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Optical Chemical Sensor Using Intensity Ratiometric Fluorescence Signals for Fast and Reliable pH Determination
摘要： Optical pH sensors enable non-invasive monitoring of pH, yet in pure sensing terms, the potentiometric method of measuring pH is still vastly superior. Here, we report a full spectrometer-based optical pH sensor system consisting of sensor chemistry, hardware and software that for the first time is capable of challenging the performance of electrode-based pH meter in specific applications such as biopharmaceutical process monitoring and in single-use bioproduction. A highly photostable triangulenium fluorophore emitting at 590 nm was immobilized in an organically modified silicon matrix that allows for fast time-response by rapid diffusion of water in and out of the resulting composite polymer deposited on a polycarbonate substrate. Fluctuations from the fiber optical sensor hardware have been reduced by including a highly photostable terrylene-based reference dye emitting at 660 nm, thus enabling intensity-based ratiometric readouts. The dyes were excited by 505 nm light from a light emitting diode. The sensor was operational within a pH range of 4.6 and 7.6, and was characterized and demonstrated to have properties that are comparable to commercial pH electrodes considering time-response (t90 < 90 s), precision (0.03 pH-units) and drift.
关键词： ORMOSIL,optical pH sensors,pH optode,chemical sensors,ratiometric
更新于2025-09-23 15:23:52
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Chemical Sensing Performance of Flower-Like ZnO/PSi Nanostructures via Electrochemical Impedance Spectroscopy Technique
摘要： ZnO nanostructures were synthesized on porous Si (PSi) structures using a method developed by this study known as electric field-assisted aqueous solution technique. The detailed characterization of this nanostructure was performed using atomic force microscopy, field emission scanning electron microscopy, x-ray diffraction, room-temperature photoluminescence and Raman spectroscopy. Electrochemical impedance spectroscopy (EIS) technique was used to detect two classifications of chemical solvents, namely polar and non-polar solvents. Nyquist plots in EIS were utilized to detect chemical solvents (ethanol, acetone, toluene and benzene) exposed to ZnO/PSi nanostructure arrays. The results showed that the grown flower-like ZnO nanostructure arrays served as good chemical sensors with high sensitivity and low power consumption. Meanwhile, the ZnO/PSi nanoflowers exposed to ethanol showed the highest sensitivity (94.6% response) compared to other chemical solutions with the least response exhibited by benzene (68.4% response). It was postulated that the interaction between the solution and oxygen species of ZnO/PSi nanostructure surface induced a resistance change resulting in the release of free electrons that migrated to the conduction band of ZnO/PSi nanoflower structures and reduced the number of surface-adsorbed oxygen species. Subsequently, the changes observed in the Nyquist semicircle diameter and Warburg impedance led to the chemical sensing response.
关键词： ZnO/PSi nanoflower,electric field-assisted aqueous solution technique,Chemical sensors,electrochemical impedance spectroscopy,Nyquist plot
更新于2025-09-23 15:23:52
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Quasi-one-dimensional silicon nanostructures for gas molecule adsorption: a DFT investigation
摘要： Porous structures offer an enormous surface suitable for gas sensing, however, the effects of their quantum quasi-confinement on their molecular sensing capacities has been seldom studied. In this work the gas-sensing capability of silicon nanopores is investigated by comparing it to silicon nanowires using first principles calculations. In particular, the adsorption of toxic gas molecules CO, NO, SO2 and NO2 on both silicon nanopores and nanowires with the same cross sections was studied. Results show that sensing-related properties of silicon nanopores and nanowires are very similar, suggesting that surface effects are predominant over the confinement. However, there are certain cases where there are remarked differences between the nanowire and porous cases, for instance, CO-adsorbed nanoporous silicon shows a metallic band structure unlike its nanowire counterpart, which remains semiconducting, suggesting that quantum quasi-confinement may be playing an important role in this behaviour. These results are significant in the study of the quantum phenomena behind the adsorption of gas molecules on nanostructure’s surfaces, with possible applications in chemical detectors or catalysts.
