Browsing by Author "Sainio, Sami"
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Item Agglomeration of nanodiamonds during deposition(2017-12-11) Sievänen, Mikael; Sainio, Sami; Sähkötekniikan korkeakoulu; Laurila, TomiAs nanodiamond (ND) has excellent mechanical, electrical and optical properties, their use in different biomedical applications is desired. However, nanodiamond agglomeration is a common issue, that is causing problems when trying to use NDs in biomedical applications, carriers in drug delivery, coating for sensor or implant materials or in nanoelectronics. This thesis goes through literature related to NDs and especially their agglomeration. NDs form resilient aggregates and single-digit NDs can’t be produced without proper deagglomeration before dispersion in solvent. According to literature, it can be stated that most common methods used in mechanical deagglomeration of NDs are media milling and beads-assisted sonic disintegrating (BASD). These techniques use small zirconium oxide balls that break ND agglomerates by colliding with them in media. The problem with these methods is that they cause zirconium contamination in ND particles. Zirconium is difficult to remove from NDs and contamination makes it harder to use NDs in applications. Laboratory experiments performed in this research indicate that ethylene glycol and dimethyl sulfoxide (DMSO) were most suitable solvents for NDs. Size of ND agglomerates were smaller in these solvents than in other commonly used ND solvents tested, such as DI water and ethanol. This observation is in line with information found in ND related literature.Item Application-Specific Catalyst Layers: Pt-Containing Carbon Nanofibers for Hydrogen Peroxide Detection(2017-02-13) Laurila, Tomi; Sainio, Sami; Jiang, Hua; Isoaho, Noora; Koehne, Jessica; Etula, Jarkko; Koskinen, Jari; Meyyappan, M.; Department of Electrical Engineering and Automation; Department of Applied Physics; Department of Chemistry and Materials Science; NanoMaterials; Microsystems Technology; NASA Ames Research CenterComplete removal of metal catalyst particles from carbon nanofibers (CNFs) and other carbon nanostructures is extremely difficult, and the envisioned applications may be compromised by the left-over impurities. To circumvent these problems, one should use, wherever possible, such catalyst materials that are meant to remain in the structure and have some application-specific role, making any removal steps unnecessary. Thus, as a proof-of-concept, we present here a nanocarbon-based material platform for electrochemical hydrogen peroxide measurement utilizing a Pt catalyst layer to grow CNFs with intact Pt particles at the tips of the CNFs. Backed by careful scanning transmission electron microscopy analysis, we show that this material can be readily realized with the Pt catalyst layer thickness impacting the resulting structure and also present a growth model to explain the evolution of the different types of structures. In addition, we show by electrochemical analysis that the material exhibits characteristic features of Pt in cyclic voltammetry and it can detect very small amounts of hydrogen peroxide with very fast response times. Thus, the present sensor platform provides an interesting electrode material with potential for biomolecule detection and in fuel cells and batteries. In the wider range, we propose a new approach where the selection of catalytic particles used for carbon nanostructure growth is made so that (i) they do not need to be removed and (ii) they will have essential role in the final application.Item Bioanturien käyttö tulehdusten havaitsemisessa(2016-10-31) Honkala, Jaakko; Sainio, Sami; Sähkötekniikan korkeakoulu; Laurila, TomiItem Biofouling affects the redox kinetics of outer and inner sphere probes on carbon surfaces drastically differently - implications to biosensing(ROYAL SOC CHEMISTRY, 2020-08-07) Peltola, Emilia; Aarva, Anja; Sainio, Sami; Heikkinen, Joonas J.; Wester, Niklas; Jokinen, Ville; Koskinen, Jari; Laurila, Tomi; Department of Electrical Engineering and Automation; Department of Chemistry and Materials Science; Microsystems Technology; Microfabrication; Physical Characteristics of Surfaces and InterfacesBiofouling imposes a significant threat for sensing probes used in vivo. Antifouling strategies commonly