#dendrimers

In research that could lead to a new age in illumination, researchers from Japan and Germany have developed an eco-friendly light-emitting electrochemical cells using new molecules called dendrimers combined with biomass derived electrolytes and graphene-based electrodes. Their findings were published in the journal Advanced Functional Materials. Electroluminescence is the phenomenon where a material emits light in response to a passing electric current. Everything from the screen you're using to read this sentence to the lasers used in cutting edge scientific research are results of the electroluminescence of different materials. Due to its ubiquity and necessity in the modern age, it is only natural that extensive resources go into research and development to make this technology better. "One such example of an emerging technology is 'light-emitting electrochemical cells' or LECs," explains Associate Professor Ken Albrechtfrom Kyushu University's Institute for Materials Chemistry and Engineering and one of the leads of the study. "They have been attracting attention because of their cost advantage over organic light emitting diodes, or OLEDs. Another reason for LECs popularity is their simplified structure."

Improved method to make branched polymers

Branched polymers, polymers that look like tiny tree branches, have significant potential for water filtration, the biomedical field, nanoelectronics, and other applications. Researchers have now come up with a better way for efficiently creating these unique structures.

Led by the lab of Mingjiang Zhong, assistant professor of chemical and environmental engineering and chemistry, the study is now published in Chem.

Polymers, which are made of repeat units of small molecules to form a larger molecule, have various structures. Zhong focuses on developing polymers with branches, or side chains, that bear their own branches. A polymer structure with a higher degree of branching means that it has a greater density of functionality without taking up more room.

A few years ago, Zhong developed a process for making these structures, also known as dendritic polymers. Their potential was limited, though, by the small-scale and moderate-efficiency process of synthesizing them. Now, with a combination of mechanistic experiments and computer simulations, his lab can make them more efficiently and with more control. With this process, they can be developed in an industry environment. It's a necessary step toward taking these polymers beyond fundamental research and into use for practical applications.  

Scientists publish a complete overview of sulfonimide dendrimers

A research team from the Skoltech Center for Design, Manufacturing and Materials (CDMM) has prepared a comprehensive overview of research on a family of sulfonimide dendrimers that holds promise for optics, photonics, and surface functionalization of materials.

The paper, titled "Sulfonimide-Based Dendrimers: Progress in Synthesis, Characterization, and Potential Applications," was published in the Polymers journal.

There are over 50 dendrimer families, of which some are well studied and amply described in the literature. Some dendrimers are already marketed under various brand names and used in medical applications, while others, such as sulfonimide dendrimers, show great potential for further research and application. Sulfonimide dendrimers are chemically stable, crystalline, and non-toxic, and have a high melting point (120-250 °C) and a high glass transition temperature (135-162 °C). Besides this, they are biologically compatible with the human body, which makes them promising drug carriers and contrast agents. Their most remarkable advantage is that their desired properties are easily attained by making the right design and attaching various functional chemical groups onto a dendrimer's surface. Thanks to their valuable properties and easy modification, dendrimers can be used in organic synthesis, materials science, and biomedical chemistry.

Smaller than ever—exploring the unusual properties of quantum-sized materials

The development of functional nanomaterials has been a major landmark in the history of materials science. Nanoparticles with diameters ranging from 5 to 500 nm have unprecedented properties, such as high catalytic activity, compared to their bulk material counterparts. Moreover, as particles become smaller, exotic quantum phenomena become more prominent. This has enabled scientists to produce materials and devices with characteristics that had been only dreamed of, especially in the fields of electronics, catalysis, and optics.

But what if we go smaller? Sub-nanoparticles (SNPs) with particle sizes of around 1 nm are now considered a new class of materials with distinct properties due to the predominance of quantum effects. The untapped potential of SNPs caught the attention of scientists from Tokyo Tech, who are currently undertaking the challenges arising in this mostly unexplored field. In a recent study published in the Journal of the American Chemical Society, a team of scientists from the Laboratory of Chemistry and Life Sciences, led by Dr. Takamasa Tsukamoto, demonstrated a novel molecular screening approach to find promising SNPs.

Development of a 3-D titanium-based structure to improve bone implants

A research team from the University of Malaga, the Andalusian Centre for Nanomedicine and Biotechnology-BIONAND, the Canary Islands Technological Institute, the company Osteobionix, and the CIBER (Networking Centre for Biomedical Research) has developed a coating for titanium prostheses based on 3-D branching polymers which can incorporate substances that facilitate bonding with the bone. This mechanism facilitates bone cell recognition of the implant, thus improving osseointegration and preventing both rejection and wear of the bone mass and the implant itself.

