Quartz Crystal Microbalance Measurements Research Articles

Cholesterol- and ssDNA-binding fusion protein-mediated DNA tethering on the plasma membrane.

DNA modification of the plasma membrane is an excellent approach for controlling membrane-protein interactions, modulating cell-cell/cell-biomolecule interactions, and extending the biosensing field. The hydrophobic insertion of DNA conjugated with hydrophobic anchoring molecules is utilized for tethering DNA on the cell membrane. In this study, we developed an alternative approach to tether DNA on the plasma membrane based on ssDNA- and cholesterol-binding proteins. We designed a fusion protein (Rep-ALOD4) composed of domain 4 of anthrolysin O (ALOD4), which binds to cholesterol in the plasma membrane, and a replication initiator protein derived from porcine circovirus type 2 (Rep), which forms covalent bonds with single-stranded DNA (ssDNA) with a Rep recognition sequence. Rep-ALOD4 conjugates ssDNA to Rep and binds to the plasma membrane via cholesterol, thus tethering ssDNA to the cells. Quartz crystal microbalance measurements showed that membrane cholesterol binding of Rep-ALOD4 to the lipid bilayer containing cholesterol was accelerated above 20% (w/w) cholesterol in the lipid bilayer. Rep-ALOD4 was conjugated to fluorescein-labeled ssDNA (S-FITC-Rep-ALOD4) and used to treat human cervical tumor HeLa cells. The green signal assigned to S-FITC-Rep-ALOD4 was detected along HeLa cells, whereas diminished by cholesterol removal with methyl β-cyclodextrins. Moreover, ssDNA-conjugated Rep-ALOD4 tethered ssDNA-conjugated functional proteins on the HeLa cell plasma membrane via complementary base pairing. Collectively, Rep-ALOD4 has the potential as an ssDNA-tethering material via plasma membrane cholesterol to extend cell surface engineering.

A High‐Performance Miniaturized Frequency Shift Detection System for QCM‐Based Gravimetric Sensing

AbstractMicro‐gravimetric sensors, such as quartz crystal microbalance (QCM) are capable of detecting trace substances and even single nanoparticles in various fields due to their high sensitivity, selectivity, and stability. As a resonant sensor, the detection response of QCM requires frequency analysis instruments with high precision like a frequency counter and a vector network analyzer to measure its frequency shift during mass sensing. However, such bulky and high‐cost instruments undoubtedly hinder the applications of QCM‐based sensors outside the laboratory such as in situ and portable detection. In this paper, a high‐performance miniaturized frequency shift detection system based on a phase‐locked loop (PLL) circuit, is developed for QCM measurement. The designed system achieves high detection sensitivity of frequency shift as 1.859 mV Hz−1 with the Allan deviation of 0.49 mV at 0.15s and frequency resolution of 0.26 Hz, which is conducive to achieving the detection of trace substance by QCM. The excellent measuring performance is further validated by measuring the frequency response of QCM during mass sensing in a gaseous environment and aqueous solution. As a result, compared with a commercial frequency counter, the superior linearity and accuracy of over 98.4% were confirmed with a mean relative error (MRE) of less than 0.92%.

Study on Adsorption and Desorption Mechanism of CuO Particles on the Post-CMP Wafer Surface of Multi-Layered Copper

In the process of chemical mechanical polishing (CMP), the removal of surface pollution contamination on the wafer surface is an urgent problem to be solved, and the CuO removal is important for the cleaning after CMP. In this paper, a new type of alkaline cleaning solution based on composite complexing agent was proposed for CuO particles removal. The optimal concentration of the cleaning solution was explored using static corrosion rate and electrochemical quartz crystal microbalance measurements. When the components were 200 ppm FA/OII chelating agent and 0.1 vol% ammonium citrate, CuO residue on copper surface can be effectively removed. It can be confirmed that CuO cleaning depends mainly on the complexation of composite complexing agent. Scanning electron microscopy showed that a lower surface roughness was obtained after cleaning. X-ray photoelectron spectroscopy and UV–vis measurements confirmed that the synergistic effect of FA/OII chelating agent and ammonium citrate could effectively remove copper oxide contamination on the surface. The ratio of copper oxide on copper surface after CMP decreased significantly to 8.86%.