utilize a protective layer on top of the electrode but this may compromise performance of the electrode. Here, we investigated the effect of surface topography and chemistry on fouling without additional protective layers. We have utilized two different carbon materials; tetrahedral amorphous carbon (ta-C) and SU-8 based pyrolytic carbon (PyC) in their typical smooth thin film structure as well as with a nanopillar topography templated from black silicon. The near edge X-ray absorption fine structure (NEXAFS) spectrum revealed striking differences in chemical functionalities of the surfaces. PyC contained equal amounts of ketone, hydroxyl and ether/epoxide groups, while ta-C contained significant amounts of carbonyl groups. Overall, oxygen functionalities were significantly increased on nanograss surfaces compared to the flat counterparts. Neither bovine serum albumin (BSA) or fetal bovine serum (FBS) fouling caused major effects on electron transfer kinetics of outer sphere redox (OSR) probe Ru(NH3)63+ on any of the materials. In contrast, negatively charged OSR probe IrCl62- kinetics were clearly affected by fouling, possibly due to the electrostatic repulsion between redox species and the anionically-charged proteins adsorbed on the electrode and/or stronger interaction of the proteins and positively charged surface. The OSR probe kinetics were less affected by fouling on PyC, probably due to conformational changes of proteins on the surface. Dopamine (DA) was tested as an inner sphere redox (ISR) probe and as expected, the kinetics were heavily dependent on the material; PyC had very fast electron transfer kinetics, while ta-C had sluggish kinetics. DA electron transfer kinetics were heavily affected on all surfaces by fouling (ΔEp increase 30-451%). The effect was stronger on PyC, possibly due to the more strongly adhered protein layer limiting the access of the probe to the inner sphere.Item Carbon based hybrid nanomaterials for electrochemical detection of neurotransmitters(Aalto University, 2017) Sainio, Sami; Sähkötekniikan ja automaation laitos; Department of Electrical Engineering and Automation; Sähkötekniikan korkeakoulu; School of Electrical Engineering; Laurila, Tomi, Prof., Aalto University, Department of Electrical Engineering and Automation, FinlandApplying carbon-based sensors to detect neurotransmitters in vitro and to take them towards in vivo is a goal of many research groups. The motivation arises from the increased occurrence of neurological disorders, diseases and age-related illnesses. Thus far, carbon-based materials used as sensors lack the sensitivity and selectivity for neurotransmitter detection, in addition to fouling and stability issues. This thesis presents several methods for tailoring and forming new carbon-based hybrid nanomaterials for the reliable detection of neurotransmitters. The hypothesis of this thesis is that by controllably integrating different carbon allotropes, it is possible to produce hybrid materials with unique properties. The objectives of this thesis are to (i) introduce new carbon-based hybrid materials and their unique properties, (ii) provide a detailed chemical and structural description of the materials and (iii) show the potential of detecting dopamine by using hybrid carbon-based materials in physiologically relevant concentrations for in vivo applications. By using hybrid structures, such as tetrahedral amorphous carbon (ta-C) and nickel as a seed layer for carbon nanofiber (CNF) growth, it is possible to produce a CNF with completely different morphology and properties, compared with a CNF grown on a traditional nickel seed layer. Tailoring of materials at the nanoscale enables the creation of 3D hybrid structures for targeted applications. Furthermore, this work has considered rarity of critical materials, such as platinum, and kept their use to a minimum.Item Carbon thin films as electrode material in neural sensing(2014-11-25) Kaivosoja, Emilia; Sainio, Sami; Lyytinen, Jussi; Palomäki, Tommi; Laurila, Tomi; Kim, Sung I.; Han, Jeon G.; Koskinen, Jari; Department of Electrical Engineering and Automation; Department of Materials Science and Engineering; Department of Chemistry and Materials ScienceItem Characterization and electrochemical properties of iron-doped tetrahedral amorphous carbon (ta-C) thin