Sensitive Electrode Research Articles

Analytical Eco-Scale for Evaluating the Uniqueness of Voltammetric Method used for Determination of Antiemetic Binary Mixture Containing Doxylamine Succinate in Presence of its Toxic Metabolite

Green analytical procedures are gaining popularity in the pharmaceutical research area as a way to reduce environmental impact and improve analyst health safety. The current work presents a green and sensitive electrochemical carbon paste electrode that has been chemically modified with zirconium dioxide and multi-walled carbon nanotubes for estimation of pyridoxine HCl (PYR) and doxylamine succinate (DOX) using the square wave voltammetric technique. Under optimum conditions, the linearity ranges were 20.00–2000.00 ng mL−1 and 2.00–20.00 µg mL−1 for both drugs in the 1st linear segment and 2nd linear segment, respectively. Stability testing assesses how the quality of a drug substance changes over time, depending on environmental and laboratory factors. DOX was found to undergo oxidative degradation when refluxed for 7 h using 30% H2O2 and the degraded product (DOX DEG) (toxic metabolite) was successfully characterized utilizing LC–MS. The developed electrode showed selectivity for the determination of binary mixture in pure form, pharmaceutical form, and in the presence of DOX DEG and common interfering molecules with good recovery. The proposed method was found to be eco-friendlier than the reported method in terms of the use of hazardous chemicals and solvents, energy consumption, and waste generation.Graphical

Aminoxyl Catalyzed Electrochemical Ethanol Detection: Development of a New Breathalyzer Using Molecular Catalysis

Blood alcohol concentration (BAC) is the indicator of alcohol intoxication, and its measurement has emerged as the most common analytical procedure requested by law enforcement. Due to its volatility, ethanol vapor can be detected in breath, and its vapor concentration is proportional to BAC. Currently available instrumentation used for breath alcohol content (BrAC) analysis include gas chromatography (GC) and GC coupled with mass spectrometry, infrared (IR) spectroscopy, and fuel cell based electrochemical sensors. GC and IR spectroscopy devices have some drawbacks such as size, initial cost, and operational expense. Electrochemical sensors are capable of miniaturization and are available as portable and handheld breathalyzers. However, the lack of a single use and disposable sensing element, resulting memory effect and the need for frequent recalibration is the main drawback of currently available electrochemical breathalyzers. There have been few attempts at designing a sensing element to improve the current methods of alcohol detection by electrochemical techniques, all relying on enzymatic alcohol oxidation.1 Herein, we report a proof-of-concept non-enzymatic breathalyzer, harnessing the unique catalytic activity of the aminoxyl radical/oxoammonium redox couple toward alcohol oxidation.2 The relatively low redox potentials of aminoxyls, the mild conditions required for use, and their selective interactions with ethanol are their advantages compared to currently available Pt based breathalyzers. Our functional sensing element consists of a screen-printed electrode in which the graphene oxide-based working electrode is modified with aminoxyl derivatives, of which 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl benzoate (TMB) was the most efficient derivative. Exposing this modified electrode to simulated breath that contains ethanol, while applying the required potential for oxidation of the aminoxyl radical, generates an electrocatalytic current proportional to the ethanol concentration in the breath. These simple, sensitive, durable, and inexpensive electrodes may contribute to the development of a single-use reliable ethanol sensor for personal or law enforcement applications. Heikenfeld, J.; Jajack, A.; Rogers, J.; Gutruf, P.; Tian, L.; Pan, T.; Li, R.; Khine, M.; Kim, J.; Wang, J.; Kim, J. Wearable Sensors: Modalities, Challenges, and Prospects. Lab Chip 2018, 18, 217.Nutting, J. E.; Rafiee, M.; Stahl, S. S. Tetramethylpiperidine N-Oxyl (TEMPO), Phthalimide N-Oxyl (PINO), and Related N-Oxyl Species: Electrochemical Properties and Their Use in Electrocatalytic Reactions. Chem. Rev. 2018, 118, 4834.

