Intense Sharp Band Research Articles

Enhanced UVB 311 emission in Sb2O3–SiO2 glasses doped with Gd2O3 and tailored Pb3O4 content for potential phototherapy

This study investigates the enhancement of the sharp 311 nm UVB emission from Gd3+ ions in antimony silicate glass system doped with a fixed concentration of Gd2O3 (1.0 mol%) and varying amounts of red lead (40–10 mol%). The emission spectra revealed an intense sharp UVB band at 311 nm, originating from the 6P7/2 → 8S7/2 transition of gadolinium ions upon excitation at 273 nm. Interestingly, the intensity of this band nearly doubles as the Pb3O4 content decreases from 40 to 10 mol%. Such improvement was attributed to the decomposition of Pb3O4 into various phases that include α-PbO2, β-PbO2 polymorphs, and PbO. Out of these decomposition products, PbO acted as modifiers, reduced phonon losses and consequently enhanced the emission intensity. The decrease in Pb3O4 content is also hypothesized to promote de-clustering of Gd3+ ions within the glass matrix. This de-clustering reduced cross-relaxation losses, further contributed to the observed emission enhancement. In summary, this study demonstrated a successful strategy for boosting the UVB emission from Gd3+ ions in antimony silicate glasses by manipulating the content of Pb3O4.

Doubly Fused Unsymmetrical Calixdicarbahexaphyrins.

Three novel doubly fused unsymmetrical calixdicarbahexaphyrins were synthesized by mild acid-catalyzed (4+2) condensation of dicarbatetrapyrrane with dipyrroethene diol followed by oxidation. The condensation formed doubly fused calixdicarbahexaphyrins instead of π-conjugated dicarbahexaphyrins, due to the unusual fusion of the pyrrole N with the α-carbon of the adjacent pyrrole ring to form a tripentacyclic ring and one usual fusion of the pyrrole N with the adjacent phenylene C to form a fused moiety containing two pentacycles and one hexacycle ring. Both fusions occurred on one side of the macrocycle, making the macrocycles unsymmetric. The crystal structure obtained for one of the macrocycles exhibited a saddle-shaped structure with two benzene rings and four pyrrole rings connected via two ethylene and four methene meso-carbon atoms. The crystal structure also revealed unusual fusions in the macrocyclic framework and the presence of one sp3 carbon that disrupts the π-electron delocalization. 1H, 1H-1H COSY, NOESY, 13C, and HMBC NMR techniques were used to characterize the macrocycles. The absorption spectra of the macrocycles showed one intense sharp band at ∼485 nm along with a shoulder in the lower-energy region, suggesting its non-aromatic nature. Electrochemical studies indicated their electron rich nature, and DFT/TD-DFT studies corroborated the experimental observations.

Osmium(IV) pyrophosphate: Synthesis, Crystallization, and Ligand‐Field Analysis of the [OsIVO6] Chromophore

AbstractTwo polymorphs of burgundy‐red OsP2O7, with cubic (ZrP2O7 structure type, Z=4, a=7.8276(4) Å, 3×3×3 superstructure with a’=3a=23.484(2) Å) and triclinic symmetry (ruby‐red crystals, single‐crystal X‐ray structure determination, GeP2O7 structure type, (no. 2), Z=2, a=4.8072(7) Å, b=6.8993(13) Å, c=8.050(1) Å, α=91.82(2)°, β=92.92(1)°, γ=107.42(2)°, 98 parameters, R1=0.045, wR2=0.144, 3006 unique reflections with |Fo|>4σ(Fo)) have been obtained reducing OsO4 by phosphorus in sealed silica ampoules followed by subsequent chemical vapour transport. Reaction with the wall led to mixed SiIV/OsIV silicophosphates (Os1−xSix)3[Si2O(PO4)6] {x=0.84, pale orange, SiIV3[Si2O(PO4)6] structure type, , Z=3, a=7.893(1) Å, c=24.409(5) Å, 59 parameters, R1=0.058, wR2=0.160, 1311 unique reflections with 1033 |Fo|>4σ(Fo); x=0.47, orange, GeIV3[Si2O(PO4)6] structure type, , Z=2, a=7.9979(3) Å, c=16.4625(5) Å, 59 parameters, R1=0.040, wR2=0.094, 902 unique reflections with 749 |Fo|>4σ(Fo)}. Both structures were refined from single‐crystal data. Above 25 K triclinic OsP2O7 shows temperature independent paramagnetism with a strong temperature dependence of pointing to as electronic ground state for Os4+ (d4) with strong spin‐orbit coupling leading to =0 and the non‐magnetic ground state of the octahedral [OsIVO6] chromophore.. Optical spectra of both polymorphs of OsP2O7 show similar combinations of intense sharp and broad absorption bands typical for dn electronic systems systems with both, spin‐orbit coupling and ligand field splitting, being strong. The observations are consistent with the ligand‐field parameters Δo=20000 cm−1, B=704 cm−1, and ζ=3454 cm−1 for the octahedral [OsIVO6] chromophore.

