Chuanyi Tao

Long-period fiber grating sensor with a styrene-acrylonitrile nano-film incorporating cryptophane A for methane detection

This paper presents a novel sensor design and application of long period fiber grating (LPFG) for detection of methane. A styrene-acrylonitrile nano-film incorporating cryptophane A, which is sensitive to methane in close vicinity to the surface, is constructed onto the cladding of long-period grating. For optimal design of the LPFG sensor, the relationship between the resonant wavelength shift and the complex refractive index of sensing film is analyzed based on the coupled-mode theory. The change in refractive index of the sensing film, induced by methane, can easily be obtained as a shift in resonance wavelength. The prepared LPFG sensor with time response of 50 s and good sensitivity (~0.375 nm %(-1)) suitable for the detection of methane below 3.5 vol. % is demonstrated. The response of the sensor (wavelength shift) is linear with methane concentration within our tested range and a detection limit of about 0.2% is estimated for the new sensor.

Theoretical investigation for the EPR g-factors of the mixed ground state in NaCl: Ag(2+) crystals

In this paper, it is considered that the local structure of the (AgCl6)4- cluster for the NaCl: Ag2+ crystal is of the axially elongational D4h symmetry which possesses the weaker rhombic distortion at <001> lattice site. The mechanism for an admixture of the 2A1g into the ground state 2B1g is taken into account. The electron paramagnetic resonance (EPR) g factors of NaCl: Ag2+ are studied by using the double spin-orbit coupling model and an approximation of a semiempirical molecular orbit. The EPR g factors for the NaCl: Ag2+ crystals are reasonably explained as well as the good agreement between the calculated values and the experimental data is obtained.

Silica Nanowires Decorated with Cryptophane-A for Sensing Methane

Silica nanowires (NWs) were prepared on the Si wafer with a modified thermal evaporation of silicon monoxide and cryptophane-A was fixed to the surface of the silica NWs for methane sensing. Scanning electron microscopy equipped with EDS was used to characterize the morphology and composition of the sensitive material. A fiber optical device was designed to operate via luminescence reflection and the methane sensing properties were characterized at room temperature. The sensing material shows a stable and strong blue luminescence when excited by UV light source at wavelength of 380 nm, and it is efficiently quenched by molecular methane within the methane concentration range between 0.2% and 3.5% (v/v). This novel methane sensing material has significant advantages and might have application potential.