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Die Detektion von Explosivstoffen stellt ein zentrales Feld der zivilen Sicherheitsforschung dar. Eine besondere Herausforderung liegt hierbei in dem Nachweis verpackter Substanzen, wie es bei Unkonventionellen Spreng- und Brandvorrichtung (USBV) häufig der Fall ist. Derzeit eingesetzte Verfahren arbeiten meist mit bildgebenden Techniken, durch die sich ein Anfangsverdacht ergibt. Der tatsächliche chemische Inhalt der USBV lässt sich jedoch nicht exakt ermitteln. Eine genaue Beurteilung der Gefährdung durch solche Substanzen ist allerdings von großer Bedeutung, insbesondere wenn die Entschärfung des Objekts in bewohntem Gebiet stattfinden muss. In der vorliegenden Arbeit wird ein Verfahren vorgestellt, das sich als Verifikationsverfahren bei bestehendem Anfangsverdacht gezielt einsetzen lässt. Hierzu wird mittels Laserbohrtechnik zunächst die äußere Hülle des zu untersuchenden Gegenstandes durchdrungen. Anschließend finden eine lasergestützte Probenahme des Inhalts sowie die Detektion unter Verwendung geeigneter Analysemöglichkeiten statt. Der Bohr- und Probenahmefortschritt wird über verschiedene spektroskopische und sensorische Verfahren begleitend überwacht. Zukünftig soll das System abstandsfähig auf Entschärfungsrobotern eingesetzt werden.
In der vorliegenden Arbeit wird ein neuartiges Verfahren zur Echtzeitüberwachung von Laserbohrprozessen vorgestellt. Die Untersuchungen werden an unterschiedlichen Materialien unter Einsatz eines passiv-gütegeschalteten Nd:YAG Lasers durchgeführt. Prozessbegleitend findet eine Aufzeichnung der akustischen Emissionen mit anschließender Analyse durch schnelle Fourier-Transformation statt. Hierdurch lassen sich der Durchbruch beim Bohren durch ein Material sowie der Materialübergang mehrschichtiger Systeme detektieren. Die akustischen Messungen werden durchAuswertung der Pulsfolge des Lasers mittels einer Fotodiode gestützt. Hierbei zeigt sich eine gute Übereinstimmung der im akustischen Spektrum dominanten Frequenz mit der jeweils im Laserburstauftretenden Pulsfrequenz. Das vorgestellte Verfahren ermöglicht eine Echtzeitüberwachung beim Laserbohren mittels kostengünstiger und einfacher Hardware. Zudem zeichnet es sich im Gegensatz zu bestehenden Verfahren durch eine hohe Robustheit gegen äußere Störeinflüsse aus, da eine frequenzbasierte Auswertung stattfindet.
In this work, the surface reactions of the homemade explosive triacetone triperoxide on tungsten oxide (WO3) sensor surfaces are studied to obtain detailed information about the chemical reactions taking place. Semiconductor gas sensors based on WO3 nanopowders are therefore produced and characterized by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. To analyze the reaction mechanisms at the sensor surface, the sensor is monitored online under operation conditions using Raman spectroscopy, which allows to identify the temperature-dependent sensor reactions. By combining information from the Raman spectra with data on the changing resistivity of the underlying semiconductor, it is possible to establish a correlation between the adsorbed gas species and the physical properties of the WO3 layer. In the results, it is indicated that a Lewis acid–base reaction is the most likely mechanism for the increase in resistance observed at temperatures below 150 °C. In the results, at higher temperatures, the assumption of a radical mechanism that causes a decrease in resistance is supported.
