Facile hydrothermal synthesis of Ti3C2Tx-TiO2 nanocomposites for gaseous volatile organic compounds detection at room temperature.

The gaseous volatile organic compounds (VOCs) sensors with high-selectivity and low-power consumption have been expected for practical applications in environmental monitoring and disease diagnosis. Herein, we demonstrate a room-temperature VOCs gas sensor with enhanced performance based on Ti3C2Tx-TiO2 nanocomposites. The Ti3C2Tx-TiO2 nanocomposites with regular morphology are successfully synthesized via a facile one-step hydrothermal synthesis strategy by using Ti3C2Tx itself as titanium source. Attributed to the formation of interfacial heterojunctions and the modulation of carrier density, the Ti3C2Tx-TiO2 sensor exhibits about 1.5-12.6 times enhanced responses for the detection of various VOCs at room temperature than pure MXene sensor. Moreover, the nanocomposite sensor has better response to hexanal, both an air pollutant and a typical lung cancer biomarker. The gas response of the Ti3C2Tx-TiO2 sensor towards 10 ppm hexanal is about 3.4%. The hexanal gas sensing results display that the nanocomposite sensor maintains a high signal-to-noise ratio and the lower detection limit to hexanal gas is as low as 217 ppb. Due to the low power consumption and easy fabrication process, the Ti3C2Tx-TiO2 nanocomposite sensor is promising for application in IoT environmental monitoring as well as real-time health monitoring.

Retraction: Yang, B. et al. Nitrogen Doped Intercalation TiO2/TiN/Ti3C2Tx Nanocomposite Electrodes with Enhanced Pseudocapacitance. Nanomaterials 2020, 10, 345.

This article [1] has been retracted at the request of the authors due to data errors [...].

Nitrogen Doped Intercalation TiO2/TiN/Ti3C2Tx Nanocomposite Electrodes with Enhanced Pseudocapacitance.

Layered two-dimensional titanium carbide (Ti3C2Tx), as an outstanding MXene member, has captured increasing attention in supercapacitor applications due to its excellent chemical and physical properties. However, the low gravimetric capacitance of Ti3C2Tx restricts its rapid development in such applications. Herein, this work demonstrates an effective and facile hydrothermal approach to synthesize nitrogen doped intercalation TiO2/TiN/Ti3C2Tx with greatly improved gravimetric capacitance and excellent cycling stability. The hexamethylenetetramine (C6H12N4) in hydrothermal environment acted as the nitrogen source and intercalants, while the Ti3C2Tx itself was the titanium source of TiO2 and TiN. We tested the optimized nitrogen doped intercalation TiO2/TiN/Ti3C2Tx electrodes in H2SO4, Li2SO4, Na2SO4, LiOH and KOH electrolytes, respectively. The electrode in H2SO4 electrolyte delivered the best electrochemical performance with high gravimetric capacitance of 361 F g-1 at 1 A g-1 and excellent cycling stability of 85.8% after 10,000 charge/discharge cycles. A systematic study of material characterization combined with the electrochemical performances disclosed that TiO2/TiN nanoparticles, the introduction of nitrogen and the NH4+ intercalation efficaciously increased the specific surface areas, which is beneficial for facilitating electrolyte ions transportation. Given the excellent performance, nitrogen doped intercalation TiO2/TiN/Ti3C2Tx bodes well as a promising pseudocapacitor electrode for energy storage applications.

An assessment of the interaction for three Chrysanthemum indicum flavonoids and α-amylase by surface plasmon resonance.

This study evaluated the interaction of Chrysanthemum indicum (CI) flavonoids (luteolin, acacetin, and buddleoside) with α-amylase. Surface plasmon resonance (SPR) assay showed their equilibrium dissociation constants (KD ) are 1.9695 ± 0.12, 2.9240 ± 0.20, and 3.2966 ± 0.08 mM at pH 6.0, respectively. Furthermore, their binding affinities were influenced by KCl, MgCl2, and CaCl2. Enzymatic kinetic studies revealed that three flavonoids exhibited noncompetitive α-amylase inhibitory activity. The inhibitory sequence is luteolin > acacetin > buddleoside, which was in accordance with the results of binding affinity from SPR. 1,1-diphenyl-2-picryl hydrazyl radical assay demonstrated that antioxidant activities of three flavonoids were inhibited significantly with α-amylase. Meanwhile, the study reveals that hydroxyl on C'-4, C'-5, and C-7 of flavonoids play an important role on the interaction of three flavonoids with α-amylase. Also, SPR could be used as sensor for rapid screening inhibitors of α-amylase and provide useful information for the application of C. indicum flavonoids in food and pharmaceutical area.

