Emission Band Research Articles

Nonadiabatic Molecular Dynamics Simulations Provide Evidence for Coexistence of Planar and Nonplanar Intramolecular Charge Transfer Structures in Fluorazene.

Fluorazene is a model compound for photoinduced intramolecular charge transfer (ICT) between aromatic moieties. Despite intensive studies, both spectroscopic and theoretical, a complete model of its photophysics is still lacking. Especially controversial is the geometry of its ICT structure, or structures. In order to fill in the gaps in the state of knowledge on this important model system, in the present study I report the results of nonadiabatic molecular dynamics (NAMD) simulations of its photorelaxation process in acetonitrile solution. To afford a direct comparison to spectroscopic data, I use the simulation results as the basis for the calculation of the transient absorption (TA) spectrum. The NAMD simulations provide detailed information on the sequence of events during the excited-state relaxation of the title compound. Following initial photoexcitation into the bright S2 state, the molecule undergoes rapid internal conversion into the S1 state, leading to the locally excited (LE) structure. The LE structure, in turn, undergoes isomerization into a population of ICT structures, with geometries ranging from near-planar to markedly nonplanar. The LE → ICT isomerization reaction is accompanied by the decay of the characteristic excited-state absorption band of the LE structure near 2 eV. The anomalous fluorescence emission band of fluorazene is found to originate mainly from the near-planar ICT structures, in part because they dominate the overall population of ICT structures. Thus, the planar ICT (PICT) model appears to be the most appropriate description of the geometry of the ICT structure of fluorazene.

Effect of Mn2+ Doping and DDAB-Assisted Postpassivation on the Structural and Optical Properties of CsPb(Cl/Br)3 Halide Perovskite Nanocrystals.

Cesium lead halide perovskite (CsPbX3; X = Cl, Br, I) nanocrystals showing intense band-edge emission and high photoluminescence quantum yield are known to be a potential candidate for application in optoelectronic devices. However, controlling toxicity due to the presence of Pb2+ in lead-based halide perovskites is a major challenge for the environment that needs to be tackled cautiously. In this work, we have partially replaced Pb2+ with Mn2+ ions in the CsPb(Cl/Br)3 nanocrystals and investigated their impact on the structural and optical properties. The Rietveld refinement shows that CsPbCl2Br nanocrystals possess a cubic crystal structure with Pm3 ̅m space group, the Mn2+ doping results in the contraction of the unit cell. The CsPb(Cl/Br)3: Mn nanocrystals show a substantial change in the optical properties with an additional emission band at ~588 nm through a d-d transition, changing the emission color from blue to pink. Here, a didodecyldimethylammonium bromide (DDAB) ligand that triggers both anion and ligand exchange in the CsPb(Cl/Br)3: Mn nanocrystals have been used to regulate the exchange reaction and tune the emission color of halide perovskites by changing the peak position and the PL intensities of band-edge and Mn2+ defect states. We have also shown that oleic acid helps in the desorption of oleylamine capping from the CsPb(Cl/Br)3: Mn nanocrystal surfaces and DDAB, resulting in the substitution of Cl¯ with Br¯ as well as provides capping with shorter branched length ligand which led to increase in the overall PL intensity by many folds.

Solvent effect on the excited state photophysics of Imiquimod: A DFT/TD-DFT and spectroscopic study

Solvation plays an important role in chemistry and biology. The role of the solvent is crucial in any chemical processes such as tautomerization that controls the structure and function of biomolecules. The current study aims to explore how different solvent medium affects the tautomeric forms of an antitumor drug, Imiquimod (IMQ). We have used several spectroscopical methods, including UV–Vis absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy, and quantum mechanical (QM) calculations. Our results revealed that solvent, indeed, plays a significant role in the modulation of the photophysics of the drug. IMQ has three emission bands in protic and aprotic solvents and two bands in non-polar medium associated with different forms of the drug. Using time-resolved technique, and comparing with the predicted lifetimes from QM calculations, we succeed to assign these three forms as cation, tautomer and neutral of IMQ with 1.6 ns, 2.0 ns and 4.0 ns lifetime values, respectively. Since IMQ is a nucleobase analogue and one of the most effective medications for skin tumors; these findings about which specie of IMQ is present in a given medium, and beyond, how the medium alters the photophysics of the molecule may provide deeper insights into its structure and function.

