Journal articles: 'Conjugated Molecules for Sensors'

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Yamago, Shigeru. "New Organic Chemistry and Materials Science of Curved π-Conjugated Molecules." Impact 2020, no. 4 (October 13, 2020): 43–45. http://dx.doi.org/10.21820/23987073.2020.4.43.

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A key molecule in a number of functional materials is the π-conjugated molecule because of the impressive range of properties, including light absorption and emission, as well as charge transportation. Often used as active components of organic electronic and photoelectronic materials and sensors, they have attracted a great deal of attention from the research community for these valuable properties that have considerable potential for commercialisation. A variety of new π-conjugated molecules have been designed and synthesised, from smaller molecules to macromolecules (polymers). Professor Shigeru Yamago, from the Institute for Chemical Research at Kyoto University, is an expert in the field of radical chemistry, and heads up a research team that has developed a new and efficient method for synthesising structurally uniform curved and hooped π-conjugated molecules. Yamago and his team are seeking to clarify how the structure of these molecules affects their physical properties and reactivities. They hope to eventually find applications for them as organoelectronic and organophotoelectronic materials, sensors and other devices in materials science.

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KOYAMA, EMIKO, HIDEO TOKUHISA, ABDELHAK BELAISSAOUI, YOSHINOBU NAGAWA, MASATOSHI KANESATO, and TAKAO ISHIDA. "CONSTRUCTION OF MOLECULAR SENSORS FOR PROTONS USING π-CONJUGATED MOLECULES." International Journal of Nanoscience 04, no. 04 (August 2005): 475–81. http://dx.doi.org/10.1142/s0219581x05003589.

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The protonation/deprotonation response of a novel bipyridine containing (phenylene-ethynylene) thiol adsorbed to a Au surface was investigated with scanning tunneling microscopy (STM). STM results show reversible changes in the average heights (~50 spots) and the height distribution arising from protonation/deprotonation.

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Li, Zhiliang, Rajendra Acharya, Shanshan Wang, and Kirk S. Schanze. "Photophysics and phosphate fluorescence sensing by poly(phenylene ethynylene) conjugated polyelectrolytes with branched ammonium side groups." Journal of Materials Chemistry C 6, no. 14 (2018): 3722–30. http://dx.doi.org/10.1039/c7tc05081j.

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Miao, Zongcheng, Yaqin Chu, Lei Wang, Wenqing Zhu, and Dong Wang. "Nonlinear Optical and Ion Sensor Properties of Novel Molecules Conjugated by Click Chemistry." Polymers 14, no. 8 (April 8, 2022): 1516. http://dx.doi.org/10.3390/polym14081516.

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The molecular structure, luminescence behavior, and electronic energy level of an organic optoelectronic materials are important parameters for its synthesis. The electro-optical properties can be changed by modifying the structure of the molecule to make the electronic energy level adjustable. In this article, a series of organic conjugated micro-molecules are successfully synthesized by linking small compound units. This metal-free [2 + 2] click chemistry process generates donor–acceptor chromophore substances with high yield, high solubility, and adjustable energy levels, which can be widely used for sensors and nonlinear optics in different fields. A-TCNE, A-TCNQ, and A-F4-TCNQ molecules are characterized comprehensively via UV-Vis-NIR spectra, 1H NMR spectra, infrared spectroscopy, and mass spectrometry. The unique nonlinear optical phenomena and powerful intra-molecular charge–transfer interactions of these new materials give them fascinating potential for application as optoelectronic materials.

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Lee, Yoon Ho, Moonjeong Jang, Moo Yeol Lee, O. Young Kweon, and Joon Hak Oh. "Flexible Field-Effect Transistor-Type Sensors Based on Conjugated Molecules." Chem 3, no. 5 (November 2017): 724–63. http://dx.doi.org/10.1016/j.chempr.2017.10.005.

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Guan, Hongliang, and Zhike He. "Determination of L-Argininamide Based on Water-Soluble Fluorescent Conjugated Polymer-Aptamer." Journal of Analytical Methods in Chemistry 2013 (2013): 1–5. http://dx.doi.org/10.1155/2013/682134.

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Water-soluble fluorescent conjugated polymer is a promising material which could be used as an optical platform in highly sensitive molecular sensors. In this paper, a simple label-free DNA sensor, which consisted of a poly(3-alkoxy-4-methylthiophene) and an aptamer, was used to detect L-argininamide (L-Arm). Due to the specific binding reaction between L-Arm and its aptamer, the proposed method can easily determinate the L-Arm through the recovery of fluorescence without any modification. Other ions or similar molecules had little effect on the detection. Moreover, there was a linear relationship between fluorescence intensity and the concentration of L-Arm. The detection limit of L-Arm was as low as 4.7 nM.

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Parr, Zachary S., and Christian B. Nielsen. "Conjugated molecules for colourimetric and fluorimetric sensing of sodium and potassium." Materials Chemistry Frontiers 4, no. 8 (2020): 2370–77. http://dx.doi.org/10.1039/d0qm00157k.

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Terán-Alcocer, Álvaro, Francisco Bravo-Plascencia, Carlos Cevallos-Morillo, and Alex Palma-Cando. "Electrochemical Sensors Based on Conducting Polymers for the Aqueous Detection of Biologically Relevant Molecules." Nanomaterials 11, no. 1 (January 19, 2021): 252. http://dx.doi.org/10.3390/nano11010252.

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Electrochemical sensors appear as low-cost, rapid, easy to use, and in situ devices for determination of diverse analytes in a liquid solution. In that context, conducting polymers are much-explored sensor building materials because of their semiconductivity, structural versatility, multiple synthetic pathways, and stability in environmental conditions. In this state-of-the-art review, synthetic processes, morphological characterization, and nanostructure formation are analyzed for relevant literature about electrochemical sensors based on conducting polymers for the determination of molecules that (i) have a fundamental role in the human body function regulation, and (ii) are considered as water emergent pollutants. Special focus is put on the different types of micro- and nanostructures generated for the polymer itself or the combination with different materials in a composite, and how the rough morphology of the conducting polymers based electrochemical sensors affect their limit of detection. Polypyrroles, polyanilines, and polythiophenes appear as the most recurrent conducting polymers for the construction of electrochemical sensors. These conducting polymers are usually built starting from bifunctional precursor monomers resulting in linear and branched polymer structures; however, opportunities for sensitivity enhancement in electrochemical sensors have been recently reported by using conjugated microporous polymers synthesized from multifunctional monomers.

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Lai, Qin-Teng, Qi-Jun Sun, Zhenhua Tang, Xin-Gui Tang, and Xin-Hua Zhao. "Conjugated Polymer-Based Nanocomposites for Pressure Sensors." Molecules 28, no. 4 (February 8, 2023): 1627. http://dx.doi.org/10.3390/molecules28041627.

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Flexible sensors are the essential foundations of pressure sensing, microcomputer sensing systems, and wearable devices. The flexible tactile sensor can sense stimuli by converting external forces into electrical signals. The electrical signals are transmitted to a computer processing system for analysis, realizing real-time health monitoring and human motion detection. According to the working mechanism, tactile sensors are mainly divided into four types—piezoresistive, capacitive, piezoelectric, and triboelectric tactile sensors. Conventional silicon-based tactile sensors are often inadequate for flexible electronics due to their limited mechanical flexibility. In comparison, polymeric nanocomposites are flexible and stretchable, which makes them excellent candidates for flexible and wearable tactile sensors. Among the promising polymers, conjugated polymers (CPs), due to their unique chemical structures and electronic properties that contribute to their high electrical and mechanical conductivity, show great potential for flexible sensors and wearable devices. In this paper, we first introduce the parameters of pressure sensors. Then, we describe the operating principles of resistive, capacitive, piezoelectric, and triboelectric sensors, and review the pressure sensors based on conjugated polymer nanocomposites that were reported in recent years. After that, we introduce the performance characteristics of flexible sensors, regarding their applications in healthcare, human motion monitoring, electronic skin, wearable devices, and artificial intelligence. In addition, we summarize and compare the performances of conjugated polymer nanocomposite-based pressure sensors that were reported in recent years. Finally, we summarize the challenges and future directions of conjugated polymer nanocomposite-based sensors.

