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NT/ Researchers create intelligent electronic microsystems from ‘green’ material

Nanomaterials & nanotechnology biweekly vol.1, 31st May — 14th June

TL;DR

  • A research team from the University of Massachusetts Amherst has created an electronic microsystem that can intelligently respond to information inputs without any external energy input, much like a self-autonomous living organism. The microsystem is constructed from a novel type of electronics that can process ultralow electronic signals and incorporates a device that can generate electricity “out of thin air” from the ambient environment.
  • MIT engineers have discovered a new way of generating electricity using tiny carbon particles that can create a current simply by interacting with liquid surrounding them.
  • Researchers have developed a novel approach to mitigating electromigration in nanoscale electronic interconnects that are ubiquitous in state-of-the-art integrated circuits. This was achieved by coating copper metal interconnects with hexagonal boron nitride (hBN), an atomically-thin insulating two-dimensional (2D) material that shares a similar structure as the ‘wonder material’ graphene.
  • In a breakthrough in metamaterials, for the first time in the world, researchers at Tel Aviv University have developed an innovative nanotechnology that transforms a transparent calcite nanoparticle into a sparkling gold-like particle. In other words, they turned the transparent particle into a particle that is visible despite its very small dimensions. According to the researchers the new material can serve as a platform for innovative cancer treatments.
  • Nano-sized particles have been engineered in a new way to improve detection of tumors within the body and in biopsy tissue, a research team in Sweden reports. The advance could enable identifying early stage tumors with lower doses of radiation.
  • In the journal Nature Communications, an interdisciplinary team from the Max Planck Institute of Colloids and Interfaces presents for the first time a laser-driven technology that enables them to create nanoparticles such as copper, cobalt and nickel oxides. At the usual printing speed, photoelectrodes are produced in this way, for example, for a wide range of applications such as the generation of green hydrogen.
  • Professor Ángel Serrano, principal investigator at the Biomaterials and Bioengineering Laboratory of the Catholic University of Valencia (UCV), recently published an article in journal ACS Nano, from the American Chemical Society, which shows that carbon-based nanomaterials (CBNs) with low or zero toxicity for humans, are “promising treatments” against the pneumonia caused by COVID-19, as well as other viruses, bacteria and fungi, including those that are multi-resistant to medicines.
  • Materials scientists from Nanyang Technological University, Singapore (NTU Singapore) have developed a reusable “nanotech mask” that can filter out 99.9 percent of bacteria, viruses and particulate matter (PM), as well as kill bacteria.
  • Nanoscale sensors measure elusive water levels in leaves.
  • And more!

Nanotech Market

Nanotechnology deals with the ability to see, understand, measure, predict, produce or control matter at nanoscale (below 100 nanometers). The realm of nanotechnology lies between 0.1 and 100 nanometers, wherein a nanometer is defined as one thousandth of a micron. As a versatile technology with widespread applications in a wide range of end-use sectors, nanotechnology is currently facing a mixed bag of challenges and opportunities as the COVID-19 pandemic continues to spread across the globe. With the world fighting its biggest public health crisis in history, nanotechnology healthcare applications are storming into the spotlight led by the focus on nano intervention in terms of designing effective ways to identify, diagnose, treat and eliminate the spread of COVID-19 infections. Their role as nanocarriers has potential to design risk-free and effective immunization strategies. In the post COVID-19 period, use of nanotechnology solutions in the production of a multitude of devices & products will continue to grow.

Amid the COVID-19 crisis, the global market for Nanotechnology estimated at US$42.2 Billion in the year 2020, is projected to reach a revised size of US$70.7 Billion by 2026, growing at a CAGR of 9.2% over the analysis period. Nanocomposites, one of the segments analyzed in the report, is projected to record a 8.7% CAGR and reach US$35.4 Billion by the end of the analysis period. After a thorough analysis of the business implications of the pandemic and its induced economic crisis, growth in the Nanomaterials segment is readjusted to a revised 10.1% CAGR for the next 7-year period.

Latest News & Researches

Self-sustained green neuromorphic interfaces

by Tianda Fu, Xiaomeng Liu, Shuai Fu, Trevor Woodard, Hongyan Gao, Derek R. Lovley, Jun Yao in Nature Communications

A research team from the University of Massachusetts Amherst has created an electronic microsystem that can intelligently respond to information inputs without any external energy input, much like a self-autonomous living organism. The microsystem is constructed from a novel type of electronics that can process ultralow electronic signals and incorporates a device that can generate electricity “out of thin air” from the ambient environment.

