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Nanofluids are a class of fluids prepared by dispersing nanoparticles in conventional base fluids. Owing to their excellent thermo-physical properties, nanofluids find potential applications in manufacturing industries. They are introduced to overcome the limitation with using traditional base fluids like water having low thermal conductivity (~ 0.612 W/mK at room temperature). The thermal conductivity of a base fluid is considerably increased by adding a modest number of nanoparticles to it. In the present work, we have prepared silver nanoparticles and nanorods using the simple chemical reduction method. UV–Visible spectroscopy and field emission scanning electron microscopy were used to investigate the optical characteristics and morphology of the produced nanomaterials. Furthermore, the effect of volume loadings of produced nanomaterials (0, 2%, 4%, 6%), as well as temperature on the thermal conductivity of the base fluids was investigated. The results are compared to different silver nanoparticles (AgNPs) loadings in the base fluid. Both silver nanoparticles and nanorods have optimal heat conductivity at 2 vol%. It is interesting to note that fluids with silver nanorods (AgNRs) portrayed better results compared to nanoparticles and the maximum enhancement observed of 78.4% for AgNRs-based nanofluids at temperature 323 K, which is very high when compared to most of the previously reported values. [ABSTRACT FROM AUTHOR]

This work used Sedum praealtum leaf extract to synthesize silver nanoparticles (AgNPs) in a single step. The cytotoxicity of AgNPs was studied with the yeast Saccharomyces cerevisiae W303-1. In addition, the antioxidant activity of the DPPH radical was studied both in the extract of S. praealtum and in the AgNPs. UV–Vis spectroscopy determined the presence of AgNPs by the location of the surface plasmon resonance (SPR) band at 434 nm. TEM and XRD analyzes show AgNPs with fcc structure and hemispherical morphology. Also, AgNPs range in size from 5 to 25 nm and have an average size of 14 nm. 1H NMR, FTIR, and UV–Vis spectroscopy techniques agreed that glycosidic compounds were the main phytochemical components responsible for the reduction and stabilization of AgNPs. In addition, AgNPs presented a maximum of 12% toxicity in yeast attributed to the generation of ROS. Consequently, there was low bioactivity because glycoside compounds cover the biosynthesized AgNPs from S. praealtum. These findings allow applications of AgNPs involving contact with mammals and higher organisms. [ABSTRACT FROM AUTHOR]

The fluorescent silver nanoparticles were synthesized using trisodium citrate as a reducing and stabilizing agent in a microwave-assisted reduction process. The influence of synthesizing parameters such as reaction duration, temperature, and trisodium citrate concentration (100, 200, and 400 ppm) were examined on the characteristics and fluorescent properties of synthesized silver nanoparticles (AgNPs). The formation of AgNPs was studied by UV–Vis absorption spectroscopy, X-ray diffraction, ATR-FTIR spectra, and scanning electron microscopy. The low concentration compared to the high concentration of trisodium citrate resulted in a prolonged reduction process, and also the high concentration resulted in the formation of smaller AgNPs (44 nm). The fluorescence emission spectra of the synthesized colloidal AgNPs demonstrated a quite explicit emission peak centered around 335 nm. However, the higher reaction temperature (above 100 °C) resulted in a sharp and narrow emission peak. The synthesized silver nanoparticles exhibited a suitable fluorescent property, which was reliant on the size of synthesized AgNPs. [ABSTRACT FROM AUTHOR]

The plant extracts were applied for synthesis of Ag-nanoparticles and expected such biological processes benefit from advantages like eco-friendly, cost-effective, and safe for human use. Accordingly, polyphenol compounds and antioxidant properties of this understudy plant extract was initially qualified and quantified by GC-Mass and subsequently its ability for silver nanoparticle (AgNP) biosynthesis was examined. Consequently, under study (ethanol) extract was exposed to various content of AgNO3 solution over 0, 2.5, 5, 7.5, 10 and 15 mM for 24, 48, 72 and 96 h to search best operational conditions for AgNPs production, while sampling were done every 24 h monitoring initial absorption with UV–Vis spectroscopy. The peak with center at 460 nm emerged from surface plasmon resonance of AgNPs which is good indication of successful formation of AgNPs. The nanoparticles were characterized by DLS, SEM, TEM, XRD, and FTIR. Which reveal its spherical, shape and average diameter of 32 nm. Antioxidant activity tests showed that the half-maximal inhibitory concentration (IC50) in the C. tuberculata extract was 4.722 mg/ml. Antimicrobial activity of the AgNPs was tested by measurement of inhibition zone around discs modified with AgNPs in cultures of S. aureus, B. cereus, P. aeruginosa and E. coli. [ABSTRACT FROM AUTHOR]

