Intrinsic Carbon Defects for the Electrosynthesis of H₂O₂

Carbon materials have manifested promising potential in electrochemical reduction of O2 to H2O2. The oxygen functional groups have been identified as the catalytic sites. However, the intrinsic carbon defects abundant in carbon materials have often been neglected. Herein, a three-dimensional carbon framework with abundant intrinsic defects and oxygen functional groups (the oxygen content and chemical states of oxygen are comparable to those of commercial carbon black) was introduced and exhibited outstanding catalytic activity and selectivity toward H2O2 electrosynthesis. Through a combination of in situ Raman spectroscopy and density functional theory calculations, the intrinsic carbon defects, such as zigzag edge and zigzag pentagon sites with optimal binding energy for OOH, were also determined to be active sites. It was further revealed that intrinsic carbon defects with large negative charge density and asymmetric spin density may have high activity toward H2O2 production

Multipedal DNA Walker Biosensors Based on Catalyzed Hairpin Assembly and Isothermal Strand-Displacement Polymerase Reaction for the Chemiluminescent Detection of Proteins

In this study, two kinds of sensitive biosensors based on a multipedal DNA walker along a three-dimensional DNA functional magnet particles track for the chemiluminescent detection of streptavidin (SA) are constructed and compared. In the presence of SA, a multipedal DNA walker was constructed by a biotin-modified catalyst as a result of the terminal protection to avoid being digested by exonuclease I. Then, through a toehold-mediated strand exchange, a “leg” of a multipedal DNA walker interacted with a toehold of a catalyzed hairpin assembly (CHA)-H1 coupled with magnetic microparticles (MMPs) and opened its hairpin structure. The newly open stem in CHA-H1 was hybridized with a toehold of biotin-labeled H2. Via the strand displacement process, H2 displaced one “leg” of a multipedal DNA walker, and the other “leg” continued to interact with the neighboring H1 to initiate the next cycle. In order to solve the high background caused by the hybridization between CHA-H1 and H2 without a CHA-catalyst, the other model was designed. The principle of the other model (isothermal strand-displacement polymerase reaction (ISDPR)-DNA walker) was similar to that of the above one. After the terminal protection of SA, a “leg” of a multipedal DNA walker was triggered to open the hairpin of the ISDPR-H1 conjugated with MMPs. Then, the biotin-modified primer hybridized with the newly exposed DNA segment, triggering the polymerization reaction with the assistance of dNTPs/polymerase. As for the extension of the primer, the “leg” of a multipedal DNA walker was displaced so that the other “leg” could trigger the proximal H1 to go onto the next cycle. Due to its lower background and stronger signal, a multipedal DNA walker based on an ISDPR had a lower limit of detection for SA. The limit of detection for SA was 6.5 pM, and for expanding the application of the method, the detections of the folate receptor and thrombin were explored. In addition, these DNA walker methods were applied in complex samples successfully

Phytosterols Protect against Osteoporosis by Regulating Gut Microbiota

Osteoporosis is increasingly prevalent worldwide, representing a major health burden. However, there is a lack of nutritional strategies for osteoporotic therapy. Phytosterols, as natural bioactive compounds, have the potential to alleviate osteoporosis. In this study, a glucocorticoid-induced osteoporosis mouse model and treatment with low and high concentrations of phytosterols for 4 weeks were established. The results demonstrated that compared to the control group, low-concentration phytosterols (LP) (0.3 mg/mL) increased bone mass, improved trabecular microstructure, reduced serum levels of cross-linked C-telopeptide of type I collagen (CTX-1), and elevated serum levels of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). Conversely, high-concentration phytosterols (0.5 mg/mL) showed no effect. Additionally, we validated the effect of LP in ameliorating osteoporosis using an ovariectomized (OVX)-induced osteoporosis mouse model. Mechanistically, phytosterols altered the microbial composition to counteract glucocorticoid-induced gut microbiota disorder and improve the length and morphology of the small intestine. Particularly, based on selection strategy and correlation analysis, phytosterols increased the relative abundance of Ruminococcus and decreased the relative abundance of Bilophila, which were significantly associated with glucocorticoid-induced osteoporosis indications. Overall, these findings suggest that phytosterols regulate gut microbiota to increase bone mass, thereby exerting an antiosteoporotic effect

Stable High-Performance Flexible Photodetector Based on Upconversion Nanoparticles/Perovskite Microarrays Composite