Jun Yao, an assistant professor in the electrical and computer engineering (ECE) and an adjunct professor in biomedical engineering, led the research with his longtime collaborator, Derek R. Lovley, a Distinguished Professor in microbiology.

Both of the key components of the microsystem are made from protein nanowires, a “green” electronic material that is renewably produced from microbes without producing “e-waste.” The research heralds the potential of future green electronics made from sustainable biomaterials that are more amenable to interacting with the human body and diverse environments.

This breakthrough project is producing a “self-sustained intelligent microsystem,” according to the U.S. Army Combat Capabilities Development Command Army Research Laboratory, which is funding the research.

Tianda Fu, a graduate student in Yao’s group, is the lead author. “It’s an exciting start to explore the feasibility of incorporating ‘living’ features in electronics. I’m looking forward to further evolved versions,” Fu said.

The project represents a continuing evolution of recent research by the team. Previously, the research team discovered that electricity can be generated from the ambient environment/humidity with a protein-nanowire-based Air Generator (or ‘Air-Gen’), a device which continuously produces electricity in almost all environments found on Earth.

Also in 2020, Yao’s lab reported in Nature Communications that the protein nanowires can be used to construct electronic devices called memristors that can mimic brain computation and work with ultralow electrical signals that match the biological signal amplitudes.

“Now we piece the two together,” Yao said of the creation. “We make microsystems in which the electricity from Air-Gen is used to drive sensors and circuits constructed from protein-nanowire memristors. Now the electronic microsystem can get energy from the environment to support sensing and computation without the need of an external energy source (e.g. battery). It has full energy self-sustainability and intelligence, just like the self-autonomy in a living organism.”

The system is also made from environmentally friendly biomaterial — protein nanowires harvested from bacteria. Yao and Lovley developed the Air-Gen from the microbe Geobacter, discovered by Lovley many years ago, which was then utilized to create electricity from humidity in the air and later to build memristors capable of mimicking human intelligence.

“So, from both function and material,” says Yao, “we are making an electronic system more bio-alike or living-alike.”

“The work demonstrates that one can fabricate a self-sustained intelligent microsystem,” said Albena Ivanisevic, the biotronics program manager at the U.S. Army Combat Capabilities Development Command Army Research Laboratory. “The team from UMass has demonstrated the use of artificial neurons in computation. It is particularly exciting that the protein nanowire memristors show stability in aqueous environment and are amenable to further functionalization. Additional functionalization not only promises to increase their stability but also expand their utility for sensor and novel communication modalities of importance to the Army.”

a (Left) Fabricated protein nanowire memristor arrays on a polyimide (PI) substrate and (right) the schematics of the device structure. (Bottom) Transmission electron microscope (TEM) image of protein nanowires. Note that the actual nanowire density is much higher in assembled film. Scale bar, 100 nm. b Switching I–V curves from a memristor with the current compliance (ICC) set at different values from 5 µA to 10 nA. c Device yield (top), threshold switching voltage (black, bottom), and forming voltage (gray, bottom) in protein nanowire memristors subjected to various bending times. The error bars represent the standard deviation (s.d.). d (Left) A fabricated protein nanowire sensor with a vertical structure as shown in schematics (right). e Open-circuit voltage (Vo) and short-circuit current (inset) from the vertical protein nanowire sensor in the ambient environment (RH ~50%). f Output voltage Vo from the vertical protein nanowire sensor at different bending radius of 4–0.1 cm. g (Left) A fabricated protein nanowire sensor with a planar structure as shown in schematics (right). h Current and voltage (inset) signals generated in the planar protein nanowire sensor elicited by breathing. i Breathing-induced peak current in a planar protein nanowire sensor at a different bending radius of 4–0.1 cm.

Solvent-induced electrochemistry at an electrically asymmetric carbon Janus particle

by Albert Tianxiang Liu, Yuichiro Kunai, Anton L. Cottrill, Amir Kaplan, Ge Zhang, Hyunah Kim, Rafid S. Mollah, Yannick L. Eatmon, Michael S. Strano in Nature Communications

MIT engineers have discovered a new way of generating electricity using tiny carbon particles that can create a current simply by interacting with liquid surrounding them.

The liquid, an organic solvent, draws electrons out of the particles, generating a current that could be used to drive chemical reactions or to power micro- or nanoscale robots, the researchers say.

“This mechanism is new, and this way of generating energy is completely new,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT. “This technology is intriguing because all you have to do is flow a solvent through a bed of these particles. This allows you to do electrochemistry, but with no wires.”

