Probe System Research Articles

Obtaining plasma parameters by Langmuir probes and optical emission spectroscopy in low-pressure DC plasma

The plasma environment in low-pressure systems allows coating different materials such as glasses, textiles, metals, etc. at the atomic level. Although vacuum coating is one of the best methods for thin film coating, the coating quality is closely affected by the spatial and temporal non-uniformities inside the reactor. Therefore it is quite important to determine the plasma properties within the chamber. The determination of plasma parameters such as electron temperature, electron excitation temperature, electron and ion densities can be realized using Langmuir probe systems, and by Optical Emission Spectroscopy (OES) by using Boltzmann plot method. Knowing such parameters can provide important information about specific reaction mechanisms, as well as it provides invaluable information that can increase reproducibility in various discharge process control in thin film coating. In this study, a homemade single Langmuir probe (s-LP) and a multiple Langmuir probe system (m-LP) were used to calculate electron temperature, electron density, saturation current, and plasma potential of the plasma at different pressures and at different voltages. One of the objectives of this work was to evaluate the electron temperature and ion density inside the plasma during a coating process. The second objective was to find the spatial change of electron temperature in the axial direction between cathode and anode by m-LP system including 8 independent tips. The last objective was to measure the axial plasma electron temperature distribution inside the vacuum chamber by using OES.

A near-infrared ratiometric fluorescent probe for hydrazine and its application for gaseous sensing and cell imaging

Hydrazine (N2H4) is a widely used raw material in the chemical industry, but at the same time hydrazine has extremely high toxicity. Therefore, the development of efficient detection methods is crucial for monitoring hydrazine in the environment and evaluating the biological toxicity of hydrazine. This study reports a near-infrared ratiometric fluorescent probe (DCPBCl2-Hz) for the detection of hydrazine by coupling a chlorine-substituted D-π-A fluorophore (DCPBCl2) to the recognition group acetyl. Due to the halogen effect of chlorine substitution, the fluorophore has an elevated fluorescence efficiency and a lowered pKa value and is suitable for physiological pH conditions. Hydrazine can specifically react with the acetyl group of the fluorescent probe to release the fluorophore DCPBCl2, so the fluorescence emission of the probe system significantly shifted from 490 nm to 660 nm. The fluorescent probe has many advantages, such as good selectivity, high sensitivity, large Stokes shift, and wide applicable pH range. The probe-loaded silica plates can realize convenient sensing gaseous hydrazine with content down to 1 ppm (mg/m3). Subsequently, DCPBCl2-Hz was successfully applied to detect hydrazine in soils. In addition, the probe can also penetrate living cells and allow the visualization of intracellular hydrazine. It can be anticipated that probe DCPBCl2-Hz will be a useful tool for sensing hydrazine in biological and environmental applications.

In-situ growth of covalent organic framework on stainless steel needles as solid-phase microextraction probe coupled with electrospray ionization mass spectrometry for rapid and sensitive determination of tricyclic antidepressants in biosamples

Tricyclic antidepressants (TCAs) including amitriptyline (AT), doxepin (DOX) and nortriptyline (NT) are the first-line drugs for the clinical treatment of depression; however, monitoring TCA concentrations in biological fluids and tissues is necessary to improve therapeutic effect and determine the cause of death in patients. It is of great significance to develop a rapid and sensitive method for real-time monitoring of TCAs in various biosamples. In this work, we fabricated a novel covalent organic framework (COF) based solid-phase microextraction (SPME) probe by an in-situ step-by-step strategy, which was obtained by sequentially modifying 1,3,5-tri (4-aminophenyl) benzene (TPB) and 2, 5-divinylbenzaldehyde (DVA) on the surface of polydopamine layer. The TPB-DVA-COF-SPME probe possessed high specific surface area (1244 m2·g − 1), regular pores (3.23 nm), good hydrophobicity and stability, resulting in efficient enrichment for TCAs. Furthermore, the combination of TPB-DVA-COF-SPME probe and ambient electrospray ionization mass spectrometry system (ESI/MS) was firstly proposed for rapid and sensitive determination of TCAs in biosamples. As a result, the developed method exhibited low limits of detection (LODs) (0.1–0.5 μg∙L − 1), high enrichment factors (39–218), and low relative standard deviations (RSDs) for one probe (1.2–3.8%) and probe-to-probe (2.0–3.7%). Benefiting from these outstanding performance, TPB-DVA-COF-SPME probe was further successfully applied to biosamples (i.e., serum, liver, kidney, and brain) with excellent reusability, indicating the promising applicability of the TPB-DVA-COF-SPME-ESI/MS as a powerful tool for drug monitoring.

