scholarly journals A simplified methodology: pH sensing using an in situ fabricated Ir electrode under neutral conditions

2021 ◽  
Author(s):  
Yuqi Chen ◽  
Xiuting Li ◽  
Danlei Li ◽  
Christopher Batchelor-McAuley ◽  
Richard G. Compton
Keyword(s):  
Ph Sensor ◽  
Iridium Oxide ◽  
Ph Sensitive ◽  
Ph Sensing ◽  
Ph Dependency ◽  
Acidic Conditions ◽  
Ph Range ◽  
Neutral Conditions ◽  
Electrochemical Fabrication

AbstractHerein, a simplified fabrication method for the producing of a pH-sensitive iridium electrode is developed. The in situ electrochemical fabrication of an iridium oxide film is optimized and shown to be achievable under neutral conditions rather than the acidic conditions hitherto employed. The formation of a pH sensitive Ir(III/IV) hydrous film is confirmed via XPS. The amperometric pH-sensing properties of this electrochemically generated material were investigated using square wave voltammetry. In the pH range 2–13, the iridium oxide redox signal has a pH dependency of 86.1 ± 1.1 mV per pH unit for midpoint potentials with uncertainties being ± 0.01–0.05 pH. Finally, the newly developed pH sensor was used to measure the pH of a natural water sample with excellent results as compared to a conventional glass pH probe.

scholarly journals Printed 2D Proton Sensor for In-Situ Measurement in Glue Lines

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 990 ◽  
Author(s):  
Matic Krivec ◽  
Thomas Stockinger ◽  
Johanna Zikulnig ◽  
Friedrich Eibenst ◽  
Uwe Müller
Keyword(s):  
Cross Talk ◽  
Linear Response ◽  
Ph Sensor ◽  
In Situ Measurements ◽  
Cross Linking ◽  
Sensitive Material ◽  
Signal Change ◽  
Ph Range ◽  
Pani Layer

A screen printed pH sensor was developed using a PANI layer as a proton sensitive material for the in-situ measurements of matrix cross-linking. The sensor showed a linear response in a broad pH range (3–10) and had an evident cross-talk to Cl− ions. Preliminary in-situ measurements showed a substantial signal change during the cross-linking process.

scholarly journals TiO2 Nano Flowers Based EGFET Sensor for pH Sensing

Coatings ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 251
Author(s):  
Chih-Chiang Yang ◽  
Kuan-Yu Chen ◽  
Yan-Kuin Su
Keyword(s):  
Ph Value ◽  
Ph Sensor ◽  
High Sensitivity ◽  
Experimental Result ◽  
Ph Sensing ◽  
Voltage Reference ◽  
Ph Sensors ◽  
Oxide Substrate ◽  
Ph Range ◽  
The Relationship

In this study, pH sensors were successfully fabricated on a fluorine-doped tin oxide substrate and grown via hydrothermal methods for 8 h for pH sensing characteristics. The morphology was obtained by high-resolution scanning electron microscopy and showed randomly oriented flower-like nanostructures. The TiO2 nanoflower pH sensors were measured over a pH range of 2–12. Results showed a high sensitivity of the TiO2 nano-flowers pH sensor, 2.7 (μA)1/2/pH, and a linear relationship between IDS and pH (regression of 0.9991). The relationship between voltage reference and pH displayed a sensitivity of a 46 mV/pH and a linear regression of 0.9989. The experimental result indicated that a flower-like TiO2 nanostructure extended gate field effect transistor (EGFET) pH sensor effectively detected the pH value.

scholarly journals Near-Infrared pH Sensor Based on a SPEEK–Polyaniline Polyelectrolyte Complex Membrane

Proceedings ◽  
2018 ◽  
Vol 3 (1) ◽  
pp. 11 ◽  
Author(s):  
Nedal Y. Abu-Thabit
Keyword(s):  
Polyelectrolyte Complex ◽  
Near Infrared ◽  
Response Times ◽  
Oxidative Polymerization ◽  
Ph Sensor ◽  
Ph Sensing ◽  
Ph Values ◽  
Sensing Applications ◽  
Ph Range ◽  
Speek Membrane

