WO3 Nanoplates Decorated with Au and SnO2 Nanoparticles for Real-Time Detection of Foodborne Pathogens.

Nowadays, metal oxide semiconductor gas sensors have diverse applications ranging from human health to smart agriculture with the development of Internet of Things (IoT) technologies. However, high operating temperatures and an unsatisfactory detection capability (high sensitivity, fast response/recovery speed, etc.) hinder their integration into the IoT. Herein, a ternary heterostructure was prepared by decorating WO3 nanoplates with Au and SnO2 nanoparticles through a facial photochemical deposition method. This was employed as a sensing material for 3-hydroxy-2-butanone (3H-2B), a biomarker of Listeria monocytogenes. These Au/SnO2-WO3 nanoplate-based sensors exhibited an excellent response (Ra/Rg = 662) to 25 ppm 3H-2B, which was 24 times higher than that of pure WO3 nanoplates at 140 °C. Moreover, the 3H-2B sensor showed an ultrafast response and recovery speed to 25 ppm 3H-2B as well as high selectivity. These excellent sensing performances could be attributed to the rich Au/SnO2-WO3 active interfaces and the excellent transport of carriers in nanoplates. Furthermore, a wireless portable gas sensor equipped with the Au/SnO2-WO3 nanoplates was assembled, which was tested using 3H-2B with known concentrations to study the possibilities of real-time gas monitoring in food quality and safety.

The anti-inflammatory and haemodynamic effects of levosimendan on advanced heart failure patients: a meta-analysis of published studies.

OBJECTIVE: Increasing evidence from randomized controlled trials shows the anti-inflammatory and haemodynamic effects of levosimendan in advanced heart failure (AdHF), however, conflicting results have been reported in some studies. The aim of this study was to estimate the anti-inflammatory and haemodynamic effects of levosimendan on AdHF (registration number: INPLASY202250097). METHODS: The MEDLINE, PubMed, ClinicalTrials.com and Cochrane Library databases were systematically searched for studies published in English up to April 2019. Data were extracted from applicable articles. Meta-analyses were performed to assess interleukin (IL)-6, cardiac index, pulmonary artery pressure (PAP) and New York Heart Association (NYHA) functional class efficacy outcomes, following PRISMA 2020 guidelines. RESULTS: A total of 11 studies were included (211 patients who received levosimendan and 193 controls). Meta-analyses showed that the levosimendan group displayed significantly reduced IL-6 (standardized mean difference [SMD] -1.05; 95% confidence interval [CI] -1.44, -0.66; I2 = 50.9%), improved cardiac index (SMD 0.59; 95% CI 0.29, 0.88; I2 = 0.0%); reduced PAP (SMD -1.22; 95% CI -1.91, -0.53; I2 = 89.7%) and improved NYHA functional class (SMD -1.66; 95% CI -2.27, -1.04; I2 = 74.6%) versus controls. CONCLUSIONS: Levosimendan infusion was beneficial in patients with AdHF, displayed by anti-inflammatory and improved haemodynamic effects, and improved NYHA functional class.

Wearable Crop Sensor Based on Nano-Graphene Oxide for Noninvasive Real-Time Monitoring of Plant Water.

Real-time noninvasive monitoring of crop water information is an important basis for water-saving irrigation and precise management. Nano-electronic technology has the potential to enable smart plant sensors to communicate with electronic devices and promote the automatic and accurate distribution of water, fertilizer, and medicine to improve crop productivity. In this work, we present a new flexible graphene oxide (GO)-based noninvasive crop water sensor with high sensitivity, fast responsibility and good bio-interface compatibility. The humidity monitoring sensitivity of the sensor reached 7945 Ω/% RH, and the response time was 20.3 s. We first present the correlation monitoring of crop physiological characteristics by using flexible wearable sensors and photosynthesis systems, and have studied the response and synergistic effect of net photosynthetic rate and transpiration rate of maize plants under different light environments. Results show that in situ real-time sensing of plant transpiration was realized, and the internal water transportation within plants could be monitored dynamically. The synergistic effect of net photosynthetic rate and transpiration of maize plants can be jointly tested. This study provides a new technical method to carry out quantitative monitoring of crop water in the entire life cycle and build smart irrigation systems. Moreover, it holds great potential in studying individual plant biology and could provide basic support to carry out precise monitoring of crop physiological information.

Effects of Long-Term Repeated Freeze-Thaw Cycles on the Engineering Properties of Compound Solidified/Stabilized Pb-Contaminated Soil: Deterioration Characteristics and Mechanisms.

