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Chemosensors, Volume 6, Issue 1 (March 2018)

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Editorial

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Open AccessEditorial Acknowledgement to Reviewers of Chemosensors in 2017
Chemosensors 2018, 6(1), 2; doi:10.3390/chemosensors6010002
Received: 9 January 2018 / Revised: 9 January 2018 / Accepted: 9 January 2018 / Published: 9 January 2018
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Abstract
Peer review is an essential part in the publication process, ensuring that Chemosensors maintains high quality standards for its published papers. In 2017, a total of 32 papers were published in the journal.[...] Full article

Research

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Open AccessArticle Effect of Dangling Bonds on De-Poling Time for Polymeric Electric Field Optical Sensors
Chemosensors 2018, 6(1), 3; doi:10.3390/chemosensors6010003
Received: 26 November 2017 / Revised: 10 January 2018 / Accepted: 11 January 2018 / Published: 12 January 2018
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Abstract
This paper investigates the possible chemical changes in polydimethylsiloxane (PDMS) caused by two different techniques of fabrication for ultra-sensitive electric field optical sensors. The sensing element is a micro-sphere made from 60:1 PDMS (60 parts base silicon elastomer to one part polymer curing
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This paper investigates the possible chemical changes in polydimethylsiloxane (PDMS) caused by two different techniques of fabrication for ultra-sensitive electric field optical sensors. The sensing element is a micro-sphere made from 60:1 PDMS (60 parts base silicon elastomer to one part polymer curing agent by volume). The measurement principle is based on the morphology dependent resonances (MDR) shifts of the micro-sphere. We present the effects of curing and poling of polymer micro-spheres used as optical sensors. The degree of curing leads to changes in the de-poling time which results from dangling bonds in the polymeric chains. Consequently, the longevity of the sensitivity of the sensor can extended by two orders of magnitude. An analysis is carried out along with preliminary experiments to investigate that behavior. Full article
(This article belongs to the Special Issue Polymers Based Chemical Sensors)
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Open AccessArticle Stand-Off Chemical Detection Using Photoacoustic Sensing Techniques—From Single Element to Phase Array
Chemosensors 2018, 6(1), 6; doi:10.3390/chemosensors6010006
Received: 19 November 2017 / Revised: 18 January 2018 / Accepted: 19 January 2018 / Published: 23 January 2018
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Abstract
Technologies that can detect harmful chemicals, such as explosive devices, harmful gas leaks, airborne chemicals or/and biological agents, are heavily invested in by the government to prevent any possible catastrophic consequences. Some key features of such technology are, but not limited to, effective
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Technologies that can detect harmful chemicals, such as explosive devices, harmful gas leaks, airborne chemicals or/and biological agents, are heavily invested in by the government to prevent any possible catastrophic consequences. Some key features of such technology are, but not limited to, effective signal-to-noise ratio (SNR) of the detected signal and extended distance between the detector and target. In this work, we describe the development of photoacoustic sensing techniques from simple to more complex systems. These techniques include passive and active noise filters, parabolic sound reflectors, a lock-in amplifier, and beam-forming with an array of microphones; using these techniques, we increased detection distance from a few cm in an indoor setting to over 41 feet in an outdoor setting. We also establish a theoretical mathematical model that explains the underlying principle of how SNR can be improved with an increasing number of microphone elements in the phase array. We validate this model with computational simulations as well as experimental results. Full article
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Open AccessFeature PaperArticle CO-Sensing Properties of Diode-Type Gas Sensors Employing Anodized Titania and Noble-Metal Electrodes under Hydrogen Atmosphere
Chemosensors 2018, 6(1), 7; doi:10.3390/chemosensors6010007
Received: 21 December 2017 / Revised: 21 January 2018 / Accepted: 22 January 2018 / Published: 24 January 2018
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Abstract
CO-sensing properties of diode-type sensors employing an anodized TiO2 film and noble-metal (M) electrodes (M/TiO2 sensor, M: Pd, Pt, and Pd-nPt, n: the amount of Pt (wt %) in the Pd-nPt electrode) were investigated at 50–250