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Yuan, MingJian, YongJun Li, HuiBiao Liu, and YuLiang Li. "Chemical sensors based on π-conjugated organic molecules and gold nanoparticles." Science in China Series B: Chemistry 52, no. 6 (May 20, 2009): 715–30. http://dx.doi.org/10.1007/s11426-009-0129-5.

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Pillai, Sreenadh Sasidharan, Hiroshi Yukawa, Daisuke Onoshima, Vasudevanpillai Biju, and Yoshinobu Baba. "Quantum Dot-Peptide Nanoassembly on Mesoporous Silica Nanoparticle for Biosensing." Nano Hybrids and Composites 19 (February 2018): 55–72. http://dx.doi.org/10.4028/www.scientific.net/nhc.19.55.

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Quantum dots (QDs) are powerful luminescent probes for detecting single-molecules and imaging live cells. Despite several reports on bioimaging and biosensing applications of QDs, controlled and targeted detection of biomolecules using quantum dots is an ongoing challenge. When a QD is conjugated with an ideal chromophore, which can be a fluorescent or a non-fluorescent dye molecule, QD luminescence can be quenched by Förster resonance energy transfer (FRET) to the quencher dye. However, the photoluminescence of QD can be recovered upon on-demand release of the quencher. Our study focuses on quenching of QD photoluminescence after conjugation with a non-fluorescent dye molecule, black hole quencher 1 (BHQ-1), intermediated with a molecular sensing target peptide GPLG↓VRGK. Based on steady-state and time-resolved photoluminescence measurements of QD and the QD-peptide-BHQ-1 sensor assemblies, we attribute the quenching of photoluminescence intensity and lifetime to FRET from the QD to BHQ-1molecules. Here the intermediate peptide GPLG↓VRGK can be cleaved by matrix metalloproteinase-2 (MMP-2), an enzyme that is upregulated in cancer cells extra cellular matrix (ECM), at its Gly and Val region shown by the down headed arrow. Here the QD-pep-BHQ-1 conjugate detected the MMP-2 presence at the extra cellular matrix of H1299 cancer cells. Further the QD-pep-BHQ-1 molecules were conjugated at the surface of a mesoporous silica nanoparticle (MSN) scaffold to localize maximum target peptide in a nanospace volume for the future αvβ3 integrin receptor targeted detection of MMP-2. The luminescence quenching of MSN-QD-pep-BHQ-1 conjugates were analyzed with time resolved photoluminescence measurement.

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Masoumi, Saeid, Hassan Hajghassem, Alireza Erfanian, and Ahmad Molaei Rad. "Design and manufacture of TNT explosives detector sensors based on CNTFET." Sensor Review 36, no. 4 (September 19, 2016): 414–20. http://dx.doi.org/10.1108/sr-01-2016-0014.

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Purpose Miniaturized smart sensors that can perform sensitive and selective real-time monitoring of target analytes are tremendously valuable for various sensing applications. So, the purpose of this paper is to provide details of sensors based on selective nanocoatings by combining trinitrotoluene (TNT) receptors bound to conjugated polydiacetylene (PDA) polymers with single-walled carbon nanotube field-effect transistors (CNTFETs) for detecting explosives TNT. Design/methodology/approach Following an introduction, this paper describes the way of creating an FET with CNTs, which are functionalized by the peptide based on TNT molecule recognition elements and PDA, to offer a system which has the capability of answering the presence of related target molecules (TNT). Finally, brief conclusions are drawn. Findings Single-wall nanotubes and reduced graphene oxide are interesting materials for creating biosensors of FETs at nanoscale because of unique electrical, mechanical, geometrical and biocompatible properties. Therefore, this sensor is designed and manufactured, and the results of applying TNT to sensor show good sensitivity and selectivity response. Originality/value In this timeframe of history, sensors based on CNTFET are required for different uses, including clinical diagnosis technologies, environmental tests and bioterrorism recognition technologies, that correspond to the military conflicts and terrorism. So, CNTFET sensor design provides real-time detection of TNT explosives.

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Jeong, Ganghoon, Seo Young Shin, Proscovia Kyokunzire, Hyeong Jun Cheon, Eunsol Wi, Minhong Woo, and Mincheol Chang. "High-Performance Nitric Oxide Gas Sensors Based on an Ultrathin Nanoporous Poly(3-hexylthiophene) Film." Biosensors 13, no. 1 (January 13, 2023): 132. http://dx.doi.org/10.3390/bios13010132.

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Conjugated polymer (CP)-based organic field-effect transistors (OFETs) have been considered a potential sensor platform for detecting gas molecules because they can amplify sensing signals by controlling the gate voltage. However, these sensors exhibit significantly poorer oxidizing gas sensing performance than their inorganic counterparts. This paper presents a high-performance nitric oxide (NO) OFET sensor consisting of a poly(3-hexylthiophene) (P3HT) film with an ultrathin nanoporous structure. The ultrathin nonporous structure of the P3HT film was created via deposition through the shear-coating-assisted phase separation of polymer blends and selective solvent etching. The ultrathin nonporous structure of the P3HT film enhanced NO gas diffusion, adsorption, and desorption, resulting in the ultrathin nanoporous P3HT-film-based OFET gas sensor exhibiting significantly better sensing performance than pristine P3HT-film-based OFET sensors. Additionally, upon exposure to 10 ppm NO at room temperature, the nanoporous P3HT-film-based OFET gas sensor exhibited significantly better sensing performance (i.e., responsivity ≈ 42%, sensitivity ≈ 4.7% ppm−1, limit of detection ≈ 0.5 ppm, and response/recovery times ≈ 6.6/8.0 min) than the pristine P3HT-film-based OFET sensors.

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Qi, Zhen-Li, Yun-Hui Cheng, Zhou Xu, and Mao-Long Chen. "Recent Advances in Porphyrin-Based Materials for Metal Ions Detection." International Journal of Molecular Sciences 21, no. 16 (August 14, 2020): 5839. http://dx.doi.org/10.3390/ijms21165839.

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Porphyrins have planar and conjugated structures, good optical properties, and other special functional properties. Owing to these excellent properties, in recent years, porphyrins and their analogues have emerged as a multifunctional platform for chemical sensors. The rich chemistry of these molecules offers many possibilities for metal ions detection. This review mainly discusses two types of molecular porphyrin and porphyrin composite sensors for metal ions detection, because porphyrins can be functionalized to improve their functional properties, which can introduce more chemical and functional sites. According to the different application materials, the section of porphyrin composite sensors is divided into five sub-categories: (1) porphyrin film, (2) porphyrin metal complex, (3) metal–organic frameworks, (4) graphene materials, and (5) other materials, respectively.

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Lu, Zhizhong, Menglin Jiang, Jieshi Huang, Xinlei Zhou, Kejie Li, Yue Zheng, Wenkai Jiang, Tao Zhang, Hangbing Yan, and Huan Xia. "Study on NO₂ gas sensitivity of metal phthalocyanine enhanced by graphene quantum dots." Journal of Physics: Conference Series 2369, no. 1 (November 1, 2022): 012083. http://dx.doi.org/10.1088/1742-6596/2369/1/012083.

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Traditional semiconductor gas sensors mainly based on metal oxides have some problems such as high working temperature, high energy consumption, low sensitivity, poor anti-interference ability and poor selectivity. Organic semiconductors, represented by metal phthalocyanine (MPc), are becoming the choice of new semiconductor gas sensors because of their advantages of abundant raw materials, low cost, simple process, strong compatibility and ability to work at room temperature. In this study, metal phthalocyanine (molecular diameter of about 1.3 nm) and graphene quantum dots (diameter distribution of 1-3 nm) are similar in size, which facilitates the construction of conjugated plane structure to achieve rapid charge transfer within the material, thus realizing the ultra-sensitive response of the sensor to specific gas molecules at room temperature. In this work, ethylenediamine was used as adhesive to bond tetracarboxylic metal phthalocyanine (MPc-COOH) and graphene quantum dots (GQDs) to form a new composite material MPc-GQD. The response value of the sensor to 100 ppm NO2 gas can reach 19.8 in 100 s at room temperature, and it has good recovery and repeatability under the premise of laser-assisted recovery. The results provide a new idea for the development of room temperature gas sensors using organic semiconductors and carbon nanomaterials.

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Dirk, Shawn M., Stephen W. Howell, B. Katherine Price, Hongyou Fan, Cody Washburn, David R. Wheeler, James M. Tour, Joshua Whiting, and R. Joseph Simonson. "Vapor Sensing Using Conjugated Molecule-Linked Au Nanoparticles in a Silica Matrix." Journal of Nanomaterials 2009 (2009): 1–9. http://dx.doi.org/10.1155/2009/481270.

