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Category: nanotechnology – Page 121

Macroscopic photonic single crystals via seeded growth of DNA-coated colloids

DNA-programmed self-assembly leverages the chemical specificity of DNA hybridization to stabilize user-prescribed crystal structures1,2. Pioneering studies have demonstrated that DNA hybridization can guide the self-assembly of a wide variety of nanoparticle crystal lattices, which can grow to micrometer dimensions and contain millions of particles3,4,5,6,7,8,9. Attention has now turned toward the goal of assembling photonic crystals from optical-scale particles (i.e., roughly 100‑1000 nm in diameter)10,11,12 using DNA-programmed interactions. To this end, progress over the past decade has established that DNA can indeed program the self-assembly of bespoke crystalline structures from micrometer-sized colloidal particles13,14,15,16,17,18,19. However, growing single-domain crystals comprising millions of DNA-functionalized, micrometer-sized colloidal particles remains an unresolved barrier to the development of practical technologies based on DNA-programmed assembly. Prior efforts have yielded either single-domain crystals no more than a few dozen micrometers in size13,14,15,16 or larger polycrystalline materials with heterogeneous domain sizes12,15,17,20. These features—small crystal domains, polycrystallinity, and size dispersity—have therefore precluded the use of DNA-coated colloidal crystals in photonic metamaterial applications.

Assembling macroscopic materials from DNA-functionalized, micrometer-sized colloids is challenging due to the vastly different length scales between the DNA molecules and the colloidal particles (Fig. 1a). This combination leads to crystallization kinetics that are extremely sensitive to temperature and prone to kinetic trapping1,21,22,23. The resulting challenges are both practical and fundamental in nature. For example, recent work has shown that crystal nucleation rates can vary by orders of magnitude over a temperature range of only 0.25 °C19. Extremely precise temperature control would therefore be required to self-assemble single-domain crystals from a bulk solution (Fig. 1b). At the same time, annealing polycrystalline materials is difficult due to the combination of the short-range attraction and the friction arising from the DNA-mediated colloidal interactions, which slows the rolling and sliding of colloidal particles at crystalline interfaces15,19,24,25.

Challenging Conventional Wisdom: New Discovery Transforms Our Understanding of Crystals

For many, the word “crystals” conjures images of shimmering suncatchers that create a prism of rainbow colors or semi-transparent stones thought to possess healing abilities. But in the realm of science and engineering, crystals take on a more technical definition. They’re perceived as materials whose components – be it atoms, molecules, or nanoparticles –are arranged regularly in space. In other words, crystals are defined by the regular arrangement of their constituents. Familiar examples include diamonds, table salt, and sugar cubes.

Superconducting-nanowire Single-photon Camera with 400,000 Pixels Will Explore Brain cells, space

A team at the National Institute of Standards and Technology in Boulder, Colorado, has reported the successful implementation of a 400,000 pixel superconducting nanowire single-photon detector (SNSPD) that they say will pave the way for the development of extremely light-sensitive large-format superconducting cameras. The camera will also prove invaluable for those doing medical research, where the ability to examine organs such as the brain without disturbing tissue is critical.

Superconducting detectors operate at very low temperatures and generate a minimum of excess noise, making them ideal for testing the non-local nature of reality, investigating dark matter, mapping the early universe, and performing quantum computation and communication. Previously there were no large-scale superconducting cameras – even the largest demonstrations have never exceeded 20 thousand pixels.

This was especially true for one of the most promising detector technologies, the superconducting nanowire single-photon detector (SNSPD). These detectors have been demonstrated with system detection efficiencies of 98.0%, sub-3-ps timing jitter, sensitivity from the ultraviolet (250nm) to the mid-infrared (10um), and dark count rates below 6.2e-6 counts per second (cps), but despite more than two decades of development they have never achieved an array size larger than a kilopixel. Here, we report on the implementation and characterization of a 400,000 pixel SNSPD camera, a factor of 400 improvement over the previous state-of-the-art. The array spanned an area 4×2.5 mm with a 5x5um resolution, reached unity quantum efficiency at wavelengths of 370 nm and 635 nm, counted at a rate of 1.1e5 cps, and had a dark count rate of 1e-4 cps per detector (corresponding to 0.13 cps over the whole array).

Light-activated molecular machines get cells ‘talking’

One of the main ways cells “talk” to each other to coordinate essential biological activities such as muscle contraction, hormone release, neuronal firing, digestion and immune activation is through calcium signaling.

Rice University scientists have used light-activated molecular machines to trigger intercellular calcium wave signals, revealing a powerful new strategy for controlling cellular activity, according to a new study published in Nature Nanotechnology. This technology could lead to improved treatments for people with , digestive issues and more.

“Most of the drugs developed up to this point use chemical binding forces to drive a specific signaling cascade in the body,” said Jacob Beckham, a chemistry graduate student and lead author on the study. “This is the first demonstration that, instead of chemical force, you can use —induced, in this case, by single-molecule nanomachines—to do the same thing, which opens up a whole new chapter in drug design.”

Quantum plasmonics with dressing EM fields: Advancing the design of nanoscale integrated circuits

Envision a realm where light can be meticulously controlled and manipulated at minuscule scales, unlocking unprecedented potentials for nanotechnology and quantum information technology. Recent breakthroughs in quantum research have propelled us closer to a reality that may be more achievable than previously realized.

In this article, we delve into the domain of surface plasmon polaritons (SPPs) and the vast possibilities they offer in revolutionizing the field of quantum optics.