Rapid gemstone mineral identification using portable Raman spectroscopy

AbstractMineral identification is the first step in gemstone characterization, which is the foundation for maintaining transparency in gemstone trading. Current techniques have complex protocols and require expensive instrumentation, severely restricting their use to trained experts or large gemological laboratories and limiting the processing speed. A simple and inexpensive automatic identification instrument can fulfill the needs of the Gemology Society. Hence, we propose a portable setup for the automatic mineral identification of gemstones based on a custom‐built 405 nm Raman spectroscopy probe system. This device enables the noninvasive mineral identification of commonly encountered loose or mounted gemstone materials in the market and generates the results in seconds. It is mechanically designed to allow safe operation under normal office conditions, and the pre‐aligned sample stage significantly simplifies the sample alignment process. Fifty‐seven types of gemstone materials in the trading market were tested with the device to prove the usability of the system. The primary purpose of this device is to automatically identify the types of minerals in the gemstones. It can also be extended to identify lab‐grown gemstones in the selected mineral species.

Processing and Characterization of Iron Oxide Nanoparticle Produced by Ball Milling Technique

In this study iron oxide (Fe2O3) nanoparticle samples was prepared using mechanical grinding method. The optical properties were studied using UV-Vis spectrophotometer within a range of 200-1100nm. The micro and crystalline size of the nanoparticle were studied using x-ray diffractometer (XRD) and scanning electron microscopy (SEM). The compositional analysis was carried out using energy dispersive x-ray spectroscopy (EDXS). Observation of the electrical properties of the nanoparticle was carried out using an electrical four-point probe system. The XRD pattern in the 2θ range from 20 to 700 revealed that iron oxide had a rhombohedral structure. The SEM result showed that the nanoparticles were well dispersed and had a uniform crystalline structure. The EDXS results showed the elemental analysis of the nanoparticles under consideration. Iron oxide nanoparticles had elemental composition of oxygen, iron, titanium and carbon. The atomic and weight concentration of iron was 14.19 and 30.89%. The four-point probe electrical resistivity result shows that iron oxide nanoparticles had a sheet resistance of 9.8x106Ώ/sq. The optical result made it known that iron oxide nanoparticles possessed a high transmittance, also iron oxide nanoparticles displayed a low reflectance and moderate absorbance. Finally, the bandgap energy of Fe2O3 dispersed in ethanol was found to be 2.74 eV. The Band gap of Fe2O3 dispersed in distilled water is 2.98 eV.

Chemical probe systems for assessing liquid-liquid mixing efficiencies of reactors

Chemical probe systems for assessing liquid-liquid mixing efficiencies of reactors

Design of an optimised movable electrostatic diagnostic for the investigation of plasma properties in a large negative ion source

This contribution describes the design of a movable Langmuir probe system to be permanently installed in the SPIDER negative ion source. This diagnostic aims at measuring the axial profiles of plasma density, electron temperature and floating potential in both the driver and the expansion region, with a view to further investigate the positive ion dynamics. Furthermore, a deeper understanding of the plasma formation mechanism and of the RF coupling can be provided, e,g. via the estimation of the Electron Energy Distribution Function (EEDF) inside the driver. Thermal analyses were performed to define both the allowable duration of the probe exposure to the plasma and the extent of the voltage sweep. The maximum exposure time for the probe shaft is 10 s, thus a fast manipulation system is included in the design. The integration in the SPIDER source is described, considering all the limitations due to the space availability, the presence of the RF generators and the vacuum-compatibility requirements. To comply with all the constraints, several solutions are proposed for the probe head design.

