Abián Bentor Socorro-Leránoz, a telecommunications engineer of the NUP/UPNA-Public University of Navarre, has designed in his PhD thesis optical resonance-based biosensors for use in medical applications like, for example, the detecting of coeliac disease. Besides achieving greater resolution and sensitivity, the materials used in these devices are much cheaper and more versatile than the ones used in current technologies (mainly gold and noble metals) so they could offer a potential alternative in the design of biomedical sensors. A biosensor is an instrument that uses biological molecules (bioreceptors) to detect other biological or chemical substances. In this thesis the bioreceptors have been antibodies, biological molecules that the body produces specifically to fight off antigens. An antigen is a substance foreign to the human body; our immune system recognises it as a threat and in the presence of it the body reacts by producing antibodies to identify and neutralise it. What is more, the biosensor is made up of a substrate (where the physical phenomenon that translates the biological reactions into intelligible information takes place) and the immobilisation layer which causes the antibodies to become attached to the substrate. “One of the unique features,” says the author, "is that for the substrate we use silicon waveguides on which we generate a specific type of resonance.” The biosensors designed are based on the movement of the wavelength of the resonances generated on the basis of the quantity of antigens detected. “When the antibodies come together with the antigens, there is a minimum change in the wavelength that our biosensors are capable of picking up.” This is possible thanks to the resolution achieved by these biosensors and their sensitivity, “which enables us to see how much resonances shift on the wavelength as the antibody-antigen links increase.” Medical application The work carried out by Abián Socorro is geared towards medical applications. Basically, the more antigens that are detected in the sample, the more advanced the disease is. “This is what we would see: if you are in an early or late phase, you will have few antigens and few antibodies, so the resonance will move towards wavelengths closer to the reference ones. If the phase is more advanced, the concentrations detected will be higher so the resonance will change a lot in the wavelength,” he explained. The technology used is based on LMRs, lossy mode resonances, in which the Sensors Laboratory of the NUP/UPNA-Public University of Navarre is a pioneer. “This technology has shown itself to be a potential competitor of the one based on SPRS (surface plasmon resonances) which currently dominates most biosensor applications”. So this work is about optimizing the parameters of the optical waveguides used to generate resonances that provide the maximum possible resolution and sensitivity, a crucial aspect in the field of biosensors. The research conducted has resulted in two awards at the international conferences Trends in Nanotechnology 2012 and Optical Fibre Sensors 2014. In the latter conference, the biosensor was designed to detect coeliac disease and when compared with the usual values in the clinical environment succeeded in reducing the concentration of antibodies detected to diagnose this disorder.
Optical resonance-based biosensors designed for medical applications
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Framework compounds: metal-organic transformations
It is beyond imagination that one gram of a substance could have a surface area nearly as large as a soccer field. This, however, is true for compounds known as metal-organic frameworks (MOFs). In the near future, MOFs are expected to be used for absorption and reliable storage of large volumes of gases (like hydrogen or carbon dioxide) or for separate gas mixtures. An international team, including scientists from the Max Planck Institute for Solid State Research in Stuttgart, is working on new methods for custom-made and environmentally-friendly synthesis of MOFs materials. In a so-called mechanochemical synthesis, new compounds are produced directly from solid-state reactants by milling. For real-time following of the course of mechanochemical reactions, a new protocol was co-developed by the Stuttgart-based Max Planck scientists. This method provides the opportunity to identify (and thereafter isolate) hitherto unknown structures formed as intermediates during the reactions, which may be particularly useful for practical applications. Imagine two tanks, one empty and the other with filled with small amounts of powder. Maybe it comes as a surprise, but the tank with powder is capable of storing far more hydrogen than the empty one! The reason for this is rooted in a simple physical principle: if the powdered substance contains pores in the crystal structure, then there are numerous binding sites for hydrogen. As a result, the hydrogen molecules are not only stored in the emptiness of the tank, but they are also densely packed within the powder material. Unfortunately, such a tank is not commercially available, yet. Nevertheless, powders with the described properties are already known. Namely, it is likely that a metal-organic framework (MOF) material can be used for this purpose. Researchers at McGill University in Montreal, Canada, and at the Ruder Boskovic Institute in Zagreb, Croatia, are now improving our understanding of how MOFs are formed during environmentally-friendly methods of synthesis. To visualize the reactions courses they are using a special method of X-ray diffraction developed by Robert E. Dinnebier and his colleagues at the Max Planck Institute for Solid State Research. 
