Glass Electrode Research Articles

Charge Regulation during Amyloid Formation of α-Synuclein.

Electrostatic interactions play crucial roles in protein function. Measuring pKa value perturbations upon complex formation or self-assembly of e.g. amyloid fibrils gives valuable information about the effect of electrostatic interactions in those processes. Site-specific pKa value determination by solution NMR spectroscopy is challenged by the high molecular weight of amyloid fibrils. Here we report a pH increase during fibril formation of α-synuclein, observed using three complementary experimental methods: pH electrode measurements in water; colorimetric changes of a fluorescent indicator; and chemical shift changes for histidine residues using solution state NMR spectroscopy. A significant pH increase was detected during fibril formation in water, on average by 0.9 pH units from 5.6 to 6.5, showing that protons are taken up during fibril formation. The pH upshift was used to calculate the average change in the apparent pKaave value of the acidic residues, which was found to increase by at least 1.1 unit due to fibril formation. Metropolis Monte Carlo simulations were performed on a comparable system that also showed a proton uptake due to fibril formation. Fibril formation moreover leads to a significant change in proton binding capacitance. Parallel studies of a mutant with five charge deletions in the C-terminal tail revealed a smaller pH increase due to fibril formation, and a smaller change (0.5 units on average) in the apparent pKaave values of the acidic residues. We conclude that the proton uptake during the fibril formation is connected to the high density of acidic residues in the C-terminal tail of α-synuclein.

Clay minerals affect calcium (magnesium) carbonate precipitation and aging

The effects of pre-existing mineral phases on the nucleation and growth of calcium carbonates from solution are relatively poorly understood, despite the widespread co-occurrence of carbonate minerals with clays and other silicates in rocks, soils, and sediments. Previous studies suggested that sheet silicates template calcite nucleation. Moreover, the presence of certain clay minerals appeared to enhance Mg2+ incorporation, resulting in Mg-bearing calcite or protodolomite. Here, we present the results of titration experiments with an environmentally relevant experimental setup, designed to study the roles of swelling clay minerals in the formation of Mg-bearing CaCO3 phases. We added both Mg-free and Mg-rich calcian solutions to carbonate buffers both in the presence and absence of smectite, and monitored the evolution of the solutions with pH and Ca ion selective electrodes, in order to identify nucleation and phase transition events. Initial products of the titration experiments were aged in their mother solutions for a few months. Both freshly formed and aged materials were studied using a variety of transmission electron microscopy (TEM) techniques. From Mg-free, homogeneous solutions vaterite was the first phase to precipitate. The addition of smectite triggered nucleation at lower supersaturation and generated calcite rather than vaterite. In Mg-rich solutions, aragonite was the first phase to precipitate both without and with clay minerals, and precipitation occurred at similar saturation levels in both samples. In the presence of clays, however, the aragonite nanocrystals were attached to smectite flakes. After the Mg-bearing systems were aged for several months, peculiar assemblages of protodolomite and low-magnesian calcite formed in association with smectite, whereas in the clay-free systems aragonite persisted. These observations suggest that if smectite is present in an environment where carbonates precipitate, the clay mineral has important and complex roles in the formation of Mg-bearing calcium carbonate phases. In addition to enhancing the nucleation of the first carbonate solid, smectite also triggers the formation of calcite-type structures, both at nucleation and in dissolution/reprecipitation reactions during aging.

Coastal Surveillance and Water Quality monitoring in the Rejiche Sea-Tunisia.

