Preparation, Air Filtration Performance of a Fluorinated Polyimide/Polyacrylonitrile Nanofibrous Membrane by Electrospinning.

This paper reports the successful fabrication of a new nanofibrous membrane, F-PI/PAN, through electrospinning of polyacrylonitrile (PAN) and fluorinated polyimide (F-PI). The nanofibrous membrane exhibits comprehensive properties for high-temperature filtration and robust PM2.5 (particulate matter with an aerodynamic equivalent diameter of 2.5 microns or less) removal. The introduction of F enhances the hydrophobicity of the PI. The relationship between the hydrophobic performance and the filtration performance of particles is investigated. The chemical group of the composite membrane was demonstrated using FITR, while the surface morphology was investigated using field emission scanning electron microscopy. The TGA results indicated good thermal stability at 300 °C. Various ratios of F-PI membranes were prepared to characterize the change in properties, with the optimal mass ratio of F-PI being 20 wt%. As the proportion of F-PI increases, its mechanical and filtration efficiency properties and hydrophobicity become stronger. The contact angle reaches its maximum of 128 ± 5.2° when PAN:F-PI = 6:4. Meanwhile, when PAN:F-PI = 8:2, the filtration efficiency reaches 99.4 ± 0.3%, and the elongation at break can reach 76%. The fracture strength can also reach 7.1 MPa, 1.63 times that of the pure PAN membrane.

Efficient nitrogen removal from real municipal wastewater and mature landfill leachate using partial nitrification-simultaneous anammox and partial denitrification process.

Anaerobic ammonia oxidation (anammox) of municipal wastewater is a research focus, especially the combined treatment with mature landfill leachate is a current research hotspot. In this study, municipal wastewater was treated by partial nitrification via sequencing batch reactor (SBR), and its effluent and mature landfill leachate were then mixed into an up-flow anaerobic sludge blanket (UASB) for simultaneous anammox and partial denitrification reaction. Through partial nitrification, a high nitrite accumulation rate (93.0 ± 3.8 %) was achieved by low dissolved oxygen (0.5-1.6 mg/L) and controlled aerobic time (3.5 h) in SBR. The UASB system was responsible for 78.8 ± 2.1 % nitrogen removal of the entire system with a hydraulic reaction time (HRT) of 3.8 h, accompanied by the anammox contribution up to 89.4 ± 6.0 %. The overall partial nitrification-simultaneous anammox and partial denitrification (PN-SAPD) system was controlled at a total COD/TIN of 2.8 ± 0.3 and a total HRT of only 10.2 h, achieving the nitrogen removal efficiency and effluent TIN were 95.2 ± 2.2 % and 3.4 ± 1.5 mg/L, respectively. The qPCR results showed functional genes (hzsA(B), hdh) associated with anaerobic ammonia-oxidizing bacteria (AnAOB), whose high gene copy abundance and transcription expression ensured the removal of major nitrogen from municipal wastewater and mature landfill leachate. 16S amplicon sequencing showed that the Ca. Brocadia (9.72-12.6 %) was further enrichment after sodium acetate was added, and the transcription expression of Thauera (0.5-7.0 %) caused nitrate to nitrite. The high abundance of related enzymes (hao, hzs, hdh, narGHI) involved in anammox and partial denitrification processes were found in the macrogenomic sequencing, and only Ca. Brocadia was involved in multi-pathway nitrogen metabolism in AnAOB. Based on the efficient nitrogen removal by AnAOB and denitrifying bacteria, this modified PN-SAPD process provides a new option for the co-treatment of mature landfill leachate in municipal wastewater treatment plants.

[The Occurrence and Risk Factors of Stroke Complicated by Venous Thromboembolism].

Objective: To investigate the occurrence and the risk factors of stroke complicated by venous thromboembolism. Methods: A total of 2709 stroke patients who received treatment at our hospital between January 2018 and June 2021 were selected. The incidence of stroke complicated by venous thromboembolism was analyzed and the risk factors of stroke complicated by venous thromboembolism were investigated by logistic regression. Results: Among the 2709 stroke patients, 390 had venous thromboembolism, resulting in 14.39% incidence of venous thromboembolism. Among them, 383 patients (14.14%) had deep venous thrombosis (DVT), 4 patients (0.15%) had pulmonary thromboembolism (PTE), and 3 cases (0.11%) had DVT combined with PTE. According to the analysis of unconditional multivariate logistic regression model, age>60 years, concomitant hypertension, concomitant diabetes, bedrest time after admission≥3 days, D-dimer (D-D)≥0.95 mg/mL, triglyceride (TG)≥1.83 mmol/L, Barthel Index (BI) score≤9 points, and Padua score>4 points after admission were independent risk factors for stroke complicated by venous thromboembolism ( P<0.05), while anticoagulation therapy was a protective factor ( P<0.05). Conclusion: Stroke complicated by venous thromboembolism is associated, to some degree, with age, concomitant hypertension, concomitant diabetes, bedrest time, D-D, TG, BI score, Padua score, and whether anticoagulant therapy is administered or not. Interventions in line with relevant risk factors should be strengthened to effectively reduce the risk of stroke complicated by venous thromboembolism.

