Characteristic Sharp Peak Research Articles

Evidence for chiral graviton modes in fractional quantum Hall liquids.

Exotic physics could emerge from interplay between geometry and correlation. In fractional quantum Hall (FQH) states1, novel collective excitations called chiral graviton modes (CGMs) are proposed as quanta of fluctuations of an internal quantum metric under a quantum geometry description2-5. Such modes are condensed-matter analogues of gravitons that are hypothetical spin-2 bosons. They are characterized by polarized states with chirality6-8 of +2 or -2, and energy gaps coinciding with the fundamental neutral collective excitations (namely, magnetorotons9,10) in the long-wavelength limit. However, CGMs remain experimentally inaccessible. Here we observe chiral spin-2 long-wavelength magnetorotons using inelastic scattering of circularly polarized lights, providing strong evidence for CGMs in FQH liquids. At filling factor v = 1/3, a gapped mode identified as the long-wavelength magnetoroton emerges under a specific polarization scheme corresponding to angular momentum S = -2, which persists at extremely long wavelength. Remarkably, the mode chirality remains -2 at v = 2/5 but becomes the opposite at v = 2/3 and 3/5. The modes have characteristic energies and sharp peaks with marked temperature and filling-factor dependence, corroborating the assignment of long-wavelength magnetorotons. The observations capture the essentials of CGMs and support the FQH geometrical description, paving the way to unveil rich physics of quantum metric effects in topological correlated systems.

Crystal structure, Hirshfeld surface, luminescent properties and cytotoxicity of five mononuclear Ln-complexes based on 1⁃phenyl⁃3⁃methyl⁃4⁃benzoyl⁃5⁃pyrazolinone

Five novel lanthanide complexes with the general formula [Ln(pmbp)3(dmobipy)] (Ln = Eu (1-Eu), Tb (2-Tb), Ho (3-Ho), Er (4-Er) and Tm (5-Tm), Hpmbp = 1-phenyl-3-methyl-4-benzoyl-5-pyrazolinone, dmobipy = 4,4′-dimethoxy-2,2′-bipyridine) were synthesized and characterized by single-crystal X-ray diffraction. The structures of the five complexes are identical and they crystallize in the trigonal crystal system P-1 space group. Results from SHAPE software's Continuous shape measurements (CShM) indicate that the local symmetry of the central ion is close to D2d. The Hirshfeld surface analysis shows that the five complexes have a similar contribution of different contacts to the Hirshfeld surfaces, with reciprocal H…H/C/N/O contacts dominating over 92% of the total Hirshfeld surface. Solid-state luminescence studies indicate that 1-Eu, 3-Ho and 4-Er exhibit characteristic sharp peaks of their corresponding Ln3+ ions, whereas the broad bands observed in 2-Tb and 5-Tm are attributed to the PMBP− ligand. In addition, the five complexes demonstrate a low level of cytotoxicity against HeLa cells, laying the groundwork for successive fluorescence imaging experiments.

Water content significantly influences post-cryopreservation survival of air-desiccated oil palm (Elaeis guineensis Jacq.) zygotic embryos: A thermal and ultrastructural study

The present study outlines the influence of free water content in oil palm (Elaeis guineensis Jacq.) zygotic embryos after desiccation on survival post-cryopreservation. Aseptically isolated zygotic embryos were analysed for water content and resurgence ability after air-desiccation and freezing (in liquid nitrogen). The results indicated that the desiccated zygotic embryos with water content of below 0.24 and above 0.16 g H2O /g dry weight (dw) exhibited survival after freezing. The survival was maximum (80%) when the desiccated zygotic embryos contained 0.16 g H2O /g dw of water content. This optimal water content not only helped oil palm zygotic embryos to sustain their cellular integrity but also assisted to retain their regeneration potential following cryopreservation. On the contrary, the zygotic embryos with water content above 0.24 g H2O /g dw or below 0.16 g H2O /g dw lost their viability as well as their cellular integrity attributable to either excess water content or excessive loss of water, after desiccation and successive freezing. Differential scanning calorimetric analysis revealed characteristic sharp peak for zygotic embryos with high water content and reduced peaks with successively lower water content. Scanning electron microscopic and transmission electron micrographic studies also confirmed that there was no noteworthy distinction in morphology of epidermal layer and cellular integrity between zygotic embryos with different water content before and after desiccation as well as their successive freezing. The parallel trend was reflected in their revival also.