Sensoren können verschiedene Aufgaben erfüllen, wie beispielsweise die Optimierung von Prozessen, die Interaktion zwischen Geräten oder die Verbesserung der zivilen Sicherheit. [1–3] Ihr Bedarf für die Industrie oder den Alltag wächst seit Jahren stetig. Besonders mobile Gassensoren sind von großem Interesse. Jedoch ist ihre Anwendung meist durch ihre integrierte Batterie begrenzt. Gassensoren ohne oder mit einem nur sehr geringen Energieverbrauch stehen daher im Interesse bei neuen Anwendungsgebieten, beispielsweise im Brandschutz oder in der Textilindustrie. [4,5] Die Sensoren könnten zum Beispiel in die Textilien einer persönlichen Schutzausrüstung eingearbeitet werden und durch einen Farbumschlag die Anwesenheit eines Gases oder die Überschreitung des Grenzwertes toxischer Substanzen anzeigen.
A deployment of the Vehicle-2-Vehicle communication technology according to ETSI is in preparation in Europe. Currently, a policy for a necessary Public Key Infrastructure to enrol cryptographic keys and certificates for vehicles and infrastructure component is in discussion to enable an interoperable Vehicle-2-Vehicle communication. Vehicle-2-Vehicle communication means that vehicles periodically send Cooperative Awareness Messages. These messages contain the current geographic position, driving direction, speed, acceleration, and the current time of a vehicle. To protect privacy (location privacy, “speed privacy”) of vehicles and drivers ETSI provides a specific pseudonym concept. We show that the Vehicle-2-Vehicle communication can be misused by an attacker to plot a trace of sequent Cooperative Awareness Messages and to link this trace to a specific vehicle. Such a trace is non-disputable due to the cryptographic signing of the messages. So, the periodically sending of Cooperative Awareness Messages causes privacy problems even if the pseudonym concept is applied.
A deployment of the Vehicle-to-Vehicle communication technology according to ETSI is in preparation in Europe. Currently, a Public Key Infrastructure policy for Intelligent Transport Systems in Europe is in discussion to enable V2V communication. This policy set aside two classes of keys and certificates for ITS vehicle stations: long term authentication keys and pseudonymous keys and certificates. We show that from our point of view the periodic sent Cooperative Awareness Messages with extensive data have technical limitations and together with the pseudonym concept cause privacy problems.
Intimate swabs taken for examination in sexual assault cases typically yield mixtures of sperm and epithelial cell types. While powerful, differential extraction protocols to overcome such cell type mixtures by separate lysis of epithelial cells and spermatozoa can still prove ineffective, in particular if only few sperm cells are present or if swabs contain sperm from more than one individual leading to complex low level DNA mixtures. A means to avoid such mixtures consists in the analysis of single micromanipulated sperm cells. However, the quantity of DNA from single sperm cells is not sufficient for conventional STR analysis. Here, we describe a simple method for micromanipulating individual sperm cells from intimate swabs and show that whole genome amplification can generate sufficient amounts of DNA from single cells for subsequent DNA profiling. We recovered over 80% of alleles of haploid autosomal STR profiles from the majority of individual sperm cells. Furthermore, we demonstrate that in mixtures of sperm from two contributors, Y-STR and X-STR profiles of individual sperm cells can be used to sort the haploid autosomal profiles to develop the diploid consensus STR profiles of the individual donors. Finally, by analysing single sperm cells from mock sexual assault swabs with one or two sperm donors, we showed that our protocols enabled the identification of the unknown male contributors.
Design of an Active Multispectral SWIR Camera System for Skin Detection and Face Verification
(2016)
Biometric face recognition is becoming more frequently used in different application scenarios. However, spoofing attacks with facial disguises are still a serious problem for state of the art face recognition algorithms. This work proposes an approach to face verification based on spectral signatures of material surfaces in the short wave infrared (SWIR) range. They allow distinguishing authentic human skin reliably from other materials, independent of the skin type. We present the design of an active SWIR imaging system that acquires four-band multispectral image stacks in real-time. The system uses pulsed small band illumination, which allows for fast image acquisition and high spectral resolution and renders it widely independent of ambient light. After extracting the spectral signatures from the acquired images, detected faces can be verified or rejected by classifying the material as "skin" or "no-skin". The approach is extensively evaluated with respect to both acquisition and classification performance. In addition, we present a database containing RGB and multispectral SWIR face images, as well as spectrometer measurements of a variety of subjects, which is used to evaluate our approach and will be made available to the research community by the time this work is published.
