We report a new approach to convert an electrospun nanofibrous cellulose acetate mat
surface from super-hydrophilic to super-hydrophobic. Super-hydrophilic cellulose acetate
nanofibrous mats can be obtained by electrospinning hydrophilic cellulose acetate. The
surface properties of the fibrous mats were modified from super-hydrophilic to
super-hydrophobic with a simple sol–gel coating of decyltrimethoxysilane (DTMS) and
tetraethyl orthosilicate (TEOS). The resultant samples were characterized by field emission
scanning electron microscopy (FE-SEM), x-ray photoelectron spectroscopy (XPS), water
contact angle, Brunauer–Emmett–Teller (BET) surface area, atomic force microscopy
(AFM), and UV–visible measurements. The results of FE-SEM and XPS showed that the
sol–gel (I) films were formed on the rough fibrous mats only after immersion in sol–gel.
After the sol–gel (I) coating, the cellulose acetate fibrous mats formed in both 8 and 10 wt%
cellulose acetate solutions showed the super-hydrophobic surface property. Additionally, the
average sol–gel film thickness coated on 10 wt% cellulose acetate fibrous mats was
calculated to be 80 nm. The super-hydrophobicity of fibrous mats was attributed to the
combined effects of the high surface roughness of the electrospun nanofibrous mats
and the hydrophobic DTMS sol–gel coating. Additionally, hydrophobic sol–gel
nanofilms were found to be transparent according to UV–visible measurements.
SUMMARYA quartz crystal microbalance (QCM) sensor coated with a sensing film has been studied as a gas-sensing device with high gas selectivity and high sensor sensitivity. One of the problems to be solved for practical applications is that the resonant frequency of a QCM sensor drifts due to the influence of humidity. We investigated a method for compensating the humidity drift of a QCM sensor for NH 3 gas by using an element coated with a reference film that was prepared by modifying the phosphate group of zirconium phosphate in the sensing film with sodium hydroxide. The response characteristics of the reference element were measured. The results showed good agreement with the humidity response of the sensor element when not responding to ammonia gas. It was found that compensation of the humidity drift was successfully accomplished by calculating the frequency difference between the sensor element and the reference element. An application to small QCM (1.3 × 0.9 mm) is also presented. C⃝ 2015 Wiley Periodicals, Inc. Electron Comm Jpn, 98(6): 1-7, 2015; Published online in Wiley Online Library (wileyonlinelibrary.com).
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