Investigation of Optical and Electrical Property of Polyaniline-Zinc Ferrite Nanocomposites

Zinc Ferrite nanoparticles are synthesised by solution combustion method with urea as fuel. The prepared ferrite nanoparticles are added to the Polyaniline polymer during chemical oxidative polymerization to get Polyaniline-Zinc ferrite nanocomposites in different weight ratios(10%, 30% and 50%).XRD confirms the formation of the nanocomposite as the XRD spectrum of the composite has Characteristic sharp peaks of zinc ferrite and the characteristic broad peak of Polyaniline. From the UV-Vis absorption data, the optical direct band gap is estimated with the help of Tauc plot and the obtained optical band gaps are found to decrease as the content of Zinc ferrite inpolyaniline composites increases. DC conductivity increases as the percentage of zinc ferrite increases in the polyaniline matrix.

Stability, electronic, optical and thermoelectric properties of site-substituted [formula omitted

To unravel the structural and chemical stability, electronic, transport, and optical properties of pristine and site substituted lanthanum vanadate, LaVO3, we employed the density functional theory (DFT) and the dynamical mean field theory (DMFT). The generalized gradient approximation (GGA) and the DMFT with continuous time quantum Monte Carlo (CT-QMC) approach is used for the impurity solver. The variation of the spectral density are studied with different values of the onsite Coulomb interaction (U) and exchange interaction (J), as well as the thermodynamic parameter (β), to investigate the metal insulator transition (MIT) for these materials, which are useful for designing Mottronics, neuromorphic computing devices. The predicted values of U and β for the Mott–Hubbard MIT in La0.40Ca0.60V O3 are consistent with current experimental data. The studied sample’s a characteristic sharp quasi-particle peak is found to be at U = 5 eV and β = 6 (eV)−1. The Mott quantum critical point (QCP) is also computed for an elevated temperatures and it is found at U = 2.95 eV and β = 23.58 (eV)−1. With U = 5.0 eV, β = 10.0 (eV)−1, the clear Mott gaps for La0.40Ca0.60V O3 and La0.60Ca0.40V O3 are estimated as 0.74 eV and 1.64 eV, respectively. The electrical and thermal conductivities are calculated at room temperature using the BoltzTraP code, and they are found to be 2.11 (Ωms)−1 and 1.51 W/(mKs), respectively, for a given chemical potential μ = −0.14 eV of the system. The figure of merit (ZT) is estimated to be 1.78 at μ = −1.44 eV. Larger values of the Seebeck coefficient (S), ZT, and thermoelectric power factor (TPF) indicate that La0.40Ca0.60V O3 system is a good candidate of thermoelectric material. The calculated frequency dependent optical conductivity (Drude weight) on the dependency of U and β for the metal insulator transition supports the other calculations.

Effect of Alkaline earth oxides on the ionic conductivity of Boro-Tellurite glasses for solid state ion batteries

The complex impedance spectroscopy studies (electrical impedance, a.c. conductivity, dielectric constant, loss tangent) of the boro-tellurite glasses were measured as a function of the alkaline earth oxide content at broad range of frequencies and temperatures. Three series of boro-tellurite glasses containing BaO/SrO viz. BaO-TeO2-TiO2-B2O3 (BTTB), BaO-TeO2-B2O3 (BTB) and SrO-TeO2-TiO2-B2O3 (STTB) were prepared by the melt quenching method. The prepared glasses were characterized by XRD, DSC, density, FTIR and complex impedance spectroscopy experimental techniques. The XRD spectra exhibited no characteristic sharp peaks indicating the amorphous nature of the prepared glass samples. The glass transition temperature (Tg) values were evaluated from the DSC thermograms. The density values were found to increase with BaO content while they decreased with SrO content. This variation was attributed to the different density values of BaO and SrO. FTIR spectra revelated the presence of different structural units like BO3 and BO4. Impedance studies demonstrated that the replacement of TeO2 by the BaO content enhanced the ionic conductivity. The impedance plots of BTTB, BTB and STTB glasses exhibited nearlys semicircles. The bulk resistance (Rb) was calculated from the impedance plots. It was observed that the Rb values decrease with increasing BaO in BTTB and BTB glasses, while it increased with SrO in STTB glasses which may be attributed to the variation of mobile charge carriers. The Rb values vary as BTB > BTTB > STTB. The capacitance calculated from the impedance plots increased with increasing BaO mol% and decreasing SrO mol%. The capacitance also increased with increasing temperature. The power law exponent (k) values decrease with increasing temperature. Therefore, the ac conduction mechanism may follow correlated barrier hopping model. The real part of dielectric constant has high values at low frequencies, which decreased rapidly with surge of frequency. At high frequencies the contribution of charge accumulation is minimum resulting in constant