Room-temperature gas sensor based on in situ grown, etched and W-doped ZnO nanotubes functionalized with Pt nanoparticles for the detection of low-concentration H2S

The direct in-situ growth of sensitive materials on the gas-sensing electrode is a subject of great interest for the gas-sensing field. However, combining the device design with the modification of materials is still of great challenge. Herein, a high-performance room-temperature gas sensor was constructed by functionalizing the in situ grown, etched and W-doped ZnO nanotubes (EW-ZnO NTs) with Pt nanoparticles (NPs) on new-type FTO gas-sensing electrode. The effect of etching treatment on the surface characteristics was adjusted by controlling the hydrothermal reaction time to obtain ZnO NTs with uniformly W-doped polycrystalline shells. The thus-produced EW-ZnO NTs sensor was found to be improved by 223 % in response to 10 ppm H2S at room temperature compared to the ZnO nanorods (NRs) sensor. Additionally, the effect of different Pt loading amounts on the gas-sensing performance of sensitive materials was investigated. Benefiting from the good contact of sensitive materials and gas-sensing electrodes, the formation of defects and the functionalization of noble metal Pt, the Pt@EW-ZnO NTs gas sensors exhibit numerous superior advantages, including high response, low detection limit (100 ppb) and excellent selectivity. This study shows that the gas detection capability of ZnO sensors can be significantly boosted with the in-situ growth, surface modification and noble metal functionalization, which brings insights into gas sensors.

A pH Sensing Pipette for Cross-Contamination Prevention in Industrial Fermentation

The iconic pipette is integrated with an electrochemical pH sensor for preventing cross-contamination while still enabling pH measurements in industrial fermentation reactors. Contamination is a big financial cost source of the fermentation industry and periodic parameter (such as pH, dissolved oxygen, temperature, etc.) measurements are crucial for a successful fermentation run. Yet, the very act of measuring poses contamination risks to the fermentation reactors. To resolve the dichotomy between the need for pH monitoring and cross-contamination prevention, we develop a pH sensing pipette (composed of an integrated electrochemical polyaniline-based pH sensitive electrode, flowcell, and readout circuit) with a disposable pipette tip for cross-contamination-free pH measurements. This pH sensing pipette achieves a system-level sensitivity of −134.8 mV/pH, a limit of detection of pH 0.029 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> , and an average response time of 2.6–6.0 s, which is good enough for pH measurements in industrial fermentation reactors. It is then demonstrated to monitor the pH of ethanol fermentation across two days successfully, implying that this device may be used to further prevent cross-contamination risks in industrial fermentation processes.

Disposable Paper-Based Biosensors: Optimizing the Electrochemical Properties of Laser-Induced Graphene

Laser-induced graphene (LIG) on paper substrates is a desirable material for single-use point-of-care sensing with its high-quality electrical properties, low fabrication cost, and ease of disposal. While a prior study has shown how the repeated lasing of substrates enables the synthesis of high-quality porous graphitic films, however, the process–property correlation of lasing process on the surface microstructure and electrochemical behavior, including charge-transfer kinetics, is missing. The current study presents a systematic in-depth study on LIG synthesis to elucidate the complex relationship between the surface microstructure and the resulting electroanalytical properties. The observed improvements were then applied to develop high-quality LIG-based electrochemical biosensors for uric acid detection. We show that the optimal paper LIG produced via a dual pass (defocused followed by focused lasing) produces high-quality graphene in terms of crystallinity, sp2 content, and electrochemical surface area. The highest quality LIG electrodes achieved a high rate constant k0 of 1.5 × 10–2 cm s–1 and a significant reduction in charge-transfer resistance (818 Ω compared with 1320 Ω for a commercial glassy carbon electrode). By employing square wave anodic stripping voltammetry and chronoamperometry on a disposable two-electrode paper LIG-based device, the improved charge-transfer kinetics led to enhanced performance for sensing of uric acid with a sensitivity of 24.35 ± 1.55 μA μM–1 and a limit of detection of 41 nM. This study shows how high-quality, sensitive LIG electrodes can be integrated into electrochemical paper analytical devices.

