Single-Step Synthesis and Surface Plasmons of Bismuth-Coated Spherical to Hexagonal Silver Nanoparticles in Dichroic Ag:Bismuth Glass Nanocomposites

Here, we report for the first time the synthesis of bismuth-coated silver nanoparticles in dichroic bismuth glass nanocomposites by a novel and simple one-step melt quench technique without using any external reducing agent. The metallic silver nanoparticles (Ag NPs) were generated first, and subsequently, metallic bismuth was deposited on the Ag NPs and formed a thick layer. The reduction of Bi³⁺ to Bi^o and subsequently its deposition on the Ag NPs (which were formed earlier than Bi^o) in the K₂O–Bi₂O₃–B₂O₃ (KBB) glass system have been explained by their standard reduction potentials. The UV–vis absorption spectra show a prominent surface plasmon resonance (SPR) absorption band at 575 nm at lower concentrations (up to 0.01 wt%); three bands at 569, 624 and 780 nm at medium concentration (0.02–0.03 wt%); and two weak bands at 619 and 817 nm at highest concentration (0.06 wt%) of silver. They have been explained by the electrodynamics theories. TEM images reveal the conversion of spheroidal (5–15 nm) to hexagonal (10–35 nm) shaped Ag NPs with the increase in concentration of silver (up to 0.06 wt%). SAED pattern confirms the crystalline planes of rhombohedral bismuth and cubic silver. Thermal treatment at 360 °C, which is the glass transformation temperature (T _g) of the sample containing lower concentration of silver (0.007 wt%), shows red-shifted SPR band due to increase in size of NPs. Whereas the sample containing higher concentration (0.06 wt%) of silver under similar treatment exhibited changes in SPR spectral profile happened due to conversion to spherical NPs from hexagonal shape and reduction in size (10–20 nm) of NPs after heat treatment for 65 h. HRTEM images corroborate the different orientations of the NPs. FESEM images reveal hexagonal disk like structure having different orientations. Dichroic nature of the nanocomposites has been explained with the size and shape of Ag nanoparticles. We believe that this work will create new avenues in the area of nanometal–glass hybrid nanocomposites and the materials have significant applications in the field of optoelectronics and nanophotonics.     

Study of the Adsorption of Human Hemoglobin to Silver (Ag) Nanoparticle Surface for the Detection of the Unfolding of Hemoglobin

In the present report, we focused on the detail study of the optical properties and structural characterization of the Ag NPs for the nanobioconjugate analysis and detection of the conformational structural change of the Hb. The detail optical and structural analysis of Ag NPs has been studied from UV–Vis absorption, emission spectrum, XRD, and HRTEM study. The proteins/Hb are attached immediately onto Ag NPs surface when NPs touch the biological fluids, forming protein corona (PC), which gives their biological identity. The NPs-PC bioconjugate is, more specifically, the true identity of NPs in the physiological world. The adsorption of Hb with Ag NP surfaces has been studied by monitoring the soret band and tryptophan band of Hb. The dynamics of the Hb adsorption on the Ag NPs showed the time constant of surface binding t₁?=?5.79 min and 10.23 min and surface reorganization t₂?=?500 min and 251.75 min with the use of small and large concentrations of Ag NPs, respectively. The absorption peak shape and size around the wavelength, λ ≈ 406.2 nm of the bioconjugate has been examined by Gaussian and Lorentz curve fitting analysis. The bioconjugate along with the PC formation has been analyzed by HRTEM images and DLS observations. The tertiary deformation of Hb and energy transfer efficiency connecting Ag NPs and Hb are discussed from the emission-quenching phenomenon. The change of the secondary structural elements (α-helix, β-sheets, intermolecular aggregates, intramolecular aggregates) of the bioconjugate has been analyzed from FTIR spectrum.