films(2018-01-01) Etula, Jarkko; Wester, Niklas; Sainio, Sami; Laurila, Tomi; Koskinen, Jari; Department of Chemistry and Materials Science; Department of Chemistry; Department of Electrical Engineering and Automation; Physical Characteristics of Surfaces and Interfaces; Microsystems TechnologyIron-doped tetrahedral amorphous carbon thin films (Fe/ta-C) were deposited with varying iron content using a pulsed filtered cathodic vacuum arc system (p-FCVA). The aim of this study was to understand effects of iron on both the physical and electrochemical properties of the otherwise inert sp3-rich ta-C matrix. As indicated by X-ray photoelectron spectroscopy (XPS), even ∼0.4 at% surface iron had a profound electrochemical impact on both the potential window of ta-C in H2SO4 and KOH, as well as pseudocapacitance. It also substantially enhanced the electron transport and re-enabled facile outer sphere redox reaction kinetics in comparison to un-doped ta-C, as measured with electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) using outer-sphere probes Ru(NH3)6, IrCl6, and FcMeOH. These increases in surface iron loading were linked to increased surface oxygen content and iron oxides. Unlike few other metals, an iron content even up to 10 at% was not found to result in the formation of sp2-rich amorphous carbon films as investigated by Raman spectroscopy. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) investigations found all films to be amorphous and ultrasmooth with Rq values always in the range of 0.1-0.2 nm. As even very small amounts of Fe were shown to dominate the electrochemistry of ta-C, implications of this study are very useful e.g. in carbon nanostructure synthesis, where irregular traces of iron can be readily incorporated into the final structures.Item Connection between the physicochemical characteristics of amorphous carbon thin films and their electrochemical properties(IOP Publishing Ltd., 2021-10-27) Leppänen, Elli; Aarva, Anja; Sainio, Sami; Caro, Miguel A.; Laurila, Tomi; Department of Electrical Engineering and Automation; Department of Chemistry and Materials Science; Microsystems Technology; Centre of Excellence in Quantum Technology, QTFConnecting a material's surface chemistry with its electrocatalytic performance is one of the major questions in analytical electrochemistry. This is especially important in many sensor applications where analytes from complex media need to be measured. Unfortunately, today this connection is still largely missing except perhaps for the most simple ideal model systems. Here we present an approach that can be used to obtain insights about this missing connection and apply it to the case of carbon nanomaterials. In this paper we show that by combining advanced computational techniques augmented by machine learning methods with x-ray absorption spectroscopy (XAS) and electrochemical measurements, it is possible to obtain a deeper understanding of the correlation between local surface chemistry and electrochemical performance. As a test case we show how by computationally assessing the growth of amorphous carbon (a-C) thin films at the atomic level, we can create computational structural motifs that may in turn be used to deconvolute the XAS data from the real samples resulting in local chemical information. Then, by carrying out electrochemical measurements on the same samples from which x-ray spectra were measured and that were further characterized computationally, it is possible to gain insight into the interplay between the local surface chemistry and electrochemical performance. To demonstrate this methodology, we proceed as follows: after assessing the basic electrochemical properties of a-C films, we investigate the effect of short HNO3 treatment on the sensitivity of these electrodes towards an inner sphere redox probe dopamine to gain knowledge about the influence of altered surface chemistry to observed electrochemical performance. These results pave the way towards a more general assessment of electrocatalysis in different systems and provide the first steps towards data driven tailoring of electrode surfaces to gain optimal performance in a given application.Item Correlation between microstructure and surface chemistry of carbon nanofibers grown using different adhesive layers(Elsevier BV, 