The aim of this study is to determine physiochemical and bacteriological properties of seawater and sediments from the coast of Tunisia during six successive months. The conductivity was measured using previously calibrated Hach Conductivity meter. Total suspended solid was determined using Whatman GF/C glass fiber filter (Sigma Aldrich), and the turbidity was assessed using a spectrophotometer (UV/Vis). The pH was measured using pH electrodes. Other physiochemical parameters were determined using Pastel UV multiparameter water analyzer (Secomam, aqualabo). Bacterial analysis was displayed by membrane filtration method, and isolates were identified to the species level by Api strips. Susceptibility to antibiotics was determined by disk diffusion methods. Total suspended solid, turbidity, adsorbable organic halogen, chemical oxygen demand, and biochemical oxygen demand were higher than accepted norms in Tunisia. Enterococcus faecalis was detected in all the sites indicating a human fecal contamination, and all the isolates were highly resistant to rifampicin, gentamicin, chloramphenicol, ampicillin, and azithromycin. The situation in Mahdia coast is alarming particularly with the isolation of multidrug resistance strains. It is recommended that the local government provide restrict policies for the treatment and the assessment of municipal wastewater before its discharge into sea. PRACTITIONER POINTS: Coastal Surveillance and Water Quality monitoring in the Rejiche Sea - Tunisia is crucial. Enterococcus faecalis was detected in sea water and sediment samples in the coast of Rejiche. Isolated strains were highly resistant to rifampicin, gentamicin, chloramphenicol, ampicillin and azithromycin.

Development of a high‐throughput method for examining bacterial supernatant pH using ratiometric UV‐VIS spectrophotometry

Background Bacterial supernatant pH measurements are highly relevant to downstream applications, such as organoid or cell line treatment, mass spectrometry, and metabolic analysis. Although high-throughput systems have been implemented for examining bacterial growth, high-throughput systems for measuring bacterial supernatant pH are lacking. The traditional method for measuring the solution pH of bacterial supernatants uses pH meters and electrodes. However, this method is not compatible with high throughput approaches which employ microplate readers. While fluorescent dyes can be used to measure solution pH, bacterial media is highly auto-fluorescent, making this system incompatible for microbial analysis. To overcome these limitations, we have developed a simple, high-throughput assay to measure bacterial supernatant pH using ratiometric UV-VIS spectrophotometry and phenol red, the pH indicator dye contained in the medium DMEM. Phenol red exhibits a gradual transition from yellow to fuchsia from acid to basic solution pH, respectively. The aim of this study was to develop a high-throughput and accessible method to monitor pH changes in multiple samples using a standard microplate reader. Methods & Results As a proof of concept, we prepared a series of solutions with pHs that ranged from 3 to 10 in DMEM and DMEM containing a fully defined bacterial media, termed ZMBI, at a ratio 3:1. UV-VIS spectral analysis of phenol red from 350-750 nm confirmed the reported wavelengths for the isosbestic point - a specific wavelength at which the total absorbance of an indicator dye remains consistent – and the wavelength of maximum absorption (λmax) to be 470 and 560 nm, respectively. Calibration curves generated by the ratio of these two wavelengths (560 nm/470 nm) revealed a sigmodal curve, which could be fit by a four-parameter logistics curve. To test the ability of this system to correctly calculate pH, commensal gut microbes Lactobacillus reuteri and Escherichia coli were grownin ZMBI overnight anaerobically and aerobically, respectively. A comparison between standard pH electrode analysis and our newly developed wavelength analysis revealed similar calculated pHs. To generate a high-throughput system, L. reuteri and E. coli were grown in 1 mL of ZMBI in DeepWell microplates overnight. To examine bacterial growth, 100 µL of culture was transferred to flat bottomed 96-well microplates and optical density was measured at OD600nm. For pH analysis, a 200-µL volume of culture was transferred to round bottomed 96-well plates, centrifuged and cell-free supernatant was blended with ZMBI at a 3:1 ratio. Back calculated solution pH values using the sigmodal calibration curve yielded similar results to the pH electrode values. Conclusions We have successfully employed DMEM's phenol-red dye, which is well suited for a colorimetric assay, to study bacterial supernatant pH. This method allows for rapid and accurate pH measurement which can be easily be applied to multiple organisms and adapted to several downstream applications.

9‐1: Fabrication of Lateral Crystal Si on Cu Bottom‐Gate Structure via Blue‐Laser Diode Annealing (BLDA)

We report that Si lateral crystal is fabricated on bottom gate cupper electrode with having no crack and ablation of the electrode by blue laser diode annealing (BLDA). In CW laser annealing, the long irradiation time and wide beam width induce some damage to glass substrate, electrode and membrane, so our research adopted a narrow beam size (33 μm × 8.25 μm) and fast scanning speed (over 500 mm/s) in order to reduce the amount of generated thermal in annealing. In our presentation, evaluation of Si crystals fabricated on Cu electrodes, cross‐section SEM results indicating no metal damage and relationship between laser irradiation time and the damage are discussed. Our BLDA system can realize high TFT mobility and which is composed of inexpensive beam heads, therefore it is expected to be applied to Mini LED back light and OLED etc.