     

Plasmonic and Nonlinear Optical Absorption Properties of Ag:ZrO2 Nanocomposite Thin Films

Ag nanoparticles (NPs) embedded in a zirconium oxide matrix in the form of Ag:ZrO₂ nanocomposite (NC) thin films were synthesized by using the sol–gel technique followed by thermal annealing. With the varying of the concentration of Ag precursor and annealing conditions, average sizes (diameters) of Ag nanoparticles (NPs) in the nanocomposite film have been varied from 7 to 20 nm. UV–VIS absorption studies reveal the surface plasmon resonance (SPR)-induced absorption in the visible region, and the SPR peak intensity increases with the increasing of the Ag precursor as well as with the annealing duration. A red shift in SPR peak position with the increase in the Ag precursor concentration confirms the growth of Ag NPs. Surface topographies of these NC films showed that deposited films are dense, uniform, and intact during the variation in annealing conditions. The magnitude and sign of absorptive nonlinearities were measured near the SPR of the Ag NPs with an open-aperture z-scan technique using a nanosecond-pulsed laser. Saturable optical absorption in NC films was identified having saturation intensities in the order of 10¹² W/m². Such values of saturation intensities with the possibility of size-dependent tuning could enable these NC films to be used in nanophotonic applications.     

DNA Detection Based on Localized Surface Plasmon Resonance Spectroscopy of Ag@Au Biocomposite Nanoparticles

Noble metal nanoparticles (NPs) have attracted much attention due to their unique physical and chemical properties such as tunable surface plasmonics, high-efficiency electrochemical sensing, and enhanced fluorescence. We produced two biosensor chips consisting of Ag@Au bimetallic nanoparticles (BNPs) on a carbon thin film by simple RF-sputtering and RF-plasma-enhanced chemical vapor co-deposition. We deposited Au NPs with average size of 4 nm (Au₁ NPs) or 11 nm (Au₂ NPs) on a sensor chip consisting of Ag NPs with mean size of 15 nm, and we investigated the effect of shell size (Au NPs) on the chemical activities of the resulting Ag@Au₁ BNPs and Ag@Au₂ BNPs. We estimated the average size and morphology of Ag@Au BNPs by scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. X-ray diffraction (XRD) patterns revealed that Ag NPs and Au NPs had face-centered cubic (FCC) structure. We studied aging of the biosensor chips consisting of Ag@Au BNPs by localized surface plasmon resonance (LSPR) spectroscopy for up to 3 months. UV–visible aging of the prepared samples indicated that Ag@Au₁ BNPs, which corresponded to Ag NPs covered with smaller Au NPs, were more chemically active than Ag@Au₂ BNPs. Furthermore, we evaluated changes in the LSPR absorption peaks of Ag@Au₁ BNPs and bare Ag NPs in the presence of a DNA primer decamer at fM concentrations, to find that Ag@Au₁ BNPs were more sensitive biosensor chips within a short response time as compared to bare Ag NPs.

     

In Situ Optical Extinction Measurement for Locally Control of Surface Plasmon Resonance During Nanosecond Laser Irradiation of Silver Ion Exchanged Silicate Glass

Online UV/visible extinction measurement have been achieved during nanosecond Nd:YAG laser irradiation at 532 nm of a silver-exchanged silicate glass after each shot. We have explained the evolution of the integrated spectral evolution with the help of a few observed spots after the laser/glass interaction and completed them by optical and surface measurements. This optical method allows to in situ follow silver ions precipitation in nanoparticles (NPs) and the consequently surface plasmon resonance evolution (SPR). In this study, we focus on the interest of this method for one silver-exchanged soda-lime glass by direct observation of the sample surface. Scanning electron microscopy measurement and optical microscopy were used to identify the various ablation mechanisms. Profilometry was used to evaluate the material distribution and the surface roughness evolution (Rms parameter). Thus, we explain the silver NPs effect on glass matrix at various micrometric scales according to the deposited fluence and silver concentration.     

