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Quantification of the Adsorption Kinetics of a Model Corrosion Inhibitor on Gold using QCM-D

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Authors: Kushal Singla, Hubert Perrot, Bruce Brown, Srdjan Nešić

Journal: CORROSION 

Abstract: In the present study, a quartz crystal microbalance with dissipation monitoring (QCM-D) was used to investigate the adsorption of a model corrosion inhibitor compound, tetradecyldimethylbenzylammoniumbromide (BDA-C14), on gold electrode. Sauerbrey’s equation was used to analyze the equilibrated normalized frequency change for estimation of the adsorbed mass and adsorbed layer thickness at different bulk inhibitor concentrations after careful validation. Average adsorbed layer thickness for BDA-C14 at tested experimental conditions lie in the range of 1-1.4 nm. Time dependent part of the frequency change was analyzed using Langmuir adsorption isotherm to calculate the kinetic constants (kA = 0.075 ± 0.02 mM−1∙s−1, kD = 0.0023 ± 0.0007 s−1 and KAD = 32.2 mM−1). Equilibrium surface coverage (θeq) was estimated at each bulk inhibitor concentration tested: 0.69 for 25 ppm(w), 0.74 for 50 ppm(w) and 0.91 for 100 ppm(w). Some theoretical calculations are also shown explaining the use of known molecular geometry and adsorption kinetics information from QCM-D analysis to reasonably speculate the predominant adsorbed layer configuration. A conscious effort is made to state and validate each assumption made for the analysis of the experimental results.

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Site-specific sulfations regulate the physicochemical properties of papillomavirus–heparan sulfate interactions for entry

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Authors: Fouzia Bano, Laura Soria-Martinez, Dominik van Bodegraven, Konrad Throsteinsson, Anna M. Brown, Ines Fels, Nicole L. Snyder, Marta Bally, Mario Schelhaas

Journal: Science Advances

Abstract: Certain human papillomaviruses (HPVs) are etiological agents for several anogenital and oropharyngeal cancers. During initial infection, HPV16, the most prevalent cancer-causing type, specifically interacts with heparan sulfates (HSs), not only enabling initial cell attachment but also triggering a crucial conformational change in viral capsids termed structural activation. It is unknown, whether these HPV16-HS interactions depend on HS sulfation patterns. Thus, we probed potential roles of HS sulfations using cell-based functional and physicochemical assays, including single-molecule force spectroscopy. Our results demonstrate that N-sulfation of HS is crucial for virus binding and structural activation by providing high-affinity sites, and that additional 6O-sulfation is required to mechanically stabilize the interaction, whereas 2O-sulfation and 3O-sulfation are mostly dispensable. Together, our findings identify the contribution of HS sulfation patterns to HPV16 binding and structural activation and reveal how distinct sulfation groups of HS synergize to facilitate HPV16 entry, which, in turn, likely influences the tropism of HPVs.

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Quartz crystal microbalance with dissipation monitoring for studying soft matter at interfaces

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Authors: Diethelm Johannsmann & Ilya Reviakine

Journal: Nature Reviews Methods Primers

Abstract: Quartz crystal microbalance with dissipation monitoring (QCM-D) probes interfaces by subjecting them to a periodic shear stress exerted by an acoustic resonator. The changes in the resonance frequency, Δf, and the half-width at half-maximum of the resonance, ΔΓ (closely related to the changes in the dissipation, ΔD), measured with the QCM-D are proportional to the in-phase and out-of-phase components of the area-averaged transverse stress at the resonator surface, respectively. Amounts, organization and properties of soft matter at an interface between the resonator and a liquid or a gas are derived from the measurements of Δf and ΔΓ on multiple overtones at megahertz frequencies. The properties include viscoelasticity and stress relaxation dynamics on the timescale of the oscillation period. This Primer offers guidelines on instrument design, experimental procedures and data analysis for interpreting frequency and bandwidth changes in terms of structure and dynamics of the sample. There is a focus on recent progress in the analysis of the acoustic ratio, ΔΓ/(−Δf), and numerical methods of modelling. Limitations of the existing approaches for data analysis are discussed. Challenges and possible future developments are formulated in an outlook.

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Portable Surface Acoustic Wave device platform coupled with a paper-based capillary fluidics for real-time biosensing applications

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Authors: Angelos Ntimtsas and Electra Gizeli