Voltammetric Electrochemical Behavior of Carbon Paste Electrode Containing Intrinsic Silver for Determination of Cysteine

In this paper, the electrochemical behavior of cysteine is described, using carbon paste electrodes (CPEs) modified with ternary silver-copper sulfide containing intrinsic silver at two pH values (pH 3 and 5). Experiments have revealed that presence of cysteine has a large impact on the electrochemical behavior of modified CPEs. Observed phenomena take place in solution, as well as at the surface of the modified CPEs, and can be applied for electroanalytical purposes. Based on the electrochemical behavior observed in the examined system, differential pulse voltammetry (DPV) was selected as an electroanalytical method for determination of cysteine. The effects of the various parameters on the electroanalytical signal, such as the amount of electroactive material, electroanalytical parameters, pH etc., were investigated using differential pulse voltammograms. The results indicated that electrochemical signal characterized with well-defined cathodic peak at 0.055 V vs. Ag/AgCl (3 M) in acetic buffer solution at pH 5 can be used for indirect electrochemical determination of cysteine. The optimization procedure revealed that the most sensitive and stabile electrode was that containing 5% modifier. The DPV response of the electrode, in the presence of cysteine, showed two different linear concentration ranges of 0.1 to 2.5 μM, and 5.6 to 28 μM. The explanation of the origin of two linear ranges is proposed. The lower concentration range was characterized by remarkable sensitivity of the 11.78 μA μM−1, owing to the chosen indirect method of determination. The calculated limit of detection (LOD), as well as limit of quantification (LOQ) were 0.032 and 0.081 μM, respectively. The influence of interfering agents on the electroanalytical response was examined, and low or no interference on the DPVs was observed. The proposed method was validated and applied for the determination of cysteine in pharmaceutical preparations with satisfactory recoveries in the range of 97 to 101.7%.

Roles of MXene in Pressure Sensing: Preparation, Composite Structure Design, and Mechanism.

Flexible pressure sensors are one of the most important components in the fields of electronic skin (e-skin), robotics, and health monitoring. However, the application of pressure sensors in practice is still difficult and expensive due to the limited sensing properties and complex manufacturing process. The emergence of MXene, a red-hot member of the 2D nanomaterials, has brought a brand-new breakthrough for pressure sensing. Ti3 C2 Tx is the most popular studied MXene in the field of pressure sensing and shows good mechanical, electrical properties, excellent hydrophilicity, and extensive modifiability. It will ameliorate the properties of the sensitive layer and electrode layer of the pressure sensor, and further apply pressure sensing to many fields, such as e-skin flexibility. Herein, the preparation technologies, antioxidant methods, and properties of MXene are summarized. The design of MXene-based microstructures is introduced, including hydrogels, aerogels, foam, fabrics, and composite nanofibers. The mechanisms of MXene pressure sensors are further broached, including piezoresistive, capacitive, piezoelectric, triboelectric, and potentiometric transduction mechanism. Moreover, the integration of multiple devices is reviewed. Finally, the chance and challenge of pressure sensors improved by MXene smart materials in future e-skin and the Internet of Things are prospected.

Modeling surface pH measurements of oocytes

The transport of gases across cell membranes plays a key role in many different cell functions, from cell respiration to pH control. Mathematical models play a central role in understanding the factors affecting gas transport through membranes, and are the tool needed for testing the novel hypothesis of the preferential crossing through specific gas channels. Since the surface pH of cell membrane is regulated by the transport of gases such as CO2 and NH3, inferring the membrane properties can be done indirectly from pH measurements. Numerical simulations based on recent models of the surface pH support the hypothesis that the presence of a measurement device, a liquid-membrane pH sensitive electrode on the cell surface may disturb locally the pH, leading to a systematic bias in the measured values. To take this phenomenon into account, it is necessary to equip the model with a description of the micro-environment created by the pH electrode. In this work we propose a novel, computationally lightweight numerical algorithm to simulate the surface pH data. The effect of different parameters of the model on the output are investigated through a series of numerical experiments with a physical interpretation.

