Tag Archives: Jwa-Min Nam

Climate change and black gold

A July 3, 2019 news item on Nanowerk describes research coming from India and South Korea where nano gold is turned into black nanogold (Note: A link has been removed),

One of the main cause of global warming is the increase in the atmospheric CO2 level. The main source of this CO2 is from the burning of fossil fuels (electricity, vehicles, industry and many more).

Researchers at TIFR [Tata Institute of Fundamental Research] have developed the solution phase synthesis of Dendritic Plasmonic Colloidosomes (DPCs) with varying interparticle distances between the gold Nanoparticles (AU NPs) using a cycle-by-cycle growth approach by optimizing the nucleation-growth step. These DPCs absorb the entire visible and near-infrared region of solar light, due to interparticle plasmonic coupling as well as the heterogeneity in the Au NP [gold nanoparticle] sizes, which transformed golden gold material to black gold (Chemical Science, “Plasmonic colloidosomes of black gold for solar energy harvesting and hotspots directed catalysis for CO2 to fuel conversion”).

A July 3, 2019 Tata Institute of Fundamental Research (TIFR) press release on EurekAlert, which originated the news item, provides more technical detail,

Black (nano)gold was able to catalyze CO2 to methane (fuel) conversion at atmospheric pressure and temperature, using solar energy. They also observed the significant effect of the plasmonic hotspots on the performance of these DPCs for the purification of seawater to drinkable water via steam generation, temperature jump assisted protein unfolding, oxidation of cinnamyl alcohol using pure oxygen as the oxidant, and hydrosilylation of aldehydes.

This was attributed to varying interparticle distances and particle sizes in these DPCs. The results indicate the synergistic effects of EM and thermal hotspots as well as hot electrons on DPCs performance. Thus, DPCs catalysts can effectively be utilized as Vis-NIR light photo-catalysts, and the design of new plasmonic nanocatalysts for a wide range of other chemical reactions may be possible using the concept of plasmonic coupling.

Raman thermometry and SERS (Surface-enhanced Raman Spectroscopy) provided information about the thermal and electromagnetic hotspots and local temperatures which was found to be dependent on the interparticle plasmonic coupling. The spatial distribution of the localized surface plasmon modes by STEM-EELS plasmon mapping confirmed the role of the interparticle distances in the SPR (Surface Plasmon Resonance) of the material.

Thus, in this work, by using the techniques of nanotechnology, the researchers transformed golden gold to black gold, by changing the size and gaps between gold nanoparticles. Similar to the real trees, which use CO2, sunlight and water to produce food, the developed black gold acts like an artificial tree that uses CO2, sunlight and water to produce fuel, which can be used to run our cars. Notably, black gold can also be used to convert sea water into drinkable water using the heat that black gold generates after it captures sunlight.

This work is a way forward to develop “Artificial Trees” which capture and convert CO2 to fuel and useful chemicals. Although at this stage, the production rate of fuel is low, in coming years, these challenges can be resolved. We may be able to convert CO2 to fuel using sunlight at atmospheric condition, at a commercially viable scale and CO2 may then become our main source of clean energy.

Here’s an image illustrating the work

Caption: Use of black gold can get us one step closer to combat climate change. Credit: Royal Society of Chemistry, Chemical Science

A July 3, 2019 Royal Society of Chemistry Highlight features more information about the research,

A “black” gold material has been developed to harvest sunlight, and then use the energy to turn carbon dioxide (CO2) into useful chemicals and fuel.

In addition to this, the material can also be used for applications including water purification, heating – and could help further research into new, efficient catalysts.

“In this work, by using the techniques of nanotechnology, we transformed golden gold to black gold, by simply changing the size and gaps between gold nanoparticles,” said Professor Vivek Polshettiwar from Tata Institute of Fundamental Research (TIFR) in India.

Tuning the size and gaps between gold nanoparticles created thermal and electromagnetic hotspots, which allowed the material to absorb the entire visible and near-infrared region of sunlight’s wavelength – making the gold “black”.

The team of researchers, from TIFR and Seoul National University in South Korea, then demonstrated that this captured energy could be used to combat climate change.

