Sensitive fluorescence assay of chloramphenicol coupled with two-level isothermal amplification using a self-powered catalyzed hairpin assembly and entropy-driven circuit.

Two levels of nucleic acids-based isothermal amplification normally require a long reaction time due to the low concentration of catalyst, which limits its practical application. A sensitive fluorescence assay of chloramphenicol (CAP) was developed coupled with two-level isothermal amplification using a self-powered catalyzed hairpin assembly (CHA) and entropy-driven circuit (EDC). CAP can bind with its aptamer to open its closed structure. The opened hairpin can initiate self-powered CHA and EDC. The product of CHA can circularly catalyze the CHA with increasing concentration. In principle, the product of CHA plays the role of catalyst and increases with the progression of the reaction. Compared with the normal two levels of amplification, the amplification efficiency of our strategy is much higher due to the self-powered reaction by the CHA product. Thus, the reaction time is shortened to 110 min in this strategy. Moreover, the detection limit for CAP can achieve 0.1 pM and shows promising prospects for practical application.

Comprehensive Study Addressing the Challenge of Efficient Electrocatalytic Biomass Upgrading of 5-(Hydroxymethyl)Furfural (HMF) with a CH3 NH2 Ionic Liquid on Metal-Embedded Mo2 B2 MBene Nanosheets.

Amine-containing derivatives are important intermediates in drug manufacturing; sustainable synthesis of amine compounds from green carbon-based biomass derivatives has attracted increasing attention, especially the reductive amination of biomass molecules via electrochemical upgrading. To achieve efficient reductive amination of 5-(hydroxymethyl)furfural (HMF) via electrocatalytic biomass upgrading, this work proposes a new HMF biomass upgrading strategy based on metal supported on Mo2 B2 MBene nanosheets using a density functional theory comprehensive study. HMF and methylamine (CH3 CH2 ) can be reduced to 5-(hydroxymethyl) aldiminefurfural (HMMAMF) via electrocatalytic biomass upgrading, which is identified as a promising technology to produce pharmaceutical intermediates. Based on the proposed reaction mechanisms of HMF reductive amination, this work performs a systematic study of HMF amination to HMMAMF using an atomic model simulation method. This study aims to design a high-efficiency catalyst based on Mo2 B2 @TM nanosheets via the reductive amination of 5-HMF and provide insights into the intrinsic relation between thermochemical and material electronic properties and the role of dopant metals. This work establishes the Gibbs free energy profiles of each reaction HMF Biomass Upgrading on Mo2 B2 systems and obtained the limiting potentials of the rate-determining step, which included the kinetic stability of dopants, HMF adsorbability, and the catalytic activity and selectivity of the hydrogen evolution reaction or surface oxidation. Furthermore, charge transfer, d-band center (εd ), and material property (φ) descriptors are applied to establish a linear correlation to determine promising candidate catalysts for reductive amination of HMF. The candidates Mo2 B2 @Cr, Mo2 B2 @Zr, Mo2 B2 @Nb, Mo2 B2 @Ru, Mo2 B2 @Rh, and Mo2 B2 @Os are suitable high-efficiency catalysts for HMF amination. This work may contribute to the experimental application of biomass upgrading catalysts for biomass energy and guide the future development of biomass conversion strategies and utilization.

Dual-amplification colorimetric detection of bisphenol A based on catalytic hairpin assembly and DNAzyme-caused fragment self-assembly hybridization chain reaction.

An efficient and innovative strategy for colorimetric detection of bisphenol A (BPA) is shown here based on target-induced catalytic hairpin assembly (CHA) and DNAzyme-caused fragment self-assembly hybridization chain reaction (HCR). BPA can bind with its aptamer hairpin to trigger CHA, thus forming Y-shaped DNA nanostructures with an enzyme-strand (E-DNA) tail. Subsequently, the E-DNA can cyclically cleave the substrate hairpin, generating many fragments which can cause self-assembly HCR to form long strand DNA. Finally, the formed long strand DNA can hybridize with short single strand DNA on AuNPs, causing the color change of AuNPs from red to blue. Six important detection conditions of the proposed aptasensor were optimized. Under optimal conditions, the biosensor has high sensitivity for BPA detection at concentrations ranging from 0.8 pM to 500 pM and the detection limit is as low as 0.2 pM, providing a promising prospective ultrasensitive detection of BPA.

Enhanced soft magnetic properties and high-frequency stability of FeNiMo powder cores by coating SiO2 insulation layer.