New disposable ion-selective sensors for the determination of dabigatran etexilate: The oral anticoagulant of choice in patients with non-valvular atrial fibrillation and COVID-19 infection

Selective, sensitive, and reproducible ion-selective electrodes containing dabigatran etexilate- phosphotungstate ion pair as a modifier have been fabricated to determine dabigatran etexilate in pure and pharmaceutical dosage form. The modified electrodes ion selective carbon paste electrode and ion selective pencil graphite electrode showed fast and linear responsewithin a concentration range of 1.0 × 10−5to 1.0 × 10−2 M and 1.0 × 10−6to 1.0 × 10−2 M with a detection limit of 4.36 × 10−6 M and 4.26 × 10−7 M by ISCPE and ISGPE, respectively. Electrodes are selective to dabigatran etexilate over common excipients. The present study demonstrated the determination of dabigatran etexilate in pure and pharmaceutical dosage forms with high accuracy and precision.

Sleeping Heart Monitoring Using Hydrogel-Textile Capacitive ECG Electrodes

In the application on sleeping heart monitoring by using capacitive electrocardiogram (cECG), a raw cECG signal with high quality is usually difficult to be obtained due to the low coupling capacitance composed of human skin, pajamas, bed sheet and sensing electrodes. This is mainly caused by a low relative dielectric constant of bed sheet and pajamas. In order to overcome this challenge, this study proposed a cECG system containing hydrogel-textile electrode for sleeping heart monitoring. The hydrogel layer was applied in an array pattern onto conductive textile to become a sensitive electrode in order to increase the coupling capacitance and lower the equivalent impedance as well, which was helpful to improve the quality of raw cECG signals. The reference electrode was linked to the circuit of the signal acquisition circuit to decrease the common-mode noises. The system incorporates eight membrane pressure sensors to capture the body’s sleep postures and detect the cECG signals from different sleep postures. The experimental results on tests with three different human sleep postures showed that the signal-noise ratio of the proposed system was close to the wet-electrode based ECG system. The sleeping heart monitoring experiments were conducted involving eight subjects with no constraint conditions through a period of two hours, the R-wave of the cECG signal was analyzed using RR interval extraction algorithms and the heart rate (HR) was calculated. The results showed that all subjects’ HRs during sleep state falls into a normal range, indicating that no signs of tachycardia and bradycardia can be observed.

Highly Sensitive and Selective Chromium Oxide Nanoparticles Modified Carbon Paste Membrane Electrode to Determine Cr Concentration in Different Solutions

Highly Sensitive and Selective Chromium Oxide Nanoparticles Modified Carbon Paste Membrane Electrode to Determine Cr Concentration in Different Solutions

Effect of the Ni3TeO6 phase in a Ni2Te3O8/expanded graphite composite on the electrochemical monitoring of metribuzin residue in soil and water samples

Growing food demand and climate change have led to the development of various pest control agents to increase crop yields. Although pesticides help meet the food demand, they cause harm to human health and the environment. Metribuzin (MTBZ) is one of the common herbicides used for controlling weeds. Therefore, monitoring MTBZ residues in soil and water bodies is essential for decreasing risk to the environment and human health. This paper reports a highly selective and sensitive electrochemical sensor electrode based on a Ni3TeO6-phase-integrated Ni2Te3O8/expanded graphite (referred to here as NTO-eGR) composite for the detection of MTBZ. The NTO-eGR composite was prepared by a one-step low-temperature hydrothermal method and characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and electron microscopy techniques. The Ni3TeO6 phase was found to be an active component in the NTO/eGR composite, which exhibited satisfactory analytical performance in MTBZ detection with a sensitivity of 1.454 µA µM−1 cm−2. Moreover, the NTO-eGR electrode exhibited high selectivity to MTBZ even in the presence of a five-fold excess of interfering species in water and soil samples. The studies on practical applicability revealed that NTO-eGR exhibits good reproducibility with a relative standard deviation of 2.67% (n = 5). Moreover, good recoveries of greater than 90% were achieved in the determination of MTBZ in soil and water samples. Hence, the NTO-eGR sensor electrode is highly suitable for the rapid on-site determination of MTBZ.