In a new study describing this phenomenon, the researchers showed that they could use this electric current to drive a reaction known as alcohol oxidation — an organic chemical reaction that is important in the chemical industry.

Strano is the senior author of the paper. The lead authors of the study are MIT graduate student Albert Tianxiang Liu and former MIT researcher Yuichiro Kunai. Other authors include former graduate student Anton Cottrill, postdocs Amir Kaplan and Hyunah Kim, graduate student Ge Zhang, and recent MIT graduates Rafid Mollah and Yannick Eatmon.

The new discovery grew out of Strano’s research on carbon nanotubes — hollow tubes made of a lattice of carbon atoms, which have unique electrical properties. In 2010, Strano demonstrated, for the first time, that carbon nanotubes can generate “thermopower waves.” When a carbon nanotube is coated with layer of fuel, moving pulses of heat, or thermopower waves, travel along the tube, creating an electrical current.

That work led Strano and his students to uncover a related feature of carbon nanotubes. They found that when part of a nanotube is coated with a Teflon-like polymer, it creates an asymmetry that makes it possible for electrons to flow from the coated to the uncoated part of the tube, generating an electrical current. Those electrons can be drawn out by submerging the particles in a solvent that is hungry for electrons.

To harness this special capability, the researchers created electricity-generating particles by grinding up carbon nanotubes and forming them into a sheet of paper-like material. One side of each sheet was coated with a Teflon-like polymer, and the researchers then cut out small particles, which can be any shape or size. For this study, they made particles that were 250 microns by 250 microns.

When these particles are submerged in an organic solvent such as acetonitrile, the solvent adheres to the uncoated surface of the particles and begins pulling electrons out of them.

“The solvent takes electrons away, and the system tries to equilibrate by moving electrons,” Strano says. “There’s no sophisticated battery chemistry inside. It’s just a particle and you put it into solvent and it starts generating an electric field.”

The current version of the particles can generate about 0.7 volts of electricity per particle. In this study, the researchers also showed that they can form arrays of hundreds of particles in a small test tube. This “packed bed” reactor generates enough energy to power a chemical reaction called an alcohol oxidation, in which an alcohol is converted to an aldehyde or a ketone. Usually, this reaction is not performed using electrochemistry because it would require too much external current.

“Because the packed bed reactor is compact, it has more flexibility in terms of applications than a large electrochemical reactor,” Zhang says. “The particles can be made very small, and they don’t require any external wires in order to drive the electrochemical reaction.”

In future work, Strano hopes to use this kind of energy generation to build polymers using only carbon dioxide as a starting material. In a related project, he has already created polymers that can regenerate themselves using carbon dioxide as a building material, in a process powered by solar energy. This work is inspired by carbon fixation, the set of chemical reactions that plants use to build sugars from carbon dioxide, using energy from the sun.

In the longer term, this approach could also be used to power micro- or nanoscale robots. Strano’s lab has already begun building robots at that scale, which could one day be used as diagnostic or environmental sensors. The idea of being able to scavenge energy from the environment to power these kinds of robots is appealing, he says.

“It means you don’t have to put the energy storage on board,” he says. “What we like about this mechanism is that you can take the energy, at least in part, from the environment.”

a Schematic illustration of Janus microparticles generating electricity to power electrochemical redox reactions (e.g., Fe2+ → Fe3+ or Cu2+ → Cu0) in situ, in lieu of a potentiostat as a voltage source. b Schematic illustration of the electricity generation mechanism of the Janus microparticle. Asymmetric chemical doping is realized via spatially asymmetric polymer coating. The partial electron transfer induced by CH3CN molecules adsorbed on the o-SWNT surface withdraws electron density from the adsorption site, thereby lowering the corresponding Fermi energy (EF), drawing electron flow following the prescribed EF gradient15. c Surface profile of two 500 µm × 250 µm × 250 µm o-SWNT/PTFE Janus particles (color bar range, 0–500 µm; scale bar, 100 µm). d Raman spectroscopic map showing the intensity of the G band of the o-SWNT side of two 500 µm × 250 µm × 250 µm o-SWNT/PTFE Janus particles (scale bar, 100 µm). e Scanning electron micrograph showing the vertical interface of o-SWNT/PTFE interface of the Janus particle (scale bar, 1 µm). f Top: Raman spectroscopic measurement of o-SWNT G band shift for CH3CN exposed o-SWNT (Raman 1) and polymer protected o-SWNT (Raman 2). Note a spectroscopic window on the polymer protected side was opened up to avoid polymer interference in Raman measurement. Scale bar, 100 µm. Bottom: Raman G band shift of o-SWNT before (red) and after (blue) CH3CN addition for the exposed (left, Raman 1) and polymer protected (right, Raman 2) side. g Top: schematic illustration of closed-circuit measurements to quantify the electrical output of such Janus particles, in which the particles are lowered into a reservoir of CH3CN, and the current and voltage profiles across a known external load are recorded. Bottom: Measured voltage profiles across a 5000 kΩ external resistor for particle generators of various sizes but identical aspect ratios (black or volume ×1, 500 µm × 250 µm × 250 µm; red or volume ×2, 636 µm × 315 µm × 315 µm, blue or volume ×3, 720 µm × 360 µm × 360 µm). h Top: schematic illustration of Janus particles of the same volume (2 mm3), but different aspect ratios (AR) of 0.5 (blue), 1 (red) and 2 (black). Bottom: Current–voltage characteristics of the three particles represented above. Error bars represent standard deviations of different measurements using different replica of devices (n = 3). Colored squares represent the maximum output power of devices at each AR if the external resistance is impedance-matched to the device internal resistance.

