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Abstract Environmentally benign silver nanoparticles (Ag NPs) were synthesized at different temperatures using leaf extract of Platycodon grandiflorum. The apparent UV–Vis spectrum maxima clearly displayed plasmon resonance bands at 442 and 457 nm for nanoparticles synthesized at 37 °C and 50 °C, respectively. The morphology of Ag NPs were investigated by FESEM, FETEM and AFM analysis and the results showed the formation of uniform spherical nanoparticles with average sizes of 19 and 21 nm for Ag NPs produced at 37 °C and 50 °C, respectively, with slightly larger nanoparticles formed at 50 °C owing to agglomeration. Further characterization by XRD, XPS, and FTIR confirmed their crystal nature, while stability was confirmed by zeta potential analysis. The strong XRD diffraction pattern confirmed the face-central cubic crystalline nature of the nanoparticles. Moreover, XPS revealed Ag 3d doublet (3d 5/2 and 3d 3/2) with C1s peaks of the catalysts that were turned into C H (283.68) C C, C C (284.16 eV), C O (285.34 eV), and C O (288.55 eV). The O1s spectra were also exhibited with binding energy at 530.94, 531.96 and 532.53 for AgO, C O and C O, respectively, and FTIR confirmed the peaks of plant extract appeared on Ag NPs. Overall, Ag NPs synthesized at 50 °C had good shape and structure with a high stability (−5.23). The nanoparticles also exhibited antibacterial activity against Escherichia coli and Bacillus subtilis. The biosynthesized Ag NPs have the potential for use in various applications, particularly in the field of biomedicine. Graphical abstract Image 1 Highlights • AgNPs were synthesized from balloon flower plant at different temperature. • Monodispersed and uniform spherical nanoparticles were synthesized. • AgNPs morphology was investigated by FE-SEM, FE-TEM and AFM analysis. • AgNPs from P. grandiflorum shows strong inhibition against gram positive bacteria. [ABSTRACT FROM AUTHOR]

This study focused on the evaluation of antimicrobial activity of silver nanoparticles (AgNPs) after their green synthesis by means of a Solanum trilobatum bark extract. The obtained product with an intense surface plasmon resonance band at ∼442 nm with UV–visible spectroscopic analysis indicated the formation of AgNPs. The morphology of AgNPs was observed under transmission electron microscopy and field emission scanning electron microscopy, displayed that the eco-friendly synthesized AgNPs have a spherical shape with an average size of ∼25 nm in diameter. X-ray powder diffraction and selected area electron diffraction analyses confirmed that the AgNPs are crystalline in nature. Fourier transform infrared spectroscopy indicated that the AgNPs capped with active ingredients of the bark extract. X-ray photoelectron spectroscopy revealed elemental composition of the AgNPs. The performance of S. trilobatum bark extract-capped AgNPs in terms of inhibition of microbial growth was studied by disc diffusion and well diffusion assays. Eco-friendly synthesized S. trilobatum extract-capped AgNPs were found to possess enhanced antimicrobial properties: growth inhibition of gram-negative and gram-positive bacteria and of fungal species. These results demonstrated the potential applications of the indigenous medicinal plants to the field of nanotechnology. [ABSTRACT FROM AUTHOR]

The “Green” synthesis of metallic nanoparticles and investigation of their optical properties has become a useful application between nanoscience and medicine. In this work, silver nanoparticles (Ag-NPs) were successfully prepared through a facile and green method by treating silver ions with chitosan. Preparation of Ag-NPs in silver nitrate solution (0.01 M) resulted in small and spherical shapes of Ag-NPs with a mean diameter of 10.2 nm. The formation of Ag-NPs was approved by surface Plasmon resonance (SPR) absorption peaks, using UV–vis spectrophotometer, while Ag-NPs were successfully employed in colorimetric sensing of H 2 O 2 via an analytical procedure. Degradation process of Ag-NPs, encouraged by the catalytic decomposition of H 2 O 2 , causes a significant change in the absorbance intensity of SPR band depending on the H 2 O 2 concentration. The cytotoxicity effect of synthesized Ag-NPs was examined on HEK293 cell line. The results illustrate a concentration-dependent toxicity for the tested cells, while15.07 μg/mL of IC 50 was obtained. [ABSTRACT FROM AUTHOR]