An extremely sensitive carbon paste electrode modified with Prussian blue analogue (PbA @CPE) for the electrochemical determination of Tetramisole HCl anthelmintic drug as a food contaminant in beef cuts and infant formula milk powder

Tetramisole hydrochloride (TMS) - the drug of choice for ascariasis- is used as an anthelmintic. In this paper, both qualitative and quantitative determination of TMS in bulk, infant milk powder, and frozen cuts-up bovine meat samples were developed to provide consumersafety. In this paper, chemically modified carbon paste with Prussian blue analogue nanoparticles (PbA-NPs /CP) was developed for determination of TMS utilizing cylic voltammetry (CV), square wave voltammetry (SWV) and chronoamperometry methods. In this regard, Prussian blue analogue (PbA) was synthesized by the chemical co-precipitation route. XRD technique was used for crystal structure analysis indicating that the fabricated nanopowder belongs to a cubic structure with lattice constants a=b=c=10.176AThe grain size was estimated approximately equal 20 nm, and the dislocation density was 25×10-4nm-2. The molecular structure was analyzed using Raman spectroscopy, and the elements C, N, O, Co, Ni, Cr, Ir were recorded by EDX spectrum. SEM images showed the particles very fine in spherical shape. Transmittance and reflectance spectra have been measured through wavelength range from 200 nm to 900 nm.Energy gap (Eg) and refractive index (n) of the films were determined suggesting the strong optical absorption. Finally, this method was carried out at pH 4.0 within a linearity range (10.0 × 10−9–1.0 × 10−4) M and a minimum detection limit of 2.7 × 10−9M.

Sensitive, Highly Stable, and Anti-Fouling Electrode with Hexanethiol and Poly-A Modification for Exosomal microRNA Detection

It remains a huge challenge to integrate the sensitivity, stability, reproducibility, and anti-fouling ability of electrochemical biosensors for practical applications. Herein, we propose a self-assembled electrode combining hexanethiol (HT), poly-adenine (poly-A), and cholesteryl-modified DNA to meet this challenge. HT can tightly pack at the electrode interface to form a hydrophobic self-assembled monolayer (SAM), effectively improving the stability and signal-to-noise ratio (SNR) of electrochemical detection. Cholesteryl-modified DNA was immobilized at the electrode through the hydrophobic interaction with HT to avoid the competition between the SAM and the DNA probe on the gold site. Thus, the assembly efficiency and uniformity of the DNA probe as well as the detection reproducibility were increased remarkedly. Poly-A was added on the HT assembled electrode to occupy the unreacted sites of gold to further enhance the anti-fouling ability. The combination of HT and poly-A allows the electrode to ensure favorable anti-fouling ability without sacrificing the detection performance. On this basis, we proposed a dual-signal amplification electrochemical biosensor for the detection of exosomal microRNAs, which showed excellent sensitivity with a detection limit down to 1.46 aM. Importantly, this method has been successfully applied to detect exosomal microRNA-21 in cells and human serum samples, proving its potential utility in cancer diagnosis.

A dual-functional flexible sensor based on defects-free Co-doped ZnO nanorods decorated with CoO clusters towards pH and glucose monitoring of fruit juices and human fluids

