Tag Archive for: Wrapped 5 MHz QCM

Publication on AWSensors technology

Methods for Calibrating the Electrochemical Quartz Crystal Microbalance: Frequency to Mass and Compensation for Viscous Load

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Authors: Claes-Olof A. Olsson, Anna Neus Igual-Muñoz and Stefano Mischler

Journal: Chemosensors (2023)

 

Abstract

The main output from an Electrochemical Quartz Crystal Microbalance is a frequency shift. This note describes how to separate the mass- and viscous load contributions to this shift by a calibration procedure. The mass calibration is made by electroplating from a copper sulfate solution in ethanol/water with 100% current efficiency. An estimate of viscous load is obtained by measuring the energy dissipation and is related to frequency change using the Kanazawa–Gordon equation. Two approaches are discussed: either by performing calibration experiments in a series of water–glycerol mixtures or by following oscillations in frequency and dissipation by collecting data during the stabilization phase of the experiment.

 

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Publication on AWSensors technology

Comparison of Thin-Film Capacitor Geometries for the Detection of Volatile Organic Compounds Using a ZIF-8 Affinity Layer

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Authors: Aleksander Matavž, Margot F. K. Verstreken, Jorid Smets, Max L. Tietze, and Rob Ameloot

Journal: ACS Sensors (2023)

 

Abstract

Their chemical diversity, uniform pore sizes, and large internal surface areas make metal–organic frameworks (MOFs) highly suitable for volatile organic compound (VOC) adsorption. This work compares two geometries of capacitive VOC sensors that use the MOF material ZIF-8 as an affinity layer. When using a permeable top electrode (thickness < 25 nm), the metal–insulator–metal (MIM) sandwich configuration exhibits superior sensitivity, an improved detection limit, and a smaller footprint than the conventional interdigitated electrode layout. Moreover, the transduction of VOC adsorption in ZIF-8 via MIM capacitors is more sensitive to polar VOCs and provides better selectivity at high loadings than gravimetric and optical transductions.

 

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Publication on AWSensors technology

Fouling of Reverse Osmosis Membrane with Effluent Organic Matter: Componential Role of Hydrophobicity

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Authors: Noa Stein, Revital Sharon-Gojman, Meagan S. Mauter, Roy Bernstein and Moshe Herzberg

Journal: ACS ES&T Water (2023)

 

Abstract

Organic matter dissolved in tertiary effluents (effluent organic matter, EfOM) is the predominant organic membrane foulant in tertiary wastewater reverse osmosis (RO) desalination, ultimately causing biofouling. The interrelated effects of EfOM fractions of different hydrophobicity and polarity on membrane performance were studied by (i) examining each fraction’s overall effect on membrane permeability; (ii) analyzing the intrinsic hydraulic resistance induced by each fraction; (iii) studying their adsorption on the active layer of an RO membrane using a quartz crystal microbalance with dissipation monitoring (QCM-D); (iv) assessing their “dry” molecular mass when adsorbed on polyamide using localized surface plasmon resonance (LSPR) sensing; (v) analyzing their hydrodynamic radii by dynamic light scattering (DLS); and (vi) characterization using excitation–emission matrix (EEM) analysis and parallel-factor (PARAFAC) modeling. Hydrophobic and transphilic neutral fractions (containing ∼12.5% total organic carbon) have the greatest effect on membrane flux reduction and the highest hydraulic resistance and adhere most strongly to polyamide surfaces, resulting in the highest adsorbed “dry” mass. Therefore, in terms of their effect on RO permeate flux reduction, these fractions are the most detrimental in the EfOM mix. EEM analysis and associated PARAFAC modeling indicate that the main components causing this effect are mixtures of protein-like compounds, together with humic-like substances. Novel LSPR-based analysis elucidated the role of the fractions most detrimental to membrane permeability through measurement of dry mass surface concentration on a polyamide mimetic sensor. This study provides valuable insights into the roles of different EfOM fractions in RO membrane fouling and enhances our understanding of fouling during tertiary wastewater desalination.