Charge-Discharge Behavior of NMC111 Cathode in Aqueous Zinc Battery

Currently, aqueous zinc batteries (AZBs) with zinc anode and aqueous electrolyte are focused on as one of the post-lithium-ion batteries because they can be a safe and inexpensive energy storage device. To date, a number of compounds, such as manganese oxide, vanadium oxide, Prussian blue analogues, and so on, have been investigated as cathode materials for AZBs. Although these materials are promising, suitable materials for cathode are still being studied for practical use. A variety of charge-discharge mechanisms are found in cathode of AZBs, which is influenced by many factors such as the composition, crystal structure, and morphology of the compounds used. Therefore, it is essential to understand the reaction mechanism to study new AZB systems.Previously, we investigated the applicability of Li(Ni0.33Mn0.33Co0.33)O2 (NMC111) as a cathode for AZBs1. In the report, it is found for the first time that NMC111 can be used as an AZB cathode by delithiation in 1 M KOH aq. (delithiation treatment). In order to implement the NMC cathode in AZB in the future, it is important to understand its delithiation treatment and charge-discharge behavior. During the delithiation process, it was found that water molecules inserted into the interlayer spaces and expanded the interlayer spacing, thereby facilitating the ion diffusion and redox activity2. The purpose of this study was to reveal the charge-discharge behavior of NMC111 cathode by characterization and electrochemical measurement, leading to the improvement of the performance of NMC111 cathode in AZB.The cathode was prepared by mixing NMC111, acetylene black, Ketjen black, polyvinylidene difluoride (PVdF) (45 : 4 : 1 : 4 in weight ratio) diluted with an amount of N-methyl-2-pyrrolidinone (NMP) and coated it on a Ni porous substrate. A beaker cell was used for delithiation treatment with an NMC111 cathode as the working electrode, a Cu foil as the counter electrode, a Hg/HgO electrode as the reference electrode, and 1 M KOH aq. as the electrolyte. Then a constant current of 170 mA g-1 was applied to an NMC111 cathode for 1 hour to deintercalate Li+ from NMC111. Charge-discharge tests were performed using a beaker cell with a delithiated NMC111 cathode, a Zn plate anode, a Hg/HgO reference electrode, and 1 M KOH (sat. ZnO) electrolyte, with a C rate of 0.1 C (= 17 mA g-1) and cut-off potentials of -0.4－0.7 V vs. Hg/HgO. Then characterizations, X-ray Diffraction analysis (XRD) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), were performed on the NMC111 cathode after charge-discharge tests. In addition, the WE used for Electrochemical Quartz Crystal Microbalance (EQCM) measurements was prepared by using a 6 MHz Au-coated quartz crystal (1.33 cm2) as a substrate, mixing NMC111 and PVdF (99 : 1), diluting it with an appropriate amount of NMP, and loading about 10－50 μg onto the gold. Then, delithiation treatment and electrochemical measurement were performed in EQCM cell.First, the crystal structures of NMC111 cathodes after charge-discharge test were confirmed by ex-situ XRD. The results showed that there was a single peak attributed to the interlayer spacing of the cathode after charge, while the peak after discharges was split into two peaks (Figure 1). The interlayer spacing was calculated to be 0.702 nm after charging, it changed to 0.694 and 0.714 nm after discharging. These results suggests that the charge-discharge reaction of NMC111 occurs by intercalation of ions. In addition, both an increase and a decrease in the interlayer spacing were observed during the discharge process, which indicated that ions could be inserted into the interlayer in stages. Next, the cathode composition was measured by ICP-OES after charge and discharge to identify the intercalants. The concentration changes of potassium, lithium, and zinc in the NMC111 cathode after charge and discharge were small, less than 5 mAh g-1 converted to specific capacity. Considering that the discharge capacity is about 120 mAh g-1, the dominant intercalants are not Zn2+, K+, or Li+. Thus, insertion of OH-, H+, and H3O+ may have occurred since this battery system doesn't contain other ions. Finally, EQCM measurements could detect the weight of intercalants inserting into the cathode interlayer. The result of intercalant identification by EQCM measurements will be also discussed.[1] H. Hayashi, et al., 63rd Battery Symposium in Japan, Abstr., 1H22 (2022). [in Japanese][2] H. Hayashi, et al., 91st ECSJ Annual Meeting, Abstr., S8-3_3_12 (2024). [in Japanese]Figure 1 (a) Charge-Disharge curves of 1st cycle (b) XRD profiles at each point Figure 1

