Micro Humidity Sensor with High Sensitivity and Quick Response/Recovery Based on ZnO/TiO_(2) Composite Nanofibers

ZnO/TiO_(2) composite nanofibers are synthesized by an electrospinning method and characterized by x-ray diffraction,scanning electron microscopy,and transmission electron microscopy.A micro humidity sensor is fabricated by spinning the precursors of these nanofibers on a ceramic substrate with Ag-Pd interdigitated electrodes.Humidity sensing investigation reveals that this micro sensor offers high sensitivity and quick response/recovery at an operating frequency of 100 Hz.The corresponding impedance changes more than four orders of magnitude within the whole humidity range from 10%to 90%relative humidity(RH),and the response and recovery times are about 4 and 12 s,respectively.The maximum hysteresis is around 2%RH.The humidity sensing mechanism is also discussed based on the nanofiber structure and morphology.

Synthesis of flowerlike nickel particles and their microwave absorbing properties

Two kinds of nickel particles with flower-like structures assembled with a number of nano-flakes were synthesized and the relationship of their morphology and microwave absorbing properties was studied.The electromagnetic parameters of these flower-like Ni were measured with vector network analyzer at 2-18 GHz frequency and the reflection losses(RL) with different sample thicknesses were calculated.The results indicate that the flower-like nickel-wax composites with the sample thickness less than 2 mm show excellent absorbing ability.This result is expected to play a guiding role in the preparation of the highly efficient absorber.

Synthesis of Silica Hollow Spheres with Diameter Around 50 nm by Anionic Surfactant

Silica hollow spheres（SHSs） have attracted great attention because of their low toxicity, low density, large surface area, high chemical and thermal stability, and surface permeability. They can be widely applied in storage^[l], catalysis^[2], drug deli- very^[3,4], low-dielectric-constant materials^[5], low-refractive materials^[6-8], and so on. Up to now, there have been various methods to produce SHSs. Inorganic^[9] or organic particles^[10], such as polystyrene or calcium carbonate, were used as hard templates to create hollow cavities, However, the multistep synthetic process and the lack of structural robustness of the shells upon template removal process weaken their applica- tion. Soft templates, including oil-in-water emulsions^[11,12], vesicles^[13], micelle^[14,15] and gas bubbles^[16], are applied widely.

Influence of post-annealing on the properties of Ta-doped In_2O_3 transparent conductive films

Ta-doped In_2O_3 transparent conductive oxide films were deposited on glass substrates using radio-frequency (RF) sputtering at 300°C.The influence of post-annealing on the structural,morphologic,electrical and optical properties of the films was investigated using X-ray diffraction,field emission scanning electron microscopy,Hall measurements and optical transmission spectroscopy.The obtained films were polycrystalline with a cubic structure and were preferentially oriented in the (222) crystallographic direction.The lowest resistivity,5.1×10 4 cm,was obtained in the film annealed at 500°C,which is half of that of the un-annealed film (9.9×10 4 cm).The average optical transmittance of the films was over 90%.The optical bandgap was found to decrease with increasing annealing temperature.

Chiral hierarchical structure of bone minerals

Chirality is an indispensable integral of biological system.As an important part of organisms,chiral organic structure of bone has been extensively investigated.However,the chirality of bone minerals is unclear and not fully determined.Here,we report nine levels of fractal-like chirality of bone minerals by combining electron microscopic and spectrometric characterizations.The primary helically twisted acicular apatite crystals inside collagen fibrils and between fibrils merge laterally to form secondary helical subplatelets.The chiral arrangement of several subplatelets forms tertiary spiral mineral platelets.Further coherent stepwise stacking of mineral platelets with collagen fibrils leads to quaternary to ninth levels,which reconciled the previous conflicting models.The optical activities in the UV-visible,infrared and terahertz regions demonstrated chirality from atomic to macroscopic scales based on circularly selective absorption and Bragg resonance at different levels of chirality.Our findings provide new insight into the structural integrity of bone,osteology,forensic medicine and archaeology and inspire the design of novel biomaterials.

Handedness inversion of chiral mesoporous silica: A diffuse-reflectance circular dichroism study

Chiral mesoporous silica ribbons and rods with inversed handedness have been synthesized with the same enantio pure N-acylaminoacidat temperatures of 0℃and 20℃ respectively. With involving Cu^(2+)and meso-tetra(4-sulfonatophenyl)porphyrin(TPPS) as probes, ribbons and rods revealed opposite signals in diffuse-reflectance circular dichroism(DRCD) spectra, indicating the existence of inversed supramolecular chiral imprintings through helical stacking of amphiphiles. The structural evolution was systematically studied by the freeze-dried products sampled at different time after the addition of silica precursors. The H-bonding-depended molecular orientation probably controls the chiral sense upon forming chiral molecular stacking, which would be the origin of such handedness inversion