Bis-(Fluorene)-Embedded Hexaphyrins.

The polyaromatic hydrocarbon containing expanded porphyrins, bis-(fluorene)-embedded hexaphyrins, were synthesized by condensing fluorene-based tripyrrane with pentafluorobenzaldehyde in CH2Cl2 in the presence of 1 equiv of BF3·OEt2 under an inert atmosphere followed by oxidation with DDQ in open air at room temperature. The reaction worked only when 1 equiv of BF3·OEt2 was added to the reaction mixture under concentrated reaction conditions. The bis-(fluorene)-embedded macrocycles were characterized and studied by high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR), absorption, electrochemical, and density functional theory (DFT)/time-dependent (TD)-DFT techniques. In 1H NMR, the hexaphyrins showed a few broad unresolved resonances at room temperature, but the NMR spectra were well-resolved at lower temperatures, indicating that the hexaphyrins were very flexible. The DFT-optimized structures indicated that the two fluorene units at the crossing point of the figure-eight loop makes an angle of ∼79.73° with each other, the fluorene moieties maintained their own planarity, and one of the fluorene moieties was not involved in conjugation with the rest of the macrocycle. The absorption spectra of hexaphyrins showed one intense sharp band in the higher energy region and a broad band in the lower energy region. The electrochemical studies indicated that expanded hexaphyrins are relatively electron-rich and showed three easier oxidations and one reduction. The DFT/TD-DFT studies are in agreement with the experimental observations.

Electron-Deficient Heteroacenes that Contain Two Boron Atoms: Near-Infrared Fluorescence Based on a Push-Pull Effect*.

Electron-deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of silicon-bridged precursors. X-ray crystallographic analysis revealed quinoidal structures, which give rise to two-step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near-infrared (NIR) region. These properties originate from the push-pull effect along the long axis of the molecule derived from the electron-donating ether moieties and the electron-accepting boron moieties. Of particular note is the NIR emission of the thienothiophene-centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm-1 in cyclohexane. A Franck-Condon analysis revealed the crucial role of the sterically less-hindered thienothiophene spacer in achieving this sharp emission band.

Electron‐Deficient Heteroacenes that Contain Two Boron Atoms: Near‐Infrared Fluorescence Based on a Push–Pull Effect**

AbstractElectron‐deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of silicon‐bridged precursors. X‐ray crystallographic analysis revealed quinoidal structures, which give rise to two‐step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near‐infrared (NIR) region. These properties originate from the push–pull effect along the long axis of the molecule derived from the electron‐donating ether moieties and the electron‐accepting boron moieties. Of particular note is the NIR emission of the thienothiophene‐centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm−1 in cyclohexane. A Franck–Condon analysis revealed the crucial role of the sterically less‐hindered thienothiophene spacer in achieving this sharp emission band.