At previous SIAS conferences, we presented a novel opto-electronic safety sensor system for skin detection at circular saws jointly developed with the Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA). This work now presents the development results of our consecutive research on a prototype of a sensor system for more general production machine applications including robot workplaces. The system uses offthe shelf LEDs and photodiodes in combination with dedicated optics and a microcontroller system to implement a so-called spectral light curtain.
This paper presents recent research on an active multispectral scanning sensor capable of classifying an object's surface material in order to distinguish between different kinds of materials and human skin. The sensor itself has already been presented in previous work and can be used in conjunction with safeguarding equipment at manually-fed machines or robot workplaces, for example. This work shows how an extended sensor system with advanced material classifiers can be used to provide additional value by distinguishing different materials of work pieces in order to suggest different tools or parameters for the machine (e.g. the use of a different saw blade or rotation speed at table saws). Additionally, a first implementation and evaluation of an active multispectral camera system addressing new safety applications is described. Both approaches intend to increase the productivity and the user's acceptance of the sensor technology.
Microcontroller-based sensor systems offer great opportunities for the implementation of safety features for potentially dangerous machinery. However, in general they are difficult to assess with regard to their reliability and failure rate. This paper describes the safety assessment of hardware and software of a new and innovative sensor system. The hardware is assessed by standardized methods according to norm EN ISO 13849-1, while the use of model checking is presented as an approach to solve the problem of validating the software.
The detection of human skin in images is a very desirable feature for applications such as biometric face recognition, which is becoming more frequently used for, e.g., automated border or access control. However, distinguishing real skin from other materials based on imagery captured in the visual spectrum alone and in spite of varying skin types and lighting conditions can be dicult and unreliable. Therefore, spoofing attacks with facial disguises or masks are still a serious problem for state of the art face recognition algorithms. This dissertation presents a novel approach for reliable skin detection based on spectral remission properties in the short-wave infrared (SWIR) spectrum and proposes a cross-modal method that enhances existing solutions for face verification to ensure the authenticity of a face even in the presence of partial disguises or masks. Furthermore, it presents a reference design and the necessary building blocks for an active multispectral camera system that implements this approach, as well as an in-depth evaluation. The system acquires four-band multispectral images within T = 50ms. Using a machine-learning-based classifier, it achieves unprecedented skin detection accuracy, even in the presence of skin-like materials used for spoofing attacks. Paired with a commercial face recognition software, the system successfully rejected all evaluated attempts to counterfeit a foreign face.
Persons entering the working range of industrial robots are exposed to a high risk of collision with moving parts of the system, potentially causing severe injuries. Conventional systems, which restrict the access to this area, range from walls and fences to light barriers and other vision based protective devices (VBPD). None of these systems allow to distinguish between humans and workpieces in a safe and reliable manner. In this work, a new approach is investigated, which uses an active near-infrared (NIR) camera system with advanced capabilities of skin detection to distinguish humans from workpieces based on characteristic spectral signatures. This approach allows to implement more intelligent muting processes and at the same time increases the safety of persons working close to the robots. The conceptual integration of such a camera system into a VBPD and the enhancement of person detection methods through skin detection are described and evaluated in this paper. Based upon this work, next steps could be the development of multimodal sensor systems to safeguard working ranges of collaborating robots using the described camera system.
A series of reactive binaphthyl‐diimine‐based dopants is prepared and investigated with respect to their potential for the chiral induction of structural coloration in nematic liquid crystal mixture E7 and the selective photonic sensing of nitrogen dioxide (NO2). Studies of the helical twisting power (HTP) in 4‐cyano‐4′‐pentylbiphenyl (5CB) reveal HTP values as high as 375 µm‐1 and the tremendous impact of structural compatibility and changes of the dihedral binaphthyl angle on the efficiency of the chiral transfer. Detailed investigation of the sensing capabilities of the systems reveals an extraordinarily high selectivity for NO2 and a response to concentrations as low as 100 ppm. The systems show a direct response to the analyte gas leading to a concentration‐dependent shift of the reflectance wavelength of up to several hundred nanometers. Incorporation of copper ions remarkably improves the sensor's properties in terms of sensitivity and selectivity, enabling the tailored tweaking of the system's properties.