Professor Polshettiwar said: “It not only harvests solar energy but also captures and converts CO2 to methane (fuel). Synthesis and use of black gold for CO2-to-fuel conversion, which is reported for the first time, has the potential to resolve the global CO2 challenge.

“Now, like real trees which use CO2, sunlight and water to produce food, our developed black gold acts like an artificial tree to produce fuel – which we can use to run our cars,” he added.
Although production is low at this stage, Professor Polshettiwar (who was included in the RSC’s 175 Faces of Chemistry) believes that the commercially-viable conversion of CO2 to fuel at atmospheric conditions is possible in the coming years.

He said: “It’s the only goal of my life – to develop technology to capture and convert CO2 and combat climate change, by using the concepts of nanotechnology.”

Other experiments described in the Chemical Science paper demonstrate using black gold to efficiently convert sea water into drinkable water via steam generation.

It was also used for protein unfolding, alcohol oxidation, and aldehyde hydrosilylation: and the team believe their methodology could lead to novel and efficient catalysts for a range of chemical transformations.

Here’s a link to and a citation for the paper,

Plasmonic colloidosomes of black gold for solar energy harvesting and hotspots directed catalysis for CO2 to fuel conversion by Mahak Dhiman, Ayan Maity, Anirban Das, Rajesh Belgamwar, Bhagyashree Chalke, Yeonhee Lee, Kyunjong Sim, Jwa-Min Nam and Vivek Polshettiwar. Chem. Sci., 2019, Advance Article. DOI: 10.1039/C9SC02369K First published on July 3, 2019

This paper is freely available in the open access journal Chemical Science.

Nanoparticle computing

I’m fascinated with this news and I’m pretty sure it’s my first exposure to nanoparticle computing so am quite excited about this ‘discovery of mine’.

A February 25, 2019 news item on Nanowerk announces the research from Korean scientists,

Computation is a ubiquitous concept in physical sciences, biology, and engineering, where it provides many critical capabilities. Historically, there have been ongoing efforts to merge computation with “unusual” matters across many length scales, from microscopic droplets (Science 315, 832, 2007) to DNA nanostructures (Science 335, 831, 2012; Nat. Chem. 9, 1056, 2017) and molecules (Science 266, 1021, 1994; Science 314, 1585, 2006; Nat. Nanotech. 2, 399, 2007; Nature 375, 368, 2011).

However, the implementation of complex computation in particle systems, especially in nanoparticles, remains challenging, despite a wide range of potential applications that would benefit from algorithmically controlling their unique and potentially useful intrinsic features (such as photonic, plasmonic, catalytic, photothermal, optoelectronic, electrical, magnetic and material properties) without human interventions.

This challenge is not due to the lack of sophistication in the the current state-of-the-art of stimuli-responsive nanoparticles, many of which can conceptually function as elementary logic gates. This is mostly due to the lack of scalable architectures that would enable systematic integration and wiring of the gates into a large integrated circuit.

Previous approaches are limited to (i) demonstrating one simple logic operation per test tube or (ii) relying on complicated enzyme-based molecular circuits in solution. It should be also noted that modular and scalable aspects are key challenges in DNA computing for practical and widespread use.

A February 23, 2019 Seoul National University press release on EurekAlert, which originated the news items, dives into more detail,

In nature, the cell membrane is analogous to a circuit board, as it organizes a wide range of biological nanostructures (e.g. proteins) as (computational) units and allows them to dynamically interact with each other on the fluidic 2D surface to carry out complex functions as a network and often induce signaling intracellular signaling cascades. For example, the membrane proteins on the membrane take chemical/physical cues as inputs (e.g. binding with chemical agents, mechanical stimuli) and change their conformations and/or dimerize as outputs. Most importantly, such biological “computing” processes occur in a massively parallel fashion. Information processing on living cell membranes is a key to how biological systems adapt to changes in external environments.

This manuscript reports the development of a nanoparticle-lipid bilayer hybrid-based computing platform termed lipid nanotablet (LNT), in which nanoparticles, each programmed with surface chemical ligands (DNA in this case), are tethered to a supported lipid bilayer to carry out computation. Taking inspirations from parallel computing processes on cellular membranes, we exploited supported lipid bilayers (SLBs)–synthetic mimics for cell surfaces–as chemical circuit boards to construct nanoparticle circuits. This “nano?bio” computing, which occurs at the interface of nanostructures and biomolecules, translates molecular information in solution (input) into dynamic assembly/disassembly of nanoparticles on a lipid bilayer (output).