Filigree cages: Using a variant of powder X-ray diffraction co-developed by scientists at the Max Planck Institute for Solid State Research, an international team has discovered a previously unknown structure of the metal-organic framework compound ZIF-8. The researchers named the new structure katsenite. (© Nature Communications) New crystal structure of a known metal-organic framework This method makes it possible to continuously monitor structural changes during the chemical reaction, providing valuable information for subsequent modifications of the manufacturing process. The protocol helps to identify – and produce - MOFs with hitherto unknown structures and potentially useful properties. For example, recently, the scientists discovered a previously unknown crystal structure of an important and commercially available MOF. The chemical composition of MOFs dictates their crystal structure, which is often interesting for many applications. MOFs are constructed of metal atoms (such as zinc, copper or chromium, to name a few) interconnected by organic linkers. Together, these metal-organic building blocks form highly regular, three-dimensional structures with large pores within the framework. These resulting pores are able to selectively absorb gases. Storing hydrogen fuel in the tank of a car is only one of many potential applications for MOFs. Depending on the size and cross-section of the pores and channels, MOFs are also suitable for separating gas mixtures. For example, they could be used to separate carbon dioxide from flue gas mixtures, which could then be disposed and sequestered underground. Moreover, gases can undergo reactions within the pores, with the metal atoms acting as catalysts, and speed-up industrially important reactions. Chemistry in the mill Generally, to synthesise an MOF, chemists use a solvent in which a salt of the desired metal is dissolved to react with the organic substance, which serves as a bridge between the metal centres. After the reaction, the solvent evaporates leaving the MOF in a solid form. Taken that this final step costs a lot of energy and using of solvents is environmentally harmful, scientists are working on methods that require no solvents. One alternative is mechanosynthesis, in which a metal compound and an organic substance are simply mixed together in the solid state. The energy required for the reaction is provided by milling and grinding the mixture. For the commercially available MOF ZIF-8 (zeolitic imidazolate framework 8), it was already shown that it can be obtained by grinding zinc oxide together with 2-methylimidazone. “It was not known what actually happens during such mechanosyntheses and how the reactions proceed,” says Robert E. Dinnebier, who heads the Central Scientific Facility X-Ray Diffraction at the Max Planck Institute for Solid State Research. Until now, it was necessary to stop the reaction in order to study the formed products. The reaction can be monitored with the help of high-energy X-rays In a project involving researchers from Canada, Croatia and France, Dinnebier’s team showed how the mechanical synthesis of ZIF-8 can be followed almost continuously in real-time. A technique known as powder X-ray diffraction, which measures the angles at which a powder sample diffracts X-rays was used. The reflections at specific diffracted angles and their intensities provide information on the position of individual atoms and on the atomistic crystal structure. 