• κ-Carrageenan capped silver nanoparticles (CAR-SNP) prepared by green synthesis. • CAR-SNP based antioxidant capacity (AC) method was designed for AC measurement. • CAR-SNP based AC method was based on growth-enlargement of monodisperse NPs. • Surface functional groups of CAR-SNPs were effective in antioxidant reduction of Ag+. • Proposed method provided higher sensitivity for antioxidants than other similar assays. A novel antioxidant capacity (AC) method was designed exploiting the formation and growth mechanism of green synthesized silver nanoparticles (SNPs) using κ-carrageenan. Carrageenan, a natural polysaccharide derived from edible red algae, was used for the green biosynthesis of κ-carrageenan capped SNPs (CAR-SNP). Silver ion (Ag+) was reduced by antioxidants to spherical SNPs around silver seeds formed by κ-carrageenan. After reaction with antioxidants, symmetrically enlarged SNPs displayed a surface plasmon resonance (SPR) absorption band at 420 nm superimposed onto a monotonous background due to the underlying monodisperse CAR-SNPs. The surface functional groups of CAR-coated, negatively-charged SNPs may be responsible for a net SPR peak emerging after the facilitated chemical reduction of Ag+ with antioxidants. AC was determined using the proposed CAR-SNP method by measuring the linear increase in SPR absorbance of the enlarged SNPs in the presence of increasing antioxidant concentrations. The CAR-SNP based AC method was applied to selected antioxidant compounds, synthetic antioxidant mixtures, and tea infusions. The LOD and LOQ for trolox were found as 0.023 and 0.077 μM, respectively, which were well below those found by conventional electron-transfer based AC assays having similar mechanism. The CAR-SNP based AC method was validated for performance parameters (linearity, additivity, precision, and recovery). AC values obtained by the proposed method for tea infusions were correlated with those obtained by the classical CUPRAC method. The CAR-SNP based AC method is compatible with green chemistry principles of nanoparticle synthesis and application, and provides simple, rapid, low-cost, and sensitive AC determination. [Display omitted] [ABSTRACT FROM AUTHOR]

There are several biomimetic approaches to synthesize silver nanoparticles (AgNPs). The present investigation describes a solitary method for the synthesis of AgNPs in one-pot by means of Spirulina platensis extract. The as-formed AgNPs were characterized by the following methods. Initially, UV–Vis spectrophotometer indicated a distinctive surface plasmon resonance peak for AgNPs at 417 nm. Fourier Transform Infrared Spectroscopy (FTIR) indicated the particle capping by organics of the extract. Transmission electron microscopy (TEM) confirmed the formation of spherical AgNPs with an average size of 13 nm. X-ray diffraction (XRD) analysis elucidated the crystalline nature of AgNPs. The average particle size and polydispersity index (PDI) of AgNPs were 74.8 nm and 0.285 as recorded by dynamic light scattering (DLS). Thermal gravimetric analysis (TGA) indicated the thermal stability of AgNPs at elevated temperatures. Among all other active components of the algal extract, the proteins could play a major role in reduction, stabilization and encapsulation of AgNPs. Further, the antibacterial activity was assessed against seven different species of bacterial pathogens present in respiratory tract. The AgNPs were found promising against the test pathogens. Image 1 • The active components of the algal extract, the proteins, could have acted as reduced, stabilized and encapsulated the AgNPs. • The antibacterial activity of those nanoparticles was assessed against seven different pathogens of the respiratory tract. • The AgNPs were found to be effective against the seven tested pathogens. [ABSTRACT FROM AUTHOR]