Tag Archives: Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS)

Antimicrobial ‘safe-tea’ with silver nanoparticles and green tea

This work is not about drinking tea with silver nanoparticles in it or ingesting colloidal silver by any means, a dangerous practice as Nicole Karlis’s January 7, 2024 article for Salon highlights, Note: Links have been removed,

The HBO docuseries “Love Has Won: The Cult of Mother God” begins with a jarring image. The corpse of the cult leader, Amy Carlson, laying in a bed, wrapped in blankets and string lights. She is noticeably gaunt and her face is a very blue color. When Carlson died in 2021 at the age of 45, a coroner’s report deemed her cause of death to be “alcohol abuse, anorexia and chronic colloidal silver ingestion.”

Most medical experts advise against ingesting silver — especially in large amounts. That’s because too much of it can build up in a person’s body and lead to argyria, which is the condition that Carlson and Stan Jones both had that turned them a blue. While argyria alone isn’t a serious health condition, it doesn’t go away when a person stops ingesting silver. Plus, too much silver can be fatal. [emphasis mine]

A November 17, 2023 news item on phys.org announced research from the Polish Academy of Sciences into improving antimicrobial activity, Note: A link has been removed,

Researchers at the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) have demonstrated that green tea–silver nanoparticles as a powerful tool against pathogens such as bacteria and yeast. Their work is published in Nanoscale Advances.

An undated Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) press release (also published on EurekAlert and dated November 17, 2023), which originated the news item, describes this work, which is intended for medical applications, in more detail,

Once upon a time, people believed to be invincible against bacterial diseases, thanks to the antibiotics. Does this sound like a fairy tale? By all means! Nothing could be further from the truth. Despite widespread access to antibiotic therapy, many lives are lost due to pathogens invisible to the eye. The ability to develop drugs that can combat resistant strains of bacteria has not kept pace with the spread of resistance. So far, innovations to defeat antimicrobial-resistant strains of bacteria are in high demand. Recently, researchers at the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) demonstrated green tea-silver nanoparticles as a powerful tool against pathogens such as bacteria and yeast. Their goal was to develop an efficient method to combat bacteria that are otherwise unaffected by antimicrobial agents, such as antibiotics.

Following the discovery of antibiotics, there came a change in the curse of mankind by accelerating the development of medicine and extending human life expectancy. Their successful implementation led to the rapid development of pharmacy, providing more and more drugs against many pathogens. Nevertheless, the overuse of antibiotics has led to the emergence of resistance to these compounds, becoming one of the biggest health threats worldwide. As a result, antibiotic resistance has emerged faster than the advancement of antibiotics . The appearance of new drugs on the horizon to combat these pathogens is a short-lasting spark. Even if we seem to be on the losing end, there is still a chance to defeat an invisible enemy.

This hitch was researched by the team of scientists from the IPC PAS under the supervision of Prof. Jan Paczesny, who proposed new nanoformulations for use against widespread and challenging pathogens such as ESKAPE bacteria (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.) and other problematic yeast pathogens such as Candida auris or Cryptococcus neoformans. These microorganisms, treated with commercially available antibiotics, rapidly develop antibiotic resistance. Researchers chose ESKAPE as the target group since these pathogens lead to serious diseases, from sepsis to even cancer. How? This is where the story begins.

A few months ago, Paczesny’s team decided to try combining silver nanoparticles, which are known for their antimicrobial and antifungal properties, and tea extracts rich in polyphenols additionally possessing antioxidant properties. The concept was built to enhance broad-spectrum efficacy against pathogens using green hybrid silver nanoparticles (AgNPs), which are significantly more effective than all ingredients and even more effective than certain antibiotics. Why are these hybrid particles so special? In their work, three well-known tea varieties: black tea (B-Tea), green tea (G-Tea) and Pu-erh tea (R-Tea) were used as a capping agent, which acts as a stabilizer to protect the synthesized  particles from aggregation. In this way, the particles offer a high active surface area compared to other formulations. Additionally, such synthesis is eco-friendly for the use of natural ingredients during precipitation. The structures produced vary in shape and size from 34 to 65 nm, depending on the type of tea used during synthesis, and show different reactivity towards microorganisms.