Precursor Vapor Pressure Estimation and Precise QCM Measurement for ALD Process Development with Ideal ALD Characteristics

Atomic Layer Deposition (ALD) produces thin films by alternately supplying precursors and reaction gases. In this process, a film with one atomic layer or fewer is formed in a single cycle. By properly controlling the number of cycles, the film thickness can be precisely controlled and reproducible film formation is possible. This technology is widely used in the production of semiconductor integrated circuits (ULSIs). The amount of growth per cycle is called GPC, and it is well known that GPC remains constant over a temperature range known as the ALD Window, within which ideal ALD film-formation characteristics can be obtained. Therefore, a wide ALD window is important for constructing an easy-to-use ALD process. The GPC is constant in the ALD Window because the coverage factor of the chemisorbed precursor is nearly unity. Therefore, it is necessary to consider the conditions under which saturated chemisorption occurs during the adsorption process of the precursor. The surface coverage factor depends on the adsorption constant K and precursor concentration C according to the "Langmuir-Hinshelwood equation," as shown below.θ=KC/(1+KC)If the product of the adsorption equilibrium constant K and the precursor concentration C is large (e.g., 100 or more), the coverage factor θ is almost constant at unity, even at different substrate surface temperatures; that is, even if the values of K differ slightly, or even if the concentration C differs slightly between the center and the edge of the wafer. This is the main reason for the good thickness reproducibility and uniformity of the ALD process.We developed a method to precisely estimate the precursor concentration, that is, the saturated vapor pressure, using quantum chemical calculations (the Modified COSMO-SAC method). This allowed us to identify compounds that could be supplied at appropriate concentrations as ALD precursors. This vapor pressure estimation is also effective for constructing the Atomic Layer Etching (ALE) process.The adsorption equilibrium constant K of the precursor can be determined by quantum chemical calculations; however, this is time-consuming and computationally expensive. For the synthesized precursor compounds, the adsorption equilibrium constant K can be easily determined experimentally using precise Quartz Crystal Microbalance (QCM) measurements. As QCM is very sensitive to the temperature change, we have specially made “AT cut” Quartz Crystal which is insensitive to the temperature fluctuation at the desired temperature. The combination of a custom-made oscillation circuit for the above AT cut crystal and a frequency counter enables measurement of weight change with a sensitivity of 0.3 ng/cm2 or less and measurement of weight change over time due to adsorption or reaction with high time resolution of 20 points/sec. We combined these calculations with experiments to develop ALD systems that exhibit ideal ALD properties.

(Invited) Edlc Characterization of Carbon Electrodes with Micro to Narrow Mesopores

