AbstractDiode laser-based light sources allow the implementation of features to meet specific application requirements. Besides output power and specific wavelength, this can also include spectral tunability, an alternating operation between two different wavelengths, or a well-defined parallel operation at two wavelengths. Potential applications involve spectroscopic systems and applications, e.g., in Raman spectroscopy, especially shifted excitation Raman difference spectroscopy (SERDS) or sequentially shifted Raman spectroscopy, absorption spectroscopy, or the generation of THz radiation. To meet these demands, diode laser based light sources often use a multi-contact layout. Their operation may require multiple individually adjustable current sources, adjustable galvanically isolated current sources, regulated temperature stabilization and heat removal. Moreover, an interface, e.g., a fiber coupling unit is required to transfer the laser light to the experiment. In this paper, a compact turnkey system is reported meeting these requirements with up to 10 current sources, 2 galvanically isolated current sources, integrated temperature control and an interface for laser light transfer is presented. The system has dimensions of 177 mm × 124 mm × 48 mm and is controlled via a standard USB interface. It additionally provides a synchronization signal for implementation into multi-instrument setups. The current sources are based on implemented dual continuous wave p-type laser diode drivers. Ten current sources with 750 mA enabling switching frequencies up to 1000 Hz and four galvanically isolated current sources with 2 W are available. For temperature control, a TEC controller is used. An effective cooling system allows 10 W of thermal load to be removed. The integration of this turnkey-system into a portable shifted excitation Raman difference spectroscopy sensor system is briefly presented as an example application.

AbstractDuring zeolite synthesis, exploring the growth of nanoparticles is crucial for studying the crystallization mechanism. Synchrotron radiation small angle X-ray scattering (SAXS) is a powerful technique for the in-situ characterization of zeolite crystallization. Herein, a microreactor was developed for use at the Beijing Synchrotron Radiation Facility (BSRF) to achieve the in-situ SAXS characterization of the nucleation and growth of zeolite crystallization. The results show that the fractal structure convert from surface fractal during induction nucleation to mass fractal during crystal growth. The surface fractal dimension first fluctuated slightly and increased rapidly, while the mass fractal dimension gradually increased, reflecting the particle growth. This work provides important information for further exploring zeolite crystallization.

AbstractA microfluidic platform is reported that utilizes magnetophoresis for the sequential and automated extraction of nucleic acid from biological samples. The system incorporates multiple microfluidic chips to process biological samples and extract nucleic acid using magnetic bead separation. The design is detailed, highlighting its efficiency and functionality. The injection pumps play a vital role in nucleic acid extraction by loading samples, cell lysis fluid, and magnetic nanoparticles into the microfluidic chips. These pumps enable the precise delivery of the required substances, allowing for efficient and effective extraction of nucleic acids. One embodiment of the microfluidic automated system provides a circuit design and implementation method. The programmable, fully automated system integrates various sensors and electronic components to enable efficient execution of the extraction process for multiple biomedical samples. The microfluidic system adopts a sequential automated process, enabling rapid delivery and minimizing the risk of sample contamination.

AbstractEmitted X-ray energies, line shapes, fluorescence yields, absorption probabilities and absorption edges of the elements are X-ray fundamental parameters that are of practical significance because they facilitate compositional analysis of complex materials. They are also a potent test of atomic theory. The chemical effects may cause changes in the energy of the X-ray lines and line shapes, such as the full width at half maximum and asymmetry index values depending on the chemical state of the substance. Although these effects vary for each element, the causes of these differences have been investigated. In this study, changes in chemical action values of lanthanide group compounds were investigated using a single crystal wavelength dispersive X-ray spectrometer equipped with a rhodium anode X-ray tube. The Ll and Lη X-ray emission lines are characterized by fitting of the Lorentz function. The chemical shift was investigated according to the chemical bond type, molecular structure, and oxidation number.

AbstractHere is reported an adaptive polymerase chain reaction (PCR) temperature control algorithm based on improved hybrid fuzzy proportional integral derivative (PID) control. The algorithm adopts fuzzy control in the rapid temperature changing stage for monitoring and reduces the overshoot. In the constant temperature stage, the PID controller's initial parameters are automatically calculated online through the relay self-tuning algorithm. The output of the system is pre-compensated by feedforward compensation algorithm, and adjusted by the variable universe fuzzy PID algorithm, which avoids the explosion of fuzzy rules to a certain extent. The experimental results show that the average heating rate of the improved hybrid fuzzy PID control algorithm is 4.2 °C/s, with an average cooling rate is 3.2 °C/s. The system stabilizes within 5 s with a maximum overshoot of less than 1.2 °C and a static error of ± 0.1 °C at various ambient temperatures.