A polyelectrolyte complex (PEC) membrane based on sulfonated poly (ether ether ketone) and polyaniline (SPEEK-PANI) was developed for pH sensing applications. Aniline was polymerized in the presence of the SPEEK membrane by using in situ chemical oxidative polymerization to yield an ionically crosslinked SPEEK-PANI membrane. The fabricated membrane exhibited sensitivity in the physiological pH range of 2–8. The PEC membrane pH sensor showed good absorption properties in the near-infrared region (NIR). The membrane showed fast response during a de-doping process (≈90 s), while longer response times are essential for doping processes from the alkaline/neutral pH region to the acidic pH region, which is attributed to the presence of highly acidic sulfonic acid groups with a high buffering capacity in the PEC membrane. The SPEEK-PANI membrane exhibited slightly higher water uptake compared to the neat SPEEK membrane. The membrane exhibited good stability, as it was stored in 1M HCl solution for more than 2 years without physical or visual deterioration. A preconditioning step in 1M HCl ensured that the results were reproducible and allows the pH sensor to be used repeatedly. The PEC sensor membranes are suitable for applications that start at low pH values and move upwards to higher pH values in the 2–8 pH range.

The V-ATPase a2-subunit as a putative endosomal pH-sensor

2007 ◽  
Vol 35 (5) ◽  
pp. 1092-1099 ◽  
Author(s):  
V. Marshansky
Keyword(s):  
Crucial Role ◽  
Molecular Mechanisms ◽  
Ph Sensor ◽  
Small Gtpases ◽  
Ph Sensitive ◽  
Ph Sensing ◽  
Degradative Pathway ◽  
Histidine Residues ◽  
Endosomal Acidification

V-ATPase (vesicular H+-ATPase)-driven intravesicular acidification is crucial for vesicular trafficking. Defects in vesicular acidification and trafficking have recently been recognized as essential determinants of various human diseases. An important role of endosomal acidification in receptor–ligand dissociation and in activation of lysosomal hydrolytic enzymes is well established. However, the molecular mechanisms by which luminal pH information is transmitted to the cytosolic small GTPases that control trafficking events such as budding, coat formation and fusion are unknown. Here, we discuss our recent discovery that endosomal V-ATPase is a pH-sensor regulating the degradative pathway. According to our model, V-ATPase is responsible for: (i) the generation of a pH gradient between vesicular membranes; (ii) sensing of intravesicular pH; and (iii) transmitting this information to the cytosolic side of the membrane. We also propose the hypothetical molecular mechanism involved in function of the V-ATPase a2-subunit as a putative pH-sensor. Based on extensive experimental evidence on the crucial role of histidine residues in the function of PSPs (pH-sensing proteins) in eukaryotic cells, we hypothesize that pH-sensitive histidine residues within the intra-endosomal loops and/or C-terminal luminal tail of the a2-subunit could also be involved in the pH-sensing function of V-ATPase. However, in order to identify putative pH-sensitive histidine residues and to test this hypothesis, it is absolutely essential that we increase our understanding of the folding and transmembrane topology of the a-subunit isoforms of V-ATPase. Thus the crucial role of intra-endosomal histidine residues in pH-dependent conformational changes of the V-ATPase a2-isoform, its interaction with cytosolic small GTPases and ultimately in its acidification-dependent regulation of the endosomal/lysosomal protein degradative pathway remain to be determined.

scholarly journals Fabrication of PANI-modified PVDF nanofibrous yarn for pH sensor

e-Polymers ◽  
2021 ◽  
Vol 22 (1) ◽  
pp. 69-74
Author(s):  
Hongmei Zhao ◽  
Zhang Dai ◽  
Tian He ◽  
Shufang Zhu ◽  
Xu Yan ◽  
...  
Keyword(s):  
Wound Healing ◽  
Potential Application ◽  
Polyvinylidene Fluoride ◽  
Maxillofacial Surgery ◽  
Ph Sensor ◽  
Electrospinning Process ◽  
Oral And Maxillofacial Surgery ◽  
Nanofibrous Yarn ◽  
Ph Range

Abstract In recent years, with the rise of an intelligent concept, oral and maxillofacial surgery smart dressing had also attracted the interest of researchers, especially for the pH sensor with flexible medium. In this study, polyvinylidene fluoride (PVDF) nanofibrous yarn was fabricated by a conjugate electrospinning process and modified with in situ polymerization of polyaniline (PANI) forming a PANI/PVDF yarn. By a weaving process, these yarns could be weaved into a fabric. It was found that both the PANI/PVDF yarn and the fabric showed a sensitivity to pH, about −48.53 mV  per pH for yarn and −38.4 mVper pH for fabric, respectively, in the pH range of 4.0–8.0. These results indicated that the prepared PANI-modified PVDF yarn and fabric might have a potential application in intelligent oral and maxillofacial surgery dressings for monitoring wound healing.