关键词： Sensing,Chemical sensors,Silicon nanowires,Density functional theory,Molecule adsorption,Porous silicon
更新于2025-09-23 15:23:52
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Functional Sensing Interfaces of PEDOT:PSS Organic Electrochemical Transistors for Chemical and Biological Sensors: A Mini Review
摘要： Organic electrochemical transistors (OECTs) are promising devices for applications in in vitro and in vivo measurements. OECTs have two important sensing interfaces for signal monitoring: One is the gate electrode surface; the other is the channel surface. This mini review introduced the new developments in chemical and biological detection of the two sensing interfaces. Specific focus was given on the modification technological approaches of the gate or channel surface. In particular, some unique strategies and surface designs aiming to facilitate signal-transduction and amplification were discussed. Several perspectives and current challenges of OECTs development were also briefly summarized.
关键词： organic electrochemical transistors,interface functionalization,chemical sensors,biosensors
更新于2025-09-23 15:22:29
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Novel color standards for digital color analysis of optochemical sensor arrays
摘要： The indicator-based polymeric color standards for color referencing in digital color analysis (DCA) of optical chemical sensors (optodes) are proposed. In the novel standards, the colors referring to the actual absorption bands of the protonated and deprotonated forms of the indicator are mixed in constant proportions. The standards are based on the lipophilic pH-indicators: ETH5350 and ETH2439, commonly used in optodes, and the lipophilic electrolyte TBATBB. The dependence of the standard color on the TBATBB concentration in the optode is established and found to be linear. The standard colors remain unchanged upon varying the solution pH and the nature and the concentration of the electrolyte. Calibration curves of the indicator pH-optodes obtained in horse serum and referenced to the developed standards demonstrate lower error to span ratio, broader span and higher sensitivity as compared to the same data processed with the conventional gray standard. The colorimetric signal of the pH-optodes array measured in serum sample and referenced to the developed standards allowed accurate determination of the sample pH thus demonstrating practical prospects of the proposed color standards.
关键词： color standards,digital color analysis,optical chemical sensors,polymeric optodes
更新于2025-09-23 15:22:29
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Organic Transistor-Based Chemical Sensors for Wearable Bioelectronics
摘要： Bioelectronics for healthcare that monitor the health information on users in real time have stepped into the limelight as crucial electronic devices for the future due to the increased demand for “point-of-care” testing, which is defined as medical diagnostic testing at the time and place of patient care. In contrast to traditional diagnostic testing, which is generally conducted at medical institutions with diagnostic instruments and requires a long time for specimen analysis, point-of-care testing can be accomplished personally at the bedside, and health information on users can be monitored in real time. Advances in materials science and device technology have enabled next-generation electronics, including flexible, stretchable, and biocompatible electronic devices, bringing the commercialization of personalized healthcare devices increasingly within reach, e.g., wearable bioelectronics attached to the body that monitor the health information on users in real time. Additionally, the monitoring of harmful factors in the environment surrounding the user, such as air pollutants, chemicals, and ultraviolet light, is also important for health maintenance because such factors can have short- and long-term detrimental effects on the human body. The precise detection of chemical species from both the human body and the surrounding environment is crucial for personal health care because of the abundant information that such factors can provide when determining a person’s health condition. In this respect, sensor applications based on an organic-transistor platform have various advantages, including signal amplification, molecular design capability, low cost, and mechanical robustness (e.g., flexibility and stretchability).
关键词： organic transistor-based chemical sensors,health monitoring,wearable bioelectronics,environmental monitoring,point-of-care testing
更新于2025-09-23 15:21:01
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Chemical and Biomolecule Sensing with Organic Field-Effect Transistors
摘要： The strong and controllable chemical sensitivity of organic semiconductors (OSCs) and the amplification capability of transistors in circuits make use of OSC-based field-effect transistors compelling for chemical sensors. Analytes detected and assayed range from few-atom gas-phase molecules that may have adverse health and security implications to biomacromolecules (proteins, nucleic acids) that may be markers for physiological processes and medical conditions. This review highlights recent progress in organic field-effect transistor (OFET) chemical sensors, emphasizing advances from the past 5 years and including aspects of OSC morphology and the role of adjacent dielectrics. Design elements of the OSCs and various formats for the devices are illustrated and evaluated. Challenges associated with the present state of the art and future opportunities are also discussed.