A Colorimetric Aptasensor for Ochratoxin A Detection Based on Tetramethylrhodamine Charge Effect-Assisted Silver Enhancement.

A novel colorimetric aptasensor based on charge effect-assisted silver enhancement was developed to detect ochratoxin A (OTA). To achieve this objective, gold nanoparticles (AuNPs), which can catalyze silver reduction and deposition, were used as the carrier of the aptamers tagged with a positively charged tetramethylrhodamine (TAMRA). Due to the mutual attraction of positive and negative charges, the TAMRA attracted and retained the silver lactate around the AuNPs. Thus, the chance of AuNP-catalyzed silver reduction was increased. The charge effect-assisted silver enhancement was verified by tagging different base pair length aptamers with TAMRA. Under optimized conditions, the as-prepared OTA aptasensor had a working range of 1 × 102-1 × 106 pg mL-1. The detection limit was as low as 28.18 pg mL-1. Moreover, the proposed aptasensor has been successfully applied to determine OTA in actual samples with satisfactory results.

Origin of humidity influencing the excited state electronic properties of silicon quantum dot based light-emitting diodes.

One of the challenges of silicon quantum dots (Si QDs) in practical application as quantum dot-based light-emitting diodes is the irreversible degradation induced by humid conditions, revealing their excited state electronic properties strongly influenced by the surface water; however, the photoluminescence (PL) mechanism associated with the change of excited state electronic properties remains elusive. Here, we performed the time-dependent density functional theory calculations to investigate how the PL of Si29H36, as typical spherical Si QDs, is determined by dipole-dipole interactions between water molecules and different surface substituent groups. Relative to the hydrophobic group of pure hydrogen passivation, the substituent effect with a hydrogen atom replaced by a fluorine atom almost has no influence on the PL of Si QDs with the adsorption of water clusters. Interestingly, although a hydrophilic hydroxyl group substitution itself will partly change the surface state with the slight blue-shift of PL, the intensive dipole-dipole interaction between a hydroxyl group and water molecules can drastically induce the delocalized electrons to be localized, resulting in a dual-band peak observed in the PL spectra of Si29H35OH surrounded by four or five water molecules. This distinct PL mechanism originates from the adsorption of water molecules through dipole-dipole interactions inducing the existence of surface trap states. The presence of highly polarizable double-bonded oxygen will trigger the electron distribution centered on the silicon-oxygen double bond, resulting in the corresponding PL spectrum of Si29H35O unaffected by the water molecules. This study reveals that the PL of Si QDs with the substituent hydroxyl group is extremely sensitive to humidity and lays a foundation for the practical application of Si QDs as optoelectronic devices.

Single-Atom Iron Anchored on 2-D Graphene Carbon to Realize Bridge-Adsorption of O-O as Biomimetic Enzyme for Remarkably Sensitive Electrochemical Detection of H2O2.

Single-atom catalysis is mainly focused on its dispersed high-density catalytic sites, but delicate designs to realize a unique catalysis mechanism in terms of target reactions have been much less investigated. Herein an iron single atomic site catalyst anchored on 2-D N-doping graphene (Fe-SASC/G) was synthesized and further employed as a biomimetic sensor to electrochemically detect hydrogen peroxide, showing an extremely high sensitivity of 3214.28 µA mM-1 cm-2, which is much higher than that (6.5 µA mM-1 cm-2) of its dispersed on 1-D carbon nanowires (Fe-SASC/NW), ranking the best sensitivity among all reported Fe based catalyst at present. The sensor was also used to successfully in situ monitor H2O2 released from A549 living cells. The mechanism was further systematically investigated. Results interestingly indicate that the distance between adjacent single Fe atomic catalytic sites on 2-D graphene of Fe-SASC/G matches statistically well with the outer length of bioxygen of H2O2 to promote a bridge adsorption of -O-O- for simultaneous 2-electron transfer, while the single Fe atoms anchored on distant 1-D nanowires in Fe-SASC/NW only allow an end-adsorption of oxygen atoms for 1-electron transfer. These results demonstrate that Fe-SASC/G holds great promise as an advanced electrode material in selective and sensitive biomimetic sensor and other electrocatalytic applications, while offering scientific insights in deeper single atomic catalysis mechanisms, especially the effects of substrate dimensions on the mechanism.

