Average Size Range Research Articles

Photoluminescence and PhotoCatalytic Properties of Zinc doped Strontium Sulphide Nanocrystals

Photoluminescence and PhotoCatalytic Properties of Zinc doped Strontium Sulphide Nanocrystals Pure Strontium Sulphide (SrS) and Zn doped SrS nanocrystals have been synthesized by solid state diffusion method. Crystallographic characterization carried out by using powder X-ray diffractometer confirmed the single phase rock salt with average particle size in the range of 24.7 nm. Topographic and Morphological studies were carried out by using Scanning electron microscope (SEM) and Transmission electron microscope (TEM) respectively. EDS studies confirm elemental composition of nanoparticles. TEM studies confirm spherically distributed nanoparticles with average size in nm range. Band gap and. Photoluminescence (PL) studies confirmed dopant dependant behavior. Photo-Catalytic activity confirms that SrS is a good degrading agent.

Biogeography and ecology of endemic invertebrate species in Austria: A cross-taxon analysis

Austria supports a considerable number of endemic invertebrate species, but a cross-taxon analysis is currently lacking. Based on a recent national inventory, we analysed distribution patterns, ecology and conservation biogeography of 361 endemic species and subspecies (beetles: 174taxa; butterflies and moths: 34taxa; caddisflies: 16taxa; snails: 80taxa; spiders and harvestmen: 57taxa) within Austria. Endemic species were very unevenly distributed with highest numbers of endemic species found in the North-eastern Calcareous Alps followed by the Southern Alps and the easternmost Central Alps. The location of hot spots (=grid cells of c. 35km2 size with highest endemic species numbers) varied substantially between taxonomic groups. The range size of endemic invertebrate taxa was skewed towards very narrow distributions – 222taxa are restricted to <10grid cells (total area c. 350km2), of which 71taxa were known from a single grid cell only. Between taxonomic groups we found substantial differences in elevation distribution. Whereas beetles and butterflies and moths were most species-rich at high elevations (1900–2000m a.s.l.), caddisflies (1000–1200m) and snails (400–500m) were most species-rich at mid to low elevations. Endemics associated with different broad habitat types differed markedly in average range size, endemics of habitats with limited and patchy distribution (caves, springs) had the smallest ranges. The endemic taxa of the five groups showed substantial differences in their habitat association. We found a strong positive correlation of range size with elevation range, whereas the number of habitats colonized was only weakly associated with range size. Thus, different features of niche breadth differed in their correlation with endemic species range sizes. Finally, we found that the conservation status of Austrian endemics is poor since 54% of the endemic species are nationally red-listed. Thus, a dedicated conservation strategy is urgently needed to conserve the endemic fauna of Austria.

Green synthesis and characterization of silver nanoparticles using Artemisia absinthium aqueous extract--A comprehensive study.

Unlike chemical synthesis, biological synthesis of nanoparticles is gaining tremendous interest, and plant extracts are preferred over other biological sources due to their ample availability and wide array of reducing metabolites. In this project, we investigated the reducing potential of aqueous extract of Artemisia absinthium L. for synthesizing silver nanoparticles (AgNPs). Optimal synthesis of AgNPs with desirable physical and biological properties was investigated using ultra violet-visible spectroscopy (UV-vis), dynamic light scattering (DLS), transmission electron microscopy (TEM) and energy-dispersive X-ray analysis (EDX). To determine their appropriate concentrations for AgNP synthesis, two-fold dilutions of silver nitrate (20 to 0.62 mM) and aqueous plant extract (100 to 0.79 mg ml(-1)) were reacted. The results showed that silver nitrate (2mM) and plant extract (10 mg ml(-1)) mixed in different ratios significantly affected size, stability and yield of AgNPs. Extract to AgNO3 ratio of 6:4v/v resulted in the highest conversion efficiency of AgNO3 to AgNPs, with the particles in average size range of less than 100 nm. Furthermore, the direct imaging of synthesized AgNPs by TEM revealed polydispersed particles in the size range of 5 to 20 nm. Similarly, nanoparticles with the characteristic peak of silver were observed with EDX. This study presents a comprehensive investigation of the differential behavior of plant extract and AgNO3 to synthesize biologically stable AgNPs.

White Light Emission Through Downconversion of Terbium and Europium Doped CeF3 Nanophosphors.