2023-03) Pande, Ishan; Sainio, Sami; Sainio, Jani; Liljeström, Ville; Jiang, Hua; Laurila, Tomi; Department of Chemistry and Materials Science; Department of Electrical Engineering and Automation; Department of Applied Physics; OtaNano; Microsystems Technology; Surface Science; NanoMaterialsCarbon nanofibers (CNFs) have applications in a wide range of technological and scientific fields. The connections between their micro- and macrostructure and observed performance are, however, currently lacking. This hinders the realization of their full potential. In this paper, we correlate the microstructure of CNFs grown on two types of substrates: (1) Si + 20 nm Ti + 20 nm Ni, and (2) Si + 80 nm Cr + 20 nm Ni, to their surface chemistry. We use transmission electron microscopy (TEM), supported by energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis, to describe the morphology and structure of CNFs as well as the underlying interfacial layers. Then, we study the similarities and differences in chemistry of these two types of CNFs using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) and correlate them with the observed structural features of the fibers. Vertically aligned, tip-type fiber growth was observed on both substrates. TEM micrographs show that the CNFs grown on the Cr + Ni substrates have a slightly distorted herringbone-like structure, whereas fibers grown on the Ti + Ni substrates have relatively ill-defined structure with basal planes pointing outwards. Consequently, the latter possess a richer surface chemistry, which is apparent from the wider peaks and more spectral features observed during XAS and XPS measurements. This analysis provides us with some of the missing structure-chemistry connections, which can subsequently be expanded towards including correlations of these features with observed performance of the CNFs in different applications. Ultimately, this enables us to tailor features of the CNFs for specific target fields.Item Effect of Electrochemical Oxidation on Physicochemical Properties of Fe-Containing Single-Walled Carbon Nanotubes(John Wiley and Sons Ltd, 2020-10-01) Leppänen, Elli; Sainio, Sami; Jiang, Hua; Mikladal, Bjørn; Varjos, Ilkka; Laurila, Tomi; Department of Electrical Engineering and Automation; Department of Applied Physics; Microsystems Technology; NanoMaterials; Canatu Oy; SLAC National Accelerator LaboratoryMetal catalysts are necessary for fabricating carbon nanotubes, but are often considered impurities in the end products, and arduous steps are used to remove catalyst residues from the nanotube structure. However, as metals can be electrocatalytic, instead of removing them we can utilize their role in detection of analgesics. Herein, we study the physicochemical properties of Fe-containing single-walled carbon nanotubes (SWCNTs), and the effect of simple oxidative pretreatment on them. We show that a gentle anodic pretreatment i) increased the amount of oxidized Fe nanoparticles, most likely exhibiting phases Fe3O4 and Fe2O3 and ii) effectively removed disordered carbonaceous material from SWCNT bundles surfaces. Pretreatment had only a marginal effect on sensitivity towards analgesics. However, interestingly, selectivity of Fe-SWCNTs towards paracetamol and morphine could be modified with pretreatment. Through this kind of in-depth investigation, we can, to a certain extent, correlate various material properties of SWCNTs with the observed electrochemical performance. This approach allows us to evaluate what factors in SWCNTs truly affect the electrochemical detection of biomolecules.Item Electrochemical characterization of tetrahedral amorphous carbon and detonation nanodiamond hybrid electrode for detection of dopamine(2017-01-23) Leppänen, Elli; Sainio, Sami; Sähkötekniikan korkeakoulu; Laurila, TomiItem Electrochemical deposition of copper for through silicon via applications.