Co3O4 Nanoparticles Uniformly Dispersed in Rational Porous Carbon Nano-Boxes for Significantly Enhanced Electrocatalytic Detection of H2O2 Released from Living Cells.

A facile and ingenious method to chemical etching-coordinating a metal-organic framework (MOF) followed by an annealing treatment was proposed to prepare Co3O4 nanoparticles uniformly dispersed in rational porous carbon nano-boxes (Co3O4@CNBs), which was further used to detect H2O2 released from living cells. The Co3O4@CNBs H2O2 sensor delivers much higher sensitivity than non-etching/coordinating Co3O4, offering a limit of detection of 2.32 nM. The wide working range covers 10 nM-359 µM H2O2, while possessing good selectivity and excellent reproducibility. Moreover, this biosensor was used to successfully real-time detect H2O2 released from living cells, including both healthy and tumor cells. The excellent performance holds great promise for Co3O4@CNBs's applications in electrochemical biomimetic sensing, particularly real-time monitor H2O2 released from living cells.

Design, synthesis and imaging of a novel mitochondrial fluorescent nanoprobe based on distyreneanthracene-substituted triphenylphosphonium salt.

Targeting and monitoring the dynamics of mitochondria are of great significance because mitochondria are involved in a variety of physiological and pathological processes. For achieving this purpose, highly sensitive, photostable, tolerance and specific fluorescent probe is necessary. To obtain a superior mitochondrial fluorescent probe, (4-distyreneanthracenoxybutyl) bis(triphenylphosphonium) bromide (DSA-TPP) with aggregation-induced emission (AIE) characteristic was designed and synthesized for mitochondrial targeting. DSA-TPP dots with high fluorescence quantum yield (Φ = 17.9) and small particle size (8 nm) can be easily prepared by self-assembly formation. DSA-TPP dots had the ability of lightning mitochondria in living cells with high brightness, superior photostability and strong tolerance to cell environment change.

A simple yet sensitive colorimetric nitrite ions assay based on diazotization with p­Aminobenzoic and coupling with phloroglucinol in acidic medium.

Immoderate intake of nitrite (NO2-) is deleterious human health and may result in causing dangerous diseases. In this study, nitrite detection system was successfully fabricated based on a unique diazo-coupling reaction of p­Aminobenzoic acid (PABA) and phloroglucinol (1, 3, 5­trihydroxybenzene). Upon the presence of NO2- in an acid medium, p­Aminobenzoic acid could not only form diazonium ion easily but also couple with p­Aminobenzoic acid, and results forming yellow water-soluble azo dye that shows maximum absorption at 434 nm. Under the further accurate determination condition, such as acid concentration, amount of reagents and time required, the naked-eye detection of NO2- showed excellent selectivity in compared with some anions. Especially, diazotization and coupling reaction proposed here is very fast and control of pH and temperature are unnecessary. Moreover, the color is stable for several days and Beer's law is obeyed over a wide range. Reliable detection can be made in the range of 0.05 to 1 p.p.m. of nitrite ion. Detection limit was calculated to be 0.024 p.p.m. (0.52 µâ€¯M) by UV-visible spectroscopy and 0.05 p.p.m. (1.09 µâ€¯M) by naked-eye. By using an electrochemical method, IR, SEM, and 1HNMR, the sensing mechanism can be easily verified. More importantly the proposed method was successfully applied for the determination of nitrite in a real water sample.

A colorimetric indicator-displacement assay for cysteine sensing based on a molecule-exchange mechanism.

In this study, we developed an ingenious yet effective strategy for cysteine detection. The colorimetric cysteine assay is established through an indicator displacement process, where Cu2+ and pyrocatechol violet (PV) was employed as receptor and indicator, respectively. Proof-of-concept trials demonstrated that the stronger binding affinity of Cu2+ receptor toward cysteine than PV indicator endowed our colorimetric sensor with high selectivity and excellent sensitivity as well as with a lower detection limit (4.60µM and 120µM, S/N =3) by UV-visible spectroscopy and the naked eye as the signal readout, respectively. More importantly, the proposed molecule-exchange process in the indicator displacement process could be successfully used to the fabrication of a colorimetric INHIBIT logic gate and even converted into a facile naked eye analysis through paper-based analytical devices for conveniently and reliably detecting cysteine (CySH) in practical applications.