Carbon Materials Based Ion Sensitive Field Effect Transistor (ISFET)

2017 ◽  
pp. 334-360
Author(s):  
Mohammad Javad Kiani ◽  
M. H. Shahrokh Abadi ◽  
Meisam Rahmani ◽  
Mohammad Taghi Ahmadi ◽  
F. K. Che Harun ◽  
...  
Keyword(s):  
Ph Value ◽  
Enzymatic Reaction ◽  
Electrical Measurement ◽  
Hydrogen Ion ◽  
Monolayer Graphene ◽  
Full Potential ◽  
Electrical Detection ◽  
Ion Concentrations ◽  
Detection Model ◽  
Ph Buffer

Graphene and SWCNT-based Ion Sensitive FET (ISFET) as a novel material with organic nature and ionic liquid gate is intrinsically sensitive to pH changes. pH is an important factor in enzymes stabilities which can affect the enzymatic reaction and broaden the number of enzyme applications. More accurate and consistent results of enzymes must be optimized to realize their full potential as catalysts accordingly. In this chapter, an appropriate structure to ISFET device is designed for the purpose of electrical measurement of different pH buffer solutions. Electrical detection model of each pH value is suggested using conductance modelling of monolayer graphene. In addition, ISFET based on nanostructured SWCNT is studied for the purpose of electrical detection of hydrogen ion concentrations. Electrical detection of hydrogen ion concentrations by modelling the conductance of SWCNT sheets is proposed. pH buffer as a function of gate voltage is assumed and sensing factor is defined. Finally, the proposed new approach improving the analytical model is compared with experimental data and shows good overall agreement.

scholarly journals Apparatus for Rapid Electrometric Titration

1930 ◽  
Vol 16 (2) ◽  
pp. 519-527
Author(s):  
R. G. Neill
Keyword(s):  
Ph Value ◽  
Hydrogen Ion ◽  
Dilute Solutions ◽  
Ion Concentrations ◽  
Electrometric Titration

This apparatus was assembled at Millport for the electrometric titration of solutions which, being highly coloured, cannot well be titrated with an indicator. It may be used also for highly dilute solutions, unless they are so slightly buffered that their pH value is appreciably changed by the addition of a small quantity of quinhydrone. Measurement of hydrogen-ion concentrations at the quinhydrone electrode has also been attempted with the apparatus. The apparatus is suitable for use at sea.

scholarly journals Evaluation of Enzyme Inhibitory Activity of Flavonoids by Polydopamine-Modified Hollow Fiber-Immobilized Xanthine Oxidase

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3931
Author(s):  
Cong-Peng Zhao ◽  
Guo-Ying Chen ◽  
Yuan Wang ◽  
Hua Chen ◽  
Jia-Wen Yu ◽  
...  
Keyword(s):  
Xanthine Oxidase ◽  
Hollow Fiber ◽  
Inhibitory Activity ◽  
Ph Value ◽  
Enzymatic Reaction ◽  
Amino Acid Residues ◽  
Reaction Conditions ◽  
Docking Analysis ◽  
Dopamine Concentration ◽  
Immobilization Time

In this study, a polydopamine (PDA)-modified hollow fiber-immobilized xanthine oxidase (XOD) was prepared for screening potential XOD inhibitors from flavonoids. Several parameters for the preparation of PDA-modified hollow fiber-immobilized XOD, including the dopamine concentration, modification time, XOD concentration and immobilization time, were optimized. The results show that the optimal conditions for immobilized XOD activity were a dopamine concentration of 2.0 mg/mL in 10.0 mM Tris-HCl buffer (pH 8.5), a modification time of 3.0 h, an XOD concentration of 1000 μg/mL in 10.0 mM phosphate buffer (pH 7.5) and an immobilization time of 3.0 h. Subsequently, the enzymatic reaction conditions such as the pH value and temperature were investigated, and the enzyme kinetics and inhibition parameters were determined. The results indicate that the optimal pH value (7.5) and temperature (37 °C) of the PDA-modified hollow fiber-immobilized XOD were consistent with the free enzyme. Moreover, the PDA-modified hollow fiber-immobilized XOD could still maintain above 50% of its initial immobilized enzyme activity after seven consecutive cycles. The Michaelis–Menten constant (Km) and the half-maximal inhibitory concentration (IC50) of allopurinol on the immobilized XOD were determined as 0.25 mM and 23.2 μM, respectively. Furthermore, the PDA-modified hollow fiber-immobilized XOD was successfully applied to evaluate the inhibitory activity of eight flavonoids. Quercetin, apigenin, puerarin and epigallocatechin showed a good inhibition effect, and their percentages of inhibition were (79.86 ± 3.50)%, (80.98 ± 0.64)%, (61.15 ± 6.26)% and (54.92 ± 0.41)%, respectively. Finally, molecular docking analysis further verified that these four active compounds could bind to the amino acid residues in the XOD active site. In summary, the PDA-modified hollow fiber-immobilized XOD is an efficient method for the primary screening of XOD inhibitors from natural products.

scholarly journals The acidity of muscle during maintained contraction

1922 ◽  
Vol 93 (654) ◽  
pp. 406-410
Keyword(s):  
Manganese Dioxide ◽  
Hydrogen Ion ◽  
Ion Concentrations

In 1913, I described a method for recording changes in hydrogen-ion concentrations in tissues, by means of a manganese dioxide electrode in combination with a calomel electrode (1). By this method it was shown that the acidity of muscle probably increased at the same time as, or slightly before, the tension increased, and that the acidity decreased as the muscle relaxed (2). In a paper, which appeared as this note was being prepared for publication, Ritchie states that he has been unable to detect a variation in acidity by the use of manganese dioxide electrodes. I am inclined to think that his failure is due to the injury to the muscles on insertion of wires into its substance. In my own experiments the wires rest on the surface of the muscle.