The effects of long-term repeated freeze-thaw cycles and pollution levels on the engineering properties (qu, E50, φ, c, and k) of Pb-contaminated soils were investigated in various laboratory tests. These soils were solidified/stabilized (S/S) with three types of cement-based combined binders (C2.5S5F5, C5S2.5F2.5, and C5S5, cement, lime, and fly ash, mixed in different proportions; these materials are widely used in S/S technology). The strength and permeability coefficient of compound solidified/stabilized Pb-contaminated soils (Pb-CSCSs) were determined based on measurements of unconfined compressive strength (UCS), direct shear, and permeability. CT scanning, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) tests were employed to analyse the deterioration mechanisms under various repetitions of freeze-thaw cycles. The results showed that, under repeated freeze-thaw cycles, the engineering properties of Pb-CSCSs all degraded to varying degrees, though degradation tended to stabilise after 30 days of freeze-thaw cycles. The study also found that the pollutants obstruct hydration and other favourable reactions within the soil structure (such as ion exchanges and agglomerations and pozzolanic reactions). The activation of hydration reactions and the rearrangement of soil particles by freeze-thaw cycles thus caused the engineering properties to fluctuate, and soils exhibited different deterioration characteristics with changes in Pb2+ content.

Influence of Freeze-Thaw Cycles and Binder Dosage on the Engineering Properties of Compound Solidified/Stabilized Lead-Contaminated Soils.

The solidification/stabilization (S/S) method is the usual technique for the remediation of soils polluted by heavy metal in recent years. However, freeze-thaw cycles, an important physical process producing weathering of materials, will affect the long-term stability of engineering characteristics in solidified contaminated soil. In addition, it is still questionable whether using large dosages of binders can enhance the engineering properties of solidified/stabilized contaminated soils. In this study, the three most commonly used binders (i.e., cement, quicklime, and fly ash), alone and mixed in different ratios, were thus added to lead-contaminated soil in various dosages, making a series of cured lead-contaminated soils with different dosages of binders. Afterward, unconfined compression strength tests, direct shear tests, and permeability tests were employed on the resulting samples to find the unconfined compressive strength (UCS), secant modulus ( E 50 ), internal friction angle ( φ ), cohesion ( c ), and permeability coefficient ( k ) of each solidified/stabilized lead-contaminated soil after 0, 3, 7, and 14 days of freeze-thaw cycles. This procedure was aimed at evaluating the influence of freeze-thaw cycle and binder dosage on engineering properties of solidified/stabilized lead-contaminated soils. Results of our experiments showed that cement/quicklime/fly ash could remediate lead-contaminated soils. However, it did not mean that the more the dosage of binder, the better the curing effect. There was a critical dosage. Excessive cementation of contaminated soils caused by too much binder would result in loss of strength and an increase in permeability. Furthermore, it was found that UCS,   E 50 , φ , c , and k values generally decreased with the increase in freeze-thaw cycle time-a deterioration effect on the engineering characteristics of solidified lead-contaminated soils. Avoiding excessive cementation, 2.5% cement or quicklime was favorable for the value of E 50 while a 2.5% fly ash additive was beneficial for the k value. It is also suggested that if the freeze-thaw cycle continues beyond the period supported by excessive cementation, such a cycle will rapidly destroy the original structure of the soil and create large cracks, leading to an increase in permeability. The results also showed that the contaminated soils with a larger dosage of binders exhibited more significant deterioration during freeze-thaw cycles.

Substrate-Induced Graphene Chemistry for 2D Superlattices with Tunable Periodicities.

2D graphene superlattices are fabricated down to the nanometer scale by a universal substrate-engineering approach, based on substrate-induced site-selective chemical reactions on the graphene basal plane. Various 2D graphene superlattices with tunable periodicities and chemical functionalities are made by using SiO2 nanosphere assemblies and other nanostructured substrates.

Nanoscale Electric Characteristics and Oriented Assembly of Halobacterium salinarum Membrane Revealed by Electric Force Microscopy.

Purple membranes (PM) of the bacteria Halobacterium salinarum are a unique natural membrane where bacteriorhodopsin (BR) can convert photon energy and pump protons. Elucidating the electronic properties of biomembranes is critical for revealing biological mechanisms and developing new devices. We report here the electric properties of PMs studied by using multi-functional electric force microscopy (EFM) at the nanoscale. The topography, surface potential, and dielectric capacity of PMs were imaged and quantitatively measured in parallel. Two orientations of PMs were identified by EFM because of its high resolution in differentiating electrical characteristics. The extracellular (EC) sides were more negative than the cytoplasmic (CP) side by 8 mV. The direction of potential difference may facilitate movement of protons across the membrane and thus play important roles in proton pumping. Unlike the side-dependent surface potentials observed in PM, the EFM capacitive response was independent of the side and was measured to be at a dC/dz value of ~5.25 nF/m. Furthermore, by modification of PM with de novo peptides based on peptide-protein interaction, directional oriented PM assembly on silicon substrate was obtained for technical devices. This work develops a new method for studying membrane nanoelectronics and exploring the bioelectric application at the nanoscale.

