Modeling of optical properties of hybrid metal-organic nanostructures

To model spectral characteristics of hybrid metal-organic nanostructures, the extended Mie theory was used, which makes it possible to calculate the extinction efficiency factor (Qext) and the scattering efficiency factor in the near zone (QNF) of two-layer spherical particles placed in an absorbing matrix. Two-layer plasmon nanospheres consisting of a metallic core (Ag, Cu) coated with dielectric shells and located into the copper phthalocyanine (CuPc) matrix were considered. The influence of dielectric shell thickness and refractive index on the characteristics of the surface plasmon resonance of absorption (SPRA) was studied. The possibility of the SPRA band tuning by changing the optical and geometrical parameters of dielectric shells was shown. It was established that dielectric shells allow to shift the surface plasmon resonance band of plasmonic nanoparticles absorption both to short- and long-wavelength spectral range depending on the relation between shell and matrix refractive indexes.

Protective role of foliar application of green-synthesized silver nanoparticles against wheat stripe rust disease caused by Puccinia striiformis

Green-synthesized nanoparticles have a tremendous antimicrobial potential to be used as an alternative to hazardous fungicides. In this study, the green synthesis of silver nanoparticles (AgNPs) was performed by using Moringa oleifera leaf extract as a reducing and stabilizing agent. The synthesized AgNPs were subjected to different characterization techniques. UV-visible spectroscopy confirmed the surface plasmon resonance band in the range of 400–450 nm, and zeta analysis revealed that the synthesized AgNPs ranged 4–30 nm in size. Scanning electron microscopy depicted tiny fused rectangular segments and the crystalline nature of the synthesized AgNPs was confirmed using X-ray diffraction. Energy dispersive X-ray (EDX) detector confirmed the presence of metallic silver ions. Fourier-transform infrared analysis revealed the presence of phenols as main reducing agents in the plant extract. Foliar application of different concentrations (25, 50, 75, and 100 ppm) of AgNPs was applied on wheat plants inoculated with Puccinia striiformis to assess the disease incidence against stripe rust disease. AgNPs at a conc. of 75 ppm were found to be more effective against wheat stripe rust disease. Furthermore, the application of AgNPs enhanced morpho-physiological attributes and reduced nonenzymatic compounds and antioxidant enzymes in wheat. The present study highlights the potential role of the green-synthesized AgNPs as a biological control of yellow rust disease.

Phyto-Functionalized Silver Nanoparticles Derived from Conifer Bark Extracts and Evaluation of Their Antimicrobial and Cytogenotoxic Effects

Silver nanoparticles synthesized using plant extracts as reducing and capping agents showed various biological activities. In the present study, colloidal silver nanoparticle solutions were produced from the aqueous extracts of Picea abies and Pinus nigra bark. The phenolic profile of bark extracts was analyzed by liquid chromatography coupled to mass spectrometry. The synthesis of silver nanoparticles was monitored using UV-Vis spectroscopy by measuring the Surface Plasmon Resonance band. Silver nanoparticles were characterized by attenuated total reflection Fourier transform infrared spectroscopy, Raman spectroscopy, dynamic light scattering, scanning electron microscopy, energy dispersive X-ray and transmission electron microscopy analyses. The antimicrobial and cytogenotoxic effects of silver nanoparticles were evaluated by disk diffusion and Allium cepa assays, respectively. Picea abies and Pinus nigra bark extract derived silver nanoparticles were spherical (mean hydrodynamic diameters of 78.48 and 77.66 nm, respectively) and well dispersed, having a narrow particle size distribution (polydispersity index values of 0.334 and 0.224, respectively) and good stability (zeta potential values of −10.8 and −14.6 mV, respectively). Silver nanoparticles showed stronger antibacterial, antifungal, and antimitotic effects than the bark extracts used for their synthesis. Silver nanoparticles obtained in the present study are promising candidates for the development of novel formulations with various therapeutic applications.