Initially, silver nanoparticles produced in the presence of tea extracts (B-TeaNPs, G-TeaNPs and R-TeaNPs) were used to treat Gram-negative (E. coli) and Gram-positive (E. faecium) bacterial strains to test the effect on strains with different cell envelope morphologies. They looked at the interactions between the manufactured nanoparticles and the pathogens to determine efficacy, comparing the results with commercially available antibiotics. The ESKAPE pathogens were then tested according to a protocol for the most effective concentration and composition of the particles, revealing up to a 25% decrease in the number of bacterial cells in E. faecium and a 90% decrease in the case of E. cloacae. Interestingly, the green silver nanoparticles also showed antifungal activity, leading to an 80% decrease in the number of viable cells of C. auris and about a 90% decrease for C. neoformans.

The first author, Sada Raza claims “What is more, the size of nanoparticles is usually related to the cytotoxic effect of nanomaterials, with smaller particles being more cytotoxic. This should favor control AgNPs and R-TeaNPs over G-TeaNPs and B-TeaNPs in our experiments. This was not the case. In most experiments, C-AgNPs and R-TeaNPs showed the lowest antimicrobial efficacy. This is in line with other studies, which demonstrated that size is not a primary factor affecting the antimicrobial activity of AgNPs.

The antibacterial and antifungal properties of silver nanoparticles made with tea extracts are greater than those of silver nanoparticles alone due to their high content of phenolic compounds, isoflavonoids (especially catechins such as epigallocatechin (EGC) and epigallocatechin gallate (EGCG)). These combinations, using biologically active tea extracts and smaller amounts of silver nanoparticles, appear to be a potential way to combat a range of infections and even replace antibiotics in some applications.

“We established that silver nanoparticles synthesized with tea extracts have higher antibacterial properties than silver nanoparticles alone. Therefore, lower dosages of TeaNPs could be used (0.1 mg mL−1). We confirmed that in some cases, the synergistic effect of tea extracts and silver nanoparticles allowed for efficacy higher than that of antibiotics (ampicillin) when tested at the same concentrations (0.1 mg mL−1) and after a relatively short exposure time of three hours.” – remarks Mateusz Wdowiak, co-author of this work.

The researchers found that the antimicrobial hybrid nanoparticles resulted in a significant reduction in bacteria compared to antibiotics or compounds separately. Although not all bacteria were killed, this is a significant improvement that could aid the treatment of superbugs using much lower doses than other commercially available compounds. The amount of hybrid silver nanoparticles needed to overcome bacteria or fungal infections is extremely low, making them cost-effective, so the key to using them well is not only functionality, but also the low cost of application.

It is an approach that can also be adapted to combat other difficult-to-treat bacterial infections. The new nanoparticles developed by researchers at the IPC PAS could bring us one step closer to effectively killing deadly drug-resistant superbugs, providing an alternative to antibiotics against Gram-negative and Gram-positive bacteria. This study also shows how much more work there is to be done in this field. Compounds used separately were much less effective than the green hybrid.

In the future, the researchers’ main goal is to use nanoparticles in everyday life, starting with agricultural applications, replacing harmful compounds used in fields to overcome infestations in plants and bring us closer to organic farming. On a larger scale, the proposed material could also be used in biomedical applications, such as an additive for wound dressings to protect against Gram-negative and Gram-positive bacteria. They hope to use nanotechnology to develop more targeted treatments for drug-resistant superbugs.

Their work was published in Nanoscale Advances journal and was financed by the National Science Centre, Poland, within the SONATA BIS grant number 2017/26/E/ST4/00041 and Foundation for Polish Science from the European Regional Development Fund within the project POIR.04.04.00-00-14D6/18-00 ‘Hybrid sensor platforms for integrated photonic systems based on ceramic and polymer materials (HYPHa)’ (TEAM-NET program).