Influence of apple phytochemicals in ZnO nanoparticles formation, photoluminescence and biocompatibility for biomedical applications

The new green-synthesised ZnO nanoparticles (NPs) using apple (var. Starking) phytochemicals present a great potential for bioimaging applications. These NPs, when compared with ZnO microparticles synthesised with pure phytochemicals (quercetin or sucrose), and water, revealed that sizes and shapes were widely dependent on the organic precursors used. Based on these findings, new insights into the synthesis of ZnO NPs using apple phytochemicals were presented.The photoluminescent properties, characterized by steady-state and time resolve photoluminescence measurements, revealed that besides the intense sharp near-UV band edge emission observed for all particles, with sub-nanosecond lifetime, a strong broad emission band peak at 2.20 eV was detected for microparticles, with longer decay times being associate to crystal defects. Additionally, the photoluminescent properties of ZnO particles, further explored by fluorescence lifetime imaging microscopy (FLIM), suggested adequacy for imaging applications. The cytotoxicity, evaluated in human dermal fibroblasts, proving the biosafety of ZnO NPs by an unaffected cellular viability, total mitochondrial activity and F-actin cytoskeleton organization, contrasted with some degree of cytotoxicity depicted for microparticles. The influence of the phytochemicals in ZnO cytotoxicity was discussed.To the authors' best knowledge this is the first report of ZnO NPs synthesised with apple extracts. The novelty of choosing a fruit widely used in the food industry will render affordable NPs through the concept of circular economy. The proved biosafety of these ZnO NPs together with their intrinsic photoluminescent properties, open perspectives for the development of cost-effective bioimaging materials with potential to be further directed into biomedical applications.

Enhanced luminous efficiency in Pr3+ activated Ca0.5La(MoO4)2 red phosphor with blue excitation for WLED applications

In this article, we have investigated the down-conversion luminescence properties of Ca0.5La(MoO4)2 doped with trivalent Pr3+ (substitute for La3+ site) and codoped with Mn2+ (substitute for Ca2+ site). The powder X-ray diffraction patterns confirm that the single crystalline phosphor powders belong to the scheelite-type tetragonal crystal structure. The photoluminescence (PL) excitation spectra of Ca0.5La(MoO4)2:Pr3+ exhibits a charge transfer band centered at 276 nm along with three intense sharp absorption bands identified at 449, 475, and 488 nm which are attributed to the f–f electronic transitions of 3H 4 (1) → 3P2, 3H 4 (1) → 3P1, 3H 4 (1) → 3P0 of Pr3+, respectively. Upon optical excitation, the depopulation of excited 3P0 level into the 3F2 lower levels of Pr3+ is governed by radiative transfer of energy, as a result, high intense red emission peak was observed at 647 nm. The change in PL emission intensity as a function of Pr3+ concentrations, Mn2+ concentrations, and different excitation wavelengths have been investigated in detail. Further, the codoping of alkali metal chlorides MCl (M = Na, K, Li) into the Ca0.5La(MoO4)2:Pr3+ phosphor greatly improves the luminescence intensity of the transition 3P0 → 3F2 which can be explained by charge compensation effect. To ensure the colour richness and quality of its emission, the photometric parameters were estimated using spectral energy distribution functions of Ca0.5La(MoO4)2:Pr3+. The luminous efficacy of radiation for NaCl codoped Ca0.5La(MoO4)2:Pr3+ phosphor was estimated to be 154 lm/W and the percentage of luminous efficiency is 23 %.

Raman and Infrared Spectroscopic Study of the Borate Mineral Kaliborite

We have studied the mineral kaliborite. The sample originated from the Inder B deposit, Atyrau Province, Kazakhstan, and is part of the collection of the Geology Department of the Federal University of Ouro Preto, Minas Gerais, Brazil. The mineral is characterized by a single intense Raman band at 756 cm−1 assigned to the symmetric stretching modes of trigonal boron. Raman bands at 1229 and 1309 cm−1 are assigned to hydroxyl in-plane bending modes of boron hydroxyl units. Raman bands are resolved at 2929, 3041, 3133, 3172, 3202, 3245, 3336, 3398, and 3517 cm−1. These Raman bands are assigned to water stretching vibrations. A very intense sharp Raman band at 3597 cm−1 with a shoulder band at 3590 cm−1 is assigned to the stretching vibration of the hydroxyl units. The Raman data are complimented with infrared data and compared with the spectrum of kaliborite downloaded from the Arizona State University database. Differences are noted between the spectrum obtained in this work and that from the Arizona State University database. This research shows that minerals stored in a museum mineral collection age with time. Vibrational spectroscopy enhances our knowledge of the molecular structure of kaliborite.