Surface reactivity and in vitro biological evaluation of sol gel derived silver/calcium silicophosphate bioactive glass

Ag ions are known for their antibacterial effects. Ag containing silicate glasses have been extended to create bioactive glasses that exhibit inhibitory effects on bacterial growth using different techniques. In this work, calcium and calcium/silver silicophosphate glasses were synthesized from the sol-gel process and their physicochemical and in vitro biological properties were studied and compared. The effect of silver concentration on in vitro bioactivity and antibacterial properties of the glasses was investigated. Ag₂O was substituted for CaO in the glass formula up to 2 mol% and in vitro bioactivity of the samples was evaluated by soaking them in simulated body fluid followed by structural characterization using XRD, FTIR and SEM techniques. The results showed that both glasses favored precipitation of the calcium phosphate layer when they were soaked in simulated body fluid; however, the morphology of apatite crystals changed for the 2% mol silver containing sample. Substitution of 2% mol Ag₂O for CaO seemed to slightly stimulate the rate of precipitation. The in vitro biodegradation rate of the silver/ calcium silicophosphate glasses was lower than that of the silver-free one (control). Also, the antibacterial properties of the samples indicated that these effects were improved by increasing silver concentration in bioactive glass composition.     

Fluorescence enhancement monitoring of pyrromethene laser dyes by metallic Ag nanoparticles

Fluorescence enhancement monitoring of pyrromethene laser dyes using their complexation with Ag nanoparticles (Ag NPs) was studied. The size of the prepared Ag NPs was determined by transmission electron spectroscopy and UV/Vis absorption spectroscopy. Mie theory was also used to confirm the size of NPs theoretically. The effect of different nanoparticle concentrations on the optical properties of 1 × 10^‐4 M PM dyes shows that 40%of Ag NPs concentration (40%C Ag NPs) in complex is the optimum concentration. Also, the effects of different concentrations of PM dyes in a complex was measured. Emission enhancement factors were calculated for all samples. Fluorescence enhancement efficiencies depended on the input pumping energy of a Nd‐YAG laser (wavelength 532 nm and 8 ns pulse duration) were reported and showed the lowest energy (28 and 32 mJ) in the case of PM567 and PM597, respectively. Copyright © 2014 John Wiley & Sons, Ltd.     

Investigating Fluorescence Quenching of ZnS Quantum Dots by Silver Nanoparticles

Water dispersible zinc sulfide quantum dots (ZnS QDs) with an average diameter of 2.9 nm were synthesized in an environment friendly method using chitosan as stabilizing agent. These nanocrystals displayed characteristic absorption and emission spectra having an absorbance edge at 300 nm and emission maxima (λ _emission) at 427 nm. Citrate-capped silver nanoparticles (Ag NPs) of ca. 37-nm diameter were prepared by modified Turkevich process. The fluorescence of ZnS QDs was significantly quenched in presence of Ag NPs in a concentration-dependent manner with K _sv value of 9 × 10⁹ M⁻¹. The quenching mechanism was analyzed using Stern–Volmer plot which indicated mixed nature of quenching. Static mechanism was evident from the formation of electrostatic complex between positively charged ZnS QDs and negatively charged Ag NPs as confirmed by absorbance study. Due to excellent overlap between ZnS QDs emission and surface plasmon resonance band of Ag NPs, the role of energy transfer process as an additional quenching mechanism was investigated by time-resolved fluorescence measurements. Time-correlated single-photon counting study demonstrated decrease in average lifetime of ZnS QDs fluorescence in presence of Ag NPs. The corresponding F?rster distance for the present QD–NP pair was calculated to be 18.4 nm.     

Bioengineered silver nanoparticles using Curvularia pallescens and its fungicidal activity against Cladosporium fulvum

Microorganisms based biosynthesis of nanomaterials has triggered significant attention, due to their great potential as vast source of the production of biocompatible nanoparticles (NPs). Such biosynthesized functional nanomaterials can be used for various biomedical applications. The present study investigates the green synthesis of silver nanoparticles (Ag NPs) using the fungus Curvularia pallescens (C. pallescens) which is isolated from cereals. The C. pallescens cell filtrate was used for the reduction of AgNO₃ to Ag NPs. To the best of our knowledge C. pallescens is utilized first time for the preparation of Ag NPs. Several alkaloids and proteins present in the phytopathogenic fungus C. pallescens were mainly responsible for the formation of highly crystalline Ag NPs. The as-synthesized Ag NPs were characterized by using UV–Visible spectroscopy, X-ray diffraction and transmission electron microscopy (TEM). The TEM micrographs have revealed that spherical shaped Ag NPs with polydisperse in size were obtained. These results have clearly suggested that the biomolecules secreted by C. pallescens are mainly responsible for the formation and stabilization of nanoparticles. Furthermore, the antifungal activity of the as-prepared Ag NPs was tested against Cladosporium fulvum, which is the major cause of a serious plant disease, known as tomato leaf mold. The synthesized Ag NPs displayed excellent fungicidal activity against the tested fungal pathogen. The extreme zone of reduction occurred at 50 μL, whereas, an increase in the reduction activity is observed with increasing the concentration of Ag NPs. These encouraging results can be further exploited by employing the as synthesized Ag NPs against various pathogenic fungi in order to ascertain their spectrum of fungicidal activity.     