CeF3 nanophosphors have been extensively investigated in recent years for lighting and numerous bio-applications. Downconversion emissions in CeF3:Eu(3+)/Tb(3+) phosphors were studied with the objective of attaining a white light emitting composition, by means of a simple co-precipitation method. The material was characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FT-IR) and Photoluminescence (PL). Uniformly distributed nanoparticles were obtained with an average particle size range of 8-10 nm. Various studies were undertook utilizing different doping concentrations and respective fluorescence studies were carried out to optimize dopant concentrations while achieving maximum luminescence intensity. From PL results, it was observed that the efficient energy transfers from the donor to the acceptor ions. Different concentrations of Tb(3+), Eu(3+) were doped in order to achieve a white light emitting phosphor for UV-based Light Emitting Diodes (LEDs). The nanoparticles showed characteristic emission of respective dopants (Eu(3+), Tb(3+)) when excited at the 4f → 5d transition of Ce(3+). The chromaticity coordinates for CeF3 doped with Eu(3+) and Tb(3+) were calculated and an emission very close to white light was observed.

One-Pot Synthesis of Environmental Friendly Ni&lt;sub&gt;3&lt;/sub&gt;S&lt;sub&gt;2&lt;/sub&gt; Quantum Dots

A one-pot synthetic method for non-toxic Ni3S2 quantum dots (QDs) was proposed by using commercial available nickel acetate as the precursor. The obtained quantum dots were characterized by photoluminescence spectroscopic, powder X-ray diffraction, and transmission electron microscopy. The maximum fluorescence emission peak of Ni3N2 QDs is at 469 nm under the 365 nm ultraviolet light irradiation in PL Spectra. The TEM data reveals that the predominance of particles with a polyhedron structure and the range of average particle size are between 5 and 11 nm.

Catalytic thermal decomposition of ammonium perchlorate and combustion of composite solid propellants over green synthesized CuO nanoparticles

This paper reports on the synthesis of CuO nanoparticles (NPs) by the leaves extract of Calotropis gigantea plant in aqueous medium through green synthesis and their characterizations in terms of morphology, structure, crystallinity and catalytic properties. The synthesized CuO NPs are crystalline in nature having the average sizes in range of 30–40nm. Green synthesized CuO NPs are utilized as effective catalyst in the thermal decomposition of ammonium perchlorate (AP) and combustion of composite solid propellants (CSPs) by measuring the thermo gravimetric analysis–differential scanning calorimetry (TGA–DSC), ignition delay and burning rate. High catalytic activity to AP decomposition and high burning rate for CSPs containing hydroxyl terminates polybutadiene (HTPB) as binder and AP as oxidizer have observed over the surface of green synthesized CuO NPs. Kinetics of thermal decomposition of AP with and without green synthesized CuO NPs was also studied by isoconversional method using isothermal TG data.

Home Ranges of Ishasha Lions: Size and Location in Relation to Habitat and Prey Availability

ABSTRACT The sizes of African lion home ranges vary widely but tend to correlate with characteristics of the prey populations (e.g. prey density and preferred prey weight). Lion home ranges should be expected to temporally fluctuate according to changes in prey biomass. Here we quantified and compared the home range sizes of lions in Uganda with data collected in the 1970's and that collected in the 2000's. Average range sizes of individual lions were 34.0 and 38.1 km2 for the two prides studied, while pride range was 35.7 and 43.1 km2 (Fixed-kernel method). Surprisingly, we found little variation in size of these home ranges between the two periods assessed. Across both periods, lion home ranges tended to be associated with grassland and wooded grassland to woodland, riverine forest and bushland habitats. The core lion home ranges typically overlapped with habitat where Uganda kob (preferred prey in this region) were most abundant and where most kills were made. Buffalo, topi, and waterbuck are avoided w...

Study on mixing and segregation behaviors in particulate fluidized bed system for mineral processing

In order to identify the mixing and segregation behaviors in a mineral processing operation, present study aimed on the hydrodynamics of solid–liquid fluidization. The study was carried out in a fluidization column with tapings at different height of the bed to collect the sample. The binary particles considered in this study are hematite (4800kg/m3) and quartz (2600kg/m3) at different size fractions in the range of average size 87×10−6m to 400×10−6m. It is observed that for various binary mixtures, both quartz and hematite particles share the equal composition by mass (50%) at a particular height of fluidized bed, referred as “locus point” of mixing. Study indicates that the mixing zone volume will increase for a continuous fluidized bed plant operation. It is observed that the number of locus points varies from 1 to 3 signifying their dependency on the size ratios of binary mixture. Whenever, the difference in terminal velocity between quartz and hematite particles approaches to zero, mixing is enhanced. Further, the present study is extended to find the segregation index for the different size ratios of quartz and hematite particles. It is evident that depending on the size ratios, various regions such as complete segregation, partial mixing and complete mixing can be observed.

