Multi-aptamer-mediated hairpin allosteric and aptamer-assisted CRISPR system for detection of S. pneumoniae and S. aureus.

A novel nucleic acid aptamer nanoprobes-mediated hairpin allosteric and aptamer-assisted CRISPR system for detection of Streptococcus pneumoniae and Staphylococcus aureus is presented. In this fluorescence assay system, utilizing the hairpin allosteric effect caused by the aptamer binding to the target bacteria, the detection of S. pneumoniae is first achieved through changes in fluorescence due to FRET. Subsequently, a Cas12a protein mixture is added to detect S. aureus. The amplified output signal is triggered by two methods to ensure the sensitivity of the method: the synergistic FRET effect is achieved by the assembly of multi-aptamer through the conjugation of streptavidin-biotin, and the trans-cleavage function of CRISPR/Cas 12a. Under the optimized conditions, the proposed hairpin allosteric aptasensor could achieve high sensitivity (a detection limit of 135 cfu/mL) and broad-concentration quantification (dynamic range of 103-107 cfu/mL) of S. pneumoniae. The aptamer-assisted CRISPR system for S. aureus detection showed good linearity (R2 = 0.996) in the concentration range 102-108 cfu/mL, with a detection limit of 39 cfu/mL. No cross-reactivity with other foodborne pathogenic bacteria was observed in both systems. Taking only 55 min, this method of multiple pathogen detection proved to be promising.

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.

[Study on the preparation and properties of novel silica microporous antireflective coating by sol-gel process].

Silica sol was prepared by acid catalyzed sol-gel process using tetraethylorthosilicate (TEOS) as precursor and dimethyldietoxysilane (DDS) as pore-forming agent. A novel kind of monolayer microporous silica anti-reflective (AR) coating was obtained on K9 glass substrate by dip-coating technique and then heat treated at 500 degrees C. The effects of different DDS/TEOS molar ratios on refractive index, transmittance and hardness were investigated. A positive correlation was found between the transmittance and the DDS/TEOS molar ratio due to the increasing porosity. The maximum transmittance can reach 99.7% with the molar ratio of DDS/TEOS rising to 1 : 1. Meanwhile, the refractive index was found quite close to the ideal value 1.22. Nevertheless, higher molar ratio will lead to a bad film-forming property. On the other hand, the hardness of the coatings decreased with the DDS increasing but still remained more than 2 h when the transmittance reached highest. Besides, these coatings exhibit a well abrasion-resistance and excellent adhesivity. The maximum transmittance was only dropped by 0.071% and 0.112% after abrasion for 500 and 1 000 times respectively. Accelerated corrosion tests indicated that the transmittance of traditional coatings rapidly fell down to the substrate level (-92%) after immersion for 5 min, while the transmittance of our novel coating almost linearly decreased and was kept 93.2% after 56 min. In other words, the environment-resistance of our novel silica AR coating is ten times higher than that of traditional ones. The promotions of the coating performances benefit from its micropore structure (-0. 4 nm) with which water molecule can be effectively prevented. With its high transmittance, good mechanical properties and high environment-resistance, this kind of novel coating has a potential application in the field of solar glass modification to improve its anti-reflective properties.

[Synthsis and photoluminescence properties of low-T(g), photorefractive polymers of double function].

A group of low-T(g) photorefractive polymers of double function with carbazole and p-nitrodiazencarbazole called P-2, P-3 and P-4 were synthesized by means of different proportional diazonium salts being diazo-coupled with the poly [bis(6-carbazolhexyloxy)] phosphazene(P-1). P-2, P-3 and P-4 were characterized by 31P NMR, 1H NMR, IR, UV-Vis, GPC, TG and DSC. The result showed that P-2, P-3 and P-4 have good heat stability (T(d) approximately 300 degrees C) and a lower glass transition temperature (T(g) approximately 30-40 degrees C). Their fluorescence properties were studied by photoluminescence and the result showed that P-1 has a stronger fluorescence properties and fluorescence intensity. P-2, P-3 and P-4 have varying degrees of quenching after nitro joining. The fluorescence properties were related with numbers of carbazole and nitro and their molecular space structure.

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.