STUDY ON TIME-CONSTANT MODELS OF SnO2pH SENSOR

2009 ◽  
Vol 21 (06) ◽  
pp. 449-452
Author(s):  
Chi-Wei Chen ◽  
Jung-Chuan Chou ◽  
Tai-Ping Sun ◽  
Shen-Kan Hsiung
Keyword(s):  
Time Constant ◽  
Electrochemical Impedance ◽  
Ph Value ◽  
Ph Sensor ◽  
Membrane Resistance ◽  
Hysteresis Effect ◽  
Equivalent Model ◽  
Resistance Change ◽  
Ph Buffer ◽  
Function Relationship

The aim of this study was to discuss the hysteresis effect of SnO2 pH sensor based on separative extended gate field effect transistor (SEGFET). Based on the theorem of three time-constants model, hysteresis model is linked with drift effect. Function relationship of pH value and time constant is also derived from the drift effects with difference pH value. Besides, electrochemical impedance spectroscopy (EIS) is utilized to interpret the mechanism of hysteresis effect. Experiments of EIS are carried out in different pH buffer solutions. An equivalent model of sensing membrane is obtained by theorem of EIS. The experimental results indicate that the equivalent circuit elements, such as membrane capacitance and membrane resistance, change with pH. This phenomenon is compared with other literatures and discussed on hysteresis effect.

scholarly journals Pre-fermentative treatment of a model wine with aim to serve as a functional food with decreased alcohol content

2017 ◽  
Vol 63 (01) ◽  
pp. 47-53
Author(s):  
Irina Mladenoska ◽  
Verica Petkova ◽  
Tatjana Kadifkova Panovska
Keyword(s):  
Enzyme Activity ◽  
Gluconic Acid ◽  
Functional Food ◽  
Ph Value ◽  
Enzymatic Reaction ◽  
Alginate Beads ◽  
High Concentration ◽  
Ph Optimum ◽  
Enzyme Preparations ◽  
Initial Ph

The effect of substrate concentration on the enzyme activity in the reaction of glucose conversion into gluconic acid was investigated by using three different enzyme preparations in media with two different glucose concentrations. The media were simulating the conditions in the must, thus named as minimal model must, and were composed form combination of several organic acids and glucose. Those media were having initial pH of 3.5 that is a very unfavorable for glucose oxidase activity having a pH optimum at the pH value of 5.5. Among the three preparations used, the bakery additive, Alphamalt Gloxy 5080, was the most active in the medium with glucose concentration of 10 g/L, showing conversion of more than 70% for the period of 24 h, while the same enzyme preparation in the medium with 100 g/L glucose converted only about 7% of glucose. The pH value of the medium at the beginning and at the end of the enzymatic reaction was a good indicator of the enzyme activity. It seems that for the conversion of glucose in higher concentration, enzymatic preparation in high concentration should also be used. The preliminary attempt of immobilization of two preparations of glucose oxidases in alginate beads was also performed and a successful immobilization procedure for utilization in food industry was preliminarily developed. Keywords: glucose oxidases, enzymatic pretreatment, glucose, gluconic acid, model wine, functional food

scholarly journals THE RELATION OF THE PNEUMOCOCCUS TO HYDROGEN ION CONCENTRATION, ACID DEATH-POINT, AND DISSOLUTION OF THE ORGANISM

1919 ◽  
Vol 30 (4) ◽  
pp. 389-399 ◽  
Author(s):  
Frederick T. Lord ◽  
Robert N. Nye
Keyword(s):  
Hydrogen Ion ◽  
Ion Concentration ◽  
Direct Relation ◽  
Hydrogen Ion Concentration ◽  
Ion Concentrations ◽  
Cent Glucose ◽  
Fluid Media

1. In the growth and death of the pneumococcus in fluid media containing 1 per cent glucose the production of acid is the most important bactericidal factor. 2. 1 per cent glucose bouillon cultures of the pneumococcus allowed to grow and die out usually reach a final acidity of a pH of about 5.1. 3. At a hydrogen ion concentration of about 5.1 or higher, the pneumococcus does not survive longer than a few hours. 4. In hydrogen ion concentrations of about 6.8 to 7.4 the pneumococcus may live for at least many days. 5. In the intervening hydrogen ion concentrations, between 6.8 and 5.1, the pneumococcus is usually killed with a rapidity which bears a direct relation to the hydrogen ion concentration; i.e., the greater the acidity the more rapid is the death. 6. Cloudy suspensions of washed pneumococci in hydrogen ion concentrations varying from 8.0 to 4.0 show, after incubation, dissolution of organisms in lower hydrogen ion concentrations than about 5.0. This dissolution is most marked at about 5.0 to 6.0. Some dissolution also takes place toward the more alkaline end of the scale. No dissolution occurs at the most acid end of the scale.

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