Three-dimensional tomography of scattering inhomogeneities by a cylindrical multistatic probing system

A method of three-dimensional ultrasonic tomography based on multi-view probing with multiple emitters and multiple receivers on a cylindrical surface in a wide frequency band is proposed. Emitters and receivers are placed on a ring that moves along the vertical axis. Signal processing is based on the use of matched filtering and is reduced to the calculation of cyclic convolution along the angle and vertical axis, which makes it possible to implement a fast algorithm for recovering of three-dimensional images. To test the method, an experimental setup was developed consisting of 32 emitters and 64 receivers uniformly placed on a ring with a radius of 205 mm. During the experiments, sounding was carried out in air at frequencies from 38 kHz to 43 kHz. As a result, a three-dimensional object of a complex shape is visualized, which confirms the applicability of the proposed method.

An Ultrawideband Asymmetric Calibration Method for a Simultaneously Electromagnetic Near-Field Probing System

Calibration for asymmetry of the simultaneously electromagnetic near-field probing system is a good way of improving the performance of a two-port probe. The previous rotating asymmetric calibration method (RACM) based on microstrip line measurements at two directions of 0° and 90° is limited to 12 GHz. In this article, a nonrotating asymmetric calibration method (NRACM) is proposed for ultrawideband calibration of a simultaneously near-field probing system. A four-port vector network analyzer and a highly symmetric grounded coplanar waveguide (GCPW) calibrator are used to solve the calibration matrix in the proposed method. It only needs to place the probe at one direction of 0° instead of measurements at two directions and uses the time-domain reflectometry (TDR) for localization of the probe loop. These simplified measurement steps in the proposed method reduce the impact of positioning error. The non-TEM effect is automatically avoided because of no 90° measurement. A highly symmetric ultrawideband GCPW calibrator without soldering is adopted to excite standard electromagnetic fields for calibration. The measurement results of standing waves demonstrate that the proposed method is suitable for asymmetric calibration at a frequency as high as 20 GHz.

13C surface characterization of midplane and crown collector probes on DIII-D

A dual collector probe system has been implemented on DIII-D for scrape-off-layer (SOL) impurity transport studies. These experiments injected isotopically enriched methane (13CD4) and sampled the impurities from this extrinsic, primary source with graphite collector probes at the outboard midplane and crown of upper single null L-mode plasmas. Using a stable isotopic mixing model, results suggest that 13C from methane injections prior to these experiments has built up on the walls of DIII-D to act as a secondary, intrinsic source of enriched 13C to the collector probes. This secondary source accounts for nearly 60% of the deposits on the midplane collector probes and nearly 90% of the deposition on the collector probes in the crown. These results lay the foundation for future impurity transport models and suggest that further simulation of impurity transport during the methane injection experiments will require two sources of enriched impurities in order to accurately model the SOL impurity profiles of 13C.

Rapid skin biomarker discovery using hydrogel-phase sampling followed by semi-automated liquid-phase re-extraction high-resolution mass spectrometry

A facile and rapid skin metabolomics protocol is proposed. The liquid microjunction-surface sampling probe system has been partly automated, and used in conjunction with hydrogel probes for skin metabolite analysis. A control device was built to precisely control the segmented solvent flow and analyte re-extraction into the liquid microjunction. This mode provides rapid online re-extraction of the analytes from hydrogel probes. Humectant was added to the hydrogel, and moist heat treatment was used to make the hydrogel probes rugged for sampling in the clinical setting. The developed method was validated for the analysis of choline – a putative biomarker of psoriasis. A linear relationship over six calibration levels from 3.18 × 10−5 to 3.18 × 10−4 mol m−2 has been obtained. The limit of detection was 6.6 × 10−6 mol m−2, while the recoveries range from 92 to 109%. The within-run and between-run precision were evaluated and the coefficients of variation range from 1.84 to 7.13%. Furthermore, the developed method has been used to screen patients (n = 10) and healthy participants (control group; n = 10) for psoriasis-related skin metabolites. Metabolomic profiling of the skin excretion-related signals identified potential biomarkers of psoriasis: choline, pipecolic acid, ornithine, urocanic acid, and methionine.

Integrated Probe System for Measuring Soil Carbon Dioxide Concentrations.