With the increasing demand for ultrapure water in the pharmaceutical and semiconductor industry, the need for precise measuring instruments for those applications is also growing. One critical parameter of water quality is the amount of total organic carbon (TOC). This work presents a system that uses the advantage of the increased oxidation power achieved with UV/O3 advanced oxidation process (AOP) for TOC measurement in combination with a significant miniaturization compared to the state of the art. The miniaturization is achieved by using polymer-electrolyte membrane (PEM) electrolysis cells for ozone generation in combination with UV-LEDs for irradiation of the measuring solution, as both components are significantly smaller than standard equipment. Conductivity measurement after oxidation is the measuring principle and measurements were carried out in the TOC range between 10 and 1000 ppb TOC. The suitability of the system for TOC measurement is demonstrated using the oxidation by ozonation combined with UV irradiation of defined concentrations of isopropyl alcohol (IPA).
In this paper, we introduce an optical sensor system, which is integrated into an industrial push-button. The sensor allows to classify the type of material that is in contact with the button when pressed into different material categories on the basis of the material's so called "spectral signature". An approach for a safety sensor system at circular table saws on the same base has been introduced previously on SIAS-2007. This contactless working sensor is able to distinguish reliably between skin, textiles, leather and various other kinds of materials. A typical application for this intelligent push-button is the use at possibly dangerous machines, whose operating instructions include either the prohibition or the obligation to wear gloves during the work at the machine. An exemple of machines at which no gloves are allowed are pillar drilling machines, because of the risk of getting caught in the drill chuck and being turned in by the machine. In many cases this causes very serious hand injuries. Depending on the application needs, the sensor system integrated into the push-button can be configured flexibly by software to prevent the operator from accidentally starting a machine with or without gloves, which can decrease the risk of severe accidents significantly. Especially two-hand controls are incentive to manipulation for easier handling. By equipping both push-buttons of a two-hand control with material classification properties, the user is forced to operate the controls with his bare fingers. That limitation disallows the manipulation of a two-hand control by a simple rodding device.
Vorrichtung zur Authentifikation einer Person anhand mindestens eines biometrischen Parameters
(2008)
Die Vorrichtung zur Authentifikation einer Person anhand mindestens eines biometrischen Parameters, insbesondere anhand eines Fingerabdrucks, ist versehen mit einem Biometrie-Detektor (20) zur Detektion eines biometrischen Parameters, einem Haut-Detektor (24) zur berührungslosen Erkennung lebender menschlicher Haut innerhalb eines Erfassungsbereichs. Der Haut-Detektor (24) weist mindestens eine Gruppe aus mindestens einer Strahlungseinheit (26, 28) und mindestens einer Empfangseinheit (30) auf. Die mindestens eine Strahlungseinheit (26, 28) gibt in Richtung auf den Erfassungsbereich Strahlung bei mindestens zwei unterschiedlichen Wellenlängen im Wellenlängenbereich zwischen 400 nm und 1500 nm ab, wobei mindestens eine der Wellenlängen (26, 28) im Wellenlängenbereich von 900 nm bis 1500 nm liegt und die mindestens eine Empfangseinheit (30) aus dem Erfassungsbereich reflektierte Strahlung empfängt. Ferner ist die Vorrichtung versehen mit einer mit dem Biometer-Detektor (20) und dem Haut-Detektor (24) verbundenen Signalauswerteeinheit (22) zur Auswertung der Intensität der von der Empfangseinheit (30) empfangenen reflektierten Strahlungen der Strahlungseinheit (26, 28). In der Signalauswerteeinheit (22) ist anhand der Intensitäten der von der Empfangseinheit (30) empfangenen reflektierten Strahlungen der Strahlungseinheit (26, 28) bei den zwei unterschiedlichen Wellenlängen ermittelbar, ob der Haut-Detektor lebende menschliche Haut erkennt.
