearly decreased. Positive solvatochromism has been observed in both absorbance and photoluminescence spectra for all investigated compounds. As the concluding task, bulk-heterojunction (BHJ) photovoltaic (PV) structures, consisting of polyazomethines blended with the fullerene derivative, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) have been prepared and tested in the context of potential application in solar cells. All investigated polymers have shown the photovoltaic effect, but the best power conversion efficiency and other PV parameters have been obtained for polyazomthine with octyloxy side chains.

Ravishing blue emission from Ce3+ activated lithium borate glasses for photonic applications

Lithium borate glasses activated with specific concentrations of Ce3+ ions have been processed by melt quenching technique. X-ray diffraction and SEM with EDAX carried out structural and surface morphology with elemental confirmation respectively. The nebulous nature of glassy matrices have been affirmatively confirmed by XRD and it was corroborated with SEM analysis. A distinguished absorption band is noticed in the ultraviolet region and the photoluminescence spectra displays a broad and intense blue emission band in the region from 395 nm to 570 nm which is centered at 447 nm (5d→4f) by exciting with 350 nm in Ce3+: LBZ glassy matrices. The dazzling blue emission intensity was significantly ameliorated by improving the addition of Ce3+ ion concentration in the glass matrix. The blue emission intensity has been found to be decreased at higher concentrations due to concentration quenching and the optimal concentration of Ce3+ ions is estimated to be 0.5 mol%. The fluorescence decay time has been evaluated as 0.86 ms from the decay profile of 0.5 mol% Ce3+: LBZ glass. Chromaticity coordinates were determined from the luminescence spectra, which are found to be falls in the bright blue region. The obtained blue emission CIE coordinates are close to standard EBU and NTSC coordinates for blue illumination. In view of these spectral features, 0.5 mol% Ce3+: LBZ glass could be recommended as promising candidate for the applications of blue emissive photonic devices.

A Novel ‘On‐Off’ Rhodamine Based Sensor for Colorimetric Detection of CN−and Its Application as Encoder‐Decoder and Molecular Keypad Lock

AbstractA novel rhodamine‐phenalenedicarbonitrile based “on‐off” sensor (Rho‐Pdc) has been synthesized which is characterized by 1H NMR, 13C NMR and mass spectrometry. The photophysical studies of the dyad suggest its existence in spirolactam ring open form of rhodamine. ICT (Intramolecular Charge Transfer) active sensor displays an absorption band at 577 nm with a shoulder at 520 nm and fluorescence band at 593 nm. The treatment of dyad Rho‐Pdc with different anions shows its sensitivity and selectivity towards CN− ions in aqueous methanolic solution with lowest detection limit of 0.13 μM and the binding constant was determined to be 1.17 × 104 M−1 by applying Benesi‐Hildebrand equation. The presence of CN− ions hinder the ICT process of dyad Rho‐Pdc and shows a blue shift in absorption band of dyad Rho‐Pdc with formation of new band at 488 nm as well as decrease in the intensity of emission band. Rho‐Pdc has also been used for the colorimetric detection of CN− ions among different anions and concentrations. The reversibility of Rho‐Pdc.CN−complex has been achieved with Fe3+ ions which formed the basis for the construction of multiple molecular logic circuits.

J-O study of a novel Dy-doped Lu3Al5O12 transparent ceramic for potential application in yellow laser generation

A novel Dy:LuAG transparent ceramic was fabricated by a solid-state method, and it has the potential to be used as the gain medium of yellow laser generated by blue LD pumping. The spectroscopic parameters were determined by the Judd-Ofelt theory, and Ω2, Ω4, Ω6 were calculated to be 0.57 × 10−20 cm2, 1.44 × 10−20 cm2, 0.68 × 10−20 cm2, respectively. An intense yellow emission band, corresponding to the 4F9/2 → 6H13/2 transition located at 581 nm, was observed in the visible region. The non-exponential curve was fitted to the Inokuti–Hirayama model to understand the energy-transfer mechanism. The fluorescence lifetime of the 4F9/2 level was about 339 μs, and the quantum efficiency was 21.7%.

Sol-gel synthesis and study of praseodymium substitution effects in yttrium aluminium garnet Y3-xPrxAl5O12

In this study, praseodymium substituted yttrium aluminium garnet (Y 3-x Pr x Al 5 O 12 ; YPrAG (0 ≤ x ≤ 3)) powders were synthesized by an aqueous sol-gel method and investigated. YPrAG samples were characterized by X-ray diffraction (XRD) analysis, solid state nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscopy (SEM). Luminescence measurements of YPrAG samples were performed as well. It was demonstrated, that three phase regions exist depending on the substitutional level of Pr 3+ in Y 3-x Pr x Al 5 O 12 . The single-phase cubic garnets have formed up to x = 0.30. The mixture of garnet and trigonal perovskite (Y 1-x Pr x AlO 3 ) phase have formed when x is between 0.45 and 2.00. The perovskite phase was the main crystalline phase with further increasing amount of praseodymium, no garnet structure was observed. The amorphous impurity phases were detected by solid state NMR spectroscopy. Two broad and intense emission bands in the UV region peaked at 325 and 381 nm and several sharp emission bands in the visible region were determined by investigating the luminescence properties of the Y 3-x Pr x Al 5 O 12 mixed-metal oxides. • Y 3-x Pr x Al 5 O 12 specimens were synthesized using aqueous sol-gel synthesis method. • Monophasic garnets obtained at low substitution of yttrium by praseodymium. . • The region of coexisting phases have been evidently deduced by solid state NMR spectroscopy. . • The Pr 3+ emission in the range of 300–750 was observed in Y 3-x Pr x Al 5 O 12 garnets. • The decay times for the Y 3-x Pr x Al 5 O 12 garnets decreased with increasing Pr 3+ amount. .

Investigation of extreme ultraviolet spectra from highly charged holmium ions in 1 μ m laser-produced plasmas

Absolute intensity calibrated extreme ultraviolet spectra radiated by highly charged holmium (Ho) ions from 1 μm Nd:YAG laser generated plasmas in the 1–8 nm wavelength spectral range were measured and investigated. The spectral features show a broad structured continuum-like emission band, most prominent in the wavelength range 6–8 nm, which accounts for more than half of the emitted power. Assuming local thermodynamic equilibrium (LTE) in the laser produced plasmas and using the flexible atomic code and Cowan suite of codes, the wavelengths and LTE-gA values of unresolved transition arrays (UTAs) from E 1-contributing transition arrays 4p–4d, 4d–4f and super transition arrays such as 4p64d k−14f + 4p54d k+1–4p64d k−24f2 + 4p44d k+2 + 4p54d k 4f and 4d10(5s5p) k 4f m−k –4d9(5s5p) k 4f m−k+1 were calculated and shown to be responsible for the strongest observed spectral structure. Transitions between these excited to excited states are considered, since even if only weakly present, they will not be influenced by opacity effects unlike resonance transitions involving ground configurations. Another two intense continuous emission bands at 3–6 nm and 2–3 nm that dominate the spectra in the shorter wavelength range mainly arise from 4d–5p, 4d5s–4d5s5p, 4f–5g, 4f5s–4f5s5g and 4d–5f, 4d5s–4d5s5f, 4p–5s transitions. Spectral line shape parameters of Gaussian fits to the LTE-gA weighted radiation spectra of each Ho ion were given, enabling direct explanation of recorded spectra. Based on the LTE-gA UTAs formalism parameters, reasonable agreement is obtained between the synthetic spectrum and experimental result enabling some of the observed spectral features to be identified.