Visible light activated time dependent phosphorescence colors from carbon dots based materials

To endow carbon dots (CDs)-based materials with time dependent phosphorescence colors (TDPCs) activated by visible light will benefit high-level data encryption and anticounterfeiting. It needs multiple emission centers of triplet state stabilized by noncovalent bonds. In this work, levofloxacin and ethanolamine were applied to synthesize CDs (LEE-CDs), in which, aromatic moieties and multiple emissive centers were formed by the reaction between fluorinated quinolone moieties and ethanolamine. Melamine (MA) and cyanuric acid (CA) with large π systems were selected as matrices, and urea and biuret without π systems were selected as the comparison matrices. Interestingly, LEE-CDs encapsulated in MA (LEE-CDs@MA) exhibited visible-light-activated TDPCs varying from red to yellow green, while LEE-CDs@CA displayed TDPCs from red to yellow green after excited by visible light, yellow to green after excited by UV light. However, LEE-CDs@Urea and LEE-CDs@Biuret could only generate a single color RTP after excited by visible or UV light. It can be inferred that π-π stacking interactions combining with hydrogen bonds activated the O-related triplet state with a short lifetime, and hydrogen bonds only retained the N-related triplet state in LEE-CDs with a long lifetime and the emissive center of matrices with an intermediate lifetime. Therefore, the dynamic ratio of the RTP emissive bands from the three centers changing over time resulted in TDPCs.

On the properties of ZnO nanorods (ZnO NRs)/NiO heterostructure prepared by double chemical bath deposition

We report on the ZnONRs and ZnONRs/NiO heterostructure synthesized by the chemical bath deposition technique. The samples were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, Raman spectroscopy, and UV–vis spectroscopy techniques. XRD, Raman spectroscopy, and SEM analysis revealed the formation of ZnONRs/NiO heterostructure. Raman spectra showed a decrease in intensity of low-frequency non-polar and active (E 2 (low)) vibrational mode when NiO is deposited onto ZnONRs. The PL spectra revealed ultraviolet and visible emission bands, whose intensities decreased when NiO grew onto ZnONRs. The Au/NiO/ZnONRs/FTO heterostructure Schottky diode performed better than the Au/ZnONRs/FTO Schottky diode. The Au/NiO/ZnONRs/FTO heterojunction demonstrated a current rectification ratio of 3.03 × 102 at ± 2 V and a forward current of 1.51 × 10−3 A, which is higher than that of Au/ZnONRs/FTO having a rectification ratio of 6.79 × 101 at ± 2 V and a forward current of 1.651 × 10−5 A.

Antimicrobial photodynamic therapy against Escherichia coli by exploiting endogenously produced Protoporphyrin IX- In vitro study.

Due to antimicrobial drug resistance, there is a growing interest in the development of light based alternative antibacterial therapies. This research work is focused on the inactivation of Escherichia coli (E. coli) by exploiting the absorption bands 405, 505, 542, 580 and 631nm of its indigenously produced Protoporphyrin IX (PpIX) excited by three LEDs with broad emission bands at 418, 522 and 630nm and two laser diodes with narrow emission bands at 405 and 635nm. Fluorescence spectroscopy and plate count method have been employed for studying the inactivation rate of E. coli strain in autoclaved water suspension. It has been found that LEDs at 418, 522 and 630nm produced pronounced antimicrobial photodynamic effect on E. coli strain comparing laser diodes at 405 and 635nm, which might be attributed to the overlapping of broad emission bands of LEDs with the absorption bands of PpIX than narrow emission bands of laser diodes. Particular effect of LED at 522nm has been noticed because its broad emission band overlaps three absorption bands 505, 542 and 580nm of PpIX. The gold standard plate count method strongly correlates with Fluorescence spectroscopy, making it an innovative tool to administer bacterial inactivation. The experimental results suggested the development of a light source that entirely overlap absorption bands of PpIx to produce a pronounced antimicrobial photodynamic effect, which might become an effective modality for in vivo disinfection of antibiotic resistant microbes in wounds and lesions.

