Tag Archive for: Quartz Crystal Microbalance with Dissipation

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Chemical and Mechanical Properties of Drying Oils during Polymerization

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Author: Gwen dePolo

PhD Thesis: Northwestern University (September 2023)

 

Abstract

Drying oils have been used as a binding medium for oil paints since the 15th century. These oil paints transition from a liquid-like paste to a solid-like film as a result of crosslinks forming between the oil molecules. These reactions have been extensively studied chemically, but other material properties are not as well characterized for drying oils. Oil paints are typically used in complex composite structures where the mechanical properties matter just as much as the chemical properties. This thesis focuses on understanding the evolution of mechanical properties during drying oil polymerization.

 

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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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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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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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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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Polyelectrolyte Complexes of Random Copolymers and their Applications in Environmental Remediation

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Author: Jeremy Wang

PhD Thesis: Northwestern University (March 2023)

 

Abstract

As polymer science has advanced as a field, so too have the uses for polymeric materials. We encounter polymers and plastics on a daily basis, and while their presence has greatly improved our quality of life, they have also had a profound and often negative impact on our environment. Plastic waste and pollution are currently problems of great concern, and recent trends in terms of micro– and nanoplastic pollution, and chemical pollution of water continue to exacerbate such worries. In this thesis, we explore how polyelectrolyte complexes of random copolymers can be used to effectively address some of these environmental concerns. The combination of charged interactions and disorder of polymer sequence can provide a novel combination of interactions which are well suited for removing contaminants from water, and even promoting the enzymatic degradation of plastic. The results obtained demonstrate that this research into new polymeric materials not only advances our understanding of fundamental polymer properties but yields relevant applications to the issues we encounter in the present day.

 

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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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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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Effect of Noise on Determining Ultrathin-Film Parameters from QCM-D Data with the Viscoelastic Model

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Authors: Diethelm Johannsmann, Arne Langhoff, Christian Leppin, Ilya Reviakine, and Anna M. C. Maan

Journal: Sensors (2023)

 

Abstract

Quartz crystal microbalance with dissipation monitoring (QCMD) is a well-established technique for studying soft films. It can provide gravimetric as well as nongravimetric information about a film, such as its thickness and mechanical properties. The interpretation of sets of overtone-normalized frequency shifts, Δf/n, and overtone-normalized shifts in half-bandwidth, ΔΓ/n, provided by QCMD relies on a model that, in general, contains five independent parameters that are needed to describe film thickness and frequency-dependent viscoelastic properties. Here, we examine how noise inherent in experimental data affects the determination of these parameters. There are certain conditions where noise prevents the reliable determination of film thickness and the loss tangent. On the other hand, we show that there are conditions where it is possible to determine all five parameters. We relate these conditions to the mathematical properties of the model in terms of simple conceptual diagrams that can help users understand the model’s behavior. Finally, we present new open source software for QCMD data analysis written in Python, PyQTM.

 

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Acoustic Array Biochip Combined with Allele-Specific PCR for Multiple Cancer Mutation Analysis in Tissue and Liquid Biopsy

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Authors: Nikoletta Naoumi, Kleita Michaelidou, George Papadakis, Agapi E. Simaiaki, Román Fernández, Maria Calero, Antonio Arnau, Achilleas Tsortos, Sofia Agelaki, and Electra Gizeli

Journal: ACS Sens. (2022)

Abstract

Regular screening of point mutations is of importance to cancer management and treatment selection. Although techniques like next-generation sequencing and digital polymerase chain reaction (PCR) are available, these are lacking in speed, simplicity, and cost-effectiveness. The development of alternative methods that can detect the extremely low concentrations of the target mutation in a fast and cost-effective way presents an analytical and technological challenge. Here, an approach is presented where for the first time an allele-specific PCR (AS-PCR) is combined with a newly developed high fundamental frequency quartz crystal microbalance array as biosensor for the amplification and detection, respectively, of cancer point mutations. Increased sensitivity, compared to fluorescence detection of the AS-PCR amplicons, is achieved through energy dissipation measurement of acoustically “lossy” liposomes binding to surface-anchored dsDNA targets. The method, applied to the screening of BRAF V600E and KRAS G12D mutations in spiked-in samples, was shown to be able to detect 1 mutant copy of genomic DNA in an excess of 104 wild-type molecules, that is, with a mutant allele frequency (MAF) of 0.01%. Moreover, validation of tissue and plasma samples obtained from melanoma, colorectal, and lung cancer patients showed excellent agreement with Sanger sequencing and ddPCR; remarkably, the efficiency of this AS-PCR/acoustic methodology to detect mutations in real samples was demonstrated to be below 1% MAF. The combined high sensitivity and technology-readiness level of the methodology, together with the ability for multiple sample analysis (24 array biochip), cost-effectiveness, and compatibility with routine workflow, make this approach a promising tool for implementation in clinical oncology labs for tissue and liquid biopsy.

 

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