Composition of Organically Modified Silica for the Superhydrophobic Surface with Low Sliding Angle.

Extremely water-repellent surfaces with low sliding angle (SA) have been obtained with a facile single-step sol-gel strategy via co-condensation of tetraethoxysilane (TEOS) and hexadecyltrimethoxysilane (HDTMS) in basic media with an efficient self-cleaning property. We investigated the effect of the molar ratio of HDTMS and TEOS on the properties of the modified silica-coated poly(ethylene terephthalate) (PET) film. A high water contact angle (WCA) of 165° and a low SA of 1.35° were obtained at a molar ratio of 0.125. The dual roughness pattern for the low SA was developed by a one-step coating of the modified silica with a molar ratio of 0.125. The evolution of the surface to the dual roughness pattern by nonequilibrium dynamics depended on the size and shape factor of modified silica. The primitive size and the shape factor of the organosilica with a molar ratio of 0.125 were 70 nm and 0.65, respectively. We also presented a new method to determine the superficial surface friction (ζ) of the superhydrophobic surface. The ζ was a physical parameter that characterized the slip and rolling behavior of water droplets on the superhydrophobic surface along with the equilibrium property WCA and the static frictional property SA.

The Accuracy of Wearable Photoplethysmography Sensors for Telehealth Monitoring: A Scoping Review.

Background and Objectives: Photoplethysmography (PPG) sensors have been increasingly used for remote patient monitoring, especially during the COVID-19 pandemic, for the management of chronic diseases and neurological disorders. There is an urgent need to evaluate the accuracy of these devices. This scoping review considers the latest applications of wearable PPG sensors with a focus on studies that used wearable PPG sensors to monitor various health parameters. The primary objective is to report the accuracy of the PPG sensors in both real-world and clinical settings. Methods: This scoping review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). Studies were identified by querying the Medline, Embase, IEEE, and CINAHL databases. The goal was to capture eligible studies that used PPG sensors to monitor various health parameters for populations with a minimum of 30 participants, with at least some of the population having relevant health issues. A total of 2,996 articles were screened and 28 are included in this review. Results: The health parameters and disorders identified and investigated in this study include heart rate and heart rate variability, atrial fibrillation, blood pressure (BP), obstructive sleep apnea, blood glucose, heart failure, and respiratory rate. An overview of the algorithms used, and their limitations is provided. Conclusion: Some of the barriers identified in evaluating the accuracy of multiple types of wearable devices include the absence of reporting standard accuracy metrics and a general paucity of studies with large subject size in real-world settings, especially for parameters such as BP.

Electrophoretic deposition of MXenes and their composites: Toward a scalable approach.

Over the past decade, MXenes, a novel class of advanced 2D nanomaterials, have manifested as a prominent electrode material with diverse applications. Their unique layered structures, negative zeta potential, charge carrier mobility, mechanical properties, adjustable bandgap, hydrophilicity, metallic nature, and surface chemistry collectively contribute to the abundance of active redox sites on the surface and a reduction in the ion diffusion pathway. Despite such promising attributes of MXene, challenges like aggregation and restacking reduce the accessibility of active surface sites for electrolyte ions. Amongst approaches such as surface functionalization, addition of spacers, or facilitating pore formation, the electrophoretic deposition (EPD) of MXene on substrates has commenced to gain attention aiming to mitigate these issues. More importantly, it offers large-scale film fabrication in a short time without the necessity of using a charge-inducing agent. This review compiles recent advances in the use of EPD for preparing MXene-based electrodes and discusses the effect of EPD parameters on the relevant device performance. Recognition is given to understanding the relation of MXene colloidal composition in aqueous (and in some cases, non-aqueous) dispersions, deposition times, and other relevant parameters on respective device performances. In conclusion, the potential avenues offered by MXenes for future research on electrode materials are emphasized.

Photoplethysmography Enabled Wearable Devices and Stress Detection: A Scoping Review.

