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The synergy of CHEF and ICT toward fluorescence ‘turn-on’ probes based on push-pull benzothiazoles for selective detection of Cu2+ in acetonitrile/water mixture
(2021-06-15)
Nootem, Jukkrit
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Daengngern, Rathawat
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Sattayanon, Chanchai
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Wattanathana, Worawat
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Wannapaiboon, Suttipong
New push-pull schiff base ligands based on benzothiazole (BZ) unit were developed for the selective detection of Cu2+ through fluorescence ‘turn-on’ mechanism. These derivatives with electron withdrawing trifluoromethyl (-CF<inf>3</inf>) and cyano (-CN) substituents (BZ2 and BZ3) demonstrated a prominent fluorescence enhancement upon copper ion binding which could be the results from the synergistic effect between the chelation-enhanced fluorescence (CHEF) and the intramolecular charge transfer (ICT) processes. In addition, these compounds displayed 1:1 binding with Cu2+ with low limits of detection of 0.77 μM and 0.64 μM for BZ2 and BZ3, respectively, in acetonitrile-water (3:1 v/v) media. The electronic and photophysical properties of these BZ ligands and the copper ion complexes were modelled by the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT) calculations, respectively. Analysis of X-ray absorption spectra probed at Cu K-edge of Cu2+-BZ mixtures revealed the complex formation of BZ ligands with the targeted Cu2+ and confirmed the non-centrosymetric structures of the complexes as predicted by the DFT calculation. The electron density distributions of the HOMO-LUMOs in the computational results as well as large stokes shifts of the ligand-metal complexes in the experimental data confirmed the strong ICT effect after Cu2+ binding which is a key process promoting fluorescence ‘turn-on’ mechanism.
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Reduced graphene oxide thin film prepared by electrostatic spray deposition technique
(2019-03-15)
Songkeaw, Potiyan
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Onlaor, Korakot
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Thiwawong, Thutiyaporn
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Tunhoo, Benchapol
Reduced graphene oxide (rGO) thin films were prepared by one-step electrostatic spray deposition (ESD) technique with a precursor solution of graphene oxide in mixed alcohol solvent. The deposited rGO films showed decreasing thicknesses ranging from approximately 340 nm–120 nm as substrate temperature increased from 150 °C to 275 °C. Raman spectroscopy indicated lowest intensity ratio of D to G band (I <inf>D</inf> /I <inf>G</inf> ) of the rGO films at substrate temperature of 275 °C. Highest carbon per oxygen (C/O) ratio was also obtained at substrate temperature of 275 °C. The ESD technique was used for film deposition on an area of 5 × 5 cm 2 , while an acetone gas sensor based on single layer rGO film was fabricated by one-step ESD technique. Results indicated the possibility of controlling thickness components in the rGO film, and the capability of large-area production by this scalable ESD method.
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Development of sensor module for detecting the magnetron power based on microwave oven frequency
(2018-12-10)
Satthamsakul, Sutham
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Sriratana, Witsarut
This study presents the design of sensor module to be used in analyzing the electromagnetic power created from magnetron by using microwave as the case study on basis of Rectenna (Rectifying antenna) consisting of 2 main parts including sensing part and transduction part. On part of sensing part, the design would be made on the basic principle of monopole antenna; on part of transduction part, the design would be made on the basis of rectifier circuit, to function in converting the electromagnetic power received from magnetron to be in form of DC current, here the Hall Effect Sensor that was installed inside the current sensor module was used as the measuring equipment, with Arduino UNO R3 as the controller for recording electrical current including temperature. The experimental results would be used to analyze the appropriate form of sensor module. This research compared sensor module for 3 forms including Type A, Type B, and Type C, with different sizes of diameter of wires consisting, by comparing the efficiency in preventing the leak of measured power. According to the test of sensor modules in 3 forms on the same condition, it was found that the means of electrical current from converting the electromagnetic power of microwave.
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Analysis of capacitive variation using parallel-plates method
(2009-12-01)
Tanachaikhan, Lerdlekha
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Sriratana, Witsarut
Capacitive variation of capacitive sensor was analyzed by using two parallel plates coated by 0.4 mm- thick nylon and fixed together by resin to maintain the distance of those two plates at 2.5 mm and 5 mm. In this study, stainless and copper were used for development of capacitive sensor. In this paper Ethel alcohol solution is used as a case study. Ethel alcohol solution with the concentration ranging from 95% to 5% with 10% step decrease of concentration diluted by distilled water was experimented under the controlled temperature of 23°C and the frequency was varied from 100 Hz to 2 kHz with 500 Hz interval. The capacitive variation analyzed from the equivalent circuit which was obtained from the developed sensor was then compared to the electrical circuit obtained from the Good Will R-L-C instrument model CRT to analyze for the appropriate material and the distance between two parallel plates (d) of the sensor. This proposed methodology was developed with consideration of the simple design for easy fabrication and low costs with high accuracy and reliability of the results. ©2009 IEEE.
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Design of capacitive sensor for concentration measurement
(2006-12-01)
Thong-un, Natee
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Sriratana, Witsarut
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Tanachaikhan, Lerdlekha
This paper presents the analysis of ideal equivalent circuit of the developed concentration sensor probe for chemical solutions by regarding to reasonable costs and reliability of device. The designed sensor probe consists of 2 parallel electrode plates that are coated by Nylon with 0.4 mm thick and mounted together by Resin with 2.5 mm of gap (0.09 times greater than electrode width). Any capacity changes will be compared with the electric circuit that is obtained from the Good Will R-L-C standard instrument, model CTR, at the frequency extending from 100Hz to 2 kHz. From the experiments, it was found that the sensor designed for Ethyl Alcohol solution within concentration of 5% to 95% and 10% concentration interval, at room temperature of 23°C and frequency of 100 Hz, can provide the results with high linearity as well as high resolution of capacity change which is 2 pF per 1% of concentration. © 2006 ICASE.

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