Tuning of structure, surface morphology and optical properties of spray-coated nickel tin oxide thin films by heat treatment

In this work, nickel tin oxide (NiSnO3) in a 1:1 ratio was synthesized using a simple spray pyrolysis technique followed by annealing at 450°C for different time durations. The X-ray diffraction (XRD) revealed the polycrystalline nature with perovskite structure of NiSnO3 without the formation of any secondary phases. Annealing improved the crystallinity of the films. The annealed films exhibited a preference for orientation along the (310) plane. The largest crystallite size was obtained for 4 hours of annealed film. The scanning electron microscopy (SEM) images of the films distinctly illustrate enhanced crystallinity following the annealing process. Energy-dispersive X-ray spectroscopy (EDS or EDX) indicates that the film possesses a near-stoichiometric composition. All the films resulted in more than 70% transmittance in the visible region except for 8 hours annealed. The gradual reduction of energy bandgap was observed for the sample. The four peaks at 358 nm, 415 nm, 436 nm, and 460 nm were observed in photoluminescence (PL) spectra corresponding to near band emission and defects related emissions respectively. The determined optical parameters from the present study indicate that the 4-hour annealed film holds promise as a favourable option for optoelectronic and photonic devices.

Investigating Optical Variability of the Blazar S5 0716+714 on Diverse Timescales

We present the results of the observational study of the blazar S5 0716+716 in the optical bands B, V, R, and I between 2019 March and 2023 August to investigate its variability on diverse timescales. The blazar was followed up by the T60 robotic telescope in Türkiye for 416 nights to obtain long-term variability during this period. In order to search for the intraday variability of the object, we have carried out 21 nights of observations with the T100 telescope for at least 1 hr. The blazar showed a ∼2.47 mag variation in the optical R band during our monitoring period, the brightest state on 2020 January 18 (MJD 58866) as R = 12.109 ± 0.011 mag and the faintest state on 2019 March 23 (MJD 58565) as R = 14.580 ± 0.013 mag. We employed the nested ANOVA test and the power-enhanced F-test to quantify intraday variability, which showed that the blazar was significantly variable in the R band on 12 out of 21 nights. Correlation analysis of the light curves shows that the emission in the BVRI optical bands was strongly correlated both in the short and long term without any time lag. The blazar has likely quasiperiods of 186 ± 30 and 532 ± 76 days in the optical R-band light curve according to the weighted wavelet Z-transform and Lomb–Scargle periodogram. The intraday variation and long-term variation features are discussed within the frame of prospective scenarios.

Multiple pathways for lanthanide sensitization in self-assembled aqueous complexes

Lanthanide photoluminescence (PL) emission has attracted much attention for technological and bioimaging applications because of its particularly interesting features, such as narrow emission bands and very long PL lifetimes. However, this emission process necessitates a preceding step of energy transfer from suitable antennas. While biocompatible applications require luminophores that are stable in aqueous media, most lanthanide-based emitters are quenched by water molecules. Previously, we described a small luminophore, 8-methoxy-2-oxo-1,2,4,5-tetrahydrocyclopenta[de]quinoline-3-phosphonic acid (PAnt), which is capable of dynamically coordinating with Tb(III) and Eu(III), and its exchangeable behavior improved their performance in PL lifetime imaging microscopy (PLIM) compared with conventional lanthanide cryptate imaging agents. Herein, we report an in-depth photophysical and time-dependent density functional theory (TD–DFT) computational study that reveals different sensitization mechanisms for Eu(III) and Tb(III) in stable complexes formed in water. Understanding this unique behavior in aqueous media enables the exploration of different applications in bioimaging or novel emitting materials.

