Helical Biphenyl Bisazo Polyurethane: Preparation,Characterization and Analysis of Polymeric Thermo-Optic Switch

The bisazo chromophore molecule (CAAPM) and helical biphenyl bisazo polyurethane (HBBPU) were synthesized. The structures of CAAPM and HBBPU were characterized by FT-IR and UV-vis spectroscopic techniques. The measurements of refractive index and thermo-optic coefficient (dn/dT) of HBBPU were demonstrated at different wavelengths and different temperatures by the ATR technique. By using CCD digital imaging devices, transmission loss of the internal waveguide was measured. The refractive index dispersions and Sellmeyer coefficients of HBBPU were obtained by the Sellmeyer equation. A Y-branched switch based on the thermo-optic effect was proposed and the performance of the switch was simulated. With a branching angle of 0.143° and the FD-BPM method, the result showed that the power consumption of the thermo-optic switch could be only 3.6 mW, and the response time of the switch could reach about 8 ms. This is a significant improvement in reducing power consumption compared with the normal Y-branched polymer thermo-optic switch.     

Sequence-Dependent DNA Functionalization of Upconversion Nanoparticles and Their Programmable Assemblies

DNA-modified lanthanide-doped upconversion nanoparticles (DNA-UCNPs) that combine the functions of DNA and the optical features of UCNPs have shown great promise in a wide range of fields. However, challenges remain in precisely tethering and orienting the DNA strands on the UCNP surface. Herein, we systematically investigate the sequence dependence of DNAs in their interactions with UCNPs, and reveal that poly-cytosine (poly-C) has high affinity for the UCNP surface. A general approach to synthesize monodispersed DNA-UCNP conjugates is developed using poly-C-containing diblock DNA strands. The poly-C segment of the DNA strand binds to the surfaces of UCNPs and the second segment is oriented perpendicularly on the UCNP surface, making the DNA-UCNPs highly stable and monodispersed in aqueous solution. The dense layer of DNA on the UCNP surface enables the programmable assembly of UCNPs with other DNA-functionalized nanoparticles or DNA origamis through hybridization, resulting in the formation of well-organized complex structures.     

Sequence‐Dependent DNA Functionalization of Upconversion Nanoparticles and Their Programmable Assemblies

DNA‐modified lanthanide‐doped upconversion nanoparticles (DNA‐UCNPs) that combine the functions of DNA and the optical features of UCNPs have shown great promise in a wide range of fields. However, challenges remain in precisely tethering and orienting the DNA strands on the UCNP surface. Herein, we systematically investigate the sequence dependence of DNAs in their interactions with UCNPs, and reveal that poly‐cytosine (poly‐C) has high affinity for the UCNP surface. A general approach to synthesize monodispersed DNA‐UCNP conjugates is developed using poly‐C‐containing diblock DNA strands. The poly‐C segment of the DNA strand binds to the surfaces of UCNPs and the second segment is oriented perpendicularly on the UCNP surface, making the DNA‐UCNPs highly stable and monodispersed in aqueous solution. The dense layer of DNA on the UCNP surface enables the programmable assembly of UCNPs with other DNA‐functionalized nanoparticles or DNA origamis through hybridization, resulting in the formation of well‐organized complex structures.     

Acid‐treated g‐C3N4‐Cu2O composite catalyst with enhanced photocatalytic activity under visible‐light irradiation

Acid‐treated g‐C₃N₄‐Cu₂O was prepared by hydrothermal reduction followed by high temperature calcination and acid exfoliation. The structures and properties of as‐synthesized samples were characterized using a range of techniques, such as X‐ray photoelectron spectroscopy, scanning electron microscopy, Photoluminescence Spectroscopy and the Brunauer–Emmett–Teller (BET) theory. The photocatalytic activity was evaluated by measuring the photodegradation of methyl orange under visible‐light irradiation. Based on the results of TEM, XPS, EPR and other techniques, it was verified that a heterojunction was formed. The acid treatment process can increase the specific surface area to form abundant heterojunction interfaces as channels for photo‐generated carrier separation, thereby enhancing its light utilization and quantum efficiency. Results indicate that acid‐treated g‐C₃N₄‐Cu₂O possesses a large specific surface area, which provides plentiful activated sites for heterojunctions to form; in addition, it showed a high visible light effect and the minimum charge‐transfer resistance. Furthermore, the g‐C₃N₄‐Cu₂O material exhibits high levels of effectiveness and stability. Electron paramagnetic resonance and a series of radical trapping experiments demonstrate that the holes and ?O₂^? could be the main active species in methyl orange photodegradation. This work could provide new insights into the fabrication of composite materials as high‐performance photocatalysts, and facilitate their application in addressing environmental protection issues.     

Synthesis of azo benzothiazole polymer and its application of 1 × 2 Y-branched and 2 × 2 Mach–Zehnder interferometer switch

The azo benzothiazole polyurethane–urea (ABPUU) was synthesized from chromophore molecule 4-[(6-nitrobenzothiazole-2-yl)diazenyl]phenyl-1,3-diamine NBDPD, polyether polyol (NJ-210) and isophorone diisocyanate (IPDI). The structure, thermal property, mechanical property and physical property were characterized and investigated. The refractive index (n) and thermo-optic coefficient (dn/dT) of ABPUU was determined at different temperature and wavelength (532 nm, 650 nm and 850 nm) using attenuated total reflection (ATR) technique. Using the CCD digital imaging devices, transmission loss of ABPUU was measured. A 1 × 2 Y-branched and 2 × 2 Mach–Zehnder interferometer (MZI) switch with two rib waveguides, dual driving electrodes and two critical 3-dB couplers polymeric thermo-optic switches based on thermo-optic effect of prepared ABPUU were designed and simulation. The power consumption of the Y-branched switch is less than 0.84 mW. The Y-branched and MZI switching rising and falling times obtained are 0.8 ms and 0.2 ms, respectively.     

