Size-controlled synthesis of nanoparticles of less than a few nanometers in size is a challenge due to the spatial resolution limit of most scattering and imaging techniques used for their structural characterization. We present the self-consistent analysis of the extended x-ray absorption fine-structure (EXAFS) spectroscopy data of ligand-stabilized metal nanoclusters. Our method employs the coordination number truncation and the surface-tension models in order to measure the average diameter and analyze the structure of the nanoparticles. EXAFS analysis was performed on the two series of dodecanethiol-stabilized gold nanoparticles prepared by one-phase and two-phase syntheses where the only control parameter was the gold/thiol ratio xi, varied between 6:1 and 1:6. The two-phase synthesis resulted in the smaller particles whose size decreased monotonically and stabilized at 16 A when xi was lowered below 1:1. This behavior is consistent with the theoretically predicted thermodynamic limit obtained previously in the framework of the spherical drop model of Au nanoparticles.

Human exposure to air pollution and especially to nanoparticles is increasing due to the combustion of carbon-based energy vectors. Fibrous filters are among the various types of equipment potentially able to remove particles from the air. Nanofibers are highly effective in this area; however, their utilization is still a challenge due to the lack of studies taking into account both nanoparticle collection efficiency and antibacterial effect. The aim of this work is to produce and evaluate novel silver/polyacrylonitrile (Ag/PAN) electrospun fibers deposited on a nonwoven substrate to be used as air filters to remove nanoparticles from the air and also showing antibacterial activity. In order to determine the optimum manufacturing conditions, the effects of several electrospinning process parameters were analyzed such as solution concentration, collector to needle distance, flow rate, voltage, and duration. Ag/PAN nanofibers were characterized by Xray diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier Transform Infra-Red spectroscopy (FTIR), Energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and Scanning Electron Microscopy (SEM). In addition, filtration performances were determined by measuring the pressure drop and collection efficiency of sodium chloride (NaCl) aerosol particles (9 to 300 nm diameters) using Scanning Mobility Particle Sizers (SMPS). Filters with high filtration efficiency (≈100%) and high-quality factor (≈0.05 Pa -1 ) were obtained even adding different concentrations of Ag nanoparticles (AgNPs) to PAN nanofibers. The resultant Ag/PAN nanofibers showed excellent antibacterial activity against 10 4 CFU/ml E.coli bacteria.The crystallinity of the silver nanoparticles was analyzed using X-ray diffraction analysis and shown in Figure S1. The peak observed at 17° for the 0AgF samples corresponds to (110) plan of PAN. Crystalline peak corresponds to silver nanoparticles were absent in all samples (1AgF, 10AgF, and 50AgF) which is due to the small size (<5nm) of silver nanoparticles.

Synthetic polymers are widely employed for bone tissue engineering due to their tunable physical properties and biocompatibility. Inherently, most of these polymers display poor antimicrobial properties. Infection at the site of implantation is a major cause for failure or delay in bone healing process and the development of antimicrobial polymers is highly desired. In this study, silver nanoparticles (AgNps) were synthesized in polycaprolactone (PCL) solution by in-situ reduction which was further extruded into PCL/AgNp filaments. Customized 3D structures were then fabricated using the PCL/AgNp filaments through 3D printing technique. As demonstrated by scanning electron microscopy, the 3D printed scaffolds exhibited interconnected porous structures which are crucial for cell infiltration. Furthermore, X-ray photoelectron spectroscopy analysis revealed the reduction of silver ion.Transmission electron microscopy along with energy-dispersive X-ray spectroscopy analysis revealed the formation of silver nanoparticles throughout the PCL matrix. In vitro enzymatic degradation studies showed that the PCL/AgNps scaffolds displayed 80% degradation in 20 days. The scaffolds were cyto-compatible, as assessed by using MG63 cells and their antibacterial activity was demonstrated on Escherichia coli. Due to their interconnected porous structure, mechanical and antibacterial properties, these cyto-compatible multifunctional 3D printed PCL/AgNps scaffolds are highly suitable for bone tissue engineering.

Often, solid matter is separated from particle-laden flow streams using electrospun filters due to their high specific surface area, good ability to capture aerial particulate matter, and low material costs. Moreover, electrospinning allows incorporating nanoparticles to improve the filter’s air filtration efficiency and bacterial removal. Therefore, a new, improved polyacrylonitrile (PAN) nanofibers membrane that could be used to remove air pollutants and also with antibacterial activity was developed. We engineered three different filters that are characterized by the different particles embedded in the PAN nanofibers: titanium dioxide (TiO2), zinc oxide (ZnO), and silver (Ag). Then, their filtration performance was assessed by quantifying the filtration of sodium chloride (NaCl) aerosol particles of 9 to 300 nm in diameter using a scanning mobility particle sizer. The TiO2_F filter displayed the smallest fiber diameter and the highest filtration efficiency (≈100%). Conversely, the Ag_F filter showed the highest quality factor (≈0.06 Pa−1) because of the lower air pressure drop. The resulting Ag_F nanofibers displayed a very good antibacterial activity using an Escherichia coli suspension (108 CFU/mL). Moreover, the quality factor of these membranes was higher than that of the commercially available nanofiber membrane for air filtration.

Polylysine decorated diblock copolymer nano-objects are prepared by polymerization-induced self-assembly via RAFT dispersion polymerization of 2-hydroxypropyl methacrylate. Antimicrobial properties of the resulting nano-objects evaluated using a gram positive bacteria.

The aim of this study was to synthesize stable gelatin electrospun mats (ESM) (cross-linked by Glutaraldehyde (GTA) vapors) with tunable drug release properties using pH as a stimuli. Gelatin ESM loaded with rhodamine as a model drug was first synthesized. The in vitro release of rhodamine was characterized to understand the mechanisms of drug release and the effects of both cross-linker concentration and pH on the drug release. An optimal cross-linker concentration of 5 % was evidenced to provide ESM allowing both sustainable release of drugs at pH 7 and burst release at pH 2. The release profiles were then fitted with a power law model to describe the release kinetic. Chlorhexidine antibiotic drug was finally loaded into the optimal electrospun mat and its bactericidal activity was demonstrated against Gram-negative (E. coli) and Gram-positive (S. epidermidis) bacteria by agar diffusion tests. This biocompatible material was shown to efficiently destroy bacterial biofilms and prevent bacterial growth within a short time (3 h), while maintaining its antibacterial activity up to at least 72 h. This study provides a promising material, which could treat infected sites and prevent infections, with tunable drug releasing property using pH as a stimulus. Figure 8: Evolution kinetics of the mean areas S (cm 2 ) of the clear zones formed around the 5GD material, for both tests (A and B) and for both bacteria (E. coli and S. epidermidis) (n = 3).

International audiencePolarized stainless steel cathodes in pure cultures of Geobacter sulfurreducens generated reduction currents of up to 30 A/m2 even when the sole electron acceptor contained in solution was completely reduced. It was shown here that these currents were driven by the carbon dioxide that was provided to the solution. It was postulated that CO2 reduction consumed succinate and produced glycerol, which remained stored inside the cells and was released under the effect of stress

To develop material with good photocatalytic properties for organic compound degradation and bacterial removal, we produced Ag/TiO2 and BN–Ag/TiO2 composite nanofibers that included controlled amounts of boron nitride (BN) nanosheets and silver (Ag).