In this paper, a new nanomaterial catalyst for methylene blue reduction was prepared. The design rationale is explained as follows: (1) silicon nanowires (SiNWs) show a number of remarkable advantages, such as easy surface modification with various noble metal nanoparticles (NMNPs), large surface-to-volume ratio, and stability to atmosphere environment. However, metal particles usually have large size and low density because of their aggregation; (2) Sodium dodecyl sulfate (SDS) is used as stabilizer, therefore metal nanoparticle size can be effectively controlled; furthermore, due to the weak-interaction between SiNWs and NMNPs, the catalytic activity may be mantained. Therefore, it is anticipated that the SiNWs can be modified by NMNPs with high density so as to become high efficient catalysts. In details, SiNWs were grown on Si wafers by thermal evaporation of SiO powder at 1350 ℃ for 6 h, under a 300 Torr flowing gas mixture of 5% H2-Ar. The as-prepared SiNWs were etched 3 min with aqueous HF to remove their surface oxide layer. With SDS as protector, noble metal nanoparticles (NMNPs) were loaded on silicon nanowires (SiNWs) via the redox reaction between MB+ and HF-treated SiNWs for 5 minutes. In order to gain AuNPs/SiNWs composites with high coverage density and uniform size of AuNPs, experiment parameters were adjusted, such as the SDS/Au molar ratio (200 : 1, 1000 : 1, 1200 : 1), the HAuCU concentration (1.0×10-1, 2.5×10-5, 4.0×10-5 mol/L), and reaction temperature (15, 30 V). Meanwhile, Different NMNPs/SiNWs composites, such as PtNPs/SiNWs and AgNPs/SiNWs were also prepared. Finally, AuNPs/SiNWs were used in the reduction of methylene blue in the presence of sodium borohydride. In a representative reduction experiment, 0.1 mL of methylene blue solution (2.5 ×10-3 mol/L) was mixed with 2.8 mL of Na2CO3/NaHCO3 buffer solution (pH=9.5), and purged with N2 gas for 5~6 min to remove all dissolved oxygen. The solution showed a λmax at 664 nm. Then 5 mg the as-prepared catalysts and 0.15 mL 0.01 mol/L of freshly prepared sodium borohydride were added. The progress of the reaction was monitored by a spectrophotometer. As a result, 55% methylene blue was reduced in 60 min, which showed AuNPs/SiNWs had excellent catalytic activity. And it was found that 62% methylene blue was reduced in 100 min, and the reduction was going on even after 160 min reaction. These composites could be separated from reaction solution, thus ensuring recycling of nanocatalysts.%以十二烷基硫酸钠(SDS)作为保护剂,利用贵金属阳离子(Mn+)与HF处理后的硅纳米线(SiNWs)之间的氧化还原反应,在SiNWs表面负载了贵金属纳米粒子.通过调控SDS/Mn+物质的量比、反应物浓度、反应温度等实验参数,制备出了金属纳米粒子粒径均一且负载密集的AuNPs/SiNWs,PtNPs/SiNWs复合材料.将AuNPs/SiNWs复合材料应用在亚甲基蓝的还原反应,实验结果显示,60 min内AuNPs/SiNWs可以将55％的亚甲基蓝还原,表明AuNPs/SiNWs具有良好的催化活性.这种复合材料易于从反应溶液中分离出来,可以实现纳米催化剂的循环使用.
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