This paper demonstrated a flexible humidity sensor based on tin dioxide/reduced graphene oxide (RGO) nanocomposite film. The humidity sensor was fabricated on a polyimide substrate with microelectrodes by using a facile one-step hydrothermal route. The hydrothermal synthesized SnO 2 nanoparticles and SnO 2 /RGO hybrid nanostructures were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The humidity sensing properties of the presented SnO 2 /RGO nano-hybrid sensor were investigated by exposing it to a broad humidity range of 11–97%RH at room temperature. Compared with traditional humidity sensors, the SnO 2 modified graphene sensor demonstrated an ultrahigh sensitivity and a rapid response/recovery characteristic over a full humidity range measurement, highlighting the unique advantages of hydrothermal synthesis for sensors fabrication. Finally, the possible humidity sensing mechanism of the proposed sensor was discussed by using complex impedance spectra and bode diagrams. These observed results demonstrate that RGO modified with metal oxide is promising nanomaterials for constructing high performance humidity sensors in widespread applications.

Fabrication and characterization of an ultrasensitive humidity sensor based on metal oxide/graphene hybrid nanocomposite

Biomarkers are described as characteristics that provide information about biological conditions whether normal or pathological. Detection of biomarkers at the earliest stage of the cancer is of utmost importance for clinical diagnosis. Electrochemical biosensors allow detecting the low levels of specific analytes in blood, urine or saliva and providing a sensitive approach for direct measurement for cancer biomarker detection. Moreover, the integration of electrochemical devices with nanomaterials, such as carbon nanotubes, gold and magnetic particles offer amplification and multiplexing capabilities for simultaneous measurements of cancer biomarkers very sensitively. This review summarizes the recent developments of electrochemical biosensors systems for the detection of cancer biomarkers with emphasis on voltammetric, amperometric and impedimetric biosensors. A special attention is paid to aptamers and miRNAs that are very promising for the ultra-sensitive and specific cancer biomarker detection.

Electrochemical Biosensors for Cancer Biomarkers Detection: Recent Advances and Challenges

Molecular imprinting technology has been widely applied to various fields, owing to unique features of structure predictability, recognition specificity and application universality. Microorganism imprinting has attracted significant interests attributing to the high selectivity, simplicity rapidity, and excellent stability as well as low cost and eco-friendliness. Herein, we purpose to review the recent advances of MIT for microorganism analysis, concerning imprinting methods, analytical detection methods and typical applications. Various imprinting methods including direct and indirect imprinting for microorganism-MIPs preparation are comprehensively summarized. MIPs based biosensors containing fluorescence, electrochemical, piezoelectric and surface plasmon resonance for analytical detection of microorganisms is highlighted. Representative applications of microbiological imprinting are discussed, involving detection and quantification of bacteria, identification of bacterial species, and determination of yeast growth status. Finally, we propose the remaining challenges and future perspectives to accelerate the development and utilization of MIT in microorganism analysis and thereby push forwards microorganism identification and determination.

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Molecular imprinting technology for microorganism analysis

The financial support received from the Slovak Scientific Grant Agency VEGA 2/0137/18 and 2/0090/16 and the Slovak Research and Development Agency APVV 17-0300 and APW-15-0227 is acknowledged. The research received funding from the European Research Council (no. 311532). This publication is the result of the project implementation: Centre for materials, layers and systems for applications and chemical processes under extreme conditions - Stage I, ITMS No.: 26240120007, supported by the ERDF.

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Electrochemical Impedance Spectroscopy Based Biosensors: Mechanistic Principles, Analytical Examples and Challenges towards Commercialization for Assays of Protein Cancer Biomarkers

Electroanalytical technologies as a beneficial subject of modern analytical chemistry can play an important role for abused drug analysis which is crucial for both legal and social respects. This article reports a novel aptamer-based biosensing procedure for cocaine analysis by combining the advantages of aptamers as selective recognition elements with the well-known advantages of biosensor systems such as the possibility of miniaturization and automation, easy fabrication and modification, low cost, and sensitivity. In order to construct the aptasensor platform, first, polythiophene bearing polyalanine homopeptide side chains (PT-Pala) was electrochemically coated onto the surface of an electrode and then cocaine aptamer was attached to the polymer via covalent conjugation chemistry. The stepwise modification of the surface was confirmed by electrochemical characterization. The designed biosensing system was applied for the detection of cocaine and its metabolite, benzoylecgonine (BE), which exhibited a ...

