scholarly journals Arrays of Copper Microelectrodes from Disposable Chips: Fabrication and Characterization

Author(s):  
Giane Higino ◽  
Ítalo Machado ◽  
Gabriel Nascimento ◽  
Jairo Pedrotti

A simple, fast, and low-cost process to fabricate arrays of copper microelectrodes (CuMEs) based on disposable electronic microchips is described. Arrays with 8 to 20 CuMEs were characterized by energy-dispersive X-ray spectroscopy and cyclic voltammetry techniques. The closest interelectrode distance in the arrays is 358 ± 22 μm, and the minor radius ranged from 10.6 to 13.5 μm. The microchips with CuMEs were sealed in epoxy resin to fabricate the rod and flat-shaped platforms, allowing the CuMEs to be addressed separately. Glucose, hydrazine, and nitrate were used as analyte models for voltammetric and amperometric detection at CuMEs arrays, showing excellent performance in batch and flow-through cells. Glucose measurements carried out with flow injection analysis system with amperometric detection at an array of 20 CuMEs showed a wide linear range (0.020-4.0 mmol L-1), high sensitivity (734.1 μA L mmol-1 cm-2), and a limit of detection of 1.7 μmol L-1.

2018 ◽  
Vol 5 (4) ◽  
pp. 172128 ◽  
Author(s):  
Ming Ding ◽  
Kailiang Wang

A practical method for the determination of cyanide in bamboo shoots has been developed using microdiffusion preparation integrated with ion chromatography–pulsed amperometric detection (IC-PAD). Cyanide was released from bamboo shoots after Conway cell microdiffusion, and then analysed by IC-PAD. In comparison with the previously reported methods, derivatization and ion-pairing agent addition were not required in this proposed microdiffusion combined with IC-PAD method. The microdiffusion parameters were optimized including hydrolysis systems, temperature, time, and so on. Under the optimum conditions, the linear range of the calibration curve for cyanide was 0.2–200.0 µg kg −1 with satisfactory correlation coefficients of 0.9996 and the limit of detection was 0.2 µg kg −1 ( S/N  = 3). The spiked recovery range was from 92.8 to 98.6%. The intra-day and inter-day relative standard deviations of cyanide were 2.7–14.9% and 3.0–18.3%, respectively. This method was proved to be convenient in operation with high sensitivity, precision and accuracy, and was successfully applied in the determination of cyanide in bamboo shoot samples.


1977 ◽  
Vol 21 ◽  
pp. 171-185 ◽  
Author(s):  
J.M. Jaklevic ◽  
W.R. French ◽  
T.W. Clarkson ◽  
M.R. Greenwood

We describe an adaptation of photon excited x-ray fluorescence analysis which is optimized for the analysis of small samples. A fine focus x-ray tube is used in conjunction with small diameter detector collimators in order to focus on a small sample volume with as high sensitivity as possible. Sample areas of less than 1 mm diameter can be analyzed with ppm detectability. In applications involving the analysis of human hair samples, a minimum detectable limit of 10 ppm Hg can be realized in a 1 mm long segment of a single hair in a counting time of 200 seconds. Simultaneous measurements of the sample mass can be obtained from the intensity of the incoherent scattering. An automated x-ray fluorescence analysis system using the technique for the scanning of elemental profiles in such hair samples will be described.


Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 445 ◽  
Author(s):  
Xiangfeng Guan ◽  
Yongjing Wang ◽  
Peihui Luo ◽  
Yunlong Yu ◽  
Dagui Chen ◽  
...  

The development of high-performance acetone gas sensor is of great significance for environmental protection and personal safety. SnO2 has been intensively applied in chemical sensing areas, because of its low cost, high mobility of electrons, and good chemical stability. Herein, we incorporated nitrogen atoms into the SnO2 nanostructure by simple solvothermal and subsequent calcination to improve gas sensing property for acetone. The crystallization, morphology, element composition, and microstructure of as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Electron paramagnetic resonance (EPR), Raman spectroscopy, UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and the Brunauer–Emmett–Teller (BET) method. It has been found that N-incorporating resulted in decreased crystallite size, reduced band-gap width, increased surface oxygen vacancies, enlarged surface area, and narrowed pore size distribution. When evaluated as gas sensor, nitrogen-incorporated SnO2 nanostructure exhibited excellent sensitivity for acetone gas at the optimal operating temperature of 300 °C with high sensor response (Rair/Rgas − 1 = 357) and low limit of detection (7 ppb). The nitrogen-incorporated SnO2 gas sensor shows a good selectivity to acetone in the interfering gases of benzene, toluene, ethylbenzene, hydrogen, and methane. Furthermore, the possible gas-sensing mechanism of N-incorporated SnO2 toward acetone has been carefully discussed.


