High responsivity photodetectors based on graphene/WSe_(2) heterostructure by photogating effect

Graphene, with its zero-bandgap electronic structure, is a highly promising ultra-broadband light absorbing material.However, the performance of graphene-based photodetectors is limited by weak absorption efficiency and rapid recombination of photoexcited carriers, leading to poor photodetection performance. Here, inspired by the photogating effect, we demonstrated a highly sensitive photodetector based on graphene/WSe_(2) vertical heterostructure where the WSe_(2) layer acts as both the light absorption layer and the localized grating layer. The graphene conductive channel is induced to produce more carriers by capacitive coupling. Due to the strong light absorption and high external quantum efficiency of multilayer WSe_(2), as well as the high carrier mobility of graphene, a high photocurrent is generated in the vertical heterostructure. As a result, the photodetector exhibits ultra-high responsivity of 3.85×10~4A/W and external quantum efficiency of 1.3 × 10~7%.This finding demonstrates that photogating structures can effectively enhance the sensitivity of graphene-based photodetectors and may have great potential applications in future optoelectronic devices.

Synthesis,Crystal Structure and Photoluminescence Property of Ag(I)with N,N-dimethyl-4-(pyridine-4-yldiazenyl)aniline

A 2D plane coordination compound [Ag_2（Dpya）_2.（NO_3）_2]n was synthesized and characterized by FT-IR,elemental analysis and TG analysis.The red crystal was obtained via solvent diffusion method at room temperature and is slightly soluble in organic solvents.Its structure was determined by single-crystal X-ray diffraction analysis.It crystallizes in monoclinic,space group P1 with a = 10.7995（13）,b = 7.4748（8）,c = 18.364（2） A,β = 98.916（4）o,V = 1464.5（3） A^3,Z = 2,C_（26）H_（28）Ag_2N_（10）O_6,M_r = 792.32,Dc = 1.302 Mg/m^3,F（000） = 792,μ（Mo Ka） = 1.356 mm^-1,R = 0.0575 and w R = 0.0826.The compound [Ag_2（Dpya）_2.（NO_3）_2]_n is a two-dimensional structure and there are two kinds of coordination configurations about the Ag atoms in the compound.The Ag（1） center is tetrahedrally coordinated with two O atoms of NO_3^-and two N atoms from the ligand Dpya.Meanwhile,the Ag（2） is five-coordinated by five O atoms from three NO_3^-anions.The Ag centers（Ag（1） and Ag（2）） connect to themselves as well as with each other by the bridging NO_3^-anions.And the coordination compound shows photoluminescence with an emission peak at 530 nm（λex = 450 nm） as the ligand Dpya.

Effect of Vector Density and Competence on Macromolecular Vector Transformation Efficiency

To research the effects of vector quantity and competence on the positive cloning rate,with a known gene sequence but in the absence of DNA template,we artificially designed 26 primers to synthesize a target gene of 835 bp in vitro using overlapping PCR technique. The whole experiment design with two factors and six levels( 36 combinations) was applied to study the effects of the vector density and competent cells on the macromolecular vector transformation efficiency. Based on the 1 500 ng target gene,the vector density grades were designed( 50,100,150,200,250,300 ng),and then the recombinant plasmids were transformed into Top10F',DH5,Stbl3,Epi400,JM108,SCSI. Results showed that the positive cloning rates of different vector amount from big to small were in the order of 200,250,300,150,100 and 50 ng.The maximum positive cloning rate of 200 ng reached 75%; and the average value was 28. 5%. The positive cloning rates of different competent cells from big to small were in the order of stbl3,Top10F',DH5,JM108,Epi400 and SCSI. Stbl3 was higher than other competent cells under any vector density,and its average positive cloning rate was 42. 4%. Both the vector density and competent cells had significant effects on the macromolecular vector transformation efficiency. The optimal combination was C4 with 200 ng vector density and Stbl3,the positive cloning rate of which could reach 75%.

A Graphic Algorithm of＂Track＂ Effect in 3D Games

In 3D games, a lot of weapons in the movement will drag a ＂follow the shadow＂ effect, which is called the ＂track＂. In this paper, we first analyze the change rule of the ＂track＂, and then put forward a kind of algorithm to realize the ＂track＂. The calculation of this algorithm is small, but the effect is very real, has been successfully applied to a variety of 3D games.

Synthesis of Heterometallic Rare Earth(Ⅲ)-Cobalt(Ⅱ)Complexes and Their Application in Alternating Copolymerization of Cyclohexene Oxide and Carbon Dioxide

Comprehensive Summary Four heterometallic rare earth(Ⅲ)-cobalt(Ⅱ)complexes(rare earth=Y(1),Sm(2),Nd(3),La(4))stabilized by an o-phenylenediamine-bridged tris(phenolato)ligand(L)have been synthesized and characterized.In these tetranuclear complexes,one polydentate L coordinates to one rare earth(Ⅲ)ion,and one cobalt(Ⅱ)ion,respectively,while two rare earth ions are bridged by four acetate groups.These complexes were applied in the copolymerization of cyclohexene oxide and CO_(2),which showed good activity(TON up to 440)and high poly(cyclohexene carbonate)selectivity(>99%).Kinetic studies determined the equation as rate=k[CHO]1[CO_(2)]0[initiator]1,which proves a first-order dependence on initiator concentrations and implies a synergistic mechanism with rare earth and cobalt ions cooperating in epoxide ring-opening and chain propagation.

