Strategy and Characteristics of Polypyrrole Deposited on Silver Substrates with Silver-Containing Nanocomplexes

Chemical versus electrochemical synthesis of carbon nano-onion/polypyrrole composites for supercapacitor electrodes

The development of high-surface-area carbon electrodes with a defined pore size distribution and the incorporation of pseudo-active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano-onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission- and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g(-1) for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g(-1) for the CNOs/Ppy bilayer (electrochemical deposition).

Simple strategy to improve surface-enhanced Raman scattering based on electrochemically prepared roughened silver substrates

We develop an easy and effective pathway to improve surface-enhanced Raman scattering (SERS) effects of probe molecules of Rhodamine 6G (R6G) adsorbed on electrochemically prepared roughened Ag substrates. In general SERS studies, SERS-active metal substrates are first prepared. Then probe molecules are adsorbed on them to evaluate the relative SERS effects. In this study, we employ electrochemical oxidation-reduction cycle (ORC) treatments in 0.1 M KCl solutions containing probe molecules of 2 x 10(-5) M R6G to prepare R6G-adsorbed SERS-active Ag substrates for one step. Encouragingly, based on this strategy, the SERS intensity of adsorbed R6G can be increased by 1 order of magnitude, as compared with that of R6G adsorbed on a roughened Ag substrate beforehand, which was generally shown in the literature. Moreover, this improved SERS effect based on this strategy is also effective for 2 x 10(-9) M probe molecules, which is at a level of single molecule detection based on Ag colloids. It is also effective for probe molecules of ClO(4)(-) with low Raman cross section and for other electrochemically prepared SERS-active substrates of Au. Further analyses indicate that the increase in SERS activity in this new method is most likely due to the incorporation of more chloride ions into the substrate.

Improved surface-enhanced Raman scattering on optimum electrochemically roughened silver substrates

In this work, the effects of preparation conditions used in roughening silver substrates by electrochemical triangular-wave oxidation-reduction cycles (ORC) on surface-enhanced Raman scattering (SERS) were first investigated. The optimum roughening conditions for obtaining strongest SERS of Rhodamine 6G (R6G) are as follows. Ag electrodes were cycled in deoxygenated aqueous solutions containing 0.1 M NaCl from -0.3 to +0.2 V versus Ag/AgCl at 25 mV s(-1) for five scans. The SERS of R6G adsorbed on this optimum procedure-prepared roughened Ag substrate exhibits a higher intensity by one order of magnitude, as compared with that of R6G adsorbed on a normally roughened Ag substrate.