Comparative Study of Antimicrobial Activity of AgBr and Ag Nanoparticles (NPs)

The diverse mechanism of antimicrobial activity of Ag and AgBr nanoparticles against gram-positive and gram-negative bacteria and also against several strains of candida was explored in this study. The AgBr nanoparticles (NPs) were prepared by simple precipitation of silver nitrate by potassium bromide in the presence of stabilizing polymers. The used polymers (PEG, PVP, PVA, and HEC) influence significantly the size of the prepared AgBr NPs dependently on the mode of interaction of polymer with Ag⁺ ions. Small NPs (diameter of about 60–70 nm) were formed in the presence of the polymer with low interaction as are PEG and HEC, the polymers which interact with Ag⁺ strongly produce nearly two times bigger NPs (120–130 nm). The prepared AgBr NPs were transformed to Ag NPs by the reduction using NaBH₄. The sizes of the produced Ag NPs followed the same trends – the smallest NPs were produced in the presence of PEG and HEC polymers. Prepared AgBr and Ag NPs dispersions were tested for their biological activity. The obtained results of antimicrobial activity of AgBr and Ag NPs are discussed in terms of possible mechanism of the action of these NPs against tested microbial strains. The AgBr NPs are more effective against gram-negative bacteria and tested yeast strains while Ag NPs show the best antibacterial action against gram-positive bacteria strains.     

Differently Environment Stable Bio-Silver Nanoparticles: Study on Their Optical Enhancing and Antibacterial Properties

Generally, limited research is extended in studying stability and applicational properties of silver nanoparticles (Ag NPs) synthesized by adopting ‘green chemistry’ protocol. In this work, we report on the synthesis of stable Ag NPs using plant-derived materials such as leaf extract of Neem (Azadirachta indica) and biopolymer pectin from apple peel. In addition, the applicational properties of Ag NPs such as surface-enhanced Raman scattering (SERS) and antibacterial efficiencies were also investigated. As-synthesized nanoparticles (NPs) were characterized using various instrumentation techniques. Both the plant materials (leaf extract and biopolymer) favored the synthesis of well-defined NPs capped with biomaterials. The NPs were spherical in shape with an average particle size between 14-27 nm. These bio-NPs exhibited colloidal stability in most of the suspended solutions such as water, electrolyte solutions (NaCl; NaNO₃), biological solution (bovine serum albumin), and in different pH solutions (pH 7; 9) for a reasonable time period of 120 hrs. Both the bio-NPs were observed to be SERS active through displaying intrinsic SERS signals of the Raman probe molecule (Nile blue A). The NPs were effective against the Escherichia coli bacterium when tested in nutrient broth and agar medium. Scanning and high-resolution transmission electron microscopy (SEM and HRTEM) images confirmed cellular membrane damage of nanoparticle treated E. coli cells. These environmental friendly template Ag NPs can be used as an antimicrobial agent and also for SERS based analytical applications.     