1968 ◽  
Vol 12 ◽  
pp. 165-173 ◽  
Author(s):  
Arthur N. Chester ◽  
Fred B. Koch

AbstractThe silicon diode array camera tube, recently developed for PICTURFPHONE® service, was modified to permit X-ray imaging. High quantum efficiency is attained without the use of a phosphor screen, since each photon absorbed in the silicon target generates several hundred hole-electron pairs for each keV of its energy, most of which can he usefully collected. The sensitivity and resolution are adequate to allow a continuous television display of the diffracted intensity as a crystal is oriented. Particular advantages of this technique include; high resolution (< 25 μm); electronically variable magnification; direct oscilloscope measurement of X-ray spot Intensity profiles and relative spot intensities because signal current is directly proportional to photon flux; high sensitivity in the range of 0.6 to 5.0 Å, potentially limited only "by counting statistics; integration times variable from < 1/60 second to minutes; and expected low cost, since the camera tube has no complicated electron imaging, and is directly interchangeable Mith a standard television vidicon. Applications which are described include crystal orientation and X-ray topography.


Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 3141 ◽  
Author(s):  
Xiao-Liang Guo ◽  
Yan Chen ◽  
Hong-Lan Jiang ◽  
Xian-Bo Qiu ◽  
Du-Li Yu

Formaldehyde is one of the most dangerous air pollutants, which can cause sick building syndrome. Thus, it is very crucial to precisely determine formaldehyde with a low cost and simple operation. In this paper, a smartphone-based microfluidic colorimetric sensor is devised for gaseous formaldehyde determination with high sensitivity and selectivity. Specifically, a novel microfluidic chip is proposed based on the 4-aminohydrazine-5-mercapto-1,2,4-triazole (AHMT) method to determine formaldehyde; the chip consists of two reagent reservoirs, one reaction reservoir and a mixing column. In this design to prevent the fluid from flowing out while letting the gas molecule in, a hydrophobic porous poly tetra fluoroethylene (PTFE) membrane is put on the top of the reaction reservoir. Using the microfluidic chip sensor, a smartphone-based formaldehyde determination system is developed, which makes the measuring process automated and simple. As per the experiment results, the limit-of-detection (LOD) of the system is as low as 0.01 ppm, which is much lower than the maximum exposure concentration (0.08 ppm) recommended by the World Health Organization (WHO). Moreover, the sensor is hardly affected by acetaldehyde, volatile organic compounds (VOCs) or acidic-alkaline, which shows great selectivity. Finally, the performance of the proposed sensor is verified by using it for the determination of formaldehyde in a newly decorated house.


Author(s):  
Intizar Aliyeva Intizar Aliyeva ◽  
Rasul Hajıyev Rasul Hajıyev

The article discusses various limited considerations and assumptions on the positive or negative impact of geochemical features chemical elements found in rocks, ores, soil, plants, water and in the air of the territories of populated areas, factories, the mining and agro-industrial complexes to the environment and the role of analytical geochemistry in this process. According to the author, one of the main points on which the light should be shed is the role of finding elements (independent, combination or isomorphic mixture) rather than their existence in different amounts in the environment. Thus, the chemical elements can be more or less hazardous to environment regardless its amount, but the finding methods. Chemical and natural combinations can be either very hazardous or very useful to all living creatures depending on their characteristics, so it’s better to determine their environmental hazardousness via their impact to a particular human or animal organ which in turn facilitates the solution of the problem. Moreover, it should be noted that the most environmentally dangerous and active chemical elements are the ones with fluctuating valence. Some elements are not so hazardous when they are independent or in solid form since they change weakly. But they are very dangerous when they turn into liquid or gas forms and create mineral compounds with other elements such as halkofil group of elements which in turn can easily decompose and dissolve in water by causing dangers to all living creatures in the nature. Approximately any chemical element can either react negatively or in most cases stimulate the life functions of the organs of animals and plants depending on its finding forms. The study of geochemical parameters in different natural objects such as surface and subsoil water, air, rocks and ores can be very helpful in organizing the protection of environmetal and the solution of its problems. X-ray Spectral analysis is particularly highlighted in this article for identifying various chemical elements in geological and ecological objects. There are several advantages of X-ray Spectral analysis such as its productiveness and low cost, the expressiveness and simplicity of analysis operations, having slightly high sensitivity, universality, high range of elements identification features, etc. To conclude some authors claim that the following problems can be solved with the help of analytic geochemistry: Identifying the main source of pollution and the evaluation of its impact on the environment; Identification of quantitative and qualitative parameters of sources of natural, techno and agro genic pollution in the settlements, industrial objects and in the regions of developed mining complexes; Eco-geochemical and biochemical evaluation of the negative impact of water, weather and harmful geochemical anomalies on live organisms. We hope the elimination of this type of problems can pave the way to the ecologically clean environment. Keywords: ore, soil, plant, water, weather.


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