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

Enhancing the antimicrobial activity of silver nanoparticles against ESKAPE bacteria and emerging fungal pathogens by using tea extracts by Sada Raza, Mateusz Wdowiak, Mateusz Grotek, Witold Adamkiewicz, Kostiantyn Nikiforow, Pumza Mente, and Jan Paczesny. Nanoscale Adv., 2023,5, 5786-5798 DOI: https://doi.org/10.1039/D3NA00220A

This paper is licensed under a Creative Commons Attribution 3.0 Unported Licence. “You can use material from this article in other publications without requesting further permissions from the RSC [Royal Society of Chemistry], provided that the correct acknowledgement is given.” Or, consider it an open access paper.

Finally, this is not a recommendation not is it an endorsement for the ingestion of colloidal silver.

Synthetic genetics and imprinting a sequence of a single DNA (deoxyribonucleic acid) strand

Caption: A polymer negative of a sequence of the genetic code, chemically active and able to bind complementary nucleobases, has been created by researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw. Credit: IPC PAS, Grzegorz Krzyzewski

Those are very large hands! In any event, I think they left out the word ‘model’ when describing what the researcher is holding.

A Jan. 19, 2017 news item on phys.org announces the research from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS),

In a carefully designed polymer, researchers at the Polish Academy of Sciences have imprinted a sequence of a single strand of DNA. The resulting negative remained chemically active and was capable of binding the appropriate nucleobases of a genetic code. The polymer matrix—the first of its type—thus functioned exactly like a sequence of real DNA.

A Jan. 18, 2017 IPC PAS press release, which originated the news item, provides more detail about the breakthrough and explains how it could lead to synthetic genetics,

Imprinting of chemical molecules in a polymer, or molecular imprinting, is a well-known method that has been under development for many years. However, no-one has ever before used it to construct a polymer chain complementing a sequence of a single strand of DNA. This feat has just been accomplished by researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw in collaboration with the University of North Texas (UNT) in Denton, USA, and the University of Milan in Italy. In an appropriately selected polymer, they reproduced a genetically important DNA sequence, constructed of six nucleobases.

Typically, molecular imprinting is accomplished in several steps. The molecules intended for imprinting are first placed to a solution of monomers (i.e. the basic “building blocks” from which the future polymer is to be formed). The monomers are selected so as to automatically arrange themselves around the molecules being imprinted. Next, the resulting complex is electrochemically polymerized and then the imprinted molecules are extracted from the fixed structure. This process results in a polymer structure with molecular cavities matching the original molecules with their size and shape, and even their local chemical properties.

“Using molecular imprinting, we can produce, e.g. recognition films for chemical sensors, capturing molecules of only a specific chemical compound from the surroundings – since only these molecules fit into the existing molecular cavities. However, there’s no rose without a thorn. Molecular imprinting is perfect for smaller chemical molecules, but the larger the molecule, the more difficult it is to imprint it accurately into the polymer,” explains Prof. Wlodzimierz Kutner (IPC PAS).

Molecules of deoxyribonucleic acid, or DNA, are really large: their lengths are of the order of centimetres. These molecules generally consist of of two long strands, paired up with each other. A single strand is made up of nucleotides with multiple repetitions, each of which contains one of the nucleobases: adenine (A), guanine (G), cytosine (C), or thymine (T). The bases on both strands are not arranged freely: adenine on one strand always corresponds to thymine on the other, and guanine to cytosine. So, when we have one thread, we can always recreate its complement, which is the second strand.

The complementarity of nucleobases in DNA strands is very important for cells. Not only does it increase the permanence of the record of the genetic code (damage in one strand can be repaired based on the construction of the other), but it also makes it possible to transfer it from DNA to RNA in the process known as transcription. Transcription is the first step in the synthesis of proteins.

