Yolk-Shell Nanocrystals with Movable Gold Yolk: Next Generation of Photocatalysts

The synthesis of yolk-shell nanostructures involves sulfidation on an Au@Cu2O core-shell nanocrystal template to convert the shell composition to various metal sulphides.
Credit: Tokyo Institute of Technology

Owing to their unique permeable, hollow shell structures with inner, movable cores, yolk-shell nanocrystals are suitable for a wide variety of applications. Yolk-shell nanocrystals consisting of a gold core with various semiconductor shells have been developed by Tokyo Tech researchers, using a novel sequential ion-exchange process. These metal-semiconductor yolk-shell nanocrystals can serve as highly effective photocatalysts for many applications.

Yolk-shell nanocrystals are unique materials with fascinating structural properties, such as a permeable shell, interior void space, and movable yolk. These nanocrystals are suitable for a variety of applications, depending on the choice of materials used for their fabrication.

For example, if the inner surface of their shells are reflective, yolk-shell nanocrystals can make for a reliable photovoltaic device. A mobile core can can act as a stirrer, capable of mixing solutions held within the shell. The inner and outer surfaces of the shell provide plenty of active sites for reactions, and the yolk-shell structure's fascinating properties (a result of electronic interactions and charge-transfer between the surfaces of the structure) make these nanocrystals ideal for photocatalysis applications. Understandably, yolk-shell nanocrystals have earned the attention of researchers worldwide.

New nanoparticles aid sepsis treatment in mice

Shaoqin “Sarah” Gong
Source: University of Wisconsin–Madison

Sepsis, the body’s overreaction to an infection, affects more than 1.5 million people and kills at least 270,000 every year in the U.S. alone. The standard treatment of antibiotics and fluids is not effective for many patients, and those who survive face a higher risk of death.

In new research published in the journal Nature Nanotechnology today, the lab of Shaoqin “Sarah” Gong, a professor with the Wisconsin Institute for Discovery at the University of Wisconsin–Madison, reported a new nanoparticle-based treatment that delivers anti-inflammatory molecules and antibiotics.

The new system saved the lives of mice with an induced version of sepsis meant to serve as a model for human infections, and is a promising proof-of-concept for a potential new therapy, pending additional research.

The new nanoparticles delivered the chemical NAD+ or its reduced form NAD(H), a molecule that has an essential role in the biological processes that generate energy, preserve genetic material and help cells adapt to and overcome stress. While NAD(H) is well known for its anti-inflammatory function, clinical application has been hindered because NAD(H) cannot be taken up by cells directly.

“To enable clinical translation, we need to find a way to efficiently deliver NAD(H) to the targeted organs or cells. To achieve this goal, we designed a couple of nanoparticles that can directly transport and release NAD(H) into the cell, while preventing premature drug release and degradation in the bloodstream,” says Gong, who also holds appointments in the Department of Biomedical Engineering and the UW School of Medicine and Public Health’s Department of Ophthalmology and Visual Sciences.

The interdisciplinary work was led by Gong along with Mingzhou Ye and Yi Zhao, two postdoctoral fellows in the Gong lab. John-Demian Sauer, a professor in the Department of Medical Microbiology and Immunology, also collaborated on the project.

Making colors out of gold and DNA

In this experiment, the gel is being activated by a red LED before the researchers measure the light it transmits.
Photo: Joonas Ryssy

Folk belief says there’s a pot of gold at the end of the rainbow, but a new technology is turning that idea on its head – using particles of gold to make colors. With further work, the method developed at Aalto University could herald a new display technology.

The technique uses gold nanocylinders suspended in a gel. The gel only transmits certain colors when lit by polarized light, and the color depends on the orientation of the gold nanocylinders. In a clever twist, a collaboration led by Anton Kuzyk’s and Juho Pokki’s research groups used DNA molecules to control the orientation of gold nanocylinders in the gel.