FeNiMo/SiO2 powder cores were prepared using the sol-gel method. Tetraethyl orthosilicate (TEOS) was added to produce an amorphous SiO2 coating outside the FeNiMo particles to form a core-shell structure. The thickness of the SiO2 layer was designed by varying the concentration of TEOS, and the optimized permeability and magnetic loss of the powder core could achieve 78.15 and 633.44 kW m-3 at 100 kHz and 100 mT, respectively. Compared with other soft magnetic composites, these FeNiMo/SiO2 powder cores have a significantly higher effective permeability and a lower core loss. Surprisingly, the high-frequency stability of permeability could be substantially enhanced through the insulation coating process in which µf/µ100 kHz could reach 98.7% at 1 MHz. In comparison with 60µ commercial products, the comprehensive soft magnetic properties of the FeNiMo/SiO2 cores were superior to most manufacturers, which would be potentially applied to high-performance inductance devices in high-frequency ranges.

Electrocatalytic Biomass Upgrading of Furfural using Transition-Metal Borides via Density Functional Theory Investigation.

Electrocatalytic biomass upgrading has proven to be an effective technique for generating value-added products. Herein, the design and development of furfural upgrading using transition-metal borides (MBenes) with simultaneous production of hydrogen are presented. Using density functional theory, the stabilities, selectivities, and activities of 13 MBene candidates are systematically evaluated for furfural upgrading. This research suggests that Fe2 B2 can serve as a promising electrocatalyst for the formation of furoic acid (FAC), with a limiting potential of -0.15 V, and 5-hydroxy-2(5H)-furanone (HFO), with a limiting potential of -0.93 V. Furthermore, Fe2 B2 and Mn2 Fe2 are shown to exhibit favorable limiting potentials of -1.35 and -1.36 V, respectively, for producing 6-hydroxy-2.3-dihydro-6H-pyrano-3-one (HDPO), indicating that they may also serve as electrocatalysts. Based on Sabatier's principle, a descriptor (φ) of material properties is developed for screening catalysts with high catalytic activity considering the electronegativities and d-electron number of metals. Additionally, surface redox potential, electronic properties, and charge-density differences are determined for Fe2 B2 , which is estimated to exhibit high catalytic activity for the oxidation of furfural to FAC and HFO.

Simultaneous and ultra-sensitive detection of Cu2+ and Mg2+ in wine and beer based on dual DNA tweezers and entropy-driven three-dimensional DNA nanomachine.

Simultaneous and ultra-sensitive detection strategy of Cu2+ and Mg2+ in wine and beer was developed based on dual DNA tweezers and entropy-driven three-dimensional DNA nanomachine. The dual DNAzyme can simultaneously respond to two kinds of metal ions and cause two kinds of "turn-on" fluorescent signals. The working principle of this strategy was indirectly proven. In addition, some key experimental parameters were also optimized. Under the optimum conditions, the limit of detection was 10 pM for Cu2+ and 2 nM for Mg2+ respectively which was significantly improved by entropy driven amplification. This strategy also showed good selectivity and specificity. It was successfully used to detect of Cu2+ and Mg2+ in wine and beer with 5.26% to 9.12% of relative standard deviation and 90.4% to 110.5% of recoveries.

Two-color, ultra-sensitive fluorescent strategy for Ochratoxin A detection based on hybridization chain reaction and DNA tweezers.

A two-color fluorescent DNA tweezers was developed for ultrasensitive detection of Ochratoxin A (OTA) based on hairpin-locked aptamer and hybridization chain reaction (HCR) amplification strategy. OTA can bind with hairpin-locked aptamer and then trigger the HCR reaction to produce a long double-strand DNA. The side-chains of the long duplex can separately hybridize with the two locker sequences of DNA tweezer, causing the opening of DNA tweezer and the recovery of two-color fluorescent signals. It shows a good linear range from 0.02 to 0.8 ppb with limit of detection of 0.006 ppb for FAM and 0.014 ppb for Cy5, which is beyond the requirement of actual application. In addition, the two-color fluorescent strategy can greatly reduce the false positive rate. It shows excellent performance for detection of OTA in practical food sample.

Heterogeneous Interface Design to Enhance the Photocatalytic Performance.