The capacitance of carbon electrodes on electric double-layer capacitors (EDLCs) is improved by controlling the pore structure to increase the surface area where the electric double-layer can form. Porous carbon electrodes with micropores and narrow mesopores, through which bare electrolyte ions can invade, exhibit a high capacitance [1-3]. Because the electrolyte ions exist as a solvated state with solvent molecules in the electrolyte solution, a desolvation process in pores is required to improve EDLC performance. The desolvation of electrolyte ions spontaneously occurs in certain pore structures. The unique phenomena in nanopores, which are different from those in the bulk phase, were reported in the 1990s [4-6]. One of the representative phenomena is called as "quasi-pressure effect," in which molecules introduced into the pore behave as if they were in a high-pressure field [7-9]. The abnormality in the carbon pores is caused by the strong interaction between the molecules and ions introduced into the pores and the carbon atoms forming the pore walls. Such a strong interaction may be a trigger for desolvation. Accordingly, the pore structure of carbon electrodes must be carefully evaluated to design an ideal porous structure that maximizes EDLC capacitance. Gas adsorption isotherm analysis is one of the techniques used to clarify the porous structure of carbon electrodes. Many analytical methods to determine the specific surface area and pore size distribution (PSD) of adsorption isotherms have been reported. However, the calculated values differed based on analytical methods. The PSD depends on the calculation theories and pore structure models to determine the theoretical adsorption isotherms, whose fitting with the experimental adsorption isotherm provides the PSD of the target porous carbons. Simple pore structures such as slit and cylinder structures have been widely used as pore models. Recently, a set of realistic three-dimensional porous structures was proposed as a model pore structure for porous carbons [10]. Such a realistic model is expected to be effective for evaluating the pore structures of carbon electrodes with micropores and narrow mesopores. On the other hand, it is also considered effective to select Mg ions, which are multivalent ions, as carriers to enhance capacitance. However, Mg ions have a higher solvation energy than Li ions: it is necessary to determine a suitable pore structure for Mg ions. In this study, we designed optimal porous structures of carbon electrodes by clarifying the electric double-layer formation of Li and Mg ions on micro-mesoporous carbons using electrochemical quartz crystal microbalance (EQCM) measurements, while comparing various pore structure determination methods for adsorption isotherms. Reference: [1] J. Chmiola, G. Yushin, Y. Gogotsi, C. Portet, P. Simon, P. L. Taberna, Science, 313, 1760-1763 (2006). [2] K. Urita, N. Ide, H. Furukawa, I. Moriguchi, ACS Nano, 8, 3614-3619 (2014). [3] K. Urita, C. Urita, K. Fujita, K. Horio, M. Yoshida, I. Moriguchi, Nanoscale, 29, 15643-15649 (2017). [4] S. Granick, Science 1991, 253, 1374-1379. [5]T. Iiyama, K. Nishikawa, T. Ohba, K. Kaneko, J. Phys. Chem., 99, 10075-10076 (1995). [6]L. D. Gelb, K. E. Gubbins, Rep. Prog. Phys., 62, 1573-1660 (1999). [7] J. Imai, M. Souma, S. Ozeki, T. Suzuki, K. Kaneko, J. Phys. Chem., 95, 9955-9960 (1991). [8]K. Urita, T. Fujimori, H. Notohara, I. Moriguchi, ACS Appl. Energy Mater., 1, 807-813 (2018). [9]Y. Komine, K. Urita, H. Notohara, I. Moriguchi, Chem. Lett., 51, 118-120 (2022). [10]F. Vallejos-Burgos, C. de Tomas, N. J. Corrente, K. Urita, S. Wang, C. Urita, I. Moriguchi, I. Suarez-Martinez, N. Marks, M. H. Krohn, R. Kukobat, A. V. Neimark, Y. Gogotsi, and K. Kaneko, Carbon, 215, 118431 (2023).

Depolymerization and Etching of Poly(lactic acid) via TiCl4 Vapor Phase Infiltration.

This study investigates the use of TiCl4 vapor phase infiltration (VPI) to cleave ester groups in the main chain of a polymer and drive depolymerization and film etching. Prior investigations have demonstrated that the infiltration of TiCl4 into PMMA results in dealkylation of its ester bond, cleaving its side groups. This study investigates the VPI of TiCl4 into poly(lactic acid), which is a prototypical polymer with an ester group in its main chain. Utilizing in situ quartz crystal microbalance (QCM) measurements and spectroscopic ellipsometry, PLA is observed to depolymerize readily at 135 °C with extended TiCl4 precursor exposure, resulting in significant thickness and mass reduction, whereas at 90 °C, depolymerization is significantly slower and etching is negligible. Utilizing Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and a residual gas analyzer (RGA), dealkylation is shown to be the primary depolymerization mechanism. FTIR and XPS analyses reveal the consumption of carbonyl and methoxy groups and the emergence of hydroxyl, chlorine, and titanium moieties. In situ RGA measurements provide further insights into the byproducts formed during the TiCl4 and water exposure steps, indicating that the depolymerized components undergo further breakdown into other substances. Residuals left after 135 °C TiCl4 VPI are easily removed with a 0.1 M HCl aqueous solution. These findings highlight the expanding functionality of VPI, revealing its capability as both an additive and subtractive process and suggesting its broader applications.

Study on the synergism mechanism of composite surfactants for oily sludge treatment using microemulsion method

The nonionic surfactant was considered to be the most effective surfactant for the treatment of oily sludge. In this paper, Tween20 and Span80 (T/S) composite surfactant was chosen as emulsifier for the preparation of microemulsion, and their synergistic effect was explored. Clint equation and molecular dynamics simulation was used to interpret the formation of mixed micelles and the results showed that T/S composite surfactant with the mass ratio of 11:1 exhibited the good synergetic effect. Then, the microemulsion prepared using composite surfactants was applied for the treatment of oily sludge. Under the optimal conditions of solid-liquid ratio of 1:1(g: mL), stirring temperature of 40 °C, stirring time of 30 min and stirring speed of 400 rpm, the residual oil rate was reduced to 0.25%, which was much lower than other reported results using chemical methods. Interface tensiometer and quartz crystal microbalance measurement showed that the interfacial tension decreased significantly after the addition of composite surfactant. This work provides a feasible strategy for oily sludge treatment using microemulsion, which promoted the development of oily sludge treatment processes based on microemulsion in practical industry.

