Sensorsysteme zur Spurendetektion nitroaromatischer Gefahrstoffe mittels Fluoreszenz-Quenching

Diese Arbeit umfasst die Entwicklung von Sensorsystemen sowie die Untersuchung von Sensorarrays zur Spurendetektion nitroaromatischer Gefahrstoffe mittels Fluoreszenz-Quenching. Da sich nitroaromatische Spuren häufig in Sprengstoffen nachweisen lassen, stehen sicherheitsrelevante Anwendungen, wie die Sprengstofferkennung bei Grenzkontrollen, im Vordergrund der Arbeit. Darüber hinaus stellen Nitroaromaten aufgrund ihres hochtoxischen, karzinogenen, mutagenen und reproduktionstoxischen Charakters ein immenses Risiko für Mensch und Umwelt dar. Daher wird auch die Säuberung kontaminierter Gebiete und Altlasten untersucht. Somit umfassen die dargestellten Ergebnisse nicht nur die Detektion nitroaromatischer Spuren in Luft, sondern auch in Wasser. Da aktuelle Technologien, wie der Einsatz von Spürhunden oder die Verwendung von Ionen-Mobilitäts-Spektrometern (IMS), noch nicht alle Anwendungs- und Benutzeranforderungen erfüllen, wird als erstes Ergebniskapitel der Entwurf optoelektronischer Detektionssysteme erläutert. Systeme auf Basis des Fluoreszenz-Quenchings stellen hierbei eine neuartige Alternative und Ergänzung zu Spürhunden und IMS-Systemen dar. Für die vorliegende Arbeit wird daher ausgehend von Laboraufbauten die Entwicklung verschiedener tragbarer Detektionssysteme vorgestellt. Die Entwicklung einer neuartigen Temperaturstabilisierung mit Entfeuchtungswirkung bietet darüber hinaus eine praktische Komponente für den realen Einsatz solcher Systeme. Im Anschluss an die Systementwicklung werden das Design und die Realisierung optoelektronischer Nasen für die Sprengstofferkennung eingehend untersucht. Durch eine Prüfung verschiedener Herstellungsmethoden wird dabei das Aerosol-Jet-Drucken als geeignetes Verfahren zur Herstellung von Sensorarrays identifiziert. Hierbei werden die Vorteile und Stärken des Digitaldrucks für die reproduzierbare Herstellung von Sensorarrays nachgewiesen. Für die Interpretation der Sensorarraysignale wird außerdem die lineare Diskriminanzanalyse (LDA) als geeignetes Mustererkennungsverfahren demonstriert. Damit können nitroaromatische Analyten bei verschiedenen Konzentrationen unterschieden werden. Für die Analyse kontaminierter Gewässer werden außerdem das Design und die Realisierung optoelektronischer Zungen thematisiert. Neben Voruntersuchungen in Toluol werden mikrofluidische Experimente in Wasser demonstriert. Hierbei zeigen die Aerosol-Jet gedruckten Sensorarrays erneut ein hohes Potential zur Identifizierung und Quantifizierung einzelner Nitroaromaten auf. Insgesamt können auf Basis der dargestellten Ergebnisse potenziell kostengünstige Sensorarrays mittels Aerosol-Jet-Druckens hergestellt werden. Mithilfe von Mustererkennungsverfahren sind diese optoelektronischen Nasen bzw. Zungen in der Lage, detektierte Analyten zu identifizieren und zu quantifizieren. Die für die optoelektronischen Nasen demonstrierte Reproduzierbarkeit und Robustheit ermöglicht dabei einen potenziell geringen Anlernaufwand für die Mustererkennung. Dadurch eröffnen sich neue Möglichkeiten sowie ein tendenziell kostengünstiger kommerzieller Einsatz dieser Sensortechnologie in flexibel und modular verwendbaren Detektionssystemen. Aufgrund druckbarer Photodioden und der Vision gedruckter ultraviolett (UV) emittierender Leuchtdioden (LEDs), bildet die vorliegende Arbeit darüber hinaus einen grundlegenden Baustein auf dem Weg zu vollständig gedruckten Sensorsystemen, die in hochintegrierter Form völlig neue Anwendungen ermöglichen

