Bottom-up fabrication of three-dimensional nanoporous gold from Au nanoparticles using nanowelding

使用纳米焊接从金纳米粒子自下而上制备三维纳米多孔金

Three-dimensional(3D)nanoporous gold(NPG)shows promising applications in various fields.However,its most common fabrication strategy(i.e.,dealloying)faces the problems of high energy consumption,resource waste,the use of corrosive solvent,and residue of the sacrificial component.Here,we report a general bottom-up nanowelding strategy to fabricate high-purity NPG from Au nanoparticles(NPs),accomplished via interfacial self-assembly of the Au NPs into monolayer Au NP film,its subsequent layer-by-layer transfer onto a solid substrate,and direct current(DC)nanowelding.We show that the DC nanowelding process can gradually evolve the layered Au NP film into NPG at low temperatures within 10 s,while not damaging their spherical structure.This is because during the nanowelding,electrons are preferred to be localized at the high-resistance NP/NP junctions,whose electrostatic repulsion in turn strengthens their surface atom diffusion to initiate a mild solid-state diffusion nanowelding.Furthermore,when using differently sized Au NPs as the starting building blocks,this strategy allows readily tuning the thickness,ligament size,and pore size,thereby offering great flexibility to create functional porous nanomaterials,e.g.,electrocatalyst for methanol electrooxidation.Surely,low-temperature nanowelding can play a role for the production of diverse nanoporous materials from other NPs beyond Au NPs.

三维纳米多孔金具有高的比表面积、高的导电性和等离激元特性等众多优异的物理化学性质,可以应用于多个领域.然而,其最常见的制备方法,即脱合金,面临着高能耗、资源浪费、需使用腐蚀性液体和牺牲组分的残留等问题.本文中,我们报道了一种较普适性的自下而上的纳米焊接方法,用于从金纳米粒子制造高纯度三维纳米多孔金.该方法先将化学合成的金纳米粒子在液-液界面自组装成致密的单层金纳米粒子薄膜,随后将其逐层转移到固体基底上形成多层的金纳米粒子膜,最后对该多层金纳米粒子膜在空气中通直流电进行纳米焊接.研究结果表明,直流电纳米焊接工艺可在10 s内在低温下将层状金纳米颗粒薄膜逐渐转变为纳米多孔金,同时不会破坏母体金纳米粒子的球形结构.这是因为在纳米焊接过程中,电子更倾向于聚集在高电阻的粒子/粒子结点处,造成该处的表面原子受到较强的静电排斥作用,从而强化了该处的表面原子扩散并引发温和的固态扩散纳米焊接.此外,当使用不同尺寸的金纳米粒子作为起始构筑单元时,该方法可有效调整纳米多孔金的厚度、韧带尺寸和孔径,从而为构筑功能性多孔纳米材料(如用于甲醇电氧化的电催化剂)提供极大的灵活性.可以预料,该低温纳米焊接方法也可用于除金纳米粒子以外的其他纳米粒子为起始构筑单元构筑其他类型的纳米多孔材料.