Review—Non-Invasive Monitoring of Human Health by Exhaled Breath Analysis: A Comprehensive Review

Exhaled human breath analysis is a very promisingfield of research work having great potential for diagnosis of diseases in non-invasive way. Breath analysis has attracted huge attention in thefield of medical diagnosis and disease monitoring in the last twodecades. VOCs/gases (Volatile Organic Compounds) in exhaled breath bear thefinger-prints of metabolic and biophysicalprocesses going on in human body. It’s a non-invasive, fast, non-hazardous, cost effective, and point of care process for diseasestate monitoring and environmental exposure assessment in human beings. Some VOCs/gases in exhaled breath are bio-markers ofdifferent diseases and their presence in excess amount is indicative of un-healthiness. Breath analysis has the potential for earlydetection of diseases. However, it is still underused and commercial device is yet not available owing to multiferrious challenges.This review is intended to provide an overview of major biomarkers (VOCs/gases) present in exhaled breath, importance of theiranalysis towards disease monitoring, analytical techniques involved, promising materials for breath analysis etc. Finally, relatedchallenges and limitations along with future scope will be touched upon.will be touched upon

Metal oxides based electrochemical pH sensors: Current progress and future perspectives

Electrochemical pH sensors are on high demand in numerous applications such as food processing, health monitoring, agriculture and nuclear sectors, and water quality monitoring etc., owing to their fast response (<10 s), wide pH sensing range (2–12), superior sensitivity (close to Nernstian response of 59.12 mV/pH), easy integration on wearable/flexible substrates, excellent biocompatibility and low cost of fabrication. This article presents an in-depth review of the wide range of MOx materials that have been utilized to develop pH sensors, based on various mechanisms (e.g. potentiometric, conductimetric, chemi-resistors, ion sensitive field effect transistor (ISFET) and extended-gate field effect transistor etc.). The tools and techniques such as potentiometric and electrochemical impedance spectroscopic that are commonly adopted to characterize these metal oxide-based pH sensors are also discussed in detail. Concerning materials and design of sensors for various practical application, the major challenges are toxicity of materials, interfernce of other ions or analytes, cost, and flexibility of materials. In this regard, this review also discusses the metal oxide-based composite sensing (active) material, designs of pH sensors and their applications in flexible/wearable biosensors for medical application are examined to present their suitability for these futuristic applications

The 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry

The 1st International Electronic Conference on Chemical Sensors and Analytical Chemistry was held on 1–15 July 2021. The scope of this online conference was to gather experts that are well-known worldwide who are currently working in chemical sensor technologies and to provide an online forum for the presention and discussion of new results. Throughout this event, topics of interest included, but were not limited to, the following: electrochemical devices and sensors; optical chemical sensors; mass-sensitive sensors; materials for chemical sensing; nano- and micro-technologies for sensing; chemical assays and validation; chemical sensor applications; analytical methods; gas sensors and apparatuses; electronic noses; electronic tongues; microfluidic devices; lab-on-a-chip; single-molecule sensing; nanosensors; and medico-diagnostic testing

Metal Oxide Nanomaterials

This is a timely collection of recent diverse work on metal oxide nanomaterials, connecting their fundamental aspects and application perspectives in a concise fashion to give a broad view of the current status of this fascinating field. This book presents eight original research articles and two comprehensive reviews to highlight the recent development and understanding of different types of metal oxide nanoparticles and their use for applications in luminescence, photocatalysis, water–oil separation, optoelectronics, gas sensors, energy-saving smart windows, etc. It presents just the tip of the iceberg of the broad, dynamic, and active fundamental research and applications in the developing field of metal oxide nanomaterials by collecting a few examples of the latest advancements

Elaboration and characterization of humidity sensors for environmental monitoring

