新型三元互穿聚合物网络阻尼材料的研制

采用平衡溶胀工艺,合成了具有宽温域、高阻尼值的新型三元互穿聚合物网络。透射电镜证明了乳液交联反应的发生和互穿网络的结构。分别通过对乳液及乳胶膜性能的测试和比较,发现三元互穿聚合物网络相容性和阻尼性均优于二元互穿聚合物网络。     

Ternary supramolecular quantum-dot network flocculation for selective lectin detection

We present a versatile, tuneable, and selective nanoparticle-based lectin biosensor, based on flocculation of ternary supramolecular nanoparticle networks (NPN), formed through the sequential binding of three building blocks. The three building blocks are β-cyclodextrin-capped CdTe quantum dots, tetraethylene glycol-tethered mannose-adamantane cross-linkers (ADTEGMan), and the tetravalent lectin Concanavalin A (ConA). The working principle of this selective sensor lies in the dual orthogonal molecular interactions of the linker, uniting adamantane-β-cyclodextrin and mannose-lectin interaction motifs, respectively. Only when the lectin is present, sequential binding takes place, leading to in situ self-organization of the sensor through the formation of ternary supramolecular networks. Monitoring the loss of fluorescence signal of the quantum dots in solution, caused by controlled network formation and consecutive flocculation and sedimentation, leads to selective, qualitative, and quantitative lectin detection. Fluorescent sedimented networks can be observed by the naked eye or under UV illumination for a lectin concentration of up to 10^?8 M. Quantitative detection is possible at 100 min with a lower detection limit of approximately 5 × 10^?8 M.

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Switchable Adhesion of Micropillar Adhesive on Rough Surfaces

Switchable structured adhesion on rough surfaces is highly desired for a wide range of applications. Combing the advantages of gecko seta and creeper root, a switchable fibrillar adhesive composed of polyurethane (PU) as the backing layer and graphene/shape memory polymer (GSMP) as the pillar array is developed. The photothermal effect of graphene (under UV irradiation) changes GSMP micropillars into the viscoelastic state, allowing easy and intimate contact on surfaces with a wide range of roughness. By controlling the phase state of GSMP via UV irradiation during detachment, the GSMP micropillar array can be switched between the robust‐adhesion state (UV off) and low‐adhesion state (UV on). The state of GSMP micropillars determines the adhesion force capacity and the stress distribution at the detaching interface, and therefore the adhesion performance. The PU‐GSMP adhesive achieves large adhesion strength (278 kPa), high switching ratio (29), and fast switching (10 s) at the same time. The results suggest a design principle for bioinspired structured adhesives, especially for reversible adhesion on surfaces with a wide range of roughness.     

Switchable circular-to-point converter based on holographic polymer-dispersed liquid-crystal technology

We demonstrate the use of a switchable circular-to-point converter (SCPC) device based on holographic polymer-dispersed liquid-crystal technology for application in lidar detection and optical telecommunication. A SCPC device converts the Fabry-Perot ring pattern into a single point or an array of points, while an external electrical field on the SCPC deactivates the conversion. Stacking different SCPC elements gives a random optical switch for applications in lidar detection and optical telecommunication. Two types of SCPC designs are analyzed and one is chosen and built for testing.     

Photoluminescence properties of nanocrystalline ZnS on nanoporous silicon

This paper embodies the report on the microwave solvothermal synthesizing of nanocrystalline ZnS particles for optoelectronic device. The effect of different parameters such as time, temperature, solvents, molar ratio of zinc and thiourea on the phase(s) formation of nanocrystalline Zinc Sulphide was investigated. The obtained nanosize ZnS materials were characterized by the X-ray diffraction, Optical absorption measurements, TEM and Photoluminescence studies. The crystallite size of the ZnS nanoparticles was estimated from the X-ray diffraction pattern by using Scherrer's formula. The as prepared material was obtained in the cubic phase, which showed a perfect match with the earlier reports. The Optical absorption edge of ZnS were blue shifted from the absorption edge of bulk ZnS. The estimated band gap value of ZnS was 4.01 eV. The ZnS nano materials were coated on nano porous silicon by screen-printing technique. Luminescence studies indicated room temperature emission in the wavelength ranges from 422.6 to 612 nm, which cover the blue emission to red emission. The emitted light that depending on the created pore size from porous silicon and the size of the ZnS nano particles.     