Methylammonium lead halide perovskite has emerged as a new class of low-temperature-processed high-performance semiconductors for optoelectronics, but with photoresponse limited to the UV–visible region and low environmental stability. Herein, we report a flexible planar photodetector based on MAPbI₃ microarrays integrated with NaYF₄:​Yb/​Er upconversion nanoparticles (UCns) that offers promise for future high performance and long-term environmental stability. The promise derives from the confluence of several factors, including significantly enhanced photons absorption in the visible spectrum, efficient energy transition in the near-infrared (NIR) region, and inhibition of water attack by the hydrophobic UCns capping layer. The UCns layer aided in remarkably enhanced photodetection capability in the visible spectrum with detectivity (<i>D*</i>) reaching 5.9 × 10¹² Jones, among the highest reported values, due to the increased photocarrier lifetime and decreased reflectivity. Excellent NIR photoresponse with spectral responsivity (<i>R</i>) and <i>D*</i> as high as 0.27 A W^–1 and 0.76 × 10¹² Jones were obtained at 980 nm, respectively, superior to the reported values of state-of-the-art organic-perovskite NIR photodetectors. Moreover, the hydrophobic UCns capping layer serving as a moisture inhibitor allowed significantly enhanced long-term environmental stability, e.g., 70% vs 27% performance retained after 1000 h exposure in 30–40% RH humidity air without encapsulation for the bilayer and the neat MAPbI₃ devices, respectively. These results suggest that the composite based on perovskite and UCns is promising for constructing high-performance broadband optoelectronic devices with long-term stability

Investigation on the Performance of a Block Polyether Demulsifier Based on Polysiloxane for the Treatment of Aged Oil

Using a silicone demulsifier is an efficient approach in the treatment of environmental pollution caused by aged oil. A new type of silicone demulsifier was prepared in this work by following a two-step synthesis method based on SP169 (octadecanol block polyether) and AE16 (monoamine aliphatic alkyl block polyether). Reaction conditions, such as reaction time, temperature, etc., were optimized for the synthesis of poly­(ether ester) intermediates and silicone demulsifier. Both the proton nuclear magnetic resonance and infrared spectra confirmed the successful preparation of poly­(ether ester) intermediates from acrylic acid based on the presence of the CC and CO bonds provided, indicating the successful modification of the silicone demulsifier by the polysiloxane and poly­(ether ester) intermediates. The thermal degradation interval of the silicone demulsifier is 325–390 °C according to thermogravimetric analysis. In addition, the diffusion and adsorption of the silicone demulsifier, which were measured by a quartz crystal microbalance with dissipation, indicated that the silicone demulsifier forms a compact and uniform adsorbed layer, which contributed to the demulsification. The dehydration rate was 86.87% when the poly­(ether ester) ratio, silicone demulsifier dosage, demulsification temperature, and time were 2:1, 150 mg/L, 65 °C, and 1.5 h, respectively, during the demulsification tests. The silicone demulsifier has great potential application in oil/water separations of aged oil

Template-Free and Stretchable Conductive Fiber with a Built-In Helical Structure for Strain-Insensitive Signal Transmission

With the rapid development of intelligent electronic devices, conductive fibers have become very critical to signal transmission devices. However, metal-based rigid conductive wires, such as high-modulus copper and silver wires, are prone to signal failure owing to tensile breakage under large strain conditions. Therefore, strain-insensitive stretchable conductive fibers for signal transmission are critical for next-generation wearable devices. Herein, a stretchable conductive fiber with a built-in helical structure is constructed by a “speed discrepancy” fiber-coating strategy with mass scalable production (60 cm/min). Such a “speed discrepancy” strategy is the key mechanism to template-free fabricate a built-in helical structure of the stretchable conductive fiber. The resultant fiber exhibits high conductivity (873 S/cm), stable insensitive signal transmission with a high quality factor (47.4), and a low relative resistance change (∼6%) under large strain. The built-in helical structure inspired by loofah whiskers endows the fiber with excellent strain insensitivity, and it can withstand large strains. On the proof of concept, our fiber can be seamlessly knitted, woven, and braided into smart textiles as an ideal signal transmission device under large strains, which will undoubtedly promote the development of intelligent electronic textiles and next-generation wearable devices