“Our idea was to try to imprint in the polymer a sequence of a single-stranded DNA. At the same time, we wanted to reproduce not only the shape of the strand, but also the sequential order of the constituent nucleobases,” says Dr. Agnieszka Pietrzyk-Le (IPC PAS).

In the study, financed on the Polish side by grants from the Foundation for Polish Science and the National Centre for Science, researchers from the IPC PAS used sequences of the genetic code known as TATAAA. This sequence plays an important biological role: it participates in deciding on the activation of the gene behind it. TATAAA is found in most eukaryotic cells (those containing a nucleus); in humans it is present in about every fourth gene.

A key step of the research was to design synthetic monomers undergoing electrochemical polymerization. These had to be capable of accurately surrounding the imprinted molecule in such a way that each of the adenines and thymines on the DNA strand were accompanied by their complementary bases. The mechanical requirements were also important, because after polymerization the matrix had to be stable. Suitable monomers were synthesized by the group of Prof. Francis D’Souza (UNT).

“When all the reagents and apparatus have been prepared, the imprinting itself of the TATAAA oligonucleotide is not especially complicated. The most important processes take place automatically in solutions in no more than a few dozen minutes. Finally, on the electrode used for electropolymerization, we obtain a layer of conductive polymer with molecular cavities where the nucleobases are arranged in the TTTATA sequence, that is, complementary to the extracted original”, describes doctoral student Katarzyna Bartold (IPC PAS).

Do polymer matrices prepared in this manner really reconstruct the original sequence of the DNA chain? To answer this question, at the IPC PAS careful measurements were carried out on the properties of the new polymers and a series of experiments was performed that confirmed the interaction of the polymers with various nucleobases in solutions. The results leave no doubt: the polymer DNA negative really is chemically active and selectively binds the TATAAA oligonucleotide, correctly reproducing the sequence of nucleobases.

The possibility of the relatively simple and low-cost production of stable polymer equivalents of DNA sequences is an important step in the development of synthetic genetics, especially in terms of its widespread applications in biotechnology and molecular medicine. If an improvement in the method developed at the IPC PAS is accomplished in the future, it will be possible to reproduce longer sequences of the genetic code in polymer matrices. This opens up inspiring perspectives associated not only with learning about the details of the process of transcription in cells or the construction of chemosensors for applications in nanotechnologies operating on chains of DNA, but also with the permanent archiving and replicating of the genetic code of different organisms.

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

Programmed transfer of sequence information into molecularly imprinted polymer (MIP) for hexa(2,2’-bithien-5-yl) DNA analog formation towards single nucleotide polymorphism (SNP) detection by Katarzyna Bartold, Agnieszka Pietrzyk-Le, Tan-Phat Huynh, Zofia Iskierko, Marta I. Sosnowska, Krzysztof Noworyta, Wojciech Lisowski, Francesco Maria Enrico Sannicolo, Silvia Cauteruccio, Emanuela Licandro, Francis D’Souza, and Wlodzimierz Kutner. ACS Appl. Mater. Interfaces, Just Accepted Manuscript
DOI: 10.1021/acsami.6b14340 Publication Date (Web): January 10, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall.

Monitoring the life of bacteria in microdroplets

Trying to establish better ways to test the effect of drugs on bacteria has led the Institute of Physical Chemistry of the Polish Academy of Sciences to develop a new monitoring technique. From a Jan.  11, 2017 news item on Nanowerk,

So far, however, there has been no quick or accurate method of assessing the oxygen conditions in individual microdroplets. This key obstacle has been overcome at the Institute of Physical Chemistry of the Polish Academy of Sciences.

Not in rows of large industrial tanks, nor on shelves laden with test tubes and beakers. The future of chemistry and biology is barely visible to the eye: it’s hundreds and thousands of microdroplets, whizzing through thin tubules of microfluidic devices. The race is on to find technologies that will make it possible to carry out controlled chemical and biological experiments in microdroplets. At the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw a method of remote, yet rapid and accurate assessment of oxygen consumption by micro-organisms living in individual microdroplets has been demonstrated for the first time.