Structural and optical characterisation of CdSe1−ySy

In this work presents the structural and optical characterisation of cadmium selenide sulphur (CdSe1−ySy) deposited by chemical bath deposition (CBD) technique at a deposited temperature of 20±2°C varying the sulphur molar fraction from 0% to 42.13%, which is realized by varying the thiourea volume added to the growth solution in the range from 0 to 30ml. The CdSe1−ySy chemical stoichiometry was determined by energy-dispersive X-ray spectroscopy (EDS). X-ray diffraction (XRD) analysis and Raman spectroscopy reveal that CdSe1−ySy deposited nanofilms showed hexagonal wurtzite crystalline phase. The average grain size range of the films was from 1.48–9.2nm that was determined using the Scherrer–Debye equation from W(200) crystalline direction, which was confirmed by high resolution transmission electron microscopy (HRTEM). CdSe1−ySy band gap energy can be varied from 1.86 to 2.15eV by varying the sulphur molar fraction incorporated in the nanofilms. The room temperature photoluminescence presents a dominant band about 3.0eV that may be associated with the grain size of the nanoparticles.

Determination of the relationship between particle size and electrochemical performance of uncoated LiFePO4 materials

The current literature generally reports the relationship between particle size and electrochemical performance of carbon-coated LiFePO4 (LFP). However, besides the factor of particle size, the quality of carbon coating will affect the electrochemical performance of LiFePO4 simultaneously. Logistically, each independent equation is solvable when it contains just one variable and is not solvable when it contains two or more variables. Therefore, we decide to study the relationship between particle size and electrochemical performance of uncoated LiFePO4, of which the relevant literature is sparse. To prepare samples within a wide range for average particle sizes, a traditional precipitation approach was employed to prepare the LFP materials with different average particle sizes of 30–500 nm. Carbon-coated LiFePO4 materials were prepared for the purpose of comparison studies. Both pristine LiFePO4 and carbon-coated LiFePO4 were investigated by XRD, FESEM, as well as charge/discharge testing (in the form of coin cells). The details of materials syntheses were discussed. Without the influence of carbon coating, the discharge capacity of pristine LiFePO4 exhibited a “volcano”-type relationship versus the average primary particle size in the size range of 50–500 nm and reaches a maximum value at the optimum size of about 200 nm. This finding may drive the development of power grade LFP cathode nanomaterials toward more precise particle size optimization.

A hydrodynamic fragmentation model based on boundary layer stripping

Fuel Coolant Interactions (FCIs) are important issues in nuclear reactor severe accident analysis, which have drawn much attention by experts all over the world for many years. The boundary layer stripping is one of the mechanisms that result in hydrodynamic fragmentation during FCIs, and has been studied for many years. However, the results and trends predicted by the existing fragmentation rate models based on such a mechanism are still very different from the experimental data. In this study, in order to develop a fragmentation rate model of a liquid droplet, induced by boundary layer stripping, a new velocity distribution in boundary layer is proposed, which covers two very significant parameters. Then, based on theoretical modeling and experimental data, semi-empirical correlations which can predict the fragmentation rate and the average size of fragments are established, which are verified by typical experimental data and are compared with previous model predictions. The result shows that the fragmentation rate calculated by the present model and the certain range of average fragment size are in good agreement with the experimental data, which proves that the two new parameters involved can reflect the velocity distribution in boundary layers of both the melt and coolant more appropriately and reliably. With the help of the model from IFCI and CULDESAC codes, there is reason to believe the present hydrodynamic fragmentation model could be applied in FCI codes in the future.

Synthesis, characteristics and antimicrobial activity of ZnO nanoparticles

The utilization of various plant resources for the bio synthesis of metallic nano particles is called green technology and it does not utilize any harmful protocols. Present study focuses on the green synthesis of ZnO nano particles by Zinc Carbonate and utilizing the bio-components of powder extract of dry ginger rhizome (Zingiber officinale). The ZnO nano crystallites of average size range of 23–26nm have been synthesized by rapid, simple and eco friendly method. Zinc oxide nano particles were characterized by using X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive X-ray spectroscopy (EDX). FTIR spectra confirmed the adsorption of surfactant molecules at the surface of ZnO nanoparticles and the presence of ZnO bonding. Antimicrobial activity of ZnO nano particles was done by well diffusion method against pathogenic organisms like Klebsiella pneumonia, Staphylococcus aureus and Candida albicans and Penicillium notatum. It is observed that the ZnO synthesized in the process has the efficient antimicrobial activity.