Aqueous Electrocatalytic Hydrogenation Depolymerization of Lignin β-O-4 Linkage via Selective Caryl-O(C) Bond Cleavage: The Regulation of Adsorption.

The cleavage of the benzene-oxygen (Caryl-O(C)) bond of the lignin β-O-4 linkage is expected to relieve condensation of the degradation product and improve the product value. Nevertheless, the electrochemical breaking of the Caryl-O(C) bond has not been achieved yet due to the high dissociation energy (∼409 kJ mol-1) and the easy over-reduction of aromatic compounds. Here, we report an aqueous electrochemical reduction strategy for breaking Caryl-O(C) bonds via the regulation of molecular adsorption. The density functional theory (DFT) calculations and quartz crystal microbalance (QCM) measurements reveal that the residual Cu(I) in the CuO electrocatalyst enhances the adsorption of the 2-phenoxy-1-phenylethyl alcohol (PPE) by the Caryl-O(C) bond and lowers the energy barrier of the protons attacking the oxygen atom in the β-O-4 linkage. Thus, compared to the Cu electrocatalyst (with a hydroquinone yield of 47.4% and a benzyl alcohol yield of 24.8%), the CuO nanorod exhibits a much higher yield of hydroquinone (95.3%) and benzyl alcohol (88.6%) at a potential of -0.4 V vs reversible hydrogen electrode (RHE) in an undivided cell. Moreover, the reaction pathway and the cleavage of the Caryl-O(C) bond are identified through a combination of in situ synchrotron-radiation Fourier transformed infrared spectroscopy (SR-FTIR) and DFT calculations. This effective method is utilized for poplar lignin electrolysis, yielding 10.9 wt % of guaiacylglycerol, with an outstanding selectivity of >63.0%. This work provides an efficient and mild method of cleavage of Caryl-O(C) bonds in lignin valorization.

Measurement of Pt consumption from Pt electrodes during water electrolysis using the quartz crystal microbalance (QCM) method: Effect of the water electrolysis method and the concentration of chloride ions in the aqueous solution

The consumption of the Pt electrocatalyst, which occurs when aqueous solution with neutral pH is electrolyzed with a Pt electrode to produce hydrogen or oxygen, was measured from the change in resonance frequency using the QCM method. First, it was found that the Pt consumption from the electrode during water electrolysis while applying a steady positive potential was very small, but it was almost proportional to the time the current was applied. Second, when electrolysis was performed by polarity reversal electrolysis of the anode and cathode periodically during electrolysis, the amount of Pt consumed increased in proportion to the number of polarity reversal was exchanged. The Pt consumption obtained by the QCM method was in close agreement with the value obtained by EDX method, proving the validity of the measurement method. The QCM measurement method was also proven to be a reliable method of measurement.

Synthesis and characterization of molecularly imprinted polymer nanoparticles against porcine circovirus type 2 viral-like particles

PCV2 is a significant epidemic agricultural pathogen that causes a variety of swine diseases. PCV2 infections have significant economic impact on the swine industry, making effective strategies for rapid detection of PCV2 in pigs essential. Herein, we report on the synthesis of the so-called nano-MIPs which can be utilized for molecular recognition of PCV2. The morphology and structure of nano-MIPs were characterized using scanning electron microscopy (SEM). Nano-MIPs are spherical with sizes around 120–150 nm. Binding experiments demonstrate that the fluorescence intensity of PCV2 samples decreases proportionally to increasing the concentration of nano-MIPs due to quenching, while non-imprinted polymer nanoparticles (nano-NIPs) do not affect the signal. The Stern–Volmer constant of nano-MIPs binding to PCV2 was 1.3 × 10−3 mL/µg, whereas nano-NIPs led to 7 × 10−5 mL/µg, i.e., 1.8 orders of magnitude lower. The detection limit for binding MIP particles to PCV2 by fluorescence measurements is 47 µg/mL. This affinity test allows for designing both direct and competitive quartz crystal microbalance (QCM) assays for PCV2 leading to QCM measurements. The QCM results show nano-MIPs binding to PCV2 immobilized on the sensor surface with appreciable reproducibility. QCM sensor characteristics reveal signal saturation above around 200 µg/mL at a response of − 354 Hz and an LOD of approximately 35 µg/mL. Nano-MIPs also show selectivity factors of 2–5 for CSFV and PRRSV probably because the three viruses have similar diameters around 50 nm.Graphical

