scholarly journals PREPARATION AND STABILITY OF SILVER AND PALLADIUM NANOPARTICLES STABILIZED BY POLYETHER LAPROL 5003 IN N,N – DIMETHYLFORMAMIDE MEDIA

2019 ◽  
Vol 62 (5) ◽  
pp. 50-55
Author(s):  
Alexander V. Bespalov ◽  
Yana O. Ivanova
Keyword(s):  
Palladium Nanoparticles ◽  
Metallic Nanoparticles ◽  
Potassium Thiocyanate ◽  
Reducing Agent ◽  
Spectral Studies ◽  
Optical Absorption Spectroscopy ◽  
Absorption Bands ◽  
The Stability ◽  
Average Size ◽  
Silver Cations

This paper is devoted to obtaining and investigating the stability of silver and palladium sols in N,N-dimethylformamide medium. Due to the unique properties exhibited by metals in the nanosized state, metallic nanoparticles are gaining increasing importance in various fields of application, science and technology. This makes the task of obtaining stable metal sols extremely urgent. The synthesis of aggregate-resistant organosols of metals is associated with a number of problems, since the metal sols obtained in organic media are much less stable than hydrosols. For this reason, there arises the challenge of choosing an appropriate stabilizer. In this study, the stabilizer was branched polyester Laprol 5003. A distinctive feature of the synthesis of silver sols was the absence of a special reducing agent, since N,N-dimethylformamide, used as a solvent, recovers silver cations  itself. As a result, stable sols of silver and palladium have been obtained in N,N-dimethylformamide medium. Sodium borohydride was used as the reducing agent for the synthesis of palladium nanoparticles. Spectral studies of the resulting sols were carried out. The silver and palladium nanoparticles were sized up by scanning electron microscopy. The procedure has shown that the average size of the silver particles formed in the N,N-dimethylformamide medium is 4 ± 2 nm, which is substantially smaller than the particles obtained in isopropanol medium by the borohydride method.  The silver sols aggregation in dimethylformamide under the action of potassium thiocyanate was studied via optical absorption spectroscopy. It has been found that the stability of the silver sol in dimethylformamide to the electrolyte is higher than that of the sol obtained in isopropanol. It has also been detected that several absorption bands are present in the optical spectrum of the palladium sol in dimethylformamide. The effect of the stabilizing polyester concentration on the stability of silver and palladium sols in N,N-dimethylformamide was studied. The result is that when the concentration of Laprol 5003 exceeds some quantity, a sharp increase in the aggregation time of sols is observed, which indicates a significant increase in their stability.

Spectral studies of silver nanoparticles biosynthesized by Origanum majorana

2018 ◽  
Vol 7 (2) ◽  
pp. 100-105 ◽  
Author(s):  
Moustafa Zahran ◽  
Maged El-Kemary ◽  
Shaden Khalifa ◽  
Hesham El-Seedi
Keyword(s):  
Silver Nanoparticles ◽  
Zeta Potential ◽  
Metallic Nanoparticles ◽  
Spectral Studies ◽  
Surface Plasmon Resonance Peak ◽  
Plasmon Resonance Peak ◽  
Biosynthesized Agnps ◽  
The Stability ◽  
Origanum Majorana ◽  
Average Size

AbstractSilver nanoparticles (AgNPs) were biologically synthesized in an eco-friendly manner using aqueous leaf extract ofOriganum majoranaplant and silver nitrate (AgNO3) solution. Size, shape, and crystallinity of the biosynthesized AgNPs were determined by using a transmission electron microscope (TEM). Zeta potential analyzer was used to prove the stability of the metallic nanoparticles, while Fourier transform infrared spectroscopy was used to identify the bioreducing and capping agents. AgNPs were electrochemically investigated using cyclic voltammetry (CV), while the optical properties of the metallic nanoparticles were studied using UV-Vis and fluorescence spectroscopies. According to TEM images, AgNPs are spherical with an average size of 35 nm. TEM also refers to the presence of mono and polycrystalline AgNPs. The value of zeta potential (−39 mV) proved the stability of AgNPs caused by capping molecules ofO. majoranaplant. CV studies showed that AgNPs were electrochemically investigated at 0.39 mV. AgNPs showed a surface plasmon resonance peak at 440 nm, while the emission peak was detected at 466 nm. These nanoparticles are promising for many industrial and medical applications.

scholarly journals Synthesis of Silver Nanoparticles Using Dichloromethane Extract of Chrysanthemum cinerariaefolium and Its Bioactivity