The use of manually fed machines (e.g. table saws) bares risks of injury that are clearly above the average level of other high risk workplaces.
The wide use of such machines causes severe problems for occupational safety and implies high costs for medical treatments and accident annuities.
This thesis presents a new concept of a multispectral sensor to monitor an area in front of a danger zone to detect the user’s limbs and trigger safeguarding measures to prevent an accident in time.
The sensor concept realizes a contact-free material classification, which comprises the development of a system design and specific safety requirements with respect to international safety standards.
Furthermore, a prototypical implementation using four wavebands, which were determined for skin detection through an analysis of reflectance spectra acquired specifically for this purpose, was built.
Polymer fibers with liquid crystals (LCs) in the core have potential as autonomous sensors of airborne volatile organic compounds (VOCs), with a high surface-to-volume ratio enabling fast and sensitive response and an attractive non-woven textile form factor. We demonstrate their ability to continuously and quantitatively measure the concentration of toluene, cyclohexane, and isopropanol as representative VOCs, via the impact of each VOC on the LC birefringence. The response is fully reversible and repeatable over several cycles, the response time can be as low as seconds, and high sensitivity is achieved when the operating temperature is near the LC-isotropic transition temperature. We propose that a broad operating temperature range can be realized by combining fibers with different LC mixtures, yielding autonomous VOC sensors suitable for integration in apparel or in furniture that can compete with existing consumer-grade electronic VOC sensors in terms of sensitivity and response speed.
Due to their user-friendliness and reliability, biometric systems have taken a central role in everyday digital identity management for all kinds of private, financial and governmental applications with increasing security requirements. A central security aspect of unsupervised biometric authentication systems is the presentation attack detection (PAD) mechanism, which defines the robustness to fake or altered biometric features. Artifacts like photos, artificial fingers, face masks and fake iris contact lenses are a general security threat for all biometric modalities. The Biometric Evaluation Center of the Institute of Safety and Security Research (ISF) at the University of Applied Sciences Bonn-Rhein-Sieg has specialized in the development of a near-infrared (NIR)-based contact-less detection technology that can distinguish between human skin and most artifact materials. This technology is highly adaptable and has already been successfully integrated into fingerprint scanners, face recognition devices and hand vein scanners. In this work, we introduce a cutting-edge, miniaturized near-infrared presentation attack detection (NIR-PAD) device. It includes an innovative signal processing chain and an integrated distance measurement feature to boost both reliability and resilience. We detail the device’s modular configuration and conceptual decisions, highlighting its suitability as a versatile platform for sensor fusion and seamless integration into future biometric systems. This paper elucidates the technological foundations and conceptual framework of the NIR-PAD reference platform, alongside an exploration of its potential applications and prospective enhancements.
Optical gas sensors based on chiral-nematic liquid crystals (N* LCs) forming one-dimensional photonic crystals do not require electrical energy and have a considerable potential to supplement established types of sensors. A chiral-nematic phase with tunable selective reflection is induced in a nematic host LC by adding reactive chiral dopants. The selective chemical reaction between dopant and analyte is capable to vary the pitch length (the lattice constant) of the soft, self-assembled, one-dimensional photonic crystal. The progress of the ongoing chemical reaction can be observed even by naked eye because the color of the samples varies. In this work, we encapsulate the responsive N* LC in microscale polyvinylpyrrolidone (PVP) fibers via coaxial electrospinning. The sensor is, thus, given a solid form and has an improved stability against nonavoidable environmental influences. The reaction behavior of encapsulated and nonencapsulated N* LC toward a gaseous analyte is compared, systematically. Making use of the encapsulation is an important step to improve the applicability.
