Indiana University-Purdue University Indianapolis (IUPUI) / Volatile organic compounds (VOCs) are endogenous byproducts of metabolic pathways that can be altered by a disease or condition, leading to an associated and unique VOC profile or signature. Current methodologies for VOC detection include canines, gas chromatography-mass spectrometry (GC-MS), and electronic nose (eNose). Some of the challenges for canines and GC-MS are cost-effectiveness, extensive training, expensive instrumentation. On the other hand, a significant downfall of the eNose is low selectivity. This thesis proposes to design a breathalyzer using chemiresistive gas sensors that detects VOCs from human breath, and subsequently create an interface to process and deliver the results via Bluetooth Low Energy (BLE). Breath samples were collected from patients with hypoglycemia, COVID-19, and healthy controls for both. Samples were processed, analyzed using GC-MS, and probed through statistical analysis. A panel of 6 VOC biomarkers distinguished between hypoglycemia (HYPO) and Normal samples with a training AUC of 0.98 and a testing AUC of 0.93. For COVID-19, a panel of 3 VOC biomarkers distinguished between COVID-19 positive symptomatic (COVID-19) and healthy Control samples with a training area under the curve (AUC) of receiver operating characteristic (ROC) of 1.0 and cross-validation (CV) AUC of 0.99. The model was validated with COVID-19 Recovery samples. The discovery of these biomarkers enables the development of selective gas sensors to detect the VOCs. Polyethylenimine-ether functionalized gold nanoparticle (PEI-EGNP) gas sensors were designed and fabricated in the lab and metal oxide (MOX) semiconductor gas sensors were obtained from Nanoz (Chip 1: SnO2 and Chip 2: WO3). These sensors were tested at different relative humidity (RH) levels and VOC concentrations. The contact angle which measures hydrophobicity was 84° and the thickness of the PEI-EGNP coating was 11 µ m. The PEI-EGNP sensor response at RH 85% had a signal 10x higher than at RH 0%. Optimization of the MOX sensor was performed by changing the heater voltage and concentration of VOCs. At RH 85% and heater voltage of 2500 mV, the performance of the sensors increased. Chip 2 had higher sensitivity towards VOCs especially for one of the VOC biomarkers identified for COVID-19. PCA distinguished VOC biomarkers of HYPO, COVID-19, and healthy human breath using the Nanoz. A sensor interface was created to integrate the PEI-EGNP sensors with the printed circuit board (PCB) and Bluno Nano to perform machine learning. The sensor interface can currently process and make decisions from the data whether the breath is HYPO (-) or Normal (+). This data is then sent via BLE to the Hypo Alert app to display the decision.

