Authors: Ilya Reviakine
Journal: Biointephases (2024)
Abstract
Applications of quartz crystal microbalance with dissipation to studying soft and biological interfaces are reviewed. The focus is primarily on data analysis through viscoelastic modeling and a model-free approach focusing on the acoustic ratio. Current challenges and future research and development directions are discussed.
You may read the full paper here.
AWsensors Technology Note, video, and executable QCMD Data Analysis with PyQTM.
Trace Water Effects on Crystalline 1-Ethyl-3-methylimidazolium Acetate
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.
You may read the full paper here.
Trace Water Effects on Crystalline 1-Ethyl-3-methylimidazolium Acetate
Multispecies biofilms on reverse osmosis membrane dictate the function and characteristics of the bacterial communities rather than their structure
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.
You may read the full paper here.
Multispecies biofilms on reverse osmosis membrane dictate the function and characteristics of the bacterial communities rather than their structure
Effect of Noise on Determining Ultrathin-Film Parameters from QCM-D Data with the Viscoelastic Model
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.
You may read the full paper here.
Effect of Noise on Determining Ultrathin-Film Parameters from QCM-D Data with the Viscoelastic Model
AWSensors presents a new Technology Note on the importance of dissipation measuring when working with QCMD: “The difference the “D” makes in QCMD”.
Quartz Crystal Microbalance with Dissipation, or QCMD, is having a tremendous impact on research in the soft and biological interfaces fields because of its versatility and the wealth of information it provides. In this Technology Note, we discuss the origins of dissipation in the different systems studied by QCMD, from complex fluids and polymer films to biomolecular and particle assemblies, and the information dissipation can provide, from characterizing viscoelasticity to studying molecular conformation.
In this Technical Note we discuss the origins of dissipation, how it can be used to verify the applicability of the Sauerbrey relationship and their interaction with the viscoelasticity and in the biological sensing.
You can read and download the full Technology Note in pdf file from this link. A list of our Technology Notes can be found on our Technology Web Page..