SEM, EDX and vibrational spectroscopic study of the carbonate mineral donnayite-(Y) NaCaSr3Y(CO3)6·3H2O

The mineral donnayite-(Y) has been studied by scanning electron microscopy with chemical analysis using EDX and vibrational spectroscopy. Multiple carbonate stretching modes are observed and support the concept of non-equivalent carbonate units in the donnayite-(Y) structure. Intense sharp bands at 464, 479 and 508 cm−1 are assigned to YO stretching modes. Raman bands at 765 and 775 cm−1 are assigned to the CO32−ν4 bending modes and Raman bands at 589, 611, 674 and 689 cm−1 are assigned to the CO32−ν2 bending modes. Multiple Raman and infrared bands in the OH stretching region are observed, proving the existence of water in different molecular environments in the structure of donnayite-(Y).

A vibrational spectroscopic study of tengerite-(Y) Y2(CO3)3 2–3H2O

The mineral tengerite-(Y) has been studied by vibrational spectroscopy. Multiple carbonate stretching modes are observed and support the concept of non-equivalent carbonate units in the tengerite-(Y) structure. Intense sharp bands at 464, 479 and 508cm−1 are assigned to YO stretching modes. Raman bands at 765 and 775cm−1 are assigned to the CO32− ν4 bending modes and Raman bands at 589, 611, 674 and 689cm−1 are assigned to the CO32− ν2 bending modes. Multiple Raman and infrared bands in the OH stretching region are observed, proving the existence of water in different molecular environments in the structure of tengerite-(Y).

Spectroscopic properties of halite from Kłodawa salt mine, central Poland

The dynamics of colour centre transformation was investigated in blue halite single crystals from Klodawa Salt Mine, Central Poland, using UV–vis spectroscopy. The following colour centres were considered: F, R1, R2, as well as plasmons and M centres. The R2 centres predominated in navy blue (A) and pale blue (B) halites. Other relatively large populations were plasmons found in all examined samples. In purple (C) halite samples the plasmon population is the highest one among others and R1 centres appeared to be equally significant, whereas M centres were almost absent. For A and C samples unidentified bands were observed at 26,500 to 26,200 cm−1, respectively. The bleaching process of the blue halites was investigated using temperature dependent UV–vis and micro-Raman spectroscopies. In micro-Raman 300–100 cm−1 region three very intense sharp bands were attributed to the colour centres and colloidal Na precipitation in A and B halites. The one broad band in the range 3,500 to 500 cm−1, which was characteristic even for the colourless sample D but absent in the spectra of colourless NaCl obtained after recrystallization of sample A, requires further study.

A vibrational spectroscopic study of the phosphate mineral churchite (REE)(PO4)⋅2H2O

Vibrational spectroscopy has been used to study the rare earth mineral churchite of formula (REE)(PO4)⋅2H2O. The mineral contains a range of rare earth metals including yttrium depending on the locality. The Raman spectra of churchite-(REE) are characterized by an intense sharp band at 984cm−1 assigned to the ν1(PO43-) symmetric stretching mode. A lower intensity band observed at around 1067cm−1 is attributed to the ν3(PO43-) antisymmetric stretching mode. The (PO43-) bending modes are observed at 497cm−1 (ν2) and 565cm−1(ν4). Raman bands at 649 and 681cm−1 are assigned to water librational modes. Vibrational spectroscopy enables aspects of the structure of churchite to be ascertained.

Vibrational Spectroscopic Characterization of the Phosphate Mineral Anapaite Ca2Fe2+(PO4)2 · 4(H2O)

ABSTRACT We have characterized anapaite Ca2Fe2+(PO4)2 · 4(H2O), a rare Ca and Fe phosphate, using a combination of electron microscopy and vibrational spectroscopy. The mineral occurs in soils and lacustrine sediments and is usually related to the diagenetic process in phosphorous-rich sediments. The phosphate anion is characterized by its Raman spectrum with an intense sharp band at 943 cm−1, attributed to the ν1 symmetric stretching mode. Three bands at 992, 1039, and 1071 cm−1 are attributed to ν3 antisymmetric stretching modes. The infrared spectrum of anapaite shows complexity with a series of overlapping bands. Water in the structure of anapaite is observed by OH stretching vibrations at 2777, 3022, and 3176 cm−1 (Raman) and 2744, 3014, and 3096 cm−1 (infrared). The position of these bands provides evidence for the strong hydrogen bonding of water in the anapaite structure and contributes to the stability of the mineral.