Phosphorus is needed by living organism including humans and plants, to survive. Imbalance in phosphate concentration in human body can result in numerous diseases or disorders while excess phosphorus levels in water bodies like lakes, and rivers, are responsible for the rise in incidence of algal bloom across world. Current commercial phosphate monitoring systems are dominated by colorimetric measurements while electrochemical sensors including potentiometric, amperometric and voltammetric sensors are still in the research phase. Electrochemical sensors require stable reference electrodes for reliable measurements that pose challenges for miniaturization. Solid state potentiometric sensors are widely explored due to their rapid response, easy fabrication and simple electronic measurement system. However, the sensor miniaturization is dependent both on the working and reference electrode. Metal electrodes like cobalt offers advantages such as reagent-free detection, easy to miniaturize but the sensitivity of zero-current potentiometric sensors is limited by the theoretical Nernstian limit and cobalt sensors also require chemical pretreatment in standard solution before measurement. Here, an in situ electrical pretreatment method is proposed to eliminate the need of chemical pretreatment and enhance the sensitivity of cobalt electrodes to -91.4 mV/ decade of phosphate concentration. However, this electrode still needs a reference electrode for reliable measurements. Therefore, this study has demonstrated a chemiresistive sensing platform for solid state detection of phosphate using both enzyme and enzyme-free methods. A rapid prototyping method was developed to pattern the thin metal films (~100 nm thickness) using a bench top plotter cutter. The method was used to fabricate thin gold film contact electrodes for chemiresistors. The thin gold leaf contact electrodes exhibited low-noise and offered a robust, rapid and reproducible manufacturing process for chemiresistors. The chemiresistive sensor showed a wide measuring range (0.5 ppm to 500 ppm) for hydrogen peroxide detection. The sensor was deposited with glucose oxidase to demonstrate the application of the sensor for peroxidase assays to detect glucose in standard buffer solution and human pooled plasma. Phosphate also is detected using pyruvate oxidase in presence of pyruvate to generate hydrogen peroxide as the detectable molecule. Finally, metal phthalocyanines were used to perform enzyme-free phosphate measurements. This work demonstrated the sensor technologies which could be used for in-field phosphate monitoring to prevent algal bloom and it also provides phosphate monitoring methods for rapid detection in medical diagnostics for early diagnosis for diseases like chronic kidney disease and to improve the patient’s outcomes for such diseases. / Thesis / Doctor of Philosophy (PhD) / Phosphorus is an essential element for the survival of living beings including humans and plants because it is needed in multiple physiological pathways and functions like cellular signalling, energy storage, metabolism and maintenance. Therefore, phosphate in the human body is strictly regulated and in disease conditions like chronic kidney disease, and metabolic disorders. It can increase or decrease resulting in ailments and worsening of diseases. Phosphorus is also extensively used in the agricultural field to improve the growth and crop yield. Excess phosphorus from these fertilizers can enter our water sources via agricultural water run-offs leading to the increasing incidences of algal bloom across world. Current phosphorus measuring systems require chemicals which generates toxic waste, needs manual sample collection and transport, and have narrow measuring ranges. There is an urgent need for sensors which would eliminate the need of sample collection and processing, do not require toxic chemicals and could work over a wide detection range. This study presents two solid-state sensor technologies which would simplify the phosphate detection for both environmental and medical diagnostics samples.

Failure to monitor the quality of drinking water can have devastating consequences. The development and implementation of sensing technology can be a crucial aspect of water quality control strategies. Chemiresistive sensors can be installed at any point of the distribution system and can provide real-time data on the levels of different water quality parameters. These sensors work by detecting changes in the conducting properties of a transducing element, induced by interactions with the analyte. Nanocarbon films have attracted interest as possible transducing materials because of their similarities to graphene, a two-dimensional material known for its exceptional electron transport properties. This thesis explores the fabrication and sensing performance of few layer graphene (FLG) and graphene-like carbon (GLC) films. The FLG sensors were used to detect copper ions in water, while the GLC sensors were used to monitor the concentration of free chlorine. The films were functionalized to improve selectivity and showed noticeable changes in their conducting properties as a result of charge transfer between them and the analyte. These changes were quantified by probing the sensors with a constant voltage and they were found to be dependent on the concentration of the analyte over a wide dynamic range. Overall, the work presented in this thesis suggests that, by tuning the selectivity of the films, nanocarbon based chemiresistive sensors can be a universal solution to water quality monitoring. / Thesis / Master of Science (MSc)

No description available.

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have recently emerged for potential applications in (opto-)electronics, chemiresistive sensing, and energy storage and conversion, due to their excellent electrical conductivity, abundant active sites, and intrinsic porous structures. However, developing ultrathin 2D c-MOF nanosheets (NSs) for facile solution-processing and integration into devices remains a great challenge, mostly due to unscalable synthesis, low yield, limited lateral size and low crystallinity. Here, we report a surfactant-assisted solution synthesis toward ultrathin 2D c-MOF NSs, including HHB-Cu (HHB=hexahydroxybenzene), HHB-Ni and HHTP-Cu (HHTP=2,3,6,7,10,11-hexahydroxytriphenylene). For the first time, we achieve single-crystalline HHB-Cu(Ni) NSs featured with a thickness of 4-5 nm (~8-10 layers) and a lateral size of 0.25-0.65 μm², as well as single-crystalline HHTP-Cu NSs with a thickness of ~5.1±2.6 nm (~10 layers) and a lateral size of 0.002-0.02 μm². Benefiting from the ultrathin feature, the synthetic NSs allow fast ion diffusion and high utilization of active sites. As a proof of concept, when serving as a cathode material for Li-ion storage, HHB-Cu NSs deliver a remarkable rate capability (charge within 3 min) and long-term cycling stability (90% capacity retention after 1000 cycles), superior to the corresponding bulk materials and other reported MOF cathodes.