2021 ◽  
Vol 6 (1) ◽  
pp. 1-17
Author(s):  
Caroline Jepchirchir Kosgei ◽  
Meshack Amos Obonyo ◽  
Josphat Clement Matasyoh ◽  
James J. Owuor ◽  
Moses A. Ollengo ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Silver Nanoparticles ◽  
Metallic Nanoparticles ◽  
Colour Change ◽  
Vero Cells ◽  
Ag Nps ◽  
Absorption Bands ◽  
Sem Images ◽  
Average Size ◽  
Chrysanthemum Cinerariaefolium

Common methods of synthesizing metallic nanoparticles are chemical and physical. However, they are expensive and use toxic chemicals. Green synthesis is less costly and safer hence a potential alternative. Silver nanoparticles (Ag NPs) were synthesized using dichloromethane extract of Chrysanthemum cinerariaefolium and colour change from pale green to dark brown was observed. Scanning Electron Microscopy (SEM) images were faceted and others formed clusters. Transmission Electron Microscopy (TEM) images were spherical with an average size of 22.8± 17.5 nm. EDX analysis showed the nanoparticles had percentage abundance of 67.26%. Fourier-transform Infrared Spectroscopy (FTIR) analysis showed absorption bands at 3489.59 cm-1, 3217.80 cm-1, 2384.74 cm-1 , 1633.05 cm-1, 1405.08 cm-1, 1109.32 cm-1 and 505.93 cm-1. The UV-Vis analysis showed Surface Plasmon Resonance (SPR) peak at 434 nm. The nanoparticles were more active on P. aeruginosa with an MIC of 15 µg/ml while the cytotoxicity assay showed Ag NPs had an MIC of 33.33 µg/ml hence were noncytotoxic against Vero cells.

Identical twins and developmental stability

1962 ◽  
Vol 4 (1) ◽  
pp. 144-164 ◽  
Author(s):  
C. S. Taylor
Keyword(s):  
Growth Curves ◽  
Identical Twins ◽  
Body Measurements ◽  
Frequency Distributions ◽  
Stability Of Development ◽  
Mean Size ◽  
Degree Of Maturity ◽  
The Stability ◽  
Average Size ◽  
Slow Growing

1. The stability with which dairy cattle develop in body size up to 2 years of age was studied in 60 pairs of uniformly treated identical twins, i.e. an assessment was made of the influence of season, genotype, mean size of twin pair, age and degree of maturity on the level of within-pair variability.2. The frequency distributions of size differences shown by one-egg twins were in many cases decidedly leptokurtic.3. The similarity in size of the identical twins studied was only slightly, if at all, influenced by season. Within-pair variability under free outdoor grazing was certainly not any greater than under semi-controlled conditions indoors.4. The stability with which cattle grew appeared to depend on their genotype. Identical twins of the Shorthorn breed were somewhat more alike in size than were the twins of other breed-types; crossbreds were, on average, 50 % less stable than purebreds in average size () ; although crossbreds grew with somewhat greater stability ().5. Whatever their mean size, all pairs of identical twins of the same breed appeared to grow postnatally with more or less equal stability (). Small, slow growing pairs showed a greater disparity in average size ().6. Stability of development continually changed with age but not violently. Each body measurement appeared to have its own characteristic age trend. It is false to believe that variation automatically increases with increasing age. As they grew older, identical twins tended to become less alike in their later maturing body measurements whereas their early maturing body measurements tended to decline in variability. There was an overall trend with degree of maturity; variability steadily increased to a maximum and subsequently declined.7. It is suggested that environmentally induced instability of development may remain at a minimum level so long as growth curves are not seriously distorted from their exponential path to maturity.

scholarly journals Australian agricultural scale and corporate agroholdings: environmental and climatic impacts

2017 ◽  
Vol 20 (2) ◽  
pp. 187-190 ◽  
Author(s):  
Bradley Plunkett ◽  
Andrew Duff ◽  
Ross Kingwell ◽  
David Feldman
Keyword(s):  
Large Scale ◽  
Climatic Variability ◽  
Institutional Setting ◽  
Corporate Ownership ◽  
Family Structures ◽  
Climatic Impacts ◽  
The Stability ◽  
Average Size ◽  
The Impact ◽  
Concentrate Production