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Cross-linked assemblies of nanoparticles are of great value as chemiresistor-type sensors. Herein, we report a simple method to fabricate a chemiresistor-type sensor that minimizes the swelling transduction mechanism while optimizing the change in dielectric response. Sensors prepared with this methodology showed enhanced chemoselectivity for phosphonates which are useful surrogates for chemical weapons. Chemoselective sensors were fabricated using an aqueous solution of gold nanoparticles that were then cross-linked in the presence of the silica precursor, tetraethyl orthosilicate with theα-,ω-dithiolate (which is derived from the in situ deprotection of 1,4-di(Phenylethynyl-4′,4″-diacetylthio)-benzene (1) with wet triethylamine). The cross-linked nanoparticles and silica matrix were drop coated onto interdigitated electrodes having 8 μm spacing. Samples were exposed to a series of analytes including dimethyl methylphosphonate (DMMP), octane, and toluene. A limit of detection was obtained for each analyte. Sensors assembled in this fashion were more sensitive to dimethyl methylphosphonate than to octane by a factor of 1000.

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Easley, Christopher J. "(Invited) Fast and Generalizable Electrochemical Sensing of Small Molecules, Peptides, and Proteins Using a Nucleic Acid Nanostructure with Analyte-DNA Conjugates." ECS Meeting Abstracts MA2022-01, no. 53 (July 7, 2022): 2233. http://dx.doi.org/10.1149/ma2022-01532233mtgabs.

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Sensors based on electrochemical (EC) readout offer low cost, miniaturization, and adaptability to the point-of-care (POC). Nonetheless, most EC sensors are specialized to a particular target, and there remains a need for a robust EC biosensor platform for the multitude of biomarkers that are not EC-active, do not undergo enzymatic conversion, or are not suited for potentiometry [1,2]. Impressively, aptamer-based EC sensors have been proven for sensing in living animals with temporal resolution as low as a few seconds [3], yet most method development has been target-focused, lacking generalizability [4]. Presently, the clinical EC toolbox is a conglomerate of targeted methods, and there is a pressing need to develop an EC platform amenable to rapid, generalizable, quantitative readout of multiple classes of clinically relevant targets. Direct EC sensing without added reagents or amplification steps should be ideal for this purpose. For example, the Kelley group recently developed a reagentless “molecular pendulum” EC sensor for a broad range of protein analytes [5]. Our group has been working to address this need and expand to more analyte classes for several years, and in 2019 we designed a versatile DNA-nanostructure architecture attached to gold electrode surfaces [6]. Initially, our sensors were validated with biotechnology controls, antibodies, and with a small molecule immunomodulatory drug in human serum. In this presentation, we discuss the expansion of the generalizability of our sensor platform, chiefly through custom synthesis of varied DNA-analyte bioconjugates to incorporate within the DNA-nanostructure. For peptide sensing, DNA-peptide conjugates were synthesized, purified, then ligated to the DNA-nanostructure. Sensors were validated for quantifying exendin-4 (4.2 kDa)—a human glucagon-like peptide-1 receptor agonist important in diabetes therapy—for the first time using direct EC methods, with an LOD of 6 nM [7]. Sensors for larger proteins were made using DNA-epitope conjugates. The antibody-binding epitope of creatine kinase MM (CK-MM) was conjugated into the nanostructure, allowing CK-MM sensing in the 10 to 100 nM range. Finally, DNA-steroid bioconjugates have been incorporated into the sensors. Sensing of testosterone throughout the clinically relevant range (for males) was accomplished from 1 to 50 nM (LOD of 0.9 nM), and cortisol could be easily detected in the 1 to 100 nM range, well below the 90 – 550 nM range in blood and nicely encompassing the 6 – 75 nM range in saliva. All of these sensors were functional in 98% human serum, and several detection ranges overlap with the clinical/therapeutic ranges, boding well for future applications in biosensing or therapeutic drug monitoring. Overall, this new DNA nanostructure platform provides a generalizable sensor with minimal workflow, direct-readout, and the capability to expand EC sensing to a wide variety of clinically important analytes. References: Turner, A. P., Chemical Society Reviews 2013, 42 (8), 3184-96. Wilson, G. S.; Johnson, M. A., Chem. Reviews 2008, 108 (7), 2462-81. Idili, A.; Gerson, J.; Kippin, T.; Plaxco, K. W., Anal. Chem. 2021, 93, 4023-32. Labib, M.; Sargent, E. H.; Kelley, S. O., Chem. Reviews 2016, 116 (16), 9001-90. Das, J.; Gomis, S.; Chen, J. B.; Yousefi, H.; Ahmed, S.; Mahmud, A.; Zhou, W.; Sargent, E. H.; Kelley, S. O., Nature Chem. 2021, 13 (5), 428-434. Somasundaram, S.; Easley, C. J., J. Am. Chem. Soc. 2019, 141, 11721-11726. Khuda, N; Somasundaram, S.; Easley, C. J., ACS Sensors 2021, under revision.

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Mackin, Robert T., Krystal R. Fontenot, Judson Vincent Edwards, Nicolette T. Prevost, Jacobs H. Jordan, Michael W. Easson, Brian D. Condon, and Alfred D. French. "Detection of Human Neutrophil Elastase by Fluorescent Peptide Sensors Conjugated to TEMPO-Oxidized Nanofibrillated Cellulose." International Journal of Molecular Sciences 23, no. 6 (March 13, 2022): 3101. http://dx.doi.org/10.3390/ijms23063101.

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Peptide–cellulose conjugates designed for use as optical protease sensors have gained interest for point-of-care (POC) detection. Elevated serine protease levels are often found in patients with chronic illnesses, necessitating optimal biosensor design for POC assessment. Nanocellulose provides a platform for protease sensors as a transducer surface, and the employment of nanocellulose in this capacity combines its biocompatibility and high specific surface area properties to confer sensitive detection of dilute biomarkers. However, a basic understanding of the spatiotemporal relationships of the transducer surface and sensor disposition is needed to improve protease sensor design and development. Here, we examine a tripeptide, fluorogenic elastase biosensor attached to TEMPO-oxidized nanofibrillated cellulose via a polyethylene glycol linker. The synthetic conjugate was found to be active in the presence of human neutrophil elastase at levels comparable to other cellulose-based biosensors. Computational models examined the relationship of the sensor molecule to the transducer surface. The results illustrate differences in two crystallite transducer surfaces ((110) vs. (1−10)) and reveal preferred orientations of the sensor. Finally, a determination of the relative (110) vs. (1−10) orientations of crystals extracted from cotton demonstrates a preference for the (1−10) conformer. This model study potentiates the HNE sensor results for enhanced sensor activity design.

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Kyokunzire, Proscovia, Ganghoon Jeong, Seo Young Shin, Hyeong Jun Cheon, Eunsol Wi, Minhong Woo, Trang Thi Vu, and Mincheol Chang. "Enhanced Nitric Oxide Sensing Performance of Conjugated Polymer Films through Incorporation of Graphitic Carbon Nitride." International Journal of Molecular Sciences 24, no. 2 (January 6, 2023): 1158. http://dx.doi.org/10.3390/ijms24021158.

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Organic field-effect transistor (OFET) gas sensors based on conjugated polymer films have recently attracted considerable attention for use in environmental monitoring applications. However, the existing devices are limited by their poor sensing performance for gas analytes. This drawback is attributed to the low charge transport in and the limited charge–analyte interaction of the conjugated polymers. Herein, we demonstrate that the incorporation of graphitic carbon nitride (g-C₃N₄) into the conjugated polymer matrix can improve the sensing performance of OFET gas sensors. Moreover, the effect of graphitic carbon nitride (g-C₃N₄) on the gas sensing properties of OFET sensors based on poly(3-hexylthiophene) (P3HT), a conjugated polymer, was systematically investigated by changing the concentration of the g-C₃N₄ in the P3HT/g-C₃N₄ composite films. The obtained films were applied in OFET to detect NO gas at room temperature. In terms of the results, first, the P3HT/g-C₃N₄ composite films containing 10 wt.% g-C₃N₄ exhibited a maximum charge carrier mobility of ~1.1 × 10−1 cm2 V−1 S−1, which was approximately five times higher than that of pristine P3HT films. The fabricated P3HT/g-C₃N₄ composite film based OFET sensors presented significantly enhanced NO gas sensing characteristics compared to those of the bare P3HT sensor. In particular, the sensors based on the P3HT/g-C₃N₄ (90/10) composite films exhibited the best sensing performance relative to that of the bare P3HT sensor when exposed to 10 ppm NO gas: responsivity = 40.6 vs. 18.1%, response time = 129 vs. 142 s, and recovery time = 148 vs. 162 s. These results demonstrate the enormous promise of g-C₃N₄ as a gas sensing material that can be hybridized with conjugated polymers to efficiently detect gas analytes.