Herein, ZnO nanorods were doped with Co and decorated with CoO clusters through an in situ technique to create a CoO/Co-doped ZnO (CO/CZO) heterostructure at low temperatures (150 °C) on a flexible PET substrate. In the CO/CZO heterostructure, the Co dopant has a low energy barrier to substitute Zn atoms and adsorb over oxygen atoms and their vacancies. Therefore, it decreased the charge density (ND = 2.64 × 1019 cm−3) on non-active sites of ZnO and lowered the charge transfer resistance (317 Ω) at Co-doped-ZnO/electrolyte interface by suppressing the native defects and reducing the Schottky barrier height (− 0.35 eV), respectively. Furthermore, CoO clusters induced a p-n heterostructure with Co-doped ZnO, prevented corrosion, increased the active sites for analyte absorption, and increased the ultimate tensile strength (4.85 N m−2). These characteristics enabled the CO/CZO heterostructure to work as a highly sensitive, chemically stable, and flexible pH and glucose oxidation electrode. Therefore, CO/CZO heterostructure was explored for pH monitoring in human fluids and fruit juices, demonstrating a near-Nernst-limit pH sensitivity (52 mV/pH) and fast response time (19 s) in each human fluid and fruit juice. Also, it demonstrated high sensitivity (4656 µM mM−1 cm−2), low limit of detection (0.15 µM), a broad linear range (0.04 mM to 8.85 mM) and good anti-interference capacity towards glucose-sensing. Moreover, it demonstrated excellent flexibility performances, retained 53% and 69% sensitivity of the initial value for pH and glucose sensors, respectively, after 500 bending, stretching, and warping cycles.Graphical

Blocker displacement amplification mediated PCR based screen-printed carbon electrode biosensor and lateral flow strip strategy for CYP2C19*2 genotyping

Single nucleotide variants in CYP2C19*2 are associated with clopidogrel resistance in coronary heart disease. In order the guidance the dosage of drug and personalized medicine, blocker displacement amplification was first used to specific amplify G site and A site alleles. For electrochemical strategy, forward primers were labeled electrochemical active methyl blue and ferrocene, generates signals on −0.26 for G site and 0.22 V for A site. For lateral flow strip assay, primers with specific modification were used to generates unique color in test line 1 for G site and test line 2 for A site. In conclusion, we developed a sensitive screen-printed carbon electrodes based electrochemical sensor and gold nano particle based lateral flow strip assay strategy to successfully genotyping CYP2C19*2 GG, GA and AA genotype. The proposed method can realize CYP2C19*2 analysis from multiple biological samples including whole blood, buccal swab, saliva and hair root, and showed good consistency with Sequencing. Due to the fact our proposed strategy merely relies on thermal cycler instrument and visual strip detection, this platform shows great potential in source-limited regions genotyping.

Role of hydrogen sulfide in sulfur dioxide production and vascular regulation.

Both hydrogen sulfide (H2S) and sulfur dioxide (SO2) are produced endogenously from the mammalian metabolic pathway of sulfur-containing amino acids and play important roles in several vascular diseases. However, their interaction during the control of vascular function has not been fully clear. Here, we investigated the potential role of H2S in SO2 production and vascular regulation in vivo and in vitro. Wistar rats were divided into the vehicle, SO2, DL-propargylglycine (PPG) + SO2, β-cyano-L-alanine (BCA) + SO2 and sodium hydrosulfide (NaHS) + SO2 groups. SO2 donor was administered with or without pre-administration of PPG, BCA or NaHS for 30 min after blood pressure was stabilized for 1 h, and then, the change in blood pressure was detected by catheterization via the common carotid artery. Rat plasma SO2 and H2S concentrations were measured by high performance liquid chromatography and sensitive sulfur electrode, respectively. The isolated aortic rings were prepared for the measurement of changes in vasorelaxation stimulated by SO2 after PPG, BCA or NaHS pre-incubation. Results showed that the intravenous injection of SO2 donors caused transient hypotension in rats compared with vehicle group. After PPG or BCA pretreatment, the plasma H2S content decreased but the SO2 content increased markedly, and the hypotensive effect of SO2 was significantly enhanced. Conversely, NaHS pretreatment upregulated the plasma H2S content but reduced SO2 content, and attenuated the hypotensive effect of SO2. After PPG or BCA pre-incubation, the vasorelaxation response to SO2 was enhanced significantly. While NaHS pre-administration weakened the SO2-induced relaxation in aortic rings. In conclusion, our in vivo and in vitro data indicate that H2S negatively controls the plasma content of SO2 and the vasorelaxant effect under physiological conditions.