Heterojunction photocatalysts, which can relieve the low carrier separation efficiency and insufficient light absorption ability of one catalyst, have received extensive attention. To construct an ideal heterojunction for photocatalysis, most previous studies focused on energy band structure engineering to prolong charge carrier lifetime and increase the reaction rates, which are critical to increase the photocatalytic activity. Here, the heterojunction interface was surprisingly found to be another important factor to affect the photocatalytic performance. We design three heterojunction interface models of α-Fe2O3/Bi2O3, corresponding to "ring-to-face", "face-to-face", and "rod-to-face". By tuning the heterogeneous interfaces, the photocatalytic performance of composites was significantly improved. On the basis of the type I energy band structures, the optimized face-to-face model realized a photocatalytic efficiency of 90.8% that of pure α-Fe2O3 (<30%) for degradation of methylene blue and a higher efficiency (80%) for degrading tetracycline within 60 min, which were superior to most Fe/Bi/O-based photocatalytic heterojunctions. Furthermore, the results disclosed that the enhanced performance was owing to the sufficient interfacial contact and low interfacial resistance of the face-to-face model, which provided sufficient channels for efficient charge transfer. This work offers a new direction of tuning heterojunction interface for designing composite photocatalysts.

Annealing Condition Effects on the Structural Properties of FePt Nanoparticles Embedded in MgO via Pulsed Laser Deposition.

FePt nanoparticles (NPs) were embedded into a single-crystal MgO host by pulsed laser deposition (PLD). It was found that its phase, microstructures and physical properties were strongly dependent on annealing conditions. Annealing induced a remarkable morphology variation in order to decrease its total free energy. H2/Ar (95% Ar + 5% H2) significantly improved the L10 ordering of FePt NPs, making magnetic coercivity reach 37 KOe at room temperature. However, the samples annealing at H2/Ar, O2, and vacuum all showed the presence of iron oxide even with the coverage of MgO. MgO matrix could restrain the particles' coalescence effectively but can hardly avoid the oxidation of Fe since it is extremely sensitive to oxygen under the high-temperature annealing process. This study demonstrated that it is essential to anneal FePt in a high-purity reducing or ultra-high vacuum atmosphere in order to eliminate the influence of oxygen.

A wide-frequency range dielectric tuning of BaTiO3 by embedding metal nanocrystals.

Fe nanocrystals (NCs) were embedded into the epitaxial BaTiO3 (BTO) matrix. According to optimized growth processes, a novel nanocomposite system was constructed, which consisted a well epitaxial BTO layer and three-dimensional Fe NCs. Based on this, the different dielectric response in the regions of low temperature-high frequency and low frequency-high temperature were revealed by the contribution of hopping and interfacial polarizations, respectively. With the increased amount of Fe NCs, the obvious enhancement in the low-frequency conductivity, middle frequency capacitance, and high-frequency inductive effect was found. The embedded metal NCs play an important role in tuning the dielectric behaviors and AC conductivity of oxide dielectrics. This significant rectification effect in wide-frequency ranges opens up a new direction for designing embedded nano-capacitors.

Time dependence of domain structures in potassium sodium niobate-based piezoelectric ceramics.

Piezoelectric materials, which can convert energy between electrical and mechanical forms, are widely used in modern industry. (K,Na)NbO3-based ceramics have attracted extensive attention due to their excellent performance characteristics among the lead-free materials. Piezoelectric properties are closely related to ferroelectric domain structures including the domain morphology and domain wall motion. However, time dependence of ferroelectric domains in (K,Na)NbO3-based ceramics has barely been studied. Here, we synthesized Li-doped KNN ceramics. The morphologies and crystallographic parameters of the domain structures were characterized. Two ferroelectric domains, the 60°/120° and 180° domains, were identified in the ceramic. Surprisingly, the domain structure changed naturally as time passed, and most of the change occurred in the 180° domain wall, while the 60°/120° domains remained nearly unchanged. Our results are different from those of previous studies, which showed that the non-180° domain wall was more prone to movement than the 180° domain wall.

Simultaneous detection of aflatoxin B1 and ochratoxin A in food samples by dual DNA tweezers nanomachine.

a dual DNA tweezers nanomachine was developed for one-step simultaneous detection of aflatoxin B1 (AFB1) and ochratoxin A (OTA) in food samples. The dual DNA tweezers are locked by the aptamers of mycotoxins, resulting the "turn off" of fluorescent signal. In the presence of AFB1 and OTA, the aptamers can bind with their corresponding targets, resulting the "open" of DNA tweezers and the "turn on" of the fluorescent signals. The limits of detections were 3.5 × 10-2 ppb for AFB1 and 0.1 ppb for OTA. Moreover, the applicability of the method was further demonstrated by conducting a limited survey on 5 samples collected from various sources. The recoveries of this method change from 90.0% to 110.0% for simultaneous detection of AFB1 or OTA and the RSDs vary from 4.1% to 9.2%. Detection uncertainties were within 5% (with a 95% confidence level).