Impacts of Eu2+ -doped K3LuSi2O7 phosphor and a scattering particle on conventional white light emitting diodes

The K<sub>3</sub>LuSi<sub>2</sub>O<sub>7</sub> phosphor doping Eu2+ rare-earth ions (KLS:Eu) was reported to possess broad emission band from near-ultraviolet to nearinfrared. Additionally, this phosphor showed a wide absorption band of 250-600 nm, allowing it to be excited by blue-light chip of 460 nm, making it one of the suitable phosphor materials for a light emitting diode (LED). Besides, the scattering particle material CaCO<sub>3</sub> is incorporated into the yellow phosphor layer to serve the scattering-enhancement purpose. The combination of both materials aims at accomplishing improvements in performance of commercial LED package. The concentration of KLS:Eu is constant while that of CaCO3 is modified. As a result, the scattering factor is regulated and become the key factor influencing the optical outputs of the simulated LED. The increasing CaCO<sub>3</sub> concentration enhances the phosphor scattering efficiency of light, helping to improve the lumen output and color-temperature consistency of the LED. However, the color rendering performance declines as a function of the CaCO3 growing amount, despite the presence of a KLS:Eu phosphor layer. Further works should be done to optimize the application of KLS:Eu in cooperation with scattering particles for a higher-quality LED device.

Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off

Boron−nitrogen doped multiple resonance (BN-MR) emitters, characterized by B−N covalent bonds, offer distinctive advantages as pivotal building blocks for facile access to novel MR emitters featuring narrowband spectra and high efficiency. However, there remains a scarcity of exploration concerning synthetic methods and structural derivations to expand the library of novel BN-MR emitters. Herein, we present the synthesis of a BN-MR emitter, tCz[B−N]N, through a one-pot borylation reaction directed by the amine group, achieving an impressive yield of 94%. The emitter is decorated by incorporating two 3,6-di-t-butylcarbazole (tCz) units into a B−N covalent bond doped BN-MR parent molecule via para-C−π−D and para-N−π−D conjugations. This peripheral decoration strategy enhances the reverse intersystem crossing process and shifts the emission band towards the pure green region, peaking at 526 nm with a narrowband full-width at half maximum (FWHM) of 41 nm. Consequently, organic light emitting diodes (OLEDs) employing this emitter achieved a maximum external quantum efficiency (EQEmax) value of 27.7%, with minimal efficiency roll-off. Even at a practical luminance of 1000 cd∙m−2, the device maintains a high EQE value of 24.6%.

Promising deep-red emitting Cr3+-doped SrAl12O19 phosphors for plant growth LEDs.

Recently, deep-red-emitting phosphors that can be excited by ultraviolet (UV) and near-ultraviolet (NUV) light have been extensively investigated for plant growth LED applications. However, due to the harmful effects of these high-energy rays on plants, violet- or blue-excited deep-red-emitting phosphors are considered a more appropriate solution. In this work, SrAl12O19:Cr3+ phosphors were synthesized using a simple solid-state reaction, revealing a strikingly sharp deep-red emission band centered at 694 nm and effective excitation by violet light. The optimal SrAl12O19:1.0%Cr3+ phosphor, annealed at 1500°C, exhibits an extended lifetime of 0.549 ms, an energy activation level of 0.239 eV, a good quantum efficiency (QE) of 36.2%, and superior color purity at 100%. Further, an LED prototype with a precise absorption spectrum for far-red phytochrome (Pfr) has been demonstrated. These results indicate that the synthesized SrAl12O19:1.0%Cr3+ phosphors could be used as a promising deep-red-emitting phosphor for plant growth LED.