Output and Negative‐Region Characteristics in Organic Anti‐Ambipolar Transistors

AbstractCharacteristics of anti‐ambipolar transistors (AATs) are perfectly represented by a model of series transistors, and the transistor parameters are extracted from experimentally observed characteristics, where not only the transfer but also the output characteristics follow the square dependence derived from the saturated region. The consistency of the observed and calculated results demonstrates carriers are all recombined in the lateral p–n junction region. The transfer curve has a characteristic sharp peak, but when there is an overlapped region (Vthh > Vthe), the peak is rounded because both transistors are operated in the linear regions. In such a case, a nonzero current appears even at negative VD accompanied by a constant ID region at large negative VD. This study offers a quantitative analysis of organic AATs depending on the different operation regions.

A Fluorescent Nanosensor for Silver (Ag+) and Mercury (Hg2+) Ions Using Eu (III)-Doped Carbon Dots.

Carbon dots doped with Eu3+ ions (Eu-Cdots) were prepared by a hydrothermal treatment, using citric acid and urea as precursors and Eu (NO3)3 as a europium source. The Eu3+ ions are strongly coordinated with the carboxylate groups at the surface of the Cdots and incorporated within the nanographene network in the carbon core. Vibrational spectroscopy provides evidence of such interaction with identification of bands assigned to the stretching of the Eu-O bond. Eu3+ doped Cdots have larger diameters then undoped Cdots, but they are divided into smaller domains of sp2 carbon. The UV-vis excitation spectrum provides evidence of energy transfer from the Cdots to the Eu3+. The luminescence spectrum shows the characteristic sharp peaks of Eu3+ in the red part of the visible spectrum and a broad emission of Cdots centered at 450 nm. The luminescence of the Cdots is strongly quenched by Hg2+ and Ag+, but not by other cations. The quenching mechanism differs significantly depending on the nature of the ion. Both the blue emission of Cdots and the red emission of Eu3+ are quenched in the presence of Hg2+ while only the emission of the Cdots is affected by the presence of Ag+. A ratiometric sensor can be built using the ratio of luminescence intensities of the Cdots to the Eu3+ peaks.

Bio-fabrication of selenium nanoparticles/micro-rods using cabbage leaves extract for photocatalytic dye degradation under natural sunlight irradiation

ABSTRACT This work reports the synthesis of semiconductor selenium nanoparticles/micro-rods (Se-NP/MRs) using the bio-fabrication approach and studies its photocatalytic activity under natural sunlight irradiation. Cabbage leaf extract was used as a reducing agent to fabricate Se-NP/MRs. X-ray diffraction patterns shown the crystalline structure with a crystallite size of 28.17 nm, conferring to planes of hexagonal structure. A characteristic sharp resonance peak in Raman spectra at 235 cm−1 endorsed to the Se – Se bond of crystalline Se-NP/MRs. The prominent peak in the FTIR spectra at 621 cm−1 supported the formation of Se-NP/MRs. Scanning electron micrograph revealed a nearly spherical shape with irregular layers in the 35‒95 nm size range. In contrast, the dimension of the micro-rods was observed to be ~ 10 µm in length and 2.5 µm in diameter. The bandgap energy of Se-NP/MRs was analysed to be 2.14 eV using the Tauc plot. The exciting photocatalytic performance of the bio-fabricated Se-NP/MRs revealed that the methylene blue degradation was ~ 86% in 40 min and ~ 97% in 140 min. Kinetic analysis shows that the pseudo-second-order correlation coefficient is well fitted compared to the pseudo-first-order. Therefore, this work opens the door to further exploration of nano-materials/composites with mixed nanoparticles/micro-rods morphology for sustainable applications in the removal of various textile and industrial contaminants.