scholarly journals Switchable Coumarins for Ratiometric pH Sensing

2021 ◽  
Vol 8 ◽  
Author(s):  
Mercedes M. A. Mazza ◽  
Francesca Cardano ◽  
James D. Baker ◽  
Silvia Giordani ◽  
Françisco M. Raymo
Keyword(s):  
Photophysical Properties ◽  
Molecular Switches ◽  
Heterocyclic Ring ◽  
Ph Sensitive ◽  
Ph Sensing ◽  
Fast Kinetics ◽  
Fluorescence Measurements ◽  
Aqueous Environments ◽  
Ph Range ◽  
Ratiometric Ph Sensing

A fluorescent chromophore and a pH-sensitive heterocycle were integrated within a single covalent skeleton to generate four molecular switches with ratiometric fluorescence response. Upon acidification, the pH-sensitive heterocycle opens to shift bathochromically the absorption and emission bands of the fluorescent chromophore. As a result, an equilibrium between two species with resolved fluorescence is established with fast kinetics in aqueous environments. The relative amounts of the two interconverting forms and their relative emission intensities change with pH, providing the opportunity to probe this parameter ratiometrically with fluorescence measurements. Specifically, the resolved emissions of the two species can be collected in separate detection channels of the same microscope to map their ratio across a labeled sample and reconstruct its pH distribution ratiometrically with spatial resolution at the micrometer level. Additionally, the sensitivity of these molecular switches varies with the nature of the heterocyclic ring and with its substituents, allowing the possibility of regulating their response to a given pH range of interest with the aid of chemical synthesis. Thus, a family of valuable fluorescent probes for ratiometric pH sensing in a diversity of samples can emerge from the unique combination of structural and photophysical properties designed into our innovative molecular switches.

scholarly journals Stabilization and Release of Palm Tocotrienol Emulsion Fabricated Using pH-Sensitive Calcium Carbonate

Foods ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 358
Author(s):  
Phui Yee Tan ◽  
Beng Ti Tey ◽  
Eng Seng Chan ◽  
Oi Ming Lai ◽  
Hon Weng Chang ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Droplet Size ◽  
Entrapment Efficiency ◽  
Ph Sensitive ◽  
Emulsion System ◽  
Ph Responsive ◽  
Small Droplet ◽  
Homogenization Time ◽  
Oil In Water ◽  
Ph Range

Calcium carbonate (CaCO3) has been utilized as a pH-responsive component in various products. In this present work, palm tocotrienols-rich fraction (TRF) was successfully entrapped in a self-assembled oil-in-water (O/W) emulsion system by using CaCO3 as the stabilizer. The emulsion droplet size, viscosity and tocotrienols entrapment efficiency (EE) were strongly affected by varying the processing (homogenization speed and time) and formulation (CaCO3 and TRF concentrations) parameters. Our findings indicated that the combination of 5000 rpm homogenization speed, 15 min homogenization time, 0.75% CaCO3 concentration and 2% TRF concentration resulted in a high EE of tocotrienols (92.59–99.16%) and small droplet size (18.83 ± 1.36 µm). The resulting emulsion system readily released the entrapped tocotrienols across the pH range tested (pH 1–9); with relatively the highest release observed at pH 3. The current study presents a potential pH-sensitive emulsion system for the entrapment and delivery of palm tocotrienols.

scholarly journals Titanium Nitride Thin Film Based Low-Redox-Interference Potentiometric pH Sensing Electrodes

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 42
Author(s):  
Shimrith Paul Shylendra ◽  
Wade Lonsdale ◽  
Magdalena Wajrak ◽  
Mohammad Nur-E-Alam ◽  
Kamal Alameh
Keyword(s):  
Thin Film ◽  
Titanium Nitride ◽  
Orange Juice ◽  
Ph Sensor ◽  
Reference Electrode ◽  
Cost Effective ◽  
Ph Sensing ◽  
Ph Sensors ◽  
Potential Shift ◽  
Double Junction

