Tag Archives: utkur mirsaidov

Multistep nucleation of nanocrystals in aqueous solution

N. Duane Loh, Soumyo Sen, Michel Bosman, Shu Fen Tan, Jun Zhong, Christian A. Nijhuis, Petr Král, Paul Matsudaira & Utkur Mirsaidov

Nature Chemistry 9, 77–82 (2017) doi:10.1038/nchem.2618
Received 08 May 2016 Accepted 18 August 2016 Published online 03 October 2016

The nucleation and growth of solids from solutions impacts many natural processes and is fundamental to applications in materials engineering and medicine. For a crystalline solid, the nucleus is a nanoscale cluster of ordered atoms that forms through mechanisms still poorly understood. In particular, it is unclear whether a nucleus forms spontaneously from solution via a single- or multiple-step process. Here, using in situ electron microscopy, we show how gold and silver nanocrystals nucleate from supersaturated aqueous solutions in three distinct steps: spinodal decomposition into solute-rich and solute-poor liquid phases, nucleation of amorphous nanoclusters within the metal-rich liquid phase, followed by crystallization of these amorphous clusters. Our ab initio calculations on gold nucleation suggest that these steps might be associated with strong gold–gold atom coupling and water-mediated metastable gold complexes. The understanding of intermediate steps in nuclei formation has important implications for the formation and growth of both crystalline and amorphous materials.

Read online: Nature Chemistry.

Linker-Mediated Self-Assembly Dynamics of Charged Nanoparticles

Guanhua Lin, See Wee Chee, Sanoj Raj, Petr Král, and Utkur Mirsaidov

ACS Nano, 2016, 10 (8), pp 7443–7450. DOI: 10.1021/acsnano.6b01721. Publication Date (Web): August 05, 2016

Using in situ liquid cell transmission electron microscopy (TEM), we visualized a stepwise self-assembly of surfactant-coated and hydrated gold nanoparticles (NPs) into linear chains or branched networks. The NP binding is facilitated by linker molecules, ethylenediammonium, which form hydrogen bonds with surfactant molecules of neighboring NPs. The observed spacing between bound neighboring NPs, ∼15 Å, matches the combined length of two surfactants and one linker molecule. Molecular dynamics simulations reveal that for lower concentrations of linkers, NPs with charged surfactants cannot be fully neutralized by strongly binding divalent linkers, so that NPs carry higher effective charges and tend to form chains, due to poor screening. The highly polar NP surfaces polarize and partly immobilize nearby water molecules, which promotes NPs binding. The presented experimental and theoretical approach allows for detail observation and explanation of self-assembly processes in colloidal nanosystems.

Read online: ACS Nano.

Nanodroplet-Mediated Assembly of Platinum Nanoparticle Rings in Solution

Guanhua Lin†‡§∥, Xi Zhu, Utkarsh Anand†‡§∥, Qi Liu†‡§∥, Jingyu Lu†‡§∥, Zainul Aabdin†‡§∥, Haibin Su*⊥, and Utkur Mirsaidov*†‡§∥

Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117551
Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546
§ Centre for BioImaging Sciences, Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore, 117543
NanoCore, National University of Singapore, 4 Engineering Drive 3, Singapore 117576
School of Materials Sciences and Engineering, Nanyang Technological University, Singapore 639798

Nano Lett., Article ASAP DOI: 10.1021/ acs.nanolett.5b04323 Publication Date (Web): January 4, 2016

Soft fluidlike nanoscale objects can drive nanoparticle assembly by serving as a scaffold for nanoparticle organization. The intermediate steps in these template-directed nanoscale assemblies are important but remain unresolved. We used real-time in situ transmission electron microscopy to follow the assembly dynamics of platinum nanoparticles into flexible ringlike chains around ethylenediaminetetraacetic acid nanodroplets dispersed in solution. In solution, these nanoring assemblies form via sequential attachment of the nanoparticles to binding sites located along the circumference of the nanodroplets, followed by the rearrangement and reorientation of the attached nanoparticles. Additionally, larger nanoparticle ring assemblies form via the coalescence of smaller ring assemblies. The intermediate steps of assembly reported here reveal how fluidlike nanotemplates drive nanoparticle organization, which can aid the future design of new nanomaterials.

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Learn more about Utkur Mirsaidov’s research.