Simultaneous detection of two tumor markers using silver and gold nanoparticles decorated carbon nanospheres as labels

In this work, a multiplexed electrochemical immunosensor was developed for sensitive detection of carcinoembryonic antigen (CEA) and α-fetoprotein (AFP) using silver nanoparticles (Ag NPs) or gold nanoparticles (Au NPs) coated-carbon nanospheres (CNSs) as labels. CNSs were employed as the carrier for the immobilization of nanoparticles (Ag NPs or Au NPs), thionine (Thi), and secondary antibodies (Ab₂) due to their good monodispersity and uniform structure. Au NPs reduced graphene oxide (rGO) nanocomposites were used as sensing substrate for assembling two primary antibodies (Ab₁). In the presence of target proteins, two labels were attached onto the surface of the rGO/Au NPs nanocomposites via a sandwich immunoreaction. Two distinguishable peaks, one at +0.16 V (corresponding to Ag NPs) and another at −0.33 V (corresponding to Thi), were obtained in differential pulse voltammetry (DPV). The peak difference was approximately 490 mV, indicating that CEA and AFP can be simultaneously detected in a single run. Under optimal conditions, the peak currents were linearly related to the concentrations of CEA or AFP in the range of 0.01–80 ng ml⁻¹. The detection limits of CEA and AFP were 2.8 and 3.5 pg ml⁻¹, respectively (at a signal-to-noise ratio of 3). Moreover, when the immunosensor was applied to serum samples, the results obtained were in agreement with those of the reference method, indicating that the immunosensor would be promising in the application of clinical diagnosis and screening of biomarkers.     

Identifying Metal Nanoparticle Size Effect on Sensing Common Human Plasma Protein by Counting the Sensitivity of Optical Absorption Spectra Damping

Colloidal nanoparticles (NPs) interact with biological fluids such as human plasma to form a protein coating (corona) on the surface of NPs (NP-protein complex). However, the impact of size and type of NPs on binding of the hard corona to the surface of NPs as well as damping of their optical spectra has not been systematically explored. To elucidate the interaction between biological environment (human plasma) and NPs, a photophysical measurement was conducted to quantify the interaction of two different types of NPs (gold (Au) and silver (Ag)) with common human plasma proteins. The colloidal AuNPs and AgNPs were electrostatically stabilized and varied in diameter from 10 to 80 nm in the presence of common human plasma. The sizes of the NPs were determined using transmission electron microscopy (TEM). Optical absorption spectra were obtained for the complexes. Dynamic light scattering (DLS) measurement and zeta potential were used to characterize the sizes, hydrodynamic diameters, and surface charges of the protein-NPs complexes. Protein separation was performed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to isolate and identify the protein bands. The absorption of proteins to the NPs was found to be strongly dependent on the size and type of NPs. The distance between surface of NPs by absorbed protein bound to the NPs gradually increased with size of NPs, particularly for AgNPs with primary diameter of < 50 nm. The chi-square test proved that AgNPs are a good candidate in sensing the protein complex in human plasma compared with AuNPs mainly for the AgNPs with diameter sized 50 nm.

     

Optimization of the Field Enhancement and Spectral Bandwidth of Single and Coupled Bimetal Core–Shell Nanoparticles for Few-Cycle Laser Applications

We have theoretically studied and optimized the field enhancement and temporal response of single and coupled bimetal Ag/Au core–shell nanoparticles (NPs) with a diameter of 160 nm and compared the results to pure Ag and Au NPs. Very high-field enhancements with an amplitude reaching 100 (with respect to the laser field centered at 800 nm) are found at the center of a 2-nm gap between Ag/Au core–shell dimers. We have explored the excitation of the bimetal core–shell particles by Fourier transform-limited few-cycle optical pulses and identified conditions for an ultrafast plasmonic decay on the order of the excitation pulse duration. The high-field enhancement and ultrafast decay makes bimetal core–shell particles interesting candidates for applications such as the generation of ultrashort extreme ultraviolet radiation pulses via nanoplasmonic field enhancement. Moreover, in first experimental studies, we synthesized small bimetal Ag/Au core–shell NPs and compared their optical response with pure Au and Ag NPs and numerical results.     

