Spray coating thin polymeric sensor films for Au3+

A novel polymeric sensor of the poly(sodium-4-styrenesulfonate) (PSS)-modified rhodamine B derivative (Rho) was synthesized using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC)/N,N′-dimethylpyridin-4-amine (DMAP) as coupling reagents to obtain PSS-Rho4 in 21% yield. The characterization and “Off–On” sensing phenomena were established through UV–Vis, fluorescence, NMR, and FTIR techniques. The PSS-Rho4 showed high selectivity and sensitivity for Au³⁺ over other metal ions. Upon the addition of Au³⁺, significant color change and “Off–On” fluorescence were observed due to a cation Au³⁺ induced spirolactam ring-opening process with detection limit down to micromolar values (1.2 μM). In addition, spray coating thin polymeric sensor films were produced onto the surface of material (PSS-Rho4-ITO and PSS-Rho4-filtered paper) providing a fast, portable, and easy-to-use molecular device for the detection of Au³⁺ in the real system. Reversibility was evaluated by rinsing with EDTA solution under basic condition. We believe that, this approach provides a sensitive and accurate method for the detection of Au³⁺ in environmental and biological applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48273.     

Electrical properties of a-C: Mo films produced by dual-cathode filtered cathodic arc plasma deposition

Molybdenum-containing amorphous carbon (a-C:Mo) thin films were prepared using a dual-cathode filtered cathodic arc plasma source with a molybdenum and a carbon (graphite) cathode. The Mo content in the films was controlled by varying the deposition pulse ratio of Mo and C. Film sheet resistance was measured in situ at process temperature, which was close to room temperature, as well as ex situ as a function of temperature (300–515 K) in ambient air. Film resistivity and electrical activation energy were derived for different Mo and C ratios and substrate bias. Film thickness was in the range 8–28 nm. Film resistivity varied from 3.55 × 10^− 4 Ω m to 2.27 × 10^− 6 Ω m when the Mo/C pulse ratio was increased from 0.05 to 0.4, with no substrate bias applied. With carbon-selective bias, the film resistivity was in the range of 4.59 × 10^− 2 and 4.05 Ω m at a Mo/C pulse ratio of 0.05. The electrical activation energy decreased from 3.80 × 10^− 2 to 3.36 × 10^− 4 eV when the Mo/C pulse ratio was increased in the absence of bias, and from 0.19 to 0.14 eV for carbon-selective bias conditions. The resistivity of the film shifts systematically with the amounts of Mo and upon application of substrate bias voltage. The intensity ratio of the Raman D-peak and G-peak (I_D/I_G) correlated with the pre-exponential factor (σ₀) which included charge carrier density and density of states.