Journal: Chemical Society Sensors and Actuators A: Physical

Abstract: Surface acoustic wave (SAW) sensors have emerged as prominent real-time, label-free biosensors with diverse applications in immunoassays and nucleic acid detection. However, widespread adoption in diagnostics has been impeded by challenges such as miniaturization of instrumentation, microfluidics fabrication and high attenuation in liquid environments. In this study we address these limitations by presenting a portable platform capable of real-time monitoring of a SAW microarray chip comprising up to four sensing channels, combined with a novel paper-based capillary flow channel. For the fabrication of a portable, automated and versatile sensor platform, we integrated a microcontroller, RF components, and a micropump for flow control. Calibration procedures ensured accurate measurements for both amplitude and phase, with a low drift rate (0.72 mdB/h and 1.00 mdeg./h, respectively) and high resolution (2.10 mdB and 6.10 mdeg.), indicating stable operation with minimal interface electronics. The capillary flow channel, implemented by confining the fluid on the sensing surface using a nitrocellulose strip, facilitated laminar and continuous sample flow with minimum damping of the acoustic signal. The sensor system was evaluated with two SAW devices at 100 and 200 MHz using glycerol dilutions within the range of 1% and 70%, demonstrating real-time monitoring capabilities and linear correlations between amplitude and phase changes. To prove the biosensing and clinical validity of the SAW newly developed system, DNA adsorption on a poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) functionalized SAW-surface was demonstrated with a detection limit of 0.001 μg/mL. Our study demonstrates the feasibility of a portable SAW sensor system coupled with a low-cost and replaceable capillary flow channel for real-time monitoring and biomolecular detection.

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

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Authors: Jamie W. Gittins, Kangkang Ge, Chloe J. Balhatchet, Pierre-Louis Taberna, Patrice Simon, Alexander C. Forse

Journal: Journal of the American Chemical Society

Abstract:

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.

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Revisiting the Charging Mechanism of α-MnO2 in Mildly Acidic Aqueous Zinc Electrolytes

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Authors: Lang Yuan Wu, ZhiWei Li, YuXuan Xiang, WenDi Dong, XiaoDong Qi, ZhenXiao Ling, YingHong Xu, HaiYang Wu, Mikhael D. Levi, Netanel Shpigel, XiaoGang Zhang

Journal: Small 

Abstract: In recent years, there have been extensive debates regarding the charging mechanism of MnO2 cathodes in aqueous Zn electrolytes. The discussion centered on several key aspects including the identity of the charge carriers contributing to the overall capacity, the nature of the electrochemical process, and the role of the zinc hydroxy films that are reversibly formed during the charging/discharging. Intense studies are also devoted to understanding the effect of the Mn2+ additive on the performance of the cathodes. Nevertheless, it seems that a consistent explanation of the α-MnO2 charging mechanism is still lacking. To address this, a step-by-step analysis of the MnO2 cathodes is conducted. Valuable information is obtained by using in situ electrochemical quartz crystal microbalance with dissipation (EQCM-D) monitoring, supplemented by solid-state nuclear magnetic resonance (NMR), X-ray diffraction (XRD) in Characterization of Materials, and pH measurements. The findings indicate that the charging mechanism is dominated by the insertion of H3O+ ions, while no evidence of Zn2+ intercalation is found. The role of the Mn2+ additive in promoting the generation of protons by forming MnOOH, enhancing the stability of Zn/α-MnO2 batteries is thoroughly investigated. This work provides a comprehensive overview on the electrochemical and the chemical reactions associated with the α-MnO2 electrodes, and will pave the way for further development of aqueous cathodes for Zn-ion batteries.

 

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Study of the inhibition efficiency of DTPMPA on calcium carbonate formation via advanced tools

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Authors: Soumaya Nouigues, Nelson Acevedo, Yasser Ben Amor, Christel Laberty-Robert, Hubert Perrot, Hélène Cheap-Charpentier

Journal: Desalination

Abstract: The inhibition efficiency of a scale inhibitor, named diethylene triamine penta (methylene phosphonic acid) (DTPMPA), was evaluated using fast controlled precipitation (FCP) method, electrochemical quartz crystal microbalance (EQCM), quartz crystal microbalance with dissipation (QCM-D) and pre-scaled quartz crystal microbalance (SQCM). The results showed that DTPMPA delayed the CaCO3 precipitation and decreased the precipitation rate of the CaCO3 formation in solution and on a metallic surface, depending on the inhibitor concentration. In some cases, it could completely inhibit CaCO3 formation. CaCO3 precipitation was completely inhibited in solution and on a metallic surface in the presence of 0.5 mg⋅L−1 and 4 mg⋅L−1 DTPMPA, according to FCP and EQCM results, respectively. The morphology and composition of CaCO3 crystals formed were studied using SEM and XRD showing that the presence of the inhibitor promoted the formation of calcite. This is the first time that the influence of an organic inhibitor was studied using the combination of QCM methods, where the results revealed a reduction of the surface coverage by a CaCO3 layer as the inhibitor concentration increased. The activation energies were calculated in the presence of DTPMPA and indicated that the inhibitor retarded the scaling process.