Optical and X-ray Fluorescent Nanoparticles for Dual Mode Bioimaging

by Giovanni M. Saladino, Carmen Vogt, Yuyang Li, Kian Shaker, Bertha Brodin, Martin Svenda, Hans M. Hertz, Muhammet S. Toprak in ACS Nano

Nano-sized particles have been engineered in a new way to improve detection of tumors within the body and in biopsy tissue, a research team in Sweden reports. The advance could enable identifying early stage tumors with lower doses of radiation.

In order to enhance visual contrast of living tissues, state-of-the-art imaging relies on agents such as fluorescent dyes and biomolecules. Advances in nanoparticle research have expanded the array of promising contrast agents for more targeted diagnostics, and now a research team from KTH Royal Institute of Technology has raised the bar further yet. They are combining optical and X-ray fluorescence contrast agents into a single enhancer for both modes.

Muhammet Toprak, Professor of Materials Chemistry at KTH, says the synthesis of contrast agents introduces a new dimension in the field of X-ray bio-imaging. The research was reported in the American Chemical Society journal, ACS Nano.

“This unique design of nanoparticles paves the way for in vivo tumor diagnostics, using X-ray fluorescence computed tomography (XFCT),” Toprak says.

He says the new “core-shell nanoparticles” may have a role to play in the development of theranostics, a portmanteau for therapy and diagnostics, in which for example single drug-loaded particles could both detect and treat malignant tissues.

The core-shell contrast agent gets its name from its architecture: it consists of a core combination of nanoparticles with previously-established potential in X-ray fluorescence imaging, such as ruthenium and molybdenum (IV) oxide. This core is encased in a shell comprised of silica and Cy5.5, a near-infrared fluorescence-emitting dye for optical imaging techniques such as optical microscopy and spectroscopy.

Toprak says that encapsulating the Cy5.5 dye within the silica shell improves the agent’s brightness and extends its photo-stability — enabling the dual optical/X-Ray imaging approach. In addition, silica provides the benefit of tempering the toxic effects of the core nanoparticles.

Tests with laboratory mice have shown that the XFCT contrast agents enable location of early stage tumors of only a few millimetres in size.

Toprak says the technology opens the possibility to identify early stage tumors in living tissue. That’s because the presence of multiple contrast agents increases the odds that diseased areas will show up in scans, even as the distribution of the nanoparticles becomes obscured by their interaction with proteins or other biological molecules.

“Nanoparticles of different size, originating from the same material, don’t appear to be distributed in the blood in the same concentrations,” Toprak says. “That’s because when they come into contact with your body, they’re quickly wrapped in various biological molecules — which gives them a new identity.”

A multitude of contrast agents for XFCT would enable studying the biodistribution of nanoparticles in-vivo using low-dose X-rays, he says. That would allow identifying the best size and surface chemistry of the nanoparticles for the desired targeting and imaging of the diseased region.

Laser-driven growth of structurally defined transition metal oxide nanocrystals on carbon nitride photoelectrodes in milliseconds

by Junfang Zhang, Yajun Zou, Stephan Eickelmann, Christian Njel, Tobias Heil, Sebastian Ronneberger, Volker Strauss, Peter H. Seeberger, Aleksandr Savateev, Felix F. Loeffler in Nature Communications

In the journal Nature Communications, an interdisciplinary team from the Max Planck Institute of Colloids and Interfaces presents for the first time a laser-driven technology that enables them to create nanoparticles such as copper, cobalt and nickel oxides. At the usual printing speed, photoelectrodes are produced in this way, for example, for a wide range of applications such as the generation of green hydrogen.

