DNAzyme‐Mediated Genetically Encoded Sensors for Ratiometric Imaging of Metal Ions in Living Cells

Genetically encoded fluorescent proteins (FPs) have been used for metal ion detection. However, their applications are restricted to a limited number of metal ions owing to the lack of available metal‐binding proteins or peptides that can be fused to FPs and the difficulty in transforming the binding of metal ions into a change of fluorescent signal. We report herein the use of Mg²⁺‐specific 10–23 or Zn²⁺‐specific 8–17 RNA‐cleaving DNAzymes to regulate the expression of FPs as a new class of ratiometric fluorescent sensors for metal ions. Specifically, we demonstrate the use of DNAzymes to suppress the expression of Clover2, a variant of the green FP (GFP), by cleaving the mRNA of Clover2, while the expression of Ruby2, a mutant of the red FP (RFP), is not affected. The Mg²⁺ or Zn²⁺ in HeLa cells can be detected using both confocal imaging and flow cytometry. Since a wide variety of metal‐specific DNAzymes can be obtained, this method can likely be applied to imaging many other metal ions, expanding the range of the current genetically encoded fluorescent protein‐based sensors.     

Nanoscale semiconductor Pb1−xSnxSe (x = 0.2) thin films synthesized by electrochemical atomic layer deposition

In this paper the fabrication and characterization of IV-VI semiconductor Pb_1−xSn_xSe (x = 0.2) thin films on gold substrate by electrochemical atomic layer deposition (EC-ALD) method at room temperature are reported. Cyclic voltammetry (CV) is used to determine approximate deposition potentials for each element. The amperometric I-t technique is used to fabricate the semiconductor alloy. The elements are deposited in the following sequence: (Se/Pb/Se/Pb/Se/Pb/Se/Pb/Se/Sn …), each period is formed using four ALD cycles of PbSe followed by one cycle of SnSe. Then the deposition manner above is cyclic repeated till a satisfactory film with expected thickness of Pb_1−xSn_xSe is obtained. The morphology of the deposit is observed by field emission scanning electron microscopy (FE-SEM). X-ray diffraction (XRD) pattern is used to study its crystalline structure; X-ray photoelectron spectroscopy (XPS) of the deposit indicates an approximate ratio 1.0:0.8:0.2 of Se, Pb and Sn, as the expected stoichiometry for the deposit. Open-circuit potential (OCP) studies indicate a good p-type property, and the good optical activity makes it suitable for fabricating a photoelectric switch.     

Selective determination of catecholamine in the presence of ascorbic acid or uric acid on the membrane of silver nanoparticles/poly l-phenylalanine

The silver ions and l-phenylalanine were co-deposited and formed a hybrid membrane on the surface of glassy carbon electrode by cyclic voltammetry. The membrane had good properties for catalyzing the redox of catecholamine neurotransmitters, including epinephrine (EP), norepinephrine (NE), and dopamine (DA). The electrochemical behaviors of these neurotransmitters were studied on this modified electrode. and therefore, an assay for each of them is set up and the detection limits for EP, NE, and DA are 7.2?×?10^?9, 6.4?×?10^?9, and 8.5?×?10^?9 mol L^?1, respectively. The proposed method can effectively eliminate the interference of the ascorbic acid and uric acid. The conditions which influenced the analyses were optimized. Using this method to determine the content of EP, NE, and DA in injections, the results were satisfactory.     

Construction of Rich Conductive Pathways from Bottom to Top: A Highly Efficient Charge-Transfer System Used in Durable Li/Na-Ion Batteries at −20 °C

The construction of potential electrode materials with wide temperature property for high-energy-density secondary batteries has attracted great interest in recent years. Herein, a hybrid electrode, consisting of a nitrogen-doped carbon/α-MnS/flake graphite composite (α-MnS@N-C/FG), is prepared through a post-sulfurization route. In the α-MnS@N-C/FG composite, α-MnS nanoparticles wrapped by the N−C layer are uniformly embedded onto FG, forming a novel nanofoam structure. The as-obtained α-MnS@N-C/FG shows excellent lithium/sodium storage performance, with a specific capacity of 712 mA h g⁻¹ in the 700th cycle at 1.0 A g⁻¹ or 186.4 mA h g⁻¹ in the 100th cycle at 100 mA g⁻¹ using lithium or sodium foil as the counter electrode, respectively. Moreover, even operated at −20 °C, the α-MnS@N-C/FG can still attain a high specific capacity of 350 mA h g⁻¹ after 50 cycles at 100mA g⁻¹ for LIBs. This exceptional electrochemical response is attributed to the synergetic effect of the smart design of a hybrid nanofoam structure, in which the FG skeleton and N-C coating layer can significantly enhance the conductivity of the whole electrode from bottom to top. Accordingly, the enhanced redox kinetics endow the electrode with pseudocapacitive-dominated electrochemical behavior, leading to fast electrode reactions and robust structural stability in the whole electrode.     