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On the Electrochemical Activation of Nanoporous Reduced Graphene Oxide Electrodes Studied by In Situ/Operando Electrochemical Techniques

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Authors: María del Pilar Bernicola, Mailis Lounasvuori, Jessica Padilla-Pantoja, Jose Santiso, Catherine Debiemme-Chouvy, Hubert Perrot, Tristan Petit, Jose A. Garrido, Elena del Corro

Journal: Advanced Functional Materials

Abstract: Due to the difficult access of the electrolyte into the nanoconfined space of nanoporous reduced graphene oxide (rGO) electrodes, achieving the optimal electrochemical performance of these devices becomes a challenge. In this work, the dynamics of interfacial-governed phenomena are investigated during a voltage-controlled electrochemical activation of nanoporous rGO electrodes that leads to an enhanced electrochemical performance in terms of areal capacitance and electrochemical impedance. In situ/operando characterization techniques are used to reveal the dynamics of the irreversible material changes introduced during the activation process, including ionic diffusion and water confinement within the nanopores, along with the reduction of oxygenated groups and the decrease of the rGO interlayer distance. Furthermore, operando techniques are used to uncover the origin of the complex polarization-dependent dynamic response of rGO electrodes. The study reveals that the reversible protonation/deprotonation of remaining functional groups and the cation electro-adsorption/desorption process in the graphene basal plane govern the pseudocapacitive performance of nanoporous rGO electrodes. This work brings new understanding of the complex interplay between surface chemistry, ion confinement, and desolvation processes occurring during electrochemical cycling in nanoporous rGO electrodes, offering new insights for designing high-performing electrodes based on nanoporous rGO.

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Scientific publication

Demonstrating a Quartz Crystal Microbalance with Dissipation (QCMD) to Enhance the Monitoring and Mechanistic Understanding of Iron Carbonate Crystalline Films

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Authors: Igor Efimov, Eftychios Hadjittofis, Mustafa M. Alsalem, and Kyra L. Sedransk Campbell

Journal: Langmuir

Abstract:

This paper reports the real time monitoring of siderite deposition, on both Au- and Fe-coated surfaces, using the changes in frequency and dissipation of quartz crystal microbalance with dissipation (QCMD). In an iron chloride solution saturated with carbon dioxide, buffered with sodium bicarbonate to pH 6.8, roughly spherical particles of siderite formed within 15 min, which subsequently deposited on the QCMD crystal surface. Imaging of the surface showed a layer formed from particles ca. < 0.5 μm in diameter. Larger particles are clearly deposited on top of the lower layer; these larger particles are >1 μm in diameter. Monitoring of the frequency clearly differentiates the formation of the lower layer from the larger crystals deposited on top at later times. The elastic moduli calculated from QCMD data showed a progressive dissipation increase; the modeling of the solid–liquid interface using a flat approximation resulted in a poor estimation of elastic and storage moduli. Rather, the impedance modeled as a viscoelastic layer in contact with a semi-infinite liquid, where a random bumpy surface with a Gaussian correlator is used, is much more accurate in determining the elastic and storage moduli as losses from the uneven interface are considered. A further step considers that the film is in fact a composite consisting of hard spherical particles of siderite with water in the vacant spaces. This is treated by considering the individual contributions of the phases to the losses measured, thereby further improving the accuracy of the description of the film and the QCMD data. Collectively, this work presents a new framework for the use of QCMD, paired with traditional approaches, to enhance the understanding of crystal deposition and film formation as well as quantify the often evolving mechanical properties.

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Scientific publication

First Direct Gravimetric Detection of Perfluorooctane Sulfonic Acid (PFOS) Water Contaminants, Combination with Electrical Measurements on the Same Device—Proof of Concepts

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Authors: Ivanov, G.R.; Venelinov, T.; Marinov, Y.G.; Hadjichristov, G.B.; Terfort, A.; David, M.; Florescu, M.; Karakuş, S.

Journal: Chemosensors 

Abstract:

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are pollutants of concern due to their long-term persistence in the environment and human health effects. Among them, perfluorooctane sulfonic acid (PFOS) is very ubiquitous and dangerous for health. Currently, the detection levels required by the legislation can be achieved only with expensive laboratory equipment. Hence, there is a need for portable, in-field, and possibly real-time detection. Optical and electrochemical transduction mechanisms are mainly used for the chemical sensors. Here, we report the first gravimetric detection of small-sized molecules like PFOS (MW 500) dissolved in water. A 100 MHz quartz crystal microbalance (QCM) measured at the third harmonic and an even more sensitive 434 MHz two-port surface acoustic wave (SAW) resonator with gold electrodes were used as transducers. The PFOS selective sensing layer was prepared from the metal organic framework (MOF) MIL-101(Cr). Its nano-sized thickness and structure were optimized using the discreet Langmuir–Blodgett (LB) film deposition method. This is the first time that LB multilayers from bulk MOFs have been prepared. The measured frequency downshifts of around 220 kHz per 1 µmol/L of PFOS, a SAW resonator-loaded QL-factor above 2000, and reaction times in the minutes’ range are highly promising for an in-field sensor reaching the water safety directives. Additionally, we use the micrometer-sized interdigitated electrodes of the SAW resonator to strongly enhance the electrochemical impedance spectroscopy (EIS) of the PFOS contamination. Thus, for the first time, we combine the ultra-sensitive gravimetry of small molecules in a water environment with electrical measurements on a single device. This combination provides additional sensor selectivity. Control tests against a bare resonator and two similar compounds prove the concept’s viability. All measurements were performed with pocket-sized tablet-powered devices, thus making the system highly portable and field-deployable. While here we focus on one of the emerging water contaminants, this concept with a different selective coating can be used for other new contaminants.

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