In this work, a solid-state potentiometric pH sensor is designed by incorporating a thin film of Radio Frequency Magnetron Sputtered (RFMS) Titanium Nitride (TiN) working electrode and a commercial Ag|AgCl|KCl double junction reference electrode. The sensor shows a linear pH slope of −59.1 mV/pH, R2 = 0.9997, a hysteresis as low as 1.2 mV, and drift below 3.9 mV/h. In addition, the redox interference performance of TiN electrodes is compared with that of Iridium Oxide (IrO2) counterparts. Experimental results show −32 mV potential shift (E0 value) in 1 mM ascorbic acid (reducing agent) for TiN electrodes, and this is significantly lower than the −114 mV potential shift of IrO2 electrodes with sub-Nernstian sensitivity. These results are most encouraging and pave the way towards the development of miniaturized, cost-effective, and robust pH sensors for difficult matrices, such as wine and fresh orange juice.

scholarly journals Synthesis and In Vitro Assessment of pH-Sensitive Human Serum Albumin Conjugates of Pirarubicin

2020 ◽  
Vol 14 (1) ◽  
pp. 22
Author(s):  
Kenji Tsukigawa ◽  
Shuhei Imoto ◽  
Keishi Yamasaki ◽  
Koji Nishi ◽  
Toshihiko Tsutsumi ◽  
...  
Keyword(s):  
Human Serum Albumin ◽  
Serum Albumin ◽  
Human Serum ◽  
Coupling Reaction ◽  
Synthetic Polymer ◽  
Ph Sensitive ◽  
Acidic Ph ◽  
Polymer Conjugate ◽  
Acidic Conditions

In a previous study, we reported on the development of a synthetic polymer conjugate of pirarubicin (THP) that was formed via an acid-labile hydrazone bond between the polymer and the THP. However, the synthetic polymer itself was non-biodegradable, which could lead to unexpected adverse effects. Human serum albumin (HSA), which has a high biocompatibility and good biodegradability, is also a potent carrier for delivering antitumor drugs. The objective of this study was to develop pH-sensitive HSA conjugates of THP (HSA-THP), and investigate the release of THP and the cytotoxicity under acidic conditions in vitro for further clinical development. HSA-THP was synthesized by conjugating maleimide hydrazone derivatives of THP with poly-thiolated HSA using 2-iminothiolane, via a thiol-maleimide coupling reaction. We synthesized two types of HSA-THP that contained different amounts of THP (HSA-THP2 and HSA-THP4). Free THP was released from both of the HSA conjugates more rapidly at an acidic pH, and the rates of release for HSA-THP2 and HSA-THP4 were similar. Moreover, both HSA-THPs exhibited a higher cytotoxicity at acidic pH than at neutral pH, which is consistent with the effective liberation of free THP under acidic conditions. These findings suggest that these types of HSA-THPs are promising candidates for further development.

scholarly journals Cofilin is a pH sensor for actin free barbed end formation: role of phosphoinositide binding

2008 ◽  
Vol 183 (5) ◽  
pp. 865-879 ◽  
Author(s):  
Christian Frantz ◽  
Gabriela Barreiro ◽  
Laura Dominguez ◽  
Xiaoming Chen ◽  
Robert Eddy ◽  
...  
Keyword(s):  
Actin Filament ◽  
Structural Changes ◽  
Ph Sensor ◽  
Ph Sensitive ◽  
Actin Binding ◽  
Filamentous Actin ◽  
Filament Dynamics ◽  
Ph Dependent ◽  
Dynamics Simulations

Newly generated actin free barbed ends at the front of motile cells provide sites for actin filament assembly driving membrane protrusion. Growth factors induce a rapid biphasic increase in actin free barbed ends, and we found both phases absent in fibroblasts lacking H+ efflux by the Na-H exchanger NHE1. The first phase is restored by expression of mutant cofilin-H133A but not unphosphorylated cofilin-S3A. Constant pH molecular dynamics simulations and nuclear magnetic resonance (NMR) reveal pH-sensitive structural changes in the cofilin C-terminal filamentous actin binding site dependent on His133. However, cofilin-H133A retains pH-sensitive changes in NMR spectra and severing activity in vitro, which suggests that it has a more complex behavior in cells. Cofilin activity is inhibited by phosphoinositide binding, and we found that phosphoinositide binding is pH-dependent for wild-type cofilin, with decreased binding at a higher pH. In contrast, phosphoinositide binding by cofilin-H133A is attenuated and pH insensitive. These data suggest a molecular mechanism whereby cofilin acts as a pH sensor to mediate a pH-dependent actin filament dynamics.

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