Im Rahmen dieser Arbeit wurden neuartige Materialien basierenden auf Gold-Nanopartikeln (AuNP) untersucht. AuNP kommen als Materialien für optische und chemiresistive Sensoren zum Einsatz, deren besondere optische und elektrische Eigenschaften sich je nach Form, Größe, Oberflächenchemie oder Aggregatzustand des Nanopartikels verändern kann. Außerdem kann die Kopplung von AuNP mit organischen Molekülen die optischen und elektrischen Eigenschaften dabei beeinflussen. Diese Untersuchung basiert auf dem Au-NP-Komposit, welches durch lagenweise Selbstassemblierung entweder automatisch mit einer Durchflusszelle oder manuell durch das Aufschleudern mit Spincoater hergestellt wurden. Für die Selbstassemblierung werden Dodecylamine-stabilisierte AuNP sowie Alkandithiole, Alkandiamine, Alkanbisdithiocarbamate mit unterschiedlicher Alkylenkette und Polyphenyle mit unterschiedlicher Ringzahl verwendet. In dieser Arbeit wurden die für die Untersuchungen verwendeten Methoden und Materialien beschrieben, ein besonderer Fokus lag dabei in der Anwendung verschiedener Methoden der Probenherstellung und Lagerbedingungen für die Erreichung einer optimierten Herstellungsmethode. In den folgenden Kapiteln wurden sowohl die Probenvorbereitung mit einem eigens angefertigten automatischem Aufbau betrachtet, als auch das Assemblierungsverhalten und die Eigenschaften der Proben, die mit verschiedenen organischen Molekülen verknüpft sind. Die Röntgen-Photoelektronenspektroskopie wurde angewendet, um die Filmzusammensetzung und den Grad der Vernetzung zu untersuchen. Die Empfindlichkeit der Filme wurde durch Dosierung mit Dämpfen von Toluol, 1-Propanol, 4-Methyl-2-pentanon und Wasser im Konzentrationsbereich von 100 ppm bis 5000 ppm untersucht. Alle Proben reagieren hierbei mit einer Änderung ihres elektrischen Widerstands auf die Analyte. Obwohl die Änderung des Gesamtwiderstandes eher schwach ist, zeigen die Sensoren ein hohes Signal-Rausch-Verhältnis, das für alle Testdämpfe eine Nachweisgrenze unter 100 ppm anzeigt. Die Reaktionsdynamik zeigt eine hohe Reversibilität und einen schnellen Sensormechanismus. Darüber hinaus wurden die optischen Eigenschaften der Linkers mittels UV-Vis-Spektroskopie untersucht und die Probendicke mit Profilometer gemessen. Außerdem wurde eine oberflächenverstärkten Raman-Streuung, sowie eine oberflächenverstärkten Infrarotabsorption durchgeführt, um die Möglichkeit der Umsetzung kugelförmige Dodecylamine-stabilisierte AuNP mit einer durchschnittlichen Größe von 4 nm für den optischen Nachweis zu überprüfen. Im abschließenden Teil der Arbeit wurden die Auswirkungen von Oxidationsprozessen und Alterung auf das Au-NP-Komposit untersucht. Um die Auswirkungen der Oxidation auf die dünnen Gold-Nanopartikel-Filme zu erforschen wurden die Proben mit Ozon in einer unterschiedlichen Oxidationzeit behandelt. Mit Hilfe von XPS bestimmte ich die genaue chemische Zusammensetzung und das Maß des Sauerstoffgehalts in den Filmen. Die Sorption von volatilen organischen Komponenten in den organischen MolekülenNanopartikel-Kompositen wurde untersucht, um zu verstehen, wie die Oxidation die Sensoreigenschaften beeinflusst. In Folge dessen wurden die erhaltenen Ergebnisse mit unoxidierten Proben verglichen. Das ermöglicht eine Analyse, wie sich die Selektivität und die Empfindlichkeit während der Wechselwirkungen mit der Atmosphäre ändern, und erweitert den gegenwärtigen wissenschaftlichen Kenntnisstand. Durchgeführte Messungen und Befunde bestätigen, dass sowohl die Vielzahl an Alkandithiole, Alkandiamine, Alkanbisdithiocarbamate und Polyphenyle als auch die besonderen Eigenschaften der AuNP, ein großes Potential für die Entwicklung weiterer sensorischer Anwendungen haben.:Abstract Zusammenfassung Abbreviations 1. Motivation and goals setting 2. Materials and Methods 2.1 Characteristics of gold nanoparticles 2.1.1 Characteristics of the gold nanoparticles used for the preparation of thin films 2.2 Organic linkers for gas sensors 2.2.1 Synthesis of linkers 2.3 Preparation of the substrates and transducers 2.3.1 Other materials 2.4 Assembling of the thin films 2.4.1 Manual preparation 2.4.1.1 Common preparation 2.4.1.2 Preparation with lower oxidation level 2.4.1.3 Preparation under argon atmosphere 2.4.2 Automatic layer-by-layer self-assembling using cross flow cell 2.4.3 Oxidation of the samples 2.5 Characterization methods and experimental setups 2.5.1 Profilometer 2.5.2 UV-Vis Spectroscopy 2.5.3 Raman spectroscopy 2.5.4 Infrared absorption spectroscopy 2.5.5 X-ray photoelectron spectroscopy 2.5.6 Current-voltage (I-V) measurements 2.5.7 Investigations of sensor characteristics 3. Results and discussion 3.1 Nanocomposites interlinked with polyphenyls 3.1.1. Optical investigations 3.1.1.1 UV-Vis spectroscopy 3.1.1.2 Surface-enhanced Raman spectroscopy 3.1.1.3 Surface-enhanced infrared absorption spectroscopy 3.1.2 Measurements of thickness 3.1.3 Investigations of chemical composition 3.1.3.1 Manually prepared films 3.1.3.2 Films prepared with automatic setup 3.1.4 Investigations of sensor characteristics 3.1.5 Chapter conclusions 3.2 Nanocomposites interlinked with dithiols, amines and bisdithiocarbamates 3.2.1 Layer-by-layer growth of the DT-composites 3.2.2 Layer-by-layer growth of the OBDTC- and ODA-composites 3.2.3 Thickness measurements and density calculations 3.2.4 Absorbance measurements on nanocomposite thin films 3.2.5 Investigations of chemical composition 3.2.6 Electrical characterization and sensor measurements 3.2.7 Chapter conclusions 3.3 Impact of the oxidation processes on the sensing properties of gold nanoparticle composites 3.3.1 Preparation and oxidization of the samples 3.3.2 Investigations of chemical composition 3.3.3 Investigations of sensor characteristics 3.3.4 Chapter conclusions 4. Conclusions and outlook Index of images Index of tables Appendix A Appendix B Appendix C Publications related to this dissertation Conference participations with poster Conference participations with oral talks Bibliography

