Plasmonic Effects, Size and Biological Activity Relationship of Au-Ag Alloy Nanoparticles

2018 ◽  
Vol 54 ◽  
pp. 98-111 ◽  
Author(s):  
Ahson Jabbar Shaikh ◽  
Maria Batool ◽  
Muhammad Arfat Yameen ◽  
Amir Waseem
Keyword(s):  
Biological Activity ◽  
Gradual Increase ◽  
Reducing Agent ◽  
Alloy Nanoparticles ◽  
Ag Nps ◽  
Uniform Size ◽  
Vis Spectroscopy ◽  
Plasmonic Effects ◽  
Lower Temperature ◽  
Relationship Of

The plasmonic effects of Au-Ag alloy nanoparticles, gold nanoparticles (AuNPs), and silver nanoparticles (AgNPs) are studied and compared to their size. Various factors that affect the size of alloy nanoparticles are varied such as concentration and ratio of gold and silver salt, time of addition of reducing agent, temperature and pH. Addition of reducing agent at different time intervals for the synthesis of pure and alloy Au-Ag NPs shows a gradual increase in size, as well as increase in heterogeneity of nanoparticles with delayed addition of reducing agent. Temperature dependent alloy nanoparticles also shows a gradual increase in size with increase in temperature. pH dependent alloy nanoparticles show decrease in size with increase in pH from 4 to 8. Their size is characterized by SEM and corelated with UV-Vis spectroscopy. Furthermore, alloy nanoparticles synthesized by varying temperature are also characterized for their antibacterial studies against Escherichia coli and Staphylococcus aureus strains. Nanoparticles synthesized at high temperature (100°C) have shown higher bioactivity against both organisms due to small and uniform size nanoparticles, while nanoparticles synthesized at lower temperature (50°C) have lower biological activity. Alloy nanoparticles synthesized at 60°C and 70°C are more active against E. coli while those of 80°C and 90°C are more active against S. aureus.

scholarly journals Relationship of 25-hydroxyvitamin D3 side chain structure to biological activity.

1975 ◽  
Vol 250 (1) ◽  
pp. 226-230
Author(s):  
M F Holick ◽  
M Garabedian ◽  
H K Schnoes ◽  
H F DeLuca
Keyword(s):  
Biological Activity ◽  
Chain Structure ◽  
Side Chain ◽  
Relationship Of

scholarly journals Green synthesis of silver nanoparticles: Characterization and its potential biomedical applications

2021 ◽  
Vol 10 (1) ◽  
pp. 412-420
Author(s):  
Mona S. Alwhibi ◽  
Dina A. Soliman ◽  
Manal A. Awad ◽  
Asma B. Alangery ◽  
Horiah Al Dehaish ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Aloe Vera ◽  
Inhibition Zone ◽  
Biologically Active ◽  
Noble Metal Nanoparticles ◽  
Biological Synthesis ◽  
Ag Nps ◽  
Mouse Melanoma ◽  
Therapeutic Benefits ◽  
Vis Spectroscopy

Abstract In recent times, research on the synthesis of noble metal nanoparticles (NPs) has developed rapidly and attracted considerable attention. The use of plant extracts is the preferred mode for the biological synthesis of NPs due to the presence of biologically active constituents. Aloe vera is a plant endowed with therapeutic benefits especially in skincare due to its unique curative properties. The present study focused on an environmental friendly and rapid method of phytosynthesis of silver nanoparticles (Ag-NPs) using A. vera gel extract as a reductant. The synthesized Ag-NPs were characterized by transmission electron microscopy (TEM), UV-Vis spectroscopy, Fourier transform infrared (FTIR), and dynamic light scattering (DLS). TEM micrographs showed spherical-shaped synthesized Ag-NPs with a diameter of 50–100 nm. The UV-Vis spectrum displayed a broad absorption peak of surface plasmon resonance (SPR) at 450 nm. The mean size and size distribution of the formed Ag-NPs were investigated using the DLS technique. Antibacterial studies revealed zones of inhibition by Ag-NPs of A. vera (9 and 7 mm) against Pseudomonas aeruginosa and Escherichia coli, respectively. Furthermore, the antifungal activity was screened, based on the diameter of the growth inhibition zone using the synthesized Ag-NPs for different fungal strains. Anticancer activity of the synthesized Ag-NPs against the mouse melanoma F10B16 cell line revealed 100% inhibition with Ag-NPs at a concentration of 100 µg mL−1. The phytosynthesized Ag-NPs demonstrated a marked antimicrobial activity and also exhibited a potent cytotoxic effect against mouse melanoma F10B16 cells. The key findings of this study indicate that synthesized Ag-NPs exhibit profound therapeutic activity and could be potentially ideal alternatives in medicinal applications.