Air-Stable Lead-Free Perovskite Thin Film Based on CsBi3I10 and Its Application in Resistive Switching Devices.

The development of organic-inorganic hybrid perovskite materials has been rapid in recent years; but their applications are limited by the toxicity and stability of the materials. To address these issues in the context of resistive switching devices, an inorganic lead-free perovskite namely CsBi3I10 is developed. Uniform and pinhole-free CsBi3I10 thin films can be fabricated by using CsI-rich precursor solution via a facile antisolvent-assisted spin-coating method. The nonvolatile resistive switching devices based on CsBi3I10 demonstrate a large on/off ratio (103), reliable retention properties (104 s), and endurance (150 cycles). Conductive atomic force microscopy reveals that the high- and low-resistance states are formed by breaking and formation of conductive filaments in the perovskite thin film. Because of the excellent stability of the CsBi3I10 perovskite, the devices exhibit no obvious change in resistive switching behavior even after over 2 month storage in an ambient (60% relative humidity) environment. Our work suggests that the all-inorganic lead-free CsBi3I10 perovskite has great potential in resistive switching memory as well as in other optoelectronic devices where toxicity and stability are a concern.

Investigation of the interaction for three Citrus flavonoids and α-amylase by surface plasmon resonance.

Flavonoids, a class of natural drugs with broad biological activity, exhibit inhibitory effect on α-amylase. Citrus peel is a good source of flavonoids. The real-time interactions between three Citrus flavonoids (naringin, neohesperidin, hesperidin) and α-amylase were investigated by surface plasmon resonance biosensor, and were compared with the α-amylase inhibitors, acarbose. These results showed the binding affinities of naringin, neohesperidin and hesperidin with α-amylase reach the highest at pH6 with KD values of 2.27±0.18mM, 3.09±0.20mM and 3.51±0.09mM, and can be reinforced with 0.2M NaCl and 0.1M CaCl2, respectively. The results of 1, 1-diphenyl-2-picryl hydrazyl radical assay indicate that the antioxidant activities of naringin, neohesperidin and hesperidin are significantly inhibited by interacting with α-amylase, and the inhibition percentage are 47.61±0.034%, 22.81±0.037% and 21.01±0.051%, respectively. Additionally, it is found that both the number and the position of hydroxyl group play an important role in the interaction of three Citrus flavonoids and α-amylase. These results provide useful information for rapid screening inhibitors of α-amylase from plant-based food.

Ablation of central nervous system progenitor cells in transgenic rats using bacterial nitroreductase system.

Specific ablation of central nervous system (CNS) progenitor cells in the brain of live animals is a powerful method to determine the functions of these cells and to reveal novel avenues for the treatment of several CNS-related disorders. To achieve this goal, we generated a line of transgenic rats expressing a bacterial enzyme, Escherichia coli nitroreductase gene (NTR), under control of the nestin promoter. In this system, NTR(+) cells are selectively eliminated upon application of prodrug CB1954, through activation of programmed cell death machineries. At 5 days of age, which is a time when cerebellar development is occurring, transgenic rats bearing the nestin-NTR/green fluorescent protein (GFP) gene are overtly normal and express NTR/GFP in neuronal stem cells, without any toxicity in these cells. The functional consequence of progenitor cell ablation was demonstrated by administering prodrug CB1954 into the cerebellum at this 5-day time point. Stem cell ablation in these neonates resulted in sensorimotor abnormalities, cerebellar degeneration, overall reduction in cerebellar seize, and manifestation of ataxia. In adult rats, GFP expression was not seen in the hippocampal progenitor cells and seen only at very low levels in the lateral ventricles, indicating a different NTR/GFP expression pattern between neonates and adults. In addition, application of CB1954 by intraventricular delivery reduced the number of 5-bromo-2'-deoxyuridine-labeled proliferating cells in the lateral ventricle but not hippocampus of NTR/GFP rats. These findings shows that targeted expression of NTR under a specific promoter might be of significant value in addressing the function of distinct cell population in vivo.