Structural transformation in the mill: The katsenite structure exists in two variants shown by the two structures to the right. They form during the mechanosynthesis of ZIF-8 from solid starting substances (left) in a ball mill. During the reaction, the familiar structure of ZIF-8 emerges. Mechanosyntheses can now be monitored in real-time with the help of a modified X-ray diffraction method. This could shed light on approaches for optimising such processes. (© Nature Communications) The use of this widespread method for monitoring of solid-state processes requires high-energy X-rays. Namely, the X-rays not only have to penetrate through the reaction mixture but also the reaction vessel. Therefore, short wave X-rays were used, emitted by highly accelerated electrons in particle accelerators known as synchrotrons. For the first time the researchers succeeded in observing the progress of a mechanical ZIF-8 synthesis at intervals of only a few second without any interruption of the reaction. The insights gained in the search for optimum reaction conditions The researchers encountered a surprise. Although they demonstrated that the starting substances do in fact form the familiar ZIF-8 structure within a few minutes, the structure was lost again after further grinding. Instead, two other crystal structures formed, one of which was previously unknown. These are preliminary findings and still have no immediate practical application. However, Max Planck researcher Robert E. Dinnebier believes that they provide valuable insights: “They will ultimately help to identify optimum process conditions for synthesising ZIF-8 mechanically.” The experiments were not limited to the ZIF-8 system. “With the help of powder X-ray diffraction, we can now generally study how MOF syntheses of all kinds are influenced by process conditions such as temperature, pressure, the quantities of starting substances and excipients, and by the intensity and duration of grinding,” says Dinnebier. Since MOF substances continuously attract scientific and commercial interest, it is important to produce them in an environmentally-friendly and cost-effective manner. In this regard, mechanosynthesis is a very useful technique. “It is important to know the optimum process conditions for such syntheses,” says Dinnebier. As much is known about the mechanisms by which a crystal structure is formed, the easier the production will be. References , "In situ X-ray diffraction monitoring of a mechanochemical reaction reveals a unique topology metal-organic framework" , "Real-time and in situ monitoring of mechanochemical milling reactions"
Filigree cages: Using a variant of powder X-ray diffraction co-developed by scientists at the Max Planck Institute for Solid State Research, an international team has discovered a previously unknown structure of the metal-organic framework compound ZIF-8. The researchers named the new structure katsenite. (© Nature Communications) New crystal structure of a known metal-organic framework This method makes it possible to continuously monitor structural changes during the chemical reaction, providing valuable information for subsequent modifications of the manufacturing process. The protocol helps to identify – and produce - MOFs with hitherto unknown structures and potentially useful properties. For example, recently, the scientists discovered a previously unknown crystal structure of an important and commercially available MOF. The chemical composition of MOFs dictates their crystal structure, which is often interesting for many applications. MOFs are constructed of metal atoms (such as zinc, copper or chromium, to name a few) interconnected by organic linkers. Together, these metal-organic building blocks form highly regular, three-dimensional structures with large pores within the framework. These resulting pores are able to selectively absorb gases. Storing hydrogen fuel in the tank of a car is only one of many potential applications for MOFs. Depending on the size and cross-section of the pores and channels, MOFs are also suitable for separating gas mixtures. For example, they could be used to separate carbon dioxide from flue gas mixtures, which could then be disposed and sequestered underground. Moreover, gases can undergo reactions within the pores, with the metal atoms acting as catalysts, and speed-up industrially important reactions. Chemistry in the mill Generally, to synthesise an MOF, chemists use a solvent in which a salt of the desired metal is dissolved to react with the organic substance, which serves as a bridge between the metal centres. After the reaction, the solvent evaporates leaving the MOF in a solid form. Taken that this final step costs a lot of energy and using of solvents is environmentally harmful, scientists are working on methods that require no solvents. One alternative is mechanosynthesis, in which a metal compound and an organic substance are simply mixed together in the solid state. The energy required for the reaction is provided by milling and grinding the mixture. For the commercially available MOF ZIF-8 (zeolitic imidazolate framework 8), it was already shown that it can be obtained by grinding zinc oxide together with 2-methylimidazone. “It was not known what actually happens during such mechanosyntheses and how the reactions proceed,” says Robert E. Dinnebier, who heads the Central Scientific Facility X-Ray Diffraction at the Max Planck Institute for Solid State Research. Until now, it