scholarly journals Variability and improvement of optical and antimicrobial performances for CQDs/mesoporous SiO2/Ag NPs composites via in situ synthesis

2021 ◽  
Vol 10 (1) ◽  
pp. 403-411
Author(s):  
Youliang Cheng ◽  
Mingjie Wang ◽  
Changqing Fang ◽  
Ying Wei ◽  
Jing Chen ◽  
...  
Keyword(s):  
Uv Light ◽  
Carbon Quantum Dots ◽  
Diffusion Method ◽  
Ag Nps ◽  
Uniform Size ◽  
High Antibacterial Activity ◽  
Fluorescent Materials ◽  
Potential Applications ◽  
Mesoporous Sio2

Abstract To change the optical properties and improve the antibacterial performances of carbon quantum dots (CQDs) and Ag NPs, mesoporous SiO2 spheres were combined with them to form the composites. In this paper, CQDs with a uniform size of about 3.74 nm were synthesized using glucose as carbon source. Then, CQDs/mesoporous SiO2/Ag NPs composites were obtained in situ under UV light irradiating by using mesoporous SiO2 and Ag NO3 as the carrier and silver resource, respectively. The diameter of CQDs/mesoporous SiO2/Ag NPs particles was in the range of 200–250 nm. With the increase in irradiating time, the red-shift in the UV-Vis spectrum for as-prepared CQDs/mesoporous SiO2/Ag NPs composites was found, and the adsorption peak was widened. In addition, the composites showed a high antibacterial activity against Staphylococcus aureus and Escherichia coli via disc diffusion method. These results indicated that inhibition circles for Ag NPs/mesoporous SiO2/CQDs and mesoporous SiO2/Ag NPs were similar in diameter. Furthermore, the two composites had a better bactericidal performance compared with other particles. Therefore, as-prepared CQDs/mesoporous SiO2/Ag NPs composites in this paper have great potential applications for fluorescent materials and antibacterial materials.

scholarly journals Reducing the Crystallite Size of Spherulites in PEO-Based Polymer Nanocomposites Mediated by Carbon Nanodots and Ag Nanoparticles

Nanomaterials ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 874 ◽  
Author(s):  
Ranjdar Abdullah ◽  
Shujahadeen Aziz ◽  
Soran Mamand ◽  
Aso Hassan ◽  
Sarkawt Hussein ◽  
...  
Keyword(s):  
Crystallite Size ◽  
Polymer Nanocomposites ◽  
Electron Transition ◽  
Peak Position ◽  
Carbon Nanodots ◽  
Ag Nps ◽  
Peak Broadening ◽  
Vis Spectroscopy ◽  
Solution Cast ◽  
Significant Change

The PEO-based polymer nanocomposites were prepared by solution cast method. Green approaches were used for synthesis of carbon nanodots (CNDs) and silver nanoparticles (Ag NPs). It was found that the crystallite size of spherulites of PEO was greatly scarified upon incorporation of CNDs and Ag NPs. In the present work, in opposition to other studies, broadening of surface plasmon resonance (SPR) peak of metallic Ag NPs in PEO-based polymer composites was observed rather than peak tuning. Various techniques, such as powder X-ray diffraction (XRD), SEM, UV–Vis spectroscopy, and photoluminescence (PL), were used to characterize the structural, morphological, and optical properties of the samples. Increase of amorphous phase for the PEO doped with CND particles was shown from the results of XRD analyses. Upon the addition of suspended Ag NPs to the PEO:CNDs composites, significant change of XRD peak position was seen. A field-emission scanning electron microscope (FESEM) was used to investigate the surface morphology of the samples. In the SEM, a significant change in the crystalline structure was seen. The size of PEO spherulites in the PEO nanocomposite samples became smaller and the percentage of amorphous portion became larger, owing to the distribution of CNDs and Ag NPs. The UV–Vis absorption spectra of the PEO-based polymer were found to improve and shift to higher wavelengths upon incorporation of CNDs and Ag NPs into the PEO matrix. The SPR peak broadening in the UV–Vis spectra was observed in the PEO:CNDs composites due to the Ag NPs. The absorption edge value of PEO was found to shift toward lower photon energy as the CNDs and Ag NPs are introduced. The photoluminescence (PL) spectra were also observed for the PEO:CNDs and PEO:CNDs:Ag samples and found to be more intense in the PEO:CNDs system than in the PEO:CNDs:Ag system. Lastly, the optical band gap of the samples was further studied in detail using of Tauc’s model and optical dielectric loss parameter. The types of electron transition were specified.