Previous methods produce such nanomaterials only with high energy input in classical reaction vessels and in many hours. With the laser-driven technology developed at the institute, the scientists can deposit small amounts of material on a surface and simultaneously perform chemical synthesis in a very short time using high temperatures from the laser. ‘When I discovered the nanocrystals under the electron microscope, I knew I was onto something big,’ says Junfang Zhang, first author of the study and doctoral researcher. The discovery turned into a new and environmentally friendly method for synthesizing materials that can, among other things, efficiently convert solar energy into electricity.

Without detours with sunlight to hydrogen: ‘Nowadays most of green hydrogen is produced from water using electricity generated by solar panels and stored in batteries. By employing photoelectrodes we can use solar light directly,’ says Dr. Aleksandr Savateev.

The newly developed principle works with so-called transition metal oxides, mainly copper, cobalt and nickel oxides, all of which are good catalysts. The special feature of these oxides is the variety of their crystal forms (nanocrystals such as nanorods or nanostars), which affect their surface energy. Each structure can have a different effect on catalytic reactions. Therefore, it is important that these nanostructures can be made targeted — or even untargeted, but repeatable. The developed technology could also be used to find quickly and efficiently new catalysts. ‘Laser dot by laser dot, we can create different catalysts side by side by simply varying the composition and conditions, and then also test them in parallel right away,’ says Dr. Felix Löffler adding, ‘But now we need to work on making the catalyst systems more persistent in all applications’.

Similar to the principle of a typewriter, material is transferred from a donor to an acceptor carrier. On the former is the ‘ink’, a solid polymer, which is mixed with metal salts, the latter consists of a thin carbon nitride film on a conductive electrode. Targeted laser irradiation transfers the salts to the acceptor along with the molten polymer. The brief high temperatures cause the salts to react within milliseconds and they transform into metal oxide nanoparticles with desired morphology.

Principle of the laser-driven transfer synthesis (LTRAS) process for the generation of structurally defined transition metal oxide/carbon nitride (TMO/CN) composite films. a Laser irradiation transfers material from a donor to an acceptor surface. The donor slide is prepared by spin coating a mixture of dissolved copolymer together with transition metal (TM) precursor onto a polyimide-coated glass slide. The acceptor slide is prepared by vapor deposition polymerization of CN onto a fluorine-doped tin oxide (FTO) glass slide. b The laser rapidly heats, melts, and transfers the donor material. At the same time, the decomposition temperature of the metal precursor is reached and TMO structures are formed. c After a short rinsing with acetone, the TMO/CN composite film is ready.

Mitigation of Electromigration in Metal Interconnects via Hexagonal Boron Nitride as an Ångström‐Thin Passivation Layer

by Yunjo Jeong, Ossie Douglas, Utkarsh Misra, Md Rubayat‐E Tanjil, Kenji Watanabe, Takashi Taniguchi, Michael Cai Wang in Advanced Electronic Materials

University of South Florida researchers recently developed a novel approach to mitigating electromigration in nanoscale electronic interconnects that are ubiquitous in state-of-the-art integrated circuits. This was achieved by coating copper metal interconnects with hexagonal boron nitride (hBN), an atomically-thin insulating two-dimensional (2D) material that shares a similar structure as the “wonder material” graphene.

Electromigration is the phenomenon in which an electrical current passing through a conductor causes the atomic-scale erosion of the material, eventually resulting in device failure. Conventional semiconductor technology addresses this challenge by using a barrier or liner material, but this takes up precious space on the wafer that could otherwise be used to pack in more transistors. USF mechanical engineering Assistant Professor Michael Cai Wang’s approach accomplishes this same goal, but with the thinnest possible materials in the world, two-dimensional (2D) materials.

“This work introduces new opportunities for research into the interfacial interactions between metals and ångström-scale 2D materials. Improving electronic and semiconductor device performance is just one result of this research. The findings from this study opens up new possibilities that can help advance future manufacturing of semiconductors and integrated circuits,” Wang said. “Our novel encapsulation strategy using single-layer hBN as the barrier material enables further scaling of device density and the progression of Moore’s Law.” For reference, a nanometer is 1/60,000 of the thickness of human hair, and an ångström is one-tenth of a nanometer. Manipulating 2D materials of such thinness requires extreme precision and meticulous handling.

In their recent study copper interconnects passivated with a monolayer hBN via a back-end-of-line (BEOL) compatible approach exhibited more than 2500% longer device lifetime and more than 20% higher current density than otherwise identical control devices. This improvement, coupled with the ångström-thinness of hBN compared to conventional barrier/liner materials, allows for further densification of integrated circuits. These findings will help advance device efficiency and decrease energy consumption.