Electronic Structure and Transport Properties of Superlattices: La(1-X)SrxTiO3 (X =0, 0.20, 0.80, 1)

The conventional density functional theory (DFT) and dynamical mean field theory (DMFT) is used to study the structural, electronic and the Mott-Hubbard metal-insulator phase transition of the pristine and superstructures, La(1-x)SrxTiO3 (x = 0, 0.20, 0.80, 1). The electrical and thermal conductivities, Seebeck coefficient, Figure of merit are calculated using the BoltzTraP codes. The present study reveals that the direct band gap of 2.20 eV and indirect band gap ~2.0 eV at the Γ point in the Brillouin zone of SrTiO3 is upgraded to 3.423eV by using modified Beck-Johnson (mBJ) interaction potential. The metal-insulator transition (MIT) of LaTiO3 and the superlattice La(1-x)SrxTiO3 have been investigated by using conventional density functional theory (DFT) and dynamical mean field theory (DMFT). The Mott-Hubbard metal-insulator transitions for pristine LaTiO3 for a Coulombian parameter, U = 2.5 eV and the thermodynamic parameter β = 6 (eV)-1 are consistent with the experimental results. A typical set of these correlation parameters for MIT La0.20Sr0.80TiO3 and La0.80Sr0.20TiO3 systems are found to be U = 3.5 eV and β = 10(eV)-1 and U = 3.2 eV and β = 10 (eV)-1 respectively. The characteristic sharp quasi-particle peak for a sample of La0.80Sr0.20TiO3 superlattice systems is obtained correlation parameter U = 3.0 eV and β = 6(eV)-1. A thermoelectric phase transition is observed for Seebeck Coefficient at temperature 300 K at near chemical potential, μ = 1eV of SrTiO3. The corresponding figure of merit (ZT) with chemical potential (μ) appears to be unity at near μ = 1eV.

Optimized Polyethylene Glycolylated Polymer-Lipid Hybrid Nanoparticles as a Potential Breast Cancer Treatment.

Purpose: The aim of this work is to optimize a polyethylene glycolated (PEGylated) polymer–lipid hybrid nanoparticulate system for the delivery of anastrozole (ANS) to enhance its biopharmaceutical attributes and overall efficacy. Methods: ANS loaded PEGylated polymer–lipid hybrid nanoparticles (PLNPs) were prepared by a direct emulsification solvent evaporation method. The physical incorporation of PEG was optimized using variable ratios. The produced particles were evaluated to discern their particle size and shape, zeta-potential, entrapment efficiency, and physical stability. The drug-release profiles were studied, and the kinetic model was analyzed. The anticancer activity of the ANS PLNPs on estrogen-positive breast cancer cell lines was determined using flow cytometry. Results: The prepared ANS-PLNPs showed particle sizes in the range of 193.6 ± 2.9 to 218.2 ± 1.9 nm, with good particle size uniformity (i.e., poly-dispersity index of around 0.1). Furthermore, they exhibited relatively low zeta-potential values ranging from −0.50 ± 0.52 to 6.01 ± 4.74. The transmission electron microscopy images showed spherical shape of ANS-PLNPs and the compliance with the sizes were revealed by light scattering. The differential scanning calorimetry DSC patterns of the ANS PLNPs revealed a disappearance of the characteristic sharp melting peak of pure ANS, supporting the incorporation of the drug into the polymeric matrices of the nanoparticles. Flow cytometry showed the apoptosis of MCF-7 cell lines in the presence of ANS-PLNPs. Conclusion: PEGylated polymeric nanoparticles presented a stable encapsulated system with which to incorporate an anticancer drug (ANS) with a high percentage of entrapment efficiency (around 80%), good size uniformity, and induction of apoptosis in MCF-7 cells.