Single-photon emission from Ni-related color centers in CVD diamond

Color centers in diamond are very promising candidates among the possible realizations for practical single-photon sources because of their long-time stable emission at room temperature. The popular nitrogen-vacancy center shows single-photon emission, but within a large, phonon-broadened spectrum (~100nm), which strongly limits its applicability for quantum communication. By contrast, Ni-related centers exhibit narrow emission lines at room temperature. We present investigations on single color centers consisting of Ni and Si created by ion implantation into single crystalline IIa diamond. We use systematic variations of ion doses between 10^8/cm^2 and 10^14/cm^2 and energies between 30keV and 1.8MeV. The Ni-related centers show emission in the near infrared spectral range (~770nm to 787nm) with a small line-width (~3nm FWHM). A measurement of the intensity correlation function proves single-photon emission. Saturation measurements yield a rather high saturation count rate of 77.9 kcounts/s. Polarization dependent measurements indicate the presence of two orthogonal dipoles.Comment: 8 pages, published in conference proceedings of SPIE Photonics Europe 201

The effect of interstitial clusters and vacancies on the STM image of graphite

Making use of the tight-binding Green's function technique, we have calculated the STM images of graphite with surface and sub-surface defects, while taking into account the relaxation of the lattice due to defects. We have demonstrated that two different physical mechanisms may result in the formation of hillocks in the STM images: buckling of the graphite surface due to interstitials between the uppermost graphite layers and the enhancement of the electron density of states close to the Fermi energy on the carbon atoms in the vicinity of vacancies. Our results indicate that small hillocks may originate both from the interstitial clusters and from the vacancies. By contrast, however, large hillocks in excess of 10 \AA~ in diameter can be caused only by interstitial clusters.Comment: Submitted to Surface Scienc

Fördelning av intäkter från gemensamma delar

Syftet med uppsatsen var att beskriva och analysera hur intäkter kan fördelas för delar som gemensamt används av produkter med olika varumärken, hur dessa intäkter bör fördelas samt de motiv som är orsaken till de valda metoderna för fördelning. Det empiriska materialet som presenteras i uppsatsen består av primärdata som samlats in genom intervjuer med respondenter från Saab Automobiles, Svenska Volkswagen AB och Volvo Car Corporation. Underlaget innefattar även sekundärdata som främst insamlats från fallföretagens hemsidor. Efter att ha genomfört studier med tre fallföretag besvarades problemformuleringarna. Uppmärksammas bör att resultaten inte är generaliserbara utan att de endast avser de medverkande fallföretagen. Studien fann att: 1. Fördelning av gemensamma intäkter antingen sker med hjälp av fördelningsnycklar eller med internprissättning. Uppmärksammas bör att fördelningsnycklar och internprissättning löser olika problem som de gemensamma intäkterna kan ge upphov till. 2. Valet av metod som används för att fördela gemensamma intäkter är beroende av organisationens struktur. 3. Studien bidrog även med ett antal kriterier med vars hjälp fördelningsnycklar och internprissättningssystem kan utformas

Clusters of interstitial carbon atoms near the graphite surface as a possible origin of dome-like features observed by STM

Formation of clusters of interstitial carbon atoms between the surface and second atomic layers of graphite is demonstrated by means of molecular dynamics simulations. It is shown that interstitial clusters result in the dome-like surface features that may be associated with some of the hillocks observed by STM on the irradiated graphite surface.Comment: 7 pages, 7 eps figures, submitted to Surface Scienc

A digitally printed optoelectronic nose for the selective trace detection of nitroaromatic explosive vapours using fluorescence quenching

We report on a fluorescent optoelectronic nose for the trace detection of nitroaromatic explosive vapours. The sensor arrays, fabricated by aerosol-jet printing, consist of six different commercially available polymers as transducers. We assess the within-batch reproducibility of the printing process and we report that the sensor polymers show efficient fluorescence quenching capabilities with detection limits of a few parts-per-billion in air. We further demonstrate the nose\u27s ability to discriminate between several nitroaromatics including nitrobenzene, 1,3-dinitrobenzene and 2,4-dinitrotoluene at three different concentrations using linear discriminant analysis. Our approach enables the realization of highly integrated optical sensor arrays in optoelectronic noses for the sensitive and selective detection of nitroaromatic explosive trace vapours using a potentially low-cost digital printing technique suitable for high-volume fabrication