AbstractIn small angle X-ray scattering (SAXS) experiments, there exists an optimal sample thickness to obtain measurements with the maximum signal-to-noise ratio and best statistics. In practice, the sample thickness may deviate from the optimal value due to certain conditions. For thick samples, smearing may appear for the scattering data and an equivalent sample position to compute the scattering vector. Calculations show that the sample thickness has a similar effect on SAXS for monodisperse and polydisperse systems. Qualitative and quantitative analysis has been performed to determine the deviation of equivalent sample position from the irradiated sample center.

AbstractA double-sided photonic crystal fiber (PCF) temperature and refractive index (RI) sensor based on surface plasmon resonance (SPR) is reported to simultaneously measure temperature and RI. An arc groove covered with gold is filled with chloroform for temperature detection. The D-shaped plane coated with silver is in direct contact with the analyte to provide the RI. Two independent channels distinguish temperature and RI changes, thus completely solving the cross-sensitivity problem. The sensing characteristics of the plane coating, arc coating, and inner ring coating are discussed. The influence of gold film closure on the optimum RI measurement range was identified, and the best sensing structure of chloroform as a temperature-sensitive material is obtained. The sensing characteristics of different types of metal films are investigated. It is concluded that the band separation may be achieved by plating gold film and silver film in the arc groove and D-plane, respectively. The influence of the central angle of the arc groove on the sensor characteristics was investigated. High-order resonance may be avoided at a 180° center angle. The influence of the thickness of the metal film on the sensitivity of the sensor is studied numerically, and the optimal coating thickness is 50 nm. This work simplifies the selection of the RI range of sensing materials and provides a new approach to solve the high-order resonance and band interference in SPR multi-parameter sensors.

AbstractAlternating current (AC) and direct current (DC) magnetic fields are monitored by an optical whispering gallery mode (WGM) microcapillary resonator filled with magnetostrictive material. The DC magnetic field is demodulated with the signal-to-noise ratio of an AC-modulated magnetic field at a particular frequency and a sensitivity of 2.1 dB/mT is obtained across a detection range of 0.9 mT. An AC field sensitivity of 2.08 μT/Hz−−−√ Hz Hz at 346 kHz is obtained with the same resonator. Introducing a biased DC field of 90Gs provides a four-fold improvement in AC field sensitivity. The AC and DC fields may be used to improve the corresponding DC and AC sensing. Therefore, this scheme may play a role monitoring magnetic fields in defence, biomedical analysis, and consumer electronics.

AbstractThe rapid industrialization of nations in Southeast Asia (SEA) has led to a decline in these countries’ air quality, including high levels of particulate matter (PM). Monitoring these air pollutants is crucial to understanding the pollution status of the area and developing management plans for improvement. The metrological conditions in the region present challenges as high temperature and high humidity have been known to cause errors in the measurements. This study investigated the performance of five PM monitoring instruments with different working principles. The air temperature was mostly over 25 °C with relative humidity usually remaining above 80%, which is typical of SEA weather. Measurements from all instruments had good correlations with each other as their linear regressions yielded slopes of 1 ± 0.15 and R2 > 0.65. Moreover, this study found that depending on the chosen reference instrument, not all factors affect the devices equally. In particular, using Partisol as a reference, the PM2.5 concentration, air temperature, and relative humidity had less impact upon the relative bias level compared to using Leckel as a reference. In addition, the high cost of monitoring instruments also poses financial constraints on how many monitoring stations can be deployed. To tackle this issue, this study presents ManPMS whose design is based on that of the USEPA Title 40 Part 50 with slight modifications. The cost to manufacture and assemble the instrument was only 2/3 the price of a typical instrument with similar performance.

AbstractA surface plasmon resonance based fiber optic sensor is presented experimentally using silver and nickel oxide layers. The sensitivity analysis of the sensor has been carried out. Also, the influence of the nickel oxide layer thickness upon the sensitivity has been examined. The sensitivity is enhanced with the increase in thickness of nickel oxide layer up to 10 nm and decreased at larger values. The sensor composed of 40 nm silver-10 nm nickel oxide layers provides the highest sensitivity.