The water content in surrounding air is an important factor for the well-being of humans and animals, as the level of comfort is determined by a combination of two factors: relative humidity and ambient temperature. Humidity is also an important factor for operating certain equipment such as high-impedance electronic circuits, electrostatic-sensitive components, high-voltage devices, fine mechanisms, etc. Nonetheless, moisture is the ingredient common to most manufactured goods and processed materials. Thus, humidity sensors have been receiving wide attentions since decades. Yet, despite the high request, major advances in these sensors in terms of simple structure, lower cost, better selectivity, durability and reliability are always needed. Throughout the years, a large number of materials based on polymers, composite and ceramics have been tested, due to their own features and specific operating conditions. However, great attention has been paid to ceramic materials due to their chemical inertness which allow them to operate in harsh conditions. Amongst the different studied humidity sensors, impedance-based ones are used most commonly. The operation principle of the impedance sensors is based on the dependence of the impedance (or either capacitance or resistance) of the sensor element recognizing the nature and amount of water molecules on the surface or in the bulk. The resistance or impedance of the resistive-type sensor decreases as the relative humidity (RH)increases. Ions or electrons, or both of them, are the conduction carriers for resistive-type humidity sensors. The common construction of the resistive-type ceramic humidity sensors consists of a ceramic substrate with noble metal interdigitated electrodes coated with humidity sensing ceramic materials, both deposited by screen-print technique [1]. Metal oxides and metal oxide based composites are the most popular materials to be used as resistive sensing elements: TiO2, TiO2–SnO2, TiO2–WO3, TiO2–Cu2O–Na2O, KTaO3//TiO2(bilayered), TiO2/KTaO3 (bilayered), TiO2–K2O–LiZnVO4, Al2O3, AlO(OH), SiO2, WO3, Cr2O3–WO3, SnO2, a noble metal doped SnO2, SnO2: ZrO2 (bilayered), single Sb doped SnO2, K+-dopedSnO2–LiZnVO4, MnO2 –Mn3O4, Li+-doped Fe2O3, Au3+ and Li+ co-doped Fe2O3, Li+, Zn2+ and Au3+ co-doped Fe2O3, NiMoO4–MoO3, Li+-doped NiMoO4–MoO3, CuMoO4–MoO3 and PbMoO4–MoO3 [1]. Spinel-type oxides and composites based on spinel-type oxides are also used for humidity resistive sensing elements: MgAl2O4, Sr2+-doped CoAl2O4, Sr2+-doped BaAl2O4, Sr2+-doped ZnAl2O4, MgFe2O4, MgAl2O4–MgFe2O4, Mg0.8Li0.2Fe2O4, Mg0.9Sn0.1Fe2O4, MgFe2O4–CeO2, MgCr2O4–TiO2, Zn2SnO4–LiZnVO4 and ZnCr2O4–K2CrO4 [1]. Finally, Perovskite-type oxides and composites based on perovskites have been used for humidity sensing elements too: NaH2PO4 doped BaTiO3, MnTiO3, Li+ doped Ca0.35Pb0.65TiO3, BaNbO3, LaFeO3, K+-doped nanocrystalline LaCo0.3Fe0.7O3 (La0.93K0.07Co0.3Fe0.7O3) and Sr-doped SmCrO3 (Sm0.90Sr0.10CrO3) [1]. Preparation techniques can considerably affect the physical, chemical and gas sensing properties of the metal oxide sensors. Developments of new preparative routes, as well as compositional variations, are two perspective approaches for the design of highly sensitive and selective gas sensor materials.Reference: [1] T.A. Blanka, L.P. Eksperiandova, K.N. Belikov, Recent trends of ceramic humidity sensors development: A review. Sensors and Actuators B, 228 (2016) 416–442

Elaboration and characterization of humidity sensors for environmental monitoring