Electrodeposition from ZnO nano-rods to nano-sheets with only zinc nitrate electrolyte and its photoluminescence

This very paper focuses on the synthesis of ZnO nano-structures by means of electro-chemical-deposition process. The crystalline structure and morphologies of the prepared ZnO were characterized with X-ray diffraction and scanning electronic microscopy, respectively. It is found that in case of low Zn(NO₃)₂·6H₂O electrolyte concentration the fast growth mode in the c-axis direction leaded to the formation of 1D nanostructure of ZnO. On the other hand, at high concentration, this fast growth mode was restricted because the absorbed NO₃⁻ on (0 0 0 1) plane would bond with Zn²⁺ ions, which, therefore, resulted in the formation of 2D nanostructure of ZnO. Room temperature photoluminescence performances of different ZnO structures were also investigated. A blue shift of 15 nm for ZnO nano-sheets has been found as the shapes of ZnO evolved from nano-rods to nano-sheets.     

On the generalizations of Denjoy-Wolff theorem

We consider generalizations of Denjoy-Wolff theorem on strongly pseudo-convex domains. Beardon [3] gave a general Denjoy-Wolff theorem in hyperboli domain in the complex plane. Our main results are generalizations of Beardon's result in a higher dimensional setting.     

Recent progress in the shape deformation of polymeric hydrogels from memory to actuation

Shape deformation hydrogels, which are one of the most promising and essential classes of stimuli-responsive polymers, could provide large-scale and reversible deformation under external stimuli. Due to their wet and soft properties, shape deformation hydrogels are anticipated to be a candidate for the exploration of biomimetic materials, and have shown various potential applications in many fields. Here, an overview of the mechanisms of shape deformation hydrogels and methods for their preparation is presented. Some innovative and efficient strategies to fabricate programmable deformation hydrogels are then introduced. Moreover, successful explorations of their potential applications, including information encryption, soft robots and bionomic systems, are discussed. Finally, remaining great challenges including the achievement of multiple stable deformation states and the combination of shape deformation and sensing are highlighted.

Shape deformation hydrogels, which are one of the most promising and essential classes of stimuli-responsive polymers, could provide large-scale and reversible deformation under external stimuli.     

Facile microfluidic fabrication of monodispersed self-coupling microcavity with fine tunability

Whispering gallery mode (WGM) resonators have received extensive attention because of their nonlinear optical application in lasers and sensors. Optical microcavities are excellent candidates for constructing powerful microlasers and label-free biosensors, owing to their low optical losses and small size. However, most of these microcavity syntheses rely on sophisticated fabrication methods and cannot be manipulated easily. To achieve facile and versatile microcavity fabrication, we present a robust microfluidics method for monodispersed self-coupling optical microcavity fabrication with a fine tunability. The microcavity polydispersity was less than 3%. The optical microcavity size could be varied from 10 to 30 µm with a steady quality factor (Q) of approximately 1000. The lowest laser threshold that we obtained was 0.82 µJ with a microcavity size of 20 µm. The doped fluorescent dye concentration can be tuned precisely from 0.001 to 0.05 wt% to explore an optimized fluorescent background. The experimental results and theoretical simulation match well in terms of Q and the electrometric resonance field intensity. Compared with previous precise and practical fabrication methods, we have demonstrated a facile approach for versatile optical microcavity fabrication. This method can vary the microcavity materials, size, doped fluorescent dye concentration, WGM resonance spectrum, Q factor, and laser threshold easily to adapt to various circumstances and specific applications.     

Metal–Organic Frameworks as Metal Ion Precursors for the Synthesis of Nanocomposites for Lithium-Ion Batteries

Metal–organic frameworks (MOFs) are promising materials with fascinating properties. Their widespread applications are sometimes hindered by the intrinsic instability of frameworks. However, this instability of MOFs can also be exploited for useful purposes. Herein, we report the use of MOFs as metal ion precursors for constructing functional nanocomposites by utilizing the instability of MOFs. The heterogeneous growth process of nanostructures on substrates involves the release of metal ions, nucleation on substrates, and formation of a covering structure. Specifically, the synthesized CoS with carbon nanotubes as substrates display enhanced performance in a lithium-ion battery. Such strategy not only presents a new way for exploiting the instability of MOFs but also supplies a prospect for designing versatile functional nanocomposites.