“With the growing demand for electric vehicles and autonomous driving, the demand for more efficient computing has grown exponentially. The promise of higher integrated circuits density and efficiency will enable development of better ASICs (application-specific integrated circuits) tailored to these emerging clean energy needs.” explained Yunjo Jeong, an alumnus from Wang’s group and first author of the study.

An average modern car has hundreds of microelectronic components, and the significance of these tiny but critical components has been especially highlighted through the recent global chip shortage. Making the design and manufacturing of these integrated circuits more efficient will be key to mitigating possible future disruptions to the supply chain. Wang and his students are now investigating ways to speed up their process to the fab scale.

“Our findings are not limited only to electrical interconnects in semiconductor research. The fact that we were able to achieve such a drastic interconnect device improvement implies that 2D materials can also be applied to a variety of other scenarios.” Wang added.

Golden Vaterite as a Mesoscopic Metamaterial for Biophotonic Applications

by Roman E. Noskov et al, in Advanced Materials

In a breakthrough in metamaterials, for the first time in the world, researchers at Tel Aviv University have developed an innovative nanotechnology that transforms a transparent calcite nanoparticle into a sparkling gold-like particle. In other words, they turned the transparent particle into a particle that is visible despite its very small dimensions. According to the researchers the new material can serve as a platform for innovative cancer treatments.

In a new paper an international team of scientists, coordinated by Dr. Roman Noskov and Dr. Pavel Ginzburg from the Iby and Aladar Fleischman Faculty of Engineering at Tel Aviv University, Prof. Dmitry Gorin from the Center for Photonics and Quantum Materials at the Skolkovo Institute of Science and Technology (Skoltech) and Dr. Evgeny Shirshin from M.V. Lomonosov Moscow State University, has introduced the concept of biofriendly delivery of optical resonances via a mesoscopic metamaterial, a material with properties that are not found in nature. This approach opens promising prospects for multifunctionality in biomedical systems, allowing the use of a single designer-made nanoparticle for sensing, photothermal therapy, photoacoustic tomography, bioimaging, and targeted drug delivery.

“This concept is the result of cross-disciplinary thinking at the interface between the physics of metamaterials and bioorganic chemistry, aiming to meet the needs of nanomedicine. We were able to create a mesoscopic submicron metamaterial from biocompatible components that demonstrates strong Mie resonances covering the near-infrared spectral window in which biological tissues are transparent,” says Dr. Roman Noskov.

The nanostructures capable of nanoscale light localization as well as performing several functions are highly desirable in a plethora of biomedical applications. However, biocompatibility is typically a problem, as engineering of optical properties often calls for using toxic compounds and chemicals. The researchers have resolved this issue by employing gold nanoseeds and porous vaterite (calcium carbonate) spherulites, currently considered promising drug-delivery vehicles. This approach involves controllable infusion of gold nanoseeds into a vaterite scaffold resulting in a mesoscopic metamaterial — golden vaterite — whose resonance properties can be widely tuned by changing the quantity of gold inside the vaterite. Additionally, high payload capacity of vaterite spherulites allows simultaneous loading of both drugs and fluorescent tags. To exemplify the performance of their system, the researchers demonstrated efficient laser heating of golden vaterite at red and near-infrared wavelengths, highly desirable in photothermal therapy, and photoacoustic tomography.

Prof. Pavel Ginzburg summarizes, “This novel platform enables the accommodation of multiple functionalities — as simple add-ons that can be introduced almost on demand. Alongside optical imaging and thermotherapy, MRI visibility, functional biomedical materials and many other modalities can be introduced within a miniature nano-scale particle. I believe that our collaborative efforts will lead to in-vivo demonstrations, which will pave the way for a new biomedical technology.”

Carbon-Based Nanomaterials: Promising Antiviral Agents to Combat COVID-19 in the Microbial-Resistant Era

by Ángel Serrano-Aroca et al, in ACS Nano

Professor Ángel Serrano, principal investigator at the Biomaterials and Bioengineering Laboratory of the Catholic University of Valencia (UCV), recently published an article in journal ACS Nano, from the American Chemical Society, which shows that carbon-based nanomaterials (CBNs) with low or zero toxicity for humans, are “promising treatments” against the pneumonia caused by COVID-19, as well as other viruses, bacteria and fungi, including those that are multi-resistant to medicines.