BACKGROUND: Mental and physical health are both important for overall health. Mental health includes emotional, psychological, and social well-being; however, it is often difficult to monitor remotely. The objective of this scoping review is to investigate studies that focus on mental health and stress detection and monitoring using PPG-based wearable sensors. METHODS: A literature review for this scoping review was conducted using the PRISMA (Preferred Reporting Items for the Systematic Reviews and Meta-analyses) framework. A total of 290 studies were found in five medical databases (PubMed, Medline, Embase, CINAHL, and Web of Science). Studies were deemed eligible if non-invasive PPG-based wearables were worn on the wrist or ear to measure vital signs of the heart (heart rate, pulse transit time, pulse waves, blood pressure, and blood volume pressure) and analyzed the data qualitatively. RESULTS: Twenty-three studies met the inclusion criteria, with four real-life studies, eighteen clinical studies, and one joint clinical and real-life study. Out of the twenty-three studies, seventeen were published as journal-based articles, and six were conference papers with full texts. Because most of the articles were concerned with physiological and psychological stress, we decided to only include those that focused on stress. In twelve of the twenty articles, a PPG-based sensor alone was used to monitor stress, while in the remaining eight papers, a PPG sensor was used in combination with other sensors. CONCLUSION: The growing demand for wearable devices for mental health monitoring is evident. However, there is still a significant amount of research required before wearable devices can be used easily and effectively for such monitoring. Although the results of this review indicate that mental health monitoring and stress detection using PPG is possible, there are still many limitations within the current literature, such as a lack of large and diverse studies and ground-truth methods, that need to be addressed before wearable devices can be globally useful to patients.

Mixed-dimensional heterostructures of hydrophobic/hydrophilic graphene foam for tunable hydrogen evolution reaction.

The synergetic effect of hydrophilic and hydrophobic carbon can be used to obtain tunable hydrogen evolution reaction (HER) at the interface. Herein, graphene oxide (GO-Hummers method) was coated on graphene foam (GF) synthesized via chemical vapor deposition to develop mixed-dimensional heterostructure for the observation of HER. The porosity of GF not only provides an optimized diffusion coefficient for better mass transport but also modified surface chemistry (GF/GO-hydrophobic/hydrophilic interface), which results in an onset potential 50 mV and overpotential of 450 mV to achieve the current density 10 mA/cm2. The surface analysis shows that inherent functional groups at the surface played a key role in tuning the activity of hybrid, providing a pathway to introduce non-corrosive electrodes for water splitting.

Crosslinking hydroxylated reduced graphene oxide with RAFT-CTA: A nano-initiator for preparation of well-defined amino acid-based polymer nanohybrids.

Here, we demonstrate a novel reversible addition-fragmentation chain transfer agent (RAFT-CTA)-modified reduced graphene oxide nanosheets (CTA-rGONSs) by crosslinking rGONSs with a RAFT-CTA via esterification reaction. These nano CTA-rGONSs were used to polymerize a hydrophobic amino acid-based methacrylamide (N-acryloyl-l-phenylalanine methyl ester) monomer with different monomer/initiator ratios. Thermogravimetric analysis showed that the polymer-graphene composites were thermally more stable than GO itself. Mn of the polymers increased with increasing monomer/initiator ratio, while the polydispersity index decreased, indicating controlled polymerization. The composites were stable in DMF even after two months.

Synthesis of scalable and tunable slightly oxidized graphene via chemical vapor deposition.

Semiconducting, large sheets of carbon as an active material in optoelectronic research are missing and reduced graphene oxide (rGO) can be a good candidate. However, chemical synthesis cannot produce large sheets of rGO (i.e. maximum: 20-30µm) as well as high quality rGO due to the restraints of fabrication method. Thus, a novel strategy for the synthesis of large sheets of semiconducting rGO is urgently required. Large area slightly oxidized graphene (SOG) is fabricated at the interface of silicon dioxide (SiO2) and silicon via Chemical Vapor Deposition (CVD) method, herein for the first time. Carbon atoms bond with oxygen functionalities (i.e. CO, COH) at the time of diffusion in SiO2 allowing for C/O ratios from 7 to 10 adjustable by the variation of SiO2 thickness, indicating the tunable oxidation. Moreover, electronic structure and morphology of SOG are similar to the chemically grown rGO. The fabrication mechanism of SOG is also investigated.