FEAST: Feedback in Emerging extragAlactic Star ClusTers: JWST Spots Polycyclic Aromatic Hydrocarbon Destruction in NGC 628 during the Emerging Phase of Star Formation

We investigate the emergence phase of young star clusters in the nearby spiral galaxy NGC 628. We use JWST NIRCam and MIRI observations to create spatially resolved maps of the Paα 1.87 μm and Brα 4.05 μm hydrogen recombination lines, as well as 3.3 and 7.7 μm emission from polycyclic aromatic hydrocarbons (PAHs). We extract 953 compact H ii regions and analyze the PAH emission and morphology at ∼10 pc scales in the associated photodissociation regions. While H ii regions remain compact, radial profiles help us to define three PAH morphological classes: compact (∼42%), extended (∼34%), and open (∼24%). The majority of compact and extended PAH morphologies are associated with very young star clusters (<5 Myr), while open PAH morphologies are mainly associated with star clusters older than 3 Myr. We observe a general decrease in the 3.3 and 7.7 μm PAH band emission as a function of cluster age, while their ratio remains constant with age out to 10 Myr and morphological class. The recovered PAH3.3μm/PAH7.7μm ratio is lower than values reported in the literature for reference models that consider neutral and ionized PAH populations and analyses conducted at galactic physical scales. The 3.3 and 7.7 μm bands are typically associated with neutral and ionized PAHs, respectively. While we expected neutral PAHs to be suppressed in proximity to an ionizing source, the constant PAH3.3μm/PAH7.7μm ratio would indicate that both families of molecules disrupt at similar rates in proximity to H ii regions.

Highly Fluorescent π-Conjugated Azomethines and Divalent Metal Complexes as Antibacterial and Antibiofilm Nominees.

π-Conjugated azomethine ligands differing in the naphthalene or phenylmethane-centered core structure and their divalent cobalt, nickel, copper, and zinc metal complexes were prepared and well-characterized by spectral analyses in solid state. Magnetic natures of the complexes were determined by magnetic susceptibility measurements in solid-state. Their remarkable photophysical characteristics were recorded by Uv-vis and Fluorescence spectroscopic techniques. At their excitation wavelenght of 265 nm, all molecules exhibited triple fluorescence emission bands with promising intensities above 673 nm in near infra-red region. Antibacterial and antibiofilm activities of the π-conjugated azomethines are promising for potential applications in medical and healthcare settings. Hence, the antibacterial/antibiofilm activity of the π-conjugated azomethine ligands and their metal complexes against some clinically important bacteria namely Staphylococcus aureus (MSSA), Methicillin-resistant Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa and Proteus mirabilis was investigated, and the obtained results have shown that the ligands and complexes had a remarkable antibacterial effect, especially on Proteus mirabilis. Metal complexes have been found to have a significant inhibitory effect on biofilm formation by MRSA, MSSA, and P. mirabilis compared to ligands. The copper (II) complex of ligand-2 showed the highest inhibition percentage, significantly reducing biofilm formation for MRSA and MSSA. Furthermore, cobalt (II) complexes of the ligands selectively inhibited the growth of the opportunistic pathogen P. mirabilis biofilms, indicating that metal complexes might be a good choice for future antibiofilm studies.

Ni2+ activated broadband near-infrared II germanate phosphor for pc-LED applications

The broadband near-infrared (NIR) pc-LED is considered as a new generation of light source for substance measurements based on NIR spectroscopy. The most studied Cr3+ doped broadband NIR phosphors emit in the near-infrared I region. However, there is a demand for broadband near-infrared II solid-state light sources for expanding the variety of detected substances. Herein, Ni2+ activated NIR II Mg14Ge5O24 phosphor is synthesized by high-temperature solid-state method. The phosphor shows a asymmetric broad NIR emission band peaked at 1420 nm, that is assigned to the 3T2(3F)→3A2(3F) transition of Ni2+. It is observed that the asymmetric emission band is contributed from two Ni2+ centers, Ni2+(I) and Ni2+(II), occupying Ge4+ site with the emission peaked at 1313 nm and Mg2+ site with the emission peaked at 1435 nm, respectively. It is found that the addition of Ti4+ and B3+ can significantly change the intensity ratio of the two Ni2+ centers and enhance the overall emission intensity. Moreover, the addition of Mn4+ results in only Ni2+(II) emission. The origin of the unique features mentioned above is discussed. The temperature dependence of the NIR emissions is also studied. Finally a broadband NIR II pc-LED with a moderate electro-optical conversion efficiency of 1.4 % is fabricated based on a 400 nm LED chip. The results indicate that the modified Mg14Ge5O24:Ni2+ is a potential broadband NIR II phosphor for pc-LED applications.