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CO-sensing properties of diode-type sensors employing an anodized TiO2 film and noble-metal (M) electrodes (M/TiO2 sensor, M: Pd, Pt, and Pd-nPt, n: the amount of Pt (wt %) in the Pd-nPt electrode) were investigated at 50–250 °C in dry or wet H2. All the M/TiO2 sensors showed nonlinear IV characteristics as a diode device in air and N2, but the IV characteristics of the sensors were actually linear in H2 because of the negligible small height of Schottky barrier at their M/TiO2 interface. The Pd/TiO2 sensor showed no CO response in H2, but the Pt/TiO2 and Pd-nPt/TiO2 sensors responded to CO in H2. Among them, the Pd-64Pt/TiO2 sensor showed the largest CO response at 100 °C in H2. The reason why the mixing of Pd with Pt was effective in improving the CO response is probably because of a decrease in the amount of dissolved hydrogen species, an increase in the amount of dissociatively adsorbed hydrogen species, and an increase in the amount of adsorbed CO species in CO balanced with H2 by the mixing of Pt into Pd. The interference from moisture in the target gas on the CO response should be largely improved from a practical application perspective. Full article
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Open AccessFeature PaperArticle Synthesis, Curing Behavior and Swell Tests of pH-Responsive Coatings from Acryl-Terminated Oligo(β-Amino Esters)
Chemosensors 2018, 6(1), 10; doi:10.3390/chemosensors6010010
Received: 19 January 2018 / Revised: 19 February 2018 / Accepted: 22 February 2018 / Published: 23 February 2018
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Abstract
The ability of acryl-terminated oligo(β-amino esters) (AOBAE) to be coated on fibers and printed electronics without solvents and to be cross-linked to a pH-responsive coatings, makes AOBAE-based coatings a potential type of pH-sensor coating. However, there are currently no reports of
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The ability of acryl-terminated oligo( β -amino esters) (AOBAE) to be coated on fibers and printed electronics without solvents and to be cross-linked to a pH-responsive coatings, makes AOBAE-based coatings a potential type of pH-sensor coating. However, there are currently no reports of AOBAEs used as a pH-responsive coating material in sensor applications. Here we present an investigation of the synthesis, curing behavior and swell tests of AOBAEs. AOBAEs were synthesized from reacting an excess of asymmetric diacrylates with piperazine without the use of any solvents. They were then cross-linked to an insoluble network by UV-curing. Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the AOBAEs. NMR was used to clarify the irregular structure of the AOBAE. FTIR was used to monitor the effects of UV-curing dose and air exposure on monomer conversion during curing. An interferometric technique was used to monitor the swelling behavior of the coating in response to pH variations. Swell experiments showed that the AOBAE also responded to pH variations after polymerization. Therefore, AOBAE is an interesting class of material with potential use as a pH responsive coating in optical-and printed electronics pH-sensors applications. Full article
(This article belongs to the Special Issue Thin Film Based Sensors)
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Review

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Open AccessFeature PaperReview Recent Advances in the Detection of Neurotransmitters
Chemosensors 2018, 6(1), 1; doi:10.3390/chemosensors6010001
Received: 3 December 2017 / Revised: 31 December 2017 / Accepted: 2 January 2018 / Published: 4 January 2018
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Abstract
Neurotransmitters are chemicals that act as messengers in the synaptic transmission process. They are essential for human health and any imbalance in their activities can cause serious mental disorders such as Parkinson’s disease, schizophrenia, and Alzheimer’s disease. Hence, monitoring the concentrations of various
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Neurotransmitters are chemicals that act as messengers in the synaptic transmission process. They are essential for human health and any imbalance in their activities can cause serious mental disorders such as Parkinson’s disease, schizophrenia, and Alzheimer’s disease. Hence, monitoring the concentrations of various neurotransmitters is of great importance in studying and diagnosing such mental illnesses. Recently, many researchers have explored the use of unique materials for developing biosensors for both in vivo and ex vivo neurotransmitter detection. A combination of nanomaterials, polymers, and biomolecules were incorporated to implement such sensor devices. For in vivo detection, electrochemical sensing has been commonly applied, with fast-scan cyclic voltammetry being the most promising technique to date, due to the advantages such as easy miniaturization, simple device architecture, and high sensitivity. However, the main challenges for in vivo electrochemical neurotransmitter sensors are limited target selectivity, large background signal and noise, and device fouling and degradation over time. Therefore, achieving simultaneous detection of multiple neurotransmitters in real time with long-term stability remains the focus of research. The purpose of this review paper is to summarize the recently developed sensing techniques with the focus on neurotransmitters as the target analyte, and to discuss the outlook of simultaneous detection of multiple neurotransmitter species. This paper is organized as follows: firstly, the common materials used for developing neurotransmitter sensors are discussed. Secondly, several sensor surface modification approaches to enhance sensing performance are reviewed. Finally, we discuss recent developments in the simultaneous detection capability of multiple neurotransmitters. Full article
