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镍-磷（Ni-P）涂层是许多工业应用中广泛使用的涂层，由于其具有杰出的机械和化学性质，如高硬度和良好的耐腐蚀/耐磨性质。Ni-P涂层可以通过不同的技术包括电镀和化学电镀形成。镍电镀可用于装饰工程和电铸，也可用于改善工业设备的耐腐蚀性。尽管Ni-P涂层有许多优点，但它也有不足之处。首先，为了获得较高的耐腐蚀性，Ni-P涂层必须有电沉积铬层涂于其顶部，这使其过程更加复杂。另一个实质的缺点是Ni-P涂层过程不能形成复杂形状的完整涂层。
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楼主 Date: 2008-04-01 14:08:29

gerdie

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BACKGROUND: Numerous works have been published on the chemical modification of chitosan; this polymer is still being modified, leading to various derivatives with improved properties. In the present study, heterocyclic aldehydes including furan-2-carbaldehyde, 5-methylfuran-2-carbaldehyde, 3-pyridine carboxyaldehyde, benzo[d][1,3]dioxole-5-carbaldehyde and 4-oxo-4H-chromene-3-carbaldehyde were reacted with chitosan by a reductive alkylation reaction to produce for the first time five new N-heterocyclic chitosan derivatives to improve the biological activity of chitosan against themost important economic plant pests including fungi and insects, in particular the cotton leafworm Spodoptera littoralis.
RESULTS: The chemical structures of the synthesized compounds were confirmed by 1H NMR spectroscopy and the degree of substitution ranged from 0.30 to 0.43. The fungicidal assessment was investigated in vitro using a mycelia radial growth inhibition technique against soil-borne pathogenic fungi Fusarium oxysporum and Pythium debaryanum and the rice leaf blast Pyricularia grisea. The results showed that N-[(5-methylfuran-2-yl)methyl]
chitosan was the most active against P. grisea with an EC50 value of 0.919mg mL−1 while N-(benzo[d][1,3]dioxol-5-ylmethyl) chitosan and N-(methyl-4H-chromen-4-one) chitosan exhibited the most potent fungicidal activity against P. debaryanum and F. oxysporum. An insecticidal bioassay against the larvae of S. littoralis showed that N-(methyl-4H-chromen-4-one) chitosan exhibited a significant growth inhibition and antifeedant activity among the synthesized compounds.
CONCLUSION: The chemical modification of chitosanmolecule with a heterocyclicmoiety led to an enhancement in the biological activity against the plant pathogenic fungi F. oxysporum, P. debaryanum and P. grisea and the cotton leafworm insect S. littoralis.
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Date: 2008-04-01 14:21:28

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