Picture a serene lake on a sunny day. As you drop a small stone into the water, it sets in motion gentle ripples that traverse the surface. Now, imagine light as akin to those undulating ripples. When light encounters the interface of a metal and a dielectric material, it has the power to generate waves, much like the ripples on the lake. This phenomenon is even more intriguing because these light waves can interact with the metal’s microscopic constituents, such as electrons. Remarkably, the light waves and electrons synchronize their oscillations, giving rise to an SPP wave.

Jean-Pierre Sauvage, Nobel Laureate in Chemistry: ‘Work is being done on machines that will travel through the blood to kill cancer’

Last year, the chemist – who is an emeritus professor at the University of Strasbourg – published a book titled The Elegance of Molecules. In the pages, he lets his imagination run wild. “Over time, most of the chemical reactions that govern nature could be controlled or imitated by a nanorobot: counter-offensives by the immune system, the production of antibodies, hormones on demand, the repairing of damaged cells and organs [or] the correction of anomalies in the genetic text,” Sauvage writes. “None of this will belong in the realm of science fiction in the long-term.”

Sitting in the hotel’s restaurant, however, the researcher’s realism contrasts with his futuristic fantasy. “Today, we can’t do much. Molecular machines are a somewhat new concept: we can make molecules that move as we choose [and] we can make a fairly complex molecule perform a rotary motion. Or we can make it behave like a muscle, stretching and contracting. The applications will arrive in the future, but we’re not there yet,” he stresses.

The French researcher has been developing these molecular muscles since 2002 alongside a Spanish chemist – María Consuelo Jiménez – from the Polytechnic University of Valencia. “The first thing was to show that we can make a molecule that contracts and stretches. Now, you can think of making materials – especially fibers – that can contract and stretch. Perhaps artificial muscles could be made to replace damaged muscles in people, but that will be in the future. At the moment, there are no real applications,” Sauvage clarifies.

Optoelectronics Nanotechnology Innovation: MIT Grows Precise Arrays of nanoLEDs

A new technique produces perovskite nanocrystals right where they’re needed, so the exceedingly delicate materials can be integrated into nanoscale.

The nanoscale refers to a length scale that is extremely small, typically on the order of nanometers (nm), which is one billionth of a meter. At this scale, materials and systems exhibit unique properties and behaviors that are different from those observed at larger length scales. The prefix “nano-” is derived from the Greek word “nanos,” which means “dwarf” or “very small.” Nanoscale phenomena are relevant to many fields, including materials science, chemistry, biology, and physics.

Scientists track nanoscale processes of CRISPR-Cas complexes

Scientists at Leipzig University, in collaboration with colleagues at Vilnius University in Lithuania, have developed a new method to measure the smallest twists and torques of molecules within milliseconds. The method makes it possible to track the gene recognition of CRISPR-Cas protein complexes, also known as “genetic scissors”, in real time and with the highest resolution. With the data obtained, the recognition process can be accurately characterised and modelled to improve the precision of the genetic scissors. The results obtained by the team led by Professor Ralf Seidel and Dominik Kauert from the Faculty of Physics and Earth Sciences have now been published in the prestigious journal Nature Structural and Molecular Biology.

When bacteria are attacked by a virus, they can defend themselves with a mechanism that fends off the genetic material introduced by the intruder. The key is CRISPR-Cas protein complexes. It is only in the last decade that their function for adaptive immunity in microorganisms has been discovered and elucidated. With the help of an embedded RNA, the CRISPR complexes recognize a short sequence in the attacker’s DNA. The mechanism of sequence recognition by RNA has since been used to selectively switch off and modify genes in any organism. This discovery revolutionized genetic engineering and was already honored in 2020 with the Nobel Prize in Chemistry awarded to Emmanuelle Charpentier and Jennifer A. Doudna.

Occasionally, however, CRISPR complexes also react to gene segments that differ slightly from the sequence specified by the RNA. This leads to undesirable side effects in medical applications. “The causes of this are not yet well understood, as the process could not be observed directly until now,” says Dominik Kauert, who worked on the project as a PhD student.

Dr. Khalid Salaita, PhD — Emory University — Developing Novel DNA-Based Mechano-Technologies

Developing Novel DNA-Based Mechano-Technologies For Human Health — Dr. Khalid Salaita, Ph.D. — Emory University

Dr. Khalid Salaita, Ph.D. (https://www.salaitalab.com/salaita) is a Professor of Chemistry at Emory University in Atlanta, Georgia (USA), program faculty in the Department of Biomedical Engineering at Georgia Tech and Emory, program member of Cancer Cell Biology at Winship Cancer Institute, and most recently is the recent winner Future Insight Prize given by Merck KGaA, Darmstadt, Germany (https://www.emdgroup.com/en/research/open-innovation/futurei…aming.html) for his cutting edge work in the area of mechanobiology.

Dr. Salaita earned his B.S. in Chemistry, from Old Dominion University, his Ph.D. in Chemistry from Northwestern University, completed a postdoctoral fellowship in the Department of Chemistry at the University of California, Berkeley, and then started his own lab at Emory University, investigating the interface between living systems and engineered nanoscale materials. To achieve this goal, his group has pioneered the development of tools like molecular force sensors, DNA mechano-technology, smart therapeutics, and nanoscale mechanical actuators to help manipulate living cells.

In recognition of his work, Dr. Salaita has received a number of awards, most notably: the Alfred P. Sloan Research Fellowship, the Camille-Dreyfus Teacher Scholar award, the National Science Foundation Early CAREER award, and the Kavli Fellowship.

Dr. Salaita is currently a member of the Enabling Bioanalytical and Imaging Technologies (EBIT) study Section and an Associate Editor of Smart Materials. His program has been supported by NSF, NIH, and DARPA.

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