Hydrogen sensing performance of silica microfiber elaborated with Pd nanoparticles

A hydrogen sensor has been proposed by coating Pd nanoparticles-PMMA composite organic sol on silica microfiber independent on any expensive or complex chemical process. The thickness of cladding layer and the diameter of elaborated microfiber were determined as ∼20 μm and ∼57.93 μm, respectively. Due to the evanescent wave excited by silica microfiber and the amorphous structure of PMMA film, the Pd nanoparticles effectively absorbed the hydrogen molecules and resulted in the shift of resonance wavelength. The experimental results match well with an exponential curve with an average sensitivity of 5.58 nm/%, which is comparable to other electrochemical hydrogen sensors reported recently.The authors thank the support from the National Natural Science Foundation of China (NSFC) under Grants (61405032, 61403074, 61605031); and Doctoral Scientific Research Startup Foundation of Liaoning Province under Grant (201501144); and Fundamental Research Funds for the Central Universities under Grants (N150404022, N150401001); and China Scholarship Council (201606085023)

Recent developments in electrochemical sensors based on nanomaterials for determining glucose and its byproduct H2O2

The development in glucose and H2O2 electrochemical sensors has significantly progressed using some original nanomaterials, such as nanoparticles and nanowires in metal, metal oxide, or carbon nanomaterials. In this review, we discussed and analyzed the mechanism, performance, and characteristics of the enzyme/nonenzyme glucose and H2O2 electrochemical sensors based on some pure metal (Au, Pd, Ni, Pt, and Cu), metal oxide (ZnO, NiO, CuO (x) , TiO2, and Co3O4), and carbon (nanotubes and graphene) nanomaterials. Although the introduction of nanomaterials can effectively improve the sensitivity of enzyme glucose/H2O2 sensors by enhancing the activity of protein enzyme, the enzymes are sensitive to the biochemical environment. Meanwhile, the sensing performance of nonenzyme glucose/H2O2 sensors significantly depends on the morphology, uniformity, and distribution of nanomaterials.This work was supported by the National Natural Science Foundation of China (NSFC) under Grants (Numbers 61405032, 61403074, 61605031, 61425003); and Doctoral Scientific Research Startup Foundation of Liaoning Province under Grant (Number 20150 1144); and Fundamental Research Funds for the Central Universities under Grants (Numbers N1504 04022, N150401001). Jin Li acknowledges the financial support from the China Scholarship Council for his Research Scholarship No. 201606085023

Refractive index sensor based on silica microfiber doped with Ag microparticles

We proposed a composite microfiber using silica capillary and Ag microparticles, and demonstrated its optical sensing characteristics by changing the refractive index of surrounding environment using different concentrations of NaCl solution. Either the diameter or doping density of Ag microparticles contributes to the sensitivity change. The experimental results reveal that the diameter uniformity and distribution of Ag microparticles exerted impact on the sensing performance. The highest sensitivity of −7246 dB/RIU has been experimentally demonstrated in this work. The selectivity of this composite microfiber sensor will be explored by decorating its surface with some enzyme or other sensitive materials.This work was supported by the National Natural Science Foundation of China (NSFC) under Grants (number 61405032, 61403074, 61605031, 11504072); and Doctoral Scientific Research Startup Foundation of Liaoning Province under Grant (number 201501144); and Fundamental Research Funds for the Central Universities under Grants (number N150404022, N150401001). Jin Li acknowledges the financial support from the China Scholarship Council for his Visiting Scholarship No. 201606085023

The optical response of the silver nano-sphere with two spindle-shaped cavities in a sub-wavelength quartz fiber

We propose and experimentally study a fiber-optic filter in hourglass configurations, where a silver nano-sphere is trapped in the quartz fiber and two air spindle-shaped cavities are formed on both sides of it. By using two fiber tapers as the input source and the probe, we measured the transmission and reflection spectra of the configuration. The results show that it is transparent for resonance wavelength and absorptive for other wavelengths, respectively. The 1544 nm and 1557 nm resonance peaks were observed in the single and double hourglass configuration. Such a device can be useful in optical filters and biochemical sensors

Study for Longitudinal Deformation of Shield Tunnel in Side of Foundation Pit Based on Virtual Image Technique

A prediction model of enclosure structure deformation caused by the excavation of foundation pit is established. Based on the virtual image technique, the soil deformation caused by sidewall deformation is calculated. Meanwhile, the deformation model considering rotating and staggering of shield tunnel is used to establish a calculation method of longitudinal deformation of adjacent shield tunnel. The result suggests that: (a) The horizontal displacement of adjacent shield tunnel is normally distributed. (b) With increasing retaining structure deformation, it is obvious that deformation value and range of adjacent shield tunnel also increase. (c) As the distance between the adjacent shield tunnel and the enclosure structure increases, the horizontal displacement of the side shield tunnel decreases nonlinearly. (d) The shield tunnel with shallow buried depth is greatly affect by the excavation of adjacent foundation pit. As the depth of the tunnel increases, the impact gradually decreases

Predicting band offset of lattice matched ZnO and BeCdO heterojunction from first principles

Using first-principles approach, we calculated the band gaps of wurtzite ${\rm Be}_{1-x}$ Cd $_x{\rm O}$ ternary alloy and the band offset of the lattice matched ${\rm ZnO}/{\rm Be}_{0.44}{\rm Cd}_{0.56}{\rm O}[1\,1\,\overline {2}\,0]$ heterojunction, where the modified Becke–Johnson semi-local exchange was used to determine the band gap and the coherent potential approximation was applied to deal with doping effect in disordered alloys. The ${\rm ZnO}/{\rm Be}_{0.44}{\rm Cd}_{0.56}{\rm O}$ heterojunction was determined to have a type II band alignment, with valence and conduction band offset being 0.28 and 0.50 eV, respectively. The calculation approach and procedure demonstrated here can be used to predict the band offset of more lattice matched semiconductor heterojunctions