The Multifaceted Role of Boric Acid in Nickel Electrodeposition and Electroforming

This study involved an investigation of the role of boric acid in nickel electroforming from sulfamate electrolytes, especially in relation to its ability to minimise interfacial pH changes during electrodeposition. Initial speciation calculations indicated that buffering by polyborate species and nickel-borate complexes are most likely responsible for this effect. However, the concentration of nickel-borate complexes was too low even at elevated pH to be a significant electroactive species. Polarisation and electrochemical quartz crystal microbalance measurements indicated that, in the absence of boric acid, electrodeposits typically contained Ni(OH)2, while boric acid additions resulted in pure Ni being deposited with a current efficiency approaching unity. Boric acid additions substantially modified the nickel and hydrogen partial currents, and influenced the overall current efficiency. Studies in nickel-free solutions indicated that boric acid adsorbs on the surface which explains the suppression of H2O reduction observed in the electroforming experiments. Collectively, solution buffering due to polyborate and nickel-borate species and inhibition of H2O reduction by adsorbed boric acid minimised interfacial pH changes and prevented the formation of nickel hydroxide.

Sensor parameters and adsorption behaviour of rhodamine-based polyacrylonitrile (PAN) nanofiber against dichloromethane vapour

This study is focused on the determination of sensor and adsorption parameters ofrhodamine-based polyacrylonitrile (PAN) nanofiber during the dichloromethane vapour exposure due to a very limited investigation of the rhodamine-based PAN nanofiber sensor. Quartz crystal microbalance (QCM) measurement system is employed to monitor the sensor response to dichloromethane vapour. This nanofiber sensor demonstrates a highly sensitive, stable, reproducible response and concentration dependence behaviour. A good stability, with an excellent recovery occurred. Sensor parameters such as the limit of detection (153 ppm), the limit of quantification (465 ppm), the sensitivity (0.0215 Hz/ppm), response (2 s) and recovery (3 s) times are determined using QCM measurement results. Pseudo first-order and Elovich adsorption models have proved that dichloromethane vapours are adsorbed bythis nanofiber sensor andthe amount of vapour adsorption rate is increased when the concentration of dichloromethane vapour increases.Owing to its achieved sensor parameters, high adsorption feature and simple fabrication process with a low cost, this proposed sensing device is expected to be a promising alternative for monitoring dichloromethane vapour sensing application at room temperature.

Electrochemical and surface characterisation of poly(3,4-ethylenedioxythiophene) dodecylbenzenesulfonate layers

Poly(3,4-ethylenedioxythiophene) (PEDOT) films were electrochemically synthesised with sodium dodecylbenzenesulfonate (DBS) and chloride acting as dopant anions within the polymer matrix. Upon redox switching of the PEDOT/DBS film between conducting and non-conducting states, the DBS anion remained within the polymer and cation insertion and expulsion occurred, as confirmed by Electrochemical Quartz Crystal Microbalance (EQCM) measurements. Electrolytes composed of alkali metal cations of varying masses (Li+, Na+, K+) were employed to investigate the cation insertion/expulsion processes, thereby resulting in varying mass changes being observed upon film redox switching. The charging and discharging of bulky anion doped polymer films presented higher capacitance upon charging and lower capacitance when discharging, which is expected during doping and de-doping as confirmed by AC impedance. In this work, the main results obtained by chemical-physical characterisation are presented and critically discussed, with regard to the possible use of a viable conducting polymer as a drug delivery vehicle.