A selective voltammetric pH sensor using graphitized mesoporous carbon/polyaniline hybrid system

Development of a new pH sensor system, which is simple to prepare, sensitive, selective and workable with low volume, is demanding research in biomedical and environmental studies. In the literature, organic molecules like methylene blue, toluidine blue, hydroquinone, catechol, anthraquinone and polyaniline-based redox probes have been widely used for this purpose. In general, these redox probes have easily interfered with common biochemicals such as dopamine, ascorbic acid, NADH, H2O2, cysteine, hydrazine, and some transition metal ions, etc., and in turn to marked potential and current drifts (pH-false positive response). In this work, a highly redox-active, stable and interference-free redox polymer based on poly(4-chloroaniline) (PANI(4-Cl)) modified graphitized mesoporous carbon (GMC), designated as GMC@PANI(4-Cl), has been prepared using 4-chloroaniline as a monomer in pH 7 phosphate buffer solution. The new redox polymer system showed a distinct redox peak at Eo’= 0.15 V vs Ag/AgCl with a stable voltammetric response. Transmission electron microscope analysis of the redox polymer composite had shown adhesion of black polymeric solid due to polyaniline like the molecular system as a surface layer on the GMC material. The constructed calibration plot was linear in the pH window 2-11 with a slope and regression values − 58 mV pH−1 and 0.9997, respectively. The GMC@PANI(4-Cl) modified electrode showed a sensitive and selective pH monitoring without any interference from the common biochemicals as listed above. As a practical application, pH sensing of commercial pH solutions, undiluted urine and saliva samples were demonstrated. Also, a three-in-one screen-printed carbon modified GMC@PANI(4-Cl) was explored for pH monitoring of a bacterial (E.coli) growth, which showed a comparable response with the conventional pH electrode.

Recording and Simulating Proton-Related Metabolism in Bacterial Cell Suspensions

Proton release and uptake induced by metabolic activities were measured in non-buffered cell suspensions by means of a pH electrode. Recorded data were used for simulating substrate turnover rates by means of a new freeware app (proton.exe). The program applies Michaelis-Menten or first-order kinetics to the metabolic processes and allows for parametrization of simultaneously ongoing processes. The simulation includes changes of the transmembrane ΔpH, membrane potential and ATP gains, and demonstrates the principles of chemiosmotic energy conservation. In our experiments, the versatile sulfate-reducing bacterium Desulfovibrio desulfuricans CSN (DSM 9104) was used as model organism. We analysed sulfate uptake by proton-sulfate symport, scalar alkalinization by sulfate reduction to sulfide, as well as nitrate and nitrite reduction to ammonia, and electron transport-coupled proton translocation. Two types of experiments were performed: In oxidant pulse experiments, cells were kept under H2, and micromolar amounts of sulfate, nitrate or nitrite were added. For reductant pulse experiments, small amounts of H2-saturated KCl were added to cells incubated under N2 with an excess of one of the above-mentioned electron acceptors. To study electron-transport driven proton translocation, the membrane potential was neutralized by addition of KSCN (100 mM). H+/e– ratios of electron-transport driven proton translocation were calculated by simulation with proton.exe. This method gave lower but more realistic values than logarithmic extrapolation. We could verify the kinetic simulation parameters found with proton.exe using series of increasing additions of the reactants. Our approach allows for studying a broad variety of proton-related metabolic activities at micromolar concentrations and time scales of seconds to minutes.