Indiana University-Purdue University Indianapolis (IUPUI) / The link between volatile organic compounds (VOCs) from breath and various diseases and specific conditions has been identified since long by the researchers. Canine studies and breath sample analysis on Gas chromatography/ Mass Spectroscopy has proven that there are VOCs in the breath that can detect and potentially predict hypoglycemia. This project aims at developing a smart nanosensor system to detect hypoglycemia from human breath. The sensor system comprises of 1-Mercapto-(triethylene glycol) methyl ether functionalized goldnanoparticle (EGNPs) sensors coated with polyetherimide (PEI) and poly(vinylidene fluoride -hexafluoropropylene) (PVDF-HFP) and polymer composite sensor made from PVDF-HFP-Carbon Black (PVDF-HFP/CB), an interface circuit that performs signal conditioning and amplification, and a microcontroller with Bluetooth Low Energy (BLE) to control the interface circuit and communicate with an external personal digital assistant. The sensors were fabricated and tested with 5 VOCs in dry air and simulated breath (a mixture of air, small portion of acetone, ethanol at high humidity) to investigate sensitivity and selectivity. The name of the VOCs is not disclosed herein but these VOCs have been identified in-breath and are identified as potential biomarkers for other diseases as well. The sensor hydrophobicity has been studied using contact angle measurement. The GNPs size was verified using Ultra-Violent-Visible (UV-VIS) Spectroscopy. Field Emission Scanning Electron Microscope (FESEM) image is used to show GNPs embedded in the polymer film. The sensors sensitivity increases by more than 400\% in an environment with relative humidity (RH) of 93\% and the sensors show selectivity towards VOCs of interest. The interface circuit was designed on Eagle PCB and was fabricated using a two-layer PCB. The fabricated interface circuit was simulated with variable resistance and was verified with experiments. The system is also tested at different power source voltages and it was found that the system performance is optimum at more than 5 volts. The sensor fabrication, testing methods, and results are presented and discussed along with interface circuit design, fabrication, and characterization. / 2022-05-8