Salinity effect on corrosion inhibition of 2-mercaptopyrimidine as an inhibitor in CO2-containing solution

In this work, the effects of Cl-, Ca2+, and Mg2+ on the corrosion inhibition performance of 2-mercaptopyrimidine (2-MP) were investigated. The analysis reveals a marked reduction in the inhibition efficiency of 2-MP, from 91.24 % to 76.29 %, as the NaCl content in the solution rises from 1 wt% to 20 wt%. UV–visible absorption spectroscopy and quartz crystal microbalance measurements indicate that the desorption of 2-MP worsens with an increasing content of corrosive ions. Molecular dynamics simulations reveal the inhibitor desorption mechanism. This work enhances understanding of ion effects on corrosion inhibition and film degradation in high salinity environments.

Layer‐by‐Layer Construction of Hybrid Film Based on PEI Polymer and Preyssler‐Type Polyoxometalates: Its Electrochemical and Quartz Crystal Microbalance Measurement

AbstractIn this work, Preyssler‐type POM (NH4)14[NaP5W30O110].44H2O (NH4P5W30), has been synthesised and its electrochemical behaviour in solution was examined at the surface of glassy carbon (GC) and gold electrodes. Furthermore, multilayer assemblies of NH4P5W30 POM were constructed onto the surfaces of GCE, gold electrode, and gold quartz electrode via the electrostatic Layer‐by‐Layer (LBL) technique employing polyethyleneimine as the cationic layer and POM as an anionic layer. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and electrochemical quartz crystal microbalance measurements (EQCM) were used to monitor the LBL assembly as the NH4P5W30 POM layer was being built. These techniques revealed significant differences in film growth. The multilayer film exhibited well‐defined redox couples associated with POM's tungsten‐oxo framework and showed surface‐confined behaviour up to 100 mVs−1 on both the GC and gold electrodes. The pH dependency and stability of the film were investigated. EIS demonstrated that when the POM layer was the outer layer, the layers were less conductive, and resistance increased as the number of layers increased. In addition, the charge transfer resistance values (Rct) for the layers were calculated. The solvation of ions into the film associated with POM redox activity was studied employing an in‐situ EQCM.

Template bacteria-free fabrication of surface imprinted polymer-based biosensor for E. coli detection using photolithographic mimics: Hacking bacterial adhesion

As one class of molecular imprinted polymers (MIPs), surface imprinted polymer (SIP)-based biosensors show great potential in direct whole-bacteria detection. Micro-contact imprinting, that involves stamping the template bacteria immobilized on a substrate into a pre-polymerized polymer matrix, is the most straightforward and prominent method to obtain SIP-based biosensors. However, the major drawbacks of the method arise from the requirement for fresh template bacteria and often non-reproducible bacteria distribution on the stamp substrate. Herein, we developed a positive master stamp containing photolithographic mimics of the template bacteria (E. coli) enabling reproducible fabrication of biomimetic SIP-based biosensors without the need for the “real” bacteria cells. By using atomic force and scanning electron microscopy imaging techniques, respectively, the E. coli-capturing ability of the SIP samples was tested, and compared with non-imprinted polymer (NIP)-based samples and control SIP samples, in which the cavity geometry does not match with E. coli cells. It was revealed that the presence of the biomimetic E. coli imprints with a specifically designed geometry increases the sensor E. coli-capturing ability by an “imprinting factor” of about 3. These findings show the importance of geometry-guided physical recognition in bacterial detection using SIP-based biosensors. In addition, this imprinting strategy was employed to interdigitated electrodes and QCM (quartz crystal microbalance) chips. E. coli detection performance of the sensors was demonstrated with electrochemical impedance spectroscopy (EIS) and QCM measurements with dissipation monitoring technique (QCM-D).

A novel aptasensor platform for the detection of carcinoembryonic antigen using quartz crystal microbalance

