Characteristic Broad Band Research Articles

M-Pyripentaphyrins(1.0.0.0.0): BIII Complexes and β-β Directly Linked Dimers.

m-Pyripentaphyrins(1.0.0.0.0) were synthesized by Suzuki-Miyaura coupling of 3,5-bis(5-borylpyrrol-2-yl)-BODIPY with 2,6-dibromopyridine. Upon treatment with PhBCl2, pyripentaphyrin 1 provided mono- and bis-BIII complexes sequentially. The Mono-BIII complex shows a distorted tetrahedral coordinated BIII with a σ-phenyl ligand on the BIII and the bis-BIII complex shows an additional distorted tetrahedral coordinated BIII with a B-H bond. Bromination of the pyripentaphyrins with N-bromosuccinimide (NBS) resulted in regioselective formation of 8-bromopyripentaphyrins, which were dimerized to 8,8'-linked dimers by reductive coupling with Ni(cod)2. While all these pyripentaphyrins are nonaromatic, they exhibit characteristic broad absorption bands at long wavelength near the NIR region, indicating the presence of effective macrocyclic conjugation.

Enhancing photocatalytic dye degradation efficiency through the utilization of shock wave effects on neodymium oxide (Nd2O3)

This article delves into the impact of shockwaves on neodymium oxide (Nd2O3) nanoparticles, aiming to evaluate their physical and chemical stability. Nd2O3 nanoparticles were subjected to varying sets of shock pulses (100, 200, and 300) in photocatalytic dye degradation. The nanoparticles crystallinity and unit cell volume after shockwave exposure were examined using powder X-ray diffraction (PXRD) analysis with unit-cell software. PXRD data revealed no alterations in the crystalline structure, lattice parameter and unit cell volume. Comparisons between pre- and post-shockwave field emission scanning electron microscopy (FE-SEM) portraying data demonstrate that repeated shockwave application causes a decrease in particle size. Raman spectroscopy, under ambient conditions, shows a high intensity after shock conditions intensity will decrease. Furthermore, FTIR spectroscopy revealed the characteristic strong and broad absorption band associated with metal-oxygen (Nd-O) groups in the Nd2O3 nanoparticles. UV–Vis diffuse reflectance spectroscopy (DRS) was used to investigate the bandgap of the Nd2O3 nanoparticles. Initially, the bandgap was measured at 5.96 eV under ambient conditions, but following the shockwave exposure, it was decreased to approximately 5.91 eV. Interestingly, the surface area of the shockwave-treated Nd2O3 nanoparticles is increased and exhibited an increased efficiency in photocatalytic dye degradation. This finding holds promising implications for environmental remediation applications.

Insights into luminescence and energy transfer processes in Ce3+- and Tb3+ co-doped (Gd, Y)3Al2Ga3O12 garnet single crystals

Driven by the pursuit of optimizing the luminescent properties of garnet-based single crystals for X-ray imaging applications, this work reports on the successful synthesis and in-depth characterization of GYAGG crystals doped with Ce³⁺ or Tb³⁺ ions, and doubly-doped with both of them. Micro-pulling down synthesis yielded crystals with a single cubic phase confirmed by X-ray diffraction. Photoluminescence (PL) and radioluminescence (RL) measurements on Ce³⁺,Tb³⁺ co-doped GYAGG revealed bidirectional energy transfer processes. Characteristic broadband 5d1→4f emission of Ce³⁺ centers peaking at 530 nm and narrow 4f→4f emission lines of Tb³⁺ ions starting from 5D4 level within 480–630 nm were observed. At higher doping levels, cross-relaxation in Tb³⁺ pairs resulted depleted 5D3 state and only the emission from 5D4 one was observed in the spectra. Analysis of PL decay characteristics corroborated the spectral observations, confirming progressively decreasing Ce³⁺ decay time (down to 40 ns at 15 % Tb3+) due to enhanced Ce³⁺→Tb³⁺ energy transfer. Similarly, the Tb³⁺ decay time accelerated by more than 60 % after the Ce³⁺ co-doping. Notably, co-doping with 0.5 % Ce³⁺ and 10–15 % Tb³⁺ doubled the luminescence intensity of RL spectra compared to 0.5 % Ce³⁺-doping alone, attributed to the increased density of emitting centers.