Statistical variation in Soil Nutrient Characteristics near Industrial Area of Mayiladuthurai Taluk of Mayiladuthurai District in Tamilnadu, India

Surface soil samples were collected from the 0-50 centimeter depth and assessed the soil statistical variation in physico-chemical parameters. The soil grain class of the surface layer is (0-58 centimeter) of the shape. Soil samples of the experimental field were clay loam while it was clay for the subsurface (25-100 Centimeter) layers of the profile. The soil samples were air-dried, crushed and passed through a 2 mm sieve before analyzing it for Nitrogen, Phosphorus, Potassium, Organic Carbon, Organic Matter, pH and exchangeable bases. Soil pH was measured electrometrically with a glass electrode pH meter, EC was determined are by using Conductivity meter. Alkaline permanganate method, colorimetric method and Flame Photometer method is used to determine Macronutrients like N P and K. Walkley and Black method is used to determine Organic Carbon (OC) and Organic Matter (OM). While the SAR, ESP% and Cation Exchange Capacity (CEC) were calculated. Micronutrients like Zinc(Zn), Copper(Cu), Iron(Fe) and Manganese(Mn) were determined by using Atomic Absorption Spectrophotometer (AAS). Available Soil pH ranged between 7.3 to 7.9. The available Electrical Conductivity (EC) values ranged from 0.18 to 0.5dsm-1 within the range for optimal growth of plants. The ranges of available Organic Carbon are ranged between 0.23% and 0.36%, Organic matter content ranged between 0.46 and 1.11 %. Nitrogen 39.2 kg/ha-1 and 72.8 kg/ha-1 are lower than that of the control soil. Available Phosphorus is ranged between 30.00 kg/ha-1 and 67.5 kg/ha-1 and is slightly higher than that of the control soil and potassium 169 kg/ha-1 and 370 kg/ha-1 content were high respectively. Cu is available between 0.72 – 0.92 ppm and Cu was found in 100% sufficient in study area. Zn is noticed between 0.62-0.82 ppm and Zn was found in 100% deficient in study area. Mn is available between 1.18-3.92 ppm and Mn was found in 70.0% deficient and 30.0% sufficient in study area. The available concentration of Fe ranged between 3.09-4.88 ppm and Fe was found in 100% sufficient in the study area. Where all below the recommended limits. Our aim is to support the farmers to characterize the soil based on their nutrition status for best suited crops which can be used effectively for crop production and enhanced productivity [1]. The statistical variation in soil nutrition is focused in Mayiladuthurai taluk in the present study at industrial based agriculture land area of Mayiladuthurai taluk in Mayiladuthurai district. The recommendations of fertilizer can be made for the crops to enhance the productivity. Soil test assessed and recommends the application of balanced fertilizers would go a long way in enhancing soil fertility and productivity.

Photoelectrochemical Reduction of CO2 at Poly(4‐Vinylpyridine)‐Stabilized Copper(I) Oxide Semiconductor: Feasibility of Interfacial Decoration with Palladium Cocatalyst

Poly(4‐vinylpyridine)‐modified copper(I) oxide photocathodes, bare or decorated with palladium nanoparticles, can be used for the visible‐light‐driven selective reduction of CO2, mostly to methanol and carbon monoxide (in the absence of Pd cocatalyst) or formic acid and carbon monoxide (in the presence of Pd cocatalyst). The photocathode materials, which are composed of hierarchically deposited (onto transparent fluorine‐doped conducting glass electrode) Cu2O (inner layer) and poly(4‐vinylpyridine) (P4VP) polyelectrolyte film (outer‐layer), with or without dispersed Pd nanoparticles, have been fabricated and examined using electrochemical methodology, atomic force microscopy, and various spectroscopic techniques, including the Raman approach. While the physicochemical characteristics of Cu2O, including the oxide identity and its semiconducting properties, are not largely affected by the interfacial modification with P4VP, the photostability of the hybrid photocathode is significantly improved. The P4VP‐modified Cu2O exhibits reasonable durability during photoelectrochemical reduction of CO2 upon illumination with sunlight in semi‐neutral medium (Na2SO4). While Cu2O can be identified using Raman spectroscopy as the sole bulk component of the semiconducting film, the XPS data imply that the Cu2O surface is likely to be partially reduced during prolonged operation. Introduction of palladium cocatalyst seems to improve distribution (collection and transport) of photoelectrons at the photoelectrochemical interface and affects the CO2‐electroreduction mechanism.