This article outlines the design and implementation of an internet-of-things (IoT) platform for the monitoring of soil carbon dioxide (CO2) concentrations. As atmospheric CO2 continues to rise, accurate accounting of major carbon sources, such as soil, is essential to inform land management and government policy. Thus, a batch of IoT-connected CO2 sensor probes were developed for soil measurement. These sensors were designed to capture spatial distribution of CO2 concentrations across a site and communicate to a central gateway using LoRa. CO2 concentration and other environmental parameters, including temperature, humidity and volatile organic compound concentration, were logged locally and communicated to the user through a mobile (GSM) connection to a hosted website. Following three field deployments in summer and autumn, we observed clear depth and diurnal variation of soil CO2 concentration within woodland systems. We determined that the unit had the capacity to log data continuously for a maximum of 14 days. These low-cost systems have great potential for better accounting of soil CO2 sources over temporal and spatial gradients and possibly flux estimations. Future testing will focus on divergent landscapes and soil conditions.

Channel Gap Measurements of Irradiated Plate Fuel and Comparison with Post-Irradiation Plate Thickness

One of the salient nuclear fuel performance parameters for new fuel types under development is changes in fuel thickness. To test the new commercially fabricated U-10Mo monolithic plate-type fuel, an irradiation experiment was designed that consisted of multiple mini-plate capsules distributed within the Advanced Test Reactor (ATR) core, the mini-plate 1 (MP-1) experiment. Each capsule contains eight mini-plates that were either fueled or “dummy” plates. Fuel thickness changes within a fuel assembly can be characterized by measuring the gaps between the plates ultrasonically. The channel gap probe (CGP) system is designed to measure the gaps between the plates and will provide information that supports qualification of U-10Mo monolithic fuel. This study will discuss the design and the results from the use of a custom-designed CGP system for characterizing the gaps between mini-plates within the MP-1 capsules. To ensure accurate and repeatable data, acceptance and calibration procedures have been developed. Unfortunately, there is no “gold” standard measurement to compare to CGP measurements. An effort was made to use plate thickness obtained from post-irradiation measurements to derive channel gap estimates for comparison with the CGP characterization.

Optically Controlling Broadband Terahertz Modulator Based on Layer-Dependent PtSe2 Nanofilms

In this paper, we propose an optically controlling broadband terahertz modulator of a layer-dependent PtSe2 nanofilm based on a high-resistance silicon substrate. Through optical pump and terahertz probe system, the results show that compared with 6-, 10-, and 20-layer films, a 3-layer PtSe2 nanofilm has better surface photoconductivity in the terahertz band and has a higher plasma frequency ωp of 0.23 THz and a lower scattering time τs of 70 fs by Drude-Smith fitting. By the terahertz time-domain spectroscopy system, the broadband amplitude modulation of a 3-layer PtSe2 film in the range of 0.1-1.6 THz was obtained, and the modulation depth reached 50.9% at a pump density of 2.5 W/cm2. This work proves that PtSe2 nanofilm devices are suitable for terahertz modulators.

Developing a Simple Scanning Probe System for Soft X-ray Spectroscopy with a Nano-focusing Mirror

Developing a Simple Scanning Probe System for Soft X-ray Spectroscopy with a Nano-focusing Mirror

Sensitive and selective impedimetric determination of TNT using RSM-CCD optimization

Detection of trace amounts of 2,4,6-Trinitrotoluene as a widely used explosive in the military and industrial sectors is of vital importance due to security and environmental concerns. The sensitive and selective measurement characteristics of the compound still is considered a challenge for analytical chemists. Unlike conventional optical and electrochemical methods, the electrochemical impedance spectroscopy technique (EIS), has a very high sensitivity, but it faces a significant challenge in that it requires complex and expensive steps to modify the electrode surface with selective agents. We reported the design and construction of an inexpensive, simple, sensitive, and selective impedimetric electrochemical TNT sensor based on the formation of a Meisenheimer complex between magnetic multiwalled carbon nanotubes modified with aminopropyl triethoxysilane (MMWCNTs @ APTES) and TNT. The formation of the mentioned charge transfer complex at the electrode-solution interface blocks the electrode surface and disrupts the charge transfer in [(Fe (CN) 6)] 3−/4- redox probe system. Charge transfer resistance changes (ΔRCT) were used as an analytical response that corresponded to TNT concentration. To investigate the influence of effective parameters on the electrode response, such as pH, contact time, and modifier percentage, the response surface methodology based on central composite design (RSM-CCD) was used. The calibration curve was achieved in the range of 1–500 nM with a detection limit of 0.15 nM under optimal conditions, which included pH of 8.29, contact time of 479 s, and modifier percentage of 12.38% (w/w). The selectivity of the constructed electrode towards several nitroaromatic species was investigated, and no significant interference was found. Finally, the proposed sensor was able to successfully measure TNT in various water samples with satisfactory recovery percentages.