AbstractRapid and easy detection of pathogens, especially bacteria, plays an important role in daily life in the face of increasing environmental pollution. Nanosensors focus on carbon nanotubes, which can bind various molecules to large surfaces and have high electron conductivity. They are widely used in the development of electrochemical biosensors. In this study, a new design of electrochemical biosensors is presented by integrating gold-coated tungsten wires (GC-TW) and acid-functionalized multi-walled carbon nanotubes (MWCNTs) in a two-step coating process. GC-TWs are coated with acid-functionalized short MWCNTs. Fourier transforms infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) results show efficient immobilization of the electrodes. The performance for Escherichia coli (E. coli) K-12 is evaluated based upon the change in current following antibody-antigen interactions. Bioimpedance measurements are performed from 50 Hz to 10 MHz to achieve optimal coverage of impedance changes. The measurements show that the electrode has a detection limit of 0.8 CFU/mL. The response of the electrode saturates when the bacterial concentration is increased to 1.70 x 102 CFU/mL. The biosensor is capable of detecting E. coli between 0.8 and 1.70 × 102 CFU/mL. The data show that this MWCNT-based biosensor can be developed into a highly sensitive device for E. coli.

AbstractIn order to solve the problem that the optical fiber surface plasmon resonance (SPR) sensor is insufficiently sensitive for biomolecule detection, a novel sensing probe was proposed and designed, where the semiconductor material α-Fe2O3 was introduced for the first time. The α-Fe2O3 with high refractive index enhances the electric field and evanescent field depth at the interface between the α-Fe2O3 film and the ambient medium, resulting a sensitive performance. The characteristics of the sensors with gold film and α-Fe2O3 film at different thicknesses were analyzed and compared by finite element method. The thicker the α-Fe2O3 film, the higher the sensitivity. When the thickness of gold nanofilm is 50 nm and the thickness of α-Fe2O3 nanofilm is 20 nm, the highest figure of merit (FOM) is 50.98 RIU−1, corresponding to a sensitivity of 4800 nm/RIU, which is 2.16 times more sensitive than the traditional SPR sensor. In addition, three α-Fe2O3 film thickness-assisted SPR sensors were successfully prepared with the highest sensitivity of 4173.1 nm/RIU, which is nearly two times higher than without the α-Fe2O3 film. The enhancement after introducing α-Fe2O3 nanofilms and its promising application in the field of biosensing were confirmed through experiments and simulations.

AbstractToday packaging waste is a prevalent issue due to the increase in deliveries from online shopping. Here a new approach to this issue of cardboard box packaging waste is proposed by adapting an image processing algorithm based on camera vision-based measurement that computes the optimal cuboid bounding algorithm of irregular shape products. The end result is utilized so that packaging workers select the appropriate product box. This approach may also be used as a preliminary process to optimize the packaging of many products into a single cardboard box. The system setup with two cameras is prepared to capture the overhead and sideview images, estimating the box’s width, depth, and height in pixels. This system may then evaluate feasible cuboids that minimize waste, in which the traditional Otsu’s thresholding method, proposed Otsu’s scheme, and 1-D gradient means are utilized to avoid inaccuracies created by shadows. Calibration is performed with a Rubik’s cube to convert the measurement from computer simulations to real-life dimensions. The computer simulations from the overhead and sideview images compared to the actual bounding box of the object show that the proposed algorithm yields superior performance by reducing the area error of the bounding box (%) of an overhead image and the height error (%) of a sideview image than the conventional Otsu’s method.

AbstractIt is important to classify coal in the industry to improve its utilization. Herein, coal classification was performed using laser-induced breakdown spectroscopy (LIBS) combined with K-nearest neighbor (KNN) chemometrics. The principal component analysis was used to determine the optimum component of the original data. Eight elements (Al, Fe, Ca, Na, Mg, Si, Ti, and K) were selected as the indices for coal classification, while 11 elements were further divided into four categories as indicators for coal classification using the KNN model. The standard coal samples were divided based upon the ash and volatile values and the elemental content. The results were satisfactory, achieving an optimum accuracy of 97.73%. In contrast to traditional methods, LIBS significantly reduced the analysis time, simplified the process, and maintained high accuracy.

AbstractAlthough the synthesis of nanoparticles (NPs) by low-pressure plasma-based sputtering onto liquids offers many advantages as compared to classic wet-chemistry-based approaches, not much is known about the nanoparticle formation mechanism in these conditions. Here, we report about an operando absorption spectrophotometry setup which allows recording time- and space-resolved spectra of the liquid into which the sputtered metal atoms are incorporated. The measurements are carried out during the plasma treatment but also afterward while keeping the sample inside the vacuum chamber. The device capabilities therefore allow studying the evolution of unstable systems, i.e., combination of sputtered atoms and host liquids for which aggregation may appear even during the plasma treatment time. As a model system, silver atoms are deposited onto a silicone oil which may be stirred or not. Our operando analysis provides qualitative and quantitative data and highlights that the nanoparticle formation and aggregation dynamics vary according to the process conditions.

