Silver nanoparticles (NPs) stored in pore-arrays (pa) SU-8 photoresist layer were utilized as an antibacterial nanocomposition against E. coli bacteria. The pa-SU-8 matrix was fabricated by an optical interference lithography method resulting in small pores with a diameter of ∼50 nm and a depth of ∼100 nm. The Ag NPs were deposited on the soft polymeric matrix at different drying temperatures of 50 and 90 °C. X-ray photoelectron spectroscopy showed that the deposited silver NPs were substantially in the metallic state, independent from the drying condition. However, the concentration of the immobilized Ag NPs on the film surface increased (by a factor of 2.5) at the higher drying temperature. This increase was consistently observed in the strengthening of the surface plasmon resonance absorption peak of the Ag NPs. The size of the Ag NPs released from the Ag NPs/pa-SU-8 film was found to be in the range 7–15 nm. Antibacterial activity of the Ag NPs/pa-SU-8 films was investigated at different temperatures (37, 55 and 75 °C) of the solution containing the film. The relative rate of reduction of the viable bacteria was calculated to be 4.5 × 10−2 (2.8 × 10−2) min−1 at 37 °C, for the film dried at 90 (50) °C. By increasing the temperature to 75 °C, the rate of reduction increased to 8.4 × 10−2 (4.1 × 10−2) min−1, corresponding to 60 (120) min required time to kill all the bacteria. Silver ion release measurements showed that the higher drying temperature (90 °C) provided more diffusion of Ag NPs in the porous soft matrix to store a considerable amount of Ag NPs in it, resulting in a lasting antibacterial activity. The amount of silver released from the Ag NPs/pa-SU-8 film, and thus its antibacterial activity, can be controlled by small variation (∼20 °C) of the environmental temperature.
Broadband antireflection layers have been fabricated by two dimensional (2D) photonic crystals (PCs) with tapered pillars on the Si substrate. These PCs have been produced by interference lithography and reactive ion etching (RIE) techniques. The effect of depth and the filling factor (FF) of the PCs on the reflectance magnitude and bandwidth has been investigated. The obtained reflectance was less than 1% in the broad spectral range from 400 to 2100 nm. Our numerical simulation shows the PC pillars slope has an essential effect in the reduction of the reflection. However, our results show that the existence of RIE grasses in the PCs, which are created in the RIE process, does not influence the performance of the antireflection layer. This leads to a simpler fabrication process.
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