A material combination principle for highly efficient polymer solar cells investigated by mesoscopic phase heterogeneity.

Organic solar cells have become a promising energy conversion candidate because of their unique advantages. Novel fullerene derivatives, as a common acceptor, can increase power conversion efficiency (PCE) by increasing the open-circuit voltage. As a representative acceptor, Indene-C60 bisadduct (ICBA) can reach high efficiency with poly(3-hexylthiophene) (P3HT). On the other hand, the novel synthesized polymers mainly aimed to broaden the optical absorption range have steadily promoted efficiency to higher than 9%. However, it is challenging to obtain the desired result by simply combining ICBA with other high-efficiency donors. Thus, P3HT or a high-efficiency polymer PBDTTT-C-T (copolymer of thienyl-substituted BDT with substituted TT) is used as donor and PCBM or ICBA as acceptor in this article to clarify the mechanism behind these materials. The optical and photovoltaic properties of the materials are studied for pair-wise combination. Among these four material groups, the highest PCE of 6.2% is obtained for the PBDTTT-C-T/PCBM combination while the lowest PCE of 3.5% is obtained for the PBDTTT-C-T/ICBA combination. The impact of the mesoscopic heterogeneity on the local mesoscopic photoelectric properties is identified by photo-conductive AFM (pc-AFM), and the consistence between the mesoscopic properties and the macroscopic device performances is also observed. Based on these results, an interface combined model is proposed based on the mesoscopic phase heterogeneity. This study provides a new view on the rational selection of photovoltaic materials, where, aside from the traditional energy level and absorption spectrum matching, the matching of mesoscopic heterogeneity must also be considered.

Determination of the surface charge density and temperature dependence of purple membrane by electric force microscopy.

We report here the measurement of the temperature-dependent surface charge density of purple membrane (PM) by using electrostatic force microscopy (EFM). The surface charge density was measured to be 3.4 × 10(5) e/cm(2) at room temperature and reaches the minimum at around 52 °C. The initial decrease of the surface charge density could be attributed to the reduced dipole alignment because of the thermally induced protein mobility in PM. The increase of charge density at higher temperature could be ascribed to the weakened interaction between proteins and the lipids, which leads to the exposure of the charged amino acids. This work could be a benefit to the direct assessment of the structural stability and electric properties of biological membranes at the nanoscale.

Evolution of polymer photovoltaic performances from subtle chemical structure variations.

Conjugated polymers are promising replacements for their inorganic counterparts in photovoltaics due to their low cost, ease of processing, and straightforward thin film formation. New materials have been able to improve the power conversion efficiency of photovoltaic cells up to 8%. However, rules for rational material design are still lacking, and subtle chemical structure variations usually result in large performance discrepancies. The present paper reports a detailed study on the crystalline structure, morphology, and in situ optoelectronic properties of blend films of polythiophene derivatives and [6,6]-phenyl C61-butyric acid methyl ester by changing the alkyl side chain length and position of polythiophene. The correlation among the molecular structure, mesoscopic morphology, mesoscopic optoelectronic property and macroscopic device performance (highest efficiency above 4%) was directly established. Both solubility and intermolecular interactions should be considered in rational molecular design. Knowledge obtained from this study can aid the selection of appropriate processing conditions that improve blend film morphology, charge transport property, and overall solar cell efficiency.

Observation of molecular inhibition and binding structures of amyloid peptides.

Unveiling interactions between labeling molecules and amyloid fibrils is essential to develop new detection methods for studying amyloid structures under various conditions. This review endeavours to reflect the progress in studying interactions between molecular inhibitors and amyloid peptides using a series of experimental approaches, such as X-ray diffraction, nuclear magnetic resonance, scanning probe microscopy, and electron microscopy. The revealed binding mechanisms of anti-amyloid drugs and target proteins could benefit the rational design of drugs for prevention or treatment of amyloidal diseases.

Beta structure motifs of islet amyloid polypeptides identified through surface-mediated assemblies.

