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Synthesis of single-crystalline hollow β-FeOOH nanorods via a controlled imcomplete-reaction coure

溶液合成方法举例. Synthesis of single-crystalline hollow β-FeOOH nanorods via a controlled imcomplete-reaction coure. Abstract. Single-crystalline β -FeOOH hollow nanorods have been synthesized though a two-step route. The formation process of hollow space is from inside to outside.

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Synthesis of single-crystalline hollow β-FeOOH nanorods via a controlled imcomplete-reaction coure

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  1. 溶液合成方法举例 Synthesis of single-crystalline hollow β-FeOOH nanorods via a controlled imcomplete-reaction coure

  2. Abstract • Single-crystalline β-FeOOH hollow nanorods have been synthesized though a two-step route. The formation process of hollow space is from inside to outside.

  3. Recently, much effort has been devoted to synthesis of hollow inorganic materials because of their low density and high surface area compared with bulk materials. These materials may be find a wide range of potential applications in many areas, such as catalysts, potential drug carriers, coatings, low-density materials and nano-reactor.Many hollow inorganic materials including metals, non-oxides and metal oxides have been synthesized.

  4. The general approach for synthesizing such materials is based on the use of hard-template or soft-template such as polystyrene beads, colloid particles, emulsions, vesicles and droplets. Moreover, most of products are polycrystalline submicrometer spheres aggregated of nanoparticles. To my best knowledge,only several non-sphere and single-crystalline hollow structures have been prepared.

  5. In this paper, we present a novel selftemplate route for fabricating single-crystalline β-FeOOH hollow nanorods with length in the range of 70-110 nm and width in the range of 20-30 nm. Hollow cavitys will be gained by controlling the degree of the phase transition from Fe(OH)3 to β-FeOOH and the Ostwald ripening process happening at the interior of nanorods.

  6. Ostwald ripening process • Many small crystals form in a system initially but slowly disappear except for a few that grow larger, at the expense of the small crystals. The smaller crystals act as "nutrients" for the bigger crystals. As the larger crystals grow, the area around them is depleted of smaller crystals

  7. Explanation for the occurrence of Ostwald ripening • Larger crystals are more energetically favored than smaller crystals. While the formation of many small crystals is kinetically favored, (i.e. they nucleate more easily) large crystals are thermodynamically favored. Small crystals have a larger surface area to volume ratio than large crystals. Molecules on the surface are energetically less stable than the ones already well ordered and packed in the interior. Large crystals, with their greater volume to surface area ratio, represent a lower energy state. Thus, many small crystals will attain a lower energy state if transformed into large crystals and this is what we see in Ostwald ripening.

  8. Pictorial example of crystal ripening from a precipitate Day 6. A single crystal has appeared in the precipitate. The precipitate feeds the growth of the crystal and a zone of depletion appears around the crystal as it grows. This depletion zone looks like a halo around the crystal.

  9. Day 10

  10. Day 13

  11. Day 16

  12. 配置CS溶液(壳聚糖的醋酸溶液) 黄色沉淀 2mLCS溶液15mL0.3mol/L FeCl3溶液15mL正丙醇0.408g尿素82℃2h 乙醇洗涤、干燥 高压釜内乙醇热

  13. 产物的表征采用以下仪器和条件 • (1)XRD:Rigaku D/max-γA200,CuKα, • (2)TEM: JEM-100CXII, 加速电压80kV • (3)HRTEM: Technai F30, 加速电压300kV • (4)FT-IR: Bio-Rad model FTS-165 IR 红外分析仪 • (5)TGA: Mettler Toledo SDTA851e, N2, 升温速率20℃/min

  14. 82℃保温20min后先得到无定型Fe(OH)3 随着加热时间的延长,无定型Fe(OH)3纳米颗粒经过聚集-脱水过程形成多晶态β-FeOOH纳米棒

  15. 醇热反应在180℃进行2h后,由于纳米棒中Fe(OH)3的分解,该纳米棒逐渐变成多孔棒。醇热反应在180℃进行2h后,由于纳米棒中Fe(OH)3的分解,该纳米棒逐渐变成多孔棒。 Ostwald熟化过程,结果多孔结构由内向外崩溃形成较大的中空结构。