“Devices for the cultivation of bacteria in microdroplets have the chance to revolutionize work on the development of new antibiotics and the study of mechanisms responsible for the acquisition of drug resistance by bacteria. In one small microfluidic system it is possible to accommodate several hundred or even several thousand microdroplets – and to carry out a different experiment in each of them, for example with different types of microorganisms and at different concentrations of antibiotic in each drop,” describes Prof. Piotr Garstecki (IPC PAS), then explains: “For such studies to be possible, one has to provide the bacteria with conditions for development for even a few weeks. Thus, knowledge about the flow of oxygen to the droplets and the rate of its consumption by the microorganisms becomes extremely important. In our latest system we demonstrate how to read this key information.”

A Jan. 11, 2017 IPC PAS press release on EurekAlert, which originated the  news item, describes the work in more detail,

The bioreactors of the future are water droplets with culture medium suspended in a carrier liquid with which they are immiscible (usually this is oil). In the channel of the microfluidic device each droplet is longer than it is wide and it almost completely fills its lumen; sizes matched in this manner ensure that the drops do not swop places in the channel and throughout the duration of the experiment they can be identified without any problems. At the same time, there has to be a thin layer of oil maintained continuously between each microdroplet and the wall of the channel. Without this, the bacteria would be in direct contact with the walls of the channel so they would be able to settle on them and move from drop to drop. Unfortunately, when the microdroplet is stationary, with time it pushes out the oil separating it from the walls, laying it open to contamination. For this reason the drops must be kept in constant motion – even for weeks.

Growing bacteria need culture medium, and waste products need to be removed from their environment at an appropriate rate. Information about the bacterial oxygen consumption in individual droplets is therefore crucial to the operation of microbioreactors.

“It is immediately obvious where the problem lies. In each of the hundreds of moving droplets measurements need to be carried out at a frequency corresponding to the frequency of division of the bacteria or more, in practice at least once every 15 minutes. In addition, the measurement cannot cause any interference in the microdroplets,” says PhD student Michal Horka (IPC PAS), a co-author of the publication in the journal Analytical Chemistry.

Help was at hand for the Warsaw researchers from chemists from the Austrian Institute of Analytical Chemistry and Food Chemistry at the Graz University of Technology. They provided polymer nanoparticles with a phosphorescent dye, which after excitation emit light for longer the higher the concentration of oxygen in the surrounding solution (the nanoparticles underwent tests at the IPC PAS on bacteria in order to determine their possible toxicity – none was found).

Research on monitoring oxygen consumption in the droplets commenced with the preparation of an aqueous solution with the bacteria, the culture medium and a suitable quantity of nanoparticles. The mixture was injected into the microfluidic system constructed of tubing with Teflon connectors with correspondingly shaped channels. The first module formed droplets with a volume of approx. 4 microlitres, which were directed to the incubation tube wound on a spool. In the middle of its length there was another module, with detectors for measuring oxygen and absorbance.

“In the incubation part in one phase of the cycle the droplets flowed in one direction, in the second – in another, electronically controlled by means of suitable solenoid valves. All this looks seemingly simple enough, but in practice one of the biggest challenges was to ensure a smooth transition between the detection module and the tubing, so that bacterial contamination did not occur at the connections,” explains PhD student Horka.

During their passage through the detection module the droplets flowed under an optical sensor which measured the so-called optical density, which is the standard parameter used to evaluate the number of cells (the more bacteria in the droplets, the less light passes through them). In turn, the measurement of the duration of the phosphorescence of the nanoparticles, evaluating the concentration of oxygen in the microdroplets, was carried out using the Piccolo2 optical detector, provided by the Austrian group. This detector, which looks like a big pen drive, was connected directly to the USB port on the control computer. Comparing information from both sensors, IPC PAS researchers showed that the microfluidic device they had constructed made it possible to regularly and quickly monitor the metabolic activity of bacteria in the individual microdroplets.