This study aims to examine the biosynthesis and characterization of silver nanoparticles using Lavatera cretica (LCAgNPs) leaf extract mixed with silver nitrate and improving their glucose bigotry. The biosynthesis was first confirmed by the color change from colorless (metal salt solution) to brown (nanoparticle colloidal dispersion). The occurrence of the nanoparticles was further ascertained by several physicochemical studies including UV–Vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray (EDX) tomography, Fourier transform-infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The UV–Vis spectroscopy of LCAgNPs indicated the surface plasmon resonance signature of Ag NPs at around 440 nm. The TEM analysis revealed a well-dispersed sphere that varied in size from 5 to 24 nm. The EDX results established that Ag was the major element and others such as C, O and Cl were also present, which specified that the biomolecules coincided the AgNPs. The FT-IR spectroscopic study exhibited that the functional groups such as O–H, C–O, N–H, C–H and C=O were accountable for the synthesis of AgNPs. The XRD pattern represented the crystalline nature of metallic Ag. In this results, it could be clinched that the silver nitrate was reduced to silver nanoparticles of small size and high stability, which were devoid of impurities. Hence, this study has proved that L. cretica leaf is a good source for the synthesis of AgNPs and their improved glucose bigotry. [ABSTRACT FROM AUTHOR]

The rapid formation of spherical and hexagonal silver nanostructures (Ag colloid particles of different shapes) through microwave irradiation was investigated. Silver nanoparticles were successfully fabricated by reduction of Ag+ in a water medium and using polyvinylpyrrolidone as stabilizing and ethanol as reducing agents, while varying microwave power. The preliminary synthesis of silver nanoparticles was observed through the color change of the solution, from colorless transparent to brown. Morphological observations using transmission electronic microscopy indicated the formation of spherical-shaped particles at the nanoscale regime (2–100 nm) with high crystalline nature. Elementary analysis confirms the purity of AgNPs and surface plasmon resonance reactivity of their specific surface. UV–Visible spectroscopy revealed the existence of two kinds of AgNPs: metallic and ionic species exhibiting an interesting optical property in the ultraviolet range. The auto-correlation function measured by dynamic light scattering displayed a monodispersed character of AgNPs with an average particle size around 111 nm. Additionally, the antibacterial activity measured by Kirby–Bauer method indicated that silver nanoparticles exhibit high antibacterial activity against Gram+ bacteria such as Staphylococcus aureus M55A and Gram− such as Escherichia coli BCSE, Klebsiella pneumoniae Kpc+ , Salmonella spp. [ABSTRACT FROM AUTHOR]

Bio-inspired synthesis of iron oxide nanoparticles (FeONPs) has been carried out by eco-friendly, low cost, and facile method using an aqueous extract of Psidium guajava (PG) leaf as a potential reducing agent. The obtained FeONPs were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and energy-dispersive spectroscopy techniques. The surface plasmon resonance peak of FeONPs was found to be 310 nm. The FTIR spectra analysis indicates the presence of various functional groups in PG extract that are responsible for the biosynthesis of FeONPs. The XRD confirmed that FeONPs were indexed into the cubic spinel lattice structure. The SEM and TEM analysis confirmed the spherical morphology of FeONPs with particle size ranging from 1 to 6 nm. The superparamagnetic nature of the formulated FeONPs was determined using VSM. The FeONPs formulated inhibit the growth of six human pathogenic strains with strong activity chiefly against Escherichia coli and Staphylococcus aureus at low concentration when compared to other standard antibacterial drugs. It is noteworthy that the formulated FeONPs are efficient as an antibacterial agent. [ABSTRACT FROM AUTHOR]

In this study, silver nanoparticles (Ag NPs) were profitably synthesized from aqueous Amorphophallus paeoniifolius leaf extract at room temperature, using one step and eco-friend green synthesis. The leaf extract acts as reducing agent to the formation of Ag NPs from Ag+ ions. The development of Ag NPs through aqueous medium was confirmed by UV–Vis spectroscopy and the spectra show characteristic surface plasmon resonance of Ag NPs at 428 nm. Crystalline nature of the synthesized samples was affirmed by the XRD studies. The particles are predominantly grown via (111) plane of Ag crystal and the particles size was fall in the range of 20–26 nm calculated by Scheerrer's formula. Size and shape of Ag NPs were observed from the SEM and TEM characterization. The samples are almost having spherical shape particles and the size of the particles is lies between 20 and 30 nm. The energy peak at 3 keV in the EDS spectrum strongly supported that the synthesized sample is Ag. FTIR spectra exhibit the leaf extract containing various characteristic functional groups which should responsible for the reduction of Ag+ ions. Synthesized Ag NPs displayed as potential antibacterial candidate against both gram positive and gram negative bacterial. [ABSTRACT FROM AUTHOR]