  16. 影响因素的研究 • 壳聚糖和正丙醇在中空β-FeOOH纳米棒的形成过程中起保护作用。研究还发现,如果将正丙醇换成乙醇,只能得到实心的颗粒。 • 影响材料形貌、粒度和结构的因素包括壳聚糖的用量、正丙醇与水的比例、反应温度和时间。如果实验中没有壳聚糖,反应的最终产物是α-Fe2O3;

  17. Templates for Synthesizing Nanoparticles 溶液合成方法举例

  18. 模板及其作用 • 硬模板:阳极氧化铝(AAO), 碳纳米管、线,其他。 • 软模板:表面活性剂及其不同的聚集状态 高分子化合物 其他。

  19. 硬模板-纳米碳管 Carbon Nanotube

  20. 硬模板-氧化铝管的制备

  21. 软模板-表面活性剂的特点 • 阴离子表面活性剂:十二烷基硫酸钠SDS;十二烷基苯磺酸钠SDBS;AOT • 阳离子表面活性剂:三甲基十六烷基溴化铵CTAB • 非离子表面活性剂:Triton-X :t-octyl-(OCH2CH2)xOH,

  22. 表面活性剂的聚集状态 • 胶束和反胶束:球形、棒状、片状胶束的形成和表面活性剂浓度的关系。

  23. 表面活性剂的聚集状态 • 微乳液:表面活性剂-助表面活性剂-水

  24. Redox synthesis by NiSO4 and NaH2PO2 in cyclohexane-water-polyglycol emulsion system

  25. 将Fe3+和Fe2+混合溶液与阴离子表面活性剂SDS混合,通过烧结的陶瓷板向溶液中吹入高压空气,利用重力将多余的液体分离,得到稳定干燥的泡沫。将此干燥泡沫与氨溶液接触一定时间,发生水解。结果表明,得到了FeOOH,随后焙烧转化为Fe2O3。将Fe3+和Fe2+混合溶液与阴离子表面活性剂SDS混合,通过烧结的陶瓷板向溶液中吹入高压空气,利用重力将多余的液体分离,得到稳定干燥的泡沫。将此干燥泡沫与氨溶液接触一定时间,发生水解。结果表明,得到了FeOOH,随后焙烧转化为Fe2O3。

  26. 氧化氢氧化铁 FeOOH 氧化铁 Fe2O3

  27. 溶液合成方法举例 Shape control and associated magnetic properties of spinel cobalt ferrite nanocrystals JACS 2004, 102, 126, 6164-6168

  28. 合成基本思路 • 将非水解过程和晶种生长法结合,以铁、钴的乙酸乙酰盐为原料,利用非水解法先合成5nm球状CoFe2O4;再以它为晶种,生长得到较大的球状或立方状纳米晶。

  29. 具体实验 • 2mmol Co(acac)2,40mL二苯醚,20mmol 1,2-十六烷基二醇,10mL油酸,18mL十八烯胺混合加热到140℃,然后滴加由4mmol Fe(acac)3和30mL二苯醚组成的混合溶液;迅速升温到260℃,加热回流30min。最后,冷却到室温,加入乙醇,离心分离,得到5nm球状产物。

  30. 具体实验 • 取100mg上述产物作为晶种,在由1mmol Co(acac)2、2mmol Fe(acac)3、10mmol 1-十八醇、5mL油酸、5mL十八烯胺组成的混合溶液中,按照10~15℃/min速度升温到260℃并保温30min。冷却后,加入乙醇使之沉淀。如此,就可以得到8nm球状CoFe2O4。

  31. 纳米晶体的生长速度决定了产品的形状。前驱体分解温度大约为190℃;油酸是一种表面活性剂,起稳定纳米晶的作用;十八烯胺提供了形成尖晶石所必需的碱性环境;长链醇对于成核和生长也是必要的,它可以加速CoFe2O4纳米晶的形成;升温速度慢可以保证前驱体分解产生的金属离子浓度较低;而反应温度低可以降低晶体生长的速度。纳米晶体的生长速度决定了产品的形状。前驱体分解温度大约为190℃;油酸是一种表面活性剂,起稳定纳米晶的作用;十八烯胺提供了形成尖晶石所必需的碱性环境;长链醇对于成核和生长也是必要的,它可以加速CoFe2O4纳米晶的形成;升温速度慢可以保证前驱体分解产生的金属离子浓度较低;而反应温度低可以降低晶体生长的速度。

