Hydrophobically Modified Sulfobetaine Copolymers with Tunable Aqueous UCST through Postpolymerization Modification of Poly(pentafluorophenyl acrylate)

Polysulfobetaines, polymers carrying highly polar zwitterionic side chains, present a promising research field by virtue of their antifouling properties, hemocompatibility, and stimulus-responsive behavior. However, limited synthetic approaches exist to produce sulfobetaine copolymers comprising hydrophobic components. Postpolymerization modification of an activated ester precursor, poly(pentafluorophenyl acrylate), employing a zwitterionic amine, 3-((3-aminopropyl)dimethylammonio)propane-1-sulfonate, ADPS, is presented as a novel, one-step synthetic concept toward sulfobetaine (co)polymers. Modifications were performed in homogeneous solution using propylene carbonate as solvent with mixtures of ADPS and pentylamine, benzylamine, and dodecylamine producing a series of well-defined statistical acrylamido sulfobetaine copolymers containing hydrophobic pentyl, benzyl, or dodecylacrylamide comonomers with well-controllable molar composition as evidenced by NMR and FT-IR spectroscopy and size exclusion chromatography.This synthetic strategy was exploited to investigate, for the first time, the influence of hydrophobic modification on the upper critical solution temperature (UCST) of sulfobetaine copolymers in aqueous solution. Surprisingly, incorporation of pentyl groups was found to increase solubility over a wide composition range, whereas benzyl groups decreased solubility—an effect attributed to different entropic and enthalpic contributions of both functional groups. While UCST transitions of polysulfobetaines are typically limited to higher molar mass samples, incorporation of 0–65 mol % of benzyl groups into copolymers with molar masses of 25.5–34.5 kg/mol enabled sharp, reversible transitions from 6 to 82 °C in solutions containing up to 76 mM NaCl, as observed by optical transmittance and dynamic light scattering. Both synthesis and systematic UCST increase of sulfobetaine copolymers presented here are expected to expand the scope and applicability of these smart materials

Intelligent Detection of Adventitious Sounds Critical in Diagnosing Cardiovascular and Cardiopulmonary Diseases

A Multi-Channel Stethograph System (STG system) was designed and developed as an electronic auscultation system for recording heart, lung, and trachea sounds non-invasively through an acoustic sensor array. The STG system consists of 16 acoustic sensors, a signal conditioning board, and a data logger (data acquisition, wireless transmission, sound visualization). The STG system captures breath with any adventitious sound event in 16 locations simultaneously to maximize the information of the specific sound event (for example, detection of the origin of mother adventitious sound and extracting its features), when compared with a single-channel stethoscope. This system can be an efficient tool to aid doctors or physicians in analyzing the adventitious sound from respiration diseases. However, it still requires the need for an experienced doctor or physician in the diagnosis and validation of adventitious sound. This paper presents a computerized method with an intelligent algorithm for detecting various adventitious sounds that are the key characteristics of cardiopulmonary diseases (CD) and assists the doctor/physician in the continuous diagnosis of lungs, which potentially can be beneficial during the COVID-19 progression. The proposed algorithm was able to detect breath patterns using trachea sound; location of the mother adventitious event using lung sounds (14 channels); determine the type of adventitious sound by correlating lung sound with trachea sound. The algorithm consists of breath pattern detection, candidate audio selection, breath pattern extraction, and adventitious sound detection. Digital signal processing techniques such as filtering, windowing, enveloping, discrete Fourier transform, and thresholds were used for identifying and classifying the inhalation and exhalation patterns in the lung sound in an independent (automatic) and intelligent way. The auscultation diagnosis algorithm can identify and distinguish discontinuous adventitious sounds which include wheeze, rhonchi, wheeze & rhonchi, and squawk, with an accuracy of 96.9%, 95.3%, 90%, and 100%. The algorithm was able to fully utilize the advantage of the multichannel system to simultaneously detect breath patterns, types of adventitious sound, and the location of the mother adventitious event that other algorithms cannot achieve. It has the potential to aid doctors/physicians in the early detection and monitoring of any lung disorders by providing objective evidence on adventitious sounds