(2014-12-15) Heikkurinen, Jukka; Sainio, Sami; Sähkötekniikan korkeakoulu; Laurila, TomiThis thesis aims to demonstrate through silicon via (TSV) fabrication in semiconductor applications, the generic reliability issues concerning copper TSVs and novel approaches to handle these issues. The TSV is the key enabling technology for three-dimensional electronics (Chapter 1&2). It permits vertical connections to be made in a silicon wafer, which enables the fabrication of very high-density electronics that would not be possible with traditional methods due to physical limitations. The fabrication of TSV can be divided into following steps: etching, liner/barrier/seed layer deposition (Chapter 3), electroplating (Chapters 4&5) and post-processing. This thesis focuses mostly on the bottom-up electroplating step. The bottom-up electroplating can be achieved either chemically by using additives that form inhibiting surfaces locally (Chapter 6), or electronically by controlling the waveform attributes (Chapter 7). Electroplating has been chosen as the primary filling method because high-quality structured metallization can be achieved quickly. Copper metallization is chosen over aluminum or tungsten since copper has excellent electrical conductivity and electromigration resistance. Copper metallization, in damascene trenches or vias, exhibits a number of reliability issues that should be solved before 3-D electronics can compete with planar electronics. The most prominent failure modes have been identified (Chapter 8) and some possible solutions have been presented (Chapter 9). The coefficient of thermal expansion (CTE) mismatch between copper and silicon combined with trapped impurities in copper metallization is one of the main issues. High residual stresses are present in the metallization after post-processing which can lead to micro voiding, which in turn can reduce the electromigration resistance. One solution to this problem is to use buffer layers, such as BCB dielectrics, that allows expansion also laterally. Another solution is to process a uniform copper microstructure. Avoiding the use of additives that can be trapped into the metallization or using an additional method that hinders copper grain growth can realize the uniformity. The other primary issues concerning the copper TSVs are the liner/barrier reliability and the cost of the bottom-up metallization.Item Electrochemical Detection of Oxycodone and Its Main Metabolites with Nafion-Coated Single-Walled Carbon Nanotube Electrodes(AMERICAN CHEMICAL SOCIETY, 2020-05-15) Mynttinen, Elsi; Wester, Niklas; Lilius, Tuomas; Kalso, Eija; Mikladal, Bjørn; Varjos, Ilkka; Sainio, Sami; Jiang, Hua; Kauppinen, Esko; Koskinen, Jari; Laurila, Tomi; Department of Electrical Engineering and Automation; Department of Chemistry and Materials Science; Department of Applied Physics; Microsystems Technology; Physical Characteristics of Surfaces and Interfaces; NanoMaterials; University of Helsinki; Canatu Oy; SLAC National Accelerator LaboratoryOxycodone is a strong opioid frequently used as an analgesic. Although proven efficacious in the management of moderate to severe acute pain and cancer pain, use of oxycodone imposes a risk of adverse effects such as addiction, overdose, and death. Fast and accurate determination of oxycodone blood concentration would enable personalized dosing and monitoring of the analgesic as well as quick diagnostics of possible overdose in emergency care. However, in addition to the parent drug, several metabolites are always present in the blood after a dose of oxycodone, and to date, there is no electrochemical data available on any of these metabolites. In this paper, a single-walled carbon nanotube (SWCNT) electrode and a Nafion-coated SWCNT electrode were used, for the first time, to study the electrochemical behavior of oxycodone and its two main metabolites, noroxycodone and oxymorphone. Both electrode types could selectively detect oxycodone in the presence of noroxycodone and oxymorphone. However, we have previously shown that addition of a Nafion coating on top of the SWCNT electrode is essential for direct measurements in complex biological matrices. Thus, the Nafion/SWCNT electrode was further characterized and used for measuring clinically relevant concentrations of oxycodone in buffer solution. The limit of detection for oxycodone with the Nafion/SWCNT sensor was 85 nM, and the linear range was 0.5–10 μM in buffer solution. This study shows that the fabricated Nafion/SWCNT sensor has potential to be applied in clinical concentration measurements.Item Geometrical and chemical effects on the electrochemistry of single-wall carbon nanotube (SWCNT) network electrodes(Elsevier Ltd, 2023-10-20) Leppänen, Elli; Gustafsson, Eero; Wester, Niklas; Varjos, Ilkka; Sainio, Sami; Laurila, Tomi; Department