Spectroscopic investigations on Se/RE doped sol gel derived silica matrices

Selenium and rare earth ions co-doped inorganic luminescence silica matrices are synthesized through sol gel route. The incorporation of cubic Se quantum dots within the porous silica frame is confirmed from TEM analysis. The successful entrapment of green as well as blue color emitters within the silica frame generates evident luminescence bands in the visible region. Obtained Se/Tb3+ ions doped silica glasses give characteristic sharp emission peaks of terbium ions at 488 nm, 543 nm, 584 nm, 619 nm wavelength under UV excitations. A broad blue emission band from selenium nanodots centered at 421 nm wavelength is observed in the emission spectrum. Colorimetric studies are done with the aid of 1931 chromaticity diagram. CIE indices of the co-doped glasses are found to lie in between the CIE indices of selenium doped silica glasses (0.18, 0.21) and terbium doped silica glasses (0.28, 0.46). For a fixed concentration of Se and terbium in silica glasses, tunable luminescence without shift in peak wavelength is observed under the excitation wavelength of 340 nm to 380 nm. Varying blue to green luminescence intensity ratio (B/G) with the excitation wavelength reveals the possibility of tunable emission of the glassy matrix for their applicability in solid lighting systems.

Synthesis of ternary electrocatalysts for exploration of methanol electro-oxidation in alkaline media

In the quest for alternate and efficient electrode materials, ternary metal electrocatalysts (TMEs), part of the perovskite family, were synthesized and tested for methanol electro-oxidation in alkaline media. La0.5Ca0.5MO3 (M = Ni, Co, or Mn) was synthesized via sol-gel method. X-ray diffraction analysis revealed that the perovskite crystal structure possesses characteristic sharp and crystalline peaks for all synthesized ternary electrocatalysts. The average particle size calculated using Debye–Scherrer equation was in the order of La0.5Ca0.5NiO3 (LCNO) > La0.5Ca0.5CoO3 (LCCO)> La0.5Ca0.5MnO3 (LCMO). The elemental composition of as prepared sample, LCCO was investigated via x-ray fluorescence spectroscopy. The qualitative and quantitative analysis revealed the presence of La, Ca and Co in parent crystal structure with percentage compositions of 9.0, 3.12 and 87.82% respectively. The particle size distribution was homogenous, as determined by scanning electron and transmission electron microscopes. The electrocatalytic activity of the synthesized ternary electrocatalysts was studied electrochemically by cyclic voltammetry. The calculated diffusion coefficient values showed that electrode surface of LCNO and LCCO have limited efficiency for diffusion related phenomenon. The heterogeneous rate constants inferred better electrode kinetics of LCCO and LCNO which exhibited good electrocatalytic behavior; sharp anodic peaks were observed in the potential range of +0.3 to 0.6 V and +0.6 to 0.8 V, respectively. Methanol electro-oxidation was found minimal in case of LCMO sample. We have observed that Co substitution at B-site of perovskite electrode materials attains better electrochemical properties, thus in relation with reported literature.

Synthesis, structure, and color-tunable luminescence properties of lanthanide activator ions doped bismuth silicate as single-phase white light emitting phosphors

A series of lanthanide activator ions (Ln3+) doped bismuth silicate Bi4Si3O12 phosphors have been fabricated via the Pechini sol−gel route. The as-synthesized eulytite structured Bi4Si3O12 sample which exhibits intense green-blue emission is beneficial for host materials of lanthanide activator ions. When the Ln3+ ions (Sm3+, Dy3+, or Eu3+) are doped into the Bi4Si3O12 host, an insufficient energy transfer occurs from the host matrix to Ln3+ ions, which can be confirmed by the photoluminescence spectra and decay lifetimes of the Ln3+ doped samples. The as-synthesized Bi4Si3O12:Ln3+ phosphors show both the intrinsic broad band luminescence of Bi4Si3O12 host and the characteristic sharp peak emissions of Ln3+ ions, which can generate the tunable multicolor emissions in a single-phase phosphor by adjusting the Ln3+ doping concentrations. More importantly, three kinds of Ln3+-doped single-phase white light emitting phosphors with excellent chromaticity coordinate (x, y) and CCT in the warm white region [Sm3+: (0.336, 0.330), 5315 K; Dy3+: (0.330, 0.370), 5614 K; Eu3+: (0.340, 0.307), 5034 K] can be obtained when the doping concentrations of Sm3+, Dy3+, and Eu3+ are fixed at 0.5, 5, and 1 mol%, which are quite close to the daily use of pure white light. By integrating the Bi4Si3O12:Ln3+ phosphors into a 280 nm UV LED chip, all the fabricated WLED devices can exhibit bright white light emission, which provides direct evidence that the as-synthesized BSO:Ln3+ (Ln = Sm, Dy, and Eu) single-phase white-emitting phosphors have great potential for WLEDs and optoelectronic devices.