Threshold Functions for Factor-critical Graphs

A connected graph G is said to be k- extendable if it has a set of k independent edges and each set of k independent edges in G can be extended to a perfect matching Qf G. A graph G is k-factor-critical if G - S has a perfect matching for any k-subset S of V（G）. The basic properties of k-extendable and k-factor-critical graphs have been investigated in [11] and [13]. In this paper, we determine thresholds for k-factor-critical graphs and k- extendable bipartite graphs. For non-bipartite k-extendable graphs, we find a probability sequence, which acts the same way like a threshold.

Syntheses, Structures and Photocatalytic Degradation Properties of Two Copper(Ⅱ) Coordination Polymers with Flexible Bis(imidazole) Ligand

Two copper(Ⅱ) coordination polymers {[Cu(bib)(nip)]·1.5 H_(2)O}_(n)(1) and [Cu_(2)(bib)(glu)_(2)]_(n)(2)(bib = 1,4-bis(2-methyl-imidazol-1-yl)butane, H2nip = 5-nitroisophthalic acid, H2glu = glutaric acid) were synthesized by the hydrothermal method and characterized by single-crystal X-ray diffraction, elemental analyses, IR and solid-state diffuse-reflection spectra. 1 forms a 2D network with the point symbol of(4~4·6^(2)) and 2D → 2D polythreaded network. 2 constructs the 6-connected 3D network based on the [Cu_(2)(COO)_(2)] dimer with the point symbol of(4~4·6~(10)·8). The energy band gaps(Eg) of 1 and 2 were 2.453 and 2.162 eV, respectively. 1 and 2 present high photocatalytic activity for the degradation of methylene blue under visible light irradiation.

Building multipurpose nano-toolkit by rationally decorating NIR-Ⅱ fluorophore to meet the needs of tumor diagnosis and treatment

Phototheranostics have attracted tremendous attention in cancer diagnosis and treatment because of the noninvasiveness and promising effectiveness.Developing advanced phototheranostic agents with long emission wavelength,excellent biocompatibility,great tumor-targeting capability,and efficient therapeutic effect is highly desirable.However,the mutual constraint between imaging and therapeutic functions usually hinders their wide applications in biomedical field.To balance this contradiction,we herein rationally designed and synthesized three novel tumor-targeted NIR-Ⅱ probes(QR-2PEG_(321),QR-2PEG_(1000),and QR-2PEG_(5000)) by conjugating three different chain lengths of PEG onto an integrin α_(v)β_(3)-targeted NIR-Ⅱ heptamethine cyanine fluorophore,respectively.In virtue of the essential amphiphilic characteristics of PEG polymers,these probes display various degree of aggregation in aqueous buffer accompanying with differential NIR-Ⅱ imaging and photothermal(PTT) therapeutic performance.Both in vitro and in vivo results have demonstrated that probe QR-2PEG_(5000) has the best NIR-Ⅱ imaging performance with prominent renal clearance,whereas QR-2PEG_(321)possesses excellent photoacoustic signal as well as PTT effect,which undoubtedly provides a promising toolbox for tumor diagnosis and therapy.We thus envision that these synthesized probes have great potential to be explored as a toolkit for precise diagnosis and treatment of malignant tumors.

New Interpretation of Western Semiotics from the Perspective of Symbolic Concepts in Zhouyi

Semiotics is one of the core concepts in contemporary philosophy,linguistics and many other ideological fields.Although it is a new discipline founded in the 20th century,researchers from both the East and the West have studied the phenomena of symbols for a long time.Western semiotics came into existence as a new discipline during the 1960s,whose origin could be traced back to ancient Greek philosophy.In ancient China,there was no concept of semiotics,but Chinese ancestors practiced divination by some special symbols,which might be considered the sprouts of semiotics.Those methods in divination were called Lianshanyi in the Xia Dynasty and Guizangyi in the Shang Dynasty.In the Zhou Dynasty,the forms of divinations and their explanations were more plentiful,which were collectively called Zhouyi,posing as"the leading classics and the source of‘Tao’".The study on Zhouyi found that its symbolic concepts possessed explainable relevance to those in Western semiotics represented by Saussure,Peirce and Morris,especially between the three key elements:"hexagram image","hexagram judgment"and"hexagram meaning"in Zhouyi corresponding to the three core formulas:"Sign=Signifier+Signified","Sign=Relation(Medium,Object,Interpret)"and"M=ME+MP+MF"of Western semiotics.The study suggested that exploration into the symbolic concepts of ancient Chinese philosophical classics might provide new perspectives for the interpretation of Western semiotics.