EFFECT OF MEAN ION SIZE AND SPATIAL SPIN DISORDERS FOR (La1-xYx)2/3Ca1/3MnO3 MANGANITES

2004 ◽  
Vol 18 (26) ◽  
pp. 3451-3464 ◽  
Author(s):  
JINCANG ZHANG ◽  
YUFENG ZHANG ◽  
SHIXUN CAO ◽  
CHAO JING
Keyword(s):  
Single Phase ◽  
Bond Angle ◽  
Gradual Increase ◽  
High Concentration ◽  
Magnetic Studies ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Average Ionic Radius ◽  
Lower Temperature ◽  
Ion Size

The structure and transport properties of perovskite ( La 1-x Y x)2/3 Ca 1/3 MnO 3 (0≤x≤0.3) systems are systematically investigated. It is found that all the specimens show a single-phase structure and reveal a direct relationship between the Curie temperature Tc and the average ionic radius <rA> of La site. With increasing Y 3+ doped content, the metal-insulator transition temperature T MI (M-I) shifts to lower temperature. While the relevant resistivity peak ρp is sharp increased, for the specimens with large doping content, x=0.3, it has enhanced eight orders of magnitudes larger than the non-doped samples (x=0.0). At high concentration area, that is to say, when x>0.1, magnetic studies show a gradual increase of antiferromagnetic interaction with an increase of x, ultimately leading to a spatial-spin disorders, that is, spin-glass-like state for x=0.2 and x=0.3 compounds at about 35 K. The results show that it has connected a reduction of Tc and an increase in magnetoresistance with a decrease in the microstructural Mn - O - Mn bond angle.

scholarly journals Large-Scale Fabrication of Ultrasensitive and Uniform Surface-Enhanced Raman Scattering Substrates for the Trace Detection of Pesticides

Nanomaterials ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 520 ◽  
Author(s):  
Jia Zhu ◽  
Guanzhou Lin ◽  
Meizhang Wu ◽  
Zhuojie Chen ◽  
Peimin Lu ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Large Scale ◽  
Capillary Flow ◽  
Surface Enhanced Raman Scattering ◽  
Ag Nps ◽  
Uniform Size ◽  
Sers Substrates ◽  
Surface Enhanced ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering

Technology transfer from laboratory into practical application needs to meet the demands of economic viability and operational simplicity. This paper reports a simple and convenient strategy to fabricate large-scale and ultrasensitive surface-enhanced Raman scattering (SERS) substrates. In this strategy, no toxic chemicals or sophisticated instruments are required to fabricate the SERS substrates. On one hand, Ag nanoparticles (NPs) with relatively uniform size were synthesized using the modified Tollens method, which employs an ultra-low concentration of Ag+ and excessive amounts of glucose as a reducing agent. On the other hand, when a drop of the colloidal Ag NPs dries on a horizontal solid surface, the droplet becomes ropy, turns into a layered structure under gravity, and hardens. During evaporation, capillary flow was burdened by viscidity resistance from the ropy glucose solution. Thus, the coffee-ring effect is eliminated, leading to a uniform deposition of Ag NPs. With this method, flat Ag NPs-based SERS active films were formed in array-well plates defined by hole-shaped polydimethylsiloxane (PDMS) structures bonded on glass substrates, which were made for convenient detection. The strong SERS activity of these substrates allowed us to reach detection limits down to 10−14 M of Rhodamine 6 G and 10−10 M of thiram (pesticide).