  32. 升温速度较快时,金属离子浓度相对增加,晶体生长速度增加,各个晶面的生长速度差异减小,导致晶体生长的方向性减小,得到球状产物。升温速度较快时,金属离子浓度相对增加,晶体生长速度增加,各个晶面的生长速度差异减小,导致晶体生长的方向性减小,得到球状产物。

  33. 溶液合成方法举例 Unidirectionally Aligned Copper Hydroxide Crystalline Nanorods from Two-Dimensional Copper Hydroxy Nitrate

  34. 基本思路 • 以层状碱式硝酸铜为原料制备1D Cu(OH)2的研究。碱式硝酸铜具有与水镁石Mg(OH)2相似的层状结构,其中四分之一的OH-被NO3-代替。具有2D结构的Cu2(OH)3NO3与NaOH溶液发生阴离子交换,最终得到1D结构的Cu(OH)2。

  35. 层状结构示意图 R. Xu, H. C. Zeng, Chem. Mater., 2003, 15, 2040-2048

  36. 管状结构 1342 嵌入、柱撑、剥离 加热、卷曲

  37. 具体操作 • 将2.5g起始原料Cu2(OH)3NO3分散在蒸馏水中,然后加入2mol/L的NaOH溶液,隔绝空气,室温下,在圆底烧瓶中搅拌48h,得到蓝灰色沉淀,过滤、分别用蒸馏水、乙醇洗涤,35℃真空干燥,得到产物。

  38. 原料具有典型的层状结构。最终产物可以指标化为正交晶系Cu(OH)2物相,与JCPDS卡片13-420一致。原料具有典型的层状结构。最终产物可以指标化为正交晶系Cu(OH)2物相,与JCPDS卡片13-420一致。

  39. FTIR谱也证实了原料Cu2(OH)3NO3直接转化为Cu(OH)2。图b中,700cm-1以下的吸收对应于Cu-O振动,而3303和3567cm-1处的吸收为OH-的振动。另外,图a归于NO3-离子、处在1340cm-1附近的吸收在图b中消失,表明NO3-完全被OH-取代。FTIR谱也证实了原料Cu2(OH)3NO3直接转化为Cu(OH)2。图b中,700cm-1以下的吸收对应于Cu-O振动,而3303和3567cm-1处的吸收为OH-的振动。另外,图a归于NO3-离子、处在1340cm-1附近的吸收在图b中消失,表明NO3-完全被OH-取代。

  40. 溶液合成方法举例 溶胶凝胶法-硬模板法合成Eu2O3纳米管JACS 2004,126,5976-5977

  41. 具体实验操作 • 将硝酸铕溶解于蒸馏水中得到0.01mol/L溶液,用氨水调节溶液酸碱性至近中性,按照Eu/尿素=1/20的摩尔比加入尿素。然后,加入阳极氧化氧化铝模板。80℃保温72h。取出模板,置于管式炉内,升温至150℃保温1小时,再升温至700℃保温10小时。

  42. 产物的晶相分析在Philips X’pert PRO 衍射仪上进行,产物为立方晶系Eu2O3,晶胞参数a=1.085nm,与JCPDS标准卡86-2476一致。 为了进一步确定该纳米管的组成,进行了能谱分析,Eu和O的原子个数比近似等于2:3。

  43. The function of the Al2O3 template

  44. 模板中Eu2O3纳米管阵列的俯视图,纳米管竖直排列在模板上,几乎相互平行形成阵列,外径约50~80nm,与模板孔径尺寸相符。照片的放大相更清晰,几乎所有的孔中都填满了Eu2O3纳米管。TEM照片显示了孔的外径约70nm,壁厚约5nm。模板中Eu2O3纳米管阵列的俯视图,纳米管竖直排列在模板上,几乎相互平行形成阵列,外径约50~80nm,与模板孔径尺寸相符。照片的放大相更清晰,几乎所有的孔中都填满了Eu2O3纳米管。TEM照片显示了孔的外径约70nm,壁厚约5nm。

  45. TEM照片可以清晰地看到纳米管的开口,选区电子衍射中的衍射环表明形成了Eu2O3多晶,其中(222)晶面环特别亮,表示该晶体具有特定的生长方向。高分辨电子显微镜HRTEM照片见图b

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