Probing the Influence of Counter Electrode Structure on Electrochromic‐Device Operating Potentials and Performance Using Electrochemical Impedance Spectroscopy

AbstractThe paper reports a general methodology for the rational tuning and optimization of electrochromic devices (ECDs) that are based on a monolayer of Fe (II) (4’‐(4‐pyridyl)‐2,2’:6’,2”‐terpyridine)2 complex (Fe 4’T) covalently embedded onto a screen‐printed high‐surface area indium tin oxide working electrode. We demonstrate that the nature of the counter electrode and the resulting device configuration could drastically improve the long‐term stability of the ECD. We show that the replacement of the flat ITO glass electrode with a high surface area ITO electrode or the use of symmetrical working and counter electrode architecture leads to a much longer performance of the device. We propose a methodology to determine optimal operating conditions for ECDs by fine‐tuning the lower and upper operation potentials. In addition to using traditional cyclic voltammetry (CV), we utilize electrochemical impedance spectroscopy (EIS) to study the intrinsic properties of the devices and understand the factors that define the long‐term cycling stability, which is further described through the use of equivalent circuit models. The main reasoning behind decomposition processes in ECDs and ways to suppress them are discussed.

Preference of Proteomonas sulcata anion channelrhodopsin for NO3\u2212 revealed using a pH electrode method

Ion channel proteins are physiologically important molecules in living organisms. Their molecular functions have been investigated using electrophysiological methods, which enable quantitative, precise and advanced measurements and thus require complex instruments and experienced operators. For simpler and easier measurements, we measured the anion transport activity of light-gated anion channelrhodopsins (ACRs) using a pH electrode method, which has already been established for ion pump rhodopsins. Using that method, we successfully measured the anion transport activity and its dependence on the wavelength of light, i.e. its action spectra, and on the anion species, i.e. its selectivity or preference, of several ACRs expressed in yeast cells. In addition, we identified the strong anion transport activity and the preference for NO3− of an ACR from a marine cryptophyte algae Proteomonas sulcata, named PsuACR_353. Such a preference was discovered for the first time in microbial pump- or channel-type rhodopsins. Nitrate is one of the most stable forms of nitrogen and is used as a nitrogen source by most organisms including plants. Therefore, PsuACR_353 may play a role in NO3− transport and might take part in NO3−-related cellular functions in nature. Measurements of a mutant protein revealed that a Thr residue in the 3rd transmembrane helix, which corresponds to Cys102 in GtACR1, contributed to the preference for NO3−. These findings will be helpful to understand the mechanisms of anion transport, selectivity and preference of PsuACR_353.

Experimental and Computational Studies on the Electrochemical Behavior of Carvacrol and Menthol

In this study, the effects of solvent on the electrode potentials of menthol and carvacrol species were investigated experimentally and computationally and their antioxidant properties were compared in different solvents by calculating the half-wave potential E1/2 of species, Vand Dissociative Energy (BDE), Ionization Energy (IE), and Electron Affinity (EA). Electrochemical behavior of menthol and carvacrol species in four solvents (MeOH, EtOH, DMSO, and Heptane) were studied using cyclovoltametric technique in a glass electrode as a working electrode and the calculations for obtaining the electrode potential were performed using DFT functional including B3LYP with 6-311+G(d,p)basis set and PCM and IEFPCM models for calculation of solvent energy. Finally, the results were compared and confirmed by experimental methods. Where in the compound carvacrol represent more properties antioxidant than menthol due to lower values E1/2 in gas and solution phases. Also, the lower BDE in the gas phase is 80.19 kcal/mol compared with menthol (98.91 kcal/mol). Moreover, compound carvacrol has the IE value of 1.12 eV smaller than menthol and has the EA value of 0.35 eV higher than menthol. Calculations show that the model had no effect on computational results. Also, according to the results, the antioxidant properties of carvacrol in non-polar solvents were higher due to the smaller amount of E1/2.

