Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers with polygonal porosity and highly ordered structures. The most prominent feature of the COFs is their excellent crystallinity and highly ordered modifiable one-dimensional pores. Since the first report of them in 2005, COFs with various structures were successfully synthesized and their applications in a wide range of fields including gas storage, pollution removal, catalysis, and optoelectronics explored. In the meantime, COFs also exhibited good performance in chemical and biological sensing, because their highly ordered modifiable pores allowed the selective adsorption of the analytes, and the interaction between the analytes and the COFs’ skeletons may lead to a detectable change in the optical or electrical properties of the COFs. In this review, we firstly demonstrate the basic principles of COFs-based chemical and biological sensing, then briefly summarize the applications of COFs in sensing some substances of practical value, including some gases, ions, organic compounds, and biomolecules. Finally, we discuss the trends and the challenges of COFs-based chemical and biological sensing. 相似文献
Green synthesized silver nanoparticles (AgNPs) have enormous applications. Hence, there is an increasing demand to explore diverse bioresources for AgNP fabrication to make the process more cost‐effective and rapid as possible. Due to the abundantly present hydroxyl groups of rice starch, it provides ideal sites for metal ion complexation and thereby synthesis of nanoparticles with promising activity. So the study was designed to develop rapid, eco‐friendly and cost‐effective method for green AgNP synthesis using boiled rice water starch in the presence of sunlight irradiation. The starch‐capped nanoparticles (sAgNPs) formed in the study were found to have the surface plasmon absorbance at 439 nm. The study showed optimum yield of sAgNPs when 25% rice starch was treated with aqueous 1 mM AgNO3 for 15 min in the presence of sunlight. Fourier transform infrared spectroscopy analysis provided mechanistic insight into the role of –OH groups of starch in the reduction of AgNO3 to sAgNPs. On further characterization by X‐ray diffraction analysis, the sAgNPs were identified to have FCC crystal structure. At the same time, high‐resolution transmission electron microscopic analysis showed majority of sAgNPs to have spherical morphology, and dynamic light scattering study revealed the average particle size as 36.3 nm. Further confirmation on presence of AgNPs was carried out by energy‐dispersive X‐ray spectroscopy. Moreover, the sAgNPs exhibited promising antibacterial activity against foodborne pathogens, Salmonella Typhimurium and Staphylococcus aureus. 相似文献
Ce, Nd and Eu doped BSO crystals 20×20× 100mm3 in size have been gown by vertical Bridgman method, and the doped effects on radiation resistance of BSO have also been studied for the first time. Nd and Eu dopns were found to improve the radiation resistance of BSO. However, Cc and Nd dopings degrade the light output of BSO except that Eu doping has almost no effect on it. Therefore, Eu may be the most promising dopant candidate for improving the scintillation properties of BSO crystal. 相似文献
Abstract: By using of travelling wave amplification, we have got a soft x-ray laser with near diffraction limit output and gain saturation in the experiment of four series coupling targets with reflector. 相似文献
We consider a new form of solutions of a special lattice model for traffic system. By analyzing nearest sites’ interactions, time delay, and bumpy effects, we deduce the bifurcation lines and surfaces for stable and unstable regions and show how they vary as parameters vary. It shows that keeping other conditions unchanged, as the incoming flow increases, the traffic flow becomes unstable, opposite to when outgoing flow increases, it becomes stable. Besides, considering delayed optimal flow, multiple sites effect or artificial parameters can also help stabilize the traffic road condition. Moreover, by putting it into the framework of mKdV equations, we obtain the kink–antikink solitons involving all parameters, which show the feature of the traffic congestion. The result is original, and our model in differential or difference form can be reduced into the previous ones by choosing appropriate parameters. Since the optimal velocity function we considered involves finitely or infinitely many sites, the density waves can be in multi-mode and high dimension forms and can also be quasi-periodic, we show a new feature of the traffic lattice system.
This paper investigates a distributionally robust scheduling problem on identical parallel machines, where job processing times are stochastic without any exact distributional form. Based on a distributional set specified by the support and estimated moments information, we present a min-max distributionally robust model, which minimizes the worst-case expected total flow time out of all probability distributions in this set. Our model doesn’t require exact probability distributions which are the basis for many stochastic programming models, and utilizes more information compared to the interval-based robust optimization models. Although this problem originates from the manufacturing environment, it can be applied to many other fields when the machines and jobs are endowed with different meanings. By optimizing the inner maximization subproblem, the min-max formulation is reduced to an integer second-order cone program. We propose an exact algorithm to solve this problem via exploring all the solutions that satisfy the necessary optimality conditions. Computational experiments demonstrate the high efficiency of this algorithm since problem instances with 100 jobs are optimized in a few seconds. In addition, simulation results convincingly show that the proposed distributionally robust model can hedge against the bias of estimated moments and enhance the robustness of production systems. 相似文献