Serrano and his fellow researchers from the group have reviewed scientific literature on the antiviral activity and broad-spectrum antimicrobial properties of carbon-based nanomaterials such as fullerene, carbon dots, graphene and its by-products. In their research, they have verified that CBNs have antiviral activity against 13 positive single-stranded RNA viruses, including SARS-CoV-2.

As well as its broad-spectrum antimicrobial activity, biocompatibility, biodegradability and ability to induce tissue regeneration, the mode of action of CBNs is “mainly physical” and is characterized by a low risk of antimicrobial resistance.

Research in this field is of vital importance given the urgent need for therapeutic options against COVID-19. The treatments proposed against the viral pneumonia and acute respiratory syndrome connected to this disease have heretofore shown little or no effect in clinical practice.

The situation is worsened mainly because bacterial pathogens can significantly exacerbate the pneumonia caused by this coronavirus. Antibiotic resistance in treating the pneumonia is increasing at an alarming rate, which is why new-generation treatments such as the ones proposed in this study “can provide a lasting solution.”

General panorama for external propagated and differentiated mesenchymal stem cells (MSCs) or internal induction of many tissues containing MSCs by CBNs (G: graphene, GO: graphene oxide, F: fullerene, CDs: carbon dots, or CNT: carbon nanotubes). MSCs have various roles in COVID-19 and/or recovered patients through secretion and modulation of physiological and immunological networks. SARS-CoV-2 infection causes many pathophysiological changes such as tissue inflammation, immune system damages (leukopenia, lymphopenia), respiratory microstructure and distal organ injury and secondary infections, and microvascular system damage. CBNs in combination with MSCs have the potential to target these pathophysiological events, acting as an alternative strategy for treating COVID-19 patients.

Cupric Oxide Coating That Rapidly Reduces Infection by SARS-CoV-2 via Solids

by Mohsen Hosseini et al, in ACS Applied Materials & Interfaces

Materials scientists from Nanyang Technological University, Singapore (NTU Singapore) have developed a reusable “nanotech mask” that can filter out 99.9 percent of bacteria, viruses and particulate matter (PM), as well as kill bacteria.

Its novel antimicrobial coating kills bacteria within 45 seconds and is effective for at least 144 hours (six days). Its filtration efficiency surpasses those of N95 masks (95 percent filtration of PM0.3) and can be washed and reused over 10 times.

The N95 prototype mask made with dielectric fabric, with bottles of copper nanoparticles of various colours in the background. Credit: Nanyang Technological University

In mid-May, Singapore tightened its COVID-19 measures as the country was facing an increase in the number of infections, and the population was advised to use face masks with high filtration capability to help curb the spread of the coronavirus.

The made-in-NTU mask comprises two key components: an antimicrobial coating made from copper nanoparticles developed and patented by Professor Lam Yeng Ming, coated on a fabric mask invented by Associate Professor Liu Zheng, which has a unique dielectric property that attracts all nanoparticles and germs.

Prof Lam, who is also the Chair of NTU’s School of Materials Science and Engineering, said their mask prototype combines the two most desired properties needed to fight COVID-19, into a single filter.

“In experiments, our copper nanoparticle coating has an extremely fast and sustained antibacterial activity, with a killing efficiency of up to 99.9 percent when it meets multi-drug resistant bacteria. This coating will help to reduce the spread of bacteria as it kills microbes in droplets trapped by the mask fibers, which provide excellent filtration efficiency. This should give users a double layer of protection compared to conventional surgical masks,” explained Prof Lam.

Experiments on the antibacterial effectiveness of the mask were conducted in collaboration with scientists from the National University of Singapore (NUS). They simulated real-life conditions by introducing multi-drug resistant bacteria in droplet form onfabric surfaces and observed that almost all the bacteria were dead by 45 seconds.

The reason for the effectiveness of the antimicrobial coating was two-fold: the first is the extremely small size of the nanoparticles, which are about 1,000 times smaller than the width of a human hair. Collectively, millions of nanoparticles provide a huge surface area for the viruses and bacteria to contact, compared to bigger particles.

The second is the high level of oxidative damage caused by the copper oxide material. Copper oxide induces the generation of reactive oxygen species, resulting in DNA damage of important cell structures in the bacteria, such as the cell membrane, severely damaging it and causing the bacteria to die.

To make it easy to apply, the antimicrobial nanoparticle solution is designed to be spray-coated on all soft and hard surfaces.

Various peer-reviewed studies have shown that copper oxide is effective in killing viruses, such as the recent study by The University of Hong Kong and Virginia Tech, where door handles were coated with a layer of copper oxide material.