The water content in surrounding air is an important factor for the well-being of humans and animals, as the level of comfort is determined by a combination of two factors: relative humidity and ambient temperature. Humidity is also an important factor for operating certain equipment such as high-impedance electronic circuits, electrostatic-sensitive components, high-voltage devices, fine mechanisms, etc. Nonetheless, moisture is the ingredient common to most manufactured goods and processed materials. Thus, humidity sensors have been receiving wide attentions since decades. Yet, despite the high request, major advances in these sensors in terms of simple structure, lower cost, better selectivity, durability and reliability are always needed. Throughout the years, a large number of materials based on polymers, composite and ceramics have been tested, due to their own features and specific operating conditions. However, great attention has been paid to ceramic materials due to their chemical inertness which allow them to operate in harsh conditions. Amongst the different studied humidity sensors, impedance-based ones are used most commonly. The operation principle of the impedance sensors is based on the dependence of the impedance (or either capacitance or resistance) of the sensor element recognizing the nature and amount of water molecules on the surface or in the bulk. The resistance or impedance of the resistive-type sensor decreases as the relative humidity (RH)increases. Ions or electrons, or both of them, are the conduction carriers for resistive-type humidity sensors. The common construction of the resistive-type ceramic humidity sensors consists of a ceramic substrate with noble metal interdigitated electrodes coated with humidity sensing ceramic materials, both deposited by screen-print technique [1]. Metal oxides and metal oxide based composites are the most popular materials to be used as resistive sensing elements: TiO2, TiO2–SnO2, TiO2–WO3, TiO2–Cu2O–Na2O, KTaO3//TiO2(bilayered), TiO2/KTaO3 (bilayered), TiO2–K2O–LiZnVO4, Al2O3, AlO(OH), SiO2, WO3, Cr2O3–WO3, SnO2, a noble metal doped SnO2, SnO2: ZrO2 (bilayered), single Sb doped SnO2, K+-dopedSnO2–LiZnVO4, MnO2 –Mn3O4, Li+-doped Fe2O3, Au3+ and Li+ co-doped Fe2O3, Li+, Zn2+ and Au3+ co-doped Fe2O3, NiMoO4–MoO3, Li+-doped NiMoO4–MoO3, CuMoO4–MoO3 and PbMoO4–MoO3 [1]. Spinel-type oxides and composites based on spinel-type oxides are also used for humidity resistive sensing elements: MgAl2O4, Sr2+-doped CoAl2O4, Sr2+-doped BaAl2O4, Sr2+-doped ZnAl2O4, MgFe2O4, MgAl2O4–MgFe2O4, Mg0.8Li0.2Fe2O4, Mg0.9Sn0.1Fe2O4, MgFe2O4–CeO2, MgCr2O4–TiO2, Zn2SnO4–LiZnVO4 and ZnCr2O4–K2CrO4 [1]. Finally, Perovskite-type oxides and composites based on perovskites have been used for humidity sensing elements too: NaH2PO4 doped BaTiO3, MnTiO3, Li+ doped Ca0.35Pb0.65TiO3, BaNbO3, LaFeO3, K+-doped nanocrystalline LaCo0.3Fe0.7O3 (La0.93K0.07Co0.3Fe0.7O3) and Sr-doped SmCrO3 (Sm0.90Sr0.10CrO3) [1]. Preparation techniques can considerably affect the physical, chemical and gas sensing properties of the metal oxide sensors. Developments of new preparative routes, as well as compositional variations, are two perspective approaches for the design of highly sensitive and selective gas sensor materials.Reference: [1] T.A. Blanka, L.P. Eksperiandova, K.N. Belikov, Recent trends of ceramic humidity sensors development: A review. Sensors and Actuators B, 228 (2016) 416–442

21st Century Nanostructured Materials

Nanostructured materials (NMs) are attracting interest as low-dimensional materials in the high-tech era of the 21st century. Recently, nanomaterials have experienced breakthroughs in synthesis and industrial and biomedical applications. This book presents recent achievements related to NMs such as graphene, carbon nanotubes, plasmonic materials, metal nanowires, metal oxides, nanoparticles, metamaterials, nanofibers, and nanocomposites, along with their physical and chemical aspects. Additionally, the book discusses the potential uses of these nanomaterials in photodetectors, transistors, quantum technology, chemical sensors, energy storage, silk fibroin, composites, drug delivery, tissue engineering, and sustainable agriculture and environmental applications

Chemical sensing with 2D materials

During the last decade, two-dimensional materials (2DMs) have attracted great attention due to their unique chemical and physical properties, which make them appealing platforms for diverse applications in opto-electronic devices, energy generation and storage, and sensing. Among their various extraordinary properties, 2DMs possess high surface area-to-volume ratios and ultra-high surface sensitivity to the environment, which are key characteristics for applications in chemical sensing. Furthermore, 2DMs’ superior electrical and optical properties, combined with their excellent mechanical characteristics such as robustness and flexibility, make these materials ideal components for the fabrication of a new generation of high-performance chemical sensors. Depending on the specific device, 2DMs can be tailored to interact with various chemical species at the non-covalent level, making them powerful platforms for fabricating devices exhibiting a high sensitivity towards detection of various analytes including gases, ions and small biomolecules. Here, we will review the most enlightening recent advances in the field of chemical sensors based on atomically-thin 2DMs and we will discuss the opportunities and the challenges towards the realization of novel hybrid materials and sensing devices

