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Abstract: We demonstrate that cadmium (Cd) can catalyze the growth of single-walled carbon nanotubes (SWNTs) with high efficiency. The Cd nanocatalysts, prepared using a diblock copolymer templating method, were uniformly spaced over a large deposition area with an average diameter of 1.9nm and narrow size distribution. By using the normal-heating and fast-heating method, random and horizontally aligned arrays of SWNTs can be generated. The density of the SWNTs can be altered by the chemical vapor deposition conditions. The morphology and microstructure of the SWNTs characterized by scanning electron microscopy, Raman spectroscopy, atomic force microscopy, and high-resolution transmission electron microscopy revealed that the grown nanotubes do not have carbonaceous particles and have good crystallinity. In addition, after careful check with superlong nanotubes 735 out of 790 nanotubes were found to be deposited with Ag (93%) and only 7% SWNTs without Ag deposition. While for superlong SWNT arrays from Fe, 32% long SWNTs without Ag deposition was found, the high percentage of SWNTs with Ag deposition from Cd indicates that the SWNTs have better conductivity and better structural uniformity with less defects. [Copyright &y& Elsevier]

Paddy soils have experienced intensive fertilization in recent decades. However, our understanding of the effects of fertilization on the carbon (C) cycle remains incomplete. In the present study, we investigated soil organic matter (SOM) decomposition in a 60-day incubation in response to N, P, K, Ca, and S addition to nutrient-limited paddy soil at three low and three high concentrations. High levels of nutrient addition decreased CO 2 emission, q CO 2 , and microbial biomass. CO 2 emissions increased (12–17%) owing to low levels of nutrient addition, whereas it decreased (3–21%) in response to high levels of nutrient addition. Microbial biomass and nutrient turnover rates increased after low levels of nutrient addition. Positive priming effect occurs under nutrient-limited conditions owing to the stimulation of microbial biomass production after low amount of exogenous nutrient input. In contrast, high levels of nutrient addition decreased microbial biomass and net N mineralization. This high N, P, K, Ca, and S addition could satisfy the needs of microbial growth, thereby decreasing the dependency of the organisms on the original nutrients from SOM decomposition. Therefore, negative priming was observed after high-level nutrient addition. In conclusion, intensive fertilization (with N, P, K, Ca, and S) reduces SOM decomposition through increased microbial turnover in paddy soils, which might positively affect C sequestration. [ABSTRACT FROM AUTHOR]

Root exudates are a labile source of carbon (C) for microorganisms that can lead to increased CO 2 emission. Root exudates can vary in C:N stoichiometric ratio and their impact on microbially driven soil organic matter (SOM) turnover in paddy soils still remains unclear. The objective was to explore the underlying mechanisms involved in SOM decomposition due to root exudate (artificial) addition with three different C:N ratios (10, 20, and 40) during 45 days incubation. Different root exudates C:N ratios were obtained by adding mineral N and exudate components (glucose, oxalic acid, and glutamate) to paddy soil. N-only addition decreased dissolved organic C to limit CO 2 emissions, which is an indicative of C sequestration. Conversely, simulated C:N stoichiometric ratios of root exudates significantly increased both microbial activity and metabolism without altering the microbial biomass C:N ratio. However, soil available dissolved organic C to NH 4 + ratio decreased by exudates addition. The stoichiometric ratio of key C and N compound degrading enzymes activities increased only with C:N = 10 and remained unchanged with exudates C:N = 20 and 40. The q CO 2 values increased with decreasing N-containing compounds in root exudates (i.e. highest CO 2 emission was observed under C:N = 40 exudates addition). The results suggest that increasing exudates C:N ratio intensify CO 2 emission due to high microbial N demand. Overall result show that root exudates C:N ratio and soil available N co-regulate on CO 2 emission, which was controlled by microbial and potential extracellular enzyme activities. • Root exudate analogues significantly increased CO 2 emission from paddy soils. • Exudates addition increased microbial biomass and q CO 2 without altering microbial C:N ratio. • Root exudate inputs increased the accumulation of soil available NH 4 +. • N-only addition limited CO 2 emission and decreased dissolved organic C. [ABSTRACT FROM AUTHOR]