The NTU team tested their nanoparticle coating in harsh conditions for120 washing cycles(inthe presence of soap or its active componentsat 45 degC) and found that there was almost no copper loss — posing very little risk of toxicity to humans.

The nanoparticles are also bonded to the fibers within the mask, so there is no contact with human skin when the mask is worn. Killing viruses and bacteria would only work if the mask is able to trap and stop them from passing through. This is where Assoc Prof Liu’s breakthrough came in handy.

Last year, his team developed a way to integrate dielectric materials to plastic fibers during the manufacturing process of an unwoven fabric filter made from Polypropylene (PP), commonly used in disposable surgical masks used by hospitals. This was done in collaboration with Prof Guan Li from the Renmin University of China.

The dielectric materials have excellent electrostatic capabilities, which can attract and bind to particles possessing a negative or positive charge, similar to how magnets attract metal particles.

Made from fibers with a diameter of 200 to 300 nanometres, the mask has a higher surface area that lowers the breathing resistance — making it easy for its wearer to breathe as compared to conventional N95 respirators, which are denser.

In tests, the next-generation dielectric composite fabric had 50 percent higher filtration efficiency than pure PP masks, which are commonly rated at 95 percent BFE (Bacterial Filtration Efficiency).

Assoc Prof Liu said: “With our new composite filter, we can achieve up to 99.9 percent BFE, trapping almost all microbes and particulate matter from smoke or haze. Its filtration efficiency surpasses a N95 mask but allows the wearer to breathe much easier. More importantly, it can be mass-produced easily using the current production process. It is also washable for more than 10 times before losing filtration efficiency, making it more sustainable than current one-use disposable masks.”

In experiments, the mask was able to attract and trap a broad range of particulate matter: from PM10 (average particle size of 10 microns) to PM0.3 (0.3 microns — about 0.3 percent the diameter of a human hair) with a filtration efficiency of 99.9 percent.

The antimicrobial coating has a patent filed through NTU’s enterprise and innovation company, NTUitive, and Prof Lam’s team is already working with a local company to coat it on their products.

Strain Engineering: Tip‐Induced Nano‐Engineering of Strain, Bandgap, and Exciton Funneling in 2D Semiconductors

by Yeonjeong Koo et al, in Advanced Materials

A research team, led by Professor Kyoung-Duck Park in the Department of Physics at UNIST has succeeded in investigating and controlling the physical properties of naturally-formed nanoscale wrinkles in two-dimensional (2D) semiconductors. This is thanks to their previously-developed hyperspectral adaptive tip-enhanced photoluminescence (a-TEPL) spectroscopy. This will be a major step forward in developing paper-thin, ultra-flexible displays.

Schematic diagram of a-TEPL spectroscopy based on shear-force AFM using bottom-illumination optics with a 632.8 nm He/Ne laser. Credit: UNIST

Wrinkles are an inevitable structural deformation in 2D semiconductor materials, which gives rise to spatial heterogeneity in material properties, according to the research team. Such structural deformation has long been considered one of the top technical challenges in semiconductor manufacturing, as this would harm the uniformity in structural, electrical, and optical properties of semiconductors. Besides, because the size of these wrinkles is quite small, the accurate analysis of their structural, optical, and excitonic properties has been impossible with conventional spectroscopic tools. “Recent strain-engineering approaches have enabled to tune of some of these properties, yet there has been no attempt to control the induced strain of naturally-formed nanoscale wrinkles, while simultaneously investigating their modified nano-optical properties,” noted the research team.

In this study, the research team presented a hyperspectral TEPL nano-imaging approach, combined with nano-optomechanical strain control, to investigate and control the nano-optical and -excitonic properties of naturally-formed wrinkles in a WSe2 ML. This approach allowed them to reveal the modified electronic properties and exciton behaviors at the wrinkle, associated with the induced uniaxial tensile strain at the apex. Based on this, the research team was able to exploit the wrinkle structure as a nanoscale strain-engineering platform. The precise atomic force tip control also enabled them to engineer the excitonic properties of TMD MLs at the nano-local regions in a fully reversible fashion, noted the research team.

Schematic image, describing the characteristics of a-TEPL spectroscopy. Credit: UNIST

The research team further presented a more systematic platform for dynamic nano-emission control of the wrinkle by demonstrating programmably-operational switching and modulation modes in time and space. “We envision that our approach gives access to potential applications in quantum-nanophotonic devices, such as bright nano-optical sources for light-emitting diodes, nano-optical switch/multiplexer for optical integrated circuits, and exciton condensate devices,” said the research team.

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