ABSTRACT
The use of room-temperature ionic liquids (RTILs) as green media for electrochemical application has attracted great attention recently. However, the effects of RTILs used as additives for electrodeposition of metals have hardly been explored. In the present work, the electrochemical deposition of copper was investigated on a pure copper plate from acid cupric sulfate solutions in the presence of RTILs (1-butyl-3-methylimidazolium tetrafluoroborate, [bmim] BF4) additive by cyclic voltammetric technique, scanning electron microscope (SEM), and X-ray diffraction (XRD). For comparison, the electrodeposition of copper from acid cupric sulfate solutions was also investigated. The voltammograms showed that the cathodic peak potential shifted toward more negative potential and cathodic peak current increased when 1.0 x 10(-4) mol x L(-1) [bmim] BF4 was added into acid cupric sulfate solutions. SEM images indicated that the shinning electrodeposits of copper were lamellar structure and the size of layered grain decreased with addition of [bmim]BF4 additive. The XRD results indicated that copper deposits exhibited face-centered cubic structure and (220) highly preferred orientation. The surface-enhanced Raman scattering (SERS) activities of copper deposits were measured by using methyl orange (MO) as the probe molecules. The copper electrodeposit obtained in acid cupric sulfate solutions with [bmim]BF4 is shown to be excellent substrate for SERS measurements, demonstrating significant enhancement and good stability. The enhancement factor was calculated to be up to 4.7 x 10(5). It was also found that copper electrodeposit stored for 60 days in air shows no significant degradation in its sensitivity.
ABSTRACT
The use of room-temperature ionic liquids (RTILs) as green media for preparation of nanomaterials is very attractive. Herein, anisotropic silver nanoparticles were synthesized via chemical reduction silver nitrate with sodium hypophosphite, employing brønsted acidic functionalized ionic liquid 1-butyl-3-methyl-imidazolium dihydrogen phosphate ([bmim] H2PO4), which acted both as reaction medium and as a capping/shape-directing agent. The structure, morphology and optical absorption properties of anisotropic silver nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Visible (UV-Vis) absorption spectra. The XRD patterns revealed that the crystal was cubic structure for anisotropic silver nanoparticles. The SEM image indicated that the anisotropic silver nanoparticles were block-like with average lateral dimensions of about 30 nm, and they were self-assembled into two-dimensional disordered multilayer on the silicon wafer, and the particles appeared to be closely packed. The UV-Vis absorption spectrum exhibited a strong absorption peak around 438 nm and a weak peak at 353 nm, which came from dipole and quadrupole oscillation resonance, indicating the formation of non-spherical silver nanoparticles. The surface-enhanced Raman scattering (SERS) active of the anisotropic silver nanoparticles were investigated using trans-1,2-bis(4-pyridyl)-ethylene (BPE) as probe molecule. The results indicate that self-assembled silver film of anisotropic silver nanoparticles on the silicon wafer is excellent substrate for SERS measurements, demonstrating significant enhancement, trace detection capability, and good stability. The minimum analytic concentration was 10(-9) mol x L(-1) for trans-1,2-bis (4-pyridyl)-ethylene (BPE) molecules. It was also found that silver film stored for 90 days in air shows no significant degradation in its sensitivity.
ABSTRACT
In the present work, the electrochemical deposition of silver was investigated on a glassy carbon electrode from AgNO3 solutions in the presence of RTILs (1-butyl-3-methyl imidazolium nitrate, [bmim]NO3) additive by cyclic voltammetric technique, scanning electron microscope (SEM) and X-ray photon spectroscopy (XPS). For comparison, the electrodeposition of silver from [bmim]NO3-free AgNO3 solution was also investigated. The voltammograms showed that the cathodic peak potential shifted toward more negative potential and the cathodic peak current decreased when 5 x 10(-6) mol x L(-1) [bmim]NO3 was added into AgNO3 solutions. This indicated that [bmim]NO3 produced an inhibition of silver deposition, probably related to the adsorption of [bmim]NO3. SEM images showed that the uniform, shining electrodeposits of silver obtained in AgNO3 solutions were rather compact and that the size of silver grains decreased with the addition of [bmim]NO3 additive. The surface-enhanced Raman scattering (SERS) activities of silver deposits were measured by using methyl orange (MO) as the probe molecules. The strongly enhanced Raman scattering from the monolayer film of MO demonstrated that the as prepared silver particular film was SERS active. The enhancement factor was calculated to be up to 1.7 x 10(5) and 1.1 x 10(5) for silver film obtained in AgNO3 solutions with and without [bmim]NO3 additive, respectively.