β-Cell-tropin: relationship of structure to biological activity

1983 ◽  
Vol 11 (2) ◽  
pp. 201-201 ◽  
Author(s):  
S. DUNMORE ◽  
J. MORTON ◽  
A. BELOFF-CHAIN ◽  
G. TAYLOR ◽  
H. R. MORRIS
Keyword(s):  
Biological Activity ◽  
Β Cell ◽  
Relationship Of

scholarly journals Photocatalytic and Biological Activity of ZnO Nanoparticles Using Honey

Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1046
Author(s):  
M. Sharmila ◽  
R. Jothi Mani ◽  
Abdul Kader ◽  
Awais Ahmad ◽  
Gaber E. Eldesoky ◽  
...  
Keyword(s):  
Biological Activity ◽  
Zno Nanoparticles ◽  
Environmental Remediation ◽  
Dye Degradation ◽  
Xrd Analysis ◽  
Fungal Species ◽  
Size Estimation ◽  
Bonding Structure ◽  
Antibacterial And Antifungal Activities ◽  
Vis Spectroscopy

The innovation and development of water purification methods have been at the center of extensive research for several decades. Many nanoparticles are frequently seen in industrial waste water. In this research, zinc oxide nanoparticles (ZnO) were synthesized following an autocombustion method with and without honey capping. Structural crystallinity and bonding structure were examined via X-ray diffraction (XRD) analysis and Fourier transform infrared (FTIR) spectroscopy. Optical behavior was analyzed using ultraviolet–visible (UV–Vis) spectroscopy and photoluminescence (PL). Size estimation and surface morphology were studied using scanning electron microscopy (SEM), while energy-dispersive spectroscopy (EDS) was performed to analyze the sample purity and elemental composition. The photocatalytic degradation of methylene blue (MB) by ZnO was assessed as it is an efficient water treatment process with high potential. The biological activity of ZnO nanoparticles was also investigated in terms of antibacterial and antifungal activities against different bacterial and fungal species. Surprisingly, the as-synthesized ZnO nanoparticles were found to be substantially bioactive compared to conventional drugs. Honey-mediated nanoparticles displayed 86% dye degradation efficiency, and that of bare ZnO was 60%. Therefore, the involvement of honey in the synthesis of ZnO nanoparticles has great potential due to its dual applicability in both biological and environmental remediation processes.

scholarly journals Nanocatalytic Activity of Silver Nanoparticles (Ag-Nps) Fabricated using Camellia sinensis (Linn) Tender Leaf Extract and their Characterization

2020 ◽  
Vol 2 (1) ◽  
pp. 24
Keyword(s):  
Silver Nanoparticles ◽  
Zeta Potential ◽  
Pancreatic Enzyme ◽  
Alpha Amylase ◽  
Assay Method ◽  
Ag Nps ◽  
Visible Absorption ◽  
Biological Reduction ◽  
Vis Spectroscopy ◽  
Uv Visible

Silver nanoparticles (Ag-NPs) were prepared by the biological reduction method. Green tea extract was taken as a reducing and stabilizing agent and silver nitrate as the metal precursor for nanoparticle synthesis. The formation of the silver nanoparticles was monitored visually and using UV-Visible absorption spectroscopy. The synthesized silver nanoparticles were characterized by UV-visible spectroscopy, FTIR, Zeta sizer, Zeta potential, and antimicrobial studies. Silver nanoparticles were also subjected to investigate nanocatalytic activity with standard pancreatic alpha-amylase and bacterial amylase enzyme by the DNS assay method. UV-Vis spectroscopy revealed the formation of silver nanoparticles by exhibiting the typical surface plasmon absorption maxima at 430 nm. Four major functional groups of bio-molecules such as phenol, carboxylic acid, protein, and alkyl group were recorded in FTIR spectra. The size of the nanoparticles ranges between 5nm and 150nm. The average size and size distribution of silver nanoparticles is 59.66nm. The zeta potential of the silver nanoparticle is negatively charged and rendered as a sharp peak at -31.7mV. Antimicrobial activity of silver nanoparticles exhibited the highest inhibition against Gram-negative bacteria than Gram-positive bacteria and yeast pathogens. Starch hydrolysis of Ag-NPs was studied with pancreatic alpha-amylase (tailor made), crude and purified bacterial amylase enzyme. The formation of reducing sugar was increased about 40-fold for a purified enzyme, 11-fold for the pancreatic enzyme, and 6-fold for crude bacterial enzyme incorporated with Ag-NPs over control. The present studies recommended that Ag-NPs have a significant role in the degradation of starch into reducing sugars by acting as a nanocatalyst.

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