In situ cross-linking of stimuli-responsive hemicellulose microgels during spray drying.

Chemical cross-linking during spray drying offers the potential for green fabrication of microgels with a rapid stimuli response and good blood compatibility and provides a platform for stimuli-responsive hemicellulose microgels (SRHMGs). The cross-linking reaction occurs rapidly in situ at elevated temperature during spray drying, enabling the production of microgels in a large scale within a few minutes. The SRHMGs with an average size range of ∼1–4 μm contain O-acetyl-galactoglucomannan as a matrix and poly(acrylic acid), aniline pentamer (AP), and iron as functional additives, which are responsive to external changes in pH, electrochemical stimuli, magnetic field, or dual-stimuli. The surface morphologies, chemical compositions, charge, pH, and mechanical properties of these smart microgels were evaluated using scanning electron microscopy, IR, zeta potential measurements, pH evaluation, and quantitative nanomechanical mapping, respectively. Different oxidation states were observed when AP was introduced, as confirmed by UV spectroscopy and cyclic voltammetry. Systematic blood compatibility evaluations revealed that the SRHMGs have good blood compatibility. This bottom-up strategy to synthesize SRHMGs enables a new route to the production of smart microgels for biomedical applications.

Synthesis of Zn2+ substituted maghemite nanoparticles and investigation of their structural and magnetic properties

Maghemite and Zn2+ substituted maghemite (γ-Fe2−y Zn3y/2O3, y=0.0, 0.11, 0.24, 0.36, 0.50 and 0.66) nanoparticles were prepared by coprecipitation method. The effect of Zn2+ substitution on the structural, morphological and magnetic properties of the nanoparitcles were studied by different techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), magnetometry, magnetic thermogravimetry and Mössbauer spectroscopy. The results of XRD showed that all samples have spinel structure with an increase in lattice parameter by increasing the content of Zn2+. FTIR spectra were proved the synthesis of maghemite and Zn2+ substituted maghemite with appearance of the related absorption bands and band shift upon Zn2+ substitution. Morphological studies by FESEM demonstrated that the nanoparticles were uniform and spherical with average particle size in range of 20–24nm. Room temperature magnetic measurements showed that as Zn2+ content increases, saturation magnetization initially increase up to 75.34emu/g for y=0.11 and then decrease to 3.65emu/g for y=0.66, due to substitution of magnetic Fe3+ by non-magnetic Zn2+. Decrease in Curie temperature of the samples, from 510 for maghemite to 250°C for y=0.36, by increasing the Zn2+ substitution was a result of reduction of superexchange interactions between different sites. Then, the Curie temperature increased up to 680°C for y=0.66 which was due to migration of some Zn2+ ions from A to B sites in the structure of spinel. Room temperature Mössbauer spectra exhibited that the sample with y=0.0 was superparamagnetic, while by increasing the content of Zn2+, relaxation effect increased by weakening of A–B exchange interaction.

Facile combustion synthesis and photoluminescence properties of Ce3+ doped Sr2La8(SiO4)6O2 phosphors

The Sr2La8(SiO4)6O2:Ce3+ powder phosphor with apatite structure has been successfully synthesized via a facile route of sol-combustion technique. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and photoluminescence (PL) spectroscopy were used to characterize the as-prepared samples. Sr2La8(SiO4)6O2:Ce3+ phosphor was composed of particles with average sizes range about 300nm. The phosphor exhibited an absorption ranging from 220 to 390nm in ultraviolet range and a broad blue-violet emission band peaked at 403nm with a CIE coordinates of (0.167, 0.028). The concentration quenching mechanism was also determined to be dipole–dipole interaction.

Structural and optical characterization of wurtzite type ZnS

ZnS films were grown on (001) GaAs substrates at different temperatures by RF magnetron sputtering. The ZnS chemical stoichiometry was determined by Energy-dispersive X-ray spectroscopy (EDS), besides it allowed to find the residual impurities, mainly oxygen. The X-ray diffraction (XRD) analysis and Raman scattering reveal that ZnS deposited thin films showed hexagonal wurtzite crystalline phase. The films average crystallite size range was from 8.15 to 31.95 nm, which was determined using the Debye–Scherrer equation for the peak W(101). Besides an experimental study of first- and second-order Raman scattering of ZnS films is made. An energy level diagram involving oxygen traps and interstitial sulphur ions is used to explain the origin of the radiative transitions observed in the room temperature photoluminescence (PL) spectra.

