Effects of ZnO/trimethylsilyl cellulose nano-composite coating on anti-UV and anti-fungal properties of papers.

Trimethylsilyl cellulose (TMSC) was employed as the coating matrix for the application of zinc oxide nanoparticles (ZnO) onto paper surfaces and the protections of ZnO/TMSC coating against UV-induced damages and fungal spoilage were evaluated. Filter papers were immersed in 2% w/v TMSC solution loaded with ZnO and air-dried. Three ZnO/TMSC suspensions were prepared with 0.1, 0.5, and 1% w/v ZnO NPs. The presences of ZnO/TMSC protective layers were confirmed with ATR-IR spectroscopy. The coated papers exhibited high surface hydrophobicities. After the coated papers were subject to 365-nm UV irradiation at 400 W for 3 h, the contact angles dramatically dropped. The trimethylsilyl (TMS) groups exposed on the surface formed a moisture barrier and were partially removed on UV exposure. ATR-IR revealed that more TMS groups were removed in the protective layer with no ZnO. UV-irradiated papers turned yellow and papers protected with 1% ZnO/TMSC exhibited significantly lower color changes than that of the uncoated one. Compared to the TMSC-coated paper, the addition of ZnO resulted in a significant reduction in tensile strength at maximum. However, after UV irradiation, significant increases in both the strain at break and strength at maximum were only observed in 1% ZnO/TMSC-protected papers. Regarding their anti-fungal properties, the 1% ZnO/TMSC films were effective in growth inhibitions of Aspergillus sp. and Penicillium sp. on the nonirradiated papers. Despite being hydrophilic after UV-irradiation, growths of the molds were severely suppressed on the UV-irradiated paper.

Crystallization of Calcium Deficient Hydroxyapatite Nanocrystals on Woven Silk Fibroin Fabric via Precipitation Process.

A high bioactivity calcium deficient hydroxyapatite (Ca-def HAp) nanocrystal crystallized on a high strength woven silk fibroin (SF) fabric was characterized with the aim to utilize their advantages for the future bone implant applications. Apatite crystal was grown on SF fiber templates by precipitation reaction of Ca(NO3)2 prepared from chicken eggshells in (NH4)3PO4 solutions, adjusted pH by NH4OH solution. In the apatite crystallization process, (NH4)3PO4 solutions prepared at different pH values were poured into the glass dishes containing SF fiber templates/Ca(NO3)2 solution, allowed reaction time of only a minute. The results had shown that, the Ca/P ratio of the crystals grown on SF fiber templates were increased through increasing in initial pH value of reaction. Its morphology had been changed from the plate-shaped to particle-shaped crystals. The plainwoven SF fabric was chosen as the suitable template to grow Ca-def HAp crystal for its much higher tensile strength (840 MPa), as compared to 470 MPa for the twill-woven SF fabric. The Cadef HAp nanocrystals on plain-woven SF fabric were confirmed the Ca/P ratio at 1.52 with X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The clusters size of smaller than 100 nm Ca-def HAp nanocrystals on plain-woven SF fabric also signified the high surface area of structure which are better for cell attachment, growth and differentiation. Accordingly, the overall result indicated that the composite of combining Ca-def HAp nanocrystals on plain-woven SF fabric had been successfully prepared by the rapid precipitation. The method offers a simpler setup and a shorter processing time and the Ca-def HAp on silk possess a higher tensile strength, suitable for development for future bone implant in the high load bearing regions.

Structural and Magnetic Characterizations of Nano Sized Grain Zinc Ferrite/Hydroxyapatite Ceramic Prepared by Solid State Reaction Route.

A promising composite of bioactive hydroxyapatite (HAp) and zinc ferrite (ZnFe2O4) has potentials for future bone reinforcing formation. In present study, HAp and ZnFe2O4 composite ceramic was prepared by solid state reaction route for easier control of structural and magnetic characteristics and with low cost. HAp powder was synthesized by precipitation method from chicken eggshell. Mixed powders with varying ZnFe2O4/HAp weight ratios from 2-10 wt% were milled together and uniaxially pressed and then sintered at 1200 degrees C for 3 hours. The XRD results showing no other phases of composite ceramics with only HAp and ZnFe2O4 phases were identified, indicating high stability of HAp property. Phase fractions of ZnFe2O4 were found to increase from 10.8 to 18.73 wt% with increasing content of ZnFe2O4. FT-IR results were only revealed vibration bands of standard HAp phase. SEM results revealed primary grains sizes of the prepared ceramics in nano scale. The BET surface area and pore volume increased with increasing content of ZnFe2O4 in composite ceramics. The VSM results of composites with increasing ZnFe2O4 content had been shown with increasing magnetization from 0.05 to 1.85 emu/g while their coercivities were decreased from 44 to 24 Oe. Higher magnetization as well as higher super paramagnetic behavior could be achieved with increasing the studied ZnFe2O4 weight ratios in ZnFe2O4/HAp composite ceramics, which can be tailored for specific applications.