Surface-modification of phthalocyanine-based two-dimensional conjugated metal-organic framework (2D c-MOF) films by grafting aliphatic alkyl chains is developed for achieving high-performance polarity-selective chemiresistive sensing toward humidity and polar alcohols. 2D conjugated metal–organic frameworks (2D c-MOFs) are emerging as electroactive materials for chemiresistive sensors, but selective sensing with fast response/recovery is a challenge. Phthalocyanine-based Ni2[MPc(NH)8] 2D c-MOF films are presented as active layers for polarity-selective chemiresisitors toward water and volatile organic compounds (VOCs). Surface-hydrophobic modification by grafting aliphatic alkyl chains on 2D c-MOF films decreases diffused analytes into the MOF backbone, resulting in a considerably accelerated recovery progress (from ca. 50 to ca. 10 s) during humidity sensing. Toward VOCs, the sensors deliver a polarity-selective response among alcohols but no signal for low-polarity aprotic hydrocarbons. The octadecyltrimethoxysilane-modified Ni2[MPc(NH)8] based sensor displays high-performance methanol sensing with fast response (36 s)/recovery (13 s) and a detection limit as low as 10 ppm, surpassing reported room-temperature chemiresistors.

This corrigendum corrects an omission from the Acknowledgement section. The research leading to the results published in this manuscript was also supported by the project CALIPSOplus under Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020.

<div>The link between volatile organic compounds (VOCs) from breath and various diseases and specific conditions has been identified since long by the researchers. Canine studies and breath sample analysis on Gas chromatography/ Mass Spectroscopy has proven that there are VOCs in the breath that can detect and potentially predict hypoglycemia. This project aims at developing a smart nanosensor system to detect hypoglycemia from human breath. The sensor system comprises of 1-Mercapto-(triethylene glycol) methyl ether functionalized goldnanoparticle (EGNPs) sensors coated with polyetherimide (PEI) and poly(vinylidene fluoride -hexafluoropropylene) (PVDF-HFP) and polymer composite sensor made from PVDF-HFP-Carbon Black (PVDF-HFP/CB), an interface circuit that performs signal conditioning and amplification, and a microcontroller with Bluetooth Low Energy (BLE) to control the interface circuit and communicate with an external personal digital assistant. The sensors were fabricated and tested with 5 VOCs in dry air and simulated breath (mixture of air, small portion of acetone, ethanol at high humidity) to investigate sensitivity and selectivity. The name of the VOCs is not disclosed herein but these VOCs have been identified in breath and are identified as potential biomarkers for other diseases as well. </div><div> </div><div> The sensor hydrophobicity has been studied using contact angle measurement. The GNPs size was verified using Ultra-Violent-Visible (UV-VIS) Spectroscopy. Field Emission Scanning Electron Microscope (FESEM) image is used to show GNPs embedded in the polymer film. The sensors sensitivity increases by more than 400% in an environment with relative humidity (RH) of 93% and the sensors show selectivity towards VOCs of interest. The interface circuit was designed on Eagle PCB and was fabricated using a two-layer PCB. The fabricated interface circuit was simulated with variable resistance and was verified with experiments. The system is also tested at different power source voltages and it was found that the system performance is optimum at more than 5 volts. The sensor fabrication, testing methods, and results are presented and discussed along with interface circuit design, fabrication, and characterization.</div>