(This article belongs to the Special Issue Polymers Based Chemical Sensors)
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Open AccessFeature PaperReview Infra-Red Plasmonic Sensors
Chemosensors 2018, 6(1), 4; doi:10.3390/chemosensors6010004
Received: 30 November 2017 / Revised: 9 January 2018 / Accepted: 10 January 2018 / Published: 16 January 2018
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Abstract
Plasmonic sensors exploiting the localized surface plasmon resonance (LSPR) of noble metal nanoparticles are common in the visual spectrum. However, bio-sensors near the infra-red (NIR) windows (600–900 nm and 1000–1400 nm) are of interest, as in these regions the absorption coefficients of water,
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Plasmonic sensors exploiting the localized surface plasmon resonance (LSPR) of noble metal nanoparticles are common in the visual spectrum. However, bio-sensors near the infra-red (NIR) windows (600–900 nm and 1000–1400 nm) are of interest, as in these regions the absorption coefficients of water, melanin deoxyglobin, and hemoglobin are all low. The first part of this paper reviews the work that has been undertaken using gold (Au) and silver (Ag) particles in metal enhanced fluorescence (MEF) in the NIR. Despite this success, there are limitations, as there is only a narrow band in the visual and NIR where losses are low for traditional plasmonic materials. Further, noble metals are not compatible with standard silicon manufacturing processes, making it challenging to produce on-chip integrated plasmonic sensors with Au or Ag. Therefore, it is desirable to use different materials for plasmonic chemical and biological sensing, that are foundry-compatible with silicon (Si) and germanium (Ge). One material that has received significant attention is highly-doped Ge, which starts to exhibit metallic properties at a wavelength as short as 6 μm. This is discussed in the second part of the paper and the results of recent analysis are included. Full article
(This article belongs to the Special Issue Advances in Chemical Imaging and its Applications)
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Open AccessReview Raman and Surface-Enhanced Raman Scattering for Biofilm Characterization
Chemosensors 2018, 6(1), 5; doi:10.3390/chemosensors6010005
Received: 7 December 2017 / Revised: 11 January 2018 / Accepted: 16 January 2018 / Published: 19 January 2018
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Abstract
Biofilms are a communal way of living for microorganisms in which microorganism cells are surrounded by extracellular polymeric substances (EPS). Most microorganisms can live in biofilm form. Since microorganisms are everywhere, understanding biofilm structure and composition is crucial for making the world a
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Biofilms are a communal way of living for microorganisms in which microorganism cells are surrounded by extracellular polymeric substances (EPS). Most microorganisms can live in biofilm form. Since microorganisms are everywhere, understanding biofilm structure and composition is crucial for making the world a better place to live, not only for humans but also for other living creatures. Raman spectroscopy is a nondestructive technique and provides fingerprint information about an analyte of interest. Surface-enhanced Raman spectroscopy is a form of this technique and provides enhanced scattering of the analyte that is in close vicinity of a nanostructured noble metal surface such as silver or gold. In this review, the applications of both techniques and their combination with other biofilm analysis techniques for characterization of composition and structure of biofilms are discussed. Full article
(This article belongs to the Special Issue Advances in Chemical Imaging and its Applications)
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Open AccessFeature PaperReview Nitric Oxide Sensors for Biological Applications
Chemosensors 2018, 6(1), 8; doi:10.3390/chemosensors6010008
Received: 19 December 2017 / Revised: 24 January 2018 / Accepted: 26 January 2018 / Published: 9 February 2018
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Abstract
Nitric oxide (NO) is an essential signaling molecule within biological systems and is believed to be involved in numerous diseases. As a result of NO’s high reaction rate, the detection of the concentration of NO, let alone the presence or absence of the