Characterization and antimicrobial activity of silver nanoparticles mycosynthesized by Aspergillus brasiliensis.

Since mycosynthesis of metal nanoparticles (NPs) is advertised as a promising and ecofriendly approach. Thus, this study aims to investigate the capability of Aspergillusbrasiliensis ATCC 16404 for mycosynthesis of silver NPs (AgNPs). One-factor-at-a-time-technique was used to study the effect of different physicochemical parameters: the reaction time, pH, temperature, different stirring rates, illumination, and finally, the different concentrations of silver nitrate and fungal biomass on the mycosynthesis of AgNPs. The visual observation showed the characteristic brown colour formation due to the bioreduction of Ag+ ions to Ag0 by the mycelial cell-free filtrate (MCFF). The UV/visible spectrophotometric technique displayed a characteristic sharp peak at ʎ440 confirming the mycosynthesis of AgNPs. The zeta potential value -16·7mV assured the long-term stability of AgNPs and the dynamic light scattering analysis revealed good dispersion and average particle size 77nm. The energy dispersive X-ray spectroscopy displayed a maximum elemental distribution of silver elements. The X-ray diffraction spectroscopy demonstrated the crystallinity of the mycosynthesized AgNPs. The field emission scanning electron microscope and high-resolution transmission electron microscope revealed monodispersed spherical shaped AgNPs with average particle size of 6-21nm. The FTIR analysis showed the major peaks of proteins providing the possible role of MCFF in the synthesis and stabilization of the AgNPs. The mycosynthesized AgNPs expressed good biocidal activity against different pathogenic micro-organisms causing some water-related diseases and health problems to local residents. This study proved that A. brasiliensis ATCC 16404 MCFF has good potential for mycosynthesis of AgNPs, which exhibited good antimicrobial effect on different pathogenic micro-organisms; thus, it can be applied for water disinfection. This research provides a helpful insight into the development of a new mycosynthesized antimicrobial agent.

Sensitized luminescence from novel pyrazolone based â-diketonate complexes of Eu3+

New pyrazolone based fluorinated ligand, 3-methyl 4-(2, 2, 3, 3, 3-penta fluoro-1-hydroxypropylidene)-1-phenyl-1H-pyrazol-5(4H)-one has been synthesized and well characterized. Europium-containing complexes were synthesized by adduct formation between 3-methyl 4-(2, 2, 3, 3, 3-penta fluoro-1-hydroxypropylidene)-1-phenyl-1H-pyrazol-5(4H)-one and europium (III) complex and a bidentate neutral donor 1, 10-phenanthroline (phen). The emission spectra of the complexes display characteristic sharp peaks in the 575–700 nm region associated with the 5D0 _7FJ (J = 0–4) transitions of the Eu3+ ion.

Characterization of the location of coke deposited on spent HZSM-5 zeolite by special temperature-programmed oxidation and isothermal oxidation methods

The location of coke deposited on HZSM-5 zeolite catalyst during the supercritical catalytic cracking (400°C, 4.0MPa) of n-dodecane was systematically characterized by special temperature-programmed oxidation (TPO) and isothermal oxidation methods, and a steric hindrance model describing the interactions of the coke deposited on different locations was proposed to support the methods theoretically. Accord to the results, the sharp shoulder peak that appears on the TPO profile at high temperature range (>700°C) with low concentration of oxygen in the oxygen/nitrogen mixed carrier gas (≤2.0 Vol.%) can be ascribed to the characteristic peak representing the oxidation of the coke blocked in micropores, while the appearance of the CO peak during the isothermal oxidation at high temperature (≥550°C) using air as carrier gas provides another method to detect the coke blocked in micropores. Through checking whether the characteristic sharp shoulder peak of the TPO profile appears or not as expected according to the steric hindrance model during the re-oxidation of several samples with different coke content and spatial distribution, which were prepared by partial oxidation of the spent catalyst using TPO and isothermal oxidation methods, the special TPO and isothermal oxidation methods combined with their theoretical support of the steric hindrance model were proved to be self-consistent in the characterization of the location of coke. The location information of coke was further verified by the typical method of nitrogen adsorption-desorption analyses of a series of partially oxidized samples prepared by TPO method.

