A simple and facile method has been demonstrated to fabricate low-cost surface enhanced Raman scattering (SERS) active microfluidic paper chips using a painting brush. This strategy solves the problem of mass production of highly reproducible SERS substrates without complicated or bulky micro-or nanofabrication instruments. Rhodamine 6G (R6G) was chosen as a probe molecule to evaluate the performance of the SERS active chip. To further demonstrate the possibility of this method's potential application in environmental monitoring, trace malachite green (MG) was successfully analyzed on this chip. The performance of our chips was desirable. The paper substrates with silver nanoparticles deposited by brush were found to be cost-efficient and highly sensitive (LOD for R6G and MG are 1 nM and 10 nM, respectively), and have good reproducibility ($15% relative standard deviation).
Capacitive deionization (CDI) has emerged as a promising technique for brackish water desalination. Here, composites of polypyrrole grafted activated carbon (Ppy/AC) were prepared via in situ chemical oxidative polymerization of pyrrole on AC particles. The Ppy/AC cathode was then coupled with a MnO 2 anode for desalination in a membrane-free CDI cell. Both the Ppy/AC and MnO 2 electrodes exhibited pseudocapacitive behaviors, which can selectively and reversibly intercalate Cl − (Ppy/AC) and Na + (MnO 2 ) ions. Compared to AC electrodes, the specific capacitances of Ppy/AC electrodes increased concurrently with the pyrrole ratios from 0 to 10%, while the charge transfer and ionic diffusion resistances decreased. As a result, the 10%Ppy/AC-MnO 2 cell showed a maximum salt removal capacity of 52.93 mg g −1 (total mass of active materials) and 34.15 mg g −1 (total mass of electrodes), which was higher than those of conventional, membrane, and hybrid CDI cells. More notably, the salt removal rate of the 10%Ppy/AC-MnO 2 cell (max 0.46 mg g −1 s −1 to the total mass of active materials and 0.30 mg g −1 s −1 to the total mass of electrodes) was nearly 1 order of magnitude higher than those in most previous CDI studies, and this fast and efficient desalination performance was stabilized over 50 cycles.
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