Reduced graphene oxide composites with water soluble copolymers having tailored lower critical solution temperatures and unique tube-like structure.

Nanohybrids of graphene with water soluble polymer were synthesized using 'grafting from' method. GO, prepared by modified Hummers' method, was first reacted with sodium azide. Alkyne-terminated RAFT-CTA was synthesized by reaction of propargyl alcohol and S-1-dodecyl-S'-(α,α'-dimethyl-α"-acetic acid) trithiocarbonate. RAFT-CTA was grafted onto the GO sheets by facile click-reaction and subsequently, N-isopropylacrylamide (NIPAM) and N-ethyleacrylamide (NEAM) were polymerized on graphene sheets via RAFT polymerization method. The respective copolymers with different ratios were also prepared. The nanohybrids were characterized by FTIR, XRD, TGA, Raman, SEM, and AFM. Both SEM and AFM clearly showed rod-like structures for rGO-PNEAM. XRD showed a small peak at 2θ = 19.21°, corresponding to d-spacing ≈ 4.6 Å. In addition, the nanohybrids showed a very broad temperature range for the LCST in water between ca. 30 and 70 °C.

Sweet graphene I: toward hydrophilic graphene nanosheets via click grafting alkyne-saccharides onto azide-functionalized graphene oxide.

Water-soluble graphene nanosheets (GNS) were fabricated via functionalization of graphene oxide (GO) with mono and disaccharides on the basal plane and edges using Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition of azides and terminal alkynes (Click chemistry). To graft saccharides onto the plane of GO, it was reacted with sodium azide to introduce azide groups on the plane. Then, it was treated with alkyne-modified glucose, mannose, galactose, and maltose. In the next approach, we attached 1,3-diazideoprop-2-ol onto the edges of GO and it was subsequently clicked with alkyne-glucose. The products were analyzed by Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy, thermogravimetric analysis (TGA), and X-ray diffraction spectrometry. FTIR and TGA results showed both sugar-grafted GO sheets were reduced by sodium ascorbate during click-coupling reaction which is an advantage for this reaction. Besides, glycoside-grafted GNS were easily dispersed in water and stable for two weeks.

Synthesis of New Functionalized Citric Acid-based Dendrimers as Nanocarrier Agents for Drug Delivery.

INTRODUCTION: Citric acid-polyethylene glycol-citric acid (CPEGC) triblock dendrimers can serve as potential delivery systems. METHODS: In this investigation, CPEGC triblock dendrimers were synthesized and then imidazole groups were conjugated onto the surface of the G1, G2 and G3 of the obtained dendrimers. In order to study the type of the interactions between the functionalized dendrimers and a drug molecule, Naproxen which contains acidic groups, was examined as a hydrophobic drug in which the interactions would be of the electrostatic kind between its acidic groups and the lone pair electrons of nitrogen atom in imidazole groups. The quantity of the trapped drug and also the amount of its release were measured with UV spectrometric method in pH 1, 7.4 and 10. The average diameter of the nanocarriers was measured by Dynamic Light Scattering (DLS) technique. RESULTS: The size range of particles was determined to be 16-50 nm for different generations. The rate of the release increased in pH=10 in all generations due to the increases in Naproxen solubility and the hydrolysis of the esteric bonds in the mentioned pH. The results showed that the amount of the trapped drug increased with the increase in the generation of the dendrimer and pH. CONCLUSION: Based on our findings, we suggest CPEGC triblock dendrimers possess great potential to be used as drug/gene delivery system.