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WANG, LIHUA, YANYAN WANG, JIE ZOU, BIN LIU, and CHUNHAI FAN. "AMPLIFIED BIOSENSING STRATEGIES FOR THE DETECTION OF BIOLOGICALLY RELATED MOLECULES WITH SILICA NANOPARTICLES AND CONJUGATED POLYELECTROLYTES." COSMOS 06, no. 02 (December 2010): 207–19. http://dx.doi.org/10.1142/s0219607710000565.

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Development of rapid, field-portable and cost-effective sensors with high sensitivity and selectivity is of great importance for biomedical diagnostics, food safety and environmental monitoring. Silica nanoparticles (SiNPs) have great potential in sensor application due to their biocompatibility, controllable surface modification, excellent chemical stability and high specific surface area. On the other hand, conjugated polyelectrolytes (CPEs) have been widely used in sensor design due to their efficient Förster resonance energy transfer (FRET) to dyes and unique interaction with biomolecules. In this contribution, we briefly summarize the recent development of silica-related NP-based assays that incorporate CPEs as the signal amplifier or reporter. The silica-related NPs are used for probe immobilization, target recognition and separation, while CPEs provide amplified fluorescence signals and high sensitivity. These assays have been proven efficient for the detection of DNA, proteins, and small molecules through specific biorecognition events, such as DNA hybridization, antibody–antigen recognition and target–aptamer binding.

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Gurukandure, Asanka, Kacey G. Ortiz, Rashad R. Karimov, and Christopher J. Easley. "Electrochemical Sensing of Cortisol in Human Saliva and Serum Using DNA-Steroid Conjugation with a Versatile DNA Nanostructure Sensor." ECS Meeting Abstracts MA2022-02, no. 61 (October 9, 2022): 2270. http://dx.doi.org/10.1149/ma2022-02612270mtgabs.

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Having a generalizable point of care (POC) method for clinically relevant biomolecules would greatly enhance healthcare management and disease diagnosis. Recently our group developed a novel DNA nanostructure architecture for versatile detection of analytes which is generalizable for assaying several small molecules and their larger protein binding partners (e.g. antibodies) in human serum. The DNA nanostructure is built through on-electrode enzymatic ligation of three oligos for electrode attachment, anchor binding, and electrochemical signaling. In this study, we developed an economical synthetic approach for making oligonucleotide-steroid conjugates, and we explored the capability of these DNA nanostructure sensors for small molecule/steroid detection. Cortisol is a steroid hormone secreted by the hypothalamic-pituitary-adrenal system in response to the body’s stress level. As the main stress hormone, it controls processes such as immune, adrenal, circulatory, and metabolic. Moreover, anomalies of cortisol levels can result in serious conditions such as Addison’s disease, Cushing’s syndrome, and adrenal insufficiencies. Every year, 120,000 deaths are attributed, in part, to elevated levels of stress. To minimize these issues, a simplified method for cortisol sensing is vital. In this study, we conjugated cortisol to amine-tagged DNA and used the conjugates in our sensors. Anti-cortisol antibodies induced a 67% signal drop, validating conjugation. A calibration curve for cortisol showed a limit of detection of 800 pM and a dynamic range of 1 – 100 nM. The sensor was validated in saliva and human serum samples using the gold standard method, ELISA. Changing cortisol levels in two human patients' saliva samples were successfully detected after several collection times throughout a single day. As a potential point-of-care (POC) detection device, our novel cortisol biosensor could detect the hormone in human serum and saliva samples within 6 minutes.

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Talin, A. Alec, Andrea Centrone, Alexandra C. Ford, Michael E. Foster, Vitalie Stavila, Paul Haney, R. Adam Kinney, et al. "Tunable Electrical Conductivity in Metal-Organic Framework Thin-Film Devices." Science 343, no. 6166 (December 5, 2013): 66–69. http://dx.doi.org/10.1126/science.1246738.

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We report a strategy for realizing tunable electrical conductivity in metal-organic frameworks (MOFs) in which the nanopores are infiltrated with redox-active, conjugated guest molecules. This approach is demonstrated using thin-film devices of the MOF Cu3(BTC)2 (also known as HKUST-1; BTC, benzene-1,3,5-tricarboxylic acid) infiltrated with the molecule 7,7,8,8-tetracyanoquinododimethane (TCNQ). Tunable, air-stable electrical conductivity over six orders of magnitude is achieved, with values as high as 7 siemens per meter. Spectroscopic data and first-principles modeling suggest that the conductivity arises from TCNQ guest molecules bridging the binuclear copper paddlewheels in the framework, leading to strong electronic coupling between the dimeric Cu subunits. These ohmically conducting porous MOFs could have applications in conformal electronic devices, reconfigurable electronics, and sensors.

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Olmedo-Martinez, Cinthya Susana, Jesus Moises Hernandez-Duarte, Roberto Mejia-Olvera, Sandy Maria Pacheco-Ortin, and Esther Agacino-Valdes. "A density functional study of the coronene-pyrrole system in relation to its possible application as NO2 and NH3 sensors." European Journal of Chemistry 13, no. 4 (December 31, 2022): 371–80. http://dx.doi.org/10.5155/eurjchem.13.4.371-380.2316.

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According to recent research on the application of graphene materials as sensors and particularly polypyrrole-graphene materials, which are especially promising, the functionalization of graphene with a pyrrole molecule might be considered a viable alternative as a NO2 and NH3 sensor. In this way, a graphene sheet simulated as a coronene molecule was used in order to test whether this kind of functionalization could be useful for detecting the NO2 and NH3 toxic gases with a relatively high sensitivity. NO2 was studied as an example of an electron acceptor molecule, and NH3 as an electron donor molecule. Both molecules were adsorbed on two different regions of the functionalized adsorbent, and the energy ranges found for adsorption were reported and compared with those of the pristine graphene. The results indicated that in the coronene-pyrrole system, pyrrole tends to lie almost parallel to the coronene sheet in a π-π stacking interaction between the two conjugated systems, being the closest distances of 3.0 and 3.2 Å. The use of Δ (ΔHOMO-LUMO) as a descriptor confirmed that the coronene-pyrrole system is a good option as a NO2- and NH3-sensor; therefore, it might be an easy and suitable descriptor for characterizing the performance of a sensor; all calculations were made using a Density Functional formalism, through a functional M06-2X in combination with the 6-31G(d,p) basis set.

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Krywko-Cendrowska, Agata, Dawid Szweda, and Roza Szweda. "Well-Defined Conjugated Macromolecules Based on Oligo(Arylene Ethynylene)s in Sensing." Processes 8, no. 5 (May 3, 2020): 539. http://dx.doi.org/10.3390/pr8050539.

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Macromolecules with well-defined structures in terms of molar mass and monomer sequence became interesting building blocks for modern materials. The precision of the macromolecular structure makes fine-tuning of the properties of resulting materials possible. Conjugated macromolecules exhibit excellent optoelectronic properties that make them exceptional candidates for sensor construction. The importance of chain length and monomer sequence is particularly important in conjugated systems. The oligomer length, monomer sequence, and structural modification often influence the energy bang gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the molecules that reflect in their properties. Moreover, the supramolecular aggregation that is often observed in oligo-conjugated systems is usually strongly affected by even minor structural changes that are used for sensor designs. This review discusses the examples of well-defined conjugated macromolecules based on oligo(arylene ethynylene) skeleton used for sensor applications. Here, exclusively examples of uniform macromolecules are summarized. The sensing mechanisms and importance of uniformity of structure are deliberated.

