DST Unit of Nanoscience, Department of Chemistry, Indian Institute of Technology Madras, Chennai-600 036, India.
Langmuir. 2012 Feb 7;28(5):2671-9. doi: 10.1021/la2050515. Epub 2012 Jan 30.
Application of nanoparticles (NPs) in environmental remediation such as water purification requires a detailed understanding of the mechanistic aspects of the interaction between the species involved. Here, an attempt was made to understand the chemistry of noble metal nanoparticle-pesticide interaction, as these nanosystems are being used extensively for water purification. Our model pesticide, chlorpyrifos (CP), belonging to the organophosphorothioate group, is shown to decompose to 3,5,6-trichloro-2-pyridinol (TCP) and diethyl thiophosphate at room temperature over Ag and Au NPs, in supported and unsupported forms. The degradation products were characterized by absorption spectroscopy and electrospray ionization mass spectrometry (ESI MS). These were further confirmed by ESI tandem mass spectrometry. The interaction of CP with NP surfaces was investigated using transmission electron microscopy, energy dispersive analysis of X-rays, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS reveals no change in the oxidation state of silver after the degradation of CP. It is proposed that the degradation of CP proceeds through the formation of AgNP-S surface complex, which is confirmed by Raman spectroscopy. In this complex, the P-O bond cleaves to yield a stable aromatic species, TCP. The rate of degradation of CP increases with increase of temperature and pH. Complete degradation of 10 mL of 2 ppm CP solution is achieved in 3 h using 100 mg of supported Ag@citrate NPs on neutral alumina at room temperature at a loading of ∼0.5 wt %. The effect of alumina and monolayer protection of NPs on the degradation of CP is also investigated. The rate of degradation of CP by Ag NPs is greater than that of Au NPs. The results have implications to the application of noble metal NPs for drinking water purification, as pesticide contamination is prevalent in many parts of the world. Study shows that supported Ag and Au NPs may be employed in sustainable environmental remediation, as they can be used at room temperature in aqueous solutions without the use of additional stimulus such as UV light.
纳米粒子（NPs）在水净化等环境修复中的应用需要详细了解涉及物种之间相互作用的机械方面。在这里，我们试图了解贵金属纳米粒子-农药相互作用的化学性质，因为这些纳米系统正在被广泛用于水净化。我们的模型农药毒死蜱（CP）属于有机磷硫代酸酯类，在室温下在 Ag 和 Au NPs 上以支持和不支持的形式分解为 3,5,6-三氯-2-吡啶醇（TCP）和二乙基硫代磷酸酯。通过吸收光谱和电喷雾电离质谱（ESI-MS）对降解产物进行了表征。通过 ESI 串联质谱进一步证实。使用透射电子显微镜、X 射线能量色散分析、拉曼光谱和 X 射线光电子能谱（XPS）研究了 CP 与 NP 表面的相互作用。XPS 表明 CP 降解后银的氧化态没有变化。据推测，CP 的降解是通过形成 AgNP-S 表面络合物进行的，这一点通过拉曼光谱得到了证实。在这个络合物中，P-O 键断裂生成稳定的芳族物质 TCP。CP 的降解速率随温度和 pH 值的增加而增加。在室温下，在中性氧化铝上负载约 0.5wt%的 100mg 柠檬酸根保护的 Ag@citrate NPs 可在 3 小时内完全降解 10ml 2ppm CP 溶液。还研究了氧化铝和 NPs 单层保护对 CP 降解的影响。Ag NPs 对 CP 的降解速率大于 Au NPs。这些结果对贵金属 NPs 用于饮用水净化的应用具有重要意义，因为世界上许多地区都普遍存在农药污染。研究表明，负载的 Ag 和 Au NPs 可用于可持续的环境修复，因为它们可以在室温下在水溶液中使用，而无需使用额外的刺激物（如紫外线）。