An Eco-friendly Approach to ZnO NP Synthesis Using Citrus reticulata Blanco Peel/Extract: Characterization and Antibacterial and Photocatalytic Activity.

Emission of greenhouse gases and infectious diseases caused by improper agro-waste disposal has gained significant attention in recent years. To overcome these hurdles, agro-waste can be valorized into valuable bioactive compounds that act as reducing or stabilizing agents in the synthesis of nanomaterials. Herein, we report a simple circular approach using Citrus reticulata Blanco (C. reticulata) waste (peel powder/aqueous extract) as green reducing and capping/stabilizing agents and Zn nitrate/acetate precursors to synthesize ZnO nanoparticles (NPs) with efficient antimicrobial and photocatalytic activities. The obtained NPs crystallized in a hexagonal wurtzite structure and differed clearly in their morphology. UV-vis analysis of the nanoparticles showed a characteristic broad absorption band between 330 and 414 nm belonging to ZnO NPs. Fourier transform infrared (FTIR) spectroscopy of ZnO NPs exhibited a Zn-O band close to 450 cm-1. The band gap values were in the range of 2.84-3.14 eV depending on the precursor and agent used. The crystallite size obtained from size-strain plots from measured XRD patterns was between 7 and 26 nm, with strain between 16 and 4%. The highly crystalline nature of obtained ZnO NPs was confirmed by clear ring diffraction patterns and d-spacing values of the observed lattice fringes. ZnNPeelMan_400 and ZnNExtrMan showed good stability, as the zeta potential was found to be around -20 mV, and reduced particle aggregation. Photoluminescence analysis revealed different defects belonging to oxygen vacancies (VO+ and VO+2) and zinc interstitial (Zni) sites. The presence of oxygen vacancies on the surface of ZnAcExtrMan_400 and ZnAcPeelMan_400 increased antimicrobial activity, specifically against Gram-negative bacteria Escherichia coli (E. coli) and Salmonella enteritidis (S. enteritidis). ZnNExtrMan with a minimal inhibitory concentration of 0.156 mg/mL was more effective against Gram-positive bacteria Staphylococcus aureus (S. aureus), revealing a high influence of particle size and shape on antimicrobial activity. In addition, the photocatalytic activity of the ZnO NPs was examined by assessing the degradation of acid green dye in an aqueous solution under UV light irradiation. ZnAcPeelMan_400 exhibited excellent photocatalytic activity (94%) within 90 min after irradiation compared to other obtained ZnO NPs.

Cr3+-activated NaInSi2O6: An efficient broadband near-infrared phosphor with its applications in LED

A novel near-infrared (NIR) emitting Cr3+-doped clinopyroxene NaInSi2O6 phosphor is designed and synthesized by solid-state method. There are three absorption bands in the NaInSi2O6: 0.04Cr3+ phosphor, peaking at ∼300 nm, ∼470 nm and ∼690 nm, respectively. A broad emission band ranging from 700 nm to 1300 nm is detected at 466 nm excitation, peaking at 936 nm with a full width at half maximum (FWHM) of 151 nm. At the same time, the calculated weak crystal field strength of Cr3+ is 1.93 in the NaInSi2O6 host, resulting in its characteristic broadband emission. Furthermore, the internal quantum efficiency (IQE) and external quantum efficiency (EQE) of NaInSi2O6: 0.04Cr3+ are 68.9% and 27.4%. The integrated emission intensity of NaInSi2O6: 0.04Cr3+ at 423 K retains 55.2% of that at 293 K. By contrast, the NaInSi2O6: 0.04Cr3+-based phosphor-in-glass (PiG) exhibits better thermal stability (64.9%@423 K). A NIR phosphor-converted light emitting diode (pc-LED) was manufactured using a InGaN chip and NaInSi2O6: 0.04Cr3+, presenting the NIR output power of 30.47 mW@200 mA. Used as a NIR light source, the prepared pc-LED shows good promise in the fields of biological tissue imaging and night vision.

Near-Infrared Emission Material with Superlong Afterglow Performance and Its Multifunctional Applications.