Durch Dotierung eines nematischen Flüssigkristalles mit einer chiralen Substanz wird eine helikal strukturierte Phase induziert, die in der Lage ist, einfallendes Licht wellenlängenselektiv zu reflektieren. Bei der Reaktion des Dotiermittels mit einem gasförmigen Analyten verändern sich die Ganghöhe dieser Struktur und damit die reflektierte Wellenlänge. Liegt diese im Bereich des sichtbaren Lichts, ist eine Farbänderung mit dem menschlichen Auge zu beobachten. Es ist dabei sinnvoll den Flüssigkristall z.B. in einem Polymer einzukapseln, um ihn vor mechanischen Einflüssen und Umwelteinflüssen zu schützen. Eine Möglichkeit zur Einkapselung ist das koaxiale Elektrospinnen. Vorteile sind unter anderem die Realisierung einer großen Oberfläche und einer sehr geringen Wanddicke der schützenden Schale, die die Diffusion von Gasen durch die Wand hindurch ermöglicht. Um die Funktionsfähigkeit eines solchen Sensors zu testen, wurde ein CO2-sensitiver Flüssigkristall verwendet. Dieser wurde in eine Schale aus Polyvinylpyrrolidon (PVP) versponnen und die Reaktion mit CO2 spektroskopisch analysiert.
The application of Raman and infrared (IR) microspectroscopy is leading to hyperspectral data containing complementary information concerning the molecular composition of a sample. The classification of hyperspectral data from the individual spectroscopic approaches is already state-of-the-art in several fields of research. However, more complex structured samples and difficult measuring conditions might affect the accuracy of classification results negatively and could make a successful classification of the sample components challenging. This contribution presents a comprehensive comparison in supervised pixel classification of hyperspectral microscopic images, proving that a combined approach of Raman and IR microspectroscopy has a high potential to improve classification rates by a meaningful extension of the feature space. It shows that the complementary information in spatially co-registered hyperspectral images of polymer samples can be accessed using different feature extraction methods and, once fused on the feature-level, is in general more accurately classifiable in a pattern recognition task than the corresponding classification results for data derived from the individual spectroscopic approaches.
Forensic DNA profiles are established by multiplex PCR amplification of a set of highly variable short tandem repeat (STR) loci followed by capillary electrophoresis (CE) as a means to assign alleles to PCR products of differential length. Recently, CE analysis of STR amplicons has been supplemented by high-throughput next generation sequencing (NGS) techniques that are able to detect isoalleles bearing sequence polymorphisms and allow for an improved analysis of degraded DNA. Several such assays have been commercialised and validated for forensic applications. However, these systems are cost-effective only when applied to high numbers of samples. We report here an alternative, cost-efficient shallow-sequence output NGS assay called maSTR assay that, in conjunction with a dedicated bioinformatics pipeline called SNiPSTR, can be implemented with standard NGS instrumentation. In a back-to-back comparison with a CE-based, commercial forensic STR kit, we find that for samples with low DNA content, with mixed DNA from different individuals, or containing PCR inhibitors, the maSTR assay performs equally well, and with degraded DNA is superior to CE-based analysis. Thus, the maSTR assay is a simple, robust and cost-efficient NGS-based STR typing method applicable for human identification in forensic and biomedical contexts.
The human gut microbiota harbors untapped potential for biotechnological applications. Within the phylum of Bacteroidota, Phocaeicola vulgatus stands out as a promising candidate for sustainable production of key platform chemicals like succinate. However, genetic engineering of Phocaeicola sp. remains challenging due to its intricate molecular landscape. This study lays the groundwork for manipulating the central carbon pathways in Phocaeicola vulgatus, offering insights into overcoming genetic hurdles for increased succinate yields.