Biosynthesised Drug-Loaded Silver Nanoparticles: A Vivid Agent for Drug Delivery for Human Breast Carcinoma

The use of nanoparticles as drug carriers has been investigated, and it offers various benefits, including the controlled and targeted release of loaded or associated drugs, as well as enhanced drug bioavailability. They do, however, have certain disadvantages, such as in vivo toxicity, which affects all organs, including healthy ones, and overall disease treatment improvement, which might be undetectable or limited. Silver nanoparticles are being studied more and more due to their unique physical, chemical, and optical properties, which allow them to be used in a variety of applications, including drug delivery to specific targets in the body. Given the constraints of traditional cancer treatment, such as low bioavailability and the resulting usage of high doses that produce side effects, attempts to address these challenges are essential. In this work, Biocompatible Silver nanoparticles (AgNps) loaded with tamoxifen have been prepared using the gelation process. Tamoxifen-loaded green synthesized AgNps are reported to be amorphous. The phytochemicals present in the extract of Hemionitis arifolia leaf were responsible for the reduction of silver nitrate to AgNPs. The functional groups existing in the particles were identified with FT-IR analysis. XRD analysis state that the particles were crystalline in nature and arranged in quartzite crystal. Particle size and shape were illustrated from SEM analysis and revealed that the particles were amorphous in nature. UV-visible spectrophotometer showed the band around 440nm which was identified as “surface Plasmon resonance band”. The synthesized AgNps loaded with tamoxifen were significantly effective against Human breast cancer cells. The silver nanoparticle loaded with tamoxifen was found to be inducing apoptotic signals in the selected cells. It inhibits the breast cancer cells even at the lower concentration of AgNPs and TAM-AgNPs. Further apoptotic studies (AO/EtBr and DAPI) reveal that cell death is due to the fragmentation of nuclear material of the treated cells.

Investigation of the Influence of the Molecular Weight of Polyethyleneglycols on the Optical Properties and Dispersed Characteristics of Sols of Au Nanoparticles used in Medicine

In this work, the synthesis of Au nanoparticles stabilized with polyethyleneglycols with different molecular weights from 200 to 8000 Da was carried out. The synthesis was carried out by the method of chemical reduction in an aqueous medium using sodium citrate as a reducing agent. The dependence of the optical properties on the concentration and molar mass of polyethyleneglycol was studied in the obtained samples of Au nanoparticles. The absorption spectra were recorded using an SF-56 optical spectrometer. The studies were carried out in the visible range of the spectrum from 400 to 800 nm. It was found that the type of spectrum, the position of the surface plasmon resonance band and the optical density of the samples of Au nanoparticles stabilized with PEG-8000 with a concentration of 10 and 20% did not undergo significant changes during storage, which characterizes the high aggregate stability of these sols. The dispersed characteristics of these samples of sols of Au nanoparticles were also studied. The studies were carried out using photon-correlation spectroscopy by the method of dynamic light scattering. It is established that an increase in the concentration of the stabilizer leads to an increase in the average hydrodynamic radius of the particles. This fact is associated with an increase in the thickness of the stabilizer layer and with the "stitching" of the polymer layer of Au nanoparticles with the formation of aggregates. Thus, the best result was found in PEG-8000 samples with concentrations of 10 and 20%, since the type of spectrum, the position of the surface plasmon resonance band and the optical density did not undergo significant changes. Based on the data obtained, it can be concluded that the best stabilizer for Au nanoparticles obtained by the citrate method is PEG-8000 with a concentration of at least 10 %. It is important to note that with an increase in the concentration of the stabilizer, the average hydrodynamic radius of the particles increases. This fact is associated with an increase in the thickness of the stabilizer layer and with the "stitching" of Au nanoparticles.