Hydroxyapatite formation on metallurgical grade nanoporous silicon particles

Studies into bone-like apatite or hydroxyapatite (HA) growth on potential biomaterials when in contact with simulated body fluid (SBF) not only establish a general method for determining bioactivity but coincidently lead to the design of new bioactive materials in biomedical and tissue engineering fields. Previous studies of HA growth on porous silicon (PS) have examined electrochemically etched silicon substrates after immersion in a SBF. This study differs from previous work in that it focuses on characterising HA growth on chemically etched metallurgical grade nanoporous silicon particles. The PS used in this study is comprised of nanosponge particles with disordered pore structures with pore sizes ranging up to 10 nm on micron-sized particles. The silicon particles are analysed before and after immersion into SBF using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS). Results indicate that a HA layer forms on the surface of the nanosponge particles. Experimental analysis indicates that the morphology and calcium-to-phosphorus ratio (Ca/P) verify the formation of crystalline HA on the nanoporous silicon particles.     

pH-sensitive solid-state electrode based on electrodeposited nanoporous platinum

The nanoporous platinum oxide (H1-ePtO) as a hydrogen ion-selective sensing material is reported. Bare nanoporous platinum oxides exhibit near-Nernstian behavior (e.g., -55 mV/pH in PBS), ignorable hysteresis, a short response time, and high precision, which are remarkably better than those of flat platinum oxides. The electrode potential of a nanoporous platinum oxide responds exclusively to hydrogen ion, which implies its usefulness as a solid-state pH sensor. In the present study, the performance of nanoporous platinum oxide was investigated and compared with that of IrOx in terms of selectivity and the influences of ionic strength, temperature, complexing ligands, and surfactants. H1-ePtO functions well as a pH-sensing solid-state material, and it is viewed as a promising alternative to IrOx. Interference by redox couples was successfully suppressed by covering the H1-ePtO surface with a protective layer, e.g., an electropolymerized polyphenol thin film. Since the nanoporous platinum oxide with such a protective layer is particularly suitable for miniaturization and micropatterning, our findings suggest its usefulness in applications such as solid-state pH sensors embedded in chip-based microanalysis systems.     

泡沫碳化硅陶瓷表面纳米多孔碳化硅涂层的制备

利用硅改性树脂中硅元素和碳元素分子级均匀分散的特征,以硅改性树脂为涂层原料,在泡沫碳化硅陶瓷表面原位生成了多孔碳化硅活性涂层。在加入适量活性炭颗粒的条件下,在泡沫碳化硅陶瓷表面得到了性能良好的纳米碳化硅涂层,适合作为催化剂载体。相反,在没有活性炭颗粒加入的情况下,所得涂层龟裂、结合强度低,且碳化硅团聚成片,比表面积小。     

Towards nanoporous membranes based on ABC triblock terpolymers

Block copolymers represent an exciting class of complex materials as they self-assemble into highly regular structures of nanoscopic dimensions. When prepared as thin films, such structures can be used for a variety of applications including lithographic masks or nanoporous membranes. Reported here are nanostructures in thin films of structurally analogous polybutadiene-block-poly(2-vinyl pyridine)-block-poly(tert-butyl methacrylate) (BVT) and polystyrene-block-poly(2-vinyl pyridine)-block-poly(tert-butyl methacrylate) (SVT) triblock terpolymers, which are synthesized via sequential living anionic polymerization. The morphological behavior of annealed SVT and BVT films is investigated by scanning force and electron microscopies. The difference in the terpolymer composition results in the formation of an ordered perforated lamella phase in SVT films and hexagonally packed core/shell cylinders in BVT films. Further, the BVT films show high potential for the fabrication of composite membranes using track-etched poly(ethylene terephthalate) macroporous filters as a support.     

Growth of carbon nanotubes on nanoporous titania templates

This work reports the synthesis of multiwalled carbon nanotubes (MWCNTs) on nanoporous titanium dioxide (TiO2) templates. TiO2 nanotubular templates for MWCNTs are produced by anodization of titanium followed by pulsed electrodeposition (PED) of cobalt inside the TiO2 nanotubes. Cobalt acts as a catalyst for the growth of MWCNTs using chemical vapor deposition (CVD) technique. The cobalt catalyst initiates the growth of well graphitized MWCNTs inside the titania pores as well as beyond the titania pores. These materials have been characterized by SEM, EDS, GXRD, XPS, TEM, and ED techniques. The MWCNTs were about 10 mu in length and 80-120 nm in diameter.     