Fouling of Reverse Osmosis Membrane with Effluent Organic Matter: Componential Role of Hydrophobicity

 

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Publication on AWSensors technology

Tuning the water interactions of cellulose nanofibril hydrogels using willow bark extract

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Authors: Ngoc Huynh, Juan José Valle-Delgado, Wenwen Fang, Suvi Arola, Monika Österberg

Journal: Carbohydrate Polymers (2023)

 

Abstract

Cellulose nanofibrils (CNFs) are increasingly used as precursors for foams, films and composites, where water interactions are of great importance. In this study, we used willow bark extract (WBE), an underrated natural source of bioactive phenolic compounds, as a plant-based modifier for CNF hydrogels, without compromising their mechanical properties. We found that the introduction of WBE into both native, mechanically fibrillated CNFs and TEMPO-oxidized CNFs increased considerably the storage modulus of the hydrogels and reduced their swelling ratio in water up to 5–7 times. A detailed chemical analysis revealed that WBE is composed of several phenolic compounds in addition to potassium salts. Whereas the salt ions reduced the repulsion between fibrils and created denser CNF networks, the phenolic compounds – which adsorbed readily on the cellulose surfaces – played an important role in assisting the flowability of the hydrogels at high shear strains by reducing the flocculation tendency, often observed in pure and salt-containing CNFs, and contributed to the structural integrity of the CNF network in aqueous environment. Surprisingly, the willow bark extract exhibited hemolysis activity, which highlights the importance of more thorough investigations of biocompatibility of natural materials. WBE shows great potential for managing the water interactions of CNF-based products.

 

Cellulose nanofibrils (CNFs) are increasingly used as precursors for foams, films and composites, where water interactions are of great importance. In this study, we used willow bark extract (WBE), an underrated natural source of bioactive phenolic compounds, as a plant-based modifier for CNF hydrogels, without compromising their mechanical properties. We found that the introduction of WBE into both native, mechanically fibrillated CNFs and TEMPO-oxidized CNFs increased considerably the storage modulus of the hydrogels and reduced their swelling ratio in water up to 5–7 times. A detailed chemical analysis revealed that WBE is composed of several phenolic compounds in addition to potassium salts. Whereas the salt ions reduced the repulsion between fibrils and created denser CNF networks, the phenolic compounds - which adsorbed readily on the cellulose surfaces - played an important role in assisting the flowability of the hydrogels at high shear strains by reducing the flocculation tendency, often observed in pure and salt-containing CNFs, and contributed to the structural integrity of the CNF network in aqueous environment. Surprisingly, the willow bark extract exhibited hemolysis activity, which highlights the importance of more thorough investigations of biocompatibility of natural materials. WBE shows great potential for managing the water interactions of CNF-based products.

 

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Publication on AWSensors technology

Trace Water Effects on Crystalline 1-Ethyl-3-methylimidazolium Acetate

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Authors: Ashlee Aiello, John R. Hoffman, Anthony P. Kotula, Lucas Q. Flagg, Ruipeng Li, and Jeremiah W. Woodcock

Journal: J. Phys. Chem. B (2023)

 

Abstract

Spontaneous room-temperature crystallization of 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) was observed upon removal of trace water. Sample purity was confirmed using analytical nuclear magnetic resonance spectroscopy to ensure that trace water or other contaminants did not produce this observation. Raman spectroscopy and simultaneous quartz crystal microbalance/infrared spectroscopy measurements were used to study molecular reorganization during crystallization and decrystallization using trace water in the form of atmospheric moisture. These experimental results were supplemented with density functional theory calculations that indicate imidazolium cation ring stacking and side chain clustering with an exclusive arrangement of the acetate anion in the cation ring plane upon water removal. Crystal structure formation was confirmed using two-dimensional wide-angle X-ray scattering. This natural crystallization is attributed to the removal of trace water over extended periods of time and calls attention to the molecular-level role of water in the structure of hygroscopic ionic liquid systems.

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Publication on AWSensors technology

Multispecies biofilms on reverse osmosis membrane dictate the function and characteristics of the bacterial communities rather than their structure

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Authors: Noya Ran, Gil Sorek, Noa Stein, Revital Sharon-Gojman, Moshe Herzberg, and Osnat Gillor

Journal: Environmental Research (2023)

 

Abstract

The main reason for the deterioration of membrane operation during water purification processes is biofouling, which has therefore been extensively studied. Biofouling was shown to reduce membrane performance reflected by permeate flux decline, reduced selectivity, membrane biodegradation, and consequently, an increase in energy consumption. Studies of biofouling focused on the identification of the assembled microbial communities, the excretion of extracellular polymeric substances (EPS), and their combined role in reduced membrane performance and lifetime. However, the link between the structure and function of biofouling communities has not been elucidated to date. Here, we provide a novel insight, suggesting that bacterial functions rather than composition control biofouling traits on reverse osmosis (RO) membranes. We studied the potential activity of RO biofilms at metatranscriptome resolution, accompanied by the morphology and function of the biofouling layer over time, including microscopy and EPS composition, adhesion, and viscoelastic properties. To that end, we cultivated natural multispecies biofilms in RO membranes under treated wastewater flow and extracted RNA to study their taxonomies and gene expression profiles. Concomitantly, the biofilm structure was visualized using both scanning electron microscopy and laser scanning confocal microscopy. We also used quartz crystal microbalance with dissipation to characterize the affinity of EPS to membrane-mimetic sensors and evaluated the viscoelasticity of the Ex-Situ EPS layer formed on the sensor. Our results showed that different active bacterial taxa across five taxonomic classes were assembled on the RO membrane, while the composition shifted between 48 and 96 h. However, regardless of the composition, the maturation of the biofilm resulted in the expression of similar gene families tightly associated with the temporal kinetics of the EPS composition, adhesion, and viscoelasticity. Our findings highlight the temporal selection of specific microbial functions rather than composition, featuring the adhesion kinetics and viscoelastic properties of the RO biofilm.