Raman and infrared spectroscopic study of the mineral goyazite SrAl3(PO4)2(OH)5·H2O

We have studied the mineral goyazite using Raman and infrared spectroscopy. Goyazite is a member of the crandallite subgroup of the alunite supergroup. The crystal structure is of the alunite-type and consists of sheets of corner-sharing AlO6 octahedra parallel to (0001). The octahedrally coordinated Sr2+ cations occupy cavities between pairs of octahedral sheets and are surrounded by six oxygen atoms from the Al3+O6 octahedra.The very intense sharp band at 983cm−1 is assigned to the ν1PO43- symmetric stretching mode. The observation of a single band supports the concept that all the phosphate units are equivalent in the structure of goyazite. Raman bands observed at 1029cm−1 and 1037cm−1 are assigned to the ν3PO43- antisymmetric stretching vibrations. Two Raman bands at 895 and 927cm−1 are attributed to the stretching vibrations of H2PO4; thus indicating some hydrogen phosphate units in the structure of goyazite. Raman bands at 556, 581, 596 and 612cm−1 are assigned to the ν4PO43- bending modes, suggesting a reduction of symmetry of phosphate units. Two sharp Raman bands at 3609 and 3631cm−1 are attributed to OH stretching vibrations from the goyazite hydroxyl units. Broad Raman bands at 2924, 3043, 3210, 3429 and 3511cm−1 are assigned to water stretching vibrations. This research shows that from a vibrational spectroscopic point of view, the formula SrAl3(H PO4,PO4)2(OH)6⋅H2O is a better formulation for the mineral goyazite. Vibrational spectroscopy enables subtle details of the molecular structure of goyazite to be determined.

A Vibrational Spectroscopic Study of the So-Called Healing Mineral Papagoite CaCuAlSi2O6(OH)3

ABSTRACT Papagoite is a silicate mineral named after an American Indian tribe and was used as a healing mineral. Papagoite CaCuAlSi2O6(OH)3 is a hydroxy mixed anion compound with both silicate and hydroxyl anions in the formula. The structural characterization of the mineral papagoite remains incomplete. Papagoite is a four-membered ring silicate with Cu2+ in square planar coordination. The intense sharp Raman band at 1053 cm−1 is assigned to the ν1 (A 1g) symmetric stretching vibration of the SiO4 units. The splitting of the ν3 vibrational mode offers support to the concept that the SiO4 tetrahedron in papagoite is strongly distorted. A very intense Raman band observed at 630 cm−1 with a shoulder at 644 cm−1 is assigned to the ν4 vibrational modes. Intense Raman bands at 419 and 460 cm−1 are attributed to the ν2 bending modes. Intense Raman bands at 3545 and 3573 cm−1 are assigned to the stretching vibrations of the OH units. Low-intensity Raman bands at 3368 and 3453 cm−1 are assigned to water stretching modes. It is suggested that the formula of papagoite is more likely to be CaCuAlSi2O6(OH)3 · xH2O. Hence, vibrational spectroscopy has been used to characterize the molecular structure of papagoite.

Development of UV-Excitable Red and Near-Infrared Fluorescent Labels and Their Application for Simultaneous Multicolor Bioimaging by Single-Wavelength Excitation

We report a new type of UV-excitable red/NIR-emissive fluorescent dyads (PKF series). Conjugation of a pyrene and a novel bright red/near-infrared (NIR) fluorophore resulted in large quasi-Stokes shift while retaining intense fluorescence emission and sharp spectral bands. Labeling of PKF dyads to biomolecules was performed by means of introduction of a succinimidyl ester. Simultaneous Ca(2+)/albumin dual-color intracellular imaging by PKF in combination with fura-2 (UV-excitable/VIS-emissive Ca(2+) indicator) reveals its usefulness as a new bioimaging tool.

