ABSTRACT
This study presents the corrosion behavior and surface properties of SS304 modified by electrodeposited nickel-cobalt (Ni-Co) alloy coating with cauliflower-shaped micro/nano structures (Ni-Co/SS304) in the simulated PEMFC cathodic environment. The hydrophobicity of the as-prepared Ni-Co alloy coating can be improved simply by low-temperature annealing. The morphology and composition of the Ni-Co/SS304 were analyzed and characterized by SEM, EDS, XRD, and XPS. The polarization, wettability, and ICR tests were respectively conducted to systemically evaluate the performance of Ni-Co/SS304 in the simulated PEMFC cathode environment. As revealed by the results, the Ni-Co/SS304 can maintain its hydrophobicity under hot-water droplets as high as 80 °C and demonstrates higher conductivity than the bare SS304 substrate before and after polarization (0.6 V vs. SCE, 5 h), which is of great significance to improve the surface hydrophobicity and conductivity of bipolar plates.
ABSTRACT
In this study, an silver (Ag) plating with micro/nano-dendrite structures is prepared on the 304 stainless steel (SS304) surface by potentiostatic deposition (Ag/SS304). After being modified by n-dodecyl mercaptan (NDM) with the low surface energy, the obtained sample (NDM@Ag/SS304) exhibits stable superhydrophobicity and excellent hot-water repellency. The surface morphology and composition of NDM@Ag/SS304 are analyzed by scanning electron microscope (SEM), X-ray spectrometer (EDS), X-ray diffractometer (XRD), and X-ray photoelectron spectrometer (XPS) characterization. The electrochemical measurements, tests of water contact angle (WCA), and interfacial contact resistance (ICR) are employed to systematically study the performance of the NDM@Ag/SS304 in the simulated cathode environment of proton exchange membrane fuel cell (PEMFC). The results show that the NDM@Ag/SS304 has high corrosion potential (~0.25 V) and low corrosion current density (~4.04 µA/cm2); after potentiostatic polarization (0.6 V, 5 h), the NDM@Ag/SS304 also shows high superhydrophobic stability.
ABSTRACT
As one of the important photochromic molecules, spiropyran (SP) compounds are widely used as detectors and fluorescence probes in the environment and bio-imaging field. Although great achievements have been attained for various sophisticated spiropyrans in metal ion sensing, less success is achieved in sensing organic molecules due to the weak interaction between the spiropyran and the target of the organic molecule. In this study, a spiropyran derivative containing a hydroxyl group (SPOH) was employed for the recognition of four kinds of amines via ultraviolet-visible (UV-Vis) spectra. The aliphatic primary amines, aromatic primary amines, aliphatic secondary and tertiary amines, aromatic secondary and tertiary amines were successfully distinguished according to the shapes and trends of their UV-Vis absorption spectra. The chemical reaction between aliphatic, aromatic primary amines and SPOH as well as alkalinity are two vital interaction mechanisms for the recognition process which are testified by Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR). Although SP is generally water-insoluble, it is easy to achieve soluble by fixing SPOH inside micelle or vesicle and thus the results in this study is meaningful for amine recognition utility in environments and biological systems.
ABSTRACT
A spiropyran derivative containing an ethyl group (SPEt) was applied for fluorescent recognition of Cu2+. With Cu2+ addition, the SPEt-contained solution using a mixed solvent of DMF/H2O (9/1, v/v) showed a very strong characteristic emission peak with high quantum yield which is 4.3 times that of the pure SPEt solution. As a result, Cu2+ was successfully picked out from totally 17 kinds of common metal ions and a detection limit as low as 14.9â¯fM had been achieved in using this assay system. Particularly, the recognition process was temperature- and time-dependent and could be effectively promoted by heating. In addition, SPEt had been used to image and detect Cu2+ in mussels. Thus, our results in this study provided an exclusive Cu2+ recognition via fluorometry in wide temperature, time, and dynamic ranges of assay, enabled a femtomolar scale detection of Cu2+ by spiropyran derivative, and showed a promising imaging ability of Cu2+ in marine living organisms.