‘DNA isn’t just an information carrier – it can also be a building block. We designed the DNA molecules to have a certain melting temperature, so we could basically program the material,’ says Aalto doctoral candidate Joonas Ryssy, the study’s lead author. When the gel heats past the melting temperature, the DNA molecules loosen their grip and the gold nanocylinders change orientation. When the temperature drops, they tighten up again, and the nanoparticles go back to their original position.

A unique catalyst paves the way for plastic upcycling

Visual of two variations of the catalyst, with a segment of the shell removed to show the interior. The white sphere represents the silica shell, the holes are the pores. The bright green spheres represent the catalytic sites, the ones on the left are much smaller than the ones on the right. The longer red strings represent the polymer chains, and the shorter strings are products after catalysis. All shorter strings are similar in size, representing the consistent selectivity across catalyst variations. Additionally, there are smaller chains produced by the smaller catalyst sites because the reaction occurs more quickly.
Credit: Ames Laboratory

A recently developed catalyst for breaking down plastics continues to advance plastic upcycling processes. In 2020, a team of researchers led by Ames Laboratory scientists developed the first processive inorganic catalyst to deconstruct polyolefin plastics into molecules that can be used to create more valuable products. Now, the team has developed and validated a strategy to speed up the transformation without sacrificing desirable products.

The catalyst was originally designed by Wenyu Huang, a scientist at Ames Lab. It consists of platinum particles supported on a solid silica core and surrounded by a silica shell with uniform pores that provide access to catalytic sites. The overall amount of platinum needed is quite small, which is important because of platinum's high cost and limited supply. During deconstruction experiments, the long polymer chains thread into the pores and contact the catalytic sites, and then the chains are broken into smaller sized pieces that are no longer plastic material (see image for more details).

Secret to treating ‘Achilles’ heel’ of alternatives to silicon solar panels revealed

Solar panels 
Credit: Alachua County

The researchers used a combination of techniques to mimic the process of aging under sunlight and observe changes in the materials at the nanoscale, helping them gain new insights into the materials, which also show potential for optoelectronic applications such as energy-efficient LEDs and X-ray detectors, but are limited in their longevity.

Their results, reported in the journal Nature, could significantly accelerate the development of long-lasting, commercially available perovskite photovoltaics.

Perovksites are abundant and much cheaper to process than crystalline silicon. They can be prepared in liquid ink that is simply printed to produce a thin film of the material.

While the overall energy output of perovskite solar cells can often meet or – in the case of multi-layered ‘tandem’ devices – exceed that achievable with traditional silicon photovoltaics, the limited longevity of the devices is a key barrier to their commercial viability.

A typical silicon solar panel, like those you might see on the roof of a house, typically lasts about 20-25 years without significant performance losses.

In the heat of the wound

Empa researcher Fei Pan is working on a membrane made of nanofibers that releases medication only when the material heats up. Such a membrane could, for example, become active in a bandage as soon as inflammation starts.
Image: Empa

A bandage that releases medication as soon as an infection starts in a wound could treat injuries more efficiently. Empa researchers are currently working on polymer fibers that soften as soon as the environment heats up due to an infection, thereby releasing antimicrobial drugs.

It is not possible to tell from the outside whether a wound will heal without problems under the dressing or whether bacteria will penetrate the injured tissue and ignite an inflammation. To be on the safe side, disinfectant ointments or antibiotics are applied to the wound before the dressing is applied. However, these preventive measures are not necessary in every case. Thus, medications are wasted and wounds are over-treated.

Even worse, the wasteful use of antibiotics promotes the emergence of multi-resistant germs, which are an immense problem in global healthcare. Empa researchers at the two Empa laboratories Biointerfaces and Biomimetic Membranes and Textiles in St. Gallen wants to change this. They are developing a dressing that autonomously administers antibacterial drugs only when they are really needed.

The idea of the interdisciplinary team led by Qun Ren and Fei Pan: The dressing should be "loaded" with drugs and react to environmental stimuli. "In this way, wounds could be treated as needed at exactly the right moment," explains Fei Pan. As an environmental stimulus, the team chose a well-known effect: the rise in temperature in an infected, inflamed wound.