Unkonventionelle Spreng- und Brandvorrichtungen sind Bedrohungen in den weltweiten Konfliktherden und werden bei terroristischen Aktivitäten verwendet. Der Schutz von Menschen und Material erfordert daher effektive Gegenmaßnahmen. Dazu gehört auch die Anforderung an Sicherheitskräfte oder militärisches Personal, unbekannte Substanzfunde mit geringem zeitlichem und logistischem Aufwand vor Ort als gefährdend oder unkritisch einzustufen. Um Explosivstoffe von nicht-explosiven Materialien zu unterscheiden, kann die bei Explosivstoffen initiierbare, stark exotherme Reaktion genutzt werden. Diese resultiert in Strahlungsemissionen sowie in lokaler Druck- und Temperaturerhöhung. Die Messung dieser Reaktionseffekte und die Anforderung an eine mobile, einfach zu bedienende und robuste Analytik werden durch ein System ermöglicht, das Proben im einstelligen mg-Bereich durch schnelles Erhitzen auf mikrostrukturierten Heizern zum chemischen Umsatz anregt. Die emittierte Strahlung wird mit Photodioden im Bereich des sichtbaren und nah-infraroten Lichts aufgenommen, ein Sensor registriert die Druckerhöhung in einer geschlossenen Versuchskammer. In einem zweiten Aufbau werden die gasförmigen Reaktionsprodukte über ein Sensorarray von vier kommerziellen Gassensoren geleitet und die Signalantworten der Halbleitergassensoren mittels Hauptkomponentenanalyse ausgewertet. Die Ergebnisse zeigen, dass die schnelle thermische Aktivierung für die untersuchten primären Explosivstoffe, Treibladungspulver, sowie Trinitrotoluol (TNT) reproduzierbar erfolgt. Nicht-Explosivstoffe werden dabei im untersuchten Umfang sicher als unkritisch erkannt. Die Auswertung der Gassensorsignale liefert eine Unterscheidung von Nitrat- und Peroxid-basierten Sprengstoffen sowie von nicht-explosiven Substanzen.
Hydrogen‐Bonded Cholesteric Liquid Crystals—A Modular Approach Toward Responsive Photonic Materials
(2022)
A supramolecular approach for photonic materials based on hydrogen-bonded cholesteric liquid crystals is presented. The modular toolbox of low-molecular-weight hydrogen-bond donors and acceptors provides a simple route toward liquid crystalline materials with tailor-made thermal and photonic properties. Initial studies reveal broad application potential of the liquid crystalline thin films for chemo- and thermosensing. The chemosensing performance is based on the interruption of the intermolecular forces between the donor and acceptor moieties by interference with halogen-bond donors. Future studies will expand the scope of analytes and sensing in aqueous media. In addition, the implementation of the reported materials in additive manufacturing and printed photonic devices is planned.
Explorative experiments were done to figure out differences in the emission of volatile organic compounds (VOCs) of not infested trees and trees infested by Anoplophora glabripennis (Asian longhorn beetle, ALB), a quarantine pest. Therefore, VOCs from some native insect species, Anoplophora glabripennis infested Acer, stressed Acer, healthy Acer, Populus and Salix were obtained by enrichment on adsorbents. Qualitative analysis was done by thermal desorption gas chromatography coupled with a mass selective detector (TD-GC/MS). Altogether 169 substances were identified. 11 substances occur from ALB infested or mechanically damaged trees i.e. stressed trees, but not from healthy trees. (+)-Cyclosativene, (+)-α-longipinene, copaene and caryophyllene are detectable only from ALB-infested Acer not from mechanically damaged or healthy Acer. However, these substances are also emitted by healthy Salix. 2,4-Dimethyl-1-heptene is among all tree samples exclusively present in the ambience of ALB-infested trees. It´s rarely detectable from native insect species’ samples.
Der Asiatische Laubholzbockkäfer (Anoplophora glabripennis, kurz: ALB) ist ein Bockkäfer, der 2001 seinen Weg nach Europa fand. Er ist als Quarantäneschaderreger eingestuft und muss in Europa bekämpft werden. Eine der Möglichkeiten zum Aufspüren befallener Bäume ist der Einsatz von Spürhunden. Die Einstufung des ALB als Quarantäneschädling bringt große Probleme bei der Verwendung von Trainingsmaterial mit sich. Da es sich zudem um biologisches Material handelt, das geruchchemisch Änderungen und Variationen unterworfen ist, und da die für den Hund relevanten Geruchsstoffe nicht bekannt sind, ist es häufig schwierig, geeignete und frische Geruchsträger als Trainingshilfsmittel zur Verfügung zu stellen.