Dynamically Programmed Switchable DNA Hydrogels Based on a DNA Circuit Mechanism

Biological stimuli‐responsive DNA hydrogels have attracted much attention in the field of medical engineering owing to their unique phase transitions from gel to sol through cleavage of DNA cross‐linking points in response to specific biomolecular inputs. In this paper, a new class of biological stimuli‐responsive DNA hydrogels with a dynamically programmed DNA system that relies on a DNA circuit system through cascading toehold‐mediated DNA displacement reactions is constructed, allowing the catalytic cleavage of cross‐linking points and main chains in response to an appropriate DNA input. The dynamically programmed DNA hydrogels exhibit a significant sharp phase transition from gel to sol in comparison to another DNA hydrogel showing noncatalytic cleavage of cross‐linking points due to synchronization of the catalytic cleavage of cross‐linking points and the main chains. Further, the sol–gel phase transitions of the DNA hydrogels in response to the DNA input are easily tunable by changing the cross‐linking density. Additionally, with a structure‐switching aptamer, DNA hydrogels encapsulating PEGylated gold nanoparticles can be used as enzyme‐free signal amplifiers for the colorimetric detection of adenosine 5′‐triphosphate (ATP); this detection system provides simplicity and higher sensitivity (limit of detection: 5.6 × 10^?6 m at 30 min) compared to other DNA hydrogel‐based ATP detection systems.     

Switchable dual-wavelength fiber laser mode-locked by monolayer graphene on D-shaped fiber

A switchable mode-locking fiber laser is demonstrated by means of a monolayer graphene saturable absorber (SA) based on a D-shaped fiber. The monolayer graphene, which is grown by chemical vapor deposition, is transferred onto the D-shaped fiber and then the light–graphene interaction via the evanescent field of the fiber is enhanced greatly. Using such a graphene-based SA, the single-wavelength mode locking can be switched from 1531.5 to 1559.1 nm by appropriately adjusting the polarization controller (PC). In addition, the stable dual-wavelength mode-locking operation is also observed at the proper state of PC.     

Exploring Self-Healing and Switchable Adhesives based on Multi-Level Dynamic Stable Structure

It is a challenge to develop adhesives simultaneously capable of strong adhesion and efficient switchable ability. Herein, the authors report multifunctional switchable adhesives named Cu²⁺-curcumin-imidazole-polyurethane (CIPUs:Cu²⁺) by introducing 1-(3-aminopropyl) imidazole and curcumin into polyurethane system crossed by Cu²⁺ forming dynamic metal-ligand bonds. This CIPUs:Cu²⁺ has strong adhesion (up to 2.46 MPa) on various material surfaces due to their specially designed functional groups alike the secretions from mussels. It can achieve fast switching speed (30 s) and high switch efficiency through multiple contactless remote stimulations. Importantly, density functional theory (DFT) calculation reveals that such metal-ligand bonds consisting of two components: stronger Cu²⁺-curcumin complexes and weaker Cu²⁺-imidazole complexes can aggregate to form multi-level dynamic stable structure . The special structure can not only be acted as sacrificial sites for easily broken and reformed, allowing efficient switchable adhesion and enormous energy dissipation but also acted as firm sites to maintain the cohesion of the adhesive and the reversible reconstruction network. Intriguingly, the CIPUs:Cu²⁺ can achieve self-healing at room temperature without needing external stimuli. Overall, this strategy can further broaden the design of switchable adhesives in the fields of intelligent gadgets, wearable bio-monitoring devices, etc.     

Size effects on the mechanical behavior of nanoporous Au

Recent nanomechanical tests on submicron metal columns and wires have revealed a dramatic increase in yield strength with decreasing sample size. Here, we demonstrate that nanoporous metal foams can be envisioned as a three-dimensional network of ultrahigh-strength nanowires, thus bringing together two seemingly conflicting properties: high strength and high porosity. Specifically, we characterized the size-dependent mechanical properties of nanoporous gold using a combination of nanoindentation, column microcompression, and molecular dynamics simulations. We find that nanoporous gold can be as strong as bulk Au, despite being a highly porous material, and that the ligaments in nanoporous gold approach the theoretical yield strength of Au.     

Preparation technique for copper-plating on Si nanoporous pillar array

Silicon nanoporous pillar array (Si-NPA) is prepared by hydrothermally etching method. The copper/silicon nanocomposite thin film (Cu/Si-NPA) is obtained utilizing a reductive deposition method where Si-NPA acts both as a reducing agent and as a substrate. Microstructural analysis indicates that Si-NPA is composed of large quantities of well-separated, quasi-identical silicon pillars which are uniform and perpendicular to the surface. The pillar surface is nanoporous and the pore wall is composed of silicon nanocrystallites with a size about 4 nm. Cu/Si-NPA inherits the morphological characteristic of Si-NPA. The density of the Cu nanoparticles changes alternatively with the geometrical sites of Si-NPA, which leads to the formation of crater-like structures. These results indicate that Si-NPA might be used as an ideal template for synthesizing metal/silicon nanocomposite systems.     