Vibrational spectroscopy of the mineral meyerhofferite CaB3O3(OH)5·H2O – An assessment of the molecular structure

Meyerhofferite is a calcium hydrated borate mineral with ideal formula: CaB3O3(OH)5·H2O and occurs as white complex acicular to crude crystals with length up to ∼4cm, in fibrous divergent, radiating aggregates or reticulated and is often found in sedimentary or lake-bed borate deposits.The Raman spectrum of meyerhofferite is dominated by intense sharp band at 880cm−1 assigned to the symmetric stretching mode of trigonal boron. Broad Raman bands at 1046, 1110, 1135 and 1201cm−1 are attributed to BOH in-plane bending modes. Raman bands in the 900–1000cm−1 spectral region are assigned to the antisymmetric stretching of tetrahedral boron. Distinct OH stretching Raman bands are observed at 3400, 3483 and 3608cm−1. The mineral meyerhofferite has a distinct Raman spectrum which is different from the spectrum of other borate minerals, making Raman spectroscopy a very useful tool for the detection of meyerhofferite in sedimentary and lake bed deposits.

Infrared and Raman spectroscopic characterisation of the sulphate mineral creedite – Ca3Al2SO4(F,OH)·2H2O – and in comparison with the alums

The mineral creedite is a fluorinated hydroxy hydrated sulphate of aluminium and calcium of formula Ca3Al2SO4(F,OH)·2H2O. The mineral has been studied by a combination of electron probe analysis to determine the molecular formula of the mineral and the structure assessed by vibrational spectroscopy. The spectroscopy of creedite may be compared with that of the alums. The Raman spectrum of creedite is characterised by an intense sharp band at 986cm−1 assigned to the SO42- ν1 (Ag) symmetric stretching mode. Multiple bands of creedite in the antisymmetric stretching region support the concept of a reduction in symmetry of the sulphate anion. Multiple bands are also observed in the bending region with the three bands at 601, 629 and 663cm−1 assigned to the SO42- ν4 (Ag) bending modes. The observation of multiple bands at 440, 457 and 483cm−1 attributed to the SO42- ν2 (Bg) bending modes supports the concept that the symmetry of the sulphate is reduced by coordination to the water bonded to the Al3+ in the creedite structure. The splitting of the ν2, ν3 and ν4 modes is attributed to the reduction of symmetry of the SO4 and it is proposed that the sulphate coordinates to water in the hydrated aluminium in bidentate chelation.

Vibrational spectroscopic characterization of the phosphate mineral hureaulite – (Mn, Fe)5(PO4)2(HPO4)2·4(H2O)

This research was done on hureaulite samples from the Cigana claim, a lithium bearing pegmatite with triphylite and spodumene. The mine is located in Conselheiro Pena, east of Minas Gerais. Chemical analysis was carried out by Electron Microprobe analysis and indicated a manganese rich phase with partial substitution of iron. The calculated chemical formula of the studied sample is: (Mn3.23, Fe1.04, Ca0.19, Mg0.13)(PO4)2.7(HPO4)2.6(OH)4.78. The Raman spectrum of hureaulite is dominated by an intense sharp band at 959cm−1 assigned to PO stretching vibrations of HPO42− units. The Raman band at 989cm−1 is assigned to the PO43− stretching vibration. Raman bands at 1007, 1024, 1047, and 1083cm−1 are attributed to both the HOP and PO antisymmetric stretching vibrations of HPO42− and PO43− units. A set of Raman bands at 531, 543, 564 and 582cm−1 are assigned to the ν4 bending modes of the HPO42− and PO43− units. Raman bands observed at 414, and 455cm−1 are attributed to the ν2 HPO42− and PO43− units. The intense A series of Raman and infrared bands in the OH stretching region are assigned to water stretching vibrations. Based upon the position of these bands hydrogen bond distances are calculated. Hydrogen bond distances are short indicating very strong hydrogen bonding in the hureaulite structure. A combination of Raman and infrared spectroscopy enabled aspects of the molecular structure of the mineral hureaulite to be understood.