The fabrication of an innovative extremely sensitive nano green carbon paste electrode amended with the nanocomposite CuO/Y for electrochemical quantification of amprolium in sheep meat and liver samples

In this work, carbon paste electrode (CPE) and modified CPE with copper oxide or copper yttrium oxide were prepared for determining amprolium hydrochloride (AMP) by differential pulse voltammetry. AMP has an antiprotozoal activity for treating coccidiosis in poultry; their retaining- in sheep meat and livers- induces adversative effects for the customer. XRD pattern was employed to define the fabricated nanostructured materials; the elemental composition of the nanocomposite was examined using EDX spectra. Over a pH ranging from 2 to 8, the oxidation process of AMP was studied using phosphate buffer. The scan rates were studied over a wide range (20 to 140 mV s−1) using cyclic voltammetry. The developed sensor shows a wide linear range (1.0 × 10−8–1.0 × 10−3 M) with a detection limit of 2.32 × 10−9 M. This method can quantify AMP in pharmaceutical form, sheep meat, and liver samples.

Salivary fluoride concentration following toothbrushing with and without rinsing: a randomised controlled trial

BackgroundCaries prevalence has declined significantly since the introduction of fluoridated toothpaste. There have been several developments regarding specific active fluoride ingredients but not enough evidence to support one over the other. The purpose of this double-blind randomized controlled trial was to compare salivary fluoride concentrations of different fluoride formulations in the form of toothpaste with and without post-brushing water rinsing in adults.MethodsThe study included 120 participants who were randomly assigned to one of 12 groups (10 participants/group). The toothpaste formulas investigated included (1) fluoride-free (0 ppmF); (2) sodium fluoride (1450 ppmF); (3) sodium monofluorophosphate (1450 ppmF); (4) sodium fluoride and monofluorophosphate combined (1450 ppmF); (5) stannous fluoride and sodium fluoride combined (1450 ppmF); and (6) amine fluoride (1400 ppmF). Block randomisation was used to assign each participant to one of the 12 groups. Participants brushed with 1.0 g of one of the six different toothpaste formulations either with or without post-brushing water rinsing. Saliva was collected at six different times (baseline and at 1, 15, 30, 60, and 90 min/s post-brushing). Samples were analysed using a fluoride ion-specific sensitive electrode connected to an ion analyser.ResultsThe demographic characteristics of the participants were not significantly different among the groups (P > 0.05). Time, toothpaste formulation, and post-brushing rinsing routines had significant effects on saliva fluoride retention (P < 0.05). Amine fluoride-containing toothpaste was the only formula that showed statistically significantly higher concentrations of salivary fluoride at 90 min in both the rinsing and non-rinsing groups. Sodium monofluorophosphate toothpaste did not result in a significant difference compared to the control group at any time point, in both rinsing and non-rinsing groups.ConclusionsBased on the results from this study, no rinsing after toothbrushing in adults can be recommended when sodium monofluorophosphate containing toothpaste formula is used. It also concludes that amine fluoride resulted in a significantly higher saliva fluoride concentration at 90 min in both the rinsing and non-rinsing groups compared to other fluoride toothpaste formulations.Registry: Protocol Registration and Results System (ClinicalTrials.gov).Clinical trial registration number: NCT02740803 (15/04/2016).

A thermal conductivity sensor based on mixed carbon material modification for hydrogen detection.

In order to overcome the many shortcomings of traditional hot-wire thermal conductivity sensor design, a new design method was proposed in which a graphene-composite carbon nanotube mixed carbon material was used as a thermal conductivity sensor carrier instead of nano-alumina particles. Taking advantage of the large specific surface area and high thermal conductivity of graphene, as well as the characteristics of a large number of gas transport channels modified by carbon nanotubes, a high-efficiency gas heat exchange medium is made. In order to improve the consistency of the product, electrochemical preparation of an aluminum oxide film material is used to make the chip substrate of the thermal conductivity sensor by MEMS process technology, and the heating sensitive electrode of the sensor is made by a thick film process. Experiments show that the sensor prepared by this method has high sensitivity and zero point stability and has greatly improved the detection accuracy and response time. The sensitivity of the sensor to hydrogen detection increases to 3.287 mV/1%H2, and the response time is shorter than 5.4s. The research results have good application prospects.