Silicon Nanowire Sensors Enable Diagnosis of Patients via Exhaled Breath

Two of the biggest challenges in medicine today are the need to detect diseases in a noninvasive manner and to differentiate between patients using a single diagnostic tool. The current study targets these two challenges by developing a molecularly modified silicon nanowire field effect transistor (SiNW FET) and showing its use in the detection and classification of many disease breathprints (lung cancer, gastric cancer, asthma, and chronic obstructive pulmonary disease). The fabricated SiNW FETs are characterized and optimized based on a training set that correlate their sensitivity and selectivity toward volatile organic compounds (VOCs) linked with the various disease breathprints. The best sensors obtained in the training set are then examined under real-world clinical conditions, using breath samples from 374 subjects. Analysis of the clinical samples show that the optimized SiNW FETs can detect and discriminate between almost all binary comparisons of the diseases under examination with >80% accuracy. Overall, this approach has the potential to support detection of many diseases in a direct harmless way, which can reassure patients and prevent numerous unpleasant investigations

Mechanism of periodic height variations along self-aligned VLS-grown planar nanostructures

In this study we report in-plane nanotracks produced by molecular-beam-epitaxy (MBE) exhibiting lateral self-assembly and unusual periodic and out-of-phase height variations across their growth axes. The nanotracks are synthesized using bismuth segregation on the GaAsBi epitaxial surface, which results in metallic liquid droplets capable of catalyzing GaAsBi nanotrack growth via the vapor–liquid–solid (VLS) mechanism. A detailed examination of the nanotrack morphologies is carried out employing a combination of scanning electron and atomic force microscopy and, based on the findings, a geometric model of nanotrack growth during MBE is developed. Our results indicate diffusion and shadowing effects play significant roles in defining the interesting nanotrack shape. The unique periodicity of our lateral nanotracks originates from a rotating nucleation “hot spot” at the edge of the liquid–solid interface, a feature caused by the relative periodic circling of the non-normal ion beam flux incident on the sample surface, inside the MBE chamber. We point out that such a concept is divergent from current models of crawling mode growth kinetics and conclude that these effects may be utilized in the design and assembly of planar nanostructures with controlled non-monotonous structure

Study of the temperature distribution in Si nanowires under microscopic laser beam excitation

The use of laser beams as excitation sources for the characterization of semiconductor nanowires (NWs) is largely extended. Raman spectroscopy and photoluminescence (PL) are currently applied to the study of NWs. However, NWs are systems with poor thermal conductivity and poor heat dissipation, which result in unintentional heating under the excitation with a focused laser beam with microscopic size, as those usually used in microRaman and microPL experiments. On the other hand, the NWs have subwavelength diameter, which changes the optical absorption with respect to the absorption in bulk materials. Furthermore, the NW diameter is smaller than the laser beam spot, which means that the optical power absorbed by the NW depends on its position inside the laser beam spot. A detailed analysis of the interaction between a microscopic focused laser beam and semiconductor NWs is necessary for the understanding of the experiments involving laser beam excitation of NWs. We present in this work a numerical analysis of the thermal transport in Si NWs, where the heat source is the laser energy locally absorbed by the NW. This analysis takes account of the optical absorption, the thermal conductivity, the dimensions, diameter and length of the NWs, and the immersion medium. Both free standing and heat-sunk NWs are considered. Also, the temperature distribution in ensembles of NWs is discussed. This analysis intends to constitute a tool for the understanding of the thermal phenomena induced by laser beams in semiconductor NWs

Modeling the dielectric function of degenerately doped ZnO Al thin films grown by ALD using physical parameters

Transparent conductive thin films are a key building block of modern optoelectronic devices. A promising alternative to expensive indium containing oxides is aluminum doped zinc oxide AZO . By correlating spectroscopic ellipsometry and photoluminescence, we analyzed the contributions of different optical transitions in AZO grown by atomic layer deposition to a model dielectric function MDF over a wide range of photon energies. The derived MDF reflects the effects of the actual band structure and therefore describes the optical properties very accurately. The presented MDF is solely based on physically meaningful parameters in contrast to empirical models like e.g. the widely used Sellmeier equation, but nevertheless real and imaginary parts are expressed as closed form expressions. We analyzed the influence of the position of the Fermi energy and the Fermi edge singularity to the different parts of the MDF. This information is relevant for design and simulation of optoelectronic devices and can be determined by analyzing the results from spectroscopic ellipsometr

Kohlenhydratzufuhr und Prävention ausgewählter ernährungsmitbedingter Krankheiten

Der relative Anteil ernährungsmitbedingter Krankheiten an der Krankheitslast der Bevölkerung und den Ausgaben im Gesundheitssystem hat in den letzten Jahrzehnten kontinuierlich zugenommen. Damit wächst die Herausforderung, die Möglichkeiten zur Primärprävention von Adipositas, Stoffwechsel- und Herz-Kreislauf-Krankheiten sowie Krebs stärker zu beachten und zu nutzen. In der vorliegenden evidenzbasierten Leitlinie der Deutschen Gesellschaft für Ernährung e. V. (DGE) wurde die Bedeutung der Kohlenhydratzufuhr für die Primärprävention dieser Krankheiten systematisch bewertet. Die Hauptergebnisse waren, dass ein hoher Konsum zuckergesüßter Getränke das Risiko für Adipositas und Diabetes mellitus Typ 2 mit wahrscheinlicher Evidenz erhöht, während ein hoher Verzehr von Ballaststoffen, vornehmlich aus Getreideprodukten, bzw. von Vollkornprodukten das Risiko für Adipositas, Diabetes mellitus Typ 2, Dyslipoproteinämie, Hypertonie, koronare Herzkrankheit und kolorektales Karzinom mit wahrscheinlicher bzw. überzeugender Evidenz senkt. Daraus lassen sich praktische Konsequenzen für die aktuellen Ernährungsempfehlungen ableiten

Bioresponsive pseudoGlucosinolates (psGSLs) release Isothiocyanates (ITCs) in the Presence of Nitroreductases

Glucosinolates (GSLs) are secondary metabolites produced as part of an herbivore defence system in plants of the order Brassicales. GSLs release isothiocyanates (ITCs) upon activation by the myrosinase. Beyond their herbivore feeding deterrent properties, these ITCs have multiple interesting bioactivities. However, their release is limited by the presence of myrosinase. Here, we report the concept of pseudoglucosinolates (psGSLs) hijacking the natural release mechanism of GSLs for the release of ITCs and adapting it to nitroreductase as triggering enzymes. We provide the proof-of-concept for nitroreductase-responsive psGSLs and demonstrate their potential for peptide labelling and ITC-prodrug approaches