Optical Properties of Plasma Dimer Nanoparticles for Solar Energy Absorption

Plasmonic nanofluids have excellent optical properties in solar energy absorption and have been widely studied in solar thermal conversion technology. The absorption of the visible region of solar energy by ordinary metal nanoparticles is usually limited to a narrow resonance band, so it is necessary to enhance the coupling effect of nanoparticles in the visible spectrum region to improve absorption efficiency. However, it is still a difficult task to improve solar energy absorption by adjusting the structure and performance of nanoparticles. In this paper, a plasma dimer Ag nanoparticle is proposed to excite localized surface plasmon resonance (LSPR). Compared with an ordinary Ag nanoparticle in the visible region, the plasmonic Ag dimer nanoparticle produces more absorption peaks and broader absorption bands, which can broaden solar energy absorption. By analyzing the electromagnetic field of the nanoparticle, the resonance mode of the plasma dimer is discussed. The effects of the geometric dimensions of the nanoparticle and the embedding of two spheres on the optical properties are studied. In addition, the effects of a trimer and its special structure on the optical properties are also analyzed. The results show that the proposed plasma dimer Ag nanoparticle has broad prospects for application in solar thermal conversion technology.

Statistically Optimized Production of Saccharides Stabilized Silver Nanoparticles Using Liquid–Plasma Reduction Approach for Antibacterial Treatment of Water

Various conventional approaches have been reported for the synthesis of nanomaterials without optimizing the role of synthesis parameters. The unoptimized studies not only raise the process cost but also complicate the physicochemical characteristics of the nanostructures. The liquid–plasma reduction with optimized synthesis parameters is an environmentally friendly and low-cost technique for the synthesis of a range of nanomaterials. This work is focused on the statistically optimized production of silver nanoparticles (AgNPs) by using a liquid–plasma reduction process sustained with an argon plasma jet. A simplex centroid design (SCD) was made in Minitab statistical package to optimize the combined effect of stabilizers on the structural growth and UV absorbance of AgNPs. Different combinations of glucose, fructose, sucrose and lactose stabilizers were tested at five different levels (−2, −1, 0, 1, 2) in SCD. The effect of individual and mixed stabilizers on AgNPs growth parameters was assumed significant when p-value in SCD is less than 0.05. A surface plasmon resonance band was fixed at 302 nm after SCD optimization of UV results. A bond stretching at 1633 cm−1 in FTIR spectra was assigned to C=O, which slightly shifts towards a larger wavelength in the presence of saccharides in the solution. The presence of FCC structured AgNPs with an average size of 15 nm was confirmed from XRD and EDX spectra under optimized conditions. The antibacterial activity of these nanoparticles was checked against Staphylococcus aureus and Escherichia coli strains by adopting the shake flask method. The antibacterial study revealed the slightly better performance of AgNPs against Staph. aureus strain than Escherichia coli.

Biogenic Synthesis of Silver-Core Selenium-Shell Nanoparticles Using Ocimum tenuiflorum L.: Response Surface Methodology-Based Optimization and Biological Activity

Bimetallic nanoparticles (BNPs) have shown better biological potential compared to their monometallic counterparts owing to the synergistic effect produced by these alloys. In this study, selenium-capped silver nanoparticles (Ag@Se NPs) were synthesized using an Ocimum tenuiflorum extract. These BNPs were characterized using UV-visible, Fourier transform infrared spectroscopy, nanoparticle tracking analysis, electron microscopy and energy dispersive x-ray analysis. Response surface methodology was used to understand how extract volume and temperature influenced the zeta potential, hydrodynamic size and NP concentration. The phytoconstituents were identified using gas chromatography-mass spectrometry (GC-MS) and molecular docking studies were performed on B-DNA to determine possible genotoxicity. Antioxidant activities, in vitro cytotoxicity (3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay), and genotoxicity (Allium cepa root cells) of these BNPs, were also evaluated. A surface plasmon resonance band around 420 nm confirmed BNP formation with significant quantities of silver and selenium. The Ag@Se NPs displayed good stability, dispersity, antioxidant activity, and compatibility at low concentrations but showed significant cytotoxicity and genotoxicity at high concentrations. Molecular docking analysis showed weak interactions between the plant constituents and B-DNA, suggesting no genotoxicity. These results provide an insight into the conditions required for optimal production of eco-friendly Ag@Se NPs with interesting biological properties.