was necessary to stop the reaction in order to study the formed products. The reaction can be monitored with the help of high-energy X-rays In a project involving researchers from Canada, Croatia and France, Dinnebier’s team showed how the mechanical synthesis of ZIF-8 can be followed almost continuously in real-time. A technique known as powder X-ray diffraction, which measures the angles at which a powder sample diffracts X-rays was used. The reflections at specific diffracted angles and their intensities provide information on the position of individual atoms and on the atomistic crystal structure. Structural transformation in the mill: The katsenite structure exists in two variants shown by the two structures to the right. They form during the mechanosynthesis of ZIF-8 from solid starting substances (left) in a ball mill. During the reaction, the familiar structure of ZIF-8 emerges. Mechanosyntheses can now be monitored in real-time with the help of a modified X-ray diffraction method. This could shed light on approaches for optimising such processes. (© Nature Communications) The use of this widespread method for monitoring of solid-state processes requires high-energy X-rays. Namely, the X-rays not only have to penetrate through the reaction mixture but also the reaction vessel. Therefore, short wave X-rays were used, emitted by highly accelerated electrons in particle accelerators known as synchrotrons. For the first time the researchers succeeded in observing the progress of a mechanical ZIF-8 synthesis at intervals of only a few second without any interruption of the reaction. The insights gained in the search for optimum reaction conditions The researchers encountered a surprise. Although they demonstrated that the starting substances do in fact form the familiar ZIF-8 structure within a few minutes, the structure was lost again after further grinding. Instead, two other crystal structures formed, one of which was previously unknown. These are preliminary findings and still have no immediate practical application. However, Max Planck researcher Robert E. Dinnebier believes that they provide valuable insights: “They will ultimately help to identify optimum process conditions for synthesising ZIF-8 mechanically.” The experiments were not limited to the ZIF-8 system. “With the help of powder X-ray diffraction, we can now generally study how MOF syntheses of all kinds are influenced by process conditions such as temperature, pressure, the quantities of starting substances and excipients, and by the intensity and duration of grinding,” says Dinnebier. Since MOF substances continuously attract scientific and commercial interest, it is important to produce them in an environmentally-friendly and cost-effective manner. In this regard, mechanosynthesis is a very useful technique. “It is important to know the optimum process conditions for such syntheses,” says Dinnebier. As much is known about the mechanisms by which a crystal structure is formed, the easier the production will be. References , "In situ X-ray diffraction monitoring of a mechanochemical reaction reveals a unique topology metal-organic framework" , "Real-time and in situ monitoring of mechanochemical milling reactions"Engineer improves rechargeable batteries with MoS2 nano 'sandwich'
The key to better cellphones and other rechargeable electronics may be in tiny "sandwiches" made of nanosheets, according to mechanical engineering research from Kansas State University. Gurpreet Singh, assistant professor of mechanical and nuclear engineering, and his research team are improving rechargeable lithium-ion batteries. The team has focused on the lithium cycling of molybdenum disulfide, or MoS2, sheets, which Singh describes as a "sandwich" of one molybdenum atom between two sulfur atoms. In the latest research, the team has found that silicon carbonitride-wrapped molybdenum disulfide sheets show improved stability as a battery electrode with little capacity fading. The findings appear in Nature's in the article "Polymer-Derived Ceramic Functionalized MoS2 Composite Paper as a Stable Lithium-Ion Battery Electrode". Other Kansas State University researchers involved include Lamuel David, doctoral student in mechanical engineering, India; Uriel Barrera, senior in mechanical engineering, Olathe; and Romil Bhandavat, 2013 doctoral graduate in mechanical engineering. 
Molybdenum disulfide sheets — which are "sandwiches" of one molybdenum atom between two sulfur atoms — may improve rechargeable lithium-ion batteries. In this latest publication, Singh's team observed that molybdenum disulfide sheets store more than twice as much lithium — or charge — than bulk molybdenum disulfide reported in previous studies. The researchers also found that the high lithium capacity of these sheets does not last long and drops after five charging cycles. "This kind of behavior is similar to a lithium-sulfur type of battery, which uses sulfur as one of its electrodes," Singh said. "Sulfur is notoriously famous for forming intermediate polysulfides that dissolve in the organic electrolyte of the battery, which leads to capacity fading. We believe that the capacity drop observed in molybdenum disulfide sheets is also due to loss of sulfur into the electrolyte." To reduce the dissolution of sulfur-based products into the electrolyte, the researchers wrapped the molybdenum disulfide sheets with a few layers of a ceramic called silicon carbonitride, or SiCN. The ceramic is a