of Electrical Engineering and Automation; Department of Chemistry and Materials Science; Microsystems Technology; Department of Electrical Engineering and Automation; Canatu OySingle-wall carbon nanotube (SWCNT) network is a promising electrode material for bio detection. Unfortunately, the associations between their physical as well as chemical properties and observed electrochemical performance are not known. This hinders any systematic optimization of the network properties towards specific analytes. Here we present a consistent physicochemical and electrochemical characterization of differently treated SWCNT networks. The results unambiguously show that (i) even if the electrochemical properties of different electrodes are practically identical when assessed by surface insensitive outer sphere redox (OSR) probes their behavior with inner sphere redox (ISR) probes can be drastically different. Further, (ii) the choice of the modification method (structural, chemical, electrochemical) heavily depends on nature of the target analyte, which are typically ISR probes. Although, (iii) chemical changes in the carbon phase appeared to be minor, effects of different treatments on oxidation states of Fe appeared to have a strong effect on the electrochemical performance of the networks in the case of ISR probes.Item Hammasimplantoinnin kirurgisen ohjaimen suunnitteluohjelma(2016-04-04) Kuusela, Ville; Sainio, Sami; Kettunen, Sakari; Sähkötekniikan korkeakoulu; Laurila, TomiHammasimplantointi on yleisesti käytetty menetelmä hammasproteesien kiinnittämiseen. Implantoinnin tarkkuutta ja lopputulosta voidaan parantaa käyttämällä kirurgista ohjainta implanttikolon porauksessa ja implantin asentamisessa. Perinteisesti kirurgiset ohjaimet on valmistettu käsin. Käsintehdyt ohjaimet ovat usein epätarkkoja, alttiita inhimillisille virheille ja työläitä valmistaa. Digitaaliseen kartiokeilatomografiakuvaan voidaan suunnitella implantit huomioiden suun anatomia tarkemmin. Implanttisuunnitelman ja suun pintamallin perusteella voidaan luoda tarkka digitaalinen malli kirurgiselle ohjaimelle. Mallista voidaan valmistaa kirurginen CAM-ohjain. Tämän diplomityön ensimmäisenä tavoitteena oli luoda vaatimusmäärittely ohjelmalle, jolla voidaan implanttisuunnitelman ja suun pintamallin perusteella luoda pikavalmistettava pintamalli kirurgisesta ohjaimesta. Työn toisena tavoitteena oli kehittää prototyyppi ohjelmasta, joka luo kirurgisen ohjaimen pintamallin. Sen luomiseen hyödynnettiin pisteen ja pintamallin välisen etäisyyden laskemista. Koehenkilöiden pintamalleihin suunniteltujen ohjainten avulla todettiin käytetyn menetelmän olevan toimiva kirurgisten ohjainten digitaaliseen suunnitteluun.Item Hybrid carbon based nanomaterials for electrochemical detection of biomolecules(2017) Laurila, Tomi; Sainio, Sami; Caro, Miguel A.; Department of Electrical Engineering and Automation; Department of Applied Physics; Microsystems TechnologyBy combining different allotropic forms of carbon at the nanoscale it is possible to fabricate tailor made surfaces with unique properties. These novel materials have shown high potential especially in the electrochemical detection of different biomolecules, such as dopamine, glutamate and ascorbic acid, which are important neurotransmitters in the mammalian central nervous system. Thus, more information about their material properties must be obtained in order to realize their high potential to the maximum. The results presented in this review clearly point out that although there is an extensive amount of data available on the structural, chemical and electrochemical properties on different carbon nanoforms, the data are scattered, often inconsistent and even contradictory. Hybrid carbon nanomaterials are much less investigated than the individual allotropes, but based on the existing data they possess extremely interesting electrochemical properties. Thus, it is of utmost importance to carry out extensive step-by-step characterization of these materials by utilizing combination of detailed computational and experimental work. In this way it will become possible to avoid approaches to material design that are based solely on trial-and-error approach, which has, unfortunately, been more a rule than an exception.Item In-situ functionalization of tetrahedral amorphous