Different Concentrations Of ZnO Nanoparticles Research Articles

Effects of Soil-Plant Interactive System on Response to Exposure to ZnO Nanoparticles

The ecotoxicological effects of nanomaterials on animal, plant, and soil microorganisms have been widely investigated; however, the nanotoxic effects of plant-soil interactive systems are still largely unknown. In the present study, the effects of ZnO nanoparticles (NPs) on the soil-plant interactive system were estimated. The growth of plant seedlings in the presence of different concentrations of ZnO NPs within microcosm soil (M) and natural soil (NS) was compared. Changes in dehydrogenase activity (DHA) and soil bacterial community diversity were estimated based on the microcosm with plants (M+P) and microcosm without plants (M-P) in different concentrations of ZnO NPs treatment. The shoot growth of M+P and NS+P was significantly inhibited by 24% and 31.5% relative to the control at a ZnO NPs concentration of 1,000 mg/kg. The DHA levels decreased following increased ZnO NPs concentration. Specifically, these levels were significantly reduced from 100 mg/kg in M-P and only 1,000 mg/kg in M+P. Different clustering groups of M+P and M-P were observed in the principal component analysis (PCA). Therefore, the M-P's soil bacterial population may have more toxic effects at a high dose of ZnO NPs than M+P's. The plant and activation of soil bacteria in the M+P may have a less toxic interactive effect on each of the soil bacterial populations and plant growth by the ZnO NPs attachment or absorption of plant roots surface. The soil-plant interactive system might help decrease the toxic effects of ZnO NPs on the rhizobacteria population.

Antibacterial activity of ZnO nanoparticle on Gram-positive and Gram-negative bacteria

The aim of the present study is to determine the antimicrobial activity of ZnO nanoparticles against Gram-negative and Gram-positive bacteria. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were used as test microorganisms. The effects of particle size and concentration on the antibacterial activity of ZnO nanoparticles was studied using bacteriological tests such as disc and well diffusion agar methods, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). These tests were performed in nutrient broth and nutrient agar following standard methods. In addition, the effect of different concentrations of ZnO nanoparticles on the growth of E. coli and S. aureus was measured with respect of time. The minimum inhibitory concentration was determined using seven different concentrations of ZnO nanoparticles including 16, 8, 4, 2, 1 and 0.5 mg/ml. The MIC value for E. coli and S. aureus was 1 and 0.5 mg/ml, respectively. The results showed that ZnO nanoparticles have antibacterial inhibition zone of 29 and 19 mm at the concentration of 10 mg/ml against E. coli and S. aureus, respectively. Gram-negative bacteria seemed to be more resistant to ZnO nanoparticles than Gram-positive bacteria. It was found that the antibacterial activity of ZnO nanoparticles increased with decreasing particle size and increasing powder concentration. The antibacterial effect of ZnO nanoparticles was time dependent and takes effect gradually. ZnO bulk powder showed no significant antibacterial activity. Key word: ZnO nanoparticle, Escherichia coli, Staphylococcus aureus, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC).

Solution-processed polyfluorene–ZnO nanoparticles ambipolar light-emitting field-effect transistor

We report on a solution-processed polyfluorene (PFO)–ZnO nanoparticles composite light-emitting organic field-effect transistor (LE-OFET). The behavior of absorption, photoluminescence spectra and electroluminescence intensity of the PFO:ZnO hybrid films with different concentration of ZnO nanoparticles is analyzed. By changing the PFO/ZnO nanoparticles concentration ratio the PFO:ZnO OFET shows either unipolar or ambipolar behavior of current–voltage characteristics and operates in the hole/electron accumulation mode with current saturation behavior. The field effect mobility of charge carriers depends on the ZnO concentration. For the ambipolar PFO:ZnO OFET with modest PFO/ZnO nanoparticles ratio (1:0.2), well balanced electron and hole mobility values at 300 K are ∼0021 and ∼0029 cm 2/Vs, respectively, whereas for films with high ZnO concentration (1:1) the mobility (∼2 cm 2/Vs) is close to that of polycrystalline ZnO. The ambipolar PFO:ZnO LE-OFET emits light at both positive and negative gate bias. The working mechanism of the PFO:ZnO LE-OFET is investigated.

Toxicological Effect of ZnO Nanoparticles Based on Bacteria

Streptococcus agalactiae and Staphylococcus aureus are two pathogenetic agents of several infective diseases in humans. Biocidal effects and cellular internalization of ZnO nanoparticles (NPs) on two bacteria are reported, and ZnO NPs have a good bacteriostasis effect. ZnO NPs were synthesized in the EG aqueous system through the hydrolysis of ionic Zn2+ salts. Particle size and shape were controlled by the addition of the various surfactants. Bactericidal tests were performed in an ordinary broth medium on solid agar plates and in liquid systems with different concentrations of ZnO NPs. The biocidal action of ZnO materials was studied by transmission electron microscopy of bacteria ultrathin sections. The results confirmed that bactericidal cells were damaged after ZnO NPs contacted with them, showing both gram-negative membrane and gram-positive membrane disorganization. The surface modification of ZnO NPs causes an increase in membrane permeability and the cellular internalization of these NPs whereas there is a ZnO NP structure change inside the cells.