Polypeptide Functional Surface for the Aptamer Immobilization: Electrochemical Cocaine Biosensing.

Electrochemical impedance spectroscopy (EIS) is an electrochemical surface characterization technique and has been widely used in biosensor and chemical sensors, also provides label free detection. This technique is used as faradaic and non-faradaic measurement. The advantage of the sensitivity of faradaic impedance spectroscopy becomes useful and preferred technique. In this review we tried to answer these questions: how Nyquist plots are fitted in proper circuit and how a proper circuit element is chosen in fitting and impedance calculation steps. Nyquist plot can become very confusing to fit on a proper circuit modal and calculation of impedance (Z). Z is called in other word as electron transfer resistance (Ret), additionally electrolyte interface impedance (Rs), capacitance (C) and Warburg impedance (W) are the other elements. These all circuit elements must be constructed in a proper order to fit Nyquist plot into a good circuit model. Therefore it is very important to examine Nyquist plot for accurate calculation.

A short footnote: Circuit design for faradaic impedimetric sensors and biosensors

Non-invasive cortisol detection in saliva by using molecularly cortisol imprinted fullerene-acrylamide modified screen printed electrodes

In this chapter we discus molecular imprinting technology (MIT), molecular imprint‐ ed polymers (MIPs), and their compatibility on a proper transducer to construct a sensing system. Molecularly imprinted sensors (MISens), in other words, artificial receptor-based sensors synthesized in the presence of the target molecule, are capable of sensing target molecules by using their specific cavities and are compatible with the target molecule. This MIP technology is a viable alternative of artificial receptor technology, and the sensor technology is capable of detecting any kind of molecule without pre-analytic preparations. In this chapter, you can find examples, sensor construction techniques and fundamentals of MIP and sensor combinations to look forward in your studies. For sensor technology, we explained and discussed the new sensing technologies of MIP-based electrochemical, optical (especially surface plasmon resonance, SPR), and piezoelectric techniques. Therefore, this chapter presents a short guideline of MISens.

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Molecularly Imprinted Sensors — New Sensing Technologies

Sensor and biosensor technologies have shown rapid progress in recent years. These technologies use nanomaterials that have an important place in immobilization materials for recognition analyte molecules. Although fullerenes among these materials have attracted much attention in recent years, their number of studies is less than other carbon-based nanomaterials. Thanks to its completely closed structure and at least 30 double bonds, it can be modified from 30 points, which provides a great advantage. At these points, thanks to the ability to modify amine, thiol, carboxyl or metallic groups, modification residues can be created for all kinds of immobilization. According to the zero-dimensional nanomaterial class, fullerenes provide an extremely large surface area. Therefore, it provides more biological or non-biological recognition receptors immobilized on this surface area. Moreover, increasing the surface area with more recognition agent also increases the sensitivity. This is the most important parameter of sensor technologies, which is provided by fullerenes. In this book chapter, the development of fullerene-modified sensor and biosensor technologies are explained with examples, and fullerene modifications are given in figures as fullerene derivatives. Contribution was made in the method development stage by giving comparison of fullerene type sensor and biosensor systems.

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Fullerene Based Sensor and Biosensor Technologies

A Novel Chronoimpedimetric Glucose Sensor in Real Blood Samples Modified by Glucose-Imprinted Pyrrole-Aminophenylboronic Acid Modified Screen Printed Electrode

Hilmiye Deniz Ertuğrul Uygun

Papers

A short footnote: Circuit design for faradaic impedimetric sensors and biosensors

Non-invasive cortisol detection in saliva by using molecularly cortisol imprinted fullerene-acrylamide modified screen printed electrodes

Molecularly Imprinted Sensors — New Sensing Technologies

Fullerene Based Sensor and Biosensor Technologies

A Novel Chronoimpedimetric Glucose Sensor in Real Blood Samples Modified by Glucose-Imprinted Pyrrole-Aminophenylboronic Acid Modified Screen Printed Electrode