Herbal drugs prepared with the plant Ipomoea asarifolia has many medicinal uses throughout West Africa, including its employ as diuretic, emmenagogue and purgative. This species is a good source of acylated anthocyanins, and the methanol and ethyl acetate extracts of I. asarifolia are known for their strong acetylcholinesterase inhibitory effects. Here, green synthesis of Ag nanoparticles (Ag NPs) was performed at room temperature using the I. asarifolia leaf extract. The Ag NPs were characterized by UV-visible spectroscopy, FT-IR, XRD, AFM, SEM with EDX and TEM. AFM and SEM analyses showed that spherical morphology of I. asarifolia-synthesized Ag NPs with a size range of 20 to 60 nm. TEM revealed that I. asarifolia-synthesized Ag NPs had a mean particle size of 40 nm. The I. asarifolia-synthesized Ag NPs was tested against four bacterial pathogens using the disk diffusion method. The zone of inhibition varied significantly in a dose-dependent manner. Overall, our results underlined the potential of cheap aqueous extracts from this African medicinal plant species for the synthesis of silver nanocomplexes with wide efficacy against human pathogenic bacteria. [ABSTRACT FROM AUTHOR]

The present study reports the biosafety assessment, the exact molecular effects, and apoptosis induction of newly developed chitosan-silver hybrid nanoparticles (Cs-Ag NPs) in HepG2 cells. The investigated hybrid NPs were green synthesized using Cs/grape leaves aqueous extract (Cs/GLE) or Cs/GLE NPs as reducing and stabilizing agents. The successful formation of Cs/GLE NPs and Cs-Ag hybrid NPs has been confirmed by UV-Vis spectrophotometry, FTIR spectroscopy, XRD, and HRTEM. From the TEM analysis, the prepared Cs/GLE NPs are uniform and spherical with an average size of 150 nm, and the AgNPs (5-10 nm) were formed mainly on their surface. The UV-Vis spectra of Cs-Ag NPs showed a surface plasmon resonance (SPR) peak at about 450 nm confirming their formation. The synthesized Cs-Ag NPs were found to be crystalline as shown by XRD patterns with fcc phase oriented along the (111), (200), (220), and (311) planes. The cytotoxicity patterns, the antiproliferative activities, and the possible mechanisms of anticancer activity at molecular level of the newly developed Cs-Ag hybrid NPs were investigated. Cytotoxicity patterns of all the preparations demonstrated that the nontoxic treatment concentrations are ranged from 0.39 to 50 %, and many of the newly prepared Cs-Ag hybrid NPs showed high anticancer activities against HpG2 cells, and induced cellular apoptosis by downregulating BCL2 gene and upregulating P53. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We report an alternative approach to enhance the optical and electrical performance of a vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine:poly(3hexylthiophene) (VOPcPhO:P3HT) blending system by integrating plasmonic spherical silver into an active layer of organic solar cells. Studies of the influence of the size distribution and optical properties of the silver nanoparticles were carried out using UV-Vis spectroscopy and field emission scanning electron microscopy, respectively. Electrical characteristics with and without the presence of metallic nanostructures were analyzed using J- V characteristics to observe the plasmonic effects on the performance in the VOPcPhO:P3HT organic solar cells. [ABSTRACT FROM AUTHOR]

A stoichiometric approach to the synthesis of silver nanoparticles (AgNPs) with appreciable enhancements in the localized surface plasmon resonance is presented. Microwave irradiation afforded AgNPs, optimized to a thermodynamic equilibrium by varying the silver to trisodium citrate (Ag/citrate) stoichiometric ratio from 1:1 to 1:10, and ranging in size from 32 to 65 nm (±1-9 nm, hydrodynamic diameter). The concentration-dependent plasmonic enhancements were monitored by UV-Vis absorption spectrophotometry, showing absorption maxima typical of AgNPs, at 440-450 nm. A linear accession in plasmon absorbance intensity, approaching 1:5 (Ag/citrate), followed by a linear depletion, at larger stoichiometries (1:6-1:10), was observed. Size distribution measurements, using dynamic light scattering, showed the highest polydispersity index, 0.547, for 1:10 suspensions and the lowest, 0.305, for the thermodynamic maximum, determined to occur at 1:5. Surface charge measurements approaching 0 mV confirm the destabilizing effect of high concentrations of citrate, leading to greater instances of aggregation and large hydrodynamic diameters. Reaction kinetics data suggests an increased preference for Ag-citrate, metal/ligand complexation, at 1:10, diminishing nanoparticle production. [ABSTRACT FROM AUTHOR]