We introduced two types of nanoparticles to a lipid bilayer that differ in mobility: mobile Nano-Floaters and immobile Nano-Receptors. Due to high mobility, floaters actively interact with receptors across space and time, functioning as active units of computation. The nanoparticles are functionalized with specially designed DNA [deoxyribonucleic acid] ligands, and the surface ligands render receptor-floater interactions programmable, thereby transforming a pair of receptor and floater into a logic gate. A nanoparticle logic gate takes DNA strands in solution as inputs and generates nanoparticle assembly or disassembly events as outputs. The nanoparticles and their interactions can be imaged and tracked by dark-field microscopy with single-nanoparticle resolution because of strong and stable scattering signals from plasmonic nanoparticles. Using this approach (termed “interface programming”), we first demonstrated that a pair of nanoparticles (that is, two nanoparticles on a lipid bilayer) can carry out AND, OR, INHIBIT logic operations and take multiple inputs (fan-in) and generate multiple outputs (fan-out). Also, multiple logic gates can be modularly wired with AND or OR logic via floaters, as the mobility of floaters enables the information cascade among several nanoparticle logic gates. We termed this strategy “network programming.” By combining these two strategies (interfacial and network programming), we were able to implement complex logic circuits such as multiplexer.

The most important contributions of our paper are the conceptual one and the major advances in modular and scalable molecular computing (DNA computing in this case). LNT platform, for the first time, introduces the idea of using lipid bilayer membranes as key components for information processing. As the two-dimensional (2D) fluidic lipid membrane is bio-compatible and chemically modifiable, any nanostructures can be potentially introduced and used as computing units. When tethered to the lipid bilayer “chip”, these nanostructures can be visualized and become controllable at the single-particle level; this dimensionality reduction, bringing the nanostructures from freely diffusible solution phase (3D) to fluidic membrane (2D), transforms a collection of nanostructures into a programmable, analyzable reaction network. Moreover, we also developed a digitized imaging method and software for quantitative and massively parallel analysis of interacting nanoparticles. In addition, LNT platform provides many practical merits to current state-of-the-art in molecular computing and nanotechnology. On LNT platforms, a network of nanoparticles (each with unique and beneficial properties) can be design to autonomously respond to molecular information; such capability to algorithmically control nanoparticle networks will be very useful for addressing many challenges with molecular computing and developing new computing platforms. As the title of our manuscript suggests, this nano-bio computing will lead to exciting opportunities in biocomputation, nanorobotics, DNA nanotechnology, artificial bio-interfaces, smart biosensors, molecular diagnostics, and intelligent nanomaterials. In summary, the operating and design principles of lipid nanotablet platform are as follows:

(1) LNT uses single nanoparticles as units of computation. By tracking numerous nanoparticles and their actions with dark-field microscopy at the single-particle level, we could treat a single nanoparticle as a two-state device representing a bit. A nanoparticle provides a discrete, in situ optical readout of its interaction (e.g. association or dissociation) with another particle as an output of logic computation.

(2) Nanoparticles on LNT function as Boolean logic gates. We exploited the programmable bonding interaction within particle-particle interfaces to transform two interacting nanoparticles into a Boolean logic gate. The gate senses single-stranded DNA as inputs and triggers an assembly or disassembly reaction of the pair as an output. We demonstrated two-input AND, two-input OR and INHIBIT logic operations, and fan-in/fan-out of logic gates.

(3) LNT enables modular wiring of multiple nanoparticle logic gates into a combinational circuit. We exploited parallel, single-particle imaging to program nanoparticle networks and thereby wire multiple logic gates into a combinational circuit. We demonstrate a multiplexer MUX2to1 circuit built from the network wiring rules.

Here’s a link to and a citation for the team’s latest paper,

Nano-bio-computing lipid nanotablet by Jinyoung Seo, Sungi Kim, Ha H. Park, Da Yeon Choi, and Jwa-Min Nam. Science Advances 22 Feb 2019: Vol. 5, no. 2, eaau2124 DOI: 10.1126/sciadv.aau2124

This paper appears to be open access.