The Binding Mechanism Between Cyclodextrins and Anticancer Drug Noscapine: A Spectroscopic and Molecular Docking Study.

In this paper the binding of noscapine (NOS) as an anticancer drug with poor bioavailability and low solubility with beta and methyl-beta cyclodextrins (β-CD and M-β-CD) as the biocompatible drug carriers were discussed using ultraviolet-visible, fluorescence and nuclear magnetic resonance spectroscopy, as well as molecular docking. The absorption of NOS changed when it was bound to both cyclodextrins, resulting in a hyperchromic shift. It formed a 1:1 stoichiometry inclusion complex with both cyclodextrins according to the Benesi-Hildebrand equation. The binding affinity was larger in NOS-M-β-CD (5.9 (± 0.66) × 103 M- 1) than NOS-β-CD (3.7 (± 0.22) × 103 M- 1) complex. The fluorescence emission band of NOS at 408nm was quenched when NOS was complexed with β-CD, and enhanced in the presence of M-β-CD, while the shoulder at 350nm was enhanced selectively when NOS was complexed with M-β-CD. The fluorescence quenching of NOS with β-CD showed a negative deviation from the Stern-Volmer. The thermodynamic parameters have been estimated with the help of the Van't Hoff equation in different temperatures, and a dynamic mechanism was proposed for quenching. Also, both ΔH and ΔS have positive values thus the main interactions result in hydrophobic forces. Moreover, the negative value of ΔG indicates that the bonding process is spontaneous. 1H NMR chemical shift changes were observable for NOS and both CDs protons due to the chemical environment changes of some nuclei upon complexation. The molecular docking results revealed that the 1:1 inclusion complex possesses a good molecular shape complementarity score for their most probable structures, and indicated that the M-β-CD inclusion system gave the higher complexation efficiency. The binding energy values for β-CD and M-β-CD were determined to be -6.7 and - 9.5kcal/mol, respectively. These findings suggest the same as the result of experimental tests that the NOS-M-β-CD complex is more stable than the NOS-β-CD complex.

A sustainable methodology employing the extract of red dragon fruit peel as a fluorescence probe for detection of indigo carmine (E132) in food samples: evaluation of the method's greenness, whiteness, and blueness.

Indigo carmine dye is one of the most widely used dyes in various fields. In this study, the ethanolic extract of red dragon fruit peel (Ex-RDFP) was employed as a green fluorescence probe for measuring the synthetic dye indigo carmine. At a fluorescence excitation of 290.5 nm, the Ex-RDFP exhibits a fluorescence emission band at 341.5 nm. Meanwhile, the indigo carmine dye possesses an absorption spectrum at a maximum peak of 290 nm. Consequently, the fluorescence intensity of the Ex-RDFP was reduced upon the addition of indigo carmine solution due to the inner filter effect mechanism. This quenching in the fluorescence intensity of Ex-RDFP was substantially associated with the indigo carmine concentration at a linear scale of 1.0-7.0 μg mL-1 (r 2 = 0.9993). Furthermore, the limit of detection and the limit of quantitation of the method were found to be 0.209 μg mL-1 and 0.635 μg mL-1, respectively. The optimal analytical conditions, such as solvent used for dilution, pH, reaction time, volume of the reagent, and temperature, were examined and carefully studied. In addition, the proposed method was successfully applied to detect indigo carmine dye in various natural syrup samples, including lemon syrup, apple syrup, cantaloupe syrup, pineapple syrup, and guava syrup, with acceptable recovery values. The method's beneficial sustainability footprint was found by using an extensive greenness analysis that incorporated the modified National Environmental Methods Index (NEMI), the complex Green Analytical Procedure Index (GAPI), and the Analytical Greenness Calculator (AGREE) prep algorithms. In addition, "whiteness" and "blueness" were also assessed with the newly released (Red Green Blue 12) RGB12 and Blue Applicability Grade Index (BAGI) computational methods, emphasizing the benefit of the proposed method in terms of analytical efficiency, sustainability, and economy. The suggested technique is the answer to the worldwide popularity of ecologically conscious solutions by providing a green-and-white substitute for traditional techniques and advancing towards creating more sustainable quality control procedures in the future.

