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In the study, a hydroxypropyl guar gum (HPG) gel was prepared using modified nano-TiO2 particles as a crosslinking agent. Firstly, nano-TiO2 particles were prepared using the sol–gel method. Nano-TiO2 particles were spherical and densely distributed; the effective particle size was 29.0 nm, and particle size distribution was uniform. Then, the modified nano-TiO2 particles were synthesized by modifying nano-TiO2 with polyhydroxy carboxylate. The microstructure of nano-TiO2 and modified nano-TiO2 crosslinked HPG gel were investigated. The layered distribution and crosslinked network of the modified nano-TiO2 gel were denser than that of nano-TiO2 crosslinked HPG gel. The modified nano-TiO2 crosslinked HPG gel shows stable viscoelasticity at 60 ℃. Compared with nano-TiO2 crosslinked HPG gel, it has better temperature resistance and shear resistance, and can adapt to formation fracturing at 140 ℃, indicating that this gel may have potential application in fracturing. [ABSTRACT FROM AUTHOR]

In the study, hydroxypropyl guar gum (HPG) gel is prepared by using Nano-ZrO2 particles as the cross-linking agent. The Nan-ZrO2 particles are prepared by using oil-water interface method. The physical properties such as morphology, particle size, and crystal structure of the Nano-ZrO2 particles are analyzed by SEM, particle size analyzer, FT-IR, and XRD, respectively. The results show that the Nano-ZrO2 particles are spherical particles with a little agglomeration; these spherical particles have a tetragonal structure and higher crystallinity, and the mean diameter of the first-level grain is 24 nm. The rheological properties including shear stress, complex modulus, elasticity modulus (G′), and viscosity modulus (G′′) of the Nano-ZrO2 cross-linked HPG gel are investigated. The results show that the Nano-ZrO2 cross-linked HPG gel is a pseudo-plastic non-Newtonian fluid with higher elastic modulus (G′ > G′′) and lower tanδ (tanδ < 1, the ratio of viscous and elastic modulus), which indicate that the Nano-ZrO2 cross-linked HPG gel may have potential application in fracturing. [ABSTRACT FROM AUTHOR]

Polyaminoamide dendrimers (PAMAM) surface-modified with anionic terminal groups (PIY) for use as scale inhibitors were prepared with the fourth-generation PAMAM and sodium acrylate (SAA), via the Michael addition reaction. The chemical structures of PIY were determined using Fourier transform infrared (FT-IR) spectrometry and 1H nuclear magnetic resonance (NMR) spectra. The influence of scale inhibitor concentration, Ca2+ concentration and bath temperature on the scale inhibition efficiency was researched. The study results signified that PIY can resist calcium carbonate scale as high as 92.8%. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) patterns showed that amorphous calcium carbonate had generated in the presence of PIY dendrimers. [ABSTRACT FROM AUTHOR]

To reduce the smoke and nitrogen oxide (NOx) emissions; a detailed study concerned with exhaust gas recirculation (EGR) and diesel injection strategy was conducted on a two-stage series turbocharging diesel engine under transient operating condition. One transient process based on the constant speed of 1650 r/min and load increases linearly from 10% to 100% within 5 s was tested in this study. The effect of the EGR valve control strategy on engine transient performance was examined. The results show that better air-fuel mixing quality can be obtained with the optimized the EGR valve open loop control strategy and the smoke opacity peak decreased more than 64%. Under the EGR valve close loop control strategy; the smoke opacity peak was lower than with open loop control strategy; but higher than without EGR. The effect of fuel injection strategy on engine transient performance was examined with the EGR valve close loop control. The results show that sectional-stage rail pressure (SSRP) strategy (increasing injection pressure from a turning point load to 100% load) and optimizing fuel injection timing can improve the engine emission performance. The satisfactory results can be obtained with lower NOx (382 ppm) emissions and the smoke opacity peak (3.8%), when the turning point load is set to 60% with the injection timing delay 6° CA. [ABSTRACT FROM AUTHOR]

Herein, a novel bimodal ratiometric probe for sensitive and selective detection of biothiols (including glutathione (GSH), cysteine (Cys) and homocysteine (Hcys)) was constructed, which was based on the redox reaction between manganese dioxide nanoflakes (MnO 2 NFs) and rhodamine (RhB) and biothiols. When MnO 2 NFs was added into RhB solution, RhB was oxidized to a series of derivatives, accompanying with the colorimetric color changing from purple to light pink and fluorescence changing from red to green. In the presence of GSH, Cys or Hcys, they could reduce MnO 2 NFs to Mn2+, thereby preventing the following oxidization of RhB and the corresponding color and fluorescence changes. The absorption intensity ratio and fluorescence intensity ratio showed good linear relationships with the concentrations of biothiols. The colorimetric detection limits for GSH, Cys and Hcys were 0.057 μM, 0.140 μM and 0.087 μM, respectively. And the fluorescence detection limits were 0.177 μM, 0.282 μM and 0.161 μM. More importantly, this probe was successfully applied to monitor the concentration of GSH/Cys/Hcys in human serum samples, with satisfactory recovery. Thus, this MnO 2 NFs-RhB platform can potentially be a candidate for the detection of biothiols. Image 1 • A bimodal ratiometric probe based on RhB and MnO 2 nanoflakes was fabricated. • This probe utilized the redox reactions between MnO 2 nanoflakes and RhB and biothiols. • It had a high sensitivity and a low detection limit. • It was applied in detecting biothiols in serum sample with satisfactory recoveries. • It can be used for detection biothiols with naked eyes under daylight and UV lamp. [ABSTRACT FROM AUTHOR]