A new near-infrared (NIR) emission material, BaSi1.5Ge2.5O9:Cr3+, with outstanding long afterglow properties is designed and synthesized successfully. Its structure, photoluminescence, and long afterglow emission features are studied in detail. Cr3+ occupies six-coordinated Ba2+ and Ge4+ sites in this system, which can emit characteristic broadband NIR light in the range of 700-1200 nm, and it has a long afterglow emission of more than 10 h. We calculated the band gap of the host at about 4.1 eV, the energy level distribution after Cr3+ doping, and the distribution of oxygen vacancies through density functional theory simulation, which theoretically proved the characteristic transition of Cr3+ and that the oxygen vacancies are crucial to form the defect energy levels. This is corroborated with the reflectance spectra, three-dimensional thermoluminescence spectra, and electron spin resonance (ESR) spectra. The oxygen-deficient environment favors the formation of oxygen vacancy defects and prevents the oxidation of Cr3+ to Cr6+, which are the key points for the luminescence and afterglow properties. A mechanistic model of defect formation and electron trapping and transport processes is successfully established. Finally, its multifunctional applications in information anticounterfeiting encryption, biological tissue penetration, and internal nondestructive testing and imaging are demonstrated.

Conformation-dependent photophysical properties of butadiyne-linked π-extended BODIPY dimers

A hitherto unknown butadiyne-linked BODIPY dimer (4) has been synthesized under the conventional Glaser coupling reaction conditions using the ethynyl-substituted pyrrolyl-BODIPY (2) prepared by gold-catalyzed C-H alkynylation. Due to the [Formula: see text]-extended structure of the BODIPY chromophore in 4, a characteristic broad absorption band in the near-infrared (NIR) region has emerged. Upon photoexcitation, the environment-dependent fluorescence spectral features were observed. The fluorescent response varied with solvents, viscosity, and temperature, which was found to originate from the conformational changes between the coplanar and twisted conformers in the otherwise rigid butadiyne-bridged dimer 4. Therefore, the BODIPY dimer 4 would be a potential NIR fluorescence material for use in the probes responding to the distinct viscous environment in biological tissues.

Synthesis, crystal structure, and anti‐thermal quenching performance of Lu2Sr(1−x)Al4SiO12:xEu2+ phosphors

AbstractWith high‐temperature solid‐state reaction method, a series of Lu2Sr(1−x)Al4SiO12:xEu2+ phosphors have been synthesized. With Rietveld refinement method, the crystal structure of Lu2SrAl4SiO12 has been refined. Under the excitation of the ultraviolet and violet band light, Lu2Sr(1−x)Al4SiO12:xEu2+ emits the Eu2+ characteristic blue broadband light. The photoluminescence properties of concentration quenching, emission peak shift, reflectance spectra, and luminescence decay have been investigated. With the structure analyses, the corresponding physical mechanisms have been discussed. With the increased temperature, this phosphor shows well thermal stabilities. For the xEu = 0.06, 0.08, and 0.1 phosphors, the strong anti‐thermal quenching performance has been observed. The reason for the anti‐thermal quenching of this phosphor has been discussed. The trap capture mechanism may be the suitable physical mechanism to explain the anti‐thermal quenching of this phosphor. This phosphor shows the potential applications in the white LED lighting fields.

Synthesis and Photoluminescence Properties of White Emitting Alkaline Earth Chalcogenide Phosphors doped with Sn for Solid State Lighting

Sn2+ doped white emitting alkaline-earth chalcogenide CaS and SrS phosphors were synthesized by carbo-thermal reduction method. In this method special requirement such as H2S gas flow is not required as a source of sulphur and is comparatively easy method to prepare sulfides. The crystalline phase, morphology, and photoluminescence properties were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), and fluorescence spectrophotometer, respectively. Phosphors exhibit broad band excitation which has excellent spread over nUV as well as blue region of visible light i.e. 440–480 nm. Emission is in the form of characteristic broad band of Sn2+ covering nUV and almost entire regions of visible spectrum i.e. 400–650 nm. The XRD pattern of prepared phosphor well matches with International Center for Diffraction Data. Synthesized phosphor particles are of different sizes, with smooth surfaces, from less than 1 micron to few microns. The chromaticity coordinates of synthesized phosphors have been calculated from its corresponding emission spectra monitored at their excitation wavelengths. They observed to falls in white region of CIE diagram. These points are close to standard white point D65, corresponding to daylight with correlated color temperature (CCT) 6500 °K, indicating better color purity of the synthesized phosphor and they are promising material for a color converter using blue LED as the primary light (pumping) source in phosphor converted white LED (pc wLED) for solid state lighting.