Titanium Carbide MXene as NH3 Sensor: Realistic First-Principles Study

This work presents a more realistic study on the potential of titanium carbide MXene (Ti3C2Tx) for gas sensing, by employing first principle calculations. The effects of different ratios of different functional groups on the adsorption of NH3, NO, NO2, N2O, CO, CO2, CH4, and H2S gas molecules on Ti3C2Tx were analyzed. The results indicated that Ti3C2Tx is considerably more sensitive to NH3, among the studied gas molecules, with a charge transfer of -0.098 e and an adsorption energy of -0.36 eV. By analyzing the electrostatic surface potential (ESP) and the projected density of states (PDOS), important physical and mechanical properties that determine the strength and nature of gas-substrate interactions were investigated, and also, the significant role of electrostatic effects on the charge transfer mechanism was revealed. Further, the Bader charge analysis for the closest oxygen and fluorine atoms to NH3 molecule showed that oxygen atoms have 60% to 180% larger charge transfer than fluorine atoms, supporting that Ti3C2Tx substrate with a relatively lower ratio of fluorine surface terminations has a stronger interaction with NH3 gas molecules. The calculations show that in the presence of water molecules, approximately 90% smaller charge transfer between NH3 molecule and the Ti3C2Tx occurs. Ab initio molecular dynamics simulations (AIMD) were also carried out to evaluate the thermal stabilities of Mxenes. The comprehensive study presented in this work provides insights and paves the way for realizing sensitive NH3 sensors based on Ti3C2Tx that can be tuned by the ratio of surface termination groups

Impact of Different Ratios of Fluorine, Oxygen, and Hydroxyl Surface Terminations on Ti3C2T x MXene as Ammonia Sensor: A First-Principles Study

A first-principles study was successfully employed to investigate the impact of different ratios of functional groups such as fluorine (-F), oxygen (-O), and hydroxyl (-OH) on ammonia (NH3) sensing of titanium carbide Mxene. Density functional theory (DFT) calculations were performed for studying the adsorption energy (Eads) and charge transfer (CT) between different gases (NH3, CO 2 , NO, H2S and SO 2 ) and TbC2T x material with a high ratio of fluorine surface functional groups, TbC2(OH)o.44Fo.ssO0.66. DFT calculations showed more sensitivity to NH3, with the highest CT (0.098 e) and the lowest Eads (-0.36 eV) among the mentioned gases. The adsorption of NH3 on TbC2T x MXene with a high and low ratios of fluorine surface functional groups, TbC2(OH)o.44Fo.ssOO.66 (Substrate 1) and TbC2(OH)o.66Fo.2201.11 (Substrate 2) respectively, resulted in adsorption energies of -0.36 eV and -0.49 eV, revealing a stronger adsorption of NH3 on Substrate 2 with low ratios of fluorine. In addition, the isosurfaces representation of charge difference illustrated that fluorine atoms have smaller charge transfer than oxygen atoms when interacting with NH3 molecules. The Bader charge difference for the closest oxygen and fluorine atoms to NH3 molecule showed that oxygen atoms have 60% to 180% larger Bader charge difference, when compared to fluorine atoms, supporting that TbC2T x sensor with a lower ratio of fluorine surface termination has a stronger interaction with NH3 gas molecules

Humidity Sensing Properties of Halogenated Graphene: A Comparison of Fluorinated Graphene and Chlorinated Graphene

This work presents a comparison of humidity sensing properties of fluorinated graphene (FG) and chlorinated graphene (ClG), using experimental data and atomic-level ab-initio simulations. The fabrication of the humidity sensor included drop-casting FG and ClG suspensions on silver (Ag)based interdigitated electrodes (IDEs) to form the sensing layer. The sensitivity of FG and ClG to humidity variations was investigated by measurement of relative resistance change (\u394 R/Rb) of the fabricated humidity sensors when the relative humidity (RH) was changed from 20% to 80%, in steps of 10%, at a constant temperature of 24\ub0 C. For RH transition from 20% to 80%, the \u394 R/Rb of the FG-based and the ClG-based humidity sensors were measured as 13.3% and 10.8%, respectively, resulting in a sensitivity of 0.22%/%RH and 0.18%/%RH, respectively. Density functional theory (DFT) calculations showed adsorption energy (Eads) of-0.50 eV and-0.43 eV for the physisorption of water molecules on the FG and ClG, respectively, demonstrating the higher sensitivity of the FG to humidity. The density of states (DOS) calculations showed that the water-adsorbed FG has a larger DOS near the Fermi level when compared to water-adsorbed ClG, which can be attributed to the stronger interaction and more effective charge transfer between the FG and the water molecule