Multiple mycotoxins may co-occurred in a single product and cause serious threats to public health. Herein, a multiplex immunochromatographic assay (mICA) was developed based on novel α-Fe 2 O 3 nanocubes (FNCs) as signal tags for the simultaneous detection of deoxynivalenol (DON) and aflatoxins B 1 (AFB 1). The FNCs with eminent water-dispersibility and stability were synthesized by a one-step hydrothermal process, which can rapidly label monoclonal antibodies (mAbs) to form FNCs-mAb probe. Under optimal experimental conditions, the visual limit of detection for DON and AFB 1 were 0.18 ng/mL and 0.01 ng/mL, respectively, which were at least 2-fold improvement compared with the traditional gold nanoparticles based mICA. Furthermore, DON and AFB 1 residual in mung bean, millet and corn were successfully detected by the proposed biosensor, and the average recovery rates were 93.3%–128.3%. Thus, this work indicated that the developed FNCs-mICA provided a sensitive, rapid and reliable on-site simultaneous detection of multiple mycotoxins. • A multiplex biosensor was constructed to sensitive detect deoxynivalenol and aflatoxins B 1. • The α-Fe 2 O 3 nanocubes with eminent water-dispersibility and stability as signal tags. • The sensor can detect deoxynivalenol and aflatoxins B 1 as low as 0.18 ng/mL and 0.01 ng/mL, separately. • The approach exhibited high selectivity and real food sample testing. [ABSTRACT FROM AUTHOR]

Polymerase chain reaction (PCR) is one of the most common methods for rapid monitoring of foodborne pathogens; however, it requires purified nucleic acid as a template. Conventional nucleic acid purification is a time-consuming and laborious process. To overcome this, we developed polydopamine nanospheres (PDA NPs)-assisted direct PCR for detecting Escherichia coli O157:H7 (E. coli O157:H7). PDA NPs significantly enhanced PCR efficiency because of their strong interaction with PCR reagents, including polymerase and primers, thereby enabling regulation of the PCR performance. The optimal concentration and diameter for PDA NPs were 0.10 μg/μL and 504 nm, respectively. The PDA NPs-assisted direct PCR exhibited high sensitivity in E.coli O157:H7 detection. The detection limit of PDA NPs-assisted direct PCR was 6.7 × 104 CFU/mL, which was 10-fold lower than that of direct PCR (6.7 × 105 CFU/mL). Moreover, the sensor demonstrated excellent selectivity against E. coli O157:H7, with a negative reaction to eight other common pathogens. Most importantly, the PDA NPs-assisted direct PCR detected the order of 104−5 CFU/mL E.coli O157:H7 in milk, beef, and watermelon samples. No cultural enrichment was required, with the whole process taking <3 h. Therefore, PDA NPs-assisted direct PCR has tremendous potential in the rapid and sensitive detection of pathogens. [Display omitted] • Polydopamine nanospheres-assisted direct PCR was developed. • Direct PCR shortens the detection time due to the DNA extraction step being omitted. • Polydopamine nanospheres can improve PCR efficiency by interaction with PCR reagents. • The sensor was used in real samples for E. coli O157: H7 detection with good results. [ABSTRACT FROM AUTHOR]

• Developed a sensitive photothermal sensor for deoxynivalenol detecting in food. • Au nanoparticle-enhanced MnO 2 nanoflowers were used as photothermal-sensing probes. • Quantitative analysis was carried out by a thermal imager and infrared thermometer. A sensitive photothermal immunochromatographic test strip (PITS) for the detection of deoxynivalenol (DON) was developed using flower-like gold nanoparticle-deposited manganese dioxide nanocarrier (FMD-G NC) labeled antibodies (Abs) as the photothermal-sensing probe. FMD was used as a template to deposit small gold nanoparticles (GNPs) to synthesize FMD-G NC with large specific surface area and significant photothermal conversion property. The FMD-G-Ab probe was competitively captured by DON target and antigen coated on test line (T -line), forming colorimetric signals under naked eyes and photothermal signals under an 808 nm laser. Under optimal conditions, the PITS exhibited sensitive and specific detection of DON from 0.19 ng mL−1 to 12 ng mL−1 with detection limits of 0.013 ng mL−1, which were over 15-fold and 58-fold more sensitive than visual FMD-G-ITS and traditional GNPs-ITS. In addition, the novel FMD-G-PITS possessed a universal applicability, which could be well applied in green bean, corn, and millet. [ABSTRACT FROM AUTHOR]