Metalloporphyrins substituted with N-carbazolyl groups quadruply at meso positions

As a new family of porphyrinoids with broad absorption bands that efficiently harvest sunlight, the metal complexes of a porphyrin quadruply substituted with [Formula: see text]-carbazolyl groups at the meso positions were photometrically and structurally characterized. The porphyrins exhibited characteristic broad bands in the range of 450–500 nm, due to the charge transfer band from carbazole to porphyrin. Ligand exchange at the axial position of the zinc complex with an aquo ligand affected the absorption spectrum, and a hyper-hypsochromic shift of the broad band was observed by the coordination of methanol. Furthermore, the lowest unoccupied molecular orbital (LUMO) levels of the metalloporphyrins were lowered by the electron-withdrawing effect of the perpendicularly oriented carbazolyl groups. In the solid state, zinc-porphyrin was self-assembled into a one-dimensional coordination polymer by intermolecular axial coordination.

SrAl2O4: Eu2+, Dy3+ persistent luminescent materials functionalized with the Eu3+(TTA)-complex by microwave-assisted method

Recently, several classes of rare-earth-doped luminescent materials have been drawing attention due to structurally engineered energy converting systems, capable of tuning absorption and emission spectral ranges, outlining new materials and applications in photonics. In this scenario, this work presents the development of SrAl2O4:Eu2+,Dy3+ phosphors prepared by the Pechini method, which were further APTMS-functionalized (3-aminopropyltrimethoxysilane) by microwave-assisted synthesis, incorporating a Eu3+ β-diketonate complex embedded within a SiO2-R network to increase light absorption and promote energy transfer processes. Powder X-ray diffraction data revealed a stable characteristic monoclinic phase of the SrAl2O4 host matrix, which undergoes structural changes after functionalization. Particle morphology and elemental distribution were probed by scanning electron microscopy technique, exhibiting surface alteration effects. Photoluminescence spectra displayed a characteristic broad green emission band assigned to the 4f65d1(2D) → 4f7(8S7/2) interconfigurational transition of the Eu2+ ion. Functionalized materials presented absorption shifts coupled with an emission band intensification suggesting effective interactions between the β-diketonate complex, the SiO2-R network, and the inorganic host matrix. Increased absorption range and persistence decay time under near band gap excitation on modified materials were also observed.

Hexathianonaphyrin(1.0.0.1.0.0.1.0.0): Synthesis, optical, redox and protonation induced antiaromaticity

A simple non-rigid precursor termed as a “triheterole” comprising of 2,2[Formula: see text]-bithiophene linked to [Formula: see text]-pyrrole was prepared using a four-step synthetic strategy. This functionalized triheterole was allowed to undergo acid catalyzed condensation in the presence of Lewis acid (BF3 [Formula: see text] Et2O) to produce the [3 + 3 + 3] cyclotrimer 1 as a major product with trace formation of its higher homologues. Electronic absorption spectrum of 1exhibited a characteristic band (520 nm) and broad band in the visible region. Upon protonation, significant bathochromic shift of the band (608 nm) and the broad band towards near-IR region (ca.1250 nm) indicates its antiaromatic (4[Formula: see text] conjugated circuit. Detailed structural analyses using temperature-dependent 1D and 2D NMR along with DFT level theoretical investigations indicate that the molecule exhibits weak antiaromaticity due to its large fluxional nature.

Synthesis of Silver Nanoparticles from Mimusops elengi Extract of Raw Fruits and Characterization of PVA-Silver Polymer Nanocomposite Films

The present work concerns on the synthesis of silver nanoparticles at 25 ºC using raw fruits extract of Bakul (Mimusops elengi) tree via chemical reduction route development of poly(vinyl alcohol) PVA-silver polymer nanocomposite films. The nanocomposite films were subjected to characterization by UV-visible, FTIR, X-ray diffraction, field emission scanning electron microscope (FESEM) and thermal studies. The UV-visible spectrum shows a characteristic broad absorption band observed near 465 nm suggesting presence of silver nanoparticles in polymer nanocomposites (PNCs) film. The vibrational band shift of –OH group of poly(vinyl alcohol) in the presence of nanoparticle designated the chemical interaction between –OH group of poly(vinyl alcohol) and silver nanoparticles. The FESEM study confirmed that PVA is not only acted as a capping agent, but also a cross-linking agent. X-ray diffraction study shows that the existence of AgNPs in the poly nanocomposite film and nanoaparticles are crystalline in nature. Thermal studies suggest that the enhanced thermal stability is because of the good packing of the polar crystallites in β-PVA composites as compared to the non-polar α-phase of neat poly(vinyl alcohol) (PVA).