Rapid and sensitive detection of methyl parathion in rice based on carbon quantum dots nano-fluorescence probe and inner filter effect

A highly sensitive fluorescent sensing system of novel carbon quantum dots nano-fluorescent probe based on corn stalks was established for the determination of methyl parathion by alkaline catalytic hydrolysis and inner filter effect mechanism. The carbon quantum dots nano-fluorescent probe was prepared from corn stalks using an optimized one-step hydrothermal method. The detection mechanism of methyl parathion was revealed. The reaction conditions were optimized. The linear range, sensitivity and selectivity of the method were evaluated. Under the optimal conditions, the carbon quantum dots nano-fluorescent probe exhibited high selectivity and sensitivity to methyl parathion, achieving a linear range of 0.005–14 µg/mL. The fluorescence sensing platform was applied to the detection of methyl parathion in rice samples, and the results showed that the recoveries range from 91.64 to 104.28 %, and the relative standard deviations were less than 4.17 %. The detection limit for methyl parathion in rice samples was 1.22 µg/kg, and the limit of quantitation (LOQ) was 4.07 µg/kg, which was very satisfactory.

Naphthalene and its Derivatives: Efficient Fluorescence Probes for Detecting and Imaging Purposes.

Naphthalene, white crystalline solid having polycyclic aromatic hydrocarbon with characteristic mothball order is naturally present in crucial oils of various plants. Naphthalene derivatives are extensive drug resources and are use as wetting agents, surfactants and as insecticides. These derivatives exhibit unique photo physical and chemical properties. These characteristics make them the most studied group of organic compounds. Naphthalene dyes have rigid plane and large π-electron conjugation. Therefor they have high quantum yield and excellent photostability. Naphthalene based fluorescence probes due to hydrophobic nature exhibit excellent sensing and selectivity properties towards anions and cations and also used as a part of target biomolecules. In conjugated probe system, introducing naphthalene moiety caused improvement in photo-stability. Therefore among various conjugated framework, naphthalene derivatives are considered excellent candidate for the construction of organic electronic appliances. These derivatives are useful for a variety of applications owing to their strong fluorescence, electroactivity and photostability. This article is based upon investigation of photophysical properties of naphthalene derivatives and fluorescence detecting probe of naphthalene. For photophysical properties the techniques under investigation are UV visible spectroscopy and fluorescence spectroscopy. Concentration dependent spectra and solvatochromic shifts on UV visible spectra are also part of discussion.

1H DOSY analysis of high molecular weight acrylamide-based copolymer electrolytes using an inverse-geometry diffusion probe

Copolymers of [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETAC) and acrylamide (AAm) (AETAC-co-AAm) are polyelectrolytes used as flocculants in wastewater purification. Diffusion-ordered two-dimensional NMR spectroscopy (DOSY) experiments for AETAC-co-AAm samples with Mw ranging from 1.9 to 3.9 million and a polyacrylamide sample with Mw of 1.3 million were carried out in pure D2O and in D2O containing 0.1 or 1 M NaCl using an inverse-geometry diffusion probe system. Projections of the DOSY contour plots onto the diffusion coefficient (D) dimension gave distributions of D for the AETAC and AAm units in the samples. The D values at the maximum point of the distribution (Dp) agreed fairly well with those determined by dynamic light scattering.

Focus on test, measurement, quantum metrology, and analytical equipment

Focus on test, measurement, quantum metrology, and analytical equipment