Effect of Electrode Material on the Removal of Industrial Oil and Soap Wastewater Using Electrocoagulation Process

Treatment of oil and soap industrial wastewater using aluminum and iron electrode material has been investigated in this study to compare for each electrode, the performance of the electrocoagulation process. The effectiveness of relevant industrial wastewater characteristics such as the chemical oxygen demand (COD) and oil-grease removal effects of major operating parameters such as medium pH value, electrode material, and current density, and running time and energy consumption were studied. All experiments were done in an electrocoagulation cell with an effective volume of 500 mg/ liters. Under the same operating conditions, it was observed that aluminum electrodes have higher efficiency of removal than iron electrodes. COD and O&G removal efficiencies of 94.93%, 90.20% and 27.49%, 13.27% were observed for aluminum and iron electrode in a special case with optimum initial pH value, maximum current density, time, and initial COD concentration equal to 3, 73.33 A/m2, 30 min, 19750 mg/l, respectively. The electrode energy consumptions for each electrode material have been calculated to be 1.68, 3.04 KWh/kg COD for Aluminum and iron respectively at 15 volts. It can be concluded that the electrocoagulation process using aluminum electrodes is efficient for COD and O&G removal from industrial wastewater

Modulation of ruminal pH, milk fat secretion, and biohydrogenation intermediates by alkalizing agents in dairy cows fed starch-rich diets

We aimed to evaluate the effects of magnesium-based supplements and NaHCO3 on ruminal fermentation parameters, milk fatty acid (FA) profile, and milk fat synthesis in dairy cows fed high-starch diets. Eight second-lactation Holstein dairy cows (4 ruminally-cannulated) averaging 97 ± 12 days in milk and 33 ± 2.5 kg/d of milk were assigned to a replicated 4 × 4 Latin square design with 21-d periods. Cows were fed the following isoenergetic diets (1.64 Mcal/kg DM): (1) the control [342 g/kg starch on dry matter (DM) basis] without any buffering or alkalizing agent, (2) the control plus 8 g/kg DM NaHCO3, (3) the control plus 4 g/kg DM MgO, and (4) the control plus 8 g/kg DM CaMg(CO3)2. Ruminal pH was continuously measured for 72-h in each period using indwelling pH electrodes. Mean ruminal pH was not affected by treatments, but the duration of ruminal pH below 5.8 was shorter (P < 0.01) in cows fed NaHCO3, MgO, or CaMg(CO3)2 diets compared with those fed the control whereas NaHCO3 was more effective than magnesium-based supplements. Similar ability observed for CaMg(CO3)2 and MgO with respect to the duration of ruminal pH below 5.8 responses. The ruminal molar proportion of acetate and acetate-to-propionate ratio was greater (P < 0.05) with magnesium-based supplements and NaHCO3 compared with the control diet. However, the ruminal propionate concentration decreased (P = 0.02) with magnesium-based supplements and NaHCO3 versus the control. The milk proportion and yield of trans-10 C18:1 and total trans-FA dropped and the trans-10/trans-11 C18:1 ratio decreased further, when cows were fed magnesium-based supplements and NaHCO3 compared with the control diet (P < 0.01). Also, adding NaHCO3, MgO, or CaMg(CO3)2 significantly increased yields of trans-11 C18:1 (P < 0.01), de novo (P < 0.01), mixed (P = 0.04), and also preformed FA (P < 0.01) compared with the control diet. The yields of milk, 3.5% fat-corrected, and energy-corrected milk increased (P < 0.01) in cows fed magnesium-based supplements and NaHCO3 due to the improved concentration of milk fat. Overall, supplementing NaHCO3, MgO, and CaMg(CO3)2 in a high-starch diet appears to promote milk fat output by modulating diurnal ruminal pH and ruminal volatile fatty acids profile in dairy cows. Also, it can be concluded that CaMg(CO3)2 has similar ability of MgO in promoting milk fat synthesis and alleviating the time ruminal pH remains below 5.8. Therefore, CaMg (CO3)2 can be used effectively as an alkalizing agent in dairy cow diets containing high-starch and helps to reduce the costs of consumption of the most popular dietary buffers or alkalizers such as NaHCO3 and MgO.