carbon by filtered cathodic arc deposition(AMER INST PHYSICS, 2019-08-01) Sainio, Sami; Wester, Niklas; Titus, Charles J.; Nordlund, Dennis; Lee, Sang Jun; Koskinen, Jari; Laurila, Tomi; Department of Chemistry and Materials Science; Stanford University; Department of Electrical Engineering and AutomationModification of the surface chemistry of carbon-based nanomaterials is often necessary in order to embrace their full potential. A wide variety of different post-fabrication treatments, such as acid, oxidizing plasma and heat treatments have been described in the literature. However, their specific effects on the materials surface chemistry is typically only vaguely disclosed. Here we report an in-situ method to functionalize tetrahedral amorphous carbon (ta-C) thin films by introducing high purity oxygen into the vacuum chamber during the film fabrication. Additionally, we analyze and compare the material properties of the resulting thin films to those of nitric acid and oxygen plasma treated as well as those with no treatment at all. Using x-ray absorption spectroscopy (XAS), we show that in-situ functionalizing decreases the sp2 content of the surface and increases the amount of carboxyl-like functionalities. Subsequent oxygen plasma treatment further decreases the sp2 fraction and ketone/aldehyde content as well as increases the amount of carboxyl groups. The same trends are observed with the reference ta-C exposed to oxygen plasma treatment. For both materials, a concentrated nitric acid treatment has only a subtle effect on the surface chemistry. Capitalizing on this knowledge, we can selectively produce materials with higher surface loading of specific functional groups, paving the way for application specific material fabrication.Item Integrating Carbon Nanomaterials with Metals for Bio-sensing Applications(Humana Press, 2019-01-01) Sainio, Sami; Leppänen, Elli; Mynttinen, Elsi; Palomäki, Tommi; Wester, Niklas; Etula, Jarkko; Isoaho, Noora; Peltola, Emilia; Koehne, Jessica; Meyyappan, M.; Koskinen, Jari; Laurila, Tomi; Department of Chemistry and Materials Science; Department of Electrical Engineering and Automation; Physical Characteristics of Surfaces and Interfaces; Microsystems Technology; NASA Ames Research CenterAge structure in most developed countries is changing fast as the average lifespan is increasing significantly, calling for solutions to provide improved treatments for age-related neurological diseases and disorders. In order to address these problems, a reliable way of recording information about neurotransmitters from in vitro and in vivo applications is needed to better understand neurological diseases and disorders as well as currently used treatments. Likewise, recent developments in medicine, especially with the opioid crisis, are demanding a swift move to personalized medicine to administer patient needs rather than population-wide averages. In order to enable the so-called personalized medicine, it is necessary to be able to do measurements in vivo and in real time. These actions require sensitive and selective detection of different analytes from very demanding environments. Current state-of-the-art materials are unable to provide sensitive and selective detection of neurotransmitters as well as the required time resolution needed for drug molecules at a reasonable cost. To meet these challenges, we have utilized different metals to grow carbon nanomaterials and applied them for sensing applications showing that there are clear differences in their electrochemical properties based on the selected catalyst metal. Additionally, we have combined atomistic simulations to support optimizing materials for experiments and to gain further understanding of the atomistic level reactions between different analytes and the sensor surface. With carbon nanostructures grown from Ni and Al + Co + Fe hybrid, we can detect dopamine, ascorbic acid, and uric acid simultaneously. On the other hand, nanostructures grown from platinum provide a feasible platform for detection of H2O2 making them suitable candidates for enzymatic biosensors for detection of glutamate, for example. Tetrahedral amorphous carbon electrodes have an ability to detect morphine, paracetamol, tramadol, and O-desmethyltramadol. With carbon nanomaterial-based sensors, it is possible to reach metal-like