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González-Juárez, Edgar, Marisol Güizado-Rodríguez, Víctor Barba-López, Mario Rodríguez, Gabriel Ramos-Ortíz, and José Luis Maldonado. "Copolymers based on 3-alkylthiophene and Thiophene Functionalized with Pyrene Chromophore." MRS Proceedings 1613 (2014): 39–44. http://dx.doi.org/10.1557/opl.2014.156.

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ABSTRACTAs a preliminary study aiming to possible applications, novel polythiophenes (PTs) derivatives of 3-hexylthiophene and a thiophene functionalized with pyrene chromophore were synthesized. Homopolymer and copolymers of these monomers were obtained in different stoichiometric ratios which allow obtaining structure-property relation of each of the polymers. PTs were characterized by FT-IR, 1H NMR, UV-vis, DSC-TGA, GPC and fluorescence experiments. Polymers have λmax between 345 to 450 nm and an emission band at 485 and 542 nm. Low molecular weights distribution (Mn = 875 to 1600 g/mol) and thermostable products (Td = 336 to 474°C) were obtained. These PTs functionalized with aromatic molecules and π-conjugated systems could offer interesting applications such as optical sensors, nonlinear optics and photovoltaic cells.

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Cao, Qian, and Baris Kumru. "Polymeric Carbon Nitride Armored Centimeter-Wide Organic Droplets in Water for All-Liquid Heterophase Emission Technology." Polymers 12, no. 8 (July 22, 2020): 1626. http://dx.doi.org/10.3390/polym12081626.

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High potential of emission chemistry has been visualized in many fields, from sensors and imaging to displays. In general, conjugated polymers are the top rankers for such chemistry, despite the fact that they bring solubility problems, high expenses, toxicity and demanding synthesis. Metal-free polymeric semiconductor graphitic carbon nitride (g-CN) has been an attractive candidate for visible light-induced photocatalysis, and its emission properties have been optimized and explored recently. Herein, we present modified g-CN nanoparticles as organodispersible conjugated polymer materials to be utilized in a heterophase emission systems. The injection of a g-CN organic dispersion in aqueous polymer solution not only provides retention of the shape by Pickering stabilization of g-CN, but high intensity emission is also obtained. The heterophase all-liquid emission display can be further modified by the addition of simple conjugated organic molecules to the initial g-CN dispersion, which provides a platform for multicolor emission. We believe that such shape-tailored and stabilized liquid–liquid multicolor emission systems are intriguing for sensing, displays and photonics.

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Li, Xi, Zheng Li, and Ying-Wei Yang. "Tetraphenylethylene-Interweaving Conjugated Macrocycle Polymer Materials as Two-Photon Fluorescence Sensors for Metal Ions and Organic Molecules." Advanced Materials 30, no. 20 (March 30, 2018): 1800177. http://dx.doi.org/10.1002/adma.201800177.

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Zheng, Xiaofeng, Sohayb Khaoulani, Nadia Ktari, Momath Lo, Ahmed M. Khalil, Chouki Zerrouki, Najla Fourati, and Mohamed M. Chehimi. "Towards Clean and Safe Water: A Review on the Emerging Role of Imprinted Polymer-Based Electrochemical Sensors." Sensors 21, no. 13 (June 23, 2021): 4300. http://dx.doi.org/10.3390/s21134300.

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This review critically summarizes the knowledge of imprinted polymer-based electrochemical sensors for the detection of pesticides, metal ions and waterborne pathogenic bacteria, focusing on the last five years. MIP-based electrochemical sensors exhibit low limits of detection (LOD), high selectivity, high sensitivity and low cost. We put the emphasis on the design of imprinted polymers and their composites and coatings by radical polymerization, oxidative polymerization of conjugated monomers or sol-gel chemistry. Whilst most imprinted polymers are used in conjunction with differential pulse or square wave voltammetry for sensing organics and metal ions, electrochemical impedance spectroscopy (EIS) appears as the chief technique for detecting bacteria or their corresponding proteins. Interestingly, bacteria could also be probed via their quorum sensing signaling molecules or flagella proteins. If much has been developed in the past decade with glassy carbon or gold electrodes, it is clear that carbon paste electrodes of imprinted polymers are more and more investigated due to their versatility. Shortlisted case studies were critically reviewed and discussed; clearly, a plethora of tricky strategies of designing selective electrochemical sensors are offered to “Imprinters”. We anticipate that this review will be of interest to experts and newcomers in the field who are paying time and effort combining electrochemical sensors with MIP technology.

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Mpofu, K. T., C. Lee, G. E. M. Maguire, H. G. Kruger, and M. S. Tame. "Experimental measurement of kinetic parameters using quantum plasmonic sensing." Journal of Applied Physics 131, no. 8 (February 28, 2022): 084402. http://dx.doi.org/10.1063/5.0079896.

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Kinetic models are essential for describing how molecules interact in a variety of biochemical processes. The estimation of a model’s kinetic parameters by experiment enables researchers to understand how pathogens, such as viruses, interact with other entities like antibodies and trial drugs. In this work, we report a simple proof-of-principle experiment that uses quantum sensing techniques to give a more precise estimation of kinetic parameters than is possible with a classical approach. The interaction we study is that of bovine serum albumin (BSA) binding to gold via an electrostatic mechanism. BSA is an important protein in biochemical research as it can be conjugated with other proteins and peptides to create sensors with a wide range of specificity. We use single photons generated via parametric down-conversion to probe the BSA–gold interaction in a plasmonic resonance sensor. We find that sub-shot-noise-level fluctuations in the sensor signal allow us to achieve an improvement in the precision of up to 31.8% for the values of the kinetic parameters. This enhancement can, in principle, be further increased in the setup. Our work highlights the potential use of quantum states of light for sensing in biochemical research.

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Lipunova, Galina N., Emiliya V. Nosova, Valery N. Charushin, and Oleg N. Chupakhin. "Functionalized Quinazolines and Pyrimidines for Optoelectronic Materials." Current Organic Synthesis 15, no. 6 (August 29, 2018): 793–814. http://dx.doi.org/10.2174/1570179415666180622123434.

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Background: Quinazolines, the important group of benzodiazines, are widely known in medicinal chemistry due to their broad spectrum of biological activities. Notably, extensive research on the synthesis and application of quinazoline derivatives for electronic devices, luminescent elements, photoelectric conversion elements, and image sensors has been published recently. Objective: This review reports luminescent small molecules and chelate compounds including a quinazoline or pyrimidine ring in their scaffold highlighting their applications related to photo- and electroluminescence. Conclusion: It is clear from the review of the topic that the incorporation of quinazoline and pyrimidine fragments into π-extended conjugated systems is of great value for the creation of novel optoelectronic materials. Polyhalogen derivatives represent the major starting materials for polysubstituted fluorescent quinazolines. Electroluminescent properties of aryl(hetaryl)substituted quinazolines with π-extended conjugated systems proved to be the most important. Incorporation of benzimidazole, carbazole, triphenylene or triphenylamine fragments into quinazoline scaffold allows fabricating materials for organic light-emitting diodes, including white OLEDs and highly efficient red phosphorescent organic light-emitting diodes. Moreover, arylvinylsubstituted quinazolines are of great interest as potential structures for nonlinear optical materials and for colorimetric pH sensors. Iridium complexes based on 2-aryl(thienyl) quinazoline or pyrimidine derivatives represent high-efficiency phosphorescent materials for OLEDs. Pyrimidine push-pull systems are of considerable importance as potential photosensitizers for dye-sensitized solar cells. Pyrimidine derivatives bearing phenylacridine or phenylphenoxazine fragments at the positions 4 and 6 are capable to function as thermally activated delayed fluorescence emitters.

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Kim, Jinsang. "Assemblies of conjugated polymers: Intermolecular and intramolecular effects on the photophysical properties of conjugated polymers." Pure and Applied Chemistry 74, no. 11 (January 1, 2002): 2031–44. http://dx.doi.org/10.1351/pac200274112031.

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Conjugated polymers are emerging materials for electronic applications due to the tunability of their properties through variation of their chemical structure. Their applications, which currently include light-emitting diodes (LEDs), field effect transistors (FETs), plastic lasers, batteries, and sensors, are expanding to many new areas. The two critical parameters that determine the function of conjugated polymer-based devices are chemical structure and nanostructure of a conjugated polymer in the solid state. While the physical properties of isolated polymers are primarily controlled by their chemical structure, these properties are drastically altered in the solid state due to electronic coupling between polymer chains as determined by their interpolymer packing and conformation. However, the development of effective and precise methods for controlling the nanostructure of polymers in the solid state has been limited because polymers often fail to assemble into organized structures due to their amorphous character and large molecular weight.In this review, recent developments of organizing methods of conjugated polymers and the conformation and interpolymer interaction effects on the photophysical properties of conjugated polymers are summarized.