Using glass defect engineering to obtain order–disorder transformation in cathode for high specific capacity lithium ion battery

Vanadium-based glass shows high electronic conductivity without grain boundaries. It easily undergoes structural microcrack defects during fabrication using the melt-quenching method resulting in voids that affect its properties. This paper demonstrates that the cathode material obtained by nanocrystals precipitated by long-cycle electric fields are identical with those obtained by the heat treatment method. V2O5-Li3PO4 (VP) glass precipitates nanocrystals of Li3P and Li0.3V2O5 under heat treatment at 340 °C. It showed a prominent specific capacity of 269.4 mAh.g−1 in the first cycle at a current density of 50 mA.g−1, and 227.4 mAh.g−1 after 50 cycles with a retention rate of 86.3%, as the cathode of a lithium ion battery. Thermal field-controlled VP glass allows selective crystallization of nanocrystal of Li3P and Li0.3V2O5, which promote conductivity and charge transfer and significantly enhance the electrode reaction kinetics. Through ex-situ TEM, DSC, XRD and XPS, it was observed that discharge/charge caused disordered transitions in the amorphous VP, leading to the formation of nanocrystals of Li3P and Li0.3V2O5 after 100 cycles. Amorphous glass electrode material as a high-energy unstable state, has same tendency of precipitation of crystals to become stable under different treatment methods with long electric field cycles and thermal field induction.

A new MRPC prototype with diamond-like-carbon coated glass electrodes

The Multi-gap Resistive Plate Chamber (MRPC) has been used in many high energy physics and nuclear experiments in the last decade, such as ALICE [1] and STAR [2]. Normally, the MRPC is built with commercial floating glass (bulk resistivity ρ≈ 1012Ω· cm), which limits the rate capability to less than 1 kHz/cm2. In modern high energy physics, with the increase of colliders beam energy and luminosity, the rate capability of MRPC has to be enhanced accordingly. One normal way is to decrease the bulk resistivity ρ of the resistive plate, as the low resistive glass developed by Tsinghua University for the CBM experiment [3]. Alternatively, the surface of the electrode is also a possible path for the neutralization of the avalanche charges. Recently, we managed to carry this method out by coating a Diamond-Like-Carbon (DLC) layer on the surface of the floating glass. The DLC layer, realized by the magnetron sputtering method, has very good physical and chemical stability. The demanded surface resistivity can be achieved easily. A series of DLC-coated glasses with different resistivity has been tested in our lab. We have also made some MRPC prototypes and tested them with cosmic rays. Some preliminar results, including the operating current, the efficiency and the time resolution, have been achieved. More research is ongoing to improve the design and performance of this new method of increasing the rate capability of MRPC.

A DNA-Based MRI Contrast Agent for Quantitative pH Measurement.

Extracellular pH is important in clinical measurements due to its correlation to cell metabolism and disease progression. In MRI, T1/T2 ratiometric analysis and other methods have been previously applied to quantify pH using conventional pulse sequences. However, for nanoparticle-based approaches, heterogeneity in size and surface functionalization tends toward qualitative rather than quantitative results. To address this limitation, we developed a novel DNA-based MRI contrast agent, pH-DMRCA, which utilizes a highly programmable and reproducible nanostructure. The pH-DMRCA is a dendritic DNA scaffold that is functionalized with a pH-responsive MRI-sensitive construct, Gd(NP-DO3A), at the end of each DNA arm. We first evaluated the r1 and r2 response of our pH-DMRCA over a range of pH values (pH = 5-9) to establish a relaxometric model of pH. These MRI-based assessments of pH were validated in a separate set of samples using a pH electrode (n = 18) and resulted in a good linear correlation (R2 = 0.99, slope = 0.98, intercept = 0). A Bland-Altman analysis of the results also showed reasonable agreement between the calculated pH and measured pH. Moreover, these pH comparisons were consistent across three different pH-DMRCA concentrations, demonstrating concentration-independence of the method. This MRI-based pH quantification methodology was further verified in human blood plasma. Given the versatility of the DNA-based nanostructures, the contrast agent has a potential to be applied to a wide variety of imaging applications where extracellular pH is important including cancer, stroke, cardiovascular disease, and other important diseases.

Self-Powered Electrochromic Readout of Potentiometric pH Electrodes.