AbstractThere is a growing demand for a flexible, precise calibration facility for aerosol monitoring instruments. This study investigated ManDust11 ManDust is an exclusively registered design under the Project "Research and Manufacture Standardized Aerosol System for Verification / Calibration of Ambient Air Monitoring Instrument" signed between the Vietnam Ministry of Natural Resources (MONRE) and Environment and Vietnam Center for Research and Technology Transfer (CRETECH)., an aerosol calibration facility that is compatible with a variety of different operating principles. The facility comprises four systems: (a) a clean air supply system, (b) an aerosol generator system, (c) a diffuser tower, and (d) a sampling system. A compact and modular diffuser tower provides turbulence flow to homogeneously mix the injected aerosol before collection by custom-made isokinetic sampling probes. The velocity profile in the diffuser tower was computed and measured to be turbulent, generating a well-mix aerosol condition with spatial homogeneity of 4.38% across all sampling locations. A computational fluid dynamics (CFD) simulation conducted to confirm the dimension of the facilty was able to generate turbulence flow and mixing. The facility stably provided aerosols from 0 to 10 µm with variable concentrations from a few µg/m3 to 1000 µg/m3. The uncertainty budget in this study was calculated to be 5.98% when the facility was operated at 600 µg/m3 (95% confident level), and span drift was calculated to be 3.15% after 120 h of measurement.

AbstractComprehensive analytical validation studies of a developed ion molecule reaction – mass spectrometer (IMR-MS) were undertaken for the real-time determination of volatile organic compounds (VOCs) in air. The instrument was developed with a focus on promoting chemical ionization (CI) in the reaction chamber by direct sample loading and enhancing maintenance efficiency and reliability of the results. Instrument stability was assessed through a system check and pre-performance check process, and consequently, the instrumental and analytical conditions including the plasma generation, pressure, temperature, and flow rate were successfully optimized. Relevant performance characteristics, such as mass resolution, mass detection range, accuracy, and precision were also investigated by VOC standards composed of benzene, toluene, perfluorotoluene, propylbenzene, and octane. To evaluate whether the performance of the technology is comparable to already accepted techniques, the quantitative results of the IMR-MS were compared with those of a commercial mass spectrometer. This evaluation was successful and suggests the applicability of the technology for spillage accidents of hazardous chemicals and identification of odor-causing substances as well as for real-time gas analysis.

AbstractA temperature-compensated direct current (DC) magnetic field sensor based on a whispering gallery mode (WGM) microcapillary resonator is described in which both temperature-compensation and magnetic field sensing is realized by resonant wavelength difference in two high-order modes. A simulation and experimental results verified that the temperature response of the sensor is significantly reduced using the resonant wavelength difference between two high-order optical modes. In addition, the magnetic field response of resonant wavelength difference between two high-order optical modes was characterized. The results show that the resonant wavelength difference first blue-shifted and subsequently red-shifted as the magnetic field strength increased to provide DC magnetic field sensitivities of −0.03 and 0.01 pm/Oe from 34.79 to 62.56 Oe and 62.56 to 181.012 Oe, respectively. This temperature-compensated DC magnetic field sensor is anticipated to applications for current and rotation angle detection.

AbstractInstrumentation is reported for measuring electromotive force (EMF) from a high-impedance solid electrolyte-based electrochemical cell. Generally, concentration galvanic cells are used to study the high-temperature thermochemical properties of materials. The thermochemical results are determined by precise measurement of the high-impedance EMF and temperature of the electrochemical cell with suitable user interface software for data acquisition. The data are conditioned and processed using the unique design of the hardware and sent to a computer through the serial port. Online graphical displays of the data, averaging, trend viewing, and storage, are performed using a graphical user interface (GUI). The instrumentation was validated by conducting experiments with different materials using an electrochemical cell and its performance was demonstrated to be on par with commercial instruments. This work has enables low-cost sophisticated EMF measurements for determining the thermochemical properties of materials.

AbstractLiquid delivery and endpoint determination during titrations may be problematic if an analyst does not have adequate training or formal education. This can lead to issues with method accuracy and precision. This work is focused on the development of a simple, low-cost, automated system capable of performing potentiometric titrations with a push of a button. A single-board computer (Raspberry Pi), a stepper motor-based syringe pump, and a commercially available pH sensor circuit board were the primary components used to construct the auto-titrator system. Open-source Python programming language was used to control and coordinate components and provide a simple-to-use graphical user interface. A standard alkalinity method for drinking and raw water was evaluated and yielded an accuracy (recovery) between 92% and 104% for concentrations above 10 mg L−1. The precision of the method was less than 5% regardless of concentration. The developed titrator was tested at Lebanon, TN, and Woodruff, SC water treatment plants. The system was also certified by LabtronX to perform alkalinity measurements in Lebanon, TN, and served the plant operators for the past two years.