The average size of Australian farms in scale and revenue are the globe’s largest. This scale is a result, in part, of low average rural population densities; development patterns in broadacre production; low levels of effective public policy transfers; a stable and suitable institutional setting suitable for corporate and other large scale investment; and low yields. It is also a factor of the natural variability of the country’s climatic systems which have contributed to the scale of extensive northern cattle production; this variability has implications for the pattern of ownership of broadacre and extensive production. Corporate ownership, tends to concentrate production aggregations at sufficient scale to offset its additional overheads in areas of relative climatic stability and to replicate these agroholding aggregations spatially to protect the stability of revenue flows. Family structures are more dominant in areas of greater climatic variability. Of interest is the impact that any increasing climatic variability (versus rapid changes in technology) may have upon this pattern.

scholarly journals Spectral studies of ocean water using DOAS

2007 ◽  
Vol 4 (3) ◽  
pp. 459-489
Author(s):  
M. Vountas ◽  
T. Dinter ◽  
A. Bracher ◽  
J. P. Burrows ◽  
B. Sierk
Keyword(s):  
Spectral Studies ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Technique ◽  
Phytoplankton Absorption ◽  
Visible Wavelengths ◽  
Scanning Imaging ◽  
Atmospheric Trace Gas ◽  
First Time ◽  
Chlorophyll Concentrations

Abstract. Methods enabling the retrieval of oceanic parameter from the space borne instrumentation Scanning Imaging Absorption Spectrometer for Atmospheric ChartographY (SCIAMACHY) using Differential Optical Absorption Spectroscopy (DOAS) are presented. SCIAMACHY onboard ENVISAT measures back scattered solar radiation at a spectral resolution (0.2 to 1.5 nm). The DOAS method was used for the first time to fit modelled Vibrational Raman Scattering (VRS) in liquid water and in situ measured phytoplankton absorption reference spectra to optical depths measured by SCIAMACHY. Spectral structures of VRS and phytoplankton absorption were clearly found in these optical depths. Both fitting approaches lead to consistent results. DOAS fits correlate with estimates of chlorophyll concentrations: low fit factors for VRS retrievals correspond to large chlorophyll concentrations and vice versa; large fit factors for phytoplankton absorption correspond with high chlorophyll concentrations and vice versa. From these results a simple retrieval technique taking advantage of both measurements is shown. First maps of global chlorophyll concentrations were compared to the corresponding MODIS measurements with very promising results. In addition, results from this study will be used to improve atmospheric trace gas DOAS-retrievals from visible wavelengths by including these oceanographic signatures.

scholarly journals Synthesis of Silver Nanoparticles from Anagalis arvensis and Their Biomedical Applications

2018 ◽  
Author(s):  
Mohib Shah ◽  
Natasha Anwar ◽  
Samreen Saleem ◽  
Iqbal Munir ◽  
Niaz Ali Shah ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Reducing Power ◽  
Spherical Shape ◽  
Artemia Salina ◽  
Maximum Activity ◽  
Tem Analysis ◽  
Synthesis Of Nanoparticles ◽  
The Stability ◽  
Average Size ◽  
Biological Methods

Background. Nanotechnology is promising field for generating new applications. A green synthesis of nanoparticles through biological methods using plant extract have a reliable and ecofriendly approach to improve our global environment. Methods. Silver nanoparticles (AgNPs) were synthesized using aqueous extract of Anagalis arvensis L and silver nitrate and were physicochemically characterized. Results. The stability of AgNPs toward acidity, alkalinity, salinity and temperature showed that they remained stable at room temperature for more than two months. The SEM and TEM analysis of the AgNPs showed that they have a uniform spherical shape with an average size in the range of 40–78 nm. Further 1-Dibhenyl-2-Picrylhydrazl radical in Anagalis arvensis L.mediated AgNPs showed a maximum activity of 98% at concentration of 200μg/mL. Hydrogen peroxide scavenging assay in Anagalis arvensis L. mediated AgNPs showed a maximum activity of 85% at concentration of 200μg/mL. Reducing power of Anagalis arvensis L.Ag NPs exhibited a higher activity of 330 μg/mL at concentration of 200 μg/mL. These NPs have cytotoxic effects against brine shrimp (Artemia salina) nauplii with a value of 53% LD 178.04μg/mL. Conclusion. The AgNPs synthesized using Anagalis arvensis L. extract demonstrate a broad range of applications.

scholarly journals Síntese, caracterização e estabilidade de nanopartículas de magnetita