“We carried out our tests both with bacteria floating in water singly – this is how the common Escherichia coli bacteria behave – as well as with those having a tendency to stick together in clumps – as is the case for tuberculosis bacilli or others belonging to the same family including Mycobacterium smegmatis which we studied. Evaluation of the rate of oxygen consumption by both species of microorganisms proved to be not only possible, but also reliable,” stresses PhD student Artur Ruszczak (IPC PAS).

The results of the research, funded by the European ERC Starting Grant (Polish side) and the Maria Sklodowska-Curie grant (Austrian side) are an important step in the process of building fully functional microfluidic devices for conducting biological experiments lasting many weeks. A system for culturing bacteria in microdroplets was developed at the IPC PAS a few years ago, however it was constructed on a polycarbonate plate. The maximum dimensions of the plate did not exceed 10 cm, which greatly limited the number of droplets; in addition, as a result of interaction with the polycarbonate, after four days the channels were contaminated with bacteria. Devices of Teflon modules and tubing would not have these disadvantages, and would be suitable for practical applications.

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

Lifetime of Phosphorescence from Nanoparticles Yields Accurate Measurement of Concentration of Oxygen in Microdroplets, Allowing One To Monitor the Metabolism of Bacteria by Michał Horka, Shiwen Sun, Artur Ruszczak, Piotr Garstecki, and Torsten Mayr. Anal. Chem., 2016, 88 (24), pp 12006–12012 DOI: 10.1021/acs.analchem.6b03758 Publication Date (Web): November 23, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Polish researchers develop Superman’s kryptonite?

It’s not precisely kryptonite but rather a krypton-oxygen compound according to a March 2, 2016 news item on ScienceDaily,

Theoretical chemists have found how to synthesize the first binary compound of krypton and oxygen: a krypton oxide. It turns out that this exotic substance can be produced under extremely high pressure, and its production is quite within the capabilities of today’s laboratories.

A March 2, 2016 Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) press release (also on EurekAlert), which originated the news item, provides more information about Superman’s kryptonite, real krypton, and the new synthesized compound,

Crystals of kryptonite, a material deadly to Superman and his race, were supposed to have been created within the planet Krypton, and therefore most likely under very high pressure. The progenitor of the name, real krypton, is an element with an atomic number of 36, a noble gas considered to be incapable of forming stable chemical compounds. However, a publication in the journal Scientific Reports by a two-man team of theoretical chemists from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw, Poland, presents the possibility of synthesizing a new crystalline material in which atoms of krypton would be chemically bonded to another element.

“The substance we are predicting is a compound of krypton with not nitrogen, but oxygen. In the convention of the comic book it should, therefore, be called not so much kryptonite as kryptoxide. So if Superman’s reading this, he can stay calm – at the moment there’s no cause for panic!” laughs Dr. Patrick Zaleski-Ejgierd (IPC PAS) and adds: “Our krypton monoxide, KrO, probably does not exist in nature. According to current knowledge, deep in the interiors of planets, that is, the only place where there is sufficient pressure for its synthesis, oxygen does not exist, nor even more so, does krypton.”

Compounds of krypton have been produced before, in the laboratory under cryogenic conditions. They were, however, only single, linear and small molecules of the hydrogen-carbon-krypton-carbon-hydrogen type. The Polish chemists wondered if there were conditions in which krypton would not only bond chemically with another element, but also in which it would be capable of forming an extensive and stable crystal lattice. Their search, funded by an OPUS grant from the Polish National Science Centre, involved the researchers using genetic algorithms and models built on the so-called density functional theory. In the field of solid state physics, this theory has for years been a basic tool for the description and study of the world of chemical molecules.

“Our computer simulations suggest that crystals of krypton monoxide will be formed at a pressure in the range of 3 to 5 million atmospheres. This is a huge pressure, but it can be achieved even in today’s laboratories, by skillfully squeezing samples in diamond anvils,” says PhD student Pawe? Lata (IPC PAS).