Ultra-bright and efficient single photon generation based on N-V centres in nanodiamonds on a solid immersion lens

Single photons are fundamental elements for quantum information technologies such as quantum cryptography, quantum information storage and optical quantum computing. Colour centres in diamond have proven to be stable single photon sources and thus essential components for reliable and integrated quantum information technology. A key requirement for such applications is a large photon flux and a high efficiency. Paying tribute to various attempts to maximise the single photon flux we show that collection efficiencies of photons from colour centres can be increased with a rather simple experimental setup. To do so we spin-coated nanodiamonds containing single nitrogen-vacancy colour centres on the flat surface of a ZrO2 solid immersion lens. We found stable single photon count rates of up to 853 kcts/s at saturation under continuous wave excitation while having excess to more than 100 defect centres with count rates from 400 kcts/s to 500 kcts/s. For a blinking defect centre we found count rates up to 2.4 Mcts/s for time intervals of several ten seconds. It seems to be a general feature that very high rates are accompanied by a blinking behaviour. The overall collection efficiency of our setup of up to 4.2% is the highest yet reported for N-V defect centres in diamond. Under pulsed excitation of a stable emitter of 10 MHz, 2.2% of all pulses caused a click on the detector adding to 221 kcts/s thus opening the way towards diamond based on-demand single photon sources for quantum applications

Single photon emitters based on Ni/Si related defects in single crystalline diamond

We present investigations on single Ni/Si related color centers produced via ion implantation into single crystalline type IIa CVD diamond. Testing different ion dose combinations we show that there is an upper limit for both the Ni and the Si dose 10^12/cm^2 and 10^10/cm^2 resp.) due to creation of excess fluorescent background. We demonstrate creation of Ni/Si related centers showing emission in the spectral range between 767nm and 775nm and narrow line-widths of 2nm FWHM at room temperature. Measurements of the intensity auto-correlation functions prove single-photon emission. The investigated color centers can be coarsely divided into two groups: Drawing from photon statistics and the degree of polarization in excitation and emission we find that some color centers behave as two-level, single-dipole systems whereas other centers exhibit three levels and contributions from two orthogonal dipoles. In addition, some color centers feature stable and bright emission with saturation count rates up to 78kcounts/s whereas others show fluctuating count rates and three-level blinking.Comment: 7 pages, submitted to Applied Physics B, revised versio

Lab-on-Chip, Surface-Enhanced Raman Analysis by Aerosol Jet Printing and Roll-to-Roll Hot Embossing

Surface-enhanced Raman spectroscopy (SERS) combines the high specificity of Raman scattering with high sensitivity due to an enhancement of the electromagnetic field by metallic nanostructures. However, the tyical fabrication methods of SERS substrates suffer from low throughput and therefore high costs. Furthermore, point-of-care applications require the investigation of liquid solutions and thus the integration of the SERS substrate in a microfluidic chip. We present a roll-to-roll fabrication approach for microfluidics with integrated, highly efficient, surface-enhanced Raman scattering structures. Microfluidic channels are formed using roll-to-roll hot embossing in polystyrene foil. Aerosol jet printing of a gold nanoparticle ink is utilized to manufacture highly efficient, homogeneous, and reproducible SERS structures. The modified channels are sealed with a solvent-free, roll-to-roll, thermal bonding process. In continuous flow measurements, these chips overcome time-consuming incubation protocols and the poor reproducibility of SERS experiments often caused by inhomogeneous drying of the analyte. In the present study, we explore the influence of the printing process on the homogeneity and the enhancement of the SERS structures. The feasibility of aerosol-jet-modified microfluidic channels for highly sensitive SERS detection is demonstrated by using solutions with different concentrations of Rhodamine 6G and adenosine. The printed areas provide homogeneous enhancement factors of ~4 × 106. Our work shows a way towards the low-cost production of tailor-made, SERS-enabled, label-free, lab-on- chip systems for bioanalysis