Novel Luminescent Nanostructured Coordination Polymer: Facile Fabrication and Application in Electrochemiluminescence Biosensor for microRNA-141 Detection.

A series of novel luminescent nanostructured coordination polymers (Ce-Ru-NCPs) with tunable morphologies have been successfully synthesized on a large scale at room temperature by a facile and rapid solution-phase method using Ce3+ and tris(4,4'-dicarboxylicacid-2,2'-bipyridyl) ruthenium(II) dichloride (Ru(dcbpy)32+). Among them, the flowerlike Ce-Ru-NCP shows good cathodic electrochemiluminescence (ECL) characteristics. The ECL efficiency of the Ce-Ru-NCP/S2O82- system is about 2.34 times that of the classic tris(2,2'-bipyridyl) ruthenium(II) dichloride/S2O82- (Ru(bpy)32+/S2O82-) system. Hence, we report a sensitive ECL biosensor for microRNA-141 (miRNA-141) detection based on the flowerlike Ce-Ru-NCP as a cathodic ECL luminophore and a bipedal three-dimensional (3D) DNA walking machine as a signal amplifier. Through the bipedal 3D DNA walking machine, trace targets can be converted to substantial secondary targets (marked with the quencher dopamine), and a significant quenching effect on the ECL signal is achieved. As a result, the proposed biosensor exhibits a relatively good sensitivity for miRNA-141 detection and shows a dynamic range from 1.0 × 10-16 to 1.0 × 10-6 mol·L-1 with a limit of detection (LOD) of 33 amol·L-1 (S/N = 3). The Ce-Ru-NCP with tunable morphologies and high ECL efficiency, intensity, and stability possesses potential applications in ECL analysis.

Comparisons of prebiotic activity of polysaccharides from shoot residues of bamboo (Chimonobambusa quadrangularis) via different ethanol concentrations.

Three polysaccharide fractions from bamboo shoot (Chimonobambusa quadrangularis), CPS70, CPS75, and CPS80, were prepared using a final ethanol concentration of 70%, 75%, and 80% in the precipitation process. In vitro digestibility and the prebiotic activity of CPS70, CPS75, and CPS80 were evaluated and compared. The results indicated that all three of the CPS fractions exhibit a high degree of nondigestibility to human gastric juice (>98.5%) or α-amylase hydrolysis (>94.5%). Compared with the blank control, the three CPS fractions could not only significantly (p < .05) stimulate the proliferation of B. adolescentis, B. infantis, B. bifidum, and L. acidophilus, but also significantly (p < .05) enhance the production of lactic, acetic, propionic, and butyric acids when these polysaccharides were added as alternative carbon sources to glucose during the in vitro fermentation of four probiotics. Furthermore, when comparing the three CPS fractions, CPS75 displayed the strongest prebiotic potential, as this polysaccharide had the strongest effect on the proliferation of probiotic bacteria as well as the greatest effect on SCFAs production. These results demonstrated that the concentration of ethanol used during the precipitation process has a significant impact on the prebiotic activity of CPS. PRACTICAL APPLICATIONS: Ethanol precipitation is the first step when extracting polysaccharides from aqueous extracts as it is simple, rapid, and easy to carry out. This study focuses on how different concentrations of ethanol used in the precipitation process affect the prebiotic potential of bamboo shoot (Chimonobambusa quadrangularis) polysaccharides (CPS). The result indicated that the concentration of ethanol used during the precipitation process has a significant impact on the prebiotic activity of CPS. To our knowledge, it is the first to evaluate the effects of the concentration of ethanol during the process of precipitation on prebiotic potential of polysaccharides, which can subsequently be applied to the optimization of ethanol concentration when precipitating natural polysaccharides for the purpose of in vitro fermentation.

A simple and programmed DNA tweezer probes for one-step and amplified detection of UO22.

A simple DNA tweezer was proposed for one-step and amplified detection of UO22+ based on DNAzyme catalytic cleavage. The two arms of DNA tweezers are close in the original form. Thus, the fluorescent signal of fluorophore at the end of arm is dramatically quenched. However, the structure of DNA tweezers can be changed from "close" to "open" in the presence of UO22+, resulting the strong fluorescent signal. The linear range was obtained in the range of 0.1 nM to 60 nM and the limit of detection was 25 pM with the amplification of DNAzyme catalytic cleavage reaction. Importantly, the whole detection process is very simple and only one operation step is required. In addition, it shows great potential and promising prospects for uranyl detection in practical application.