 

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Publication on AWSensors technology

Modifying last layer in polyelectrolyte multilayer coatings for capillary electrophoresis of proteins

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Authors: Sébastien Roca, Laurent Leclercq, Philippe Gonzalez, Laura Dhellemmes, Laurent Boiteau, Gaulthier Rydzek, and Hervé Cottet

Journal: Journal of Chromatography A (2023)

 

Abstract

Protein adsorption on the inner wall of the fused silica capillary wall is an important concern for capillary electrophoresis (CE) analysis since it is mainly responsible for separation efficiency reduction. Successive Multiple Ionic-polymer Layers (SMIL) are used as capillary coatings to limit protein adsorption, but even low residual adsorption strongly impacts the separation efficiency, especially at high separation voltages. In this work, the influence of the chemical nature and the PEGylation of the polyelectrolyte deposited in the last layer of the SMIL coating was investigated on the separation performances of a mixture of four model intact proteins (myoglobin (Myo), trypsin inhibitor (TI), ribonuclease a (RNAse A) and lysozyme (Lyz)). Poly(allylamine hydrochloride) (PAH), polyethyleneimine (PEI), ε-poly(L-lysine) (εPLL) and α-poly(L-lysine) (αPLL) were compared before and after chemical modification with polyethyleneglycol (PEG) of different chain lengths. The experimental results obtained by performing electrophoretic separations at different separation voltages allowed determining the residual retention factor of the proteins onto the capillary wall via the determination of the plate height at different solute velocities and demonstrated a strong impact of the polycationic last layer on the electroosmotic mobility, the separation efficiency and the overall resolution. Properties of SMIL coatings were also characterized by quartz microbalance and atomic force microscopy, demonstrating a glassy structure of the films.

 

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Scientific publication

Synthesis and covalent immobilization of redox-active metallopolymers for organic phase electrochemistry

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Authors: Hanna Hübner, Riccardo Candeago, Deborah Schmitt, Alexander Schießer, Beichen Xiong, Markus Gallei and Xiao Su.
Journal: Polymer (2022) 244, 124656.

 

Abstract

Redox-active metallopolymers are promising stimuli-responsive platforms for a range of applications including sensing, energy storage, and selective separations. In particular, heterogeneously-functionalized metallopolymers can modulate the capture and release of target molecules, driven by redox electron-transfer. However, prior metallopolymer-functionalized electrodes have been fabricated by non-covalent methods, and tailored for aqueous phase applications. As such, despite the existing potential for heterogeneous applications in organic phase, there are significant constraints to the stability of metallopolymers in organic solvents, including high solubility in solvents such as chloroform or tetrahydrofuran. We propose the immobilization of thiol-functionalized redox-active metallopolymers on metallic surfaces as a facile way to enhance stability and cyclability in organic media, and thus broaden the applicability of redox-metallopolymers for organic phase applications. We explore the anionic polymerization of metal-containing monomers vinylferrocene (VFc) and ferrocenyldimethylsilane (FS), and their thiol end-functionalization by living anionic polymerization strategies. PFS and PVFc with molar masses ranging from 1800 to 49900 g mol−1 and 2900 to 6300 g mol−1 respectively were prepared with a segment of poly(ethylene sulfide), as characterized by size-exclusion chromatography, NMR spectroscopy, MALDI/ToF, thermogravimetry, and elemental analysis. Both metallopolymers were immobilized on gold substrates by a grafting-to protocol, with demonstrated redox-responsiveness by electrochemical control. In the case of immobilized PVFc, operando electrochemical testing demonstrated the stable and reversible electrochemical cycling capabilities (>74% maximum current retained after 100 oxidation/reduction cycles) in several organic solvents including chloroform, tetrahydrofuran, ethanol, methanol, acetonitrile, and acetone. Immobilized PFS was stable in chloroform, with a 83% maximum current retained after 100 oxidation/reduction cycles. We envision future applications of these covalently immobilized metallopolymers for a broad range of fields from selective separations to sensing and energy storage.

 

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