properties in sensing applications using only a fraction of the metal as seed for the material growth. We have also seen that by using nanodiamonds as growth catalyst for carbon nanofibers, it is not possible to detect dopamine and ascorbic acid simultaneously, although the morphology of the resulting nanofibers is similar to the ones grown using Ni. This further indicates the importance of the metal selection for specific applications. However, Ni as a continuous layer or as separate islands does not provide adequate performance. Thus, it appears that metal nanoparticles combined with fiber-like morphology are needed for optimized sensor performance for neurotransmitter detection. This opens up a new research approach of application-specific nanomaterials, where carefully selected metals are integrated with carbon nanomaterials to match the needs of the sensing application in question.Item Morphological and chemical changes of aerosolized E. coli treated with a dielectric barrier discharge(2016-03-01) Romero-Mangado, Jaione; Nordlund, Dennis; Soberon, Felipe; Deane, Graham; Maughan, Kevin; Sainio, Sami; Singh, Gurusharan; Daniels, Stephen; Saunders, Ian T.; Loftus, David; Meyyappan, M.; Koehne, Jessica; Gandhiraman, Ram P.; NASA Ames Research Center; Stanford University; Novaerus, Inc.; Department of Electrical Engineering and Automation; Dublin City University; Universities Space Research AssociationThis study presents the morphological and chemical modification of the cell structure of aerosolized Escherichia coli treated with a dielectric barrier discharge (DBD). Exposure to DBD results in severe oxidation of the bacteria, leading to the formation of hydroxyl groups and carbonyl groups and a significant reduction in amine functionalities and phosphate groups. Near edge x-ray absorption fine structure (NEXAFS) measurements confirm the presence of additional oxide bonds upon DBD treatment, suggesting oxidation of the outer layer of the cell wall. Electron microscopy images show that the bacteria undergo physical distortion to varying degrees, resulting in deformation of the bacterial structure. The electromagnetic field around the DBD coil causes severe damage to the cell structure, possibly resulting in leakage of vital cellular materials. The oxidation and chemical modification of the bacterial components are evident from the Fourier transform infrared spectroscopy and NEXAFS results. The bacterial reculture experiments confirm inactivation of airborne E. coli upon treating with DBD.Item Pt-grown carbon nanofibers for detection of hydrogen peroxide(2018) Isoaho, Noora; Sainio, Sami; Wester, Niklas; Botello, Luis; Johansson, Leena Sisko; Peltola, Emilia; Climent, Victor; Feliu, Juan M.; Koskinen, Jari; Laurila, Tomi; Department of Electrical Engineering and Automation; Department of Chemistry and Materials Science; Department of Bioproducts and Biosystems; Physical Characteristics of Surfaces and Interfaces; Bio-based Colloids and Materials; Microsystems Technology; University of AlicanteRemoval of left-over catalyst particles from carbon nanomaterials is a significant scientific and technological problem. Here, we present the physical and electrochemical study of application-specific carbon nanofibers grown from Pt-catalyst layers. The use of Pt catalyst removes the requirement for any cleaning procedure as the remaining catalyst particles have a specific role in the end-application. Despite the relatively small amount of Pt in the samples (7.0 ± 0.2%), they show electrochemical features closely resembling those of polycrystalline Pt. In O2-containing environment, the material shows two separate linear ranges for hydrogen peroxide reduction: 1-100 μM and 100-1000 μM with sensitivities of 0.432 μA μM-1 cm-2 and 0.257 μA μM-1 cm-2, respectively, with a 0.21 μM limit of detection. In deaerated solution, there is only one linear range with sensitivity 0.244 μA μM-1 cm-2 and 0.22 μM limit of detection. We suggest that the high sensitivity between 1 μM and 100 μM in solutions where O2 is present is due to oxygen reduction reaction occurring on the CNFs producing a small additional cathodic contribution to the measured current. This has important implications when Pt-containing sensors are utilized to detect hydrogen peroxide reduction in biological, O2-containing environment.