An absorbance-based colorimetric sensor array that is self-powered by an ion-selective electrode (ISE) in a short-circuited cell is presented. As the cell voltage is maintained at zero, the potential at the ISE serves as the power generator to directly transfer its power to a potential-dependent Prussian blue (PB) film in contact with an electrolyte solution in a separate detection compartment. This allows one to activate the color change of the PB film without the need for an external power supply. The potential of the PB detection element is optimized to change color between 50 and 250 mV (vs Ag/AgCl). Because the potential originates at the ISE, it is proportional to the ion activity in the sample in agreement with the Nernst equation. In this way, a higher cation activity in the sample generates a more positive potential, which enhances the PB absorbance that serves as the analytical signal. A self-powered optical sensor array coupled to poly(vinyl-chloride)-based pH electrodes based on two different ionophores is utilized here as a model. The measuring range is tuned chemically by varying the pH of the inner filling solution of each ISE, giving a measuring range from pH 2 to 10.5. As the optical sensor is driven by a potentiometric probe, the sensor output is independent of solution ionic strength. It is successfully applied for quantitative analysis in unmodified turbid/colored samples that included red wine, coke, coffee, baking soda, and antacid. The colorimetric output correlates well with the reference method, a calibrated pH electrode. Compared to earlier systems where the cell potential is dictated by an external power source, the PB film exhibits excellent reproducibility and a rapid response time of about 44 s.

Electrocatalytic Properties of a Novel β-PbO2/Halloysite Nanotube Composite Electrode

To improve the efficiency of electrochemical degradation of wastewater, lead dioxide was synthesized by a hydrothermal method with low cost, simple operation, and high conversion rate. β-PbO2/HNT composites were prepared by a hydrothermal method with Halloysite nanotubes (HNTs) and β-PbO2. The PbO2/HNT/ITO electrode was prepared by modifying the β-PbO2/HNT composite on an indium tin oxide (ITO) conductive glass electrode. The morphology of the material was characterized by scanning electron microscopy and transmission electron microscopy. The electrochemical performance of the electrode was measured by cyclic voltammetry, the galvanostatic charge–discharge method, and the AC impedance method. Electrolysis of typical dye wastewater by electrochemical oxidation was carried out. The effect of electrochemical degradation of wastewater with new electrodes was investigated and the degree of electrodes falling off was compared. The solubility of electrodes was investigated by inductively coupled plasma mass spectrometry lead element analysis of wastewater. The results showed that the β-PbO2/HNT electrodes were prepared successfully and had good charge–discharge performance and lifetime. The removal rate of electrolytic dye wastewater was 85.86%, and the degradation effect was better than that of pure PbO2 electrodes. In this work, a new type of β-PbO2/HNT/ITO electrode has been prepared, which improved the degradation efficiency of wastewater and opened up the prospect of HNT application.

Revamping a Classic Analytical Chemistry Laboratory Experiment to Improve Student Understanding of Chemical Analysis, Method Development, Validation, and Statistics

We have revamped a classic analytical chemistry laboratory experiment, “Determination of an Unknown Acid”, to provide students an opportunity to learn about new advances in the material sciences and their applications in analytical chemistry in an effort to reinforce the key concepts of chemical analysis. Specifically, students were given the opportunity to develop their own low-cost, low-maintenance, ease-of-use, multidimensional pH sensor with intrinsically conducting polyaniline material. The students tested their polyaniline pH sensor against the traditional glass pH electrode to determine an unknown acid concentration and performed statistical tests to validate the analytical capabilities of their electrochemical polyaniline pH sensor. Thus, the revamped laboratory experiment allows for the reinforcement of several fundamental analytical chemistry lecture concepts, including chemical analysis, method development, validation, and statistical practice utilizing a more cohesive hands-on laboratory learning approach. Furthermore, this revamped lab gives students the opportunity to evaluate and compare the analytical performance of the polyaniline pH sensor, such as its sensor lifetime against the glass pH electrode, and learn polyaniline’s electrochromic properties. This laboratory experiment can be easily disseminated to advance the objective of analytical curriculum, provide students an opportunity for multidimensional learning and well-connected critical thinking in analytical chemistry, and stimulate students’ creativity in developing next generation analytical sensor technology.