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Kang, Taejoon, Ilsun Yoon, Jangbae Kim, Hyotcherl Ihee, and Bongsoo Kim. "Au Nanowire-Au Nanoparticles Conjugated System which Provides Micrometer Size Molecular Sensors." Chemistry - A European Journal 16, no. 4 (January 25, 2010): 1351–55. http://dx.doi.org/10.1002/chem.200901708.

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Masoumi, Saeid, and Hassan Hajghassem. "Design of the trinitrotoluene biosensor using polydiacetylene conjugated with peptide receptors coated on GR-FETs with colorimetric response." Sensor Review 39, no. 6 (November 18, 2019): 819–27. http://dx.doi.org/10.1108/sr-11-2018-0306.

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Purpose Smart biosensors that can perform sensitive and selective monitoring of target analytes are tremendously valuable for trinitrotoluene (TNT) explosive detection. In this research, the pre-developed sensor was integrated with biological receptors in which they enhanced the sensitivity of the sensor. This is due to conjugated polydiacetylene onto a peptide-based molecular recognition element (Trp-His-Trp) for TNT molecules in graphene field-effect transistors (GR-FETs) as biosensor that is capable of responding to the presence of a TNT target with a colorimetric response. The authors confirmed the efficacy of the receptor while being attached to polydiacetylene (PDA) by observing the binding ability between the Trp-His-Trp and TNT to alter the electronic band structure of the PDA conjugated backbones. The purpose of this paper is to demonstrate a modular system capable of transducing small-molecule TNT binding into a detectable signal. The details of the real-time and selective TNT biosensor have been reported. Design/methodology/approach Following an introduction, this paper describes the way of fabrication GR-FETs with conventional photolithography techniques and the other processes, which is functionalized by the TNT peptide receptors. The authors first determined the essential TNT recognition elements from UV-visible spectrophotometry spectroscopy for PDA sensor unit fabrication. In particular, the blue percentage and the chromic response were used to characterize the polymerization parameter of the conjugated p backbone. A continuous-flow trace vapor source of nitroaromatics (two, four, six-TNT) was designed and evaluated in terms of temperature dependence. The TNT concentration was measured by liquid/gas extraction in acetonitrile using bubbling sequence. The sensor test is performed using a four-point probe and semiconductor analyzer. Finally, brief conclusions are drawn. Findings Because of their unique optical and stimuli-response properties, the polydiacetylene and peptide-based platforms have been explored as an alternative to complex mechanical and electrical sensing systems. Therefore, the authors have used GR-FETs with biological receptor-PDAs as a biosensor for achieving high sensitivity and selectivity that can detect explosive substances such as TNT. The transport property changed compared to that of the field-effect transistors made by intrinsic graphene, that is, the Dirac point position moved from positive Vg to negative Vg, indicating the transition of graphene from p-type to n-type after annealing in TNT, and when the device was tested from RT, the response of the device was found to increase linearly with increasing concentrations. Average shifting rate of the Dirac peak was obtained as 0.1-0.3 V/ppm. The resulting sensors exhibited at the limit ppm sensitivity toward TNT in real-time, with excellent selectivity over various similar aromatic compounds. The biological receptor coating may be useful for the development of sensitive and selective micro and nanoelectronic sensor devices for various other target analytes. Originality/value The detection of illegally transported explosives has become important as the global rise in terrorism subsequent to the events of September 11, 2001, and is at the forefront of current analytical problems. It is essential that a detection method has the selectivity to distinguish among compounds in a mixture of explosives. So, the authors are reporting a potential solution with the designing and manufacturing of electrochemical biosensor using polydiacetylene conjugated with peptide receptors coated on GR-FETs with the colorimetric response for real-time detection of TNT explosives specifically.

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Filla, Nicholas, Ramaraja Ramasamy, and Xianqiao Wang. "Forces, energetics, and dynamics of conjugated-carbon ring tethers adhered to CNTs: a computational investigation." Physical Chemistry Chemical Physics 20, no. 16 (2018): 11327–35. http://dx.doi.org/10.1039/c8cp00598b.

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Jo, Gyounglyul, Jaehan Jung, and Mincheol Chang. "Controlled Self-Assembly of Conjugated Polymers via a Solvent Vapor Pre-Treatment for Use in Organic Field-Effect Transistors." Polymers 11, no. 2 (February 14, 2019): 332. http://dx.doi.org/10.3390/polym11020332.

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A facile solution-processing strategy toward well-ordered one-dimensional nanostructures of conjugated polymers via a non-solvent vapor treatment was demonstrated, which resulted in enhancements to the charge transport characteristics of the polymers. The amount of crystalline poly(3-hexylthiophene) (P3HT) nanofibers was precisely controlled by simply varying the exposure time of solutions of P3HT solutions to non-solvent vapor. The effects of non-solvent vapor exposure on the molecular ordering and morphologies of the resultant P3HT films were systematically investigated using ultraviolet-visible (UV-vis) spectroscopy, polarized optical microscopy (POM), grazing incidence X-ray diffraction (GIXRD), and atomic force microscopy (AFM). The non-solvent vapor facilitates the π–π stacking in P3HT to minimize unfavorable interactions between the poor solvent molecules and P3HT chains. P3HT films deposited from the non-solvent vapor-treated P3HT solutions exhibited an approximately 5.6-fold improvement in charge carrier mobility as compared to that of pristine P3HT films (7.8 × 10−2 cm2 V−1 s−1 vs. 1.4 × 10−2 cm2 V−1 s−1). The robust and facile strategy presented herein would be applicable in various opto-electronics applications requiring precise control of the molecular assembly, such as organic photovoltaic cells, field-effect transistors, light-emitting diodes, and sensors.

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Barata, Patrícia D., and José V. Prata. "Fluorescent Calix[4]arene-Carbazole-Containing Polymers as Sensors for Nitroaromatic Explosives." Chemosensors 8, no. 4 (December 10, 2020): 128. http://dx.doi.org/10.3390/chemosensors8040128.

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Two highly fluorescent calix[4]arene-containing phenylene-alt-ethynylene-carbazolylene polymers (Calix-PPE-CBZs) were used in the detection of explosives from the nitroaromatic compounds (NACs) family, in solution and in vapour phases. Both fluorophores exhibit high sensitivity and selectivity towards NACs detection. The quenching efficiencies in solution, assessed through static Stern-Volmer constants (KSV), follow the order picric acid (PA) >> 2,4,6-trinitrotoluene (TNT) > 2,4-dinitrotoluene > (2,4-DNT) > nitrobenzene (NB). These correlate very well with the NACs electron affinities, as evaluated from their lowest unoccupied molecular orbitals (LUMOs) energies, indicating a photo-induced electron transfer as the dominant mechanism in fluorescence quenching. Moreover, and most interesting, detection of TNT, 2,4-DNT and NB vapours via thin-films of Calix-PPE-CBZs revealed a remarkably sensitive response to these analytes, comparable to state-of-the-art chemosensors. The study also analyses and compares the current results to previous disclosed data on the detection of NACs by several calix[4]arene-based conjugated polymers and non-polymeric calix[4]arenes-carbazole conjugates, overall highlighting the superior role of calixarene and carbazole structural motifs in NACs’ detection performance. Density functional theory (DFT) calculations performed on polymer models were used to support some of the experimental findings.

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Wani, Ishtiaq H., S. Hassan M. Jafri, John Warna, Aqib Hayat, Hu Li, Vivek A. Shukla, Andreas Orthaber, Anton Grigoriev, Rajeev Ahuja, and Klaus Leifer. "A sub 20 nm metal-conjugated molecule junction acting as a nitrogen dioxide sensor." Nanoscale 11, no. 14 (2019): 6571–75. http://dx.doi.org/10.1039/c8nr08417c.

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Karsten, Lennard, Lukas Goett-Zink, Julian Schmitz, Raimund Hoffrogge, Alexander Grünberger, Tilman Kottke, and Kristian M. Müller. "Genetically Encoded Ratiometric pH Sensors for the Measurement of Intra- and Extracellular pH and Internalization Rates." Biosensors 12, no. 5 (April 25, 2022): 271. http://dx.doi.org/10.3390/bios12050271.