Crystal lattices are built from atoms or molecules arranged in space in an orderly manner. The smallest repetitive fragment of such structures – the basic ‘building block’ – is called a unit cell. In crystals of table salt the unit cell has the shape of a cube, the sodium and chlorine atoms, arranged alternately, are mounted on each corner, close enough to each other that they are bound by covalent (chemical) bonds.

The unit cell of krypton monoxide is cuboid with a diamond base, with krypton atoms at the corners. In addition, in the middle of the two opposite side walls, there is one atom of krypton.

“Where is the oxygen? On the side walls of the unit cell, where there are five atoms of krypton, they are arranged like the dots on a dice showing the number five. Single atoms of oxygen are located between the krypton atoms, but only along the diagonal – and only along one! Thus, on each wall with five krypton atoms there are only two atoms of oxygen. Not only that, the oxygen is not exactly on the diagonal: one of the atoms is slightly offset from it in one direction and the other atom in the other direction,” describes Lata.

In such an idiosyncratic unit cell, each atom of oxygen is chemically bound to the two nearest adjacent atoms of krypton. Zigzag chains of Kr/O\Kr\O/Kr will therefore pass through the crystal of krypton monoxide, forming long polymer structures. Calculations indicate that crystals of this type of krypton monoxide should have the characteristics of a semiconductor. One can assume that they will be dark, and their transparency will not be great.

Theorists from the IPC PAS have also found a second, slightly less stable compound of krypton: the tetroxide KrO4. This material, which probably has properties typical of a metal, has a simpler crystalline structure and could be formed at a pressure exceeding 3.4 million atmospheres.

After formation, the two kinds of krypton oxide crystals could probably exist at a somewhat lower pressure than that required for their formation. The pressure on earth, however, is so low that on our planet these crystals would undergo degradation immediately.

“Reactions occurring at extremely high pressure are almost unknown, very, very exotic chemistry. We call it ‘Chemistry on the Edge'”. Often the pressures needed to perform syntheses are so gigantic that at present there is no point in trying to produce them in laboratories. In those cases even methods of theoretic description fail! But what is most interesting here is the non-intuitiveness. From the very first to the last step of synthesis you never know what’s going to happen,” says Dr. Zaleski-Ejgierd – and he returns to his computer where simulations of subsequent syntheses are nearing their end.

I don’t usually include images of the researchers but these guys dressed up for the occasion,

Chemists from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw have found a method of synthesizing a new crystalline material in which atoms of krypton would be chemically bonded to another element. (Source: IPC PAS, Grzegorz Krzy¿ewski) Metodê syntezy pierwszego trwa³ego zwi¹zku kryptonu znale¿li chemicy-teoretycy z Instytutu Chemii Fizycznej PAN w Warszawie. (ród³o: IChF PAN, Grzegorz Krzy¿ewski)

Chemists from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw have found a method of synthesizing a new crystalline material in which atoms of krypton would be chemically bonded to another element. (Source: IPC PAS, Grzegorz Krzy¿ewski)
Metodê syntezy pierwszego trwa³ego zwi¹zku kryptonu znale¿li chemicy-teoretycy z Instytutu Chemii Fizycznej PAN w Warszawie. (ród³o: IChF PAN, Grzegorz Krzy¿ewski)

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

Krypton oxides under pressure by  Patryk Zaleski-Ejgierd & Pawel M. Lata. Scientific Reports 6, Article number: 18938 (2016) doi:10.1038/srep18938 Published online: 02 February 2016

This paper is open access.

Back to the mortar and pestle for perovskite-based photovoltaics

This mechanochemistry (think mortar and pestle) story about perovskite comes from Poland. From a Jan. 14, 2016 Institute of Physical Chemistry of the Polish Academy of Sciences press release (also on EurekAlert but dated Jan. 16, 2016),

Perovskites, substances that perfectly absorb light, are the future of solar energy. The opportunity for their rapid dissemination has just increased thanks to a cheap and environmentally safe method of production of these materials, developed by chemists from Warsaw, Poland. Rather than in solutions at a high temperature, perovskites can now be synthesized by solid-state mechanochemical processes: by grinding powders.