Nanowire Chemical/Biological Sensors: Status and a Roadmap for the Future

Chemiresistive sensors are becoming increasingly important as they offer an inexpensive option to conventional analytical instrumentation, they can be readily integrated into electronic devices, and they have low power requirements. Nanowires (NWs) are a major theme in chemosensor development. High surface area, interwire junctions, and restricted conduction pathways give intrinsically high sensitivity and new mechanisms to transduce the binding or action of analytes. This Review details the status of NW chemosensors with selected examples from the literature. We begin by proposing a principle for understanding electrical transport and transduction mechanisms in NW sensors. Next, we offer the reader a review of device performance parameters. Then, we consider the different NW types followed by a summary of NW assembly and different device platform architectures. Subsequently, we discuss NW functionalization strategies. Finally, we propose future developments in NW sensing to address selectivity, sensor drift, sensitivity, response analysis, and emerging applications

Charakterisierung funktionaler Nanomaterialien für biomagnetische Sensoren und Atemanalyse

The presented thesis is covering materials aspects for the development of magnetoelectric sensors for biomagnetic sensing and solid state sensors for breath monitoring. The electrophysiological signals of the human body and especially their irregularities provide extremely valuable information about the heart, brain or nerve malfunction in medical diagnostics. Similar and even more detailed information is contained in the generated biomagnetic fields which measurement offers improved diagnostics and treatment of the patients. A new type of room temperature operable magnetoelectric composite sensors is developed in the framework of the CRC1261 Magnetoelectric Sensors: From Composite Materials to Biomagnetic Diagnostics. This thesis focuses on the individual materials structure-property relations and their combination in magnetoelectric composite sensors studied by electron beam based techniques, at lengths scales ranging from micrometers to atomic resolution. The first part of this thesis highlights selected studies on the structural and analytic aspects of single phase materials and their composites using TEM as the primary method of investigation. With respect to the piezoelectric phase, alternatives to AlN have been thoroughly investigated to seek for improvement of specific sensor approaches. In this context, the alloying of Sc into the AlN matrix has been demonstrated to yield high quality films with improved piezoelectric and unprecedented ferroelectric properties grown under the control of deposition parameters. Lead-free titanate films with large piezo-coefficients at the verge of the morphotropic phase boundary as alternative to PZT films have been investigated in terms of crystal symmetry, defect structure and domains of cation ordering. New morphologies of ZnO and GaN semiconductors envisioned for a piezotronic-based sensor approach were subject of in-depth defect and analytical studies describing intrinsic defects and lattice strains upon deposition as well as hollow composite structures. When the dimensions of a materials are reduced, novel exciting properties such as in-plane piezoelectricity can arise in planar transition-metal dichalcogenides. Here, the turbostratic disorder in a few-layered MoSe2 film has been investigated by nanobeam electron diffraction and Fast Fourier Transformations. From the perspective of magnetic materials, the atomic structure of magnetostrictive multilayers of FeCo/TiN showing stability up to elevated temperatures has been analyzed in detail regarding the crystallographic relationship of heteroepitaxy in multilayer composites exhibiting individual layer thicknesses below 1 nm. Further, magnetic hard layers have been investigated in the context of exchange spring concepts and ME composites based on shape memory alloy substrates have been studied regarding structural changes implied by different annealing processes. The second part of this thesis introduces materials aspects and sensor studies on gas detection in the clinical context of breath analysis. The detection of specific vapors in the human breath is of medical relevance, since certain species can be enriched depending on the conditions and processes within the human body. Hence, they can be regarded as biomarkers for the patients condition of health. The selection of suitable materials and the gas measurement working principle are considered and selected studies on solid state sensors with different surface functionalization or targeted application on basis of ZnO or CuO-oxide and Fe-oxide species are presented