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pH-sensitive fluorescent proteins as genetically encoded pH sensors are promising tools for monitoring intra- and extracellular pH. However, there is a lack of ratiometric pH sensors, which offer a good dynamic range and can be purified and applied extracellularly to investigate uptake. In our study, the bright fluorescent protein CoGFP_V0 was C-terminally fused to the ligand epidermal growth factor (EGF) and retained its dual-excitation and dual-emission properties as a purified protein. The tandem fluorescent variants EGF-CoGFP-mTagBFP2 (pK′ = 6.6) and EGF-CoGFP-mCRISPRed (pK′ = 6.1) revealed high dynamic ranges between pH 4.0 and 7.5. Using live-cell fluorescence microscopy, both pH sensor molecules permitted the conversion of fluorescence intensity ratios to detailed intracellular pH maps, which revealed pH gradients within endocytic vesicles. Additionally, extracellular binding of the pH sensors to cells expressing the EGF receptor (EGFR) enabled the tracking of pH shifts inside cultivation chambers of a microfluidic device. Furthermore, the dual-emission properties of EGF-CoGFP-mCRISPRed upon 488 nm excitation make this pH sensor a valuable tool for ratiometric flow cytometry. This high-throughput method allowed for the determination of internalization rates, which represents a promising kinetic parameter for the in vitro characterization of protein–drug conjugates in cancer therapy.

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Karsten, Lennard, Lukas Goett-Zink, Julian Schmitz, Raimund Hoffrogge, Alexander Grünberger, Tilman Kottke, and Kristian M. Müller. "Genetically Encoded Ratiometric pH Sensors for the Measurement of Intra- and Extracellular pH and Internalization Rates." Biosensors 12, no. 5 (April 25, 2022): 271. http://dx.doi.org/10.3390/bios12050271.

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pH-sensitive fluorescent proteins as genetically encoded pH sensors are promising tools for monitoring intra- and extracellular pH. However, there is a lack of ratiometric pH sensors, which offer a good dynamic range and can be purified and applied extracellularly to investigate uptake. In our study, the bright fluorescent protein CoGFP_V0 was C-terminally fused to the ligand epidermal growth factor (EGF) and retained its dual-excitation and dual-emission properties as a purified protein. The tandem fluorescent variants EGF-CoGFP-mTagBFP2 (pK′ = 6.6) and EGF-CoGFP-mCRISPRed (pK′ = 6.1) revealed high dynamic ranges between pH 4.0 and 7.5. Using live-cell fluorescence microscopy, both pH sensor molecules permitted the conversion of fluorescence intensity ratios to detailed intracellular pH maps, which revealed pH gradients within endocytic vesicles. Additionally, extracellular binding of the pH sensors to cells expressing the EGF receptor (EGFR) enabled the tracking of pH shifts inside cultivation chambers of a microfluidic device. Furthermore, the dual-emission properties of EGF-CoGFP-mCRISPRed upon 488 nm excitation make this pH sensor a valuable tool for ratiometric flow cytometry. This high-throughput method allowed for the determination of internalization rates, which represents a promising kinetic parameter for the in vitro characterization of protein–drug conjugates in cancer therapy.

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Shen, Sheng, and Shao-Fei Jiang. "Distributed Deformation Monitoring for a Single-Cell Box Girder Based on Distributed Long-Gage Fiber Bragg Grating Sensors." Sensors 18, no. 8 (August 8, 2018): 2597. http://dx.doi.org/10.3390/s18082597.

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Distributed deformation based on fiber Bragg grating sensors or other kinds of strain sensors can be used to monitor bridges during operation. However, most research on distributed deformation monitoring has focused on solid rectangular beams rather than box girders—a kind of typical hollow beam widely employed in actual bridges. The deformation of a single-cell box girder contains bending deflection and also two additional deformations respectively caused by shear lag and shearing action. This paper revises the improved conjugated beam method (ICBM) based on the long-gage fiber Bragg grating (LFBG) sensors to satisfy the requirements for monitoring the two additional deformations in a single-cell box girder. This paper also proposes a suitable LFBG sensor placement in a box girder to overcome the influence of strain fluctuation on the flange caused by the shear lag effect. Results from numerical simulations show that the theoretical monitoring errors of the revised ICBM are typically 0.3–1.5%, and the maximum error is 2.4%. A loading experiment for a single-cell box gilder monitored by LFBG sensors shows that most of the practical monitoring errors are 6–8% and the maximum error is 11%.

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Idris, Azeez O., Ekemena O. Oseghe, Titus A. M. Msagati, Alex T. Kuvarega, Usisipho Feleni, and Bhekie Mamba. "Graphitic Carbon Nitride: A Highly Electroactive Nanomaterial for Environmental and Clinical Sensing." Sensors 20, no. 20 (October 10, 2020): 5743. http://dx.doi.org/10.3390/s20205743.

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Graphitic carbon nitride (g-C3N4) is a two-dimensional conjugated polymer that has attracted the interest of researchers and industrial communities owing to its outstanding analytical merits such as low-cost synthesis, high stability, unique electronic properties, catalytic ability, high quantum yield, nontoxicity, metal-free, low bandgap energy, and electron-rich properties. Notably, graphitic carbon nitride (g-C3N4) is the most stable allotrope of carbon nitrides. It has been explored in various analytical fields due to its excellent biocompatibility properties, including ease of surface functionalization and hydrogen-bonding. Graphitic carbon nitride (g-C3N4) acts as a nanomediator and serves as an immobilization layer to detect various biomolecules. Numerous reports have been presented in the literature on applying graphitic carbon nitride (g-C3N4) for the construction of electrochemical sensors and biosensors. Different electrochemical techniques such as cyclic voltammetry, electrochemiluminescence, electrochemical impedance spectroscopy, square wave anodic stripping voltammetry, and amperometry techniques have been extensively used for the detection of biologic molecules and heavy metals, with high sensitivity and good selectivity. For this reason, the leading drive of this review is to stress the importance of employing graphitic carbon nitride (g-C3N4) for the fabrication of electrochemical sensors and biosensors.

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Glosz, Karolina, Agnieszka Stolarczyk, and Tomasz Jarosz. "Electropolymerised Polypyrroles as Active Layers for Molecularly Imprinted Sensors: Fabrication and Applications." Materials 14, no. 6 (March 11, 2021): 1369. http://dx.doi.org/10.3390/ma14061369.

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Conjugated polymers are widely used in the development of sensors, but even though they are sensitive and robust, they typically show limited selectivity, being cross-sensitive to many substances. In turn, molecular imprinting is a method involving modification of the microstructure of the surface to incorporate cavities, whose shape matches that of the “template”—the analyte to be detected, resulting in high selectivity. The primary goal of this review is to report on and briefly explain the most relevant recent developments related to sensors utilising molecularly imprinted polypyrrole layers and their applications, particularly regarding the detection of bioactive substances. The key approaches to depositing such layers and the most relevant types of analytes are highlighted, and the various trends in the development of this type of sensors are explored.

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Tsolekile, Ncediwe, Simphiwe Nelana, and Oluwatobi Samuel Oluwafemi. "Porphyrin as Diagnostic and Therapeutic Agent." Molecules 24, no. 14 (July 23, 2019): 2669. http://dx.doi.org/10.3390/molecules24142669.

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The synthesis and application of porphyrins has seen a huge shift towards research in porphyrin bio-molecular based systems in the past decade. The preferential localization of porphyrins in tumors, as well as their ability to generate reactive singlet oxygen and low dark toxicities has resulted in their use in therapeutic applications such as photodynamic therapy. However, their inherent lack of bio-distribution due to water insolubility has shifted research into porphyrin-nanomaterial conjugated systems to address this challenge. This has broadened their bio-applications, viz. bio-sensors, fluorescence tracking, in vivo magnetic resonance imaging (MRI), and positron emission tomography (PET)/CT imaging to photo-immuno-therapy just to highlight a few. This paper reviews the unique theranostic role of porphyrins in disease diagnosis and therapy. The review highlights porphyrin conjugated systems and their applications. The review ends by bringing current challenges and future perspectives of porphyrin based conjugated systems and their respective applications into light.