Facile-one pot-green synthesis, antibacterial, antifungal, antioxidant and antiplatelet activities of lignin capped silver nanoparticles: A promising therapeutic agent

The current work portrays the green synthesis of Lignin Capped Silver Nanoparticles (LCSN) and their antibacterial, antifungal, antioxidant and antiplatelet potential. The LCSN was synthesized in water using a carbohydrate based polymer ‘lignin’ as the reducing and capping agents. The peak at 406nm (λmax) in the UV–Vis., spectrum and EDX analysis confirmed 1.68% (w/w) of silver was found to be loaded on lignin. The characteristic sharp peaks appeared in the PXRD spectrum showed fcc crystalline structure LCSN. SEM and TEM images indicated that the spherical Ag-NPs were well dispersed on lignin with an average particle size of ~10–15nm. LCSN showed antibacterial and antifungal activity against human pathogens S. aureus, E. coli and A. niger and the percentage of zone of inhibition was found to be 10%, 12% and 80% respectively. Further, LCSN was evaluated for antioxidant potential using DPPH scavenging assay, interestingly it showed antioxidant activity and the percentage against positive control vitamin C was found to be 70%. Furthermore, LCSN did not interfere in plasma coagulation; however, it found to inhibit agonist ADP induced platelet aggregation of human platelet rich plasma. The observed inhibition was found to be 37% and the calculated IC50 value was found to be 9mg/mL. LCSN did not lyses RBC membrane when assayed hemolytic activity suggesting its non-toxic nature.

Luminescent properties of Ce3+/Tb3+co-doped glass ceramics containing YPO4 nanocrystals for W-LEDs

Ce3+/Tb3+ co-doped transparent glass ceramics containing YPO4 nanocrystals were prepared using high temperature melting method, and their structural and luminous properties were investigated. XRD analysis and TEM images confirmed the existence of YPO4 nanocrystals in glass ceramics. The transmission spectra proved that the glass ceramics specimens still maintained a high transparency. Then the excitation and emission spectra of the Ce3+ and Tb3+ single-doped and co-doped glass and glass ceramics were discussed, which proved that the glass ceramics had better luminescent properties. Under the near ultraviolet (331 nm) excitation, the broadband emission located at 385 nm was observed which was ascribed to 5d→2F5/2 and 2F7/2 transition of Ce3+ ions. Several characteristic sharp peaks centered at 489, 543, 578 and 620 nm originated from the 5D4 to 7FJ (J=6, 5, 4, 3) of Tb3+ ions. The decay time of Tb3+ ions at 543 nm and the relevant energy levels of Ce3+ ions and Tb3+ ions illustrated the transfer process from Ce3+ ions to Tb3+ ions. The best CIE chromaticity coordinate of the glass ceramics specimen was calculated as (x=0.3201, y=0.3749), which was close to the NTSC standard values for white (x=0.333, y=0.333). All the results suggested that the YPO4-based Ce3+/Tb3+ co-doped glass ceramics could act as potential luminescent materials for white light-emitting diodes.

Preparation and Photoluminescence Properties of SrAl2O4:Eu2+,RE3+ Green Nanophosphors for Display Device Applications

An efficient rapid gel combustion process was used to prepare divalent-europium-doped strontium aluminate (SrAl2O4:Eu2+/Eu2+,Dy3+/Eu2+,Dy3+,Nd3+) nanophosphors in the presence of boron flux in air. The prepared nanophosphors emitted green light at 507 nm upon excitation at 360 nm. The emission of green light was observed due to the 4f 65d 1 → 4f 7 transition of Eu2+ ions. The absence of the characteristic sharp emission peak at 612 nm for Eu3+ (5D0 → 7F2) indicates that efficient reduction of Eu3+ to Eu2+ occurred in the presence of the boron flux (H3BO3) as reducing agent. The x-ray diffraction pattern suggested monoclinic crystallinity, while transmission electron microscopy revealed the average size of the prepared materials to be between 20 nm and 50 nm. Coactivators in the lattices such as Dy3+ alone or Dy3+ with Nd3+ produced long persistence and enhancement of the optoelectronic properties of the prepared materials.