The result is a titanium implant coated with a three-dimensional branching nanostructure, called dendrimer, which acts as a bridge between the titanium and the bone and which also carries substances that facilitate the formation of new tissue onto the prosthesis surface. This ensures that the healthy component binds to the prosthesis making the fixation occur in a natural way, more stable and longer lasting than in the current ones.

The method proposed by the researchers in the article "Dendritic Scaffold onto Titanium Implants. A Versatile Strategy Increasing Biocompatibility," published in the journal Polymers, confers specific features to the implants, since they have a more homogeneous structure with greater integrity, which causes less wear. It also offers the possibility of controlling its composition for the administration of specific drugs in order to avoid rejections and infections.

The advances in optical devices that we expect as consumers must be supported by the development of new materials. Microcrystallites of luminescent organic compounds can act as tiny laser sources for such devices, for example for use in displays and other components. Dendrimers offer numerous advantages as luminescent materials, however so far they have not been used as microcrystallites owing to their fragility and poor crystallinity. Now a team of researchers has produced dendrimers that form robust crystals with lasing properties. Their findings are published in Angewandte Chemie.

Dendrimers are polymers that grow out from a core through the addition of small molecules to form extended branches -- which explains their name, derived from the Greek word for tree. Dendrimers have many advantages that make them interesting luminescent materials. They are highly soluble, which makes them easy to incorporate into systems; they have high quantum yields, meaning you get a lot of the light you put in back again; they are good at harvesting light; and they tend to show relatively low luminescence loss when condensed into a solid.

The researchers made a family of dendrimers -- getting larger in size as the generation number increased -- made up of carbazole units forming the branches around a highly fluorescent core. The dendrimers formed stable single crystals even when the solvent was removed, and could be analyzed by single crystal X-ray analysis. In fact, the third generation dendrimer, which has a molecular weight of 4,600 Da, is the largest organic dendrimer ever to have been analyzed in this way.

Nanocages in the lab and in the computer: How DNA-based dendrimers transport nanoparticles

How to create nanocages, i.e., robust and stable objects with regular voids and tunable properties? Short segments of DNA molecules are perfect candidates for the controllable design of novel complex structures. Physicists from the University of Vienna, the Technical University of Vienna, the Jülich Research Center in Germany and Cornell University in the U.S.A., investigated methodologies to synthesize DNA-based dendrimers in the lab and to predict their behavior using detailed computer simulations. Their results are published in the high-impact journal Nanoscale.

Nanocages are highly interesting molecular constructs, from the point of view of both fundamental science and possible applications. The cavities of these nanometer-sized objects can be employed as carriers of smaller molecules, which is of critical importance in medicine for drug or gene delivery in living organisms. This idea brought together researchers from various interdisciplinary fields who have been investigating dendrimers as promising candidates for creating such nano-carriers. Their tree-like architecture and step-wise growth with repeating self-similar units results in dendrimers containing cavities, hollow objects with controllable design. Nevertheless, decades of research have showed that vast number of different dendrimer types experience back-folding of outer branches with growing dendrimer generations, giving rise to a higher density of constituents in the molecule's interior. The effect of back-folding is enhanced upon addition of salt in the solution, whereby flexible dendrimers undergo significant shrinking, becoming compact objects with no hollow spaces in their interior.

Breakthrough in blending metals—precise control of multimetallic one-nanometer cluster formation achieved

Researchers in Japan have found a way to create innovative materials by blending metals with precision control. Their approach, based on a concept called atom hybridization, opens up an unexplored area of chemistry that could lead to the development of advanced functional materials.

Multimetallic clusters—typically composed of three or more metals—are garnering attention as they exhibit properties that cannot be attained by single-metal materials. If a variety of metal elements are freely blended, it is expected that as-yet-unknown substances are discovered and highly-functional materials are developed. So far, no one had reported the multimetallic clusters blended with more than four metal elements so far because of unfavorable separation of different metals. One idea to overcome this difficulty is miniaturization of cluster sizes to one-nanometer scale, which forces the different metals to be blended in a small space. However, there was no way to realize this idea.