Experimental field definition for the Plackett–Burman design.

<p>Experimental field definition for the Plackett–Burman design.</p

Carboxyl-Functionalized Ionic Liquid Assisted Preparation of Flexible, Transparent, and Luminescent Chitosan Films as Vapor Luminescent Sensor

Herein we present a novel method to synthesize flexible self-standing films consisting of europium­(III) complexes in nanoclay and chitosan, which are transparent and luminescent. Preparation takes place under aqueous conditions assisted by a carboxyl-functionalized ionic liquid (IL). The latter is used not only as a replacement for acetic acid to dissolve chitosan but, surprisingly, also to enhance the luminescence efficiency of the final films. A brighter luminescence is observed for the films prepared assisted with the ionic liquids compared to those by using acetic acid. The reason is that the ionic liquid used to dissolve chitosan can decrease proton strength on embedded platelets primarily through ion-exchange process and thus can increase the coordination number of europium­(III) complexes. Exposure of the films to Et₃N vapors can cause a further remarkable luminescence enhancement, while significant luminescence quenching occurred upon exposure to HCl vapors. The films are promising for applications in areas such as optoelectronics and vapor-sensitive luminescent sensors

Steepest ascent experiments to move the experimental region towards the maximum yield of PCPS.

<p>Steepest ascent experiments to move the experimental region towards the maximum yield of PCPS.</p

Elution profile of FPCPS for the determination of molecular mass in a SEC-MALLS system.

<p>Elution profile of FPCPS for the determination of molecular mass in a SEC-MALLS system.</p

Antioxidant activity of PCPS and FPCPS with comparison to Vc.

<p>(A), scavenging effect of PCPS and FPCPS on DPPH radicals compared with that of Vitamin C (standard control); (B), Scavenging effect of PCPS and FPCPS on superoxide radicals compared with that of Vitamin C (standard control); (C), scavenging effect of PCPS and FPCPS on hydroxyl radicals compared with that of Vitamin C (standard control). Results are expressed as mean ± standard deviation of three parallel measurements. Significant differences from control were evaluated using <i>t</i>-test; *<i>p</i><0.05, **<i>p</i><0.01.</p

Box–Behnken design matrix along with the experimental and predicted values of the yield of PCPS.

<p>Box–Behnken design matrix along with the experimental and predicted values of the yield of PCPS.</p

Plackett–Burman design matrix with response value.

<p>Plackett–Burman design matrix with response value.</p

FTIR spectrum of FPCPS produces by <i>P. cicadae</i>.

<p>FTIR spectrum of FPCPS produces by <i>P. cicadae</i>.</p

Elution profiles of the crude PCPS from <i>P. cicadae</i> by DEAE-52 column (A) and Sephadex G-200 column (B).

<p>Elution profiles of the crude PCPS from <i>P. cicadae</i> by DEAE-52 column (A) and Sephadex G-200 column (B).</p

Conformation plot of log (Rg²)_z^1/2 versus log M_w for FPCPS from <i>P. cicadae</i>.

<p>Conformation plot of log (Rg²)_z^1/2 versus log M_w for FPCPS from <i>P. cicadae</i>.</p