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Nitric oxide (NO) is an essential signaling molecule within biological systems and is believed to be involved in numerous diseases. As a result of NO’s high reaction rate, the detection of the concentration of NO, let alone the presence or absence of the molecule, is extremely difficult. Researchers have developed multiple assays and probes in an attempt to quantify NO within biological solutions, each of which has advantages and disadvantages. This review highlights many of the current NO sensors, from those that are commercially available to the newest sensors being optimized in research labs, to assist in the understanding and utilization of NO sensors in biological fields. Full article
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Open AccessFeature PaperReview Exploring the Emotion of Disgust: Differences in Smelling and Feeling
Chemosensors 2018, 6(1), 9; doi:10.3390/chemosensors6010009
Received: 3 November 2017 / Revised: 7 February 2018 / Accepted: 8 February 2018 / Published: 16 February 2018
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Abstract
Disgust evolved to motivate humans away from disease cues and may heighten discernment of these cues. Disease cues are often best perceived through our sense of smell, however very few studies have examined how eliciting disgust influences smell intensity or valence. In two
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Disgust evolved to motivate humans away from disease cues and may heighten discernment of these cues. Disease cues are often best perceived through our sense of smell, however very few studies have examined how eliciting disgust influences smell intensity or valence. In two novel experiments we investigated how domains of disgust induction influence odor perception. In experiment 1 participants (n = 90) were randomly allocated to one of two kinds of Disgust Induction (DI): Pathogen (DI-P), Moral (DI-M) or a Control (DI-C), followed by an evaluation of three affectively distinct odors (disgust-related, neutral, liked). Using a modified procedure in experiment 2, participants (n = 70) were again randomly assigned to one of the three disgust induction conditions, but here they evaluated one (disgust-related) odor during disgust induction. In experiment 2 we also measured feelings of disgust and anger. In experiment 1, surprisingly, we found overall ratings of odor disgust were lower in the DI-P compared to other groups, whereas in experiment 2, odor disgust was higher in the DI-P versus the DI-M/DI-C conditions, which also differed from each other. We also found that whereas feelings of disgust were higher in DI-P, in contrast, anger was higher for those individuals in the DI-M condition. These findings suggest that compared to a Control condition, inducing state Pathogen and Moral disgust lead to higher perceived odor disgust, whereas feelings of disgust/anger yield divergent effects. The work here also demonstrates that methodologies utilizing odor perception (disgust) can be a useful addition to measuring changes in state disgust. Full article
(This article belongs to the Special Issue Electronic nose’s, Machine Olfaction and Electronic Tongue’s)
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Open AccessFeature PaperReview Spectroscopic Chemical Sensing and Imaging: From Plants to Animals and Humans
Chemosensors 2018, 6(1), 11; doi:10.3390/chemosensors6010011
Received: 15 January 2018 / Revised: 16 February 2018 / Accepted: 20 February 2018 / Published: 26 February 2018
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Abstract
Chemical sensing and imaging technologies are of great importance in medical diagnostics and environmental sensing due to their ability to detect and localize chemical targets and provide valuable information in real-time. Biophotonic techniques are the most promising for in vivo applications due to
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Chemical sensing and imaging technologies are of great importance in medical diagnostics and environmental sensing due to their ability to detect and localize chemical targets and provide valuable information in real-time. Biophotonic techniques are the most promising for in vivo applications due to their minimal invasivity. Our laboratory has introduced various biophotonics-based technologies for chemical sensing and imaging for biochemical sensing, medical diagnostics, and fundamental research. Over the years, we have developed a wide variety of fluorescence and surface-enhanced Raman scattering (SERS)-based technologies for the detection of biomarkers for cancer and other diseases. This paper provides an overview of the research on chemical and biological sensors developed in our laboratory, highlighting our work on in vivo imaging and sensing, including minimally invasive detection of endogenous fluorophores associated with malignant tissue, SERS-tag localization of cancer cells and tissues, and SERS-based detection of nucleic acid biotargets and its feasibility for in vivo applications. This manuscript also presents new development on the use of Raman imaging of SERS-labeled nanoprobes incubated in leaves for use in biofuel research, laying the foundation for studies on functional imaging of nucleic acid biomarkers in plants. Full article
(This article belongs to the Special Issue Advances in Chemical Imaging and its Applications)
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