Novel dexamethasone-loaded nanomicelles for the intermediate and posterior segment uveitis.

Development and characterization of dexamethasone (DEX)-encapsulated polymeric nanomicelles have been reported. A low molecular weight di-block copolymer was synthesized and characterized for its structure, molecular weights, critical micelle concentration (CMC), and cytotoxicity in ocular cells. In order to delineate the effects of drug-polymer interactions on drug solubilization in micelle core, a response surface methodology was generated with the help of SAS 9.02 (exploratory model). The method for preparing micelle was modified based on the results obtained from exploratory model. The formulation was optimized by response surface methodology (optimization model) to achieve DEX solubility of above 1mg/mL. The optimized formulation was characterized for DEX solubility, nanomicelle size, polydispersity index, surface morphology, in vitro transport across conjunctival cell line, and ex vivo transport across excised rabbit sclera. Nanomicelles exhibited average sizes in range of 25-30nm with unimodel size distribution and low polydispersity of 0.125. Nanomicelles increased DEX permeability by 2 times across conjunctival cell line and by 2.5 times across the excised rabbit sclera as compared to DEX suspension. A design of experiment (DOE) strategy was successfully applied to understand the effects of drug-polymer interaction on drug solubility. DOE was also employed to achieve optimal formulation with high DEX solubility. Nanomicellar formulation significantly enhanced DEX permeability across the excised rabbit sclera. Therefore, nanomicellar formulation may provide therapeutic levels in the back of the eye following topical administration.

Occurrence of tar balls on the beaches of Fernando de Noronha Island, South Equatorial Atlantic.

This work reports on the widespread occurrence of tar balls on a pebble beach of Sueste Bay on Fernando de Noronha Island, a Brazilian national marine park and a preserve in the South Equatorial Atlantic. Environmental regulations preclude regular visitors to the Sueste Bay beach, and the bay is a pristine area without any possible or potential sources of petroleum in the coastal zone. In this work, these tar balls were observed for the first time as they occurred as envelopes around beach pebbles. They are black in color, very hard, have a shell and coral fragment armor, and range in average size from 2 to 6cm. The shape of the majority of the tar balls is spherical, but some can also be flattened ellipsoids. The polycyclic aromatic hydrocarbon analyses of the collected samples revealed the characteristics of a strongly weathered material, where only the most persistent compounds were detected: chrysene, benzo(b,k)fluoranthene, dibenzo(a,h)antracene and benzo(a)pyrene.

Spectroscopic Characterization of Stability and Interaction of Pd-Ag Complexes

Colloidal metal nanoparticles are of great interest because of their use as catalysts, photocatalysts, adsorbents, and sensors as well as their application in optical, electronic, and magnetic devices. Supported bimetallic systems represent a large part of heterogeneous catalysts which have been used in various reactions important in the chemical, petrochemical, and oil industry. Pd-Ag bimetallic nanocatalysts have become vitally important in some of the petrochemical industry’s processes like hydrogenation of C2–C5 olefins. A heat-treatment method for the preparation of well-stable Pd-Ag complexes is demonstrated using water, concentrated HCl and concentrated nitric acid as media. The stability and interaction of Pd-Ag complexes were characterized by UV-vis absorption spectroscopy. Pd-Ag bimetallic nanoparticles of spherical cubic and octahedral shape in the range of average particle size of 20–60 nm have been prepared and characterized by transmission electron microscopy (TEM).

Facile and economic method for preparation of nano-colloidal Silica with controlled size and stability

This study is focused on synthesis of nano-colloidal silica via alkaline water glass solution. Sodium ions of water glass were removed by cation exchanging in a resin column to obtain the silicic acid which was titrated to the solution of sodium silicate. Concentration of the colloidal silica and pH value of the solutions were controlled using different concentrations of alkaline sodium silicate and silicic acid solutions in constant temperature and titration rate. The synthesized colloidal silica was characterized by Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), X-Ray powder Diffraction (XRD), Accelerated Surface Area and Porosimetry analyzer (ASAP) and Gravimetric method. The results showed that the average particle size of colloids and their stability were also influenced by various important factors such as pH, Temperature, Concentrations of alkaline sodium silicate and silicic acid solutions. The results showed that the synthesized nano-colloidal silica suspensions in concentration up to 25 wt.% of SiO2 with average particle sizes in range of 23 to100 nm are stable more than one year. Also, surface area and pore volume of the prepared spherical colloidal silica particles were160 m 2 /g and 0.27 cm 2 /g, respectively.