ICMMS-2: Gamma-rays interactions on the spectral properties of CuO-doped lithium host barium borate glasses

Glass samples of undoped and CuO-doped barium borate host glasses were prepared. Combined optical properties together with structural FTIR spectral analysis were measured before and after gamma irradiation with a dose of 6 M rad. The optical spectral absorption of the base is characterized by prominent ultraviolet band which is correlated with trace ferric ions present as impurities. The CuO-doped glasses exhibit an extended broad visible –near IR band which is assumed to originate from octahedrally coordinated Cu2+ ions revealing obvious separation to two component peaks. The irradiation process is accompanied by an increase of the intensities of the absorption bands and can be attributed to proposed photochemical reactions between liberated electrons and formed positive holes with trace iron impurities. FTIR spectra reveal distinct two characteristic broad bands within the mid region 800-1200 cm-1 and 1200-1600 cm-1 indicating the presence of both tetrahedral borate groups and co-presence of triangular borate groups and the intensities of these two IR broad bands increase with the CuO content due to suggested polymerization of the borate network or changes in the ratio of BO4 and BO3 groups.

Synthesis and photoluminescence behavior of of SrMg2Al16O27:Eu2+ nanocrystalline phosphor

SrMg2Al16O27:Eu2+ nanocrystalline phosphor has been synthesized via rapid gel-combustion method at 600 °C in muffle furnace and detailed photoluminescence behavior is reported. The phase purity and structural properties have been examined via Powder X-ray diffraction (PXRD), transmission electron microscopy (TEM) and Fourier transformation infrared (FTIR) spectroscopy. PXRD measurements showed that prepared samples are in single phase having orthorhombic structure. TEM images demonstrate the non-agglomerated spherical particles of 40−60 nm size. The photoluminescence excitation spectrum shows a characteristic broad band at 338 nm and emission band maxima corrosponding to 4f65d1→4f 7electronic transition appears at 453 nm for SrMg2Al16O27:Eu2+ phosphor.

Efficiency of an ANC system in the tractor cabin under controlled engine workload

The noise at the driver seat of an agricultural tractor is produced mostly by the engine. Its characteristic broadband noise spectrum varies considerably with engine workload. The passive noise control techniques adopted in tractor cabins, based on the application of sound-absorbing and sound-proofing materials, are effective against medium-high frequencies noise components. The residual noise in sound-proof cabins is characterized by tonal emissions with low frequency components (< 500 Hz) but regarded as responsible for various disorders and diseases following long-term exposure. In addition to the "A" weighting filter adopted to evaluate occupational exposure to noise, other approaches are reported in the scientific literature considered more appropriate to evaluate low frequency noise (LFN), as well as studies testifying the effectiveness of active noise control (ANC) technologies in the low frequency range. In this article, the performance of an ANC system is evaluated in its ability to reduce noise levels inside the soundproof cabin of an agricultural tractor. To test this system, spectro-phonometric measurements of the equivalent linear sound pressure level were conducted under controlled and repeatable engine workloads, obtained by connecting the tractor to a dynamometric brake, while simultaneously acquiring the related engine performance curves. Altogether, three different couples of loudspeakers were tested. Frequency analysis in one-third octave band showed that the ANC system was mainly effective against LFN components (below 120 Hz) with peaks of reduction up to 20 dB. Then, on the basis of indications from previous studies, the data of linear sound pressure levels were processed applying the "A", "B", and "C" weighting filters, to show the different emphasis given to the effects of the system. Eventually, a point-by-point composition of the equivalent levels of sound pressure was drawn over the whole range of the engine, to highlight the conditions in which the ANC system was more effective.