关键词： organic field-effect transistors,organic semiconductors,dielectrics,biomacromolecules,chemical sensors
更新于2025-09-23 15:21:01
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Sensing of Furfural by Molecularly Imprinted Polymers on Plasmonic and Electrochemical Platforms
摘要： The goal of this work is to test the possibility of selective detection of furfural (2-FAL) in aqueous solutions, with a molecularly imprinted polymer (MIP) receptor exploiting two different transduction methods, for food safety applications. In particular, sensors with electrochemical and surface plasmon resonance (SPR) transduction are considered. Two concentration ranges could be investigated by the different sensing approaches since the detectable concentration level depends on the sensitivity of the detection technique employed. The determination of 2-FAL at different concentration levels in the aqueous medium of interest, as for example beverages, is becoming a very crucial task not only for the relevance of furanic compounds in affecting the flavor but also for their possible toxic and carcinogenic effects on the human beings. For these reasons, their determination by a fast, easy and low-cost method is of interest. The sensor methods here proposed appears to be particularly suitable, since, although together and not individually, they allow the determination in a wide concentration range.
关键词： furfural (2-FAL),electrochemical sensors,molecularly imprinted polymers (MIPs),optical-chemical sensors,plastic optical fibers (POFs),surface plasmon resonance (SPR)
更新于2025-09-23 15:19:57
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[IEEE 2018 IEEE SENSORS - New Delhi, India (2018.10.28-2018.10.31)] 2018 IEEE SENSORS - Contact-Printing of Zinc Oxide Nanowires for Chemical Sensing Applications
摘要： This paper presents a new method for printing zinc oxide (ZnO) nanowires (NWs) and their analysis for chemical sensing applications. High-crystal quality ZnO NWs are synthesized by chemical vapour transport (CVT) technique and directly transferred and aligned on a glass substrate by using contact-printing technique. With an accurate control of the contact-printing parameters such as load and speed over the entire printing process, a highly uniform, dense and well-aligned NWs layers are obtained on the desired substrate over large areas. The validity of the ZnO NWs as chemical sensing material is demonstrated by carrying out both cyclic voltammetry and electrochemical impedance spectroscopic measurements in different pH solutions. Results demonstrate a high stability of ZnO NWs to basic solutions (i.e. pH > 6), which shows their suitability for applications such as sweat or water quality monitoring sensors.
关键词： pH Sensors,Contact-printing,Chemical Sensors,Nanowire Assembly,ZnO Nanowires
更新于2025-09-19 17:15:36
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An Optical Fiber Chemical Sensor for the Detection of Copper(II) in Drinking Water
摘要： Highly sensitive plasmonic optical fiber platforms combined with receptors have been recently used to obtain selective sensors. A low-cost configuration can be obtained exploiting a D-shaped plastic optical fiber covered with a multilayer sensing surface. The multilayer consists of a gold film, functionalized with a specific receptor, where the surface plasmon resonance (SPR) occurs. The signal is produced by the refractive index variation occurring as a consequence of the receptor-to analyte binding. In this work, a selective sensor for copper(II) detection in drinking water, exploiting a self-assembled monolayer (SAM) of d,l-penicillamine as the sensing layer, has been developed and tested. Different concentrations of copper(II) in NaCl 0.1 M solutions at different pH values and in a real matrix (drinking water) have been considered. The results show that the sensor is able to sense copper(II) at concentrations ranging from 4 × 10?6 M to 2 × 10?4 M. The use of this optical chemical sensor is a very attractive perspective for fast, in situ and low-cost detection of Cu(II) in drinking water for human health concerns. Furthermore, the possibility of remote control is feasible as well, because optical fibers are employed.
关键词： Optical chemical sensors,surface plasmon resonance,copper(II),drinking water,human health
更新于2025-09-16 10:30:52