The in vitro effects of selected substances and nanomaterials against Diaporthe eres,Diplodia seriata and Eutypa lata

Grapevine trunk pathogens (GTPs) cause serious damage to grapevines and have significant economic impacts. There is no effective protection against grapevine trunk diseases. Newly designed AgSe nanoparticles (NPs) and CuSe NPs, single-element Ag NPs, Cu NPs, Se NPs and selected chemicals or chemical agents such as sodium arsenite, 8-hydroxyquinoline, silver nitrate, colloidal silver, Altron Silver fertilizer and silver thiosulfate complex (NH₄)₃/Ag(S₂O₃)₂ were tested in vitro against two serious GTPs Diaporthe eres, Eutypa lata and Diplodia seriata isolated from walnut. The most significant inhibition of fungal growth was observed for silver nitrate and AgSe NPs, which showed the highest level of half the maximum effective EC₅₀ concentration with the lowest concentrations. In the case of silver nitrate at a concentration of 1000 mg L⁻¹, 79% inhibition of mycelial growth was observed for the pathogen E. lata, 48% for D. seriata and 54% for D. eres. AgSe NPs, in which the concentration of silver is 2588 mg L⁻¹ and that of selenium is 902 mg L⁻¹, showed 68% inhibition of mycelial growth in the pathogen E. lata, 54% in D. seriata and 58% in D. eres.     

In vitro antimicrobial effect of metallic nanoparticles on phytopathogenic strains of crop plants

In this research, the in vitro antimicrobial effect of zinc oxide (ZnO), copper oxide (CuO) and iron oxide (Fe₂O₃) nanoparticles (NPs)—with average sizes of 20, 46 and 30 nm, respectively—on the root rot disease caused by the fungus Fusarium oxysporum and on blight disease caused by the fungus Alternaria solani were studied. Also, bacterial diseases caused by Clavibacter michiganensis and Pseudomonas syringae that infects a wide range of plant species were assessed. Different concentrations of NPs (0, 100, 250, 500, 700 and 1,000 mg/L) were prepared on PDA agar or King's B medium in a complete randomized design with four replicates. According to the results, ZnO NPs exhibited an outstanding inhibitory effect against fungi and bacteria strains. The above results were associated with the smaller particle size. Fungi strains showed a differential sensitivity depending on the kind of NPs used. A. solani showed the highest sensitivity to ZnO NPs at 1,000 mg/L (99%), followed by CuO NPs at the same dose (95%). Fe₂O₃ NPs at all evaluated doses had no inhibitory effects on the mycelia growth of this strain, although F. oxysporum revealed greater effectiveness of the CuO NPs (96%) compared with ZnO NPs since it only inhibited 91% of the mycelial growth. The antibacterial activity was studied through optical density. C. michiganensis was found to be more sensitive to ZnO NPs because a lesser dose (700 mg/L) was required to reduce the bacterial growth (90%); in comparison, P. syringae required a dose of 1,000 mg/L to inhibit its growth (67%). CuO NPs displayed the smallest growth inhibition against the bacteria strains analysed. The antimicrobial effect of the metallic NPs that were assayed increased with higher doses.     

Spectral Tuning of Plasmon Resonances of Bimetallic Noble Metal Alloy Nanoparticles Through Compositional Changes

The optical absorption properties of the bimetallic noble metal alloy (viz. Au-Ag, Au-Cu, and Ag-Cu) nanoparticles (NPs) of radii of 10 nm and 20 nm embedded in silica glass have been studied theoretically using a simple model based on the effective medium theory. Our study reveals that the spectra of the above bimetallic alloy NPs exhibit single but composition-sensitive surface plasmon resonance (SPR) peak which indicates the successful formation of alloys. The position of the SPR peak that appeared corresponding to alloy NPs is different from that of the component metals. The study further reveals that the Ag-Au and Au-Cu alloy systems are completely miscible over the entire concentration range but Ag-Cu is miscible up to a certain extent, although, their SPR peak shows a linear shift with molar concentration. It has been further observed that the phase of the Ag-Au alloy system changes with concentration of Au during the alloy formation but no such change is seen in the other two systems. Thus, our study shows that the Ag-Cu system which otherwise does not form alloy in bulk may form alloy in nanoscale with limited miscibility. A shift of the SPR peak positions from ~ 405 to ~ 535 nm for Au-Ag, from ~ 535 to ~ 590 nm for Au-Cu, and from ~ 405 to ~ 436 nm for Ag-Cu NP systems has been observed for different composition of constituent monometals. The compositional changes lead to a spectral tuning of the SPR of the system under studies.