Preparation and properties of CsMoO2F3:Mn4+ red phosphor with anti-thermal quenching and high color rendering index

The CsMoO2F3:Mn4+ red phosphors were prepared by the lower coprecipitation method. The XRD data of the powder were refined by Rietveld using GSAS software. The crystal structure of the powder was orthogonal structure, and the space group was Imma. The strongest excitation band of the sample was located at 468 nm and the strongest emission band at 633 nm. When the Mn4+ doping ratio was 11 %, the CsMoO2F3:Mn4+ red phosphor had the strongest luminescence intensity with a color purity of 99.25 %. CsMoO2F3:Mn4+ red phosphor mixed with commercial YAG:Ce3+ yellow phosphor was coated on a blue LED chip and encapsulated into a white LED. The resulting device at a drive current of 50 mA had a 95.0 color rendering index and a correlated color temperature of 4320 K, with a radiant luminous efficacy of 356.3 lm/W. CsMoO2F3:Mn4+ red phosphor had better thermal stability than the previous Mn4+-doped fluorine oxide phosphors. At 423 K, the luminous intensity at this time was 117 % of that at room temperature (303 K), with excellent heat resistance.

Investigation on Luminescence Properties of Dy3+ Ions Doped NaBaB9O15 Phosphors for Optoelectronic Applications.

A series of Dy3+ ions doped NaBaB9O15 phosphors with different dopant concentration was synthesized by solid state reaction. The phase purity was checked by X-ray diffraction analysis and the functional groups present in as prepared phosphors was investigated with the help of FTIR spectral analysis. Under 386nm excitation, the photoluminescence spectra exhibit three emission bands around 482nm, 574nm and 664nm due to 4F9/2→6HJ/2 (J = 15, 13, 11) transions respectively. The optimum doping concentration of Dy3+ ions was found to be 5mol%. The color coordinates are estimated from the emission spectra to check the dominant emission color and the color coordinates of the studied phosphors are fall on white region of CIE 1931 diagram. The decay curve analysis was made to determine the lifetime of excited state of Dy3+ ions and the decay curves are exhibited bi-exponential behavior irrespective of Dy3+ ion concentration. All these measurents are done in room temperature and the results obtained from these studies are discussed in detail to claim their usage in light emitting devices.

Multifunctional Near-Infrared Phosphors Cr3+/Ni2+ Codoped Mg3Ga2GeO8 Based on Energy Transfer from Cr3+ to Ni2.

Currently, near-infrared (NIR) light-emitting materials have been widely used in many fields, such as night vision, bioimaging, and nondestructive analysis. However, it is difficult to achieve multifunction in certain NIR light emitting phosphor. Herein, we propose a new near-infrared phosphor Mg3Ga2GeO8:Cr3+,Ni2+ that can be applied to at least three fields, i.e., identification of compounds, temperature sensing, anticounterfeiting, and other applications. The multifunctional material exhibited efficient broadband emission of 650-1650 nm under 420 nm excitation. The emission intensity of Ni2+ in Mg3Ga2GeO8:Cr3+,Ni2+ is enhanced by two times compared with that of Ni2+ in Mg3Ga2GeO8:Ni2+ due to the energy transfer process. Compared with phosphor single doped with Ni2+, Mg3Ga2GeO8:Cr3+,Ni2+ is more convincing in organic compound recognition because it is based on two emission bands: 600-1100 nm and 1100-1650 nm. As a temperature sensor, Mg3Ga2GeO8:Cr3+,Ni2+ is an ideal temperature-sensing material. This work not only provides a super broadband NIR emitting phosphor with multiple functions but also presents a practical approach for the development of high-efficiency and multifunctional NIR phosphors.