We demonstrate that the controlled distribution of nanoparticles can be achieved by employing the spin-coating method. The Co and Ag nanoparticles were uniformly distributed on the Si and SiO2 substrates with this method. The particle density was controllable by varying the concentration of colloids. The spatial distribution of the nanoparticles within the patterned area was also shown to be uniform with small boundary effect, which is favorable for current microelectronics technology. We propose that the spin-coating method can be utilized in developing mass production processes for future nanodevices.
Controlled growth of carbon nanotubes (CNTs) has been achieved by thermal chemical vapor deposition of acetylene gas over nanometer-sized cobalt particles. The well-aligned CNTs, which have a uniform diameter and high purity, are synthesized over cobalt nanoparticles distributed on substrates of large area. The alignment, density, and diameter of the CNTs are easily controlled by adjusting the density of the cobalt nanoparticles. Moreover, growth rate, density, diameter, and crystallinity of CNTs grown over the cobalt nanoparticles are also well controlled by the growth temperature. Our results demonstrate that the controlled growth of CNTs can be effectively realized by adjusting cobalt nanoparticles and growth temperature.
Antibiotics have been identified as a new type of environmental contaminant because of their increased use in farm animal production systems. Those drugs that animals are not absorbed mostly are excreted in the feces and urine and contaminates soils. However, the effects of antibiotics on crop plants are still largely unknown. In this study, we determined the effects of chlortetracycline (CTC), a veterinary drug released into the agricultural field by grazing animals or through manure application, on the growth and physiology of Brassica campestris seedlings. Differently from animals, Brassica campestris seedlings have accumulated 5-10-fold higher CTC during cultivation rather than excretion. Morphologically, CTC delays seed germination and inhibits seedling growth such as shortening primary root length and decreasing chlorophyll level. At the molecular level, CTC accumulation in plants downregulated the expression of superoxide dismutase (SOD) genes and decreased the production of hydrogen peroxide (H 2 O 2). Since H 2 O 2 is one of the signaling components involved in the regulation of root growth, exogenous application of H 2 O 2 partially restored the growth and physiology of CTC-treated seedlings. These results suggest that application of CTCcontaining manure or compost to soil delays seed germination and inhibits plant growth.
As a new area of biological integration systems ranging from fitness to costume, arable electronic devices are extensively investigated and recently focused on the development of customized and highly interactive devices with human‐friendly factors. Here, a facile method of integrating a three‐dimensional printing (3DP) with stretchable and conductive nanocomposite materials to form a multiaxial piezoresistive sensor that can detect human motion is presented. The multiaxial piezoresistive sensors are fabricated through direct 3DP of nanocomposites based on graphene nanoplatelets (GNPs), silver nanoparticles (AgNPs), and polyurethane. The sensor can detect not only compression, but also tensile strain upto more than 160%. Based on the synergy between GNPs and AgNPs, the sensor shows high sensitivity with a gauge factor of 48.2, which is a much higher value considering that most of the previously reported stretchable strain sensors are less than 35. In addition to the high sensitivity, the GNPs/AgNPs nanocomposite sensor exhibits a fast response time and excellent stability over 500 cycles. When the sensor is integrated into an LED light system, it functions as an interactive device that can control the intensity of light by detecting various human motions such as the bending of fingers.
Chemical amendments have been used to remediate soils contaminated with heavy metals. However, there is little understanding on the impacts of these amendments on the physiological and biochemical functions of plants and soil. This study used in situ microcosm experiment to understand the effect of chemical amendments on antioxidant and soil enzyme activity in plant and soil with respect to heavy metal reduction. Three chemical amendments-acid mine drainage sludge (AMDS), limestone (LS), and steel slag (SS)-were applied to soil at 3, 5, and 10% mixing ratios, and lettuce (Lactuca sativa) was cultivated in that soil for 30 days. The results showed that bioavailable Cd and Pb in soil was reduced by 9.8-40.5% and 4.2-92.5%, respectively. The most efficient amendment for heavy metal reduction was AMDS. The uptake of Cd and Pb also decreased by 0.5-66.1 and 21.6-79.5%, respectively, depending on the amendment type and application ratio. The activity of three antioxidants-catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR)-was generally higher than the control with no amendments. This result indicated that there was minimal inhibition of antioxidant activity due to the reduction of heavy metal uptake. Also, no significant difference was observed in chemical amendments applied soil compared to control in terms of soil enzyme activity. However, correlation analysis between heavy metal concentration in soil and two soil enzyme activities showed that significantly negative correlation (p < 0.01) was observed between bioavailable Pb in soil and acid-phosphatase activity. This result might indicate that impact of bioavailable Pb was much higher than Cd in terms of inhibition of soil enzyme activity. Overall, the application of chemical amendments to heavy metal polluted had a positive effect on plant physiological function and soil enzyme activity with a reduction in bioavailable heavy metals in soil and plants.
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