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.

Hydration Layer-Mediated Pairwise Interaction of Nanoparticles

Utkarsh Anand†‡§∥, Jingyu Lu†‡§∥, Duane Loh†‡, Zainul Aabdin†‡§∥, and Utkur Mirsaidov*†‡§∥

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

Nano Lett., Article ASAP DOI: 10.1021/ acs.nanolett.5b04808 Publication Date (Web): December 28, 2015

When any two surfaces in a solution come within a distance the size of a few solvent molecules, they experience a solvation force or a hydration force when the solvent is water. Although the range and magnitude of hydration forces are easy to characterize, the effects of these forces on the transient steps of interaction dynamics between nanoscale bodies in solution are poorly understood. Here, using in situ transmission electron microscopy, we show that when two gold nanoparticles in water approach each other at a distance within two water molecules (∼5 Å), which is the combined thickness of the hydration shell of each nanoparticle, they form a sterically stabilized transient nanoparticle dimer. The interacting surfaces of the nanoparticles come in contact and undergo coalescence only after these surfaces are fully dehydrated. Our observations of transient steps in nanoparticle interactions, which reveal the formation of hydration layer mediated metastable nanoparticle pairs in solution, have significant implications for many natural and industrial processes.

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Learn more about Utkur Mirsaidov’s research.

CBIS PI Shee Mei Lok awarded National Research Foundation Investigatorship

Assistant Professor Lok is one of the recipients of the prestigious National Research Foundation Investigatorship.

Dengue Virus (DENV) infects approximately 100 million people each year. Increased travel, together with global climate change will result in further geographical expansion of the territory of the dengue mosquito vector, Aedes aegypti. There is an urgent need to develop safe and effective dengue therapeutics and vaccine.

CBIS-PI-portraits-sheemeiLok
CBIS PI Shee Mei Lok at the Titan Krios at the National University of Singapore Centre for BioImaging Research

In vitro experiments have shown that non-neutralizing antibodies can enhance DENV infection of Fc receptor bearing macrophages, one of the natural host cells for the virus. This suggested that the presence of non-neutralizing epitopes in a vaccine could potentially increase the chances that a person who had received the vaccine would develop the severe form of the disease, dengue hemorrhagic fever. For this reason, a more promising approach for engineering an effective DENV vaccine is to focus on including neutralizing epitopes. Thus, mapping of neutralizing epitopes is a necessary component of DENV vaccine research. Furthermore, understanding the neutralization mechanism of antibodies and the entry of DENV into the host cells also could aid in the design of targeted therapeutics.

The research in her laboratory therefore, focuses on the understanding of the pathology of dengue virus infection and the mechanism of neutralization by antibodies and other molecules so as to facilitate the development of suitable vaccines and therapeutics. A combination of molecular, immunological, biochemical and structural techniques (x ray crystallography and cryoEM image reconstruction techniques) will be used to achieve these aims.

Read more about Associate Professor Lok’s research.