Jingchun Guo

Abstract Atomically ordered intermetallic nanoparticles exhibit improved catalytic activity and durability relative to random alloy counterparts. However, conventional methods with time‐consuming and high‐temperature syntheses only have rudimentary capability in controlling the structure of intermetallic nanoparticles, hindering advances of intermetallic nanocatalysts. We report a template‐directed strategy for rapid synthesis of Pd‐based (PdM, M=Pb, Sn and Cd) ultrathin porous intermetallic nanosheets (UPINs) with tunable sizes. This strategy uses preformed seeds, which act as the template to control the deposition of foreign atoms and the subsequent interatomic diffusion. Using the oxygen reduction reaction (ORR) as a model reaction, the as‐synthesized Pd 3 Pb UPINs exhibit superior activity, durability, and methanol tolerance. The favored geometrical structure and interatomic interaction between Pd and Pb in Pd 3 Pb UPINs are concluded to account for the enhanced ORR performance.

An S-tapered fiber sensor has been realized on the common single-mode fiber by a fusion splicer. The S fiber taper (SFT) can be considered as a compact fiber Mach-Zehnder interferometer with the total length of hundreds of microns. The spectral characteristics of the SFTs with different structure parameters including axial offsets and taper waist diameters have been studied. Sensing experiments have also been carried out to test their response to refractive index (RI) and axial strain. The SFT with an axial offset of 114 μm and a taper waist diameter of 54.6 μm exhibits the best combination property. Its RI sensitivity reaches as high as 2066 nm/RI unit in the RI range of 1.407-1.421 and the average strain sensitivity is -183.4 pm/με, which is the highest strain sensitivity, to the best of our knowledge, with one or two orders of magnitude larger than the existing fiber strain sensors.

We demonstrate an ultrasensitive temperature sensor based on an isopropanol-sealed optical microfiber taper (OMT) in a capillary. The OMT is highly sensitive to ambient refractive index (RI) with a maximum sensitivity of 18989 nm/RI unit in the range of 1.3955-1.4008. The thermo-optic effect of isopropanol and the thermal expansions of the sealant and sealed liquid turn the OMT into an ultrasensitive temperature sensor with the maximum sensitivity of -3.88 nm/°C in the range of 20°C-50°C. The temperature sensitivity contributions from different mechanisms are also investigated theoretically and experimentally.

Stroke causes ischemic brain injury and is a leading cause of neurological disability and death. There is, however, no promising therapy to protect the brain from ischemic stress to date. Here we show an exciting finding that optimal electroacupuncture (EA) effectively protects the brain from ischemic injury. The experiments were performed on rats subjected to middle cerebral artery occlusion (MCAO) with continuous monitoring of cerebral blood flow. EA was delivered to acupoints of "Shuigou" (Du 26) and "Baihui" (Du 20) with different intensities and frequencies to optimize the stimulation parameters. The results showed that 1) EA at 1.0-1.2 mA and 5-20 Hz remarkably reduced ischemic infarction, neurological deficit, and death rate; 2) the EA treatment increased the blood flow by >100%, which appeared immediately after the initiation of EA and disappeared after the cessation of EA; 3) the EA treatment promoted the recovery of the blood flow after MCAO; 4) "nonoptimal" parameters of EA (e.g., <0.6 mA or >40 Hz) could not improve the blood flow or reduce ischemic injury; and 5) the same EA treatment with optimal parameters could not increase the blood flow in naive brains. These novel observations suggest that appropriate EA treatment protects the brain from cerebral ischemia by increasing blood flow to the ischemic brain region via a rapid regulation. Our findings have far-reaching impacts on the prevention and treatment of ischemic encephalopathy, and the optimized EA parameters may potentially be a useful clue for the clinical application of EA.