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Monge, Florencia A., Adeline M. Fanni, Patrick L. Donabedian, Jonathan Hulse, Nicole M. Maphis, Shanya Jiang, Tia N. Donaldson, et al. "Selective In Vitro and Ex Vivo Staining of Brain Neurofibrillary Tangles and Amyloid Plaques by Novel Ethylene Ethynylene-Based Optical Sensors." Biosensors 13, no. 2 (January 18, 2023): 151. http://dx.doi.org/10.3390/bios13020151.

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The identification of protein aggregates as biomarkers for neurodegeneration is an area of interest for disease diagnosis and treatment development. In this work, we present novel super luminescent conjugated polyelectrolyte molecules as ex vivo sensors for tau-paired helical filaments (PHFs) and amyloid-β (Aβ) plaques. We evaluated the use of two oligo-p-phenylene ethynylenes (OPEs), anionic OPE12- and cationic OPE24+, as stains for fibrillar protein pathology in brain sections of transgenic mouse (rTg4510) and rat (TgF344-AD) models of Alzheimer’s disease (AD) tauopathy, and post-mortem brain sections from human frontotemporal dementia (FTD). OPE12- displayed selectivity for PHFs in fluorimetry assays and strong staining of neurofibrillary tangles (NFTs) in mouse and human brain tissue sections, while OPE24+ stained both NFTs and Aβ plaques. Both OPEs stained the brain sections with limited background or non-specific staining. This novel family of sensors outperformed the gold-standard dye Thioflavin T in sensing capacities and co-stained with conventional phosphorylated tau (AT180) and Aβ (4G8) antibodies. As the OPEs readily bind protein amyloids in vitro and ex vivo, they are selective and rapid tools for identifying proteopathic inclusions relevant to AD. Such OPEs can be useful in understanding pathogenesis and in creating in vivo diagnostically relevant detection tools for neurodegenerative diseases.

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Pallavi, S. G., K. A. Vishnumurthy, and K. Natarajan. "Detection of Low Concentration Ammonia Gas Using Diphenylamine Based Conjugated Polymer Sensors." Sensor Letters 16, no. 6 (June 1, 2018): 460–66. http://dx.doi.org/10.1166/sl.2018.3980.

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Errante, Paolo Ruggero, Pâmela Carolina Cruz Ebbing, Francisco Sandro Menezes Rodrigues, Renato Ribeiro Nogueira Ferraz, and Neusa Pereira Da Silva. "Flow cytometry: a literature review." Revista de Ciências Médicas e Biológicas 14, no. 2 (February 18, 2016): 221. http://dx.doi.org/10.9771/cmbio.v14i2.12182.

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Introduction: flow cytometry is a technique that employs an optical-electronic detection apparatus to analyze the physical and chemical properties of microscopic particles suspend in a liquid medium. Objective: to review the literature in search of the main studies that used flow cytometry as the main methodology. Method: Articles were selected according to their impact factor in the Journal of Citation Reports. Literature review: a light beam is direct to a continuous flow of suspended particles marked with fluorescent substances. The light is scattered differently from the beam by the particles and is captured by sensors in line and perpendicular to the light beam. These microscopic particles are conjugated with fluorescent substances that, once excited, emit light of lower frequency than the light source. The emitted light is captured by sensors and the particles are analyzed according to fluctuations in brightness of each detector and/or fluorescence emission. The result of this process is the formation of images in real time for each cell fluorescence, scattering and transmission of light. A major problem of flow cytometry is to determine whether a subset of cells labeled with fluorochrome-conjugated monoclonal antibodies is positive or negative. Gains compensation should be determined and applied correctly, and controls should be conducted concisely with the adoption of a biological control, isotype control or Fluorescence Minus One (FMO). None of these controls are considered ideal, and must be chosen according the number of different labeling done, rarity of molecule expression on surface or intracellularly in certain cell subsets, overlap of wavelengths or unspecific binding of the fluorochrome-conjugated antibodies. Conclusion: due to its great potential, flow cytometry has been expanded to diverse fields of biological sciences, and is routinely used in clinical diagnostic, biotechnology, and basic and applied research.

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Liu, Bin, and Guillermo C. Bazan. "Optimization of the Molecular Orbital Energies of Conjugated Polymers for Optical Amplification of Fluorescent Sensors." Journal of the American Chemical Society 128, no. 4 (February 2006): 1188–96. http://dx.doi.org/10.1021/ja055382t.

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Rasitanon, Natcha, Kornautchaya Veenuttranon, Hnin Thandar Lwin, Kanyawee Kaewpradub, Tonghathai Phairatana, and Itthipon Jeerapan. "Redox-Mediated Gold Nanoparticles with Glucose Oxidase and Egg White Proteins for Printed Biosensors and Biofuel Cells." International Journal of Molecular Sciences 24, no. 5 (February 28, 2023): 4657. http://dx.doi.org/10.3390/ijms24054657.

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Glucose oxidase (GOx)-based electrodes are important for bioelectronics, such as glucose sensors. It is challenging to effectively link GOx with nanomaterial-modified electrodes while preserving enzyme activity in a biocompatible environment. To date, no reports have used biocompatible food-based materials, such as egg white proteins, combined with GOx, redox molecules, and nanoparticles to create the biorecognition layer for biosensors and biofuel cells. This article demonstrates the interface of GOx integrated with egg white proteins on a 5 nm gold nanoparticle (AuNP) functionalized with a 1,4-naphthoquinone (NQ) and conjugated with a screen-printed flexible conductive carbon nanotube (CNT)-modified electrode. Egg white proteins containing ovalbumin can form three-dimensional scaffolds to accommodate immobilized enzymes and adjust the analytical performance. The structure of this biointerface prevents the escape of enzymes and provides a suitable microenvironment for the effective reaction. The bioelectrode’s performance and kinetics were evaluated. Using redox-mediated molecules with the AuNPs and the three-dimensional matrix made of egg white proteins improves the transfer of electrons between the electrode and the redox center. By engineering the layer of egg white proteins on the GOx-NQ-AuNPs-mediated CNT-functionalized electrodes, we can modulate analytical performances such as sensitivity and linear range. The bioelectrodes demonstrate high sensitivity and can prolong the stability by more than 85% after 6 h of continuous operation. The use of food-based proteins with redox molecule-modified AuNPs and printed electrodes demonstrates advantages for biosensors and energy devices due to their small size, large surface area, and ease of modification. This concept holds a promise for creating biocompatible electrodes for biosensors and self-sustaining energy devices.

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Stewart, Katherine, Saurav Limbu, James Nightingale, Katia Pagano, Byoungwook Park, Soonil Hong, Kwanghee Lee, Sooncheol Kwon, and Ji-Seon Kim. "Molecular understanding of a π-conjugated polymer/solid-state ionic liquid complex as a highly sensitive and selective gas sensor." Journal of Materials Chemistry C 8, no. 43 (2020): 15268–76. http://dx.doi.org/10.1039/d0tc03093g.

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Electric-field driven chemical doping modulation in a solution-processed organic semiconductor and solid-state ionic liquid blend in response to volatile organic compounds provides an exciting opportunity to facilitate low-power chemical gas sensors.

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Gallegos-Tabanico, Amed, Jorge Jimenez-Canale, Sergio G. Hernandez-Leon, Alexel J. Burgara-Estrella, Jose Carmelo Encinas-Encinas, and Jose A. Sarabia-Sainz. "Development of an Electrochemical Sensor Conjugated with Molecularly Imprinted Polymers for the Detection of Enrofloxacin." Chemosensors 10, no. 11 (October 28, 2022): 448. http://dx.doi.org/10.3390/chemosensors10110448.

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An electrochemical sensor was fabricated for the rapid and simple detection of enrofloxacin (EF). Modification of screen-printed gold electrodes (SPE) with molecularly imprinted polymers (MIPs) allowed the detection of enrofloxacin by square wave voltammetry (SWV), measuring the oxidation peak at +0.9 V. The detection principle of molecularly imprinted polymers (MIPs) is based on the formation of binding sites with affinities and specificities comparable with those of natural antibodies. The detection of enrofloxacin showed a linear range of 0.01–0.1 mM with a detection limit LOD of 0.02 mM. The development of a non-imprinted polymer (NIP) control sensor allowed for better and more efficient detection. In addition, the sensor is portable, having the advantage of analyzing and detecting molecules of interest without the need to take the sample to a laboratory.

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Journal articles on the topic 'Conjugated Molecules for Sensors'

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