Preparation, thermo-optic property and simulation of optical switch based on azo benzothiazole polymer

An azo chromophore molecule 4-[(benzothiazole-2-yl)diazenyl]phenyl-1,3-diamine (BTPD) was prepared with 2-amino benzothiazole and m-phenylenediamine by diazo-coupling reaction. Then, the chromophore molecule BTPD was polymerized with NJ-210 and isophorone diisocyanate (IPDI) to obtain novel azo benzothiazole polymer (BTPU). The structures of BTPD and BTPU were characterized using the Fourier transform infrared, UV–visible spectroscopy, DSC and TGA. The physical properties of the obtained BTPU were investigated. The refractive index (n) of BTPU was demonstrated at different temperature and wavelength (532, 650 and 850 nm) using attenuated total reflection technique. The transmission loss and dispersion characteristic of BTPU film were investigated using the CCD digital imaging devices and Sellmeyer equation. A Y-branch and 2 × 2 Mach–Zehnder interferometer (MZI) polymeric thermo-optic switches based on the thermo-optic effect of prepared BTPU were proposed and the performance of switches was simulated. The results indicated that the power consumption of the Y-branch thermo-optic switch could be only 0.6 mW. The Y-branch and MZI switching rising and falling times obtained were 8.0 and 1.8 ms.     

Fe3O4@chitosan-bound boric acid composite as pH-responsive reusable adsorbent for selective recognition and capture of cis-diol-containing shikimic acid

Recently, shikimic acid (SA) has aroused great concern as the starting raw material for the synthesis of antiviral drug (Tamiflu) against the spread of influenza virus in the body. In this work, magnetic chitosan composite modified with boric acid and its application in SA recognition and separation was described. Chitosan (CT) with plenty of hydroxyl and amino groups was first coated on the surface of magnetic core Fe₃O₄, then carboxylic groups were grafted to the surface of Fe₃O₄@CT via anhydride modification, followed by the introduction of 3-aminophenylboronic acid (APBA). The uniform morphology and composition analysis of the adsorbent (Fe₃O₄@CT-COOH-BA) were characterized by FT-IR, XRD, XPS, SEM, TEM and UV–visible spectroscopy. The adsorption capacity of as-prepared material was explored in detail by batch mode experiments. The adsorption kinetics fitted well with a pseudo-second order model, and the adsorption isotherms was well described by the Langmuir model with a maximum adsorption capacity of 23.8 mg g⁻¹ at 25 °C. Solution pH plays a crucial role in adsorption process and the optimized pH was 8.0. In addition, Fe₃O₄@CT-COOH-BA could be easily reused through an external magnet and the adsorption capacity reduced by only 4% after five adsorption–desorption cycles. These results prove that boric acid modified magnetic chitosan composite is an effective and practical adsorbent for specific recognition and selective adsorption of cis-diol-containing compounds.     

具有明确硬段结构的水性聚氨酯脲的研究

通过逐步反应由4,4′-二苯基甲烷二异氰酸酯、2,2-二羟甲基丙酸和1,4-丁二醇,合成了结构明确的硬段模型化合物.通过13C NMR对其序列结构进行了表征,并通过FTIR、DSC和WAXD对其形态结构进行了研究.进一步制备了具有这类规整结构硬段的水性聚氨酯脲,初步考察了水分散液及其成膜后的性能.实验结果表明,这类聚氨酯脲水分散液的粒径小于110nm,在室温下贮存期大于一年,成膜后具有优异的耐水性能以及表面疏水性能.     

Minimax Rates of ℓp-Losses for High-Dimensional Linear Errors-in-Variables Models over ℓq-Balls

In this paper, the high-dimensional linear regression model is considered, where the covariates are measured with additive noise. Different from most of the other methods, which are based on the assumption that the true covariates are fully obtained, results in this paper only require that the corrupted covariate matrix is observed. Then, by the application of information theory, the minimax rates of convergence for estimation are investigated in terms of the ℓp(1≤p<∞)-losses under the general sparsity assumption on the underlying regression parameter and some regularity conditions on the observed covariate matrix. The established lower and upper bounds on minimax risks agree up to constant factors when p=2, which together provide the information-theoretic limits of estimating a sparse vector in the high-dimensional linear errors-in-variables model. An estimator for the underlying parameter is also proposed and shown to be minimax optimal in the ℓ2-loss.     

磁流变体的制备及性能

对以羰基铁粉、硅油和烃类油为悬浮相和悬浮介质,通过适当添加剂和工艺制备的磁流变体材料,制备方法、磁流变性能及影响因素进行了研究,认为是具有良好综合性能的磁流变体材料。制备的磁流变体具有较低的零场粘度（0．4－1．5Pas),较高的剪切应力（τ=50-75kPa)和良好的稳定性及阻尼性能。