Formation Of Spherical Shaped Particles Research Articles

Formation of Silver Nanoparticles by a Novel Irradiation Method Without a Reducing Agent and Their Impact on Four Pathogenic Bacterial Strains

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.

Wet Chemical Synthesis of Molybdenum-Doped Amorphous TiO2Nanoparticles and Studies on Their Photochromic Properties

ABSTRACT Undoped and (0.5–5 at%) molybdenum-doped TiO2 nanoparticles were synthesized by a simple and scalable wet chemical method. The as-synthesized materials were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy, electron paramagnetic resistance (EPR), and ultraviolet-visible (UV-Vis) spectroscopy techniques. XRD studies showed the formation of crystalline anatase phase of undoped TiO2, whereas Mo-doped samples showed the formation of an amorphous phase. AFM studies showed the formation of spherical-shaped particles with a particle diameter of ∼23 nm in all samples. The photochromic behavior of these materials was studied by making their films in alkyd resin. Films of these materials showed a reversible photochromic color change from beige to brown on exposure to UV light. The coloration and bleaching process was recorded using UV-Vis diffuse reflectance spectroscopy. The maximum color change was observed in 2 at% Mo+6-doped nano-TiO2. The photochromic mech...