high-temperature, glassy material prepared by heating liquid silicon-based polymers and has much higher chemical resistance toward the liquid electrolyte, Singh said. "The silicon carbonitride-wrapped molybdenum disulfide sheets show stable cycling of lithium-ions irrespective of whether the battery electrode is on copper foil-traditional method or as a self-supporting flexible paper as in bendable batteries," Singh said. After the reactions, the research team also dissembled and observed the cells under the electron microscope, which provided evidence that the silicon carbonitride protected against mechanical and chemical degradation with liquid organic electrolyte. Singh and his team now want to better understand how the molybdenum disulfide cells might behave in an everyday electronic device — such as a cellphone — that is recharged hundreds of times. The researchers will continue to test the molybdenum disulfide cells during recharging cycles to have more data to analyze and to better understand how to improve rechargeable batteries. Other research by Singh's team may help improve high temperature coatings for aerospace and defense. The engineers are developing a coating material to protect electrode materials against harsh conditions, such as turbine blades and metals subjected to intense heat. The research appears in the Journal of Physical Chemistry. The researchers showed that when silicon carbonitride and boron nitride nanosheets are combined, they have high temperature stability and improved electrical conductivity. Additionally, these silicon carbonitride/boron nitride nanosheets are better battery electrodes, Singh said. "This was quite surprising because both silicon carbonitride and boron nitride are insulators and have little reversible capacity for lithium-ions," Singh said. "Further analysis showed that the electrical conductivity improved because of the formation of a percolation network of carbon atoms known as 'free carbon' that is present in the silicon carbonitride ceramic phase. This occurs only when boron nitride sheets are added to silicon carbonitride precursor in its liquid polymeric phase before curing is achieved."
Molybdenum disulfide sheets — which are "sandwiches" of one molybdenum atom between two sulfur atoms — may improve rechargeable lithium-ion batteries. In this latest publication, Singh's team observed that molybdenum disulfide sheets store more than twice as much lithium — or charge — than bulk molybdenum disulfide reported in previous studies. The researchers also found that the high lithium capacity of these sheets does not last long and drops after five charging cycles. "This kind of behavior is similar to a lithium-sulfur type of battery, which uses sulfur as one of its electrodes," Singh said. "Sulfur is notoriously famous for forming intermediate polysulfides that dissolve in the organic electrolyte of the battery, which leads to capacity fading. We believe that the capacity drop observed in molybdenum disulfide sheets is also due to loss of sulfur into the electrolyte." To reduce the dissolution of sulfur-based products into the electrolyte, the researchers wrapped the molybdenum disulfide sheets with a few layers of a ceramic called silicon carbonitride, or SiCN. The ceramic is a high-temperature, glassy material prepared by heating liquid silicon-based polymers and has much higher chemical resistance toward the liquid electrolyte, Singh said. "The silicon carbonitride-wrapped molybdenum disulfide sheets show stable cycling of lithium-ions irrespective of whether the battery electrode is on copper foil-traditional method or as a self-supporting flexible paper as in bendable batteries," Singh said. After the reactions, the research team also dissembled and observed the cells under the electron microscope, which provided evidence that the silicon carbonitride protected against mechanical and chemical degradation with liquid organic electrolyte. Singh and his team now want to better understand how the molybdenum disulfide cells might behave in an everyday electronic device — such as a cellphone — that is recharged hundreds of times. The researchers will continue to test the molybdenum disulfide cells during recharging cycles to have more data to analyze and to better understand how to improve rechargeable batteries. Other research by Singh's team may help improve high temperature coatings for aerospace and defense. The engineers are developing a coating material to protect electrode materials against harsh conditions, such as turbine blades and metals subjected to intense heat. The research appears in the Journal of Physical Chemistry. The researchers showed that when silicon carbonitride and boron nitride nanosheets are combined, they have high temperature stability and improved electrical conductivity. Additionally, these silicon carbonitride/boron nitride nanosheets are better battery electrodes, Singh said. "This was quite surprising because both silicon carbonitride and boron nitride are insulators and have little reversible capacity for lithium-ions," Singh said. "Further analysis showed that the electrical conductivity improved because of the formation of a percolation network of carbon atoms known as 'free carbon' that is present in the silicon carbonitride ceramic phase. This occurs only when boron nitride sheets are added to silicon carbonitride precursor in its liquid polymeric phase before curing is achieved."
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