Dual-entropy-driven catalytic amplification reaction for ultra-sensitive and visible detection of Hg2+ in water based on thymine-Hg2+-thymine coordination chemistry.

An ultra-sensitive and visible Hg2+ detection strategy was established. It was based on T-Hg2+-T coordination chemistry and a dual-entropy-driven catalytic reaction (EDCR). The dual EDCR was initiated by T-Hg2+-T coordination chemistry, resulting in the release of a G-rich sequence to form a hemin/G-quadruplex-HRP-mimicking DNAzyme, and then catalyzing 3,3',5,5'-tetramethylbenzidine (TMB) into TMB+, with a color change from colorless to blue. This method showed great sensitivity and excellent selectivity, and the limit of detection reached 0.6 pM. The feasibility of this method was demonstrated by real water samples. Moreover, the visible color change provided the possibility of ultra-sensitive detection of Hg2+ by the naked eye.

Tailoring Morphologies, Photocatalytic Activity, and Energy Bands of Bi25FeO40 via Valence State Transformation of Doped V Ions.

Photocatalysts with suitable nanostructures and excellent photocatalytic activity driven by solar light are in great demand for rapidly eliminating the organic pollutants from wastewater. In order to improve the photocatalytic activities, three main factors should be considered, including band gap, band structure, and morphologies. Most of the previous studies only focused on manipulating one factor, such as the band gap by element doping. However, studies on enhancing photocatalytic activities by designing the band structure and morphologies are challenging, due to the difficulity to control the three parameters at the same time. Here, the V-doped Bi25FeO40 (Bi25Fe1- xV xO40) was demonstrated as a great system to manipulate the photocatalytic activities by designing the band structure and morphologies. With the simple hydrothermal methods, Bi25Fe1- xV xO40 with different flower-like morphologies and band structures were prepared. Surprisingly, the blooming and withering processes of the artificial architectures could be precisely tuned through different V concentrations. The controllable microstructures possess the high visible light absorption and enhanced photocatalytic activity. These results offer a model to reveal how the doping element can synchronously manipulate the particle morphology, band gap, and band structures, which is a key step to design new photocatalytic materials.

Photoelectron transport tuning of self-assembled subbands.

Conventionally, electrical transport of quantum subbands occurs at very high electric fields, indicating that the medium is easy to break down. In the experiments and practical applications, the extreme condition is difficult to satisfy. For quantum information transmission, low power consumption and convenient implementation are what we expect. In this paper, we engineered a special quantum dot array (QDA) embedded in a single crystal matrix. By external optical field excitation, we found a series of subbands made of the self-assembled QDA discretely located in the matrix. Changing the spacing between the quantum dots leads to the variation of subband spacing. Artificially manipulating the microcosmic QDA system can bring interesting macroscopic effects, such as an enhanced absorption intensity in the ultraviolet range, a blue-shift of the surface plasmon resonance peak and nonlinear absorption changed from two-photon absorption to saturated absorption. The intrinsic mechanism of the subband optical response was revealed due to the strong quantum confinement effect and dominant intraband transitions. The weak surface plasmon resonance absorption of Ni QDA gave an excellent figure of merit of the order of 10(-10). The composite films are expectation enough to become a prime candidate for nonlinear applications near 532 nm. Therefore with interplay of the weak optical field and subbands, we achieved a tunable photoelectron transport process.

Room-temperature resonant quantum tunneling transport of macroscopic systems.

A self-assembled quantum dots array (QDA) is a low dimensional electron system applied to various quantum devices. This QDA, if embedded in a single crystal matrix, could be advantageous for quantum information science and technology. However, the quantum tunneling effect has been difficult to observe around room temperature thus far, because it occurs in a microcosmic and low temperature condition. Herein, we show a designed a quasi-periodic Ni QDA embedded in a single crystal BaTiO3 matrix and demonstrate novel quantum resonant tunneling transport properties around room-temperature according to theoretical calculation and experiments. The quantum tunneling process could be effectively modulated by changing the Ni QDA concentration. The major reason was that an applied weak electric field (∼10(2) V cm(-1)) could be enhanced by three orders of magnitude (∼10(5) V cm(-1)) between the Ni QDA because of the higher permittivity of BaTiO3 and the 'hot spots' of the Ni QDA. Compared with the pure BaTiO3 films, the samples with embedded Ni QDA displayed a stepped conductivity and temperature (σ-T curves) construction.