We associate the milling of chemicals less often with progress than with old-fashioned pharmacies and their inherent attributes: the pestle and mortar. [emphasis mine] It’s time to change this! Recent research findings show that by the use of mechanical force, effective chemical transformations take place in solid state. Mechanochemical reactions have been under investigation for many years by the teams of Prof. Janusz Lewinski from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) and the Faculty of Chemistry of Warsaw University of Technology. In their latest publication, the Warsaw researchers describe a surprisingly simple and effective method of obtaining perovskites – futuristic photovoltaic materials with a spatially complex crystal structure.

“With the aid of mechanochemistry we are able to synthesize a variety of hybrid inorganic-organic functional materials with a potentially great significance for the energy sector. Our youngest ‘offspring’ are high quality perovskites. These compounds can be used to produce thin light-sensitive layers for high efficiency solar cells,” says Prof. Lewinski.

Perovskites are a large group of materials, characterized by a defined spatial crystalline structure. In nature, the perovskite naturally occurring as a mineral is calcium titanium(IV) oxide CaTiO3. Here the calcium atoms are arranged in the corners of the cube, in the middle of each wall there is an oxygen atom and at the centre of the cube lies a titanium atom. In other types of perovskite the same crystalline structure can be constructed of various organic and inorganic compounds, which means titanium can be replaced by, for example, lead, tin or germanium. As a result, the properties of the perovskite can be adjusted so as to best fit the specific application, for example, in photovoltaics or catalysis, but also in the construction of superconducting electromagnets, high voltage transformers, magnetic refrigerators, magnetic field sensors, or RAM memories.

At first glance, the method of production of perovskites using mechanical force, developed at the IPC PAS, looks a little like magic.

“Two powders are poured into the ball mill: a white one, methylammonium iodide CH3NH3I, and a yellow one, lead iodide PbI2. After several minutes of milling no trace is left of the substrates. Inside the mill there is only a homogeneous black powder: the perovskite CH3NH3PbI3,” explains doctoral student Anna Maria Cieslak (IPC PAS).

“Hour after hour of waiting for the reaction product? Solvents? High temperatures? In our method, all this turns out to be unnecessary! We produce chemical compounds by reactions occurring only in solids at room temperature,” stresses Dr. Daniel Prochowicz (IPC PAS).

The mechanochemically manufactured perovskites were sent to the team of Prof. Michael Graetzel from the Ecole Polytechnique de Lausanne in Switzerland, where they were used to build a new laboratory solar cell. The performance of the cell containing the perovskite with a mechanochemical pedigree proved to be more than 10% greater than a cell’s performance with the same construction, but containing an analogous perovskite obtained by the traditional method, involving solvents.

“The mechanochemical method of synthesis of perovskites is the most environmentally friendly method of producing this class of materials. Simple, efficient and fast, it is ideal for industrial applications. With full responsibility we can state: perovskites are the materials of the future, and mechanochemistry is the future of perovskites,” concludes Prof. Lewinski.

The described research will be developed within GOTSolar collaborative project funded by the European Commission under the Horizon 2020 Future and Emerging Technologies action.

Perovskites are not the only group of three-dimensional materials that has been produced mechanochemically by Prof. Lewinski’s team. In a recent publication the Warsaw researchers showed that by using the milling technique they can also synthesize inorganic-organic microporous MOF (Metal-Organic Framework) materials. The free space inside these materials is the perfect place to store different chemicals, including hydrogen.

This research was published back in August 2015,

Mechanosynthesis of the hybrid perovskite CH3NH3PbI3: characterization and the corresponding solar cell efficiency by D. Prochowicz, M. Franckevičius, A. M. Cieślak, S. M. Zakeeruddin, M. Grätzel and J. Lewiński. J. Mater. Chem. A, 2015,3, 20772-20777 DOI: 10.1039/C5TA04904K First published online 27 Aug 2015

This paper is behind a paywall.