2021 ◽  
Vol 3 (4) ◽  
pp. 2738-2749
Author(s):  
Monise Cristina Ribeiro Casanova Coltro ◽  
Warde Antonieta da Fonseca-Zang ◽  
Joachim Werner Zang ◽  
Danilo César Silva e Sousa
Keyword(s):  
New Technology ◽  
X Ray Diffraction ◽  
Synthesis Of Nanoparticles ◽  
Research Areas ◽  
Magnetite Fe3o4 ◽  
Mineral Substance ◽  
Abundant Element ◽  
The Stability ◽  
Average Size

Nanopartículas de ferro são muito utilizadas em diversas áreas de pesquisa. O elemento químico ferro (Fe), sendo o quarto elemento mais abundante na crosta terrestre, e a substância mineral magnetita, com propriedade magnética, apresentam aplicações nas áreas industrial, ambiental, biomédica e de novas tecnologias. Este trabalho apresenta processo de síntese de nanopartículas partindo-se de sais precursores, bem como a caracterização dos produtos e as rotas para estabilizá-los. Os sais químicos precursores utilizados foram o cloreto férrico (FeCl3) e o sulfato ferroso (FeSO4) na proporção de 2:1, sob agitação por ultrassom e pH ácido. Para formação do precipitado de nanopartículas usou-se solução aquosa de hidróxido de sódio (NaOH) de pH 12. A difratometria de raio-X, mostra a presença de magnetita (Fe3O4) indicada pelos picos característicos de difração em graus 2Ө = 18° (largo), 31° (fino), 36° (bem definido), 43,4°, 45°, 53,6°, 57,7°, 63,3°. A microscopia eletrônica de transmissão mostra a morfologia dos produtos da síntese. Fatores que influenciam a estabilidade das partículas são agitação, o ajuste de pH, condições de secagem. O tamanho médio das nanopartículas de magnetitas é de aproximadamente 15 nm.   Iron nanoparticles are widely used in several research areas. The chemical element iron (Fe), being the fourth most abundant element in the earth's crust, and the mineral substance magnetite, with magnetic properties, have applications in industrial, environmental, biomedical, and new technology areas. This work presents the process of synthesis of nanoparticles starting from precursor salts, as well as the characterization of the products and the routes to stabilize them. The precursor chemical salts were ferric chloride (FeCl3) and ferrous sulfate (FeSO4) in a 2:1 ratio, under ultrasound agitation and acidic pH. For the nanoparticles growth was applied aqueous solution of sodium hydroxide (NaOH) at pH 12. X-ray diffraction shows the presence of magnetite (Fe3O4) indicated by characteristic diffraction peaks in degrees 2Ө = 18° (wide), 31° (fine), 36° (well defined), 43.4°, 45°, 53.6°, 57.7°, 63.3°. Scanning electron microscopy shows the morphology of the synthesis products. Factors that influence the stability of the particles are agitation, the pH adjustment, and the conditions of drying. The average size of the magnetite nanoparticles is approximately 15 nm.

scholarly journals Study of Zero Temperature Ground State Properties of the Repulsive Bose-Einstein Condensate in an Anharmonic Trap

2021 ◽  
Vol 13 (3) ◽  
pp. 733-744
Author(s):  
P. K. DEBNATH
Keyword(s):  
Ground State ◽  
Expansion Method ◽  
Einstein Condensate ◽  
Zero Temperature ◽  
Many Body ◽  
Ground State Properties ◽  
Potential Harmonic ◽  
The Stability ◽  
Average Size ◽  
Body Potential

The zero-temperature ground state properties of experimental 87Rb condensate are studied in a harmonic plus quartic trap [ V(r) =  ½mω2r2 + λr4 ]. The anharmonic parameter (λ) is slowly tuned from harmonic to anharmonic. For each choice of λ, the many-particle Schrödinger equation is solved using the potential harmonic expansion method and determines the lowest effective many-body potential. We utilize the correlated two-body basis function, which keeps all possible two-body correlations. The use of van der Waals interaction gives realistic pictures. We calculate kinetic energy, trapping potential energy, interaction energy, and total ground state energy of the condensate in this confining potential, modelled experimentally. The motivation of the present study is to investigate the crucial dependency of the properties of an interacting quantum many-body system on λ. The average size of the condensate has also been calculated to observe how the stability of repulsive condensate depends on anharmonicity. In particular, our calculation presents a clear physical picture of the repulsive condensate in an anharmonic trap.

Sign in / Sign up

Export Citation Format

Share Document