     

SPR Label-Free Biosensor with Oxide-Metal-Oxide-Coated D-Typed Optical Fiber: a Theoretical Study

In this article, a surface plasmon resonance (SPR) biosensor based on D-typed optical fiber coated by Al₂O₃/Ag/Al₂O₃ film is investigated numerically. Resonance in near infrared with an optimized architecture is achieved. Refractive index sensitivity of 6558 nm/RIU (refractive index unit) and detection limit of 1.5 × 10⁻⁶ RIU, corresponding to 0.4357 nm/μM and detection limit of 23 nM in BSA (bovine serum albumin) concentration sensing, are obtained. The analysis of the performance of the sensor in gaseous sensing indicates that this proposed SPR sensor is much suitable for label-free biosensing in aqueous media.

     

Mn3O4 nanoparticles: Synthesis,characterization and their antimicrobial and anticancer activity against A549 and MCF-7 cell lines

Due to their inexpensive and eco-friendly nature, and existence of manganese in various oxidation states and their natural abundance have attained significant attention for the formation of Mn₃O₄ nanoparticles (Mn₃O₄ NPs). Herein, we report the preparation of Mn₃O₄ nanoparticles using manganese nitrate as a precursor material by utilization of a precipitation technique. The as-prepared Mn₃O₄ nanoparticles (Mn₃O₄ NPs) were characterized by using X-ray powder diffraction (XRD), UV–Visible spectroscopy (UV–Vis), High-Resolution Transmission electron microscopy (HRTEM), Field emission scanning electron microscopy (FESEM), Thermal gravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FT-IR). The antimicrobial properties of the as-synthesized Mn₃O₄ nanoparticles were investigated against numerous bacterial and fungal strains including S. aureus, E. coli, B. subtilis, P. aeruginosa, A. flavus and C. albicans. The Mn₃O₄ NPs inhibited the growth of S. aureus with a minimum inhibitory concentration (MIC) of 40 μg/ml and C. albicans with a MIC of 15 μg/ml. Furthermore, the Mn₃O₄ NPs anti-cancer activity was examined using MTT essay against A549 lung and MCF-7 breast cancer cell lines. The Mn₃O₄ NPs revealed significant activity against the examined cancer cell lines A549 and MCF-7. The IC₅₀ values of Mn₃O₄ NPs with A549 cell line was found at concentration of 98 µg/mL and MCF-7 cell line was found at concentration of 25 µg/mL.     

Silver Fused Conducting Fiber Formation of Au–Ag Core-Shell Nanoparticles Mediated by Ascorbic Acid

In this paper, we report the spontaneous formation of fibrous structures consisting of assemblies of Au–Ag core-shell nanoparticles (NPs) from a solution consisting of Au–Ag core-shell NPs and l-ascorbic acid (AA). AA acted both as the reducing agent for the generation of NPs and also as the mediator for the formation of fibers. The process of fiber formation involved three steps—reduction of HAuCl₄ to Au NPs by AA, subsequent formation of Au–Ag core-shell NPs after addition of AgNO₃, and spontaneous formation of fibers from the mixtures in water. It took typically about 30 days to form complete fibers that are of lengths of several hundred micrometers to millimeters, although nanofibers started forming from the first day of solution preparation. The width of each of these fibers was typically about 1–4 μm with length of each segment of fiber bundle, on the order of 40 μm. Formation of fibers was also observed in absence of AgNO₃. These fibers consisted of Au NPs and polymer of AA degradation products and were not electrically conducting. Also, low concentrations of AgNO₃ produced fibers with low electrical conductivity. However, it was observed that increase in the amount of AgNO₃ leads to the formation of fibers that were electrically conducting with conductivity values in the range of metallic conductivity. Spectroscopic and electron microscopic investigations were carried out to establish the formation of fibers. The details of fiber formation mechanism under different conditions and electrical conductivities of the fibers are discussed in the article.