In this study, a quartz crystal microbalance (QCM) aptasensor for carcinoembryonic antigen (CEA), a well-known biomarker for various cancer types, was reported, utilizing two different aptamers. To achieve this, a nanofilm of 4-mercaptophenyl was electrochemically attached to gold-coated QCM crystal surfaces via the reduction of 4-mercaptobenzenediazonium salt (4 MB-DAT) using cyclic voltammetry. Subsequently, gold nanoparticles (AuNP) were affixed to this structure, and then aptamers (antiCEA1 and antiCEA2) modified with SH-functional ends bound to AuNPs completed the modification. The analytical performance of the CEA sensor was evaluated through simultaneous QCM measurements employing CEA solutions ranging from 0.1 ng/mL to 25 ng/mL. The detection limit (LOD) for CEA was determined to be 102 pg/mL for antiCEA1 and 108 pg/mL for antiCEA2 aptamers. Interday and intraday precision and accuracy tests yielded maximum results of 4.3 and + 3.8, respectively, for both aptasensors, as measured by relative standard deviation (RSD%) and relative error (RE%). The kinetic data of the aptasensors resulted in affinity values (KD) of 0.43 ± 0.14 nM for antiCEA1 and 0.75 ± 0.42 nM for antiCEA2. These values were lower than the reported values of 3.9 nM and 37.8 nM for both aptamers, respectively. The selectivity of the aptasensor was evaluated by measuring the signal changes caused by alpha-fetoprotein (AFP), cancer antigen (CA-125), and vascular endothelial growth factor (VEGF-165) individually and together at a concentration of 500 ng/mL, resulting in a maximum 4.1 % change, which was comparable to precision and accuracy values reported in the literature. After confirming the selectivity of the aptamers, recovery experiments were conducted using spiked commercial serum samples to simulate real samples, and the lowest recovery value obtained was 95.4 %. It was determined that two different aptasensors could be successfully used for the QCM-based detection of CEA in this study.

Understanding Electrolyte Ion Size Effects on the Performance of Conducting Metal-Organic Framework Supercapacitors.

Layered metal-organic frameworks (MOFs) have emerged as promising materials for next-generation supercapacitors. Understanding how and why electrolyte ion size impacts electrochemical performance is crucial for developing improved MOF-based devices. To address this, we investigate the energy storage performance of Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with a series of 1 M tetraalkylammonium tetrafluoroborate (TAABF4) electrolytes with different cation sizes. Three-electrode experiments show that Cu3(HHTP)2 exhibits an asymmetric charging response with all ion sizes, with higher energy storage upon positive charging and a greater charging asymmetry with larger TAA+ cations. The results further show that smaller TAA+ cations demonstrate superior capacitive performances upon both positive and negative charging compared to larger TAA+ cations. To gain further insights, electrochemical quartz crystal microbalance measurements were performed to probe ion electrosorption during charging and discharging. These reveal that Cu3(HHTP)2 has a cation-dominated charging mechanism, but interestingly indicate that the solvent also participates in the charging process with larger cations. Overall, the results of this study suggest that larger TAA+ cations saturate the pores of the Cu3(HHTP)2-based electrodes. This leads to more asymmetric charging behavior and forces solvent molecules to play a role in the charge storage mechanism. These findings significantly enhance our understanding of ion electrosorption in layered MOFs, and they will guide the design of improved MOF-based supercapacitors.

Structural properties of immune complexes formed by viral antigens and specific antibodies shape the inflammatory response of macrophages

Data on the course of viral infections revealed severe inflammation as a consequence of antiviral immune response. Despite extensive research, there are insufficient data on the role of innate immune cells in promoting inflammation mediated by immune complexes (IC) of viral antigens and their specific antibodies. Recently, we demonstrated that antigens of human polyomaviruses (PyVs) induce an inflammatory response in macrophages. Here, we investigated macrophage activation by IC. We used primary murine macrophages as a cell model, virus-like particles (VLPs) of PyV capsid protein as antigens, and a collection of murine monoclonal antibodies (mAbs) of IgG1, IgG2a, IgG2b subclasses. The inflammatory response was investigated by analysing inflammatory chemokines and activation of NLRP3 inflammasome. We observed a diverse pattern of chemokine secretion in macrophages treated with different IC compared to VLPs alone. To link IC properties with cell activation status, we characterised the IC by advanced optical and acoustic techniques. Ellipsometry provided precise real-time kinetics of mAb-antigen interactions, while quartz crystal microbalance measurements showed changes in conformation and viscoelastic properties during IC formation. These results revealed differences in mAb-antigen interaction and mAb binding parameters of the investigated IC. We found that IC-mediated cell activation depends more on IC characteristics, including mAb affinity, than on mAb affinity for the activating Fc receptor. IC formed by the highest affinity mAb showed a significant enhancement of inflammasome activation. This may explain the hyperinflammation related to viral infection and vaccination. Our findings demonstrate that IC promote the viral antigen-induced inflammatory response depending on antibody properties.