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Applying muon spin rotation to understand the magnetic behaviour of metallic bionanoparticles

应用μ子自旋旋转来了解金属生物纳米颗粒的磁性行为

基本信息

批准号：
EP/J006483/1
负责人：
Lynne Macaskie
金额：
$ 17.88万
依托单位：
University of Birmingham
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2011
资助国家：
英国
起止时间：
2011 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FJ006483%2F1
关键词：
Applying muon spin rotation understand

项目摘要

Nanoparticles (NPs) can have properties at odds with those of bulk material. Palladium and gold-NPs are excellent catalysts. Biomanufactured Pd and Au-NPs supported on bacteria have high catalytic potential in 'green chemistry' (e.g. selective hydrogenations/oxidations/production of platform chemicals) and in clean energy (fuel cell catalysts). 'Bio-Pd' and 'Bio-Au'-NPs are 5nm (Pd) to 20-60 nm (Au, Pd) supported (preventing coalescence) on the surface the bacteria that made them. Recently core-shell Pd/Au-NPs have been biomanufactured. These outperform commercially available catalysts. The free Pd atom is nonmagnetic and in bulk no spontaneous ferromagnetic order is observed. However, Pd-NPs formed by gas evaporation demonstrated ferromagnetism in a NP-population with mean diameter 5.9 nm which has been attributed to non-typical metal-metal bonding due to constraints of particle size. Ferromagnetic nano-Au is also claimed in the literature. These published conclusions are controversial.We found that Bio-Pd-NPs are magnetically active. The magnetic moment/NP size/catalytic activity are related. Biomanufacturing is NP-size-controllable and commercially scalable. Our 'position' paper (Biotech Letts) evaluated the potential of muon spin rotation (muSR) as a tool for bionanoparticle characterisation. The muon, an unstable lepton, has a magnetic moment ~3x that of the proton and is a sensitive microscopic magnetometer. Positive muons thermalise at an interstitial location and probe local magnetic fields in the regions between the atoms. The ISIS synchrotron produces a beam of positive muons with a unique momentum (29.8 MeV/c), 100% spin-polarised. Muons stop within the sample and decay, giving positrons, emitted preferentially in the direction of the muon spin, enabling the time evolution of the muon polarisation (or decay asymmetry) to be followed via the time dependence of the positron distribution. Hence one can measure the time dependent depolarisation of the muon signal and characterise the distribution and dynamics of internal fields in the sample. In insulating materials (here the residual bacteria) the implanted muon may bind an electron to form muonium, akin to H-dot. This reactive species may react with organic systems to form radicals; the muon-electron hyperfine coupling can complicate the signal measured. We precluded this.muSR has been previously applied to study heavily dislocated hydrogen-containing bulk Pd and also to ligand-capped Pd-NPs in the critical size range within which Pd is expected to demonstrate super-paramagnetic/ferromagnetic behaviour. Our pilot study was the first application of muSR as a probe for such catalytic bionanoparticles within an EPSRC project to develop these for catalysis. This one year PDRA mobility will train Dr N.Creamer in the use of muSR by embedding him into ISIS, enabling him to complete the Pd-NP study, extending this also to the study of Bio-Au and Bio-Pd/Au-NPs. This will utilise a controlled ligand-stripping method developed in the parent grant. By removing the thin layer of organic residuum capping the NPs just before the point of muSR analysis we increase the chance of acquiring magnetic data before the NPs coalesce. We aim to address a fundamental problem of magnetism: is it attributable to surface atoms, bulk atoms or both? We also aim to establish this study of the hard/matter/soft matter interface (bionanoparticles have not been muSR-probed before) and also provide the first muSR magnetic testing of Pd/Au core-shell bimetallics to inform their unique chemical activities. The outcome will be a novel biomanufacturing tool to lay the foundation to study intra-particle interfaces and surfaces via their magnetic domains, enabled by fusing life sciences, chemistry and hard physics disciplines. Dr Creamer, skilled in the former two but needing training in the third, has substantial teaching experience and is ideal to champion this new subdiscipline.

纳米颗粒(NPs)的性质可能与块状材料的性质不同。钯和金纳米粒子是很好的催化剂。以细菌为载体的生物制造钯和金纳米粒子在绿色化学(例如选择性加氢/氧化/生产平台化学品)和清洁能源(燃料电池催化剂)方面具有很高的催化潜力。‘Bio-Pd’和‘Bio-Au’-NPs是5 nm(Pd)到20-60 nm(Au，Pd)支撑(防止团聚)在制造它们的细菌表面。最近，核壳结构的Pd/Au-NPs已经被生物制备。这些催化剂的性能超过了商业上可获得的催化剂。自由Pd原子是非磁性的，整体上没有观察到自发的铁磁有序。然而，气体蒸发法制备的Pd-NPs在平均直径为5.9 nm的NP布居中表现出铁磁性，由于颗粒尺寸的限制，这被归因于非典型的金属-金属成键。文献中也提出了铁磁性纳米金的要求。这些发表的结论是有争议的。我们发现Bio-Pd-NPs具有磁性活性。磁矩/纳米颗粒大小/催化活性之间存在相关性。生物制造是NP大小可控和商业可扩展的。我们的“立场”论文(Biotech Letts)评估了Muon自旋旋转(MuSR)作为生物纳米粒子表征工具的潜力。Muon是一种不稳定的轻子，其磁矩约为质子的3倍，是一种灵敏的显微磁强计。正缪子在间隙位置发生热化，探测原子之间区域的局部磁场。ISIS同步加速器产生一束具有独特动量(29.8 MeV/c)、100%自旋极化的正µ子束。µ子在样品中停止并衰变，给出正电子，这些正电子优先沿着Muon自旋的方向发射，使得能够通过正电子分布的时间依赖来跟踪Muon极化(或衰变不对称)的时间演变。因此，人们可以测量与时间相关的Muon信号的去极化，并表征样品中内场的分布和动力学。在绝缘材料(这里是残留细菌)中，植入的Muon可能会与一个电子结合，形成类似于H点的Muonium。这种活性物种可能会与有机体系反应形成自由基；µ子-电子超精细耦合可能会使测量的信号复杂化。我们排除了这一点。muSR以前曾被应用于研究严重位错的含氢块体Pd，也被应用于Pd有望表现出超顺磁性/铁磁行为的临界尺寸范围内的配体封顶的Pd-NPs。我们的初步研究是在EPSRC项目中首次将MuSR用作此类催化纳米粒子的探针，以开发这些生物纳米粒子用于催化。这一年PDRA Mobility将通过将N.Creamer博士嵌入ISIS来培训他如何使用muSR，使他能够完成PD-NP研究，并将这一研究扩展到Bio-Au和Bio-Pd/Au-NPs的研究。这将利用母公司赠款中开发的受控配体剥离方法。通过在MuSR分析点之前去除覆盖在NPs上的薄层有机残渣，我们增加了在NPs合并之前获得磁性数据的机会。我们的目标是解决磁性的一个基本问题：它是由表面原子引起的，还是由块状原子引起的，还是两者都有？我们还致力于建立这种硬/物质/软物质界面的研究(生物纳米粒子以前从未被MuSR探测过)，并首次提供了Pd/Au核-壳双金属的MuSR磁性测试，以揭示其独特的化学活性。其成果将是一种新的生物制造工具，通过融合生命科学、化学和硬物理学科，通过其磁域为研究粒子内界面和表面奠定基础。克里默博士精通前两个学科，但需要在第三个学科接受培训，他拥有丰富的教学经验，是支持这一新分支学科的理想人选。