No abstract

No abstract

We demonstrate a detection method for heavy metal (HM) ions based on whispering gallery mode (WGM) lasing in a liquid crystal (LC) microdroplet biosensor. By doping with stearic acid, nematic LC 4-cyano-4'-pentylbiphenyl (5CB) microdroplets are biochemically functionalized and used as both optical microresonators and sensing elements. Typical WGM lasing emission is observed in stearic acid-doped 5CB microdroplets under a pulse laser pump. Our results show that quantitative spectral shift of WGMs can serve as a real-time indicator of the adsorption of HM ions on the microdroplet surface. The detection limit of our sensor is as low as 40 pM for Cu(II) ions, six orders of magnitude better than the exposure threshold defined by the World Health Organization. Furthermore, this sensing system has an ability to discriminate between heavy and light metal ions. We believe that this novel biosensor has great application potential for environmental monitoring and drinking water quality testing.

We report the observation of optically pumped lasing in self-coupled resonators constructed with dye-doped polymer nanowires. Three nanowires with a diameter of 350 nm, 360 nm and 500 nm were fabricated into different self-coupled resonators and single-mode lasing emission was obtained. The self-coupled resonators can be utilized to realize tunable laser systems and enhance the coupling efficiency of emission in ultrasmall resonators.

A flow-through method was developed for the deposition of palladium nanoparticles on a ceramic membrane support modified with aminofunctional silane to fabricate a Pd-loaded ceramic membrane support. The as-fabricated Pd-loaded ceramic membrane support was extensively characterized by energy-dispersive X-ray spectroscopy (EDS), inductively coupled plasma (ICP) emission spectroscopy, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and temperature-programmed reduction (TPR), and its catalytic properties were evaluated in the reduction of p-nitrophenol to p-aminophenol with sodium borohydride. For comparison, the palladium nanoparticles were also deposited on a silanized ceramic membrane support by a traditional impregnation method. Superior p-nitrophenol conversion and catalytic stability are observed on the Pd-loaded ceramic membrane support prepared by the flow-through method. In the flow-through method, the synthesis solution is forced to flow through the membrane pores, thus the palladium nanoparticles can be deposited both on the membrane surface and in the membrane pores, resulting in an increased loading amount of palladium nanoparticles and an enhanced p-nitrophenol conversion. The superior catalytic stability is related to the preparation process: the palladium nanoparticles deposited on the membrane support will be scoured by the synthesis solution, some palladium nanoparticles having poor interaction with the membrane support may fall off during the preparation stage, and the remaining palladium nanoparticles have stronger interactions with the membrane support and do not easily fall off during the continuous reaction cycles, leading to better catalytic stability.