We report here the identification of the key sites for the beta structure motifs of the islet amyloid polypeptide (IAPP) analogs by using scanning tunneling microscopy (STM). Duplex folding structures in human IAPP(8-37) (hIAPP(8-37)) assembly were observed featuring a hairpin structure. The multiplicity in rIAPP assembly structures indicates the polydispersity of the rat IAPP(8-37) (rIAPP(8-37)) beta-like motifs. The bimodal length distribution of beta structure motifs for rIAPP(8-37) R18H indicates the multiple beta segments linked by turns. The IAPP(8-37) analogs share common structure motifs of IAPP(8-17) and IAPP(26-37) with the most probable key sites at positions around Ser(19)/Ser(20) and Gly(24). These observations reveal the similar amyloid formation tendency in the C and N terminus segments because of the sequence similarity, while the differences in specific amino acids at each key site manifest the effect of sequence variations. The results could be beneficial for studying structural polymorphism of amyloidal peptides with multiple beta structure motifs.

Binding of blood proteins to carbon nanotubes reduces cytotoxicity.

With the potential wide uses of nanoparticles such as carbon nanotubes in biomedical applications, and the growing concerns of nanotoxicity of these engineered nanoparticles, the importance of nanoparticle-protein interactions cannot be stressed enough. In this study, we use both experimental and theoretical approaches, including atomic force microscope images, fluorescence spectroscopy, CD, SDS-PAGE, and molecular dynamics simulations, to investigate the interactions of single-wall carbon nanotubes (SWCNTs) with human serum proteins, and find a competitive binding of these proteins with different adsorption capacity and packing modes. The π-π stacking interactions between SWCNTs and aromatic residues (Trp, Phe, Tyr) are found to play a critical role in determining their adsorption capacity. Additional cellular cytotoxicity assays, with human acute monocytic leukemia cell line and human umbilical vein endothelial cells, reveal that the competitive bindings of blood proteins on the SWCNT surface can greatly alter their cellular interaction pathways and result in much reduced cytotoxicity for these protein-coated SWCNTs, according to their respective adsorption capacity. These findings have shed light toward the design of safe carbon nanotube nanomaterials by comprehensive preconsideration of their interactions with human serum proteins.

Determination of relative binding affinities of labeling molecules with amino acids by using scanning tunneling microscopy.

The binding behaviour of labeling molecule copper phthalocyanine tetrasulfonate sodium (PcCu(SO(3)Na)(4)) on the assemblies of representative polyamino acids has been studied by using scanning tunneling microscopy (STM). By directly visualizing the adsorption and distribution of the labeling species on the peptide assemblies in STM images, one could obtain relative binding affinities of the labeling molecule with different amino acid residues.

The interaction of serum proteins with carbon nanotubes depend on the physicochemical properties of nanotubes.

With more and more potential applications of carbon nanotubes (CNTs) in different fields, the risk of exposure to CNTs is increasing. The interaction between CNTs and protein in biological media can affect the way cells interact with, recognize and process the nanoparticles, and this has important implications for safety considerations. In this study, the interaction of single-walled and multiwall CNTs with various serum proteins was investigated. The adsorption kinetics of protein to CNTs was investigated and a semi-qualitative analysis was provided by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Matrix assisted laser desorption ionization/time of flight mass spectrometry (MALDI-TOF MS) was used to identify the protein species binding to CNTs and atomic force microscopy (AFM) was used to vividly demonstrate the adsorption model of protein on CNTs. All the experimental results showed that the adsorption capacity of CNTs for protein was highly dependent on the type, arrangement model, size and surface modification of CNTs. Significant quantity of proteins in serum could be quickly adsorbed by CNTs, mainly including albumin, prealbumin, transferrin, and immunoglobulin. Noncovalent functionalization of CNTs by polyethylene glycol (PEG) could decrease the protein adsorption on CNTs. These results provide crucial insights into human serum proteins binding to different kinds of CNTs, which is important for understanding the safe application of carbon nanotubes.

Cymbal piezoelectric composite underwater acoustic transducer.

The working principle of Cymbal piezoelectric composite underwater acoustic transducer was studied in this paper. PZT-5A piezoelectric ceramic disk was used as piezoelectric phase and brass foil was used as end cap electrode of the Cymbal transducer. The silicon rubber was used as the insulated proof layer of the underwater acoustic transducer. The properties of this transducer used as hydrophone, such as operation frequency, free-field voltage receiving sensitivity and directivity, were investigated. Several kinds of prototype of this transducer were fabricated and the properties of this transducer used as hydrophone were tested. The results show that the properties of this transducer used as hydrophone depend on the dimensions of Cymbal transducer because the piezoelectric properties of this transducer are dependent on the dimensions of Cymbal transducer's end caps. The appropriate dimensions for getting higher free-field voltage receiving sensitivity with -184.7 dB were obtained.