Color-Tuned Perovskite Films Prepared for Efficient Solar Cell Applications

Color-tuned perovskite films have been recognized as a promising candidate for building integrated photovoltaics; bright, colorful displays; and component cells in multijunction solar cell applications. In this paper, four representative color-tuned perovskite films with chemical formula CH₃NH₃PbBr_<i>x</i>I_3–<i>x</i> (<i>x</i> = 0, 1, 2, and 3) are successfully prepared by using a technique that combines the advantages of direct contact lead halide film with hot methylamine halide powder and intercalcation processes. The energy-dispersive X-ray spectrometry results indicate that the Br/I ratio is controlled as desired. The scanning electron microscopy imaging shows very uniform films with good surface coverage on the substrate. The highest power conversion efficiency of the perovskite solar cells with the four different compositions are 12.76%, 6.84%, 4.12%, and 3.53%, respectively

Fabrication and Characterization of a Novel Anticancer Drug Delivery System: Salecan/Poly(methacrylic acid) Semi-interpenetrating Polymer Network Hydrogel

Salecan is a novel linear extracellular polysaccharide with a linear backbone of 1–3-linked glucopyranosyl units. Salecan is suitable for preparing hydrogels for biomedical applications due to its prominent physicochemical and biological profiles. In this contribution, a variety of innovative semi-interpenetrating polymer network (semi-IPN) hydrogels consisting of Salecan and poly­(methacrylic acid) (PMAA) were developed via free radical polymerization for controlled drug delivery. The successful fabrication of the semi-IPNs was verified by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermogravimetric (TGA) measurements. Scanning electron microscopy (SEM) and rheology analyses demonstrated that the morphological and mechanical behaviors of the resultant hydrogels were strongly affected by the contents of Salecan and cross-linker <i>N</i>,<i>N</i>′-methylenebis­(acrylamide) (BIS). Moreover, the swelling properties of these hydrogels were systematically investigated, and the results indicated that they exhibited pH sensitivity. The drug delivery applications of such fabricated hydrogels were further evaluated from which doxorubicin (Dox) was chosen as a model drug for in vitro release and cell viability studies. It was found that the Dox release from the Dox-loaded hydrogels was significantly accelerated when the pH of the release media decreased from 7.4 to 5.0. Toxicity assays confirmed that the blank hydrogels had negligible toxicity to normal cells, whereas the Dox-loaded hydrogels remained high in cytotoxicity for A549 and HepG2 cancer cells. All of these attributes implied that the new proposed semi-IPNs serve as potential drug delivery platforms for cancer therapy

Solution-Processed Nb:SnO₂ Electron Transport Layer for Efficient Planar Perovskite Solar Cells

Electron transport layer (ETL), facilitating charge carrier separation and electron extraction, is a key component in planar perovskite solar cells (PSCs). We developed an effective ETL using low-temperature solution-processed Nb-doped SnO₂ (Nb:SnO₂). Compared to the pristine SnO₂, the power conversion efficiency of PSCs based on Nb:SnO₂ ETL is raised to 17.57% from 15.13%. The splendid performance is attributed to the excellent optical and electronic properties of the Nb:SnO₂ material, such as smooth surface, high electron mobility, appropriate electrical conductivity, therefore making a better growth platform for a high quality perovskite absorber layer. Experimental analyses reveal that the Nb:SnO₂ ETL significantly enhances the electron extraction and effectively suppresses charge recombination, leading to improved solar cell performance

CO₂ Plasma-Treated TiO₂ Film as an Effective Electron Transport Layer for High-Performance Planar Perovskite Solar Cells

Perovskite solar cells (PSCs) have received great attention because of their excellent photovoltaic properties especially for the comparable efficiency to silicon solar cells. The electron transport layer (ETL) is regarded as a crucial medium in transporting electrons and blocking holes for PSCs. In this study, CO₂ plasma generated by plasma-enhanced chemical vapor deposition (PECVD) was introduced to modify the TiO₂ ETL. The results indicated that the CO₂ plasma-treated compact TiO₂ layer exhibited better surface hydrophilicity, higher conductivity, and lower bulk defect state density in comparison with the pristine TiO₂ film. The quality of the stoichiometric TiO₂ structure was improved, and the concentration of oxygen-deficiency-induced defect sites was reduced significantly after CO₂ plasma treatment for 90 s. The PSCs with the TiO₂ film treated by CO₂ plasma for 90 s exhibited simultaneously improved short-circuit current (<i>J</i>_SC) and fill factor. As a result, the PSC-based TiO₂ ETL with CO₂ plasma treatment affords a power conversion efficiency of 15.39%, outperforming that based on pristine TiO₂ (13.54%). These results indicate that the plasma treatment by the PECVD method is an effective approach to modify the ETL for high-performance planar PSCs