TEM investigations on layered ternary ceramics

Layered ternary ceramics represent a new class of solids that combine the merits of both metals and ceramics.These unique properties are strongly related to their layered crystal structures and microstructures. The combination of atomic-resolution Z-contrast scanning transmission electron microscopy （STEM） and transmission electron microscopy （TEM）, selected area electron diffraction （SAED）, convergent beam electron diffraction （CBED） represents a powerful method to link microstructures of materials to macroscopic properties, allowing layered ternary ceramics to be investigated in an unprecedented detail. Vicrostructural information obtained using TEM is useful in understanding the formation mechanism, layered stacking characteristics, and defect structures for layered ternary ceramics down to atomic-scale level; and thus provides insight into understanding the ＂Processing-Structure-Property＂ relationship of layered ternary ceramics. Transmission electron microscopic characterizations of layered ternary ceramics in Ti-Si-C, Ti-Al-C, Cr-Al-C, Zr-Al-C, Ta-Al-C and Ti-Al-N systems are reviewed.     

Quantification of ternary mixtures of heavy metal cations from metallochromic absorbance spectra using neural network inversion

A new method based on artificial neural networks (ANN) for the processing of spectrophotometric data is proposed and illustrated on the example of the simultaneous quantification of ternary mixtures of zinc, cadmium, and mercury cations in aqueous solutions. Three types of commercially available metallochromic indicators were used as a simple model setup to create spectral data analogous to those normally received from an optical sensor array. In conventional ANN training methods for chemical sensors based on spectrophotometric data, a calibration is established by mathematically correlating the measured optical signal as network input with the concentration of the calibration sample as network output. In several situations, however, especially when dealing with mixed sample solutions, the relationship between a measured absorption spectrum and the corresponding ion concentrations is ambiguous, resulting in an "ill-posed problem". On the other hand, if the training direction is reversed by correlating known sample concentrations with measured optical signals, the relationship becomes reasonable for the ANN to obtain its structure. The proposed model illustrated in this paper is based on a more reasonable direct mapping and estimation by artificial neural network inversion (ANNI). In the training step, sample mixtures of known concentrations are optically measured to construct networks correlating the input data (ion concentrations) and the output data (absorption spectra). In the estimation step, the ion concentrations of unknown samples are estimated using the constructed ANN. The measured spectra of the unknown samples are fed to the output layer, and the appropriate input concentrations are determined by ANNI. When training the ANN system with 143 ternary mixtures of Zn2+, Cd2+, and Hg2+ in a concentration range from 1 to 100 microM, root-mean-square errors of prediction (RMSEP) of 0.45 (Zn2+), 0.96 (Cd2+), and 0.32 microM (Hg2+) were observed for the estimation of concentrations in 30 test samples, using the ANNI procedure. This newly proposed model, which involves the construction of an ANN based on direct mapping and estimation by ANNI, opens up one way to overcome the limitations of nonselective sensors, allowing the use of more easily accessible semiselective receptors to realize smart chemical sensing systems.     

Nonenzymatic electrochemical glucose sensor based on nanoporous PtPb networks

Here, we report on a novel nonenzymatic amperometric glucose sensor based on three-dimensional PtPb networks directly grown on Ti substrates using a reproducible one-step hydrothermal method. The surface morphology and bimetallic composition of the synthesized nanoporous PtPb materials were characterized using scanning electron microscopy and energy-dispersive X-ray spectrometry, respectively. Voltammetry and amperometric methods were used to evaluate the electrocatalytic activities of the synthesized electrodes toward nonenzymatic glucose oxidation in neutral media in the absence and in the presence of chloride ions. The synthesized nanoporous PtPb electrodes have strong and sensitive current responses to glucose. Their amperometric sensitivities increase in the order of Pt-Pb (0%) < Pt-Pb (30%) < Pt-Pb (70%) < Pt-Pb (50%). These nanoporous PtPb electrodes are also highly resistant toward poisoning by chloride ions and capable of sensing glucose amperometrically at a very low potential, -80 mV (Ag/AgCl), where the interference from the oxidation of common interfering species such as ascorbic acid, acetamidophenol, and uric acid is effectively avoided.     

Surface effects on the mechanical properties of nanoporous materials

Using the theory of surface elasticity, we investigate the mechanical properties of nanoporous materials. The classical theory of porous materials is modified to account for surface effects, which become increasingly important as the characteristic sizes of microstructures shrink to nanometers. First, a refined Timoshenko beam model is presented to predict the effective elastic modulus of nanoporous materials. Then the surface effects on the elastic microstructural buckling behavior of nanoporous materials are examined. In particular, nanoporous gold is taken as an example to illustrate the application of the proposed model. The results reveal that both the elastic modulus and the critical buckling behavior of nanoporous materials exhibit a distinct dependence on the characteristic sizes of microstructures, e.g. the average ligament width.