Decontamination of Red Pepper Using Cold Atmospheric Pressure Plasma as Alternative Technique

Background and objective: Non-thermal methods are suggested for decontamination of spices to preserve safety and quality of the products. In this study, effects of atmospheric pressure floating-electrode dielectric-barrier discharge plasma were investigated on red pepper powder, compared to gamma irradiation.Material and methods: To achieve the optimum time of treatment for decontamination, Escherichia coli, Bacillus cereus and Aspergillus flavus as microorganisms in red pepper were exposed to atmospheric pressure floating-electrode dielectric-barrier discharge plasma for 10, 20 and 30 min and the structural changes in microorganisms were investigated using scanning electron microscopy and DNA measurement following exposure. The red pepper was exposed to plasma for 20 min (optimum time) and 10 KGy gamma irradiation. Microbial count, color measurement and sensory evaluation of the samples were assessed before and after treatments.Results and conclusion: Results indicated that the density of surviving bacterial strains decreased when time of exposure increased and this decrease was significant after 10 min (P≤0.05). The complete decontamination was carried out within 20 min. The deformation of cells and destruction of cell wall structures were seen in bacteria and mold following exposure. Data revealed that cold floating-electrode dielectric-barrier discharge plasma for 20 min inactivated red pepper microorganisms as well as gamma irradiation. As a conclusion, floating-electrode dielectric-barrier discharge plasma is an appropriate method to decontaminate the red pepper powder (regardless of color change) and can replace traditional methods without changes in the product quality and taste.Conflict of interest: The authors declare no conflict of interest

Effect of Size Distribution on the Dust Acoustic Solitary Waves in Dusty Plasma with Two Kinds of Nonthermal Ions

Effect of dust size, mass, and charge distributions on the nonlinear dust acoustic solitary waves (DASWs) in a dusty plasma including negatively charged dust particles, electrons, and nonthermal ions has been studied analytically. Dust particles masses and electrical charges are assumed to be proportional with dust size. Using reductive perturbation methods the Kadomtsev-Petviashvili (KP) equation is derived and its solitary answers are extracted. The coefficients of nonlinear term of KP equation are affected strongly by the size of dust particles when the relative size (the ratio of the largest dust radius to smallest dust radius) is smaller than 2. These coefficients are very sensitive to α, the nonthermal coefficient. According to the results, only rarefactive DASWs will generate in such dusty plasma. Width of DASW increases with increasing the relative size and nonthermal coefficient, while their amplitude decreases. The dust cyclotron frequency changes with relative size of dust particles

Electrophoretic deposited gold nanoparticle thin film on silver substrate

Abstract Effects of the deposition time and voltage on the characteristics of gold nanoparticles (NPs) thin films, prepared by the electrophoretic deposition (EPD) method on the silver substrate, were investigated experimentally. Au NPs were synthesised using the pulsed laser ablation method in distilled water. The suspended solution of the gold NPs was used as the electrolyte of EPD. An irradiation was carried out by the fundamental wavelength of a Q‐switched NdYAG laser at 1064 nm and 7 ns pulse width. The electrophoretic deposition apparatus consisted of two 2 × 2 cm pieces of silver plates as the electrodes. They were immersed in parallel with a 7 mm gap in the gold NP suspension. Five samples of gold NP thin films were prepared at different deposition times and applied voltages. Results show that the roughness, thickness and surface quality of EPD prepared thin films can be strongly controlled by the deposition time and applied voltage. The thickness of deposited films was dependent on the voltage of deposition in which their roughness was increased with increasing the deposition time. Furthermore, the reflection of deposited films was affected by the surface roughness

Effect of Ag-Nanoparticles Doped in Polyvinyl Alcohol on the Structural and Optical Properties of PVA Films

The effect of silver nanoparticles doped in PVA on the structural and optical properties of composite films is studied experimentally. Samples are PVA films of 0.14 mm thickness doped with different sizes and concentrations of silver nanoparticles. Structural properties are studied using X-ray diffraction and FTIR spectrum. Using the reflectance and transmittance of samples, the effect of doped nanoparticles and their concentration on optical parameters of PVA films include absorption coefficient, optical bandgap energy, complex refractive index, complex dielectric function, complex optical conductivity, and relaxation time is extracted and discussed. The dispersion of the refractive index of films in terms of the single oscillator Wemple-DiDomenico (WD) model is investigated and the dispersion parameters are calculated. Results show that by doping silver nanoparticles in PVA, number of Bragg’s planes in the structure of polymer and its crystallinity are increased noticeably. Ag–O bonds are formed in the films and the bandgap energy of samples is decreased. Calculations based on WD model confirm that by doping nanoparticles, the anion strength of PVA as a dielectric medium is decreased

Optical properties of synthesized Au/Ag Nanoparticles using 532 nm and 1064 nm pulsed laser ablation: effect of solution concentration

Article highlights Using two laser wavelengths and different silver concentrations, lead to the synthesis BNPs with different sizes and structures. High silver concentrations are limited due to oxidation and instability in the last sample. Synthesis of stable BNPs with controlled shell thickness is possible with the applied PLAL method