On the Influence of the Characteristic Frequency and Broadband of Seismic Effects on the Vertical Rod Oscillations

The problems of longitudinal oscillations of high vertical rods with orientation to the application of results in the problems of seismic calculations are considered. Mathematical models of free, forced harmonic and forced random oscillations caused by kinematic disturbances of the lower end are obtained. Application of methods of separation of variables and finite differences in combination with visualization of calculations in Matlab environment gave own values and own functions, and then amplitudes and mean square deviations of oscillations. It is shown how the preliminary consideration of harmonic oscillations significantly simplified the solution of the stochastic problem. Influence of characteristic frequency and broadband parameter of input random process on the form and standard deviation of longitudinal oscillations is studied.

Characterization of molybdenum and tungsten phosphates compounds prepared using ammonium phosphate salt as flux

Fusion of powdered molybdenum and tungsten oxide using ammonium phosphate salt as flux (ratio: 1:25 respectively) yielded soluble products which were unstable. The yellow (Mo) and purple-blue (W) solutions in deionized water, methanol and acetone decolorized within 3–5 hours. Infrared analysis of molybdenum and tungsten products revealed characteristic broad bands bearing two minor peaks in the region of 1040–1130 cm -1 which reflects the simultaneous existence of PO 2 and PO 3 groups. SEM-EDX quantitative analysis results showed percentage weight of the identified elements in the increasing order of Mo or W < P < O with molybdenum product having 7.1%wt (Mo), 37.2%wt (P) and 53.5%wt (O) whilst tungsten product had 10.3%wt (W), 24.7%wt (P) and 46.5%wt (O). The EDX results indicated the presence of polyphosphate products whilst the SEM images showed microscopic crystalline product of molybdenum and a hygroscopic product of tungsten. XRD patterns of both molybdenum and tungsten products corresponded to the standard (JCPDS) pattern of molybdenum oxide phosphate MoO 2 (PO 3 ) 2 and tungsten oxide phosphate (WO 2 (PO 3 ) 2 ), respectively. KEY WORDS : Molybdenum, Tungsten, Ammonium phosphate flux, Polyphosphates Bull. Chem. Soc. Ethiop. 2019 , 33(1), 103-112 DOI: https://dx.doi.org/10.4314/bcse.v33i1.10

Features of diazo dye photodecomposition in aqueous solutions containing zinc, aluminum and erbium salts

Subject of research.The features of diazo dye Chicago Sky Blue 6B photodecomposition in aqueous solutions containing the salts of zinc, aluminum and erbium were studied. The paper presents the research of effect of the type and concentration of salts of these metals on the spectral properties of solutions and kinetic dependencies of the decomposition processes of a diazo dye under the action of UV radiation from DRT-240 high-pressure mercury lamp. Method. The methodology of the studies consisted in the sequential measurement of the absorption spectra of the solutions on a Perkin-Elmer Labda 650 spectrophotometer in the UV and visible parts of the spectrum after UV irradiation of various durations and analysis of the observed spectral changes. Main results. Based on the research carried out, it was shown that the absorption spectrum of the dye changes in the presence of metal salts in solutions and an additional maximum appears on the characteristic broad and intense absorption band of the dye in the visible part of the spectrum (λ = 540–680 nm). That fact suggests the behavior of dye molecular structuring. When metal salts are introduced into the solution, the mechanism of its decomposition under the action of UV radiation also changes significantly. In the presence of metal salts, along with a decrease in the intensity of the absorption band of the dye in the visible part of the spectrum, its substantial shift to the shortwave region is also observed. Studies of the dye decomposition kinetics under UV irradiation showed that the rate of the dye photodegradation sharply increases in the presence of metal nitrates in solutions. The introduction of zinc nitrate into the solution has particularly strong effect on the dye photodegradation in an aqueous solution. Practical relivance.The experimental results obtained can be used in the development of photochemical processes for the purification of water from organic pollutants.

Carbon quantum dot-sensitized and tunable luminescence of Ca19Mg2(PO4)14:Ln3+ (Ln3+ = Eu3+ and/or Tb3+) nanocrystalline phosphors with abundant colors via a sol–gel process

Efficient carbon quantum dot-sensitized luminescence of Ca19Mg2(PO4)14:Ln3+ (Ln3+ = Eu3+ and/or Tb3+) nanocrystalline phosphors with abundant colors.